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Sal’nikov, L. I., I. I. Brazovskii, V. V. Saskovets, I. A. Sal’nikova, T. I. Evseenko et G. V. Makarevich. « Heterogeneous thermoradiation processes for hydrogen production from steam ». High Energy Chemistry 44, no 3 (mai 2010) : 173–77. http://dx.doi.org/10.1134/s0018143910030021.
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Khan, Haris Mahmood, Tanveer Iqbal, M. A. Mujtaba, Manzoore Elahi M. Soudagar, Ibham Veza et I. M. Rizwanul Fattah. « Microwave Assisted Biodiesel Production Using Heterogeneous Catalysts ». Energies 14, no 23 (4 décembre 2021) : 8135. http://dx.doi.org/10.3390/en14238135.
Texte intégralRésumé :
As a promising renewable fuel, biodiesel has gained worldwide attention to replace fossil-derived mineral diesel due to the threats concerning the depletion of fossil reserves and ecological constraints. Biodiesel production via transesterification involves using homogeneous, heterogeneous and enzymatic catalysts to speed up the reaction. The usage of heterogeneous catalysts over homogeneous catalysts are considered more advantageous and cost-effective. Therefore, several heterogeneous catalysts have been developed from variable sources to make the overall production process economical. After achieving optimum performance of these catalysts and chemical processes, the research has been directed in other perspectives, such as the application of non-conventional methods such as microwave, ultrasonic, plasma heating etc, aiming to enhance the efficiency of the overall process. This mini review is targeted to focus on the research carried out up to this date on microwave-supported heterogeneously catalysed biodiesel production. It discusses the phenomenon of microwave heating, synthesis techniques for heterogeneous catalysts, microwave mediated transesterification reaction using solid catalysts, special thermal effects of microwaves and parametric optimisation under microwave heating. The review shows that using microwave technology on the heterogeneously catalysed transesterification process greatly decreases reaction times (5–60 min) while maintaining or improving catalytic activity (>90%) when compared to traditional heating.
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Miceli, Milagros, Tianling Yang, Adriana Alvarado Garcia, Julian Posada, Sonja Mei Wang, Marc Pohl et Alex Hanna. « Documenting Data Production Processes ». Proceedings of the ACM on Human-Computer Interaction 6, CSCW2 (7 novembre 2022) : 1–34. http://dx.doi.org/10.1145/3555623.
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The opacity of machine learning data is a significant threat to ethical data work and intelligible systems. Previous research has addressed this issue by proposing standardized checklists to document datasets. This paper expands that field of inquiry by proposing a shift of perspective: from documenting datasets towards documenting data production. We draw on participatory design and collaborate with data workers at two companies located in Bulgaria and Argentina, where the collection and annotation of data for machine learning are outsourced. Our investigation comprises 2.5 years of research, including 33 semi-structured interviews, five co-design workshops, the development of prototypes, and several feedback instances with participants. We identify key challenges and requirements related to the integration of documentation practices in real-world data production scenarios. Our findings comprise important design considerations and highlight the value of designing data documentation based on the needs of data workers. We argue that a view of documentation as a boundary object, i.e., an object that can be used differently across organizations and teams but holds enough immutable content to maintain integrity, can be useful when designing documentation to retrieve heterogeneous, often distributed, contexts of data production.
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Lubkov, M., et O. Zaharchuk. « MODELING OF DISPLACEMENT PROCESSES IN HETEROGENEOUS ANISOTROPIC GAS RESERVOIRS ». Visnyk of Taras Shevchenko National University of Kyiv. Geology, no 2 (93) (2021) : 94–99. http://dx.doi.org/10.17721/1728-2713.93.11.
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Nowadays there are important problems of increasing efficiency of development and exploitation of gas deposits. There are problems associated with the growth of gas production in heterogeneous anisotropic reservoirs, increasing gas recovery, achieving economic efficiency and so on. In this situation, there are popular methods of computer modeling of gas productive reservoirs, because they allow getting information of the structure and characteristics of the gas reservoir, the distribution parameters of permeability and other important factors in it. They also allow evaluating and calculating uncertainty arising from the lack of information about the gas reservoir properties outside the well. Currently there are many methods of computer modeling, allowing solving various practical problems. From another hand there are some problems related to the accuracy and adequacy of simulation of heterogeneous anisotropic permeable collector systems in real conditions of gas deposits exploitation. On the base of combined finite-element-difference method for solving the nonstationary anisotropic piezoconductivity Lebenson problem, with calculating of heterogeneous distribution of permeable characteristics of the gas reservoir, we carried out modeling of filtration processes between production and injection wells. The results of computer modeling show that intensity of the filtration process between production and injection wells depends essentially on their location both in a shifting-isotropic and anisotropic gas reservoir. Therefore, for the effective using of poorly permeable shifting-isotropic gas-bearing reservoirs, it is necessary to place production and injection wells along the main anisotropy axes of the gas-bearing layers. At the placing production and injection well systems in low-permeable anisotropic reservoirs of a gas field, the most effective exchange between them will take place when the direction of increased permeability of the reservoirs coincides with the direction of the location of the wells. Obviously, the best conditions for gas production processes in any practical case can be achieved due to optimal selection of all anisotropic filtration parameters of the gas reservoir. One can use obtained results for practical geophysical works with a purpose optimizing of gas production activity in low-permeable heterogeneous anisotropic reservoirs. Presented method for more detailed investigation of low-permeable heterogeneous anisotropic gas-bearing deposits can be used.
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Bendali, Fatiha, Eloise Mole Kamga, Jean Mailfert, Alain Quilliot et Hélène Toussaint. « Pipe-lining dynamic programming processes to synchronize both the production and the consumption of energy ». RAIRO - Operations Research 55, no 4 (juillet 2021) : 2359–83. http://dx.doi.org/10.1051/ro/2021094.
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Synchronizing heterogeneous processes remains a difficult issue in Scheduling area. Related ILP models are in trouble, because of large gaps induced by rational relaxation. We choose here to deal with it while emulating the interactions which take place between the various players of such heterogeneous processes, and propose a pipe-line decomposition of a dynamic programming process designed in order to schedule energy production and energy consumption
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Xue, L. K., T. Wang, J. Gao, A. J. Ding, X. H. Zhou, D. R. Blake, X. F. Wang et al. « Ground-level ozone in four Chinese cities : precursors, regional transport and heterogeneous processes ». Atmospheric Chemistry and Physics Discussions 14, no 14 (12 août 2014) : 20767–803. http://dx.doi.org/10.5194/acpd-14-20767-2014.
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Abstract. We analyzed measurements of ozone (O3) and its precursors made at rural/suburban sites downwind of four large Chinese cities – Beijing, Shanghai, Guangzhou and Lanzhou, to elucidate their pollution characteristics, regional transport, in situ production, and impacts of heterogeneous processes. The same measurement techniques and observation-based model were used to minimize uncertainties in comparison of the results due to difference in methodologies. All four cities suffered from serious O3 pollution but showed different precursor distributions. The model-calculated in situ O3 production rates were compared with the observed change rates to infer the relative contributions of on-site photochemistry and transport. At the rural site of Beijing, export of the well-processed urban plumes contributed to the extremely high O3 levels (up to an hourly value of 286 ppbv), while the O3 pollution observed at suburban sites of Shanghai, Guangzhou and Lanzhou was dominated by intense in-situ production. The O3 production was in a VOCs-limited regime in both Shanghai and Guangzhou, and a NOx-controlled regime in Lanzhou. The key VOC precursors are aromatics and alkenes in Shanghai, and aromatics in Guangzhou. The potential impacts on O3 production of several heterogeneous processes, namely, hydrolysis of dinitrogen pentoxide (N2O5), uptake of hydro peroxy radical (HO2) on particles and surface reactions of NO2 forming nitrous acid (HONO), were assessed. The analyses indicate the varying and considerable impacts of these processes in different areas of China depending on the atmospheric abundances of aerosol and NOx, and suggest the urgent need to better understand these processes and represent them in photochemical models.
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Nurul Aina Nasriqah Binti Ma’arof, Noor Hindryawati, Siti Norhafiza Mohd Khazaai, Prakash Bhuyar, Mohd Hasbi Ab. Rahim et Gaanty Pragas Maniam. « Biodiesel (Methyl Esters) ». Maejo International Journal of Energy and Environmental Communication 3, no 1 (7 avril 2021) : 30–43. http://dx.doi.org/10.54279/mijeec.v3i1.245153.
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Biodiesel, an environmentally friendly biomass-based fuel, is gaining popularity globally as a cost-effective way to meet rising fuel demand. However, the high cost of raw materials and catalysts continues to drive up biodiesel production. An alternative feedstock with a heterogeneously catalyzed reaction could be the most cost-effective way to stabilize industrial biodiesel growth. Understanding these issues led to the idea of using waste palm oil as a feedstock for biodiesel production. While using waste materials as feedstock for biodiesel is an elegant solution, converting high free fatty acids (FFA) directly into methyl esters has some drawbacks. High FFA processes (acid esterification, then base transesterification) are costly. The commercial processes currently use a homogeneous system with sulfuric acid to catalyze both esterification and transesterification. However, heterogeneous solid acid catalysts are preferred over hazardous mineral acids for high FFA esterification because they are less corrosive, produce less waste, and are easier to separate from reactants and products by filtration, recovery, and reusability. Heterogeneous acid catalysts can also simultaneously catalyze transesterification and esterification reactions. Thus, new waste-based support for heterogeneous catalysts (solid acid catalysts) is required to convert waste oils into biodiesel.
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Xue, L. K., T. Wang, J. Gao, A. J. Ding, X. H. Zhou, D. R. Blake, X. F. Wang et al. « Ground-level ozone in four Chinese cities : precursors, regional transport and heterogeneous processes ». Atmospheric Chemistry and Physics 14, no 23 (10 décembre 2014) : 13175–88. http://dx.doi.org/10.5194/acp-14-13175-2014.
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Abstract. We analyzed the measurements of ozone (O3) and its precursors made at rural/suburban sites downwind of four large Chinese cities – Beijing, Shanghai, Guangzhou and Lanzhou, to elucidate their pollution characteristics, regional transport, in situ production, and impacts of heterogeneous processes. The same measurement techniques and observation-based model were used to minimize uncertainties in comparison of the results due to difference in methodologies. All four cities suffered from serious O3 pollution but showed different precursor distributions. The model-calculated in situ O3 production rates were compared with the observed change rates to infer the relative contributions of on-site photochemistry and transport. At the rural site downwind of Beijing, export of the well-processed urban plumes contributed to the extremely high O3 levels (up to an hourly value of 286 ppbv), while the O3 pollution observed at suburban sites of Shanghai, Guangzhou and Lanzhou was dominated by intense in situ production. The O3 production was in a volatile organic compound (VOC)-limited regime in both Shanghai and Guangzhou, and a NOx-limited regime in Lanzhou. The key VOC precursors are aromatics and alkenes in Shanghai, and aromatics in Guangzhou. The potential impacts on O3 production of several heterogeneous processes, namely, hydrolysis of dinitrogen pentoxide (N2O5), uptake of hydro peroxy radical (HO2) on particles and surface reactions of NO2 forming nitrous acid (HONO), were assessed. The analyses indicate the varying and considerable impacts of these processes in different areas of China depending on the atmospheric abundances of aerosol and NOx, and suggest the urgent need to better understand these processes and represent them in photochemical models.
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Ramos, Dias, Puna, Gomes et Bordado. « Biodiesel Production Processes and Sustainable Raw Materials ». Energies 12, no 23 (20 novembre 2019) : 4408. http://dx.doi.org/10.3390/en12234408.
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Energy security and environmental concerns, related to the increasing carbon emissions, have prompted in the last years the search for renewable and sustainable fuels. Biodiesel, a mixture of fatty acids alkyl esters shows properties, which make it a feasible substitute for fossil diesel. Biodiesel can be produced using different processes and different raw materials. The most common, first generation, biodiesel is produced by methanolysis of vegetable oils using basic or acid homogeneous catalysts. The use of vegetable oils for biodiesel production raises serious questions about biodiesel sustainability. Used cooking oils and animal fats can replace the vegetable oils in biodiesel production thus allowing to produce a more sustainable biofuel. Moreover, methanol can be replaced by ethanol being totally renewable since it can be produced by biomass fermentation. The substitution of homogeneous catalyzed processes, nowadays used in the biodiesel industry, by heterogeneous ones can contribute to improve the biodiesel sustainability with simultaneous cost reduction. From the existing literature on biodiesel production, it stands out that several strategies can be adopted to improve the sustainability of biodiesel. A literature review is presented to underline the strategies allowing to improve the biodiesel sustainability.
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Cerón Ferrusca, Montserrat, Rubi Romero, Sandra Luz Martínez, Armando Ramírez-Serrano et Reyna Natividad. « Biodiesel Production from Waste Cooking Oil : A Perspective on Catalytic Processes ». Processes 11, no 7 (28 juin 2023) : 1952. http://dx.doi.org/10.3390/pr11071952.
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Presently, the use of fossil fuels is not ecologically sustainable, which results in the need for new alternative energies such as biodiesel. This work presents a review of the classification of the lipidic feedstocks and the catalysts for biodiesel production. It also presents the pros and cons of the different processes and feedstocks through which biodiesel is obtained. In this context, cooking oil (WCO) has emerged as an alternative with a high potential for making the process sustainable. A detected limitation to achieving this is the high content of free fatty acids (FFA) and existing problems related to homogeneous and heterogeneous catalysts. To overcome this, the use of bifunctional catalysts is being evaluated by the scientific community. Thus, this work also explores the advances in the study of bifunctional catalysts, which are capable of simultaneously carrying out the esterification of free fatty acids (FFA) and the triglycerides present in the WCO. For the sake of an improved understanding of biodiesel production, flow diagrams and the mechanisms implied by each type of process (enzymatic, homogenous, and heterogeneous) are provided. This article also highlights some of the challenges in catalyst development for sustainable biodiesel production from low-grade raw materials.
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Ruhul, A. M., M. A. Kalam, H. H. Masjuki, I. M. Rizwanul Fattah, S. S. Reham et M. M. Rashed. « State of the art of biodiesel production processes : a review of the heterogeneous catalyst ». RSC Advances 5, no 122 (2015) : 101023–44. http://dx.doi.org/10.1039/c5ra09862a.
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This study described the latest technology for fixed batch and continues biodiesel production for both laboratory and industrial scale as well as the role of the heterogeneous catalyst in biodiesel production process.
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Khana, Osama, M. Emran V., Ashok Kumar Yadava et Saurabh Kumar Guptab. « Study on Some Advanced Techniques to Produce Biodiesel from Non-edible Oils ». International Journal of Advance Research and Innovation 5, no 1 (2017) : 135–43. http://dx.doi.org/10.51976/ijari.511722.
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This paper reviews various technologies that have been used for biodiesel production till date, with a view to comparing commercial suitability of these methods on the basis of available feed stocks and associated challenges. Homogenously catalyzed processes are the conventional technologies. However, their large-scale applicability is compromised due to their characteristic challenges. Batch processes and continuous processes are used for industrial purposes and heterogeneous catalysis may be sustainable for the continuous processes. Heterogeneous catalysts from renewable sources may be both environmentally and economically viable. Reactive distillation has the major advantage of combining the reaction and separation stages in a single unit, thereby significantly reducing capital costs and increasing opportunities for heat integration. This paper is a comprehensive overview of current technologies and appropriate options for scale-up development, providing the basis for a proposal for the exploitation of heterogeneous catalysts from natural sources to optimize biodiesel production.
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Trojan, Jozef, Peter Trebuňa et Marek Mizerák. « Application of Digital Engineering Methods in Order to Improve Processes in Heterogeneous Companies ». Applied Sciences 13, no 13 (29 juin 2023) : 7681. http://dx.doi.org/10.3390/app13137681.
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In the presented article, the initial phase is focused mainly on familiarization with the production focus of individual enterprises and their financial security, which provides a basis for the proposal of possible solutions to shortcomings. A more detailed study of production through simulation studies using Process Simulate software provides a more comprehensive view of production in the assessed enterprises, where the current course of production at workplaces is evaluated in detail, and suggestions are then offered to improve the revealed shortcomings. In the end, there is an assessment of the companies from the point of view of homogeneity, so that it is then possible to make an inter-industry comparison of the revealed errors and shortcomings, with the result of finding common recommendations for a wide industrial spectrum.
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Slavinskaya, N. A., U. Riedel, V. E. Messerle et A. B. Ustimenko. « Chemical Kinetic Modeling in Coal Gasification Processes : an Overview ». Eurasian Chemico-Technological Journal 15, no 1 (24 décembre 2012) : 1. http://dx.doi.org/10.18321/ectj134.
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<p>Coal is the fuel most able to cover world deficiencies in oil and natural gas. This motivates the development of new and more effective technologies for coal conversion into other fuels. Such technologies are focused on coal gasification with production of syngas or gaseous hydrocarbon fuels, as well as on direct coal liquefaction with production of liquid fuels. The benefits of plasma application in these technologies is based on the high selectivity of the plasma chemical processes, the high efficiency of conversion of different types of coal including those of low quality, relative simplicity of the process control, and significant reduction in the production of ashes, sulphur, and nitrogen oxides. In the coal gasifier, two-phase turbulent flow is coupled with heating and evaporation of coal particles, devolatilization of volatile material, the char combustion (heterogeneous/porous oxidation) or gasification, the gas phase reaction/oxidation (homogeneous oxidation) of gaseous products from coal particles. The present work reviews literature data concerning reaction kinetic modelling in coal gasification. Current state of related kinetic models for heterogeneous/homogeneous oxidation of coal particles, included plasma assisted, is reviewed.</p>
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Saidakbarovna, Salikhanova Dilnoza. « THE CURRENT STATE OF TECHNOLOGIES FOR THE PRODUCTION AND ACTIVATED CLAY ADSORBENTS ». International Journal of Advance Scientific Research 02, no 04 (1 avril 2022) : 25–28. http://dx.doi.org/10.37547/ijasr-02-04-05.
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It is known that adsorption events, as a rule, occur in a liquid medium containing different categories of substances, are not inert in terms of composition and properties of the medium, and are directly involved in these processes. Here, the main component is the adsorbent, which is selected depending on the nature of the liquid to be cleaned, the polarity of the substances to be removed, their concentration, and so on. In addition, such processes in heterogeneous systems are mainly regulated by the properties of the adsorbents used and the technological parameters of their operation.
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Lee, Adam F., James A. Bennett, Jinesh C. Manayil et Karen Wilson. « Heterogeneous catalysis for sustainable biodiesel productionviaesterification and transesterification ». Chem. Soc. Rev. 43, no 22 (2014) : 7887–916. http://dx.doi.org/10.1039/c4cs00189c.
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Low temperature catalytic conversion of triglycerides and fatty acids sourced from renewable feedstocks represents a key enabling technology for the sustainable production of biodiesel through energy efficient, intensified processes.
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Tóth, András József, et Szilvia Schmidt. « Method for Efficient Regeneration of Solvent Mixture : Extractive Heterogeneous-Azeotropic Distillation ». Műszaki Tudományos Közlemények 15, no 1 (1 octobre 2021) : 103–7. http://dx.doi.org/10.33894/mtk-2021.15.20.
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Abstract The fine chemical and pharmaceutical industries use large amounts of various organic solvents in their manufacturing processes. By reusing them, production costs can be significantly reduced. If we can regenerate waste solvent mixtures, we have the opportunity to reuse them in the production process or in other production processes. Our study illustrates an efficient regeneration process using the example of a four-component solvent mixture. Calculations were performed in a professional process simulator to demonstrate that the highly non-ideal Water-Ethyl Alcohol-Methyl Ethyl Ketone-Ethyl Acetate solvent mixture can be efficiently decomposed into azeotropic pairs and thus regenerated by the extractive heterogeneous-azeotropic distillation technique.
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Ichihashi, Hiroshi, et Hiroshi Sato. « The development of new heterogeneous catalytic processes for the production of ε-caprolactam ». Applied Catalysis A : General 221, no 1-2 (novembre 2001) : 359–66. http://dx.doi.org/10.1016/s0926-860x(01)00887-0.
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Sakai, Tsutomu, Ayato Kawashima et Tetsuya Koshikawa. « Economic assessment of batch biodiesel production processes using homogeneous and heterogeneous alkali catalysts ». Bioresource Technology 100, no 13 (juillet 2009) : 3268–76. http://dx.doi.org/10.1016/j.biortech.2009.02.010.
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Pham, Anh Tuan, Hyuna Kwon, Alexandra Zagalskaya, Marcos Calegari et Tadashi Ogitsu. « Multiscale Modeling of Heterogeneous Interfaces for Hydrogen Production ». ECS Meeting Abstracts MA2024-02, no 42 (22 novembre 2024) : 2825. https://doi.org/10.1149/ma2024-02422825mtgabs.
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Improving performance of hydrogen production devices requires a detailed understanding of physicochemical processes at solid-gas and solid-liquid interfaces. However, probing behavior of these interfaces under working conditions remain a significant challenge for both simulations and experimental probes. In this talk, I will provide an overview of our strategy for simulating heterogeneous interfaces within the HydroGEN Advanced Water Splitting Materials Consortium, ranging from first-principles calculations of chemical reactivity to machine learning approaches for accelerating theory-experiment integration and continuum methods for understanding microstructure effects. In particular, I will discuss how computational models can be used to elucidate mechanisms of interface chemical reactions and mass transport, as well as the formation of new phases and their impacts on materials stability and performance. I will also show how simulations have been integrated with experimental probes, such as X-ray spectroscopy, to obtain new understanding of materials interfaces under operating conditions. Finally, I will discuss how this understanding is being used to guide new strategies for improving materials functionality for hydrogen production. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
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Tsai, Chi-Hung, et Wen-Tien Tsai. « Sustainable Processes Reusing Potassium-Rich Biomass Ash as a Green Catalyst for Biodiesel Production : A Mini-Review ». Processes 12, no 12 (3 décembre 2024) : 2736. https://doi.org/10.3390/pr12122736.
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To mitigate the emissions of greenhouse gases (GHGs) from fossil fuels, the use of biodiesel and its sustainable production have been receiving more attention over the past decade, especially for the reuse of waste cooking oils and non-edible oils as starting feedstocks. For the biodiesel production process, the suitability of a green catalyst is a core function in the transesterification reaction. Heterogeneous (solid-state) catalysts are generally superior to homogeneous (liquid-state) catalysts due to several significant advantages such as no saponification products formed, recyclability, and less equipment corrosion. Recent studies also revealed that heterogeneous solid base catalysts were widely used for the production of biodiesel. Furthermore, the use of biomass-based ash derived from herbaceous and agricultural biomass is increasing rapidly because of its environmental sustainability, high biodiesel yield, and low catalyst cost. To highlight alternative catalysts from biomass residues, this mini-review paper thus focused on a summary of various heterogeneous potassium-rich ash materials, which were used as green catalysts for the sustainable production of biodiesel. Due to the abundant quantity and chemical compositions, it was found that ash derived from cocoa pod husk may be the most commonly used solid base catalyst for producing biodiesel in the literature. Finally, future perspectives on biodiesel production by adopting emerging technologies and using high-potassium (K) biomass ash as a green catalyst were also addressed.
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Ejikeme, P. M., I. D. Anyaogu, C. L. Ejikeme, N. P. Nwafor, C. A. C. Egbuonu, K. Ukogu et J. A. Ibemesi. « Catalysis in Biodiesel Production by Transesterification Processes-An Insight ». E-Journal of Chemistry 7, no 4 (2010) : 1120–32. http://dx.doi.org/10.1155/2010/689051.
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Biodiesel is the mono-alkyl esters of long chain fatty acids derived from renewable lipid feedstock, such as vegetable oils and animal fats, for use in compression ignition (diesel) engines. The conversion of component triglycerides in oils to simple alkyl esters with short chain alcohols like methanol and ethanol amongst others is achieved mainly by transesterification. The transesterification reaction, a reversible process proceeds appreciably by the addition of catalysts, which can be acidic, basic or organic in nature, usually in molar excess of alcohol. The economy of the process depends on the type and quantity of catalyst used among other factors. The catalyst can be homogeneous or heterogeneous depending on whether it is in the same or different phase with the reactants; oils and alcohols. This paper attempts to give an insight into some of the various types of catalysts that have been used to effect the transesterification of vegetable, waste and animal oils in biodiesel production.
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Nnaji, J. C. « ADVANCES IN BIODIESEL SYNTHESIS : THE ROLE OF VARIOUS CATALYSTS ». Open Journal of Engineering Science (ISSN : 2734-2115) 1, no 1 (10 mars 2020) : 53–71. http://dx.doi.org/10.52417/ojes.v1i1.83.
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Biodiesel is a renewable, clean-burning, and biodegradable fuel which can be synthesized from readily available domestic and natural sources, such as edible, non-edible and waste cooking oils, which may serve as a substitute to petro-diesel. It is produced by catalytic transesterification of fats and oils. A number of researches has been devoted to discovering a benign catalyst, especially heterogeneous acid catalyst that could convert non-edible and waste cooking oils with high free fatty acid into biodiesel, in an attempt to reduce the cost of production. The cost of production of biodiesel is still far higher than that of conventional petro-diesel, owing to the cost of edible oil currently being used, processes involved, and cost of conventional heterogeneous catalysts employed. This study assessed the role of various catalysts; homogeneous, heterogenous and enzyme-catalyzed transesterification reactions, in terms of their advantages and disadvantages in biodiesel production in order to establish very promising catalysts. Some methods of heterogeneous acid catalysts were also highlighted. Amongst the common heterogeneous catalyst, carbon-based solid acid catalysts were recommended as very promising solid acid catalyst that can utilize the non-edible oils in biodiesel production. The advantages of carbon-based solid acid catalysts include cheap readily available raw materials for their synthesis, easier production processes, relative stability, high reusability and potential for utilizing waste and non-edible oils for biodiesel production.
Nnaji, J. C. | Department of Chemistry, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria
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Hasan, Noor Hadi, et Nabeel Ibrahim Hasan. « Agricultural Waste Liquefied Hydrothermally using Heterogeneous Catalyst ». IOP Conference Series : Earth and Environmental Science 1259, no 1 (1 novembre 2023) : 012032. http://dx.doi.org/10.1088/1755-1315/1259/1/012032.
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Abstract Due to its abundance and sustainability, lignocellulosic biomass is a possible replacement for petroleum oil in the production of energy and chemicals. Numerous thermochemical processes have been used in significant study to turn biomass into products with added value. One of the best methods for creating bio-fuels and bio-based compounds among them is hydrothermal liquefaction (HTL). However, a number of technological obstacles still need to be removed before HTL technology can be widely used in industry. Hydrothermal liquefaction is now thought to be amongst the most popular effective processes to converting moist biomass for bio crude, but it requires costly renovation procedures to be utilized as biofuel. It is crucial to employ catalysts that may straightforwardly improve the bio crude yield as well as the efficiency of the reaction process; the benefit of raising the operation’s overall production; the impacts of adding heterogeneous catalysts and how they affect the bio-crude yield. In lignocellulosic biomass hydrothermal liquefaction, a typical catalytic activity was discovered, dividing the various catalysts into four separate groups (transition metal, lanthanide oxide, alkaline metal oxide, and zeolite). The purpose study is to objectively evaluate the hydrothermal liquefaction of lignocellulosic biomass and know effecting of adding a zeolite catalyst on it, with a focus on increasing the production and efficiency of the biofuel. In addition, it has drawn attention to the natural stimulatory effects associated with zeolite catalysts.
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Lubkov, M. V., et O. O. Zakharchuk. « Modeling of oil phase displacement processes in heterogeneous anisotropic reservoirs ». Geofizicheskiy Zhurnal 43, no 3 (28 juillet 2021) : 170–80. http://dx.doi.org/10.24028/gzh.v43i3.236387.
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Methods of computer modeling of slightly permeable anisotropic oil-bearing layers are needed nowadays because they give us a possibility to obtain a concept on filtration processes near producing and forcing wells in different practical situations and in this way to raise the level of exploitation of such layers significantly. On the other hand, they allow evaluation and taking into account some uncertainties which appear as a result of inefficient information on the structure and properties of the layer outside the wells. In order to investigate the practical aspects of supporting efficiency of oil production in anisotropic heterogeneous low permeable reservoirs on the base of combined finite-element-difference method for solving the non-stationary anisotropic piezoconductivity problem, modeling of distribution of layer pressure was carried out in the vicinity of the production and forcing wells taking into account the anisotropy of the permeability and conditions of the oil phase infiltration on the margins of the examined layer. It has been found that the intensity of filtration process between producing and forcing wells depends essentially on their spacing in both shear-isotropic and anisotropic oil-bearing layers. In addition the effect of oil phase permeability in shear direction dominates over the effect of permeability in axes directions. Starting from the obtained information for the effective exploitation of anisotropic slightly permeable layers we need to locate producing and forcing wells in the areas with relatively low permeability of the layer and especially to avoid the places with presence of shear permeability. It is important to locate the wells in such a way that blocking the oil in the direction of reduced permeability and fast depletion of the layer in the direction of increased permeability would not happen as well as mutual exchange between producing and forcing wells would not stop. While locating the system of specified wells within anisotropic layers of oil deposit it is necessary to conduct a systemic analysis of environmental anisotropy of layers aimed at such a location of these wells which would guarantee the effective dynamics of filtration processes around them. Application of quadratic isoparametric approximation of finite-elemental net of examined area of oil-bearing layer and implicit differential time approximation brings to increase of precision and stability of numerical solution of the problem.
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Xue, L. K., T. Wang, J. Gao, A. J. Ding, X. H. Zhou, D. R. Blake, X. F. Wang et al. « Ozone production in four major cities of China : sensitivity to ozone precursors and heterogeneous processes ». Atmospheric Chemistry and Physics Discussions 13, no 10 (21 octobre 2013) : 27243–85. http://dx.doi.org/10.5194/acpd-13-27243-2013.
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Abstract. Despite a large volume of research over a number of years, our understandings of the key precursors that control tropospheric ozone production and the impacts of heterogeneous processes remain incomplete. In this study, we analyze measurements of ozone and its precursors made at rural/suburban sites downwind of four large Chinese cities – Beijing, Shanghai, Guangzhou and Lanzhou. At each site the same measurement techniques were utilized and a photochemical box model based on the Master Chemical Mechanism (v3.2) was applied, to minimize uncertainties in comparison of the results due to differences in methodology. All four cities suffered from severe ozone pollution. At the rural site of Beijing, export of the well-processed urban plumes contributed to the extremely high ozone levels (up to an hourly value of 286 ppbv), while the pollution observed at the suburban sites of Shanghai, Guangzhou and Lanzhou was characterized by intense in-situ ozone production. The major anthropogenic hydrocarbons were alkenes and aromatics in Beijing and Shanghai, aromatics in Guangzhou, and alkenes in Lanzhou. The ozone production was found to be in a VOCs-limited regime in both Shanghai and Guangzhou, and a mixed regime in Lanzhou. In Shanghai, the ozone formation was most sensitive to aromatics and alkenes, while in Guangzhou aromatics were the predominant ozone precursors. In Lanzhou, either controlling NOx or reducing emissions of olefins from the petrochemical industry would mitigate the local ozone production. The potential impacts of several heterogeneous processes on the ozone formation were assessed. The hydrolysis of dinitrogen pentoxide (N2O5), uptake of the hydroperoxyl radical (HO2) on particles, and surface reactions of NO2 forming nitrous acid (HONO) present considerable sources of uncertainty in the current studies of ozone chemistry. Further efforts are urgently required to better understand these processes and refine atmospheric models.
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Pham, Anh Tuan. « (Invited) Multiscale Modeling of Heterogeneous Interfaces for Hydrogen Production ». ECS Meeting Abstracts MA2023-02, no 48 (22 décembre 2023) : 2409. http://dx.doi.org/10.1149/ma2023-02482409mtgabs.
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Improving performance of hydrogen production devices requires a detailed understanding of physicochemical processes at solid-gas and solid-liquid interfaces. However, probing behavior of these interfaces under working conditions remain a significant challenge for both simulations and experimental techniques. In this talk, I will provide an overview of our strategy for simulating heterogeneous interfaces within the HydroGEN Advanced Water Splitting Materials Consortium, ranging from first-principles calculations of chemical reactivity to machine learning approaches for accelerating theory-experiment integration and continuum methods for understanding microstructure effects. In particular, I will discuss how computational models can be used to elucidate mechanisms of interface chemical reactions and mass transport, as well as the formation of new phases and their impacts on materials stability and performance. I will also show how simulations have been integrated with experimental probes, such as X-ray spectroscopy, to obtain new understanding of materials interfaces under operating conditions. Finally, I will discuss how this understanding is being used to guide new strategies for improving materials functionality for hydrogen production. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
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Ali Nasr Abdulkareem et Nurul Fitriah Nasir. « A Comprehensive Review of Biodiesel Production using Heterogeneous Catalyst ». Journal of Advanced Research in Micro and Nano Engineering 22, no 1 (27 août 2024) : 103–15. http://dx.doi.org/10.37934/armne.22.1.103115.
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Biodiesel, an eco-friendly alternative to petroleum diesel, is derived from vegetable oils or animal fats through transesterification. The use of heterogeneous catalysts, specifically titanium dioxide (TiO2) and calcium oxide (CaO), in biodiesel production has garnered significant attention due to their environmental benefits and potential to replace fossil fuels. This study systematically analyses biodiesel production using TiO2-CaO catalysts, highlighting their efficiency under various reaction conditions, catalyst preparation methods, and operational parameters. Different feedstocks, such as palm oil, cooking oils, and algal biomass, are evaluated. Methodologies reviewed include wet impregnation and photochemical techniques for catalyst synthesis, with varying reaction temperatures and times. The findings reveal that while TiO2 and CaO have been extensively researched, the variation in methodologies hinders the development of standardized procedures like XRD, SEM, BET, and thermal analysis. Results indicate that cooking oil is a cost-effective feedstock, yielding biodiesel efficiently under optimal conditions: a methanol-to-oil ratio of 24:1, catalyst concentration of 5%, and reaction temperatures of 55-65 °C. The highest biodiesel yield of 98% was achieved using palm oil. Further studies should focus on optimizing and standardizing biodiesel production processes using the TiO2-CaO catalyst.
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Chandra Kishore, Somasundaram, Suguna Perumal, Raji Atchudan, Ashok K. Sundramoorthy, Muthulakshmi Alagan, Sambasivam Sangaraju et Yong Rok Lee. « A Review of Biomass-Derived Heterogeneous Catalysts for Biodiesel Production ». Catalysts 12, no 12 (23 novembre 2022) : 1501. http://dx.doi.org/10.3390/catal12121501.
Texte intégralRésumé :
The scientific community is being forced to consider alternative renewable fuels such as biodiesel as a result of the sharp increases in the price of petroleum and the increased demand for petroleum-derived products. Transesterification is a technique used to create biodiesel where a variety of edible oils, non-edible oils, and animal fats are used. For this, either a homogeneous or heterogeneous catalyst is utilized. An appropriate catalyst is chosen based on the quantity of free fatty acid content in the oil. The main distinction between homogeneous and heterogeneous catalysts is that compared to the heterogeneous catalyst, the homogeneous catalyst is not affected by the quantity of free fatty acids in the oil. Early methods of producing biodiesel relied on homogeneous catalysts, which have drawbacks such as high flammability, toxicity, corrosion, byproducts such as soap and glycerol, and high wastewater output. The majority of these issues are solved by heterogeneous catalysts. Recent innovations use novel heterogeneous catalysts that are obtained from biomass and biowaste resources. Numerous researchers have documented the use of biomass-derived heterogeneous catalysts in the production of high-quality, pure biodiesel as a potentially greener manufacturing method. The catalysts were significantly altered through conventional physical processes that were both cost- and energy-effective. The present review is intended to analyze catalysts from biowaste for making biodiesel at a minimal cost. The most recent methods for creating diverse kinds of catalysts—including acidic, basic, bifunctional, and nanocatalysts—from various chemicals and biomass are highlighted in this review. Additionally, the effects of various catalyst preparation methods on biodiesel yield are thoroughly explored.
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Lantos, Joseph, Narendra Kumar et Basudeb Saha. « A Comprehensive Review of Fine Chemical Production Using Metal-Modified and Acidic Microporous and Mesoporous Catalytic Materials ». Catalysts 14, no 5 (10 mai 2024) : 317. http://dx.doi.org/10.3390/catal14050317.
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Fine chemicals are produced in small annual volume batch processes (often <10,000 tonnes per year), with a high associated price (usually >USD 10/kg). As a result of their usage in the production of speciality chemicals, in areas including agrochemicals, fragrances, and pharmaceuticals, the need for them will remain high for the foreseeable future. This review article assesses current methods used to produce fine chemicals with heterogeneous catalysts, including both well-established and newer experimental methods. A wide range of methods, utilising microporous and mesoporous catalysts, has been explored, including their preparation and modification before use in industry. Their potential drawbacks and benefits have been analysed, with their feasibility compared to newer, recently emerging catalysts. The field of heterogeneous catalysis for fine chemical production is a dynamic and ever-changing area of research. This deeper insight into catalytic behaviour and material properties will produce more efficient, selective, and sustainable processes in the fine chemical industry. The findings from this article will provide an excellent foundation for further exploration and a critical review in the field of fine chemical production using micro- and mesoporous heterogeneous catalysts.
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Miladinovic, Marija, Ivana Lukic, Olivera Stamenkovic, Vlada Veljkovic et Dejan Skala. « Heterogeneous base-catalyzed methanolysis of vegetable oils : State of art ». Chemical Industry 64, no 2 (2010) : 63–80. http://dx.doi.org/10.2298/hemind100304012m.
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Today, homogeneous base-catalyzed methanolysis is most frequently used method for industrial biodiesel production. High requirements for the quality of feedstocks and the problems related to a huge amount of wastewaters have led to the development of novel biodiesel production technologies. Among them, the most important is heterogeneous base-catalyzed methanolysis, which has been intensively investigated in the last decade in order to develop new catalytic systems, to optimize the reaction conditions and to recycle catalysts. These studies are a base for developing continuous biodiesel production on industrial scale in near future. The present work summarizes up-to-date studies on biodiesel production by heterogeneous base-catalyzed methanolysis. The main goals were to point out the application of different base compounds as catalysts, the methods of catalyst preparation, impregnation on carriers and recycling as well as the possibilities to improve existing base-catalyzed biodiesel production processes and to develop novel ones.
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Porshnev, Sergey, Andrey Borodin, Olga Ponomareva, Sergey Mirvoda et Olga Chernova. « The Development of a Heterogeneous MP Data Model Based on the Ontological Approach ». Symmetry 13, no 5 (6 mai 2021) : 813. http://dx.doi.org/10.3390/sym13050813.
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The article discusses the approaches providing symmetric access of all industrial production services to the data of business processes of the enterprise by building a single warehouse of heterogeneous data of a metallurgical production. The warehouse is a part of an automated statistic quality control system for the products of a metallurgical enterprise. The article describes an ontological storage model of data coming from various sources of information in the production process. The concept of “a unit of production of metallurgical production” is introduced that is the connecting component of the entire production life cycle of a metallurgical production. The authors propose an ontological model of the production process, in terms of information flows which are formed in an enterprise at each stage of production. Based on the constructed ontological model, the structure of recording an array of information in the heterogeneous data warehouse is justified and formed. Heterogeneous data warehouse forms a single information space of the enterprise, which serves as the basis for analytical analysis throughout the production and decision—making process. For example, timely response to the deviation reasons from the given physical and chemical properties of the finished product.
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Fernandez Arroiabe, Peru, Jon Iturralde Iñarga, Mercedes Gómez de Arteche Botas, Susana López Pérez, Eduardo Ubieta Astigarraga, Iñigo Unamuno, Manex Martinez-Agirre et M. Mounir Bou-Ali. « Design of a radiative heat recuperator for steel processes ». MATEC Web of Conferences 330 (2020) : 01034. http://dx.doi.org/10.1051/matecconf/202033001034.
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In recent years, there has been an increasing interest in the recovery of the waste heat of steel and glass processes. This work proposes a numerical study of a waste heat exchanger system for steel production processes. The radiative energy is transferred to a commercial oil, which can be used to produce electricity. The behavior of the recuperator is analysed using a 3D numerical model, considering the constrains of a real production plant. The influence of the radiation properties of the materials on the temperature and heat transfer rate are also examined. The results show that the absorptivity of the tubes influences significantly the absorbed waste heat. Furthermore, heterogeneous mass flow distribution should be applied to optimize the total heat transfer rate.
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Horak, Tibor, Peter Strelec, Michal Kebisek, Pavol Tanuska et Andrea Vaclavova. « Data Integration from Heterogeneous Control Levels for the Purposes of Analysis within Industry 4.0 Concept ». Sensors 22, no 24 (15 décembre 2022) : 9860. http://dx.doi.org/10.3390/s22249860.
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Small- and medium-sized manufacturing companies must adapt their production processes more quickly. The speed with which enterprises can apply a change in the context of data integration and historicization affects their business. This article presents the possibilities of implementing the integration of control processes using modern technologies that will enable the adaptation of production lines. Integration using an object-oriented approach is suitable for complex tasks. Another approach is data integration using the entity referred to as tagging (TAG). Tagging is essential to apply for fast adaptation and modification of the production process. The advantage is identification, easier modification, and generation of data structures where basic entities include attributes, topics, personalization, locale, and APIs. This research proposes a model for integrating manufacturing enterprise data from heterogeneous levels of management. As a result, the model and the design procedure for data integrating production lines can efficiently adapt production changes.
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Palma, Vincenzo, Daniela Barba, Marta Cortese, Marco Martino, Simona Renda et Eugenio Meloni. « Microwaves and Heterogeneous Catalysis : A Review on Selected Catalytic Processes ». Catalysts 10, no 2 (18 février 2020) : 246. http://dx.doi.org/10.3390/catal10020246.
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Since the late 1980s, the scientific community has been attracted to microwave energy as an alternative method of heating, due to the advantages that this technology offers over conventional heating technologies. In fact, differently from these, the microwave heating mechanism is a volumetric process in which heat is generated within the material itself, and, consequently, it can be very rapid and selective. In this way, the microwave-susceptible material can absorb the energy embodied in the microwaves. Application of the microwave heating technique to a chemical process can lead to both a reduction in processing time as well as an increase in the production rate, which is obtained by enhancing the chemical reactions and results in energy saving. The synthesis and sintering of materials by means of microwave radiation has been used for more than 20 years, while, future challenges will be, among others, the development of processes that achieve lower greenhouse gas (e.g., CO2) emissions and discover novel energy-saving catalyzed reactions. A natural choice in such efforts would be the combination of catalysis and microwave radiation. The main aim of this review is to give an overview of microwave applications in the heterogeneous catalysis, including the preparation of catalysts, as well as explore some selected microwave assisted catalytic reactions. The review is divided into three principal topics: (i) introduction to microwave chemistry and microwave materials processing; (ii) description of the loss mechanisms and microwave-specific effects in heterogeneous catalysis; and (iii) applications of microwaves in some selected chemical processes, including the preparation of heterogeneous catalysts.
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Conger, Muhammed, et İbrahim Develi. « Innovative 3D Heterogeneous Chip Manufacturing Approach to the Problem of Approaching Physical Limits with Traditional Chip Manufacturing Technologies ». International Conference on Recent Academic Studies 1 (12 mai 2023) : 172–78. http://dx.doi.org/10.59287/icras.691.
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The 3D heterogeneous chip manufacturing approach is an innovative technological approachthat has significant future potential. This innovative manufacturing process enables different semiconductormaterials to be used in a single chip. It also offers higher performance and more functionality thantraditional chips. 3D heterogeneous chip fabrication is accomplished by combining different semiconductormaterials. These materials may include semiconductors with different electronic properties. While allcomponents are made of the same semiconductor material in traditional chip manufacturing processes, amore complex and advanced structure is obtained by using different materials together in 3D heterogeneouschip production. 3D heterogeneous chip production brings many advantages thanks to the combination ofdifferent materials. Another advantage is to increase energy efficiency with 3D heterogeneous chipproduction. Using different materials together and in a single chip makes it possible to manage energy moreefficiently. Another advantage is that the more complex and dense logic circuits of 3D heterogeneous chipfabrication can be located on the same unit square and on top of each other. In this context, this studypresents the technical details and potential risks of the proposed solution method, along with end-to-endchip production, for the resolution of the mentioned problem.
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Meisen, Tobias, Rudolf Reinhard, Thomas Beer, Daniel Schilberg et Sabina Jeschke. « IT-Infrastructure for an Integrated Visual Analysis of Distributed Heterogeneous Simulations ». Advanced Materials Research 328-330 (septembre 2011) : 1940–46. http://dx.doi.org/10.4028/www.scientific.net/amr.328-330.1940.
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Computational simulations are used for the optimization of production processes in order to significantly reduce the need for costly experimental optimization approaches. Yet individual simulations can rarely describe more than a single production step. Hence, a set of simulations has to be used to simulate a contiguous representation of a complete production process. Besides, simulated results have to be analyzed by domain experts to gather insight from the performed computations. In this paper, an IT-infrastructure is proposed that aims at a rather non-intrusive way of interconnecting simulations and domain expert’s knowledge to facilitate the collaborative setup, execution and analysis of distributed simulation chains.
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Yadav, Gaurav, Nidhi Yadav et Md Ahmaruzzaman. « Advances in biomass derived low-cost carbon catalyst for biodiesel production : preparation methods, reaction conditions, and mechanisms ». RSC Advances 13, no 33 (2023) : 23197–210. http://dx.doi.org/10.1039/d3ra03561a.
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Biodiesel is a less hazardous, environmentally friendly biofuel. Waste biomass derived heterogeneous sulfonated catalysts were a significant focus of the most advanced biodiesel processing techniques for simple and low-cost manufacturing processes.
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Stamenkovic, Ivica, Ivana Bankovic-Ilic, Olivera Stamenkovic, Vlada Veljkovic et Dejan Skala. « Continuous biodisel productions : A review ». Chemical Industry 63, no 1 (2009) : 1–10. http://dx.doi.org/10.2298/hemind0901001s.
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Continuous biodiesel production on laboratory and industrial scale was analyzed, with focus on their advantages and disadvantages. Attention was paid to specific characteristics of industrial processes in order to point out the advanced technologies. The well-known base-catalyzed continuous biodiesel production processes are related to problems caused by the immiscibility of the reactants (alcohol and oil), application of relatively high operating temperature (usually the boiling temperature of alcohol or one near it) and obtained yield of methyl ester yields lower than desired. One way to overcome these problems is to employ special reactor design favoring the emulsion process and increasing the overall rate of biodiesel production process, even at room temperature and atmospheric pressure. The second way is to apply heterogeneous catalysts in continuous processes, which will probably be the optimal approach to economically justified and environmentally friendly biodiesel production.
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Lubkov, M., et O. Zakharchuk. « Influence of heterogeneous permeability distribution on filtration processes around the acting gas production horizontal well ». Collection of Research Papers of the National Mining University 66 (2021) : 193–204. http://dx.doi.org/10.33271/crpnmu/66.193.
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Qu, Shuhui, Kasra Yazdani et Janghwan Lee. « 32‐3 : Heterogeneous Resource Constrained Reinforcement Learning Photolithography Scheduler with Heterogeneous Graph Attention Network ». SID Symposium Digest of Technical Papers 55, no 1 (juin 2024) : 417–20. http://dx.doi.org/10.1002/sdtp.17546.
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In mass manufacturing of OLED displays, photolithography process is a critical bottleneck in production capacity. As a result, effective scheduling of the photolithography process is crucial to the overall throughput, productivity, and efficiency of the production. The processing of OLED panels depends upon heterogeneous resources. Aside from that, the complexity, stochastic nature, and highly dynamic characteristic of the processpresent considerable challenges. To address these, we propose a new framework employing a heterogeneous graph neural networkbased Rainbow algorithm. This framework optimizes the schedule used in photolithography process. Considering the constraints on machines, masks, and the stochastic nature of arrival processes, we optimize for maximizing productivity while minimizing the associated costs. We model the interactions among product lot steps, machines, and masks as a heterogeneous graph. This graph encodes the information of lot steps, machines, and masks into distinctive nodes. We then implement a Graph Attention Networkbased architecture for deep representation learning. This transforms state information into node embeddings for each step of each product lot, facilitating decision‐making. Reinforcement learning agents leverage these embeddings to prioritize products via a parameterized Q‐function. Our extensive experiments demonstrate the superior performance of our approach across multiple evaluation metrics in both static and dynamic environment benchmarks, with a higher winning rate and scheduling reward return when compared to existing reinforcement learning methods.
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José da Silva, Márcio, et Abiney Lemos Cardoso. « Heterogeneous Tin Catalysts Applied to the Esterification and Transesterification Reactions ». Journal of Catalysts 2013 (20 novembre 2013) : 1–11. http://dx.doi.org/10.1155/2013/510509.
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The interest in the development of efficient and environmentally benign catalysts for esters synthesis has increased exponentially, mainly due to the demand for biodiesel. In general, fatty esters are used as bioadditive, cosmetic ingredients, polymers, and, more recently, biofuel. Nevertheless, most of the production processes use nonrecyclable and homogenous alkaline catalysts, which results in the reactors corrosion, large generation of effluents, and residues on the steps of separation and catalyst neutralization. Heterogeneous acid catalysts can answer these demands and are an environmentally benign alternative extensively explored. Remarkably, solid acid catalysts based on tin have been shown highly attractive for the biodiesel production, mainly via FFA esterification reactions. This review describes important features related to be the synthesis, stability to, and activity of heterogeneous tin catalysts in biodiesel production reactions.
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Валентина Сергеевна, Носаева,, et Степачёва, Антонина Анатольевна. « VERATROL PRODUCTION IN THE PRESENCE OF ZEOLITEBASED CATALYSTS ». Вестник Тверского государственного университета. Серия : Химия, no 4(50) (18 janvier 2023) : 15–20. http://dx.doi.org/10.26456/vtchem2022.4.2.
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Вератрол находит широкое применение в фармацевтической, пищевой, парфюмерной промышленности. Это соединение является полупродуктом во многих синтезах. Получение вератрола сопряжено с использованием токсичных и опасных компонентов. Это приводит к необходимости в трудоемкой очистке продукта. С целью снижения себестоимости и минимизации очистки многообещающим является применение гетерогенных катализаторов метилирования. В данной работе приводятся результаты исследования возможности синтеза вератрола из гваякола с использованием кислотных катализаторов ± цеолитов. Veratrol is widely used in the pharmaceutical, food, and perfume industries. This compound is a semi-product in many syntheses. The production of veratrol involves the use of toxic and dangerous components. This leads to the need for time-consuming product purification stage. In order to reduce the cost and minimize purification, the use of heterogeneous methylation catalysts is promising. This paper presents the results of a study of the possibility of veratrol synthesis from guaiacol using acid catalysts ± zeolites.
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Safarov, N. M., F. B. Ismayilova et S. G. Hajizade. « Development of the diasgnostic method for determination of density of «water-oil-sand» type mixtures ». SOCAR Proceedings, no 2 (30 juin 2022) : 073–77. http://dx.doi.org/10.5510/ogp20220200677.
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In this article has been proposed empirical dependencies for the direct determination – without mathematical calculations or experimental measurements of density of “water-oil-sand” type rheological complex mixtures resulting from arbitrary mixing of oil with water and sand in the processes of production, collection and transportation of well products. Also, based on the application of «Colour characteristics», a new diagnostic method that allows to explain the dependence of density, which is one of the main quality indicators of heterogeneous liquids transported by pipeline, on watering and temperature factors, as well as the concentration of filler element, leads to new trivial solutions in the processes of production and transportation. Given its practical significance and expediency for use in hydraulic calculations, its application prospects have been commented. Keywords: granular filler; dispersed systems; heterogeneous liquids; suspension; density factor; empirical dependence.
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Newton, P. F., et P. A. Jolliffe. « Assessing processes of intraspecific competition within spatially heterogeneous black spruce stands ». Canadian Journal of Forest Research 28, no 2 (1 février 1998) : 259–75. http://dx.doi.org/10.1139/x97-192.
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The objective of this study was to develop and subsequently apply an individual-tree analytical approach for assessing resource competition processes within monospecific, even-aged, and spatially heterogeneous black spruce (Picea mariana (Mill.) BSP) stands. The approach consisted of five basic steps: (1) ranking competitors with respect to subject tree size using a relative scale, (2) stratifying competitors into competition strata based on their relative size differential with respect to a subject tree, (3) quantifying the intensity of competition within each stratum using spatially explicit local competition indices and subsequently formulating directional-specific cumulative indices, (4) regressing relative measures of stem growth against each directional-specific index, and (5) graphically and statistically assessing differences in resultant standardized regression coefficients as competition accumulated upward from below and downward from above. This analytical framework was used with stem growth data derived from 401 subject trees situated within 18 monospecific, even-aged, density-stressed, and spatially heterogeneous black spruce stands. The results indicated directional-specific asymmetrical relationships between subject trees and their neighbours in which increasing competition from above resulted in declines in stem production. Consequently, these results were in accord with those expected when competition is dominated by a resource preemption process.
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Kumawat, Jugal, et Virendra Kumar Gupta. « Fundamental aspects of heterogeneous Ziegler–Natta olefin polymerization catalysis : an experimental and computational overview ». Polymer Chemistry 11, no 38 (2020) : 6107–28. http://dx.doi.org/10.1039/d0py00753f.
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Chen, Xiaoyan, Taoyue Yuan, Xinyu Yang, Shunke Ding et Mengtao Ma. « Insights into Photo/Electrocatalysts for the Degradation of Per- and Polyfluoroalkyl Substances (PFAS) by Advanced Oxidation Processes ». Catalysts 13, no 9 (19 septembre 2023) : 1308. http://dx.doi.org/10.3390/catal13091308.
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Per- and polyfluoroalkyl substances (PFASs) are an emerging group of persistent organic pollutants in aquatic environments with high levels of toxicity and bioaccumulation. The risks posed by PFASs to the environment and health have attracted increasing attention. To remove them from water, advanced oxidation processes (AOPs), with the merits of high efficiency and low cost, are mainly used. Photo/electrocatalytic heterogeneous AOPs, with the assistance of nanostructured catalysts and external energy in the form of light/electricity, have emerged as one of the most powerful techniques, overcoming the difficulty associated with defluorination and achieving the effective and complete degradation of PFASs in water. The structures of photo/electrocatalysts play a critical role in the production of reactive oxygen species, the electron transfer process, and the degradation pathway and its efficiency. Herein, to elucidate the structure–performance relationship, a review of photo/electrocatalysts for the enhanced degradation of PFASs in heterogeneous AOPs, organized according to their composition and nanostructure design, is provided. This review article is mainly focused on (1) the mechanisms and pathways of PFAS degradation by heterogeneous photo/electrocatalytic AOPs, and (2) the structural designs and modifications of photo/electrocatalysts for the enhanced degradation of PFASs by heterogeneous AOPs. Finally, the challenges and prospects for future research into photo/electrocatalysts of heterogeneous AOPs in the field of PFAS remediation are discussed.
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Cooper, Khershed P., et Samuel G. Lambrakos. « Thermal Modeling of Direct Digital Melt-Deposition Processes ». Materials Science Forum 654-656 (juin 2010) : 1540–44. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1540.
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Additive manufacturing involves creating three-dimensional objects by depositing materials layer-by-layer. The freeform nature of the method permits the production of components with complex geometry. Deposition processes provide one more capability, which is the addition of multiple materials in a discrete manner to create “heterogeneous” objects with locally controlled composition. The result is direct digital manufacturing (DDM) by which dissimilar materials are added voxel-by-voxel (a voxel is volumetric pixel) following a predetermined tool-path. A typical example is functionally-graded material such as a gear with a tough core and a wear resistant surface. The inherent complexity of DDM processes is such that process modeling based on direct physics-based theory is difficult, especially due to a lack of temperature-dependent thermo-physical properties and particularly when dealing with melt-deposition processes. To overcome this difficulty the inverse problem approach is adopted to develop thermal models for multi-material, direct digital melt-deposition. This approach is based on the construction of a numerical-algorithmic framework for modeling anisotropic diffusivity such as that which would occur during energy deposition within a heterogeneous work-piece. This framework consists of path-weighted integral formulations of heat diffusion according to spatial variations in material composition and requires consideration of parameter sensitivity issues.
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FARIA, JOSE, et EUSEBIO NUNES. « RELIABILITY ENGINEERING OF LARGE JIT PRODUCTION SYSTEMS ». International Journal of Reliability, Quality and Safety Engineering 19, no 03 (juin 2012) : 1250011. http://dx.doi.org/10.1142/s0218539312500118.
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This paper introduces the rationale and the fundamental elements and algorithms of a reliability engineering methodology combining analytical and simulation tools, and discusses its application to the design of a large, multi-cell and heterogeneous production system with just-in-time (JIT) deliveries. In order to cope with the inherent complexity of such analysis, a two level hierarchical modeling and evaluation framework was developed. Local models are first obtained from the failure and repair processes of the manufacturing equipment. Then, these models are combined with the failure propagation delays introduced by the work-in-process buffers in order to obtain the system level model. The evaluation algorithm is able to deal with reliability models containing stochastic processes with generalized distributions. This fundamental requirement comes from the fact that repair and failure propagation processes typically present hyper-exponential distributions, e.g., lognormal distributions, that cannot be assessed using the conventional reliability techniques. The second part of the paper addresses several design issues of the production system that directly impact the reliability of the deliveries, and explains how the behavioral and structural characteristics of JIT production systems were explored in order to implement effective evaluation algorithms.
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Damera, Thirupathi, Ramakanth Pagadala, Surjyakanta Rana et Sreekantha Babu Jonnalagadda. « A Concise Review of Multicomponent Reactions Using Novel Heterogeneous Catalysts under Microwave Irradiation ». Catalysts 13, no 7 (24 juin 2023) : 1034. http://dx.doi.org/10.3390/catal13071034.
Texte intégralRésumé :
Multi-component reactions for the construction of heterocycles have been fascinated by microwave energy as an alternative technique of heating, owing to the advantages over traditional reflux methods. The heterogeneous catalysts contribute significantly towards recycling, harmless, easy filtration, catalyst preparation, more life span, abundance, and product yields. With novel and creative uses in organic and peptide synthesis, polymer chemistry, material sciences, nanotechnology, and biological processes, the usage of microwave energy has rapidly increased during the past 20 years. This article covers multicomponent reactions involving construction of chromenes, pyridines, pyrroles, triazoles, pyrazoles, tetrazoles, trans and cis julolidines using heterogeneous catalysts under microwave. It provides an overview of contemporary microwave-assisted heterogeneous catalytic reactions. Microwave chemistry is now an established technology with several advantages regarding reaction rate and production yield, improving energy savings as confirmed by many applications. Due to the widespread curiosity in medicinal chemistry, the heterogeneously catalysed construction of heterocycles under microwave irradiation is explored to reduce time and energy. By considering various aspects of economy, eco-friendly, and user-friendly factors, this review focuses on recent advances in the multi-component construction of heterocycles using heterogeneous catalysts under microwave irradiation. This review also discusses the benefits and limitations of reaction conditions and yields from the literature reports for the past five years.