Journal articles: 'Zeolites as catalysts'

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Peng, Peng, Xiong-Hou Gao, Zi-Feng Yan, and Svetlana Mintova. "Diffusion and catalyst efficiency in hierarchical zeolite catalysts." National Science Review 7, no. 11 (August 21, 2020): 1726–42. http://dx.doi.org/10.1093/nsr/nwaa184.

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Abstract The preparation of hierarchical zeolites with reduced diffusion limitation and enhanced catalyst efficiency has become a vital focus in the field of zeolites and porous materials chemistry within the past decades. This review will focus on the diffusion and catalyst efficiency of hierarchical zeolites and industrial catalysts. The benefits of diffusion and catalyst efficiency at two levels of hierarchies (zeolitic component level and industrial catalyst level) from a chemical reaction engineering point of view will be analysed. At zeolitic component level, three types of mesopores based on the strategies applied toward enhancing the catalyst effectiveness factor are presented: (i) ‘functional mesopores’ (raising effective diffusivity); (ii) ‘auxiliary mesopores’ (decreasing diffusion length); and (iii) ‘integrated mesopores’ (a combination thereof). At industrial catalyst level, location and interconnectivity among the constitutive components are revealed. The hierarchical pore interconnectivity in multi-component zeolite based industrial catalysts is exemplified by fluid catalytic cracking and bi-functional hydroisomerization catalysts. The rational design of industrial zeolite catalysts at both hierarchical zeolitic component and catalyst body levels can be fully comprehended using the advanced in situ and/or operando spectroscopic, microscopic and diffraction techniques.

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Erofeev, Vladimir I., Sofiya N. Dzhalilova, Mikhail V. Erofeev, Vasilii S. Ripenko, and Vladimir P. Reschetilowski. "Conversion of the Propane–Butane Fraction into Arenes on MFI Zeolites Modified by Zinc Oxide and Activated by Low-Temperature Plasma." Molecules 25, no. 11 (June 11, 2020): 2704. http://dx.doi.org/10.3390/molecules25112704.

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The effect of modification of MFI zeolite 1–5 wt.% ZnO activated by plasma on acid and catalytic properties in the conversion of the propane–butane fraction into arenes was investigated. The high-silica zeolites with silicate module 45 were synthesized from alkaline alumina–silica gels in the presence of an ‘X-oil’ organic structure-forming additive. The modification of the zeolite with zinc was carried out by impregnating the zeolite granules in the H-form with an aqueous solution of Zn(NO3)2. The obtained zeolites were characterized by X-ray phase analysis and IR spectroscopy. It is shown that the synthesized zeolites belong to the high-silica MFI zeolites. The study of microporous zeolite-containing catalysts during the conversion of C3-C4 alkanes to aromatic hydrocarbons made it possible to establish that the highest yield of aromatic hydrocarbons is observed on zeolite catalysts modified with 1 and 3% ZnO and amount to 63.7 and 64.4% at 600 °C, respectively, which is 7.7–8.4% more than on the original zeolite. The preliminary activation of microporous zeolites modified with 1–5% ZnO and plasma leads to an increase in the yield of aromatic hydrocarbons from the propane–butane fraction; the maximum yield of arenes is observed in zeolite catalysts modified with 1 and 3% ZnO and activated by plasma, amounting to 64.9 and 65.5% at 600 °C, respectively, which is 8.9–9.5% more than on the initial zeolite. The activity of the zeolite catalysts modified by ZnO and activated by plasma show good agreement with their acid properties. Activation of the zeolites modified by 1 and 3% ZnO and plasma leads to an increase in the concentration of the weak acid sites of the catalyst to 707 and 764 mmol/g in comparison with plasma-inactivated 1 and 3% ZnO/ZKE-XM catalysts at 626 and 572 mmol/g, respectively.

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Machado, Ana Vera, Isabel Neves, Gabriela Botelho, and P. Rebelo. "Thermogravimetric Study of Polyethylene Catalytic Degradation by Zeolites." Materials Science Forum 514-516 (May 2006): 901–4. http://dx.doi.org/10.4028/www.scientific.net/msf.514-516.901.

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Commercial samples of high density polyethylene were decomposed over faujasites (FAU) type zeolites (Y-type) using thermal gravimetric analysis (TGA). The catalytic activity and behavior of the FAU-zeolites catalysts were determined. It was found that the degradation temperature of polymer strongly depends on the catalytic acidity of the zeolites. HY zeolite was identified as the most active catalyst due to its strong acidity. The results showed that the activation energy decrease with the amount of catalyst added.

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Gao, Feng. "Fe-Exchanged Small-Pore Zeolites as Ammonia Selective Catalytic Reduction (NH3-SCR) Catalysts." Catalysts 10, no. 11 (November 14, 2020): 1324. http://dx.doi.org/10.3390/catal10111324.

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Cu-exchanged small-pore zeolites have been extensively studied in the past decade as state-of-the-art selective catalytic reduction (SCR) catalysts for diesel engine exhaust NOx abatement for the transportation industry. During this time, Fe-exchanged small-pore zeolites, e.g., Fe/SSZ-13, Fe/SAPO-34, Fe/SSZ-39 and high-silica Fe/LTA, have also been investigated but much less extensively. In comparison to their Cu-exchanged counterparts, such Fe/zeolite catalysts display inferior low-temperature activities, but improved stability and high-temperature SCR selectivities. Such characteristics entitle these catalysts to be considered as key components of highly efficient emission control systems to improve the overall catalyst performance. In this short review, recent studies on Fe-exchanged small-pore zeolite SCR catalysts are summarized, including (1) the synthesis of small-pore Fe/zeolites; (2) nature of the SCR active Fe species in these catalysts as determined by experimental and theoretical approaches, including Fe species transformation during hydrothermal aging; (3) SCR reactions and structure-function correlations; and (4) a few aspects on industrial applications.

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Marosz, Monika, Bogdan Samojeden, Andrzej Kowalczyk, Małgorzata Rutkowska, Monika Motak, Urbano Díaz, Antonio E. Palomares, and Lucjan Chmielarz. "MCM-22, MCM-36, and ITQ-2 Zeolites with Different Si/Al Molar Ratios as Effective Catalysts of Methanol and Ethanol Dehydration." Materials 13, no. 10 (May 22, 2020): 2399. http://dx.doi.org/10.3390/ma13102399.

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MCM-22, MCM-36, and ITQ-2 zeolites with the intended Si/Al molar ratios of 15, 25, and 50 were synthetized and tested as catalysts for dehydration of methanol to dimethyl ether and dehydration of ethanol to diethyl ether and ethylene. The surface concentration of acid sites was regulated by the synthesis of zeolite precursors with different aluminum content in the zeolite framework, while the influence of porous structure on the overall efficiency of alcohol conversion was analyzed by application of zeolitic materials with different types of porosity—microporous MCM-22 as well as microporous-mesoporous MCM-36 and ITQ-2. The zeolitic samples were characterized with respect to their: chemical composition (ICP-OES), structure (XRD, FT-IR), texture (N2 sorption), and surface acidity (NH3-TPD). Comparison of the catalytic activity of the studied zeolitic catalysts with other reported catalytic systems, including zeolites with the similar Si/Al ratio as well as γ-Al2O3 (one of the commercial catalysts for methanol dehydration), shows a great potential of MCM-22, MCM-36, and ITQ-2 in the reactions of alcohols dehydration.

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Santoso, Aman, Ida Bagus S. Sumari, Novia Nina Safitri, Anugrah Ricky Wijaya, and Daratu Eviana Kusuma Putri. "Activation of Zeolite from Malang as Catalyst for Plastic Waste Conversion to Fuel." Key Engineering Materials 851 (July 2020): 212–19. http://dx.doi.org/10.4028/www.scientific.net/kem.851.212.

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Plastic pollution is an environmental problem that has not resolved until now. Pyrolysis is able to be a solution to reduce plastic waste. The use of catalysts will reduce heating temperatures, speed up processing time, and increase product yield. Natural zeolite has the potency as a catalyst in pyrolysis process due to its micropore structure, high acidity and thermal stability. The purpose of this research is to determine the effect of active zeolite catalyst on the polypropylene pyrolysis. The main process of this study is pyrolysis of polypropylene (PP) plastic waste without catalysts and with natural zeolite catalysts which were non-activated and activated. Natural zeolites were activated by HF, HCl and NH4Cl. The well result of this research is represented by the yield, viscosity, calorific value, FTIR and GC-MS analysis. Based on the results of diffractogram analysis, natural zeolites catalyst in this study is included in modernite minerals crystalline. The ratio of Si/Al in zeolite before activation was 7.07 and the acidity was 0.697 g/mmol. After the activation process, the ratio of Si/Al and zeolite acidity increased by 62.181% and 43.84%. The use of active natural zeolite catalysts in pyrolysis PP could reduce the total reaction time by 57.14%. Pyrolysis products with active zeolite catalyst compared to without catalysts had clearer color and higher heating value, compared to pirolysis without catalyst. Based on function group analysis with FTIR, the mixture of hydrolyzed compounds containing successive functional groups are-C-H (alkanes), double bond of C=C, hydroxyl-OH group which can be determined as phenol (ArOH), alcohol (ROH), and carboxylic acid (RCOOH). The GC-MS analysis showed that pyrolysis products are composed of a mixture of alkanes, cycloalkanes, alkenes, carboxylic acids with aromatic rings, and ketones. The pyrolysis products without catalysts consist of 5-11 (C5-C11) carbon atoms, whereas the range of carbon atoms of pyrolysis products with active zeolite catalysts was 6-24 (C6-C24).

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Jeong, Sangmin, Ki-Joon Jeon, Young-Kwon Park, Byung-Joo Kim, Kyong-Hwan Chung, and Sang-Chul Jung. "Catalytic Properties of Microporous Zeolite Catalysts in Synthesis of Isosorbide from Sorbitol by Dehydration." Catalysts 10, no. 2 (January 23, 2020): 148. http://dx.doi.org/10.3390/catal10020148.

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As bisphenol A has been found to cause hormonal disturbances, the natural biomaterial isosorbide is emerging as a substitute. In this study, a method for isosorbide synthesis from sorbitol was proposed by dehydration under high temperature and high pressure reaction. Microporous zeolites and Amberlyst 35 solid acids with various acid strengths and pore characteristics were applied as catalysts. In the synthesis of isosorbide from sorbitol, the acidity of the catalyst was the main factor. MOR and MFI zeolite catalysts with high acid strength and small pore size showed low conversion of sorbitol and low yield of isosorbide. On the other hand, the conversion of sorbitol was high in BEA zeolite with moderate acid strength. Amberlyst 35 solid acid catalysts showed a relatively high conversion of sorbitol, but low yield of isosorbide. The Amberlyst 35 solid acid catalyst without micropores did not show any inhibitory effects on the production of by-products. However, in the BEA zeolite catalyst, which has a relatively large pore structure compared with the MOR and MFI zeolites, the formation of by-products was suppressed in the pores, thereby improving the yield of isosorbide.

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Lao-Ubol, Supranee, Phunthinee Somwongsa, Pracha Laoauyporn, Pasinee Panith, Siriporn Larpkiattaworn, and Shih Yuan Chen. "Effect of Silica Base Catalyst on Transformation of Methanol to Hydrocarbon." Key Engineering Materials 751 (August 2017): 512–17. http://dx.doi.org/10.4028/www.scientific.net/kem.751.512.

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Five different types of silica catalyst (SBA-15, SBA-15-PO3H2, and three different Si/Al ratio of commercial zeolites (30, 80 and 280) were used to study the transformation of methanol to hydrocarbon (MTH). The aim of this study was to investigate the effect of pore diameter and acidity in the structure of silica catalysts on the process performances in terms of methanol conversion and hydrocarbon selectivity. The mesoporous silica catalysts were prepared by co-condensation method. The catalysts samples were characterized by GC-MS, XRD, BET, and NH3-TPD techniques. The catalytic performance of synthesized and commercial catalysts for MTH process was evaluated using a homemade fixed bed reactor at temperature (300°C). It was found that the liquid hydrocarbon product provided by zeolite catalysts is aromatic hydrocarbons-rich. High Si/Al zeolites with larger pore size lead to higher selectivity and yield to paraffins (C1-C7). In contrast to commercial zeolite catalyst, SBA-15 and its modification with phosphorus species showed no conversion under studied condition. These results indicate that both pore diameter and acidity influence the product distribution in methanol to hydrocarbon process.

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Putluru, Siva Sankar Reddy, Leonhard Schill, Anker Degn Jensen, and Rasmus S. N. Fehrmann. "Selective Catalytic Reduction of NOx with NH3 on Cu-, Fe-, and Mn-Zeolites Prepared by Impregnation: Comparison of Activity and Hydrothermal Stability." Journal of Chemistry 2018 (December 10, 2018): 1–11. http://dx.doi.org/10.1155/2018/8614747.

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Cu-, Fe-, and Mn-zeolite (SSZ-13, ZSM-5, and BEA) catalysts have been prepared by incipient wetness impregnation and characterized by N2 physisorption, H2-TPR, NH3-TPD, and XPS methods. Both metal and zeolite support influence the deNOx activity and hydrothermal stability. Cu-zeolites and Mn-zeolites showed medium temperature activity, and Fe zeolites showed high temperature activity. Among all the catalysts, Cu-SSZ-13 and Fe-BEA are the most promising hydrothermally resistant catalysts. Fresh and hydrothermally treated catalysts were further examined to investigate the acidic and redox properties and the zeolite surface composition. Increased total acidity after metal impregnation and loss of acidity due to hydrothermal treatment were observed in all the catalysts. Hydrothermal treatment resulted in migration of metal or in strong metal support interations, whereby changes in reduction patterns are observed.

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Juzsakova, Tatjána, Noor Al-Jammal, Igor Cretescu, Viktor Sebestyén, Cuong Le Phuoc, Endre Domokos, Ákos Rédey, and Catalina Stan. "Case Studies for Clean Technology Development in the Chemical Industry Using Zeolite Based Catalysts." Minerals 8, no. 10 (October 17, 2018): 462. http://dx.doi.org/10.3390/min8100462.

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This paper deals with the practical implementation of cleaner technologies in the chemical industry, using two case studies as an illustration. The first case study deals with the removal of NOx and N2O gases over an iron-doped ZSM-5 catalyst developed for tail gas treatment in nitric acid manufacturing. The aim for this case study was to investigate the efficiency of the zeolitic catalyst in the DeNOx process and to compare its catalytic activity with the conventional vanadia-titania. By the experiments carried out, it can be concluded that the new technological developments could significantly contribute to a decrease in environmental pollution. The second case study focuses on zeolite-based catalysts prepared from zeolitic tuff by the impregnation method, for biodiesel production from waste sunflower vegetable oil. The effects of operating and processing variables such as reaction temperature and time were investigated. The results showed that the highest biodiesel yield was 96.7% at an 11.5 MeOH/oil molar ratio, in the presence of 6.4 wt % catalyst at a 50 °C reaction temperature and reaction time of 2 h. The properties of the biodiesel that was produced, such as the viscosity, meet the required specifications of standard JUS EN14214. The common feature of the two different case studies is that both technologies use zeolite catalysts, namely naturally-occurring zeolitic tuff and synthetic ZSM type zeolite catalyst. The examples shown emphasize the importance of the zeolites in clean chemical technologies, which contribute to the protection of the environment.

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Sidorov, A., V. Molchanov, L. Mushinskii, and R. Brovko. "Surface Characteristics Change of Zinc Modified H-ZSM-5 Zeolites in Methanol to Hydrocarbons Transformation Process." Bulletin of Science and Practice 6, no. 11 (November 15, 2020): 23–30. http://dx.doi.org/10.33619/2414-2948/60/02.

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The t-plot method is a well-known method for determining the volumes of micro- and/or mesoporous materials and the specific surface area of a sample by comparison with a reference adsorption isotherm of a non-porous material having a similar surface chemical composition. The article describes the applicability of the t-graph method to the analysis of the surface properties of zinc modified samples of zeolite H-ZSM-5 before and after the reactions of methanol transformation into hydrocarbons occur on them. Zeolites are widely used as catalysts in the petrochemical and refining industries. These materials contain active Bronsted acid sites, distributed within the microporous structure of zeolites, which leads to selective catalysis due to the difference in the pore shape of the zeolites used. The size, shape of the zeolite catalyst determines the catalytic performance in terms of both product selectivity and catalyst deactivation. In most zeolite catalyzed hydrocarbon conversion reactions, catalyst activity is lost due to carbon deposition. In this connection, the determination of the surface properties of zeolites is an important task that contributes to the disclosure of the physicochemical essence of the process of deactivation of zeolites. The recalculation of nitrogen adsorption isotherms using the t-plot model made it possible to determine the volume of micro and mesopores. Based on the t-graph data, it can be concluded that during the transformation of methanol into hydrocarbons, carbon accumulates on the surface of the zeolite. In this case, the predominant deposition of carbon on the surface of mesopores, due to the fact that in the process of decontamination, from 61 to 73% of the volume of mesopores is lost. The number of micropores also decreases, but the share of losses is 42–54%, which is 10–15% lower compared to the loss of mesopore volume.

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Kikuchi, Eiichi, Yasuhiro Mogi, and Takeshi Matsuda. "Shape Selective Disproportionation of Methylnaphthalene on ZSM-5 Catalyst." Collection of Czechoslovak Chemical Communications 57, no. 4 (1992): 909–19. http://dx.doi.org/10.1135/cccc19920909.

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The conversion of 2-methylnaphthalene (2-MN) was studied at atmospheric pressure in a flow-type fixed bed reactor using H-Y, H-beta, H-mordenite, H-ZSM-5, H-ZSM-11 and H-ZSM-48 as catalysts. H-Y and H-beta exhibited high activities for disproportionation and isomerization of 2-MN. H-Mordenite and zeolites having medium size pores were active for the conversion of 2-MN which was mainly isomerized to 1-MN. The low disproportionation activities of these zeolites resulted from their shape selective properties. Disproportionation of 2-MN on the zeolite catalysts gave 2,6- and 2,7-dimethylnaphthalenes (DMN) in higher proportions than the thermodynamically attainable level. H-ZSM-5 was the most selective catalyst to produce these DMN isomers among the zeolite catalysts tested, although 2,7-DMN was formed in a higher proportion than 2,6-DMN. On H-mordenite catalyst, 2,6-DMN was more selectively formed than 2,7-DMN. The selectivity for 2,6-DMN against 2,7-DMN increased with increasing SiO2/Al2O3 ratio of H-mordenite. It is suggested that the composition of DMN isomers produced by disproportionation of 2-MN depends on the acid strength as well as on the shape selective properties of zeolites used.

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Kovacheva, Pavlina Ch, Nadka P. Davidova, and Alvin H. Weiss. "Lead Containing Zeolites as Catalysts for Oxidative Conversion of Methane." Collection of Czechoslovak Chemical Communications 57, no. 12 (1992): 2548–52. http://dx.doi.org/10.1135/cccc19922548.

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The oxidative conversion of methane was studied over lead containing zeolites of type X, silicalite and ALPO-5 in the temperature range 750-850 °C. An impregnation of catalysts in the range 3-7 wt.% lead was found optimum for the conversion and C2 selectivity. The 6.4 wt.% lead-containing zeolite showed the best C2 hydrocarbon yield. Higher reaction temperatures caused higher C2H4/C2H6 ratios. The catalysts did not deactivate in 10 h time-on-stream. PbO and zeolitic basic sites play role in the reaction.

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Leguizamon Aparicio, María Silvia, Maria Elena Canafoglia, Marco Antonio Ocsachoque, Ileana Daniela Lick, and Irma Lia Botto. "Co-Rh modified natural zeolites as new catalytic materials to oxidize propane and naphthalene from emission sources." Open Chemistry 14, no. 1 (January 1, 2016): 335–42. http://dx.doi.org/10.1515/chem-2016-0036.

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AbstractNatural zeolites as a raw material to prepare catalytic precursors for the oxidation reaction of linear and poly-aromatic hydrocarbons are reported in this work. The process consisted in the formation of mono- and bi-metallic species containing Co and Co-Rh on natural zeolite tuffs. The materials are analyzed by different physicochemical techniques and used as catalysts for propane and naphthalene oxidation in emissions sources. Comparatively, Rh-zeolites are the most active catalysts for propane conversion. In this case, the formation of mixed oxides seems to be conditioned by surface properties. It could also be suggested that the Rh incorporation on a non-active phase in bimetallic catalysts impacts the effectiveness of the system. In addition, the NO presence increases the activity of bimetallic materials. Rh-Co zeolite systems markedly influence the naphthalene combustion temperature. Whereas in the absence of a catalyst a conversion rate of 50% and 100% is reached at 430 °C and 485 °C, respectively. It is interesting to observe that for RhCoCli-Mor and RhCoCli catalyst the 100% conversion is reached at 250 °C.

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Hadi, Mina, Hamid Reza Aghabozorg, Hamid Reza Bozorgzadeh, and Mohammad Reza Ghasemi. "The Effect of Aluminum Source on Performance of Beta-Zeolite as a Support for Hydrocracking Catalyst." Bulletin of Chemical Reaction Engineering & Catalysis 13, no. 3 (December 4, 2018): 543. http://dx.doi.org/10.9767/bcrec.13.3.2570.543-552.

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In this paper, three different kinds of aluminum sources (sodium aluminate, aluminum sulfate and aluminum isopropylate) were used for preparing of nano beta-zeolite. The as synthesized zeolites were mixed with the as prepared amorphous silica-alumina to produce the supports for hydrocracking catalyst. The prepared supports were used for preparation of NiMo/silica alumina-nano beta-zeolite by impregnation method. The influence of the aluminum source for preparation of beta-zeolite on the performance of the prepared catalysts has been studied. The samples were thoroughly characterized by X-Ray diffraction method (XRD), field emission-scanning electron microscopy (FE-SEM), N2 adsorption-desorption isotherms (BET), temperature programmed desorption (TPD) and temperature programmed reduction (TPR) methods. The catalysts performance was evaluated by vacuum gas oil (VGO) hydrocracking at 390 oC in a fixed bed reactor. The XRD patterns showed that the beta-zeolite samples obtained from the present methods were pure and highly crystalline and the crystal size of the prepared zeolites were in nanometer scale. Crystallite size of nano beta-zeolite synthesized by aluminum isopropylate [Al(iPrO)3] was smaller than those of prepared by the other aluminum sources. The catalyst containing this zeolite with higher surface area (231 m2/g) and more available acid sites (1.66 mmol NH3/g) possessed higher activity and selectivity to gas oil (71.9 %). Copyright © 2018 BCREC Group. All rights reservedReceived: 25th April 2018; Revised:22nd July 2018; Accepted: 29th July 2018How to Cite: Hadi, M., Aghabozorg, H.R., Bozorgzadeh, H.R., Ghasemi, M.R. (2018). The Effect of Aluminum Source on Performance of Beta-Zeolite as a Support for Hydrocracking Catalyst. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (3): 543-552 (doi:10.9767/bcrec.13.3.2570.543-552)Permalink/DOI: https://doi.org/10.9767/bcrec.13.3.2570.543-552

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da Costa-Serra, Javier Francisco, Cristina Cerdá-Moreno, and Antonio Chica. "Zeolite-Supported Ni Catalysts for CO2 Methanation: Effect of Zeolite Structure and Si/Al Ratio." Applied Sciences 10, no. 15 (July 26, 2020): 5131. http://dx.doi.org/10.3390/app10155131.

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The urgent need to reduce CO2 emissions requires the development of efficient catalysts for the conversion of CO2 into chemicals and fuels. In this study, a series of nickel catalysts supported on ITQ-2 and ZSM-5 zeolites have been prepared, characterized and tested in the hydrogenation reaction of CO2 towards methane. Specifically, two ITQ-2 and two ZSM 5 zeolites with different aluminum content have been studied. For both types, the higher Si/Al ratio of the material, the more active the catalyst due probably to its higher hydrophobicity. The largest difference was found for the ITQ-2 samples, being the CO2 conversion for the sample with a greater Si/Al ratio 50 points higher at 350 °C. Comparing both zeolite structures, while similar catalytic results were obtained with the samples with lower Si/Al ratio, a distinctly higher activity was found for the ITQ-2 zeolite without aluminum, pure silica. Therefore, this result suggests that the presence of aluminum is of particular relevance. Among the studied materials, the catalyst supported on the delaminated ITQ-2 zeolite without Al was the most active catalyst. Its higher activity was mainly attributed to the smaller crystallite size of nickel supported on the large external surface area presented by this zeolite.

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Clerici, Mario G. "Zeolites for Fine Chemical Production State of Art and Perspectives." Eurasian Chemico-Technological Journal 3, no. 4 (July 10, 2017): 231. http://dx.doi.org/10.18321/ectj573.

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The paper analyses the role of catalysis and that of renewable resources in the frame of a sustainable development. The possible uses of natural feedstocks for chemical production and the application of catalytic<br />methods to their transformations are reviewed, with emphasis on carbohydrates and vegetable oils and on zeolite catalysts, respectively. The problems arising from the embedment of active sites on the catalyst<br />surface are discussed, with the aid of specific examples taken from oxidation and acid catalysed reactions.

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Milojević, Maja, V. Dondur, Lj Damjanović, Vesna Rakić, Nena Rajić, and Alenka Ristić. "The Activity of Iron-Containing Zeolitic Materials for the Catalytic Oxidation in Aqueous Solutions." Materials Science Forum 555 (September 2007): 213–18. http://dx.doi.org/10.4028/www.scientific.net/msf.555.213.

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In this work, a series of iron-containing zeolitic materials has been tested as heterogeneous catalysts for decomposition of H2O2 and for oxidation of the cationic dye Methylene Blue with H2O2 in aqueous solutions. FeAPO and FeBEA zeolites, synthesized through hydrothermal crystallization of basic hydrogels, and FeY and FeZSM-5 zeolites, prepared by ionexchange procedures, have been studied. The ion exchange with Fe(III) cations was performed from different salt solutions. Fe-exchange procedure carried out in Fe-citrate solution has been identified as an attractive option for the preparation of highly effective FeZSM-5 catalysts in wet oxidation processes. It has been shown that both tetrahedral, framework Fe, and octahedral, extra-framework Fe species incorporated into zeolite structure are catalytically active in wet oxidation reactions.

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Fernandez-Ruiz, Carlos, Jorge Bedia, Javier Mario Grau, Ana Clara Romero, Daniel Rodríguez, Juan José Rodríguez, and Luisa María Gómez-Sainero. "Promoting Light Hydrocarbons Yield by Catalytic Hydrodechlorination of Residual Chloromethanes Using Palladium Supported on Zeolite Catalysts." Catalysts 10, no. 2 (February 6, 2020): 199. http://dx.doi.org/10.3390/catal10020199.

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Gas catalytic hydrodechlorination (HDC) of trichloromethane (TCM) and dichloromethane (DCM) was analyzed using Pd (1 wt.%) on different zeolites as catalysts. The aim of this study was to know the surface properties of the catalysts and reaction conditions that promote the yield to light hydrocarbons in this reaction. Five different zeolite supports were used from three commercial zeolites (KL, L-type; NaY, Faujasite; H-MOR, Mordenite). KL and NaY were submitted to ionic exchange treatments in order to increase their acidity and analyze the effect of the acidity in the activity and selectivity of the HDC reaction. Exchanged zeolites (HL and HY) showed the highest Pd dispersion due to their higher surface acidity. The best TCM/DCM conversion and selectivity to light hydrocarbons was obtained using the two non-exchanged zeolite-catalysts, KL and NaY. Low surface acidity seems to be the key aspect to promote the formation of light hydrocarbons. The formation of these products is favored at high reaction temperatures and low H2: chloromethane ratios. KL showed the highest selectivity to olefins (60%), although with a lower dechlorination degree. Non-exchanged NaY catalyst showed high selectivity to paraffins (70% and 95% for the HDC of DCM and TCM, respectively).

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Mondal, Ajoy Kanti, Chengrong Qin, Arthur J. Ragauskas, Yonghao Ni, and Fang Huang. "Effect of using regenerated combined FAU and MOR zeolites as catalysts during the pyrolysis of kraft lignin." BioResources 16, no. 1 (November 20, 2020): 417–40. http://dx.doi.org/10.15376/biores.16.1.417-440.

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The SiO2/Al2O3 mole ratio, pore size, and acid sites are the key parameters of zeolite’s activity in lignin pyrolysis. In this study, the comparison of individual Y and M zeolites, the combined ‘Y + M’ sample after regeneration, and their effect on lignin pyrolysis were studied in five cycles (regeneration and reuse). The results were explained using Brunauer, Emmet, and Teller (BET), micropore surface area (MSA), and total acid sites (TAS) analyses. In comparison with the individual Y or M zeolite sample, the consistent higher catalytic activities of the combined ‘Y + M’ sample in repeated cycles were observed. Pyrolysis heavy oils were characterized by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). The NMR analyses revealed that with increased zeolite regeneration cycles, p-hydroxy phenyl and methoxyl groups increased. Decreases in guaiacyl phenolic hydroxyl were less for the combined ‘Y + M’ sample than the individual Y and M zeolites. Lower weight average (Mw) of heavy oil for the combined ‘Y + M’ sample indicated the enhanced cleavage of lignin structures in pyrolysis. These results support the higher catalytic activity of regenerated zeolites for the combined ‘Y + M’ sample compared with individual Y and M zeolites due to the improved MSA and TAS.

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Harvey, Gillian, and Georg Mäder. "The Shape-Selective Acylation of 2-Methoxynaphthalene, Catalyzed by Zeolites Y, Beta and ZSM-12." Collection of Czechoslovak Chemical Communications 57, no. 4 (1992): 862–68. http://dx.doi.org/10.1135/cccc19920862.

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The Friedel-Crafts acylation of 2-methoxynaphthalene (2MN) was investigated using zeolites USY, Beta and ZSM-12 as catalysts under batch conditions at 100 and 180 °C. Two ketone isomers, 1-acetyl-2-methoxynaphthalene (1AC) and 2-acetyl-6-methoxynaphthalene (2AC) were produced; the selectivity of the reaction could be influenced by the zeolite used. USY produced only the 1AC isomer whereas Beta and ZSM-12 produced both. Selective synthesis of 2AC was achieved by optimization of the reaction conditions using zeolite Beta as the catalyst. It was also observed that the 1AC ketone is unstable in contact with acid zeolite catalysts and undergoes protiodeacylation, a reaction previously only observed in the presence of strong mineral acids.

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Erofeev, Vladimir, Vyacheslav Khasanov, Sofia Dzhalilova, Wladimir Reschetilowski, Anna Syskina, and Lyubov Bogdankova. "Acidic and Catalytic Properties of Zeolites Modified by Zinc in the Conversion Process of Lower C3–C4 Alkanes." Catalysts 9, no. 5 (May 5, 2019): 421. http://dx.doi.org/10.3390/catal9050421.

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The acid and catalytic properties of the modified MFI zeolite catalysts during the conversion of the propane–butane fraction of the associated petroleum gases into the aromatic hydrocarbons were studied. It was established that the high-silica zeolites synthesized with the new structure-forming additive of the alcohol fraction (ZKE-AF) belong to the high-silica MFI zeolites. The resulting zeolites were modified by 1–5 wt. % additives consisting of zinc oxide and sulfide. The influence of the modifying additive concentration containing zinc oxides and sulfides in an amount of 1–5% on the acid and catalytic properties of the catalysts in the conversion process of lower C3–C4 alkanes into liquid hydrocarbons was studied. The research of the acid properties of the modified zeolite catalysts by thermal desorption of ammonia showed that the total concentrations of the acidic centers of H-ZKE-AF modified by 3% and 5% ZnO increased. It was found that the highest yield of liquid hydrocarbons was on the zeolite catalysts modified by 3% and 5% ZnS, and is 60.6% and 60.5%, respectively, which is 9% more than in the initial H-ZKE-AF. The activity of the zeolite catalysts modified by zinc oxide and zinc sulfide was in correlation with their acid properties.

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Verdoliva, Valentina, Michele Saviano, and Stefania De Luca. "Zeolites as Acid/Basic Solid Catalysts: Recent Synthetic Developments." Catalysts 9, no. 3 (March 8, 2019): 248. http://dx.doi.org/10.3390/catal9030248.

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The zeolites are porous solid structures characterized by a particular framework of aluminosilicates, in which the incorporation of the Al+3 ions generates an excess of negative charge compensated by cations (usually alkali or alkali earth) or protons. In the latter case, they are employed as catalysts for a wide variety of reactions, such as dehydration, skeletal isomerization and cracking, while the catalytic activity of basic zeolites has not found, up to now, any industrial or whatever relevant application in chemical processes. In the present review, we firstly intend to give an overview of the fundamental chemical composition, as well as the structural features of the zeolite framework. The purpose of this paper is to analyze their key properties as acid, both Lewis and Brønsted, and basic solid support. Their application as catalysts is discussed by reviewing the already published works in that field, and a final remark of their still unexplored potential as green, mild, and selective catalyst is also reported.

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Al-Turkustani, Aisha Mahmood Abdulkareem, and Rosilda Selvin. "Enhanced Activity of Nanocrystalline Beta Zeolite for Acylation of Veratrole with Acetic Anhydride." Journal of Nanoscience and Nanotechnology 16, no. 4 (April 1, 2016): 4247–51. http://dx.doi.org/10.1166/jnn.2016.11613.

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Friedel-Craft acylation of veratrole using homogeneous acid catalysts such as AlCl3, FeCl3, ZnCl2, and HF etc. produces acetoveratrone, (3’,4’-dimethoxyacetophenone), which is the intermediate for synthesis of papavarine alkaloids. The problems associated with these homogeneous catalysts can be overcome by using heterogeneous solid catalysts. Since acetoveratrone is a larger molecule, large pore Beta zeolites with smaller particle sizes are beneficial for the liquid-phase acylation of veratrole, for easy diffusion of reactants and products. The present study aims in the acylation of veratrole with acetic anhydride using nanocrystalline Beta Zeolite catalyst. A systematic investigation of the effects of various reaction parameters was done. The catalysts were characterized for their structural features by using XRD, TEM and DLS analyses. The catalytic activity of nanocrystalline Beta zeolite was compared with commercial Beta zeolite for the acylation and was found that nanocrystalline Beta zeolite possessed superior activity.

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Lee, Su-Un, You-Jin Lee, Soo-Jin Kwon, Jeong-Rang Kim, and Soon-Yong Jeong. "Pt-Sn Supported on Beta Zeolite with Enhanced Activity and Stability for Propane Dehydrogenation." Catalysts 11, no. 1 (December 28, 2020): 25. http://dx.doi.org/10.3390/catal11010025.

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With the growing global propylene demand, propane dehydrogenation (PDH) has attracted great attention for on-purpose propylene production. However, its industrial application is limited because catalysts suffer from rapid deactivation due to coke deposition and metal catalyst sintering. To enhance metal catalyst dispersion and coke resistance, Pt-based catalysts have been widely investigated with various porous supports. In particular, zeolite can benefit from large surface area and acid sites, which favors high metal dispersion and promoting catalytic activity. In this work, we investigated the PDH catalytic properties of Beta zeolites as a support for Pt-Sn based catalysts. In comparison with Pt-Sn supported over θ-Al2O3 and amorphous silica (Q6), Beta zeolite-supported Pt-Sn catalysts exhibited a different reaction trend, achieving the best propylene selectivity after a proper period of reaction time. The different PDH catalytic behavior over Beta zeolite-supported Pt-Sn catalysts has been attributed to their physicochemical properties and reaction mechanism. Although Pt-Sn catalyst supported over Beta zeolite with low acidity showed low Pt dispersion, it formed a relatively lower amount of coke on PDH reaction and maintained a high surface area and active Pt surfaces, resulting in enhanced stability for PDH reaction. This work can provide a better understanding of zeolite-supported Pt-Sn catalysts to improve PDH catalytic activity with high selectivity and low coke formation.

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Pai, Shrivanand M., Barat L. Newalkar, and Parimal A. Parikh. "Quantifying Enhancement of Metal-Supported Zeolites Due to Hydrogen Spillover." Progress in Reaction Kinetics and Mechanism 43, no. 2 (June 2018): 157–65. http://dx.doi.org/10.3184/146867818x15233705894347.

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As bifunctional catalysts, metal-supported zeolites play an important role in refining and petrochemical processes, e.g. isomerisation, alkylation, etc. Reduction in acidity and acid strength of zeolites upon their impregnation with metals have been widely reported. Also hydrogen spillover vis-a-vis the closeness of two catalyst functions (acid and metal) has been discussed at length. Hydrogen spillover has been claimed to give rise to formation of additional acid sites on supports. Here quantification of acid sites for two zeolites, zeolite Y and ZSM-5, impregnated with different metals in various proportions after exposing them to hydrogen, has been attempted using ammonia temperature programmed desorption. The observed acidity values have been explained on the basis of metal cluster size.

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Jirátová, Květa, Hana Šnajdaufová, Lenka Morávková, and Ludmila Kubelková. "Reductive Amination of Diethylene Glycol to Morpholine over Supported Nickel Catalysts: Zeolites as Catalyst Admixtures." Collection of Czechoslovak Chemical Communications 57, no. 4 (1992): 901–8. http://dx.doi.org/10.1135/cccc19920901.

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The effect of HZSM-5, H-silicalite and amorphous silica admixtures on the surface properties of nickel catalysts as well as on their activities, selectivities and stabilities in the reductive amination of diethylene glycol was studied. It was found that, in comparison with amorphous silica, zeolites do not positively affect the catalytic properties of nickel catalysts. In addition, the acidity of the zeolites, the dispersity of the nickel phase, changes in the chemical composition during the reaction and adsorption of the reaction components or intermediates on the surface and consequent blocking of the zeolite surface played a role.

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Sarbak, Zenon, Grażyna Fabiś, and Sławomir Binkowski. "Structural and textural characterisation of NiMo catalysts supported on various zeolites." Polish Journal of Chemical Technology 9, no. 1 (January 1, 2007): 27–32. http://dx.doi.org/10.2478/v10026-007-0008-9.

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Structural and textural characterisation of NiMo catalysts supported on various zeolites Structural and textural properties of nickel-molybdenum catalysts supported on four various type of zeolites of different chemical composition and porous structure have been studied by the methods of IR, XRD and the low-temperature sorption of nitrogen. The catalysts have been obtained by the two-stage impregnation of the supports with the solutions of nickel and molybdenum salts by the method of incipient wetness. The catalysts have been shown to preserve the structure characteristic of the appropriate zeolite supports.

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Rosalia, Sira Sarungallo, Lewerang Halimaking Wilhelmus, Denny, Hariani Soekamto Nunuk, and Taba Paulina. "Study of the Use of Mamasa Natural Zeolite which is Activated by Acid as a Catalyst for Cracking Palm Oil Methyl Esters." Materials Science Forum 967 (August 2019): 155–60. http://dx.doi.org/10.4028/www.scientific.net/msf.967.155.

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A research has been conducted to activate natural zeolites from Mamasa, West Sulawesi with sulfuric acid and heating which is then used as a catalyst for cracking palm oil methyl esters. This type of research is preliminary research. The acidification process is carried out by mixing fine natural zeolites with 0.2 N H2SO4 solution, accompanied by heating at 110 °C. Then zeolite is calcined at 600 °C for 3 hours. The result of zeolite X-Ray diffraction (XRD) analysis shows that Mamasa natural zeolite has mordenite. The crystallinity of natural zeolites is 60.8%, increasing to 68.6% after activation. Catalytic cracking is carried out by heating methyl esters (biodiesel) and active zeolite zeolite catalysts in a fixed bed reactor in several temperature variations (140, 160, and 180 °C), reaction time of 5 minutes. The results of the saponification number analysis show that cracking products have a greater saponification number (224.4 mg KOH/g oil) compared to biodiesel before cracking (220.2 mg KOH/g oil), so it is assumed that the carbon cracking carbon chain is shorter.

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Mordkovich, Vladimir Z., and Lilia V. Sineva. "Water-Zeolite Interfaces for Controlling Reaction Routes in Fischer- Tropsch Synthesis of Alternative Fuels." Current Catalysis 9, no. 1 (September 10, 2020): 3–22. http://dx.doi.org/10.2174/2211544709999200420072505.

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Background: The Fischer-Tropsch Synthesis (FTS) remains an important process for motor fuel production from CO and H2. The composition of the FTS products (hydrocarbon mixtures) depends on the properties of a catalyst and on the process conditions. Summary: The introduction of zeolites into catalytic systems can alter the molecular weight distribution paving the way to tailor-made fuels, as was revealed by recent research results produced in the laboratories worldwide. The AlO4 and SiO4 tetrahedrons, which constitute the zeolites, are able to transfer electrons and ions in a way, which makes water-zeolite interfaces capable of initiating active carbonium ions. It was shown in a number of works that the water-zeolite interface plays a key role in diverting the FTS from the classical route. Conclusion: This review gives a critical analysis of literature data on the role of water-zeolite interfaces on FTS cobalt catalysts and on the interactions of hydrophobic and hydrophilic zeolites with water.

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31

Silva, F. M. N., Erivaldo Genuíno Lima, and Meiry Gláucia Freire Rodrigues. "Synthesis and Characterization of HMOR and Catalyst MoO₃/HMOR, NiO/HMOR and Co₂O₃/HMOR." Materials Science Forum 912 (January 2018): 33–38. http://dx.doi.org/10.4028/www.scientific.net/msf.912.33.

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The mordenite zeolite is one of the most important industrially zeolites, used as a solid catalyst for various reactions hydrocracking, hydroisomerization, alkylation, reforming, alkane oxidation, Fischer-Tropsch reaction. The aim of this study was to hydrothermal synthesis mordenite zeolite in its sodium form under hydrothermal conditions, in organic-free synthesis. The form HMOR of the zeolite mordenite was obtained by an ion exchange. For the preparation of the catalysts precursor salts were used: ammonium heptamolybdate, nickel nitrate, cobalt nitrate dispersed from the impregnation by incipient wetness impregnation, such impregnated supports were calcined at 550 °C/4h to obtain the catalyst. The zeolite synthesized in the sodium form NaMOR in its ammonium form NH4MOR in form acid HMOR and their catalysts MoO3/HMOR, NiO/HMOR and Co2O3/HMOR were characterized by X-ray diffraction (XRD) and Fluorescence Spectroscopy of by Energy X-ray dispersive (FRX-ED). From the results it was possible to observe the formation of zeolite phase mordenite in its sodium and acid form and the effective impregnation and formation of the proposed catalysts.

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Winata, Wahyu Fajar, Karna Wijaya, Suheryanto, Ady Mara, and Widi Kurniawati. "Conversion of Bioethanol to Diethyl Ether Catalyzed by Sulfuric Acid and Zeolite." Journal of the Indonesian Chemical Society 3, no. 3 (December 30, 2020): 151. http://dx.doi.org/10.34311/jics.2020.03.3.151.

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Ethoxy ethane, or diethyl ether, has been successfully synthesized through the condensation reaction of bioethanol produced from fruit waste fermentation using acid-activated H-Zeolite, H2SO4/H-Zeolite, and H2SO4 as catalysts. Zeolite activation was carried out using the acidification method with 1 M, 2 M, 4 M, and 6 M H2SO4 for 24 hours. Activated zeolites were characterized using infrared spectroscopy, X-ray diffraction, and NaOH titration. The condensation reaction of bioethanol was carried out by catalysis of H2SO4/H-Zeolite with various concentrations of 1 M, 2 M, 4 M, and 6 M and catalyzed by 2 M, 4 M, and 6 M acid-activated H-Zeolite. The condensation reaction process was carried out with a ratio of bioethanol to catalyst of 2:1 (w/w) using the fractional distillation method. Ethoxy ethane resulting from the condensation reaction was characterized using a GC instrument.

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Matieva, Z. M., Yu M. Snatenkova, N. V. Kolesnichenko, and S. N. Khadzhiev. "Catalysts for Synthesis of Liquid Hydrocarbons from Methanol and Dimethyl Ether: Review." Kataliz v promyshlennosti 18, no. 6 (November 20, 2018): 20–32. http://dx.doi.org/10.18412/1816-0387-2018-6-20-32.

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Various methods for improving the catalyst selectivity to conversion of oxygenates to liquid hydrocarbons are discussed. Literature analysis reveals that the key factors determining the selectivity of zeolite-containing catalysts are the structure type and acid properties of the zeolite. The strength and distribution of the acid sites are shown to depend on the structure type and chemical composition of the zeolite framework, as well as on the chemical nature of exchange cations. Methods for changing acid properties of zeolites are considered, among which are modifying with various cations, post-synthetic acid, alkali or steam treatment.

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Niu, Xiaopo, Fuxiang Feng, Gang Yuan, Xiangwen Zhang, and Qingfa Wang. "Hollow MFI Zeolite Supported Pt Catalysts for Highly Selective and Stable Hydrodeoxygenation of Guaiacol to Cycloalkanes." Nanomaterials 9, no. 3 (March 4, 2019): 362. http://dx.doi.org/10.3390/nano9030362.

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Hollow Silicalite-1 and ZSM-5 zeolites with hierarchical porous shells have been synthesized by using a dissolution-recrystallization method. The morphology, structure, and acidity of these zeolites supported Pt catalysts were characterized by XRD, FT-IR, MAS-SSNMR, FE-SEM, FE-TEM, N2-BET, XPS, NH3-TPD, and CO pulse chemisorption. Compared to the conventional ZSM-5 supported Pt catalyst, the special structure in hollow ZSM-5 zeolite significantly promotes the dispersion of metallic Pt and the synergistic effect between metal active sites and acid sites. These boost the catalytic activity, selectivity of guaiacol hydrodeoxygenation toward cycloalkanes and long-term stability over the Pt/hollow ZSM-5 catalyst combined with improved mass transfer of products and reactants derived from the hierarchical hollow porous structure. Moreover, the Pt/hollow ZSM-5 catalyst exhibits excellent low temperature catalytic activity to completely transform guaiacol into cycloalkanes with the cyclohexane selectivity of more than 93% at 220 °C, suggesting that hollow ZSM-5 zeolite is a promising support for upgrading of bio-oils.

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35

Ulan, J., and R. Gronsky. "Effect of alkali cations on the microstructure and composition of iron silicate catalysts." Proceedings, annual meeting, Electron Microscopy Society of America 47 (August 6, 1989): 268–69. http://dx.doi.org/10.1017/s0424820100153312.

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Zeolites are shape selective catalysts widely used in industry. Selectivity arises from the fact that zeolites possess channels several angstroms in diameter which limits the size of species that can easily diffuse through. Promoted iron oxide is a highly active catalyst for the synthesis of hydrocarbons from CO and H2 (Fischer-Tropsch reaction) but researchers would like to narrow product selectivity to the C7-C10 gasoline range. Selectivity is improved by dispersing iron on zeolites and efforts are now directed at maximizing the iron distribution in the zeolite channels. One approach is to first incorporate iron directly into the zeolite framework during synthesis and then remove the iron from the zeolite framework and ideally form catalytically active iron oxide particles within the channels while still maintaining the pore structure of the zeolite. Iron silicate analogs of the zeolite ZSM-5 (FeZSM-5) have been synthesized and thermal treatments have been employed to produce a catalytic active material. The complete characterization by SEM and TEM of a series of FeZSM-5 catalysts with various Si/Fe ratios and preparation conditions has been achieved. This presentation is a continuation of that work. Three series of FeZSM-5 catalysts were synthesized, two had Si/Fe ratios of 45 with different Si/Al ratios and one had a Si/Fe ratio of 25. In each series, the synthetic conditions were modified by adding alkali metal cations (Li+, Na+ and K+) to the reaction mixture. It has been shown with ZSM-5 that the addition of alkali cations during synthesis produces large single crystals. The effect of alkali cations on the growth of zeolite analogs is interesting for several independent reasons ranging from basic studies of the mechanism of zeolite growth to practical experimental considerations. Single crystals are very desirable for electron microscopy studies: results are unambiguous for a single crystallite in one orientation compared to a region with many overlapping small particles.

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Yarmo, Mohd Ambar, Raja Saadiah Raja Shariff, Siti Rohaya Omar, Juan Joon Ching, and Roziana Haron. "New Perspective in Recent Solid Acid Catalyst." Materials Science Forum 517 (June 2006): 117–22. http://dx.doi.org/10.4028/www.scientific.net/msf.517.117.

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This paper will review on the latest development on solid acid catalysts used in industries as well in research activities. Application of heterogeneous acid catalysis becomes current trend for many industries due to world wide environmental concern. Conventional synthetic or natural zeolites widely used for petrochemical processing, has some limitation because its pore size is normally smaller than reactant molecules. To overcome this challenge new delaminated zeolite process was introduced. In this process specific synthetic zeolite (i.e. ferrierite) was swelled up using specific surfactant followed by sonification to produce the delaminated zeolite. Further modification of this material such as sulfonification reaction to its surface has been found to improve the catalytic activity and selectivity for esterification reaction. Other acid catalyst systems based on mesoporous molecular sieves and Keggin heteropolyacids (HPA) are also discussed in this paper.

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Fawaz, Elyssa G., Darine A. Salam, Severinne S. Rigolet, and T. Jean Daou. "Hierarchical Zeolites as Catalysts for Biodiesel Production from Waste Frying Oils to Overcome Mass Transfer Limitations." Molecules 26, no. 16 (August 12, 2021): 4879. http://dx.doi.org/10.3390/molecules26164879.

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Hierarchical crystals with short diffusion path, conventional microcrystals and nanocrystals of ZSM-5 zeolites were used for biodiesel production from waste frying oils and were assessed for their catalytic activity in regard to their pore structure and acidic properties. Produced zeolites were characterized using XRD, nitrogen adsorption–desorption, SEM, TEM, X-ray fluorescence, and FTIR. Pore size effect on molecular diffusion limitation was assessed by Thiele modulus calculations and turnover frequencies (TOF) were used to discuss the correlation between acidic character and catalytic performance of the zeolites. Owing to the enhanced accessibility and mass transfer of triglycerides and free fatty acids to the elemental active zeolitic structure, the catalytic performance of nanosponge and nanosheet hierarchical zeolites was the highest. A maximum yield of 48.29% was reached for the transesterification of waste frying oils (WFOs) using HZSM-5 nanosheets at 12:1 methanol to WFOs molar ratio, 180 °C, 10 wt % catalyst loading, and 4 h reaction time. Although HZSM-5 nanosponges achieved high conversions, these more hydrophilic zeolites did not function according to their entire acidic strength in comparison to HZSM-5 nanosheets. NSh-HZSM5 catalytic performance was still high after 4 consecutive cycles as a result of the zeolite regeneration.

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An, Ye, David Johannes de Ridder, Chun Zhao, Klaas Schoutteten, Julie Vanden Bussche, Huaili Zheng, Gang Chen, and Lynn Vanhaecke. "Adsorption and photocatalytic degradation of pharmaceuticals and pesticides by carbon doped-TiO2 coated on zeolites under solar light irradiation." Water Science and Technology 73, no. 12 (March 16, 2016): 2868–81. http://dx.doi.org/10.2166/wst.2016.146.

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Abstract To evaluate the performance of zeolite-supported carbon-doped TiO2 composite catalysts toward target pollutants under solar light irradiation, the adsorption and photocatalytic degradation of 18 pharmaceuticals and pesticides with distinguishing features (molecular size and volume, and photolysis) were investigated using mordenite zeolites with SiO2/Al2O3 ratios of 18 and 240. Different quantities of carbon-doped TiO2 were coated on the zeolites, and then the finished composite catalysts were tested in demineralized, surface, and hospital wastewater samples, respectively. The composite photocatalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, and surface area and porosity analyses. Results showed that a dispersed layer of carbon-doped TiO2 is formed on the zeolite surface; this layer blocks the micropores of zeolites and reduces their surface area. However, these reductions did not significantly affect adsorption onto the zeolites. Our results demonstrated that zeolite-supported carbon-doped TiO2 systems can effectively degrade 18 pharmaceuticals and pesticides in demineralized water under natural and simulated solar light irradiation. In surface and hospital wastewaters, zeolite-supported carbon-doped TiO2 systems present excellent anti-interference capability against radical scavengers and competitive organics for pollutants removal, and higher pollutants adsorption on zeolites evidently enhances the removal rate of target pollutants in surface and hospital wastewater samples with a complicated matrix.

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usi, E. P. S., K. Wijaya, Wangsa, R. A. Pratika, and P. L. Hariani. "Effect of Nickel Concentration in Natural Zeolite as Catalyst in Hydrocracking Process of Used Cooking Oil." Asian Journal of Chemistry 32, no. 11 (2020): 2773–77. http://dx.doi.org/10.14233/ajchem.2020.22708.

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Zeolites impregnated with Ni were successfully synthesized through wet impregnation using activated natural zeolites (ANZs) and the nickel nitrate hexahydrate (Ni(NO3)2·6H2O) precursor at different concentrations of 1%, 2% and 3% (w/w) (hereafter referred to as ANZ/Ni 1%, ANZ/Ni 2%, and ANZ/Ni 3%). The synthesized products were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), surface area analyzer (SAA), scanning electron microscopy (SEM), total acidity measurements by employing ammonia adsorption and Brunauer-Emmett-Teller (BET) theory. The obtained catalysts were employed in the hydrocracking of waste cooking oils, and the formed products were analyzed through gas chromatography-mass spectrometry (GC-MS). The FTIR results indicated that ANZs impregnated with Ni can increase zeolite acidity. The test results of total acidity revealed that 3% ANZ/Ni catalyst exhibited the maximum total acidity of 3.70 mmol/g. XRD diffractogram confirmed the successful impregnation of Ni into ANZs, which was indicated by the characteristic diffraction peaks appearing at 2θ of 9.75º, 13.41º, 19.56º, 22.25º, 25.61º, 27.66º and 31.91º. SEM analysis indicated that the particle size of zeolite catalysts was non-uniform, but these catalysts exhibited a highly uniform surface after they were activated. Moreover, the ANZ catalysts impregnated with different concentrations of Ni exhibited a highly uniform particle size. The ANZ/Ni 3% catalyst had small uniform particle. The BET results revealed that the ANZ/Ni 2% catalyst exhibited the maximum pore volume and surface area and relatively smaller radii of pores. GC-MS was employed to determine liquid products, and its results showed that the ANZ/Ni 3% catalyst had the maximum amount of liquid products of 18%.

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KOTASTHANE, A. N., and V. P. SHIRALKAR. "ChemInform Abstract: Zeolites and Zeolite-Based Catalysts." ChemInform 26, no. 23 (August 17, 2010): no. http://dx.doi.org/10.1002/chin.199523283.

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Chrétien, Michelle N. "Supramolecular photochemistry in zeolites: From catalysts to sunscreens." Pure and Applied Chemistry 79, no. 1 (January 1, 2007): 1–20. http://dx.doi.org/10.1351/pac200779010001.

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Zeolites are nanoporous, crystalline aluminosilicate materials comprised of a series of strictly uniform channels and cavities repeating along the tri-directional structure of the lattice. Over the last 30 years, researchers have increasingly recognized the desirable properties of these materials as hosts for photochemical reactions. This review will endeavor to draw attention to the properties of zeolite materials that make them appealing substrates for hosting guest molecules during photochemical reactions. An overview of some classical examples in zeolite host-guest photochemistry will be presented along with a brief description of a new use for zeolite materials as protective encapsulators.

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42

Qiao, G. W., J. Zhou, and K. H. Kuo. "High Resolution Transmission Electron Microscopy of Some Catalysts." Zeitschrift für Naturforschung A 41, no. 3 (March 1, 1986): 478–82. http://dx.doi.org/10.1515/zna-1986-0304.

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Application of high resolution electron microscopy (HREM) to the study of Pt-Sn/γ-Al2O3 supported catalyst, zeolites, iron catalyst for ammonia synthesis, rare-earth oxide catalysts, etc., is described. Micro-twins, dislocations and other crystallographic imperfections are observed. Moreover, the structure images of channels representing columns of cages in several kinds of zeolites as well as radiation damage processes in them have been recorded in situ. The observed images of zeolites were found to be in good agreement with the structure model projections and computer simulated images.

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Xu, Hao, Jie Zhu, Longfeng Zhu, Enmu Zhou, and Chao Shen. "Advances in the Synthesis of Ferrierite Zeolite." Molecules 25, no. 16 (August 14, 2020): 3722. http://dx.doi.org/10.3390/molecules25163722.

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As one of the most important porous materials, zeolites with intricate micropores have been widely employed as catalysts for decades due to their large pore volume, high surface area, and good thermal and hydrothermal stabilities. Among them, ferrierite (FER) zeolite with a two-dimensional micropore structure is an excellent heterogeneous catalyst for isomerization, carbonylation, cracking, and so on. In the past years, considering the important industrial application of FER zeolite, great efforts have been made to improve the synthesis of FER zeolite and thus decrease the synthesis cost and enhance catalytic performance. In this review, we briefly summarize the advances in the synthesis of FER zeolite including the development of synthesis routes, the use of organic templates, organotemplate-free synthesis, the strategies of morphology control, and the creation of intra-crystalline mesopores. Furthermore, the synthesis of hetero-atomic FER zeolites such as Fe-FER and Ti-FER has been discussed.

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CHRISTENSEN, C., K. JOHANNSEN, E. TORNQVIST, I. SCHMIDT, H. TOPSOE, and C. CHRISTENSEN. "Mesoporous zeolite single crystal catalysts: Diffusion and catalysis in hierarchical zeolites." Catalysis Today 128, no. 3-4 (October 30, 2007): 117–22. http://dx.doi.org/10.1016/j.cattod.2007.06.082.

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Bemis, Restina, Novesar Jamarun, and Syukri Arief. "PENGOLAHAN LIMBAH POLIPROPILEN MENJADI BAHAN BAKAR CAIR MELALUI METODE PIROLISIS." Jurnal Riset Kimia 5, no. 2 (March 19, 2012): 158. http://dx.doi.org/10.25077/jrk.v5i2.217.

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Plastics become the biggest environmental problem when it accumulate in landfills because its non-biodegradable properties. To handle the problems, the plastics were processed to produce liquid fuels by means pyrolysis method which was in this case with and without a catalyst. In this work, polypropylene was used as a precursor and SiO2, zeolites, CaO, Fe as catalysts. FTIR spectrum of pyrolized polypropylene with and without catalysts both have shown C = C functional group at 1648 cm-1. GCMS analysis confirmed the availability of chain length of hydrocarbon between C7 -C27 which is mixture of kerosene and diesel fractions. Catalysts can lower the temperature and time reaction of pyrolysis process as they increase rendement (%) of product. Liquid fuels that produced from polypropylene pyrolysis without catalyst was 72.06%, and with catalysts were 79.59% (SiO2), 74.76%, (zeolite), 76.80% (CaO), and 76.83% (Fe).

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Sharifi, Khashayar, Rouein Halladj, and Seyed Javid Royaee. "An overview on the effects of metal promoters and acidity of ZSM-5 in performance of the aromatization of liquid hydrocarbons." REVIEWS ON ADVANCED MATERIALS SCIENCE 59, no. 1 (June 27, 2020): 188–206. http://dx.doi.org/10.1515/rams-2020-0037.

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AbstractThe use of liquid hydrocarbons, such as FCC naphtha, having olefin components makes an adverse impact on our environment. To deal with the problem, one could convert those lethal components, including olefin and paraffin structures, into aromatic compounds under aromatization processes. To this aim, generally zeolite catalysts, especially the ZSM-5 sample, are utilized to facilitate the aromatization processes. According to the general knowledge in this field, such parameters as the metal promoter and the amount of acidity of catalyst affect the performance of zeolite catalysts. In this paper, with the aim of getting acquainted with the conditions to form the desirable products under the best performance of the zeolites, numerous published papers were reviewed.

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Haw, Kok-Giap, Jean-Michel Goupil, Jean-Pierre Gilson, Nikolai Nesterenko, Delphine Minoux, Jean-Pierre Dath, and Valentin Valtchev. "Embryonic ZSM-5 zeolites: zeolitic materials with superior catalytic activity in 1,3,5-triisopropylbenzene dealkylation." New Journal of Chemistry 40, no. 5 (2016): 4307–13. http://dx.doi.org/10.1039/c5nj03310a.

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Grzechowiak, Jolanta R., Aleksandra Masalska, Tadeusz Romotowski, and Jolanta Komorek. "The Role of Ion Exchange Method of Na-ZSM-5 Zeolite and Influence Hydrogenation Components on Properties and Activity of Dewaxing Catalysts." Collection of Czechoslovak Chemical Communications 57, no. 5 (1992): 969–77. http://dx.doi.org/10.1135/cccc19920969.

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Hydrocracking of n-hexane and diesel oil fraction over presulfided NiMo, Mo and Ni catalysts has been carried out using a high pressure flow reactor system. The ion-exchanged form of ZSM-5 extrudates (50% alumina binder) was loaded with 2-20 wt.% of metals. The results indicate that, using Ni/H-ZSM-5 zeolite obtained by incorporation of nickel by ion exchange treatment of NH4-ZSM-5 from nickel nitrate solution, it is possible to obtain sufficiently active catalysts for low-temperature hydrocracking process. The catalysts containing Ni-ZSM-5 zeolites (Ni/H-ZSM-5 or Ni/Na-ZSM-5) were superior to catalyst prepared by using P/H-ZSM-5. It was found that nickel was an essential hydrogenation components of low temperature hydrocracking catalysts.

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Simons, Thomas, and Ulrich Simon. "Zeolites as nanoporous, gas-sensitive materials for in situ monitoring of DeNOx-SCR." Beilstein Journal of Nanotechnology 3 (September 26, 2012): 667–73. http://dx.doi.org/10.3762/bjnano.3.76.

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In a proof-of-concept study we demonstrate in situ reaction monitoring of DeNOx-SCR on proton-conducting zeolites serving as catalyst and gas sensor at the same time. By means of temperature-dependent impedance spectroscopy we found that the thermally induced NH3 desorption in H-form and in Fe-loaded zeolite H-ZSM-5 follow the same process, while a remarkable difference under DeNOx-SCR reaction conditions was found. The Fe-loaded catalyst shows a significantly lower onset temperature, and time-dependent measurements suggest different SCR reaction mechanisms for the two catalysts tested. These results may help in the development of catalysts for the reduction of NOx emissions and ammonia consumption, and provide insight into the elementary catalytic process promoting a full description of the NH3-SCR reaction system.

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Khan, Wasim, Xicheng Jia, Zhijie Wu, Jungkyu Choi, and Alex Yip. "Incorporating Hierarchy into Conventional Zeolites for Catalytic Biomass Conversions: A Review." Catalysts 9, no. 2 (January 31, 2019): 127. http://dx.doi.org/10.3390/catal9020127.

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Zeolites are promising catalysts that are widely used in petrochemical, oil, and gas industries due to their unique characteristics, such as ordered microporous networks, good hydrothermal stability, large surface area, tunable acidity, and shape-selectivity. Nevertheless, the sole presence of microporous channels in zeolites inevitably restricts the diffusion of bulky reactants and products into and out of the microporous networks, leading to retarded reaction rates or catalyst deactivation. This problem can be overcome by developing hierarchical zeolites which involve mesoporous and macroporous networks. The meso- and macro-porosities can enhance the mass transport of molecules and simultaneously maintain the intrinsic shape selectivity of zeolite microporosity. Hierarchical zeolites are mainly developed through post-synthesis and pre-synthesis or in situ modification of zeolites. In this review, we evaluated both pre-synthesis and post-synthesis modification strategies with more focus on post-synthesis modification strategies. The role of various synthesis strategies on the intrinsic properties of hierarchical zeolites is discussed. The catalytic performance of hierarchical zeolites in important biomass reactions, such as catalytic pyrolysis of biomass feedstock and upgradation of bio-oil, has been summarized. The utilization of hierarchical zeolites tends to give a higher aromatic yield than conventional zeolites with microporosity solely.

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Journal articles on the topic 'Zeolites as catalysts'

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