Dissertations / Theses on the topic 'Formaldehyde'
To see the other types of publications on this topic, follow the link: Formaldehyde.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Formaldehyde.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Dingle, Peter Wayne. "Personal exposure to formaldehyde." Thesis, Dingle, Peter Wayne (1995) Personal exposure to formaldehyde. PhD thesis, Murdoch University, 1995. https://researchrepository.murdoch.edu.au/id/eprint/51327/.
Full textAbstract:
The primary objective of this research was to investigate exposure to formaldehyde. There has been very little research on personal exposure to pollutants in the community and none on personal exposure to formaldehyde. In Australia, there are very little data on indoor formaldehyde concentrations. This is despite the fact that in Europe and in the United States, formaldehyde is one of the most frequently found indoor air contaminants, and is known to cause both acute and chronic health effects.
The results of this research generally support the hypothesis that fixed site monitoring in indoor environments is able to explain a substantial portion of the personal exposure to formaldehyde. However, the study also provided results in cabinet making factories which are not consistent with this hypothesis. The results did not support the hypothesis that time weighted models will improve the accuracy of personal exposure predictions relative to linear regression models of indoor and outdoor concentrations.
The research was divided into two areas. Firstly, the spatial and temporal changes in concentrations of formaldehyde in indoor environments, and the factors affecting these levels were investigated. This resulted in a comprehensive documentation of the concentrations found in typical indoor environments, and in indoor environments likely to experience elevated concentrations of formaldehyde. Secondly, an assessment of personal exposure to formaldehyde, and a comparison of these results to formaldehyde concentrations recorded at fixed sites was conducted. This enabled the comparison of different models to understand personal exposure.
Formaldehyde exposure assessment was conducted in 186 Australian homes and 60 occupied caravans and indoor measurements recorded in 132 unoccupied caravans. There were no significant differences between levels recorded in winter or summer for conventional homes monitored during different seasons, however a significant seasonal difference occurred in concentrations recorded in caravans. The highest concentrations were recorded in winter. In conventional homes a significant decrease in formaldehyde concentrations was found in levels recorded 6 months after the initial monitoring. The decrease was greatest in homes less than 10 years of age. In 13 multi-storey office buildings, levels ranged from 4 ppb to 90 ppb, with the highest concentrations being recorded in new buildings. A new four floor building was assessed for formaldehyde over fourteen months. Formaldehyde concentrations increased as the building progressed through its construction phase, and with the introduction of furnishings and carpet. After occupation, fluctuations in formaldehyde concentrations in the building were closely correlated with outdoor temperatures.
The results from 24 hour personal exposure of people, non-occupationally exposed to formaldehyde, in conventional homes and caravans suggest that the home environment is the most important predictor of formaldehyde exposure. Measurements in conventional homes were able to account for between 54% and 61% of the variation of personal exposure. Measurements in caravans were able to account for 71% of the variation in personal exposure.
For people occupationally exposed to elevated concentrations of formaldehyde, personal exposure in the workplace is the most significant exposure in accounting for variation in 24 hour personal exposure. Time weighted models were not found to improve the explanation of variation in personal exposure.
This research derived models of formaldehyde exposure for people occupationally exposed to formaldehyde and identified concentrations in the home as the major determinant of personal exposure to people nonoccupationally exposed to formaldehyde. It also highlighted the complexity of personal exposure and the need to use time weighted models with some caution. The next step in research should be aimed at expanding these tests with different population sub-groups and the use of real time personal monitoring when the equipment is developed. This would facilitate a more complete description of personal exposure to formaldehyde and more accurate exposure models to assess the potential impact of formaldehyde on public health.
2
Chongcharoen, Rotsaman. "Biodegradation of formaldehyde by methylotrophs." Thesis, University of Warwick, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269080.
Full text
3
Smith, Carina Alice. "The atmospheric photochemistry of formaldehyde." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432746.
Full text
4
Zhao, Xiaomin. "Formaldehyde mass-transfer properties study." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/51597.
Full textAbstract:
Formaldehyde, an important feedstock in industrial processes and manufacture, is widely present in numerous consumer products. Emitted by many types of consumer products and indoor materials, indoor air can contain high concentrations of formaldehyde. Exposure to formaldehyde is hazardous to human health. Thus knowledge of formaldehyde mass-transfer properties is critical to efforts to reduce formaldehyde emissions and establish related standards and regulations.
The primary objectives of this project include: 1) documenting and validating procedures and methods for analyzing and measuring formaldehyde mass-transfer characteristics; 2) evaluating and comparing formaldehyde mass-transfer properties in different materials using micro-balance sorption/desorption tests; 3) investigating observed formaldehyde mass-transfer irreversibility and the recently developed formaldehyde polymerization theory.
The procedures and methods for analyzing and measuring formaldehyde mass-transfer characteristics were developed in an effort to minimize experimental variability and were strictly followed during the research. The formaldehyde mass-transfer properties of five polymer materials (polycarbonate, polystyrene, poly(methyl methacrylate), polyethylene and polypropylene) were measured through sorption/desorption testing. Results indicated that formaldehyde solubility was highest in polyethylene while the rate of diffusion was the highest in polypropylene. Results also showed that the diffusion process in the selected polymer materials was irreversible in all cases. Furthermore, additional testing showed no detectable polyformaldehyde formation on polymer surfaces after exposure to formaldehyde. The causes of observed mass-transfer irreversibility need further study.Master of Science
5
Weiler, Michael D. "Formaldehyde Exposure During Cadaver Transport." University of Toledo Health Science Campus / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=mco1481306849010601.
Full text
6
Kalet, Brian T. "Doxorubicin and its formaldehyde conjugates." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3303814.
Full text
7
HANSMAENNEL, GERARD. "Exposition au formaldehyde et cancer." Lille 2, 1988. http://www.theses.fr/1988LIL2M258.
Full text
8
Zaza, Philippe. "Déshydrogénation catalytique du méthanol en formaldehyde /." [S.l.] : [s.n.], 1994. http://library.epfl.ch/theses/?nr=1200.
Full text
9
Fleming, Robert W. "Radinox process applied to formaldehyde oxidation." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/10923.
Full text
10
Adeosun, Ekundayo K. "Formaldehyde oxidation in Methylococcus capsulatus (Bath)." Thesis, University of Warwick, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364622.
Full text
11
Hewson, Will. "Tropospheric formaldehyde retrievals with GOME-2." Thesis, University of Leicester, 2014. http://hdl.handle.net/2381/28562.
Full textAbstract:
Biogenic Volatile Organic Compounds (BVOCs) emitted by terrestrial ecosystems impact air quality and climate. The most important BVOC for global tropospheric composition is isoprene, whose annual global emissions (400-600 Tg C/year) account for ~50% of the total global BVOC budget. Tropical ecosystems are generally thought to be responsible for 70-90% of the global isoprene budget. Satellite observations of formaldehyde (CH[subscript 2]O), a high-yield, short lifetime product of isoprene oxidation, provide top-down constraints on surface isoprene emissions. Errors in retrieved satellite slant column densities (SCD - trace gas concentration along the instrument's line of sight) are typically in the region of 40% for scenes with little cloud and aerosol contamination. Error sources arise from instability in the differential optical absorption spectroscopy (DOAS) retrieval procedure, largely due to low signal to noise ratios frequently encountered with space-borne UV spectrometers, coupled to CH[subscript 2]O's faint absorption signal. The essential conversion of SCDs to vertical column densities (VCDs - vertical trace gas concentration extending from the Earth's surface), needed for application of retrieved CH[subscript 2]O values to geochemical modelling schemes, is a further significant contributor to product error (30-60%), being strongly influenced by aerosol, cloud and albedo inhomogeneities at sub-pixel level. A new global 5 year CH[subscript 2]O product (2007-2011) generated with global ozone monitoring experiment 2 (GOME-2) satellite radiance data is presented. SCDs for this are generated with optimised spectroscopic fit settings derived from an extensive sensitivity study of input retrieval parameters for the DOAS portion of the retrieval. SCDs are then converted to vertical column densities VCDs using air mass factors calculated with a significantly upgraded retrieval scheme, accounting for atmospheric radiative transfer due to viewing geometry, surface albedo and atmospheric scattering. New GOME-2 CH[subscript 2]O VCDs are then evaluated against GEOS-Chem modelled CH[subscript 2]O VCDs, and compared to a suite of associated environmental parameters.
12
Law, James. "Molecular basis of bacterial formaldehyde sensing." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/molecular-basis-of-bacterial-formaldehyde-sensing(40c58dc5-c99b-4709-88aa-b35f9cd7ec62).html.
Full textAbstract:
Formaldehyde is a highly toxic molecule; despite this, it is produced in the cells of all living organisms as a by-product of metabolic pathways. Consequently, several pathways have evolved throughout life in order to detoxify cellular formaldehyde. These pathways need to be regulated within the cell and this study sets out to determine how these pathways are regulated in particular bacteria. Several approaches are taken to achieve this. Known or predicted transcription factors that regulate formaldehyde detoxification pathways from particular organisms are considered. These proteins are called FrmR (E. coli), HxlR1 (Bacillus subtilis), and HxlR2 (Bacillus Cereus). The transcription factors are cloned and purified using molecular biology techniques. The proteins are subject to biophysical characterisation i.e. size and secondary structure composition. Additionally, the X-ray crystal structure of HxlR2 is determined and significant progress is made towards determining the structure of FrmR. Interactions of these transcription factors towards their target DNA sequences are studied along with the effect that formaldehyde has on these interactions. A reporter system is constructed that enables the behaviour of FrmR to be studied in vivo. Residues that are likely to play important roles in DNA recognition by this regulator are identified. Additionally, this reporter system identifies a residue that is essential for formaldehyde sensing by this protein. Overall, some significant insights into how these transcription factors carry out their biological function are established.
13
James, Devona Gwen. "The degradation of drugs in formaldehyde." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1149.
Full textAbstract:
Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains xvi, 100 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 98-99).
14
Marx, Christopher James. "Formaldehyde metabolism in Methylobacterium extorquens AM1 /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/11521.
Full text
15
Dam, Thien Quang. "A study of the mechanism for methanol oxidation to formaldehyde on polycrystalline sliver catalysts /." St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16433.pdf.
Full text
16
Jamshidi, Mohammad. "Formaldehyde as a Catalyst: Investigations on the Role of Formaldehyde as a Potential Prebiotic Catalyst and Desymmetrization Agent." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36609.
Full textAbstract:
Life, as we know it, has emerged from the association of simple building blocks
(e.g. HCN, NH3, aldehydes, etc). The reactions required to form the complex subunits of life face a great entropic barrier due to the intermolecular nature of their reactivity.
Intermolecular reactions are slow at low concentrations, and therefore, the assembly of complex subunits requires the presence of a concentration mechanism. Formaldehyde, which was present in concentrations as high as 0.02 M, may have been used as a concentration mechanism on early Earth. By tethering two molecules together, formaldehyde allows catalysis via temporary intramolecularity. Moreover, formaldehyde has been shown to act as a hydrolase / hydratase mimic, allowing important rate accelerations in hydration and hydrolysis reactions which are of fundamental importance to prebiotic chemistry. Herein, the efficiency of formaldehyde as a catalyst, operating via temporary intramolecularity is demonstrated for a hydroamination reaction that occurs in dilute aqueous conditions. First, using soluble N-methylallylamine and Nmethylhydroxylamine, formaldehyde allowed catalytic turnover at prebiotically relevant formaldehyde concentrations (0.02 M) for a model hydroamination reaction. The efficiency of formaldehyde was compared to other prebiotic aldehydes, demonstrating that although other prebiotic aldehydes are capable of inducing temporary intramolecularity, they were inferior.A second small molecule which may have played a role in the origin of life is D-glyceraldehyde. Since life’s molecules are homochiral, there is a need to explain how this homochirality arose. There have been many breakthroughs by the scientific community when it comes to addressing this challenge, however there is still no general consensus on the origins of homochirality from a prebiotic perspective. Herein, we demonstrate that D-glyceraldehyde is capable of templating a challenging intermolecular reaction while also transmitting some of its chirality to the product. Though the enantiomeric excess produced was generally low (usually around 20 %), there is a significance behind these results due to prebiotically relevant amplification procedures.
Lastly, formaldehyde is examined as a possible desymmetrizing agent; coupled
with Brønsted acids, the possibility of formaldehyde to induce desymmetrization of
alpha-amino or alpha-hydroxy diesters to produce azlactones, and oxalactones,
respectively will be established. Moreover, the use of a chiral Brønsted acid would
introduce the ability to achieve this transformation in an enantioselective manner. The
resulting azlactones / oxalactones are valuable for two reasons: 1) the lactones are
present in bioactive molecules, and 2) the lactones can be hydrolyzed to produce chiral alpha-amino / alpha-hydroxy acids. Therefore, we began a systematic study of the conditions required to allow this transformation to occur. This study indicates that the desymmetrization of an alpha-amino diester is possible, producing moderate yields of the resulting azlactone. The desymmetrization of alpha-hydroxy diesters however proved more challenging, and no conversion was observed. Further investigation is required to the increase efficiency of the desymmetrizations, and experimentation with chiral Brønsted acids is required in order to discover enantioselective transformations.
17
Burkhart, John F., and John F. Burkhart. "Sorption behavior of formaldehyde to ice grains." Thesis, The University of Arizona, 2000. http://hdl.handle.net/10150/626770.
Full textAbstract:
The equilibritun partitioning of fonnaldehyde between air and snow was studied in a senes of
laboratory experitnents conducted at -S"C, -15"C and -35()C, with the intention of developing a
quantitative relationship of the ternperature dependence of the bulk partitioning transfer coefficient,
K0 , for fonnaldehyde in polar snow. The results of the experitnents it1dicate that the original field
based paratneterization of the n1odel does use realistic values for both the partitioning coefficient,
K0 , and the pseudo-fust order transfer rate coefficient, k1 ,. Measurements of K0 were 1.75, 1.97, and 2.39 (Log 1nol L-1 atm-) for -5°C, -15oC and -35()C, respectively. Estitnates of k1 , for the satne three tetnperatures in units of s-1 were 4.11 x 10-4, 1.07 x 10-4, and 1.08 x 1 o s, respectively. Attnospheric
tneasuretnents of fonnaldehyde in polar regions reveal concentrations that are higher than predicted
frotn current 1nodelll1g. Additionally, firn and firn-air concentrations of fonnaldehyde i11 the polar
snow pack have been observed to have a unique profile of preserved concentrations that are not
consistent with other reversibly deposited species. These experitnents help to further define the
behavior of fonnaldehyde sorption to ice, and the preservation of it in the snow. It has been shown
that fonnaldehyde observations it1 fun can be 1nodeled solely through the use of a parameterized
tnodel of tetnperature dependent sorption
18
Wang, Jinwu. "Cure kinetics of wood phenol-formaldehyde systems." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Spring2007/j_wang_042207.pdf.
Full text
19
Starks, Leonard J. "The polymerization of formaldehyde by coordination catalysis." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/28018.
Full text
20
Al-Haider, Sahailah Ahmed. "Monitoring and modelling direct atmospheric formaldehyde measurements." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436382.
Full text
21
Wang, Feng Hu. "Stress relaxation in phenol formaldehyde bonded particleboards." Thesis, Cardiff Metropolitan University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314859.
Full text
22
Hannan, MD Abdul. "Developing Formaldehyde Free Flame Retardant for Cellulose." Thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-20854.
Full textAbstract:
Two organophosphorus compounds, namely diethyloxymethyl-9-oxa-10- phosphaphenanthrene-10-oxide (DOPAC) and diethyl (2,2-diethoxyethyl) phosphonate (DPAC) were applied on cotton cellulose to impart non-carcinogenic and durable (in alkaline washing) flame retardant property to it. Some acidic catalysts, sodium dihydrogen phosphate (NaH2PO4), ammonium dihydrogen phosphate (NH4H2PO4) and phosphoric acid (H3PO4), were successfully used to settle acetal linkage between cellulose and flame retardant (FR) compound. Appreciable limiting oxygen index (LOI) values of 24% and 23.9% were achieved in case of the samples treated with FR compound DPAC along with the combined acidic catalyzing effect of NaH2PO4+H3PO4 and NaH2PO4+NH4H2PO4. A distinguishing outcome of total heat of combustion (THC) 3.27 KJ/g was revealed during pyrolysis combustion flow calorimetry (PCFC) test of the treated sample. In respect of thermal degradation, low temperature dehydration in conjugation with sufficient amount of char residue (30.5%) was obtained in case of DOPAC treated sample. Consistently, the temperature of peak heat release rate (TPHRR) (325°C) of DPAC treated sample supported the expected low temperature pyrolysis in condensed phase mechanism. Subsequent thermogravimetric analysis (TGA) also reported inspiring weight retention% of the treated samples. Furthermore, for both of the flame retardant compounds, effect of different catalysts, considering both individual and combined, effect of solvents, and overall the optimization of the process parameters were studied in detail.Program: Magisterutbildning i textilteknologi
23
Vaccaro, Patrick H. "Spectroscopy and kinetics of highly excited formaldehyde." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/15111.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 481-510.
by Patrick H. Vaccaro.
Ph.D.
24
Scott, Brian Cameron. "Evaluation of Phenol Formaldehyde Resin Cure Rate." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/33222.
Full textAbstract:
Cure time is often the bottleneck of composite manufacturing processes, therefore it is important to understand the cure of todayâ s thermosetting adhesives. This research attempts to characterize the cure rate of two commercial phenol-formaldehyde adhesives. Two methods are used, parallel-plate rheometry and dielectric spectroscopy. Viscosity data from a parallel-plate rheometer may be used to track the advance of polymerization as a function of temperature. This data can then be used to optimize press conditions and reduce production times and costs.
The research will further examine resin cure through dielectric analysis; such a technique could monitor resin cure directly and in real-time press situations. Hot-pressing processes could conceivably no longer require a set press schedule; instead they would be individually set based on dielectric data for every press batch. Such a system may lead to a more efficient and uniform product because press times could be based on individual press cycles instead of entire product lines. A more likely scenario, however, is the use of in situ adhesive cure monitoring for troubleshooting or press schedule development.
This research characterized the cure of two phenol-formaldehyde resins using parallel-plate rheometry, fringe-field dielectric analysis, and parallel-plate dielectric analysis. The general shape of the storage modulus vs. time curve and the gel and vitrification points in a temperature ramp were found.
Both dielectric analysis techniques were able to characterize trends in the resin cure and detect points such as vitrification. The two techniques were also found to be comparable when the cure profiles of similar conditions were examined.
Master of Science
25
Wan, Guigui. "Mechanisms of biogenic formaldehyde generation in wood." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/84503.
Full textAbstract:
This work addresses biogenic formaldehyde (CH₂O) generated by wood during the manufacture of non-structural wood-based composites, from which CH₂O emissions are regulated. The target for regulation has been anthropogenic CH₂O released from hydrolytically unstable amino resins like urea-formaldehyde. However, current regulations (the Formaldehyde Standards for Composite Wood Products Act, signed into law in 2010 and implemented in 2016) restrict allowable emissions to such low levels that biogenic CH₂O may affect regulation compliance. The industry has met the latest regulations with new amino resin technologies. Nevertheless persistent anecdotal reports suggest that biogenic CH₂O complicates regulation compliance. This work represents an industry/university cooperation to seek a more thorough understanding of biogenic CH₂O, to begin documentation of biogenic CH₂O levels in wood, and to study the conditions and chemical mechanisms of its formation.
Efforts began by establishing CH₂O analysis using the fluorimetric acetylacetone determination. A custom 12-liter chamber with controlled temperature and relative humidity, and "ultrapure" nitrogen (N₂) ventilation was created to measure CH₂O emissions from flakes sampled from four Virginia pine (Pinus virginiana) trees. Emissions from never-heated specimens varied significantly among the four trees, ranging from 0.02 – 0.19 µg CH₂O/m³g dry wood. Heating (200°C, 1 hour), followed by chamber equilibration, resulted in significantly increased emissions on the order of 50%. Sequential heating, followed by chamber equilibration (in other words, heat/equilibrate/measure emission/repeat), resulted in declining emissions suggesting that a finite chemical source of CH₂O was being depleted by the sequential heat treatment. Flake specimens were stored in the open laboratory, and over 2-3 months laboratory storage, initially high emitting specimens gradually emitted less CH₂O, and initially low emitters gradually emitted more CH₂O. Concerns over laboratory contamination were perhaps allayed when background levels of laboratory CH₂O were determined to be similar to the background levels in the ultrapure N₂ used to ventilate the chamber. Measurement of emissions was abandoned, and thereafter a simple water extraction technique (~ 94% CH₂O recovery) was used to measure the CH₂O content of never-heated and heated wood specimens, where the difference was identified as CH₂O generated due to heating.
Increment cores from living Virginia pine (Pinus virginiana), yellow-poplar (Liriodendron tulipifera), and radiata pine (Pinus radiata) trees were used to measure CH₂O content and CH₂O generation due to heating (200°C, 10 min). Significant variations within and between trees of the same species were observed. Tissue types (juvenile/mature, heartwood/sapwood) sometimes correlated to higher CH₂O contents and greater heat-generation potential; but sometimes not depending upon species. Heating increased CH₂O levels 3-60 fold. Heating with high moisture levels caused greater CH₂O generation than for dry specimens. This moisture effect and a separate serendipitous observation suggested that CH₂O generation is acid catalyzed. Radiata pine generated extraordinarily high CH₂O levels when heated, far exceeding the other two species. It was suggested that pine extractives might catalyze CH₂O generation, perhaps in lignin.
Pinus virginiana wood was heated (200°C, 10 or 60 min) while dry or after aqueous/acid or base pretreatment in order to reveal mechanisms of formaldehyde (CH₂O) generation. Among wood structural polymers, lignin was the overwhelming source of biogenic CH₂O, consistent with prior reports. The effects of wood extractives are mentioned below. The selection of acid catalyst strongly affected CH₂O generation as predicted in the acidolysis literature of lignin model compounds and isolated lignins. Lignin methoxyl cleavage was also observed, but was considered an unlikely source of thermochemical CH₂O. Alkaline pretreatments suppressed CH₂O generation. Regarding wood-based composite manufacture, the implications are that lignin reactions can be manipulated during hot-pressing. Potential benefits include reduced product emissions, and/or novel crosslinking strategies using biogenic CH₂O.
Heat generation of CH₂O in Virginia pine and radiata pine was substantially reduced by extractives removal, but there was no such effect in yellow-poplar wood. Results suggested that pine extractives promote CH₂O generation by catalyzing or otherwise promoting C2 cleavage (acidolysis) in lignin. Thioacidolysis demonstrated that pine lignin reactions were strongly dependent upon the presence or absence of the extractives. When present, pine extractives seemed to promote C2 cleavage (CH₂O generation), but otherwise reduced the overall extent of lignin degradation. When pine extractives were removed, lignin suffered substantial degradation, but apparently less C2 cleavage since CH₂O generation was reduced. In contrast, thioacidolysis showed that yellow-poplar extractives appeared to promote lignin degradation, but extractives removal had no detectable impact on CH₂O generation. Implications exist for biorefinery research because it was shown that lignin reactions can be strongly affected by wood extractives.
Two dimensional, proton-carbon, correlation NMR spectroscopy (2D NMR), and solvent submersion dynamic mechanical analysis (DMA) was used to investigate wood changes caused by heating in the presence or absence of external acid catalysis. 2D NMR was relatively insensitive to fine lignin changes that were detected using thioacidolysis. 2D NMR was effective for observing lignin changes under more extreme heating conditions, and evidence was found for lignin crosslinking reactions that probably occurred through substitution into lignin aromatic rings. DMA showed that most heating conditions caused an increase in the lignin glass transition temperature (Tg), consistent with heat-induced lignin crosslinking. Under one experimental condition of wood heating, DMA showed a reduction in the lignin glass transition temperature (Tg). This suggested that lignin cleavage without subsequent repolymerization might be promoted by carefully controlled conditions, and this has implications for biorefinery research where lignin repolymerization can be problematic.
Finally, this work strongly supported the hypothesis that lignin generates CH₂O through well-known acidolysis pathways where CH₂O is borne from the lignin gamma-methylol group. Therefore, it was predicted that upon heating corn (Zea mays L.) stalk should generate less CH₂O than wood because corn stalk lignins exhibit a high degree of coumaric acid esterfication at the gamma-methylol group. This hypothesis was perhaps verified- it was found that in 4 out of 6 experimental heating conditions that corn stalk generated significantly less CH₂O than Virginia pine.Ph. D.
26
Yang, Xing. "Organic Fillers in Phenol-Formaldehyde Wood Adhesives." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64999.
Full textAbstract:
Veneer-based structural wood composites are typically manufactured using phenol-formaldehyde resols (PF) that are formulated with wheat flour extender and organic filler. Considering that this technology is several decades old, it is surprising to learn that many aspects of the formulation have not been the subject of detailed analysis and scientific publication. The effort described here is part of a university/industry research cooperation with a focus on how the organic fillers impact the properties of the formulated adhesives and adhesive bond performance. The fillers studied in this work are derived from walnut shell (Juglans regia), alder bark (Alnus rubra), and corn cob (furfural production) residue.
Alder bark and walnut shell exhibited chemical compositions that are typical for lignocellulosic materials, whereas corn cob residue was distinctly different owing to the high pressure steam digestion used in its preparation. Also, all fillers had low surface energies with dominant dispersive effects. Surface energy of corn cob residue was a little higher than alder bark and walnut shell, which were very similar.
All fillers reduced PF surface tension with effects greatest in alder bark and walnut shell. Surface tension reductions roughly correlated to the chemical compositions of the fillers, and probably resulted from the release of surface active compounds extracted from the fillers in the alkaline PF medium.
It was shown that viscoelastic network structures formed within the adhesive formulations as a function of shear history, filler type, and filler particle size. Relative to alder bark and walnut shell, the unique behavior of corn cob residue was discussed with respect to chemical composition.
Alder bark and walnut shell exhibited similar effects with a decrease of adhesive activation energy. However, corn cob reside caused much higher adhesive activation energy.
Alder bark exhibited significant particle size effects on fracture energy and bondline thickness, but no clear size effects on penetration. Regarding corn cob residue and walnut shell, particle size effects on fracture energy were statistically significant, but magnitude of the difference was rather small. Classified corn cob residue fillers all resulted in a similar bondline thickness (statistically no difference) that was different walnut shell.Ph. D.
27
Winkler, Kyle W. "Formaldehyde Exposures in an University Anatomical Laboratory." University of Toledo Health Science Campus / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=mco1294188073.
Full text
28
Johnson, Brian James. "The carbon-13 content of atmospheric formaldehyde." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184320.
Full textAbstract:
A measurement of the stable carbon isotopic composition of atmospheric formaldehyde was undertaken as a means of testing current photochemical theories. Sulfito surfaces were shown to meet the stringent analytical requirements of the project; an extensive characterization of these surfaces was performed for the first time. Models were developed to describe the chemical evolution of the surfaces during sampling. It was established that potassium salts have more favorable properties for an atmospheric collection system than do sodium salts. Considerable selectivity in collection was also demonstrated. A highly selective multistep procedure for the isolation and chemical oxidation of collected formaldehyde was developed expressly for this project. A previously unreported combination of reagents, HgCl₂ and AgClO₄, was used in the final reaction step of the procedure. Through the use of synthetic samples, the method was shown to be isotopically reproducible and highly chemically selective. The first data for the carbon-13 content of atmospheric formaldehyde have been obtained, with an observed mean value of δ¹³C = -17‰. This value is enriched in carbon-13 over the known atmospheric sources of formaldehyde; isotopic fractionation in the atmosphere is therefore indicated. It is believed that fractionation due to photolysis can account for the observed effect.
29
Yousefi-Shivyari, Niloofar. "Isotope ratios in source determination of formaldehyde emissions." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99308.
Full textAbstract:
Formaldehyde emissions from non-structural wood composites are regulated and the regulation target is urea-formaldehyde (UF) resin. UF resins are hydrolytically unstable and constantly emit formaldehyde as a function of temperature and relative humidity. When heated, wood also generates formaldehyde, but this was of little concern until 2010 when formaldehyde regulations became much more demanding. This regulation motivated the industry to account for all formaldehyde sources, synthetic as from resin, and biogenic as from wood. This effort represents first steps towards quantifying biogenic and synthetic contributions to formaldehyde emissions in non-structural wood composites.
It is possible to distinguish the 13C/12C isotope ratio of UF resins from the isotope ratio of plant biomass. Conditions during and after composite hot-pressing promote reactions that generate formaldehyde from wood and UF resin, and the kinetic isotope effect continuously lowers the product isotope ratios as a function of yield. If such isotope fractionation did not occur, it would be a simple matter to quantify contributions of wood and UF resin to formaldehyde emissions using static isotope ratios. Isotope fractionation, therefore, complicates the requirements for distinguishing biogenic and synthetic formaldehyde in wood composite emissions. Those requirements are 1) establish the reference carbon isotope ratios in wood and in UF resin (just the formaldehyde portion of UF), and 2) estimate the kinetic isotope effects in formaldehyde generation by wood and cured UF resin. The latter requirement fixes a range for the respective isotope ratios; the numerical ranges enable a simple model of the average isotope ratio for a mixture of biogenic and synthetic formaldehyde in wood composite emissions. Finally, the measured isotope ratio of captured emissions would be compared to the model.
This work did not achieve all aspects of the requirements mentioned, but a solid foundation was established for future completion of the ultimate goals. In reference to requirement 1, the carbon isotope ratio of experimental Pinus taeda wood was accurately measured (including some isolated fractions) using isotope ratio mass spectroscopy (IRMS). IRMS of UF resin first requires removal of urea carbons- UF resin was subjected to acid hydrolysis and capture of the resin formaldehyde into aqueous ammonium hydroxide. This provided a nearly quantitative conversion (negligible isotope fractionation) of resin formaldehyde into hexamine for IRMS. Using this hexamine method, the formaldehyde carbon isotope ratios of two industrial UF resins were accurately measured, demonstrating basic feasibility for the project goal.
Estimating the kinetic isotope effect (Requirement 2) required creation of a thermochemical reactor, where wood or cured UF resin was heated under N2 flow such that the emitted formaldehyde was easily captured. In this case, conversion of captured formaldehyde into hexamine was abandoned in favor of silica gel cartridges loaded with sodium bisulfite. Isolation and IRMS of the formaldehyde-bisulfite adduct were effective and considered easily transferable to industrial settings. This system was employed to measure fractionation in cured resin as a function of relative humidity, and in Pinus taeda wood as a function of relative humidity, temperature, and time. More information about isotope fractionation is required; but most notable was the fractionation behavior in wood where evidence was found for multiple formaldehyde generating reactions. Overall, this work established feasibility for the goals and laid the foundation for future efforts.Master of Science
Home-interior products like cabinetry are often produced with wood composites adhesively bonded with urea-formaldehyde (UF) resin. UF resins are low cost and highly effective, but their chemical nature results in formaldehyde emission from the composite. High emissions are avoided, and the federal government has regulated and steadily reduced allowable emissions since 1985. The industry continuously improved UF technologies to meet regulations, as in 2010 when the most demanding regulations were implemented. At that time, many people were unaware that wood also generates formaldehyde; this occurs at very low levels but heating during composite manufacture causes a temporary burst of natural formaldehyde. Some wood types produce unusually high formaldehyde levels, making regulation compliance more difficult. This situation, and the desire to raise public awareness, created a major industrial goal: determine how much formaldehyde emission originates from the resin and how much originates from the wood. These formaldehyde sources can be distinguished by measuring the carbon isotope ratio, 13C/12C. This ratio changes and varies due to the kinetic isotope effect. Slight differences in 13C and 12C reactivity reveal the source as either petrochemical (synthetic formaldehyde) or plant-based (biogenic formaldehyde). This work demonstrates that achieving the industry goal is entirely feasible, and it provides the analytical foundation. The technical strategy is: 1) establish reference isotope ratios in wood and in UF resin, and 2) from the corresponding wood composite, capture formaldehyde emissions, measure the isotope ratio, and simply calculate the percentage contributions from the reference sources. However, a complication exists. When the reference sources generate formaldehyde, the respective isotope ratios change systematically in a process called isotope fractionation (another term for the kinetic isotope effect). Consequently, this effort developed methods to measure fractionation when cured UF resin and wood separately generate formaldehyde, with greater emphasis on wood. Isotope fractionation in wood revealed multiple fractionation mechanisms. This complexity presents intriguing possibilities for new perspectives on formaldehyde emission from wood and cured UF resin. In summary, this work demonstrated how source contributions to formaldehyde emissions can be determined; it established effective methods required to refine and perfect the approach, and it revealed that isotope fractionation could serve as an entirely novel tool in the materials science of wood composites.
30
Khan, Shaheed. "Failure of aspen wood/resorcinol-formaldehyde adhesive bond." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0035/NQ65462.pdf.
Full text
31
Kallos, Alexander. "Characterization of cure of phenol formaldehyde foaming resin." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63800.
Full text
32
Squire, Gavin Daniel. "Partial oxidation of methane to methanol and formaldehyde." Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278072.
Full text
33
Normand, Florence. "Analytical and kinetic studies of amide-formaldehyde reactions." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325648.
Full text
34
Pope, Francis David. "Photochemistry of formaldehyde relevant to the upper troposphere." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411081.
Full text
35
Taylor, Stewart John. "Monitoring the gelation mechanism of resorcinol-formaldehyde xerogels." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24824.
Full textAbstract:
Resorcinol-Formaldehyde (RF) xerogels are a type of porous material used in many applications, such as gas storage. These applications often require fine control of the material's porosity, and while it is known that the porosity of a xerogel can be changed through altering synthesis variables, it is not clear why these changes have such an impact. To understand this effect, the gelation process was studied using dynamic light scattering (DLS), with the xerogel products undergoing low temperature nitrogen adsorption measurements to determine textural properties. RF gels are composed of cross-linked clusters and DLS was used to study changes in how these clusters grow. It was found that cluster growth was a thermodynamically controlled process, and for a given catalyst, how the cluster size grows with time was independent of the catalyst concentration. However, the catalyst did kinetically control the number concentration of clusters initially formed, and in turn, the size to which they, therefore, had to grow to reach a critical volume fraction to form the gel, such that higher catalyst concentrations led to smaller clusters making up the gel. This resulted in smaller intercluster voids, hence, smaller pores. The catalysts used also demonstrated a range of different abilities to stabilise the colloidal suspension of clusters. This also affected cluster size, with less stabilising catalysts resulting in larger clusters. This knowledge led to the ability to further tailor the porosity by introducing a secondary catalyst, in various forms, into a separate gelling mixture. The different catalysts, with their varied abilities to stabilise the growing clusters, and the range of concentrations used, resulted in a variety of cluster sizes within the final gel, which changed the porosity of the xerogel products formed.
36
Lorusso, Patrizia. "Metal catalysed alkylation of carbonyl compounds with formaldehyde." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/7823.
Full textAbstract:
Formaldehyde is a chemical used widely in the manufacture of building materials. A remarkable example is represented by the Lucite two-step Alpha technology for the large scale production of methyl methacrylate (MMA), the essential building block of all acrylic-based products. Esters and ketones are important intermediates in the manufacture of acrylate esters therefore α-hydroxymethylenation of carbonyl compounds using formaldehyde as a one carbon alkylating agent and subsequent dehydration to the corresponding methylenated derivatives has been explored in the current work. We report a novel catalytic approach for the synthesis of methyl methacrylate (MMA) via one-pot α-methylenation of methyl propanoate (a chemical intermediate of the ALPHA process) with formaldehyde, generated in situ by Ru-catalysed dehydrogenation of methanol. Elucidation of the mechanism involved in the catalytic dehydrogenation of methanol along with the collateral alcohol decarbonylation reaction was gained through a combined experimental and DFT study. The development of an alternative process where anhydrous formaldehyde is produced in situ would provide a simplification over the current second step of the ALPHA technology where the formaldehyde is initially produced as formalin, subsequently dehydrated to afford anhydrous formaldehyde in order to ensure high selectivity to MMA. As an alternative approach, ketones, in particular 3-pentanone and 2-butanone, were targeted as potential substrates in order to overcome some of the problems related to competing reactions that occur at the ester group. Hydroxymethylenation, followed by dehydration and Baeyer-Villager oxidation, possibly catalysed by enzymes to reverse the normal selectivity, leads to the formation of acrylate esters. The catalytic reaction is enabled by a gold carbene hydroxide complex in such a way that the substrate undergoes C-H activation and the nascent metal alkyl acts as a nucleophile towards the electrophilic formaldehyde, supplied in the form of alcoform* (solution of paraformaldehyde in methanol).
37
Lu, Kun Swenberg James A. "Molecular binding of formaldehyde to DNA and proteins." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2767.
Full textAbstract:
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2009.Title from electronic title page (viewed Mar. 10, 2010). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Curriculum of Applied Science and Engineering." Discipline: Applied and Materials Sciences; Department/School: Applied and Materials Sciences.
38
Quiroz, Torres Jhon Jhon. "Formaldehyde catalytic oxidation over mesoporous manganese based materials." Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10095/document.
Full textAbstract:
La qualité de l'air intérieur est une préoccupation majeure de notre société. Le formaldéhyde (HCHO) est un polluant atmosphérique important et présent dans divers environnements intérieurs comme la maison, le bureau et l'industrie. L'oxydation catalytique complète du formaldéhyde est une voie prometteuse pour convertir ce polluant en produits inoffensifs. Les catalyseurs à base d’oxydes de métaux de transition sont décrits comme les plus prometteurs. Parmi ces oxydes, ceux à base d'oxydes de manganèse sont peu coûteux, non toxiques et peuvent être efficaces pour convertir le formaldéhyde à basse température. Ce travail vise à développer des catalyseurs mésoporeux à base d'oxydes de manganèse pour l'élimination catalytique à basse température du formaldéhyde. Des oxydes de manganèse mésoporeux contenant des teneurs variables en cérium ont tout d’abord été obtenus par activation chimique (traitement acide). L'optimisation de la synthèse du matériau mésoporeux sous atmosphère contrôlée a ensuite conduit à l’obtention d’une mésostructure lamellaire d’oxyde de manganèse. Le délaminage de cet oxyde, après calcination, a produit un oxyde de manganèse ayant des propriétés texturales très intéressantes et redox grandement améliorées. Le catalyseur le plus actif a pu oxyder complètement HCOH en CO2 et H2O à 110 °C. Finalement, des hydrotalcites à base de Mg, Mn et Al, activées par ultrasons, ont été synthétisées pour être employées en tant que précurseurs d’oxydes mixtes de manganèse de grandes surfaces spécifiques. L'effet de l’apport des ultrasons et de la composition en éléments du matériau (Mg/Mn) sur les propriétés structurales, texturales, basiques et catalytiques des oxydes mixtes a plus particulièrement été étudiéIndoor air quality is currently a societal concern. Formaldehyde is an important air pollutant in various indoor environments, including houses, offices and industries. The catalytic complete oxidation of formaldehyde is a promising way to convert this pollutant into harmless products. Transition metal oxides based catalysts are described as the most promising catalysts. Among these oxides, manganese oxide based materials are promising, cheap, non-toxic and effective catalysts to convert formaldehyde at low temperature. The present work aims to develop a novel mesoporous manganese oxide based catalyst for low temperature formaldehyde catalytic removal. Mesoporous manganese oxides containing variable amounts of cerium were first obtained by chemical activation (acid treatment). The optimization in the synthesis of mesoporous manganese oxide under controlled atmosphere produces a layered mesostructure manganese oxide. The delamination of this layered mesostructure oxide, after calcination, produces high surface area manganese oxides with improved redox properties and the most active catalyst completely oxidizes HCHO into CO2 and H2O at 110 °C. Finally, Mg Mn and Al hydrotalcites based compounds, activated by ultrasound, are employed as precursors to obtain high surface area mixed manganese oxide. The effect of ultrasound contribution and the elemental composition of the material (Mg / Mn) on the structural, textural, basic and catalytic properties of the resulting mixed oxides have been particularly studied
39
Quiroz, Torres Jhon Jhon. "Formaldehyde catalytic oxidation over mesoporous manganese based materials." Electronic Thesis or Diss., Lille 1, 2012. http://www.theses.fr/2012LIL10095.
Full textAbstract:
La qualité de l'air intérieur est une préoccupation majeure de notre société. Le formaldéhyde (HCHO) est un polluant atmosphérique important et présent dans divers environnements intérieurs comme la maison, le bureau et l'industrie. L'oxydation catalytique complète du formaldéhyde est une voie prometteuse pour convertir ce polluant en produits inoffensifs. Les catalyseurs à base d’oxydes de métaux de transition sont décrits comme les plus prometteurs. Parmi ces oxydes, ceux à base d'oxydes de manganèse sont peu coûteux, non toxiques et peuvent être efficaces pour convertir le formaldéhyde à basse température. Ce travail vise à développer des catalyseurs mésoporeux à base d'oxydes de manganèse pour l'élimination catalytique à basse température du formaldéhyde. Des oxydes de manganèse mésoporeux contenant des teneurs variables en cérium ont tout d’abord été obtenus par activation chimique (traitement acide). L'optimisation de la synthèse du matériau mésoporeux sous atmosphère contrôlée a ensuite conduit à l’obtention d’une mésostructure lamellaire d’oxyde de manganèse. Le délaminage de cet oxyde, après calcination, a produit un oxyde de manganèse ayant des propriétés texturales très intéressantes et redox grandement améliorées. Le catalyseur le plus actif a pu oxyder complètement HCOH en CO2 et H2O à 110 °C. Finalement, des hydrotalcites à base de Mg, Mn et Al, activées par ultrasons, ont été synthétisées pour être employées en tant que précurseurs d’oxydes mixtes de manganèse de grandes surfaces spécifiques. L'effet de l’apport des ultrasons et de la composition en éléments du matériau (Mg/Mn) sur les propriétés structurales, texturales, basiques et catalytiques des oxydes mixtes a plus particulièrement été étudiéIndoor air quality is currently a societal concern. Formaldehyde is an important air pollutant in various indoor environments, including houses, offices and industries. The catalytic complete oxidation of formaldehyde is a promising way to convert this pollutant into harmless products. Transition metal oxides based catalysts are described as the most promising catalysts. Among these oxides, manganese oxide based materials are promising, cheap, non-toxic and effective catalysts to convert formaldehyde at low temperature. The present work aims to develop a novel mesoporous manganese oxide based catalyst for low temperature formaldehyde catalytic removal. Mesoporous manganese oxides containing variable amounts of cerium were first obtained by chemical activation (acid treatment). The optimization in the synthesis of mesoporous manganese oxide under controlled atmosphere produces a layered mesostructure manganese oxide. The delamination of this layered mesostructure oxide, after calcination, produces high surface area manganese oxides with improved redox properties and the most active catalyst completely oxidizes HCHO into CO2 and H2O at 110 °C. Finally, Mg Mn and Al hydrotalcites based compounds, activated by ultrasound, are employed as precursors to obtain high surface area mixed manganese oxide. The effect of ultrasound contribution and the elemental composition of the material (Mg / Mn) on the structural, textural, basic and catalytic properties of the resulting mixed oxides have been particularly studied
40
Boddeti, Ravi Kumar. "Laser spectroscopy sensors for measurement of trace gaseous formaldehyde /." Connect to resource online, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1220624621.
Full text
41
Mason, R. P. "Nuclear magnetic resonance investigations of the interaction of formaldehyde with living cells." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383317.
Full text
42
Schlunke, Anna Delia. "Mechanism and Modelling of the Partial Oxidation of Methanol over Silver." Thesis, The University of Sydney, 2007. http://hdl.handle.net/2123/2013.
Full textAbstract:
This work involves an experimental and kinetic modelling study of the silver catalysed reaction of methanol to formaldehyde. The motivation for this was the desire to investigate the potential for Process Intensification in formaldehyde production. Formaldehyde production from methanol over silver catalyst is a fast, exothermic process where dilution is used to control heat release, and these properties are both indicators of Process Intensification potential. The process is run adiabatically and produces hydrogen (which is currently burnt). Oxygen is consumed during the reaction but is also required to activate the catalyst and is fed in understoichiometric quantities. The central overall reactions in the silver catalysed process for formaldehyde production are oxydehydrogenation CH3OH + ½ O2 -> CH2O + H2O (DH = -159kJ/mol) and dehydrogenation CH3OH <-> CH2O + H2 (DH = 84kJ/mol). When sufficient oxygen is available, formaldehyde can be further oxidised to carbon dioxide CH2O + O2 -> CO2 + H2O (DH = -519kJ/mol). Formaldehyde can decompose to carbon monoxide and hydrogen CH2O <-> CO + H2 (DH = 12.5kJ/mol). Oxidation of methanol and hydrogen also occurs and other minor products of the reaction are methyl formate, methane and formic acid. These overall reactions do not adequately describe the silver catalysed reaction mechanism. In particular, the overall dehydrogenation reaction does not include oxygen as a reactant, but it will not occur over silver that does not have active atomic oxygen species adsorbed on the surface, and these atomic oxygen species are formed from gas phase oxygen. In the absence of a complete mechanism for silver catalysed formaldehyde production, the intensification of the process was investigated using a thermodynamic model (based on the overall oxydehydrogenation and dehydrogenation reactions, not reaction kinetics). It was found that by using heat exchange (rather than heat generated from the exothermic oxydehydrogenation path) and a lower oxygen concentration in the feed stream, hydrogen selectivity could be increased while maintaining the required methanol conversion. Before this iv opportunity could be further investigated, a complete reaction mechanism that would allow the requirement of oxygen for catalyst activation to be included was required. There is agreement in the literature that two active atomic oxygen species react with methanol on silver. These are weakly bound atomic oxygen (Oa) and strongly bound atomic oxygen (Og). The location of Oa is on the surface of the silver, while the location of Og has been described as being in the silver surface (where it substitutes for silver atoms). Both species react with methanol to form formaldehyde. When the concentration of Oa is high enough, Oa will also react with formaldehyde forming carbon dioxide (while Og will not). The literature presents differing views on the extent of involvement of each atomic oxygen species in industrial formaldehyde production. There is also disagreement on the pathways for water and hydrogen formation. An extensive experimental investigation of the partial oxidation of methanol to formaldehyde was carried out using a flow reactor. The effect of temperature (250- 650°C), reactant concentration (7000-40000ppm methanol) and the feed ratio of methanol to oxygen (2.5-5.5) were studied. The extreme case of methanol reaction with Og in the absence of gas phase oxygen was also investigated. To isolate the effect of secondary reactions, the oxidation of formaldehyde, carbon monoxide and hydrogen were investigated, both in the presence and absence of silver catalyst. When methanol was exposed to silver catalyst that had been activated by being covered in Og (with this being the only source of oxygen) the catalytic nature of Og was demonstrated by the high selectivity to formaldehyde and hydrogen that was achieved (with very little carbon dioxide or water production). When gas phase oxygen was fed to the reactor along with methanol, hydrogen selectivity over silver increased up to about 40% as the concentration of reactants was increased. This result is consistent with the general rule of thumb from industrial practice that hydrogen selectivity is about 50%. When formaldehyde and oxygen were exposed to silver in the flow reactor, the only reaction products were carbon v dioxide and water and the combination of high temperature and excess oxygen was required for complete conversion of formaldehyde. A pseudo-microkinetic model (based on a Langmuir-Hinshelwood mechanism) for the partial oxidation of methanol to formaldehyde (over silver) was taken from the literature and investigated. This model predicts formaldehyde production using only Oa (no other active atomic oxygen species are included) but lacks pathways for reactions between Oa and adsorbed hydrogen or hydroxyl (so the only possible fate of adsorbed H atoms is to desorb as H2). The Oa model was combined with literature models for hydrogen desorption and the reactions involving adsorbed hydroxyl (desorption, self reaction, decomposition and reaction with adsorbed hydrogen). Comparison of this Hybrid model with experimental data showed that reactions involving Oa will predict formaldehyde formation and oxidation, but not hydrogen formation (because the rate of hydrogen desorption is too slow compared with the rate of water formation). It is concluded that any detailed model must include the reaction between methanol and Og (producing hydrogen). Although the reaction between two adsorbed OgH species has been suggested as the pathway for hydrogen formation from Og, this is not certain and so all possible reactions involving Og and hydrogen need be investigated and the appropriate pathways added to the Hybrid model. Once a complete microkinetic mechanism for the partial oxidation of methanol to formaldehyde over silver is available it can be used to further investigate the process intensification of this process. In particular, the use of staged addition of oxygen (to keep the catalyst active) combined with heat exchange (to replace the heat normally supplied by the oxydehydrogenation path) with the aim of simultaneously maximizing methanol conversion and selectivity to formaldehyde and hydrogen.
43
Schlunke, Anna Delia. "Mechanism and Modelling of the Partial Oxidation of Methanol over Silver." University of Sydney, 2007. http://hdl.handle.net/2123/2013.
Full textAbstract:
Doctor of Philosophy (PhD)This work involves an experimental and kinetic modelling study of the silver catalysed reaction of methanol to formaldehyde. The motivation for this was the desire to investigate the potential for Process Intensification in formaldehyde production. Formaldehyde production from methanol over silver catalyst is a fast, exothermic process where dilution is used to control heat release, and these properties are both indicators of Process Intensification potential. The process is run adiabatically and produces hydrogen (which is currently burnt). Oxygen is consumed during the reaction but is also required to activate the catalyst and is fed in understoichiometric quantities. The central overall reactions in the silver catalysed process for formaldehyde production are oxydehydrogenation CH3OH + ½ O2 -> CH2O + H2O (DH = -159kJ/mol) and dehydrogenation CH3OH <-> CH2O + H2 (DH = 84kJ/mol). When sufficient oxygen is available, formaldehyde can be further oxidised to carbon dioxide CH2O + O2 -> CO2 + H2O (DH = -519kJ/mol). Formaldehyde can decompose to carbon monoxide and hydrogen CH2O <-> CO + H2 (DH = 12.5kJ/mol). Oxidation of methanol and hydrogen also occurs and other minor products of the reaction are methyl formate, methane and formic acid. These overall reactions do not adequately describe the silver catalysed reaction mechanism. In particular, the overall dehydrogenation reaction does not include oxygen as a reactant, but it will not occur over silver that does not have active atomic oxygen species adsorbed on the surface, and these atomic oxygen species are formed from gas phase oxygen. In the absence of a complete mechanism for silver catalysed formaldehyde production, the intensification of the process was investigated using a thermodynamic model (based on the overall oxydehydrogenation and dehydrogenation reactions, not reaction kinetics). It was found that by using heat exchange (rather than heat generated from the exothermic oxydehydrogenation path) and a lower oxygen concentration in the feed stream, hydrogen selectivity could be increased while maintaining the required methanol conversion. Before this iv opportunity could be further investigated, a complete reaction mechanism that would allow the requirement of oxygen for catalyst activation to be included was required. There is agreement in the literature that two active atomic oxygen species react with methanol on silver. These are weakly bound atomic oxygen (Oa) and strongly bound atomic oxygen (Og). The location of Oa is on the surface of the silver, while the location of Og has been described as being in the silver surface (where it substitutes for silver atoms). Both species react with methanol to form formaldehyde. When the concentration of Oa is high enough, Oa will also react with formaldehyde forming carbon dioxide (while Og will not). The literature presents differing views on the extent of involvement of each atomic oxygen species in industrial formaldehyde production. There is also disagreement on the pathways for water and hydrogen formation. An extensive experimental investigation of the partial oxidation of methanol to formaldehyde was carried out using a flow reactor. The effect of temperature (250- 650°C), reactant concentration (7000-40000ppm methanol) and the feed ratio of methanol to oxygen (2.5-5.5) were studied. The extreme case of methanol reaction with Og in the absence of gas phase oxygen was also investigated. To isolate the effect of secondary reactions, the oxidation of formaldehyde, carbon monoxide and hydrogen were investigated, both in the presence and absence of silver catalyst. When methanol was exposed to silver catalyst that had been activated by being covered in Og (with this being the only source of oxygen) the catalytic nature of Og was demonstrated by the high selectivity to formaldehyde and hydrogen that was achieved (with very little carbon dioxide or water production). When gas phase oxygen was fed to the reactor along with methanol, hydrogen selectivity over silver increased up to about 40% as the concentration of reactants was increased. This result is consistent with the general rule of thumb from industrial practice that hydrogen selectivity is about 50%. When formaldehyde and oxygen were exposed to silver in the flow reactor, the only reaction products were carbon v dioxide and water and the combination of high temperature and excess oxygen was required for complete conversion of formaldehyde. A pseudo-microkinetic model (based on a Langmuir-Hinshelwood mechanism) for the partial oxidation of methanol to formaldehyde (over silver) was taken from the literature and investigated. This model predicts formaldehyde production using only Oa (no other active atomic oxygen species are included) but lacks pathways for reactions between Oa and adsorbed hydrogen or hydroxyl (so the only possible fate of adsorbed H atoms is to desorb as H2). The Oa model was combined with literature models for hydrogen desorption and the reactions involving adsorbed hydroxyl (desorption, self reaction, decomposition and reaction with adsorbed hydrogen). Comparison of this Hybrid model with experimental data showed that reactions involving Oa will predict formaldehyde formation and oxidation, but not hydrogen formation (because the rate of hydrogen desorption is too slow compared with the rate of water formation). It is concluded that any detailed model must include the reaction between methanol and Og (producing hydrogen). Although the reaction between two adsorbed OgH species has been suggested as the pathway for hydrogen formation from Og, this is not certain and so all possible reactions involving Og and hydrogen need be investigated and the appropriate pathways added to the Hybrid model. Once a complete microkinetic mechanism for the partial oxidation of methanol to formaldehyde over silver is available it can be used to further investigate the process intensification of this process. In particular, the use of staged addition of oxygen (to keep the catalyst active) combined with heat exchange (to replace the heat normally supplied by the oxydehydrogenation path) with the aim of simultaneously maximizing methanol conversion and selectivity to formaldehyde and hydrogen.
44
Waugh, Siobhan E. "The Kc-effect." Thesis, The University of Sydney, 2002. https://hdl.handle.net/2123/27905.
Full textAbstract:
This thesis examines an experimental and theoretical investigation into the dynamics of the reaction
HZCO (v, J, K8, K) + hv -—> HCO (v, J, N, K3, K) + H (2H). Formaldehyde molecules were cooled in a
supersonic free-jet expansion, dissociated with a laser and the ensuing formyl (HCO) fragments were probed
by laser induced fluorescence spectroscopy.
The initial experiments were carried out near the energetic threshold where very little energy is
available to the product fragments. Subsequent experiments were carried out in three higher vibrational bands
in the A( IAz) state. At these energies the dissociative surface is the formaldehyde ground state So, and the
formyl and H fragments are formed in their ground electronic and vibrational states. Formaldehyde was
prepared in numerous rotational states, characterised by J = 0 to 5, K8 = 0 to 3 and Kc = 0 to 5. The ensuing
distribution of rotational energy in the HCO fragment was measured as a function of the N, K“, K and
J = N i S quantum numbers of the fragment, and also the initial v, J, K“, Kr quantum numbers of the parent.
The results found a dependence on both N and K2, in the fragment that could be modelled well using statistical
analysis (phase space theory). This is consistent with statistical dynamics on a bound, barrierless surface.
Within le cm‘1 of the energetic threshold, a centrifugal barrier affected the populations by inhibiting product
states that require large orbital angular momentum. No dependence on the spin states, S = il/z, has been
observed.
The results also show a strong dependence on the quantum number, Kc, of both the parent and the
product. When the Kc is resolved in both the parent and product, there are large deviations from the phase
space theory model. We find that in the HCO K,l = l manifold there is always a preference (up to 5:1) for
HCO to be produced in either the higher energy Kr state (NW—1) or the lower energy state (N1,N)- This
preference is consistent over all N for any particular initial HZCO state, but may vary for different initial states.
A correlation between this Kr preference and the initial state was observed: odd Kr formaldehyde states
produce preferentially KC (lower) of HC0 and vice versa for initially even Kr states.
A “Kr—effect” has been observed previously in the photodissociation of acetaldehyde and
propionaldehyde to produce HCO. These experiments saw a strong preference for the upper energy
component of the KC doublet, irrespective of the initial parent rotational state. The other system where Kc has
been seen to play a role is the photodissociation of water. When H20 is photodissociated from a variety of
rotational states with full KC resolution, different Kr states produced different A doublet states in the OH
fragment. The similarities with these previous studies and the “Kc—effect” in formaldehyde are discussed and
used as the starting point to develop a theory to explain the “Kr-effect” observations.
45
Clark, Kathryn Kaib. "The synthesis of novel silicon-formaldehyde block co-polymers." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/27542.
Full text
46
Walser, Andreas Markus. "Time-resolved four-wave mixing spectroscopy of gaseous formaldehyde /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18044.
Full text
47
Lohilahti, J. (Jarmo). "Rotation-vibration spectroscopic studies of formaldehyde and formic acid." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514280938.
Full textAbstract:
Abstract
The thesis consists of seven studies dealing with high resolution vibration-rotation spectra of planar asymmetric tops. Six studies deal with D212CO and D213CO species of the formaldehyde molecule and one study is from DCOOH specie of the formic acid molecule. The measurements were carried out at high accuracy and the rotational analyses of the recorded spectra were performed. The observed anharmonic and Coriolis resonances were taking into account in the analyses. The rotational constants of the present and literature studies were used in evaluation of the planarity defects of formaldehyde and formic acid molecules in the summary part of the thesis. Finally, a semi-experimental structure for formaldehyde was obtained by employing experimental and theoretical data.
48
Rodezno, José M. "Transformation of formaldehyde aminals into diaminocarbenes and carbenium salts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58760.pdf.
Full text
49
Post, Glen C. "Design, synthesis, and biological evaluation of anthracycline-formaldehyde conjugates." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3219211.
Full text
50
Sutch, Peter John F. "Consumption and loss of formaldehyde in electroless copper plating." Master's thesis, University of Central Florida, 1993. http://digital.library.ucf.edu/cdm/ref/collection/RTD/id/21775.
Full textAbstract:
University of Central Florida College of Engineering ThesisThe objectives of this research were to quantify formaldehyde consumption due to plating and parasitic reactions and determine the magnitude and distribution of formaldehyde losses from the electroless copper plating process. Plating and rinse bath samples obtained from three electroless copper plating operations were analyzed for formaldehyde and copper in order to develop a mass balance analysis about the plating bath for periods of active production and no production. Fugitive air and stack releases of formaldehyde were estimated using emission factors developed from air sampling at the three facilities. It was determined that approximately 90% of the formaldehyde added to the plating process was sonsumed by some type of chemical reaction. The remaining 10% of formaldehyde represents losses from the plating operation. For the facilities with a waste plating solution stream, atmospheric losses accounted for approximately 25% of the total losses. The mass of fugitive air formaldehyde measured approximately 2.8 times that escaping through the stack. Dragout accounted for approximately 2.3% of the losses with the remaining going to the waste stream. For the facility without a plating solution waste stream, formaldehyde losses were distributed 59% to atmospheric relases and 41% to the rinse tank. Fugitive and stack releases were approximately the same at 29% of the formaldehyde losses. Formaldehyde consumption due to parasitic reactions for periods of active plating and no plating were determined for two facilities. The rate of parasitic consumption during periods of production was found to be approximately 3 times greater than that for no production. The rate of parasitic consumption was observed to increase with increasing bath temperature.
M.S.;
Civil and Environmental Engineering;
Engineering;
Environmental Engineering;
206 p.
xii, 206 leaves, bound : ill. ; 28 cm.