A celulose é o biopolímero mais abundante na natureza e apresenta grande potencial para ser processada e produzir de maneira sustentável biocombustíveis e produtos químicos. A conversão catalítica é um dos meios mais promissores para transformação da celulose. A separação entre produtos e catalisadores é uma etapa importante para indústria, o que coloca a catálise heterogênea em posição privilegiada como via de conversão, devido à facilidade de separação entre produto e catalisador. A hidrogenólise é uma via de transformação que promove a quebra de ligações C-C e a retirada de átomos de oxigênio, levando a uma gama de combustíveis e produtos químicos. Os carbetos de metais de transição suportados em carvão ativo são efetivos na quebra de ligações C-C, enquanto o paládio atua tanto na quebra de ligações C-C como em etapas de hidrogenação. Assim, este trabalho estudou as propriedades estruturais e catalíticas de catalisadores de carbeto de tungstênio suportados em carvão ativado e promovidos com paládio. Foram preparados e caracterizados catalisadores de WXC sem promotor e com 1 e 2% de Pd. As medidas de fisissorção de N2 revelou que os catalisadores são formados por uma mistura de micro e mesoporos. A análise de difração de raios X revelou predominância da fase W2C nos catalisadores promovidos por Pd, enquanto que nos catalisadores ausentes de Pd ocorreu um misto de fases carbeto. As medidas de XPS revelaram que quanto maior quantidade de Pd na amostra, se tem mais tungstênio exposto na superfície. A seguir, os catalisadores foram aplicados em reações de conversão de celulose sob pressão de hidrogênio. A conversão de celulose foi determinada por gravimetria (balanço de massa) e termogravimetria e os produtos foram identificados e quantificados por cromatografia gasosa GC e por HPLC. Foram obtidos rendimentos em torno de 40% para etileno glicol, com 77% de conversão de celulose, em reações de 120 min a 220°C com o catalisador 2% WXC/C. Além disso, foram testados diferentes substratos e catalisadores para se entender o mecanismo de conversão e o papel de cada componente do catalisador na rota reacional. A obtenção de etileno glicol a partir da celulose se passa através da hidrólise do polissacarídeo em monômeros de glicose, reação retro-aldol produzindo glicolaldeído e hidrogenação para obtenção do etileno glicol. / Cellulose is the most abundant biopolymer in nature and has great potential to be processed and to sustainably produce biofuels and chemicals. The catalytic conversion is one of the most promising ways for processing cellulose. The separation between the products and the catalysts is an important step for the industry, which puts the heterogeneous catalysis in prime position as route of conversion due to the easiness of separation of product and catalyst. Hydrogenolysis is a processing way that promotes breaking C-C bonds and the removal of oxygen atoms, leading to a variety of fuels and chemicals. The carbides of transition metals supported on activated carbon are effectives in breaking C-C bonds, while palladium acts both in breaking C-C bonds and in the hydrogenation steps. So, this work studied the structural and catalytic properties of catalysts of tungsten carbides supported on activated carbon and promoted with palladium. Catalysts WXC without promoter and 1 and 2% Pd were prepared and characterized. The N2 physisorption measurements showed that a mixture of micro and mesopores forms the catalysts. The analysis of X-ray diffraction revealed the predominance of W2C phase in the catalysts promoted with Pd, while in the catalysts absent from Pd a mixture of carbide phases occurred. XPS measurements showed that the greater amount of Pd in the sample, it is more tungsten exposed on the surface. Then, the catalysts were applied in cellulose conversion reactions under hydrogen pressure. The conversion of cellulose was determined by gravimetry (mass balance) and thermogravimetry, and the products were identified and quantified by GC and HPLC. Yields around 40% for ethylene glycol were obtained, corresponding to 77% conversion of cellulose, in reactions performed at 220 °C and 120 min reaction time, with catalyst 2% PdWXC/C. Additionally, different substrates and catalysts were tested for understanding the conversion mechanism and the role of each component of the catalyst in the reaction route. Obtaining ethylene glycol from cellulose goes through hydrolysis of the polysaccharide into glucose monomers, retro-aldol reaction producing glycolaldehyde and hydrogenating to obtain ethylene glycol.

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Chemical Engineering. / M̲i̲c̲ṟo̲f̲i̲c̲ẖe̲ c̲o̲p̲y̲ a̲v̲a̲i̲ḻa̲ḇḻe̲ i̲ṉ A̲ṟc̲ẖi̲v̲e̲s̲ a̲ṉḏ S̲c̲i̲e̲ṉc̲e̲.̲ / Vita. / Bibliography : leaves 378-385. / by John A. Wilkens. / Ph.D.

No description available.

The overuse of antibiotics in agriculture is an emerging concern, due to their potential detrimental impact to the environment. This study focuses on exploring antimicrobial properties of lignin derived compounds. Lignin is of interest as a feedstock to replacing some petroleum-based chemicals and products because it is the most abundant source of renewable aromatic compounds on the planet. Two lignin rich streams, residues from the enzymatic hydrolysis of dilute acid and alkaline pretreated corn stover, were decomposed via pyrolysis and hydrogenolysis, respectively. The resulting liquid oils were subjected to sequential extractions using a series of solvents with different polarities. Chemical compositions of the extracted fractions were characterized through HPLC and GC/MS. These extracted compounds were screened against Saccharomyces cerevisiae (S. cerevisiae), Escherichia coli, and Lactobacillus amylovorus for antimicrobial properties. Six lignin model monomers: guaiacol, vanillin, vanillic acid, syringaldehyde, 2,6-dimethoxyphenol, and syringic acid were compared to the oils and extracted fractions for antimicrobial properties. Development of lignin-derived chemicals with antimicrobial properties could provide a novel use for this underutilized natural resource.

Fluorocarbons are versatile molecules that are used in multiple industries ranging from pharmaceuticals to refrigerants, insecticides and advanced materials. More particularly hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs) are current replacements for ozone-depleting chlorofluorocarbons (CFCs) that were used for decades as refrigerants, propellants, solvents and blowing agents. However, syntheses of HFCs and HFOs involve energy-intensive processes and toxic compounds such as heavy metals and anhydrous HF. Development of more sustainable, energy efficient and "greener" synthesis of small fluorocarbons is needed, which draws attention to organometallic catalysis, especially with abundant, inexpensive and non-toxic transition metals. One approach to new organometallic routes to hydrofluorocarbons involves the formation and functionalization of fluorometallacycles. Previous work in the 1990’s by Baker et al. demonstrated the catalytic hydrodimerization of tetrafluoroethylene (TFE) using Ni catalysts with π-acidic phosphite ligands. They also demonstrated the hydrogenolysis of the d6 ferracyclopentane, Fe(CO)4(1,4-C4F8), 2-1, under high pressure and temperature with different additives to give mixtures of different hydrofluorocarbons. Since that time the reactivity of d8 fluorometallacyles has been extensively studied, leading to fundamental understanding and new catalytic applications. However less attention has been paid to d6 systems, the synthesis and reactivity of which are the focus of this Thesis. Following introduction and background in Chapter 1, Chapter 2 presents the synthesis and characterization of a series of new NHC-, phosphine- and nitrogen-ligand-substituted Fe(II) perfluorometallacycles derived from complex 2-1. This led to the discovery of the first example of a fluorinated metallacyclocarbene obtained from in situ Cα–F bond activation that afforded FeF(triphos)(1,4-C4F7), 2-6, (triphos = bis(2-diphenylphosphinoethyl)phenylphosphine) during the P-based linear tridentate ligand substitution reaction. [Fe(triphos)(1,4-C4F7)(NCMe)]+BPh4-, 2-7, and Fe(OTf)(triphos)(1,4-C4F7), 2-8, were derived from 2-6 by treatment with NaBPh4 in acetonitrile and Me3Si-OTf, respectively (Tf = triflate, SO2CF3). The same phenomenon was not observed with hard-donor N-based linear tridentate ligand, terpy’, (terpy’ = 4′-(4-methylphenyl)-2,2′:6′,2′′-terpyridine), presumably because of the less Lewis acidic metal center. Fluoride abstraction from Fe(terpy’)(CO)(1,4-C4F8), 2-9, by a Lewis acid, however allowed for Cα–F bond activation to give the cationic iron monocarbonyl carbene complex, [Fe(terpy’)(CO)(1,4-C4F7)]+OTf–, 2-10. Chapter 3 investigates further the reactivity of these new Fe(II) perfluorometallacycle complexes. The lack of reactivity of the mono- and di-substituted Fe carbonyl perfluorometallacycles with Lewis acids confirmed that Cα–F bond activation only occurs when there is enough π-backbonding into the Cα–F anti-bonding orbital, as π-acceptor phosphines and carbonyl ligands can compete for the metal back-bonding. Indeed, Cα–F abstraction is only observed with Fe(terpy’)(CO)(1,4-C4F8), 2-9, due to the poor acceptor ability of the nitrogen ligand. On the other hand, the lack of electron density on the metal center can cause the Fe center to act as an internal Lewis acid, promoting Cα–F migration as observed in situ during the triphos substitution reaction. These results show that d6 [Fe] perfluorometallacycles do not share similar reactivity with d8 [Ni] perfluorometallacycles. Moreover, the study of the character of the Fe=CF bonds suggests a nucleophilic carbene for 2-6, while 2-7, 2-8 and 2-10 all displayed electrophilic carbene character. Furthermore, hydrogenolysis of Fe(OTf)(triphos)(1,4-C4F7), 2-8, and [Fe(triphos)(1,4-C4F7)(NCMe)]+BPh4-, 2-7, at low pressure and room temperature, generated exclusively H(CF2)3CFH2, HFC-347pcc, and iron hydrides, confirming a previous hypothesis that attributed formation of this hydrofluoroalkane to an Fe carbene intermediate. In contrast, [Fe(terpy’)(CO)(1,4-C4F7)]+OTf–, 2-10, reacts with H2 to yield HF and an unidentified iron complex, showing that the nature of the ancillary ligands greatly influences the reactivity. Chapter 4 explores the reactivity of phosphine-substituted cobalt(I) carbonyl hydride complexes towards TFE to expand our work on d6 perfluorometallacycles. The most electron-rich ligands prevented metallacycle formation or slowed it down possibly due to strong π-backbonding into the CO ligands, making it harder to generate an open coordination site. Indeed, a mixture of the Co-tetrafluoroethyl complex, derived from insertion of TFE into Co–H, and the zerovalent dimer/hydrogenated TFE products, derived from the reaction of the Co–H with the 16e- CoLn(CO)3-n(CF2CF2H) intermediate, were obtained with the bulkiest ligands, CoH(dcppe)(CO)2 and CoH(Pcp3)(CO)3 (dcppe = 1,2-bis(dicyclopentylphosphino)ethane, cp = cyclopentyl). With the slightly less bulky PiBu3 ligand, further reactivity of the insertion product with TFE slowly formed a d6 metallacycle hydride complex. In contrast, with the dppe and tripod cobalt carbonyl hydrides, metallacycle product formation was evident even at short reaction times with insertion/hydrogenation ratios of 1:1, showing that using less electron-rich, steric bulky ligands prevented the bimolecular Co dimer formation, but left enough room for binding a second equivalent of TFE for metallacycle formation. Finally, Chapter 5 summarizes the findings of this Thesis and discusses future directions based on this work.

Orientador: Antonio José Gomez Cobo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-26T01:50:26Z (GMT). No. of bitstreams: 1 Queiroz_CarlaMoreiraSantos_M.pdf: 3283587 bytes, checksum: e066f63e41c49394fe6b4a9667355aab (MD5) Previous issue date: 2014 / Resumo: Com foco na sustentabilidade alinhada à obtenção de produtos de maior valor agregado, as indústrias químicas vêm investindo em pesquisas que viabilizem o processamento de matérias primas renováveis. Em particular, o sorbitol é um poliálcool proveniente da glicose, que pode ser convertido a etileno glicol e propileno glicol, derivados químicos de forte demanda industrial. Nesse contexto, o presente trabalho tem por objetivo estudar os efeitos dos suportes SiO2 kieselguhr, ?-Al2O3 e carvão ativado, assim como do método de impregnação, sobre o desempenho de catalisadores de Ru, destinados à hidrogenólise do sorbitol. Para tanto, catalisadores com uma fração mássica de 5 % de metal foram preparados através de impregnação incipiente ou úmida, a partir do precursor RuCl3.xH2O. Os sólidos preparados por impregnação incipiente foram submetidos a uma redução direta a 473 K (200 °C), sob fluxo de H2. A impregnação úmida foi realizada a 273 K (0 ºC), utilizando-se formaldeído como agente redutor. Suportes e catalisadores foram caracterizados através de técnicas para determinação da distribuição granulométrica, de titulação potenciométrica, adsorção de N2, porosimetria de Hg, microscopia eletrônica de varredura e redução à temperatura programada. Os desempenhos dos catalisadores foram avaliados na reação de hidrogenólise do sorbitol, conduzida em reatores trifásicos do tipo "slurry" e "trickle-bed". Durante os testes catalíticos, a temperatura e a pressão de H2 nos reatores foram mantidas constantes, entre 473 e 573 K (200 e 300 ºC) e entre 5 e 7 MPa (50 e 70 atm), respectivamente. Os resultados revelam que os catalisadores de Ru suportados em carvão ativado apresentam melhores desempenhos que aqueles suportados em SiO2 ou Al2O3. Maiores rendimentos de etileno glicol e propileno glicol são obtidos quando o catalisador de Ru/C é preparado por impregnação úmida / Abstract: Focusing on sustainability aligned to obtain products with higher added value, the chemical industries are investing in research that enables the processing of renewable raw materials. In particular, sorbitol is a polyalcohol derived from the glucose, which can be converted to ethylene glycol and propylene glycol, commodity chemical of strong industrial demand. In this context, the present work aims to study the supports effects SiO2 kieselguhr, ?-Al2O3 and activated carbon as well as the impregnation method on the performance of Ru catalysts for the hydrogenolysis of sorbitol. For this purpose, catalysts with a total fraction of 5 %wt. of metal were prepared by incipient or wet impregnation from the RuCl3.xH2O precursor. The solids prepared by incipient impregnation underwent direct reduction at 473 K (200 ° C) under flow H2. The wet impregnation was conducted at 273 K (0 ° C) using formaldehyde as reducing agent. Supports and catalysts were characterized by techniques for determination of particle size distribution, potentiometric titration, N2 adsorption, Hg porosimetry, scanning electron microscopy and temperature programmed reduction. The performances of the catalysts were evaluated though the sorbitol hydrogenolysis reaction, conducted in three phase reactors such as "slurry" and "trickle-bed". During the catalytic tests the temperature and H2 pressure in the reactors were kept constant between 473 and 573 K (200 to 300 ° C) and between 5 and 7 MPa (50 to 70 atm), respectively. The results indicate that the Ru catalysts supported on activated carbon have better performance than those supported on SiO2 or Al2O3. Higher yields of ethylene glycol and propylene glycol are obtained when the catalyst Ru/C is prepared by wet impregnation / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestra em Engenharia Química

Orientador: Antonio José Gomez Cobo / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-22T19:24:54Z (GMT). No. of bitstreams: 1 Zanutelo_Cristiane_D.pdf: 2910655 bytes, checksum: 8d8d65f2ea3f6afa0b73d7827013acc8 (MD5) Previous issue date: 2013 / Resumo: A hidrogenólise da sacarose é uma reação química de interesse industrial, uma vez que os produtos obtidos, sob a forma de glicóis e polióis, podem ser empregados em diversos setores produtivos, tais como indústrias farmacêuticas e de alimentos. Nesse contexto, o presente trabalho tem como objetivo estudar a preparação de catalisadores de Ni e Ru suportados em carvão ativado, destinados à hidrogenólise da sacarose em meio aquoso. Para tanto, catalisadores com uma fração mássica total de 5 % de metal foram preparados através dos métodos de impregnação incipiente e úmida, a partir de soluções aquosas de precursores clorados. Antes das impregnações, o suporte de carvão ativado comercial foi submetido a um tratamento químico com solução aquosa de KOH. Os sólidos preparados por meio da impregnação incipiente foram reduzidos a 473 K (200 ºC), sob fluxo de H2. Por sua vez, a impregnação úmida foi conduzida a 353 K (80 ºC), para diversos valores de pH, sendo a redução dos catalisadores realizada com formaldeído ou NaBH4. Os sólidos foram caracterizados através das técnicas de adsorção de N2 (método de B.E.T.), titulação de Boehm, titulação potenciométrica, espectroscopia de fotoelétrons excitados por raios X, microscopias eletrônicas de varredura e de transmissão, difratometria de raios X e redução à temperatura programada. Os desempenhos catalíticos na reação de hidrogenólise da sacarose foram conduzidos num reator Parr do tipo "slurry", à temperatura de 523 K (250 ºC) e sob pressão de H2 de 5,0 MPa (50 atm), utilizando-se uma massa de 5 g do catalisador. Os resultados revelam que os catalisadores de Ni/C preparados por impregnação úmida são mais ativos e seletivos a 1,2 propanodiol que os preparados via impregnação incipiente. A impregnação úmida também leva a catalisadores de Ru/C seletivos, que se mostram mais ativos que os preparados por impregnação incipiente. Contudo, a impregnação incipiente permite obter catalisadores igualmente seletivos, sendo que, em ambos os casos, o tratamento do suporte com KOH tem um efeito marcante no aumento do rendimento de 1,2 propanodiol / Abstract: The sucrose hydrogenolysis is a chemical reaction of industrial interest, since the obtained products, under the form of glycols and polyols, can be employed in different production sectors such as pharmaceutical and food industries. The present work aims to study the preparation of Ni and Ru catalysts supported on activated carbon, for the sucrose hydrogenolysis in aqueous media. For this purpose, catalysts with a total fraction of 5 wt % of metal were prepared by the methods of incipient and wet impregnation from aqueous solutions of chlorinated precursors. Before impregnation, the support of activated carbon was subjected to a chemical treatment in an aqueous solution of KOH. The solids prepared by incipient impregnation were reduced at 473 K (200 °C) under H2 flow. In its turn, the wet impregnation was conducted at 353 K (80 °C), for various pH values, being the catalysts reduction performed with formaldehyde or NaBH4. The solids were characterized by the techniques of N2 adsorption (B.E.T. method), Boehm titration, potentiometric titration, X ray photoelectron spectroscopy, scanning and transmission electronic microscopies, X ray diffraction and temperature programmed reduction. The catalytic performances for the sucrose hydrogenolysis were conducted in a Parr reactor of slurry type at temperature of 523 K (250 ° C) under H2 pressure of 5.0 MPa (50 atm), employing a catalyst mass of 5 g. The results reveal that the Ni/C catalysts prepared by wet impregnation are more active and selective for 1,2 propanediol than those prepared via incipient impregnation. The wet impregnation also leads to selective Ru/C catalysts, which are more active than those prepared by incipient impregnation. However, the incipient impregnation achieves also to selective catalysts, being that in both cases, the support treatment with KOH has a marked effect on increasing the yield of 1,2 propanediol / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutora em Engenharia Quimica

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第24712号 / エネ博第455号 / 新制||エネ||85(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー社会・環境科学専攻 / (主査)教授 河本 晴雄, 教授 亀田 貴之, 教授 髙野 俊幸 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

Previous investigators have studied the hydrogenolysis of sugars under high pressures and temperatures. The purpose of this investigation was to study the possibilities of producing low molecular weight polyhydric alcohols from glucose by electrochemical methods. A procedure was devised for the separation of low molecular weight polyhydric alcohols from a mixture of polyhydric alcohols which constituted extracting the mixture with acetone at a temperature of 130 ℉. The acetone proved to be a solvent for the low molecular weight polyhydric alcohols. Acetone-soluble material was produced by the electrolysis of glucose at lead or zinc cathodes in the presence of 10 per cent sodium hydroxide at a temperature of 100-110 ℉, and a current density of 7.0 amperes per square decimeter. The range of current density investigated was from 4.0 to 7.0 amperes per square decimeter. The temperature was 100-110 ℉; the cathode material was lead sheet which was given a Tafel activation; the electrolyte contained 10 per cent sodium hydroxide and 7.5 per cent sodium sulfate; and the catholyte was agitated. The effect of the current density on the reduction of glucose and the production of acetone-soluble material was negligible over this range and condition of electrolysis. The amount of acetone-soluble material produced at a current density of 7.0 amperes per square decimeter in the presence of ten per cent sodium hydroxide at a temperature of 100-110 ℉ was 80.8 per cent by weight of the glucose reduced. The amount of current passed was 14 ampere-hours. The acetone-soluble material produced in the presence of five per cent sodium hydroxide was 70.8 per cent for the same conditions and time of electrolysis. With variation of the amount of current passed to 28 and 42 ampere-hours, the acetone-soluble material produced in ten per cent sodium hydroxide was reduced to 56.9 and 15.1 per cent. The acetone-soluble material produced in the presence of five per cent sodium hydroxide was 26.4 and 11.3 per cent. The electrolysis of sorbitol in the presence of ten per cent sodium hydroxide at a lead cathode at 100-110 ℉ with the passage of 14 ampere hours of current produced no acetone-soluble material. The fractionation of the acetone-soluble material resulted in a fraction which distilled at 109-110 ℃ at 8 mm of pressure. The residue polymerized which set up to a hard water soluble, acetone-insoluble mass upon cooling. A summary of the known properties of the distillable compound, as indicated by tests performed in this investigation, is as follows: A polyhydric, methyl ketone, or aldehyde. Soluble in water, acetone, and ethanol. Insoluble in ether. Boils at 109-110 ℃ at 8 mm pressure. Forms a 2-4 dinitrophenylhydrazone derivative with an uncorrected melting point of 225-227 ℃. The compound could not be identified from the literature. / M.S.

The two main requirements for ceria-zirconia hydrodeoxygenation (HDO) catalysts are the presence of defect sites to bind oxygenates and the ability to adsorb and dissociate hydrogen. Two types of sites were identified for exchange of hydrogen and deuterium. The activation energy for one type of site was associated with H2-D2 exchange through oxygen defect sites. The activation energy for the second type of site was associated with H2-D2 exchange through hydroxyl groups and correlated with crystallite size. Ceria-zirconia can convert guaiacol, a model pyrolysis oil compound, with a high selectivity to phenol, an HDO product. Ceria-zirconia catalysts had a higher conversion of guaiacol to deoxygenated products as well as a higher selectivity towards phenol than pure ceria. They did not deactivate over the course of 72 hours on stream, whereas coking or the presence of water in the feed can cause serious decay of common HDO catalysts HDO. Therefore, ceria-zirconia catalysts are promising HDO catalysts for the first step of deoxygenation. The stability of supported Ru on ZrO2 in acidic or basic environments at reaction temperature is examined. In this study, the ruthenium dispersion is greatly increased by hydrothermal treatment in acidic and basic pH without alterations to the surface area, pore volume, pore size or crystal structure. An increase in Ru dispersion showed an increase in the selectivity to propylene glycol relative to ethylene glycol. A decrease in total Lewis acid site concentration was correlated with a decrease in the ethylene glycol yield. The conclusions of this study indicate that stability of catalysts in realistic industrial environments is crucial to the design of catalysts for a reaction.