Thesis (M.Ch.E.)--University of Delaware, 2005. / Principal faculty advisors: Jingguang Chen, Raul F. Lobo, Dept. of Chemical Engineering. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xiii, 172 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 123-125).

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The focus of this research was to investigate the role of carbon nanotubes as active catalysts in the Fischer-Tropsch reaction to derive liquid fuels from synthesis gas. Carbon nanotubes (CNTs) have unique structural and mechanical properties that make them ideal catalyst supports, but they also exhibit catalytic potential as well. This study implored the use of multi-walled CNTs on different substrates and single-walled CNTs grown from various precursors to analyze the effectiveness of the CNTs in FT synthesis. Multi-walled nanotubes (MWNTs) were tested on two different substrates: alumina pellets and inconel. The MWNTs on the alumina substrate yielded nearly all alkane and alkene products, with very little aromatic products. The amount of converted syngas reached 97% but had a high liquid product selectivity to methane, at roughly 57%. The MWNTs on inconel substrate produced nearly 80% aromatic products in one stage of the experiment, while the other three stages produces almost all alkane products with little oxygenates. Much of the liquid product yield (upwards of 73%) was between C10 and C21, which is ideal for diesel fuel. Single-walled nanotubes (SWNTs) were also tested in the FTS. All of the SWNTs were tested under a series of 6 temperatures, 300psig, and a syngas ratio of 1:1. Iron, nickel, and cobalt, which have all been proven as effective FT catalysts, were tested in trace amounts with CNTs. Fe-SWNTs (ferrocene assisted SWNTs) yielded a product of 100% C7 and C8 carbon species at two of the temperatures while 3 of the temperatures held a combination of longer chained alkanes, of C18 and longer. However, the last temperature converted 100% of the feedgas into methane and CO2. The product selectivity to CH4 and CO2 posed a problem with the Fe-SWNTs catalyst, where in all temperatures the selectivity exceeded 80%. Ni-SWNTs (nickellocene assisted SWNTs) yielded slightly better results with a higher selectivity to C2-C7, but no selectivity to longer chained hydrocarbons. Co-SWNTs (cobaltocene assisted SWNTs) tested under the same parameters yielded similar results as the Fe-SWNTs, with a very high selectivity to CH4 and CO2. Only at temperatures of 300 and 250°C were there any selectivity to compounds other than CH4 and CO2, but less than 10% selectivity to those alkanes (C2+). The final experiment consisted of a catalyst prepared from a feed solution containing a mixture of ferrocene and nickellocene. The Fe+Ni-SWNT catalyst underwent the same conditions as the other SWNT catalysts, this combination yielded favorable results with over 98% conversion of syngas over all temperatures and a high selectivity to shorter chain length hydrocarbons, namely alkanes of chain lengths between C2 and C7. Although the higher temperatures did show a selectivity to methane (roughly 45%), the CO2 selectivity was rather low, below 10% (except at 450°C, which pushed 20%).

The ever-worsening environmental crisis has stimulated development of less wasteful “green” technologies. To this end, tandem catalysis enables multiple catalytic cycles to be performed within a single reaction vessel, thereby eliminating intermediate processing steps and reducing solvent waste. Assisted tandem catalysis employs suitable chemical triggers to transform the initial catalyst into new species, thereby providing a mechanism for “switching on” secondary catalytic activity. This thesis demonstrates the importance of highly productive secondary catalysts through a comparative hydrogenation study involving prominent hydrogenation catalysts of tandem ring-opening metathesis polymerization (ROMP)-hydrogenation, of which hydridocarbonyl species were proved superior. This thesis illuminates optimal routes to hydridocarbonyls under conditions relevant to our ROMP-hydrogenation protocol, using Grubbs benzylidenes as isolable proxies for ROMP-propagating alkylidene species. Analogous studies of ruthenium methylidenes and ethoxylidenes illuminate optimal routes to hydridocarbonyls following ring-closing metathesis (RCM) and metathesis quenching, respectively. The formation of unexpected side products using aggressive chemical triggers is also discussed, and emphasizes the need for cautious design of the post-metathesis trigger phase.

Transition metals are known to be the essential part in most of the catalysts, the heterogeneous and the homogenous catalysts; however, the ligands that attached to the metal centers can also alter the reactivity of the catalyst, and that is widely observed in nature. In our project, we are interested in the metal-ligand cooperation of a special type of ligand called the pincer ligand. Our focus is mainly on the tridentate Pincer Ligands with a pyridine backbone. Also, it contains a spacer that could be deprotonated and protonated during the aromatization and dearomatization process. Aromatization and dearomatization of the pincer ligand are responsible for the unique reactivity of the pincer complexes, especially in the hydrogenation and dehydrogenation reactions. Recently, huge developments have been made in the dehydrogenative coupling of aniline and benzyl alcohol via manganese pincer complexes. The most recent papers on that subject have been done by Beller in 2016[1], Kempe 2018 [2], and Hultzsch 2019 [3]. However, rhenium complexes have not been studied enough even though it is in the same seventh row of the transition metal. Therefore, the rhenium was studied as a possible alternative. Then, the synthesis of a well-defined PN3 rhenium complex was performed from the bipy-tBu ligand and the metal precursor Re(CO)5Cl. The ligand has a unique deformity as the phosphine sidearm is not attached to the metal center. Further investigation of the aniline and benzyl alcohol dehydrogenative coupling via PN3 rhenium pincer complex has been done. An optimal reaction condition was achieved, and the substrate scope was further examined with various alcohols and amines, and the result shows good to moderate conversion with decent selectivity towards the imine. Except for the secondary alcohols.

Rhenium oxides as well as other rhenium compounds are known to display a broad spectrum of catalytic activity,^25 being resistant to attack by acids under nonoxidizing conditions, and showing a remarkable ability to resist poisoning which is a serious limiting factor in many commonly used catalysts. Rhenium catalysts are cheaper than the platinum metals with the exception of palladium. One of the most remarkable properties of the rhenium catalyst is the ability to catalyze the hydrogenation of carboxylic acids and amides to the corresponding alcohols and amines respectively. The carboxyl group (-COOH) is notoriously difficult to reduce catalytically and most of the commonly used catalysts are ineffective in catalyzing the hydrogenation of carboxylic acids. Either hydrogenolysis of the carbon-oxygen bond occurs or the carboxylic acid remains inert. It is for this reason that low molecular weight carboxylic acids are often used as inert solvents in catalytic hydrogenations. This investigation was undertaken to study the effects of various parameters upon product formation in the hydrogenation of carboxylic acids using the catalyst formed from the reduction of rhenium heptoxide i situ. Acetic acid was used throughout the investigation as the representative carboxylic acid. The parameters studied were pressures ranging from 2000 to 3000 psig, temperatures ranging from 115° to 175°, reaction time varied over the range of 0 to 24 hours, the effects on product formation from repeated use of the catalyst, and agitation of reactants during the reaction with emphasis on the optimization of these parameters. In several series of reactions repeated reuse of the catalyst showed that rhenium catalyst can be reused at least 8 times while still achieving greater than 50 per cent reduction. Relative decrease in catalyst activity appears to be greater when temperature and pressure of the hydrogenation are high compared to the range. Experimental data shows that the concentration of ethyl acetate in the product mixture as a function of time passes through a maximum between 1.0 and 1.5 hours. Beyond this maximum there is a relatively rapid decrease in ester concentration. A change in initial hydrogen pressure from 2000 to 3000 psig does not appreciably change the product composition in the reaction mixture while a modest increase, i.e., a temperature increase of 25°, was observed to improve yields of the alcohol by a very significant amount. Moreover, the investigation shows that for a reaction time of 5 hours the "optimum" conditions for reaction are a temperature of 175°, a catalyst to substrate ratio of 1.0 g Re_2O_7/50 g AcOH, and an initial hydrogen pressure of 3000 psig while reactions carried out for only 1.5 hours require a catalyst to substrate ratio of from 1.0 to 2.5 g Re_2O_7/50 g AcOH to effect a quantitative reduction optimally. Whether or not the reaction system was agitated during the warm-up period seemed to have little effect on the composition of the product mixture, however, it was observed that partial reduction takes place during the initial heating period before agitation of the reactor begins. The results of this work have shown that "optimum" conditions for quantitative reduction of acetic acid to the corresponding alcohol are the mildest yet reported and clearly confirm the superiority of the rhenium catalyst over other catalysts in the hydrogenation of carboxylic acids.

Part I. Although substituted cinnolines have been studied quite thoroughly as to the products derived from their hydrogenation, very little work has been done on the catalytic reduction of cinnoline. The purpose of this investigation was to partially complete our knowledge concerning the chemistry of cinnoline by studying its catalytic hydrogenation. Cinnoline was hydrogenated using five different catalysts: 5% Rh/Al_2O_3, 5% Rh/C, 5% Pd/C, RuO_2, and PtO_2. Each of these catalysts was used under neutral and acid conditions with variations in temperature and pressure. Seven compounds were isolated from these hydrogenations, six of which were positively identified as: 1,4-dihydrocinnoline; 1,2,3,4-tetrahydrocinnoline; o-aminophenethylamine; indole, 2,3-dihydroindole; and cis-octahydroindole. The seventh compound that was not positively identified is proposed to be 1,1',4,4' -tetrahydro-4,4'-bicinnoline. An authentic sample of indole was obtained commercially; whereas, 2,3-dihydroindole and cis-octahydroindole were prepared by the hydrogenation of indole by known procedures. An authentic sample of o-aminophenethylamine was prepared by a new unambiguous route, which is reported in this investigation. 1,4-Dihydrocinnoline and 1,2,3,4-tetrahydrocinnoline were identified by their physical constants and infrared spectra. Gas chromatography and thin-layer chromatography were used to identify the products from the catalytic hydrogenation of cinnoline. Qualitative as well as quantitative analyses were carried out using the gas chromatograph, and thin-layer chromatography provided additional qualitative data. Possible mechanisms for the formation of the various compounds resulting from the hydrogenation of cinnoline are discussed. Low-pressure hydrogenations (60 p.s.i. or less) under neutral conditions provided good yields of 1,4-dihydrocinnoline and 1,1',4,4'-tetrahydro-4,4'-bicinnoline. Under acid conditions with low pressure, all catalysts except Adam's catalyst (PtO_2) produced 1,4-dihydrocinnoline-hydrochloride. 1,2,3,4-Tetrahydrocinnoline was the major product from the low-pressure reduction of cinnoline under acid conditions using Adam's catalyst. High-pressure hydrogenations (2000 p.s.i. or greater) were carried out at temperatures of about 125°; these conditions produced more highly reduced products than the low-pressure hydrogenations as would be expected. Very little selectivity is shown by the different catalysts at high pressures. Part II. Gilsonite is a black-shiny carbonaceous material found only in huge vertical fissures located in the Uintah Basin of eastern Utah. While superficially resembling certain types of asphalt, it is remarkable for its unusually high softening temperature and low ash content. These properties make it unique among naturally-occurring hydrocarbon deposits. Gilsonite is presently being used as raw material for gasoline and electrolytic coke. Since the amount of gilsonite available will be consumed before too many years have gone by, it was considered desirable to study some of the naturally-occurring components which make up gilsonite. A knowledge of these components might provide better utilization of this material. Preliminary fractionation of gilsonite was accomplished by extraction with acetone and the removal of the asphaltenes from the acetone extract by precipitation with n-pentane. Further fractionation of the acetone extracts was accomplished using column chromatography followed by thin-layer chromatography. Three fractions were isolated from gilsonite. The first was an asphaltenic mixture obtained by precipitation with n-pentane; the separation of this complicated mixture was not pursued further in this work. The second fraction was a yellow material obtained by elution of the n-pentane soluble fraction with benzene from an alumina chromatographic column. The second fraction was not identified. The third fraction, which was red in color, was obtained chromatographically homogeneous after extensive purification by means of column and thin-layer chromatography. From chemical and spectral data, it is proposed that the red material isolated from gilsonite is a mixture of at least two nickel porphyrins.

The rapid global climate change associated with increasing planetary CO$_2$ levels is possibly one of the greatest challenges existing currently. In order to address this grave problem, a variety of solutions and approaches have been proposed. It is likely that a combination of these approaches would be required to solve the multi-dimensional problem of climate change. One potential approach to mitigate carbon emissions is the concept of a ‘Circular Carbon Economy’. This approach encompasses the concept of capturing carbon emissions and reusing the captured CO$_2$ to make fuels and chemicals using renewable energy. Use of fuels and chemicals manufactured via this approach would thus avoid ‘new’ CO$_2$ emissions and prevent the accumulation of additional CO$_2$ in the atmosphere as these products will be CO$_2$-neutral. The use of CO$_2$-neutral fuels would especially be beneficial as not only would it cause a significant impact on CO$_2$ emissions in terms of volume but also it would provide a way to store energy from intermittent sources like solar, wind etc. Furthermore, these fuels can be used without requiring a significant overhaul of the energy infrastructure. One of the most promising routes for the synthesis of fuels and chemicals from CO$_2$ is via the thermal hydrogenation of CO$_2$ using multifunctional heterogeneous catalysis. Multifunctional catalysis refers to the combination of catalysts having different functionalities into a single reactor (one-pot). This catalytic route is a powerful tool for tuning the product distribution during a reaction and for enhancing the yield of target products. Thus, this PhD Thesis describes the design of several multifunctional catalyst combinations which have been applied for producing various hydrocarbon products of interest from CO$_2$ ranging from light olefins, aromatics and fuel range paraffins. The catalyst combinations consisted of a metal/metal oxide and a zeolite and depending on the configuration used, enhanced the selectivity to target products. Various advanced characterization techniques have also been utilized in order to reveal the status of active species and the underlying reaction mechanism(s).

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第23292号 / エネ博第417号 / 新制||エネ||79(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 石原 慶一, 教授 上髙原 浩 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM