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No description available.

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The purpose of this research project was to evaluate the feasibility of producing hydrocarbons by liquid phase hydrogenation of carbon dioxide. Initial studies dealt with the evaluation of ruthenium (III) chloride over a wide range of reaction conditions. High conversions were observed and were found to vary with catalyst concentration, temperature and time. Conversion of carbon dioxide reached 73% after twenty-four hours at a catalyst concentration of 0.75g/mole of CO2 feed. The hydrogen to carbon dioxide ratio was found to have a significant effect on product distribution and amount of methane produced. For example, low ratios of H2/CO2 gave large amounts of high molecular weight hydrocarbons, while relatively more methane was formed at high H2/CO2 ratios. An attempt was made to determine whether the reaction was taking place in the gas phase or the liquid phase or both. A number of solutions were tested, with sodium hydroxide solutions exhibiting the best results. Since the carbon dioxide feed gas dissolves in this solution immediately to form carbonate species, it is assumed that the hydrogenation reaction takes place through a carbonate species in solution. This mechanism is supported by the observation that the carbonate molarity in solution strongly affected the conversion. The conversion of carbon dioxide over different molarities of sodium hydroxide was observed to exhibit a maximum at the concentration of sodium hydroxide, which give the maximum NaHCO3 concentration. Sodium carbonate and sodium bicarbonate solutions were also tested as starting reagents in the hydrogenation reaction. Conversion was found to be 10.68% for sodium carbonate and 15.88% for sodium bicarbonate, compared with 19% conversion of carbon dioxide under the same reaction conditions. These data suggest that the major part of the hydrogenation reaction takes place through a HCO3 species in solution. The rate of hydrogenation of sodium bicarbonate and sodium carbonate were found to be first order in catalyst concentration. A linear relationship was also found to exist between conversion of carbonate species and temperature in the range of 150-300°C. Three catalyst systems; RuCl3, Ru metal and 1% Ru supported on graphite were tested in the hydrogenation of carbon dioxide over sodium hydroxide solutions. One percent Ru on graphite exhibited the fastest rate at which equilibrium was achieved, with a 76-77% conversion of carbon dioxide to methane, and higher hydrocarbons being observed after 24 hours. Thea activity of Ru metal catalysts was observed to decrease during the course of the reaction, probably because of the loss of active catalyst sites, due to fusing of the catalyst on the surface of the glass liner. The rate of reaction between carbon dioxide and hydrogen over RuCl3 in the gas phase was found to be faster than the rate of this reaction in the liquid phase. In the gas phase reaction, equilibrium was achieved after 24 hours, with 89% conversion of carbon dioxide to methane and higher hydrocarbons, compared with 70% conversion in the liquid phase, under the same reaction conditions. One percent Ru supported on graphite exhibited a faster rate of reaction in the gas phase than in the liquid phase. But the rate of the reaction over Ru metal was faster in the liquid phase than in the gas phase. Table I summarized the comparison between the gas phase and the liquid phase hydrogenation reaction for the three catalytic systems under the same reaction conditions.

The feasibility of separating piperylene (1,3-pentadiene) from a mixture of five-carbon olefins and diolefins with Linde 5A Molecular Sieves was investigated. Olefins and especially diolefins are very reactive and tend to polymerize on the highly polar adsorptive surface thereby clogging the pores of themolecular sieve. It is believed that the acid sites within the zeolite cages catalyze this polymerization reaction and that poisoning of these sites by adsorption of a nitrogenous base (ethylenediamine, dimethylamine or ammonia) or hydrogen sulfide inhibits the formation of polymers. Two criteria were used in the evaluation of the polymerization inhibitors tested. First, a series of consecutive runs (adsorption, purge, and desorption cycle) were made with the pretreated molecular sieves. The adsorption capacity (grams adsorbate/grams of molecular sieve) and percent desorption of adsorbate (grams desorbed adsorbate/grams adsorbate) were plotted to determine the relative amount of polymer buildup on the molecular sieve with the various candidate polymerization inhibitors. Secondly, the desorbed adsorbate (product) collected from a cold trap during the desorption step was analyzed by gas chromatography and the product quality, with respect to 1,3-pentadiene, was determined. Dimethylamine was found to be the best polymerization inhibitor of those tested when evaluated in this manner.

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Detection, identification and separation of polycyclic aromatic compounds in environmental samples are of extreme importance since many of these compounds are well known for their potential carcinogenic and/or mutagenic activities. Selective quenching of molecular fluorescence can be utilized effectively to analyze mixtures containing different polycyclic aromatic hydrocarbons. Molecularly organized assemblies are used widely in detection and separation of these compounds mainly because of less toxicity and enhanced solubilization capabilities associated with these media. Feasibility of using nitromethane and the alkylpyridinium cation as selective fluorescence quenching agents for discriminating between alternant versus nonalternant polycyclic aromatic hydrocarbons (PAHs) is critically examined in several molecularly organized micellar solvent media. Fluorescence quenching is used to probe the structural features in mixed micelles containing the various combinations of anionic, cationic, nonionic and zwitterionic surfactants. Experimental results provide valuable information regarding molecular interactions between the dissimilar surfactants.