Thesis (M.S.)--Villanova University, 2007. / Chemistry Dept. Includes bibliographical references.

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 16, 2007) Includes bibliographical references (p. 85-89).

Thesis (M.Eng.). / Written for the Dept. of Chemical Engineering. Title from title page of PDF (viewed ). Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains xvi, 108 p. : ill. Includes abstract. Includes bibliographical references (p. 98-108).

Thesis (Ph. D.)--University of Nebraska, 1934.

Liquid organic chemical hydride is a promising candidate for hydrogen storage and transport. Methylcyclohexane (MCH) to toluene (TOL) cycle has been considered as one of the feasible hydrogen carrier systems, but selective dehydrogenation of MCH to TOL has only been achieved using the noble Pt-based catalysts. The aim of this study is to develop non-noble, cost-effective metal catalysts that can show excellent catalytic performance, mainly maintaining high TOL selectivity achievable by Pt based catalysts. Mono-metallic Ni based catalyst is a well-known dehydrogenation catalyst, but the major drawback with Ni is its hydrogenolysis activity to cleave C-C bonds, which leads to inferior selectivity towards dehydrogenation of MCH to TOL. This study elucidate addition of the second metal to Ni based catalyst to improve the TOL selectivity. Herein, ubiquitous bi-metallic nanoparticles catalysts were investigated including (Ni–M, M: Ag, Zn, Sn or In) based catalysts. Among the catalysts investigated, the high TOL selectivity (> 99%) at low conversions was achieved effectively using the supported NiZn catalyst under flow of excess H2. In this work, a combined study of experimental and computational approaches was conducted to determine the main role of Zn over Ni based catalyst in promoting the TOL selectivity. A kinetic study using mono- and bimetallic Ni based catalysts was conducted to elucidate reaction mechanism and site requirement for MCH dehydrogenation reaction. The impact of different reaction conditions (feed compositions, temperature, space velocity and stability) and catalyst properties were evaluated. This study elucidates a distinctive mechanism of MCH dehydrogenation to TOL reaction over the Ni-based catalysts. Distinctive from Pt catalyst, a nearly positive half order with respect to H2 pressure was obtained for mono- and bi-metallic Ni based catalysts. This kinetic data was consistent with rate determining step as (somewhat paradoxically) hydrogenation of strongly chemisorbed intermediate originating from TOL. DFT calculation indicated that Zn metal prefers to occupy the step sites of Ni where unselective C–C bond breaking was considered to preferentially occur, explaining suppression of hydrogenolysis activity. Additionally, it confirmed that the H-deficient species at methyl position group (C6H5CH2) was stable on the surface, making its hydrogenation being rate determining step, consistent with positive order in H2 pressure on TOL formation rate. This may explain the conclusive role by H2 in facilitating desorption of the H-deficient surface species that was produced through further dehydrogenation of TOL.

No description available.

Abstract Not Provided / Thesis / Master of Science (MSc)

The sulfonation of chlorobenzene, chlorobenzene-benzene, and toluene-benzene mixtures by sulfur trioxide in liquid sulfur dioxide at -12.5° C. was studied to obtain isomer distribution and relative rate data. The isomer distribution for the reaction on chlorobenzene was determined by an isotope dillution technique. Relative rate experiments were conducted by sulfonating C14 labeled benzene in competition with nonradioactive chlorobenzene and toluene and the count rate of the products was used to determine product composition. Ultraviolet spectrophotometry was also used to investigate variations in isomer distributions as a function of sulfur trioxide concentration. The apparent relative rates of sulfonation (kX/kB) as calculated by Ingold's equation, vary with both the initial ratio of arenes and the concentration of sulfur trioxide. The ortho/para ratio decreases with increasing sulfur trioxide concentration. These observations are explained in terms of secondary sulfonation reactions which produce significant amounts of product sulfonic acids by reaction of the arenes with reagents other than sulfur trioxide. The secondary sulfonating agents are presumed to be sulfonic acid anhydrides and/or pyrosulfonic acids. The secondary reactions contribute proportionately more to the total product of that species formed in the smaller amounts by the primary reaction. Criteria for the applicability of Ingold's equation are discussed in connection with the possibility of secondary reactions. Relative rate constants for competitive chlorobenzene:benzene and toluene:benzene sulfonation with sulfur trioxide, corrected for secondary reaction effects, are 0.087±0.002 and 27.0±1.0 respectively. The observed isomer distribution for the sulfonation of chlorobenzene is o = 0.95 ± 0.03%, m = 0.09 ± 0.02%, and p = 98.96 ± 0.12%. Partial rate factors calculated for the sulfonation of chlorobenzene and toluene are pf = 0.517, of = 0.0025, mf = 0.00024 and pf = 144.6, of = 81.2, and mf = 0.59 respectively. Neither sulfonation fits the selectivity relationship predicted for it, although correction for secondary reaction effects greatly improves the fit for the toluene data. The deviation of the toluene data from the selectivity relationship probably results from a low percentage of meta isomer in the reported isomer distribution for toluene.

Groundwater contamination by man-made chemicals is increasingly being reported in the United States. The potential for detrimental health effects is substantial and has been addressed by the environmental engineering profession. Typically, contaminated groundwater is pumped to the surface and treated in a variety of methods including air stripping, carbon adsorption, and biodegradation. In situ biodegradation is increasingly being considered as an alternative to pump-and-treat technology. The primary goal of this research was to determine the fate of an organic chemical adsorbed to a subsurface soil when exposed to acclimated bacteria. Toluene was chosen as a representative compound because it is a major constituent of groundwater contaminated by gasoline. In addition, toluene is known to be both biodegradable and adsorbable. Sybron Biochemical, Inc. supplied the aerobic bacteria Psgudomonas gutjga known to readily transform toluene. Soil microcosms were established in test-tubes and conditions simulated those of a saturated, aerobic aquifer. Gas chromatography was used to quantify changes in toluene concentration due to adsorption and biodegradation. The addition of an aqueous toluene solution to sterile microcosms resulted in the rapid and extensive adsorption of toluene to the soil. Subsequent analysis revealed the slow adsorption of an additional small fraction of toluene. Biodegradation studies entailed the addition of acclimated bacteria to sterile soil microcosms in which substantial toluene adsorption had occurred. Addition of small doses of hydrogen peroxide effectively maintained aerobic conditions for biodegradation. As a result, E, putjda was able to transform all measurable toluene in the microcosms. Additional desorption studies revealed that a "resistant" component of toluene remained adsorbed to the soil during biodegradation. This component was neither acted upon by bacteria nor readily extractable by methylene chloride. However, slow desorption of toluene was shown to occur at a rate comparable to slow adsorption. To achieve complete removal, groundwater treatment methods must address the rate-controlled desorption of the resistant toluene component. / Master of Science