Jennifer S. Holmgren

Solid base catalysts for mercaptan oxidation

Abstract Aqueous alkali can be completely replaced in the mercaptan oxidation reaction by incorporating solid basic materials into the catalyst formulation. The ability to use a solid oxide base to replace aqueous alkali will have a positive environmental impact because aqueous alkalis, such as caustic, are becoming a serious disposal problems for petroleum refiners and chemical manufacturers. The basic oxide system used contains cobalt phthalocyanine (CoPc) supported on a metal oxide solid solution (MOSS). Although active for mercaptan oxidation, this catalyst does not meet the lifetime requirements for commercial application. Three deactivation mechanisms have been identified: rehydration of the MOSS back to the layered double hydroxide (LDH) (because this rehydration causes a reduction in the basicity of these materials), deactivation by adsorption of heavy hydrocarbon species in the feed, and irreversible adsorption of acidic species from the feed. Knowledge of the deactivation mechanisms has allowed the design of a process that meets the required catalyst lifetime requirements. This process represents one of the first applications of solid base catalysis to a commercial process. Catalyst performance, factors affecting deactivation, and methods of preventing deactivation are discussed.

Spectroscopic investigations of borosiloxane bond formation in the sol-gel process*

The formation of borosilicate glass by the sol-gel process has been monitored during all stages, from the initial alkoxide solution to the final heat-treated product, using nuclear magnetic resonance and infrared spectroscopy as well as chemical analysis. The reactions of boric acid and trialkyl borates with silicon alkoxides and their hydrolysis mixtures have been studied for various compositions and catalysts. For all samples it was found that there exists only a small number of borosiloxane (-B-O-Si-) bonds at the time of gelation, the majority of boron being in the form of boric acid. This boric acid is condensed to borosiloxane bonds only upon heat treatment of the dried gel. For compositions having higher boron contents a small number of -B-O-B- bonds are also formed, which do not convert to -B-O-Si- upon heating to 500 °C.

Solid state 29Si and 11B NMR studies of sol-gel derived borosilicates☆

Abstract Gels in the system SiO 2 B 2 O 3 were prepared from metal alkoxides. The structural evolution of these gels as a function of thermal treatment was studied by high field 29 Si and 11 B NMR spectroscopy, using magic angle spinning. The results corroborate earlier work on this system using infrared spectroscopy to follow the formation of borosiloxane bonds during heat treatment. While incorporation of boron into the silica backbone is negligible in gels dried at room temperature only, thermal treatment drives the borosiloxane bond formation with removal of excess water. Initial boron incorporation involves the formation of terminal BOSi groups with tetrahedral boron environments. Further heating causes the condensation of boron into symmetric trigonal BOSi sites. Boron is fully incorporated by 450°C. In addition to the symmetric trigonal boron environment of borosiloxane bonds, a small signal is also observed from 11 B nuclei in asymmetric trigonal environments in the gels heated to ⩾ 450°C, presumably due to the formation of borate chains (BOB) which were previously observed with infrared spectroscopy.

27Al and 29Si NMR study of sol-gel derived aluminosilicates and sodium aluminosilicates

Solid state 27Al and 29Si NMR was used to examine the structures of aluminosilicates and sodium aluminosilicates prepared by the sol-gel method from metal alkoxides. In contrast to the borosilicate system, where B-O-Si bonds are not formed until heat treatment above 150° C, Al-O-Si formation appears complete upon gelation. Aluminium occupies tetrahedral [AlO4]− sites in the polymer network and octahedral [Al(H2O)6]3+ (or similar) sites in the intersticies for charge balance. When sodium is added as a counter ion the octahedral aluminium is converted to tetrahedral aluminium in the oxide network. In gels of high aluminium content prepared from (BusO)2Al-O-Si(OEt)3, some aluminium in five coordinate environments is also observed. All gels remain amorphous on heating to 800° C.

Methylene-carbonyl coupling: formation of bridging .eta.3-ketene and .eta.4-oxaallyl complexes.

Etude structurale et par RMN des complexes Ru 3 (CO) 7 (η 3 -(C,C,O), μ 3 -COCH 2 )(μ-CH 2 )(dppm) et Ru 2 (CO) 5 (η 4 -C,C,C,O), μ-CH 2 C(O)CH 2 )(dppm)

Strategies and applications of combinatorial methods and high throughput screening to the discovery of non-noble metal catalyst

Abstract The integrated End-to-End™ combinatorial process for catalyst preparation and screening, with emphasis on its capability to vary both process and compositional parameters will be demonstrated. Additionally, each step of the combinatorial screening process has been validated against results from traditional screening methods. The greatest challenge of all has been the adherence to the core concepts of the combinatorial approach. Catalyst libraries have been made and tested for naphthalene dehydrogenation chemistry. The preparation of these libraries has included the application of high throughput techniques for: 1. metal impregnation; 2. catalyst finishing; 3. catalyst screening. The catalyst screening system has been used to find a non-noble metal catalyst system that can replace Pt in dehydrogenation applications in the petroleum industry. A proprietary catalytic composition was developed for the dehydrogenation of methylcyclohexane (MCH) to toluene starting with four non-noble metals of different proportions and four different supports (alumina, titania, zirconia and silica) prepared in different ways and applying a statistical design of experiments. These data demonstrate that all steps of catalyst preparation and screening are performed in a rapid, useful, high throughput manner. Data will be presented from the catalyst screening efforts will demonstrate that optimized metal composition is dependent on the support type.

Solid-state 29Si NMR study of polycondensation during heat treatment of sol-gel-derived silicas

Abstract Solid-state magic angle spinning (MAS) and cross-polarization (CP)-MAS 29 Si NMR spectroscopy was used to monitor polycondensation in alkoxide-derived silica gels during thermal treatment from 25 to 800°C. Gels prepared from tetramethylorthosilicate under both neutral and basic conditions were studied and differences in the evolution of chemical structure during thermal treatment are readily observed by NMR. As thermal treatment proceeds the extent of condensation parallels the BET surface area. For uncatalyzed gels, the amount of cross-linking increases and the BET surface area decreases on each step of heating through 800°C. The base-catalyzed gel depolymerizes slightly on heating from 150 to 450°C, accompanied by a slight increase in BET area, then undergoes extensive cross-linking on heating from 450 to 800 °C, with a large decrease in surface area. After heating to 800°C both gels have similar degrees of cross-linking and surface area.

Observation and interpretation of HH coupling in 1H187Os satellite NMR spectra

Abstract The single hydride resonance observed for each of the compounds H 3 Os 3 (CO) 9 CX (X = OMe, Br, H) has one set of 187 Os satellites which are further split into doublets by HH coupling. The implications of this observation for structural assignments based on 187 Os satellites are discussed.

DIRECT IMAGING OF ZIRCONIA PILLARS IN MONTMORILLONITE BY ANALYTICAL ELECTRON MICROSCOPY

Analytical electron microscopy was used to confirm the location of pillars of zirconia in pillared montmorillonite. Data show that the pillared clay is of “high” quality, with surface areas ranging from 200 to 250 m2/g and (001) spacings in the 17–18 Å range. The zirconia-rich pillars were observed using bright-field imaging, annular dark-field imaging, and energy-filtered imaging. The composition of the pillars was confirmed by performing nano-analysis using energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy. The pillars apparently have an irregular shape <50 Å in size. The shape and relatively large size of the pillars suggest that zirconia dispersion is not ideally distributed in this sample. This study is apparently the first report of electron microscopy observation of pillaring material in clays.

Scaling Up of Catalysts Discovered from Small-Scale Experiments

The chemical industry faces a challenging business climate due to difficult economic conditions in much of the world, strong international competition, and worldwide environmental concern. In addition, innovation in this industry has slowed as catalyst and process technology has matured. The need for a methodology that can increase catalyst innovation while continuing to decrease cycle times has been recognized by the Council for Chemical Research (Catalysis Roadmap, Vision 2020) [1]. In the 1980s, the pharmaceutical industry faced similar circumstances. Downward pressure on drug prices became incompatible with the high cost of drug discovery. Combinatorial chemistry, based on advances in laboratory automation, high-throughput synthesis, and activity screening, allowed the pharmaceutical companies to break the innovation impasse [2, 3].