Rayford G. Anthony

Methane and methanol synthesis over supported palladium catalysts

Abstract Hydrogenation of carbon monoxide has been studied between 260 and 340 °C and 5 and 50 atm of pressure over palladium supported on three different silicas and on HY and NaY zeolites. Fresh and used catalysts were characterized by chemisorption, temperature-programmed desorption, X-ray diffraction, electron microscopy, and photoelectron spectroscopy studies. The selectivity and the activity of the catalysts are strongly dependent on the nature of the support and on the state of the metal on its surface. Methanol is produced on the catalysts exhibiting small size crystallites on which CO is weakly adsorbed, whereas the formation of methane is directly related to the density of acidic sites at the surface of the support. Under the experimental conditions the palladium undergoes structural and electronic modifications due to transformations into hydride phases. These transformations lead to a cracking of the metal crystallites and to changes in the reaction rate expressions.

Kinetic studies of upgrading pine pyrolytic oil by hydrotreatment

Pyrolytic oil, produced by the Tech-Air Corporation from Southern Pine sawdust and bark, was hydrotreated in a trickle bed reactor system. Changes in product composition as a function of reaction temperature, hydrogen pressure, space velocity and catalyst type were determined quantitatively by size exclusion chromatography - gas chromatography (SEC-GC) analyses and elemental analyses. The catalysts used in the reactions were Pt/Al2O3/SiO3, and sulfided CoMo/γ-Al2O3, Ni-W/γ-Al2O3 and Ni-Mo/γ-Al2O3. The reaction temperatures ranged from 623 K to 673 K, and the reaction pressures varied from 5,272 kPa (750 psig) to 10,433 kPa (1,500 psig). Weighthourly space velocity was changed from 0.5 to 3.0 h−1. Two models, one for overall oxygen removal and the other for the compositional changes in hydrotreated oil, were developed. Oxygen removal was not a function of space velocity and was modeled by an empirical function of temperature and pressure. A pseudo first order reaction network was used to relate the kinetics of a five “lump” model.

Selective adsorption and ion exchange of metal cations and anions with silico-titanates and layered titanates

Metal ions may be removed from aqueous wastes from metal processing plants and from refineries. They may also be used in concentrating radioactive elements found in dilute, aqueous, nuclear wastes. A new series of silico-titanates and alkali titanates are shown to have specific selectivity for cations of lead, mercury, and cadmium and the dichromate anion in solutions with low and high pH. Furthermore, one particular silico-titanate, TAM-5, was found to be highly selective for Cs+ and Sr2+ in solutions of 5.7 M Na+ and 0.6 M OH−. A high potential exists for these materials for removing Cs+ and Sr2+ from radioactive aqueous wastes containing high concentrations of Na+ at high and low pH.

An NMR study of acid sites on sulfated-zirconia catalysts using trimethylphosphine as a probe

Concentrations of Brønsted and Lewis acid sites on sulfated-zirconia catalysts were determined using the31P MAS NMR spectra of adsorbed trimethylphospine. A sample that had been calcined and exposed to air for a long period exhibited only Brønsted acidity; however, treatment of the sample at progressively higher temperatures resulted in the development of at least three types of Lewis acidity, along with a decrease in the concentration of Brønsted acid sites. In a related study the activity of these catalysts for the alkylation of isobutane with 2-butene was determined. The aged catalyst was inactive, but activation of the material at 100°C resulted in the most active catalyst. Thermal treatment at higher temperatures resulted in a loss in activity which paralleled the decrease in the Brønsted acid sites. These results are consistent with a model in which strong Brønsted acidity is a result of the interaction between bisulfate groups and adjacent Lewis acid sites.

Characterization of organically pillared zirconium phosphates

Abstract Samples of α-zirconium phosphates and of zirconium phosphates pillared by phenyl, dimethylphenyl, and diphenyl have been characterized by BET surface area, surface acidity, adsorption capacity and pore sizes, TGA, X-ray powder diffraction, and activity for isopropanol decomposition. The BET surface areas of pillared zirconium phosphates have been found to increase with the increase in size and number of organic groups in the interlayers. The total number of surface acidic sites of α-zirconium phosphates has been found to be greater than any one of the pillared catalysts. It is concluded from this study that α-zirconium phosphate pillared by diphenyl has interlayer openings large enough to sorb isopropanol, and its decomposition takes place mainly in the interlayers of this catalyst. In contrast, the phenyl and dimethylphenyl pillared zirconium phosphates have less free space between the interlayers so that the reactions of isopropanol take place on the outer surface of the catalysts. The dehydration of isopropanol to propylene has been found to be the primary reaction for all the catalysts.

Synthesis and characterization of CoAPO-5, a cobalt-containing AlPO4-5

Abstract Samples of AlPO 4 -5, containing a partial substitution of Co(II) for Al(III), were prepared. The results clearly indicated that, as the level of Co(II) added increased, so did the amount of an impurity phase. At low levels of Co addition, the impurity phase was white and may largely be AlPO 4 -5. Above about 14 mole% of cobalt addition, an amorphous cobalt aluminum phosphate impurity phase was formed and increased in content until no crystallization was observed at a 35 mole% Co addition level. Addition of base (NH 4 OH, NaOH) resulted in increased impurity levels but promoted single crystal growth. Analytical, X-ray, ion exchange, thermogravimetric, and surface-area measurements indicated that only a portion of the cobalt substituted for aluminum, whereas some was present in the ion-exchange sites. The results further indicate that excess alumina is occluded in the CoAPO-5 channels.

Separation of coal-derived liquids by gel permeation chromatography

Abstract Coal-derived liquids, obtained from pilot plants and bench-scale reactors, have been separated by gel permeation chromatography into aromatic, phenolic, and asphaltenic fractions, where asphaltenes and long-chain hydrocarbons are in the same fraction. The Chromatographie system uses 10 nm μStyragel columns and solvents such as tetrahydrofuran (THF) and toluene. The separation is reasonably clean and almost devoid of overlapping. The saturated hydrocarbons are separated from the asphaltenes by vacuum distillation. Aromatic, phenolic and aliphatic fractions are characterized by high-resolution gas chromatography—mass spectrometry. The phenolic fraction contains alkylated phenols, indanols, and naphthols. The aromatic fraction is composed of alkylated benzenes, indans, naphthalenes and small amounts of multi-ring aromatics such as alkylated fluorenes and pyrenes. Most of the long-chain hydrocarbon fraction is of straight-chain alkanes ranging from tetradecane to tetratetracontane. Some branched alkanes, such as pristane and phytane, are also present. If olefins are present in the sample they also separate with the long-chain hydrocarbon fraction. Although various analytical data such as i.r., n.m.r., molecular size distribution and elemental composition of asphaltenes have been obtained, the chemical characterization is not complete. The gel permeation Chromatographie separation technique, as discussed in this paper, is very useful for fast analysis of any coal-derived liquid.

Chemistry of Texas lignite liquefaction in a hydrogen-donor solvent system

Abstract To study the nature of chemical cleavage and resultant product transfer from solid lignite phase to liquid phase, autoclave (300 cm 3 ) experiments have been carried out at pressures ranging up to 34 MPa and temperatures of 380–390 °C. The charge to the autoclave was freshly mined wet lignite, tetralin and hydrogen or helium. To obtain an indication of the reaction mechanisms underlying the liquefaction process, liquid and gas samples from the reactor at different time intervals were analysed. The gas samples were analysed by use of a multi-column, multi-valve automated gas Chromatograph, a system specially fabricated for coal-derived gas analysis. The liquid sample was filtered through Millipore filters and separate into three fractions by gel permeation chromatography. Fraction 1 is mostly colloidal carbon and high-molecular-weight species which cannot be separated on a g.c. Fractions 2 and 3 were analysed by gas chromatography — mass spectrometry (g.c.-m.s.). Fraction 2 represents the liquid products released from lignite and fraction 3 is mostly the tetralin and tetralin-derived products. Gel permeation chromatography (g.p.c.) followed by gas chromatography (g.c.) was used to devise a method for monitoring the extent of liquefaction. The production of carbon dioxide is at a maximum before the liquefaction reactions are at a significant rate. The source of carbon dioxide appears to be the carboxylic groups in lignite. The liquefaction reactions consume hydrogen from tetralin which undergoes dehydrogenation to form naphthalene. Once the lignite has undergone depolymerization, the tetralin to naphthalene conversion slows down. The continued heating of lignite conversion products in excess of tetralin does not appear to alter the molecular size distribution of the liquid product. The distillable fraction of lignite-derived liquid is composed of various alkylated phenols and aromatics and alkanes, and they are formed simultaneously.

CATALYTIC CONVERSION OF METHANOL TO LOW MOLECULAR WEIGHT OLEFINS

Abstract Methanol is converted by use of an ion exchanged Chabazite catalyst to ethylene, propylene and propane with yields of 35, 30 and 25%respectively. The presence of water in the feed increases the selectivity towards ethylene. An increase in pressure from one to 27 atmospheres decreases the yield of ethylene while increasing the yields of propylene and propane. Carbon disulfide in the feed at 6000 ppm changes the character of the catalyst from an olefin producing catalyst to a dehydrogenation catalyst. Carbon disulfide in the feed at 2000 ppm, increases the life of the catalyst in producing olefins. Dimethyl ether accelerates the deactivation process in conversion to olefins. The use of a chabazite catalyst as described herein offers an attractive alternative route for producing olefins from coal based methanol.

Mathematical simulations of the performance of trickle bed and slurry reactors for methanol synthesis

Abstract Three- and two-phase reactor models were developed to simulate the performance of trickle bed and slurry reactors for methanol synthesis. The combination of orthogonal collocation and quasi-linearization was used to solve the trickle bed reactor model incorporating resistance to interparticle and intraparticle diffusion and resistance to mass transfer between gas and liquid phases. Model parameters were estimated independently from either published correlations or literature data. The model predicts significant resistance to intraparticle diffusion on the performance of trickle bed reactors. However, comparisons between pilot size trickle bed and slurry reactors illustrate the superior performance of trickle bed reactors over the slurry reactors for methanol synthesis even with diffusion limitations.