Norman I. Dowling

Conversion of CS2 and COS over alumina and titania under Claus process conditions: reaction with H2O and SO2

Catalytic conversion of CS2 in the Claus process using either alumina or titania has always been assumed to proceed via hydrolysis. Although this conclusion is supported by the results of this study, data reported here show that the high CS2 conversion activity of titania may be due, in part, to the reaction of CS2 with SO2, a process which proceeds almost quantitatively at 320°C. This reaction was also shown to have an appreciable rate at 250°C, suggesting that some of the CS2 conversion activity of titania at second Claus converter conditions may be due to reaction with SO2. COS was identified as an intermediate product of the reaction of CS2 with SO2. Although these studies confirmed that alumina promotes hydrolysis of CS2, the industrial observation that it is not as efficient a catalyst as titania for the conversion of CS2 may be due to the limited ability of alumina to promote reaction of CS2 with SO2.

The chemistry of organosulphur compound types occurring in heavy oils: 4. the high-temperature reaction of thiophene and tetrahydrothiophene with aqueous solutions of aluminium and first-row transition-metal cations

In the reactions of thiophene and tetrahydrothiophene with aqueous solutions of first-row transition-metal and aluminium cations at 240 °C and 3.4 MPa all the metal species accelerated the decomposition of the thiophenes in relation to equivalent reactions with pure water. Al3+, Sc3+, VO2+, Cr3+, Ni2+ and Cu2+ were most reactive towards thiophene and Al3+, VO2+, Cr3+ and Cu2+ were most reactive towards tetrahydrothiophene. Principal products were H2S and complex mixtures of organic products. The presence of CO2 and oxygen-containing organic products revealed that water was involved in direct chemical reaction with the substrates. It is likely that these model reactions parallel more complex processes that occur during the steam-stimulated recovery of oil-sand bitumen and other high-sulphur oils.

Chemistry of organosulphur compound types occurring in heavy oil sands: 5. Reaction of thiophene and tetrahydrothiophene with aqueous Group VIIIB metal species at high temperature

Abstract As part of a study of organosulphur compounds in heavy oil sands, the interaction of thiophene (1) and tetrahydrothiophene (10) with aqueous solutions of Group VIIIB metal species at 200–240 °C has been investigated. Thiophene was the more reactive and the greatest degree of reaction was observed with the second- and third-row members of the Group VIIIB metals. Aqueous Pt(IV) gave most reaction for both substances. Desulphurization of the sulphur compounds was significant, although conversion to more complex organic substances, including dithienyls and benzothiophene, account for > 50 wt % of the total reaction for most metal species. The presence of CO2 in the products showed that water was involved in the reaction. Reactions with thiophene produced only minor amounts of C1C4 hydrocarbons, but significant quantities were obtained from reactions with tetrahydrothiophene.

COMMENTS ON THE ROLE OF H2S IN THE CHEMISTRY OF EARTH'S EARLY ATMOSPHERE AND IN PREBIOTIC SYNTHESIS

Abstract: Free energy calculations and experimental measurements have been used to show that H2S/CO2 mixtures outgassing from a prebiotic Earths crust would have produced a reducing gas mixture containing CO, H2, H2O, and Sx as principal components. Due to rapid recombination of H2, CO, and Sx to H2S and CO2 on cooling from a high temperature to ambient conditions, reducing components would have been retained only if efficient quenching of the reduced gas mixture had been possible. Consequently, subsea vents or vents with efficient infusion of water would have been ideal sites for retention of reduced species and for prebiotic organic synthesis. It is suggested that C/H/O/S ratios are important factors in controlling the degree of prebiotic organic synthesis and, hence, the emergence of life, since if oxygen is abundant, CO2 and SO2 would have been dominant species.

Capture of solar energy using elemental sulfur

Use of the equilibrium sulfur vapour system as the basis for a thermochemical solar energy conversion system is suggested. This chemical system is shown to be both thermodynamically and kinetically well suited, as well as possessing several other desirable features. A key advantage is provided by reliance on the proven mature Claus technology for materials handling and the heat recovery stage of the proposed scheme.

Oxidative dehydrogenation of propane to propene in the presence of H2S at short contact times

The oxidative dehydrogenation of propane to propene at short contact times over V2O5/A12O3 was remarkably enhanced by the introduction of H2S in the feed mixture. Overall conversion of propane over this catalyst at 700 °C and 5 ms contact time was 53.7% with selectivity to propene of 56.5%, providing a net propene yield of 30.4%.

Analytical procedure for the determination of trace carbon impurity in elemental sulfur

An analytical procedure has been developed for determining trace levels of carbon in elemental sulfur based on the standard combustion technique and incorporating gas chromatographic (GC) analysis of the products. Laboratory testing has shown a relative error of 5 ppmw or 5%, whichever is greater, in the results of the analysis for carbon contents of 50 ppmw and above and detection threshold of 15 ppmw carbon, along with good reproducibility.