Showing papers in "Preprints-American Chemical Society Division of Petroleum Chemistry in 2005"

Biodesulfurization of dibenzothiophene by immobilized cells of Pseudomonas stutzeri up-1

Abstract: Immobilization of the bacterium Pseudomonas stutzeri UP-1 was isolated from soil and sewage in the Shengli Oilfield. Biodesulfurization (BDS) of dibenzothiophene (DBT) was carried out using immobilized P. stutzeri UP-1 (CGMCC No. 0974) in model system. The results show that sodium alginate (SA) is an appropriate material of immobilization. The optimized operation immobilization condition was 4 °C; the concentration of SA was 3% (w/v); and the ratio of SA (ml) to cells (g) was 20. The stability and life-time of immobilized cells were much better than those of the non-immobilized cells. The life-time of immobilized cells could reach 600 h by reactivation.

Growth kinetics of ethane hydrate from a seawater solution at an ethane gas interface

Abstract: The growth rate and morphology of discs of natural gas hydrate at an interface between seawater and ethane gas is reported. Ethane hydrate crystals, that has the macroscopic appearance of concentric rings, were nucleated and grown from a seawater solution under a range of supersaturation conditions. The nucleation rate was determined by plotting the increase in the number of observed particles with time. Growth consistently approached a maximum rate, which suggests a diffusion-limited process. The disks eventually agglomerated to completely cover the interface.

Effects of gas hydrates on the chemical and physical properties of seawater

Abstract: Huge deposits of oceanic methane hydrate (MH) exist on the seafloor on continental margins. MH transforms into water and methane (CH 4 ) gas in bubbles when it dissociates in seawater. That CH 4 may be oxidized (via bacteria) into carbon dioxide (CO 2 ) before the bubbles rise to the sea surface or dissolve into seawater again. Similarly, nitrogen hydrate is expected to exist in seawater. The nitrogen coming out of nitrogen hydrate can be fixed and oxidized into nitrate. Analysis of the relationship among seawater temperature, “apparent oxygen utilization” (AOU) and the concentration of CO 2, , based on WOCE ocean observations, reveals some characteristics that are not part of a stoichiometry relation. Analysis of individual profiles implies that the dissociation of gas hydrates occurs according to temperature and pressure (depth) at hydrate phase boundary. A quantity, named as virtual oxygen utilization (VOU), is calculated to account for the depletion of dissolved oxygen in seawater due to biochemical oxidation processes. The results show a good agreement between AOU and VOU at depth greater than the level where hydrates dissociate. The VOU is less than AOU in the layer of seawater beneath the euphotic zone. That is attributed to the escape of CO 2 into the atmosphere. The oceanic MH provides a huge biochemical fuel source to generate heat internal to world oceans. This may explain the observed ocean warming at the intermediate depth during last several decades. The role of microbes in altering the chemical and physical properties of seawater and the course of climate change cannot be ignored.

The correlation between double bond isomerization, water gas-shift and acid production during Fischer-Tropsch synthesis

Abstract: Fischer-Tropsch synthesis (FTS) over an iron catalyst is mainly focused on producing waxy crude, fuels and olefins. Essentially low concentrations of oxygenates are produced. These oxygenates include alcohols, aldehydes, ketones and acids. Acid production is of immense importance because of downstream refinery workup. During the evaluation of a wide range of iron catalysts for Low Temperature Fischer-Tropsch (Fe-LTFT) a correlation was found between the degree of isomerization and the acid production. Oxidation of the catalyst surface by water to form magnetite results in an increase of Water-Gas-Shift (WGS) activity. The increase in WGS activity corresponded to an increase in rate of acid production. Furthermore, the increase in acid production corresponded to a decrease in the isomerization of alphaolefins.

The role of accumulated carbon in deactivating cobalt catalysts during FT synthesis in a slurry-bubble-column reactor

Abstract: The H 2 reactivity of carbon-related phases in slurry-bubble column used FT catalysts was studied using TGA-MS techniques. While the hydrogen treatment is quite effective at removing paraffinic wax components at relatively low temperature, about 250°C, a fraction of the carbon was resistant to hydrogen even at 350°C. This fraction of the carbon in used FT catalysts increases as on-stream-time increases. Regenerating the catalyst with a procedure that includes an oxidation step removes much of this residual carbon. However, a small fraction of the H 2 -resistant carbon can still be present in the regenerated FT catalyst. Based on chemisorption measurements, H 2 -resistant carbon interacts with metallic Co, considerably decreasing its active surface. Loss of catalyst productivity is found to be proportional to the amount of this hydrogen-resistant carbon remnant. Therefore, a slow, secondary production of this, likely polymeric, carbon, during the FT synthesis, is one of the causes for catalyst deactivation.

Development of bimodal cobalt catalysts for Fischer-Tropsch synthesis

Abstract: Abstract A new and simple method for preparing multi-functional nano-sized silica-silica or zirconia-silica bimodal pore catalyst support was developed by direct introduction of silica or zirconia sols into silica gel. The pores of the obtained bimodal pore supports distributed distinctly as two kinds of main pores. On the other hand, the increased BET surface area and decreased pore volume, compared to those of original silica gel, indicated that the obtained bimodal pore supports formed according to the designed route, and it is found that the zirconia-silica bimodal support improved catalyst activity significantly via not only spatial effect, the intrinsic property of the bimodal structure, but also chemically promotional effect of zirconia, when this kind of support was applied in the liquid-phase Fischer–Tropsch synthesis (FTS) as a cobalt-loading catalyst.

Synthetic lubricants: Advances in Japan up to 1945 based on Fischer-Tropsch derived liquids

Abstract: A review of Japanese technology regarding lubricants from Fischer-Tropsch derived liquids that was developed before and during World War II is presented. Extensive studies were performed on cracking FT liquids to make charge stock for an AlCl3 polymerization plant to make an aircraft lubricating oil. The physical properties and oxidation stability of these oils will be compared with U. S. oils available at that time.

Preparation of amorphous RU-ZN-B/AL2O3 catalyst and its application in benzene selective hydrogenation

Abstract: Amorphous Ru-Zn-B/Al 2 O 3 catalyst for selective hydrogenation of benzene was prepared by chemical reduction, influence of the concentration of RuCl 3 precursor and molar ratio of Ru/Zn on catalytic performance had been investigated. It was concluded that there exist optimum value of Ru concentration and Ru/Zn ratio.