Assignment of most genes encoding major peroxisomal polypeptides to chromosomal band V of the asporogenic yeast Candida tropicalis

The peroxisomes of the asporogenic yeast Candida tropicalis contain about 20 major polypeptides (PXPs). We have isolated a number of genes encoding them; 11 POX genes encoded independent PXPs and three POY genes were likely to encode three other PXPs. To locate these genes on the chromosomes, chromosomes of C. tropicalis were separated by pulsed-field gel electrophoresis. Eight chromosomal bands were observed over the range of 1.0 Mbp (band 1) to 2.8 Mbp (band VIII); the genome size was estimated to be about 20 Mbp. Southern blot analysis showed that ten genes were on band V, three genes were on band IV, and the other gene was on band VI. Three genes gave hybridization signals of nearly equal intensity on two different chromosomal bands: POX6A and POX8B, on bands V and VII; and POX8A, on bands IV and VI. Ribosomal RNA genes also hybridized to two bands, VI and VII. Most genes assigned to only one band hybridized to two restriction fragments produced by either NotI or SfiI endonuclease. The results suggested that C. tropicalis was diploid and that restriction sites were conserved little between homologues. The three POX genes that were found on two chromosomal bands hybridized to not more than two restriction fragments, implying that the allelic genes were present on different chromosomal bands.     

Partial oxidation (POX) reforming of gasoline for fuel-cell powered vehicles applications

As a part of the development of a gasoline processor for integration with a proton-exchanged membrane (PEM) fuel cell, we carried out the POX reforming reaction ofiso-octane, toluene and gasoline over a commercial methane reforming catalyst, and investigated the reaction conditions required to prevent the formation of carbon and the effect of fuel constituents and sulfur impurities in gasoline. The H₂ and CO compositions increased with increasing reaction temperature, while those of CO₂ and CH₄ decreased. It is desirable to maintain an O/C molar ratio of more than 0.6 and an H₂O/C molar ratio of 1.5 to 2.0 for vehicle applications. It has been found that carbon formation in the POX reforming ofiso-octane occurs below 620 °C, whereas in the case of toluene it occurs below 640 °C. POX reforming of gasoline constituents led to the conclusion that hydrogen production is directly related to the constituents of fuels and the operating conditions. It was also found that the coke formation on the surface of catalysts is promoted by sulfur impurities in fuels. For the integration of a fuel processor with PEM fuel cell, studies are needed on the development of new high-performance transition metal-based catalysts with sulfur and coke-resistance and the desulfurization of fuels before applying the POX reformer based on gasoline feed.     

La0.8Sr0.2Cr0.95Ru0.05O3−x and Sm0.8Ba0.2Cr0.95Ru0.05O3−x as partial oxidation catalysts for diesel

La_0.8Sr_0.2Cr_0.95Ru_0.05O_3−x (LSCR) and Sm_0.8Ba_0.2Cr_0.95Ru_0.05O_3−x (SBCR), Ru-substituted perovskite catalysts, are investigated for the partial oxidation (POX) of diesel to produce hydrogen-rich gases for fuel cell applications. Metal-substituted perovskite materials have been investigated as reforming catalysts because the metal atoms are well-dispersed in the perovskite structure. However, Ru de-mixing and a secondary phase of LSCR and SBCR are observed after reduction at high temperature. The thermal stability, sulfur tolerance and aromatic decomposition over LSCR and SBCR are compared to those over Ru on Ce_0.9Gd_0.1O_2−x (CGO). During the thermal stability test, the catalytic activities of LSCR and SBCR improve after operating at 1000 °C. The sulfur tolerance and aromatic decomposition activity of LSCR and SBCR improve when the temperature increases to 950 °C. The improvements are attributed to the de-mixed Ru from the perovskite structure at high temperatures under a reductive atmosphere.     

High-efficiency power production from natural gas with carbon capture

A unique electricity generation process uses natural gas and solid oxide fuel cells at high electrical efficiency (74%HHV) and zero atmospheric emissions. The process contains a steam reformer heat-integrated with the fuel cells to provide the heat necessary for reforming. The fuel cells are powered with H₂ and avoid carbon deposition issues. 100% CO₂ capture is achieved downstream of the fuel cells with very little energy penalty using a multi-stage flash cascade process, where high-purity water is produced as a side product. Alternative reforming techniques such as CO₂ reforming, autothermal reforming, and partial oxidation are considered. The capital and energy costs of the proposed process are considered to determine the levelized cost of electricity, which is low when compared to other similar carbon capture-enabled processes.     

POX处理钼精矿研究新进展

POX法(Oxygen Pressure Oxidation)与传统的钼精矿氧化焙烧法比较,既可用于钼精矿生产工业氧化钼,又可用于由低品位钼精矿或钼中间产品生产钼酸铵或纯三氧化钼。评述了经过多年的研发,目前POX法已从实验室转入产业化,该工艺钼资源利用率高,产品质量好,环境友好和节能。     

Redox potential measurement during pressure oxidation (POX) of a refractory gold ore

Pressure oxidation (POX) leaching has been commercially applied to refractory gold ores since the 1980s. In the process, sulphide material is oxidised and dissolved in order to release the gold encapsulated in the sulphide matrix, making the gold available for further recovery. Redox potential is a significant parameter during POX; however, it is measured ex situ only at atmospheric conditions. In situ redox potential measurement would provide instant information that allows adjusting the process parameters accordingly. In the present study, redox potential measurements were performed during POX of sulphide material at high temperatures and high pressures. The working electrode was an Ir electrode combined with a flow-through reference electrode in a novel and robust configuration. Experiments were performed in a 2?L titanium autoclave, at 200–220°C, 345–760?kPa oxygen overpressure, and 10–30% solids mass fraction. Temperature and oxygen pressure conditions were selected in order to reflect POX of refractory gold ores. Results show that the Ir electrode is consistent with theory and is able to perform well under these conditions, showing promise as a new in situ sensor.     

POX和NSC研究进展

POX氧压氧化辉钼矿精矿工艺可用于生产工业氧化钼;从低品位钼精矿生产纯三氧化钼;生产高溶性氧化钼;钼精矿除铜和从废催化剂中回收钼和镍等.POX工艺过程环境友好,钼回收率较高.NSC氮氧化物催化压力浸出低品位钼精矿温度低、压力低、作业费用低,硫化钼转入溶液硫呈元素硫存在,研究进展十分引人注目.