In the upgrading of heavy petroleum oils and residues by hydrotreating, multiple-reactor fixedbed units loaded with different types of catalysts are extensively used. Catalysts for such hydrotreating processes are chosen on the basis of activity, selectivity, and life. The performance of the overall hydrotreating process with regard to various reactions, such as hydrodemetallation (HDM), hydrodesulfurization (HDS), hydrodenitrogenation (HDN), asphaltenes cracking (HD-Asph), and conversion to distillate and catalyst life-on-stream, is clearly linked to the performance of the catalyst in different reactors. Information regarding the activity, selectivity, kinetics parameters, and deactivation of the individual catalysts are, therefore, highly desirable for optimizing reactor loading in a multiple catalyst system. In the present work, a comparative study was conducted on the kinetics of various reactions such as HDS, HDV, HDNi, HDN, CCR reduction, and asphaltenes conversion in hydrotreating Kuwaiti atmospheric residue (KU-AR) over three types of catalysts. The results showed diverse kinetics behavior of different hydrotreating reactions. The diverse kinetics behavior of the different reactions and the strong dependence of the kinetics parameters on catalyst type are consistent with the kinetic aggregation theory. The results are discussed in comparison with those available in published literature.
Distal limb ischemia may occur as a serious complication related to the use of femoral cannulation during veno-arterial cardiopulmonary support (CPS). We developed a simple cannula for femoral arterial cannulation with two holes in the side wall, which could provide the distal limb blood flow without additional cannulation or surgical procedure. This cannula can be inserted into the femoral artery by routine Seldinger technique. The distal blood flow from the side holes can be confirmed by Doppler detector without specialized techniques. In porcine experimental model, the distance between the position where the blood flow was first detected and those where the blood leakage took place was at least more than 10 mm. When this cannula and its side holes were adequately positioned, the mean distal limb flow ranged from 75 to 90 mL/min under CPS at a flow of 1.5 L/min. We employed this cannula for six patients in clinical settings. Three patients showed a good distal limb blood flow at the introduction position without its adjustment. The other three patients showed distal limb ischemia at the introduction position, but the limb ischemia was soon recovered after a slight adjustment of its position. There was no blood leakage from the percutaneous entry into the artery in all cases. We currently use this cannula as the first choice for patients undergoing a prolonged CPS.
Proton-transfer reactions of disulfide-intact and -reduced lysozyme ions (7+ through 14+) to 2,6-dimethylpyridine were examined in the gas phase using tandem mass spectrometry with electrospray ionization. By changing temperature of a collision cell from 280 to 460 K, temperature dependence of reaction rate constants and branching fractions was measured. Absolute reaction rate constants for the protein ions of specific charge states were determined from intensities of parent and product ions in the mass spectra. Remarkable change was observed for the rate constants and distribution of product ions. The rate constants for disulfide-intact ions changed more drastically with change of charge states and temperature than those for disulfide-reduced ions. Observed branching fractions for parent and product ions were represented by calculated reaction rate constants with a scheme of sequential process. The reaction rate constants are closely related to conformation changes with change of temperature, which are profoundly influenced by amputation of disulfide bonds.
A new residual oil upgrading process has been developed. Residual oils were cracked over an iron oxide catalyst with simultaneous generation of hydrogen. The newly‐developed iron oxide catalyst containing CaO and Cr2O3 was found to be a good catalyst for this process because it exhibited stable activity in the steam‐iron reaction in the laboratory experiment and also in a large scale pilot plant. Effects of these foreign oxides on redox cycles were investigated. The catalyst was designed so as to maintain the stoichiometric balance between the reduction of magnetite and the oxidation of wustite by adding CaO and Cr2O3.
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