Studies on catalysis by molten metals. 14. Catalytic cracking of asphalts at low temperature

The catalytic effects of liquid metals for low-temperature (336 °C) asphalt-cracking have been examined using a semi-batch reactor. All the liquid metals examined (Bi, Cd, Ga, In, Pb and Sn) effectively catalysed the reduction of molecular weight with minimal gasification (<1 wt%). Gasification had a positive correlation with the reduction in molecular weight in the processed asphalts. The catalytic activities of liquid metals tor these two reactions were proportional to a parameter which represents the interaction between the atoms of the catalyst metal and the radicals formed in the course of the reaction. Mass flow among four fractions (saturates, aromatics, resins and asphaltenes) had two independent paths: conversion of resins to saturates and of aromatics to asphaltenes. The former path dominated when catalytic dehydrogenation activity was relatively low, whereas the latter dominated when the catalytic activity was high.     

Kinetics and reaction scheme of coal liquefaction over molten tin catalyst

Rates of formation of gases, oils, asphaltenes and preasphaltenes during non-solvent liquefaction of coal over molten tin catalyst have been measured. A probable reaction scheme and the rate constants for the pathways comprising the scheme have been presented. The results show that the catalyst greatly accelerates the conversion of preasphaltenes to asphaltenes. It also accelerates two other reactions, i.e., coal to preasphaltenes and coal to asphaltenes. By contrast, the catalyst does little to promote gasification and formation of oils.     

Towards Tuneable Retaining Glycosidase‐Inhibiting Peptides by Mimicry of a Plant Flavonol Warhead

Retaining glycosidases are an important class of enzymes involved in glycan degradation. To study better the role of specific enzymes in deglycosylation processes, and thereby the importance of particular glycosylation patterns, a set of potent inhibitors, each specific to a particular glycosidase, would be an invaluable toolkit. Towards this goal, we detail here a more in‐depth study of a prototypical macrocyclic peptide inhibitor of the model retaining glycosidase human pancreatic α‐amylase (HPA). Notably, incorporation of l ‐DOPA into this peptide affords an inhibitor of HPA with potency that is tenfold higher (K_i=480 pm ) than that of the previously found consensus sequence. This represents a first successful step in converting a recently discovered natural‐product‐derived motif, already specific for the catalytic side‐chain arrangement conserved in the active sites of retaining glycosidases, into a tuneable retaining glycosidase inhibition warhead.     

Catalysis by Molten Metals and Molten Alloys

Abstract

It appears pertinent for the opening of this review to cite the work of Ipatiew [1]. In 1901 he reported that certain metals catalyzed the decomposition of alcohols even above the melting points of the catalyst metals, However, he gave no special attention to the catalytic activity of the molten metal (liquid metal), and thus 20 years or more elapsed without any significant advances in the research on the catalysis of the liquid metal.     

高压下N_2、Ar、CH_4、CO_2和N_2O气体在丝光沸石上的吸附平衡及关联

本文用定容型吸附量测定装置,在压力为3.04×10~3至1.43×10~7Pa范围内,温度为—196、0、25、50和75°C下测定了N_2、Ar、CH_4、CO_2和N_2O等气体在氢型丝光沸石上的吸附平衡数据.实验结果表明:N_2、Ar和CH_4的吸附量随压力增加而增加,直到在6.08×10~6Pa附近达到饱和;CO_2和N_2O的吸附等温线出现了极大值,且不同温度同一吸附质的吸附等温线出现了相互交叉的现象.用扩展了的吸附势理论进行关联,取得了满意的结果.     

A novel method of examining carbonaceous deposits on spent catalyst surfaces

Xenon ion-bombardment used in conjunction with Auger electron spectroscopy was able to discriminate two types of carbonaceous materials accumulated on the surfaces of iron oxide and rhenium/iron-oxide catalysts spent for CO hydrogenation at 250°C and 2.1 MPa. One of the carbonaceous materials was easily eliminated from the surfaces by ion bombardment or by heat-treatment in vacuo at 150°C. On iron oxide only this “soft” carbonaceous material was present. On rhenium/iron oxide, bombardment-resistant “hard” carbonaceous material was also found. The presence of this hard carbonaceous material had little effect on the level of CO hydrogenation activity or the deactivation behavior of this catalytic system.     

Optimum shape design of truss structures based on reliability

A procedure is presented for the shape optimization of truss structures based on the reliability concept. Nodal coordinates are taken as the shape design variables together with the sizing design variables such as the cross-sectional areas of the members. These variables are determined to minimize the structural volume under the constraint on the structural failure probability.