На лабораторной установке изучен пиролиз гидроочищенного вакуумного газойля, полученного по технологии гидрокрекинга “T-Star”. При температуре в реакторе 820°C, времени контакта 0.6 с, соотношении газоль/водяной пар = 0.8, выход этилена составил 25.7 мас. %.

Pyrolysis of hydrotreated vacuum gas oil obtained using the T-Star hydrocracking process has been studied in a laboratory unit. At a reactor temperature of 820°C, a contact time of 0.6 s, and a gas oil/steam ratio of 0.8, the ethylene yield is 25.7 wt %.

A new reductive dimerization and oligomerization reaction of (C5 and C6) cycloalkanols and cycloalkanones, benzaldehyde, and benzyl alcohol to hydrocarbons containing as many, or more, carbon atoms as the reactant oxygenated compound on a promoted, fused iron catalyst proceeds at a temperature of 250–350°C, a hydrogen pressure of 0.1–1 MPa, a specific feed rate of oxygenated reagent of 80–320 g h−1kg−1Ct, and a hydrogen space velocity of 1 × 103 to 20 × 103 h−1. Possible reaction mechanisms have been considered.

The reductive dehydration of cyclic (C5, C6) and aliphatic (C2-C4) alcohols into polycycloalkanes and alkanes whose carbon skeleton has at least twice as many atoms as that of the original substrate is reported for the first time. This reaction takes place at 250–350°C and 7–50 atm in the presence of a polymetallic catalytic system based on an iron-containing fused catalyst or a hydrided iron- and titanium-containing intermetallide mixed with a small amount of Pt/Al2O3. The mechanism of this new reaction is discussed in terms of the mechanisms of known reactions of alcohols and aldehydes enlarging the carbon skeleton.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Investigation of the mechanism of the selective reduction of NOx by propane over the individual samples of commercial catalysts NTK, STK, and Ni–Cr-oxide catalyst and over their binary mechanical mixtures has shown that the synergistic effect observed in the latter case is caused by the oxidative activation of propane on the STK and Ni–Cr-oxide surface which results in the formation of more effective reducing agents, propylene and hydrogen correspondingly. In the case of the Ni–Cr-oxide and NTK catalytic system, hydrogen forms over the former catalyst in propane oxidation, migrates through the gas phase to the latter catalyst, where NOx is activated with the formation of nitrate structures which interact with the said hydrogen giving the products of the overall reaction, N2 and H2O. When the pair of NTK and STK is concerned, the interaction of C3H8 and O2 over the latter catalyst gives stable products of partial propane oxidation and/or oxidative dehydrogenation which are transported due to interphase diffusion to NTK surface. The nature of observed synergistic enhancement of catalysis in the case of binary mixtures is proposed under the terms of “remote control” mechanism described in literature and can serve a useful purpose in the design of catalysts for this reaction.

According to X-ray diffraction analysis data, the test catalyst was a Ni-Cr spinel with an impurity of NiO. With the use of in situ IR spectroscopy, it was found that nitrite, nitrate, and acetate surface complexes occurred under the reaction conditions of the selective catalytic reduction of nitrogen oxides by propane in the presence of oxygen on the nickel-chromium catalyst. As the temperature was increased, the nitrite complexes were converted into nitrate species. The molar absorption coefficient of surface nitrate complexes was determined. According to IR-spectroscopic and TPD data, the nitrate complexes were bound relatively weakly to the surface. The temperature region of their existence was 50–200°C. The temperature region of existence of the surface acetate complexes was 200–400°C. The individual adsorption of oxygen was not observed; however, oxygen-containing surface sites (Cr5+=O) participated in the formation of the surface complexes of reactants.

В обзоре проведен анализ работ, посвященных изучению явления синергизма в катализе на механических смесях катализаторов. Рассмотрены методики проведения эксперимента, формулы для расчета величины эффекта синергизма. Приведены гетерогенно-каталитические реакции, широко используемые в нефтехимии и органическом синтезе, в которых ярко выражен синергизм.

Studies concerning the phenomenon of synergism in catalysis over mechanical catalyst mixtures are surveyed. Experimental procedures and formulas for calculating the magnitude of a synergistic effect are considered. Heterogeneous catalytic reactions widely used in petroleum chemistry and organic synthesis that exhibit pronounced synergism are discussed.

Works on catalytic methods of cleaning gas emissions of NOx that appeared within 1996-2001 are surveyed. Basic attention is given to the reduction of NOx with hydrocarbons. Catalyst active sites and the structure of transient surface compounds are discussed. Schemes of reaction mechanisms proposed on the basis of information about surface complexes are presented.

The molecular mass distribution (MMD) of paraffinic hydrocarbons with the normal structure was studied. It was found that the MMD of n-alkanes C12H26-C37H76 obeyed with a satisfactory accuracy the statistical Schulz-Flory distribution with a distribution parameter of of alpha = 0.77 +/- 0.01.

Based on a spectrokinetic study (simultaneous measurements of the concentrations of surface complexes and reaction rate usingin situ IR spectroscopy), a hypothesis is proposed which explains synergism in the reaction of NO reduction by propane on a mechanical mixture of commercial oxide catalysts.

In the reaction of NO reduction by propane in excess oxygen, the activity of a binary mixture of commercial oxide catalysts is higher than should be expected if it were proportional to the activities of separate catalyst components. This synergism reveals itself in the fact that the conversion of NO and C 3 H 8 is higher when the catalyst is a mechanical mixture than the sum of conversions over separate catalysts, all other conditions being the same. Based on the kinetic and thermal desorption measurements, the experimental conditions are found under which the synergism is observed. A hypothetical mechanism is proposed.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A study has been made of the reaction of n-butyl caprylate with H-2 at a temperature of 180-240 degrees C on copper-zinc-aluminium oxide catalyst SNM-1 and on reduced, promoted, sintered iron catalysts of different composition. The degree of conversion of the ester amounts to 88-97%, and the n-octanol yield reaches 98% of the reacted n-butyl caprylate. (C) 1997 Elsevier Science Ltd.

In the temperature range 200-550 degrees C, an investigation has been made of the selective reduction of nitrogen oxide by methane in the presence of oxygen on polycomponent oxide compositions consisting of binary mechanical mixtures of industrial catalysts with a different mass ratio of components: MK1 (1, 2, 3) - nickel-chromium oxide and NTK-10-1; MK2 (1, 2, 3) - STK and NTK-10-1. It has been established that the degree of conversion of NO to N-2 on MK1 and MK2 in gas mixtures not containing oxygen amounts to 90-99% at 200-400 degrees C; when 4-5% oxygen is added to the gas mixture, the degree of conversion of NO on these catalytic compositions amounts to 30-99% in the temperature range 350-500 degrees C. It has been established for the first time that catalytic systems MK1 (2, 3) exhibit synergistic properties during the reduction of nitrogen oxide by methane both in the presence of oxygen and without it, whereas on the MK2 (3) system synergism is found only in a gas mixture not containing oxygen. (C) 1998 Elsevier Science Ltd. All rights reserved.