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And spillover on hydrodesulphurisation catalysts
321 studies of Parera et al who suggest that the optimum CrcGcentration for maximuw hydrogen spillover corresoonds to a surface on which nearly half the hydroxyls of alumina are substituted bv chlorine. Under these conditions the ,r&e of coke formation is lower because the hydrogen spillover keeps the support surface relatively free of polyolefinic coke precursors. These three studie.snot only strengthen the experimental evidence for hydrogen spillover but also signal a new era in which this phenomenon begins to make its impact on industrial catalysis. P.G. Menon And Spillover on Hydrodesulphurisation Catalysts Spillover of hydrogen from one part of a catalyst to another is also invoked in a new theory recently put forward by B. Dalmon to explain the synergy between MoS2 and CO9SB in hydrodesulphurisationcatalysts. In this (see Comptes Rendus, 1979, C 289, 173; Bull. Sot. Chim. Belg., 197%-B% 979; React. Kinet. Catal. Lett., 19m, 20, 639; and Proc. 7th Int. Congr. lZta1.. 1422), he proposes that the synergy exists by remote control of the active centres=earouDIb sulphide through partial reduction, by means of hydrogen s ilt-over from e group VIII the unreduced form o&i--sul phide. Hydrogenation activity occurs on moderately reduced centres and hydrogenolysis of the sulphur containing species occurs on deeply reduced centres. The theory can explain many observations made by Delmon's group as well as by others; for example, the effects of catalyst composition, hydrogen or H2S pressure and the existence of reduced species.
the Netherlands, in May this year, (see J. Molec. Catal., 11, May 1981) various examples were presZiitedof fixation or heterogenizationof organic complexes, but the catalysts were tested, in most cases, only in stirred or non-stirred autoclaves. It will be clear that in such tests, no impression is gained of the influence of important variables such as space velocity, partial pressures, etc., on the catalytic performance, and the stability (or life-time) of the catalyst is seldom determinable. The study by N. A. de Munck, J. P. A. Notenboom, J. E. de Leur and J. J. F. Scholten, (J. Molec. Catal., 1981, 11, 233), on the gas-phase hydrofonaylZion of allylalcohol (CH =CH-CH20H) over a supported liquid phase cazalyst, (SLPC), is an exception. The Wilkinsontype catalyst used, hydridocarbonyltris (triphenylphosphine)Rh(I), was dissolved in triphenylphosphineor in tri-p-tolylphosphine, and capillary-condencedin the pores of a porous support material. The catalytic performance was continuously studied in a flow apparatus suited for total pressures up to 0.6 MPa and temwratures UD to 2000C. Verv hiqh selectivities for the industrially-desired product, 4-hydroxybutyraldehyde (HO-C&I-CHP-CHP-CHO)were obtained, and io slgk of-catalyst'deactivationwas observed even after 250 hrs of testing. It was shown that the undesired side reaction of ally1 alcohol to propionaldehyde (CH3CH2CHO) is caused mainly by the catalytic action of the support material and, by the use of silica with a low aluminium content, this problem was circumvented. It is to be hoped that in future further promising heterogenizedorganometallic catalysts will be tested under realistic technologicalconditions. J. J. F. S. Review of Molybdenum Catalysts
Technical Application of Inaaobilized iietal-OrganicCatalysts; The Rydroformylation of Ally1 ATcohol
A very useful monograph entitled "The Role of Molybdenum in Catalysis" has been written by Professor J. Haber (Cracow, Poland). It covers topics An increasing number of laboratory such as hydrocarbon oxidation (Bi and studies have been performed in which transition metal molybdates), hydraattempts have been made to combine the desulohurisation(DrOIMted MoS2) and attractive properties of homogeneous epoxidation (molybhates and complexes). organo-metallic catalysts with the The monograph is published by Climax advantages of heterogeneous design. At Molybdenum Company Ltd., and copies are the International Conference on the obtainable from them at Imperial House, Relations between Homogeneous and Heterogeneous Catalysis, held in Groningen, l/3 Grosvenor Place, London, SWlX 7DL.
the Netherlands, in May this year, (see J. Molec. Catal., 11, May 1981) various examples were presZiitedof fixation or heterogenizationof organic complexes, but the catalysts were tested, in most cases, only in stirred or non-stirred autoclaves. It will be clear that in such tests, no impression is gained of the influence of important variables such as space velocity, partial pressures, etc., on the catalytic performance, and the stability (or life-time) of the catalyst is seldom determinable. The study by N. A. de Munck, J. P. A. Notenboom, J. E. de Leur and J. J. F. Scholten, (J. Molec. Catal., 1981, 11, 233), on the gas-phase hydrofonaylZion of allylalcohol (CH =CH-CH20H) over a supported liquid phase cazalyst, (SLPC), is an exception. The Wilkinsontype catalyst used, hydridocarbonyltris (triphenylphosphine)Rh(I), was dissolved in triphenylphosphineor in tri-p-tolylphosphine, and capillary-condencedin the pores of a porous support material. The catalytic performance was continuously studied in a flow apparatus suited for total pressures up to 0.6 MPa and temwratures UD to 2000C. Verv hiqh selectivities for the industrially-desired product, 4-hydroxybutyraldehyde (HO-C&I-CHP-CHP-CHO)were obtained, and io slgk of-catalyst'deactivationwas observed even after 250 hrs of testing. It was shown that the undesired side reaction of ally1 alcohol to propionaldehyde (CH3CH2CHO) is caused mainly by the catalytic action of the support material and, by the use of silica with a low aluminium content, this problem was circumvented. It is to be hoped that in future further promising heterogenizedorganometallic catalysts will be tested under realistic technologicalconditions. J. J. F. S. Review of Molybdenum Catalysts
Technical Application of Inaaobilized iietal-OrganicCatalysts; The Rydroformylation of Ally1 ATcohol
A very useful monograph entitled "The Role of Molybdenum in Catalysis" has been written by Professor J. Haber (Cracow, Poland). It covers topics An increasing number of laboratory such as hydrocarbon oxidation (Bi and studies have been performed in which transition metal molybdates), hydraattempts have been made to combine the desulohurisation(DrOIMted MoS2) and attractive properties of homogeneous epoxidation (molybhates and complexes). organo-metallic catalysts with the The monograph is published by Climax advantages of heterogeneous design. At Molybdenum Company Ltd., and copies are the International Conference on the obtainable from them at Imperial House, Relations between Homogeneous and Heterogeneous Catalysis, held in Groningen, l/3 Grosvenor Place, London, SWlX 7DL.