ISSN:0165-0513    

DOI:10.1002/recl.19961150403

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWater‐soluble catalysts offer significant advances in homogeneous catalysis: the “heterogenization” of the catalyst in a second, immiscible liquid phase immobilises the catalyst phase, thus combining the advantages of heterogeneous catalysis,e.g.long lifetime, easy separation of product from catalyst, with those of the homogeneous type, namely, defined species of catalyst, gentle reaction conditions, high activity and selectivity.The first successful large‐scale application of aqueous catalysts is the oxo process of Ruhrchemie/Rhône‐Poulenc, using a HRh(CO)[P‐(3‐sulfophenyl‐Na)3]3catalyst, dissolved in water. This survey reviews 10 years' experience of this process against the background of biphasic catalyses, especially the way in which this environmental benign technique, which is highly economic and thus very environmentally sound, r

ISSN:0165-0513    

DOI:10.1002/recl.19961150404

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractGlucose and gluconate aqueous solutions (2 mol/l) were oxidized with air (atmospheric pressure, 333K, pH 7) on active charcoal‐supported, platinum catalysts (catalytic ratios substrate/Pt ≥ 787); some catalysts were promoted with bismuth or gold. The activity of unpromoted Pt/C catalysts for glucose oxidation was comparable with that of Pd‐Bi/C catalysts and there was no deactivation; gluconate formed transiently was oxidized into glucarate, the final selectivity did not exceed 50%. The oxidation of gluconate on very well dispersed Pt catalysts prepared by cationic exchange or anionic adsorption leads to higher glucarate selectivities than those previously reported, in spite of the fact that the present solutions were much more concentrated and reduced amounts of platinum were used. Addition of bismuth adatoms by surface redox reaction produces a shift in selectivity towards 2‐ketogluconate. Addition of gold adatoms on platinum decreases the catalyst deact

ISSN:0165-0513    

DOI:10.1002/recl.19961150405

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe selective oxidation of 2‐mercaptobenzothiazole to 2‐hydroxybenzothiazole with molecular oxygen at temperatures of 50‐150°C and pressures of 0.3‐0.7 MPa has been studied in the presence of transition metal catalysts. The reaction proceeds via corresponding sulfinic and sulfonic acids which are quickly decomposed to the desired product in acetic acid as solvent at the reaction temperature. At temperatures below 90°C, the main reaction product is 2,2′‐dithiobis(benzothiazole) which is resistant to further oxidation. The type of central atom and ligand of the metal catalyst has a strong influence on the selectivity of 2‐hydroxybenzothiazole formation. In the presence of FeCl2as catalyst, 85% selectivity at 95% conversi

ISSN:0165-0513    

DOI:10.1002/recl.19961150406

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractZeolite H‐BEA and other solid acids have been shown to be effective catalysts for the production of coumarin derivatives from activated phenols and acids or esters possessing an additional alkylation function, or β‐keto esters (Pechmann reaction). These heterogeneous catalysts eliminate the production of acidic waste streams associated with conventional (Lewis) acid catalysts. Zeolite H‐BEA proved to be the preferred ca

ISSN:0165-0513    

DOI:10.1002/recl.19961150407

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractDifferent amides have been selectively mono‐N‐alkylated using catalytic heterogeneous palladium and carbonyl compounds as alkylating agents. The same salt free method has been applied to the synthesis of ethers from alcohols. Reaction parameters have been studied in detail and a mechanism is propo

ISSN:0165-0513    

DOI:10.1002/recl.19961150408

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe enantioselective enzyme‐catalyzed reduction of ketones in an enzyme membrane reactor coupled to a membrane‐based extractive product separation was developed for the production of chiral hydrophobic alcohols. Enantiomerically pure (S)‐1‐phenylpropan‐2‐ol, (S)‐4‐phenylbutan‐2‐ol and (S)‐6‐methylhept‐5‐en‐2‐ol (sulcatol) were obtained with high purities.In spite of low substrate concentrations (9‐12 mM) space‐time yields higher than 100 g/(l·d) and concentrated product solutions were obtained.Formate‐dehydrogenase‐catalyzed regeneration of cofactor, together with process‐integrated recycling of cofactor, led to total‐turnover numbers for NAD+of up to 1350 molP/molNAD, which means a 25‐fold increase in comparison with standard techniques without cofactor retention.Because of the closed‐loop design of the reactor the process can be run almost without

ISSN:0165-0513    

DOI:10.1002/recl.19961150409

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe oxidation of the sulfide group in penicillin G potassium salt to the sulfoxide with hydrogen peroxide has been investigated using a wide range of polyoxometalates immobilized on high‐surface‐area supports. The highest activity and selectivity for the sulfur oxidation of the penicillin compound was obtained with ammonium molybdate supported on to strongly basic anion‐exchange resin. The oxidation proceeds smoothly at ambient and sub‐ambient temperatures in water or water/alcohol solvents. The use of supported oxidation catalysts has been extended to the transformation of benzenethiol to benzenesulfonic acid which was found to proceed in high yield and selectivity employing phosphotungstic acid on γ‐alumina. The use of a supported catalyst with H2O2as the primary oxidant allows the circumvention of environmental and product isolation problems to be overcome simply and ec

ISSN:0165-0513    

DOI:10.1002/recl.19961150410

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractOver the last seven years Shell has developed a novel, economically attractive, and environmentally benign process for the production of methyl methacrylate (MMA). The process is based on the highly efficient Palladium‐catalysed methoxycarbonylation of propyne (methyl‐acetylene or MA) under mild, non‐corrosive reaction conditions (temperatureca.50°C, CO pressure ca. 10 bar) according to the equation:MeOH + CO + HC ≡ C − Me(MA) →H2C = C(Me) −C(O)OMe(MMA)The activity (>20000 mol‐MMA/mol‐Pd.h) and selectivity (>99%mol) of the homogeneous Pd catalyst are very high making a once‐through process with minimal waste possible.The MA feedstock for the process, together with propadiene (PD), is separated from a steam‐cracker C3stream by extractive distillation with DMF. Subsequently, PD is removed from this MA + PD/DMF mixture and isomerized over a heterogeneous K2O/Al2O3catalyst to yield additional MA.Crude MMA obtained from the methoxycarbonylation of MA can easily be purified by a ‘topping and tailing’ procedure to yield MMA of very high purity (>99.99 w%).This article describes some of the R&D work carried out at the ‘Koninklijke/Shell‐Laboratorium, Amsterdam’ which has enabled the design of a plant

ISSN:0165-0513    

DOI:10.1002/recl.19961150411

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe non‐toxic compound dimethyl carbonate (DMC) can be used as a methylating and a methoxycarbonylating agent in place of methyl chloride and phosgene, respectively. We report here that DMC and other dialkyl carbonates (DAlkCs: dimethyl, diethyl and dibenzyl carbonates) allow very selective alkylations of a variety of CH2‐acidic compounds. Both arylacetonitriles and alkyl arylacetates react with DAlkCs to yield the mono‐C‐alkylated derivatives (α‐alkyl‐α‐arylacetonitriles and alkyl α‐alkyl‐α‐arylacetates) with a selectivity of up to 99%, at complete conversion. Likewise, the mono‐C‐methylation by DMC proceeds selectively also on (aryloxy)acetonitriles and methyl (aryloxy)acetates. The reactions are carried out at temperature of 180‐220°C in the presence of weak bases (usually K2CO3); under such conditions, DAlkCs efficiently replace the common and very toxic alkylating agents (dialkyl sulfates and alkyl halides). In addition to the high selectivity obtained and the intrinsic safety of the dialkyl carbonates, the reported reactions give rise to neither organi

ISSN:0165-0513    

DOI:10.1002/recl.19961150412

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY