Supported phosphoric acid

Propylation of benzene with propylene, catalyzed by supported phosphoric acid (or related catalysts such as AlCl ), gives cumene [98-82-8] in another important industrial process. Cumene (qv), through the intermediacy of cumene hydroperoxide, is used in the manufacture of phenol (qv). Resorcinol similarly can be made from y -diisopropylbenzene (6). 

Currently, almost all cumene is produced commercially by two processes ( /) a fixed-bed, kieselguhr-supported phosphoric acid catalyst system developed by UOP and (2) a homogeneous AlCl and hydrogen chloride catalyst system developed by Monsanto. 

Manufacture. Much of the diethyl ether manufactured is obtained as a by-product when ethanol (qv) is produced by the vapor-phase hydration of ethylene (qv) over a supported phosphoric acid catalyst. Such a process has the flexibiHty to adjust to some extent the relative amounts of ethanol and diethyl ether produced in order to meet existing market demands. Diethyl ether can be prepared directly to greater than 95% yield by the vapor-phase dehydration of ethanol in a fixed-bed reactor using an alumina catalyst (21). 

In this paper we report the use of supported heteropoly acid (silicotungstic acid) and supported phosphoric acid catalysts for the acylation of industrially relevant aromatic feedstocks with acid anhydrides in the synthesis of aromatic ketones. In particular, we describe the acylation of thioanisole 1 with iso-butyric anhydride 2 to form 4-methyl thiobutyrophenone 3. The acylation of thioanisole with acetic anhydride has been reported in which a series of zeolites were used as catalysts. Zeolite H-beta was reported to have the highest activity of the zeolites studied (41 mol % conversion, 150°C) (2). 

As the loading of STA on the catalyst support is decreased, incomplete anhydride conversion is observed and significant hydrolysis of the anhydride to form iso-butyric acid is observed (Table 2). Use of silica supported phosphoric acid results in lower ketone yields and significant hydrolysis of the iso-butyric anhydride. Blank reactions (catalyst and anhydride, 90°C, 30 min) indicates that hydrolysis of anhydride is observed in the presence of these catalysts and may result from either dehydroxylation of the silica support or residual water in the catalyst, ffowever this reaction is slow (42%STA/silica, 44% conversion and 70%P[3PO4/silica, 86% conversion respectively). 

Skeletal isomerization requires higher temperature and stronger acid catalysts than do double-bond migration and cis-trans isomerization. Butylenes, for example, are transformed to isobutylene over supported phosphoric acid catalysts.98 The equilibrium mixture at 300°C contains approximately equal amounts of straight-chain and branched butenes. Similar studies were carried out with pentene isomers.99 Side reactions, however, may become dominant under more severe conditions.100... 

The related manufacture of cumene (isopropylbenzene) through the alkylation of benzene with propylene is a further industrially important process, since cumene is used in the synthesis of phenol and acetone. Alkylation with propylene occurs more readily (at lower temperature) with catalysts (but also with hydrogen fluoride and acidic resins) similar to those used with ethylene, as well as with weaker acids, such as supported phosphoric acid (see further discussion in Section 5.5.3). 

Thus, the partial pressure of water is not really involved in the rate expression for the reaction catalysed by supported phosphoric acid, as for the other mentioned catalysts [300,303,304] [eqn. (18)]. 

In the alkylation of ethylbenzene with ethylene, with conventional acid catalysts under usual conditions,. veobutyl benzene is a byproduct. rec-Butylbenzene was detected when the reaction was carried out over catalysts such as supported phosphoric acid,189 ferric phosphate,189 or AICI3—NiO—Si02-190 When Nafion-H or AICI3 are used, no such byproduct is detected, probably due to fast dealkylation of sec-butylbenzene under the more acidic conditions. 

A gas-phase hydration using a fixed-bed-supported phosphoric acid catalyst... 

Friedel-Crafts alkylation processes were traditionally operated at 65-70°C with AICI3 and at 40-60°C with HF. A variety of solid acid catalysts have been developed at the laboratory level, mainly based on zeolites, heteropolyacids or sulfated zirconia (zirconia treated with sulfuric acid). The most recent industrial achievement is the Detal process (UOP-CEPSA) which is based on silica-alumina impregnated with HF. The selectivity towards linear alkylbenzenes exceeds 95%. The cymene processes use AICI3 in the liquid phase or supported phosphoric acid as catalysts. 

In the second step, the dioxanes are vaporized, superheated, and then cracked on a solid catalyst (supported phosphoric acid) in the presence of steam. The endothermic reaction takes place a about 200 to 2S0°C and 0.1 to OJ. 10 Pa absolute. The heat required is supplied by the introduction of superheated steam, or by heating the support of the catalyst, which operates in a moving, fluidized or fixed bed, and, in this case, implies cyclic operation to remove the coke deposits formed. Isoprene selectivity is about SO to 90 mole per cent with once-through conversion of 50 to 60 per cent The 4-4 DMD produces the isoprene. The other dioxanes present are decomposed into isomers of isoprene (piperylene etc.), while the r-butyl alcohol, also present in small amounts, yields isobutene. A separation train, consisting of scrubbers, extractors and distillation columns, serves to recycle the unconverted DMD, isobutene and fonnol, and to produce isoprene to commercial specifications. 

Cao, G., Viola, A., Baratti, R., Morbidelli, M., Sanseverino, L., and Cruccu, M., Lumped kinetic model for propene-butene mixtures oligomerization on a supported phosphoric acid catalyst. Adv. Catal. 41,301 (1988). 

The reaction of u-butenes to give isobutylene is cataly zed by a wide variety of solid acids but requires relatively high temperature. Typical catalysts include alumina, halogenated alumina, amorphous silica-alumina, supported phosphoric acid, and supported tungsten or molybdemmi oxide. The most characteristic features of the skeletal isomerization of n-butenes... 

About 10% of the propylene produced is consumed for the alkylation of benzene to produce cumene. Use of a supported phosphoric acid catalyst and a high-purity stream of propylene in the presence of a large excess of benzene (to minimize dialkylation and oligomer formation) gives cumene with a 90+% yield based on ethylene, 96+% yield on benzene (Eq. 19.48). 

This example shows that the problem of avoiding liquid acid waste was already solved for cumene synthesis using supported phosphoric acid, but the main problems were (i) the loss of H3PO4, which also causes problems of corrosion and deactivation, (ii) the impossibility of regeneration of the catalyst due to the type of carbon-species that accumulate on it and (iii) the formation of relatively high amounts of diisopropylbenzene (3.0-3.5%), which, even if converted by trans-... 

Catalysts active in the dimerization are (i) strong cation-exchange resins, (ii) solid supported phosphoric acid, (iii) zeolites, (iv) amorphous Si02/Al203 and (v) supported oxides. Resins give the best results and are mainly used in the cited processes. Different organics could be used as solvents. 

Some processes use dUvie acid under high pressures/ an increased yield of alcohol being obtained with a corresponding decreased yield of ether. The jdeld of ether may be also decreased by removal of alcohol from contact with unreacted sulfate liquor, as rapidly as it is formed, by immediate distillation in hot water. Brooks and others have shown the advantages of absorption of ethylene under pressure. Various catalysts are used in these processes, and ethyl alcohol has also been prepared by the direct combination of ethylene with water in the presence of catalysts and under pressure. The two most promising catalysts are supported phosphoric acid and promoted tungsten oxide. ... 

The direct hydration of propylene and higher olefins has also been accomplished. The tungsten oxide type of catalyst was the best found, although supported phosphoric acid gave good results. ... 

Short-chain olefin oligomerization can provide gasoline, middle distillate, or lubricant oils. Typical acids used to catalyze these reactions are now solid-type catalysts such as silica-supported phosphoric acids or zeolites. 

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