Michel Gubelmann

Acylation of phenol with acetic acid over a HZSM5 zeolite, reaction scheme

Abstract The scheme of the gas phase phenol acylation with acetic acid on a HZSM5 zeolite was established from the effect of contact time (hence of conversion) on the product distribution. Phenyl acetate and o -hydroxyacetophenone are primary products, O-acylation being much faster than C-acylation. At high conversion, part of the o -hydroxyacetophenone results from the acylation of phenol with phenyl acetate. The formation of p -hydroxyacetophenone which does not occur through phenol acylation involves the hydrolysis of p -acetoxyacetophenone selectively formed through the autoacylation of phenyl acetate. The ortho -selectivity of phenol acylation can be related to a pronounced stabilization of the transition state while the para -selectivity of phenyl acetate autoacylation could be due to a steric hindrance to the approach of the acetyl group in the ortho -position of phenyl acetate.

Phenol acylation: unexpected improvement of the selectivity to o-hydroxyacetophenone by passivation of the external acid sites of HZSM5

The acylation of phenol by acetic acid on zeolite ZSM5 is unexpectedly oriented towards o-hydroxyacetophenone by dealumination of the outer surface of the crystallites, which can be ascribed to the existence of two different pathways for the formation of o- and p-hydroxyacetophenones.

Mechanism of Phenylacetate Transformation on Zeolites

Summary The transformation of phenylacetate was carried out over two zeolites: HY (Si/Al = 20) and HZSM5 (Si/Al = 40) at 400°C under atmospheric pressure. The reactivities of the products and intermediates were also studied under the same conditions. On both catalysts the main product was phenol which means that ketene was also formed. HY led mainly to ortho-hydroxyacetophenone while HZSM5 gave both ortho- and para-hydroxyacetophenones in equal amounts. 2-Methylchromone and 4-methylcoumarine were formed on HY only and supposedly resulted from an intramolecular condensation of ortho-acetoxyacetophenone which was not observed among the products. On HZSM5 dehydroacetic acid and 4-acetoxy 6-methyl 2-pyrone were formed presumably through autocondensation of ketene. Para-acetoxyacetophenone was observed on both catalysts. Water had practically no effect on the activity and selectivity of HY while it increased the stability of HZSM5 markedly.

Process for the hydroxylation of phenols and phenol ethers

Process for the hydroxylation of phenols and phenol ethers with hydrogen peroxide. More precisely, the invention consists of a process for the hydroxylation of phenols and phenol ethers and preferably of phenol, with hydrogen peroxide, characterised in that the reaction is conducted in the presence of an effective quantity of an acidic clay of TOT structure, which has a pH lower than 7 in aqueous suspension.

EXCHANGE OF HALOGENS BETWEEN AROMATIC COMPOUNDS IN THE PRESENCE OF CU-HZSM-5 ZEOLITE

Abstract The reactions between various haloaromatics in binary mixtures which were approximately equimolar, were studied in gas-phase (673 K, atmospheric pressure) in the presence of a 2 wt % Cu-HZSM-5 zeolite. The exchange of halogens (ipso substitution) between the two compounds was assumed to occur either through a radical mechanism involving an electron transfer between an atom of copper (I) and one aromatic molecule or through a nucleophilic substitution involving arylcopper complexes as intermediates.

ACYLATION OF PHENOL AND TRANSFORMATION OF PHENYLACETATE OVER ZEOLITES

The transformation over two zeolites HY (Si/Al = 15) and HZSM5 (Si/Al = 35) at 400°C of phenylacetate and of equimolar mixtures of phenylacetate + water and of phenol + acetic acid are compared. With phenylacetate alone, the deactivation of the zeolites is very rapid. The stability is much better with the mixtures as reactants. Moreover the activity of the zeolites is regenerated when the phenylacetate-water mixture is substituted for pure phenylacetate. The increase in stability could be due to a decrease in the rate of formation of ketene and of its condensation products. On both zeolites, the ratio of the rates of O/C phenol acylation by acetic acid is initially close to 1, C acylation leading mainly to o-hydroxyacetophenone (o/p ratio equal to 20 with HY and to 9 with HZSM5). The O/C acylation rate ratio increases with time on stream while the o/p hydroxyacetophenone ratio decreases, probably because of diffusion limitations created by coke deposits.

Process for the dehydrocyanation of aliphatic dinitriles

Abstract of EP0571298The present invention relates to a process for the dehydrocyanation of aliphatic dinitriles in the vapour phase. More precisely, it consists of a process for the dehydrocyanation of branched, saturated dinitriles, characterised in that vapours of one or more of the said branched, saturated dinitriles are brought into contact with a partially or completely acidified cation exchanger. The branched, saturated dinitriles which are subjected to the dehydrocyanation according to the present process are more particularly 2-methylglutaronitrile, 2-ethylsuccinonitrile, their mixtures with each other or industrial mixtures containing them.

Nitric Acid Associated with Inorganic Solids: A Versatile Reagent and Catalyst in the Chemistry of Aromatics

Abstract The behaviour of the “nitric acid-solid acid” couples in the functionalization of aromatic substrates depends essentially on their ability to trap water produced by the nitration process. In the liquid phase applications, the solid acts either as an acid catalyst or as a dessicant. It is shown, that accumulation of water rapidly inhibits the acid component and leads toward oxidation patterns, whereas a good dessicant allows interesting nitration performances.

A Selective Process For The Synthesis of Para-Nitrophenol

Abstract The selective nitration of phenylcarbonate into the 4,4′-dinitro isomer has been described in the literature. In this work we show that basic solids, such as CsF and CS 2 CO 3 as well as basic organic resins, do catalyse the transcarbonation of the nitrated phenylcarbonate into paranitrophenol and recyclable phenylcarbonate, which is a considerable advantage compared with homogeneous stoichiometric techniques. The overall sequence is an attractive alternative for the synthesis of paranitrophenol.