Abstract: The invention relates to a method for preparing a hydroconversion catalyst based on mesoporous silica or silica-alumina, comprising the following steps: (A) deposition of alumina on a mesoporous material having interconnected pores by treatment with at least one aluminium-based reactant, so as to obtain a compound having a Si/Al ratio of between 0.1 and 1000; (B) addition of at least one catalytically active species chosen from the group formed by the metals of group VIII and/or of group VIB; and (C) drying followed by thermal and/or chemical treatment according to the invention. The invention also relates to the catalyst thus obtained as well as a method of hydroconverting (hydrocracking, hydroisomerizing) a hydrocarbon feedstock, which comprises bringing the feedstock to be treated into contact with the hydroconversion catalyst according to the invention.

Abstract: The present invention concerns a process for the hydroxyalkylation of a carbocyclic aromatic ether.The invention preferably relates to the preparation of 3-methoxy-4-hydroxybenzyl alcohol by the hydroxymethylation of guaiacol.It also concerns the oxidation of the hydroxyalkylated ethers obtained, in particular the oxidation of 3-methoxy-4-hydroxybenzyl alcohol to 3-methoxy-4-hydroxybenzaldehyde, commonly known as "vanillin".The process for the hydroxyalkylation of a carbocyclic aromatic ether of the invention consists of reacting the aromatic ether with a carbonyl compound in the presence of a catalyst and is characterized in that the hydroxyalkylation reaction is carried out in the presence of an effective quantity of a zeolite.

Abstract: A method of cycloalkylating naphthalene with at least one cyclic group, characterized by the following points:a) as catalyst, there is used a zeolite of faujasite structure having pore openings greater than 6.7 .ANG., the silica/alumina ratio of this zeolite being greater than 2.5 and its residual content of alkaline ion(s) being less than 3%;b) the reaction is carried out batchwise in heterogenous liquid/solid phase at a temperature of between 20.degree. C. and 250.degree. C., under a pressure at most equal to 30 bars. Cycloalkylated naphthalenes are obtained by this method, in particular 2,6-dicyclohexyl naphthalene.

Abstract: A method of preparing an alkylated aromatic product (12) by alkylation of an aromatic compound (1), the alkylation producing several alkylated aromatic products, this method being characterized by the following points:(a) the aromatic compound (1) is reacted with an alkylating agent (2) in the presence of an alkylation zeolite (4);(b) the alkylated aromatic product (12) is separated by crystallization from the products of the alkylation;(c) the uncrystallized part (13) of the alkylated aromatic products is subjected to a dealkylation in the presence of a dealkylation zeolite (15);(d) the regenerated aromatic compound (1.sub.b) is recycled in order to react it again with the alkylating agent (2) in the presence of the alkylation zeolite (4). Alkylated aromatic compounds (12) obtained by this method, in particular 2-6 dicyclohexyl naphthalene.