Patent ID: 7718836
Filing Date: 2010-05-18
Classification: C07C,Y02P

Abstract:
1. A process for the preparation of high purity 2,6-dimethylnaphthalene starting from hydrocarbon mixtures comprising naphthalene and/or isomers of methylnaphthalene and/or isomers of dimethylnaphthalene and/or isomers of polymethylnaphthalene, and from a methylating agent which are reacted in a benzene solvent in the presence of a catalyst comprising a zeolite, the process comprising: enriching, by means of distillation, of the hydrocarbon mixture of interest with the consequent production of a first hydrocarbon fraction comprising a high concentration of the above naphthalene compounds and a second fraction comprising prevalently non-naphthalene compounds; treating the mixture of naphthalene compounds obtained in the previous step with an acid catalyst in a methylated benzene solvent; alkylating the mixture comprising said solvent and said naphthalene compounds by reaction with a methylating agent in a benzene solvent in the presence of a catalyst comprising a zeolite; transalkylating the hydrocarbon mixture consisting of naphthalene and/or isomers of dimethylnaphthalene and/or isomers of polymethylnaphthalene, carried out in the presence of a solid acid catalyst, which may be based on acid zeolites, and a mixture of methylated benzene solvents consisting essentially of benzene, toluene and xylenes with an overall molar ratio between methyls and benzene ring of less than 2, in order to obtain a hydrocarbon mixture characterized by a higher concentration of methylnaphthalene isomers; at least one separating phase, by distillation, of the mixtures resulting from said alkylating or said transalkylating; at least one purifying phase of the mixtures coming from said alkylating or said translkylating, by means of crystallization operations and washings carried out in the presence of a low molecular weight alcohol selected from the group consisting of methanol, ethanol, propanol, and a glycol, in order to obtain the separation of the 2,6-dimethyl-naphtalene from the fraction prevalently consisting of dimethylnaphtalene.