Process for the preparation of an aromatic hydrocarbon mixture using iron crystalline silicates

#The invention relates to a process for the preparation of an aromatic hydrocarbon mixture from a mixture of aliphatic compounds.

#Aromatic hydrocarbon mixtures are used on a large scale as gasoline. By distillation and extraction, individual aromatic compounds can be isolated from them such as benzene, toluene, the xylenes, and ethylbenzene which are used on a large scale as base materials for the chemical industry. Until recently, aromatic hydrocarbon mixtures suitable for the above-mentioned applications were prepared mainly by catalytic reforming of aliphatic hydrocarbon mixtures.

#In an investigation concerning the preparation of aromatic hydrocarbon mixtures from aliphatic compounds, it was found that certain crystalline silicates which were recently synthesized for the first time, and described in Netherlands Patent Application No. 7,613,957 incorporated herein by reference, are suitable for use as catalyst for the preparation of aromatic hydrocarbon mixtures from aliphatic oxygen-containing hydrocarbons having the general formula C.sub.n H.sub.m O.sub.p. By contacting a compound of this type at an elevated temperature with a catalyst containing one of these crystalline silicates, a hydrocarbon mixture is obtained which can be separated into a mixture of aliphatic hydrocarbons with from one to four carbon atoms in the molecule and an aromatic hydrocarbon mixture of which the components contain five and more carbon atoms in the molecule.

#The invention will now be further explained with reference to the following example.

#A crystalline iron-aluminum silicate (silicate A) was prepared as follows: a mixture of Fe(NO.sub.3).sub.3, Al(NO.sub.3).sub.3, SiO.sub.2, NaNO.sub.3, and [(C.sub.3 H.sub.7).sub.4 N]OH in water with the molar composition Na.sub.2 O.4.5](C.sub.3 H.sub.7).sub.4 N].sub.2 O. 0.5 Al.sub.2 O.sub.3.0.5 Fe.sub.2 O.sub.3.29.1 SiO.sub.2. 428 H.sub.2 O was heated in an autoclave at 150.degree. C. under autogenous pressure for 48 hours. After the reaction mixture had cooled down, the silicate formed was filtered off, washed with water until the pH of the washed water was about 8, and dried for two hours at 120.degree. C. Silicate A, thus prepared, had the following chemical composition: 0.86[(C.sub.3 H.sub.7).sub.4 ].sub.2 O. 0.3 Na.sub.2 O. 0.55 Fe.sub.2 O.sub.3. 0.45Al.sub.2 O.sub.3. 32 SiO.sub.2. 8H.sub.2 O. The silicate had an x-ray powder diffraction pattern substantially as given in Table B of Netherlands Patent Application No. 7,613,957. The silicate was thermally stable up to temperatures higher than 1,000.degree. C. and was capable, after dehydration at 400.degree. C. in vacuum, of adsorbing 7.8%w water at 25.degree. C. and saturated water vapor pressure. With silicate A as the starting material, silicate B was prepared by successively calcining silicate A at 500.degree. C., boiling with 1.0 molar NH.sub.4 NO.sub.3 solution, washing with water, boiling again with 1.0 molar NH.sub.4 NO.sub.3 solution and washing, drying at 120.degree. C., and calcining at 500.degree. C.

#Three experiments were carried out in which methanol, acetic acid, and a 5:1 molar mixture of methanol and acetic acid were contacted with silicate B as the catalyst at a temperature of 375.degree. C., a pressure of 3 bar and a space velocity of 0.67 1.1.sup.-1.h.sup.1. The results of these experiments are given in the following table: