Abstract: 2-Methylalk-2-enals of the formula ##STR1## where R.sup.1 and R.sup.2 are each hydrogen, alkyl or an aromatic radical, are prepared by isomerization of an acrolein derivative of the formula ##STR2## with a zeolite catalyst, an aluminum silicate and/or an aluminum phosphate.

Abstract: Hard, fracture-resistant catalysts are prepared from zeolites of the pentasil family by a process in which water, organic additives which increase the viscosity and a silicate are added to the zeolite powder, and the material is molded, dried and calcined.The fracture-resistant zeolites obtained are used as catalyst carriers.

Abstract: Dienes are prepared by dehydration of aldehydes at elevated temperatures by a method in which the dehydration is carried out using a zeolite as a catalyst.

Abstract: Novel crystalline ZBH borosilicate zeolites of the pentasil type are prepared by hydrothermal crystallization of silicon dioxide and boric acid in the presence of alkali metal salts, at from 80.degree. to 140.degree. C. in an ethereal or aqueous-ethereal mixture.

Abstract: C.sub.2 -C.sub.4 -olefins are prepared by catalytic conversion of methanol and/or dimethyl ether in the presence of a zeolite catalyst at elevated temperatures, by a process in which the catalyst used is a pure borosilicate zeolite which has been tableted or extruded without a binder and treated with hydrofluoric acid and hydrochloric acid. The treatment of the catalyst with hydrofluoric acid is carried out using 0.001-1N HF, and that with hydrochloric acid is carried out using 3-25% strength acid. The time-on-stream of the catalyst is improved.

Abstract: C.sub.2 -C.sub.4 -olefins are prepared by catalytic conversion of methanol and/or dimethyl ether in the presence of a zeolite catalyst at elevated temperatures by a process wherein the catalyst used is a borosilicate zeolite which is treated with hydrogen fluoride, molded together with an amorphous aluminosilicate as a binder and then treated with hydrochloric acid.

Abstract: A process for the preparation of a crystalline aluminosilicate of the pentasil type by hydrothermal crystallization of SiO.sub.2 and Al(OH).sub.3 in the presence of an alkali metal salt at from 80.degree. to 250.degree. C., wherein the crystallization is carried out in ether or aqueous ether. Particularly suitable solvents include the ethers from the group of the poly-(ethylene glycol) dimethyl ethers and mixtures of these ethers with water. The use of these crystalline aluminosilicates as catalysts for alkylating aromatics, and for preparing olefins and/or aromatics from methanol and/or dimethyl ether is also described.

Abstract: A process for the preparation of olefins from methanol and/or dimethyl ether by conversion in the presence of a zeolite catalyst, in particular a borosilicate zeolite, at elevated temperature, with the addition of a small amount of an electron donor.

Abstract: A process for the preparation of lower olefins from methanol or dimethyl ether by catalytic conversion at from 300.degree. to 550.degree. C. in two stages over borosilicate zeolites, wherein C.sub.2 -C.sub.4 -olefins and C.sub.1 -C.sub.4 -paraffins are removed after the first reaction stage, the C.sub.5.sup.+ hydrocarbons are passed to the second reaction stage, the aromatics are removed from the reaction product of the second stage and the remaining reaction products are recycled. The advantage of this process is an improvement in the yield of olefins.

Abstract: The process for the preparation of olefins by converting methanol and/or dimethyl ether in the presence of a zeolite catalyst is improved by treating the catalyst with hydrogen fluoride. Aluminosilicate zeolites and borosilicate zeolites, especially those of the pentasil type, are chiefly used.