Abstract: The aluminoborosilicate containing an alkaline earth metal element, e.g. calcium, characterized by the chemical composition and the X-ray diffraction pattern is prepared by the hydrothermal reaction of a reaction mixture containing the source materials of boron and the alkaline earth in a similar procedure to that for the preparation of ZSM-5 type zeolites. Different from the conventional ZSM-5 zeolites into which calcium ions are introduced by ion exchange, the calcium ions in the inventive aluminoborosilicate are not replaceable by ion exchange with protons or alkali metal ions. The aluminoborosilicate of the invention after conversion into the hydrogen form is an excellent catalyst for the conversion of methyl alcohol or dimethyl ether into lower olefins such as ethylene and propylene in respect of the selectivity and durability of the catalytic activity with remarkably decreased deposition of carbonaceous materials.

Abstract: Here is disclosed a method for preparing lower olefins by bringing methanol and/or dimethyl ether into contact with a catalyst in a gaseous phase. In this method, the contact between the methanol and/or dimethyl ether and the catalyst is carried out at a weight hourly space velocity of 0.1 to 20 hr.sup.-1 at a reaction temperature of 300.degree. to 650.degree. C. under a total pressure of 0.1 to 100 atm by the use of, as the catalyst, an alkaline earth metal-modified alkaline earth metal-containing zeolite catalyst; the alkaline earth metal-modified alkaline earth metal-containing zeolite catalyst being prepared as disclosed in the Specification by modifying an alkaline earth metal-containing aluminoborosilicate so that the alkaline earth metal in an amount of at least 0.25% by weight in terms of the metal may be mixed with or supported in the zeolite catalyst.