Hydrothermally stable catalysts of high activity and methods for their preparation

摘要

1,141,955. Crystalline aluminosilicate catalysts. MOBIL OIL CORP. 30 March, 1967 [30 March, 1966], No. 14577/67. Heading C1A. [Also in Division C5] Hydrothermally stable catalysts of high hydrocarbon conversion activity are prepared by calcining a crystalline ammonium aluminosilicate, having a silica/alumina mol ratio of at least 3, in the presence of rapidly flowing steam and base-exchanging the product of the calcination with an ammonium salt, e.g. NH 4 Cl. The process is particularly applicable to the ammonium form of zeolite Y. The calcination, e.g. at 900-1300‹ F. for 1À5- 12À5 hours, is believed to cause the formation of lattice aluminium defects and aluminiumcontaining cations, the resulting product being a hydrogen aluminium aluminosilicate: thus, after the base-exchange stage, a hydrogen ammonium alumino-silicate is obtained. Steam throughput may be 700-1000 ml./min. and the partial pressure of water-vapour therein may be greater than 0À3 atm. Preferably, chelation at pH 7-9 is than effected to remove amorphous aluminium - containing material formed during calcination, using an ammonium salt of ethylenediaminotetra-acetic acid, e.g. the diammonium dihydrogen salt. A similar chelation may be carried out in a pretreatment stage to remove amorphous agglomerates present in the channels of the starting material. The base-exchange and chelation steps carried out after the calcination may be reversed in order; ammonium chloride base-exchange may be eliminated if the amount of suitable chelating agent is increased to provide sufficient ammonium ions for exchange with aluminium cations formed by steaming. A finishing heattreatment in a steam-free environment may be employed.