Abstract: A high silica content zeolite-based catalyst for use in a reaction which uses a feedstock containing an aromatic hydrocarbon or which gives a product containing an aromatic hydrocarbon, which catalyst satisfies the following requirements (1), (2), (3) and (4): (1) the zeolite constituting a zeolite-based catalyst has an SiO2/Al2O3 molar ratio of from 20 to 200; (2) the zeolite constituting a zeolite-based catalyst has a primary particle diameter of from 0.3 to 3 &mgr;m; (3) when a zeolite-based catalyst is converted into H type, the H type zeolite-based catalyst has a ratio of the number of surface acid sites to the total number of acid sites is from 0.03 to 0.15; and (4) a zeolite-based catalyst exhibits a pyridine-desorbed amount (B) as measured at a temperature of from 500° C. to 900° C. by a hot desorption method when converted into H type after being subjected to a steam treatment at an H2O partial pressure of 0.8 atm and a temperature of 650° C.

Abstract: Disclosed is a method for producing aromatic hydrocarbons, which comprises contacting a light hydrocarbon feedstock comprising olefins and/or paraffins with a zeolite catalyst in a fixed-bed, adiabatic reactor containing a fixed catalyst bed comprised of the zeolite catalyst, to thereby effect a catalytic cyclization reaction of the light hydrocarbon feedstock, wherein the catalytic cyclization reaction is performed under conditions which satisfy the following requirements: (1) the zeolite catalyst has an initial stage-catalytic activity of 0.2 (sec.sup.-1) or more in terms of the initial stage, first-order reaction rate constant of the decomposition of n-hexane catalyzed by the zeolite catalyst; (2) the catalyst bed has a temperature of from 450.degree. C. to 650.degree. C.

Abstract: A method for partially dealuminating a zeolite catalyst by steaming, which comprises feeding steam to and flowing the steam through a reactor containing a catalyst bed of a zeolite catalyst to contact the zeolite catalyst with the steam for 0.1 to 50 hours under temperature distribution conditions which satisfies the following requirements (1) and (2):(1) 500.degree. C..ltoreq.T.sub.0 .ltoreq.T.ltoreq.T.sub.2 .ltoreq.700.degree. C. wherein T.sub.0 is the temperature (.degree.C.) of the fed steam; T.sub.2 is the maximum temperature (.degree.C.) of the catalyst bed; and T is the average temperature (.degree.C.) of the catalyst bed, which is defined by the formula: ##EQU1## wherein T.sub.i is the time average temperature (.degree.C.) of the i-th block of n equilength blocks of the catalyst bed, which are arranged along the direction of steam flow; and(2) cv(T).times.1000.ltoreq.