Mild hydrocracking process using catalysts containing dealuminated y-zeolites

A process for mild hydrocracking of a hydrocarbon feedstock having a substantial proportion of components boiling below about 1000.degree. F., said process comprising contacting said hydrocarbon feedstock under conditions of elevated temperature and a hydrogen pressure of less than about 1500 psig with a particulate catalyst comprising about 1.0 to about 6.0 wt. % of an oxide of a Group VIII metal;

• about 12.0 to about 25.0 wt. % of an oxide of molybdenum and 0.1 to about 3.0 wt. % of an oxide of phosphorus all supported on a porous support comprising (1) a matrix selected from the group consisting of precipitated alumina and silica-alumina containing about 1.0 to about 3.0 wt. % of silica and (2) about 5.0 to about 35 wt. %, based on the weight of the support, of hydrogen form, acidified, dealuminated Y-zeolite having a silica to alumina mole ratio of about 10-120, a secondary pore volume of about 0.14-0.20 cc/g, a unit cell size of about 24.23-24.33 .ANG., a secondary pore mode of about 115-145 .ANG., a secondary pore diameter of about 100-600 .ANG., a surface silicon to aluminum atom ratio of about 24-45, and an acid site density of about 1-5 cc NH.sub.3 /g of zeolite, in such a manner that the molybdenum gradient of the catalyst ranges from about 1 to about 20, said conditions being such as to yield about a 10 to about a 60 Vol % conversion of the hydrocarbon feedstock boiling above 650.degree. F. to hydrocarbon products boiling at or below 650.degree. F., wherein the said catalyst is characterized by having about 40 to about 65% of the total pore volume in pores of diameters from about 20 .ANG. below the pore mode diameter to about 20 .ANG. above the pore mode diameter and the pore mode diameter is in the range of about 80 to about 120 .ANG. and wherein the said catalyst is further characterized by having a total surface area of about 200 to about 300 m.sup.2 /g and a total pore volume of about 0.55 to about 0.75 cc/g, with a pore volume distribution such that micropores having diameters less than 100 .ANG. constitute less than 40%, pores having diameters of 100-160 .ANG. constitute about 25 to about 50%, pores having diameters greater than 160 .ANG. constitute about 25 to about 50% of the total pore volume of the catalyst, macropores having diameters greater than 250 .ANG. constitute about 15 to about 40%, and macropores having diameters greater than 1500 .ANG. constitute less than 10% of the total pore volume.