Hydrocarbon conversion process employing essentially alumina-free zeolites

DETAILED DESCRIPTION What is claimed is: 1.
A process for converting a hydrocarbonaceous feedstock by subjecting the feedstock to catalytic reactions in three zones, the process comprising the steps of catalytically hydroprocessing the feedstock in a first reaction zone, contacting the product of the first zone in a second reaction zone under cracking conditions including a temperature of from about 650.
degree.
-1100.
degree.
F.
, a pressure of from about 0-2000 psig and an LHSV of from about 0.
1-10 with a first catalyst comprising an essentially alumina-free intermediate pore size zeolite and, immediately thereafter, contacting the product of the second reaction zone in a third reaction zone with a second catalyst comprising an essentially alumina-free intermediate pore size zeolite under cracking conditions less severe than the cracking conditions in the second reaction zone including a temperature of from about 400.
degree.
-700.
degree.
F.
, a pressure of from about 0-2000 psig and an LHSV of from about 0.
1-10 wherein the less severe cracking conditions are obtained by maintaining a lower temperature in the third reaction zone than in the second reaction zone so as to favor polymerization in the third zone of olefins formed in the second zone whereby selectivity to C.
sub.
5.
sup.
+ is increased.
2.
The process of claim 1 wherein the second and third reaction zones are contained within different reactors.
3.
The process of claim 1, wherein the first reaction zone is contained in a first reactor and the second and third reaction zones are contained in a second reactor.
4.
The process of claim 1 wherein the first and second catalysts comprise a ZSM-5 type crystalline silicate having a mole ratio of oxides SiO.
sub.
2 :Al.
sub.
2 O.
sub.
3 of greater than about 200.
5.
The process of claim 1 wherein the first and second catalysts comprise a ZSM-5 type crystalline silicate having a mole ratio of oxides SiO.
sub.
2 :Al.
sub.
2 O.
sub.
3 greater than about 500.
6.
The process of claim 1 wherein the first and second catalysts comprise a ZSM-5 type crystalline silicate having a mole ratio of oxides SiO