Hydrocarbon cracking process for converting gas oil preferentially to middle distillate and lower olefins

1. A hydrocarbon cracking process for converting a heavy hydrocarbon feedstock preferentially to middle distillate and lower olefins, wherein said hydrocarbon cracking process comprises:

catalytically cracking said heavy hydrocarbon feedstock within a riser reactor zone by contacting under suitable catalytic cracking conditions within said riser reactor zone said heavy hydrocarbon feedstock with a middle distillate selective cracking catalyst in combination with a shape selective zeolite additive that are introduced into said riser reactor zone,

wherein said middle distillate selective cracking catalyst comprises a molecular sieve component, an alumina component, and an inorganic refractory matrix component,

wherein said middle distillate selective cracking catalyst comprises a zeolitic surface area less than 130 m 2 /g,

whereby said heavy hydrocarbon feedstock is preferentially converted to middle distillate and lower olefins.

2. A hydrocarbon cracking process as recited in claim 1 , wherein said alumina component of said middle distillate selective cracking catalyst is present therein in an amount in the range of from 40 wt. % to 65 wt. %, with the weight percent being based upon the total weight of the middle distillate selective cracking catalyst.

3. A hydrocarbon cracking process as recited in claim 2 , wherein said molecular sieve component of said middle distillate selective cracking catalyst provides a total zeolitic surface area within said middle distillate selective cracking catalyst of less than 110 m 2 /g, and wherein said inorganic refractory matrix component of said middle distillate selective catalyst provides a total matrix surface area within said middle distillate selective cracking catalyst in the range of from 20 m 2 /g to 90 m 2 /g.

4. A hydrocarbon cracking process as recited in claim 3 , wherein the ratio of total zeolitic surface area to total matrix surface area is in the range of from 1:1 to 2:1.

5. A hydrocarbon cracking process as recited in claim 4 , wherein the weight ratio of said middle distillate selective cracking catalyst to said heavy hydrocarbon feedstock introduced into said riser reactor zone is in the range of from 0.1:1 to 20:1.

6. A hydrocarbon cracking process as recited in claim 5 , wherein the amount of said shape selective zeolite additive introduced into said riser reactor zone is in the range upwardly to 30 weight percent of said middle distillate selective cracking catalyst introduced into said riser reactor zone.

7. A hydrocarbon cracking process as recited in claim 6 , further comprising: introducing steam into said riser reactor zone in an amount such that the weight ratio of steam introduced into said riser reactor zone to said heavy hydrocarbon feedstock introduced into said riser reactor zone is in the range of upwardly to 15:1.