Kh. Lee et al., CATALYTIC CRACKING OF VACUUM GAS OIL OVER THE MODIFIED MORDENITES ANDY-TYPE ZEOLITES MIXED WITH ALUMINA, Industrial & engineering chemistry research, 37(5), 1998, pp. 1761-1768
Catalytic cracking of vacuum gas oil has been studied over pure zeolit
es modified by steaming and acid treatment, and zeolite/alumina cataly
sts containing any of the former zeolite (35 wt %) and alumina (65 wt
%) with a different pore size distribution. The conversion of vacuum g
as oil (VGO) over zeolite/alumina catalysts with a wide pore size dist
ribution is almost the same as that over pure zeolites, but less coke
is formed over zeolite/alumina compared to that over pure zeolites. Th
e catalysts containing zeolite Y show higher conversion of VGO than on
the catalysts containing mordenite. In addition, the catalysts contai
ning modified mordenite, resulting in the development of mesopores, ha
ve improved activity and selectivity for gasoline compared to those co
ntaining mordenite with a micropore structure. Selectivity of olefin i
s higher on the catalysts containing mordenites compared to the cataly
sts containing zeolite Y because of low-bimolecular hydrogen-transfer
reaction rates. The distribution of paraffin and olefin in gasoline pr
oducts does not depend on the addition of alumina in mixed catalysts b
ut rely on mainly the zeolite type. The influence of shape selectivity
on products distribution causes the catalysts containing zeolite Y wi
th large kinetic diameter to produce more branched aromatics than thos
e containing mordenites. The modified mordenite catalysts having mesop
ores in the 4-nm range yield more aromatics compared to the catalysts
containing mordenite with mostly micropore. Catalysts containing zeoli
te Y give the highest yield of xylene whereas the catalysts containing
mordenites produce a maximum yield of toluene.