Abstract: The pore structure, aluminum distribution and acid properties of Beta zeolite were adjusted by the dealumination with organic acid and subsequent the phosphoric acid modification. The modified Beta zeolite was characterized to investigate its physicochemical properties, hydrothermal stability and the catalytic performance for producing isobutylene. The results showed that after modification, the hydrothermal stability of modified Beta zeolite is improved and the channel is more open due to removal of non-framework aluminum. The ratio of Bronsted acid to Lewis acid is increased. The microactivity of modified Beta zeolite aged under the conditions of 800℃，17h，and 100% steam is close to that of USY zeolite due to increased hydrothermal stability. The addition of additives containing modified Beta zeolite into FCC catalyst significantly increases the FCC isobutylene yield. The commercial results proved that adding the additives increases the LPG yield by 2.68%, in which the yields of propylene and isobutylene increase by 1.01% and 0.54%, respectively.

Key words: catalytic cracking, isobutene, Beta zeolite, modification, organic acid, phosphorus