Synthesis of ITQ-2 zeolite under static conditions and its properties

摘要

Using silica gel as the precursor, MCM-22(p) was synthesized under the static conditions. Then ITQ-2 zeolite was obtained by using n-cetyltrimethylammonium bromide (CTAB) and tetrapro-pylammonium hydroxide (TPAOH) as the swelling agents to swell the pores of MCM-22(p). The obtained zeolite was characterized by XRD, SEM, BET, NH_3-TPD. The results show that the zeolite had the best swelling when MCM-22(p):CTAB:TPAOH = 1:4:1. The synthesis duration and temperature did not influence significantly the pore swelling. Except TPAOH, CTAB can also be used together with tetrabuthylammonium hydroxide (TBAOH) as the pore swelling agent. There was contribution of surface area and pore volume from the mesoporous pores in the ITQ-2 zeolite and it also showed weaker acidity than MCM-22. However, the ITQ-2 supported NiW catalyst showed higher activity and selectivity to the middle distillates in the hydrocracking of vacuum gasoil (VGO) than MCM-22 supported catalyst. This implied that the diffusion of large molecules of heavy oil in the catalyst was facilitated due to the presence of the mesoporous pores and hence higher activity and selectivity to middle distillates.