Synthesis of bi-phases composite zeolites MFZ and its hierarchical effects in isopropylbenzene catalytic cracking

Composite zeolites composed of MOR and FAU (denoted as MFZ) were synthesized by a two-step hydrothermal crystallization procedure, in which the mixture of pre-synthesized mordenite zeolite acts as the nutrients for the growth of post-synthesized Y zeolite. The structural, crystalline, and textural properties of the as-synthesized materials, as well as the references Y and mordenite zeolite samples, were characterized by XRD, FT-IR, in situ IR spectrometry of pyridine, NH3-TPD, N2 adsorption–desorption and SEM; the composite zeolites and the corresponding physical mixture were investigated during isopropylbenzene catalytic cracking. The results show that the ratio of MOR to FAU in the as-synthesized composite zeolites largely depends on the second-step crystallization time. When the crystallization time is 10–17 h, a composite with different ratio of MOR to FAU can be obtained; as compared with the corresponding physical mixture, the composite sample has a higher isopropylbenzene conversion and a longer catalytic life due to the introduced hierarchical pores system. The catalytic activity of isopropylbenzene cracking over the catalysts has a linear dependence with the revised hierarchy factor (HF′).

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► Hierarchically structured composite zeolites composed of MOR and FAU were prepared.
► Excessive introduction of mesopores into composite zeolites is not beneficial.
► Penalty paid in micropore volume and areas results in a less efficient catalyst.