Catalytic cracking of light-naphtha over MFI-zeolite/metal-oxide composites for efficient propylene production

The proprietary cracking catalysts for producing propylene efficiently from light-naphtha were developed in the present study in order to meet future demand for propylene and utilize various light paraffinic hydrocarbons (e.g., light-naphtha derived from crude oil, condensates recovered from natural gas and GTL-naphtha). The composite catalysts, consisting of Al-MFI zeolites containing two kinds of heteroatom (Fe, Ga) and metal oxides (e.g., aluminum oxide), were employed for n-hexane cracking at around 550 °C. Since these catalysts reduced acid strength by Fe atoms and accelerated dehydrogenation for paraffinic hydrocarbons by Ga atoms, selective production of propylene was accomplished by suppressing formation of aromatics under mild conditions, resulting in the high propylene yields (18–31 wt%). Moreover, catalytic activities were maintained for ca. 80 h in cracking of n-hexane without dilution, suggesting that the energy-saving process for propylene production from light-naphtha could be realized in the fixed-bed operation by using the present catalysts.