Controlling hydrocarbon oligomerization in phosphorus-modified CHA zeolite for a long-lived methanol-to-olefin catalyst

The catalytic performance of phosphorus-modified CHA zeolites, synthesized by direct phosphorus modification using tetraethylphosphonium as a phosphorus-modifying agent (P-MA), was investigated for the methanol-to-olefin (MTO) reaction. Comparative catalytic testing in the MTO reaction revealed that the phosphorus modification effectively prolonged the catalyst lifetime while hardly affecting the ethene and propene selectivities. The initial ethene and propene selectivities over CHA zeolite with P/Al ratio of 0.44 were 28.7 and 37.5 C %, respectively, and the catalytic life time improved from 4 to 7 h compared with the catalyst without phosphorus modification. The relative amount of non-aromatic hydrocarbons retained in the zeolite catalysts with respect to those of the aromatic ones increased with increasing degree of phosphorus modification. This demonstrates that the suppression of excess oligomerization of the hydrocarbon species results in a prolonged lifetime in the phosphorus-modified catalyst.