Hydrothermal stability of sapo-34 in the methanol-to-olefins process

Abstract EN

A new methanol-to-olefins (MTO) process for the produetion of ethylene, propylene, and butenes has been jointly developed by UOP and Norsk Hydro.

The process converts methanol to 49 mol-% ethylene, 32 mol-% propylene, and 10 mol-% butenes (based on carbon) at near 100% conversion.

The SAP034 catalyst used in this process retires fre^ent carbon-burn regenerations to remove nonvolatile coke deposits from within the micropores of the molecular sieve.

The paper describes the results of accelerated hydrothermal aging of SAP034 powder to understand what structural changes might occur during the multiple reaction-regeneration cycles of the MTO process.

No degradation of the SAPO-34 molecular sieve structure is seen after either lower temperature hydrothermal aging (450°C) or 205 cycles of reaction and regeneration in the MTO process.

Partial SAPO-34 structural collapse to a dense-phase crystalline aluminophosphate and condensed silica has been found to occur at severe hydrothermal conditions (650°C).

Both the pure SAPO-34 powder and spray-dried catalyst undergo this transformation to a similar extent.

These findings indicate that the SAPO-34 structure collapse does not appear to be a major concern for the long-term stability of the MTO catalyst.