Lifetime improvement in methanol-to-olefins catalysis over chabazite materials by high-pressure H2 co-feeds

• Published in: Nature catalysis Vol. 1; no. 9; pp. 666 - 672
• Main Authors: Arora, Sukaran S., Nieskens, Davy L. S., Malek, Andrzej, Bhan, Aditya
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24-08-2018
• Subjects: 639/638/77/887; 639/638/898; Catalysis; Chemistry; Chemistry and Materials Science
• ISSN: 2520-1158; 2520-1158
• DOI: 10.1038/s41929-018-0125-2

Mitigating catalyst deactivation in the industrially deployed process of methanol-to-olefins conversion over HSAPO-34 is a critical challenge. Here, we demonstrate that lifetime in methanol-to-olefins catalysis over HSAPO-34 at sub-complete methanol conversion, as determined by the cumulative turnover capacity per Brønsted acid site towards hydrocarbon products in the effluent before complete catalyst deactivation (~15% carbon final conversion), can be enhanced with increasing efficacy (~2.8× to >70×) by co-feeding H
2
at increasing partial pressures (400–3,000 kPa) in the influent with methanol compared with co-feeding helium at equivalent pressures. The lifetime improvement in the presence of high-pressure H
2
co-feeds is observed to be more prominent at complete methanol conversion than at sub-complete conversion. The improvements in catalyst lifetime by co-feeding H
2
are rendered without any deleterious effects on C
2
–C
4
olefins selectivity, which remains ~85% carbon irrespective of the inlet H
2
pressure. These observations can be rationalized based on the participation of H
2
in hydrogen transfer reactions, and in effect, the interception of pathways that promote the formation of deactivation-inducing polycyclic species.
Small-pore zeolites that engender high selectivity for light olefins in the conversion of methanol to olefins deactivate rapidly due to the accumulation of unreactive carbonaceous deposits. Now, experiments show that high-pressure hydrogen added to the methanol feed can substantially enhance catalyst lifetime without compromising selectivity.