Modulating the Formation of Coke to Improve the Production of Light Olefins from CO2 Hydrogenation over In2O3 and SSZ-13 Catalysts
Artikel i vetenskaplig tidskrift, 2023

Moderately acidic aluminophosphates (SAPOs) are often integrated with methanol synthesis catalysts for the hydrogenation of CO2 to olefins, but they suffer from hydrothermal decomposition. Here, an alternative SSZ-13 zeolite with high hydrothermal stability is synthesized and coupled with an In2O3 catalyst in a hybrid system. Its performance regarding selectivity for olefins and coke formation was investigated for CO2 hydrogenation under varying temperatures and pressures. Various reactions occur, producing mainly CO and different hydrocarbons. The results indicate that the hydrogenation of hydrocarbons are dominant at high temperatures (around 400 °C) over SSZ-13 zeolite with a high acid density and that the coke deposition rate is slow. Polymethylbenzenes are the main coke species, but the selectivity for light olefins is low among hydrocarbons at high temperatures. However, at low temperatures (around 325 °C), and especially under high pressure (40 bar), methanol disproportionation becomes significant. This results in an increased selectivity for light olefins; however, it also leads to a rapid coke deposition, which gives inactive adamantanes as the main coke species that block the pores and cause rapid deactivation. However, after coking at 325 °C and regeneration at 400 °C under the reaction atmosphere, the accumulated adamantanes can be decomposed into smaller coke species, which reopens the channel structure and generates modulated active sites within the zeolite, resulting in a higher yield of olefins without deactivation. The performances of acidic SSZ-13 zeolites, with varying ratios of Si/Al in transient experiments, further verified that a dynamic balance exists between the formation and degradation of coke within the SSZ-13 zeolite during a long-term CO2 hydrogenation reaction. This balance can be achieved by optimizing the reaction conditions to match the acid density of the catalyst. Using the conditions of 20 bar and 375 °C, with a H2 to CO2 mole ratio of 3, the results obtained for the precoked hybrid catalysts of In2O3 and SSZ-13 (Si/Al = 25) exhibited very stable activity, with the selectivity for light olefins (based on hydrocarbons formed) of max. 70% after 100 h time-on-stream. This work provides new insights into the design of stable hybrid catalysts, especially the influence of a precoking process for SSZ-13 zeolite in the production of light olefins.

Catalysts

Zeolites

Selectivity

Hydrocarbons

Coke

Författare

Wei Di

Chalmers, Kemi och kemiteknik, Kemiteknik

Abdenour Achour

Chalmers, Kemi och kemiteknik, Kemiteknik

Hoang Phuoc Ho

Chalmers, Kemi och kemiteknik, Kemiteknik

Sreetama Ghosh

Chalmers, Kemi och kemiteknik, Kemiteknik

Oleg Pajalic

Perstorp Specialty Chemicals AB

Lars Josefsson

Josefsson Sustainable Chemistry AB

Louise Olsson

Chalmers, Kemi och kemiteknik, Kemiteknik

Derek Creaser

Chalmers, Kemi och kemiteknik, Kemiteknik

Energy & Fuels

0887-0624 (ISSN) 1520-5029 (eISSN)

Vol. 37 22 17382-17398

Ämneskategorier

Kemiska processer

Materialkemi

Annan kemiteknik

DOI

10.1021/acs.energyfuels.3c03172

Mer information

Senast uppdaterat

2024-03-07