Identification of C2-C5 products from CO2 hydrogenation over PdZn/TiO2-ZSM-5 hybrid catalysts.

Jonathan Ruiz Esquius,Michael Bowker,Graham J Hutchings,Hasliza Bahruji

doi:10.1039/d0fd00135j

Jonathan Ruiz Esquius, Michael Bowker + Show 2 more

Open Access

https://doi.org/10.1039/d0fd00135j

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Abstract

The combination of a methanol synthesis catalyst and a solid acid catalyst opens the possibility to obtain olefins or paraffins directly from CO2 and H2 in one step. In this work several PdZn/TiO2-ZSM-5 hybrid catalysts were employed under CO2 hydrogenation conditions (240-360 °C, 20 bar, CO2/N2/H2 = 1 : 1 : 3) for the synthesis of CH3OH, consecutive dehydration to dimethyl ether and further oxygenate conversion to hydrocarbons. No significant changes after 36 h reaction on the methanol synthesis catalyst (PdZn/TiO2) were observed by XRD, XAS or XPS. No olefins were observed, indicating that light olefins undergo further hydrogenation under the reaction conditions, yielding the corresponding alkanes. Increasing the aluminium sites in the zeolites (Si : Al ratio 80 : 1, 50 : 1 and 23 : 1) led to a higher concentration of mild Brønsted acid sites, promoting hydrocarbon chain growth.

Highlights

The sustainable production of energy is one of the major challenges of modern society.[1,2] Several technologies have been developed to harvest renewable energy in the form of electricity.[2]
In addition to PdZn/TiO2 employed as a CH3OH synthesis catalyst,[20,21,22,23] commercial ZSM-5 zeolites with various sites in the zeolites (Si)/Al ratios (23, 50 and 80) were used as solid acid catalysts to promote consecutive CH3OH dehydration to DME27–30 and further methanol to ole ns (MTH)/dimethyl ether to ole ns (DMTH).[32,33,34]
Comparable CO2 conversion and CO productivity to PdZn/TiO2 were observed for all PdZn/TiO2–ZSM-5 hybrid catalysts (Fig. 2), indicating that the activity of the methanol synthesis catalyst is not altered by the proximity of solid acid zeolites, and that ZSM-5 zeolites are not active towards the reverse water gas shi (RWGS)

Summary

Introduction

The sustainable production of energy is one of the major challenges of modern society.[1,2] Several technologies have been developed to harvest renewable energy (e.g., solar panels, wind farms) in the form of electricity.[2]. In addition to PdZn/TiO2 employed as a CH3OH synthesis catalyst,[20,21,22,23] commercial ZSM-5 zeolites with various Si/Al ratios (23, 50 and 80) were used as solid acid catalysts to promote consecutive CH3OH dehydration to DME27–30 and further MTH/DMTH.[32,33,34] XRD patterns, pore sizes and BET surface areas for the commercial ZSM-5 zeolites a er annealing (static air, 550 C, 10 C minÀ1, 6 h) can be found in the ESI (Fig. S1 and Table S1,† respectively).

Results

Conclusion