CO2 hydrogenation to formic acid over heterogenized ruthenium catalysts using a fixed bed reactor with separation units

Abstract

Along with the mitigation of CO2 emission, recently, the CO2-derived formic acid process has drawn attention as a promising platform for the renewable-energy-derived hydrogen storage cycle by using formic acid as a liquid organic hydrogen carrier (LOHC). Here, a heterogenized Ru molecular catalyst on a bpyTN-30-CTF support is prepared and successfully implemented in an integrated trickle-bed reactor system for continuous CO2 hydrogenation to produce formic acid. The bpyTN-30-CTF support with an alternative structure of the bpy and TN motif increases the porosity and metal anchoring sites. The Ru/bpyTN-30-CTF catalyst prepared using the bpyTN-30-CTF support displays sufficient catalytic activity for commercialization. Under the continuous process, the catalyst exhibits substantial catalytic performance with the highest productivity of 669.0 gform. gcat-1 d-1 with CO2 conversion of 44.8% for a superficial gas velocity of 72 cm s-1. Furthermore, the catalyst shows excellent stability in the continuous hydrogenation process with a trickle-bed reactor over 30 days of operation, reaching a total turnover number of 524 000 without any significant deactivation. Based on kinetic data, a new process to produce formic acid by CO2 hydrogenation has thus been proposed here. © 2020 The Royal Society of Chemistry.