Study on Process Parameters for Highly Selective Synthesis of Ethanol from Methanol, Carbon Dioxide and Hydrogen

Abstract

This study investigates the highly selective synthesis of ethanol from methanol, CO2, and H2 over a Ru-Co bimetallic catalyst, focusing on reaction condition optimization, kinetics, scale-up feasibility, and catalyst stability. The optimal reaction conditions were identified as 170 °C, a (CO + CO2)/H2 initial pressure ratio of 1:13.33, a CO/CO2 initial pressure ratio of 1:3, a methanol/catalyst solution mass ratio of 1:18.96, and a reaction time of 1~4 h, at which the space–time yield (STY) of ethanol exceeded 2 g·L−1·h−1 while the ethanol selectivity remained above 93%. Kinetic analysis confirmed the methanol–CO hydrogenation pathway (Ea = 43.42 kJ·mol−1) as the dominant route for ethanol formation, with the reverse water–gas shift (RWGS) reaction serving as the temperature-sensitive key step for in situ CO generation. Scale-up from a 20 mL to 3 L reactor showed similar catalytic performance. Notably, the catalyst showed excellent long-term stability over 30 recycling runs (150 cumulative hours). This work provides a mild, efficient, and scalable route for ethanol production from CO2 and methanol, aligned with carbon neutrality strategies.