Reaction Condition Optimization and Lumped Kinetics Study for Lower Alcohols Synthesis from Syngas Using a Two-Stage Bed Catalyst Combination System

Abstract

A novel two-stage catalyst combination system for CO hydrogenation was applied. First, the thermal coupling conditions between modified Fisher–Tropsch (FT) synthesis catalyst Cu25Fe22Co3K3/SiO2 and methanol synthesis catalyst Cu/ZnO/Al2O3 were investigated. Then, the loading mode and volume of Cu/ZnO/Al2O3 and Cu25Fe22Co3K3/SiO2 catalyst combination system for lower alcohols synthesis was optimized. The obtained thermal coupling conditions were as follows: (reduction conditions) T = 400 °C, P = 0.5 MPa, and GSHV = 840 h–1; (reaction conditions) T = 280 °C, P = 5.5 MPa, and GSHV = 2800 h–1. Under these conditions, the per-pass conversion of CO and yield of lower alcohols reached 48.3% and 492.0 g kg–1 h–1, respectively, over the two-stage bed catalyst combination system of Cu25Fe22Co3K3/SiO2 (2.5 mL)//Cu/ZnO/Al2O3 (2.5 mL). It was indicated that the combined loading mode in a two-stage bed reactor showed better catalytic performances than single or mixed loading mode in a single bed reactor. Through a lumped kinetics study over the Cu25Fe22Co3K3/SiO2 (2.5 mL)//Cu/ZnO/Al2O3 (2.5 mL) two-stage bed catalyst combination system, this can be due to the improvement of methanol synthesis over the lower Cu/ZnO/Al2O3 catalyst which was promoted by the generated CO2 from the upper Cu25Fe22Co3K3/SiO2 catalyst.