Zn‐Al hydrotalcite‐derived Co x Zn y AlO z catalysts for hydrogen generation by auto‐thermal reforming of acetic acid

Abstract

Auto-thermal reforming (ATR) of acetic acid (HAc) is considered as a promising route for hydrogen generation from renewable resources, while oxidation, coking, and sintering need to be addressed for durable catalysts in ATR. In the current work, Zn-Al hydrotalcite-derived CoxZnyAlOz catalysts were prepared by co-precipitation and evaluated in a fixed-bed tubular quartz continuous-flow reactor. The Co0.70Zn3.30AlO5.5 ± δ catalyst presented a HAc conversation near 100% and a stable hydrogen yield near 3.01 mol-H2/mol-HAc. The characterization results of XRD, H2-TPR, BET, SEM, XPS, and TG indicated that the hydrotalcite structure was obtained via co-precipitation method; over the hydrotalcite-derived mixed oxides, (a) the specific surface area was increased with high dispersion of Co, (b) the phases of ZnO with spinel of ZnAl2O4,CoAl2O4, Co3O4, and ZnCo2O4 were beneficial to improve resistance to coking and oxidation, and (c) the relative stability of Co species over ZnO and spinel phases helps to suppress sintering. Meanwhile, ratio of O/C and temperatures near 0.28 and 650 °C, respectively, were also evaluated and proposed as optimized conditions for hydrogen generation, and the durable Co0.70Zn3.30AlO5.5 ± δ catalyst produced a rate of 114.9 mmol-H2/s/g-catalyst in a 15-hour ATR test, showing promising potential for hydrogen generation.