Enhancement of higher alcohols selectivity in Fischer-Tropsch synthesis using Walnut and Almond shell derived biochars as Copper/Cobalt catalyst support

Abstract

The production of higher alcohols from synthesis gas using biochar-supported copper-cobalt catalysts is investigated. Biochars were prepared via pyrolysis of Walnut shells and Almond shells and were subsequently activated through physical and chemical methods. A 15 wt% Copper and 5 wt% Cobalt was loaded on the activated biochars via the impregnation technique. The chemical and physical properties of the catalysts were studied using various methods. The catalytic performance of the catalysts was assessed in a fixed-bed microreactor at 20 bars, 320 °C, and, an H2/CO ratio of 2, and the results were compared with the γ-Alumina supported catalyst. Strong interaction between cobalt and copper particles and the formation of bimetallic CuCo2O4 species were observed. The catalysts' reducibility was enhanced by a factor of 1.42. The catalytic studies revealed a significant enhancement in the rate of carbon monoxide hydrogenation. The catalyst supported on low-cost Almond shell-derived biochar demonstrated the best performance. The total alcohol selectivity increased from 22.2 wt% to 34.2 wt%, and the C2+ alcohol selectivity rose from 78.3 wt% to 91.1 wt%, as compared to the industrial catalyst supported on alumina. However, the selectivity for C5+ liquid hydrocarbons decreased to 16.8 wt%. Notably, biochar-supported catalysts also exhibited good stability.