Synthesis of Higher Alcohols on Silver-promoted LaCo- and LaCoCu-Perovskites

LaCoO3 and LaCo0.7Cu0.3O3 perovskites supported on highly dispersed mesoporous silica KIT‑6 were impregnated with silver nitrate (nAg/nCo = 4/99 and 8/99). The phase composition of the initial samples and samples after catalytic tests in syngas conversion and catalytic characteristics have been investigated. The regularities of the transformation of samples in the process of reduction in a hydrogen-containing gas have been studied. It is shown that, for the LaCoO3 sample, with an increase in the silver content, the activity and selectivity for higher alcohols increase from 6 to 23 %. The maximum interaction of cobalt with silver is observed at a silver content of 4 %. At a higher content, part of the cobalt is reduced regardless of the influence of silver due to its faster agglomeration. This leads to a stronger amorphization of the reduced sample and a sharp increase in its activity. The LaCo0.7Cu0.3O3 sample exhibits a higher selectivity for higher alcohols (36 %) due to the effect of copper. Silver promotion of the sample allows achieving the maximum selectivity for higher alcohols of 56 % with a silver content of 4 %. A further increase in the silver content leads to a sharp decrease in the selectivity for higher alcohols (41 %) and the appearance of CO2 due to the saturation of copper-containing particles with silver and a decrease in the interaction of cobalt with copper

Lignin Syngas Bioconversion by Butyribacterium methylotrophicum: Advancing towards an Integrated Biorefinery

Hybrid bio-thermochemical based technologies have the potential to ensure greater feedstock flexibility for the production of bioenergy and bioproducts. This study focused on the bioconversion of syngas produced from low grade technical lignin to C2-/C4-carboxylic acids by Butyribacterium methylotrophicum. The effects of pH, medium supplementation and the use of crude syngas were analyzed. At pH 6.0, B. methylotrophicum consumed CO, CO2 and H2 simultaneously up to 87 mol% of carbon fixation, and the supplementation of the medium with acetate increased the production of butyrate by 6.3 times. In long-term bioreactor experiments, B. methylotrophicum produced 38.3 and 51.1 mM acetic acid and 0.7 and 2.0 mM butyric acid from synthetic and lignin syngas, respectively. Carbon fixation reached 83 and 88 mol%, respectively. The lignin syngas conversion rate decreased from 13.3 to 0.9 NmL/h throughout the assay. The appearance of a grayish pellet and cell aggregates after approximately 220 h was indicative of tar deposition. Nevertheless, the stressed cells remained metabolically active and maintained acetate and butyrate production from lignin syngas. The challenge that impurities represent in the bioconversion of crude syngas has a direct impact on syngas cleaning requirements and operation costs, supporting the pursuit for more robust and versatile acetogens.

Comparative Techno-Economic and Exergetic Analysis of Circulating and Dual Bed Biomass Gasification Systems

In this work, the techno-economic and exergy analyses of two gasification technologies with integration into heat and power combined cycles are presented: i). Circulating fluidized bed (CFB) and ii). Dual fluidized bed (DFB) systems. As feedstock, lignocellulosic biomass (sugarcane bagasse, SCB) was considered. The gasification process of the fluidized-bed systems (circulating and dual bed) and the syngas conversion were performed using Aspen Plus® software. The process design includes biomass drying and gasification, syngas cleaning, combustion, power generation, and heat recovery. The SCB-DFB system has the lowest irreversibility rate and, as a result, the highest overall performance and power generation (achieving 32% in the gasification system and 53% of exergy efficiency when coupled with the combined cycle). From the techno-economic assessment, the SCB-DFB system has the lowest total production costs per unit of energy. Hence, the dual fluidized bed systems could be a more competitive technology for the agro-industrial sector to generate power from lignocellulosic materials.