Sulphur poisoning of alumina supported Rh catalyst during dry reforming of methane

Low cost and renewable H2S-biofilter inoculated with Trichoderma harzianum

The use of biogas to produce hydrogen is currently gaining more attention. One of the drawbacks for the valorization of biogas is the presence of H2S, a hazardous molecule that can cause damage in the metallic internal structures of industries. In this study, the H2S-removal performance of a fungi-based biofilter was investigated. First, an H2S-resistant fungal species was isolated from an industrial digestate and identified as Trichoderma harzianum. The capacity of this microorganism to metabolize H2S in a mineral medium was confirmed. Then, a bioreactor was constructed and put in place to monitor the elimination of gaseous H2S. A mix of cardboard, perlite, woodchips, and wood pellets was used as filling. Microbial development and the outlet gas composition were monitored during a 60-day experimental process during which H2S was completely removed. 97% of the introduced sulphur was detected in the used filling material (fungal species + packing material) by elemental analysis. 24% of the detected sulphur was identified by ion-exchange chromatography as SO42-. Elemental analysis, gas chromatography, and ion-exchange chromatography were used to determine the bioreactor sulphur balance. Metagenomic analysis underlined that H2S elimination was due to the presence of Trichoderma harzianum with a H2S-specific bacterial consortium.

Optimization of a renewable hydrogen production system from food waste: A combination of anaerobic digestion and biogas reforming

In this study, hydrogen production using food waste was optimized by investigating the effect of agitator types in anaerobic digestion reactors and catalysts for biogas reforming. The applied agitators were pitched blade and hydrofoil, and their effect on homogeneity was estimated using computational fluid dynamics. Reactors with different agitators were operated for 60 days for biogas production. Increased biogas production was observed in the reactor equipped with a hydrofoil agitator owing to its high homogeneity. In addition, Ni-CeZrO₂ catalysts promoted with La₂O₃, CaO, or MgO were investigated for stable hydrogen production during the biogas reforming reaction using simulated gas based on biogas from the anaerobic digestion equipped the hydrofoil. Among the promoted catalysts, the MgO-promoted Ni-CeZrO₂ catalyst displayed the best results for hydrogen production without significant deactivation. The stable catalytic performance of the MgO-promoted catalyst resulted from the close interaction between Ni and MgO, and its high oxygen storage capacity. Thus, 1216 L hydrogen and 646 L carbon monoxide were produced per kilogram volatile solid via the hydrogen production system that included anaerobic digestion and biogas reforming.

Catalytic Reaction of Carbon Dioxide with Methane on Supported Noble Metal Catalysts

The conversion of CO2 and CH4, the main components of the greenhouse gases, into synthesis gas are in the focus of academic and industrial research. In this review, the activity and stability of different supported noble metal catalysts were compared in the CO2 + CH4 reaction on. It was found that the efficiency of the catalysts depends not only on the metal and on the support but on the particle size, the metal support interface, the carbon deposition and the reactivity of carbon also influences the activity and stability of the catalysts. The possibility of the activation and dissociation of CO2 and CH4 on clean and on supported noble metals were discussed separately. CO2 could dissociate on metal surfaces, this reaction could proceed via the formation of carbonate on the support, or on the metal–support interface but in the reaction the hydrogen assisted dissociation of CO2 was also suggested. The decrease in the activity of the catalysts was generally attributed to carbon deposition, which can be formed from CH4 while others suggest that the source of the surface carbon is CO2. Carbon can occur in different forms on the surface, which can be transformed into each other depending on the temperature and the time elapsed since their formation. Basically, two reaction mechanisms was proposed, according to the mono-functional mechanism the activation of both CO2 and CH4 occurs on the metal sites, but in the bi-functional mechanism the CO2 is activated on the support or on the metal–support interface and the CH4 on the metal.

Promising Utilization of CO2 for Syngas Production over Mg2+- and Ce2+-Promoted Ni/γ-Al2O3 Assisted by Nonthermal Plasma

Dry reforming of methane is conducted in a catalyst packed-bed dielectric barrier discharge (DBD) reactor aiming to improve the reaction efficiency. The MgO- and CeO₂-promoted Ni/γ-Al₂O₃ catalyst is tested to carry out the reaction. An interesting observation is that Ni/MgO_Al₂O₃ integration provides ∼35 and 13% conversion of CH₄ and CO₂, respectively. The highest syngas ratio of 0.94 is obtained with Ni/MgO_Al₂O₃, whereas the ratio is only 0.57 with Ni/CeO₂_Al₂O₃ and 0.64 with bare DBD. In addition, Ni/CeO₂_Al₂O₃ offers the highest selectivity (68%) of CO due to the oxygen buffer property of CeO₂. Finally, the optimal acid/base property is highly desirable for the dry reforming reaction.

Molybdenum and tungsten carbides can shine too

In this perspective, we argue that transition metal carbides such as molybdenum and tungsten hold great potential for the catalytic conversions of future feedstocks due to their ability to remain active in the presence of impurities in the feedstock.