Renewable Carbonaceous Materials from Biomass in Catalytic Processes: A Review.

This review paper delves into the diverse ways in which carbonaceous resources, sourced from renewable and sustainable origins, can be used in catalytic processes. Renewable carbonaceous materials that come from biomass-derived and waste feedstocks are key to developing more sustainable processes by replacing traditional carbon-based materials. By examining the potential of these renewable carbonaceous materials, this review aims to shed light on their significance in fostering environmentally conscious and sustainable practices within the realm of catalysis. The more important applications identified are biofuel production, tar removal, chemical production, photocatalytic systems, microbial fuel cell electrodes, and oxidation applications. Regarding biofuel production, biochar-supported catalysts have proved to be able to achieve biodiesel production with yields exceeding 70%. Furthermore, hydrochars and activated carbons derived from diverse biomass sources have demonstrated significant tar removal efficiency. For instance, rice husk char exhibited an increased BET surface area from 2.2 m2/g to 141 m2/g after pyrolysis at 600 °C, showcasing its effectiveness in adsorbing phenol and light aromatic hydrocarbons. Concerning chemical production and the oxidation of alcohols, the influence of biochar quantity and pre-calcination temperature on catalytic performance has been proven, achieving selectivity toward benzaldehyde exceeding 70%.

Biomass gasification, catalytic technologies and energy integration for production of circular methanol: New horizons for industry decarbonisation.

The Intergovernmental Panel on Climate Change (IPCC) recognises the pivotal role of renewable energies in the future energy system and the achievement of the zero-emission target. The implementation of renewables should provide major opportunities and enable a more secure and decentralised energy supply system. Renewable fuels provide long-term solutions for the transport sector, particularly for applications where fuels with high energy density are required. In addition, it helps reducing the carbon footprint of these sectors in the long-term. Information on biomass characteristics feedstock is essential for scaling-up gasification from the laboratory to industrial-scale. This review deals with the transformation biogenic residues into a valuable bioenergy carrier like biomethanol as the liquid sunshine based on the combination of modified mature technologies such as gasification with other innovative solutions such as membranes and microchannel reactors. Tar abatement is a critical process in product gas upgrading since tars compromise downstream processes and equipment, for this, membrane technology for upgrading syngas quality is discussed in this paper. Microchannel reactor technology with the design of state-of-the-art multifunctional catalysts provides a path to develop decentralised biomethanol synthesis from biogenic residues. Finally, the development of a process chain for the production of (i) methanol as an intermediate energy carrier, (ii) electricity and (iii) heat for decentralised applications based on biomass feedstock flexible gasification, gas upgrading and methanol synthesis is analysed.

Hydrochar and synthetic natural gas co-production for a full circular economy implementation via hydrothermal carbonization and methanation: An economic approach.

Herein we study the economic performance of hydrochar and synthetic natural gas co-production from olive tree pruning. The process entails a combination of hydrothermal carbonization and methanation. In a previous work, we evidenced that standalone hydrochar production via HTC results unprofitable. Hence, we propose a step forward on the process design by implementing a methanation, adding value to the gas effluent in an attempt to boost the overall process techno-economic aspects. Three different plant capacities were analyzed (312.5, 625 and 1250 kg/hr). The baseline scenarios showed that, under the current circumstances, our circular economy strategy in unprofitable. An analysis of the revenues shows that hydrochar selling price have a high impact on NPV and subsidies for renewable coal production could help to boost the profitability of the process. On the contrary, the analysis for natural gas prices reveals that prices 8 times higher than the current ones in Spain must be achieved to reach profitability. This seems unlikely even under the presence of a strong subsidy scheme. The costs analysis suggests that a remarkable electricity cost reduction or electricity consumption of the HTC stage could be a potential strategy to reach profitability scenarios. Furthermore, significant reduction of green hydrogen production costs is deemed instrumental to improve the economic performance of the process. These results show the formidable techno-economic challenge that our society faces in the path towards circular economy societies.

CO2 Conversion via Reverse Water Gas Shift Reaction Using Fully Selective Mo-P Multicomponent Catalysts.

The reverse water gas shift reaction (RWGS) has attracted much attention as a potential means to widespread utilization of CO2 through the production of synthesis gas. However, for commercial implementation of RWGS at the scales needed to replace fossil feedstocks with CO2, new catalysts must be developed using earth abundant materials, and these catalysts must suppress the competing methanation reaction completely while maintaining stable performance at elevated temperatures and high conversions producing large quantities of water. Herein we identify molybdenum phosphide (MoP) as a nonprecious metal catalyst that satisfies these requirements. Supported MoP catalysts completely suppress methanation while undergoing minimal deactivation, opening up possibilities for their use in CO2 utilization.

Au and Pt Remain Unoxidized on a CeO2-Based Catalyst during the Water-Gas Shift Reaction.

The active forms of Au and Pt in CeO2-based catalysts for the water-gas shift (WGS) reaction are an issue that remains unclear, although it has been widely studied. On one hand, ionic species might be responsible for weakening the Ce-O bonds, thus increasing the oxygen mobility and WGS activity. On the other hand, the close contact of Au or Pt atoms with CeO2 oxygen vacancies at the metal-CeO2 interface might provide the active sites for an efficient reaction. In this work, using in situ X-ray absorption spectroscopy, we demonstrate that both Au and Pt remain unoxidized during the reaction. Remarkable differences involving the dynamics established by both species under WGS atmospheres were recognized. For the prereduced Pt catalyst, the increase of the conversion coincided with a restructuration of the Pt atoms into cuboctahedrical metallic particles without significant variations on the overall particle size. Contrary to the relatively static behavior of Pt0, Au0 nanoparticles exhibited a sequence of particle splitting and agglomeration while maintaining a zero oxidation state despite not being located in a metallic environment during the process. High WGS activity was obtained when Au atoms were surrounded by oxygen. The fact that Au preserves its unoxidized state indicates that the chemical interaction between Au and oxygen must be necessarily electrostatic and that such an electrostatic interaction is fundamental for a top performance in the WGS process.

The Success Story of Gold-Based Catalysts for Gas- and Liquid-Phase Reactions: A Brief Perspective and Beyond.

Gold has long held the fascination of mankind. For millennia it has found use in art, cosmetic metallurgy and architecture; this element is seen as the ultimate statement of prosperity and beauty. This myriad of uses is made possible by the characteristic inertness of bulk gold; allowing it to appear long lasting and above the tarnishing experienced by other metals, in part providing its status as the most noble metal.