Electrochemical routes for biomass conversion

Photochemical Synthesis of Nitriles from Alcohols

Nickel-catalyzed hydrocyanation of 1,3-butadiene with hydrogen cyanide gas is the predominant method for the synthesis of adiponitrile, which is an important precursor for polymer production. However, the use of fossil-derived alkenes raises environmental concerns, and hydrogen cyanide is highly volatile and extremely toxic. Herein, we report the use of biomass-derived 1,4-butanediol, as well as other primary alcohols, for photochemical synthesis of linear and branched nitriles and dinitriles, including adiponitrile, with 1,4-dicyanobenzene as the CN source. This mild, sustainable method does not require hydrogen cyanide gas or an air- or moisture-sensitive metal catalyst and is applicable for the production of dinitriles as precursors of diamines, which have potential utility for the development of novel polyamides.

A review on recent environmental electrochemistry approaches for the consolidation of a circular economy model

Availability of raw materials in the chemical industry is related to the selection of the chemical processes in which they are used as well as to the efficiency, cost, and eventual evolution to more competitive dynamics of transformation technologies. In general terms however, any chemically transforming technology starts with the extraction, purification, design, manufacture, use, and disposal of materials. It is important to create a new paradigm towards green chemistry, sustainability, and circular economy in the chemical sciences that help to better employ, reuse, and recycle the materials used in every aspect of modern life. Electrochemistry is a growing field of knowledge that can help with these issues to reduce solid waste and the impact of chemical processes on the environment. Several electrochemical studies in the last decades have benefited the recovery of important chemical compounds and elements through electrodeposition, electrowinning, electrocoagulation, electrodialysis, and other processes. The use of living organisms and microorganisms using an electrochemical perspective (known as bioelectrochemistry), is also calling attention to "mining", through plants and microorganisms, essential chemical elements. New process design or the optimization of the current technologies is a major necessity to enhance production and minimize the use of raw materials along with less generation of wastes and secondary by-products. In this context, this contribution aims to show an up-to-date scenario of both environmental electrochemical and bioelectrochemical processes for the extraction, use, recovery and recycling of materials in a circular economy model.

Ni(1−x)Pdx Alloyed Nanostructures for Electrocatalytic Conversion of Furfural into Fuels

A continuous electrocatalytic reactor offers a promising method for producing fuels and value-added chemicals via electrocatalytic hydrogenation of biomass-derived compounds. However, such processes require a better understanding of the impact of different types of active electrodes and reaction conditions on electrocatalytic biomass conversion and product selectivity. In this work, Ni1−xPdx (x = 0.25, 0.20, and 0.15) alloyed nanostructures were synthesized as heterogeneous catalysts for the electrocatalytic conversion of furfural. Various analytical tools, including XRD, SEM, EDS, and TEM, were used to characterize the Ni1−xPdx catalysts. The alloyed catalysts, with varying Ni to Pd ratios, showed a superior electrocatalytic activity of over 65% for furfural conversion after 4.5 h of reaction. In addition, various experimental parameters on the furfural conversion reactions, including electrolyte pH, furfural (FF) concentration, reaction time, and applied potential, were investigated to tune the hydrogenated products. The results indicated that the production of 2-methylfuran as a primary product (S = 29.78% after 1 h), using Ni0.85Pd0.15 electrocatalyst, was attributed to the incorporation of palladium and thus the promotion of water-assisted proton transfer processes. Results obtained from this study provide evidence that alloying a common catalyst, such as Ni with small amounts of Pd metal, can significantly enhance its electrocatalytic activity and selectivity.

Bioresource Upgrade for Sustainable Energy, Environment, and Biomedicine

We conceptualize bioresource upgrade for sustainable energy, environment, and biomedicine with a focus on circular economy, sustainability, and carbon neutrality using high availability and low utilization biomass (HALUB). We acme energy-efficient technologies for sustainable energy and material recovery and applications. The technologies of thermochemical conversion (TC), biochemical conversion (BC), electrochemical conversion (EC), and photochemical conversion (PTC) are summarized for HALUB. Microalgal biomass could contribute to a biofuel HHV of 35.72 MJ Kg-1 and total benefit of 749 $/ton biomass via TC. Specific surface area of biochar reached 3000 m2 g-1 via pyrolytic carbonization of waste bean dregs. Lignocellulosic biomass can be effectively converted into bio-stimulants and biofertilizers via BC with a high conversion efficiency of more than 90%. Besides, lignocellulosic biomass can contribute to a current density of 672 mA m-2 via EC. Bioresource can be 100% selectively synthesized via electrocatalysis through EC and PTC. Machine learning, techno-economic analysis, and life cycle analysis are essential to various upgrading approaches of HALUB. Sustainable biomaterials, sustainable living materials and technologies for biomedical and multifunctional applications like nano-catalysis, microfluidic and micro/nanomotors beyond are also highlighted. New techniques and systems for the complete conversion and utilization of HALUB for new energy and materials are further discussed.

Explaining the structure sensitivity of Pt and Rh for aqueous-phase hydrogenation of phenol

Phenol is an important model compound to understand the thermocatalytic (TCH) and electrocatalytic hydrogenation (ECH) of biomass to biofuels. Although Pt and Rh are among the most studied catalysts for aqueous-phase phenol hydrogenation, the reason why certain facets are active for ECH and TCH is not fully understood. Herein, we identify the active facet of Pt and Rh catalysts for aqueous-phase hydrogenation of phenol and explain the origin of the size-dependent activity trends of Pt and Rh nanoparticles. Phenol adsorption energies extracted on the active sites of Pt and Rh nanoparticles on carbon by fitting kinetic data show that the active sites adsorb phenol weakly. We predict that the turnover frequencies (TOFs) for the hydrogenation of phenol to cyclohexanone on Pt(111) and Rh(111) terraces are higher than those on (221) stepped facets based on density functional theory modeling and mean-field microkinetic simulations. The higher activities of the (111) terraces are due to lower activation energies and weaker phenol adsorption, preventing high coverages of phenol from inhibiting hydrogen adsorption. We measure that the TOF for ECH of phenol increases as the Rh nanoparticle diameter increases from 2 to 10 nm at 298 K and −0.1 V vs the reversible hydrogen electrode, qualitatively matching prior reports for Pt nanoparticles. The increase in experimental TOFs as Pt and Rh nanoparticle diameters increase is due to a larger fraction of terraces on larger particles. These findings clarify the structure sensitivity and active site of Pt and Rh for the hydrogenation of phenol and will inform the catalyst design for the hydrogenation of bio-oils.