Lignocellulosic biomass typically contains more than 50 wt% sugars that can be upgraded to valuable platform molecules, such as levulinic acid (LA) and gamma-valerolactone (GVL). This article focuses ...on upgrading GVL produced from lignocellulosic biomass to various chemicals and fuels, such as polymers, fuel additives, and jet fuel. We also review the use of GVL as a solvent for biomass processing, which led to significant improvements in product yields and a more simplified process for producing biomass-derived chemicals such as LA, furfural, and hydroxymethylfurfural.
Gamma-valerolactone is a promising platform molecule derived from biomass that can be upgraded to both chemicals and fuels. Gamma-valerolactone production is closely linked to levulinic acid, which can be obtained from C
6
and C
5
sugars derived from lignocellulosic biomass.
The design of heterogeneous catalysts relies on understanding the fundamental surface kinetics that controls catalyst performance, and microkinetic modeling is a tool that can help the researcher in ...streamlining the process of catalyst design. Microkinetic modeling is used to identify critical reaction intermediates and rate-determining elementary reactions, thereby providing vital information for designing an improved catalyst. In this review, we summarize general procedures for developing microkinetic models using reaction kinetics parameters obtained from experimental data, theoretical correlations, and quantum chemical calculations. We examine the methods required to ensure the thermodynamic consistency of the microkinetic model. We describe procedures required for parameter adjustments to account for the heterogeneity of the catalyst and the inherent errors in parameter estimation. We discuss the analysis of microkinetic models to determine the rate-determining reactions using the degree of rate control and reversibility of each elementary reaction. We introduce incorporation of Brønsted–Evans–Polanyi relations and scaling relations in microkinetic models and the effects of these relations on catalytic performance and formation of volcano curves are discussed. We review the analysis of reaction schemes in terms of the maximum rate of elementary reactions, and we outline a procedure to identify kinetically significant transition states and adsorbed intermediates. We explore the application of generalized rate expressions for the prediction of optimal binding energies of important surface intermediates and to estimate the extent of potential rate improvement. We also explore the application of microkinetic modeling in homogeneous catalysis, electro-catalysis, and transient reaction kinetics. We conclude by highlighting the challenges and opportunities in the application of microkinetic modeling for catalyst design.
Research interest in biomass conversion to fuels and chemicals has increased significantly in the last decade as the necessity for a renewable source of carbon has become more evident. Accordingly, ...many different reactions and processes to convert biomass into high-value products and fuels have been proposed in the literature. Special attention has been given to the conversion of lignocellulosic biomass, which does not compete with food sources and is widely available as a low cost feedstock. In this review, we start with a brief introduction on lignocellulose and the different chemical structures of its components: cellulose, hemicellulose, and lignin. These three components allow for the production of different chemicals after fractionation. After a brief overview of the main reactions involved in biomass conversion, we focus on those where bimetallic catalysts are playing an important role. Although the reactions are similar for cellulose and hemicellulose, which contain C(6) and C(5) sugars, respectively, different products are obtained, and therefore, they have been reviewed separately. The third major fraction of lignocellulose that we address is lignin, which has significant challenges to overcome, as its structure makes catalytic processing more challenging. Bimetallic catalysts offer the possibility of enabling lignocellulosic processing to become a larger part of the biofuels and renewable chemical industry. This review summarizes recent results published in the literature for biomass upgrading reactions using bimetallic catalysts.
Levulinic acid and its esters are converted to γ-valerolactone over metal oxide catalysts by catalytic transfer hydrogenation via the Meerwein-Ponndorf-Verley reaction.
Biomass has the potential to serve as a sustainable source of energy and organic carbon for our industrialized society. The focus of this Review is to present an overview of chemical catalytic ...transformations of biomass-derived oxygenated feedstocks (primarily sugars and sugar-alcohols) in the liquid phase to value-added chemicals and fuels, with specific examples emphasizing the development of catalytic processes based on an understanding of the fundamental reaction chemistry. The key reactions involved in the processing of biomass are hydrolysis, dehydration, isomerization, aldol condensation, reforming, hydrogenation, and oxidation. Further, it is discussed how ideas based on fundamental chemical and catalytic concepts lead to strategies for the control of reaction pathways and process conditions to produce H₂/CO₂ or H₂/CO gas mixtures by aqueous-phase reforming, to produce furan compounds by selective dehydration of carbohydrates, and to produce liquid alkanes by the combination of aldol condensation and dehydration/hydrogenation processes.
A combination of periodic, self-consistent density functional theory (DFT-GGA-PW91) calculations, reaction kinetics experiments on a SiO₂-supported Pd catalyst, and mean-field microkinetic modeling ...are used to probe key aspects of H₂O₂ decomposition on Pd in the absence of cofeeding H₂. We conclude that both Pd(111) and OH-partially covered Pd(100) surfaces represent the nature of the active site for H₂O₂ decomposition on the supported Pd catalyst reasonably well. Furthermore, all reaction flux in the closed catalytic cycle is predicted to flow through an O–O bond scission step in either H₂O₂ or OOH, followed by rapid H-transfer steps to produce the H₂O and O₂ products. The barrier for O–O bond scission is sensitive to Pd surface structure and is concluded to be the central parameter governing H₂O₂ decomposition activity.
Concerns about diminishing fossil fuel reserves along with global warming effects caused by increasing levels of CO
2
in the atmosphere are driving society toward the search for new renewable sources ...of energy that can substitute for coal, natural gas and petroleum in the current energy system. Lignocellulosic biomass is abundant, and it has the potential to significantly displace petroleum in the production of fuels for the transportation sector. Ethanol, the main biomass-derived fuel used today, has benefited from production by a well-established technology and by partial compatibility with the current transportation infrastructure, leading to the domination of the world biofuel market. However, ethanol suffers from important limitations as a fuel (
e.g.
, low energy density, high solubility in water) than can be overcome by designing strategies to convert non-edible lignocellulosic biomass into liquid hydrocarbon fuels (LHF) chemically similar to those currently used in internal combustion engines. The present review describes the main routes available to carry out such deep chemical transformation (
e.g.
, gasification, pyrolysis, and aqueous-phase catalytic processing), with particular emphasis on those pathways involving aqueous-phase catalytic reactions. These latter catalytic routes achieve the required transformations in biomass-derived molecules with controlled chemistry and high yields, but require pretreatment/hydrolysis steps to overcome the recalcitrance of lignocellulose. To be economically viable, these aqueous-phase routes should be carried out with a small number of reactors and with minimum utilization of external fossil fuel-based hydrogen sources, as illustrated in the examples presented here.
Biomass can be converted to liquid hydrocarbon fuels chemically identical to those currently used in cars, trucks and jets avoiding many of the shortcomings of ethanol as a transportation fuel.
Using gamma-valerolactone (GVL) as solvent, the cellulosic fraction of lignocellulosic biomass can be converted into levulinic acid (LA), while at the same conditions the hemicellulose fraction can ...be converted into furfural. This process allows for the conversion of hemicellulose and cellulose simultaneously in a single reactor, thus eliminating pre-treatment steps to fractionate biomass and simplifying product separation.
High yields of HMF from glucose can be achieved using biomass-derived solvents and a combination of solid Lewis and Broensted catalysts in a salt-free reaction system. The HMF produced in this system ...can be oxidized to FDCA or hydrogenated to DMF, both being high-value chemicals.
We demonstrated the self-assembly of transition metal carbide nanoparticles coated with atomically thin noble metal monolayers by carburizing mixtures of noble metal salts and transition metal oxides ...encapsulated in removable silica templates. This approach allows for control of the final core-shell architecture, including particle size, monolayer coverage, and heterometallic composition. Carbon-supported Ti0.1W0.9C nanoparticles coated with Pt or bimetallic PtRu monolayers exhibited enhanced resistance to sintering and CO poisoning, achieving an order of magnitude increase in specific activity over commercial catalysts for methanol electrooxidation after 10,000 cycles. These core-shell materials provide a new direction to reduce the loading, enhance the activity, and increase the stability of noble metal catalysts.
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