Increasing demand for sustainable chemicals and fuels has pushed academia and industry to search for alternative feedstocks replacing crude oil in traditional refineries. As a result, an immense academic attention has focused on the valorisation of biomass (components) and derived intermediates to generate valuable platform chemicals and fuels. Zeolite catalysis plays a distinct role in many of these biomass conversion routes. This contribution emphasizes the progress and potential in zeolite catalysed biomass conversions and relates these to concepts established in existing petrochemical processes. The application of zeolites, equipped with a variety of active sites, in Bronsted acid, Lewis acid, or multifunctional catalysed reactions is discussed and generalised to provide a comprehensive overview. In addition, the feedstock shift from crude oil to biomass involves new challenges in developing fields, like mesoporosity and pore interconnectivity of zeolites and stability of zeolites in liquid phase. Finally, the future challenges and perspectives of zeolites in the processing of biomass conversion are discussed.

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Potential and challenges of zeolite chemistry in the catalytic conversion of biomass

Levulinic acid is a sustainable platform molecule that can be upgraded to valuable chemicals and fuel additives. This article focuses on the catalytic upgrading of levulinic acid into various chemicals such as levulinate esters, δ-aminolevulinic acid, succinic acid, diphenolic acid, γ-valerolactone, and γ-valerolactone derivatives such valeric esters, 5-nonanone, α-methylene-γ valerolactone, and other various molecular-weight alkanes (C9 and C18-C27 olefins).

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Levulinic Acid Biorefineries: New Challenges for Efficient Utilization of Biomass

Fast pyrolysis is a promising thermochemical technology that breaks down renewable and abundant lignocellulosic biomass into a primary liquid product (bio-oil) in seconds. The bio-oil can then be potentially catalytically upgraded into transportation fuels and multiple commodity chemicals. Hemicellulose is one of the three major components of lignocellulosic biomass and is characterized as a group of cell wall polysaccharides that are neither cellulose nor pectin. The composition and structural features of hemicellulose (mixture of different heterogeneous polysaccharides) and different specific hemicellulose polysaccharides are reviewed. Particular focus is then given to reviewing the status of hemicellulose pyrolysis in terms of experimental investigations, reaction mechanisms, and kinetic modeling. For each aspect, recent results, challenges, and future prospects are addressed.

A critical review on hemicellulose pyrolysis

Faujasite (X, Y, and USY) zeolites represent one of the most widely-applied and abundant catalysts and sorbents in the chemical industry. In the last 5 years substantial progress was made in the synthesis, characterisation, and catalytic exploitation of hierarchically-structured variants of these zeolites. Hererin, we provide an overview of these contributions, highlighting the main advancements regarding the evaluation of the nature and functionality of introduced secondary porosity. The novelty, efficiency, versatility, and sustainability of the reported bottom-up and (predominately) top-down strategies are discussed. The crucial role of the relative stability of faujasites in aqueous media is highlighted. The interplay between the physico-chemical properties of the hierarchical zeolites and their use in petrochemical and biomass-related catalytic processes is assessed.

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Synthesis, characterisation, and catalytic evaluation of hierarchical faujasite zeolites: milestones, challenges, and future directions

Hierarchical zeolites: Synthesis and catalytic properties

Conversion of carbohydrate biomass to methyl levulinate with Al2(SO4)3 as a simple, cheap and efficient catalyst

Hydrolysis of hemicellulose catalyzed by hierarchical H-USY zeolites – The role of acidity and pore structure

A facile and efficient method to improve the selectivity of methyl lactate (MLA) in the chemical conversion of glucose in methanol catalyzed by homogeneous Lewis acid was established. The yield of MLA was efficiently improved through controlling the acidity of the reaction solution by neutralization of protons generated from the hydrolysis/methanolysis of SnCl4. The mechanism of glucose conversion to MLA catalyzed by SnCl4-NaOH was explored. The effects of the concentration of catalyst and substrate and the reaction temperature and time were systematically studied. The catalyst system of SnCl4-NaOH can efficiently convert glucose, fructose, and sucrose to MLA with yields of 47%, 57%, and 51% at 160 degrees C for 2.5 h, respectively. The catalyst can be regenerated and reused at least three times in the conversion of glucose to MLA without significant loss of activity and selectivity. (c) 2014 Elsevier B.V. All rights reserved.

A facile and efficient method to improve the selectivity of methyl lactate in the chemocatalytic conversion of glucose catalyzed by homogeneous Lewis acid

Conversion of dihydroxyacetone to methyl lactate catalyzed by highly active hierarchical Sn-USY at room temperature

Au/NaY was prepared by deposition–precipitation (DP) method using HAuCl4 as gold source. The samples were characterized by X-ray diffraction, N2 adsorption, transmission electron microscopy and inductively coupled plasma atomic emission spectrometry. It was found that the adjustment of the surface acidity of NaY, the pH and concentration of HAuCl4 solution, and the temperature and time for DP affected the particle size, the loading and the morphology of Au on NaY. The catalytic performance of Au/NaY was studied in the oxidation of alcohols to the corresponding carboxylic acids with molecular oxygen as oxidant under basic conditions. About 100% conversion of benzyl alcohol with 95.2% isolated yield of benzoic acid was obtained at the reaction temperature of 80 °C for 8 h. The catalyst was recycled for four times without loss of catalytic activity. In addition, the catalyst worked well for the catalytic oxidation of various alcohols including aromatic and aliphatic alcohols to the corresponding carboxyl acids.

Lin Wu

Papers

Conversion of carbohydrate biomass to methyl levulinate with Al2(SO4)3 as a simple, cheap and efficient catalyst

Hydrolysis of hemicellulose catalyzed by hierarchical H-USY zeolites – The role of acidity and pore structure

A facile and efficient method to improve the selectivity of methyl lactate in the chemocatalytic conversion of glucose catalyzed by homogeneous Lewis acid

Conversion of dihydroxyacetone to methyl lactate catalyzed by highly active hierarchical Sn-USY at room temperature

Nanocrystalline gold supported on NaY as catalyst for the direct oxidation of primary alcohol to carboxylic acid with molecular oxygen in water