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

This review gives an overview of recent advances in the potential applications of superhydrophobic materials. Such properties are characterized by extremely high water contact angles and various adhesion properties. The conception of superhydrophobic materials has been possible by studying and mimicking natural surfaces. Now, various applications have emerged such as anti-icing, anti-corrosion and anti-bacterial coatings, microfluidic devices, textiles, oil–water separation, water desalination/purification, optical devices, sensors, batteries and catalysts. At least two parameters were found to be very important for many applications: the presence of air on superhydrophobic materials with self-cleaning properties (Cassie–Baxter state) and the robustness of the superhydrophobic properties (stability of the Cassie–Baxter state). This review will allow researchers to envisage new ideas and industrialists to advance in the commercialization of these materials.

Recent advances in the potential applications of bioinspired superhydrophobic materials

Superhydrophobicity is the tendency of a surface to repel water drops. A surface is qualified as a superhydrophobic surface only if the surface possesses a high apparent contact angle (>150°), low contact angle hysteresis (<10°), low sliding angle (<5°) and high stability of Cassie model state. Efforts have been made to mimic the superhydrophobicity found in nature (for example, lotus leaf), so that artificial superhydrophobic surfaces could be prepared for a variety of applications. Due to their versatile use in many applications, such as water-resistant surfaces, antifogging surfaces, anti-icing surfaces, anticorrosion surfaces etc., many methods have been developed to fabricate them. In this article, the fundamental principles of superhydrophobicity, some of the recent works in the preparation of superhydrophobic surfaces, their potential applications, and the challenges confronted in their new applications are reviewed and discussed.

Superhydrophobic surfaces: a review on fundamentals, applications, and challenges

The aerobic oxidation of 5-hydroxymethylfurfural (HMF), a key platform compound in cellulose transformation, into 2,5-furandicarboxylic acid (FDCA), a promising renewable alternative to petroleum-derived terephthalic acid, is one of the most attractive reactions for establishing biomass-based sustainable chemical processes. Supported Au catalysts have shown encouraging performance for this reaction, but the need of an excess amount of base additives makes the process less green and less cost-effective. Here, we report a stable and efficient carbon nanotube (CNT)-supported Au–Pd alloy catalyst for the aerobic oxidation of HMF to FDCA in water without any bases. The functionalization of CNT surfaces is crucial for FDCA formation. We have clarified that the CNT containing more carbonyl/quinone and less carboxyl groups favors FDCA formation by enhancing the adsorption of the reactant and reaction intermediates. Significant synergistic effects exist between Au and Pd in the alloy for the base-free oxidation of...

Base-Free Aerobic Oxidation of 5-Hydroxymethyl-furfural to 2,5-Furandicarboxylic Acid in Water Catalyzed by Functionalized Carbon Nanotube-Supported Au–Pd Alloy Nanoparticles

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

Conversion of biomass derived carbohydrates to alkyl levulinates is an important process due to the wide application of alkyl levulinates as chemicals and biofuel additives. Efficient conversion of cheap and abundant glucose to alkyl levulinates over easily separated and regenerated solid catalyst is highly desirable. Here, the transformation of glucose to methyl levulinate (MLE) was studied over dual solid acid catalysts. The synergistic effect of solid Bronsted (B) acid and solid Lewis (L) acid was observed. A combined catalyst system consisting of both B acid and L acid was found to be more efficient for the production of MLE from glucose. 62% yield of MLE was given over the combined catalyst of SO 4 2− /ZrO 2 and Sn-Beta prepared by postsynthesis method at 170 °C for 24 h. The roles of L acid sites of SO 4 2− /ZrO 2 and Sn-Beta, and B acid sites of SO 4 2− /ZrO 2 were discussed in detail. Alternative biomass-derived carbohydrates also gave moderate to good yields of MLE. Recyclability studies indicated that the combined catalyst system can be reused without significant change in the yield of MLE, proving its easy recovery and thermal stability during regeneration.

Direct catalytic conversion of carbohydrates to methyl levulinate: Synergy of solid Bronsted acid and Lewis acid

Depolymerization of cellulose to glucose by oxidation–hydrolysis

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

http://www.rsc.org/suppdata/CC/C0/C0CC03926H/C0CC03926H.PDF

Lipeng Zhou

Papers

Direct catalytic conversion of carbohydrates to methyl levulinate: Synergy of solid Bronsted acid and Lewis acid

Depolymerization of cellulose to glucose by oxidation–hydrolysis

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

Superhydrophobic materials as efficient catalysts for hydrocarbon selective oxidation.