Zhanrong Zhang

Catalytic Transformation of Lignocellulose into Chemicals and Fuel Products in Ionic Liquids

Innovative valorization of naturally abundant and renewable lignocellulosic biomass is of great importance in the pursuit of a sustainable future and biobased economy. Ionic liquids (ILs) as an important kind of green solvents and functional fluids have attracted significant attention for the catalytic transformation of lignocellulosic feedstocks into a diverse range of products. Taking advantage of some unique properties of ILs with different functions, the catalytic transformation processes can be carried out more efficiently and potentially with lower environmental impacts. Also, a new product portfolio may be derived from catalytic systems with ILs as media. This review focuses on the catalytic chemical conversion of lignocellulose and its primary ingredients (i.e., cellulose, hemicellulose, and lignin) into value-added chemicals and fuel products using ILs as the reaction media. An outlook is provided at the end of this review to highlight the challenges and opportunities associated with this interesting and important area.

Biomass-derived γ-valerolactone as an efficient solvent and catalyst for the transformation of CO2 to formamides

Efficient conversion of carbon dioxide (CO2) into valuable chemicals is a very attractive topic. Herein, we conducted the first work on the utilization of biomass-derived γ-valerolactone (GVL) as the solvent and catalyst for transformation of CO2 with various primary and secondary amines in the presence of phenylsilane (PhSiH3), and the corresponding desired formamides were produced with high yields without any additional catalyst. Systematic studies indicated that the lactone structure of GVL played a key role in the formation of the active silyl formates and the activation of N–H bonds in amines, thus leading to the excellent performance of GVL for the catalytic reactions.

Synthesis of Hierarchical Porous Metals using Ionic Liquid-Based Media as Solvent and Template

It was found that nanodomains existed in the ionic liquid (IL)-based ternary system containing IL 1-ethyl-3-methylimidazole tetrafluoroborate (EmimBF4 ), IL 1-decyl-3-methylimidazole nitrate (DmimNO3 ) and water, and the size distribution of the domains varied continuously with the composition of the solution. A strategy to synthesize hierarchical porous metals using IL-based media as solvent and template is proposed, and the hierarchical porous Ru and Pt metals were prepared by the assembly of metal clusters of about 1.5 nm using this new method. It is demonstrated that the metals have micropores and mesopores, and the size distribution is tuned by controlling the composition of the solution. Porous Ru was used for a series of hydrogenation reactions. It has an outstanding catalytic performance owing to its special morphology and structure.

Highly selective photocatalytic oxidation of biomass-derived chemicals to carboxyl compounds over Au/TiO2

Highly selective transformation of biomass-derived chemicals into value-added chemicals is of great importance. In this work, selective photooxidation of various biomass-derived chemicals, including ethanol, glucose, xylose, 2-furaldehyde, 5-hydroxymethyl-2-furfural, and furfuralcohol to the corresponding carboxyl compounds was studied using atmospheric air as the oxidant at ambient temperature. It was found that the reactions could be carried out efficiently over Au nanoparticles (AuNPs) supported on TiO2 (AuNPs/TiO2) under both ultraviolet (UV) and visible light in Na2CO3 aqueous solution. Under the optimized conditions, the selectivities for desired products were higher than 95% for all the reactions. Detailed studies indicated that the surface plasmon resonance of AuNPs and the band-gap photoexcitation of TiO2 were responsible for visible-light-responding and UV-light-responding activities, respectively. Na2CO3 acted as the promoter for the visible-light-induced oxidation and the inhibitor of reactive oxygen species with strong oxidation power under UV light.

Direct Synthesis of Ultrasmall Ruthenium Nanoparticles on Porous Supports Using Natural Sources for Highly Efficient and Selective Furfural Hydrogenation

The synthesis of noble‐metal nanoparticles (NPs) with ultrasmall particle sizes (<2 nm) is crucially important but challenging. Making use of the unique structure of natural sources for the preparation of functional materials is an attractive topic. By taking advantage of the coordination effect between polyphenols and metal ions, we report a straightforward strategy for the synthesis of porous heterogeneous catalysts containing ultrasmall Ru NPs. These catalysts exhibit excellent catalytic activity for the selective hydrogenation of furfural. We envisage that this strategy will find a broad range of applications in the near future.

Transformation of alcohols to esters promoted by hydrogen bonds using oxygen as the oxidant under metal-free conditions

Ionic liquid initiates and promotes oxidative esterification of alcohols to esters under metal-free conditions in oxygen. One-pot oxidative transformation of alcohols into esters is very attractive, but metal-based catalysts are used in the reported routes. We discovered that the basic ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM] OAc) could effectively catalyze this kind of reaction using O2 as an oxidant without any other catalysts or additives. The oxidative self-esterification of benzylic alcohols or aliphatic alcohols and cross-esterification between benzyl alcohols and aliphatic alcohols could all be achieved with high yields. Detailed study revealed that the cation with acidic proton and basic acetate anion could simultaneously form multiple hydrogen bonds with the hydroxyl groups of the alcohols, which catalyzed the reaction very effectively. As far as we know, this is the first work to carry out this kind of reaction under metal-free conditions.

Pd Nanoparticles/Polyoxometalate-Ionic Liquid Composites on SiO2 as Multifunctional Catalysts for Efficient Production of Ketones from Diaryl Ethers

The high stability of C–O bonds in diaryl ethers limits the valorization of lignin. Herein, reductive hydrolysis of C–O bonds in diaryl ethers was achieved over Pd nanoparticle/polyoxometalate–ionic liquid composite supported on SiO2 (Pd/H2[POM-IL]@SiO2) in water, selectively yielding ketones free from their alcohol counterparts in unprecedentedly high yields (>80%).

Naturally occurring gallic acid derived multifunctional porous polymers for highly efficient CO2 conversion and I2 capture

Assembly of naturally occurring building blocks into functional materials is of great importance. Herein, we utilized plant-derived polyphenols as building blocks to prepare porous organic polymers (POPs) with multifunctional sites, and a typical POP (denoted as GA-azo-POP) could be achieved from gallic acid through an azo-coupling strategy. As a superior support, GA-azo-POP supported Ag nanoparticles could efficiently catalyze the carboxylative cyclization of propargyl alcohols with CO2 with a very low usage of Ag (0.14 mol%). Meanwhile, the GA-azo-POP showed a high capacity for I2 adsorption (up to 287 mg g−1), which was higher than that of the reported solid materials at a similar I2 concentration. More interestingly, after adsorbing I2, the GA-azo-POP could efficiently catalyze the formation of cyclic carbonates from CO2. The excellent performance of the GA-azo-POP resulted from the co-existence of aromatic, azo, and phenolic OH functional groups and its porous structure.

Efficient Generation of Lactic Acid from Glycerol over a Ru‐Zn‐CuI/Hydroxyapatite Catalyst

The biodiesel production process generates a significant amount of glycerol as a byproduct. A drive to add value has attracted worldwide attention, with the aim of improving the overall effectiveness and profitability of biodiesel production. Herein, we report hydroxyapatite (HAP)-supported Ru-Zn-CuI (Ru-Zn-CuI /HAP) as effective catalysts for the transformation of glycerol to lactic acid (LA).The catalysts were characterized by using different techniques. The effects of catalyst composition, reaction time, and temperature on the conversion and product distribution were investigated. It was revealed that Ru nanoparticles of less than 2 nm were dispersed uniformly on HAP. CuI could effectively inhibit the cleavage of C-C bonds, which led to improved yields of LA. Under optimized conditions, the yield of LA could reach 70.9 % over Ru-Zn-CuI /HAP. Furthermore, the catalyst could be reused at least four times without an obvious loss of activity or selectivity.