Chun Hui Zhou

Catalytic conversion of lignocellulosic biomass to fine chemicals and fuels

Lignocellulosic biomass is the most abundant and bio-renewable resource with great potential for sustainable production of chemicals and fuels. This critical review provides insights into the state-of the-art accomplishments in the chemocatalytic technologies to generate fuels and value-added chemicals from lignocellulosic biomass, with an emphasis on its major component, cellulose. Catalytic hydrolysis, solvolysis, liquefaction, pyrolysis, gasification, hydrogenolysis and hydrogenation are the major processes presently studied. Regarding catalytic hydrolysis, the acid catalysts cover inorganic or organic acids and various solid acids such as sulfonated carbon, zeolites, heteropolyacids and oxides. Liquefaction and fast pyrolysis of cellulose are primarily conducted over catalysts with proper acidity/basicity. Gasification is typically conducted over supported noble metal catalysts. Reaction conditions, solvents and catalysts are the prime factors that affect the yield and composition of the target products. Most of processes yield a complex mixture, leading to problematic upgrading and separation. An emerging technique is to integrate hydrolysis, liquefaction or pyrolysis with hydrogenation over multifunctional solid catalysts to convert lignocellulosic biomass to value-added fine chemicals and bio-hydrocarbon fuels. And the promising catalysts might be supported transition metal catalysts and zeolite-related materials. There still exist technological barriers that need to be overcome (229 references).

Recent Advances in Catalytic Conversion of Glycerol

The article underlines and discusses the state-of-the-art accomplishments in the catalytic conversion of glycerol (1,2,3-propanetriol) to fuels and value-added chemicals in the past five years (2008–2012). The reactions include steam reforming, aqueous-phase reforming, hydrogenolysis, oxidation, dehydration, esterification, etherification, carboxylation, acetalization, and chlorination. Typical products are hydrogen, propanediols, dihydroxyacetone, glyceric acid, acrolein, glyceride, polyglycerol, glycerol carbonate, acetals, ketals, and epichlorohydrine. Recent studies on the catalysts, reaction conditions, and possible pathways are primarily discussed. They indicate that major breakthroughs are achieved by the use of multifunctional catalysts, process intensification and integrated reactions. Literature survey suggests that future work on the catalytic conversion of glycerol for commercial goals particularly requires new catalysts, innovative reactor engineering, and close multidisciplinary partnership.

Preparation and functionality of clay-containing films

This article provides an insight into state-of-the-art advances in the preparation and functionalization of clay-containing thin films. Layered clay minerals and their synthetic counterparts such as cationic montmorillonite, saponite, laponite and anionic layered double hydroxides are often used as main components or functional fillers in the hybrid films. Strategic assembly of clay minerals or layered double hydroxides with functional molecules has led to a variety of nanostructured clay-containing hybrid films. Frequently used approaches are the solvent casting, the spin-coating, the layer-by-layer (LbL) assembly and the Langmuir–Blodgett (LB) techniques. The type of clay mineral, solvent, pH, organic components and functional molecules generally play a pivotal role in the formation and structure of a desired functional film. Different processes result in differences in the thickness, surface morphology and internal structure in the resultant clay-containing films. Functional polymers, dye molecules, transition metal complexes and protein molecules and even their combination have been exploited to fabricate and functionalize clay-containing films. Many studies have suggested that the functional clay-containing films have potential applications in many areas such as catalysis, modified electrodes and optoelectronic devices, anti-corrosion and packaging materials. Finally, the prospects for the future preparation and applications of clay-containing films are discussed.

Novel hydrothermal carbonization of cellulose catalyzed by montmorillonite to produce kerogen-like hydrochar

Abstract The conversion of cellulose to petroleum-like fuel is a very challenging yet attractive route to developing biomass-to-fuel technology. Many attempts have been made in liquefaction, pyrolysis and gasification of cellulose to produce fuels or intermediate chemicals. Previous studies indicate that these processes are tough. Hence, the present work is concerned with the development of new technologies for the conversion of cellulose into materials which are analogies to the precursor of petroleum. Montmorillonite-catalyzed hydrothermal carbonization of microcrystalline cellulose for the production of kerogen-like hydrochar under mild conditions was investigated. It was revealed that the hydrothermal carbonization of microcrystalline cellulose alone resulted in hydrochar with type III kerogen-like structure, whereas in the presence of montmorillonite, the hydrothermal carbonization of microcrystalline cellulose yielded a hydrochar-mineral complex, of which the isolated organic fraction was oil-prone type II kerogen-like structure. Results suggested that further improved montmorillonite-aided biomass conversion to more oil-prone kerogen-like solid products could be an alternative efficient route to obtain biofuel and chemicals.

Modification of inorganic porous materials as gene vectors: an overview

Abstract The use of porous materials as gene vectors is becoming more important and striking than their traditional uses in catalysis and separation. This article highlights recent advances in the modification of typical inorganic porous materials which are specifically and necessarily conducted for their uses as gene vectors. Literature survey indicates that carbon nanotubes, layered double hydroxides, mesoporous silica and carbon nanoparticles and the related hierarchical materials have received particular attention in recent years. Though these inorganic porous materials have high surface area and porosity, to choose surface modification judiciously is often required for improving their performances in the loading of genes, targeted delivery and controlled release of genes. Major modification methods are adsorption or grafting of other molecules onto the surface of these inorganic porous materials. In addition, modification by adding magnetic nanoparticles to the porous materials has been investigated. Nevertheless, thus far most studies on the modification have aimed merely at the improvement of the loading, the delivery and the release of gene. Exact biocompatibility and in vivo therapy effectiveness remains elusive and are still in question.

Acid-activated and WOx-loaded montmorillonite catalysts and their catalytic behaviors in glycerol dehydration

Abstract The use of H 2 SO 4 -, HCl-, H 3 PO 4 -, and CH 3 COOH-activated montmorillonite (Mt) and WO x /H 3 PO 4 -activated Mt as catalysts for the gas-phase dehydration of glycerol was investigated. The WO x /H 3 PO 4 -activated Mt catalysts were prepared by an impregnation method using H 3 PO 4 -activated Mt (Mt-P) as the support. The catalysts were characterized using powder X-ray diffraction, Fourier-transform infrared spectroscopy, N 2 adsorption-desorption, diffuse reflectance ultraviolet-visible spectroscopy, temperature-programmed desorption of NH 3 , and thermogravimetric analysis. The acid activation of Mt and WO x loaded on Mt-P affected the strength and number of acid sites arising from H + exchange, the leaching of octahedral Al 3+ cations from Mt octahedral sheets, and the types of WO x (2.7 ≤ x ≤ 3) species (i.e., isolated WO 4 /WO 6 -containing clusters, two-dimensional [WO 6 ] polytungstates, or three-dimensional WO 3 crystals). The strong acid sites were weakened, and the weak and medium acid sites were strengthened when the W loading on Mt-P was 12 wt% (12%W/Mt-P). The 12%W/Mt-P catalyst showed the highest catalytic activity. It gave a glycerol conversion of 89.6% and an acrolein selectivity of 81.8% at 320 °C. Coke deposition on the surface of the catalyst led to deactivation.

Catalytic Thermochemical Processes for Biomass Conversion to Biofuels and Chemicals

Abstract Biomass is the most abundant and biorenewable resource with great potential for sustainable production of chemicals and fuels. Thermochemical conversion technologies (pyrolysis, gasification and hydrothermal liquefaction) are a promising option for transforming biomass feedstocks into liquid oils and chemicals. In the article, for the thermal process of biomass for biofuels and chemicals, the effect of reaction conditions, reactors, solvents and catalysts on the yield and distribution of the products are reviewed. Fast pyrolysis of cellulose is primarily conducted over catalysts with proper acidity/basicity and has undergone many pilot tests. Gasification is typically conducted over supported noble metal catalysts and has been profiled as being CO2-neutral, having a high potential to provide power, chemicals and fuels. Catalytically hydrothermal liquefaction of biomass produces a very complex mixture of liquid products; therefore, novel technology for separation and extraction of downstream products from hydrothermal liquefaction of lignocellulosic biomass need to be developed.

Immobilization of lipase onto aminopropyl-functionalized MSU-H type mesoporous silica and esterification

Candida rugosa lipase (CRL) was immobilized on an aminopropyl-functionalized MSU-H type mesoporous silica (AFMS) through physical adsorption and a covalent cross-linking. It was evaluated as a class of biocatalysts in the esterification of conjugated linoleic acid (CLA) isomers with ethanol. AFMS materials with varied content of aminopropyl were prepared by a simple co-condensation at near neutral pH condition. Introduction of aminopropyl chains and CRL molecules onto the AFMS supports was confirmed by Fourier transform infrared (FT-IR) spectra. CRL was immobilized on the AFMS through electrostatic and covalent interactions. The covalently cross-linked CRL gave a loading amount of 34.3mg CRL/g-support and a hydrolytic activity of 2471.5U/g-catalyst. It exhibited high operational stability and remained 23.9-27.5% of total esterification in 32 h consecutive four runs in the esterification of CLA with ethanol. Moreover, the immobilized CRLs catalyzed 2.8-3.8 times of esterification of cis-(c)9, trans-(t)11-CLA faster than that of t10, c12-CLA.

PREPARATION OF ORGANO-MONTMORILLONITES AND THE RELATIONSHIP BETWEEN MICROSTRUCTURE AND SWELLABILITY

Hydrophobicity, swellability, and dispersion are important properties for organo-montmorillonites (OMnt) and have yet to be fully characterized for all OMnt configurations. The purpose of the present work was to examine the preparation of OMnt from the reaction of Ca2+-montmorillonite (Ca2+-Mnt) with a high concentration of surfactant and to reveal the relevant properties of hydrophobicity and dispersion of the resultant OMnt. A series of OMnt samples were prepared using a small amount of water and cetyltrimethylammonium bromide (CTAB) with a concentration more than the CTAB critical micelle concentration (CMC). The relationship between OMnt microstructure and the hydrophobicity and swellability properties was investigated in detail. The resulting OMnt samples were characterized using powder X-ray diffraction patterns (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric and differential thermogravimetry (TG-DTG), water contact angle tests, swelling indices, and transmission electron microscopy (TEM). The addition of CTAB and water in the OMnt preparation affected the OMnt microstructure and properties. An increase in CTAB concentration led to a more ordered arrangement of cetyltrimethylammonium (CTA+) cations in the interlayer space of the OMnt and a large amount of CTA+ cations on the outer surfaces of the OMnt. The swelling indices and the water contact angles of OMnt samples depended on the distribution of the CTAB surfactant on OMnt and the orientation of the surfactant hydrophilic groups on the inner and on the outer surfaces of OMnt. A maximum swelling index of 39 mL/g in xylene was achieved with an average water contact angle of 62.0° ± 2.0° when the amount of CTAB added was 2 times the cation exchange capacity (CEC) of Mnt and the lowest water to dry Mnt mass ratio was 3 during the preparation of OMnt samples. The platelets of OMnt aggregated together in xylene by electrostatic attraction and by hydrophobic interactions.

Article (Special Issue on Nanoscience and Catalysis)Acid-activated and WOx-loaded montmorillonite catalysts and their catalytic behaviors in glycerol dehydration

Abstract The use of H 2 SO 4 -, HCl-, H 3 PO 4 -, and CH 3 COOH-activated montmorillonite (Mt) and WO x /H 3 PO 4 -activated Mt as catalysts for the gas-phase dehydration of glycerol was investigated. The WO x /H 3 PO 4 -activated Mt catalysts were prepared by an impregnation method using H 3 PO 4 -activated Mt (Mt-P) as the support. The catalysts were characterized using powder X-ray diffraction, Fourier-transform infrared spectroscopy, N 2 adsorption-desorption, diffuse reflectance ultraviolet-visible spectroscopy, temperature-programmed desorption of NH 3 , and thermogravimetric analysis. The acid activation of Mt and WO x loaded on Mt-P affected the strength and number of acid sites arising from H + exchange, the leaching of octahedral Al 3+ cations from Mt octahedral sheets, and the types of WO x (2.7 ≤ x ≤ 3) species (i.e., isolated WO 4 /WO 6 -containing clusters, two-dimensional [WO 6 ] polytungstates, or three-dimensional WO 3 crystals). The strong acid sites were weakened, and the weak and medium acid sites were strengthened when the W loading on Mt-P was 12 wt% (12%W/Mt-P). The 12%W/Mt-P catalyst showed the highest catalytic activity. It gave a glycerol conversion of 89.6% and an acrolein selectivity of 81.8% at 320 °C. Coke deposition on the surface of the catalyst led to deactivation.