Zaihui Fu

Microwave-assisted hydrolysis of crystalline cellulose catalyzed by biomass char sulfonic acids

The development of an environmentally benign process for the hydrolysis of cellulose into reducing sugars can be one of the key technologies for making full use of cellulosic biomass in the future. Here, a biomass char sulfonic acid (BC-SO3H)-catalyzed hydrolysis of cellulose in water was achieved under microwave irradiation. The BC-SO3H catalysts prepared cheaply from natural bamboo, cotton and starch, showed a much higher turnover number (TON, 1.33-1.73) for this reaction compared to a dilute H2SO4 solution (TON, 0.02), which was likely due to their strong affinity to β-1,4-glycosidic bonds of cellulose. In addition, microwave irradiation played key roles in activating cellulose molecules and strengthening particle collision, which can lead to a remarkable acceleration effect on this heterogeneously catalytic process.

Highly effective Cu-HMS catalyst for hydroxylation of phenol

Transition metals copper and titanium substituted mesoporous silicas (Cu-HMS and Ti-HMS) were synthesized at ambient temperature by using dodecylamine (DDA) surfactant as templating agent. XRD measurements prove that incorporating titanium and especially copper into the mesostructures causes the d100 peaks of mesoporous silicas to become shifted to lower angles, indicating progressive expansion of the lattice d-spacings upon heteroatoms Ti and especially Cu incorporating. FT-IR measurements indicate that the calcined Cu-HMS and Ti-HMS samples all exhibit a weaker absorption band near 960 cm-1 which may be rather a fingerprint of the heteroatom on the matrix of [SiO4] units whatever its crystallization state. Cu-HMS possesses relatively high catalytic activity for the hydroxylation of phenol with 30% aq. H2O2 in aqueous solution (about 36% phenol conversion and more than 95% selectivity for dihydroxybenzene isomers), but Ti-HMS has no catalytic activity under the same reaction conditions. The product distribution obtained from Cu-HMS is completely different from that of the microporous titanium silicalite zeolites (TS zeolites). This is attributed to the porous structural differences between Cu-HMS and TS zeolites. The catalytic activity of the Cu-HMS is strongly dependent on the nature of the solvent; the Cu-HMS does not have any catalytic activity in the presence of organic solvents such as methanol or acetone instead of water. A reusing test of the recovered Cu-HMS indicates that the recovered catalyst suffers almost loss of activity and must be regenerated by calcination in air at 873 K in order to recover its activity.

Synthesis, characterization and catalytic properties of titanium and boron co-substituted silicalite zeolites

Abstract Titanium and boron co-substituted silicalite-2 (TBS-2) has been synthesized by using TBAOH as a templating agent in hydrothermal conditions. The main factors affecting Ti and B co-incorporated into the framework of silicalite-2 (S-2) such as the used amounts of H 2 O 2 (for dissolving hydrous Ti oxides) and H 3 BO 3 (used as boron source) and the addition of TMAOH were studied in detail. XRD, FT-IR, SEM, and NH 3 -TPD, were used to characterize the influences of Ti and B co-incorporation on the unit cell parameters of S-2, framework IR bands, crystalline morphology, and acid properties, respectively. The epoxidation of styrene and the rearrangement of styrene oxide were respectively used to check the oxidative and acidic catalytic properties of TBS-2.

Characterization of modified ZSM-5 catalysts for propane aromatization prepared by a solid state reaction

Abstract This paper describes a simple preparation method using a solid state reaction for Zn-, Mo-, and Cr-ZSM-5 catalysts for propane aromatization. NH 3 -temperature-programmed desorption, infrared, temperature-programmed reduction and electron spin resonance techniques were used to characterize the interaction of H-ZSM-5 with ZnO, MoCl 5 and CrO 3 , respectively, which leads to introduction of cations into the channels of the zeolite. A solid-exchange mechanism is suggested here. Zn-ZSM-5 is the most active catalyst for propane conversion and gives a better benzene, toluene and xylenes selectivity. Over Mo-ZSM-5, propane mainly undergoes cracking to methane and ethane, and the loading ZSM-5 with Cr 5+ enhances the propane dehydrogenation to propene.

Ionic liquid-functionalized biochar sulfonic acid as a biomimetic catalyst for hydrolysis of cellulose and bamboo under microwave irradiation

The development of a highly efficient and environmentally friendly process for the hydrolysis of cellulose into reducing sugars could be one of the key technologies for large-scale use of cellulosic biomass in the future. In order to pursue this goal, an ionic liquid (IL)-grafting biochar sulfonic acid catalyst (BC-SO3H-IL) was proposed and conveniently prepared with bamboo powder as a carbon resource and 1-(trimethoxy propyl silane)-3-methyl imidazolium chloride as the IL. Its catalytic performance for the heterogeneous hydrolysis of cellulose and bamboo was checked under microwave irradiation. The designed BC-SO3H-IL catalyst was found to show much higher turnover number (TON, 3.22–6.23 for cellulose and 0.26–2.53 for bamboo) and excellent repeatability for this hydrolysis compared to the corresponding biochar sulfonic acid (BC-SO3H, TON, 1.51–1.81 for cellulose and 0.14–1.33 for bamboo). This is likely to be because the IL groups flexibly joined to biochar sulfonic acid, like cellulose binding domain (CBD) of cellulase, efficiently breaks in the hydrogen bonding network of cellulose molecules. On the other hand, they probably play a harmonious role in the SO3H groups (as a catalysis domain (CD) of cellulase) catalyzing cleavage of the β-1,4 glycosidic bonds of cellulose, as supported by TGA characterization and catalytic reaction results.

Biochar sulfonic acid immobilized chlorozincate ionic liquid: an efficiently biomimetic and reusable catalyst for hydrolysis of cellulose and bamboo under microwave irradiation

A chlorozincate ionic liquid-functionalized biochar sulfonic acid (BC-SO3H-IL-Zn) was designed and conveniently prepared via multistep processes, involving the syntheses of biochar sulfonic acid (BC-SO3H) and 1-trimethoxysilylpropyl-3-methylimidazolium chloride (IL)-ZnCl2 (IL-Zn), followed by grafting the IL-Zn onto BC-SO3H. The proposed catalyst was found to show a much higher turnover number (TON, 5.91 for cellulose and 1.78 for bamboo) for the microwave-assisted hydrolysis of cellulose and bamboo to reducing sugars (RSs) in water compared to the corresponding IL-functionalized BC-SO3H (BC-SO3H-IL, TON, 3.23 for cellulose and 0.46 for bamboo) and BC-SO3H (TON, 1.51 for cellulose and 0.15 for bamboo). Furthermore, it, like BC-SO3H-IL, possessed an excellent repeatability for cellulose hydrolysis. The excellent catalytic performance of BC-SO3H-IL-Zn is likely due to the following reasons: Firstly, the introduction of ZnCl2 bestows the catalyst with a delignification function. Secondly, in comparison with the OH groups of BC-SO3H, the IL and especially IL-Zn groups flexibly bound to BC-SO3H, like cellulose binding domain of cellulose, show an stronger affinity for cellulose molecules, on the other hand, they play a better synergistic role and improved acidity in the SO3H groups (as a catalysis domain of cellulase) catalyzing cleavage of the β-1,4-glycosidic bonds of cellulose, as supported by the adsorption experiments of catalysts to oligosaccharides, their thermogravimetric analysis and catalytic reaction results.Graphical AbstractChlorozincate ionic liquid functionalized biochar sulfonic acid (BC-SO3H-IL-Zn) proposed by us was found to be an efficiently biomimetic catalyst for the heterogeneous hydrolysis of cellulose and lignocelluloses to RSs and 5-hydroxymethyl furfural (5-HMF) under microwave irradiation.

Mild, one-step hydrothermal synthesis of carbon-coated CdS nanoparticles with improved photocatalytic activity and stability

Abstract Carbon-coated CdS (CdS@C) nanoparticles were conveniently prepared by a one-step hydrothermal carbonization method at temperature as low as 130 °C, in which cadmium acetate and glucose were used as the cadmium and carbon sources, respectively, and thiourea was used as the sulfur source and catalyst for the hydrothermal carbonization of glucose. The prepared CdS@C particles possess a smaller size, better dispersion, and more uniform distribution than pure CdS particles prepared under the same conditions. Furthermore, the hydrothermal carbonization of glucose easily induces the prior formation of metastable cubic CdS crystals. In addition, the carbonaceous species coated on the surface of CdS expands the range of absorption light and slightly decreases the band gap of CdS, as well as reduces the recombination of the photogenerated electron-hole pairs of CdS and its photo-oxidative corrosion, which can improve the photocatalytic activity and stability of CdS for the photo-oxidative degradation of methyl orange in aqueous solution under visible light irradiation.

Vanadium-Substituted Tungstophosphoric Acids as Efficient Catalysts for Visible-Light-Driven Oxygenation of Cyclohexane by Dioxygen

This paper discloses that the oxygenation of cyclohexane by dioxygen (O2) to cyclohexanol and cyclohexanone over three vanadium‐substituted tungstophosphoric acids (PW11V1, PW10V2, PW9V3) can occur in MeCN under visible‐light irradiation, but provides very low cyclohexane conversion (0.8–2.4 %) with modest cyclohexanone selectivity (51–58.3 %). Importantly, an HCl aqueous solution was found to drastically promote this photooxygenation catalyzed by PW10V2 and especially PW9V3 acids, respectively providing approximately 20.4 and 23.4 % cyclohexane conversion and approximately 82.5 and 87.1 % cyclohexanone selectivity, with a concomitant formation of a small amount of chlorocyclohexane. However, such promoting effect was negligible in the PW11V1‐ photocatalyzed oxygenation and the other acids and the chlorine‐containing salts did not show any promotion effect on the present photocatalysis reaction. Notably, the HCl‐promoted photocatalytic oxygenation was significantly influenced by the amount of water. The cyclohexanone selectivity continuously and significantly increased with water amount, but photooxygenation efficiency drastically decreased if a slight excess amount of water was added. Based on these findings and the UV/Vis spectral and cyclic voltammetric measurements, a free‐radical mechanism initiated by the Cl atoms generated in the present photocatalysis system was proposed.

Highly efficient and recyclable alkylammonium hydrosulfate catalyst for formation of bisphenol F by condensation of phenol with formaldehyde

Several C1–C4 alkylammonium hydrosulfates [R3NH][HSO4] have been conveniently prepared from the cheap raw materials sulfuric acid and alkylamines. Their acidities were measured by chemical titration and determined using UV-vis spectroscopy with a basic indicator 4-nitroaniline. The catalytic performance of these hydrosulfates for the condensation of phenol with formaldehyde to bisphenol F (BPF) was evaluated in detail on a batch reactor. The results indicated that the proposed catalysts are very active for such condensation due to its homogeneous catalysis characteristics in reaction conditions. Among the catalysts examined, [H3NCH2CH2NH3][HSO4]2 shows the best catalytic performance and it can achieve a complete conversion of formaldehyde, providing a higher than 90% selectivity for BPF under the optimal conditions. Furthermore, the catalyst can be recovered from the reaction mixture via an azeotropic distillation with cyclohexane to remove water and then filtration and used repeatedly six times almost without loss of activity, showing an excellent reusability. It is suggested that the present catalytic process combines the characteristics of a homogenized reaction and heterogenized recovery so might provide a highly-efficient, environmentally-friendly and low-cost route for synthesis of bisphenol F.

Synthesis, Characterization and Catalytic Properties of TBS-2 Zeolites

Titanium and B co-substituted silicate-2 zeolites were characterized using XRD, FT-IR and NH3-TPD, and the TBS-2′s bifunctional catalytic properties as oxidative and acidic catalysts were investigated using the epoxidation of styrene and rearrangement of styrene oxide.