Selective Hydrogenation of Furfural to Furfuryl Alcohol in the Presence of a Recyclable Cobalt/SBA-15 Catalyst.

The hydrogenation of furfural to furfuryl alcohol was performed in the presence of a Co/SBA-15 catalyst. High selectivity (96 %) at a conversion higher than 95 % is reported over this catalytic system. As the conversion of furfural to furfuryl alcohol occurs over metallic Co sites, the effect of reduction temperature, H2 pressure, and reaction temperature were studied. Optimum reaction conditions were: 150 °C, 1.5 h, 2.0 MPa of H2 . The catalyst was recyclable, and furfuryl alcohol was recovered with a purity higher than 90 %. The effect of the solvent concentration was also studied. With a minimum of 50 wt % of solvent, the selectivity to furfuryl alcohol and the conversion of furfural remained high (both over 80 %). Likewise, the activity of the catalyst is maintained even in pure furfural, which confirms the real potential of the proposed catalytic system. This catalyst was also used in the hydrogenation of levulinic acid to produce γ-valerolactone selectively.

Nanosized transition metals in controlled environments of phyllosilicate-mesoporous silica composites as highly thermostable and active catalysts.

Stabilization of transition metals in nano-phyllosilicate phases generated by digestion of mesoporous silica is reported as an efficient route for the formation of highly dispersed metallic nanoparticles with outstanding catalytic activity.

Composition-dependent morphostructural properties of Ni-Cu oxide nanoparticles confined within the channels of ordered mesoporous SBA-15 silica.

NiO and NiO-CuO polycrystalline rodlike nanoparticles were confined and stabilized within the channels of ordered mesoporous SBA-15 silica by a simple and viable approach consisting in incipient wetness impregnation of the calcined support with aqueous solutions of metal nitrates followed by a mild drying step at 25 °C and calcination. As revealed by low- and high-angle XRD, N2 adsorption/desorption, HRTEM/EDXS and H2 TPR analyses, the morphostructural properties of NiO-CuO nanoparticles can be controlled by adjusting their chemical composition, creating the prerequisites to obtain high performance bimetallic catalysts. Experimental evidence by in situ XRD monitoring during the thermoprogrammed reduction indicates that the confined NiO-CuO nanoparticles evolve into thermostable and well-dispersed Ni-Cu heterostructures. The strong Cu-Ni and Ni-support interactions demonstrated by TPR and XPS were put forward to explain the formation of these new bimetallic structures. The optimal Ni-Cu/SBA-15 catalyst (i.e., Cu/(Cu+Ni) atomic ratio of 0.2) proved a greatly enhanced reducibility and H2 chemisorption capacity, and an improved activity in the hydrogenation of cinnamaldehyde, as compared with the monometallic Ni/SBA-15 or Cu/SBA-15 counterparts, which can be associated with the synergism between nickel and copper and high dispersion of active components on the SBA-15 host. The unique structure and controllable properties of both oxidic and metallic forms of Ni-Cu/SBA-15 materials make them very attractive for both fundamental research and practical catalytic applications.

Immobilization of Thermoanaerobium brockii alcohol dehydrogenase on SBA-15.

The activity of Thermoanaerobium brockii alcohol dehydrogenase (TBADH) adsorbed on mesoporous silica SBA-15 was compared with that of the free enzyme in water and in biphasic system (water phase up to 50% v/v water). TBADH was active at a water concentration ≥10% v/v. In the reduction reaction of sulcatone to sulcatol carried out in biphasic systems, the yield obtained with SBA-15-adsorbed TBADH was up to 5.5-fold higher than that with the free enzyme, which suggests a higher stability of the immobilized enzyme toward the organic solvent. The nature of the organic solvent substantially influenced the degree of conversion that, for example, was 7.4% in toluene and 31.6% in petroleum ether.

Hydrogenation of Unsaturated Carbonyl Compounds on non-Calcined LDHs. I. Synthesis and Characterization of ZnNiCuAl Hydrotalcite-like Materials.

Several Zn/Ni/Cu/Al layered double hydroxides (LDH) with variable Ni/Cu ratios but constant Zn/Al, as well as M2+/M3+ ratios, were synthesized by coprecipitation method with CO32- as compensating anion. The main goal of the study was to investigate the influence of the catalysts composition, especially Ni/Cu ratio, on the physical and catalytic properties of these materials. The XRD results show that all the LDHs samples are well crystallized and contain only pure phases. Moreover, the spectral techniques (FT-IR and DR-UV-VIS) indicated that both Ni and Cu species are present in the brucite-like layers of LDHs. The shape of the nitrogen physisorption isotherms obtained at -196 °C indicates a predominantly mesoporous materials; the surface areas and pore volumes are in the specific ranges between 37-86 m2.g-1 and 0.31-0.75 cm3.g-1, respectively. Three characteristic weight losses between 30 and 400 °C are identified by TG analysis for the hydrotalcite-like materials synthesized in this study. Moreover, an influence of the Ni/Cu ratios on the amount of the physisorbed water was noticed. The preliminary catalytic test revealed unusual catalytic properties of the non-calcined samples in the liquid phase hydrogenation of trans-cinnamaldehyde.

Removal of dimethylsulfoxide from wastewater using mild oxidation with H2O2 over Ti-based catalysts.

The mild catalytic oxidation of dimethylsulfoxide (DMSO) into biodegradable dimethylsulfone is proposed as an efficient pretreatment of wastewaters subjected to biological treatment processes. A SiO(2)-TiO(2) mesoporous xerogel prepared by a non-hydrolytic route, as well as titanium silicalite TS-1 showed very good activity and stability in the catalytic oxidation of DMSO with H(2)O(2) in dilute aqueous solution, at room temperature.

Non-hydrolytic synthesis of mesoporous silica-titania catalysts for the mild oxidation of sulfur compounds with hydrogen peroxide.

A SiO(2)-TiO(2) mesoporous xerogel prepared in one-step by a non-hydrolytic route shows excellent performance in the mild oxidation of sulfides, sulfoxides and thiophenes with aqueous solutions of H(2)O(2).

Catalytic oxidation processes for removing dimethylsulfoxide from wastewater.

An effective method for removing dimethylsulfoxide (DMSO) from wastewater, based on the mild selective catalytic sulfoxidation with H(2)O(2), is proposed in this study. The catalysts are W-containing layered double hydroxides (LDH), and they were obtained by ionic exchange of the nitrate anions from MAl-LDH precursors (M=Mg(2+) or Zn(2+)) with both WO(4)(2-) and W(7)O(24)(6-) species. Results of X-ray diffraction (XRD), N(2) adsorption, thermal gravimetric analysis (TGA), diffuse reflectance ultraviolet spectroscopy (DRUV) and Raman spectroscopy confirmed the formation of the W-oxospecies inside the interlayer space and the modification of the textural properties upon the exchange process. All catalysts showed very good activity and stability in the DMSO conversion into dimethylsulfone with dilute H(2)O(2) aqueous solution, at low temperatures (20-50 degrees C). The efficiency of the H(2)O(2) was higher than 95% and the behaviour of the water as solvent was very close to that of the organic solvents (ethanol, acetonitrile, 1,4-dioxane).

Can an inactivating agent increase enzyme activity in organic solvent? Effects of 18-crown-6 on lipase activity, enantioselectivity, and conformation.

Lipase from Burkholderia cepacia (lipase BC) and lipase B from Candida antarctica (CALB) show an increase of the transesterification activity in toluene (up to 2.4- and 1.7-fold, respectively), when lyophilized with 18-crown-6. Nevertheless, the increase was observed only for low (less than 100) 18-crown-6/lipase molar ratio, while at higher ratios, the activity decreased for both enzymes to values lower than those obtained in the absence of the additive. In 1,4-dioxane, the activation is lower for lipase BC (1.7-fold) and for CALB (1.5-fold). Concerning enantioselectivity, tested in the kinetic resolution of 6-methyl-5-hepten-2-ol, only in the case of CALB, an effect of the additive (the E value varied from about 120 to 280) was observed. In water, 4% (w/w) of 18-crown-6 caused a loss of activity in the hydrolysis of p-nitrophenyl laurate of about 88 and 99.75%, compared to that observed in the absence of the crown ether for CALB and lipase BC, respectively. These data and the conformational analysis of both lipases, carried out by FT/IR spectroscopy indicate that the enzyme inactivation in water and in organic solvents at 18-crown-6/lipase molar ratios, higher than 100 might be due to conformational changes caused by the additive. Instead, at molar ratios lower than 100, 18-crown-6 might increase the activity - particularly, in toluene - thanks to the fact that in its presence, the enzyme has an hydrogen bonds pattern, more similar to that in water. This suggests that the additive would be able to provide the enzyme with more water.

Physical and chemical adsorption of Mucor javanicus lipase on SBA-15 mesoporous silica. Synthesis, structural characterization, and activity performance.

In this work a sample of SBA-15 mesoporous silica was synthesized and characterized by TEM, XRD, and N2 adsorption. The sample had a high value of specific surface area (1007 m2 g(-1)) and total pore volume (2.1 cm3 g(-1)). The pore diameter was 67 angstroms, so it was large enough to accommodate protein molecules inside the channels. Immobilization by physical adsorption of a commercial lipase preparation from Mucor javanicus was performed at different pH values (pH 5-8). pH 6 gave the highest lipase loading and hydrolytic activity of the corresponding biocatalyst. Chemical modification of the SBA-15 via glutardialdehyde allowed also the enzyme immobilization through chemical adsorption. This preparation was active toward tributyrin hydrolysis. On the contrary, very low activity toward triolein hydrolysis was observed. The reduction of the size of the channels due the immobilization process has been suggested as a possible explanation.