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9Three different bimetallic Ru:Ni catalysts supported on a mesoporous silica MCM-48 10 were prepared by consecutive wet impregnations, with a total metal loading of ca. 3 % 11(w·w -1 ). Ru:Ni ratios spanned in the range of 0.15 -1.39 (w·w -1 ) and were compared with

The extraction/hydrolysis process of arabinoxylans from destarched wheat bran was studied in this work using different mesoporous silica supports and the corresponding RuCl3-based catalysts. The effects of temperature, time, catalyst supports and ruthenium catalysts were investigated and discussed in terms of the arabinoxylans extraction yield and their polymerization degree. Relatively high temperatures (180 ºC), short extraction times (10 minutes) and RuCl3 supported on Al-MCM-48 led to a high amount of arabinoxylans extracted (78%) with a low molecular weight (9 KDa). Finally, a relation between the operating conditions, the arabinoxylans extraction yield and the molecular weight was stablished based on the obtained results. Abbreviation: AXs, arabinoxylans; DWB, destarched wheat branKeywords: Hemicelluloses fractionation, wheat bran, arabinoxylans, heterogeneous catalysis, hydrothermal process, biomass Chemical compounds studied in this articleXylose (PubChem CID: 135191); Arabinose (PubChem CID: 439195) Highlights:-Effects of ruthenium catalyst, temperature, time and catalyst support are discussed -RuCl3-based catalysts show good activity for the arabinoxylans extraction from wheat bran -Liquid extracts are characterized in terms of sugars, molecular weight and purity

Supercritical water hydrolysis is an effective pretreatment for hexitol synthesis over Ru/MCM-48.

Highlights 1. Crystalline cellulose is hydrolyzed into glucose with a yield of 63.8% 2. The Ag(I) ions exchanged allowed the hydrolysis of cellulose 3. The incorporation of silver produces a redistribution of acid sites 4. Al(III) species which are octahedrically coordinated were detected

Pd nanoparticles have been embedded on silica aerogel by using three different techniques. In each of them the metal was loaded in the matrix at different steps of the production: the direct synthesis, the wet impregnation and the supercritical impregnation of the previously dried aerogels. The resultant materials have been characterized to analyze the differences depending on the applied technique for its impregnation. Atomic absorption, nitrogen physisorption, X-ray diffraction, infrared spectroscopy and transmission electron microscopy where performed. In all the techniques the concentration of metal has been varied (from 0.13 to 1.61 % wt.) by modifying the concentration of the suspension (Pd-polyvinylpyrrolidone nanoparticles used in the direct synthesis) or of the solution of the metallic precursor (palladium acetylacetonate), both in the organic solvent and the supercritical media. The characterization had generally shown a good distribution of the metallic particles in the matrix, and the negligible effect of the metal on the textural properties. Finally, considerable variations where observed on the silanol groups on the surface of the catalysts. These materials were tested in D-glucose hydrogenation, observing significant differences on the performance of the catalyst depending on the synthesis technique employed.

The simultaneous catalytic hydrolysis and hydrogenation of cellobiose, as a model constituent of biomass has been studied over Ru/Al-MCM-48. The catalyst, presenting both acidic and hydrogenating functions has been synthesized and characterized by means of N 2 adsorptiondesorption, SAXS, H 2-TPR, XRD, TEM and NH 3-TPD. A kinetic model is proposed, and possible reaction pathways and key intermediate compounds of conversion of cellobiose to hexitols are discussed. In the kinetic study the effects of pressure, temperature and time on the one-pot reaction were evaluated. A maximum yield around 91 % of hexitols was achieved at 180 ºC, 5 MPa of H 2 and 7 min, where sorbitol was the main compound in the final product with 82 % yield. Cellobitol was the main reaction intermediate. Temperatures in the range of 140-180 ºC and pressures in the range of 3-5 MPa of H 2 were studied and it was concluded that higher temperatures and pressures had a positive effect in order to maximize the production of hexitols. The developed kinetic model predicted with high accuracy the concentration of the different compounds involved in the proposed reaction pathway and served to calculate the specific reaction rate and activation energy values for the different steps of the catalytic process.

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