Preparation Of New Amorphous Alloy Catalysts, Structural Characterization And Solvent Effect In The Hydrogenation Of Furfural

Chemists and chemical engineers are now focusing on researching new materials,improving catalytic efficiency and eliminating environmental pollution. The latter twomakes fundamental essentials for green chemistry. Therefore, it became crucial forscientists to develop novel catalytic materials.Amorphous alloys represent a variety of special materials with short-rangeordering while long-range disordering structure that may provide pathways to theexcellent catalytic properties. i.e., good anti-poisoning ability, the higher catalyticactivity and selectivity in homogeneous hydrogenation of α,β-unsaturated aldehyde,the low and even none environment pollution.Up to now, in hydrogenation of furfural to furfuryl alcohol, the most commonlyused catalysts are Cu-Cr, dopant Cu-Cr, and Raney Ni et al. However, highly toxicityand reactor-blockage restrained wide application to Cu-Cr catalyst. No matter howhigh activity Raney Ni has, it could not play an important role in the hydrogenationreaction, because of its various undesired by-products and environmentalcontamination. Therefore, the amorphous alloy, possessing excellent catalyticproperties in different reaction, would be applied in hydrogenation of furfuralIn the present thesis, the ultrafine Co-B, Co-Fe-B amorphous alloys andsupported Co-B/SiO₂ have been prepared by chemical reduction. The catalyticperformance of all amorphous alloy catalysts mentioned above was measured duringliquid phase hydrogenation of furfural to furfuryl alcohol, together with the kineticstudies. The relationship between the catalyst performance and the structure ofcatalyst, surface electronic state of the amorphous alloy has been systematicallystudied based on series of characterization of catalysts(XRD,XPS,TEM,SEM,BET,TPD). Meanwhile, the promoting effects of the support on the thermal stabilityand catalytic activity of the amorphous alloy catalysts have been discussed.Furthermore, by alternating the kinds of the additives and their amount in theamorphous alloys, the modification of several admixtures on the structure of theamorphous alloy has been investigated, which could account for their promotingeffect on the catalytic behaviors. The researching work in the present thesis could besummarized as follows: 1. Catalyst preparation. By adding KBH4 into a solution containing (1) CoCl2solution, (2) both CoCl2and FeCl3, the ultrafine amorphous alloys of Co-B, Co-Fe-Bwere prepared, which were thoroughly washed with distilled water and the reactionsolvent and then stored in the latter before next step. Meanwhile, the Co-B/SiO2 amorphous catalyst was prepared by impregnatingthe SiO2 support with CoCl2solution, and drying, calcinating at 573 K for 2.0 h, thencooled to ambient temperature, followed by KBH4 reducing. The resulting Co-B/SiO2sample was washed in the similar way mentioned above and also kept in the reactionsolvents. 2. Activity test. All the furfural hydrogenation reactions were carried out in anautoclave containing certain amount of the as-prepared catalysts, furfural and solvent.RH2 was determined by monitoring the drop of the hydrogen pressure inside the mautoclave. The conversion of the furfural and the selectivity to furfuryl alcohol wasobtained according to the product analysis by gas chromatograph. All the amorphousalloy catalysts exhibited much higher catalytic activity than Cu-Cr, which was widelyused in industrial process of furfural hydrogenation, showing a good potential inindustrial application, the choice of solvents have some effect to the selectivity andthe reaction activity. 3. Correlation of the catalytic performance to the structure of the catalysts. (1) The amorphous alloys usually exhibited much higher activity than theircorresponding crystalline counterpart. On one hand, in viewpoint of the structuraleffect, this could be attributed to the unique amorphous structure (i.e., the short-rangeordering but long range-disordering structure), the homogeneous distribution of theactive sites, and the highly coordinative insaturation of these active sites. On the otherhand, this could also be ascribed to the electronic interaction between the metal andthe metalloid in the amorphous alloy. For all metal-B amorphous alloys, the metalalways accepted partial electrons from the alloying B, making it electron-enriched...