Synthesis of hollow mesoporous spheres modified with ZrO2 and non-noble metals for the one-step reaction of furfural to 1,4-pentanediol.

Abstract

The synthesis of these porous SiO2 nanospheres modified with ZrO2 was based on a previous work to which different metal loadings were co-precipitated to obtain a family of catalysts ranging from 15% Cu to 15% Co. For the synthesis of the nanospheres, SiO2 of pore size 0.2-0.3 μm was used, previously dried in an oven and avoiding contact with the atmosphere. Toluene was added and once the silica was dispersed, Zr n-propoxide was added taking care that the atmosphere was kept inert with a continuous stream of He. It was stirred at 115°C for 12 hours. The solid was centrifuged, filtered with a Buchner funnel, washed with toluene and left to dry in an oven at 60°C. For the incorporation of the metal load, the determined amount of nitrate of the metal was dissolved in 100 mL of deionised water and then, the support was added. The pH of the solution was increased adding a NaOH solution to reach a pH of 9 and aged for at least one hour. Filtration is carried out again with a Büchner funnel, the solid is dried and calcined in an oven at about 500°C for 2 hours. EDX images show that the synthesis has generated spheres where Zr, Co and Cu are covering the silica particles. Regarding to the porosity of the catalysts, it can be seen how the introduction of metals decreases both, the BET surface area and the pore volume and size, with Cu being the metal that most reduces these parameters, which was to be expected since its atomic ratio is lower than Co atomic ratio. The catalytic tests were carried out at 170°C and (3-48 h) using different H2 pressures (1-4 MPa). The catalytic results show an almost total conversion of furfural from 3 hours of reaction and an average yield of 10-15% of 1,4-PD, obtaining the highest yield in pentanediols (1,4-PD+1,5-PD) for Zr-HMS-7.5Cu7.5Co catalyst. Other products of interest such as furfuryl alcohol (FOL), tetrahydrofurfuryl alcohol (THFA), 1-pentanediol (1-Pent), 2-methylfuran (2-MF) and 2-methyltetrahydrofuran (2-MTHF) are also obtained.