A Phyllosilicate-DerivedCu–Ni Alloy Catalystfor Efficient Hydrogenation of High-Concentration Xylose Aqueous Solutionto Xylitol

Abstract

Hydrogenation of xylose is an important industrial process for the production of xylitol, which is known as a healthy sweetener. In this work, bimetallic phyllosilicate-derived Cu–Ni alloy catalysts were constructed via an ammonia evaporation method followed by reduction under hydrogen and applied for the hydrogenation of a high-concentration xylose aqueous solution for the production of xylitol. The Cu–Ni alloy catalysts exhibited higher xylose conversion than the corresponding monometallic Cu and Ni catalyst. And the xylitol yield was increased with the increase of the ratio of nickel to copper for the bimetallic alloy catalyst. The higher xylose conversion was obtained at elevated reaction temperature and H₂ pressure. In addition, reduction conditions, especially temperature, were found to significantly influence the catalytic activity of the phyllosilicate-derived Cu–Ni alloy sample. The 5Cu15Ni-EA catalyst activated at 700 °C exhibited excellent performance for xylose hydrogenation in terms of xylose conversion (>99%) and xylitol selectivity (>99%) under moderate conditions (100 °C and 4 MPa H₂). The performance of the 5Cu15Ni-EA catalyst is also superior to the reported consequences of xylitol manufacture via hydrogenation over a Raney nickel catalyst and a co-impregnation-derived bimetallic catalyst. Furthermore, the xylitol yield did not change obviously for 5Cu15Ni-EA during the 200 h of continuous reaction in a fixed bed reactor. The XRD, XPS, HRTEM–EDS mapping, and line scan results of the fresh reduced 5Cu15Ni-EA sample verified the existence of a highly dispersed Cu–Ni alloy. The formation of these uniformly dispersed Cu–Ni alloy sites induced efficient performance for the hydrogenation of a high-concentration xylose aqueous solution.