2.3.1 Catalyst preparation
The Cu/ZnO-based hydrogenation catalysts were prepared by the co-precipitation method. In a typical synthesis, 1 mol of copper nitrate, 1 mol of zinc nitrate, and 2 mol of sodium silicate were respectively dissolved in 500 mL of deionized water. The solutions were simultaneously added dropwise into a beaker in 1 h at room temperature under mechanical stirring at 500 rpm. The precipitates were formed during the addition. Then, the precipitates were aged for 12 h. The precipitates were filtrated and washed 10 times with deionized water. The filter cake was dried at 383 K for 24 h and calcined at 623 K with a heating rate of 5 K min–1 for 12 h. The resulting catalyst precursor was pelletized, crushed, sieved to 30–50 meshes, and denoted as Cu1Zn1Si2.
The Cux Zn1Si2catalysts (x = 0, 0.5, 0.75, 1, 1.25, 1.5, and 2) and Cuy Zn2–y Si2catalysts (y = 0.5, 0.75, 1, 1.25, 1.5, 1.75, and 2) were prepared by the procedures described above except for the amounts of the copper and zinc salts used. The Cu1Zn1Si2La0.1catalyst was also prepared in a similar manner except for the addition of 0.1 mol of lanthanum nitrate during the preparation.