2.1 Catalyst Preparation
The preparation method of Cu25Fe22Co3K3 catalyst (60–80 mesh, namely 0.180–0.250 mm according to standard ASTM E-11) was described elsewhere.(6) The Cu4.5Zn4.5Al1 catalyst was prepared by a two-step coprecipitation method. At first, an aqueous solution of Al(NO3)3 and an aqueous solution of Na2CO3 with same molar concentration were dropped simultaneously into a vessel under continuous stirring at 70 °C and pH = 7.0 to generate a mother liquid. Then, a mixed aqueous solutions of Cu(NO3)2 and Zn(NO3)2 and an aqueous solution of Na2CO3 with same molar concentration were dropped parallelly into the above-mentioned mother liquid under continuous stirring at 80–85 °C and pH = 8.0. The precipitate was aged statically at room temperature for 20 h, washed with deionized water to remove Na+ in the filtrate, then dried at 110 °C overnight, at last calcined in air at 350 °C for 6 h. The obtained catalyst was crushed and sieved to 60–80 mesh (0.180–0.250 mm) and combined together with Cu25Fe22Co3K3 catalyst to produce lower alcohols from syngas. The main catalyst characteristics are listed in Table S1 (Supporting Information).