Abstract: Activated carbon (AC) was treated with nitric acid of different concentrations prior to the preparation of Co-Zr-La/AC higher alcohol synthesis catalysts. The effect of acid pretreatment on the catalyst activity was studied. The surface properties of the samples were investigated by Boehm titration and N₂ physisorption. And the Co dispersion, reduction properties, and physical structure of the catalysts were characterized by CO chemisorption, temperature-programmed reduction, and X-ray diffraction (XRD), respectively. The results show that the nitric acid pretreatment causes the surface oxygen groups on the AC surface increase significantly and the XRD peak intensities of Co and Co₂C in the catalysts vary dramatically. As a result, CO conversion increases from 9.9% to 65.3%, and the selectivity for total alcohol decreases from 62.3% to 40.5%. Although total alcohol selectivity decreases after the pretreatment, the selectivity for C₆₊ alcohols increases from about 12.6% to 40.3% when there are suitable amounts of Co and Co₂C active sites in the catalyst that is treated with 4.6 mol/L nitric acid.

Key words: syngas, higher alcohol, activated carbon, cobalt, zirconium, lanthanum, nitric acid, acidic group