Abstract
Influence of gold loading on methanol yield using Au/C4ZA at 220–260°C with 4.0 and 6.0MPa.
•The addition of 1wt.% Au to Cu–Zn–Al leads to most active Au contained catalyst.•The cooperative effect between copper and gold exists in the form of Cu–Au interface.•Better methanol yield was due to higher adsorption ability to CO, H2 at interface.•Hydrogen spillover on Au–Cu surface reduces the reaction selectivity to CO.•Cu interacts with Zn forming Cu0.3Zn0.7 while Cu and Au do not interact chemically.
Methanol synthesis from CO2 via gas phase hydrogenation was carried out on Au/Cu–Zn–Al catalysts. The base Cu–Zn–Al with different Cu contents was synthesized by rapid precipitation method and subsequently gold (0.5–3wt.%) was deposited on the base Cu–Zn–Al by deposition–precipitation method. Solid catalysts investigated in this study were characterized by BET surface area, XRD, HR-TEM, XPS and CO2, CO and H2-TPD techniques. Formation of methanol in this study was influenced by the copper content in base Cu–Zn–Al and also on gold loading. Among the catalysts studied 1Au/C4ZA (1wt.% Au deposited on Cu:Zn:Al=4:1:1 mole ratio) exhibited maximum methanol yield of 16.6% mass. Among the catalysts studied the decreasing order of CO2 conversion is as follows: 1Au/C4ZA>0.5Au/C4ZA>C4ZA>3Au/C4ZA at GHSV 7000h−1. The greater methanol yield on 1Au/C4ZA attributed to: (i) H2 spillover in Au–Cu–Zn–Al, (ii) higher adsorption capacities to H2 and CO at Cu–Au interface and (iii) Cu/Au ratio on the surface ∼5. To the best of our knowledge, this is the first report for gold influence on Cu–Zn–Al system in CO2 hydrogenation process.