Abstract
Mesoporous alumina has been successfully prepared using sucrose as templates. Mesoporous alumina-based catalysts, neat and impregnated with metal chlorides, were tested for gas phase methyl chloride synthesis from methanol and HCl. The catalysts were characterized with Transmission electron microscope (TEM), N2-physisorption, X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) to identify the relationship between the catalyst characteristics and their activity and selectivity. Experimental studies revealed that the alumina acidity decreases with increasing calcination temperature, and the catalytic activity is strongly related to the acidity. The catalytic activity of mesoporous alumina (named as Al2O3-500 °C) is higher than that of the commercial alumina under the same experimental conditions. The metal chlorides-modified alumina has more Lewis acid sites than the neat alumina. Impregnation by alcohol is more effective for increasing the amount of Lewis acid sites than impregnation by water. The total Lewis acid concentration of the modified alumina decreases in the following order: ZnCl2/Al2O3-E > ZnCl2/Al2O3-W > FeCl3/Al2O3-E > FeCl3/Al2O3-W, Where E and W respectively indicate that the catalyst impregnation solution is ethanol and water, which agrees well with the catalytic performance order. The effect of ethanol as a solvent in the impregnation could be due to the inhibition of the hydrolysis of metal chloride. The catalyst delivered a stable performance during a 100 h test that was significantly higher than that of commercial alumina.
Highlights
Methyl chloride is an important material for the production of higher chlorinated products, silicones, rubber and methyl cellulose and is applied as a methylating agent
It was found that increasing calcination temperature could widen the pore size distribution of mesoporous alumina and leads to the formation of larger pores
The alumina synthesized with sucrose as the template and aluminium iso-propoxide as the aluminium source have high surface areas, uniform pore structures and narrow pore-size distributions
Summary
Methyl chloride is an important material for the production of higher chlorinated products, silicones, rubber and methyl cellulose and is applied as a methylating agent. The hydrochlorination of the methanol pathway has attracted much more attention in industry This process can be carried out in the liquid phase catalytically in the presence of zinc chloride or in the gas phase over alumina catalysts. Considering the hydrolytic nature of zinc chloride and the interaction between zinc chloride and support, it is difficult to study the chemical state of zinc on the catalyst surface and relevant catalytic performance by water impregnation method. Loading metal chloride with different solvent provide convenience to study the difference of chemical state of zinc on alumina and relevant catalytic performance on methyl chloride synthesis. Mesoporous γ-alumina was modified by FeCl3 and ZnCl2 using water and ethanol as solvents to understand the effect of the solvent on the chemical state of zinc and iron and the relevant catalytic performance
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