Direct hydrogenation of CO2 to dimethyl ether (DME) over hybrid catalysts containing CuO/ZrO2 as a metallic function and heteropolyacids as an acidic function

Abstract

Dimethyl ether (DME) is considered as a substitution of diesel oil. It can be used in diesel engines because of its high cetane number (> 55). The combustion process does not generate particle matter (PM) or sulphur oxides (SOx) pollutions. One of the methods to obtain DME is direct synthesis from a CO2 and H2 mixture. On the other hand, CO2 is an attractive reagent, which is a safe and economical source of carbon. The aim of this work was to obtain DME in the direct process from the mixture CO2 and H2 in the presence of hybrid catalyst. In these catalytic the CuO/ZrO2 was selected as a metallic function. The montmorillonite K10 modified by heteropolyacids was selected as an acidic function. The catalysts were obtained by different preparation methods and contained various types of heteropolyacids. The catalysts were characterized by following methods: BET/BJH, XRD, SEM, DCS/TG, NH3-TPD and FT-IR. The direct hydrogenation of CO2 was performed in the high pressure fixed-bed flow reactor connected online with GC equipped with TCD and FID detectors. It was shown that both synthesis method of metallic function and the type of heteropolyacids have influence on the total catalytic activity of the hybrid catalyst. The acidity and thermal stability of HPAs are identified as the most important parameters having a decisive influence on the overall catalytic activity of the samples.