CuO-ZnO-Al2O3 and MCM-41 destekli tungstofosforik asitin fiziksel karışımı üzerinde karbodioksitten doğrudan dimetil eterin sentezi

Carbon dioxide (CO2) plays an important role in the natural carbon cycle. However, increase in CO2 emissions causes global warming and climate changes because of the so-called 'greenhouse effect'. Therefore, the chemical recycling of CO2 to alternative fuels offers a prospective solution for these environmental concerns and provides new opportunities for sustainable future. In this view, conversion of CO2 into liquid fuels is a promising approach. Among possible alternative products, such as methanol, hydrocarbons, and dimethyl ether (DME), DME can be used as an intermediate to produce several value-added products or as an alternative fuel. And it is the simplest ether without any C‒C bonds; it is a colorless, nontoxic, and environmentally friendly. Because of its similar physical and chemical properties, it has a potential of substituting liquid petroleum gas (LPG). Besides, it is considered as a prospective future synthetic fuel owing to its high cetane number, more complete combustion, and low emission of toxic gases, such as SOx, NOx The aim of this thesis is to develop an efficient catalyst for the conversion of CO2 into DME. For this purpose, here, MCM-41-supported tungstophosphoric acid (TPA) and a commercial CuO-ZnO-Al2O3 methanol synthesis catalyst were physically mixed and the mixing ratios and reaction conditions were optimized for the highest DME production rate from CO2 hydrogenation in a single-pass flow reactor. Data demonstrated that the highest DME space time yield was achieved at a TPA loading of 60 wt% in the TPA/MCM-41 catalyst and at a CuO-ZnO-Al2O3:TPA/MCM-41 mixing ratio of 4:1 using a gas hourly space velocity of 40 000 mL CO2 gcat-1 h-1 with an H2:CO2 ratio of 3:1 at 250 °C and 45 bar. At these conditions, the physical mixture provided a DME production rate of 1551.5 gDME kgcat-1 h-1, to the best of our knowledge, is more than twice of the rate reported previously as the highest rate for DME production from CO2 hydrogenation in a single-pass. Data suggested that this high performance was originated from the high density of acid sites in TPA/MCM-41 catalyst owing to exceptionally high surface area of MCM-41 offering a monolayer dispersion of TPA clusters even at a TPA loading of 60 wt%. Having a high density of acid sites in the physical mixture with a methanol synthesis catalyst offers a high efficiency in subsequent conversion of methanol into DME in a single pass reactor. Considering that this high DME production rate was obtained in a physical mixture containing a commercial methanol synthesis catalyst, optimized specifically for synthesis gas, results of this thesis present a broad potential of TPA/MCM-41 solid acid catalysts for single-pass DME production from CO2 hydrogenation, when used together with a methanol synthesis catalyst specifically designed for CO2 hydrogenation.