Abstract
The direct synthesis of dimethyl ether (DME) is an ideal process to achieve the environmental objective of CO2 conversion together with the economic objective of DME production. The effect of the reaction conditions (temperature, pressure, space time) and feed composition (ternary mixtures of H2 + CO + CO2 with different CO2/CO and H2/COx molar ratios) on the reaction indices (COx conversion, product yield and selectivity, CO2 conversion) has been studied by means of experiments carried out in a fixed-bed reactor, with a CuO-ZnO-MnO/SAPO-18 catalyst, in order to establish suitable ranges of operating conditions for enhancing the individual objectives of CO2 conversion and DME yield. The optimums of these two objectives are achieved in opposite conditions, and for striking a good balance between both objectives, the following conditions are suitable: 275–300 °C; 20–30 bar; 2.5–5 gcat h (molC)−1 and a H2/COx molar ratio in the feed of 3. CO2/CO molar ratio in the feed is of great importance. Ratios below 1/3 are suitable for enhancing DME production, whereas CO2/CO ratios above 1 improve the conversion of CO2. This conversion of CO2 in the overall process of DME synthesis is favored by the reverse water gas shift equation, since CO is more active than CO2 in the methanol synthesis reaction.
Highlights
Dimethyl ether (DME) is receiving increasing attention as alternative fuel and raw material.Its properties are suitable for its use as fuel in different sectors [1,2,3]
The results indicate that COx conversion increases with pressure (Figure 3a), which is which is characteristic of the dimethyl ether (DME) synthesis reaction, given that it involves a reduction in mole characteristic of the DME synthesis reaction, given that it involves a reduction in mole number
The results obtained with the CuO-ZnO-MnO/SAPO-18 catalyst evidence the capacity of the DME synthesis process in a single-step for the utilization of the CO2 co-fed with syngas
Summary
Dimethyl ether (DME) is receiving increasing attention as alternative fuel and raw material.Its properties (low toxicity and ease of storage, transport, and distribution, high cetane index) are suitable for its use as fuel in different sectors (domestic, automotive, and electric power generation) [1,2,3]. DME is a potential raw material for the production of diesel fuels (such as dimethoxymethane and polyoxymethylene dimethyl ethers, via oligomerization) [4], and chemicals (methyl acetate, formaldehyde, ethanol, among others) [5], replacing methanol. It can replace methanol for light olefin production [6,7] and it is a H2 vector through steam reforming [8,9,10]. The demand corresponds in a 65% to the consumption in Asia (mainly in China) as domestic fuel, replacing liquefied petroleum gases (LPG), being its price dependent on the market of methanol and of LPG, which can be estimated as the 75 to
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