Theoretical Study On Dimethyl Ether Synthesis From Syngas In Typical Solvent Dimethyl Ether Of A Slurry Reactor

Compared with fixed bed reactor, the slurry reactor has been recently attracted more and more attention because of its efficient heat transfer, constant temperature operation, low gas recycle ratio and low heat loss. Catalysis in the slurry bed uses a traditional catalytic mechanism of the gas-solid phase, but there are some limitations of traditional catalytic mechanism used for solid-liquid-gas phase reaction. Therefore, the interaction mechansim between the reactants and catalyst sites in slurry bed at the micro-scale is not clear, and there is urgent need for the theoretical research in the slurry reactor.In this paper, liquid paraffin of typical solvent in the slurry reactor and syngas as reaction environment and probe, the gas-solid-liquid models of syngas adsorption on Cu（110） and methanol adsorption on γ-Al2O3（110） are established to study the similarities and differences of methanol synthesis from syngas and dimethyl ether synthesis from methanol dehydration in liquid paraffin and gas phase environment. Conclusions are as follows:1. Comparing with the dimethyl ether synthesis from syngas in liquid paraffin and vacuum, it is found that the binding strengths of CO, H, HCO, H₂ CO, H₃ CO, H₂ COH, CO₂, OH, O and CH₃OCH₃ in liquid paraffin are similar with that in vacuum. However, the binding strengths of COH, HCOH, H₃ COH, bi-HCOO, COOH, H₂ COO, HCOOH, H₂ COOH and H₂ O in liquid paraffin are smaller than that in vacuum by 0.11 0.66 eV.2. For methanol synthesis from CO hydrogenation, the reaction pathways in liquid paraffin and vacuum are CO â†' HCO â†' H₂ CO â†' H₃ CO â†' H₃COH; in the case of WGS, the reaction pathways in liquid paraffin and vacuum are CO + 2H₂ O â†' CO + 2OH + 2H â†' CO + H₂ O + O + H₂ â†' CO₂ + H₂ O + H₂; the reaction pathways of methanol synthesis from CO₂ hydrogenation in liquid paraffin and vacuum are CO₂ + H â†' HCOO â†' H₂ COO â†' H₂ CO â†' H₃ CO â†' H₃ COH and CO₂ + H â†' HCOO â†' HCOOH â†' H₂ COOH â†' H₃ CO â†' H₃ COH, respectively. For dimethyl ether synthesis from methanol, the reaction pathways in liquid paraffin and vacuum are CH₃ OH â†' CH₃ O + H,2CH₃ O â†' CH₃OCH₃ + O. The result shows that liquid paraffin does not affect the reaction mechanisms of methanol synthesis from CO, WGS and dimethyl ether synthesis from methanol, but it alters the reaction mechanisms of methanol synthesis from CO₂ hydrogenation.3. Hirshfeld charge and the d-band centers of the first Cu layer in liquid paraffin and vacuum show liquid paraffin changes Cu（110） surface properties, and the d-band centers of the first Cu（110） layer indicate the catalytic activity of Cu（110） in liquid paraffin is less than that in vacuum.