Liquid-Phase Preparation Technology For DME Slurry Catalysts Using Pseudo-Boehmite As Aluminium Source

Dimethyl ether (DME) is used in many fields, mainly used as refrigerant, solvent, extraction, aerosol, propellants and special material. Importantly, it can also be used as substitute for diesel oil and LPG due to its low pollution. So DME displays an important effect on alleviating pollution and improving global ecological environment.In recent years, slurry phase DME synthesis has received much attention because the slurry reactor has many merits such as good heat and mass transfer, easily gained material gas, less investment and convenient operation. But the stability of catalyst has proved to be bottleneck of the process scale-up of the slurry phase DME synthesis. A novel preparation method of slurry catalyst named as complete liquid phase preparation technology to adapt the operational characteristics of the catalyst in slurry reactor has been presented by our group. Its main innovative thought lies in preparing the slurry catalysts directly from solution. Our prior research result indicated that the catalyst prepared by complete liquid-phase technology showed good stability and excellent selectivity, but because the AIP was used as aluminum resource, the production cost was higher.In this paper, Al-based slurry catalysts used pseudo-boehmite as the aluminum source were prepared by complete liquid-phase technology and the influence of different raw material composition, pseudo-boehmite mass fractions, addition amount of acid, feeding modes, solvents and DCCA were studied. The catalysts were characterized by XRD, BET, XPS, TPR. The activity of catalysts for direct synthesis of DME from syngas was evaluated in a slurry reactor. The aim of this paper was to provide lower cost and easily industrialized Al-based catalyst. The main conclusions were drawn as follows:1. When prepared under the same conditions, the catalysts used AIP and pseudo-boehmite as aluminum source were similar in phase structure and pore structure, but had difference in dispersion and surface structure, which lead to different .catalytic performance.2. Using pseudo-boehmite as aluminum source, the optimum technological conditions were as follow: n(Cu):n(Zn):n(Al)=1:1:4, mass fraction of pseudo-boehmite was 13% of, n(H~+):n(AlOOH)=0.1, copper and aluminum or copper and zinc was added simultaneously.3. Compared with water, the organic solvent can improve catalytic performance. The catalyst showed better CO conversion and lower DME selectivity when glycol used as solvent. However, using ethanol as solvent favored the production of DME. 4. As a neutral drying control chemical additives(DCCA), glycerin can enhance catalytic performance very well. The CO conversion and DME selectivity of catalyst used pseudo-boehmite as aluminum source was better than that of AIP. This showed good prospect for preparing the Al-based slurry catalyst used pseudo-boehmite as aluminum source.