| China has little of oil resources, but plenty of coal resources. Coal is recognized as the basic energy resources in china. For making better use of coal resources, it is a novol way to develop the clean conversion of coal resources into chemical products with high-added value. Transformation of coal via dimethyl ether into aromatics (DMTA) is an important branch of coal conversion. Such technology can not only provide a new approach to use coal resource, but also can replace oil as raw material to produce light aromatics, and It will also pay an important role in national energy security.In this paper, unloaded HZSM-5 was firstly investigated in the aromatization of DME, and effect of reaction temperature, Si/Al ratio, acidities on the catalytic performance was also studied. By studying conversion of ethylene, ethylene-water, DME over molecular sieves with different pore diameters, a reaction mechanism was suggested. Secondly, Zn- and Ni- modified HZSM-5 were investigated in DMTA process. At last, conversion of DME over H-beta catalyst was studied. The detailed results were summarized as follows:1. The results of thermodynamic analysis showed that of DMTA reactions were under zero between 550 K and 800 K, which indicated these reactions could proceed spontaneously thermodynamically. Conversion of DME into aromatics was exothermic reactions; the equilibrium constants of these reactions were decreased with increased temperature.ΔrGθm2. At the reaction temperature of 360℃, the content of total aromatics was about 50% and mainly comprised of light aromatics. This indicated that HZSM-5 was an effective catalyst for DMTA process. The total aromatics composition was increased when the reaction temperature was enhanced. This was inconsistent with the thermodynamic results. This implied that aromatization of DME was not controlled by thermodynamics. Improving the reaction temperature might accelerate the rate of slow-reaction, so that higher aromatic composition could be achieved.3. The Si/Al ratio of catalysts had obvious effect on the content of effluent products in DMTA process. Lower Si/Al ratio had better catalytic performace. As the Si/Al ratio decreased from 50 to 25, the composition of total aromatics was increased by 7.9%. In addition, when HZSM-5 was treated with KOH, the aromatics composition decreased obviously, and more KOH was loaded, worse performance was obtained. This suggests the acidic centers played an important role in the conversion of DME.4. After dealuminization by citric acid treatment, catalytic performance of the catalysts decreased greatly. Higher concentration of citric acid was used, lower aromatics content was obtained. The performance of HZSM-5 treated at high temperature in advance was better than those treated by citric acid. When the catalyst was heated at 650℃, the catalyst had the best catalytic performance.5. ZnO introduced into HZSM-5 could greatly improve the aromatization properties. When the reaction temperature was enhancedd from 360℃to 480℃, the content of total aromatics was increased by about 12 %.6. The loading of NiO over HZSM-5 could also significantly improve the aromatization performance. Increasing the reaction temperature, the aromatization performance was improved firstly. At 450℃, the catalyst had highest aromatics composition. the aromatics content decreased when the temperature was increased furtherly. This might be caused by the formation of abundant methane.7. Ni-Co-Mo/H-beta was prepared by co-impregnation method and was studied in the conversion of DME. It was shown that such catalyst had certain aromatization performance, and the aromatics content reached up to 44.8%, which mainly comprised of solid aromatics. The hexamethylbenzene had the highest selectivity among all aromatics. In this paper, the effect of temperature on the space time yield of solid aromatics was also investigated. At 280℃, the solid aromatics had the highest space time yield, which was up to 85 mg/ (g-cat·h).
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