【作者】 褚睿智；

【导师】 魏贤勇；

【作者基本信息】 中国矿业大学 ， 化学工艺， 2010， 博士

【摘要】 二甲醚（DME）用途广泛,具有广阔的市场前景。合成气一步法制取二甲醚（Syngas to Dimethyl ether,简称STD）可以打破合成甲醇的热力学平衡限制,大大提高原料的转化率,尤其适用于大规模煤基合成气转化的工业生产。目前,IGCC制取工艺下的煤基合成气通过酸性气体粗脱硫后,仍残留至少40 ppm的硫,而当前工业上用于甲醇合成的Cu/ZnO/Al₂O₃催化剂往往会因合成气中含有超过0.1 ppm H₂S而发生中毒,因此开发耐硫型催化剂,缩短合成气精制工艺流程对发展DME生产工业意义重大。同时,利用微波技术实现微波作用下催化剂的可控制备,简化催化剂制备工艺,对微波在催化剂制备工艺中的应用也具有非常高的理论价值。本论文针对STD工艺的研究现状,采用微波技术开发了具有较好耐硫效果的Pd系二甲醚合成催化剂,具体从以下三方面进行了研究开发。首先,进行了Pd系STD反应催化剂制备研究。分别以γ-Al₂O₃、HZSM-5和Al-MCM-41为载体,采用浸渍法制备了三个系列负载型Pd金属催化剂,通过调控焙烧条件、Pd负载量、助剂类型和复合方式及助剂添加量等实现了对催化剂表面的物相及吸附特性、还原特性、表面酸性等性能的控制,探讨了催化剂STD反应活性与样品本身所固有特性的关系。确定不同载体条件下的Pd催化剂的优化制备条件、助剂成分不尽相同,γ-Al₂O₃、HZSM-5和Al-MCM-41系列催化剂的微波处理功率分别为420 W、560 W和560 W。Pd/γ-Al₂O₃体系的优化助剂类型和添加量为2% CeO₂^-1% ZrO₂-2% Pd,Pd/HZSM-5体系为硅铝比50,2% CeO₂^-1% CaO-2% Pd,Pd/Al-MCM-41体系为0.4 mol SO+₄^2-1% ZrO₂-2% Pd。相比之下,2% CeO₂^-1% CaO-2% Pd/HZSM-5催化性能更稳定,最高能达到34.75 mmol·g^-1·h^-1的DME时空收率。其次,进行了Pd系催化剂耐硫机理研究。以H₂S和噻吩为探针毒物研究硫中毒实验和再生实验后Pd催化剂用于STD反应性能,考察了催化剂载体和助剂类型对Pd催化剂耐硫性能的影响,运用多种表征手段对催化剂的物性结构和反应物化学结构进行表征,分别揭示了Pd金属表面和酸中心上的硫化物吸附形态和吸附特点,分析发现载体表面B酸中心越强,越有利于弱化金属钯与硫化物的反应能力,降低结合硫的生成,提高Pd金属中心的抗硫能力,CeO₂或CeO₂-CaO助剂添加可以降低CeO₂-CaO-Pd/HZSM-5表面的Pd金属的硫化度,提高再生样品的酸活性位的保留率进而有效提高CeO₂-CaO-Pd/HZSM-5催化剂的抗硫性能。最后利用GC-MS分析确定了有机硫和无机硫毒物在CeO₂-CaO-Pd/HZSM-5催化剂表面的吸附位置,并推测出其表面的硫化物转化机理。最后,对CeO₂-CaO-Pd/HZSM-5催化剂的STD反应动力学进行了研究。选取STD反应活性和耐硫性能优异的CeO₂-CaO-Pd/HZSM-5催化剂进行了STD反应工艺条件研究,确定优化工艺条件范围为:反应温度240³00 oC,反应压力3⁴ MPa,空速2000³000 L·kg^-1·h^-1,n（H₂）/n（CO）为2³;在此范围内,建立了CeO₂-CaO-Pd/HZSM-5双功能催化剂颗粒的动力学方程,统计检验显示该模型可靠,模型计算值与实验值吻合良好。该论文有图73幅,表42个,参考文献167篇。更多还原

【Abstract】 Dimethyl ether （DMA） is an important chemical, used in many areas, therefore, production of DME have attracted ever-increasing attentions. Direct syngas to DME （STD） is especially suitable for industrial production of large-scale coal-hased syngas conversion, which can break the limit of thermodynamic equilibrium in themethanol synthesis, greatly improve the conversion rate of raw materials, reactivity under very mild reaction condition. Today the integrated gasification combined cycle （IGCC） is a new process schemes for the synthesis of DME from coal. However, IGCC syngas still contains at least 40 ppm sulfur if desulfurized by acid gas removal technologies, while commonly used Cu/ZnO/Al₂O₃ catalysts for CH3OH synthesis do not tolerate more than 0.1 ppm H2S, thus developed sulfur-resistance catalyst to shorten the production process are significant to develop DME poductions industry. At the same time, utilizing modern microwave technology to shorten the catalyst preparation process, and realize the controllable preparation of catalyst, which has a very high theory value for the application of microwave to catalysts preparation technology. According to the development of the STD technology, in this work, the hybrid catalyst preparation of Palladiuman （Pd） metal-support for DME synthesis by microwave technology has been studied and developed, which has a good effect of sulfur tolerance. All research is divided into following three sections.Firstly, Pd metal-support catalyst for STD reaction has been researched. Three series of Palladiuman catalysts supported on different carriers,γ-Al₂O₃, HZSM-5 and Al-MCM-41 respectively, were prepared by impregnation. The properties of catalysts, such as surface phase structure and adsorption, reduction properties, surface acidity have been controlled by changing calcination condition, Pd loading, or single and binary promoters and its added amount. The relationship between STD reactivity and the intrinsic characteristics of the catalyst had been investigated. The results show that there are different optimum preparation conditions and promoters for the Pd catalysts with different carriers. The suitable microwave power of Pd/γ-Al₂O₃, Pd/HZSM-5 and Pd/Al-MCM-41 catalysts is 420 W, 560 W and 560 W respectively. And the best preparation conditions for Pd/γ-Al₂O₃ series catalysts is 2%CeO₂ -1%ZrO₂-2%Pd, Pd/HZSM-5 series catalysts is silicon-aluminum ratio 50 and 2%CeO₂-1%CaO-2%Pd and Pd/Al-MCM-41 series catalysts is 0.4molSO42-1%ZrO₂-2%Pd. By coMParison, 2%CeO₂^-1%CaO-2%Pd/HZSM-5 has higher stability and better catalysis ability, over which the DME space-time yield could reach 34.75 mmol·g^-1·h^-1.Secondly, the sulfur-tolerant mechanism of Pd catalysts has been researched. The STD activity of catalysts after the process of sulfur poisoning with H2S or thiophene and regeneration with syngas has been investigated, the influence of carriers type and promoters type on the catalysts’sulfur tolerance has been analysis, the catalysts’structure and the reactants’chemical structures were characterized based on various characterizations, and then the adsorption patterns and characteristics of sulfide on Pd metal active sides and acid active sides were revealed. It was found that the stronger of Bronsted acid on the carrier, the weaker reaction ability between palladium and sulfide, and the less formation of combinable sulfur, ultimately, the sulfur-tolerant performance of Pd metal was improved. Adding CeO₂ or CeO₂-CaO promoters can reduce Pd metal sulfide of CeO₂-CaO-Pd/HZSM-5 catalyst, improve the acid sides retention rate of regeneration catalyst and thus effectively improve sulfur-tolerant performance of CeO₂-CaO-Pd/HZSM-5 catalyst.Finally, adsorption position of organic sulfur poisons and inorganic sulfur poisons on in CeO₂-CaO-Pd/HZSM-5 catalyst was determined based on GC-MS, and the possible transformation mechanism of sulfides on catalyst were suggested.Finally, the kinetics of STD reaction over CeO₂-CaO- Pd/HZSM-5 catalyst has been researched. Because owing to good STD reactivity and sulfur tolerant, STD process conditions over CeO₂-CaO- Pd/HZSM-5 catalyst was further studied. The results show that the best process conditions are: reaction temperature 240³00 oC, reaction pressure 3⁴ MPa, weight hourly space velocit 2000³000 L·kg^-1·h^-1 and n（H₂）/n（CO）=2:1. The kinetic equations for STD reaction over CeO₂-CaO- Pd/HZSM-5 catalyst in a fixed-bed reactor within the process conditions above were established. Statistical test shows the data calculated by the mechanism models are consistent with the experiments, so these models are reliable. 73 figs., 42 tabs. , 167 refs.更多还原