【作者】 刘明刚；

【导师】 梁斌； 曹永生；

【作者基本信息】 四川大学 ， 化学工程， 2003， 硕士

【摘要】 低温液相合成甲醇可以有效的提高甲醇合成的单程转化率和甲醇的选择性，催化剂的性能对低温液相甲醇合成反应具有决定性的作用。本论文通过对催化剂体系、合成机理、反应过程和工艺、动力学模型以及失活机理等问题进行细致的分析，采用了络合沉淀法制备低温液相合成甲醇的铜铬催化剂，根据对不同催化剂的催化活性评价结果对催化剂制备的优化条件及反应工艺条件进行了详细的研究，并提出了中间试验的概念流程和设计参数。 活性评价结果表明，络合沉淀法得到的催化剂具有更高的比表面积(92m~2／g)，沉淀物的晶粒尺寸小而均匀，得到的微晶在40-50nm范围内。因此，络合法得到的催化剂具有比普通沉淀法更高的反应活性，在110℃的低温条件下便具有很好的反应活性。Cu-Cr催化剂制备中，各种制备条件对催化剂的催化性能有很大的影响。Cu／Cr比对催化剂活性和选择性的影响较大，Cu／Cr比为0.9-1.0时，催化剂的活性和选择性达到最高；沉淀母液的PH值对反应的活性影响较大，对选择性的影响较弱，而实验条件范围内没有发现沉淀物的老化时间和老化温度对催化性能存在明显的影响。沉淀物加热分解温度和气氛都对反应结果有很大的影响，在氮气气氛下分解得到的催化剂催化反应性能比在空气气氛下分解获得的催化剂要好；试验结果表明，催化剂的加热分解温度在340-350℃为宜。 实验表明溶剂介电常数对低温甲醇合成反应速率有明显的影响，选择非极性介电常数小和强极性非质子型溶剂，如二甲苯、丙酮、四氢呋喃等对合成甲醇有利。实验确定了适宜的低温液相合成甲醇的工艺条件为：温度110-120℃，压力4.5-5.0MPa，甲醇初始浓度2.5-3％(wt)，甲醇钠用量4％(wt)； 通过对催化剂体系失活原因的初步探索，认为催化剂体系的失活主要由羰化催化剂甲醇钠失活造成，但反应的速率控制步骤是氢解反应，提高氢解反应速率可以加快总反应速率，也可以减缓甲醇钠催化剂的失活。更多还原

【Abstract】 Liquid phase synthesis of methanol (LPSM) at lower temperature can effectively raise the conversion degree and selectivity of the methanol synthesis. The reaction performance of this reaction is greatly relied on the catalyst used. In this work, the catalytic effects, reaction mechanism, reaction process and parameters, kinetics and deactivation of the catalysts were systematically discussed. A Cu/Cr catalyst for LPSM was prepared with a complex precipitation technique. Based on the activity measurement, the optimal parameters for the catalyst preparation and reaction operation were well investigated. A principle process for LPSM was proposed.The catalyst prepared by the complex precipitation method has a higher surface area (92 m2/g). The precipitate possesses a uniform and smaller crystal size, about 40-50 nm. The activity measurement showed that this catalyst had a higher activity than the catalyst obtained from a traditional precipitation method. The preparation condition of the catalyst showed great influence on the performance of the catalyst. The atomic ratio of Cu/Cr in catalyst significantly affects the activity and selectivity. The Optimal ratio was found in the range of 0.9-1.0. The PH value of the precipitation solution influenced on the activity, but it did not influence on the selectivity. In our experimental condition, the effects of aging time and aging temperature on both activity and selectivity were negligible. The results also showed that calcining the catalyst in a nitrogen atmosphere brought about a better performance than in an air atmosphere. The preferred temperature for calcinations is 340-350.Solvent effects on the reaction were examined. The results show that the dielectric constant of the solvent has a significant influence on the reaction rate. Nonpolar solvents with lower dielectric constant or non-protonic polar solvents, suchas xylene, acetone and tetrhydric furan, can enhance the synthesis reaction. The optimal operation parameters for the LPSM are suggested to be 110-120 , 4.5-5.0 MPa, 2.5-3.0%(wt) of initial methanol concentration and 4%(wt) of sodium methoxide concentration.The deactivation of the catalytic system was tested. The deactivation of this catalytic system is due to the deactivation of sodium methoxide catalyst. The hydrogenolysis process is the rate-limiting step of the synthesis. The deactivation of sodium methoxide can be lowered and the reaction rate increased by improving the hydrogenolysis process.更多还原