【作者】 易丽丽；

【导师】 李小年；

【作者基本信息】 浙江工业大学 ， 工业催化， 2004， 硕士

【摘要】 二氧化碳的大量排放给全球带来了严重的生态及环境等问题（温室效应），已经引起了人们的密切关注。同时，二氧化碳也被认为是地球上储量最为丰富的碳源之一。二氧化碳甲烷化作为有效利用碳源解决温室效应的方法之一具有长远的战略意义。不仅如此，甲烷化反应在实际工业应用中也占据重要地位。如，在制备氨合成气和纯氢过程中，通常需要采用CO₂和CO甲烷化反应脱除气体中的少量CO₂和CO实现气体的完全净化，同时使后续的反应中的催化剂不被毒化。在活性炭载钌催化剂氨合成催化过程中，载体活性炭在氨合成气氛条件下的甲烷化行为是影响活性炭载钌催化剂工业化的主要障碍，但是关于活性炭载钌催化剂在氨合成气氛中的甲烷化行为没有系统研究的报道；同时活性炭载钌催化剂被认为具有抗CO、CO₂、和H₂O毒化的性能，但是，在氨合成条件下，CO₂气体是否会造成活性炭载体发生气化反应等至今未见有任何报道。因此，本文选择负载型Ru催化剂为研究对象，系统比较了不同载体负载Ru催化剂的甲烷化性能，同时分别考察了活性炭载Ru催化剂在CO₂和H₂、CO₂、H₂等不同气氛条件下的甲烷化行为、活性炭载体的气化行为等。 1．活性组分 研究了γ-Al₂O₃为载体不同活性组分的影响，结果表明催化剂活性顺序为：Ru/γ-Al₂O₃＞Co/γ-Al₂O₃＞Ni/γ-Al₂O₃＞Pd/γ-Al₂O₃，负载型钌催化剂具有最低的活化能和最高的活性。 2．载体 研究了不同载体对负载型钌催化剂的影响。结果表明，不同载体负载钌催化剂的活性顺序为：Ru/TiO₂＞Ru/ZrO₂＞Ru/MgO＞Ru/Al₂O₃＞Ru/C＞Ru/SiO₂。载体的比表面积并不是影响催化剂活性的重要因素，随着氧化物载体比表面积的减小，二氧化碳转化率增大。 3．Ru/γ-Al₂O₃催化剂研究了Ru负载量以及制备方法（等体积浸渍法和醇还原法）的影响。结果表明，随着Ru负载量增加，二氧化碳转化率和甲烷的选择性均随之升高，Ru负载量5wt％时二氧化碳的转化率接为98.97％。在Ru负载量为1wt％时，使用醇还原法制备的催化剂金属颗粒明显小于传统的等体积浸渍法制备的催化剂，催化活性也有所提高。 4．Ru／C催化剂通过原位TG表征研究了不同气氛（CO₂+Ar、H₂+Ar、CO₂+浙江工业大学硕士学位论文H:）、温度和CO:含量等条件下催化剂的失重。结果表明，在二氧化碳甲烷化反应过程中除发生二氧化碳加氢甲烷化反应外，还发生了C十CO:的气化反应和C+H:的甲烷化反应。氢气的存在抑制了活性炭载体‘J一几氧化碳之间的气化反应。催化剂的失重速率随着温度的升高先增加后减小。 研究了Ru负载量、助剂、及制备条件（浸渍时问和还原温度）等对催化剂的影响。结果表明，随着Ru负载量增加，一二氧化碳的转化率增加，甲烷选择J性坦逐渐升高:当负载量超过5w’t%时，甲烷选择性超过了100%;催化剂的失重速率也先增大后减小。不论是添加Ni、Pd和C。等Vlll族金属还是添加Ca、Mg和K等非VHI族金属组分，催化剂的活性均有不同程度的下降。添加了促进剂钾后的催化剂载体活性炭的流失减少。催化剂制备过程中合适的浸渍时间为24小时，合适的还原温度为200℃左右。 研究了空速、原料气的配比和反应温度对R川C催化剂上二氧化碳甲烷化反应的影响。结果表明，空速等于7200h一‘时，催化剂的活性出现峰值，二氧化碳转化率和甲烷的选择性都最大;二氧化碳的转化率随着CO;和H:的比值的下降而急剧升高，甲烷选择性在coZ:H:的值为1:4时最高;随着反应温度的升高，COZ的转化率先升高后下降。 最后，给出了全文工作的总结以及对今后研究工作的展望。更多还原

【Abstract】 Much more attentions have been attracted to the global environmental problem i.e. the greenhouse effect, which resulted from the huge CO2 emissions. In addition, CO2 has been regarded as one of most abundant carbon source on the earth. As far as using the carbon source and solving the environmental problem concerned, the study on methanation of CO2 has been considered as a strategic task. Furthermore, the methanation of CO2 has been used in various industrial processes. For example, during ammonia synthesis and other hydro-procedures, the feed gases should be purified by the procedure of CO and CO2 methanation. For the ammonia synthesis catalyzed by Ru/C, the methanation of carbon support in the reaction environment has been regarded as the major defect. However, the fundamental studies on the methanation of carbon support with hydrogen have not been conducted. Moreover, Ru/C has been believed to be able to resist the poison of a trace CO2, CO and H2O in synthetic gas for ammonia synthesis, while it has been not revealed that whether the gasification of support carbon and CO2 would take place during the synthesis process. Therefore, in this dissertation it has been highlighted that the tests of the methanation behaviors of Ru catalysts supported on oxides or carbon in the mixture gas of CO2 and H2, and the gasification and methanation behaviors of carbon support of Ru/C under temperature of hydrogenation of CO2 in the three atmospheres i.e. the mixture gas of CO2andH2,CO2orH2.The methanation performances of a series of 7-Al2O3 supported transition metal catalysts have been explored by the employment of activity test. The order of catalytic activity (CO2 conversion) is shown as follows: Ru/ -Al2O3>Co/ -Al2O3> Ni/ -Al2O3 >Cu/ -Al2O3 >Pd/ -Al2O3. Among the catalysts, Ru/ -Al2O3 catalyst has the highest activity for the hydrogenation of CO2 with the least activation energy.The effect of supports on the hydrogenation of CO2 of Ru catalysts has been investigated. The order of activity is shown as follows: Ru/TiO2 > Ru/ZrO2 > Ru/MgO>Ru/Al2O3>Ru/ORu/SiO2, which can not be ascribed to the change of specific surface area of supports. This result is generally attributed to the electrondonation of transition metal oxides.The influences of Ru loading and preparation method of Ru/y-AhOj on the activity of catalysts have been investigated. The catalytic activity will be increased with the increase of the Ru loading. Compared with the catalyst prepared by impregnation method, the catalyst prepared by alcohol reduction method performs higher activity due to the finer Ru particle and narrow distribution of particle size.The behaviors of Ru/C in the three atmospheres i.e. the mixture gas of CO2 and H2, CO2 or H2 have been studied. The experimental results showed that there are three reactions: methanation of CO2 and H2, the methantion of carbon and hydrogen, and the gasification of carbon and CO2 in the reaction system, which occur simultaneously. The gasification of carbon with CO2 is more significant than the methanation of carbon with hydrogen at 400 . Furthermore, the present of H2 in the reaction system could restrain the gasification reaction of carbon support with CO2. The carbon loss rate will increase with the increase of reaction temperature.The influences of Ru loading, promoters and preparation condition on activity of Ru/C catalyst have been investigated, the conversion of CO2 and the selectivity to CH4 increase with the increase of Ru loading. As Ru loading of Ru/C is greater than 5 wt%, the selectivity to CH4 will be over 100 %. The addition of promoters of VIII metal and non-VIII metal into the single Ru metal catalyst will result in the decrease of catalytic activity. The carbon loss of catalyst can be resisted by the addition of K promoter. For the preparation of Ru/C catalyst for hydrogenation of CO2, the suitable impregnation time and reduction temperature should be 24 h and 200 掳C respectively.The optimal reaction conditions are space velocity 7200h-1, 1:4 of ratio of CO2 and H2, and更多还原