【作者】 张加赢；

【导师】 辛忠；

【作者基本信息】 华东理工大学 ， 化学工程， 2014， 博士

【摘要】 中国能源格局的特点是“富煤缺油少气”,煤制天然气不仅可以实现煤炭资源的清洁利用,而且可以满足我国对天然气的快速增长的需求。合成气甲烷化是煤制天然气的关键过程,而甲烷化催化剂是该技术的关键。本文分别采用浸渍法与水热合成法制备了以镍为活性组分的甲烷化催化剂,并在连续流动固定床反应器中对其进行了催化活性,耐高温性能以及积碳性能测试,研究了助催化剂Mo对其结构与性能的影响,筛选出较优的甲烷化催化剂,最后对Ni-0.5%Mo-Si02催化剂的甲烷化动力学进行了研究。采用等体积浸渍法分别以MCM-41, A12O3和SiO2为载体制备了三种镍基甲烷化催化剂,采用XRD、BET、TG及H2-TPR等技术手段对催化剂进行了表征,Ni/MCM-41, Ni/Al2O3和Ni/SiO2的比表面积分别为750、126和252m2/g,孔径分别为2.7、11.6和2.7nm,Ni颗粒大小分别为15.5、24.9和29.6nm。结合催化活性评价结果可知影响催化剂催化活性的主要因素是Ni颗粒的大小,其中Ni/MCM-41催化剂具有更好的催化活性。考察了Ni负载量对Ni/MCM-41催化剂催化活性的影响,结果发现随着Ni负载量的增加,CO转化率和CH4收率逐步提高,且在Ni负载量高于10m01%时趋于稳定。当选择n(H2):n(CO)=3:1、压力1.5MPa、温度350℃及质量空速12000m1·h-1·g-1反应条件时,10%Ni/MCM-41的CO转化率接近100%,CH4选择性约95%。其100h寿命试验中表现出良好的催化活性稳定性,其催化活性无明显下降。以MCM-41为载体采用浸渍法制备了Mo摩尔含量为1%-7%的Ni-Mo/MCM-41催化剂,并研究了Mo对其催化合成气甲烷化反应催化活性的影响。实验发现Mo03的添加可以明显提高Ni/MCM-41催化剂的低温(250℃C)催化活性。在350℃、1.0MPa、12000ml/g/h和n(H2):n(CO)=3反应条件下,Mo含量达到3mol%时(Ni-3%Mo/MCM-41)CO转化率和CH4选择性可以分别达到100%和94%。与Ni/MCM-41催化剂相比,Ni-Mo/MCM-41表现出更好的抗烧结性能,其经过700℃高温煅烧2h后催化活性无明显下降。在100h的稳定性试验中,Ni-3%Mo/MCM-41的催化活性无明显下降,其CO转化率和CH4选择性分别保持在100%和89%。采用BET、CO化学吸附、TEM、SEM-EDS、 ICP、XRD、H2-TPR和XPS对催化剂进行了表征,结果表明由Mo03到金属镍的电子转移是Ni-Mo/MCM-41在低温(250℃)下催化活性提高的主要原因。Mo03的添加以Ni-Mo合金的形式来提高金属镍与载体间的相互作用力,从而抑制催化剂的烧结。采用水热合成法制备了Ni摩尔含量为1%-10%的Ni-MCM-41催化剂,采用FTIR, ICP,XRD,H2-TPR, TG-DTA和TEM等技术对催化剂进行了表征,结果表明当金属镍的摩尔含量达到10%时,其MCM-41的介孔结构仍保持良好。在350℃、1.0MPa、12000ml/g/h和n(H2):n(CO)=3反应条件下,Ni含量为10mol%时(10%Ni-MCM-41),甲烷化反应的CO转化率和CH4收率分别达到100%和96%。与采用浸渍法制备的10%Ni/MCM-41催化剂相比,10%Ni-MCM-41具有更好的抗烧结性能,其经过700℃高温煅烧2h后催化剂活性无明显下降。在100h的稳定性试验中,10%Ni-M表现出良好的催化活性稳定性,其CO转化率和CH4选择性分别保持在100%和82%。XRD,H2-TPR和TG-DTA的结果表明,在Ni-MCM-41催化剂中,镍物种与载体间存在着较强的相互作用力,其可以有效的抑制催化剂的烧结。采用水热合成法制备了Mo03摩尔含量为0.5%-5.0%的Ni-Mo-SiO2催化剂,发现由于在M003与金属镍之间存在着电子转移,M003的添加可以明显提高Ni-SiO2催化剂的催化活性。过量MoO3(>3.0mol%)的添加会导致活性金属镍的部分覆盖以及Ni-Mo合金的形成,从而导致催化剂催化活性的下降。在400℃、2.0MPa、12000ml/g/h和n(H2):n(CO)=3反应条件F,Ni-0.5%Mo-SiO2的CO转化率和CH4收率可以分别达到100%和99%。TG和TPR结果表明,M003可以有效抑制Ni-SiO2催化剂的积碳行为并且过量MoO3(>1.0mol%)会减弱会属镍与载体间的相互作用力。XRD,TPR和TG结果表明催化剂烧结是导致催化剂在稳定性试验和热稳定性实验中催化活性失活的主要原因。以Ni-0.5%Mo-SiO2为催化剂,采用加压微型反应器,在250-450℃温度范围内,分别测定了0.1～1.5MPa下测得甲烷化反应本征动力学实验数据,并经过实验数据检验证明实验结果是基本可靠的。采用双曲线函数型反应动力学模型,经过若干次模型拟合,得到了最佳的拟合模型。并用残差检验、统计检验和Arrhenius关系检验模型,结果表明,模型拟合情况良好,残差分布合理,能真实反映该催化剂的反应特征。其动力学表达式为：更多还原

【Abstract】 Basic energy landscape of China is characterized by " rich in coal, poor in oil and natural gas". Coal to Synthetic Natural Gas can not only realize the clean use of coal resources, but also meet the constant demand for natural gas in China. Syngas methanation is one of the key processes and the development of methanation catalyst is the key of this technique.In this paper, the methanation catalyst with nickel as the active component were prepared by the impregnation method and hydrothermal synthesis method, respectively, and its catalytic activity, high temperature performance and carbon performance were tested in a fixed bed reactor. The effect of Mo on structures and properties of catalysts were also studied and the better methanation catalyst was selected. At last, methanation kinetics based on Ni-0.5%Mo-SiO2catalyst was studied.The nickel based catalysts with different nickel content were prepared by the impregnation method with MCM-41, Al2O3and SiO2as the supports. The catalysts were characterized using XRD, BET, TG and H2-TPR and the results showed that the Ni particle size could obviously affect the catalytic performances of the catalysts and Ni/MCM-41showed better catalytic performance. The effect of Ni content on the catalytic performance of Ni/MCM-41was investigated and it was found that the catalytic activity of Ni/MCM-41increased with Ni loading increasing and kept stable with the Ni loading of above10mol%.10%Ni/MCM-41showed a high CO conversion of100%and a CH4yield of95%at350℃under1.5MPa and12000ml·h-1·g-1with a3:1molar ratio of H2to CO and it also exhibited excellent catalytic activity and stability in the catalytic stability test.Several Ni-Mo based catalysts with Mo content from1mol%to7mol%were prepared by the impregnation method with MCM-41as the support and the effect of Mo content on the catalyst activity was investigated. The addition of MoO3could obviously improve the activity of Ni/MCM-41at250℃. Ni-3%Mo/MCM-41showed the best activity with a CO conversion of100%and a CH4selectivity of94%at350℃under1.0MPa and12000ml/g/h with a3:1molar ratio of H2to CO. Compared with Ni/MCM-41, Ni-Mo/MCM-41showed higher resistance to sintering and no decrease in the catalytic activity after calcination at700℃for2h. In the100h stability test, CO conversion and CH4selectivity obtained on Ni-3%Mo/MCM-41maintained at about100%and89%, respectively, suggesting an excellent catalytic stability of this catalyst. The catalysts were characterized by different technologies, and the results showed that electron transfer from MoO3to metal nickel was the main cause of activity improvement of Ni-Mo/MCM-41at250℃. The addition of MoO3could enhance the interaction between metal nickel and the support in the way of Ni-Mo alloy, which inhibited the catalyst sintering.Several nickel incorporated MCM-41catalysts with a nickel molar content from1%to10%were prepared by a hydrothermal synthesis method, and characterized by FTIR, ICP, XRD, H2-TPR, TG-DTA and TEM. The results showed that mesoporous structure of MCM-41still maintained well when Ni molar content was up to10%.10%Ni-MCM-41showed the best catalytic activity with a high CO conversion of almost100%, and a CH4yield of96%at350℃with3:1molar ratio of H2to CO under1.0Mpa and12000ml/h/g. Compared with10%Ni/MCM-41,10%Ni-MCM-41showed a higher resistance to sintering and no decrease in catalytic activity after calcination at700℃for2h. In the100h stability test, CO conversion and CH4yield obtained on10%Ni-MCM-41maintained at about100%and82%, respectively, suggesting an excellent catalytic stability. The results of XRD, H2-TPR and TG-DTA showed that there was a strong interaction between the Ni species and the support, which inhibited the catalyst sintering.Several Ni incorporated SiO2catalysts with MoO3molar content in range of0.5%to5.0%were prepared by the hydrothermal synthesis method. MoO3can significantly improve the activity of Ni-SiO2due to electron transfer from MoO3to Ni species, while excessive MoO3(>3.0mol%) will reduce the catalyst activity due to partial coverage of active metal by MoO3and formation of Ni-Mo alloy. Ni-0.5%Mo-SiO2achieves the best activity with100%CO conversion and about99%CH4yield at400℃,2.0MPa and12000mL/g/h. The results of TG and TPR show that MoO3can inhibit carbon deposition of Ni-SiO2and excessive MoO3(>1.0mol%) will weaken the interaction between metal Ni and the support. The results of XRD, TPR and TG show that catalyst sintering rather than carbon deposition leads to catalyst deactivation in catalytic stability and thermal stability tests.Based on the Ni-0.5%Mo-SiO2catalyst, the intrinsic kinetics of CO methanation reaction were measured in a differential reactor at250～450℃and0.1～1.5MPa.The measured kinetics experimental data of methanation reaction is proved reliable. Hyperbolic functional was adopted as the reaction kinetics model and the best fitting model was obtained after several model fitting. The results of residual test, statistical testing and Arrhenius relationship test model showed that the kinetics model fits well and the residual distribution is reasonable. It can truly reflect the response characteristics of the catalyst. The dynamic expression is:更多还原