甲烷与二氧化碳催化氧化重整制合成气的研究
刘远凤
学位类型博士
导师侯震山 ; 吾满江.艾力
2013-06-01
学位授予单位中国科学院大学
学位授予地点北京
学位专业有机化学
关键词甲烷 二氧化碳重整 合成气 Ni 催化剂
其他摘要

甲烷催化转化制合成气是目前最有前景的产业化利用途径之一。甲烷同时氧化和二氧化碳重整制合成气反应为天然气的合理利用及缓解温室气体排放提供了有效的途径。该反应不仅可实现能量上的耦合,而且产物中H2/CO 比可根据后续工艺的要求进行调控,同时O2 的加入可以消除催化剂表面的积碳。

本论文以氧化铝和蛭石为载体,通过添加不同的金属助剂改性来制备镍基催化剂,结合XRDBETTPRTGSEMXPS 等表征手段,对镍基催化剂上甲烷同时氧化和二氧化碳重整制合成气反应的催化性能及反应失活机理进行了系统的研究。

主要得到如下结果:

镍负载量为12wt.%Ni/Al2O3 催化剂活性最高。随焙烧温度的增加,金属-载体相互作用增强,Ni/Al2O3 催化剂的活性和稳定性提高。在12Ni/Al2O3 催化剂中添加MgCaCeLa Cu,能有效提高催化活性和稳定性。碱土金属改性的镍基催化剂活性和稳定性优于碱金属改性的催化剂。添加不同金属助剂对金属镍与载体间的相互作用都有不同程度的促进。La 的添加促进了Ni 的分散,阻止了金属Ni 颗粒在反应过程中烧结。在目前合并的反应过程中,积碳能被O2 消除,活性金属组分的烧结

似乎是12Ni-2Na/Al2O3 催化剂失活的主要原因。蛭石可作为催化剂载体替代传统的氧化铝。改性蛭石为载体制备的镍基催化剂初活性与Ni/Al2O3 相当,12Ni/VT1 活性和稳定性最好,反应53h 甲烷和二氧化碳转化率仅下降了5%左右。蛭石负载的镍基催化剂金属-载体相互作用较弱,镍物种容易还原。活性金属烧结或由于形成尖晶石化合物导致活性镍中心减少似乎是催化剂失活的主要原因。不同载体负载的贵金属催化剂活性均随反应温度的增加而增加。923 K 反应,添加贵金属能有效提高12Ni/VT1 催化剂活性,活性依次为:Pd > Ru > Rh。三种贵金属催化剂抗积碳性能依次为:Rh > Ru > PdAl2O3 负载的贵金属催化剂具有自活化能力。贵金属的添加促进了镍物种的还原,尤其是Rh。活性金属组分的烧结似乎是催

化剂失活的主要原因。

;

The conversion of methane to syngas is one of the most promising industrial utilization approaches for natural gas. The reaction of simultaneous oxidative conversion and CO2 reforming of methane to syngas provides effective approaches for reasonable utilization of natural gas and emission of greenhouse gases, which has attracted great attention during the past decades. This process can couple the endothermic CDRM with the exothermic POM for low-energy requirements and adjust H2/CO ratio in the product by controlling the feed composition according to the need of the post processing. In addtion, oxygen in feed is helpful to eliminate carbon deposition on the surface of catalyst. In this paper, the modified Ni-based catalysts have been prepared with alumina and vermiculite as supports and different metals as promoter, and characterized by XRD, BET, TGA, TPR, SEM, XPS and TEM. The catalytic performance and deactivation mechanism of catalysts have been investigated in the simultaneous oxidative conversion and CO2 reforming of methane to syngas. The Ni/Al2O3 catalyst with Ni loading of 12wt% exhibited the highest catalytic activity. The catalytic activity and stability of Ni/Al2O3 catalyst increased with calcined temperature increasing due to the stronger interaction between nickel particles and the support. The addition of Mg, Ca, Ce, La and Cu into Ni/Al2O3 effectively enhanced the catalytic activity and stability of catalysts. The alkaline earth metal-modified Ni catalysts exhibited better catalytic activity and stability than alkali metal-modified ones. The addition of different metals as promoter improved metal-support interaction to some degree. The addition of La into Ni/Al2O3 promoted the dispersion of Ni and prevented the sintering of Ni particles. In the present combined process, deposited carbon was eliminated by O2 under the reaction conditions. Thus, active metal sintering appears to be the main cause for the deactivation of 12Ni-2Na/Al2O3. The vermiculite is desirable alternatives of alumina as catalyst support. The modified-vermiculite supported Ni catalysts showed the same initial catalytic activity with Ni/Al2O3. Among these catalysts, 12Ni/VT1 exhibited the highest catalytic activity and stability, and the conversion of both CH4 and CO2 only decreased 5% during 53 h of reaction. Ni oxides supported on vermiculite was reduced more easily due to the weaker metal-support interaction. The active metal sintering or the loss of active Ni center due to the formation of spinel compound appears to be the main reason for the deactivation of the catalysts. The catalytic activity of different carrier-supported noble metal catalysts increased with reaction temperature increasing. The addition of noble metals into Ni/VT1 effectively enhanced the catalytic activity of catalysts at 923 K, and the order of catalytic activity was Pd > Ru > Rh. The ability of inhibiting cabon deposition is Rh > Ru > Pd. The Al2O3-supported noble metal catalyst has self-activation ability.The addition of noble metals promoted the reduction of nickel species, especially for Rh. The active metal sintering appears to be the main reason for the deactivation of the catalysts.

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/2478
专题新疆维吾尔自治区精细化工工程技术研究中心
作者单位中国科学院新疆理化技术研究所
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刘远凤. 甲烷与二氧化碳催化氧化重整制合成气的研究[D]. 北京. 中国科学院大学,2013.
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