Influence of Ca/Al molar ratio on structure and catalytic reforming performance of Ni/CaO-Al2O3 catalyst
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摘要: 合成兼具催化、吸附性能的复合催化剂是实现CO2吸附强化CH4/H2O重整制氢过程的关键。研究采用共沉淀法制备了一系列具有类水滑石结构前驱体的Ni/CaO-Al2O3复合催化剂，考察了制备过程中Ca/Al物质的量比对复合催化剂结构及性能的影响。结果表明，Ca/Al物质的量比可调控活性组分Ni与载体之间的相互作用力，进而调变复合催化剂的比表面积和活性组分Ni的分散度。当Ca/Al物质的量比为3时，Ni与载体之间相互作用力适宜，复合催化剂具有最大的比表面积（12.9 m2/g）和最高的Ni分散度（1.07%）；该复合催化剂在CO2吸附强化CH4/H2O重整制氢过程中可得到95%的H2浓度和88%的CH4转化率，循环10次后，H2浓度仍能保持在93%以上。Abstract: CO2 enhanced sorption methane steam reforming for hydrogen production is a potential approach to economically provide hydrogen and to reduce CO2 emission. The key point for this process is to develop a composite catalyst with high catalytic and adsorptive capacity. Considering the tunable structure of hydrotalcite-like compounds, co-precipitation method was employed to synthesize Ni/CaO-Al2O3 composite catalysts by varying the molar ratio of Ca to Al. The results show that the specific surface area and Ni dispersion of the as-synthesized composite catalysts are greatly influenced by molar ratio of Ca to Al, which derives from the variable interaction between Ni and the support. When the molar ratio of Ca to Al is 3, the composite catalyst obtains a specific surface area of 12.9 m2/g and Ni dispersion of 1.07%. Catalytic evaluation shows that the composite catalyst possesses a H2 concentration of 95% and a CH4 conversion of 88%, and H2 concentration exceeds 93% even after 10 cyclic runs.
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图 1 不同Ca/Al物质的量比复合催化剂前驱体的XRD谱图
Figure 1 XRD patterns of the precursors for the composite catalysts with different molar ratio of Ca to Al
图 2 不同Ca/Al物质的量比复合催化剂的XRD谱图
Figure 2 XRD patterns of the composite catalysts with different molar ratio of Ca to Al
图 3 不同Ca/Al物质的量比复合催化剂的H2-TPR谱图
Figure 3 H2-TPR profiles of the composite catalysts with different molar ratio of Ca to Al
图 4 不同Ca/Al物质的量比复合催化剂的循环吸附性能
Figure 4 CO2 cyclic sorption performance of the composite catalysts with different molar ratio of Ca to Al
图 5 复合催化剂3-cat首次CO2吸附强化CH4/H2O重整反应性能
—■— H2; —●— CH2; —▲— CO2; —▼— CO; —◆— CH4
Figure 5 Catalytic performance of 3-cat for the CO2 sorption enhanced methane steam reforming in the first cycle
图 6 复合催化剂3-cat的10次CO2吸附强化CH4/H2O重整反应的H2浓度
Figure 6 H2 concentration variation during 10 loops of the CO2 sorption enhanced methane steam reforming
表 1 不同Ca/Al物质的量比复合催化剂金属分散度与颗粒粒径
Table 1 Metal surface area, metal dispersion and particle size of the composite catalysts with different molar ratio of Ca to Al
表 2 不同Ca/Al物质的量比复合催化剂比表面积和孔结构
Table 2 BET specific surface area and pore structure of the composite catalysts with different molar ratio of Ca to Al
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