基于程序升温氢化表征的Ni-Al2O3催化剂上CO2-CH4重整反应积炭研究

采用水热沉积法制备Ni-Al₂O₃催化剂，用于CO₂-CH₄重整反应；基于程序升温氢化（TPH）表征，研究了反应时间、温度、原料气CO₂/CH₄比例和空速等因素对CO₂-CH₄重整反应过程中Ni-Al₂O₃催化剂上表面积炭行为的影响。结果表明，表面积炭是导致催化剂重整反应失活的重要原因。随反应时间的延长，催化剂表面积炭量增多，虽未成比例增加，但其TPH峰温有向高温方向移动的趋势，表明所积之炭的石墨化程度增加。反应温度和空速对催化剂表面积炭也有一定影响，且空速的影响更大。另外，由于CO₂消炭反应（CO₂+C=2CO）的存在，CO₂/CH₄比例对表面积炭的影响也很大。CO₂/CH₄比例太低，不能明显抑制积炭；随着CO₂/CH₄比例增加，积炭将得到有效抑制，但CO₂/CH₄比例过高，CO₂在产物中的分离和回收再利用将使成本增加。

A study on the carbonaceous deposition on Ni-Al2O3 catalyst in CO2-CH4 reforming on the basis of temperature-programmed hydrogenation characterization

Ni-Al₂O₃ catalyst was prepared by hydrothermal deposition method and used in the reaction of CO₂-CH₄ reforming. The effect of reaction time, temperature, CO₂/CH₄ ratio and feed space velocity on the carbonaceous deposition on the Ni-Al₂O₃ catalyst surface in CO₂-CH₄ reforming was investigated, on the basis of temperature-programmed hydrogenation (TPH) characterization. The results indicate that the carbonaceous deposition is an important factor for the deactivation of Ni-Al₂O₃ catalyst in CO₂-CH₄ reforming. The amount of deposited carbon increases with the prolongation of reaction time; meanwhile, the hydrogenation peak in the TPH profiles shifts towards higher temperature, indicating that the graphitization degree of the deposited carbon also increases with prolonging the reaction time. The reaction temperature and feed space velocity, especially the later one, also have an influence on the carbon deposition. In addition, due to the carbon elimination reaction by CO₂ (CO₂+C=2CO), the ratio of CO₂/CH₄ in the feed shows a great influence on the type and amount of carbon deposited on the Ni-Al₂O₃ catalyst. A low CO₂/CH₄ ratio may not achieve a significant inhibition on the coke formation; with the increase of CO₂/CH₄ ratio, the carbon deposition can then be increasingly inhibited; however, a higher CO₂/CH₄ ratio also means higher cost for CO₂ separation and recovery in the product.