Design of alkali salt supported gasification catalyst and combustion of particulate in the exhaust gas from diesel engine

在673-773 K温度范围内，以活性炭、氧化铝和钙钛矿型氧化物（La_ Sr_ Cr_ Mn_ Pt_ O_3，LSCMP）为载体，研究了碱金属碳酸盐对活性炭颗粒燃烧的催化活性<0.8><0.2><0.5><0.45><0.05>。作为一种典型的过渡金属氧化物催化剂，V_2O_5/γ -Al_2O_3的催化活性也进行了比较。在723 K时，碳载碳酸钾催化剂的初始燃烧速率最大，而3 h内的转化率几乎与碱金属与碳的比例成正比。V_2O_5-γ-Al_2O_3的转化率也随催化剂用量的增加而线性增加，但斜率小得多，表明催化转化数是有限的。相比之下，负载在LSCMP上的碳酸盐在碱金属与碳的比率低至0.012时显示出高转化率，表明非常大的催化转换数，而初始活性与相同盐在碳上的活性相当。而单独负载于γ-Al_2O_3和LSCMP上的碳酸盐催化剂活性很低。在673 K时，LSCMP负载的碳酸盐比碳负载的碳酸盐具有更高的活性.碱金属碳酸盐似乎在较低温度下对LSCMP具有活性。还测量了其他碱金属碳酸盐的活性以检查LSCMP载体的作用。从碱金属盐的还原活化、催化燃烧过程中活性物种在载体上的升华、捕集和逃逸等方面对实验结果进行了讨论。推导了LSCMP的独特作用。

Catalytic activity of alkali metal carbonates was studied for the combustion of activated carbon grains at 673-773 K by supporting the carbonates on carbon, almina, and a perovskite-type oxide (La_<0.8> Sr_<0.2> Cr_<0.5> Mn_<0.45> Pt_<0.05> O_3, LSCMP). Catalytic activity of V_2O_5/γ -Al_2O_3 as a typical transition metal oxide catalyst was also measured for comparison. Potassium carbonate supported on the carbon exhibited the largest initial rate of the combustion among the catalysts at 723 K, while the achieved conversion within 3h increased almost proportional to the ratio of alkali metal to carbon. V_2O_5γ-Al_2O_3 also showed linear increase of achieved conversion with the amount of catalyst, although the slope was much smaller, indicating that the catalytic turnover number is limited. In contrast, the carbonate supported on LSCMP showed high conversion at an alkali metal to carbon ratio as low as 0.012, indicating a very large catalytic turnover number while the initial activity was comparable to that of the same salts on carbon. However, the carbonate supported on γ-Al_2O_3 and LSCMP alone showed very limited activity. The carbonate supported on LSCMP showed higher activity than carbonates supported on carbon at 673 K. The alkali carbonate seems to be active at lower temperatures on LSCMP. The activities of other alkali carbonates were also measured to examine the role of LSCMP support. Results are discussed from the view point of the reductive activation of the alkali metal salts, sublimation, trapping, and escape of the active species on the support in the catalytic combustion. The unique roles of LSCMP are deduced.