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

通过碳、氧化铝和钙钛矿型氧化物（La_<0.8> Sr_<0.2> Cr_<0.5> Mn_<0.45> Pt_<0.05> O_3， LSCMP）负载碱金属碳酸盐，研究了碱金属碳酸盐在673-773 K下对活性炭颗粒燃烧的催化活性。比较了V_2O_5/γ -Al_2O_3作为典型过渡金属氧化物催化剂的催化活性。在723 K时，碳负载的碳酸钾表现出最大的初始燃烧速率，而在3h内实现的转化率几乎与碱金属与碳的比例成正比。V_2O_5γ-Al_2O_3的转化率也随催化剂用量的增加呈线性增加，但斜率要小得多，说明催化转化率有限。相比之下，LSCMP上负载的碳酸盐在碱金属与碳的比低至0.012时表现出很高的转化率，表明其催化周转数非常大，而初始活性与相同的盐在碳上的活性相当。而单独以γ-Al_2O_3和LSCMP为载体的碳酸盐的活性非常有限。在673 K时，LSCMP上负载的碳酸盐比碳上负载的碳酸盐具有更高的活性。在LSCMP上，碱碳酸似乎在较低的温度下具有活性。还测定了其他碱碳酸盐的活性，以检验LSCMP支持的作用。从催化燃烧中碱金属盐的还原活化、载体上活性物质的升华、捕获和逸出等方面对结果进行了讨论。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.