A major problem in biomass or coal gasification is removal of syngas byproducts such as H₂S, NH₃, and tars (heavy hydrocarbons) that cause catalyst deactivation and clogging problems downstream. Rare earth oxides (REOs) doped with transition metals (TMs) are promising catalysts for tar reforming. With propane as a model compound, we compared such catalysts to a typical supported Ni catalyst, and also to recent density functional theory (DFT) results modeling these systems. The REO/TM catalysts are active over the range 920–1000 K, with no significant deactivation in non-sulfur containing feeds. In particular, a Mn/CeO₂ catalyst showed good reforming activity with low carbon, CO₂, and CH₄ yields. This catalyst also maintained some activity in the presence of 40 ppm H₂S. Kinetics calculations showed that most such catalysts have near zero order kinetics with respect to water, making them usable with a variety of gasifier effluents. Characterization of used catalysts by multiple techniques suggests that the metal-doped REOs do not undergo much (if any) phase separation in extended use under tar reforming conditions, with Mn- and La-doped CeO₂ being especially stable.

中文翻译：

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用于合成气焦油重整的稀土/过渡金属氧化物：复合模型研究

生物质或煤气化中的主要问题是去除合成气副产物，例如H ₂ S，NH ₃和焦油（重烃），这些副产物导致催化剂失活和下游的堵塞问题。掺有过渡金属（TM）的稀土氧化物（REO）是焦油重整的有前途的催化剂。以丙烷为模型化合物，我们将此类催化剂与典型的负载型Ni催化剂进行了比较，并与对这些系统进行建模的最新密度泛函理论（DFT）结果进行了比较。REO / TM催化剂在920–1000 K范围内具有活性，并且在不含硫的进料中没有明显的失活。特别地，Mn / CeO ₂催化剂在低碳，CO ₂和CH _4的情况下表现出良好的重整活性。产量。该催化剂在40 ppm H ₂ S的存在下也保持了一定的活性。动力学计算表明，大多数此类催化剂相对于水具有接近零级的动力学，使其可用于各种气化器流出物。通过多种技术对用过的催化剂进行表征表明，在焦油重整条件下，长期使用时，金属掺杂的REO不会发生很多（如果有的话）相分离，其中Mn和La掺杂的CeO ₂尤其稳定。