Li Junhui, Davis Robert J
Department of Chemical Engineering, University of Virginia, 102 Engineers Way, Charlottesville, Virginia 22904-4741, USA.
J Phys Chem B. 2005 Apr 21;109(15):7141-8. doi: 10.1021/jp045092j.
Cesium-exchanged zeolite X was impregnated with cesium acetate (Cs(Ac)/CsX) or cesium carbonate (Cs(2)CO(3)/CsX) and subsequently calcined to yield a basic catalyst. The Raman spectra of calcined Cs(Ac)/CsX and Cs(2)CO(3)/CsX exhibited a new peak at 1036 cm(-1) associated with the occluded species. No evidence for cesium peroxide or superoxide was observed. The occluded cesium species in both samples is proposed to be an oxycarbonate, which is a metastable intermediate between cesium carbonate and cesium oxide. The isomerization of 1-butene to cis- and trans-2-butene was catalyzed by cesium-loaded zeolite X. Although CO(2) readily poisoned the active base sites for catalysis, pretreatment of a basic zeolite with O(2) at 373 K did not. Co-feeding O(2) with 1-butene at 373 K, however, completely deactivated the base sites. Analysis of the reactor effluent at 473 K and the IR spectrum of the catalyst indicated the formation of carbon dioxide, which irreversibly adsorbed on the basic sites of the catalyst. Deactivation of basic catalysts by O(2) is proposed to occur through a low temperature oxidation of 1-butene to carbon dioxide, which strongly adsorbs on the active sites.
将醋酸铯（Cs(Ac)/CsX）或碳酸铯（Cs₂CO₃/CsX）浸渍到铯交换的X型沸石上，随后进行煅烧以得到碱性催化剂。煅烧后的Cs(Ac)/CsX和Cs₂CO₃/CsX的拉曼光谱在1036 cm⁻¹处出现了一个与包藏物种相关的新峰。未观察到过氧化铯或超氧化铯的迹象。两个样品中的包藏铯物种被认为是一种氧碳酸盐，它是碳酸铯和氧化铯之间的亚稳中间体。负载铯的X型沸石催化1-丁烯异构化为顺-2-丁烯和反-2-丁烯。尽管CO₂很容易使催化活性碱位中毒，但在373 K下用O₂对碱性沸石进行预处理则不会。然而，在373 K下将O₂与1-丁烯共进料会使碱位完全失活。对473 K下反应器流出物的分析以及催化剂的红外光谱表明形成了二氧化碳，它不可逆地吸附在催化剂的碱性位点上。碱性催化剂被O₂失活被认为是通过1-丁烯低温氧化为二氧化碳而发生的，二氧化碳强烈吸附在活性位点上。
