Adsorption-Desorption and Hydrogenation of CO on Supported Fe_2(CO)_ 9 Complexes and Dispersed Fe Catalysts

担载于Al_2O_3和zrO_2上的fE_2（CO）_9络合物的羰基在真空中极易脱附，在Ar或H_2中250℃左右也可完全脱羰而成分散型催化剂.以zrO_2为载体者在Ar中低温下易发生表面歧化反应而生成CO_2，高温下生成少量CH_4.吸附于分散型催化剂上的CO在Ar或H_2中均易发生岐化反应，以zrO_2为载体者在H_2中发生加氢反应而生成CH_4，在CO加氢中其反应物除了大量CO_2外还有少量CH物.原位fT-Ir谱表明以zrO_2为载体者在HE中或CO和H_2中均出现相当于多种中间物种的C-H振频带.根据实验结果提出了以zrO_2为载体的fE_2（CO）_9络合物在脱羰基过程中和在CO加氢反应过程中生成CH物种的机理.The decarbonylation of Fe_2(CO)_ 9 complex supported on Al_2O_3 or ZrO_2,and the adsorptiondesorption and the surFace reaction of CO on the dispersed Fe catalysts derived From the supported complexes have been studied by IR and programmed temperature tech niques.It is Found that the carbonyls of surFace complexes are easily desorbed in vacuum at room temperature.During the TPDE run of supported complexes in Ar or H2 stream, the carbonyls are Fully desorbed at about 250℃.The TPDE products of Fe_2 (CO)_9/ZrO_2 complex in Ar stream are composed mainly of CO2,with less amounts of CO and CH4.The TPDE products of Fe_2(CO)_9/Al_2O_3 complex are composed mainly of CO,with less amount of CO_2.TPD-GC and TPSR-GC profiles show that CO on the supported iron catalysts derived From the Fe_2(CO)_9 complex are very easily decomposed by the disproportionation reaction.It is noticed that CO on the ZrO_2-supported iron catalyst can be hydrogenated to Form hydrocarbons at temperatures above 300℃."In situ"FT-IR spectra show that some bands of C-H stretching Frequencies corresponding to various species appeared du ring the TPDE and CO hydrogenation run of ZrO_2-supported Fe_2(CO)_9 catalyst.The mechanism of CO hydrogenation For the ZrO_2-supported catalyst is proposed.This proposal involves adsorption and dissociation of CO on the catalyst prior to reaction with H_2 to Form CHx and CHO intermediates.In addition,the abilities of adsorption and catalytic reaction For CO on the ZrO_2-supported iron catalyst is higher than that of the A1_2O_3-supported iron catalyst.国家自然科学基

DECARBONYLATION AND SURFACE HYDROGENATION of SUPPORTED Ru_3 (CO)_(12)-Fe_2(CO)_9 MIXED CLUSTER

担载于zrO2上的ru3（CO）12-fE（CO）9混合簇的红外光谱表明，ru3（CO）12以ru（CO）2O2表面络合物存在.混合族在真空中随温度升高而发生脱羰基作用，500℃左右羰基完全脱掉；以Al2O3为载体者其羰基不易脱除，升高温度出现多种羰基带.混合簇中的fE2-（CO）9极易脱羰基.担载混合簇在Ar气中进行TPdE时，低温时以脱羰基为主，高于150℃时发生表面歧化反应而生成CO2；在H2气中，低温时仍以脱羰基为主，高于150℃时发生表面加氢反应而生成CH4.混合簇的脱羰基和表面反应能力与ru/fE比及载体有关.担载混合簇在CO加氢反应中以ru（CO）2O2和分散fE存在，还出现-CHX多种表面物种.The decarbonylation and the surFace reaction of mixed cluster Ru3(CO)12-Fe2 (CO)9 supported on ZrO2 or Al2O3 have been studied by IR spectroscopy and TPDE-GC technique.IR spectra show that the Fe2(CO)9 in the mixed cluster easily desorbs its carbonyls and disperses on the carrier in Fe Form.on ZrO2, the carbonyl bands of Ru3 (CO)12 disappear and the characteristic bands corresponding to Ru (CO)2O2 appear, and the carbonyl bands Fully vanish at about 500℃ in vacuum.On Al2O3, the carbonyl bands are hardly removed.TPDE-GC rasults show that the weaker carbonyls in the mixed cluster are desorbed at lower temperature, and the stronger ones are disproportionated to CO2 in Ar and hydrogenated to CH4 in H2 at higher temperature.It is also Found that the TPDE character of the supported mixed cluster is similar to that of supported Ru3 (CO)12 cluster.During CO hydrogenation at 250℃, three C- H stretching bands corresponding to various-CHxspecies and the characteristic carbonyl bands of Ru (CO)2O2 surFace complex are observed by in silu FT-IR spectroscopy.国家自然科学基金;厦门大学固体表面物理化学国家重点实验室资