The Effect of Carbon Dioxide on Hydroformylation of 1-Hexene by an Immobilized Rhodium Catalyst
In situ high-pressure Diffuse Reflectance Infrared Fourier Transform Spectroscopy was performed to investigate the hydroformylation of 1-hexene in supercritical carbon dioxide. A rhodium complex was immobilized on phosphinated silica and used as a catalyst. The changes in the infrared spectrum over time showed the reaction profile, which was used to evaluate the effect of pressure on the reaction mechanism. Increasing the reaction pressure by adding carbon dioxide increased 1-hexene conversion and hydroformylation activity. Specific changes observed in the infrared spectrum when the supported complex interacted with carbon monoxide, hydrogen and/or mixture of carbon monoxide and hydrogen in the presence and absence of carbon dioxide at elevated pressures revealed the nature of the reacting species over time and pressure, and clearly demonstrated the role of carbon dioxide when it was used as the solvent. The catalyst activity and structure were compared for reaction in supercritical carbon dioxide with that in nitrogen in order to more completely delineate the role of the supercritical solvent on the reaction mechanism. It was found that the resting state of the catalyst was HRh(CO) 2 L x , L=PPh 2 CH 2 CH 2 bound to silica, independent of the reaction pressure and the presence of carbon dioxide or nitrogen.
School:University of Toledo
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:immobilized rhodium catalyst carbon dioxide
Date of Publication:01/01/2005