Study Of Selective Hydrogenation Of Crotonaldehyde On Supported Ir-Fe Catalysts

α,β-unsaturated alcohols and their derivatives have important applications in medicine, flavors and fine chemicals industries, it usually obtained by the selective hydrogenation of α,β-unsaturated aldehyde. However, in the α,β-unsaturated aldehydes there were conjugated the C= C bond and the C= O bond, the energy (615 kJ mol-1) of C= C bond is less than the energy (715 kJ mol-1) of C= O bond, therefore the C= C bond is more prone to hydrogenation reaction. To prepared α,β-unsaturated alcohols industrially, we often using a reducing agent (such as sodium borohydride and LiAlH4) to directly hydrogenation α,β-unsaturated aldehydes, but, it would results to separate from the product difficultily and cause environmental pollution. In recent years, with the development of green catalytic industry, a growing number of catalytic technologies are developed and applied, choosing a suitable green catalyst in the process of the preparation of α,β-unsaturated alcohols can be reduced waste generation, reduced environmental pollution and separated of the product easily, therefore, heterogeneous catalysis in the process of the preparation of a, p unsaturated alcohols has been widely used and also has important research value. Studying the activity and law of Ir/Fe catalyst on selective hydrogenation of crotonaldehyde through the following three aspects:1. Effect of different carriers on the Selective Hydrogenation of Ir/Fe CatalystThis chapter studies the influence of the carrier on the selective hydrogenation of Ir/Fe catalyst, and discussed the reason of causing deactivation of catalyst. The study found that with the change of carrier, the activity catalyst is correspondingly changed. When the carrier is MCM-41 or SBA-15. high the initial activity of the catalyst is high, but it deactivate soonly, when the carrier is SiO2, although the initial activity of the catalyst is not high, the inactivation rate is very low. in this case, the selectivity to crotyl alcohol is highest (88%). The reason for this situation may be that the carrier of MCM-41 and SBA-15 has mesoporous structure and large surface area, which would decline the contact rate of Ir species and Fe species, reduce the Ir-FeOx interface, it also may be due to the both have smaller pores, the organic matter would clogged pores in the reaction.2. The impact of calcination temperature of the SiO2 for selective hydrogenation properties on the Ir/Fe/SiO2 catalystsThis chapter studies the influence of calcination temperature of the carrier SiO2 for selective hydrogenation properties on the Ir/Fe/SiO2 catalyst, as well as to analyze the specific surface area and the internal structure of the catalyst. The study found that when the carrier SiO2 calcined at 700℃, the conversion of crotonaldehyde crotyl and the selectivity of crotonaldehyde alcohol of the catalyst are best, the conversion rate stabilized at around 51%, the selectivity stabilized at around 90%. Howere, when the carrier SiO2 calcined at 900℃, the conversion rate and selectivity are worst, the conversion rate remained stabilized at around 10% and the selectivity stabilized at around 80%. The reason for this may be that with the increase of the calcination temperature, the specific surface area of the carrier decreases (when the calcination temperature is 700℃, the specific surface area of SiO2 becomes 294.2 m2/g, when the calcination temperature is 900℃, the specific surface area of SiO2 becomes 3.982 m2/g), which would cause the active sites on the precious metal reducing, thus affecting the activity of the catalyst.3.The impact of calcination atmosphere for selective hydrogenation properties on the Ir/Fe/SiO2 catalystsThis chapter studies the effect of calcination atmosphere for selective hydrogenation properties on the Ir/Fe/SiO2 catalysts, the study found that the initial activity is high when Ir/Fe/SiO2 catalyst calcinate at N2 atmospher, which could reach around 98%, but when react about 10h the catalyst presence deactivation the activity down to 52%, while calcined at O2 atmosphere there were no deactivation apparent stable at around 50%, but the selectivity of crotyl alcohol on N2 calcined catalyst (65%) is significantly lower than the O2 calcined catalyst (88%). The reason for this may be that the presence of the organic matter on the catalyst surface which can not be removed through firing.