Selective Catalytic Hydrogenation Of Unsaturated Aldehydes And Diaromatics

The selective hydrogenation of unsaturated aldehydes and diaromatics is an important reaction for organic synthesis. In this thesis, the selective hydrogenation of C=O, C=C bond and benzene ring were systematicly investigated.The selective hydrogenation of3,4,5-trimethoxybenzaldehyde (TMB) to3,4,5-trimethoxytoluene (TMT) was studied over skeletal nickel catalyst. The hydrogenation of TMB was investigated over skeletal Ni catalyst without any additives, and1,2,3-trimethoxybenzene was obtained via directly cleavaging C-C bond. Under190℃and3.0MPa, the selectivity of1,2,3-trimethoxybenzene was as high as83.1%and no by-products for the hydrogenation of aromatic ring were detected during the whole reaction process. In addition, under the optimized reaction condtions of165℃,6.5MPa, the selectivity of TMT was up to98.6%at100%conversion of TMB over Mo modified skeletal nickel catalyst. It is found that Mo as modified components play a key role in controlling the selectivity for the hydrodeoxygenation of C=O bond. XPS analysis demonstrated that the peak for metallic Ni disappeared after skeletal Ni catalyst was modified by Mo componetent. The possible reason for high selectivity of TMT was attributed to the effective inhibition for the side reaction of decarbonylation.The selective hydrogenation of α,β-unsaturated aldehydes were investigated and cinnamaldehyde (CAL) was chosen as a model substrate for the study of reaction mechanism. Results showed that Co-Mo-B alloy catalyst exhibited good performance for the hydrogenation of C=O bond. Under the optimal reaction conditions, the selectivity of cinnamic alcohol was up to86.3%when the conversion of CAL was98.8%. On the other hand, K2CO3has played a significant role in improving the selectivity of hydrocinnamicaldehyde (HCAL) over Pd/C catalyst. Under the optimal reaction conditions, the selectivity of HCAL was as high as98.6%with95.0%conversion of CAL.Supported nano-Ru catalyst was employed for the selective hydrogenation of MDA and BPA to corresponding aliphatic compounds. The selectivity of H12MDA can be as high as99.2%and trans-trans isomer was lower than25%under160℃,8.0MPa with100%conversion of MDA. The conversion of MDA can still reach100%even after recycling for thirty times. Similarly, the selectivity of H12BPA can be up to98.4%at110℃,6.0MPa with100%conversion of BPA.