Study On The Synergistic Effect Of Pt (Pd) -Mo <2> / N (WN) Catalytic Selective Hydrogenation

Selective hydrogenation of α,β-unsaturated aldehydes has attracted much attention in recent years, because the products are widely used in pharmaceuticals, perfumes and flavors. It’s well known that the supported noble metals are much more active in the hydrogenation of α, β-unsaturated aldehydes. However, for large-scale practical application, it is very essential to enhance the efficiency and selectivity of noble metals and decrease the usage of noble metals due to its high cost and scarcity.In this study, various supports modified with small-size Mo2 N or WN were synthesized by anchoring the heteropoly acid clusters on aminated supports, and followed by the nitridation in NH3 atmosphere. Then, the ternary catalysts were obtained by the controlling growth of precious metals onto the composites; and it’s investigated the synergistic effect of noble metal and nitrides on the hydrogenation of cinnamaldehyde via C=O bond and C=C bond, respectively. The main research contents are as following:(1)The small-size and high dispersed Mo2N/rGO and WN/rGO are prepared by anchoring heteropolyacid on polyethyleneimine modified graphite oxide, following by hydrothermal treating and nitridition under NH3. Then, Pt-Mo2N(WN)/rGO and PdMo2N(WN)/rGO are obtained by supporting noble metal on these composites. The performance of Pt-Mo2N(WN)/rGO is investigated for the hydrogenation of cinnamaldehyde via C=O bond, while the performance of Pd-Mo2N(WN)/rGO is also investigated for the hydrogenation of cinnamaldehyde via C=C bond. The synergistic effect of Pt and nitride can enhance the performance of Pt, but the effect of Pd and nitrides isn’t obtained.(2) The SBA-15 modified with well-dispersed Mo2 N nanoparticles(NPs) is synthesized by anchoring the phosphomolybdic acid on the aminated-SBA-15 primarily, and followed by the nitridation treatment under NH3. After loading Pt, the Pt-Mo2N/SBA-15 catalyst can be formed with closed contacted Pt and Mo2 N NPs. The ternary Pt-Mo2N/SBA-15 catalysts show the superior performance for the selective hydrogenation of cinnamaldehyde via C=O bond. The TOF over the 1% Pt-Mo2N/SBA-15 catalyst is close to that of the 3% Pt/SBA-15 catalyst, but its selectivity to cinnamyl alcohol is 2.5 times as that of the 3% Pt/SBA-15.(3) A series of catalysts made of Pd-WN on various supports are synthesized. Their catalytic performances are evaluated for the hydrogenation of cinnamaldehyde via C=C bond. Among these catalysts, Pd-WN/SBA-15 shows best performance with highest hydrocinnamaldehyde yield(97.1%). Moreover, it was reused 5 times successively without significant loss of catalytic activity and selectivity. The effect of WN on the active energy is investigated by dynamics. Meanwhile, the universality of the synergistic effect between Pd and nitrides is explored by the performance of Pd-Mo2N/SBA-15 for the hydrogenation of cinnamaldehyde via C=C bond.