Enhanced Selective Hydrogenation Of Citral By Nitrogen-modified Ordered Mesoporous Carbon-supported Ruthenium Catalysts

Citral is an important ?,?-unsaturated aldehyde,and its hydrogenation products,nerol and geraniol,are widely used in the production of flavors and the synthesis of important pharmaceutical intermediates.In the current international market,the demand for neroli alcohol and geraniol exceeds the supply,and in the actual production and preparation process,it is mainly obtained by catalyzing the selective hydrogenation of citral by metal catalysts.However,on the one hand,the bond energy(715 k J/mol)of the C=O double bond is greater than the bond energy of the C=C double bond(615 k J/mol),on the other hand,compared with the C=C double bond,the adsorption energy of the C=O double bond on the surface of some metals is small,which makes it very difficult to obtain high-purity nerolisol and geraniol by selective hydrogenation of the C=O double bond during the catalytic reaction.Therefore,at present,the efficient and selective hydrogenation of citral to produce neroli alcohol and geraniol has broad application prospects.In this paper,a series of ordered mesoporous carbon-loaded ruthenium catalysts(3 wt%Ru-N/OMC)with different nitrogen doping amounts were synthesized by hydrothermal synthesis in one step,and applied them to catalyze the selective hydrogenation of citral to neroli and geraniol.Highly ordered mesoporous carbon confinement effect and coordination between nitrogen species and metallic ruthenium,the ruthenium nanoparticles in the prepared 3 wt%Ru-N/OMC catalyst were uniformly dispersed in the pore channel and remained highly stable during the catalytic citral hydrogenation reaction.In the process of selective hydrogenation of catalyzing citral,the nitrogen content in the 3 wt%Ru-N/OMC catalyst had no significant effect on its activity,but ru and N coordination lost electrons,making positively charged Ru more conducive to the adsorption of C=O double bonds,which greatly promoted the selectivity of the target products neroliter and geraniol,of which the ruthenium catalyst with the highest nitrogen content(6.08 wt%)showed the highest selectivity(>).80.1 %),and maintained good conversion rate and selectivity after 5 cycles.The results of ICP test and the thiol "capture experiment" show that the metal ruthenium in this series of catalysts does not lose during the catalytic reaction,which proves that the nitrogen-modified mesoporous carbon-supported ruthenium catalyst has excellent stability and anti-poisoning properties.