Surface/Interface Of Metal Catalysts For The Selective Reduction Of Nitrogenous Compounds

In the field of heterogeneous catalysis,more and more attention has been paid to the catalytic reduction of nitro-compounds.Until now,the design of efficient and environment-friendly catalysts and the target of sustainable and green production are hardly realized,which would restrain the development of catalytic reduction of nitrocompounds.Considering the structural complexity of heterogeneous catalysts,the controversy about the reduction mechanism of nitro-compounds is still existing.Based on these facts,we designed a series of well-defined catalytic interfaces(Pt-DICY,PtIn2O3-x,and Cu(II)-TiOx interfaces),and elucidated the mechanisms of nitrocompounds reduction at the molecular/atomic scales,which should provide a significant guideline for the green catalysis of nitro-compounds.Chapter 1.The surface/interface modification strategies to control the selectivity for catalytic hydrogenation were systematically reviewed.Meanwhile,the research progress on the catalytic reduction of nitro-compounds was discussed.Chapter 2.In anology to enzymatic hydrogenase,we proposed the DICYmodified Pt nanocubes(Pt NCs)would be heterogeneous hydrogenases,which showed an extremely high selectivity for the hydrogenation of p-chloronitrobenzene(p-CNB)to p-chloroaniline(p-CAN).By means sophicated experiments and theoretical calculations,it was found that the Pt-DICY interface prevented the contact of p-CNB with Pt surface,which was different from the traditional p-CNB hydrogenation.However,H2 had the ability to permeate through the DICY layer to the Pt surface and was dissocated into H atoms that were transformed into protons and electrons.Interestingly,the protons were able to migirate to the DICY hydrogen bonding network while the electrons remained on the surface of Pt metal.For the separated protons and electrons,the-NO2 with strong electrophilic properties could be hydrogenated through the electron transfer followed by the proton transfer,which was facilitated by the hydrogen bonding network formed by adsorbed DICY.However,hydrodehalogenation could not be carried out in this pathway,which accounts for the high selectivity towards corresponding halogenated anilines.Chapter 3.We showed that the well-defined Pt/In2O3-x interface exhibited higher activity and selectivity for the reaction of nitrocyclohexane(NO)hydrogenation to cyclohexanone oxime than the commercial Pt/C catalyst.The mechanistic investigation showed that oxygen vacancies in In2O3-x would act as an active site for the deoxygenation of-NO2 and accelerate the transfer of proton to-NO2 through ethylenediamine.Such a unique non-contact catalytic strategy would provide more room for the optimization of hydrogenation catalysts.Chapter 4,CuTiOx/Al2O3 with a uniform Cu(Ⅱ)-TiOx interface was synthesized with Ti4O(OEt)15(CuCl)as the precursor.In the NH3-SCR reaction,CuTiOx/Al2O3 exhibited a higher denitration activity than Cu/Al2O3 with single Cu(Ⅱ)active center.Mechanistic study indicated that in comparison with Cu(Ⅱ),the Cu(Ⅱ)-TiOx interface facilated the adsorption and the activation of O2,which would effectively enhance the oxidation of NO to NO2 while inhibite the formation of nitrite and nitrite species.We proposed that the excellent performance of NH3-SCR at Cu(Ⅱ)-TiOx interface might benefit from the involvement of the fast-SCR.