Controllable Preparation Of Pd Based Metal-acid-alkali Multifunctional Catalysts For One-pot Synthesis Of Mibk

Methyl isobutyl ketone(MIBK)is one of the important chemicals which is widely used in the field of coatings and organic synthesis including special paint solvents,high-quality dewaxing solvent and high-performance rubber antioxidant.With the rapid development of economy,the annual demand and the price of MIBK increase by years.Because of the huge market demand and extensive application,the efficient production of MIBK has become a hotspot.In particular,30%of the domestic MIBK demand depends on the import due to the limited production capacity.Furthermore,the technology of domestic manufacturers is relatively backward,resulting in the severe environmental pollution.Therefore,it is of great significance to synthesis of MIBK by green process to improve the atomic economy,break the international technical barriers as well as meet the needs of domestic market demand.At present,the most green and efficient preparation method for MIBK is one-step synthesis of MIBK from acetone.This process includes the condensation,dehydration and hydrogenation reaction,and the key points is the catalyst.According to the characteristic of this process,the catalyst should have different kinds of active sites to ensure efficient conversion from reactants to products.Therefore,the preparation of multifunctional catalysts with high activity and selectivity and the corresponding structure-performance relationship investigation is necessary to improve the efficiency of MIBK production.In this paper,noble metal Pd was supported on the solid acid(CeO2,TiO2,Al2O3 and SiO2)or the solid base(La2O3,CaO and MgO)with rich acid sites or base sites.The obtained catalysts were then applied in the one-step synthesis of MIBK from acetone.The catalytic results showed that both the Pd/solid acid and the Pd/solid base bifunctional catalysts could catalyze the cascade reaction,and the Pd/solid base bifunctional catalysts showed higher performance than that of Pd/solid acid bifunctional catalysts.Detailly,Pd/MgO catalyst exhibited 30.67%acetone conversion and 27.61%MIBK yield.The results also showed that the basic sites(the strong Lewis basic sites)were favorable for the condensation of acetone,while the acid sites(medium acid sites)were in favor for the dehydration reaction.However,Pd/La2O3 catalyst with strong Lewis basic site did not perform the highest yield of MIBK,indicating that the synergistic effect of the different kinds sites on Pd bifunctional catalyst also had an important influence on the catalytic performance in one-pot synthesis of MIBK reaction.A series of complex oxides(MgTiOx,MgAlOx,CaTiOx,CaMgAlOx and TiMgAlOx)were prepared by hydrothermal and deposition-precipitation methods,which were then used as support to prepare Pd multifunctional catalysts by wet impregnation.The catalytic test showed that Pd/MgAl-MMO multifunctional catalyst achieved the highest catalytic activity and yield of MIBK.XRD,C02-TPD,NH3-TPD,Py-IR,C02-IR and HRTEM were used to investigate the structure of catalysts as well as the structure-performance relationship together with catalytic data.The results showed that Pd/Mg3Al-MMO multifunctional catalyst with 0.4 acid/base molar ratio exhibited the best catalytic performance in the one-step synthesis of MIBK from acetone(38.20%acetone conversion and 31.63%MIBK yield).The research on the proximity of active sites on Pd/Mg3Al-MMO multifunctional showed that the separation of any active site(acid sites,base sites or Pd sites)from the multifunctional would notably decrease the activity and selectivity compared to that over multifunctional catalyst.In addition,Pd/Mg3Al-MMODP catalyst was prepared by deposition-precipitation(DP)method.An enhanced conversion of acetone(42.11%)and yield of MIBK(37.20%)were achieved,which could be ascribed to the improved density of acid and base on the surface of multifunctional catalyst.