Preparation And Study On The Thermal Catalysis Of Porous Composite Combustion Catalyst

As a kind of combustion catalyst,metal oxide is an important component of solid propellant,and its physical and chemical properties have a great influence on combustion performance of solid propellant.The research shows that the modification and optimization of the size,morphology,dispersion and surface activity of metal oxide can effectively improve the thermal catalytic properties of the energetic components in solid propellants.Metal organic frameworks material(MOFs)is a porous coordination polymer.It has the characteristics of large specific surface area,uniform porosity,adjustable structure and size,accessible active sites and so on.The combination of MOFs and metal oxide is expected to regulate and improve the physical and chemical properties of metal oxides,thus improving the combustion catalytic properties of the composites,which is of great scientific significance and research value for the development of a new type of high efficiency combustion catalyst.In this subject,two kinds of MOFs materials(HKUST-1,ZIF-8)were combined with metal oxides to obtain "MxOy@MOFs" composite products.At the same time,the preparation method of the composite products was systematically studied.Various methods were compared and valued,and the corresponding products were characterized.The catalytic combustion properties of composite materials for nitrocellulose(NC),a main energetic component of propellant,were studied,and the mechanism of catalytic combustion was also discussed.The main contents are as follows:1.Synthesis and characterization of Fe2O3@MOFs composite productsNanoscale spherical Fe2O3 was prepared by the glycine assisted synthesis method.Two kinds of MOFs materials,HKUST-1 and ZIF-8,were synthesized and combined with Fe2O3.The effects of two method,"layer by layer"(LBL)method and "epitaxial growth"(EG)method,on products were compared,and the corresponding products were characterized.The results showed that the composite products can be prepared by "LBL" method and "EG"method.Relative "EG" method is more beneficial to the growth of MOFs crystal than that of“LBL" method,in which the Fe2O3@ZIF-8 complex prepared by the "epitaxial growth" method has obvious structure of coating and the particle size of the crystalline product is uniform(0.3?m).2.Synthesis and characterization of CuO@MOFs composite productsRod like CuO(R)and globular CuO(G)were prepared by hydrothermal method.The composite products of HKUST-1,ZIF-8 and CuO were prepared by "self template"(ST)method,"LBL" method and "EG" method respectively.The composite products were characterized.The results showed that the three preparation methods all obtained"CuO@MOFs" composite products.The crystal form of MOFs was more regular prepared by"ST" method and "EG" method,while the crystal shape of MOFs was not satisfactory prepared by "LBL" method.3.Study on thermal propertiesThe compound of MxOy@MOFs and NC were mixed,and then the thermal decomposition reaction of the product was studied.The thermal catalytic properties of the composites were studied and analyzed,the related thermodynamic function and the thermal dynamic equation,and the corresponding catalytic mechanism was discussed.The experimental results show that both MxOy@MOFs composite products play a catalytic role in the thermal decomposition reaction of NC.Compared with raw MxOy,the composite products are superior to the corresponding indexes of MxOy in the thermal catalytic properties of NC.The thermal decomposition rate increases 6.8?9.4%,apparent activation energy Ea reduces 24.5?53.0 kJ·mol-1 and Critical temperature of thermal explosion Tbp0 is reduced the 7.3?20.0?,Critical temperature of hot point fire Tbe0 decreased by 5.8?11.4?,and the catalytic effect was more prominent.The calculation of reaction kinetics shows that,the thermal catalytic process of the MxOy@ZIF-8 composite on NC follows the kinetic function 14 Avrami-Erofeev equation,same as pure metal oxide and does not change the reaction mechanism,while the catalytic process of CuO(R)@HKUST-1 follows the kinetic function 33 Reaction order equation.It shows the obvious difference between the influence of HKUST-1 and ZIF-8 on the kinetics of catalytic reaction.