Research On Preparation And Properties Of Manganese-based Oxides Catalysts By MOF Template Method

Chlorine-containing volatile organic compounds（CVOCs）are a class of highly toxic and carcinogenic compounds,which are extremely harmful to humans and nature.At present,there are many processing methods for CVOCs,among which the degradation technology represented by the catalytic combustion method has become a research hotspot,and the key of the catalytic combustion method is to develop the highly efficient catalysts at low temperature.Metal organic frameworks（MOFs）materials have become one of the research hotspots in the field of catalysis as a typical representative catalytic materials of abundant porous structure and high surface area.In combination with high activity of manganese oxides,a series of CuO/MnO_x catalysts with strong redox capacity was developed by using Mn-MIL-100 as a template for catalytic combustion of chlorobenzene（CB,as model compound of CVOCs）,and the optimal Cu/Mn loading ratio was also obtained.The real-time monitoring of intermediate products in catalytic reaction was carried out,and the uniformly distributed composite metal oxide was further explored from Mn-MOF.However,how to maintain the structure of MOF materials after calcination so that they have better resistance to chlorine poisoning for catalytic combustion of chlorobenzene（CB）is still a challenging subject.The main work of this paper has been shown below.Mn-MIL-100 was used as the template to explore the effect of the addition amount of lauric acid（2-5g）on its morphology,and then MnO_x catalyst was formed after the Mn-MIL-100 was calcined in air.The results showed that different amounts of lauric acid had a great impact on the final morphology.However,the structure of MnO_x calcined from Mn-MIL-100 collapsed without adding lauric acid and the structure of MnO_x calcined from Mn-MIL-100 with lauric acid remained intact and exhibited porous octahedron lamellar structure.When the addition of lauric acid is3.80g,the size of MnO_x catalyst is the smallest.A series of CuO/MnO_x composites with CuO mass ratios from 10-40wt%has been synthesized by incipient wetness impregnation and Mn-MIL-100,followed by calcination.The catalytic activity has been tested in oxidation of chlorobenzene（CB）.The catalytic activity test revealed that the catalytic activity of MnO_x improved remarkably after loading Cu,particularly the catalyst with 30 wt%CuO（30Cu/MnO_x）exhibited the best catalytic activity in CB combustion,whose T_90%was 290°C at GHSV of 15000 h^-1.The excellent catalytic performance of 30Cu/MnO_x could be attributed to the abundant mesoporous structure,improved reducibility,surface-enriched Mn⁴⁺species and active adsorbed oxygen species.Moreover,the TPSR-MS data showed that30Cu/MnO_x exhibited higher dechlorination ability and better resistance to chlorine poisoning during CB degradation process.The uniformly distributed composite metal oxide was explored and prepared.Ni/Mn-MOF nanosheets were synthesized by a one-step hydrothermal method.The products obtained under different hydrothermal reaction times（2-24h）have different structures.When the reaction time reached 20h,the thickness of obtained nanosheets is thinnest and the distribution of obtained nanosheets is more uniform.Ni Mn₂O₄composite metal oxides are formed after calcination,which show a porous nanosheet structure.The thickness of the nanosheets is 23±15nm.