Preparation Of CaCO₃-Based Catalysts By Mechanochemistry And Their Structure-Activity Relationship

As an important industrial raw material and chemicals,calcium carbonate is widely used in pharmaceutical,food,rubber,cosmetics,catalytic and other fields due to advantages and low quality and low-processed,good processed,durable,and renewable.Especially in the field of catalytic,calcium carbonate,as a carrier of catalyst,has the characteristics of non-pollution,low cost,renewable and recycling and other characteristics to reactors and products,thereby reducing waste of resource and environmental pollution.However,calcium carbonate has a limited application of impurities and active components a single problem.Although the current problems can be effectively solved through the later processing of calcium carbonate that are synthesized by artificially synthetic,due to factors such as a large amount of solvents,long-time crystallization process,and lower surface area of calcium carbonate during the synthesis process,it has seriously limited its large-scale industrialized application essence based on the principle of solid physical chemistry,the mechanochemistry is based on high-energy ball mill,high-energy ultrasonic and high-pressure shear,and uses mechanical energy to promote chemical reactions without solvents.In combination with the advantages of mechanochemistry and calcium carbonate,this thesis uses mechanochemistry to synthesize calcium carbonate catalysts,which solves the problem of active components in the reaction in the reaction.It also retains the advantages of high stability of calcium carbonate itself.The specific work can be divided into the following two parts:1.By adding green pores NaCl auxiliary mechanochemistry method,it successfully prepared a porous calcium carbonate of up to 108 m²/g,which is 27 times that of commercial calcium carbonate.During the preparation process,the low thermal stability of the calcium oxalate and manganese oxalate front drives causes its easy decomposition.During this process,a large amount of CO₂ will be generated.These gases form many pores when spreading.In addition,the removal of NaCl templates will further create more pores,which significantly increases the comparison surface area of calcium carbonate.At the same time,the highly decentralized MnO_X species can be introduced into a porous CaCO₃ during the ball mill,further constructing a dual-function catalyst rich in alkaline-rich sites-oxidation reducing sites:Mn₂₅/CaCO₃.TOF:813.15 h^-1).The TOF value of the catalyst Mn₂₅/CaCO₃ in the reaction of the catalyst prepared by the mechanical chemistry is compared with 3 times and 7 times the comparison catalyst Mn₂₅/CaCO₃-DP and Mn₂₅/CaCO₃-PR.The theoretical calculation results indicate that Mn₂₅/CaCO₃ has the lowest response energy barrier compared to other comparison catalysts in the activation process of ethylene,which further proves the synergy of the alkaline site of CaCO₃ and the center of oxidation and restore in the MnO_X species..2.A series of Pd-based catalysts based on a mechanical chemical legal system are used.By changing different ball mill media,front-wheel drive,and ball mill time,you can get high-efficiency catalyst Pd/H-CaCO₃（compared to the surface area:101 m²/g）.The role of mechanical power prompted the height of the front-drive body such as calcium chloride and chloride.After roasting and reducing,the 3.62 nm Pd NPs（Nanoparticles,NPs）generated in situ is highly dispersed and limited to calcium carbonate.In grade pore structure.The catalyst shows higher TOF（1.01×10⁴/h）and stability（no significantly reduced activity after 10 cycles）in the reaction of nitrogen benzene-selective hydrogenation（the activity without reduction after 10 cycles）.This strategy has a high degree of universality and can be used to prepare Pt/H-CaCO₃ and Rh/H-CaCO₃ catalysts,and it also has excellent catalytic activity in the reaction.In addition,after the preparation scale of the catalyst expands 5 times and 10 times,the Pd/H-CaCO₃ still maintains a good catalytic activity,and the catalyst can completely degrade the dye wastewater in the short time（10 s and 25 s）in the short time（10 s and25 s）.Methylene Blue（MB）and Rhodamine B（Rhodamine B,Rh B）indicate that it is a multi-functional high-efficiency catalyst with potential for large-scale preparation and application.