Exploration And Application Of Nano-catalyst Immobilization Technology

The technique of immobilizing a functional material onto the corresponding substrate is called immobilization.This technology is widely used in catalysis and photocatalysis.The preparation of composite catalytic materials by immobilization technology can not only enhance the catalytic performance of the catalyst,but also make the catalyst have higher mechanical stability,which is easy to use.Nowadays,many nanocomposites with high catalytic activity have been prepared.But their limitations have prevented them from being used on a large scale in industry.We suspect that this may be due to the following reasons:first,when the nanocatalyst is applied to a reaction system,the catalyst is not easy to be separated from the reaction system;Second,if continuous,flow-through production is performed using a fluidized bed reactor,nanoscale catalysts may be carried by the reaction solution to the next reaction process module.And that might prevent the next reaction from happening.Therefore,it is of great significance and necessary to explore the immobilization technology of nanocatellite.Therefore,we have systematically studied the immobilization technology of graphene-based catalyst and CDS-based nanocatellite,developed some new catalytic materials with certain application prospects,and preliminarially discussed their applications in the field of catalysis and photocatalysis.The main research work and results are as follows:（1）Graphene was first immobilized on the surface of the titanium mesh by electrodeposition method,and then a catalytic system（Ti-RGO-Ag）consisting of graphene nanosheets modified with Ag nanoparticles was prepared by in-situ photoreduction method.According to the characteristics of the obtained catalytic system,a flow reactor was designed and built.Subsequently,a self-made reactor was used to investigate the catalytic activity of the catalytic system for 4-nitrophenol reduction and the influence of p H,p-nitrophenol concentration,flow rate and other factors on the catalytic activity.In addition,the reactor is modularized,and the overall performance of the reactor is preliminarily investigated when the connection mode of the reactor units is different.The results show that the catalytic system prepared by electrodeposition technology is an efficient catalyst for the removal of 4-nitrophenol from water and is suitable for continuous flow systems.When 4-nitrophenol solution was passed through the Ti mesh at a flow rate of 3 ml min^-1,92%of 4-nitrophenol(100 m L,10^-4mol L^-1)could be removed within 150 min.In addition,the integrated catalyst has quite satisfactory durability.After two applications,the catalytic activity remained 84%of that of fresh samples in the third cycle.On the other hand,the reactor we have designed can be regarded as a modular unit.If multiple such devices are assembled,a large reactor can be easily constructed.The reactor has great application potential in the treatment of a large amount of wastewater containing4-nitrophenol.（2）A 1000 m L large capacity array hydrogen production reactor was assembled.Using IR120 cation exchange resin commonly used in wastewater treatment plants as substrate,a photocatalytic hydrogen production catalyst was developed by immobilizing Cd S nanomaterials on the resin surface through in situ reaction.On this basis,the activity and stability of the obtained photocatalyst for hydrogen production from photocatalytic reduced water and recycling were evaluated.The results show that the cation exchange resin has satisfactory photocatalytic hydrogen production activity and cycle stability.Under the optimum conditions,the hydrogen displacement rate of the catalyst can reach 0.78 mmol g^-1.This indicates that the immobilization technology we used has no significant effect on the photocatalytic hydrogen production activity of the catalyst,and may be extended to other catalysts.The obtained catalysts may be used in fluidized bed photocatalytic hydrogen production process.（3）In order to solve the problems of insufficient light penetration distance and difficult separation of nanocatalyst in the suspension system of nanocatalyst,we investigated the possibility of preparing a photocatalytic hydrogen production catalyst that can float on the water surface and is easy to be separated by immobilizing Sr WO₄/Cd S nanoparticles on nanocellulose.The results show that when Sr WO₄/Cd S nanoparticles are immobilized on nanocellulose,the photocatalytic activity of Sr WO₄/Cd S nanoparticles is higher than that before immobilization.In addition,the catalyst can be easily separated from the reaction system and can also be converted into a good quality catalyst film on a solid substrate.This indicates that our immobilization technique is a promising immobilization technique which may be extended to the immobilization of other catalytic systems.The prepared catalyst may be used in fixed-bed photocatalytic hydrogen production process.