Preparation Of Large-scale Pt/SDB Hydrophobic Catalyst And Study On Hydrogen Isotope Exchange Performance

Hydrogen isotope exchange has important applications in the extraction of tritium from heavy water and the treatment of tritium-containing wastewater.The performance of the hydrophobic catalyst is the core of the process.Although domestic scientific researchers have done lots of related work on catalyst preparation and application performance,so far,the treatment of tritium-containing wastewater has not been industrialized in our country.The main reason is that the existed catalyst particle size is too small and the catalyst bed pressure is too high.Therefore,the practical significance of researching and developing large-size support and preparing large-size hydrophobic catalysts becomes more apparent.In this paper,styrene（St）is used as monomer,divinylbenzene（DVB）is used as cross-linking agent,toluene and n-heptane are used as mixed porogen,benzoyl peroxide is used as initiator,and DM regulator is added to prepare the organic phase.The organic phase is added to the aqueous phase containing surfactants,and the large-size and controllable（Φ=3 mm-10 mm）styrene-divinylbenzene copolymer SDB hydrophobic carrier is prepared by the suspension polymerization method.The method of etching combined with chemical etching realizes roughening of the surface of the SDB hydrophobic support.Using BET,static contact angle,TG and other analytical techniques to characterize the structure and performance of SDB,the results show that when n（St）:n（DVB）=1:1,the specific surface area of the obtained SDB can reach 472.7m²/g,The pore volume is 0.464 cm³/g,the pore diameter is 2.01 nm,the compressive strength is 48.6 N,the hydrophobic angle is 145.4°,the surface dangling double bond content is 1.22 mmol/g,and the yield can reach about 85%.Polymerization temperature,polymerization time,initiator dosage,and porogen dosage will all affect the synthesis process of SDB.The optimal synthesis process conditions for SDB hydrophobic carrier are:the polymerization temperature is 80℃,the polymerization time is 5 h,and initiator dosage of 7.5%of the monomer weight,the volume ratio of toluene to n-heptane is 1:2.The impact of the crosslinking agent DVB on the hydrophobicity,thermal stability and surface dangling double bonds of SDB was mainly investigated.With the increase of DVB dosage,the content of surface dangling double bonds increased significantly.The TG curve shows that the decomposition temperature of SDB gradually rises and its thermal stability is improved.The static contact angle also increases with the increase of DVB dosage.This shows that the amount of DVB used in the SDB polymerization process plays an extremely critical role.The active component of the catalyst is loaded on the surface of the prepared SDB hydrophobic support by the immersion method in H₂Pt Cl₆-i-POL solution,and the Pt/SDB hydrophobic catalyst is obtained after hydrogen reduction.The H-D exchange evaluation device is used to catalyze the H-D exchange performance of the catalyst Make an evaluation.The prepared catalyst surface active component Pt is in a highly dispersed state,with a dispersion degree of about 46%.The main particle size of the catalyst active component Pt is distributed in the range of 4 nm-7 nm,and agglomeration will not occur with the extension of working time.The optimal conditions for H-D catalytic exchange are:the reaction temperature is 90℃,the reaction space velocity is 3000 h^-1,and the impregnating solution concentration is 400mg/L.H-D catalytic exchange efficiency increases with the increase of reaction temperature.At relatively low temperatures,the catalyst efficiency is affected by space velocity.When the temperature increases to 80℃-90℃,the space velocity has little effect on H-D exchange efficiency..The linear adsorption and bridge adsorption of CO on the surface of the active component Pt poison the catalyst,and the activity will decrease significantly.Using inert gas,argon,purging at 250℃-300℃ can achieve partial regeneration of the catalyst.The lifetime evaluation test shows that the H-D exchange efficiency of the catalyst does not fluctuate significantly,and the H-D exchange efficiency is maintained at a relatively high level of over 95%at 90℃.