Preparation Of Pt/SDB Hydrophobic Catalyst And Study On The Catalytic Performance

Hydrogen isotope separation technology has great application value in the tritium extraction and upgrading of heavy water in nuclear power plant reactors.The hydrophobic catalyst with excellent performance is the key factor to realize the industrial application of hydrogen isotope separation technology.The preparation process of catalyst carrier directly determines the physical performance and catalytic efficiency of the catalyst.Researchers have carried out a lot of studies on the hydrophobic carrier stylene-vinylidene styrene copolymer（SDB）,and the SDB particle size is generally small,which leads to excessive pressure of catalyst bed,resulting in"liquid flooding"phenomenon and lower catalytic efficiency.Large size SDB particles can effectively reduce or avoid the occurrence of"liquid flooding"phenomenon,so it is of great practical significance to study and prepare large size SDB particles.Using styrene as monomer,vinylbenzene as crosslinking agent,toluene and n-octane as pore-causing agent,benzoyl peroxide as initiator,appropriate substances as density regulator and surfactant,suspension polymerization method was used to prepare 5 mm or above SDB spherical carrier with controllable size,and physical etching method was used to achieve surface rough of SDB.The pore structure,hydrophobic performance,surface morphology,thermal stability and other properties of SDB were measured by nitrogen absorption and desorption method,mercury injection method,video optical contact angle measuring instrument,scanning electron microscope,thermos gratings-differential thermal analysis and other characterization methods,and the reasons for the differences in performance of SDB under different preparation conditions were described.The optimal process conditions were obtained as follows:The dosage ratio of monomer to crosslinking agent was 1:1,the dosage ratio of monomer to pore-causing agent was 1:1,and the ratio of mixed pore-causing agent was toluene:n-octane=1:1.The temperature control method of 72～80℃gradient temperature rise was adopted,and the dosage of initiator was 3wt%of the amount of monomer.The average values of SDB tests after process optimization are as follows:specific surface area is 394.0 m²/g,pore volume is 0.369 cm³/g,pore diameter is 1.90 nm,mechanical strength is 168.8 N,hydrophobic angle is 145.8°,and initial temperature of thermal decomposition is about 350℃.The etched SDB was mixed with the prepared chloroplatinic acid solution.The immersion reduction method was used to achieve the adhesion of platinum on SDB,and potassium borohydride was used as reducing agent for normal temperature reduction.X-ray photoelectron spectroscopy,ultraviolet spectrophotometer and pulse titration quantitative analysis were used to analyze and characterize Pt/SDB.The results showed that the content of zero-valent platinum was 40%after potassium borohydride reduction at room temperature,and the content of Pt⁰in Pt/SDB remained basically unchanged after catalytic reaction,indicating that the active component had a good combination with SDB.The utilization rate of Pt in the loading process is 82.15%.Under the premise of ensuring high loading capacity,the agglomeration phenomenon caused by hydrogen reduction at high temperature is reduced,indicating that the method of KBH₄reduction at room temperature is feasible.The results of pulse titration showed that the dispersion of Pt was about 54%,the active metal area on Pt/SDB was about 130 m²/g,and the average grain size was about 2 nm.The hydrogen isotope catalytic exchange performance of Pt/SDB was determined by a gas-phase catalytic exchange device and a liquid-phase catalytic exchange device,and the hydrogen-oxygen recombination performance of Pt/SDB was determined by a dissolved oxygen removal device,and the variation rules of each variable and catalytic efficiency were analyzed.The optimal reaction conditions are as follows:hydrogen flow rate is 100 m L·min^-1,catalyst bed temperature is 90℃,and only catalyst is loaded in the catalyst bed.The optimal reaction conditions of liquid phase catalytic exchange reaction were as follows:hydrogen flow rate of 200 m L·min^-1,catalyst bed temperature of 70℃,inner diameter of hydrophilic packing of 3 mm,catalyst:packing=1:3.The optimal reaction conditions of liquid phase hydrogen-oxygen complex reaction are as follows:hydrogen dosage is 200 m L,catalyst bed temperature is 45℃,catalyst dosage is 4 g/L.The optimal reaction conditions of gas-phase catalytic exchange reaction and liquid-phase catalytic exchange reaction were maintained,and the H-D exchange efficiency of Pt/SDB/CC was 92%and 52.1%,respectively.