Preparation And Performance Of Pt/PTFE/Foam SiC Structured Hydrophobic Catalysts For Gas-Liquid Catalytic Isotope Exchange

In this paper, the preparation of Pt/PTFE/Foam SiC structured hydrophobic catalyst has been investigated. Hydrophobic treatment method of the carrier, the mechanical properties of Foam SiC carrier, technical conditions for preparing Pt/PTFE/Foam SiC structured hydrophobic catalyst and the reaction conditions for gas-liquid catalytic isotope exchange (LPCE) were studied.Foam SiC carrier was hydrophobic treated by polytetrafluoroethylene (PTFE). The results showed that the initial contact angle of Single-treatment was 77.5°, and the dynamic contact angle decreased with time change. At 20s, the contact angle suddenly reduced to 19.4°, so Foam SiC with single hydrophobic treatment did not meet the requirement for LPCE. The initial contact angle of Foam SiC with double hydrophobic treatment was 117.6°, and the dynamic contact angle reduced to 108.8° in 60s. The initial contact angle of Triple-treatment was 134.2°, and the curve of dynamic contact angle was stabilization. Therefore, Foam SiC with triple hydrophobic treatment was accordingly chosen as the carrier for subsequent experiments.The organic carrier, SDB, was chosen to study the influence of impregnation time on Pt loading. The results showed that 24h and 48h impregnation loaded Pt on the surface of SDB. Extended impregnation time, such as 72h and 96h, Pt-organic solution would went into SDB through the microporous. This impregnation method would not only improve Pt loading, but also prevent the loss of active metals. It also apply to PTFE/Foam SiC, which has organic surface with microporous.The electron universal testing machine was chosen to test the mechanical property of Foam SiC. The results showed that the compressive property Pt/PTFE/Foam SiC structured hydrophobic catalyst was 3.2MPa, weaker than Foam SiC. Compared with the mechanical properties of Foam Nickel (FN) and Pt/PTFE/FN structured hydrophobic catalyst, Pt/PTFE/Foam showed excellent mechanical property. The results meant Foam SiC has good properties of corrosion resistance and compression resistance.XRD, XPS and TEM were chosen to study the influence of reduction temperature on the preparation of Pt/PTFE/Foam SiC structured hydrophobic catalyst.200?,250? and 300? were chosen as the reduction temperatures to prepare the different catalysts. The results showed that the average particle size of Pt particles of the three catalysts reduced by 200?, 250? and 300? were 9.3nm?6.8nm and 7.4nm, respectively. The average particle size of Pt did not grow up with a rise of temperature.Among the three catalysts, the catalyst reduced by 250? had the least size distribution and the best dispersion. Bad dispersion and obvious aggregation were observed in the one reduced by 300?. Three valences, Pt(0), Pt(II) and Pt(?) exist in these catalysts, and Pt(0) is the key for catalytic isotope exchange. Pt(0) proportion of the catalyst reduced by 250? was much more than Pt(0) proportion of the other two catalysts.The influence of impregnation solution on preparation of Pt/PTFE/Foam SiC was studied. The results showed that Pt(0) of the catalysts prepared by chloroplatinic acid ethylene glycol solution and chloroplatinic acid ethanol solution was the main valence. The average particle size of Pt of the catalyst prepared by chloroplatinic acid ethylene glycol solution was 3.6nm, the smallest among the three catalysts.This catalyst also had the least size distribution and the best dispersion. Some agglomerates can be observed and should be optimized.The reaction conditions of LPCE were studied. The optimal filling ratio and reaction temperature were 25% and 80 ?, respectively. And, the optimum way of packing was multiple catalytic layers.Analyzed the catalytic performances for LPCE and the characterization of different catalysts, the optimal impregnation solution was chloroplatinic acid ethylene glycol solution and the optimum reduction temperature was 250 ?. The results also showed that the average size of Pt was the key factor to influence the column efficiency, when the Pt(0) proportion of different catalysts were close. In addition, the ?=6mm catalyst had a higher column efficiency than the big one. In 30-day test, the catalytic active of Pt/PTFE/Foam SiC structured hydrophobic catalyst was stable.In this paper, the low properties of corrosion resistance and compression resistance were solved, and Pt loading was improved. Technical conditions for preparing Pt/PTFE/Foam SiC structured hydrophobic catalyst and the reaction conditions for gas-liquid catalytic isotope exchange were studied. This work established a good outset for applying the hydrophobic catalyst to distill tritium from heavy water and water detriation system (WDS).