疏水性铂催化剂常温氢氧复合性能

Performance of H2-O2 recombination on hydrophobic Pt catalysts at ambient temperature

摘要:

以Al2O3为载体、H2PtCl6水溶液为浸渍液，通过真空浸渍还原法得到疏水性Pt催化剂Ⅰ；以OTMS（十八烷基三甲氧基硅烷）为载体表面修饰剂，通过改变修饰液中OTMS质量分数〔w（OTMS）=0.5%（以修饰液中甲苯重量为基准，下同）、1.2%和2%〕，分别得到疏水性催化剂Ⅱ、Ⅲ和Ⅳ，4种催化剂中Pt的负载量皆为1.5%（以Al2O3载体重量为基准，下同）。分别在干燥、高湿及水相环境中对所制备催化剂进行氢氧复合性能评价，采用XRD、FTIR、CA、SEM、BET和脉冲氢氧滴定对催化剂进行了表征。结果表明：相比未进行OTMS修饰的催化剂Ⅰ，催化剂Ⅱ可以在高湿条件下保持相对稳定的氢氧复合性能，氢转化率保持在96.25%，在水相环境下其也表现出一定的活性，但氢转化率在40h内由61.25%下降至43.75%；催化剂Ⅲ和Ⅳ无论在高湿环境还是在水相环境下都表现出了相对稳定的氢氧复合性能，在高湿环境下氢转化率分别为93.75%和87.5%，而在水相环境下分别为76.25%和63.75%；随着修饰液中OTMS质量分数的增加，催化剂的疏水性、抗湿和抗水性能得到逐渐增强，但也导致了催化剂比表面积、Pt分散度和Pt活性比表面积逐渐减小，进而影响了催化剂在干燥、高湿及水相环境中的催化活性。

Abstract:

Hydrophobic Pt catalystsⅠwas prepared by vacuum impregnation-reduction with Al2O3 as carrier and H2PtCl6 as impregnation solution. With OTMS (n-octadecyltrimethoxysilane) as modifier, Hydrophobic catalystsⅡ, Ⅲ and Ⅳ were attained through changing the OTMS concentrations〔w（OTMS）=0.5% (based on the weight of toluene, the same below), 1.2% and 2%〕. The catalyst loadings of these four catalysts were 1.5% (based on the weight of Al2O3 carrier, the same below). The catalytic performances of H2-O2 recombination on conditions of dry, wet and water were studied. The catalysts were also characterized with XRD, FTIR, CA, SEM, BET and pulsed hydrogen-oxygen titration techniques. The results showed that, compared with catalystⅠwithout modified in OTMS solution, catalystⅡcan catalyze H2-O2 recombination more steadily on wet condition，and the H2 conversion is 96.25%. In the water phase, catalystsⅡ also has catalytic activity，but the H2 conversion decreases to 43.75% from 61.25% during the 40h-testing. Catalysts Ⅲ and Ⅳ can catalyze H2-O2 recombination steadily on wet and water conditions. The H2 conversion of catalysts Ⅲ and Ⅳ are 93.75%, 87.5% on wet condition and 76.25%, 63.75% on water condition. As the OTMS concentrations in the solution increase，the catalysts attain better hydrophobic performance, wet resistance and water resistance, but the specific surface area、Pt disparity and Pt active specific surface area decrease and then have effect on catalytic activity of these catalysts on dry, wet and water conditions.