甲醛还原Pt/TiO2催化剂用于温和条件下高效催化氧化甲醛

通过浸渍法(IM)和沉积-沉淀(DP)法制备了一系列Pt/TiO2(P25)催化剂,并分别用甲醛溶液和氢气还原处理催化剂.利用原位红外监测催化剂表面吸附物种在反应过程中的变化,探究了催化剂制备和还原条件及Pt负载量对催化剂结构和催化氧化甲醛活性的影响.结果显示,用DP法制备并用甲醛还原的Pt/P25催化剂中Pt颗粒分散均匀,并具有合适的粒径和高浓度的表面活性氧,显示出良好的甲醛氧化活性.在空速30000 ml/(g·h)、反应温度30°C和甲醛初始浓度50 mg/m3的条件下,0.4%Pt/P25(DP-HCHO)上的甲醛转化率达到98%,并能稳定运行100 h以上.相比之下, Pt/P25(DP-H2)由于表面活性氧较少,不利于甲酸盐氧化,活性较低. Pt/P25(IM-H2)虽然具有高浓度的表面活性氧,却同时具有最大的Pt颗粒粒径,在甲醛转化为甲酸盐和甲酸盐氧化两步反应中的活性均较差,因而甲醛氧化活性最差.

Titania-supported Pt catalyst reduced with HCHO for HCHO oxidation under mild conditions

A series of Pt/TiO2(P25) catalysts were prepared by both impregnation (IM) and deposi‐tion‐precipitation (DP) methods followed by reduction using either a HCHO solution or a H2 stream. The effects of the preparation and reduction conditions and the Pt loading level on structural prop‐erties and performance during HCHO oxidation were then studied based on the assessment of ad‐sorbed species on the catalyst surfaces using in‐situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results indicated that Pt/P25 prepared by DP and reduced with HCHO exhibited homogeneously dispersed Pt nanoparticles with appropriate particle size in addition to a high concentration of chemisorbed oxygen, and also showed high activity for HCHO oxidation. A HCHO conversion of 98%with stable performance over more than 100 h was achieved over Pt/P25 produced using DP and HCHO reduction at 30 °C, even with a 0.4%Pt loading. Pt/P25 synthesized using DP with H2 reduction was less effective at promoting formate decomposition and thus showed less HCHO oxidation activity, likely because of lower levels of chemisorbed oxygen. The Pt/P25 made using IM and H2 reduction had the highest amount of chemisorbed oxygen but also the largest Pt particles, resulting in the lowest activity for both the formation of formate species and formate decomposition into CO species, and thus showed low HCHO oxidation activity.