Influence of preparative method on Al2O3-doped Pt/WO3-ZrO2 catalyst for n-heptane isomerization

Alumina-doped Pt/WO3/ZrO2 catalysts were prepared using either a constant or variable pH method. The obtained catalyst samples were characterized using N2 adsorption, X-ray diffraction, ultraviolet-visible diffuse reflectance, CO chemisorption, X-ray photoelectron spectroscopy, 27Al magic-angle spinning nuclear magnetic resonance, and infrared spectroscopy of adsorbed pyridine. Compared to the catalyst prepared using the variable pH method, the catalyst prepared using the constant pH method had a higher surface area and Pt dispersion. More Brönsted acid sites were generated in the presence of H2 on the latter catalyst, and this was responsible for its higher catalytic activity in n-heptane hydroisomerization. When the reaction temperature was 200 °C and the weight hourly space velocity of n-heptane was 0.9 h−1, the Pt/WO3/Al2O3-ZrO2 catalyst prepared using the constant pH method gave 70.0% conversion of n-heptane, which was significantly greater than the conversion obtained using the corresponding catalyst prepared using the variable pH method (43.5%).

摘要采用恒pH法和非恒pH法制备了Al2O3掺杂的Pt/WO3/ZrO2催化剂, 并用N2吸附-脱附、X射线衍射、紫外-可见漫反射、CO化学吸附、X射线光电子能谱、27Al魔角旋转核磁共振和吡啶吸附红外等技术对催化剂进行了表征. 结果表明, 相比于非恒pH法制备的催化剂, 恒pH法制备的催化剂具有较高的比表面积和Pt分散度, 在H2气氛中产生更多的B酸位, 从而表现出更高的催化正庚烷临氢异构化反应活性; 在200 °C和质量空速0.9 h−1的反应条件下, 正庚烷转化率达70.0%, 明显高于非恒pH法制备的催化剂(43.5%).

Graphical AbstractAn Al2O3-doped Pt/WO3/ZrO2 catalyst prepared using a constant pH method exhibited significantly higher activity in n-heptane hydroisomerization than did the corresponding catalyst prepared using a variable pH method. This was because more Brnsted acid sites were generated on the former catalyst in the presence of H2.Figure optionsDownload full-size imageDownload as PowerPoint slide