载体的酸处理条件对整体式钌—堇青石催化剂性能的影响

Effect of acid treatment conditions of cordierite support on catalytic performance of Ru/cordierite for ammonia synthesis

研究了堇青石经硝酸处理后对整体式钌基氨合成催化剂性能的影响.利用BET、XRD、X射线荧光半定量分析(XRF)和Boehm滴定等测试手段对酸处理前后的堇青石进行表征,并对催化剂的反应性能进行评价.结果表明:堇青石经硝酸处理后,Mg、A l离子溶出,载体表面酸性增强,并且随着酸处理强度的增加,表面酸性进一步增加,与未经酸处理的堇青石相比,总酸量可以增加一个多数量级.同时,酸处理条件对堇青石的表面织构也有较大的影响,如温和的酸处理条件并不能改变堇青石的孔结构以及比表面积,而苛刻的酸处理条件可以有效地提高堇青石的比表面积、比孔容积,改善堇青石的孔径分布.但是,酸处理并没有改变堇青石载体的物相结构.催化剂的活性随着堇青石载体的酸处理强度的增加而降低,即比表面积越大、表面酸性越强催化剂的活性越低,可见,载体的表面酸性是决定催化剂活性的主要因素.

The effect of cordierite treatment with HNO3 on Ru/cordierite ammonia synthesis catalyst was investigated. The treated cordierite has been studied by BET surface area measurements, XRD, XRF analysis and Boehm titration. The results indicated that Mg, Al ions removed from the cordierite structure with the acid treatment, which increased the acidity of the support, and shows strong acidity with the strong acid treatment. Acid treatment conditions play an important role in the texture of the cordierite support. No changes after treatment under mild conditions （ diluted at room temperature）, but it can obtain a high BET surface area, pore volume, and a suitable pore - size distribution after serious acid treatment. Additionally, peaks have been weakened but no changes for the crystalline phase observed after acid treatment. The activity of the ruthenium catalyst decreased with the strength of the acid treatment conditions, indicating that the acidity strength of the surface of the cordierite support is the primary factor for the catalyst activity.