硝酸预处理对Pd/C催化剂微观结构的影响

采用不同浓度的硝酸对椰壳活性炭进行预处理,然后以浸渍法制备了精对苯二甲酸精制用Pd/C催化剂。通过SEM、TEM、EDS、XRD及比表面积和孔结构测试等手段,研究了硝酸预处理对Pd/C催化剂微观结构的影响,并探讨了其结构与催化活性的关系。SEM、TEM及孔结构测试的结果表明,适宜浓度(1.2 mol/L)的硝酸预处理可在一定程度上增大活性炭的平均孔径和中孔体积,减小Pd晶粒尺寸,提高Pd在载体上的分散性。EDS表征结果显示,硝酸预处理使催化剂表面新增7.57%(w)的氧元素。XRD表征结果显示,硝酸预处理对催化剂的物相基本无影响。硝酸预处理使活性炭载体表面产生含氧基团,增大载体孔径、中孔体积和有效负载面积,抑制Pd晶粒的增大,促进Pd的分散,从而提高其催化活性。

Influence of HNO3 Pretreatment on Microstructure of Pd/C Catalysts

Pd/C catalysts used in the hydro-purification of terephthalic acid were prepared using the impregnation method based on the active carbon pretreated by HNO3 with different concentration.The effects of HNO3 concentration on the microstructure and the activity of the catalysts were investigated by means of SEM,TEM,EDS,XRD and pore structure test.The relationship between the microstructure and the activity was discussed.The results of the SEM,TEM and pore structure test show that HNO3 with suitable concentration(1.2 mol/L) can increase the average pore diameter and mesopore volume of the active carbon,reduce the Pd particle size and improve the dispersity of Pd particles on the carbon surface.The EDS result indicates that the oxygen element on the catalyst surface increases by 7.57%(w) after the pretreatment with HNO3.The XRD patterns show that HNO3 pretreatment has little effect on the catalyst phase.So,the catalytic activity of Pd/C catalysts is enhanced due to the HNO3pretreatment.