Abstract:

Cordierite honeycomb ceramic (CHC) was modified by high-temperature calcination and hydrofluoric acid instantaneous etching. The framework microstructures and pore surface morphologies before and after treatment were characterized using SEM, XRD and TEM. The effect of ceramic structure on mechanical strength, morphology of carbon nanotubes, and property of complex carrier were studied. Catalytic performance of Pd/CNTs@CHC-HFn and amount of catalyst on degree of polystyrene hydrogenation were evaluated. High-temperature calcination eliminated internal pores of ceramic framework and ceramic surface became flat and dense. Instantaneous etching increased surface roughness and facilitated CNT growth on the surface. However, increase of etching cycles reduced mechanical strength of carriers as a result of over-etching into framework and CNT growth inside framework pores. CNTs growing on modified CHC-HFn surface significantly improved homogeneous dispersion of palladium and subsequently enhanced hydrogenation performance. The average particle size of palladium was 3.6 nm in the complex catalyst. At catalyst amount of 3.0 g cat·(g PS)^-1, which contained 0.378 g CNTs and 0.054 g Pd, the degree of hydrogenation for polystyrene to poly(vinylcyclohexane) reached up to 100% in 6 h reaction time.

Key words: cordierite monolith, monolithic catalyst, carbon nanotubes, polystyrene, catalytic hydrogenation

摘要：

通过高温焙烧和氢氟酸瞬间蚀刻修饰堇青石蜂窝陶瓷骨架和孔壁表面结构，采用XRD、SEM、TEM表征修饰前后结构和形貌变化，探究陶瓷结构对机械强度、碳纳米管形貌结构及复合载体性质的影响，考察Pd/CNTs@CHC-HFn催化剂催化聚苯乙烯（PS）加氢性能及催化剂用量与加氢度的关系。结果表明，高温焙烧消除了骨架内部孔道，陶瓷表面变得平整密实；瞬间蚀刻增大了表面粗糙度，易于CNTs在表面生长，但蚀刻次数增加，导致蚀刻由表面向骨架内部侵入、CNTs在骨架内部生长，降低载体的机械强度。CNTs@CHC-HFn载体表面的CNTs可显著提高复合催化剂的加氢性能，其中加氢活性位Pd分布均匀，平均粒径为3.6 nm，当催化剂用量为3.0 g cat·（g PS）^-1时，其中含0.378 g CNTs和0.054 g Pd，反应6 h加氢度可达100%。

关键词: 堇青石陶瓷, 整体式催化剂, 碳纳米管, 聚苯乙烯, 催化加氢