2,6-二甲基苯酚催化胺化过程Pd/γ-Al_2O_3催化剂的失活和改性

The Deactivation and Modification of Pd/γ-Al_2O_3 Catalyst for Catalytic Amination of 2,6-Dimethylphenol

采用固定床反应器,研究了Pd/γ-Al2O3催化剂在催化2,6-二甲基苯酚气相胺化合成2,6-二甲基苯胺反应中的稳定性,实验结果发现该催化剂较易失活。采用BET、XPS、TG、TEM和IR手段对失活前后的Pd/γ-Al2O3催化剂进行了表征分析,并采用BaO对Pd/γ-Al2O3进行改性。结果表明,Pd/γ-Al2O3催化剂失活的原因主要是反应过程生成的胺类化合物吸附在γ-Al2O3载体的酸性中心产生积炭沉积所致。Pd/γ-Al2O3催化剂添加BaO,生成了铝钡尖晶石结构,有效地减少了Pd/γ-Al2O3的酸性,加快了反应中生成的2,6-二甲基环己胺和2,6-二甲基苯胺的脱附,有效地避免了催化剂因积炭失活,提高了催化剂的稳定性。

The catalytic performance of Pd/γ-Al2O3 in gas-phase amination of 2,6-dimethylphenol to 2,6-dimethylaniline was investigated in fixed-bed reactor,and the deactivation of Pd/γ-Al2O3 was observed.The fresh and deactivated Pd/γ-Al2O3 catalysts were characterized by BET,XPS,TG,TEM and IR.It was found that carbon deposition was responsible for the deactivation of Pd/γ-Al2O3,which was formed when amino compounds were adsorbed on the acid sites of γ-Al2O3 support.Additionally,when Pd/γ-Al2O3 was doped BaO,the spinel BaAl2O4 was generated,then the acid capacity of Pd/γ-Al2O3 was significantly decreased,which accelerated the desorption of amino compounds from Pd/γ-Al2O3 and inhibited the formation of carbon deposition,therefore,the stability of Pd/γ-Al2O3-BaO was enhanced.