2,6-二甲基苯酚催化胺化过程Pd/γ-Al2O3催化剂的失活和改性

 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催化剂进行改性。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碳沉积所致。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 Deactivation and Modification of Pd/γ-Al2O3 Catalyst for Catalytic Amination of 2,6-Dimethylphenol

The catalytic performance of Pd/γ-Al₂O₃ in gas-phase amination of 2,6-dimethylphenol to 2,6-dimethylphenylamine was investigated in the 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-Al₂O_{3 ,} 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 ihhibited the formation of carbon deposition, therefore, the stability of Pd/γ-Al₂O₃ -BaO was enhanced.