Catalytic Acetylation of Aromatics with Metal Chlorides and Solid Acids − a Comparative Study

Evaluation of catalytic performances of selected metal chlorides such as AlCl 3 , SnCl 4 , ZnCl 2 , FeCl 3 , InCl 3 and GaCl 3 with solid acids such as sulfated zirconia, and zeolite beta was accomplished for acetylation of anisole, toluene and naphthalene. Presence of super acidity (Lewis or Bronsted acid) is found to be indispensable for activation of substrates towards acetylation reactions. In addition, presence of redox centers would further complement with the Lewis acid sites rendering catalytic stamina against deactivation. Strength of Lewis acid basically determines the activity of the metal chlorides towards acetylation. Among the Lewis acids investigated, FeCl 3 , InCl 3 and GaCl 3 exhibit their catalytic behaviour mostly through redox property as is evident from the conservation of Turn over number even after first cycle. Sulfated zirconia surpasses all the acid catalysts including metal chlorides and exhibits extended catalytic activity in acetylation of anisole. The pre-eminence of sulphated zirconia over other catalytic systems is owing to the synergistic effect of Lewis and Bronsted acidity.

对选定的金属氯化物（如AlCl₃、SnCl₄、ZnCl₂、FeCl₃、InCl₃和GaCl₃）与固体酸（如硫酸化氧化锆和β沸石）在苯甲醚、甲苯和萘的乙酰化反应中的催化性能进行了评估。发现超强酸性（路易斯酸或布朗斯特酸）的存在对于底物在乙酰化反应中的活化是必不可少的。此外，氧化还原中心的存在将进一步与路易斯酸位点相互补充，从而使催化剂具有抗失活的能力。路易斯酸的强度基本上决定了金属氯化物在乙酰化反应中的活性。在所研究的路易斯酸中，FeCl₃、InCl₃和GaCl₃主要通过氧化还原性质表现出其催化行为，从即使在第一个循环后周转数仍保持不变就可以明显看出这一点。硫酸化氧化锆优于包括金属氯化物在内的所有酸性催化剂，并且在苯甲醚的乙酰化反应中表现出持久的催化活性。硫酸化氧化锆优于其他催化体系是由于路易斯酸和布朗斯特酸的协同作用。