The Effect of Type of Acid Sites in Molecular Sieves on Activity and Selectivity in Acylation Reactions

Abstract

The role of the type of acid site (Broensted vs. Lewis) on the activity and selectivity of molecular sieve catalysts was investigated in ferrocene and toluene acylation. H-, Zn-, Fe-, Al- and La-forms of zeolite Beta, USY and mesoporous molecular sieves (Al)MCM-41, (Al)SBA-15 were tested. It was observed that addition of metal cations acting as Lewis acid sites can increase the acidity of various molecular sieve catalysts. No general relationship between the type of cation and conversion of individual substrate was found. While the highest activity in ferrocene acylation was observed after addition of Zn, in the case of toluene acylation Al-forms of catalysts were the most active. The results indicate that the acid strength of cationic Lewis sites controls their activity in acylation reactions.

Recent Advances in Catalysis Over Mesoporous Molecular Sieves

“…Mesoporous molecular sieves are also active in acylation of ferrocene [81]. (Al)MCM-41 modified with different divalent and trivalent metal cations exhibited conversions of ferrocene in ferrocene acylation with acetic anhydride up to 90% after 5 h of the reaction performed at 140°C.…”

“…This was further documented over (Al)MCM-41 exchanged to Al, Zn, Fe and La forms in toluene acylation with isobutyryl derivatives. Ion-exchanged (Al)MCM-41exhibited a high conversion evidencing the effect of Lewis acidity in acylation reactions [81]. Acylation of nitrobenzene and its derivatives by benzoyl chloride was reported using GaCl x -and GaAlCl x -grafted on mesoporous (Si)MCM-41 showing a nice reusability [82] while anisole was successfully acylated over mesoporous alumina modified with silicotungstic acid [83].…”

Selective Monoacylation of Ferrocene with Bulky Acylating Agents over Mesoporous Sieve AlKIT‐5

“…[22,30] As a continuation of our research, we now turned our attention to acylation of ferrocene with bulky acylating agents that provide useful synthetic intermediates [31] as well as products of interest for further applications. [32] In this study, we describe acylation reactions of ferrocene with 1-adamantoyl chloride (1), benzoyl chloride (2), cinnamoyl chloride (5), 2-chlorobenzoyl chloride (4), or benzoic anhydride (3; Scheme 2) over a new type of advanced catalyst: mesoporous AlKIT-5 sieves with different Si/Al ratios.…”

Acylation of Ferrocene with Adamantoyl Chloride and Cinnamoyl Chloride

“…The replacement of homogeneous catalysts by heterogeneous ones in acylation reactions is rather challenging. The most frequently used heterogeneous catalysts for acylation reactions are zeolites [13][14][15][16][17], mesoporous molecular sieves [18][19][20], clays [7,14], sulfated zirconia [14,21,22], heteropoly acids [14,23,24] and Nafion [14,25]. K10-montmorillonite was active and stable catalyst for acylation of ferrocene but the reaction needed reaction temperature as high as 150°C and reaction time of 24 h [7].…”

“…Conversions of ferrocene were 100% 300 min of the reaction in both cases. On the other hand, ferrocene conversion over Fe-Beta was 78% (0.6 g ferrocene, 1.9 ml acetic anhydride, 8 ml decahydronaphthalene, 0.6 g catalyst, 140°C) [18]. Ferrocene acylation was tested as well as with linear, branched and aromatic anhydrides and chlorides over zeolite Beta.…”