In situ inhibitor (HCl) removal promoted heterogeneous Friedel–Crafts reaction of polystyrene microsphere with Lewis acids catalysts

Friedel–Crafts (FC) acylation is regarded as one of the key routes for graft substitution reaction. In this study, by-product HCl formed in the FC reaction has a major drawback inhibitory effect on the Lewis acid catalysts’ activity, and therefore reduces the FC reaction yield. With the need for more environmentally and economically benign processes, in situ inhibitor removal approach can be applied as a new strategy on one pot heterogeneous FC acylation. The inhibitor can be taken away from the vicinity of the catalysts as soon as it is formed. The chlorine weight percentage after FC acylation on polystyrene (PSt) microspheres under mild reaction conditions can be enhanced from 3.2% to 4.0% in acetone, from 2.9% to 3.6% in methanol, and from 4.4% to 5.3% in chloroform, respectively. It is important to note that the key feature of this reaction is operational simplicity and high yield.

With the need for more catalyst activity and economically benign processes, in situ mineral acid removal can avoid direct contact between by-product and Lewis-acids in liquid environment, and increase the yield of a given catalysis process by overcoming inhibitory or toxic effects of by-product to allow continuous formation at maximal production level.Figure optionsDownload high-quality image (151 K)Download as PowerPoint slideHighlights
► Acid proton inhibited the heterogeneous Friedel–Crafts reaction.
► Remove the by-product from the vicinity of the catalysts as soon as it was formed.
► The process efficiency of the catalysis reaction was improved.