The vapour phase reaction of tert-butylbenzene and tert-butyl acetate over Al-MCM-41 molecular sieves

Hydrothermal synthesized Al-MCM-41 with different Si/Al ratios (30, 54, 78 and 107) were characterized by XRD, ICP-AES, BET, acidity measurement by pyridine adsorbed FT-IR spectroscopy, 29Si and 27Al MAS NMR techniques. The catalytic activity of these materials was tested in the vapour phase alkylation of tert-butylbenzene (TBB) with tert-butyl acetate (TBA) in the temperature range 200–400 °C. The products were found to be 1,4-di-tert-butylbenzene (1,4-DTBB), 1,3-di-tert-butylbenzene (1,3-DTBB), 4-acetyl-tert-butylbenzene (4A-TBB), 3-acetyl-tert-butylbenzene (3A-TBB), 2-acetyl-tert-butylbenzene (2A-TBB) and 2-acetyl-1,4-di-tert-butylbenzene (2A-1,4-DTBB). The selectivity towards 1,3-DTBB increased with increase in temperature, conversely the selectivity of 1,4-DTBB decreased. The selectivity to 4A-TBB, which is higher than that of other compounds, also increased with increase in temperature. The effect of temperature, flow rate and feed ratio was also studied over all the catalysts to arrive optimum conditions for higher conversion with product selectivity. The effect of time-on-stream was studied over all the catalysts and the results are discussed.

tert-Butyl acetate is a novel alkylating agent for tert-butylbenzene in the vapour phase over Al-MCM-41. It also functions as an acylating agent. Para-selective alkylation predominates over others. Brønsted active sites are the active sites for alkylation and defective acid sites aid acylation. In addition to direct alkylation and acylation, isomerization is also observed. Figure optionsDownload as PowerPoint slide