Para-selective ethylation of phenol with diethyl carbonate over mesoporous Al-MCM-41 molecular sieves

Mesoporous aluminosilicate Al-MCM-41 with Si/Al = 33, 52, 75, and 114 were synthesized using cetyltrimethylammonium bromide (CTAB) as the structuring agent. The materials were characterized using several techniques. The mesoporous structure was confirmed by X-ray diffraction (XRD) technique. The surface area, pore size and pore volume were given by BET equation and BJH method using nitrogen sorption technique. Fourier transform-infrared (FT-IR) spectroscopy was used in order to obtain information on incorporated aluminum atoms in the mesoporous structure of Al-MCM-41. Silicon magic angle spin NMR (Si-29-MAS NMR) was used to determine the types of silicon present in the mesoporous material. Aluminum magic angle spin NMR ((29)Ai-MAS NMR) was used to determine the octahedral and tetrahedral coordination present in the Al-MCM-41. Thermogravimetric analysis-differential thermogravimetry (TGA-DTG) was used to determine the thermal stability of the materials. The effect of reaction temperature, WHSV and phenol: diethyl carbonate ratios on the selectivity of p-ethyl phenol were studied. The study of time on stream has been carried out to compare the activity of the catalysts and the results are discussed. The Al-MCM-41 (33) exhibited excellent selectivity for p-ethyl phenol obtained on ethylation of phenol using diethylcarbonate as the ethylating agent. (C) 2004 Elsevier B.V. All rights reserved.