Abstract:

Molecular sieve catalysts with different pore structures and acidity were prepared by acid pickling and alkali washing modification of β-molecular sieve with n(Si)：n(Al)=15：1. The structure, properties, and the application of β-molecular sieve catalysts in alkylation of benzene were investigated by scanning electron microscopy(SEM), X-ray diffraction(XRD), N₂ adsorption-desorption, NH₃-TPD(temperature programmed desorption) and Py-FTIR(Fourier transform infrared spectroscopy). The results show that hydrochloric acid leaching can enlarge the pore size, specific surface area and pore volume of β-molecular sieve, but weaken the acidity, while the sodium hydroxide solution leaching results in the collapse of molecular sieve skeleton, leading to the destruction of the acidity and the pore structure. Modification by urea not only improves the pore structure of molecular sieve, but also has little effect on the acidity of molecular sieve. It is a mild and effective way to modify the molecular sieve. β-molecular sieve catalyst modified with urea has the best activity in alkylation of benzene with coal-based cold trap oil:the conversion of olefin is 91.2%, and the selectivities of 2-HAB(heavy alkylbenzene) and 3-HAB isomers are 50.1% and 33.55%, respectively, accounting for 84% of the total alkylation product.

Key words: β-molecular sieve;, coal-based cold trap oil, alkylation reaction, urea