Complex Reactions of Hydration and Etherification of Isobutene over La-Modified β Molecular Sieve

The La/β molecular sieve catalyst was prepared by the ion-exchange method using microwave heating and conventional heating. The catalyst was characterized by infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy. Hydration and etherification reactions of isobutylene with an ethanol-water mixture to produce a fuel mixture were carried out over these catalysts. The effects of the preparation method and La loading on the catalytic performance of La/β catalysts were studied, and the reaction mechanism was proposed. The results indicated that the ion-exchange degree and La loading of the La/β catalyst prepared by the microwave heating method were higher than the one prepared by the conventional heating method, and the ion-exchange time was shorter. The conversion of water and ethanol over the modified La/β molecular sieve catalyst was increased by 10%～20% compared with the unmodified Hβ molecular sieve, and the catalyst activity increased with the La loading. The hydration and the etherification mainly occurred on the external surface of the β molecular sieve catalyst. Bridging Al-OH-Si acid sites, i.e., Brnsted acid sites, were the main active sites, and the carbonium ion was formed during the reaction.