Structure And Acid Properties Of Phosphate-Modified Mcm-49 Zeolites And Their Catalysis Performance For The Alkylation Of Benzene With Propylene In Liquid

MCM-49 zeolite was synthesized hydrothermally in a 10 L autoclave by dynamic method. The phosphate-modified MCM-49 zeolites were prepared by impregnation. The resulting solids were characterized by different techniques, such as XRD, N-2 adsorption-desorption, NH3-TPD, FTIR and (27)AI NMR. Benzene alkylation with propylene was carried out by using MCM-49 and phosphate-loaded MCM-49 zeolite as the catalysts. Both the amounts of Bronsted and Lewis acid on phosphate-modified MCM-49 were decreased. Al-27 NMR spectrum reveals that the loading of phosphate onto MCM-49 results in a increase of the amounts of extraframework aluminum, and two new signals corresponding to Al(OP)(6) and Al( PO)(4) can be found, respectively. Loading of phosphate onto MCM-49 greatly enhances the selectivity to IPB in benzene alkylation with propylene. The, phosphate-modified MCM-49 catalyst containing 2.0% ( mass fraction) phosphorus, at a reaction temperature of 140 degrees C, exhibits 81.1% selectivity to IPB and 97.2% selectivity-to all alkyaltion products(including IPB, DIPBs and TIPB) with a similar conversion of propylene in comparision with MCM-49.