Synthesis of Sn-Containing Nanosized Beta Zeolite As Efficient Catalyst for Transformation of Glucose to Methyl Lactate

Rapid synthesis of Sn-containing nanosized all-silica Beta zeolite was developed in this work. The method employed all-silica Beta (Si-Beta) as parent, which was crystallized in several hours by the hydrothermal method, and incorporated Sn to Si-Beta through grinding with SnCl 4 ·5H 2 O and subsequent calcination procedure. The prepared Sn-Beta zeolites were analyzed by several methods including XRD, SEM, N 2 physisorption, FT-IR spectroscopy of deuterated acetonitrile and pyridine adsorption, UV–vis DR, and XPS. The mechanism of incorporation of Sn sites into the framework of zeolite was revealed. The results show that the successful incorporation of Sn sites strongly depends on the crystallinity of the parent Si-Beta. Si-Beta with lower crystallinity (<90%) had a considerable amount of silanols which provided sites for Sn incorporation into the framework sites. For Si-Beta with higher crystallinity and less silanols, desilication was used to generate more silanols for the incorporation of Sn sites. The prepared Sn-Beta zeolites were effective for the transformation of glucose to methyl lactate (MLA). Its catalytic activity is better than those of Sn-Beta-P prepared by dealumination–stannation of Al-Beta and Sn-Beta-F synthesized through the traditional hydrothermal method. Turnover frequency (TOF) was calculated on the amount of framework Sn sites to measure the intrinsic and initial activity of active Sn sites. TOF values varied in the sequence of nano Sn-Beta ≫ Sn-Beta-F ≫ Sn-Beta-P. The high MLA yield for nano Sn-Beta is due to its higher mesoporosity. The prepared Sn-Beta zeolite was recycled eight times in the transformation of glucose to MLA without any decrease of catalytic activity. Additionally, the effect of potassium salt on the formation of MLA from glucose over Sn-Beta catalyst was studied.