Synthesis of Al-containing Sn-beta with tunable brønsted and lewis acidity for conversion of glucose to 5-hydroxymethylfurfural

Abstract

Sn–Al-Beta zeolites with less silanol defects were synthesized in fluoride media. The effects of the amount of organic template (tetraethylammonium hydroxide, TEAOH), mineralizer (NH4F), Al and Sn on the synthesis, acidity and catalytic performance were systematically studied. The synthesized Sn–Al-Beta zeolites were characterized by XRD, SEM, 27Al MAS NMR, UV–vis DRS and FT-IR spectroscopy of hydroxy region and pyridine adsorption. The optimum values of nTEAOH/nSi and nF-/nSi were same (0.3) for synthesizing Sn–Al-Beta with high crystallinity at 140 °C for 7 d. Moreover, decreasing nF-/nSi facilitated the incorporation of Al into the framework. The crystallization rate of Sn–Al-Beta is similar with that of Sn-Beta. Sn was promoted to enter the framework with the increase of Al content, while elevating Sn content has no effect on the incorporation of Al into the framework. The catalytic performance of Sn–Al-Beta was investigated for conversion of glucose to 5-hydroxymethylfurfural in water-containing solvent. Sn–Al-Beta synthesized in fluoride media is more stable than the post-synthesized sample.