Etherification of glycerol and isobutylene catalyzed over rare earth modified Hβ-zeolite

Rare earth (RE) modified Hβ-zeolites were prepared by ion exchange with various rare earth cations (La3 +, Ce3 +, Nd3 + and Eu3 +), and investigated for the etherification of glycerol with isobutylene to synthesize glycerol ethers. XRD, EDS, BET and NH3-TPD analysis methods had been used to characterize these catalysts. The analytic results indicate that the surface strong acidity was enhanced by RE-ion exchange while the framework structure of Hβ-zeolites was slightly changed. Among all modified Hβ-zeolites, Nd/Hβ-zeolite had the highest quantity of Brönsted acid sites which would be helpful for etherification, and exhibited the best catalytic performance. Under the optimal reaction conditions of isobutylene to glycerol of 3:1, a catalyst-to-glycerol mass ratio of 6 wt.%, a reaction temperature of 343 K, and a reaction time of 2 h, 92% glycerol was transformed into a mixture of glycerol ethers including mono-tert-butyl ethers of glycerol (MTBGs), di-tert-butyl ethers of glycerol (DTBGs) and tri-tert-butyl ether of glycerol (TTBG). The selectivity toward the desired DTBG and TTBG were 65% and 8%, respectively.