Renewable Butene Production through Dehydration Reactions over Nano-HZSM-5/γ-Al2O3 Hybrid Catalysts
Arno de Reviere, Tom Vandevyvere, Maarten K. Sabbe, An Verberckmoes
Abstract
The development of new, improved zeolitic materials is of prime importance to progress heterogeneous catalysis and adsorption technologies. The zeolite HZSM-5 and metal oxide γ-Al2O3 are key materials for processing bio-alcohols, but both have some limitations, i.e., HZSM-5 has a high activity but low catalytic stability, and vice versa for γ-Al2O3. To combine their advantages and suppress their disadvantages, this study reports the synthesis, characterization, and catalytic results of a hybrid nano-HZSM-5/γ-Al2O3 catalyst for the dehydration of n-butanol to butenes. The hybrid catalyst is prepared by the in-situ hydrothermal synthesis of nano-HZSM-5 onto γ-Al2O3. This catalyst combines mesoporosity, related to the γ-Al2O3 support, and microporosity due to the nano-HZSM-5 crystals dispersed on the γ-Al2O3. HZSM-5 and γ-Al2O3 being in one hybrid catalyst leads to a different acid strength distribution and outperforms both single materials as it shows increased activity (compared to γ-Al2O3) and a high selectivity to olefins, even at low conversion and a higher stability (compared to HZSM-5). The hybrid catalyst also outperforms a physical mixture of nano-HZSM-5 and γ-Al2O3, indicating a truly synergistic effect in the hybrid catalyst.