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.
Highlights
Due to increasing environmental awareness, there has been a shift toward bio-based products and the design of sustainable, renewable technologies [1,2,3]
HZSM-5 and γ-Al2 O3 are widely used materials in heterogeneous catalysis and they could be key materials to process bio-derived compounds. To attenuate their disadvantages and combine their advantages, a hybrid catalyst composed of nano-HZSM-5 crystals dispersed on a γ-Al2 O3 surface was in-situ hydrothermally synthesized
Through characterization of the materials, it was found that for the hybrid catalyst, the nanozeolite crystals were dispersed on the alumina surface, while in the physical mixture, there were domains of HZSM-5 and domains of γ-Al2 O3
Summary
Due to increasing environmental awareness, there has been a shift toward bio-based products and the design of sustainable, renewable technologies [1,2,3]. In light of a transition to a more sustainable chemical industry, there has been a lot of interest in the production and use of bio-alcohols [4,5]. Zeolites and γ-Al2 O3 could play a key role in the transition from a fossil-based industry into a renewable industry as they are of the most important materials used in traditional oil processing and heterogeneous catalysis [12,13,14,15]. HZSM-5 is known for its shape selectivity, strong intrinsic acidity [19], and thermal stability, but is prone to coking [22,23]
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