(769e) Tuning Acidity of Mesoporous Silicates with Earth-Abundant Metals and Beneficial Effects during Catalytic Dehydration of Linear Alcohols

Catalytic dehydration of biomass-derived alcohols is capable of providing new olefin sources for the chemical industry. Recently, Hensley et al. reported production of an ethanol-rich mixed alcohol stream from bio-syngas as an alternative to conventional biological pathways.¹ A suitable dehydration catalyst with tunable acidity and pore size is desirable to produce olefins from such bio-alcohol streams. We synthesized metal-incorporated mesoporous silicates Zr-KIT-6 which exhibited mainly Lewis acidity and were fairly active in catalyzing ethanol dehydrations. However, comparative studies showed that while Zr-KIT-6 materials are highly selective for olefin production, they are much less active than catalysts that exhibit predominantly Brønsted acidity, such as H-ZSM-5.² Therefore we explored the addition of alternative metal Nb as well as co-addition of Zr and Nb into KIT-6 framework in an effort to enhance/tune the acidity and thereby the activity of the catalysts. While Nb-KIT-6 exhibits good activity at 350 °C, the selectivity for ethylene is fairly low compared to Zr-KIT-6², γ-alumina³ or HZSM-5². Kinetic study on Nb-KIT-6 showed higher activation energy for ethylene production of (169.3 ± 6.7) kJ/mol, than the values of (79 ± 1) kJ/mol on Zr-KIT-6 and 95.6 kJ/mol on γ-alumina. These results along with those obtained with bimetallic mesoporous silicates, some of which exhibit remarkable synergy in intensifying the olefin yield, will be presented.

1. Hensley JE, Lovestead TM, Christensen E, Dutta A, Bruno TJ, McCormick R. Compositional Analysis and Advanced Distillation Curve for Mixed Alcohols Produced via Syngas on a K-CoMoSx Catalyst. Energy & Fuels. June 20, 2013 2013;27:3246-3260.

2. Nash CP, Ramanathan A, Ruddy DA, et al. Mixed alcohol dehydration over Brønsted and Lewis acidic catalysts. Applied Catalysis A: General. January 25, 2016 2016;510:110-124.

3. DeWilde JF, Chiang H, Hickman DA, Ho CR, Bhan A. Kinetics and Mechanism of Ethanol Dehydration on γ-Al2O3: The Critical Role of Dimer Inhibition. ACS Catalysis. April 5, 2013 2013;3:798-807.