Monday, June 3, 2019: 2:09 PM
Texas Ballroom EF (Grand Hyatt San Antonio)
A gas-phase carbonylation of dimethyl ether (DME) to methyl acetate (MA) on the zeolites has been largely investigated to produce the value-added useful chemical intermediates [1]. Although a lot of solid-acid zeolites such as MFI, BEA, and MOR can be applied for DME carbonylation to produce MA, DME conversion on those solid-acid catalysts was relatively lower and deactivated significantly [2], where DME can be mainly produced by CO and CO2 hydrogenation using bifunctional hybrid Cu-ZnO-Al2O3/zeolites [3,4]. Based on our previous results [5,6], DME carbonylation was investigated by using a lab-made FER with high crystallinity to prohibit the coke depositions effectively for a stable long-term activity in terms of crystallinity and dispersion of active metallic sites on FER-based heterogeneous catalysts. The seed-derived ferrierite (FER@FER) with a high crystallinity was applied for a gas-phase DME carbonylation to methyl acetate (MA), and it was further applied for the direct syngas conversions through CO and (or) CO2 hydrogenation to DME on the bifunctional Cu-ZnO-Al2O3/FER (CZA/FER). The observed higher catalytic activity and stability were mainly attributed to the larger amounts of active Brønsted acid sites with less defected acidic sites of the FER@FER. The typical gas-phase carbonylation reaction of DME to MA was carried out by using the FER zeolite having different Si/Al molar ratios of 10.4 – 12.5 as well as high crystallinity synthesized by using various zeolite seed materials such as the MOR, ZSM-5 and USY. The enhanced crystallinity of the FER prepared by simply using the FER seed (FER@FER) having newly formed mesopore structures was responsible for an increased amount of the active Brønsted acid sites. The highly crystalline FER@FER revealed the suppressed depositions of aromatic coke precursors due to less presence of defect sites. Compared to other zeolite seed-derived FER zeolites, the less amount of defect sites (extra-framework Lewis acidic Al species) on the FER@FER was successfully controlled. The active Brønsted acid sites for DME carbonylation reaction were originated from the preferential formations of the stable tetrahedral Al sites (especially, T2 sites of the Al-O-Si-O-Al framework of FER) on the 8 and 10-membered ring channels of the FER@FER. The FER@FER synthesized with different FER-seed content without using any organic structure-directing agent (OSDA) showed a highly active and stable activity for carbonylation of dimethyl ether (DME) to methyl acetate (MA) at an optimal amount of previously synthesized FER-seed with 15wt%. The FER-seed played an important role to maximize the number of Bronsted acid sites with less coke deposition by concomitant decrease of defect sites through its recrystallization possibly, where the defected Lewis acidic sites on the FER surfaces can be responsible for the preferential coke depositions as well as for the retarded CO insertion rate by preventing the formation of surface acetyl groups. In addition, the selective synthesis of ethanol from syngas through multi-step reactions via methyl acetate (MA) intermediate is possible using a highly crystalline FER and hybridized bifunctional CZA/FER as well. The extent of crystallinity of the FER played a crucial role for catalytic activities of syngas conversion to DME, DME carbonylation to MA as well as MA hydrogenation to ethanol. The CZA/FER can be utilized to convert MA to ethanol with a similar equilibrium yield of ~42 mol%. The highly crystalline of FER@FER, which was synthesized by using a FER seed, showed a higher DME conversion to MA and stability due to the abundant presence of Bronsted acid sites with less defect sites.
References
1 J. Liu, H. Xue, X. Huang, P.H. Wu, S.J. Huang, S.B. Liu, W. Shen, Chin. J. Catal. 31 (2010) 729.
2 A. Bhan, A.D. Allian, G.J. Sunley, D.J. Law, E. Iglesia, J. Am. Chem. Soc. 129 (2007) 4919.
3 J.W. Jung, Y.J. Lee, S.H. Um, P.J. Yoo, D.H. Lee, K.W. Jun, J.W. Bae, Appl. Catal. B: Environ. 126 (2012) 1.
4 H. Ham, J. Kim, S.J. Cho, J.H. Choi, D.J. Moon, J.W. Bae, ACS Catal. 6(9) (2016) 5629.
5 S.Y. Park, C.H. Shin, J.W. Bae, Catal. Commun. 75 (2016) 28.
6 H. Ham, J. Kim, J.H. Lim, W.C. Sung, D.H. Lee, J.W. Bae, Catal. Today 303 (2018) 93.
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