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Gas Phase Catalytic Hydrogenation of C4 Alkynols over Pd/Al2O3

Chemical Engineering, School of Engineering and Physical Sciences, Heriot Watt University, Edinburgh EH14 4AS, Scotland, UK
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Catalysts 2019, 9(11), 924; https://doi.org/10.3390/catal9110924
Received: 28 September 2019 / Revised: 28 October 2019 / Accepted: 1 November 2019 / Published: 6 November 2019
(This article belongs to the Special Issue Catalysis by Precious Metals, Past and Future)
Alkenols are commercially important chemicals employed in the pharmaceutical and agro-food industries. The conventional production route via liquid phase (batch) alkynol hydrogenation suffers from the requirement for separation/purification unit operations to extract the target product. We have examined, for the first time, the continuous gas phase hydrogenation (P = 1 atm; T = 373 K) of primary (3-butyn-1-ol), secondary (3-butyn-2-ol) and tertiary (2-methyl-3-butyn-2-ol) C4 alkynols using a 1.2% wt. Pd/Al2O3 catalyst. Post-TPR, the catalyst exhibited a narrow distribution of Pdδ- (based on XPS) nanoparticles in the size range 1-6 nm (mean size = 3 nm from STEM). Hydrogenation of the primary and secondary alkynols was observed to occur in a stepwise fashion (-C≡C- → -C=C- → -C-C-) while alkanol formation via direct -C≡C- → -C-C- bond transformation was in evidence in the conversion of 2-methyl-3-butyn-2-ol. Ketone formation via double bond migration was promoted to a greater extent in the transformation of secondary (vs. primary) alkynol. Hydrogenation rate increased in the order primary < secondary < tertiary. The selectivity and reactivity trends are accounted for in terms of electronic effects. View Full-Text
Keywords: gas phase hydrogenation; alkynols; 3-butyn-1-ol; 3-butyn-2-ol; 2-methyl-3-butyn-2-ol; alkenols; triple bond electron charge; Pd/Al2O3 gas phase hydrogenation; alkynols; 3-butyn-1-ol; 3-butyn-2-ol; 2-methyl-3-butyn-2-ol; alkenols; triple bond electron charge; Pd/Al2O3
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MDPI and ACS Style

González-Fernández, A.; Pischetola, C.; Cárdenas-Lizana, F. Gas Phase Catalytic Hydrogenation of C4 Alkynols over Pd/Al2O3. Catalysts 2019, 9, 924.

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