Gas Phase Catalytic Hydrogenation of C4 Alkynols over Pd/Al2O3

Abstract

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.

Gas-Phase Catalytic Hydrogenation/Isomerization in the Transformation of 3-Butyn-2-ol over Pd-Ni/Al2O3

“…4,5 We have recently reported the formation of 2-butanol and 2-butanone as by-products in the continuous hydrogenation of 3-butyn-2-ol over a commercial Pd/Al 2 O 3 catalyst. 6 Four possible reaction pathways are associated with the hydrogenation of 3-butyn-2-ol, 4 as shown in Figure 1. Path A involves partial hydrogenation to the target product, 3-buten-2-ol.…”

“…The existing literature on alkynol hydrogenation has focused on tertiary alkynols, notably 2-methyl-3-butyn-2-ol . The only reported transformation of secondary alkynols involved liquid-phase conversion of 3-butyn-2-ol using Pd/Al 2 O 3 in pressurized (oscillatory baffled vs stirred tank) reactors. , We have recently reported the formation of 2-butanol and 2-butanone as by-products in the continuous hydrogenation of 3-butyn-2-ol over a commercial Pd/Al 2 O 3 catalyst . Four possible reaction pathways are associated with the hydrogenation of 3-butyn-2-ol, as shown in Figure .…”

Acidic Electrocatalytic Semihydrogenation of Alkynols to Alkenols on Copper Phosphide at Industrial‐Level Current Density

“…[ 11 ] In order to improve the alkynol conversion and alkenol selectivity, elevated temperatures (50—160 °C) are essential. [ 12‐13 ] Although the hydrogenation of several alkynols proceeds at room temperature, a long reaction time (>5 h) is necessary to achieve high conversion. [ 14 ] In addition, costly noble metal Pd‐based thermocatalysts are indispensable for activating and dissociating H 2 molecules into active H* species, which eventually promote subsequent hydrogenation of alkynols.…”

CuO-Fe2O3 Nanoparticles Supported on SiO2 and Al2O3 for Selective Hydrogenation of 2-Methyl-3-Butyn-2-ol

“…Traditionally, the Lindlar catalyst (5-10% Pd/CaCO 3 inhibited by Pb complexes or quinoline) is highly effective in the selective hydrogenation of unsaturated compounds, however the instability of the CaCO 3 support, the suppression of hydrogenation by an excess of quinoline, and the toxicity of Pb limits its application, especially in view of the concept of "green" chemistry [2,3]. A number of scientific papers published over the last decade have been devoted to the development and research of palladium catalysts for the hydrogenation of acetylene compounds, the study of the influence of the nature of the carrier, the preparation conditions, as well as the study of synergism in bimetallic Pd-Me systems in terms of the catalytic properties [4][5][6][7][8].…”