Continuous 2-Methyl-3-butyn-2-ol Selective Hydrogenation on Pd/γ-Al2O3 as a Green Pathway of Vitamin A Precursor Synthesis

Abstract

In this work, the effect of pretreatment conditions (10% H2/Ar flow rate 25 mL/min and 400 °C, 3 h or 600 °C, 17 h) on the catalytic performance of 1 wt.% Pd/γ-Al2O3 has been evaluated for hydrogenation of 2-methyl-3-butyn-2-ol in continuous-flow mode. Two palladium catalysts have been tested under different conditions of pressure and temperature and characterized using various physicochemical techniques. The catalytic performance of red(400 °C)-Pd/γ-Al2O3 and red(600 °C)-Pd/γ-Al2O3 are affected by the coexistence of several related factors like the competition between PdH and PdCx formation during the reaction, structure sensitivity, hydrogen spillover to the alumina support and presence or absence of Pd–Al species. High-temperature reduction leads to formation of Pd–Al species in addition to pure Pd. The Pd–Al species which reveal unique electronic properties by decreasing the Pdδ− surface concentration via electron transfer from Pd to Al, leading to a weaker Pd–Alkyl bonding, additionally assisted by the hydrogen spillover, are the sites of improved semi-hydrogenation of 2-methyl-3-butyn-2-ol towards 2-methyl-3-buten-2-ol (97%)—an important intermediate for vitamin A synthesis.

Designing a Green Replacement for the Lindlar Catalyst for Alkyne Semi-hydrogenation Using Silica-Supported Nickel Nanoparticles Modified by N-Doped Carbon

“…Many of these materials are composed of supported nanoparticles modified by nitrogen-doped carbon, which is known to anchor the metal onto the support. , A prominent strategy has been developed to form the nitrogen-doped carbon layer via pyrolysis of metal salts complexed with nitrogen-containing ligands supported on a porous material (Scheme ). , Catalysts prepared via this method have been applied to many reactions including the hydrogenation of nitroarenes, − nitriles, , and heterocycles. ,, This and similar methods have been employed to prepare catalysts for the semi-hydrogenation of alkynes using cobalt, copper, nickel, − and even transition metal-free ones. − However, these systems are generally only applicable for simple alkynes, with precursors for fine products and vitamins normally limited to palladium or other precious metal-based catalysts. ,,, It is therefore of significant interest to develop non-noble metal catalysts for the preparation of vitamins and fine chemicals.…”

“…53−55 However, these systems are generally only applicable for simple alkynes, with precursors for fine products and vitamins normally limited to palladium or other precious metal-based catalysts. 1,2,13,56 It is therefore of significant interest to develop non-noble metal catalysts for the preparation of vitamins and fine chemicals.…”

The development of a lead-free replacement for the Lindlar catalyst for alkyne semi-hydrogenation using silica supported, N-doped carbon modified cobalt nanoparticles

“…[56][57][58] However, these non-noble metal catalyst systems are mainly applicable to simple alkynes, with catalysts for vitamins and more diverse fine chemicals limited to precious metals. 2,3,16,20,59 Recently, our group developed a nickel nanoparticle catalyst supported on silica which allowed hydrogenation of vitamin E precursors at 5 bar H 2 and 100 °C with good selectivity. 60 Unfortunately, the activity of this catalyst material significantly decreased upon re-use.…”

Unraveling the Role of Interfacial Water Structure in Electrochemical Semihydrogenation of Alkynes

“…As illustrated in Figure S7, the ECSH of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-butene-2-ol (MBE) is selected as a model reaction at the cathode while the selective oxidation of anisyl alcohol to value-added anisaldehyde is paired at the anode. MBE is an important intermediate for producing fine chemicals such as Vitamin A and pseudoionone. , In contrast to the sluggish oxygen evolution reaction (OER), the oxidation of anisyl alcohol at the anode is kinetically faster, accelerating the semihydrogenation at the cathode (Figure S8). The products from the cathode are determined by gas chromatography (GC) and quantified using calibration curves (Figure S9).…”

“…MBE is an important intermediate for producing fine chemicals such as Vitamin A and pseudoionone. 19,20 In contrast to the sluggish oxygen evolution reaction (OER), the oxidation of anisyl alcohol at the anode is kinetically faster, accelerating the semihydrogenation at the cathode (Figure S8). 21 The products from the cathode are determined by gas chromatography (GC) and quantified using calibration curves (Figure S9).…”