Selective Hydrogenation of 2-Methyl-3-butyn-2-ol Over Supported Cu Nanocatalysts

Nanosized copper is an interesting alternative to noble metal-based catalysts in gas phase selective hydrogenation, but little is known about its performance in liquid phase catalysis. We investigated the activity and selectivity of 2 and 7 nm Cu on SiO₂ catalysts for the three-phase partial hydrogenation of 2-methyl-3-butyn-2-ol, a highly relevant reaction for fine chemical synthesis. Next to the desired 2-methyl-3-buten-2-ol, also 2-methyl-2-butanol was formed as a result of over-hydrogenation. The 7 nm Cu nanoparticles were intrinsically 2.5 times more active than 2 nm Cu (in terms of turnover frequency), and they were also more selective. At 180 °C the selectivity was only 15 % at 50 % conversion, but lowering the reaction temperature to 160 and 140 °C led to 80 % and even ~100 % selectivity (at 50 % conversion). The unselective step was around two times faster than the selective one, hence the high selectivity is due the stronger adsorption of the reactant than of the desired product, which limits over-hydrogenation.