Specific catalytic hydrogenation of 2-butyne-1,4-diol to butane-1,4-diol

Butane-1,4-diol (BDO) is a crucial platform compound for producing tetrahydrofuran, γ-butyrolactone, polytetramethylene ether glycol, and polybutylene terephthalate. A novel supported Pd catalyst was prepared, over which 2-butyne-1,4-diol (BYD) can be completely converted to BDO in the yield of 99.8 % in methanol under 3 MPa of H₂ at 35 °C for 80 min. Such mild conditions are far superior to the NVIDTA technology over a rodlike supported nickel under 30 MPa of H₂ at 130–135 °C in industry, so our technology is more practical for industry. The mechanisms for the formation of both BDO and by-products (BPs) were revealed. The type of active hydrogen species generated from H₂ activation has a great influence on the formation of BPs. H^…H transfer plays an essential role in hydrogenating C≡C in BYD to produce BDO, while H⁺ and H^- transfer leads to the generation of the BPs. The BPs from BYD hydrogenation in methanol and ethanol are 2-methoxytetrahydrofuran and 2-hydroxytetrahydrofuran, respectively.