Effect of the conditions for the aqueous-phase hydrogenation of furfural over Pd/C catalysts on the reaction routes

Abstract

It was shown that the conditions for the hydrogenation of furfural in the presence of palladium catalysts based on carbon supports of different nature (carbon nanotubes, CNTs, carbon nanoglobules, CNGs) affect the rate of catalytic conversions and the yield of main products. An increase in temperature from 323 to 473 K leads to an increase in the specific catalytic activity of Pd catalysts by a factor of 5–7. Under mild reaction conditions (323 and 373 K), the main product is furfuryl alcohol. Under more severe reaction conditions (423 and 473 K), the main routes of catalytic transformations are associated with the participation of water. A catalyst supported on CNTs is more selective in the formation of cyclopentanone, whereas the selectivity to 4-oxopentanal and 5-hydroxy-2-pentanone is higher for a catalyst supported on CNGs. It was found that an increase in pressure from 1 to 5 MPa leads to an increase in the specific catalytic activity of Pd catalysts by almost 10 times. In the presence of a catalyst based on CNTs, an increase in pressure leads to a decrease in the yield of 4-oxopentanal and to an increase in the yield of cyclopentanone. In the presence of a catalyst based on CNGs, the main direction of transformations at any pressure is the hydrolytic opening of the furan ring to form 4-oxopentanal and 5-hydroxy-2-pentanone.