Fast and continuous synthesis of biobased adipic acid in micropacked-bed reactors

Production of biobased adipic acid through hydrogenation of cis,cis-muconic acid has received worldwide attention, but suffers from low efficiency and high cost caused by utilization of noble metal-based catalysts in organic solvent with low initial concentrations. Herein, we propose a new paradigm to produce biobased adipic acid by development and application of a Ni/Al₂O₃ catalyst system in conjunction with a micropacked-bed reactor. Catalyst screening and effects of reaction conditions have been systematically investigated in a batch reactor, achieving 99.4 % yield using sodium muconate aqueous solution (170 g/L) as the substrate. Furthermore, 99.9 % yield is also obtained with only 110 s residence time and 100 g/L initial concentration. The space-time yield is as high as 21.0 mg/min/mL, which is 2-4 orders of magnitude higher than those of Pd (0.178 mg/min/ml) or Pt (0.0044 mg/min/ml) catalysts. This work may be constructive for efficient production of biobased chemicals in microreactors.