Continuous Hydrogenation of Aqueous Furfural Using a Metal-Supported Activated Carbon Monolith

Abstract

Continuous hydrogenation of aqueous furfural (4.5%) was studied using a monolith form (ACM) of an activated carbon Pd catalyst (∼1.2% Pd). A sequential reaction pathway was observed, with ACM achieving high selectivity and space time yields (STYs) for furfuryl alcohol (∼25%, 60–70 g/L-cat/h, 7–15 1/h liquid hourly space velocity, LHSV), 2-methylfuran (∼25%, 45–50 g/L-cat/h, 7–15 1/h LHSV), and tetrahydrofurfuryl alcohol (∼20–60%, 10–50 g/L-cat/h, <7 1/h LHSV). ACM showed a low loss of activity and metal leaching over the course of the reactions and was not limited by H2 external mass transfer resistance. Acetic acid (1%) did not significantly affect furfural conversion and product yields using ACM, suggesting Pd/ACM’s potential for conversion of crude furfural. Limited metal leaching combined with high metal dispersion and H2 mass transfer rates in the composite carbon catalyst (ACM) provides possible advantages over granular and powdered forms in continuous processing.

Bi-Metal-Supported Activated Carbon Monolith Catalysts for Selective Hydrogenation of Furfural

“…As noted in Figure , our STYs for FA (143 g/Lcat/h or 1089 g/kg-cat/h) and THFA (272 g/Lcat/h or 574 g/kg-cat/h) approach these values, indicating possible industrial viability. It is possible that STYs could be increased by increasing the FUR feed rates and optimizing the H 2 gas and liquid flow rates to generate a Taylor flow in the carbon monoliths (our calculations in the past work under the conditions employed in this work indicate that we were in film flow) . The Taylor flow regime could increase the H 2 mass transfer and allow one to process higher FUR concentrations or feed rates. , …”

“…Each monolith structure has a diameter and length of 1 in, 529 cells/in 2 , a wall thickness of 0.01 in, a cell spacing of 0.0435 in, a geometric surface area of 70.84 in 2 /in 3 , and an open frontal area of 0.593 in 2 . Details on the ACM production procedure and pictures of ACM have been previously published. − Four cores of ACM were loaded into a Parr Packed Bed Reactor System (details have been previously described). − ACM catalysts were reduced for 4 h prior to the reaction in the 100 mL/min flow of pure hydrogen at 250 °C. Next, aqueous FUR hydrogenation reactions were conducted at liquid flow rates of 0.5 to 16 mL/min, temperatures of 120–180 °C, and pressures of atm to 300 psig using a feedstock of 44 g/L FUR (purchased from Sigma-Aldrich, 99%) dissolved in DI water.…”

“…Next, aqueous FUR hydrogenation reactions were conducted at liquid flow rates of 0.5 to 16 mL/min, temperatures of 120–180 °C, and pressures of atm to 300 psig using a feedstock of 44 g/L FUR (purchased from Sigma-Aldrich, 99%) dissolved in DI water. After each reaction, liquid samples were recovered and analyzed by gas chromatography–flame ionization detection (GC–FID) using a method previously described . The concentrations of FUR (99%, Sigma-Aldrich), FA (98%, Sigma-Aldrich), THFA (98%, Sigma-Aldrich), 2MF (99%, Sigma-Aldrich), 2MTHF (99%, Sigma-Aldrich), CP (95%, Sigma-Aldrich), and 5H2P (95%, Sigma-Aldrich) were measured according to a four-point standard curve (each point run in triplicate).…”

“…The temperature of the sample was equilibrated at 40 °C before ramping at a rate of 10 °C/min to 800 °C. Coke was estimated as the difference in weight loss or % mass loss between the spent catalyst and the fresh catalyst measured under the same TGA conditions over the same defined temperature ranges . Elemental analysis of fresh and spent catalysts was performed following the Environmental Protection Agency (EPA) ICP method 200.8.…”

Methods for the Synthesis of γ-Acetopropyl Alcohol

“…Recent study of the kinetics of furfural hydrogenation [ 74 ] showed that ( I ) forms from both ( VII ) and ( II ). Similar palladium catalyst on monolithic active carbon gives up to 10 wt % of (I) in water at 180°С [ 75 ].…”