Simple and rapid hydrogenation of p-nitrophenol with aqueous formic acid in catalytic flow reactors

Abstract

SummaryThe inner surface of a metallic tube (i.d. 0.5 mm) was coated with a palladium (Pd)-based thin metallic layer by flow electroless plating. Simultaneous plating of Pd and silver (Ag) from their electroless-plating solution produced a mixed distributed bimetallic layer. Preferential acid leaching of Ag from the Pd–Ag layer produced a porous Pd surface. Hydrogenation of p-nitrophenol was examined in the presence of formic acid simply by passing the reaction solution through the catalytic tubular reactors. p-Aminophenol was the sole product of hydrogenation. No side reaction occurred. Reaction conversion with respect to p-nitrophenol was dependent on the catalyst layer type, the temperature, pH, amount of formic acid, and the residence time. A porous and oxidized Pd (PdO) surface gave the best reaction conversion among the catalytic reactors examined. p-Nitrophenol was converted quantitatively to p-aminophenol within 15 s of residence time in the porous PdO reactor at 40 °C. Evolution of carbon dioxide (CO2) was observed during the reaction, although hydrogen (H2) was not found in the gas phase. Dehydrogenation of formic acid did not occur to any practical degree in the absence of p-nitrophenol. Consequently, the nitro group was reduced via hydrogen transfer from formic acid to p-nitrophenol and not by hydrogen generated by dehydrogenation of formic acid.

One‐Pot Synthesis of Cobalt‐Doped Pt–Au Alloy Nanoparticles Supported on Ultrathin α‐Co(OH)2 Nanosheets and Their Enhanced Performance in the Reduction of p‐Nitrophenol

“…4‐Aminophenol (4‐AP) is an important intermediate in the fine chemicals industry that is used widely in the preparation of analgesic and antipyretic drugs, dyes, and so on . The synthesis of 4‐AP is usually achieved through the reduction of 4‐NP by NaBH 4 with the help of platinum or palladium catalysts.…”

Managing Hazardous Reactions and Compounds in Process Chemistry

“…As with batch reactions, transfer hydrogenations can be used in flow to avoid the use of hydrogen gas (49,270,271). The reaction can be asymmetric (272).…”

“…In addition to hydrogen, formic acid can be used as the reductant. This approach was used for the reduction of p-nitrophenol with the catalyst plated on the reactor wall (49).…”

A Combined Mechanochemical and Calcination Route to Mixed Cobalt Oxides for the Selective Catalytic Reduction of Nitrophenols

“…To investigate applicability of our catalyst in a flow process [116][117][118][119][120], we simulated a flow reactor with a simple proof-of-concept model. Catalyst Co@350 was loaded onto two 0.22 µm nylon syringe filters; 8 mg in filter (i) and 4 mg in filter (ii), then stacked sequentially ( Figure 8A).…”