Fabrication of a Monolith Reactor in a Copper Tube by Polymerization of Acetylene for Flow Catalysis

Abstract

Continuous-flow processing is considered as a disruptive technology in the synthesis of active pharmaceutical ingredients and other fine chemicals. However, it remains extremely challenging to immobilize heterogeneous catalysts in the channels of microreactors in a facile and flexible manner. In the present investigation, a polymer monolith coiled copper reactor was fabricated by Cu-catalyzed polymerization of acetylene at atmospheric pressure in the temperature range of 290–370 °C. The polymerization yielded a cotton-like structure of carbonaceous fibers, which were able to assemble by themselves to form a monolith inside the copper tube. The characterization results revealed that unsaturated CC groups, which are favorable for post-surface modification, were present on the carbonaceous fibers. After air oxidation at 160 °C for 10 h, a fraction of the CC groups were converted to CO groups. By strong interaction with CO groups, Pd was immobilized in the polymer monolith by circulating an ethanol solution of palladium acetate through the copper tube. A 1000 mm-long monolith tube reactor with an inner diameter of 2 mm with a Pd loading of 1.15 wt % was fabricated and used in the continuous Suzuki–Miyaura coupling reaction. An ethanol–water (2:1 in volume) solution of iodobenzene (0.0125 M), phenylboronic acid (0.0188 M), and potassium carbonate (0.0250 M) was used as the feed, and the reaction took place at 100 °C and 1.0 MPa. The selectivity to biphenyl was kept at >99% with complete conversion of iodobenzene in a 100 h run.

Continuous conversion of furfural to furfuryl alcohol by transfer hydrogenation catalyzed by copper deposited in a monolith reactor

“…The fibers were in bundles, and were similar to those obtained in the previous investigation. 23 The FT-IR spectra of the carbonaceous fibers before and after air oxidation at various temperatures are shown in Fig. 2.…”

“…2 mm) were optimized. 23 Under the optimal conditions, the polymer monolith reactor was prepared by air oxidation at 335 °C, hydrogen reduction at 350 °C, and growth of carbonaceous fibers by acetylene polymerization at 350 °C. Fig.…”

“…A monolith structure in a copper tube was fabricated by an in situ growth method, and the experimental details are reported in our previous publication. 23 In brief (Scheme 1), a copper tube ( φ 2 mm × 1600 mm) was cleaned with acetone (2 mL min −1 , 10 min) to remove soluble organic pollutants, and then the tube was purged with a nitrogen flow (40 mL min −1 , 20 min). The copper tube was further treated with a 4 mol L −1 hydrochloric acid solution (2 mL min −1 , 10 min) to remove copper oxide in the internal surface, and washed with deionized water until pH = 7 was reached in the effluent.…”

“…In our previous investigation, we developed a facile method of fabricating a monolith reactor by polymerization of acetylene in a copper tube. 23 In this study, carbonaceous fibers (CFs) were treated with air and sulfanilic acid, and Cu species were anchored on the sulphonated surface of the polymer monolith. The prepared Cu/CF-SO 3 H catalytic monolith reactor was investigated for transfer hydrogenation of furfural to furfuryl alcohol under flow conditions.…”