Abstract
Novel heterogeneous catalysts are needed to selectively anchor metal nanoparticles (NPs) into the internal space of carbon nanotubes (CNTs). Here, supercritical CO2 (SC-CO2) was used to fabricate the Ru@CNT composite microsponge via impregnation. Under SC-CO2 conditions, the highly dispersive Ru NPs, with a uniform diameter of 3 nm, were anchored exclusively into the internal space of CNTs. The CNTs are assembled into a microsponge composite. The supercritical temperature for catalyst preparation, catalytic hydrogenation temperature, and time all have a significant impact on the catalytic activity of Ru@CNTs. The best catalytic activity was obtained at 100 °C and 8.0 MPa: this gave excellent selectivity in the hydrogenation of p-chloronitrobenzene at 100 °C. This assembly strategy assisted by SC-CO2 will be promising for the fabrication of advanced carbon composite powder materials.
Highlights
Received: 7 January 2022Organic nanotubes open intriguing possibilities to introduce other matter into the cavities, which may lead to nanocomposite materials with interesting properties or behavior different from the bulk [1,2,3]
An average internal diameter of 5–10 nm was observed for carbon nanotubes (CNTs)
The average particle size of Ru NPs prepared in supercritical CO2 (SC-CO2) is concentrated at about 3 nm
Summary
Organic nanotubes open intriguing possibilities to introduce other matter into the cavities, which may lead to nanocomposite materials with interesting properties or behavior different from the bulk [1,2,3]. Many advanced powder materials and other components can be designed via assembly of CNTs [21,22,23]. CNTs have been used for the first time to support ruthenium NPs for the hydrogenation of p-chloronitrobenzene (p-CNB) to selectively produce p-chloroaniline, which is one order of magnitude higher than a commercial Ru/Al2 O3 catalyst [24]. The high surface tension of the immersion medium prevents the catalyst components from entering into the internal surface of the CNTs. some new strategies must be explored. The SC-CO2 fluid-assisted method may be developed into an effective strategy for facile construction of advanced powder materials. The Ru@CNT microsponge was used as a catalyst for the selective hydrogenation of p-CNB with high catalytic activity and selectivity. The Ru@CNT microsponge is an excellent heterogeneous powder catalyst and can be separated from reaction mixtures. The SC-CO2 may be a superior reaction medium for high-performance catalyst preparation
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