‘‘Hydrogen-Free’’ Hydrogenation of Nitrobenzene Over Cu/SiO2 Via Coupling with 2-Butanol Dehydrogenation

Abstract

The feasibility of a coupled reaction system for the simultaneous production of 2-butanone (from 2-butanol dehydrogenation) and aniline (from nitrobenzene hydrogenation) over Cu/SiO 2 in continuous gas phase operation without an external H 2 supply has been established. Two (15.9 and 1.8 % w/w) Cu/SiO 2 catalysts were prepared by deposition-precipitation and characterised in terms of N 2 physisorption, temperature programmed reduction (TPR), H 2 chemisorption, powder XRD, STEM and XPS analysis. Following TPR, the higher Cu loading showed a wider particle size distribution (1-15 nm, mean 7.8 nm) than 1.8 % w/w Cu/SiO 2 (1-6 nm, mean 3.1 nm), where the latter exhibited a modified electronic character based on XPS measurements and a (fourfold) higher H 2 uptake capacity. The reactions showed antipathetic (dehydrogenation) and sympathetic (hydrogenation) structure sensitivity in terms of turnover frequency (TOF) dependence on Cu size. We have achieved, for the first time, 100 % yield to both target products (2-butanone and aniline) with appreciably (by a factor of 50) enhanced hydrogen utilisation in the coupled system relative to conventional nitrobenzene reduction using pressurised H 2 . Our results establish in situ hydrogen generation via catalytic dehydrogenation as a viable hydrogenation route to commercially important products.

Phenylacetylene hydrogenation coupled with benzyl alcohol dehydrogenation over Cu/CeO2: A consideration of Cu oxidation state

“…This suggests copper nanoparticles >4 nm in the high loading Cu/CeO2 catalysts, in agreement with previous studies [57,58] that have reported Cu nanocrystals of 8-18 nm for oxide (SiO2, Al2O3) supported copper catalysts with similar loading (16-20% wt.) prepared by IM and DP.…”

Structure and Reactivity of Cu-doped Au(111) Surfaces

“…Alloying with other metals such as nickel and palladium have been shown to enhance hydrogenation rates [75,76]. A recent report of supported copper catalysts being used to hydrogenate nitrobenzene using hydrogen supplied by the simultaneous dehydrogenation of 2-butanol [77], points to the possibility of using bimetallic Cu/Au catalysts to carry out similar coupled reactions exploiting the activity of copper for dehydrogenation chemistry and the very high selectivity of gold for a number of important hydrogenation reactions. A key advantage of the use of coupled reactions of this type is that there is no requirement for gas phase H 2 [77].…”

Gas Phase Hydrogenation of Furaldehydes via Coupling with Alcohol Dehydrogenation over Ceria Supported Au-Cu

“…The presence of Au δ − nanoparticles is consistent with the adsorption/activation of the -C=O functionality in HMF via π-back donation [ 32 ]. The XPS spectrum for Au-Cu/CeO 2 over the Cu 2 p region ( Figure 4 (IB)) is characterised by a Cu 2 p 3/2 contribution at BE = 928.7 eV, corresponding to Cu 0 (35%) [ 59 ]. A signal at higher BE (= 932.0 eV) with greater intensity can be linked to the presence of Cu + (65%) [ 59 ].…”

“…The XPS spectrum for Au-Cu/CeO 2 over the Cu 2 p region ( Figure 4 (IB)) is characterised by a Cu 2 p 3/2 contribution at BE = 928.7 eV, corresponding to Cu 0 (35%) [ 59 ]. A signal at higher BE (= 932.0 eV) with greater intensity can be linked to the presence of Cu + (65%) [ 59 ]. The surface composition and oxidation state of copper from XPS measurements is consistent with TPR results.…”