Effective NbO_x-Modified Ir/SiO₂ Catalyst for Selective Gas-Phase Hydrogenation of Crotonaldehyde to Crotyl Alcohol

Abstract

NbO x -modified Ir/SiO 2 catalyst (Ir-NbO x /SiO 2 ) showed high activity and selectivity for gas-phase hydrogenation of crotonaldehyde, and Ir-NbO x /SiO 2 with Nb/Ir molar ratio of 0.5 (Ir-NbO x /SiO 2 (Nb/Ir = 0.5)) provided high crotyl alcohol yield of 87%. This is the highest crotyl alcohol yield among those in gas-phase over reported heterogeneous catalysts. The activities (TOF per surface Ir atom) at low conversion level (40%, W/F = 0.37 g cat •h•mol −1 ) and high conversion level (97%, W/F = 2.2 g cat •h•mol −1 ) were calculated to be 0.21 and 0.08 s −1 , which are more than 3 times higher than those over reported heterogeneous catalysts. High activity and high yield are derived from the combination of Ir metal with NbO x species. Based on the spectroscopic and kinetic studies, the high activity and high selectivity are attributed to strong adsorption of crotonaldehyde on NbO x species by the high Lewis acidity, and suppression of over-hydrogenation of the produced crotyl alcohol at high conversion level. It is suggested that the formation of hydride species at the interface between Ir metal and NbO x species can promote the selective hydrogenation considering the reaction order with respect to hydrogen pressure. High yield and high activity of Ir-NbO x /SiO 2 can contribute to energy saving, cost reduction, and waste reduction, which are directly connected to realization of sustainability.

The Catalytic Reduction of Carboxylic Acid Derivatives and CO2 by Metal Nanoparticles on Lewis‐Acidic Supports

“…A plausible mechanism could start with the dissociation of molecular H 2 on the Pt surface, followed by a reaction with the amide, in which the C=O bond is weakened by the Lewis‐acidic site of the support, resulting in the formation of the corresponding amine. These observations clearly indicate that in‐situ FT‐IR spectroscopy may serve as a powerful tool to rationalize and predict the catalytic performance in these reactions …”

Incorporation of Nanostructured ReO3 in Silica Matrix and Their Activity Toward Photodegradation of Blue Methylene

“…If the preparation methods (all in solution) for ReO3 oxides are scarce [4][5][6][7][8][9], more limited are those for the oxides into SiO2, being the only one the core/shell ReO3/SiO2 structures reported by Ghosh et al [8]. In this work we propose the incorporation of ReO3 into sol-gel SiO2 by The broad peak around 2θ = 15°-25° observed in all these nanocomposites is typical of amorphous SiO2 as matrix in metal oxide nanostructured inside [10][11][12][13][14][15][16][17][18][19][20][21][22]. Unfortunately, the diffraction peaks of ReO3 are not clearly observed probably due to their small size, as it will be later confirmed by HR-TEM.…”

Recent Developments of Heterogeneous Catalysts for Selective Hydrogenation of Unsaturated Carbonyl Compounds to Unsaturated Alcohols

“…As for the M M'Ox catalysts, Luo and co-workers found that FeOx-modified Ir/SiO2, (FeOx CrOx)modified Ir/SiO2 and FeOx-modified Ir/BN catalysts showed higher selectivity and yield for crotyl alcohol, and the activity was comparatively high 115) 117) , indicating that FeOx modification is effective for Ir metal species in the selective hydrogenation of the carbonyl groups. Recently, we reported that Ir _ NbOx/SiO2 was an effective heterogeneous catalyst for the gas-phase selective hydrogenation of crotonaldehyde, providing high yield of crotyl alcohol (87 %) with comparatively high activity 77) . In this section, the details of the Ir _ NbOx/SiO2 catalyst are introduced below.…”

“…3, 2019 catalysts in the gas-phase selective hydrogenation of crotonaldehyde as a model reaction are shown in Fig. 4 77) . ReOx, MoOx, FeOx, NbOx and WOx were selected as modifiers because these metal oxides showed high selectivity for crotyl alcohol in the liquid phase selective hydrogenation of crotonaldehyde (Fig.…”

“…The M M'Ox catalyst system forms hydride and proton species from H2 at the interface of the noble metals and metal oxides, so will be applicable to the hydrogenation of unsaturated carbonyl compounds to unsaturated alcohols by selective hydrogenation of the carbonyl groups. Our laboratory reported that Ir _ ReOx/SiO2 75) and Ir _ MoOx/SiO2 76) are effective heterogeneous catalysts for the liquid-phase selective hydrogenation of unsaturated aldehydes, Ir _ NbOx/SiO2 77) is effective for the gas-phase selective hydrogenation of unsaturated aldehydes, and Fe cationmodified Ir/MgO (Ir/MgO Fe(NO3)3) 78) is effective for the selective hydrogenation of unsaturated ketones.…”