Vapor phase deoxygenation of heptanoic acid over silica-supported palladium and palladium-tin catalysts

Abstract

Silica-supported Pd and PdSn catalysts were prepared by ion exchange or incipient wetness impregnation and characterized with H 2 chemisorption, X-ray diffraction, in situ Sn K-edge X-ray absorption near edge structure (XANES), and transmission electron microscopy. The activity of the catalysts was evaluated in the deoxygenation of vapor-phase heptanoic acid at 0.1 MPa and 573 K. A Pd catalyst synthesized via ion exchange formed nanoparticles of 1.1 ± 0.4 nm and was more stable in heptanoic acid conversion compared to a Pd catalyst synthesized via incipient wetness impregnation having nanoparticles of 2.4 ± 0.5 nm. The addition of Sn to a Pd catalyst by either co-impregnation of precursors or physical mixing of supported monometallic catalysts improved the overall catalyst stability. Moreover, Sn addition expanded the reaction network from primarily decarbonylation over Pd to include dehydration and decarboxylative ketonization over PdSn. Electron microscopy confirmed the physical migration of Sn during catalytic reaction. In situ XANES analysis during the deoxygenation of a carboxylic acid suggests that partially reduced SnO x is the active Sn phase associated with Pd nanoparticles under reaction conditions.

Atomically Dispersed Co and Cu on N-Doped Carbon for Reactions Involving C–H Activation

“…As references, supported Co (5 wt %) and Cu (1.5 wt %) nanoparticles were prepared by incipient-wetness impregnation using an aqueous solution of Co­(NO 3 ) 2 ·6H 2 O or Cu­(NO 3 ) 2 ·3H 2 O as the metal precursor and silica, carbon black, or N-C as the support. After impregnation, the Co precursors on carbon or N-doped carbon were decomposed by thermal treatment in a flow of N 2 (100 cm 3 min –1 ) at 973 K. The C or N-C-supported Cu nanoparticles were prepared by reduction of the impregnated Cu­(NO 3 ) 2 under a flow of H 2 at 623 K. The nanoparticles on Co/SiO 2 were prepared by reduction of the impregnated support under a flow of H 2 at 923 K. Nitrogen-doped carbon layers were subsequently added to carbon-supported Co and Cu nanoparticles by a modified pyrolysis method using 4-aminoantipyrine as the N-C precursor. , Additionally, a well-dispersed nominal 2.5 wt % Co/SiO 2 catalyst (denoted as CoO x -SiO 2 ) was synthesized by an ion exchange method as described elsewhere. , Briefly, 4.875 g of acid-washed silica was dispersed in 98 cm 3 of DI water under vigorous stirring and then the mixture was heated to 373 K. A solution containing 0.573 g of Co­(NH 3 ) 6 Cl 3 , 2.765 cm 3 of aqueous ammonia, and 104 cm 3 of DI water was added dropwise over 10 min to the SiO 2 slurry, followed by stirring at 373 K for 1 h. Afterward, the mixture was cooled to room temperature, washed in DI water, dried, and calcined in air (100 cm 3 min –1 ) at 573 K for 2 h after heating with a 1 K min –1 ramp rate. As references, commercial carbon-supported 3 wt % Pt nanoparticles (Pt/C) (from Sigma-Aldrich) with a surface Pt fraction of 0.59 were evaluated in the alcohol oxidation reaction, and silica-supported Pt nanoparticles (Pt/SiO 2 ) were prepared by incipient-wetness impregnation (details described elsewhere) with a surface Pt fraction of 0.40 and evaluated in the propane dehydrogenation reaction.…”

“…46,47 Additionally, a well-dispersed nominal 2.5 wt % Co/SiO 2 catalyst (denoted as CoO x -SiO 2 ) was synthesized by an ion exchange method as described elsewhere. 48,49 Briefly, 4.875 g of acid-washed silica was dispersed in 98 cm 3 of DI water under vigorous stirring and then the mixture was heated to 373 K. A solution containing 0.573 g of Co(NH 3 ) 6 Cl 3 , 2.765 cm 3 of aqueous ammonia, and 104 cm 3 of DI water was added dropwise over 10 min to the SiO 2 slurry, followed by stirring at 373 K for 1 h. Afterward, the mixture was cooled to room temperature, washed in DI water, dried, and calcined in air (100 cm 3 min −1 ) at 573 K for 2 h after heating with a 1 K min −1 ramp rate. As references, commercial carbon-supported 3 wt % Pt nanoparticles (Pt/C) (from Sigma-Aldrich) with a surface Pt fraction of 0.59 50 were evaluated in the alcohol oxidation reaction, and silica-supported Pt nanoparticles (Pt/SiO 2 ) were prepared by incipient-wetness impregnation (details described elsewhere 51 ) with a surface Pt fraction of 0.40 and evaluated in the propane dehydrogenation reaction.…”

Mechanistic Studies of Single-Step Styrene Production Catalyzed by Rh Complexes with Diimine Ligands: An Evaluation of the Role of Ligands and Induction Period

“…Silica-supported Rh nanoparticle catalysts were prepared via an ion exchange of the Rh precursor using Davisil 636 silica (Sigma-Aldrich) as a support. , For example, the rhodium­(III) chloride hydrate precursor (0.250 g, 99%, Sigma-Aldrich) was dissolved in a solution of aqueous ammonia (5.428 cm 3 ammonium hydroxide, ACS plus, Fisher Scientific, in 282 cm 3 distilled deionized water). The metal solution was added dropwise over 10 min to 4.75 g of acid-washed Davisil 636 silica in 114 cm 3 of distilled deionized water at 343 K. The metal salt and silica slurry was stirred for 60 min at 343 K and, then, cooled to room temperature.…”

Hydroprocessing Catalysts Containing Noble Metals: Deactivation, Regeneration, Metals Reclamation, and Environment and Safety

“…The smaller size of Pd particles in Ti−Pd/SiO 2 catalysts compared with the Pd/ SiO 2 catalyst was responsible for better performance of the former. 152 The addition of Sn to Pd/SiO 2 catalyst stabilized the size of Pd particles during the deoxygenation of heptanoic acid at 573 K. 153 The dispersion of Pd on SiO 2 support could be stabilized by the addition of Nb. 132 This was confirmed by the increased activity of PdNb/SiO 2 catalysts during the HDO of DBF (275 °C, 1.5 MPa of H 2 , WHSV = 0.8 h −1 ).…”