Pumice-Supported Palladium Catalysts: II. Selective Hydrogenation of 1,3-Cyclooctadiene

doi:10.1006/jcat.1994.1328

Journal of Catalysis

Volume 150, Issue 1, November 1994, Pages 127-134

https://doi.org/10.1006/jcat.1994.1328 Get rights and content

Abstract

Two series of pumice-supported palladium catalysts (W and U) have been tested in the liquid-phase selective hydrogenation of 1,3-cyclooctadiene (1,3-COD) to cyclooctene (COE). The two series of catalysts, obtained via organometallic precursors, differ in the preparation procedure. In the W series the reduced metal derives only from Pd intermediates anchored to pumice; in the U series the metal originates also from unreacted Pd(allyl)₂ species in solution. The U catalysts present agglomerated metal particles. The hydrogenations, free of any diffusion problems, were performed at constant pressure of hydrogen (1 atm). Analysis of the data suggests that the rate-determining step is a surface reaction involving activated 1,3-COD. Selectivity is very high since cyclooctane (COA) is detected only when all 1,3-COD is consumed. The turnover frequencies (TOF₁) of the first semihydrogenation do not change with palladium dispersion, determined from the Porod diameter D_p up to D_x < 35%, but thereafter they slowly decrease. Experimental evidence, such as the absence of oxidation when exposed to air and the negative shift of binding energy of the Pd 3d level in XPS measurements, indicate a different behavior of the present catalysts in comparison with other supported palladium catalysts. These differences are attributed to the presence of alkali metal ions (Na⁺, K⁺) on the pumice surface and are explained on the basis of the change in electron density and/or in the ensemble size of the supported palladium. Several interesting features and differences in activity and selectivity between the two series of catalysts can be accounted for by the presence of agglomerated palladium particles in the U series and are discussed in terms of the evolution of parameters with dispersion.

References (0)

Cited by (52)

Synthesis, characterisation, and catalytic properties of halloysite-supported metal nanoparticles
2019, Materials Research Bulletin
Citation Excerpt :
The production of cyclooctane was linear in all observed cases, the maximum conversion rate observed being 66 μmol hr−1 g-1 with the Pd/HNC catalyst, which was twice the rate observed for the Al2O3- or SiO2-supported systems. These represent some of the highest activities for 1,5-COD hydrogenation by heterogeneous platinum-group catalysts, with the exception of the remarkably high activity of the Pd/pumice catalysts reported by Deganello et al. [36]. Like with 1-octene, some degree of isomerisation was observed during the hydrogenation, with the products at 30 min containing an average of 5.0% 1,5-COD isomers for the Pt catalysts, 6.4% for the Rh catalysts, and a much higher 33.5% for the Pd catalysts.
A facile synthetic method is reported for the immobilisation of metal nanoparticles on halloysite, an aluminosilicate material with a unique nanotubular structure. A one-step colloidal synthesis was developed, from which nine different catalysts were prepared. The materials were tested in three different catalytic hydrogenations, and the halloysite-supported catalysts were found to outperform alumina- or silica-supported catalysts prepared in the same fashion. Electron microscopy showed that the activity was closely linked to the spatial distribution of the supported metal particles, which in turn affected the shapes of certain surface-associated peaks in the infrared and nuclear magnetic resonance spectra. From this data insight is gained into the nature of the interaction between metal nanoparticles and the surfaces of these support materials.
Stereo-selective hydrogenation of 3-hexyne over low-loaded palladium catalysts supported on mesostructured materials
2010, Applied Catalysis A: General
Citation Excerpt :
Several authors [47–52] have reported differences in the specific activity as the particle size decreases or increases, whereas others found the TOF to increase upon increasing metal dispersion [53]. For the hydrogenation of dienes, the specific activity is constant up to certain dispersion value between 20% and 35% depending on the support but then decreases with increasing palladium dispersion [54,55]. This apparent disagreement may be understood by considering that these reactions have been carried out under different experimental conditions.
This paper studies the effect of mesostructured materials in the stereo-selective hydrogenation of 3-hexyne at 298 K and 40 psig pressure of H₂ over Pd-supported catalysts at different substrate:palladium (S:Pd) molar ratios. The catalysts were prepared by impregnation using a toluene solution of Pd(acac)₂ to obtain a metal content close to 1 wt.% over SBA-15 with one-dimensional hexagonal structure, MCM-48 silica with cubic structure and three-dimensional pore system and MSU-γ alumina with a lathlike particle morphology. All the supports were characterised by nitrogen adsorption–desorption isotherms at 77 K, TEM, XRD and H₂ chemisorption and TEM measurements. The reactions were found to be zero order with respect to 3-hexyne concentration. The starting 3-hexyne produces primarily cis-3-hexene, which subsequently is either hydrogenated to hexane or isomerized to trans-3-hexene and 2-hexenes that are found in very small amounts depending on the nature of the support used. Palladium catalysts supported on SBA-15 was the most active and selective catalyst.
Pt catalysts supported on zeolitized-pumice for the selective hydrogenation of campholenic aldehyde: A characterization and kinetic study
2008, Applied Catalysis A: General
A detailed characterization study of Pt catalysts supported on a novel zeolitized-pumice (Z-PM) support is reported. Two catalysts, named Pt(Cl)/Z-PM and Pt(Ac)/Z-PM, prepared by impregnation from H₂PtCl₆ and Pt(acac)₂ as precursors and subsequent reduction under H₂ at 623 K, were investigated in terms of microstructure, chemical and surface properties by using X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS).
Characterization data showed that the microstructural stability of the support was preserved by using Pt(acac)₂ as precursor. It was verified instead that, by using H₂PtCl₆, the microstructure of the support changed during the thermal activation step under hydrogen, favouring a strong interaction between Pt and support as well as the formation of bimetallic Pt–Fe alloys. Moreover, a moderate increase of Pt d-band vacancies with respect to metallic Pt was observed in this catalyst by XPS.
The above catalysts were tested in the selective hydrogenation of campholenic aldehydes to the corresponding unsaturated alcohol, naturanol. In comparison to the Pt(Ac)/Z-PM sample, the ex-chloride Pt(Cl)/Z-PM catalyst showed a higher selectivity to naturanol. This behaviour was interpreted on the basis of the different microstructural and electronic properties as evinced by the characterization data.
Zeolitized-pumice as a new support for hydrogenation catalysts
2008, Catalysis Communications
A zeolitized-pumice (Z-PM), obtained from a pumice mine waste by extraction of most of the silica contained, has been proposed as a new catalyst support. The as prepared Z-PM material was characterized by surface area and porosity measurements, XRD, SEM and TEM-EDX, showing a high content of crystalline zeolite Pc (about 60%) and a higher (33 m²/g) surface area compared to starting pumice.
Pt and Pt–Sn supported on Z-PM were prepared by impregnation and their catalytic properties in the selective hydrogenation of campholenic aldehyde to naturanol investigated in detail. Results highlighted the better performance of Pt and Pt–Sn/Z-PM catalysts in the selective reduction of –CO group in comparison to corresponding silica-supported catalysts.
Stereoselective hydrogenation of phenyl alkyl acetylenes on pillared clays supported palladium catalysts
2005, Journal of Molecular Catalysis A: Chemical
The stereospecific hydrogenation of phenyl alkyl acetylenes at 298 K and atmospheric pressure of hydrogen over Pd supported catalysts has been studied. The catalysts were prepared by impregnation Al-PILC and Ca-Mont with Pd(acac)₂ precursor, with metal content close to 1 wt.%. All the solids were characterised by nitrogen adsorption–desorption isotherms at 77 K, TPR, H₂ and CO chemisorption, XRD and TEM measurements. The reactions were found to be zero order concerning the alkyne concentration. At conversion levels up to 80% (reaction time lower than 90 min), only a limited overhydrogenation occurred. It was found that at higher reactant molecule:Pd atom ratios (R:P = 7000), the activity is approximately half of that obtained at lower R:P (R:P = 3500). The results suggested that the hydrogenation of phenyl alkyl acetylenes to cis-alkene is “structure insensitive”. All catalysts displayed high selectivity to cis-alkene isomer being the 1% Pd/Al-PILC the most active catalyst.
The synthesis of structured Pd/C hydrogenation catalysts by the chemical vapor deposition of Pd(allyl)Cp onto functionalized carbon nanotubes anchored to vapor grown carbon microfibers
2005, Catalysis Today
Vapor grown carbon fibers (VGCF) were prepared by the iron-catalyzed decomposition of methane. The as-grown microfibers were treated by HNO₃, and iron nanoparticles were deposited onto the fiber surface by impregnation. Carbon nanotubes (CNT) were grown homogeneously as branches on the microfiber surface by tuning the process parameters of the methane decomposition. A composite carbon nanotube–carbon microfiber (CNT–VGCF) system was thus obtained and used as support for palladium nanoparticles. Oxygen-containing functional groups were introduced into the CNT–VGCF system by plasma treatment in a fluidized-bed reactor. The Pd/C catalyst was prepared by chemical vapor deposition on the CNT–VGCF support using Pd(allyl)Cp as a precursor (MOCVD) in a fixed-bed reactor. The effects of the surface treatment and the deposition of palladium were investigated by X-ray photoelectron spectroscopy (XPS). Only traces of palladium were detected after deposition on as-grown fibers, whereas a significantly higher concentration was found on plasma-treated fibers. The catalytic activity of the Pd/C catalyst was evaluated by the hydrogenation of cyclooctene in a fixed-bed microreactor under plug-flow conditions. The CNT–VGCF system was found to be a suitable structured support for Pd nanoparticles.

View all citing articles on Scopus

View full text

Regular ArticlePumice-Supported Palladium Catalysts: II. Selective Hydrogenation of 1,3-Cyclooctadiene

Abstract

Regular Article
Pumice-Supported Palladium Catalysts: II. Selective Hydrogenation of 1,3-Cyclooctadiene