The influence of the structural and electronic characteristics of palladium on the activity and selectivity of Pd/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Pd-Co/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts for the hydrogenation of acetylene hydrocarbons

The influence of the structural and electronic characteristics of nonpromoted and cobalt-promoted Pd catalysts on their adsorption and catalytic properties is studied. It is shown that the conversion of vinylacetylene depends on the dispersion of palladium for both types of catalysts synthesized from acetate and acetylacetonate complexes. The palladium acetylacetonate catalysts have a higher palladium dispersion than the samples obtained from acetate complex solutions, thus leading to a higher conversion of vinylacetylene. It is established that the selectivity of vinylacetylene conversion into 1,3-butadiene on palladium acetate and acetylacetonate catalysts depends on the state of the 3d orbitals of surface Pd atoms. The palladium acetate catalysts are characterized by a higher electron density on the 3d orbital in comparison with the acetylacetonate samples, thus producing higher selectivities of vinylacetylene conversion into 1,3-butadiene. The introduction of cobalt into Pd/δ-Al₂O₃ catalyst synthesized from acetylacetonate complex leads to the formation of bimetallic Pd-Co particles, in which Pd atoms have higher electron density than those in the nonpromoted Pd/δ-Al₂O₃ catalyst, due probably to the donation of electron density from promoter atoms, with a resulting decline in the adsorption ability of bimetallic particles with regard to 1,3-butadiene and hydrogen. As a consequence, the selectivity of vinylacetylene conversion into 1,3-butadiene increases. Requirements for the size, dispersion, and electronic characteristics of the active component in the catalysts for the selective hydrogenation of vinylacetylene are formulated, and two techniques for their synthesis are proposed.     

The choice of an optimal composition and preparation method of non-promoted Pd/Al2O3 and promoted Pd-Co/Al2O3 catalysts for the selective hydrogenation of vinylacetylene

For the purpose of optimizing the chemical composition and technology of synthesis of the catalyst for the acetylene hydrocarbons hydrogenation in industrial streams of butadiene and ethyl-vinylacetylene fractions, the influence of the palladium initial compound nature, the active component concentration, the promotion by cobalt, the molar ratio of palladium to cobalt, the phase composition of the supporter on physical chemical properties, and the activity and selectivity to 1,3-butadiene of the catalysts was studied. The effect of acidic-base characteristics of the supporter on its ability to oligomerize unsaturated hydracarbons has been investigated. It has been established, than the δ-Al₂O₃ supporter is characterized by a low concentration of Bronsted and Lewis acidic sites, decreasing the quantity of oligomers formed on its surface. The optimal composition of the non-promoted KGV-07 catalyst, recommended for the raw butadiene fraction hydrogenation, is 0.5% of Pd deposited from palladium acetate on δ-Al₂O₃ with palladium particles of 16 nm in size, on which the vinylacetylene conversion of 100% and the selectivity to 1,3-butadiene of 69.9% are reached at a temperature of 20°C at the reactor input, hourly space velocity (HSV) of hydrocarbon raws of 700 h⁻¹, molar ratio of hydrogen to ethyl-vinylacetylenes of 4: 1, summary concentration of 49% of acetylene hydrocarbons, and 1.5% of 1,3-butadiene in hydrocarbon raws. The synthesis of the cobalt-promoted KGVP-07 catalyst with 0.5% of Pd deposited from palladium acetylacetonate on δ-Al₂O₃ and molar ratio of Pd: Co = 1: 1 has been developed for the hydrogenation of an ethyl-vinylacetylene fraction with a concentration of acetylene hydrocarbons to 6 wt %, with the vinylacetylene conversion of 100% and the selectivity to 1,3-butadiene of 61.3%, at HSV of the hydrocarbon stream of 700 h⁻¹, temperature of 6°C at the reactor input, and molar ratio of hydrogen to ethyl-vinylacetylene admixtures of 4: 1. Promotion by cobalt leads to the formation of palladium particles at the zero oxidation level and to an increase in their average size from 11 to 14 nm in comparison with the non-promoted Pd-catalyst. In the work, IR-spectroscopy, transmission electron microscopy (TEM), and physicochemical methods have been used to characterize the catalysts texture and supporter phase composition. Pilot tests of the KGV-07 and KGVP-07 catalysts on the Etilen plant unit have proven the correctness of the choice for the catalysts’ optimal chemical composition.     

Deactivation and coke formation on palladium and platinum catalysts in vegetable oil hydrogenation

Deactivation of palladium and platinum catalysts due to coke formation was studied during hydrogenation of methyl esters of sunflower oil. The supported metal catalysts were prepared by impregnating γ-alumina with either palladium or platinum salts, and by impregnating α-alumina with palladium salt. The catalysts were reused for several batch experiments. The Pd/γ-Al₂O₃ catalyst lost more than 50% of its initial activity after four batch experiments, while the other catalysts did not deactivate. Samples of used catalysts were cleaned from remaining oil by repeated extractions with methanol, and the amount of coke formed on the catalysts was studied by temperature-programmed oxidation. The deactivation of the catalyst is a function of both the metal and the support. The amount of coke increased on the Pd/γ-Al₂O₃ catalyst with repeated use, but the amount of coke remained approximately constant for the Pt/γ-Al₂O₃ catalyst. Virtually no coke was detected on the Pd/α-Al₂O₃ catalyst. The formation of coke on Pd/α-Al₂O₃ may be slower than on the Pd/γ-Al₂O₃ owing to the carrier’s smaller surface area and less acidic character. The absence of deactivation for the Pt/γ-Al₂O₃ catalyst may be explained by slower formation of coke precursors on platinum compared to palladium.     

A Pd–B/γ-Al2O3 amorphous alloy catalyst for hydrogenation of tricyclopentadiene to tetrahydrotricyclopentadiene

A Pd–B/γ-Al₂O₃ amorphous alloy catalyst was prepared by impregnation and chemical reduction with borohydrine aqueous solution. Crystallized Pd–B/γ-Al₂O₃ catalysts were obtained by thermal treatment of the prepared amorphous catalyst at elevated temperatures. For comparison, a conventional H₂-reduced Pd/γ-Al₂O₃ catalyst was also prepared. The catalysts were characterized by ICP, XRD, SEM, TEM, DSC and TPD, and were used for the hydrogenation of tricyclopentadiene. All the catalysts demonstrated similar activities for partial hydrogenation of tricyclopentadiene to dihydrotricyclopentadiene. However, the amorphous alloy catalyst showed significantly higher activity for the further hydrogenation of dihydrotricyclopentadiene to the final product tetrahydrotricyclopentadiene.     

Characterization of supported Pd-Cu bimetallic catalysts by SEM, EDXS, AES and catalytic selectivity measurements

Pd-Cu/γ-Al₂O₃ bimetallic catalysts were prepared according to different impregnation sequences of γ-Al₂O₃ and characterized by XRD, SEM, EDXS and AES. The catalysts were tested for the selective hydrogenation of aqueous nitrate solutions to nitrogen. The reaction selectivity was found to be dependent on the catalyst preparation procedures, which affect the spatial distribution of metallic copper and palladium phases. A catalyst prepared by impregnating γ -Al₂O₃ with copper followed by palladium gives higher selectivity to nitrogen than a catalyst prepared by impregnating the support with palladium followed by copper. The AES examination shows that in the catalyst exhibiting a higher nitrogen production yield, a reaction zone for the liquid-phase nitrate reduction is located in the interior of particles and covered by a layer of Pd atoms. This revised version was published online in July 2006 with corrections to the Cover Date.     

Experimental study on two-stage catalytic hydroprocessing of middle-temperature coal tar to clean liquid fuels

Special Mo–Co/γ-Al₂O₃ and W–Ni/γ-Al₂O₃ catalysts with different metal loadings were prepared applying new synthesis technologies that combine ultrasonic-assisted impregnation and temperature-programming methods. Clean liquid oil was obtained from middle-temperature coal tar via hydrogenation in two-stage fixed beds filled with the laboratory made catalysts. The Mo–Co/γ-Al₂O₃ catalyst with 12.59 wt.% Mo and 3.37 wt.% Co loadings, and the W–Ni/γ-Al₂O₃ catalyst with 15.75 wt.% W and 2.47 wt.% Ni loadings were selected. The effects of pressure and liquid hourly space velocity on hydrogenation performance were investigated while other experimental conditions remained constant. Gasoline (?180 °C) and diesel (180–360 °C) fractions were separated from the oil product and analyzed. The two-stage reacting system was capable of removing nitrogen and sulfur from 1.69 and 0.98 wt.% in the feed to less than 10 ppm and 100 ppm, respectively in the products. The results indicated that the raw coal tar could be considerably upgraded through catalytic hydroprocessing and high-quality fuels were obtained.     

Gas-phase hydrogenation of maleic anhydride to butyric acid over Cu/TiO2/γ-Al2O3 catalyst promoted by Pd

The promoter effect of palladium on the Cu/TiO₂/γ-Al₂O₃ catalyst was investigated for the gas-phase selective hydrogenation of maleic anhydride to butyric acid at atmospheric pressure. The results show that Pd is added rarely into the Cu/TiO₂/γ-Al₂O₃ catalyst for the hydrogenation of maleic anhydride, the higher selectivity to butyric acid can be obtained. In the absence of Pd (or Cu) in the Cu–Pd/TiO₂/γ-Al₂O₃ catalyst, the selectivity to butyric acid (BA) is nearly zero. Using the Cu–Pd/TiO₂/γ-Al₂O₃ (Pd/Cu=3/100 (atom)) catalyst, 56.2% selectivity to BA and 100% conversion of maleic anhydride were obtained at 280 °C.     

Selection of the optimum composition of an alumina support of Pd/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts for pyrolysis gasoline hydrogenation

To optimize the chemical composition of catalysts for the selective hydrogenation of diene and vinyl aromatic hydrocarbons in pyrolysis gasoline, we study the effect of the acid-base and textural characteristics of a support modified with additives of sodium compounds on the activity and stability of the catalysts in reactions of hydrogenation and oligomerization of unsaturated compounds. It is shown that the rate of formation of oligomeric compounds depends on the number of Lewis (Q _CO > 34 kJ/mol) and Brönsted sites (ν_OH = 3688 cm^?1). An increase in their total amount on the catalyst surface leads to an increase in the rate of formation of oligomeric hydrocarbons. The amount of surface condensation products is determined by the concentration of strong aprotic sites with Q _CO > 35 kJ/mol. Alumina support samples with a high surface concentration of medium-strong Lewis sites, wedge-shaped or conical pores, and the preferential distribution of porometric volume in pores with a diameter of 5–15 nm are characterized by a significant ability to oligomerize unsaturated compounds. Catalysts that contain 0.5 wt % Na exhibit the lowest oligomerization ability and a high stabile activity in reactions of hydrogenation of diene and vinyl aromatic hydrocarbons in pyrolysis gasoline. For the selective hydrogenation of diene and vinyl aromatic hydrocarbons in pyrolysis gasoline, we recommend a catalyst with 0.5 wt % Pd supported from palladium acetylacetonate on δ-Al₂O₃ modified with 0.5 wt % sodium; it is characterized by the absence of wedge-shaped or conical pores, the preferential (60.7%) distribution of porometric volume in a range of d _p > 15 nm, and a low aprotic acidity (L = 3.1 μmol/g), which contributes to the decrease in the amount of resulting condensation products (V = 3.6 μg/(gcat h)) and a high stable activity (DN = 0.68 g J₂/100 g) in reactions of hydrogenation of unsaturated compounds.     

Palladium and platinum catalysts supported on carbon nanofiber coated monoliths for low-temperature combustion of BTX

In this work carbon nanofiber (CNF)-coated monoliths with a very thin, homogeneous, consistent and good adhered CNF layer were obtained by means of catalytic decomposition of ethylene on Ni particles.The catalytic behaviour of Pt and Pd supported on the CNF-coated monoliths was studied in the low-temperature catalytic combustion of benzene, toluene and m-xylene (BTX) and compared with the performance of Pt and Pd supported on γ-Al₂O₃ coated monoliths.The catalysts supported on CNF-coated monoliths were the most active, independent of the metal catalyst or the type of the tested aromatic compound. TPD experiments showed that the γ-Al₂O₃ phase retained important amounts of the water molecules produced during the reaction. When water vapour was supplied to the reactant flow, the activity of Pd catalysts decreased much stronger than the Pt ones, and the activity of the Pt catalysts supported on the γ-Al₂O₃ was more affected than that of the catalysts supported on CNF.BTX combustion reactions seem to be catalyzed by Pt and Pd through different kinetic mechanisms, explaining why Pt catalysts always were more active than the Pd ones deposited on the same type of support. Pd catalyzed combustion of benzene is strongly inhibited by oxygen and by water.Catalysts supported on CNF-coated monoliths showed a selectivity to burn benzene better than toluene or m-xylene, attributed to a better aromatic-CNF surface interaction.     

Hydrogen production on Ni–Pd–Ce/γ-Al2O3 catalyst by partial oxidation and steam reforming of hydrocarbons for potential application in fuel cells

A series of catalysts of nickel–palladium–cerium supported upon alumina have been investigated in order to obtain a suitable catalyst that could be used in the process of producing hydrogen for the potential application in fuel cell by partial oxidation and steam reforming (POSR) of mixtures of hydrocarbons. Investigated results showed that little addition of cerium into Ni–Pd catalyst could definitely improve its stability of hydrogen production from mixtures of hydrocarbons by POSR method. The experimental results also showed that the optimum compositions of Ni–Pd–Ce catalyst were the molar ratio of Ni to Pd as 1:0.09 and containing of Ce 0.5 wt%, shortened as Ni–Pd–Ce-0.5 catalyst. XRD results for the typical catalysts showed that it mainly displayed the γ-Al₂O₃ and Ni peaks. SEM and TG results for the fresh and used Ni–Pd–Ce-0.5 catalysts, lasted for 540 h, did not show much difference on their surface patterns and TG curves, respectively. This indicated this catalyst would be a practical catalyst to produce hydrogen from liquid fuel by POSR method for potential application in fuel cells.     

Characterization of Pd/γ-Al2O3 Catalysts Prepared Using [Pd(hfac)2] in Liquid CO2

A series of Pd/γ-Al₂O₃ catalysts was prepared from [Pd(hfac)₂] (hfac = hexafluoroacetylacetonate) in liquid carbon dioxide using the method reported by Kim et al. [Chem Mater 18:4710 (2006)]. The catalysts were characterized using CO pulse chemisorption, diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray absorption fine structure (XAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron microscopy. The catalysts were reduced initially in the high-pressure CO₂ reaction cell using H₂ at 75 °C. Samples were removed, stored in a desiccator, and re-reduced in situ at 250 °C prior to pulse chemisorption, DRIFTS and XAFS. CO pulse chemisorption evidenced that the Pd dispersion decreased from 55% to 5% as the Pd loading increased from 0.58 to 3.94 wt.%. The as-prepared 0.58 and 1.77 wt.% Pd/γ-Al₂O₃ catalysts (after air exposure) contained oxidized Pd species that were converted after in situ reduction to supported Pd particles. The average Pd particle sizes of these two catalysts (16 and 23 Å, respectively) estimated from the first-shell Pd–Pd coordination numbers are in good agreement with the CO chemisorption results. DRIFTS evidenced a prevalence of weakly bound linear CO (ν_CO = 2083 cm^?1) adsorbed on the 0.58 wt.% Pd catalyst. A 2.95 wt% Pd catalyst (49 Å average particle size) also exhibited a strong linear CO band (ν_CO = 2093 cm^?1). In contrast, CO chemisorption on a commercial 1 wt.% Pd/Al₂O₃ catalyst (37 Å average particle size) gave predominantly 2-fold bridging CO species. We infer that the supported Pd particles prepared from [Pd(hfac)₂] are rougher on the atomic scale (with a higher percentage of edge and corner atoms) than equivalently sized particles in conventionally prepared Pd/γ-Al₂O₃ catalysts.     

Promotional SMSI Effect on Supported Palladium Catalysts for Methanol Synthesis

High-temperature reduction (HTR) of palladium catalysts supported on some reducible oxides, such as Pd/CeO₂, and Pd/TiO₂ catalysts, led to a strong metal-support interaction (SMSI), which was found to be the main reason for their high and stable activity for methanol synthesis from hydrogenation of carbon dioxide. But low-temperature-reduced (LTR) catalysts exhibited high methane selectivity and were oxidized to PdO quickly in the same reaction. Besides palladium, platinum exhibited similar behavior for this reaction when supported on these reducible oxides. Mechanistic studies of the Pd/CeO₂ catalyst clarified the promotional role of the SMSI effect, and the spillover effect on the HTR Pd/CeO₂ catalyst. Carbon dioxide was decomposed on Ce₂O₃, which was attached to Pd, to form CO and surface oxygen species. The carbon monoxide formed was hydrogenated to methanol successively on the palladium surface while the surface oxygen species was hydrogenated to water by spillover hydrogen from the gas phase. A reaction model for the hydrogenation of carbon dioxide was suggested for both HTR and LTR Pd/CeO₂ catalysts. Methanol synthesis from syngas on the LTR or HTR Pd/CeO₂ catalysts was also conducted. Both alcohol and hydrocarbons were formed significantly on the HTR catalyst from syngas while methanol formed predominantly on the LTR catalyst. Characterization of these two catalysts elucidated the reaction performances.     

Selective hydrogenation of cyclopentadiene over supported metal catalysts

The selective hydrogenation of cyclopentadiene to cyclopentene has been studied in the liquid phase using Pd and Pd Me/Al₂O₃ bimetallic catalysts (Me = Mn, Ni, Co, W). The highest activity was obtained with Pd Co and Pd W/Al₂O₃. For these catalysts, no hydrogen or CO chemisorption was detected although Pd could be seen by XPS at 335·8 eV; it is considered that new species, more active for the selective hydrogenation of cyclopentadiene, appeared at the catalyst surface. The sulfur resistance towards thiophene has also been studied. It was observed that the highest sulfur resistance is coincident with the highest activity. XPS analysis shows that the poisoning species is thiophene adsorbed on the catalyst surface.     

Selective hydrogenation of (E)-2-hexenal to (E)-2-hexen-1-ol over Co-based bimetallic catalysts

Hydrogenation of (E)-2-hexenal was carried out in a liquid phase using Co-based bimetallic catalysts (M–Co/Al₂O₃, M=Pd, Pt, Ru, Rh, Sn, Fe, or Cu). Pd–Co/Al₂O₃ showed the highest activity among the catalysts tested and catalyzed the hydrogenation of CC bond predominantly to produce hexanal and 1-hexanol. Pt–Co/Al₂O₃ was more active than monometallic Co/Al₂O₃ for the hydrogenation of CO bond. The excellent result, 92% selectivity to (E)-2-hexen-1-ol formation at 90% conversion, was obtained by the hydrogenation over Pt–Co/Al₂O₃ bimetallic catalyst. No improved activities were observed for the other bimetallic catalysts.     

Preparation of Pd–Pb/α-Al2O3 catalysts for selective hydrogenation using PbBu4: the role of metal–support boundary atoms and the formation of a stable surface complex

Pd–Pb/α-Al₂O₃ catalysts were prepared by reacting PbBu₄ with supported palladium samples derived from Pd(AcAc)₂, both in the presence and absence of hydrogen. The amount of lead fixed depends mainly on the concentration of palladium on the metal–support boundary. In the presence of hydrogen, all butyl groups are released during the anchoring process. When the Pd/α-Al₂O₃ was reduced and then purged with nitrogen, two butyl groups remained attached to the lead atom and a stable surface complex was formed. The analysis of gaseous products evolved during the PbBu₄–Pd/α-Al₂O₃ interaction and subsequent temperature‐programmed reaction experiments indicate that a (]‐L)₂–Pb(Bu)₃ complex was obtained. Upon reduction at 573 K, the Pd–Pb/α-Al₂O₃ catalysts became very selective for the hydrogenation of acetylene in the presence of ethylene. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of Zeolite Structures, Exchanged Cations, and Bimetallic Formulations on the Selective Hydrogenation of Acetylene Over Zeolite-Supported Catalysts

Supported PdAg bimetallic catalysts were evaluated for the selective hydrogenation of acetylene in the presence of ethylene. The effects of different zeolite structures and cations were investigated using flow reactor studies, with K⁺-β-zeolite supported PdAg showing the lowest activity but highest selectivity comparing to the γ-Al₂O₃ support and other alkaline metal exchanged β-zeolite supports. The K⁺ promoter effect on γ-Al₂O₃ was also tested, which showed that adding K⁺ to γ-Al₂O₃ increased activity and selectivity. Bimetallic catalysts consisting of Pd and a Group IB metal were also compared. It was found that the PdAg bimetallic catalyst had similar activity but better selectivity comparing to PdCu, while the PdAu catalyst showed the highest activity but lowest selectivity.     

Hydrocracking of vegetable oil on boron-containing catalysts: Effect of the nature and content of a hydrogenation component

Catalysts based on metals (Pt, Pd) and metal oxides (NiO, Co₃O₄, MoO₃, WO₃), supported on the surface of borate-containing aluminum oxide (B₂O₃–Al₂O₃), in the hydrocracking of sunflower oil at a temperature of 400°C, a pressure 4.0 MPa and a mass hourly space velocity MHSV 5.0 h^–1 are compared. H₂ TPR and IR spectroscopy of adsorbed CO and ESDR show that the hydrogenation catalyst components are Pt⁰ and Pd⁰, a mixture of Ni²⁺ + Ni⁰, Co²⁺ + Co⁰, or a mixture of the highest and partially reduced oxides of Mo and W. It is established that catalysts containing Pt, Pd, NiO and Co₃O₄, ensure complete oil hydrodeoxygenation. The main oxygen removal reactions in Ptand Pd-systems are decarboxylation and hydrodecarbonylation. For catalysts with NiO and Co₃O₄, characteristic reactions are reduction and methanation. The highest yield of the diesel fraction was obtained on Pt/B₂O₃-Al₂O₃ catalysts with metal contents of 0.3–1.0 wt %. Along with n-alkanes, the diesel fractions obtained on these catalysts include cycloalkanes and iso-alkanes (up to around 40 wt %) and aromatic hydrocarbons present in trace amounts. Hydrocracking on the Pt system at 400°C for 20 h with MHSV of 1.0 h^–1 produces a diesel fraction with a yield of at least 82.0 wt % and the content of iso-alkanes at least 76.1 wt %.     

Fabrication of supported Pd–Ir/Al2O3 bimetallic catalysts for 2‐ethylanthraquinone hydrogenation

A series of χ wt % Pd‐(1‐χ) wt % Ir (χ = 0.75, 0.50, and 0.25) catalysts supported on γ‐Al₂O₃ have been prepared by co‐impregnation and calcination‐reduction, and subsequently employed in the hydrogenation of 2‐ethylanthraquinone—a key step in the manufacture of hydrogen peroxide. Detailed studies showed that the size and structure of the bimetallic Pd–Ir particles vary as a function of Pd/Ir ratio. By virtue of its small metal particle size and the strong interaction between Pd and Ir, the 0.75 wt % Pd–0.25 wt % Ir/Al₂O₃ catalyst afforded the highest yield of H₂O₂, some 25.4% higher than that obtained with the monometallic 1 wt % Pd catalyst. Moreover, the concentration of the undesired byproduct 2‐ethyl‐5,6,7,8‐tetrahydroanthraquinone (H₄eAQ) formed using the Pd–Ir bimetallic catalysts was much lower than that observed with the pure Pd catalyst, which can be assigned to the geometric and electronic effects caused by the introduction of Ir. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3955–3965, 2017     

Hydrogenation of Sunflower Oil over M/SiO2 and M/Al2O3 (M = Ni,Pd, Pt,Co, Cu) Catalysts

This work is aimed at evaluating the performance of several catalysts in the partial hydrogenation of sunflower oil. The catalysts are composed of noble (Pd and Pt) and base metals (Ni, Co and Cu), supported on both silica and alumina. The following order can be proposed for the effect of the metal on the hydrogenation activity: Pd > Pt > Ni > Co > Cu. At a target iodine value of 70 (a typical value for oleomargarine), the production of trans isomers is minimum for supported nickel catalysts (25.7–32.4 %, depending on the operating conditions). Regarding the effect of the support, Al₂O₃ allows for more active catalysts based on noble metals (Pd and Pt) and Co, the effect being much more pronounced for Pt. Binary mixtures of catalysts have been studied, in order to strike a balance between catalyst activity and product distribution. The results evidence that Pd/Al₂O₃–Co/SiO₂ mixture has a good balance between activity and selectivity, and leads to a very low production of trans isomers (11.8 %) and a moderate amount of saturated stearic acid (13.5 %). Consequently, the utilization of cobalt‐based catalysts (or the addition of cobalt to other metallic catalysts) could be considered a promising alternative for the hydrogenation of edible oil.     

Catalytic behaviors and gas permeation properties of palladium-containing phenophthalein poly(ether sulfone)

Palladiumsupported on a high-temperature-withstanding polymer, phenophthalein poly(ether sulfone) (PES-C), exhibits very high catalytic activity both in the carbonylation of allyl bromide and in the hydrogenation of 1-octene at 40°C and atmospheric pressure. The initial activities are up to 345 mol CO/mol Pd min and 493 mol H₂/mol Pd min, respectively. The polymer-supported palladium catalysts prepared by refluxing the mixture of PdCl₂ and PES-C immersed in benzene/ethanol (1/3, v/v) prior to the preparation of the catalyst show higher catalytic activity than those obtained by refluxing the mixture of PdCl₂ and PES-C in benzene/ethanol. The Pd-containing PES-C membranes made from the polymer-supported palladium catalysts are endowed with a very specific permeability of H₂ and the corresponding Pd-containing membrane catalysts can also exhibit considerable catalytic activity for the hydrogenation of 1-octene. © 1996 John Wiley & Sons, Inc.