Magnetic Fe₃O₄@SiO₂/Pd and Fe₃O₄@SiO₂/Pd‐M (M=Ag, Cu and Zn) Catalysts for Selective Hydrogenation of Phenylacetylene

Abstract

Magnetic core-shell monometallic Fe 3 O 4 @SiO 2 /Pd and bimetallic Fe 3 O 4 @SiO 2 /PdÀM (M= Ag, Cu and Zn) catalysts with low Pd loading were prepared using a modified Stö ber method followed by an ion-exchange technique, and applied to the selective hydrogenation of phenylacetylene. The structure and magnetism of the catalysts were investigated using N 2 physisorption, XRD, FT-IR, ICP-OES, H 2 -TPR, CO chemisorption, DRIFTS, HRTEM and vibrating sample magnetometer. The characterization results showed that the magnetic catalyst had smaller Pd particle size than the non-magnetic catalyst; the thinner the silica shell of the magnetic catalyst, the stronger the magnetic intensity and hence the smaller the Pd particle size; the PdM alloy was formed for bimetallic catalysts and geometric and electronic effects occur. By comparing the activity and selectivity of different catalysts, it was found that the catalyst with smaller Pd particle size generally exhibited a higher apparent activity and selectivity to styrene but a lower specific activity, demonstrating the structure-sensitive catalytic activity for selective hydrogenation of phenylacetylene on the magnetic Pd supported catalysts. In addition, all the bimetallic catalysts displayed higher selectivity but lower activity than the monometallic catalysts as a result of the presence of the PdM alloy. In particular, a Fe 3 O 4 @SiO 2 /PdÀZn catalyst with the shell thickness of about 80 nm and the Pd and Zn loadings of 0.31 and 1.79 wt%, respectively, showed the best selectivity to styrene, being 86.1 % at above 99.5 % conversion of phenylacetylene. Furthermore, this catalyst maintained its activity and selectivity even after being reused ten times.[a] Dr.

Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts

“…Recently, considering the peculiar features of magnetite particles related to their lower sensitivity to oxidation, strong ferromagnetic behavior and easy recovery (aided by an external magnetic field) and reuse, the preparation of Pd/Fe 3 O 4 catalyst in nanometric scale of different property and composition attracted a lot of interest [196]. Fang and co-workers [197], developed a synthetic route based on the Stöber method and ion-exchange technique to synthesize magnetic core-shell monometallic Fe 3 O 4 -SiO 2 /Pd and bimetallic Fe 3 O 4 -SiO 2 /Pd-M (M = Ag, Cu and Zn) catalysts at low Pd loading (<0.5 wt %). In this procedure, the syntheses of Fe 3 O 4 and ferrite microspheres were carried out in a solvothermal system, by modified reduction reactions between FeCl 3 and ethylene glycol.…”

A protector-free one-pot strategy to synthesize highly dispersed Pd hydrogenation catalysts in a broad loading range on polystyrene

“…According to the constructive comments of a reviewer, we have reported the features of some typical methods in literature to prepare Pd nanocatalysts and these features are shown in Table 2. In comparison with the various inorganic materialsupported Pd nanocatalysts, [22][23][24][25][26][27][28] the researches focused on the fact that Pd catalysts supported by organic materials just occupied a small fraction, 29,30 which might attribute to the relatively higher thermal stability of inorganic materials compared to that of the PS-like polymer materials. However, this thermal stability of inorganic supports also implied the inconvenience in adjusting their state, especially the surface state that would signicantly impact the conjunctive function with metal components.…”

“…For instance, the higher temperatures were always required for preparing or processing oxide or zeolite-supported metal nanocatalysts to the desired active state. [22][23][24][25][26] At high temperatures, there was inevitable thermodynamic tendency of isolated metals to leach or agglomerate, leading to the difficulty in controlling the particles within narrow nanoscale. [23][24][25] In addition, although some inorganic supports such as active carbon materials possessed rich functional groups on the surface and their nature could be easily manipulated at a proper temperature for optimizing the interaction with the loaded metal, controlling the size distribution of particles was still difficult 27,28 due to the uneven dispersing density of the functional groups on the surface, especially when metal loadings were altered to a relative higher amount.…”

“…Mimic size-dependent catalytic performance of Pd catalysts for the selective hydrogenation of phenylacetylene could be also found in literature. The styrene yields with the corresponding size of Pd particles in various catalysts [22][23][24][25][26][27][28][29][30] are listed in Table 2; in general, employing smaller Pd particles as catalysts could be more benecial to obtain higher styrene yields. However, note that no matter what the nature of the supports (inorganic or organic materials) was, the smallest Pd nanocatalysts such as particles around 2.0 or 1.5 nm were always present in colloid deposition systems, meaning that a signicant coverage of protectors (for instance, PVP) on the metal surface was necessary for obtaining and using these predened small Pd particles.…”

A practical and highly efficient synthesis of densely functionalized nicotinonitrile derivatives catalyzed by zinc oxide‐decorated superparamagnetic silica attached to graphene oxide nanocomposite

“…Consequently, the catalytic activity of the final magnetic nanocomposite is extremely dependent on the nature of modifying supports and linkers. Large surface area, strong metal‐support interactions and the presence of active sites that can participate in the consecutive reaction steps are the essential requirements for an appropriate support . Inorganic metal oxides, especially SiO 2 , as well as organic polymers or active carbons that display large surface areas are typically used insoluble solid supports for the magnetic heterogeneous catalysts .…”