Fe Co alloy nanoparticles supported on IR pyrolyzed chitosan as catalyst for Fischer-Tropsch synthesis

Fe-Co Alloy Nanoparticles Dispersed in Polymer-Derived Carbon Support: Effect of Initial Polymer Nature on the Size, Structure and Magnetic Properties

Fe-Co alloy nanoparticles with different sizes, supported by carbon derived from several polymers, namely polyacrylonitrile, polyvinyl alcohol and chitosan, have been synthesized by a one-pot method involving simultaneous metal nanoparticle formation and polymer carbonization. The method involves the joint dissolution of metal salts and a polymer, followed by annealing of the resulting dried film. Detailed XRD analysis confirmed the formation of Fe-Co alloy nanoparticles in each sample, regardless of the initial polymer used. Transmission electron microscopy images showed that the Fe-Co nanoparticles were all spherical, were homogeneously distributed within the carbon support and varied by size depending on the initial polymer nature and synthesis temperature. Fe-Co nanoparticles supported by polyacrylonitrile-derived carbon exhibited the smallest size (6-12 nm), whereas nanoparticles on chitosan-derived carbon support were characterized by the largest particle size (13-38 nm). The size dependence of magnetic properties were studied by a vibrating sample magnetometer at room temperature. For the first time, the critical particle size of Fe-Co alloy nanoparticles with equiatomic composition has been experimentally determined as 13 nm, indicating the transition of magnetic properties from ferromagnetic to superparamagnetic.

One-Step Synthesis of Bimetallic Cobalt–Palladium Nanoparticles and a Carbon Support Based on Pyrolyzed Chitosan

Abstract

A procedure is proposed for synthesizing monometallic (Co, Pd) and bimetallic Co–Pd nanoparticles immobilized in a carbon support based on pyrolyzed chitosan. A feature of the procedure is the simultaneous formation of metal nanoparticles and a carbon support during the heat treatment of a precursor based on a joint solution of a polymer and metal compounds under the effect of IR radiation. The phase composition, morphology of samples, and structural features of the carbon support are shown, depending on the nature of the metals that are used.

Preparation of low carbon olefins on a core-shell K-Fe5C2@ZSM-5 catalyst by Fischer-Tropsch synthesis

In this study, a core–shell catalyst based on Fe₅C₂@ZSM-5 (ZSM-5 capped Fe₅C₂ as active phase) is prepared by the coating-carbonization method for Fischer–Tropsch synthesis (FTS). Further, the designed ZSM-5 zeolites are utilized to screen the low carbon hydrocarbons from the products generated on the iron carbide active centre, and for catalytic disassembly of the long-chain hydrocarbons into low carbon olefins. Prior to utilization, the physical–chemical properties of the prepared catalysts are systematically characterized by various techniques of X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM) observations, in addition to the effects of coating-carbonization, molecular sieve coating amount, and K-doping on core–shell iron-based catalysts. Next, the performance of Fischer–Tropsch synthesis is investigated in a micro-fixed bed reactor. The results manifest that, comparing with Fe₅C₂ and a supported Fe/ZSM-5 catalyst prepared by the traditional impregnation method, the core–shell Fe₅C₂@ZSM-5 catalysts show higher CO conversion rate, reaction activity and selectivity to low-carbon olefins. Comparatively, the Fe₅C₂@ZSM-5C catalyst prepared by carbonization after the coating method exhibited more surface area, smaller average pore size, and more reactive active sites, resulting in the improvement of screening of high carbon hydrocarbons and the enhancement of selectivity to low carbon olefins, in comparison to those prepared by the carbonization-coating method. In conclusion, the K-doping catalyst had significantly improved the reactive activity of the core–shell Fe₅C₂@ZSM-5 catalyst and the selectivity to low carbon olefins, while the CO conversion on K–Fe₅C₂@ZSM-20C still remained good.

In this study, a core–shell catalyst based on Fe₅C₂@ZSM-5 (ZSM-5 capped Fe₅C₂ as active phase) is prepared by the coating-carbonization method for Fischer–Tropsch synthesis (FTS).

Novel Polyacrylonitrile-Based C/Co-Ru Metal-Carbon Nanocomposites as Effective Catalysts for Ethanol Steam Reforming

One-step preparation method of metal-carbon nanocomposites based on bimetallic Co–Ru nanoparticles supported and IR carbonized polyacrylonitrile was proposed. IR pyrolysis of the precursor based on joint solution of polyacrylonitrile and metal compounds leads to the simultaneous formation of carbon support and bimetallic metal nanoparticles. The metal reduction occures due to the release of hydrogen during decomposition of backbone polymer chain. Furthermore, IR radiation shortens fabrication time significantly. It was shown that the presence of cobalt and ruthenium in the system provides the creation of alloy Co–Ru nanoparticles. In addition, cobalt provides a formation of structured carbon shells around bimetallic nanoparticles. The nanocomposites were tested as catalysts for the hydrogen production through ethanol steam reforming. The dependence of structural and functional properties on the metal loading was demonstrated. The high yield of hydrogen was recorded for all three samples, whereas the by-product yield was relatively low.