Shirun Yan

FexOy@C Spheres as an Excellent Catalyst for Fischer−Tropsch Synthesis

We demonstrate a one-pot hydrothermal cohydrolysis-carbonization process using glucose and iron nitrate as starting materials for the fabrication of carbonaceous spheres embedded with iron oxide nanoparticles. It is verified by TEM, (57)Fe Mossbauer, and Fe K-edge XAS that iron oxide nanoparticles are highly dispersed in the carbonaceous spheres, leading to a unique microstructure. A formation mechanism is also proposed. This route is also applicable to a range of other naturally occurring saccharides and metal nitrates. A catalytic study revealed the remarkable stability and selectivity of the reduced Fe(x)O(y)@C spheres in the Fischer-Tropsch synthesis, which clearly exemplifies the promising application of such materials.

Highly Effective Oxidative Dehydrogenation of Propane Over Vanadia Supported on Mesoporous SBA-15 Silica

Vanadia-containing mesoporous SBA-15 catalysts were prepared and characterized for the oxidative dehydrogenation (ODH) of propane. It is demonstrated that the vanadia-supported SBA-15 catalysts exhibit a much higher catalytic activity than those reported in the literature obtained over vanadium-supported mesoporous MCM-41 catalysts in the ODH of propane. The high catalytic performance of the mesoporous SBA-15 catalysts is attributed to the particularly large pore diameters and low surface acidity.

Oxidative Dehydrogenation of Propane over Mesoporous HMS Silica Supported Vanadia

Vanadium-containing mesoporous HMS catalysts have been prepared and characterized for the oxidative dehydrogenation (ODH) of propane. It is demonstrated that the vanadium supported HMS catalysts exhibit a much higher catalytic activity than the literature results obtained over the vanadium supported MCM-41 catalysts in the ODH of propane. The improved catalytic activity of the V-HMS catalysts has been attributed to the presence of high concentration of well-dispersed vanadium species on the surface of the mesoporous HMS materials.

ε -Iron carbide as a low-temperature Fischer–Tropsch synthesis catalyst

ε-Iron carbide has been predicted to be promising for low-temperature Fischer-Tropsch synthesis (LTFTS) targeting liquid fuel production. However, directional carbidation of metallic iron to ε-iron carbide is challenging due to kinetic hindrance. Here we show how rapidly quenched skeletal iron featuring nanocrystalline dimensions, low coordination number and an expanded lattice may solve this problem. We find that the carbidation of rapidly quenched skeletal iron occurs readily in situ during LTFTS at 423-473 K, giving an ε-iron carbide-dominant catalyst that exhibits superior activity to literature iron and cobalt catalysts, and comparable to more expensive noble ruthenium catalyst, coupled with high selectivity to liquid fuels and robustness without the aid of electronic or structural promoters. This finding may permit the development of an advanced energy-efficient and clean fuel-oriented FTS process on the basis of a cost-effective iron catalyst.

A highly selective Raney Fe@HZSM-5 Fischer–Tropsch synthesis catalyst for gasoline production: one-pot synthesis and unexpected effect of zeolites

A novel Raney Fe@HZSM-5 Fischer–Tropsch synthesis catalyst was synthesized via a facile one-pot strategy using an FeAl alloy as the Fe precursor and as the Al source. Aside from cracking/isomerization of heavy hydrocarbons, HZSM-5 also stabilizes Hagg carbide, resulting in excellent selectivity to gasoline fraction and unexpectedly enhanced C5+ selectivity.

An environmentally benign and catalytically efficient non-pyrophoric Ni catalyst for aqueous-phase reforming of ethylene glycol

A non-pyrophoric Ni catalyst (NP Ni) was prepared by alkali leaching of a Ni50Al50 alloy using only ∼ 1/10 of the amount of NaOH required for the preparation of the conventional Raney Ni catalyst. Characterizations reveal that the as-prepared NP Ni catalyst can be looked at as a Ni–Al(OH)3 composite catalyst with Ni in the metallic state and Al(OH)3 in forms of gibbsite and bayerite. After 100 h on stream in aqueous-phase reforming (APR) of ethylene glycol, phase transformation of gibbsite and bayerite to flake-like boehmite occurred, along with the growth of Ni crystallites and partial oxidation of metallic Ni to Ni(OH)2. Under identical reaction conditions for APR of ethylene glycol, the NP Ni catalyst is about 40–52% more active than Raney Ni in terms of the conversion of ethylene glycol to gas products, which is attributed to the stabilizing effect of hydrated alumina on Ni crystallites. The higher selectivity toward H2 and the lower concentration of CO in the product gas on the NP Ni catalyst are attributed to the activation of water by hydrated alumina which is beneficial to the water-gas shift reaction.

Rare earth (Y, La, Ce)-promoted V-HMS mesoporous catalysts for oxidative dehydrogenation of propane

The effect of rare earth (Y, La, Ce) oxides on hexagonal mesoporous silicas (HMS) silica supported vanadia catalysts for the oxidative dehydrogenation of propane was investigated. The doping of Y, La oxides into the V-HMS catalyst affords a significant promotion in the selectivity to propylene while the Ce oxide exhibits a reverse effect for the oxidative dehydrogenation process. The characterization results show that the doping of rare earth oxides results in a significant modification of the redox and acid properties of the V-HMS catalysts. In addition, the formation of a new active phase of rare earth orthovanadates over the modified V-HMS catalysts was also identified. The correlation between the structural changes and the selectivity of the catalysts implied that the formation of new active phase of LaVO4 and YVO4 might be responsible for the improved catalytic performance.

Amorphous Ni-B hollow spheres synthesized by controlled organization of Ni-B nanoparticles over PS beads via surface seeding/electroless plating

The synthesis of amorphous Ni-B hollow spheres, exhibiting superior catalytic properties in acetophenone hydrogenation compared to their nanoparticle form, has been achieved by a combination of polystyrene microsphere templating and electroless plating.

One‐Pot Approach to a Highly Robust Iron Oxide/Reduced Graphene Oxide Nanocatalyst for Fischer–Tropsch Synthesis

Graphene is a two-dimensional single-layer sheet of graphite with p electrons fully delocalized on the graphitic basal plane. For physicists, the high lattice perfection of graphene is appealing, because it allows exceptional mobility of charge carriers, it shows superior thermal conductivity, and it displays fascinating quantum Hall effects, all of which promote the fascinating functionalities of graphene-based devices . For chemists, perfect graphene is too “slippery”, as it is difficult for metal/metal oxide nanoparticles (NPs) deposited on its surface to keep their original size at elevated temperatures as a result of weak van der Waals interactions of graphene and the high surface energy of the NPs. Theoretical calculations revealed low activation energies (0.14–0.8 eV) for the diffusion of metal atoms on perfect graphene. The high mobility of the atoms on graphene may explain the predominant utilization of metal/metal oxide NPs–graphene hybrid materials in ambientor moderate-temperature processes. Recently, by utilizing deviations from perfect graphene, that is, graphene having oxygen-containing groups and atomic defects, Dai and coworkers designed a two-step method that can limit the dimension of the metal oxide NPs to approximately 5 nm on reduced graphene oxide (rGO) by hydrothermal treatment at 453 K. 5b, d, 9a] However, doubt surrounding the thermal stability of such small metal/metal oxide NPs on graphene at elevated temperatures over the long term remains, which shadows the prospect of using these new graphene-relating materials in practical applications. Although wrapping of the metal/metal oxide NPs by graphene 9d, e] may physically restrict them from aggregating, the graphene overlayer is expected to cover the active sites and thus deteriorate the catalytic efficiency in heterogeneous catalysis. Herein, we demonstrate a facile one-pot hydrothermal hydrolysis–reduction (HHR) strategy that is able to fabricate gFe2O3 NPs that are sub-3 nm in size that are highly dispersed on rGO by using iron(III) acetylacetonate [Fe(acac)3] and graphene oxide (GO) as starting materials (Scheme 1). This Fe–rGO nanohybrid material exhibited impressively high thermal stability in high-temperature reduction at 723 K for 16 h and in a successive long-term Fischer–Tropsch synthesis (FTS) reaction at 543 K. Moreover, the Fe–rGO nanohybrid afforded much higher FTS activity and better selectivities for C5 + and C5–C11 hydrocarbons (gasoline fraction) than Fe/p-rGO, which was fabricated by using prereduced graphene oxide (p-rGO) instead of GO as the starting material (also illustrated in Scheme 1), and Fe/AC, which was prepared with commercial Vulcan X-72 activated carbon (AC) as the support. We further validated that the one-pot HHR strategy can be extended to the fabrication of other metal-oxide-on-graphene materials with small and uniform particle sizes. During the preparation, GO was synthesized according to the modified Hummers method from natural flake graphite. Then, Fe(acac)3 was mixed with an aqueous suspension of GO

Simultaneous Aqueous-Phase Reforming and KOH Carbonation to Produce COx-Free Hydrogen in a Single Reactor

abstraction duringthe reforming process will help in displacing the equilibrium ofthe WGS reaction towards product formation, making this re-action more favorable than CO methanation. In addition themethanation of CO 2 , [9h] which also consumes H 2 , will be kineti-cally hindered when it is abstracted. It is practical to take ad-vantage of the unique aqueous-phase character of the reform-ing process by introducing KOH as a process modifier throughsimply switching the aqueous feedstock from ethylene glycolto a mixed solution of ethylene glycol and KOH without alter-ing the set-up of the reactor, as schematically illustrated inScheme 1. We found that by using this improved approachCO x -free H 2 could be successfully produced in a single reactor,even on an unpromoted non-precious-metal catalyst. Thesefeatures make the approach economical and very appealingfrom an environmental point of view.The employed non-precious-metal catalyst is a non-pyro-phoric (NP) Ni catalyst that has been described previously.