Ruijuan Chai

Structured Ni‐CeO2‐Al2O3/Ni‐Foam Catalyst with Enhanced Heat Transfer for Substitute Natural Gas Production by Syngas Methanation

Concerns about the clean utilization of coal and the development of sustainable energy have provided a particular impetus for the exploration into the production of substitute natural gas (SNG) by syngas methanation in some parts of world. Owing to heat‐transfer limitations, current SNG technology based on a series of fixed‐bed reactors packed with oxide‐supported Ni catalysts suffers from issues such as high costs, low efficiency, and catalyst sintering. We report a monolithic Ni‐Ce‐Al2O3/Ni‐foam catalyst obtainable by modified wet‐chemical etching of Ni foam. Such a catalyst, with significantly enhanced heat transfer, is highly active, highly selective, and very stable for syngas methanation. Computational fluid dynamics calculations and experimental measurements consistently show a large reduction in the “hotspot” temperature in the Ni‐foam‐structured catalyst bed owing to high thermal conductivity. We anticipate that our approach will open a new opportunity for next‐generation SNG plant design.

Tailoring nano-catalysts: turning gold nanoparticles on bulk metal oxides to inverse nano-metal oxides on large gold particles

Highly active/stable inverse catalysts of nano-oxides on large gold particles are designed and tailored. For the gas-phase oxidation of alcohols as a model reaction, the experimental and theoretical results verify that the catalyst activity depends on the gold-oxide interface, and the anti-sintering feature of such an inverse structure endows the catalyst with high stability.

Foam-Structured NiO-MgO-Al2O3 Nanocomposites Derived from NiMgAl Layered Double Hydroxides In Situ Grown onto Nickel Foam: A Promising Catalyst for High-Throughput Catalytic Oxymethane Reforming

Catalytic oxymethane reforming is an effective and efficient route to produce syngas, but the commonly used Ni catalysts suffer from coke deposition, Ni sintering, and heat‐transfer limitations. A Ni‐foam‐structured NiO‐MgO‐Al2O3 nanocomposite catalyst was developed by thermal decomposition of NiMgAl layered double hydroxides (LDHs) in situ hydrothermally grown onto the Ni‐foam. Originating from the lattice orientation effect and topotactic decomposition of the LDH precursor, NiO, MgO, and Al2O3 are highly distributed in the nanocomposite, and thus, this catalyst shows enhanced resistance to coke and sintering. At 700 °C and a gas hourly space velocity of 100 L g−1 h−1, 86.5 % methane conversion and selectivities of 91.8/88.0 % to H2/CO are achieved with stability for at least 200 h. We believe this type of tailoring strategy and the as‐obtained materials can open up new opportunities for future applications in other high‐throughput and high‐temperature reactions.

Copper‐Fiber‐Structured Pd–Au–CuOx: Preparation and Catalytic Performance in the Vapor‐Phase Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Cu‐fiber‐structured ternary Pd–Au–CuOx catalysts engineered from nano‐ to macro‐scales have been developed for the vapor‐phase dimethyl oxalate (DMO) hydrogenation to ethylene glycol (EG), with the aid of galvanic deposition of Pd and Au onto a thin‐sheet microfibrous structure using 8 μm Cu fiber. Effects of Pd and Au loadings and their ratio have been investigated on the catalyst performance as well as the reaction conditions including reaction temperature and pressure, liquid weight hourly space velocity, and H2/DMO ratio. The promising 0.1 Pd–0.5 Au–CuOx/Cu‐fiber catalyst is capable of converting 97–99 % DMO into EG product at a selectivity of 90–93 %. This catalyst is stable for at least 200 h. The Pd–Au–Cu2O synergistically promotes the hydrogenation activity and stabilizes Cu+ sites to suppress deep reduction deactivation.

Titanium‐Microfiber‐Supported Binary‐Oxide Nanocomposite with a Large Highly Active Interface for the Gas‐Phase Selective Oxidation of Benzyl Alcohol

Thin‐sheet sinter‐locked Ti‐microfiber‐supported binary‐oxide‐nanocomposite catalysts engineered on the micro‐ to macroscales were developed for the gas‐phase aerobic oxidation of benzyl alcohol to benzaldehyde. The catalysts demonstrated higher activity than single‐oxide and noble‐metal catalysts with good stability and regenerability. The catalysts were obtained by placing transient metal (e.g., Ni, Co, Cu, Mn) nitrates onto a Ti‐microfiber surface by impregnation, and the supported nitrates were subsequently in situ transformed into the binary‐oxide composites in the real reaction stream at 300 °C. Among them, CoO‐2.5–CuOx‐2.5/Ti‐fiber was found to be the best catalyst; it delivered 93.5 % conversion of benzyl alcohol (b.p. 210 °C) with 99.2 % selectivity to benzaldehyde at 230 °C. In situ induced formation of “CoO@Cu2O” ensembles (i.e., larger CoO nanoparticles partially covered with smaller Cu2O clusters and/or nanoparticles) was identified, which by nature resulted in a large Cu2O–CoO interface and led to a significant improvement in the low‐temperature activity.

High sintering-/coke-resistance Ni@SiO2/Al2O3/FeCrAl-fiber catalyst for dry reforming of methane: one-step, macro-to-nano organization via cross-linking molecules

A thin-felt, microfibrous-structured Ni@SiO2/Al2O3/FeCrAl-fiber catalyst was fabricated by one-step, top-down macro–micro–nano organization with the aid of cross-linking molecules followed by a calcination treatment. This catalyst is active, selective and stable for the strongly endothermic dry reforming of methane (DRM), as the result of its enhanced resistance to coke and Ni sintering arising from its core–shell-like nanostructure. Notably, no sign of catalyst deactivation is observed, with almost no carbon deposition even after 500 h testing at 800 °C and a gas hourly space velocity of 5000 mL g−1 h−1.