Jiawei Hu

Bio: Jiawei Hu is an academic researcher from National University of Singapore. The author has contributed to research in topics: Chemical looping combustion & Catalysis. The author has an hindex of 9, co-authored 16 publications receiving 284 citations. Previous affiliations of Jiawei Hu include East China University of Science and Technology & Ghent University.

Advanced Chemical Looping Materials for CO2 Utilization: A Review

Abstract: Combining chemical looping with a traditional fuel conversion process yields a promising technology for low-CO2-emission energy production. Bridged by the cyclic transformation of a looping material (CO2 carrier or oxygen carrier), a chemical looping process is divided into two spatially or temporally separated half-cycles. Firstly, the oxygen carrier material is reduced by fuel, producing power or chemicals. Then, the material is regenerated by an oxidizer. In chemical looping combustion, a separation-ready CO2 stream is produced, which significantly improves the CO2 capture efficiency. In chemical looping reforming, CO2 can be used as an oxidizer, resulting in a novel approach for efficient CO2 utilization through reduction to CO. Recently, the novel process of catalyst-assisted chemical looping was proposed, aiming at maximized CO2 utilization via the achievement of deep reduction of the oxygen carrier in the first half-cycle. It makes use of a bifunctional looping material that combines both catalytic function for efficient fuel conversion and oxygen storage function for redox cycling. For all of these chemical looping technologies, the choice of looping materials is crucial for their industrial application. Therefore, current research is focused on the development of a suitable looping material, which is required to have high redox activity and stability, and good economic and environmental performance. In this review, a series of commonly used metal oxide-based materials are firstly compared as looping material from an industrial-application perspective. The recent advances in the enhancement of the activity and stability of looping materials are discussed. The focus then proceeds to new findings in the development of the bifunctional looping materials employed in the emerging catalyst-assisted chemical looping technology. Among these, the design of core-shell structured Ni-Fe bifunctional nanomaterials shows great potential for catalyst-assisted chemical looping.

Bifunctional Ni-Ca based material for integrated CO2 capture and conversion via calcium-looping dry reforming

Abstract: Effective integration of CO2 capture and its conversion is an attractive strategy to reduce the anthropogenic CO2 emissions meanwhile achieve the potential revenue of CO2 molecule. Calcium-looping dry reforming of methane (CaLDRM) has emerged as such a promising process, implemented over a bifunctional reactor combining a CaO-based sorbent and a Ni-based catalyst, to achieve CO2 capture and in-situ conversion with CH4 into syngas. Herein, we synthesize a bifunctional Ni-Ca based material, i.e. Ni and CeO2 nanoparticles co-loaded on ZrO2-coated CaCO3, which enables isothermal capture and release of CO2 at the temperature favorable for DRM reaction, allowing to operate CaLDRM process in a single reactor by simple gas switching. Thanks to the stabilization effect of the ZrO2 layer, both CaO and Ni particles are exempted from severe sintering, maintaining the activity of capture and catalysis. The addition of CeO2 contributes not only to combat the accumulation of inactive carbon during long-term DRM but also to activate CO2 and CH4, accordingly enhancing syngas production, during cyclic CaLDRM. Importantly, the bifunctional material can succesfully drive CaLDRM cycles, converting over 40 % of CH4 and CO2, under 5 vol% CO2 feed concentration (as low as real flue gas) at 720 °C, which is a thermodynamically extremely unfavorable condition (equilibrium conversion below 3 %).

CO2 conversion to CO by auto-thermal catalyst-assisted chemical looping

Abstract: A bifunctional 9 wt.%NiO-16 wt.%Fe 2 O 3 /MgAl 2 O 4 material was prepared for CO 2 conversion to CO by auto-thermal catalyst-assisted chemical looping. This process is designed to maximize CO 2 conversion. The generation of CO from CO 2 was investigated between 873 K and 1023 K. The high endothermicity of methane dry reforming and the material deactivation by coke deposition were avoided by the simultaneous feeding of CH 4 , CO 2 and O 2 in a 1:1:0.5 molar ratio during the reduction half-cycle of chemical looping. In this half-cycle, interaction of Ni with Fe leads to Ni-Fe alloy formation. The resulting Ni-based catalyst converts CH 4 + CO 2 + O 2 into a mixture of CO and H 2 , which both reduce Fe 3 O 4 , producing CO 2 and H 2 O. In the CO 2 re-oxidation half-cycle, CO is produced and the Ni-Fe alloy decomposes into Ni and Fe 3 O 4 . The reduction capacity ( R c ) of the gas mixture strongly depends on the ratio R c between reducing and oxidizing gases. Based on thermodynamic calculations, high conversion of Fe 3 O 4 to reduced state can be reached if R c > 2 and T > 873 K. During prolonged auto-thermal chemical looping at 1023 K, the 9 wt.%NiO–16 wt.%Fe 2 O 3 /MgAl 2 O 4 suffers from deactivation in the first five cycles, after which a more stable operation is established. Based on TEM measurements, sintering was found to be the main cause for the initial decrease of CO production.

Selective hydrogenation of phenylacetylene over a nano-Pd/α-Al2O3 catalyst

Abstract: Selective hydrogenation of phenylacetylene is an important reaction for increasing the purity of the styrene monomer. In this study a series of supported nano-Pd/α-Al 2 O 3 catalysts were prepared and applied to the selective hydrogenation of phenylacetylene. The preparation procedure consisted of two steps: synthesis of colloidal Pd nanoparticles by a reduction-by-solvent method, followed by impregnation onto α-Al 2 O 3 . In the first step, NaBH 4 was used as a reducing agent to reduce Pd 2+ ions in the C 2 H 5 OH/H 2 O solvent system, and polyvinylpyrrolidone (PVP) was used as a protecting agent to stabilize Pd nanoparticles. The prepared colloids and catalysts were characterized by N 2 physisorption, CO chemisorption, XRD, UV–vis, FT-IR, ICP and HRTEM techniques. It was found that the amounts of NaBH 4 , C 2 H 5 OH and PVP had effects on the Pd particle size, which in turn influenced the catalyst performance. The selective hydrogenation of phenylacetylene was sensitive to the structure of the nano-Pd/α-Al 2 O 3 catalysts. In the case where the Pd particle size varied from 3.8 to 6.6 nm, the specific activity and the selectivity to styrene increased with increasing particle size, but when the particle size increased in the range of 6.6–12.1 nm, the specific activity increased slowly and the selectivity to styrene decreased gradually. Nano-Pd/α-Al 2 O 3 can be reused several times without loss of activity and selectivity and no distinct variation in the Pd particle size was observed, indicating its good stability in the selective hydrogenation of phenylacetylene.

Catalyst-assisted chemical looping auto-thermal dry reforming: Spatial structuring effects on process efficiency

Abstract: Catalyst-assisted chemical looping auto-thermal dry reforming (CCAR) is an environment-friendly energy conversion process, performed over a reactor bed with double function, composed of a catalyst and an oxygen storage material (OSM). It converts CH4 and CO2 into industrial syngas, while simultaneously utilizing CO2 from the atmosphere. Two reactor bed configurations were tested, based on the concept of double- and single-zone distribution of catalyst and OSM. Combinations of core-shell structured materials were applied, such as Ni/ZrO2@ZrO2 catalyst, Fe2O3/ZrO2@ZrO2 OSM and Fe/Zr@Zr-Ni@Zr bifunctional catalyst, to assess the spatial structuring at both reactor bed and pellet scale. Samples from different reactor beds were characterized before and after use by ex- or in-situ XRD, N2 adsorption, XPS and STEM-EDX. 25 redox cycles of CCAR were performed to investigate the effect of spatial structuring on the activity and stability. The Fe/Zr@Zr-Ni@Zr bifunctional catalyst possesses higher activity and stability for catalytic CH4 conversion in the reduction half-cycle than the Ni/ZrO2@ZrO2 catalyst due to its small Ni particle size (

Core–shell structured catalysts for thermocatalytic, photocatalytic, and electrocatalytic conversion of CO2

Abstract: Catalytic conversion of CO2 to produce fuels and chemicals is attractive in prospect because it provides an alternative to fossil feedstocks and the benefit of converting and cycling the greenhouse gas CO2 on a large scale. In today's technology, CO2 is converted into hydrocarbon fuels in Fischer-Tropsch synthesis via the water gas shift reaction, but processes for direct conversion of CO2 to fuels and chemicals such as methane, methanol, and C2+ hydrocarbons or syngas are still far from large-scale applications because of processing challenges that may be best addressed by the discovery of improved catalysts-those with enhanced activity, selectivity, and stability. Core-shell structured catalysts are a relatively new class of nanomaterials that allow a controlled integration of the functions of complementary materials with optimised compositions and morphologies. For CO2 conversion, core-shell catalysts can provide distinctive advantages by addressing challenges such as catalyst sintering and activity loss in CO2 reforming processes, insufficient product selectivity in thermocatalytic CO2 hydrogenation, and low efficiency and selectivity in photocatalytic and electrocatalytic CO2 hydrogenation. In the preceding decade, substantial progress has been made in the synthesis, characterization, and evaluation of core-shell catalysts for such potential applications. Nonetheless, challenges remain in the discovery of inexpensive, robust, regenerable catalysts in this class. This review provides an in-depth assessment of these materials for the thermocatalytic, photocatalytic, and electrocatalytic conversion of CO2 into synthesis gas and valuable hydrocarbons.

A review on catalyst development for dry reforming of methane to syngas: Recent advances

Abstract: The abrupt and massive deactivation of methane dry reforming catalysts especially Ni-based is still a monumental impediment towards its industrialization and commercialization for production of value-added syngas via Fischer-Tropsch process. The need for further and more critical understanding of inherent and tailored interactions of catalyst components for performance and stability enhancement during reforming reaction cannot be over-emphasized. This review provides a contemporary assessment of progresses recorded on synergistic interplay among catalyst components (active metals, support, promoters and binders) during dry reforming using state-of-the-art experimental and theoretical techniques. Advancements achieved during interplay leading to improvements in properties of existing catalysts and discovery of novel ones were stated and expatiated. Reaction pathways, catalytic activities, selection of appropriate synthesis route and metal/support deactivation via sintering or carbon deposition have over time been successfully studied and explained using information from these crucial component interactions. This perspective describes the roles of these interactions and their applications towards development of robust catalysts configurations for successful industrial applications.

Super-dry reforming of methane intensifies CO2 utilization via Le Chatelier’s principle

Abstract: Efficient CO2 transformation from a waste product to a carbon source for chemicals and fuels will require reaction conditions that effect its reduction. We developed a “super-dry” CH4 reforming reaction for enhanced CO production from CH4 and CO2. We used Ni/MgAl2O4 as a CH4-reforming catalyst, Fe2O3/MgAl2O4 as a solid oxygen carrier, and CaO/Al2O3 as a CO2 sorbent. The isothermal coupling of these three different processes resulted in higher CO production as compared with that of conventional dry reforming, by avoiding back reactions with water. The reduction of iron oxide was intensified through CH4 conversion to syngas over Ni and CO2 extraction and storage as CaCO3. CO2 is then used for iron reoxidation and CO production, exploiting equilibrium shifts effected with inert gas sweeping (Le Chatelier’s principle). Super-dry reforming uses up to three CO2 molecules per CH4 and offers a high CO space-time yield of 7.5 millimole CO per second per kilogram of iron at 1023 kelvin.

Chemical looping beyond combustion – a perspective

Abstract: As a promising approach for carbon dioxide capture, chemical looping combustion has been extensively investigated for more than two decades. However, the chemical looping strategy can be and has been extended well beyond carbon capture. In fact, significant impacts on emission reduction, energy conservation, and value-creation can be anticipated from chemical looping beyond combustion (CLBC). This article aims to demonstrate the versatility and transformational benefits of CLBC. Specifically, we focus on the use of oxygen carriers or redox catalysts for chemical production – a $4 trillion industry that consumes 40.9 quadrillion BTU of energy. Compared to state-of-the-art chemical production technologies, we illustrate that chemical looping offers significant opportunities for process intensification and exergy loss minimization. In many cases, an order of magnitude reduction in energy consumption and CO2 emission can be realized without the needs for carbon dioxide capture. In addition to providing various CLBC examples, this article elaborates on generalized design principles for CLBC, potential benefits and pitfalls, as well as redox catalyst selection, design, optimization, and redox reaction mechanism.

FeO6 Octahedral Distortion Activates Lattice Oxygen in Perovskite Ferrite for Methane Partial Oxidation Coupled with CO2 Splitting.

Abstract: Modulating lattice oxygen in metal oxides that conducts partial oxidation of methane in balancing C-H activation and syngas selectivity remains challenging. This paper describes the discovery of distorting FeO6 octahedra in La1-xCexFeO3 (x = 0, 0.25 0.5, 0.75, 1) orthorhombic perovskites for the promotion of lattice oxygen activation. By combined electrical conductivity relaxation measurements and density functional theory calculations studies, this paper describes the enhancement of FeO6 octahedral distortion in La1-xCexFeO3 promoting their bulk oxygen mobility and surface oxygen exchange capability. Consequently, La0.5Ce0.5FeO3 with the highest FeO6 distortion achieves exceptional syngas productivity of ∼3 and 8 times higher than LaFeO3 and CeFeO3, respectively, in CH4 partial oxidation step with simultaneous high CO2 conversion (92%) in the CO2-splitting step at 850 °C. The results exemplify the feasibility to tailor the active lattice oxygen of perovskite by modulating the distortion of BO6 in ABO3, which ultimately influences their reaction performance in chemical looping processes.