Jason

Biomass valorization: This Review discusses most recent advances on catalytic pathways of holocellulosic biomass to value‐added chemicals such as biomass‐derived sugar alcohols, organic acids, furans and biohydrocarbons. The goal is to provide a general overview of the wide spectrum of recent catalytic production technologies and the correlation between their physicochemical properties as well as the economic aspects to efficiently scale up the synthesis of these platform chemicals industrially.

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This Review discusses novel catalytic pathways of lignocellulosic biomass to value‐added chemicals including biomass‐derived sugar alcohols, organic acids, furans and biohydrocarbons. These production approaches are undertaken by biological, chemical and thermochemical transformations or a combination of them. Nevertheless, the majority of research in this area is focused on the design of heterogeneous catalysts to convert value‐added products from holocellulosic biomass. Biorefineries represent the peak of biomass processes in order to produce valuable chemicals and liquid fuels avoiding the utilization of corroding and toxic elements. The aim of the present Review is to offer the readers a broad overview of recent holocellulosic‐based chemical and fuels production technologies via heterogeneous catalysis. There is also an overview of the economic aspects to efficiently produce these platform chemicals at industrial scale. To summarize this Review, an outlook and conclusions of the reported processes to date is provided.

Room at the active site: A room‐temperature redox approach is used to prepare a composite core–shell‐structured Au@CeO₂ electrocatalyst (see figure) composed of small gold nanoparticles (<10 nm) and rich oxygen vacancies in CeO₂ nanoparticles to synergistically boost the electrocatalytic activity toward the N₂ reduction reaction (NRR) to NH₃.

Abstract

Electrosynthesis of NH₃ through the N₂ reduction reaction (NRR) under ambient conditions is regarded as promising technology to replace the industrial energy‐ and capital‐intensive Haber–Bosch process. Herein, a room‐temperature spontaneous redox approach to fabricate a core–shell‐structured Au@CeO₂ composite, with Au nanoparticle sizes below about 10 nm and a loading amount of 3.6 wt %, is reported for the NRR. The results demonstrate that as‐synthesized Au@CeO₂ possesses a surface area of 40.7 m² g⁻¹ and a porous structure. As an electrocatalyst, it exhibits high NRR activity, with an NH₃ yield rate of 28.2 μg h⁻¹ cm⁻² (10.6 μg h⁻¹ mg⁻¹ _cat., 293.8 μg h⁻¹ mg⁻¹ _Au) and a faradaic efficiency of 9.50 % at −0.4 V versus a reversible hydrogen electrode in 0.01 m H₂SO₄ electrolyte. The characterization results reveal the presence of rich oxygen vacancies in the CeO₂ nanoparticle shell of Au@CeO₂; these are favorable for N₂ adsorption and activation for the NRR. This has been further verified by theoretical calculations. The abundant oxygen vacancies in the CeO₂ nanoparticle shell, combined with the Au nanoparticle core of Au@CeO₂, are electrocatalytically active sites for the NRR, and thus, synergistically enhance the conversion of N₂ into NH₃.

Publication date: April 2019

Source: Molecular Catalysis, Volume 467

Author(s): Eo Jin Lee, Joongwon Lee, Minzae Lee, Hyung-Ki Min, Seungwon Park, Do Heui Kim

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Publication date: January 2019

Source: Journal of Catalysis, Volume 369

Author(s): Xiao Jiang, Xiaowa Nie, Xiaoxing Wang, Haozhi Wang, Naoto Koizumi, Yonggang Chen, Xinwen Guo, Chunshan Song

Staining a porous catalyst

Staining a porous catalyst, Published online: 05 November 2018; doi:10.1038/s41557-018-0168-7

The structural features and catalytic performances of catalyst particles have now been correlated using a fluorescence microscopy approach, by tracking nanoprobes as well as fluorescent reaction products. Such mapping enables exploration of structure–function relationships, which is essential for the design of better catalysts.

Publication date: August 2018
Source:Journal of Catalysis, Volume 364
Author(s): Yuan Tan, Xiao Yan Liu, Lin Li, Leilei Kang, Aiqin Wang, Tao Zhang
The effect of the divalent metal ions on the hydrotalcite (HT) (MAl-HT; M = Mg, Zn, Ni)-supported thiolated Au25 nanoclusters (NCs) as the precatalysts for the chemoselective hydrogenation of 3-nitrostyrene to 3-vinylaniline was investigated. The highest chemoselectivity was obtained over the Au25/ZnAl-HT-300 (calcined at 300 °C) catalyst, with a maintained selectivity of desired product above 98%. The Au25/NiAl-HT-300 catalyst exhibited the highest activity, although the particle size of gold (3.2 nm) was greater than those of the Au25/MgAl-HT-300 (2.2 nm) and Au25/ZnAl-HT-300 (1.7 nm) catalysts. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results of CO adsorption revealed that Ni interacting intimately with gold could be reduced easily, which affected the catalytic behavior of the Au25/NiAl-HT-300 catalyst. Furthermore, the results of the in situ DRIFTS of the adsorption of nitrostyrene at 10 bar of hydrogen suggested that, besides the condensation route, it also followed the direct route to produce aniline on Au25/NiAl-HT-300, which was different from the other two catalysts. This work provides new insight into the support effect over the gold catalysts for selective hydrogenation reactions.

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Publication date: January 2018
Source:Journal of Catalysis, Volume 357
Author(s): Yujun Zhao, Ziyuan Guo, Haojie Zhang, Bo Peng, Yuxi Xu, Yue Wang, Jian Zhang, Yan Xu, Shengping Wang, Xinbin Ma
An ordered hierarchical porous silica (HPS) presenting both mesopores and micropores was fabricated and used for supporting copper catalysts (Cu/HPS). In the prepared Cu/HPS catalysts, high dispersion of both Cu⁰ and Cu⁺ species together with ordered porous structure were achieved. The anchoring effect of micropores hindered the agglomeration of copper species, while the formation of Cu-O-Si species, derived from the strong interaction between surface silica and copper precursor, was prompted by the ammonia evaporation approach. The Cu/HPS catalysts were tested in the hydrogenation of diesters to diols. It shows excellent activity on dimethyl adipate hydrogenation with a 1,6-hexanediol space-time yield of 0.72 g/(g∙h) under WHSV = 1.2 h⁻¹. It was further investigated that the activity in dimethyl adipate hydrogenation, in contrast to that of dimethyl oxalate hydrogenation, would be readily limited by pore diffusion, due to the porous structure of HPS.

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Publication date: 25 August 2017
Source:Applied Catalysis A: General, Volume 544
Author(s): Tuan Ngoc Phan, Young-Kwon Park, In-Gu Lee, Chang Hyun Ko
Mesoporous TiO2, Al2O3, silica (SBA-15), and nonporous conventional TiO2 (P25) were used as supports for Ru catalysts in the hydrodeoxygenation (HDO) of anisole. The catalytic reaction was performed in a batch reactor at 200°C and 5–30bar H2 pressure. It was shown that the selectivity of this catalytic system towards benzene strongly depended on the H2 pressure, being higher at low pressure. Moreover, significant differences in the product distribution were observed for these catalysts suggesting the strong influence of the nature of supports on controlling the reaction pathway. The SBA-15-supported Ru catalyst (Ru/SBA-15) catalyzed the reaction primarily by the hydrogenation (HYD) pathway. The mesoporous-Al2O3-supported Ru (Ru/meso-Al2O3) promoted the reaction via the HYD and demethylation pathways simultaneously. Mesoporous-TiO2-supported Ru (Ru/meso-TiO2) and P25-supported Ru (Ru/P25) promoted higher yield of benzene, indicating its high selectivity for the direct deoxygenation (DDO) route. The use of meso-TiO2 facilitated the spillover effect, leading to the formation of numerous Ti³⁺ defect sites and oxygen vacancies. As a result, Ru/meso-TiO2 with anatase phase exhibited higher selectivity for the DDO pathway compared to nonporous P25 with a mixed rutile and anatase phase. The results indicated that the phase and mesoporous structure of TiO2 plays an important role in promoting its interaction with Ru particles and in selecting the HDO reaction pathway.

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Real-time tracking of the three-dimensional (3D) evolution of colloidal nanoparticles in solution is essential for understanding complex mechanisms involved in nanoparticle growth and transformation. We used time-resolved small-angle and wide-angle x-ray scattering simultaneously to monitor oxidation of highly uniform colloidal iron nanoparticles, enabling the reconstruction of intermediate 3D morphologies of the nanoparticles with a spatial resolution of ~5 angstroms. The in situ observations, combined with large-scale reactive molecular dynamics simulations, reveal the details of the transformation from solid metal nanoparticles to hollow metal oxide nanoshells via a nanoscale Kirkendall process—for example, coalescence of voids as they grow and reversal of mass diffusion direction depending on crystallinity. Our results highlight the complex interplay between defect chemistry and defect dynamics in determining nanoparticle transformation and formation.

The synthesis of a carbon nanobelt, comprising a closed loop of fully fused edge-sharing benzene rings, has been an elusive goal in organic chemistry for more than 60 years. Here we report the synthesis of one such compound through iterative Wittig reactions followed by a nickel-mediated aryl-aryl coupling reaction. The cylindrical shape of its belt structure was confirmed by x-ray crystallography, and its fundamental optoelectronic properties were elucidated by ultraviolet-visible absorption, fluorescence, and Raman spectroscopic studies, as well as theoretical calculations. This molecule could potentially serve as a seed for the preparation of structurally well-defined carbon nanotubes. Authors: Guillaume Povie, Yasutomo Segawa, Taishi Nishihara, Yuhei Miyauchi, Kenichiro Itami

There remains considerable debate over the active form of gold under operating conditions of a recently validated gold catalyst for acetylene hydrochlorination. We have performed an in situ x-ray absorption fine structure study of gold/carbon (Au/C) catalysts under acetylene hydrochlorination reaction conditions and show that highly active catalysts comprise single-site cationic Au entities whose activity correlates with the ratio of Au(I):Au(III) present. We demonstrate that these Au/C catalysts are supported analogs of single-site homogeneous Au catalysts and propose a mechanism, supported by computational modeling, based on a redox couple of Au(I)-Au(III) species. Authors: Grazia Malta, Simon A. Kondrat, Simon J. Freakley, Catherine J. Davies, Li Lu, Simon Dawson, Adam Thetford, Emma K. Gibson, David J. Morgan, Wilm Jones, Peter P. Wells, Peter Johnston, C. Richard A. Catlow, Christopher J. Kiely, Graham J. Hutchings

Nature Chemistry. doi:10.1038/nchem.2740

Authors: Guoliang Liu, Alex W. Robertson, Molly Meng-Jung Li, Winson C. H. Kuo, Matthew T. Darby, Mohamad H. Muhieddine, Yung-Chang Lin, Kazu Suenaga, Michail Stamatakis, Jamie H. Warner & Shik Chi Edman Tsang

Converting oxygen-rich biomass into fuels requires the removal of oxygen groups through hydrodeoxygenation. MoS2 monolayer sheets decorated with isolated Co atoms bound to sulfur vacancies in the basal plane have now been synthesized that exhibit superior catalytic activity, selectivity and stability for the hydrodeoxygenation of 4-methylphenol to toluene when compared to conventionally prepared materials.

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