Catalytic System Research Articles

Direct evidence from STXM analysis of enhanced oxygen storage capacity in ceria through the addition of Cu and Mg: Correlation of HT-WGS reaction performance

Here, scanning transmission X-ray microscopy (STXM) analysis was utilized to directly present visual evidence of changes in oxygen storage capacity (OSC) when small amounts of an additive were incorporated into CeO2. Specifically, the chemical map measured by STXM analysis differentiated between Cu-rich and Ce-rich areas to derive the proportion of Ce3+. Additionally, we found that the dispersion of Cu significantly influenced the formation of OSC. The findings were applied to the high-temperature water–gas shift reaction for producing high-purity hydrogen from waste-derived syngas, establishing a correlation with catalyst performance. Consequently, the CCM75 (Ce/Mg = 75/25) catalyst demonstrated the highest Cu dispersion and OSC values (6.9 %, 800.3 μmolO/gcat), and it also showed the highest CO conversion (79 % at 450 °C) and stability (−7.7 % at 450 °C after 50 h), attributed to the significant presence of active Cu. This study confirms previously reported interactions between Cu and CeO2 and uncovers the significant roles of Cu and Mg in this catalysis system, providing new understanding of the mechanisms that facilitate OSC improvement.

Synthesis of a symmetrically meta-substituted poly(diphenylacetylene) bearing chiral amide groups and its application as a chiral stationary phase for high-performance liquid chromatography

Abstract A symmetrically meta-substituted poly(diphenylacetylene) bearing chiral amide groups was synthesized by reacting (R)-1-phenylethylamine with a carboxy-group-containing precursor polymer, which was obtained by polymerizing the corresponding ester-containing diphenylacetylene using a modified Mo(V)-based catalytic system followed by hydrolysis. The polymer formed a one-handed helical conformation when thermally annealed in a solvent. The chiral recognition ability of the polymer before and after thermal annealing was investigated when used as a chiral stationary phase for high-performance liquid chromatography.

Natural shellac-based microcapsules as lipase carriers for recyclable efficient Pickering interfacial biocatalysis

Enzyme is an important class of catalyst. However, the efficiency of enzyme-catalyzed reactions is constrained by the limited contact between the enzyme and its substrate. In this study, to overcome this challenge, lipase-loaded microcapsules were prepared from natural shellac and nanoparticles using the emulsion template method. These microcapsules can perform dual roles as stabilizers and enzyme carriers to construct a water-in-oil Pickering interfacial biocatalytic system. The results showed that the hydrolytic conversion of the microcapsules could reach 90% within 20 min, which was significantly higher than that of the traditional biphasic system. The catalytic activity was influenced by the oil-to-water volume ratio and the microcapsule content. The microcapsules remained highly catalytic efficiency even after storage for three months or seven cycles of reuse. These microcapsules were prepared without the use of any cross-linkers or harsh solvents. This green and efficient catalytic system has great application prospects in the food industry.

A dual-thermosensitive hydrogel catalyst with Ag nanoparticles capable of single/tandem/non catalytic switchable ability

Thermosensitive hydrogels are among the most promising class of catalysts for self-controlled tandem catalytic systems. In this study, we developed a bi-layered, molecularly imprinted, thermosensitive hydrogel catalyst that is loaded with silver metal nanoparticles (Ag NPs) and acidic sites. This catalyst is capable of regulating alternating single and tandem reactions, making it a valuable tool for complicated catalytic applications. The catalyst displays two key phase transition temperatures, at 37 °C and 46 °C, by combining positive and negative response temperature-sensitive hydrogel layers together, enabling crossing range responsive ability of the "open" or "closed" state of the substrate channels. Meanwhile, the hydrogel layers can effectively separate the different catalytic sites to prevent active sites and intermediate products from mixing and causing cross-reactions. The opposite thermosensitive characteristics of the hydrogels coupled together produce a swelling-contraction behavior, enabling efficient sequencing of single/tandem/non-catalytic reactions. Overall, this study presents a promising strategy for the development of smart hydrogel catalysts in self-controlling tandem catalytic systems.

A concise and mild condition for Pd-catalyzed C(sp2)–H arylation

It is particularly significant to develop mild and efficient methods to construct 2-aryl-substituted benzoic acids framwork due to their wide existence in many important natural organic compounds. Here, we report a concise and mild method to synthesize ortho-arylation of benzoic acids. In this mild catalytic system, decarboxylation byproducts were not observed. Meanwhile, the high yields could be obtained in the absence of ligands.

Highly selective oxidation of 5-HMF to HMFCA via a facile Pt-Ag co-catalytic strategy

5-Hydroxymethyl-2-furancarboxylic acid (HMFCA) is an important feedstock in chemical and pharmaceutical industries. Its production through aerobic conversion of 5-hydroxymethylfurfural (5-HMF) has promising prospects but is challenged by the over-oxidation. In this work, we develop a refined Pt-Ag co-catalytic strategy to tailor the selectivity of 5-HMF’s aerobic oxidation. By simple in situ addition of AgNO3 to the thermal catalytic system of Pt nanoparticles, the main products of 5-HMF oxidation could be shifted from 2,5-furandicarboxylic acid (FDCA) to HMFCA with an ultrahigh selectivity of over 99%. Density functional theory calculations demonstrate that such strategy could alter the HMFCA adsorption sites from Pt to Ag sites and prevent the oxidation of hydroxymethyl group. In addition, this strategy can be extended to other Ag species, such as AgCl, Ag2O and AgO. This work provides insights into the Pt-Ag synergistic catalysis and opens up a simple avenue to control the product selectivity for biomass refinement.

Unexplored catalytic potency of a magnetic CoFe2O4/Ni-BDC MOF composite for the one-pot sustainable synthesis of 5-substituted 1-H tetrazoles

Within the domain of materials science and engineering, significant progress has led to the emergence of innovative materials based on magnetic MOFs, positioning them as promising candidates in the field of catalysis. This research aims to elaborate on the development of a finely tailored magnetic MOF composite; Ni-BDC (Nickel benzene-1,4-dicarboxylate) microflakes which was synthesized through a straightforward in-situ solvothermal approach. Extensive investigations into the structural properties of the resultant hybrid composite were carried out using various characterization techniques encompassing X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis, atomic absorption spectroscopy (AAS), energy-dispersive X-ray spectroscopy (EDX), energy-dispersive X-ray fluorescence (ED-XRF), and vibrating sample magnetometry (VSM). The developed material demonstrated remarkable efficiency in expediting the synthesis of a diverse array of pharmaceutically active 5-substituted 1H-tetrazole derivatives through a multicomponent coupling reaction involving substituted aldehydes, malononitrile, and sodium azide as key components. A noteworthy feature of this approach is its adherence to environmentally friendly reaction conditions, thus making it superior in comparison to previously established methodologies. Furthermore, a plausible mechanistic pathway has been proposed to elucidate the impressive performance of the developed catalytic system in the targeted reaction. It is anticipated that the current research will not only contribute to the purposeful designing of advanced magnetic MOF-based architectures but will also play a pivotal role in promoting sustainable practices in industrial processes, addressing pressing environmental and economic concerns.

The Mn-Doped CeO2 Nanoparticles with Enhanced Peroxidase-like Activity for One-Pot Analysis of Glucose at Neutral pH based on Bio-inorganic Cascade Reactions

Enzyme catalytic cascade reactions based on peroxidase nanozymes and natural enzymes have aroused extensive attention in analytical fields. However, a majority of peroxidase nanozymes perform well only in acidic environments, resulting in their optimal pH mismatch with a neutral pH of natural enzymes, further restricting their application in biochemical sensing. Herein, Mn-doped CeO2 (Mn/CeO2) performing enhanced peroxidase-like activity at neutral conditions was prepared via a facile and feasible strategy. An effective enzyme cascade catalysis system via integrating glucose oxidase (GOx) with Mn/CeO2 was developed for one-pot detection of glucose in serum at neutral conditions. Using one-pot multistep catalytic reactions, this work provided a detection platform that allows for faster detection and easier operations than traditional methods. Under optimized conditions, our assay performed a sensitive detection of glucose ranging from 2.0 μΜ to 300 μΜ and a low detection limit of 0.279 μΜ. Notably, favorable analytical outcomes for glucose detection in serum samples were obtained, exhibiting potential applications in clinical diagnosis.

PRODUCTION OF COMPOSITE CARBON ADSORBENTS BASED ON TEXTILE CORD OBTAINED FROM CAR TIRE RESIDUES

Carbon chemistry opens up very wide prospects in obtaining compositions based on carbon-containing raw materials, due to the achievements of recent years in this field. Due to their unique properties, extremely high chemical resistance, thermal resistance, heat resistance and specific strength, carbon materials have found application for the manufacture of carbon-containing refractory, high-temperature composite materials, modified electrodes as fillers for the tire and rubber industry, catalytic systems based on carbon-containing raw materials, etc. Frequently used carbon materials do not meet the requirements of the technological process, in some cases their use is economically unjustified, since they are expensive and have a small raw material base. Therefore, obtaining new efficient and cheap natural carbon materials from available types of industrial raw materials is one of the urgent tasks currently facing scientists and technologists. Textile wire, a product of processing rubber organic waste, can become a promising new raw material for the production of carbon-containing materials. Porous carbon materials were obtained in a laboratory installation, optimal parameters were determined, and the physico-chemical properties of the feedstock and the obtained adsorbents (ash content, humidity, volatility, density, sumar pore volume, elemental composition) were studied.

One-step fabrication of a self-driven point-of-care chip by femtosecond laser direct writing and its application in cancer cell H2O2 detection via semiconductor-based SERS

Self-driven microfluidic systems have attracted significant attention and demonstrated great potential in the field of point-of-care (POC) testing due to their device simplicity, low power consumption, increased portability, and reduced sample consumption. To develop POC detection chips with diverse characteristics that meet different requirements, there is a strong demand for feasible strategies that enable easy operation and reduce processing time. Here, a one-step processing approach using femtosecond laser direct writing technology was proposed to fabricate a capillary-actuated POC microfluidic chip. The driving force of the chip is highly dependent on its surface wettability, which can be easily adjusted by changing the laser processing parameters. This POC microfluidic chip allowed for the detection of intracellular H2O2 through a catalytic reaction system that incorporated 5-aminosalicylic acid -sensitized colloidal TiO2 nanoparticles and horse radish peroxidase, with integrating semiconductor-based surface-enhanced Raman scattering (SERS) quantitative technique. The concentration of H2O2 was determined by the SERS signal of the catalytic products in the microfluidic chip, resulting in rapid detection with minimal sample consumption. Our method provides a simple, feasible, and alternative strategy for POC testing of H2O2, with a linear range of 10−2∼10−6 M and a limit of detection of 0.55 μM. This approach was successfully applied to rapid detection of intracellular H2O2 in MCF-7 breast cancer cells with high sensitivity and minimal sample consumption. Additionally, this study not only demonstrates the exceptional advantages of femtosecond laser processing technology in fabricating diverse microfluidic chips for various applications, but also presents an efficient POC testing strategy for detecting cell signaling molecules.

Pulsed laser induced plasma and thermal effects on molybdenum carbide for dry reforming of methane

Dry reforming of methane (DRM) is a highly endothermic process, with its development hindered by the harsh thermocatalytic conditions required. We propose an innovative DRM approach utilizing a 16 W pulsed laser in combination with a cost-effective Mo2C catalyst, enabling DRM under milder conditions. The pulsed laser serves a dual function by inducing localized high temperatures and generating *CH plasma on the Mo2C surface. This activates CH4 and CO2, significantly accelerating the DRM reaction. Notably, the laser directly generates *CH plasma from CH4 through thermionic emission and cascade ionization, bypassing the traditional step-by-step dehydrogenation process and eliminating the rate-limiting step of methane cracking. This method maintains a carbon-oxygen balanced environment, thus preventing the deactivation of the Mo2C catalyst due to CO2 oxidation. The laser-catalytic DRM achieves high yields of H2 (14300.8 mmol h−1 g−1) and CO (14949.9 mmol h−1 g−1) with satisfactory energy efficiency (0.98 mmol kJ−1), providing a promising alternative for high-energy-consuming catalytic systems.

Advancements in the Heterogeneous Catalytic Hydrogenation of Furfural to Downstream Products

AbstractFurfural is a 5‐membered heterocyclic compound derived from biomass and can be converted into various chemicals and biofuels through hydrogenation. Furfural conversion invariably requires the involvement of catalysts. The performance of these catalysts predominantly hinges on the characteristics of the metal active sites, the properties of the support, and the regulation of reaction conditions. Therefore, the selection of metals and supports, the preparation methods of catalysts, as well as the determination of reaction solvents, temperature, pressure, and catalyst dosage are the factors that researchers need to consider. Based on this, this present review focuses on the production process and heterogeneous catalytic system selection of furfural hydrogenation to prepare downstream products since 2018. It provides a brief introduction to the corresponding catalytic reaction mechanisms, focuses on the effects of different metals and supports on catalytic performance, and provides an outlook on this research direction.

Hydroprocessing of Gasoline on Modified Alumina Catalysts

The hydroprocessing of gasoline on modified alumina catalysts makes it possible to obtain high-octane products. The implementation and development of the process have largely become possible due to the development of modified alumina catalysts that do not contain noble metals and exhibit special catalytic properties. This article discusses topical issues of petrochemistry, namely the creation of catalysts with improved characteristics for the production of high-octane gasoline with low sulfur content. New catalytic systems based on alumina and other carriers modified with transition metals, lanthanum and phosphorus were synthesized. Вy physico-chemical methods of analysis TPD of ammonia, TEM and XRD, we studied the acid–base and structural characteristics of the developed catalysts. The activity of the developed catalysts in the studied process of hydrotreating gasoline fractions depends on the structure and condition of the active centers. The process of hydrotreating straight-run gasoline in the presence of synthesized catalysts was carried out on a laboratory flow unit. It was shown that, during the hydrotreating of straight-run gasoline on the NiO-MoO3-La-P-HZSM-HY-Al2O3 catalyst, the octane number in the final product increased to 88.6, and the sulfur content decreased from 0.0088 to 0.001%. It was found that the minimum sulfur content in the gasoline hydrotreating product of 0.0005% was achieved on the catalyst CoO-WO3-La-P-HZSM-HY-Al2O3, which is significantly lower than for other studied catalytic systems. The obtained results of the sulfur content in the hydrotreating products fully comply with the Euro-5 standard. Thus, the efficiency of hydrotreating the gasoline fractions studied in this work was mainly determined by the nature of the carriers and modifiers used for the synthesis of catalysts and the technological parameters of the process. The synthesized catalysts showed high activity and selectivity, resulting in high-octane gasoline with a low sulfur content that meets international quality standards.

Development of a Cobalt Catalyst from ZIF‐67 and Application in the Hydrogenation of N‐Heteroarenes

AbstractHydrogenation of N‐heteroarenes to saturated N‐heterocycles is an important reaction in organic synthesis. Hydrogen is a green reducing reagent and has been widely applied in industrial production. The development of an appropriate catalyst to realize hydrogenation at low pressure and temperature is desired. In this study, we developed a cobalt‐based catalyst derived from ZIF‐67 that exhibits high activity for N‐heteroarene hydrogenation under 5–20 bar hydrogen, which is a relatively low pressure as compared to reported catalytic systems. This nano‐cobalt catalyst shows broad substrate scope and can be reused without obvious activity loss.

Modification of electron transfer paths in CdS-TiO2 Z-type heterojunction by cobalt-based complexes for boosting visible-light photocatalytic hydrogen evolution

Ti-oxo clusters as photocatalytic heterojunction precursor materials are a promising strategy for preparing TiO2. Enhancing the utilization of photogenerated electrons and increasing the delivery channel of these electrons can improve the performance of photocatalytic materials for H2 evolution significantly. Hereby, a novel ternary [TiO2-CdS QDs-5/Co(bpy)3Cl2] photocatalyst for highly efficient photocatalytic HER was reported for the first time. In this paper, a TiO2-CdS QDs-5 binary Z-type heterojunction was identified, and the photocatalytic HER yield was further improved by [Co(bpy)3Cl2]. The above-mentioned ternary system is advantageous for separating and transferring photogenerated electron-hole pairs. The photocatalytic HER rate of this catalytic system was 4440.84 μmol·h−1·g−1, which was 7.1 times more than that of TiO2-CdS QDs-5. The results indicate that the system is capable of maintaining stability and enhancement of the photocatalytic HER under visible light irradiation. In this study, we investigated photogenerated electron transfer pathways to improve the photocatalytic HER of TiO2 and we also revealed the electron transfer mechanism of TiO2-CdS QDs-5 Z-typed heterojunction with [Co(bpy)3Cl2] through DFT calculation. More importantly, this study presents a novel Z-type heterojunction catalyst, which enhance the electron transport path and this work provides an effective design concept for the development of TiO2-based materials for efficient photocatalytic HER.

Copper‐Catalyzed Regiodivergent Asymmetric Difunctionalization of Terminal Alkynes

We herein describe the first example of ligand‐controlled, copper‐catalyzed regiodivergent asymmetric difunctionalization of terminal alkynes through a cascade hydroboration and hydroallylation process. The catalytic system, consisting of (R)‐DTBM‐Segphos and CuBr, could efficiently achieve asymmetric 1,1‐difunctionalization of aryl terminal alkynes, while ligand switching to (S,S)‐Ph‐BPE could result in asymmetric 1,2‐difunctionalization exclusively. In addition, alkyl substituted terminal alkynes, especially industrially relevant acetylene and propyne, were also valid feedstocks for asymmetric 1,1‐difunctionalization. This protocol is characterized by good functional group tolerance, a broad scope of substrates (> 150 examples), and mild reaction conditions. We also showcase the value of this method in the late‐stage functionalization of complicated bioactive molecules and simplifying the synthetic routes toward the key intermediacy of natural product (bruguierol A). Mechanistic studies combined with DFT calculations provide insight into the mechanism and origins of this ligand‐controlled regio‐ and stereoselectivity.

Copper Catalyzed Borylation of Alkynes: An Experimental Mechanistic Study.

The copper catalyzed hydroboration of alkynes with B2pin2 was studied by in detail studies of individual relevant steps along the catalytic pathway. A number of reaction steps were retraced by in situ NMR spectroscopy as well as central intermediates and side-products were isolated and comprehensively characterized. A copper boryl complex is central to the catalytic process by inserting the terminal alkyne substrate into the B-Cu bond. The selectivity of this step - depending on the NHC auxiliary ligand - determines the α/β selectivity observed in the product. The latter complex is protonated by the auxiliary alcohol reagent resulting in hydroboration product formation and formation of a Cu alkoxido complex. Reaction of the latter with B2pin2 results in the regeneration of the central copper boryl complex. This alcoholysis step depends on the acidity of the alcohol, in particular on the relative acidity of the alcohol vs. the alkyne substrate. A number of side reactions leading to the hydrogenation product of the alkyne substrate and a bis hydroborated product were identified and studied in some detail. It is concluded that the performance of a particular catalytic system depends crucially on the relative acidities of the reagents and generalizations may be difficult.

Copper hydride species activated hypophosphite hydrolysis towards litre-level and high-purity hydrogen production

Large-scale generation of high-purity hydrogen (H2) from simple hydrolysis strategy is vital, but the traditional technologies remain problems of economy and efficiency. Herein, a new and low-cost technical route is highlighted to realize the litre-level and efficient production of high-purity H2 from sodium hypophosphite (NaH2PO2) hydrolysis at room temperature. The formation and stabilization of CuH species on the designed Cu–Cu2O/CuH catalyst plays a key role in stimulating a continuous reversible NaH2PO2 hydrolysis cycle for H2. Impressively, this new technology achieves the high generated rate of 3.3 L h−1•cm−2 for H2 in alkaline media, which outperforms the other existing hydrolysis technologies. The proposed catalytic mechanism involves renewable CuH active species catalyzing the spontaneous reaction of NaH2PO2 and H2O to form H2 gas and phosphate. From the view of practical application, the developed coupling catalytic system also operates efficiently in deionized water, seawater and tap water solutions, shows unique interference immunity and high stability of convenient H2 generation.

Manganese/Enzyme Sequential Catalytic Pathway for the Production of Optically Active γ-Functionalized Alcohols.

A brief, practical catalytic process for the production of optically active γ-functionalized alcohols from relevant alkenes has been developed by using a robust Mn(III)/air/(Me2SiH)2O catalytic system combined with lipase-catalyzed kinetic resolution. This approach demonstrates exceptional tolerance toward proximal functional groups present on alkenes, enabling the achievement of high yields and exclusive enantioselectivity. Under this sequential catalytic system, the chiral alkene precursors can also be converted into γ-functionalized alcohols and related acetates as separable single enantiomers.

Catalysed Aryl Amine Syntheses via Azides: From Azidation of Aryl Halides to Azide Reduction and Direct Amination

AbstractThis review summarises and discusses aryl amine and azide syntheses from aryl halides employing azides. The majority of the reported reactions proceed with copper catalysis or mediation. Often, an aryl azide is formed in the first step, which is then reduced in situ to an aryl amine in a second step. The occurrence of the second step, the reduction, depends on the chosen reaction conditions and the substrates. The formation of only aryl azides through Cu‐mediated C−N bond formations is discussed, followed by mediated and catalytic aryl azide reduction employing different catalytic systems, and azidation with in situ azide reduction to amines, viz. azidation‐amination strategies. The azidation‐amination allows for the synthesis of complex heterocycles in multi‐step one‐pot procedures, of which several are summarised here. Examples of the application of azidation‐amination for synthesising important aryl amines employed in or as biologically active compounds, catalysis and materials science are also summarised. Finally, conducted control reactions have been collected and discussed in combination with mechanistic proposals. This literature survey allows us to pinpoint design criteria for the azide reduction to valuable amines, which includes the choice of reaction conditions such as solvent system and additives, involved metal and promising substrates.