Combination Of Catalysis Research Articles

Acrylate-Induced β-H Elimination in Coordination Insertion Copolymerizaton Catalyzed by Nickel.

Polar monomer-induced β-H elimination is a key elementary step in polar polyolefin synthesis by coordination polymerization but remains underexplored. Herein, we show that a bulky neutral Ni catalyst, 1Ph, is not only a high-performance catalyst in ethylene/acrylate copolymerization (activity up to ∼37,000 kg/(mol·h) at 130 °C in a batch reactor, mol % tBA ∼ 0.3) but also a suitable platform for investigation of acrylate-induced β-H elimination. 4Ph-tBu, a novel Ni alkyl complex generated after acrylate-induced β-H elimination and subsequent acrylate insertion, was identified and characterized by crystallography. A combination of catalysis and mechanistic studies reveals effects of the acrylate monomer, bidentate ligand, and the labile ligand (e.g., pyridine) on the kinetics of β-H elimination, the role of β-H elimination in copolymerization catalysis as a chain-termination pathway, and its potential in controlling the polymer microstructure in polar polyolefin synthesis.

Catalytically active membranes for esterification: A review

Esterification is an important process in the food industry and can be carried out via homogeneous or heterogeneous catalysis. The homogeneous catalyst, despite providing high conversion, can cause corrosion in reactors, which is not observed with the use of heterogeneous catalysts. However, some of these catalysts require a high process temperature and may lose their catalytic activity with reuse. Thus, catalytic membranes have been proposed as a promising alternative. The combination of catalysis and separation in a single module provides greater conversion, reduction of excess reagents, compact industrial plant, making the process more efficient. Within this context, this work aims to present a literature review on the catalytic membrane for the synthesis of esters, improving the understanding of the production and development. This review examines the materials, catalysts used, and synthetic pathways. A comparison between the methods, as well as limitations and gaps in the literature, are highlighted.

Hybrid Nanocomposites Formed by Lanthanide Nanoparticles in Zr-MOF for Local Temperature Measurements during Catalytic Reactions

Zr-metal organic frameworks (MOFs) are waterstable materials with high surface properties and chemical stabilities and are often employed for catalysis. They can also become hosts for various upconverting nanoparticles via selfassembly, which opens up possibilities to use such nanocomposite materials for combined catalysis-thermometry applications. In our work, we show that the NaGdF4:Er, Yb@UiO-66-NH2, NaGdF4:Tm,Yb@UiO-66-NH2, and NaYF4:Er,Yb@NaYF4@UiO-66-NH2 nanocomposite materials display excellent temperaturedependent luminescence properties. Additionally, these nanocomposite materials can perform as a stable and reusable catalyst for the esterification of lauric acid (biomass-derived free fatty acid) with methanol to obtain methyl laurate. The NaGdF4/NaYF4 nanoparticles incorporated in the MOF do not significantly decrease their catalytic performance. At the same time, photoluminescence measurements can be performed in a working catalytic environment and the temperature can be read out from the ratio of the H-2(11/2) and S-4(3/2) transition peaks of Er3+ or F-3(3) and H-3(4) transition peaks of Tm3+ from the nanocomposites. The correlation between temperature, luminescent intensities, and catalytic reactivity was studied and showed that all the three factors depend on each other, but do not interfere. To the best of our knowledge, the combination of catalysis and luminescence thermometry in a MOF hybrid material has not been reported to date. However, it opens a wide range of possibilities, keeping in mind the large and versatile number of MOFs as well as different thermometry systems that can be incorporated into inorganic nanoparticles.

Pnictogen-Bonding Catalysis and Transport Combined: Polyether Transporters Made In Situ

The combination of catalysis and transport across lipid bilayer membranes promises directional access to a solvent-free and structured nanospace that could accelerate, modulate, and, at best, enable new chemical reactions. To elaborate on these expectations, anion transport and catalysis with pnictogen and tetrel bonds are combined with polyether cascade cyclizations into bioinspired cation transporters. Characterized separately, synergistic anion and cation transporters of very high activity are identified. Combined for catalysis in membranes, cascade cyclizations are found to occur with a formal rate enhancement beyond one million compared to bulk solution and product formation is detected in situ as an increase in transport activity. With this operational system in place, intriguing perspectives open up to exploit all aspects of this unique nanospace for important chemical transformations.

In Vivo Assembly of Artificial Metalloenzymes and Application in Whole-Cell Biocatalysis*.

We report the supramolecular assembly of artificial metalloenzymes (ArMs), based on the Lactococcal multidrug resistance regulator (LmrR) and an exogeneous copper(II)–phenanthroline complex, in the cytoplasm of E. coli cells. A combination of catalysis, cell‐fractionation, and inhibitor experiments, supplemented with in‐cell solid‐state NMR spectroscopy, confirmed the in‐cell assembly. The ArM‐containing whole cells were active in the catalysis of the enantioselective Friedel–Crafts alkylation of indoles and the Diels–Alder reaction of azachalcone with cyclopentadiene. Directed evolution resulted in two different improved mutants for both reactions, LmrR_A92E_M8D and LmrR_A92E_V15A, respectively. The whole‐cell ArM system required no engineering of the microbial host, the protein scaffold, or the cofactor to achieve ArM assembly and catalysis. We consider this a key step towards integrating abiological catalysis with biosynthesis to generate a hybrid metabolism.

In Vivo Assembly of Artificial Metalloenzymes and Application in Whole‐Cell Biocatalysis**

AbstractWe report the supramolecular assembly of artificial metalloenzymes (ArMs), based on the Lactococcal multidrug resistance regulator (LmrR) and an exogeneous copper(II)–phenanthroline complex, in the cytoplasm of E. coli cells. A combination of catalysis, cell‐fractionation, and inhibitor experiments, supplemented with in‐cell solid‐state NMR spectroscopy, confirmed the in‐cell assembly. The ArM‐containing whole cells were active in the catalysis of the enantioselective Friedel–Crafts alkylation of indoles and the Diels–Alder reaction of azachalcone with cyclopentadiene. Directed evolution resulted in two different improved mutants for both reactions, LmrR_A92E_M8D and LmrR_A92E_V15A, respectively. The whole‐cell ArM system required no engineering of the microbial host, the protein scaffold, or the cofactor to achieve ArM assembly and catalysis. We consider this a key step towards integrating abiological catalysis with biosynthesis to generate a hybrid metabolism.

Plasma-catalytic dry reforming of methane: Screening of catalytic materials in a coaxial packed-bed DBD reactor

The combination of catalysis with non-thermal plasma is a promising alternative to thermal catalysis. A dielectric-barrier discharge reactor was used to study plasma-catalytic dry reforming of methane at ambient pressure and temperature and a fixed plasma power of 45 W. The effect of different catalytic packing materials was evaluated in terms of conversion, product selectivity, and energy efficiency. The conversion of CO2 (~22%) and CH4 (~33%) were found to be similar in plasma-only and when introducing packing materials in plasma. The main reason is the shorter residence time of the gas due to packing geometry, when compared at identical flow rates. H2, CO, C2-C4 hydrocarbons, and oxygenates were identified in the product gas. High selectivity towards H2 and CO were found for all catalysts and plasma-only, with a H2/CO molar ratio of ~0.9. The lowest syngas selectivity was obtained with Cu/Al2O3 (~66%), which instead, had the highest alcohol selectivity (~3.6%).

Predicted Influence of Plasma Activation on Nonoxidative Coupling of Methane on Transition Metal Catalysts

The combination of catalysis and non-thermal plasma holds promise for enabling difficult chemical conversions. The possible synergy between both depends strongly on the nature of the reactive plasm...

Microwaves and Heterogeneous Catalysis: A Review on Selected Catalytic Processes

Since the late 1980s, the scientific community has been attracted to microwave energy as an alternative method of heating, due to the advantages that this technology offers over conventional heating technologies. In fact, differently from these, the microwave heating mechanism is a volumetric process in which heat is generated within the material itself, and, consequently, it can be very rapid and selective. In this way, the microwave-susceptible material can absorb the energy embodied in the microwaves. Application of the microwave heating technique to a chemical process can lead to both a reduction in processing time as well as an increase in the production rate, which is obtained by enhancing the chemical reactions and results in energy saving. The synthesis and sintering of materials by means of microwave radiation has been used for more than 20 years, while, future challenges will be, among others, the development of processes that achieve lower greenhouse gas (e.g., CO2) emissions and discover novel energy-saving catalyzed reactions. A natural choice in such efforts would be the combination of catalysis and microwave radiation. The main aim of this review is to give an overview of microwave applications in the heterogeneous catalysis, including the preparation of catalysts, as well as explore some selected microwave assisted catalytic reactions. The review is divided into three principal topics: (i) introduction to microwave chemistry and microwave materials processing; (ii) description of the loss mechanisms and microwave-specific effects in heterogeneous catalysis; and (iii) applications of microwaves in some selected chemical processes, including the preparation of heterogeneous catalysts.

Correction to “A Study on CO2 Decomposition to CO and O2 by the Combination of Catalysis and Dielectric-Barrier Discharges at Low Temperatures and Ambient Pressure”

Correction to “A Study on CO₂ Decomposition to CO and O₂ by the Combination of Catalysis and Dielectric-Barrier Discharges at Low Temperatures and Ambient Pressure”

Catalytically Active Oil-Based Lubricant Additives Enabled by Calcining Ni-Al Layered Double Hydroxides.

Layered double hydroxides (LDHs) have lately been hailed as robust lubricant additives for improving tribological properties and as ideal catalysts for synthesizing carbon-based nanomaterials. In this paper, in situ analytical tools are used to track the evolution of the crystal structure and chemical composition of LDHs during calcination. Nickel oxide and elemental nickel can be produced by calcining NiAl-LDH in air (LDH-C-Air) and argon (LDH-C-Ar), respectively. For the base oil with 1 wt % LDH-C-Air, negligible wear can be detected even after a 2 h friction test under a severe contact pressure (∼637 MPa). A relatively thick tribofilm (∼60 nm) with a better mechanical property is formed, which protects the solid surface from severe wear. In addition, the possible formed carbon debris may also prevent the direct collision of asperities and effectively improve the wear resistance. This work provides a unique vision for the application of calcined LDHs with the combination of catalysis and tribology.

Ultrasound-assisted synthesis and catalytic activity of mesostructured FeOx/SBA-15 and FeOx/Zr-SBA-15 catalysts for the oxidative desulfurization of model diesel

Abstract Two series of FeOx/SBA-15 and FeOx/Zr-SBA-15 mesoporous catalysts were synthesized with ultrasound-assisted method by varying Fe content from 10 wt% to 20 and 30 wt%. The crystalline structure, textural properties, surface morphologies, surface acidity, and phase composition of the catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM), in situ Fourier transform infrared spectroscopy (FTIR). The XRD, Raman and Mossbauer spectroscopic characterizations showed that both γ-Fe2O3 and α-Fe2O3 nanoparticles were present in all the catalysts and Fe3+ ions were dispersed on the surface of SBA-15 with different coordination. In the oxidation desulfurization (ODS) of a model diesel, the reaction parameters (temperature, time, and catalyst mass), Fe content, zirconium doping, and surface acidity of the catalysts were all critical for the ODS in a biphasic reaction system. All catalysts chiefly contained Lewis acidity which was related to iron content and zirconium modification and could correlate well with catalytic activity. Zirconium incooperating into the SBA-15 solid increased surface acidity and promoted γ-Fe2O3 formation by inhibiting the amorphous iron oxide in the Fe/Zr-SBA-15 catalysts, thus improved the ODS efficiency. The reaction temperature 60 °C was the optimal for ODS reaction, temperature greater than 80 °C led to oxidant partial decomposition. Under the optimal reaction condition, 0.1 g of the best catalysts (30%Fe/SBA-15 and 30%Fe/Zr-SBA-15) could remove all dibenzothiophene (DBT) (300 ppm DBT in 100 ml n-hexadecane) at 60 °C within 30 min. Thus, the combination of catalysis, oxidation and extraction in our polar-nonpolar-solid reaction system was simultaneously realized in one unit, which will be promising for effectively removal of organosulfur compounds for production of ultralow sulfur fuels.

Strategies for Hot Electron-Mediated Catalytic Reactions: Catalytronics

A pulse of high kinetic energy electrons can be generated after deposition of external energy to a metallic surface, such as the absorption of light or exothermic chemical processes. These energetic electrons are not at thermal equilibrium with the phonons of the metal atoms and are called “hot electrons”. The detection of hot electrons on the surface of a catalyst is an active subject in the field of surface science. More significantly, it has been found that surface processes, including desorption, diffusion, and chemical rearrangement of atomic and molecular species, are driven by the flow of hot electrons on the surface. The strong correlation between hot electron generation and surface phenomena suggests that hot electrons can be used to control surface chemical reactions, which is known as hot electron chemistry. In this Perspective, research strategies for electronic control of catalytic reactions by engineering metal–oxide interfaces and manipulating hot electron flux are discussed. Catalytic nanodiodes consisting of a metal catalyst film, semiconductor layers, and Ohmic contact pads have revealed a strong correlation between the hot electron flux (chemicurrent) and catalytic activity under CO oxidation and hydrogen oxidation. We highlight recent results on new architecture for hot electron collection, including a Au/TiO2 nanodiode and a graphene/TiO2 nanodiode, that show that hot electrons can be used for quantitative measurement of catalytic activity. We show that the direct conversion of photon energy to hot electron flows can be achieved in metal–semiconductor nanodiodes. Hot electrons and surface plasmons can be used to change the catalytic activity using metal–oxide nanocatalysts. This strategy requires an understanding of both the electronic and chemical properties of metal–oxide interfaces, as well as the combined measurement of electronic and chemical signals on nanoscale electronic devices during catalytic reactions, and therefore can be referred to as “catalytronics”, which is the combination of catalysis and electronics.

A Study on CO2 Decomposition to CO and O2 by the Combination of Catalysis and Dielectric-Barrier Discharges at Low Temperatures and Ambient Pressure

CO2 decomposition to CO and O2 was investigated in a dielectric-barrier discharge (DBD) reactor packed with BaTiO3 balls, glass beads with different sizes, and a mixture of a Ni/SiO2 catalyst and BaTiO3 balls at lower temperatures and ambient pressure. The property of packing beads and the reactor configuration affected the reaction significantly. The Ni/SiO2 catalyst samples were characterized by SEM, XRD, BET, and TEM. The combination of a DBD plasma and a Ni/SiO2 catalyst can enhance CO2 decomposition apparently, and a reaction mechanism of the plasma assisted CO2 dissociation over the catalyst was proposed. In comparison with the result packed with glass balls (3 mm), the combination of BaTiO3 beads (3 mm) with a stainless steel mesh significantly enhanced the CO2 conversion and energy efficiency by a factor of 14.8, and that with a Ni/SiO2 catalyst by a factor of 11.5 in a DBD plasma at a specific input energy (SIE) of 55.2 kJ/L and low temperatures (<115 °C).

ChemInform Abstract: Toward a Symphony of Reactivity: Cascades Involving Catalysis and Sigmatropic Rearrangements

AbstractReview: [165 refs.

Toward a symphony of reactivity: cascades involving catalysis and sigmatropic rearrangements.

Catalysis and synthesis are intimately linked in modern organic chemistry. The synthesis of complex molecules is an ever evolving area of science. In many regards, the inherent beauty associated with a synthetic sequence can be linked to a certain combination of the creativity with which a sequence is designed and the overall efficiency with which the ultimate process is performed. In synthesis, as in other endeavors, beauty is very much in the eyes of the beholder. It is with this in mind that we will attempt to review an area of synthesis that has fascinated us and that we find extraordinarily beautiful, namely the combination of catalysis and sigmatropic rearrangements in consecutive and cascade sequences.

Antimicrobial properties of enzymatically triggered self-assembling aromatic peptide amphiphiles.

The combination of catalysis and self-assembly influences many key processes in living systems. Synthetic analogues of such systems may provide opportunities to direct biological processes. Previously, it has been demonstrated that enzyme triggered assembly of peptide derivatives can influence bacterial cell death by intracellular fibre formation. In this article, we discuss the self-assembly of 9-fluorenylmethyloxycarbonyl (Fmoc) protected dipeptide amphiphiles, FY, YT, YS, YN and YQ, designing phosphorylated precursors to be alkaline phosphatase responsive. We use microscopy techniques, fluorescence and FTIR to demonstrate differences in molecular assembly and nanoscale architecture in vitro- indicating fibre formation of FY, YT, YS and YN, and spherical self-assembled structures of YQ. As the enzyme is naturally occurring in E. coli, we manipulate conditions to over-express the enzyme and demonstrate the conversion of precursors to self-assembling aromatic peptide amphiphiles in vivo. Furthermore, we test whether antimicrobial activity can be differentially controlled by the introduction of varying aromatic peptide amphiphiles, with the results indicating a similar antimicrobial response for each treatment.

The simultaneous catalytic removal of VOCs and O 3 in a post-plasma

The use of non-thermal plasma (NTP) technology for volatile organic compounds (VOCs) control has been limited because of its drawbacks. Although the combination of catalysis in plasma can avoid some of the limitations, there are still disadvantages such as the O 3 byproduct. In this study, catalysts were combined in the post-plasma. It is found that not only O 3 is efficiently eliminated, but also the removal of toluene is greatly enhanced due to O 3 decomposition. The effect of catalysts, humidity and the initial O 3 concentration on simultaneous catalytic removal of toluene and O 3 was studied. Results show that the performance of catalysts for toluene conversion is closely related to that for O 3 decomposition. The increase of O 3 concentration benefits toluene conversion, whereas water has a negative effect on the toluene conversion. Catalytic ozonation is mainly responsible for the toluene decomposition in the post-plasma.

Novel Fibrous Catalyst in Advanced Oxidation of Photographic Processing Effluents

A novel fibrous catalyst was used to destroy the pollutants in Kodak Non-Silver-Bearing (NSB) photographic processing effluents with high chemical oxygen demand (COD) value. The oxidation activity of the catalyst was evaluated in terms of COD reduction of the effluent. The effects of concentrations of hydrogen peroxide and effluent, amount of catalyst, reaction time and temperature on the COD reduction were studied. In addition, the combination of catalysis with UV treatment on the COD reduction of the effluent was also investigated. Based on the experimental results, room temperature is preferred for the catalytic oxidation of NSB effluent. It was found that COD reduction of the effluent depends on the amount of hydrogen peroxide added to the feed in relation to the mass of catalyst used. Significant COD reduction (up to 52%) is achieved after 4 hours of catalytic treatment. Extending the duration of catalysis up to 24 hours gives further slight decrease in COD value.

Development of Catalysts for Diesel Particulate NOxReduction

While diesel vehicles feature high fuel economy with low CO2 emissions, further suppression of particulate matter (PM) and NOx in the exhaust stream is demanded worldwide. We have been working to develop a new diesel particulate-NOx reduction (DPNR) system to decrease both PM and NOx emissions by combining the NOx storage-reduction catalyst for direct injection gasoline engines with the most advanced engine control technologies. This paper describes the development of the DPNR system, a post-treatment technology for PM and NOx, which was achieved through a combination of catalysis and engine control technologies.