Monthly Archives: September 2023

Recent Advances in Bimetallic Catalysts for Methane Steam Reforming in Hydrogen Production: Current Trends, Challenges, and Future Prospects

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Recent Advances in Bimetallic Catalysts for Methane Steam Reforming in Hydrogen Production: Current Trends, Challenges, and Future Prospects

The primary method for hydrogen production is through methane steam reforming (MSR) of natural gas. This process involves the reaction between methane and steam to create a synthesis gas (syn gas). Following this, a step referred to as water-gas shift (WGS) is employed. During the WGS process, the hydrogen content is enhanced as H2O reacts with CO at lower temperatures. Subsequently, hydrogen is extracted from the gas using pressure swing adsorption (PSA). The remaining off-gas is combusted with additional natural gas to generate the heat necessary for MSR. It is imperative to emphasize the significance of synthesizing steam reforming catalysts with high activity and durability to enable large-scale hydrogen production. Recent advancements in bimetallic catalysts for steam reforming have led to enhanced performance in steam methane reforming. This improvement is attributed to the synergistic interaction between two metals in the catalyst.


Abstract

As energy demand continues to rise and the global population steadily grows, there is a growing interest in exploring alternative, clean, and renewable energy sources. The search for alternatives, such as green hydrogen, as both a fuel and an industrial feedstock, is intensifying. Methane steam reforming (MSR) has long been considered a primary method for hydrogen production, despite its numerous advantages, the activity and stability of the conventional Ni catalysts are major concerns due to carbon formation and metal sintering at high temperatures, posing significant drawbacks to the process. In recent years, significant attention has been given to bimetallic catalysts as a potential solution to overcome the challenges associated with methane steam reforming. Thus, this review focuses on the recent advancements in bimetallic catalysts for hydrogen production through methane steam reforming. The review explores various aspects including reactor type, catalyst selection, and the impact of different operating parameters such as reaction temperature, pressure, feed composition, reactor configuration, and feed and sweep gas flow rates. The analysis and discussion revolve around key performance indicators such as methane conversion, hydrogen recovery, and hydrogen yield.

Glu‐derived zwitterionic micelles with conquering the intestinal mucosal barrier toward oral delivery

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Amino acid transporters with different categories are highly expressed in intestinal epithelial cells for maintaining the essential metabolism of body. The zwitterioninc property of amino acid with α-amino and α-carboxyl also has tremendous potential to conquer the mucus barrier. Therefore, two glutamic acid (Glu)-derived amphiphilic block polymers [poly(lactic acid)-b-poly(glutamine)25 (PPQ) and poly(lactic acid)-b-poly(glutamate)25 (PPD)] were rational designed and further prepared Glu-derived zwitterionic micelles (PPQ-M and PPD-M) toward oral delivery. In comparison with PEG-M (PEG micelles), two Glu-derived zwitterionic micelles revealed superior mucus permeability. In addition, enhanced cellular internalization was also confirmed in both zwitterionic micelles, which were mainly mediated by multiple amino acid transporters. It was speculated that the uptake efficiency of PPQ-M was obviously higher than that of PPD-M due to PPQ-M with higher affinity of glutamine structural unit. Furthermore, the retrograde pathway played an important role in the intracellular transport of both zwitterionic micelles as well as transcytosis transport. Excellent villi absorption in situ of Glu-derived zwitterionic micelles were observed, which gave a convincing evidence for oral delivery potential. The results of this research demonstrated that Glu-derived zwitterionic micelles with unquestionable capacity of conquering intestinal mucosal barrier, have promising application toward oral delivery.

Accuracy of expectation values of one‐electron operators obtained from Hartree–Fock wavefunctions expanded using Lambda functions

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Accuracy of expectation values of one-electron operators obtained from Hartree–Fock wavefunctions expanded using Lambda functions

The number of significant figures (SF) of the cusp condition (CC) is approximately half that of the Hartree–Fock total energy (TE). The SFs of expectation values of the other one-electron properties are also smaller than for the TE.


Abstract

The accuracy of the expectation values (<A>$$ <A> $$) of one-electron operators is examined using Hartree–Fock wavefunctions expanded using Λ$$ \Lambda $$ functions. In this expansion, 150 terms, then 149, 148, and 147 terms are used for the s-, p-, d-, and f-symmetries, respectively. The systems investigated are He–Ne and the Group 18 atoms of Ar–Og. The one-electron properties investigated are the cusp condition (CC), the electron density at the nucleus (ρ(0)$$ \rho (0) $$), and <ri>$$ <{r}^i> $$ (i=−2,…,9$$ i=-2,\dots, 9 $$). Convergence of <A>$$ <A> $$ is examined by increasing the number of expansion terms (N$$ N $$) up to the given limit (150). The number of significant figures (SF) of <A>$$ <A> $$ is counted by comparing the calculated value at N$$ N $$=150 (<A(150)>$$ <A(150)> $$) with the extrapolated value <A(∞)>$$ <A\left(\infty \right)> $$. For He, the SF of CC is found to be 26. For the atoms under consideration, the SF of CC is approximately half that of the total energy (TE). The SFs of expectation values of the other properties are also smaller than for the TE.

XMe ‐ Xiamen Molecular Electronics code: an intelligent and open‐source data analysis tool for single‐molecule conductance measurements

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Comprehensive Summary

Charge transport characterization of single-molecule junctions is essential for the fundamental research of single-molecule physical chemistry and the development towards single-molecule electronic devices and circuits. Among the single-molecule conductance characterization techniques, the single-molecule break junction technique is widely used in tens of worldwide research laboratories which can generate a large amount of experimental data from thousands of individual measurement cycles. However, data interpretation is a challenging task for researchers with different research backgrounds, and the different data analysis approaches sometimes lead to the misunderstanding of the measurement data and even reproducibility issues of the measurement. It is thus a necessity to develop a user-friendly all-in-one data analysis tool that automatizes the basic data analysis in a standard and widely accepted way. In this work, we present the XMe Code (Xiamen Molecular Electronics Code), an intelligent all-in-one data analysis tool for the comprehensive analysis of single-molecule break junction data. XMe code provides end-to-end data analysis that takes in the original experimental data and returns electronic characteristics and even charge transport mechanisms. We believe that XMe Code will promote the transparency of the data analysis in single-molecule electronics and the collaborations among scientists with different research backgrounds.

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Efficient Synthesis and Microwave‐Assisted Sonogashira Reactions of Triflate‐Substituted Porphyrin

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Porphyrins that bear halogens at the meso-aryl positions are useful building blocks for the preparation of light-harvesting arrays and materials through cross-coupling procedures. Despite the wide use of such intermediates, their scale-up and purification are usually hampered by tedious chromatographic separations because of the statistical nature of the synthetic protocol and the similar polarity of the different products. Here, we propose the use of porphyrins bearing a triflatophenyl group as alternative starting materials for palladium cross-coupling reactions. In particular, purification of the zinc 5,10,15-triaryl-20-(4-triflatophenyl)porphyrin (ZnP-OTf) model compound by column chromatography proved to be much easier compared to porphyrin analogues that carry halogen substituents. This is the result of the increased polarity of compounds functionalized by highly polar triflate groups if compared to those substituted by halogens. To show the value of the triflatophenylporphyrin model compound in cross-coupling reactions, we developed a microwave-assisted Sonogashira protocol that quantitatively converts the ZnP-OTf to the corresponding alkynylphenylporphyrin, in relatively short reaction times. Finally, we showed that the proposed ZnP-OTf building block can be conveniently converted into an alkynyl-linked molecular wire to bridge the zinc porphyrin donor with the [60]fullerene acceptor in a molecular dyad.

Application of an Oscillatory Plug Flow Reactor to Enable Scalable and Fast Reactions in Water Using a Biomass‐Based Polymeric Additive

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The utilization of water as a sustainable reaction medium has important advantages over traditional organic solvents. Hydroxypropyl methylcellulose has emerged as a biomass-based polymeric additive that enables organic reactions in water through hydrophobic effects. However, such conditions imply slurries as reaction mixtures, where the efficacy of mass transfer and mixing decreases with increasing vessel size. In order to circumvent this limitation and establish an effectively scalable platform for performing hydroxypropyl methylcellulose-mediated aqueous transformations, we utilized oscillatory plug flow reactors that feature a smart dimensioning design principle across different scales. Using nucleophilic aromatic substitutions as valuable model reactions, rapid parameter optimization was performed first in a small-scale instrument having an internal channel volume of 5 mL. The optimal conditions were then directly transferred to a 15 mL reactor, achieving a three-fold scale-up without re-optimizing any reaction parameters. By precisely fine-tuning the oscillation parameters, the system achieved optimal homogeneous suspension of solids, preventing settling of particles and clogging of process channels. Ultimately, this resulted in a robust and scalable platform for performing multiphasic reactions under aqueous conditions.

Understanding the Buoy Effect of Surface‐Enriched Pt Complexes in Ionic Liquids: A combined ARXPS and Pendant Drop Study

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Recently, we demonstrated that Pt catalyst complexes dissolved in the ionic liquid (IL) [C4C1Im][PF6] can be deliberately enriched at the IL surface by introducing perfluorinated substituents, which act like buoys dragging the metal complex towards the surface. Herein, we extend our angle-resolved X-ray photoelectron spectroscopy (ARXPS) studies at complex concentrations between 30 and 5%mol down to 1%mol and present complementary surface tension pendant drop (PD) measurements under ultra clean vacuum conditions. This combination allows for connec­ting the microscopic information on the IL/gas interface from ARXPS with the macroscopic property surface tension. The surface enrichment of the Pt complexes is found to be most pronounced at 1%mol. It also displays a strong temperature dependence, which was not observed for 5%mol and above, where the surface is already saturated with the complex. The surface enrichment deduced from ARXPS is also reflected by the pronounced decrease in surface tension with increasing concentration of the catalyst. We furthermore observe by ARXPS and PD a much stronger surface affinity of the buoy-complex as compared to the free ligands in solution. Our results are highly interesting for an optimum design of ionic catalyst solutions contact areas with a surrounding reactant/product phase, such as in SILP catalysis.

Inclusion Complexes of a Metastable‐State Photoacid with High Acidity and Chemical Stability

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Inclusion Complexes of a Metastable-State Photoacid with High Acidity and Chemical Stability

Metastable-state photoacid MCH1 (see image) and cyclodextrins (CDs) can form inclusion complexes [MCH1 ⋅ (CD)2] [CD=2-hydroxypropyl-β-CD (HP-β-CD), γ-CD,β-CD and HP-γ-CD] with stronger ground and metastable-state acidity and slower thermal relaxation (SP1→trans-MCH1) rates than free MCH1. The inclusion complexes except [MCH1 ⋅ (HP-γ-CD)2] have better stability against hydrolysis than free MCH1. Appropriate host molecules can regulate the properties of metastable-state photoacids to meet various needs.


Abstract

Metastable-state merocyanine photoacids (MCHs) have been widely applied to various chemical, material and biomedical areas to drive or control chemical processes with light. In this work, stoichiometry and association constants have been determined for inclusion complexes of a photoacid MCH1 ((E)-3-(2-(2-hydroxystyryl)-3,3-dimethyl-3H-indol-1-ium-1-yl)propane-1-sulfonate) with β-cyclodextrin (β-CD), 2-hydroxypropyl-β-CD (HP-β-CD), γ-CD and HP-γ-CD by means of UV-Vis absorption spectroscopic titrations. The inclusion complexes were studied to enhance acidity and chemical stability. Kinetic study showed that CDs stabilized the acidic metastable state and slowed its thermal relaxation. The acidity of the ground and metastable state (pK a GS and pK a MS) increased upon addition of CDs. The pK a MS of [MCH1 ⋅ (γ-CD)2] is as low as 0.92 in comparison with 2.24 for MCH1, which is close to the lowest pK a MS values (1.20 and 1.03) reported previously, in which case the MCH1 was structurally modified with alkylammonium side chains. Addition of CDs also significantly enhanced the chemical stability of MCH1 against hydrolysis, which is one of the major concerns for the application of MCHs. In particular, the addition of HP-β-CD increased the half-life of MCH1 in aqueous solution more than four-fold. Moreover, the quantum chemical calculations confirmed the stoichiometry and analyzed the binding sites and hydrogen bonds of the inclusion complexes.

Chromatographic and Biological Screening of Chosen Species of Schisandraceae Family: Schisandra chinensis, S. rubriflora, S. sphenanthera, S. henryi and Kadsura japonica

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Chromatographic and Biological Screening of Chosen Species of Schisandraceae Family: Schisandra chinensis, S. rubriflora, S. sphenanthera, S. henryi and Kadsura japonica


Abstract

HPLC and TLC profiling was carried out for leaf and fruit extracts of five Schisandraceae species: Schisandra chinensis, S. rubriflora, S. spehenanthera, S. henryi and Kadsura japonica. HPLC measurements confirmed presence of lignans and phenolic compounds in fruits and leaves of all tested species. The most abundant in lignans was S. chinensis fruit extract in which 15 compounds were detected (e. g.: schisandrol A, schisanhenol, γ-schisandrin, gomisin N). The effect-directed detection, i. e., TLC-direct bioautography against Bacillus subtilis, showed exceptionally high activity for S. chinensis and S. rubriflora fruit extracts. On the other hand, TLC-DB enzyme tests (α-glucosidase, lipase, tyrosinase and acetylcholinesterase (AChE) inhibition assays) showed that all fruit and leaf extracts have ability to inhibit the above-mentioned enzymes (except for the K. japonica fruit). The leaf extracts showed much stronger antioxidant activity than the fruit ones, which were assessed and compared using both TLC-direct bioautography and spectrophotometric measurements based on ABTS, DPPH and FRAP tests.

Autocatalysis and CO2: carbon capture and utilization (CCU) meets natural processes

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Autocatalytic reactions were proposed to play a key role at the beginning of life starting from the first reduction of CO2 to formate, acetate and C1-C4 hydrocarbons. In carbon capture and utilization (CCU) processes, the same reactions were demonstrated to be autocatalytic and, in some cases, promoted by catalysts of the same composition. Through evolution, CO2 reduction then turned into complex autocatalytic networks such as photosynthesis, where CCU chemists found inspiration for the development of more advanced systems for the synthesis of value-added chemicals. Less evolved systems than photosynthesis, however, may be easier to emulate and provide valuable inspiration into CO2 reduction chemistry for CCU. Other manmade systems were also demonstrated to be autocatalytic demonstrating that CO2 reactions and autocatalysis are closely connected. In this concept article, the relationship between natural, artificial and bio-inspired autocatalytic CO2 reduction processes is summarized and discussed. The accomplishments resulting from the integration of autocatalysis and CCU strategies, along with their inherent benefits and future prospectives are also outlined.