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1.
Small ; : e2404865, 2024 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-38984733

RESUMO

Aqueous zinc metal batteries are regarded as a promising energy storage solution for a green and sustainable society in the future. However, the practical application of metallic zinc anode is plagued by the thermodynamic instability issue of water molecules in conventional electrolytes, which leads to severe dendrite growth and side reactions. In this work, an ultra-thin and high areal capacity metallic zinc anode is achieved by utilizing crystalline water with a stable stoichiometric ratio. Unlike conventional electrolytes, the designed electrolyte can effectively suppress the reactivity of water molecules and diminish the detrimental corrosion on the metallic zinc anode, while preserving the inherent advantages of water molecules, including great kinetic performance in electrolytes and H+ capacity contribution in cathodes. Based on the comprehensive performance of the designed electrolyte, the 10 µm Zn||10 µm Zn symmetric cell stably ran for 1000 h at the current density of 1 mA cm-2, and the areal capacity of 1 mAh cm-2, whose depth-of-discharge is over 17.1%. The electrochemical performance of the 10 µm Zn||9.3 mg cm-2 polyaniline (PANI) full-cell demonstrates the feasibility of the designed electrolyte. This work provides a crucial understanding of balancing activity of water molecules in aqueous zinc metal batteries.

2.
Environ Sci Pollut Res Int ; 31(35): 47911-47922, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-39009818

RESUMO

It is desirable but challenging to develop highly-efficient catalysts for the direct synthesis of dimethyl carbonate (DMC) from methanol and CO2. The vacancy-mediated incorporation of heteroatom into surface reconstruction is an efficient method of defect engineering for enhancing the catalytic properties. In this work, manganese-doped cerium oxide porous nanoribbons (Mn/CeO2-BTC) were prepared derived from a Ce-BTC by a sacrificial template approach. It is found that the catalytic activity of Mn/CeO2-BTC catalysts can be readily controlled by varying the amount of Mn dopants and the as-synthesized 0.1-Mn/CeO2-BTC exhibited an outstanding activity for the synthesis of DMC from CO2 and methanol, which reached a high DMC yield (6.53 mmolDMC/gcat.) without any dehydrating agents. Based on characterization results, the enhanced performance may be attributed to the defective structures caused by Mn doping and the porous nanoribbons of the CeO2 crystals, which provide more surface oxygen vacancies and acidic-basic sites, favoring adsorption and activation of CO2 and methanol.


Assuntos
Dióxido de Carbono , Cério , Formiatos , Manganês , Metanol , Metanol/química , Cério/química , Catálise , Formiatos/química , Dióxido de Carbono/química , Porosidade , Manganês/química , Adsorção , Nanotubos de Carbono/química
3.
Forensic Sci Int ; 360: 112063, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38776711

RESUMO

In previous work, a novel pathway for the synthesis of ephedrine/pseudoephedrine and methamphetamine using the precursors benzaldehyde, nitroethane and dimethyl carbonate was investigated, and an impurity profile presented. This paper presents chiral and stable isotope ratios of ephedrine/pseudoephedrine and methamphetamine synthesised by this pathway. Based on the chiral profile and the more negative δ13C (avg. -33.2‰) and more positive δ2H values, it is possible to distinguish ephedrine/pseudoephedrine and methamphetamine prepared from this pathway from those of "fully synthetic", "semi-synthetic" or "natural" origin. The more positive δ2H values of methamphetamine from this pathway allowed for differentiation from methamphetamine produced from phenyl-2-propanone. It was noted, however, that the use of stable isotope profiling would likely be limited when a benzaldehyde source having a negative δ2H value was used as a precursor. Furthermore, the stable isotope values alone could not be used to differentiate from methamphetamine prepared by the Akabori-Momotani reaction, highlighting the need for combination with impurity profiling.

4.
Angew Chem Int Ed Engl ; 63(25): e202401311, 2024 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-38606491

RESUMO

Electrocatalytic carbonylation of CO and CH3OH to dimethyl carbonate (DMC) on metallic palladium (Pd) electrode offers a promising strategy for C1 valorization at the anode. However, its broader application is limited by the high working potential and the low DMC selectivity accompanied with severe methanol self-oxidation. Herein, our theoretical analysis of the intermediate adsorption interactions on both Pd0 and Pd4+ surfaces revealed that inevitable reconstruction of Pd surface under strongly oxidative potential diminishes its CO adsorption capacity, thus damaging the DMC formation. Further theoretical modeling indicates that doping Pd with Cu not only stabilizes low-valence Pd in oxidative environments but also lowers the overall energy barrier for DMC formation. Guided by this insight, we developed a facile two-step thermal shock method to prepare PdCu alloy electrocatalysts for DMC. Remarkably, the predicted Pd3Cu demonstrated the highest DMC selectivity among existing Pd-based electrocatalysts, reaching a peaked DMC selectivity of 93 % at 1.0 V versus Ag/AgCl electrode. (Quasi) in situ spectra investigations further confirmed the predicted dual role of Cu dopant in promoting Pd-catalyzed DMC formation.

5.
Chempluschem ; 89(7): e202300778, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38441412

RESUMO

A series of KF/Mg-Fe oxides were fabricated via the solid-state reaction between KF and Mg-Fe oxides. Especially, when 20 wt % KF was supported on the Mg-Fe bi-metal oxides and calcined at 400-600 °C, the solid material with more basic sites than the support itself was obtained. When applied as catalyst to dimethyl carbonate (DMC) synthesis through transesterification of ethylene carbonate (EC) and methanol, this material can afforded up to 88 % yield and 97 % selectivity toward DMC in 2 h under reflux conditions with the molar ratio of methanol to ethylene carbonate set at 8. It is worth noting that the catalyst was easily separated and reused, retaining at least 89 % catalytic activity during the first four recycles. Although an attenuated activity was still observed due to the inevitable filtration loss and dissolution, this solid base can still provide clues to the development recyclable catalyst in green synthesis of DMC.

6.
J Colloid Interface Sci ; 663: 869-879, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38447401

RESUMO

Over the last few decades, significant research efforts have been devoted to developing new cleaning systems aimed at preserving cultural heritage. One of the main objectives is to selectively remove aged or undesirable coatings from painted surfaces while preventing the cleaning solvent from permeating and engaging with the pictorial layers. In this work, we propose the use of electrospun polyamide 6,6 nonwovens in conjunction with a green solvent (dimethyl carbonate). By adjusting the electrospinning parameters, we produced three distinct nonwovens with varying average fiber diameters, ranging from 0.4 µm to 2 µm. These samples were characterized and tested for their efficacy in removing dammar varnish from painted surfaces. In particular, the cleaning process was monitored using macroscale PL (photoluminescence) imaging in real-time, while post-application examination of the mats was performed through scanning electron microscopy. The solvent evaporation rate from the different nonwovens was evaluated using gravimetric analysis and Proton Transfer Reaction- Time-of-Flight. It was observed that the application of the nonwovens with small or intermediate pore sizes for the removal of the terpenic varnish resulted in the swollen resin being absorbed into the mats, showcasing a peel-off effect. Thus, this protocol eliminates the need for further potentially detrimental removal procedures involving cotton swabs. The experimental data suggests that the peel-off effect relates to the microporosity of the mats, which enhances the capillary rise of the swollen varnish. Furthermore, the application of these systems to historical paintings underwent preliminary validation using a real painting from the 20th century.

7.
Angew Chem Int Ed Engl ; 63(19): e202402053, 2024 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-38494439

RESUMO

Direct synthesis of dimethyl carbonate (DMC) from CO2 plays an important role in carbon neutrality, but its efficiency is still far from the practical application, due to the limited understanding of the reaction mechanism and rational design of efficient catalyst. Herein, abundant electron-enriched lattice oxygen species were introduced into CeO2 catalyst by constructing the point defects and crystal-terminated phases in the crystal reconstruction process. Benefitting from the acid-base properties modulated by the electron-enriched lattice oxygen, the optimized CeO2 catalyst exhibited a much higher DMC yield of 22.2 mmol g-1 than the reported metal-oxide-based catalysts at the similar conditions. Mechanistic investigations illustrated that the electron-enriched lattice oxygen can provide abundant sites for CO2 adsorption and activation, and was advantageous of the formation of the weakly adsorbed active methoxy species. These were facilitating to the coupling of methoxy and CO2 for the key *CH3OCOO intermediate formation. More importantly, the weakened adsorption of *CH3OCOO on the electron-enriched lattice oxygen can switch the rate-determining-step (RDS) of DMC synthesis from *CH3OCOO formation to *CH3OCOO dissociation, and lower the corresponding activation barriers, thus giving rise to a high performance. This work provides insights into the underlying reaction mechanism for DMC synthesis from CO2 and methanol and the design of highly efficient catalysts.

8.
ChemSusChem ; 17(12): e202301805, 2024 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-38361160

RESUMO

As a crucial strategy towards a sustainable chemical industry, the direct synthesis of dimethyl carbonate (DMC) from renewable carbon dioxide (CO2) and methanol (MeOH) is studied using CeO2 nanoparticles modified with 1-butyl-3-methylimidazolium hydrogen carbonate ([BMIm][HCO3]) devoid of stoichiometric dehydrating agents. The synthesized CeO2@[BMIm][HCO3] catalyst having high thermal stability harnesses the unique physicochemical properties of CeO2 and the ionic liquid to exhibit a DMC yield of 10.4 % and a methanol conversion of 16.1 % at optimal conditions (pressure of CO2=5 MPa; temperature=130 °C). The catalytic behavior of CeO2@[BMIm][HCO3] studied with a detailed XRD, XPS, CO2 and NH3-TPD, Raman spectroscopy, TGA, FTIR, SEM and TEM suggests that the synergy between the two catalytic components originating from an increased surface oxygen vacancies boosts the overall catalytic performance. After several recycling tests, the catalyst demonstrated no significant reduction in DMC yield and methanol conversion. This platform is an attractive approach to synthesize thermally stable nanoparticle@ionic liquid that retains and merges the physical attributes of both materials for producing useful bulk chemicals from readily available chemical resources.

9.
Chem Biodivers ; 21(4): e202302124, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38409929

RESUMO

Ficus drupacea is a medicinal tree found in temperate regions. Various parts of this plant had been used traditionally for the treatment of various ailments such as root powder applied externally for skin infections. Analysis was carried out on the bioactive lipids extracted from Ficus drupacea fruit using both petroleum-based solvent (Hexane) and an environmentally friendly solvent Dimethyl carbonate (DMC). The results showed that DMC extraction yielded a high oil content in Ficus drupacea fruit (6.51 %). When examining the fatty acid composition using GC-FID analysis, Ficus drupacea oil extracted with DMC contained significant proportions of essential fatty acids such as linoleic acid (32.317 %), oleic acid (20.946 %), palmitic acid (25.841 %), etc. Additionally, DMC extraction resulted in higher levels of total phenolics in Ficus drupacea fruit oil compared to hexane. Moreover, DMC extracted oil exhibited stronger antioxidant properties, such as radical scavenging, anti- arthritic, photoprotective activity while displayed similar anti-inflammatory and anti-microbial activity as hexane-extracted oil. In summary, these findings demonstrate that DMC is an efficient and safer alternative to conventional solvent hexane for extracting oils from Ficus drupacea fruit. It is rich in bioactive compounds essential for human nutrition, including polyunsaturated fatty acids, flavonoids, and phenolic compounds, with enhanced biological activities.


Assuntos
Ficus , Humanos , Solventes , Hexanos , Lipidômica , Antioxidantes/farmacologia , Antioxidantes/análise , Óleos
10.
J Chromatogr A ; 1713: 464530, 2024 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-38035518

RESUMO

Preparative liquid chromatography in reversed phase conditions (RPLC) is the most common approach adopted in the downstream processing for the purification of therapeutic peptides at industrial level. Due to the strict requirements on the quality imposed by the Regulatory Agencies, routinary methods based on the use of aqueous buffers and acetonitrile (ACN) as organic modifier are commonly used, where ACN is practically the only available choice for the purification of peptide derivatives. However, ACN is known to suffers of many shortcomings, such as drastic shortage in the market, high costs and, most importantly, it shows unwanted toxicity for human health and environment, which led it among the less environmentally friendly ones. For this reason, the selection of a suitable alternative becomes crucial for the sustainable downstream processing of peptides and biopharmaceuticals in general. In this paper, a promising green solvent, namely dimethyl carbonate (DMC) has been used for the separation of a peptide not only in linear conditions but also for its purification through non-linear overloaded chromatography. The performance of the process has been compared to that achievable with the common method where ACN is used as organic modifier and to that obtained with two additional solvents (namely ethanol and isopropanol), already used as greener alternatives to ACN. This proof-of-concept study showed that, thanks to its higher elution strength, DMC can be considered a green alternative to ACN, since it allows to reduce method duration while reaching good purities and recoveries. Indeed, at a target purity fixed to 98.5 %, DMC led to the best productivity with respect to all the other solvents tested, confirming its suitability as a sustainable alternative to ACN for the purification of complex biopharmaceutical products.


Assuntos
Cromatografia de Fase Reversa , Peptídeos , Humanos , Cromatografia de Fase Reversa/métodos , Solventes/química , Acetonitrilas/química , Cromatografia Líquida de Alta Pressão/métodos
11.
J Chromatogr A ; 1712: 464477, 2023 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-37944433

RESUMO

Nowadays, environmental problems are drawing the attention of governments and international organisations, which are therefore encouraging the transition to green industrial processes and approaches. In this context, chemists can help indicate a suitable direction. Beside the efforts focused on greening synthetic approaches, currently also analytical techniques and separations are under observation, especially those employing large volumes of organic solvents, such as reversed-phase liquid chromatography (RPLC). Acetonitrile has always been considered the best performing organic modifier for RPLC applications, due to its chemical features (complete miscibility in water, UV transparency, low viscosity etc); nevertheless, it suffers of severe shortcomings, and most importantly, it does not fully comply with Environmental, Health and Safety (EHS) requirements. For these reasons, alternative greener solvents are being investigated, especially easily available alcohols. In this work, chromatographic performance of the most common solvents used in reversed-phase chromatography, i.e., acetonitrile, ethanol and isopropanol, have been compared to a scarcely used solvent, dimethyl carbonate (DMC). The analytes of interest were two small molecules, caffeine and paracetamol, whose kinetics and retention behaviour obtained with the four solvents have been compared, and all contributions to band broadening have been assessed. Results about kinetic performance are very promising, indicating that a small amount (7 % v/v) of DMC is able to produce the same efficiency as a 2.5-times larger ACN volume (18 % v/v), and larger efficiency than alcohols. This paper reports, for the first time, fundamental studies concerning the mass transfer phenomena when DMC is used as an organic solvent in RPLC, and, together with the companion paper, represents the results of a research whose final aim was to discover whether DMC is suitable for chromatographic applications both in linear and preparative conditions.


Assuntos
Cromatografia de Fase Reversa , Etanol , Cromatografia de Fase Reversa/métodos , Solventes/química , Etanol/química , Acetonitrilas/química , Cromatografia Líquida de Alta Pressão/métodos
12.
J Colloid Interface Sci ; 652(Pt B): 1984-1993, 2023 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-37690306

RESUMO

Cerium(IV) oxide (CeO2)-based materials are effective catalysts for the synthesis of dimethyl carbonate (DMC) from carbon dioxide (CO2) and methanol (CH3OH). Herein, 5% Y-CeO2 was synthesized by the co-precipitation method. It forms a solid solution structure, which leads to the highest concentration of oxygen vacancies. The Y-VO-Ce active site created by Y3+ doping enhances the adsorption and activation of CO2 based on moderately passivating CH3OH adsorption. Consequently, 5% Y-CeO2 exhibited the highest CH3OH conversion rate of 0.8% and a DMC yield of 15 mmol⋅(g cat)-1, which is 1.4 times of pure CeO2 (reacting in a stainless-steel autoclave at 140 °C with a stirring speed of 1000 r⋅min-1 and an initial pressure of 3.0 MPa for 2 h). An adsorption test and in situ diffuse reflectance infrared Fourier transform spectroscopy showed that 5% Y-CeO2 could effectively inhibit the formation of triple-bonded methoxy species, and promote the formation of bidentate carbonate and bridged methoxy intermediates, which is conducive to the improvement of reaction activity.

13.
Nano Lett ; 23(16): 7650-7657, 2023 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-37535702

RESUMO

The chemical fixation of CO2 as a C1 feedstock is considered one of the most promising ways to obtain long-chain chemicals, but its efficiency was limited by the ineffective activation of CO2. Herein, we propose a grain boundary engineering strategy to construct polarized active pairs with electron poor-rich character for effective CO2 activation. By taking CeO2 as a model system, we illustrate that the polarized "Ce4+-Ce3+-Ce4+" pairs at the grain boundary can simultaneously accept and donate electrons to coordinate with O and C, respectively, in CO2. By the combination of synchrotron radiation in situ technique and density functional theory calculations, the mechanism of the catalytic reaction has been systematically investigated. As a result, the CeO2 nanosheets with a rich grain boundary show a high DMC yield of 60.3 mmol/gcat with 100% atomic economy. This study provides a practical way for the chemical fixation of CO2 to high-value-added chemicals via grain boundary engineering.

14.
Colloids Surf B Biointerfaces ; 227: 113355, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37216726

RESUMO

This study reports significant steps toward developing anti-biofilm surfaces based on superhydrophobic properties that meet the complex demands of today's food and medical regulations. It presents inverse Pickering emulsions of water in dimethyl carbonate (DMC) stabilized by hydrophobic silica (R202) as a possible food-grade coating formulation and describes its significant passive anti-biofilm properties. The final coatings are formed by applying the emulsions on the target surface, followed by evaporation to form a rough layer. Analysis shows that the final coatings exhibited a Contact Angle (CA) of up to 155° and a Roll-off Angle (RA) lower than 1° on the polypropylene (PP) surface, along with a relatively high light transition. Dissolving polycaprolactone (PCL) into the continuous phase enhanced the average CA and coating uniformity but hindered the anti-biofilm activity and light transmission. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed a uniform coating by a "Swiss-cheese" like structure with high nanoscale and microscale roughness. Biofilm experiments confirm the coating's anti-biofilm abilities that led to the reduction in survival rates of S.aureus and E.coli, by 90-95% respectively, compared to uncoated PP surfaces.


Assuntos
Biofilmes , Staphylococcus aureus , Emulsões/química , Interações Hidrofóbicas e Hidrofílicas , Água
15.
Molecules ; 28(9)2023 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-37175195

RESUMO

Cerium dioxide (CeO2) was pretreated with reduction and reoxidation under different conditions in order to elucidate the role of surface Ce4+ and oxygen vacancies in the catalytic activity for direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol. The corresponding catalysts were comprehensively characterized using N2 physisorption, XRD, TEM, XPS, TPD, and CO2-FTIR. The results indicated that reduction treatment promotes the conversion of Ce4+ to Ce3+ and improves the concentration of surface oxygen vacancies, while reoxidation treatment facilitates the conversion of Ce3+ to Ce4+ and decreases the concentration of surface oxygen vacancies. The catalytic activity was linear with the number of moderate acidic/basic sites. The surface Ce4+ rather than oxygen vacancies, as Lewis acid sites, promoted the adsorption of CO2 and the formation of active bidentate carbonates. The number of moderate basic sites and the catalytic activity were positively correlated with the surface concentration of Ce4+ but negatively correlated with the surface concentration of oxygen vacancies. The surface Ce4+ and lattice oxygen were active Lewis acid and base sites respectively for CeO2 catalyst, while surface oxygen vacancy and lattice oxygen were active Lewis acid and base sites, respectively, for metal-doped CeO2 catalysts. This may result from the different natures of oxygen vacancies in CeO2 and metal-doped CeO2 catalysts.

16.
Molecules ; 28(5)2023 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-36903558

RESUMO

The separation of dimethyl carbonate (DMC) and methanol is of great significance in industry. In this study, ionic liquids (ILs) were employed as extractants for the efficient separation of methanol from DMC. Using the COSMO-RS model, the extraction performance of ILs consisting of 22 anions and 15 cations was calculated, and the results showed that the extraction performance of ILs with hydroxylamine as the cation was much better. The extraction mechanism of these functionalized ILs was analyzed by molecular interaction and the σ-profile method. The results showed that the hydrogen bonding energy dominated the interaction force between the IL and methanol, and the molecular interaction between the IL and DMC was mainly Van der Waals force. The molecular interaction changes with the type of anion and cation, which in turn affects the extraction performance of ILs. Five hydroxyl ammonium ILs were screened and synthesized for extraction experiments to verify the reliability of the COSMO-RS model. The results showed that the order of selectivity of ILs predicted by the COSMO-RS model was consistent with the experimental results, and ethanolamine acetate ([MEA][Ac]) had the best extraction performance. After four regeneration and reuse cycles, the extraction performance of [MEA][Ac] was not notably reduced, and it is expected to have industrial applications in the separation of methanol and DMC.

17.
ACS Appl Mater Interfaces ; 15(12): 15396-15408, 2023 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-36917679

RESUMO

Frustrated Lewis pairs (FLPs), discovered in the last few decades for homogeneous catalysts and in the last few years also for heterogeneous catalysts, are stimulating the scientific community's interest for their potential in small-molecule activation. Nevertheless, how an FLP activates stable molecules such as CO2 is still undefined. Through a careful spectroscopic study, we here report the formation of FLPs over a highly defective CeO2 sample prepared by microwave-assisted synthesis. Carbon dioxide activation over FLP is shown to occur through a bidentate carbonate bridging the FLP and implying a Ce3+-to-CO2 charge transfer, thus enhancing its activation. Carbon dioxide reaction with methanol to form monomethylcarbonate is here employed to demonstrate active roles of FLP and, eventually, to propose a reaction mechanism clarifying the role of Ce3+ and oxygen vacancies.

18.
Polymers (Basel) ; 15(6)2023 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-36987272

RESUMO

This study aimed to develop tannin-based non-isocyanate polyurethane (tannin-Bio-NIPU) and tannin-based polyurethane (tannin-Bio-PU) resins for the impregnation of ramie fibers (Boehmeria nivea L.) and investigate their mechanical and thermal properties. The reaction between the tannin extract, dimethyl carbonate, and hexamethylene diamine produced the tannin-Bio-NIPU resin, while the tannin-Bio-PU was made with polymeric diphenylmethane diisocyanate (pMDI). Two types of ramie fiber were used: natural ramie without pre-treatment (RN) and with pre-treatment (RH). They were impregnated in a vacuum chamber with tannin-based Bio-PU resins for 60 min at 25 °C under 50 kPa. The yield of the tannin extract produced was 26.43 ± 1.36%. Fourier-transform infrared (FTIR) spectroscopy showed that both resin types produced urethane (-NCO) groups. The viscosity and cohesion strength of tannin-Bio-NIPU (20.35 mPa·s and 5.08 Pa) were lower than those of tannin-Bio-PU (42.70 mPa·s and 10.67 Pa). The RN fiber type (18.9% residue) was more thermally stable than RH (7.3% residue). The impregnation process with both resins could improve the ramie fibers' thermal stability and mechanical strength. The highest thermal stability was found in RN impregnated with the tannin-Bio-PU resin (30.5% residue). The highest tensile strength was determined in the tannin-Bio-NIPU RN of 451.3 MPa. The tannin-Bio-PU resin gave the highest MOE for both fiber types (RN of 13.5 GPa and RH of 11.7 GPa) compared to the tannin-Bio-NIPU resin.

19.
Small ; 19(18): e2208238, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-36734211

RESUMO

The acid-base properties of supports have an enormous impact on catalytic reactions to regulate the selectivity and activity of supported catalysts. Herein, a train of Pd-X-UiO-66 (X = NO2 , NH2 , and CH3 ) catalysts with different acidity/alkalinity functional groups and encapsulated Pd(II) species is first developed, whose activities in dimethyl carbonate (DMC) catalysis are then investigated in details. Thereinto, the Pd-NO2 -UiO-66 catalyst with acidity functionalization exhibits the best catalytic behavior: the DMC selectivity stemmed from methyl nitrite (MN) is up to 68%, the conversion of CO is 73.4%. The obtained experimental results demonstrate that the NO2 group not only affected the interaction between X-UiO-66 and Pd(II) active sites but also play an indispensable role in the adsorption and activation of MN and CO, which remarkably promote the formation of the COOCH3 * intermediate and DMC product.

20.
Membranes (Basel) ; 13(2)2023 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-36837663

RESUMO

Poly(2,2'-biquinoline-6,6'-dicarbohydrazide)-co-(bistrimelliteimide)methylene-bisanthranylide (PHI) and its metal-polymer complex PHI-Cu(I) containing several types of functional groups (hydrazide, carboxyl, amide, and imide fragments) were synthesized to prepare two types of dense nonporous membranes. The study on morphology using scanning electron microscopy (SEM), measurements of mechanical, thermal, and transport properties of the membrane samples was carried out. The main mechanical properties of both membranes do not differ significantly, but the values of ultimate deformation differ palpably as a result of a non-uniform character of the deformation process for the PHI membrane. The thermal analysis based on the curves of thermogravimetric (TGA) and differential thermal (DTA) analyses of the PHI and PHI-Cu(I) membranes revealed peculiarities of the membrane structure. Transport properties were studied in pervaporation (PV) of methanol (MeOH) and dimethyl carbonate (DMC) mixtures including an azeotropic point. Intrinsic properties of the penetrant-membrane system were also determined. It was found that the total flux is higher through the PHI membrane, but the PHI-Cu(I) membrane exhibits a higher separation factor. Calculation of the pervaporation separation index (PSI) allowed to conclude that the PHI-Cu(I) membrane exhibits better transport properties as compared with the PHI membrane.

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