Methyl Cation Research Articles

Formation of the methyl cation by photochemistry in a protoplanetary disk.

Forty years ago, it was proposed that gas-phase organic chemistry in the interstellar medium can be initiated by the methyl cationCH3+ (refs. 1-3), but so far it has not been observed outside the Solar System4,5. Alternative routes involving processes on grain surfaces have been invoked6,7. Here we report James Webb Space Telescope observations ofCH3+ in a protoplanetary disk in the Orion star-forming region. We find that gas-phase organic chemistry is activated by ultraviolet irradiation.

Rhodium‐Catalyzed C−H Alkylation for the Stereoselective Synthesis of β,β‐Disubstituted Dehydroamino‐Acid Motifs

AbstractIn this article, we describe the stereoselective formation of β,β‐disubstituted dehydroamino acids (ΔAAs) in peptides using a cationic rhodium catalyst and methyl trifluoroborate salt. Using this approach, an alkyl group was directly installed on a β‐monosubstituted ΔAA in the peptide chain and both isomers of dehydroisoleucine, an important yet usually inaccessible ΔAA, were successfully obtained.

Improving toxic dye removal and remediation using novel nanocomposite fibrous adsorbent

Materials with regulated nanoscale morphology provide capabilities to remove dangerous pollutants from wastewater, by adsorption. In this study, the chitosan-based composite fibrous adsorbent was fabricated and used as a novel and facile eliminator in the process of removing cationic methyl orange (MO) from the water medium. Different methods were applied to check the properties of the desired composite fibrous adsorbent. The removal value showed that the chitosan-embedded composite fibrous adsorbent has super characteristics and can be removed the organic dye from the water. The influence of pH, time, temperature, eliminator quantity, and MO content was explored. With increasing time and eliminator quantity, the adsorption efficiency increased. The composite fibrous adsorbent with the advantage of its high functionality and combined micro-nanomorphology features, has emerged as a very promising candidate for obtaining versatile and robust adsorbents. This work presents how the tunned synthesis of composite fibrous adsorbent tailored their nanoarchitecture giving rise to adsorption capacities toward cleaning aqueous samples polluted with MO dye. The composite fibrous adsorbent was prepared by the direct immobilization method, with normal aging temperature, in order to study the effect of synthesis conditions on the adsorption properties of MO dye. The solution acidity was exhibited as the key factor, and a suitable pH of 5.50 was selected based on the efficiency. The competing ions were not adversely affected in the dye adsorption as defined by the stable bonding mechanism. The adsorption data were highly fitted with the Langmuir adsorption model with monolayer coverage. The determined maximum adsorption was 175.45 mg/g, which was comparable with the other forms of materials. The adsorbed MO dye elution was evaluated using ethanol and then the composite fibrous adsorbent was ready to use for MO dye adsorption after washing with water without significant loss in its functionality. Therefore, we explored the tunned morphology of composite fibrous adsorbent for obtaining performant adsorbents for the elimination of refractory pollutants in wastewater.

Enhanced adsorptive removal of hazardous methyl violet 2B and methyl orange dyes by Algerian diatomite-loaded polysaccharide-based hydrogel beads

The present paper is devoted to the synthesis of hybrid biocomposites through immobilization of Algerian treated diatomite (TD) within the semi-interpenetrating network of carboxymethyl cellulose/dextran sulfate (CMC/DS). The physicochemical properties of the cross-linked beads were investigated by SEM, XRD, FTIR and TGA. Biocomposite beads were explored as adsorbents for the removal of cationic methyl violet 2B-(MV2B) and anionic methyl orange-(MO) dyes. The swelling ability in different media were studied. The outcomes revealed that the TD was successfully immobilized in CMC/DS matrix through hydrogen bonding which improved the structural stability of biocomposites. TD depicted to improve the adsorption capacity of hydrogels. Indeed, the beads prepared at low TD levels (5 and 10 % (w/w)) showed higher adsorption capacities (925.92 and 892.86 mgg−1) compared to the matrix (877.19 mg g−1). MV2B adsorption modeling showed the process well fitted the pseudo-second order kinetics and Langmuir models. Furthermore, the role of TD was better considered during the MO adsorption study. Pristine hydrogel were not able to effectively remove it (10 %), while for biocomposites the efficiency reached 62–98 %. The suggested mechanism for MO adsorption involved ion exchange, pore-filling and π-electron specific interactions. Lastly, reusability study confirm that C/D-TD biocomposites are promising materials for anionic/cationic dyes adsorption.

Sustainable utilization metal ions of acid leaching clay wastewater to fabricate adsorbents for high-efficient removing Congo red and Methyl violet

Recycling waste into efficient adsorbents to remove pollutants again provides a compatible solution for the sustainable development of water resources. Here, Mg2+, Al3+, and Fe3+ metal ions from oxalic acid leaching mixed-dimensional palygorskite clay wastewater were successfully converted into mixed metal oxides (MMOs) through a simple precipitation-calcination process. MMOs prepared under different precipitation pH conditions or different washing schemes were used to remove the anionic dye Congo red (CR) and cationic dye Methyl violet (MV). The relatively pure Mg-Al-Fe MMO obtained at pH 13 with thorough washing had ultrahigh adsorption capacity for CR, up to 1369 mg/g. In the presence of sodium oxalate byproducts without washing, the prepared MMOs containing Fe3O4, sodium carbonate, and carbon byproducts had higher removal capacities for cationic dye MV, with a maximum of 1098 mg/g. Moreover, the series of MMOs exhibited strong removal capability for CR + MV mixed dyes and satisfactory cycle stability. This work provided a new perspective on the sustainable utilization of mineral resources and water resources.

Facile synthesis of magnetic and porous zeolite/SnFe2O4 nanocomposite for cationic and anionic dyes deterioration

This study introduces a new, accessible, and cost-effective nanocatalyst for wastewater remediation. Here, tin ferrite nanoparticles (SnFe2O4) were loaded onto the surface of zeolite using a one-step solvothermal method. The characteristics of the zeolite/SnFe2O4 nanocomposite were thoroughly investigated using a range of techniques including SEM, EDX, VSM, XRD, TEM, BET, and FTIR. The nanocomposite was used as a heterogeneous catalyst along with H2O2 (a green oxidant) to degrade cationic (methyl green) and anionic (methyl blue) dyes in both individual and mixed systems. The amounts of zeolite/SnFe2O4, H2O2, and dyes substantially affected the degradation rate. Moreover, as the pH rose, both dyes deteriorated at a faster rate. The magnetic nanocomposite demonstrated exceptional separation and regeneration performance throughout 5 cycles. Moreover, when the two dyes were combined into a single solution, the nanocomposite showed a significant removal ability, indicating a potential benefit in wastewater treatment.

Reaction nanoscopy of ion emission from sub-wavelength propanediol droplets.

Droplets provide unique opportunities for the investigation of laser-induced surface chemistry. Chemical reactions on the surface of charged droplets are ubiquitous in nature and can provide critical insight into more efficient processes for industrial chemical production. Here, we demonstrate the application of the reaction nanoscopy technique to strong-field ionized nanodroplets of propanediol (PDO). The technique's sensitivity to the near-field around the dropletallows for the in-situ characterization of the average droplet size and charge. The use of ultrashort laser pulses enables control of the amount of surface charge by the laser intensity. Moreover, we demonstrate the surface chemical sensitivity of reaction nanoscopy by comparing droplets of the isomers 1,2-PDO and 1,3-PDO in their ion emission and fragmentation channels. Referencing the ion yields to gas-phase data, we find an enhanced production of methyl cations from droplets of the 1,2-PDO isomer. Density functional theory simulations support that this enhancement is due to the alignment of 1,2-PDO molecules on the surface. The results pave the way towards spatio-temporal observations of charge dynamics and surface reactions on droplets.

Supramolecular self-assembling hydrogel film based on a polymer blend of chitosan/partially hydrolyzed polyacrylamide for removing cationic dye from water

The supramolecular self-assembling hydrogel film was designed using a polymer blend of chitosan and partially hydrolyzed polyacrylamide (CS/PHPA), which was constructed with a controllable sol-gel transition, using a green one-pot external salt-assisted sol-gel transition and aqueous solution casting method that does not employ any toxic chemical crosslinking agents. The structure of hydrogel film was confirmed by zeta potential, FT-IR, XRD, SEM, EDX, and TG/DTGA. The swelling properties of gels were well investigated and the results revealed a rapid swelling rate. Notably, the composite hydrogel film exhibited remarkable thermo- and pH-induced sol-gel transitions. The zeta potential of supramolecular CS/PHPA hydrogel was −51.5 mV (pH 7.0), which provided a good adsorption performance for the cationic dye methyl blue (MB). The adsorption process obeyed the pseudo-second-order kinetic model and the maximum adsorbed amount for MB was high up to 282 mg/g. The adsorption equilibrium data correlated well with the Langmuir model, suggesting that the MB was removed through the monolayer and physical adsorption mechanism. After five adsorption/desorption cycles using a mixture of (HCl:1-Butanol) as eluent, the dye adsorption efficiency decreased from 96.45 to 79.80%. The possible adsorption mechanism is believed to be the non-covalent interactions (the electrostatic interactions together with hydrogen bonding between the N atom of MB and the H atom of functional groups of the hydrogel. Overall, the “green” gelation process provides a new opportunity for the rational design of self-assembling physical hydrogels as adsorbents for cationic and anionic dye removal.

Cost effective porous areca nut carbon nanospheres for adsorptive removal of dyes and their binary mixtures

Novel porous nanospheres from areca nuts (ACNPs) were synthesized via one-step pyrolysis without the use of any chemical treatment and the materials were used as adsorbents for the removal of cationic methylene blue (MB) and anionic methyl orange (MO) as well as their binary mixtures. Around, 6–7 tonnes of areca nut biowaste is generated every year which are then burnt due to their slow rate of decomposition resulting in higher carbon footprints. Biosorbents are generally a preferable alternative for dye adsorption but involve chemical modification for surface enhancement and complex sample treatment. In this work, ACNPs, were investigated for their efficiency in the raw form and were characterized by SEM, EDS, FTIR, XRD, and BET techniques before and after subjecting to the dye adsorption studies. The BET analysis of the adsorbents showed a high specific surface area of 693.8 m2/g when prepared at 1000 °C, while the N2 adsorption-desorption plot showed type-IV isotherm, suggesting the microporous nature of the carbon matrix. Batch equilibrium studies showed the removal efficiency of >95% for both the dyes and their binary mixtures under the optimum conditions of 0.15 g/L dosage, 10 μM concentration and contact time of 70 min. Due to the synergistic effects of the binary dyes, higher removal efficiency of MB compared to MO was observed in the binary mixture. Adsorption results were tested using Langmuir, Freundlich, Temkin, Redlich-Peterson, and Elovich isotherms to assess the best fit of the models. The qm value of MB was found to be 97.37 mg/g, while that of MO was 71.22 mg/g which is higher compared to individual dye components having lower values of 86.12 mg/g and 50.35 mg/g, respectively. Extended Langmuir and Jain and Snoeyink isotherms were used for binary data interpretation. The kinetic results showed good agreement with the Pseudo-second order equation, indicating internal diffusion. The possible mechanism involved electrostatic and ᴨ-ᴨ interactions between the dye molecules and ACNPs. This approach is comprehensible and cost effective and can be utilized for dye removal in textile industries.

Carrier-Envelope Phase Controlling of Ion Momentum Distributions in Strong Field Double Ionization of Methyl Iodide

In strong field ionization of methyl iodide initiated by elliptically polarized few-cycle pulses, a significant correlation was observed between the carrier-envelope phases (CEPs) of the laser and the preferred ejection direction of methyl cation arising from dissociative double ionization. This was attributed to the carrier-envelope phase dependent double ionization yields of methyl iodide. This observation provides a new way for monitoring the absolute CEPs of few-cycle pulses by observing the ion momentum distributions.

Carbon template synthesis of CeO2 catalyst for direct conversion of methanol and carbon dioxide to dimethyl carbonate

Dimethyl carbonate (DMC) is an interesting, value added chemical and a high energy additive to fuels. In this study, several CeO2 catalysts were successfully synthesized through carbon template method using two renewable sources of activated carbon. The structure of catalysts was fully resolved by XRD, SEM, N2-adsorption, NH3-TPD, CO2-TPD and XPS. CeO2 catalysts prepared using coconut shell activated carbon (CAC) template exhibit better surface morphology and improved catalytic performance compared to walnut shell activated carbon (WAC)-supported catalysts. We demonstrated a correlation between the efficiency of DMC synthesis and the abundance of moderately acidic and moderately basic active sites on the catalyst. It was found that the presence of oxygen vacancies (Vo) facilitates carbonyl bond cleavage of CO2. The best-performing catalyst was 4% CeO2/CAC owing to the richest Vo and the optimum acid/base properties. Moreover, a plausible catalytic mechanism of DMC formation was proposed, and includes the interaction between methoxy carbonate (CH3OCO2−) formed with the aid of Vo and moderately basic sites and methyl cation (CH3+) formed on the moderately acidic sites.

Low Energy Collision-Induced Dissociation of Azepine Pictet-Spengler Adducts of Nω-Methylserotonin.

Cimitrypazepines are a class of natural products produced by Pictet-Spengler condensation of Nω-methylserotonin and aldehydes in a manner that produces a seven-membered azepine ring. In this study, the fragmentation behavior of this class of molecules under low-energy CID was investigated in detail. Proposed mechanisms of fragmentation were supported by deuterium labeling and DFT calculations. Loss of methylamine and methylenimine were dominant fragmentation pathways of analogs containing an aliphatic side chain. Loss of methylenimine was found to proceed via unusual methyl cation transfer. Fragmentation of analogs containing an aromatic side chain was strongly influenced by the nature of the substituents and proceeded via a novel retro-Pictet-Spengler pathway and involvement of ion-neutral complexes. In some cases, a gas-phase interconversion between the azepine and β-carboline ring was observed during fragmentation. Detailed analysis of fragmentation behavior provided in this study will serve as a valuable guide for the discovery of new analogs from natural sources.

Adsorption of anionic and cationic dyes from aqueous solutions on fly ash-based porous geopolymer

<p>Fly ash, solid waste from coal-fired power plant, had been utilized as raw material for porous geopolymer by alkaline activation and addition of hydrogen peroxide (H2O2) blowing agent. Porous geopolymer had higher surface area and total pore volume compared to fly ash and geopolymer without blowing agent, namely 45.511 m2 g-1 and 0.05131 cc g-1, respectively. Porous geopolymer was applied as adsorbent for anionic dyes Eriochrome Black T (EBT) and cationic dyes Methyl Violet (MV) from aqueous solutions. In this paper, factors affecting adsorption process such as adsorbent dosage, pH, time, and initial concentration were studied, in addition to adsorption kinetics and isotherm studies. Adsorbent dosage, time, and initial concentration factors had the same effect on the adsorption process for both EBT and MV dyes. The optimum removal efficiency was obtained at adsorbent dosage of 2 g L-1 and adsorption time of 90 minutes. The increase of the initial concentration of dyes would decrease the removal efficiency. For pH factor, adsorption of EBT dyes was better at pH of 2, while adsorption of MV dyes was better at pH of 10. Both adsorption of EBT and MV dyes by porous geopolymer followed pseudo-second-order kinetics model and Langmuir isotherm model with maximum adsorption capacity of 45.454 mg g-1 and 49.261 mg g-1, respectively.</p>

A new type of highly efficient fir sawdust-based super adsorbent: Remove cationic dyes from wastewater

It is still a challenge to prepare dye adsorbents with a favorable separation capacity, a remarkable adsorption capacity, a high removal rate and certain reusability. In this study, a new type of gel (i.e., AA-DWF-PAM) was prepared with treated fir sawdust and verified to be an effective adsorbent for removing cationic dyes in water. The adsorption properties of AA-DWF-PAM were systematically explored by taking methylene blue (MB) and methyl violet (MV) as representative cationic dyes and methyl orange (MO) and carmine (CM) as representative anionic dyes. Through experiments, it is concluded that the most ideal adsorption effect will be achieved under the following parameters: the particle size of AA-DWF-PAM: 60–100 meshes, content: 5 g/L, pH of the solution: 4, temperature: 35 ℃. Furthermore, the adsorption process shows good correlations with the Langmuir isotherm and the pseudo-second-order kinetic model. The maximum adsorption capacities of AA-DWF-PAM for MB and MV are 499.27 mg/g and 481.71 mg/g, respectively, and it is easy to desorb in 0.05 mol/L HCl solution. In addition, through the molecular dynamics simulation technology, it is verified that the adsorption mechanisms behind the adsorption of AA-DWF-PAM include both physical and chemical adsorption represented by electrostatic interaction, hydrogen bonds and van der Waals force. Due to its sustainability, low cost and excellent adsorption performance, AA-DWF-PAM is expected to serve as an adsorbent applied to water treatment.

Synthesis of Carbon Nitride Supported POM‐based IL for Deep Oxidative Desulfurization of Dibenzothiophene

AbstractThe organic cation methyl imidazolium 1‐(3‐sulfonic) propyl (MIMPs) and the polyoxometalate (H3PMo6W6O40) were combined to synthesis [MIMPs]3PMo6W6O40 successfully, which was loaded on graphitic carbon nitride (g‐C3N4). The composite materials [MIMPs]3PMo6W6O40/g‐C3N4 catalysts were characterized by means of FT‐IR, XRD, TEM, XPS and nitrogen adsorption–desorption analysis (BET). Verified by various characterizations, synthesis and immobilization process could occur electron migration to improve the electronic and textural properties of [MIMPs]3PMo6W6O40/g‐C3N4 catalyst. At the optimal conditions of mcatalyst/VOil=0.1 g/10 mL, m[MIMPs]3PMo6W6O40: m[MIMPs]3PMo6W6O40/g‐C3N4=30 %, O/S=5 (molar ratio), the desulfurization rate reaches 100 % within 40 min. In addition, the concentration of aromatics had little effect on the reaction. Furthermore, the catalyst also shows high rate of desulfurization on real oil. The ODS reaction mechanism of this catalyst is also investigated.

Amphoteric cellulose microspheres for the efficient remediation of anionic and cationic dyeing wastewater

Amphoteric cellulose porous microsphere adsorbents (ACM) with high contents of functional groups were prepared by carboxylation and amination reactions. The obtained ACM possess similar contents of carboxyl groups (1.52 mmol/g) and amino groups (1.51 mmol/g). In addition, the modified microspheres exhibited excellent mechanical properties benefiting from the dense porous structures. The ACM could simultaneously remove the cationic dye methyl orange (MO) as well as the anionic dye methylene blue (MeB) with adsorption capacities as high as 345.32 mg/g and 616.12 mg/g, respectively. Another the microspheres are also with good regeneration that the adsorption capacities still maintained more than 90 % after 8 cycles.

Fabrication of porous adsorbents from eco-friendly aqueous foam for high-efficient removal of cationic dyes and sustainable utilization assessment

Porous materials applied in environmental remediation have received researchers’ extensive attention recently, but the related green and convenient preparation method is rarely reported. Here, we recommended a green and convenient strategy for the fabrication of porous material via aqueous foam templates, which was synergistically stabilized by Codonopsis pilosula (CP) and clay minerals of attapulgite (APT). The characterization results revealed that the APT was modified by organic molecules leached from CP and anchored at the air-water interface, which improved the foam stability significantly. The novel porous material of polyacrylamide/Codonopsis pilosula/attapulgite (PAM/CP/APT) templated from the aqueous foam via a polymerization reaction had excellent adsorption capacity for the cationic dyes methyl violet (MV) and methylene blue (MB), and the adsorption capacity can reach 755.85 mg/g and 557.64 mg/g, respectively. More importantly, the adsorption capacity of spent adsorbent material was still over 200 mg/g after being recycled five times through a simple carbonization process, and then it was added to the plant pot, the total biomass was increased by about 86.42%. This study provided a green and sustainable pathway for the preparation, application and subsequent processing of porous materials.

Explaining the High Catalytic Activity in Bis(indenyl)methyl Zirconium Cation Using Combined EDA-NOCV/QTAIM Approach.

The main purpose of this study is to elucidate some discrepancies already observed in the catalytic activity values of some zirconocene methyl cations. The EDA-NOCV scheme was employed for a theoretical description of the interactions between an ethylene molecule and five catalysts of zirconocene methyl cation. The nature of the chemical interactions has been elucidated through the QTAIM topological analysis. The steric hindrance due to the ligands was evaluated qualitatively by means of an IRI-based analysis and quantitively through Fisher information. The findings prove that the indenyl ligand seems to favor the orbital interaction between the ethylene molecule and the metal centre of zirconocene methyl cation. Both electrostatic and orbital contributions play a crucial role in stabilising the studied complexes. Based on the NOCV deformation density contributions, the strongest orbital interaction is reached with the bis(indenyl)methyl zirconium cation, which is the only one exhibiting covalent interactions. Especially, the strong contribution of π-back donation (occurring from the occupied orbitals of the zirconium atom to the π* anti-bonding orbital of ethylene) may be a key to understand why this catalyst has a higher polymerisation yield than the other studied catalysts. This work suggests a perspective for predicting values of catalytic activity when theoretically designing novel catalysts of zirconocene type.

High-efficiency adsorption removal of CR and MG dyes using AlOOH fibers embedded with porous CoFe2O4 nanoparticles

Owing to the toxicity and difficulty in degradation, how to the effective separation for the residual dyes in the aqueous solution is still an issue with great challenge in the area of environmental protection. Now, to high-efficiency removal of organic dyes from the aqueous solution, we design a unique AlOOH/CoFe2O4 adsorbent with porous CoFe2O4 nanoparticles embedded on the AlOOH fibers using a simple hydrothermal technique and calcination process. The structural properties and surface characteristics of the AlOOH/CoFe2O4 composites are detailedly analyzed by XRD, FTIR, XPS, TEM and SEM. Here, the high SBET and specific porous structure are beneficial to improve the adsorption performance of AlOOH/CoFe2O4 adsorbents. Especially, when the molar ratio of AlOOH to CoFe2O4 in the AlOOH/CoFe2O4 fibers is 1:1, an optimal performance on adsorbing anionic Congo red (CR) and cationic methyl green (MG) dyes can be obtained at pH = 6.29, where the corresponding maximum adsorption capacities reach up to 565.0 and 423.7 mg g−1, respectively. Factors leading to the change in the ability of adsorbing CR and MG dyes are systematically discussed, including contact time, temperature, initial concentrations, and pH values of the solutions. Meanwhile, the uptake of CR and MG dyes can best conform to Langmuir isotherm model and pseudo-second-order adsorption kinetics. The thermodynamic analysis verifies that the dye adsorption process is spontaneous and endothermic. Moreover, from the point view of practical application, the good reusability further makes the as-synthesized magnetic AlOOH/CoFe2O4 composite be a perfect adsorbent with efficiently removing both anionic and cationic dyes from aqueous solutions.

Characterization and photocatalytic properties of BiVO4 synthesized by combustion method

In this study, visible-light-driven BiVO4 photocatalyst was synthesized by chemical combustion method using Bi(NO3)3⋅5H2O and V2O5 as staring materials and citric acid as fuel with 400–550 °C calcination. XRD patterns of as-synthesized BiVO4 samples were indexed to the pure monoclinic scheelite BiVO4 phase. SEM and TEM images show that the morphologies and size distributions of BiVO4 samples were controlled by calcination temperature. FTIR and Raman spectra of BiVO4 show asymmetric and symmetric stretching vibration of V–O bond containing in VO43−. DRS spectra of the BiVO4 samples show excellent visible-light absorption. The photocatalytic properties of as-prepared BiVO4 samples were monitored through the degradation of cationic methylene blue (MB) and anionic methyl orange (MO) under visible light irradiation. Among them, the BiVO4 with 400 °C calcination showed the highest photocatalytic degradation of MB and MO under visible light irradiation. The role of ●O2−, ●OH and h+ radicals in degrading MB over BiVO4 was also investigated and discussed.