Methyl Trifluoroacetate Research Articles

Enabling Stable Operation of Lithium-Ion Batteries under Fast-Operating Conditions by Tuning the Electrolyte Chemistry.

Inferior fast-charging and low-temperature performances remain a hurdle for lithium-ion batteries. Overcoming this hurdle is extremely challenging primarily due to the low conductivity of commercial ethylene carbonate (EC)-based electrolytes and the formation of undesirable solid electrolyte interphases with poor Li+-ion diffusion kinetics. Here, a series of EC-free fast-charging electrolytes (FCEs) by incorporating a fluorinated ester, methyl trifluoroacetate (MTFA), as a special cosolvent into a practically viable LiPF6-dimethyl carbonate-fluoroethylene carbonate system, is reported. With a solvent-dominated solvation structure, MTFA facilitates the formation of thin, yet robust, interphases on both the cathode and anode. Commercial 1 Ah graphite|LiNi0.8Mn0.1Co0.1O2 pouch cells filled with the FCE exhibit ≈80% capacity retention over 3000 cycles at 3 C and 4 C (15min) charging rates in the full range of 0-100% state-of-charge. Moreover, even at a low operating temperature of -20 °C, the 1 Ah cell retains a high capacity of 0.65 Ah at a 2 C discharge rate and displays virtually no capacity fade on cycling at a C/5 rate. The work highlights the power of electrolyte design in achieving extra-fast-charging and low-temperature performances.

Fluorine-Rich Electrolyte Additive for Achieving Dendrite-Free Lithium Anodes at Low Temperatures.

The practical application of lithium metal anodes is significantly impeded by poor interfacial stability and uncontrolled dendrite growth. Herein, we introduce methyl trifluoroacetate (MTFA), a low-melting-point small molecule, as an electrolyte additive in an ether-based electrolyte. This additive facilitates the formation of an in situ composite solid electrolyte interphase (SEI) layer that is rich in LiF and features an ester-based flexible matrix. The resulting composite layer exhibits high ionic conductivity and mechanical stability, effectively regulating the lithium deposition behavior over a broad temperature range and inhibiting dendrite formation. Based on MTFA, the Li||Li symmetrical cell achieves a lifespan exceeding 5000 h at room temperature and 800 h at -20 °C, both with ultralow overpotential and exceptional cycling stability. In Li||LiFePO4 full cells with a high-area loading (10.52 mg cm-2) and an N/P ratio of 1.68, an average capacity decay of merely 0.096% per cycle is observed over 200 cycles. Even at -20 °C, the Li||LiFePO4 cell shows a CE of over 99% and maintains stable cycling performance. This work provides an innovative approach for optimizing lithium metal anode interfaces and enhancing low-temperature operation capabilities through the use of electrolyte additives.

Economically viable co-production of methanol and sulfuric acid via direct methane oxidation

The direct oxidation of methane to methanol has been spotlighted research for decades, but has never been commercialized. This study introduces cost-effective process for co-producing methanol and sulfuric acid through a direct oxidation of methane. In the initial phase, methane oxidation forms methyl bisulfate (CH3OSO3H), then transformed into methyl trifluoroacetate (CF3CO2CH3) via esterification, and hydrolyzed into methanol. This approach eliminates the need for energy-intensive separation of methyl bisulfate from sulfuric acid by replacing the former with methyl trifluoroacetate. Through the superstructure optimization, our sequential process reduces the levelized cost of methanol to nearly two-fold reduction from the current market price. Importantly, this process demonstrates adaptability to smaller gas fields, assuring its economical operation across a broad range of gas fields. The broader application of this process could substantially mitigate global warming by utilizing methane, leading to a significantly more sustainable and economically beneficial methanol industry.

A Plant Dye for Photocatalytic Methane Conversion.

A metal-free natural dye has been developed to selectively convert methane to methyl trifluoroacetate (CH3 TFA) using visible light, probably due to the formation of a chloride-bridged dimer undergoing fast intra-complex charge transfer.

Reaction mechanism of methyl trifluoroacetate (CH3TFA) with lithium polysulfides (Li2S6) in gas and solvent phase

Reaction mechanism of methyl trifluoroacetate (CH3TFA) with lithium polysulfides (Li2S6) in gas and solvent phase

Temperature-dependent interphase formation and Li+ transport in lithium metal batteries

High-performance Li-ion/metal batteries working at a low temperature (i.e., <−20 °C) are desired but hindered by the sluggish kinetics associated with Li+ transport and charge transfer. Herein, the temperature-dependent Li+ behavior during Li plating is profiled by various characterization techniques, suggesting that Li+ diffusion through the solid electrolyte interface (SEI) layer is the key rate-determining step. Lowering the temperature not only slows down Li+ transport, but also alters the thermodynamic reaction of electrolyte decomposition, resulting in different reaction pathways and forming an SEI layer consisting of intermediate products rich in organic species. Such an SEI layer is metastable and unsuitable for efficient Li+ transport. By tuning the solvation structure of the electrolyte with a lower lowest unoccupied molecular orbital (LUMO) energy level and polar groups, such as fluorinated electrolytes like 1 mol L−1 lithium bis(fluorosulfonyl)imide (LiFSI) in methyl trifluoroacetate (MTFA): fluoroethylene carbonate (FEC) (8:2, weight ratio), an inorganic-rich SEI layer more readily forms, which exhibits enhanced tolerance to a change of working temperature (thermodynamics) and improved Li+ transport (kinetics). Our findings uncover the kinetic bottleneck for Li+ transport at low temperature and provide directions to enhance the reaction kinetics/thermodynamics and low-temperature performance by constructing inorganic-rich interphases.

Conversion of methane to methyl trifluoroacetate by NHC ruthenium complexes under mild conditions

Liquid-phase methane activation by ruthenium complexes has been studied using a combination of experiments and quantum-chemical calculation. Surprisingly, methane can be converted to methyl trifluoroacetate efficiently under mild conditions, and the bis(NHC) ligand outperforms the other two employed. The associated electronic origins of the excellent performance of the ruthenium complex – in particular the ligand effects – have been discussed, and the dative C → Ru interaction as well as the structural distortion of the bis(NHC) plane are found responsible. This work reveals the promising role ruthenium may play in the construction of organometallic catalysts for efficient methane conversion.

Partial Oxidation of Methane Enabled by Decatungstate Photocatalysis Coupled to Free Radical Chemistry

The decatungstate anion, [W10O32]4– or DT, is a useful photocatalyst for organic transformations involving C–H functionalization. Herein, we leverage the unique photoredox properties of DT to generate a chlorine radical from chloride ion for the photochemical partial oxidation of methane. Under optimized conditions, the DT–chloride–iodine ensemble achieves methane to methyl trifluoroacetate conversion with >350 photocatalyst turnovers at ∼60% yield based on methane in trifluoroacetic acid solvent. Methyl trifluoroacetate exhibits excellent stability under reaction conditions with minimal amounts of degradation (<6%) detected after 41 h. Based on density functional theory calculations, we propose a mechanism that involves synergistic relationships among the DT, chloride, and iodine species with the following key features: (1) photoredox electron transfer reaction of DT with Cl– to generate Cl•, (2) reaction of photoexcited DT with methane to generate methyl radicals via net hydrogen atom abstraction, (3) a Cl/I radical-based pathway in which methane is converted to MeTFA, and (4) reoxidation of reduced DT species by dioxygen. This mechanism takes advantage of the unique redox potential of DT and the ability of DT to mediate both electron transfer and hydrogen atom transfer reactions, ultimately generating an efficient pathway for aerobic methane partial oxidation.

Transesterification of the ethyl ester of trifluoroacetic acid to its methyl ester using Amberlyst-15: reaction and purification

Esters of trifluoroacetic acid are compounds having important applications in the process industry. Methyl trifluoroacetate (MTFA) is useful as an intermediate in the manufacture of valuable pharmaceutical and agriculture chemicals. This work has investigated transesterification of ethyl trifluoroacetate (ETFA) to MTFA using Amberlyst-15. Evaluation of reaction kinetics was followed by regression to obtain kinetic parameters. Packed bed reactor experiments were performed thereafter to improve the process and to make the process continuous, wherein conversion of 76% was achieved in 5 h under the conditions used. Starting from a mixture of reactants, a complete process to obtain pure MTFA was developed in this work. For this, liquid-liquid extraction, adsorption over molecular sieves followed by distillation was used.

Heterogeneous Mn-Based Catalysts for the Aerobic Conversion of Methane-to-Methyl Trifluoroacetate

Methane conversion strategies that protect methanol via in situ esterification achieve higher yields compared to direct methane conversion without product protection; however, most of these high-yield systems operate under unfavorable conditions. To date, there is very limited work in developing heterogeneous catalysts for methane-to-methyl-ester conversion, and studies demonstrating the activity of manganese for methane conversion are limited. We have prepared a series of silica-, titania-, and zirconia-supported manganese catalysts and measured the activity of these catalysts for the aerobic conversion of methane to methyl trifluoroacetate in diluted trifluoroacetate acid. The silica-supported catalyst exhibits high overall activity, but significant amounts of homogeneously active manganese are observed. Titania- and zirconia-supported manganese catalysts catalyze the reaction heterogeneously with activities up to 613 μmol gcat–1 h–1 and show nondetectable leaching. Manganese oxide is poorly dispersed on titania and zirconia, whereas high dispersion is realized on silica. This work demonstrates a facilely synthesized supported manganese catalyst that converts methane heterogeneously in satisfactory yields under improved conditions in a diluted acid, compared to those of conventional methane-to-methyl-ester systems.

Tetrachlorocobaltate-Catalyzed Methane Oxidation to Methyl Trifluoroacetate

In ongoing attempts to efficiently utilize abundant natural gas, there has been steady scientific and industrial interest in using an environmentally benign and inexpensive oxidant (dioxygen O2) for the direct catalytic oxidation of methane to oxygenate products under mild conditions. Here, we report the homogeneous bis(tetramethylammonium) tetrachlorocobaltate ([Me4N]2CoCl4)-catalyzed methane oxidation to methyl trifluoroacetate (MeTFA) with dioxygen O2 in trifluoroacetic acid (HTFA) media. [Me4N]2CoCl4 had the highest catalytic activity among previously reported homogeneous cobalt-based catalyst systems; the turnover of methane to MeTFA reached 8.26 molester molmetal−1h−1 at 180 °C. Results suggest that the ionic form of the catalyst makes the Co species more soluble in the HTFA media; consequently, an active catalyst form, [CoTFAxCly]2−, can form very rapidly. Furthermore, chloride anions dissociated from CoCl42− appear to suppress oxidation of the solvent HTFA, thereby driving the reaction toward methane oxidation. The effects of reaction time, catalyst concentration, O2 and methane pressure, and reaction temperature on MeTFA production were also investigated.

Methane oxidation to methyl trifluoroacetate by simple anionic palladium catalyst: Comprehensive understanding of K2S2O8-based methane oxidation in CF3CO2H

The partial oxidation of methane to methyl trifluoroacetate (MeTFA) in trifluoroacetic acid (HTFA) is one of the most selective methane conversion reactions. We report that the simple anionic form of palladium, PdCl42- can effectively convert methane to MeTFA compared to neutral PdCl2 in the K2S2O8-HTFA oxidation system. The anionic catalyst form appears to increase the Pd solubility in the polar protic HTFA solvent, thereby facilitating transformation to PdTFA42- which is supposed to be the real catalytic species in this PdCl42- - catalyzed methane oxidation. It was found that not only methane oxidation but also solvent HTFA oxidation proceeded to a substantial degree, which limited the yield of MeTFA by consuming the oxidant, K2S2O8. Furthermore, for the first time, the role of trifluoroacetic anhydride (TFAA) was identified; it removes water produced by KHSO4 and HF, which are the reduced form of K2S2O8 and the oxidation byproduct of HTFA, respectively. The reaction equations for methane to MeTFA, and HTFA to CO2 in K2S2O8-HTFA system are suggested.

Manganese Catalyzed Partial Oxidation of Light Alkanes

The catalytic partial oxidation of methane is achieved at low temperatures (<200 °C) using manganese oxides and manganese salts in mixtures of trifluoroacetic acid and trifluoroacetic anhydride. Dioxygen is used as the in situ terminal oxidant. For Mn oxides (e.g., MnO2, Mn2O3, and Mn3O4), we studied stoichiometric methane partial oxidation in HTFA (TFA = trifluoroacetate). Using a Mn trifluoroacetate salt, at 180 °C and under 25 psig of methane, product selectivity for the mono-oxidized product methyl trifluoroacetate (MeTFA) is observed to be >90% at ∼35% methane conversion at approximately 6 turnovers. Under our catalytic methane oxidation reaction conditions, MeTFA is stable against overoxidation, which explains the likely high selectivity at conversions >15%. Using combined experimental studies and DFT calculations, a mechanism involving soluble and molecular Mn species in the catalytic cycle is proposed. The proposed reaction pathway involves initial activation of MnII by dioxygen, cleavage of a methane C–H bond by a MnIII hydroxo intermediate, rebound of the methyl radical to generate MeTFA, and finally regeneration of the starting MnII complex. Also, this process is shown to be applicable to the oxidation of ethane, favoring the mono-oxidized product ethyl trifluoroacetate (EtTFA) and reaching ∼46% conversion.

Protic ionic liquid—2,2,2‐trifluoroacetic acid—methyl trifluoroacetate mixture distillation process

AbstractThe work provides experimental data of the methyl trifluoroacetate (MeTFA)—2,2,2‐trifluoroacetic acid (TFA) mixture distillation process in the presence of N‐Methyl‐2‐pyrrolidone (NMP) at atmospheric pressure (99.2 kPa) and within a temperature range of T ≤ 230°C. Forming PIL between TFA and NMP (methylpyrrolidonium trifluoroacetate [HNMP]+[CF3COO]−) leads to a significant volatility increase of the MeTFA relative to TFA. The pure MeTFA was recovered from the MeTFA‐TFA‐[HNMP]+[CF3COO]− mixture in the quantity of 70% from the MeTFA initial mole charge; the total mole recovery was 100%. A significant result of the above experiment is that TFA mole recovery from the MeTFA‐TFA‐[HNMP]+[CF3COO]− mixture within a temperature range of T &lt; 187°C exceeds 96%. The distillation of TFA and NMP mixture at T ≤ 230°C demonstrates strong binding of TFA anion that can be seen from the final liquid phase composition TFA/NMP ≈ 0.53/0.47. At the concentration and the temperature ranges under study, there is no NMP in the vapour phase.

Aerobic Partial Oxidation of Alkanes Using Photodriven Iron Catalysis

Photodriven oxidations of alkanes in trifluoroacetic acid using commercial and synthesized Fe(III) sources as catalyst precursors and dioxygen (O2) as the terminal oxidant are reported. The reactions produce alkyl esters and occur at ambient temperature in the presence of air, and catalytic turnover is observed for the oxidation of methane in a pure O2 atmosphere. Under optimized conditions, approximately 17% conversion of methane to methyl trifluoroacetate at more than 50% selectivity is observed. It is demonstrated that methyl trifluoroacetate is stable under catalytic conditions, and thus overoxidized products are not formed through secondary oxidation of methyl trifluoroacetate.

Heterogeneously Catalyzed Aerobic Oxidation of Methane to a Methyl Derivative

AbstractA promising strategy to break through the selectivity‐conversion limit of direct methane conversion to achieve high yields is the protection of methanol via esterification to a more stable methyl ester. We present an aerobic methane‐to‐methyl‐ester approach that utilizes a highly dispersed, cobalt‐containing solid catalyst, along with significantly more favorable reaction conditions compared to existing homogeneously‐catalyzed approaches (e.g. diluted acid, O2 oxidant, moderate temperature and pressure). The trifluoroacetic acid medium is diluted (&lt;25 wt %) with an inert fluorous co‐solvent that can be recovered after the separation of the methyl trifluoroacetate via liquid–liquid extraction at ambient conditions. Silica‐supported cobalt catalysts are highly active in this system, with competitive yields and turnovers in comparison to known aerobic transition metal‐based catalytic systems.

Atmosphere-Pressure Methane Oxidation to Methyl Trifluoroacetate Enabled by a Porous Organic Polymer-Supported Single-Site Palladium Catalyst

The efficient conversion of methane into methanol at low temperature under low pressure remains a great challenge largely because of the inertness and poor solubility of methane. Herein, we report ...

Evoking High Donor Number-assisted and Organosulfur-mediated Conversion in Lithium-Sulfur Batteries.

The solution-mediated behavior of lithium-sulfur (Li-S) batteries presents a wide range of opportunity for evaluating and improving the performance at practical lean-electrolyte conditions. Here, we introduce methyl trifluoroacetate (CH3TFA) as an additive to the Li-S electrolyte to evaluate the joint effects of two distinct strategies: high donor number solvents/salts and organosulfur-mediated discharge. CH3TFA is shown to react with lithium polysulfides in-situ to form lithium trifluoroacetate (LiTFA) and dimethyl polysulfides. We find that both the methyl group and trifluoroacetate anion considerably enhance Li-S discharge behavior over the course of cycling, though they have distinctly beneficial effects. The TFA anion impacts solution coordination behavior, improving polarization and discharge kinetics during cycling. Meanwhile, the derivatization to dimethyl polysulfides improves the solubility of intermediate species, enhancing overall utilization under lean-electrolyte conditions. CH3TFA thus represents a new class of additives for Li-S batteries, enabling an in-situ systematic molecular engineering of intermediate species for improved performance.

Energy-Dependent Relative Cross Sections in Carbon 1s Photoionization: Separation of Direct Shake and Inelastic Scattering Effects in Single Molecules.

We demonstrate that the possibility of monitoring relative photoionization cross sections over a large photon energy range allows us to study and disentangle shake processes and intramolecular inelastic scattering effects. In this gas-phase study, relative intensities of the carbon 1s photoelectron lines from chemically inequivalent carbon atoms in the same molecule have been measured as a function of the incident photon energy in the range of 300-6000 eV. We present relative cross sections for the chemically shifted carbon 1s lines in the photoelectron spectra of ethyl trifluoroacetate (the "ESCA" molecule). The results are compared with those of methyl trifluoroacetate and S-ethyl trifluorothioacetate as well as a series of chloro-substituted ethanes and 2-butyne. In the soft X-ray energy range, the cross sections show an extended X-ray absorption fine structure type of wiggles, as was previously observed for a series of chloroethanes. The oscillations are damped in the hard X-ray energy range, but deviations of cross-section ratios from stoichiometry persist, even at high energies. The current findings are supported by theoretical calculations based on a multiple scattering model. The use of soft and tender X-rays provides a more complete picture of the dominant processes accompanying photoionization. Such processes reduce the main photoelectron line intensities by 20-60%. Using both energy ranges enabled us to discern the process of intramolecular inelastic scattering of the outgoing electron, whose significance is otherwise difficult to assess for isolated molecules. This effect relates to the notion of the inelastic mean free path commonly used in photoemission studies of clusters and condensed matter.

Methyl Trifluoroacetate as a Methylation Reagent for N−H, O−H, and S−H Functionalities under Mild Conditions

AbstractA methylation reagent for compounds bearing N−H, O−H, and S−H functionalities was developed. Methyl trifluoroacetate (MTFA) was commonly considered as trifluoroacetylating reagent or trifluoromethylating reagent. In this work, we report the methylation behavior of MTFA under mild conditions with good functional group tolerance, allowing the transformation of a wide range of substrates, including N,H‐heteroaromatic compounds, phenolic compounds, carboxylic acids, thiophenols, secondary amides and imides, in high yields. This method was preliminarily applied to the chemoselective methylation of bifunctionalized secondary amide.