草酸酯合成

An electrochemical approach has been leveraged to underpin a new conceptual platform for dehydration reactions, which has been demonstrated in the context of esterification. Esters were prepared from the corresponding acid and alcohol partners at room temperature without acid or base additives and without consuming stoichiometric reagents. This methodology therefore addresses key complications that plague esterification and dehydration reactions more broadly and that represent a leading challenge in synthetic chemistry.

The large-scale synthesis of several kinds of monoalyl oxalates, which are half-esters of dialkyl oxalates, under practical and environmentally friendly conditions is described by applying the selective monohydrolysis reaction of symmetric diesters that we reported previously. The most suitable conditions were examined for the kinds of base, equivalent, cosolvent, and reaction time for large-scale production of five kinds of monoalkyl oxalate, monomethyl oxalate, monoethyl oxalate, monopropyl oxalate, monoisopropyl oxalate, and monobutyl oxalate, which are among the most versatile building blocks, but the commercial availabilities are limited. The conditions are mild, simple, and environmentally benign, and the half-esters were produced in high yields, exhibiting high purities in only a few hours without requiring special equipment. Therefore, the synthetic advantage of this reaction is anticipated.

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ABSTRACT Significant efforts have been directed toward the advancement of active and durable Pd−based catalysts for the gas−solid phase oxidative coupling of carbon monoxide (CO) to dimethyl oxalate (DMO). The reaction takes place under moderate conditions with high selectivity above > 95% following the C1 chemistry route and converting C1 feedstocks, i.e. CO and methanol (CH3OH) to DMO product. The inaugural plant capable of processing 200,000 tons annually, was commissioned in 2009, and as of 2023 more than 30 such plants are in operation. Noteworthy attention has been dedicated to enhancing catalytic activity while minimizing the Pd active component, achieved through the construction of efficient nanostructured catalysts. In this review, we highlight the recent advances in the CO oxidative coupling to DMO, particularly focusing on the design of Pd−based catalysts, structure−function relationship, catalytic reaction mechanism and process intensification utilizing structured catalysts. Additionally, an overview addressing challenges and opportunities for future research associated with CO oxidative coupling to DMO is presented. Graphical abstract

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The catalytic co‐coupling of carbon monoxide and methyl nitrite to synthesize dimethyl oxalate (DMO) is a crucial step in the conversion of syngas to ethylene glycol. Recent advancements in numerical simulation methodologies substantially enhanced the potential for optimizing chemical production processes, thereby improving cost effectiveness and efficiency. Numerical simulation techniques were applied to model a shell‐and‐tube reactor and a radial reactor. The distributions of pressure, velocity, reaction, and temperature fields were analyzed for both reactor configurations under similar operating conditions. The findings indicate that the radial reactor has different advantages, including a smaller volume, a more uniform temperature distribution, and a lower pressure drop, highlighting its potential benefits in the DMO synthesis process.

Ethylene glycol (EG) is an indispensable substance in the chemical industry and polyester fiber supply chain. The synthesis of dimethyl oxalate (DMO) by carbon monoxide gas-phase catalytic coupling is a key step in the coal-based syngas to ethylene glycol process route. The strong coupling between the reaction unit and the feedstock regeneration unit, as well as the risk of feedstock gas explosion, poses a great challenge to the stability control and safety of the dimethyl oxalate production process. In this paper, the dimethyl oxalate production process is studied from three aspects: steady-state modeling, dynamic modeling and fault simulation. First, the dimethyl oxalate pro-duction process was comprehensively modeled using Aspen Plus software. Second, a dynamic model was constructed on the basis of the steady-state model to fit the actual production process. Finally, deep learning algorithms were combined with dynamic simulation techniques. Using the fault scenarios and data in the dynamic model, the T-DOAE algorithm is used to study the fault detection in the production process of dimethyl oxalate, which is of great significance to ensure the safe and stable operation of the gas-phase coupling process of dimethyl oxalate production in the process of coal chemical industry.

Abstract Diethyl oxalate (DEO) is widely used in fine chemical industry. In comparison with traditional esterification process, carbon monoxide coupling process is a novel routine for DEO production. This environmentally friendly process provides better selectivity and yield. Its unique feature is that a closed regeneration-coupling circulation is formed. Toxic byproduct-nitric oxide (NO) from coupling reaction is recycled to re-produce ethyl nitrite through regeneration reaction. This avoids significant amount of NOx emission. However, due to a few NOx emission, a contaminant handling system is applied for environmental protection. A systematical environmental analysis is also carried out to assess this process. Regeneration-coupling circulation brings interaction behaviors and some trade-offs including reactor size and recycle flowrate, regeneration and coupling reaction, loss of reactants and NO emission. Thus, a rigorous steady simulation is established to investigate these trade-offs. Then DEO process is optimized to obtain the optimal design. Finally a more economic flowsheet to produce DEO is proposed.

CO oxidative coupling to dimethyl oxalate (DMO) is an important approach for the product of ethylene glycol and CO elimination. In this work, the Co doped Pd/Al2O3 nanocatalyst was highly effective for CO oxidative coupling and enhanced remarkably CO conversion and the formation of DMO. The maximum DMO STY reached 1082 g L−1 h−1 over the Pd/Al2O3@1/20Co catalyst at 130 °C for 2 h under the space velocity of 3000 h−1, which is two times higher than that over the Pd/Al2O3 catalyst. The Co modification and its influence on the structure of the Pd/Al2O3 catalyst were also studied systematically by XRD, TEM, CO‐TPD, N2 physical adsorption and XPS techniques. An appropriate Co doing was confirmed to promote distinctly the generation of smaller Pd particles and the adjustment of the adsorption or activation of CO over the catalyst. A positive interaction between Pd nanoparticles and the modulated support with Co doping was demonstrated and favored the enhanced activity of the catalyst for the reaction.

The formation of dimethyl oxalate (DMO) via CO catalytic coupling on a series of catalysts including Pdn (n = 1, 2, 3, 4 and 6) clusters loaded on TiO2-V has been explored by density functional theory (DFT) calculation. The results show that different Pdn clusters have a remarkable influence on DMO formation. The Pd1/TiO2-V catalyst is not suitable for the CO catalytic coupling reaction since CO is easily bound to the O atom on the surface of TiO2-V leading to the formation of CO2. The activity of four catalysts complies with the following order of Pd4/TiO2-V > Pd6/TiO2-V > Pd2/TiO2-V > Pd3/TiO2-V by comparing the activation energy barriers of the rate-determining steps in the optimal paths. Charge analysis implies that less charge is transferred from the Pd4/TiO2-V and Pd6/TiO2-V catalysts to CO than on the other catalysts, which leads to the relatively weak adsorption of CO, and therefore CO has a greater tendency to react with other species on the surface. In addition, Pd6/TiO2-V also exhibits relatively higher selectivity toward DMO than the other three catalysts. Therefore, Pd6 is regarded as a suitable cluster, which is supported on TiO2-V demonstrating high catalytic activity and selectivity to DMO.

The direct esterification of CO involves processes using CO as the starting material and ester chemicals as products. Dimethyl oxalate (DMO) and dimethyl carbonate (DMC) are two different products of the direct CO esterification reaction. However, the effective control of the reaction pathway and direct synthesis of DMO and DMC are challenging. In this review, we summarize the recent research progress on the direct esterification of CO to DMO/DMC and reveal the functional motifs responsible for the catalytic selectivity. Firstly, we discuss the microstructure of catalysts for the direct esterification of CO to DMO and DMC, including the valence state and the aggregate state of Pd. Then, the influence of characteristics of the support on the selectivity is analyzed. Importantly, the aggregate state of the active component, Pd is deemed as a vital functional motif for catalytic selectivity. The isolated Pd is conducive for the formation of DMC, while the aggregated Pd is beneficial for the formation of DMO. This review will provide rational guidance for the direct esterification of CO to DMO and DMC.

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This work reports a fully exposed palladium cluster catalyst that exhibits superior activity and selectivity for methyl nitrite (MN) carbonylation compared to atomically dispersed Pd catalysts and Pd nanoparticles. Mechanistic studies reveal that the distinct geometric structure of the fully exposed palladium cluster enables surface-mediated Langmuir-Hinshelwood reactions, efficiently producing dimethyl carbonate (DMC) while minimizing dimethyl oxalate (DMO) formation. In contrast, atomically dispersed Pd catalysts rely on Eley-Rideal mechanisms, leading to lower activity, while the continuous surface sites of Pd NPs promote DMO formation. This work provides a foundation for the rational design of novel catalysts for industrial carbonylation processes.

Pd-Based heterogeneous catalysts have been demonstrated to be efficient in numerous heterogeneous reactions. However, the effect of the support resulting in covalent metal-support interaction (CMSI) has not been researched sufficiently. In this work, a Lewis base is modulated over MgAl-LDH to investigate the support effects and it is further loaded with Pd clusters to research the metal-support interactions. MgAl-LDH with ultra-low Pd loading (0.0779%) shows CO conversion (55.0%) and dimethyl oxalate (DMO) selectivity (93.7%) for CO oxidative coupling to DMO, which was gradually deactivated after evaluation for 20 h. To promote the stability of Pd/MgAl-LDH, Zn2+ ions were introduced into the MgAl-LDH support to strengthen the CMSI by forming Pd-Zn bonds, which further increased the adsorption energy of the Pd clusters on ZnMgAl-LDH, and this was verified by X-ray absorption fine structure (XAFS) measurements and density functional theory (DFT) calculations. The stability of the Pd/ZnMgAl-LDH catalyst could be maintained for at least 100 h. This work highlights that covalent metal-support interactions can be strengthened by forming new metal-metal bonds, which could be extended to other systems for the stabilization of noble metals over supports.

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The support of MgO/γ-Al2O3 was initially prepared by a multiple impregnation method and Pd was placed on the surface of the MgO/γ-Al2O3 support via incipient wetness impregnation. Pd/MgO/γ-Al2O3 (Pd/MAO) catalysts were systematically characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), CO2-temperature-programmed desorption (TPD), transmission electron microscopy (TEM), CO-Fourier transform infrared (CO-FTIR), and X-ray photoelectron spectroscopy (XPS) and tested in the CO oxidative coupling to dimethyl oxalate (DMO) reaction. Compared to Pd/γ-Al2O3, the catalytic activities of the Pd/MAO catalysts improved significantly. The Pd/MAO catalyst with a 30% mass ratio of Mg to γ-Al2O3 delivers 3 times higher STY of DMO than that of Pd/γ-Al2O3. It has been demonstrated that MgO covered γ-Al2O3 layer-by-layer forming MAO supports, which can increase surface basicity and the interaction between Pd particles and the MAO supports. Moreover, the relationship between metal and support interaction and catalytic performance was discussed.

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The C1 chemical species, potassium formate (K(HCO2)), known as a two-electron reducing agent, finds application in the synthesis of multi-carbon compounds, including oxalate, and plays a crucial role not only in the food and pharmaceutical industries but also across various sectors. However, the direct hydrogenation of CO2 to produce K(HCO2) remains a challenge. Addressing this issue, efficient production of K(HCO2) is achieved by integrating CO2 hydrogenation in a trickle-bed reactor using a heterogeneous catalyst with a novel separation method that utilizes potassium ions from biomass ash for formic acid derivative product isolation. Through alkaline-mediated CO2 hydrogenation using N-methylpyrrolidine (NMPI), a concentrated 5 M NMPI solution of formic acid N-methylpyrrolidine complex ([NMPIH][HCO2]) was formed, facilitating the synthesis of K(HCO2) with over 99% purity via reaction with excess K ions contained within Bamboo ash. Notably, 80% of CO2 was converted to formate ions, and NMPI was expected to be effectively recycled as it was completely removed during the evaporation process for K(HCO2) separation. Additionally, this process yielded SiO2 by-product particles with sizes ranging from 10 to 20 nm. This research highlights a novel strategy contributing to sustainable environmental management and resource recycling by effectively utilizing CO2 as a valuable feedstock while concurrently producing valuable chemical compounds from waste materials.

This work explores the benefits of single-phase oxalate precursors for the preparation of spinel ferrites by thermal decomposition. A direct comparison between the genuine oxalate solid solution and the physical mixture of simple oxalates is presented using the case study of cobalt ferrite preparation. The mixing of metal cations within a single oxalate structure could be verified prior to its thermal decomposition by several non-destructive experimental techniques, namely Mössbauer spectroscopy, X-ray powder diffraction (XRD) and energy-dispersive X-ray spectroscopy. In-situ XRD experiments were conducted to compare the decomposition processes of the solid solution and the physical mixture. Additionally, the decomposition products of the FeCo oxalate solid solution were studied ex-situ by means of N 2 adsorption, Mössbauer spectroscopy and XRD. The results obtained for different reaction temperatures demonstrate the possibilities to easily control the physical properties of the prepared oxides.