Hydrogenation Of Dimethyl Oxalate Research Articles

CH2 Linkage Effects on the Reactivity of Bis(aminophosphine)\u2013Ruthenium Complexes for Selective Hydrogenation of Esters into Alcohols

A novel ruthenium complex binding to two subtly different aminophosphine ligands, (o-PPh2C6H4CH2NH2)(o-PPh2C6H4NH2)RuCl2, was successfully isolated. This bis(aminophosphine)–ruthenium complex shows efficient activity in both dimethyl oxalate (DMO) and methyl benzoate (MB) hydrogenation. On the contrast, similar complexes (o-PPh2C6H4NH2)2RuCl2 and (o-PPh2C6H4CH2NH2)2RuCl2, can only effectively catalyze the hydrogenation of DMO and MB, respectively. Our experimental studies in combination of theoretical calculations reveal that the remarkable substrate selectivity in the hydrogenation of esters arises from the nonbonding interactions operated by the CH2 linkage of the ligand.

Effective anchoring of silver nanoparticles onto N-doped carbon with enhanced catalytic performance for the hydrogenation of dimethyl oxalate to methyl glycolate

Silver nanoparticles supported on nitrogen-doped activated carbon (Ag/AC-N) are demonstrated as promising catalysts for the chemoselective hydrogenation of dimethyl oxalate to methyl glycolate. Characteristic studies by TPR, XPS, and Raman indicate that AC-N benefits the dispersion of silver nanoparticles due to the strong electronic interactions between nitrogen and silver species. The optimized Ag/AC-N catalyst shows intensified performance in terms of high activity and excellent stability. It is inferred that the co-existence of Ag0 and Ag+ derived from the strong interactions of nitrogen with Ag species renders the superior catalytic performance of Ag/AC-N.

Highly Active and Stable ZrO2 -SiO2 -Supported Cu-Catalysts for the Hydrogenation of Dimethyl Oxalate to Methyl Glycolate

A series of Cu/ZrO2-SiO2 catalysts with different ZrO2-SiO2 contents were prepared using an ammonia-evaporation method. The catalysts were used for the hydrogenation of dimethyl oxalate to methyl glycolate. The catalytic activity and stability of the Cu/ZrO2-SiO2 catalyst was greatly enhanced with an optimized ZrO2-SiO2 content when compared with the Cu/SiO2 and Cu/ZrO2 catalyst. The catalysts were characterized by N2 physisorption, X-ray diffraction, H2 temperature-programmed reduction, and X-ray photoelectron spectroscopy. The results showed that adding an appropriate amount of zirconium to Cu/SiO2 catalyst strengthened the interaction between the cupreous species and the support, diminished the copper crystallite size, improved the copper dispersion, and adjusted the surface [Cu+] species

Synergism from interfaces between Cu and crystalline ZrO2 nanosheets fabricated by acetic complex method for oxalates hydrogenation

Herein, the Cu species uniformly combining with highly crystalline ZrO2 nanosheets had been prepared by a one-pot acetic complex method. The selectivity to ethylene glycol of 98.9%, which corresponds to 99.8% conversion of diethyl oxalate was obtained over the one prepared by using acetic acid (AC) both as the complex agent and solvent. In addition, a stable performance was achieved (life span of >160h). It also showed good performance in hydrogenation of dimethyl oxalate (95.7h−1 turnover frequency). Essentially, solvents with different dielectric constant employed in complexation process had a prominent influence on the structure and catalytic activity of Cu/ZrO2 catalyst via solvation. Besides, complexation process was also important since AC could be regarded as L-type ligands in a low dielectric constant solvent, forming of ion-clusters which resulted in exclusive formation of the Cu-O-Zr interface after calcination. Evidently, the surface synergistic effect held the key to the continuous hydrogenation reaction related to the activation of the carbonyl groups and the hydrogen dissociation, thus creating a synergetic nanoenvironment for the successful completion of the “multi step turning into one-step” in the series reaction.

Synergistic Effect of a Boron-Doped Carbon-Nanotube-Supported Cu Catalyst for Selective Hydrogenation of Dimethyl Oxalate to Ethanol.

Heteroatom doping is a promising approach to improve the properties of carbon materials for customized applications. Herein, a series of Cu catalysts supported on boron-doped carbon nanotubes (Cu/xB-CNTs) were prepared for the hydrogenation of dimethyl oxalate (DMO) to ethanol. The structure and chemical properties of boron-doped catalysts were characterized by XRD, TEM, N2 O pulse adsorption, CO chemisorption, H2 temperature-programmed reduction, and NH3 temperature-programmed desorption, which revealed that doping boron into CNT supports improved the Cu dispersion, strengthened the interaction of Cu species with the CNT support, introduced more surface acid sites, and increased the surface area of Cu0 and especially Cu+ sites. Consequently, the catalytic activity and stability of the catalysts were greatly enhanced by boron doping. 100 % DMO conversion and 78.1 % ethanol selectivity could be achieved over the Cu/1B-CNTs catalyst, the ethanol selectivity of which was almost 1.7 times higher than that of the catalyst without boron doping. These results suggest that doping CNTs with boron is an efficient approach to improve the catalytic performance of CNT-based catalysts for hydrogenation of DMO. The boron-doped CNT-based catalyst with improved ethanol selectivity and catalytic stability will be helpful in the development of efficient Cu catalysts supported on non-silica materials for selective hydrogenation of DMO to ethanol.

Stabilization of copper catalysts for hydrogenation of dimethyl oxalate by deposition of Ag clusters on Cu nanoparticles

Novel Ag/Cu/SiO2 catalysts have been fabricated by galvanic deposition of Ag clusters on Cu nanoparticles for the first time. Although the Ag clusters in Ag/Cu/SiO2 covered about 20 to 30% of the Cu active surface, the turnover frequency is remarkably enhanced, resulting in a great improvement in the final DMO hydrogenation activity. More importantly, the obtained Ag/Cu/SiO2 catalyst achieves a lasting catalytic activity up to 1100h due to the strong interaction between Cu and Ag, which is among the best records for Cu-based catalysts.

A new low-cost and effective method for enhancing the catalytic performance of Cu–SiO2 catalysts for the synthesis of ethylene glycol via the vapor-phase hydrogenation of dimethyl oxalate by coating the catalysts with dextrin

The influence of low-cost dextrin coating on the performance of Cu–SiO2 catalysts for the vapor-phase hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG) was systematically investigated. On the 0.05D-Cu–SiO2 catalyst, 99.8% DMO conversion and 92.3% EG selectivity could be obtained at 463K under 2.0gg-catal−1h−1 weight liquid hourly space velocity, which is almost four times higher than that of the catalyst without coating with dextrin. Characterization methods including N2 physisorption, XRD, TEM, H2 TPR, and XPS were carried out to elucidate the structure–performance relationship. Experimental results indicated that copper phyllosilicate contents decreased while well-dispersed CuO and Cu–O–Si units increased. The improved morphology with more compact nanosized crystalline copper structure resulted in more Cu+ species, which lead to better DMO conversion and EG selectivity in a long-term stability test.

Promotive Effect of Sn2+ on Cu0/Cu+ Ratio and Stability Evolution of Cu/SiO2 Catalyst in the Hydrogenation of Dimethyl Oxalate

The influence of Sn2+doping on the structure and performance of silica supported copper catalyst was systematically investigated and characterised. Catalytic evaluation showed that the suitable content of Sn2+ introduced into a Cu/SiO2 catalyst evidently improved the catalytic activity and stability of ethylene glycol synthesis from dimethyl oxalate. X-ray diffraction and X-ray auger electron spectroscopy indicated that the Cu0/Cu+ ratio gradually increased with increasing Sn2+ content, and an appropriate proportion of Cu0/Cu+ ratio played a very significant role in this reaction. Transmission electron microscopy revealed that the active copper particles in the Cu-xSn/SiO2 catalyst were smaller than those of the Cu/SiO2 catalyst. This result may be due to the introduction of Sn2+ species transformed into SnO2. Furthermore, SnO2 effectively segregated the active copper. These effects are beneficial in inhibiting the aggregation of copper in the catalysts, thereby improving the stability of the catalyst and prolonging the life span.

Structure evolution of mesoporous silica supported copper catalyst for dimethyl oxalate hydrogenation

A modified ammonia evaporation method with an ordered mesoporous silica as the precursor of the support was applied to prepare the well dispersed copper-based catalysts. Appropriate amount of ammonia was used during the aging stage to prevent the destruction of the ordered mesoporous structure, which can ensure the homogeneous pre-distribution of the copper precursor ([Cu(NH3)4]2+) in the mesopores. Then the formation of copper phyllosilicate or surface Cu–O–Si species can be prompted during the ammonia evaporation stage, resulting in large surface areas of both Cu0 and Cu+ species in the final catalysts. It was also revealed that the formation of copper phyllosilicate led to the destruction of mesoporous silica structure in the ammonia evaporation stage especially at the higher copper loading. The catalysts with various copper loading were systematically characterized and applied in the hydrogenation of dimethyl oxalate to ethylene glycol (EG). An excellent low-temperature catalytic performance and stability were achieved on 20Cu/OMS with EG selectivity of 98.2% at 453K, due to the superior surface areas of both Cu0 and Cu+, as well as the highest ratio of Cu+/(Cu0+Cu+).

High-performance Ag-CuOx nanocomposite catalyst galvanically deposited onto a Ni-foam for gas-phase dimethyl oxalate hydrogenation to methyl glycolate

A foam-structured Ag-CuOx nanocomposite catalyst obtained by sequential galvanic-deposition of 0.4wt% Ag and 28wt% Cu onto a Ni-foam, is highly active, selective and stable for the gas-phase hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG). The best catalyst 0.4-Ag-28-CuOx/Ni-foam was capable of converting more than 96% DMO into MG with a high selectivity of more than 96% and was stable for at least 200h at 210°C and a WLHSVDMO of 0.25h−1 for a feed of 13wt% DMO dissolved in MeOH. Silver is responsible to apportion the proportion of Cu+ and Cu0 to an appropriate scale of optimal potency for converting DMO-to-MG.

Promoting effect of boron oxide on Ag/SiO2 catalyst for the hydrogenation of dimethyl oxalate to methyl glycolate

A highly active and stable catalyst for the hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG) had been developed. The Ag-B2O3/SiO2 catalysts were prepared by impregnation method with boric acid (H3BO3). The properties and the structures of the catalysts were fully characterized by BET, XRD, H2-TPR, NH3-TPD, FTIR, XPS and TEM. Compared with Ag/SiO2 catalyst, the Ag-B2O3/SiO2 catalyst exhibited significantly enhanced catalytic performance and high stability for the hydrogenation of DMO to MG under relatively milder reaction conditions (180°C, 0.5MPa). A high yield of 96.1% for MG was achieved over Ag-B2O3/SiO2 catalyst, while the yield of MG was only 54.3% over Ag/SiO2 catalyst. The excellent catalytic performance for Ag-B2O3/SiO2 catalyst was attributed to the introduction of B2O3. The addition of B2O3 to Ag/SiO2 catalyst favored the formation of highly dispersed Ag centers with electron-deficient state, which can strongly bind and activate the ester and acyl groups of DMO in the hydrogenation processes. Besides its effectiveness, the catalyst showed an excellent stability which can be performed for 264h under the reaction conditions of 180°C, 0.5MPa H2 and the weight space velocity of 0.2h−1.

Design and optimization of dimethyl oxalate (DMO) hydrogenation process to produce ethylene glycol (EG)

In this work, the steady state design of ethylene glycol (EG) production process by the dimethyl oxalate (DMO) hydrogenation is investigated. In comparison with the conventional ethylene oxide hydration process for EG production, this novel process provides better conversion and selectivity. The DMO hydrogenation process is comprised of a reaction section and a sequence of distillation columns as separation section. In reaction section, DMO is dissolved in methanol, and this DMO solution is then reacted with hydrogen to become EG and side products. Then, the raw product stream is fed into the sequence of distillation columns to obtain the EG product stream at the specified purity. After the initial process design is completed, the DMO hydrogenation process is optimized to obtain the optimal design with the minimum total annual cost (TAC). During process optimization, it is found that the mole ratio of hydrogen to DMO (HDMR) has global influences on TAC, and thus it is the last variable to be optimized. In this paper, the optimal case with HDMR=40 is obtained through optimization.

Highly selective and stable Cu/SiO2 catalysts prepared with a green method for hydrogenation of diethyl oxalate into ethylene glycol

Dimethyl oxalate (DMO) hydrogenation for ethylene glycol (EG) production is problematic due to environmental concerns and safety regulations. Therefore, development of improved methods for diethyl oxalate (DEO) hydrogenation based EG production is desirable. The objective of this research was to develop a cost-effective and environmentally benign approach for the synthesis of highly active and stable Cu/SiO2 catalysts for selective hydrogenation of diethyl oxalate (DEO) to ethylene glycol (EG). Here, ammonium carbonate is used to prepare Cu/SiO2 catalysts through deposition precipitation instead of the conventional pollution-producing evaporation process associated with the use of ammonia. The Cu/SiO2 catalysts prepared with the new method achieved 6.9–13.1% higher selectivity and showed better stability. The improved stability and selectivity resulted from increased chemical adsorption of DEO and H2 due to the high Cu2O concentration and Cu+/(Cu0+Cu+) ratio (reduced from ion-exchanged CuOSi units), and reduced carbon deposition on the Cu/SiO2 catalyst. The Cu2O reduced from CuOSi units in the Cu/SiO2 catalyst prepared by the new method was more stable than the Cu+ species reduced from copper phyllosilicate in the Cu/SiO2 catalyst prepared by the conventional method. Therefore, the new Cu/SiO2 catalyst preparation method appears most promising.

Effect of Different Nano-Sized Silica Sols as Supports on the Structure and Properties of Cu/SiO2 for Hydrogenation of Dimethyl Oxalate

Cu/x-SiO2 catalysts with 4, 10, and 20 nm silica sols as supports was produced by ammonia evaporation method and characterized. Different nano-sized silica sols as supports significantly affected the structure and catalytic properties of the copper catalysts for ethylene glycol synthesis from dimethyl oxalate. Compared with Cu/20-SiO2 and Cu/4-SiO2 catalysts, the catalytic performance and stability of Cu/10-SiO2 catalyst were greatly enhanced. The Cu/10-SiO2 catalyst showed 99.9% conversion with 94% EG selectivity and a lifetime of over 3080 h if it is calculated by industrial weight liquid hourly space velocity (WLHSV) of 0.5 h−1. The Cu/10-SiO2 catalyst has one of the longest lifetimes among the catalysts and is a good alternative catalyst for this reaction. Improvement in the catalytic performance and stability of Cu/10-SiO2 is attributed to the proper SBET, Dp and larger dispersion of copper. In addition, the supports of Cu/10-SiO2 catalyst have smaller particles than that of Cu/20-SiO2; thus, the migration and growth of copper species in catalysts are restrained during the reaction.

Design of an Autoreduced Copper in Carbon Nanotube Catalyst to Realize the Precisely Selective Hydrogenation of Dimethyl Oxalate

AbstractAn autoreduced catalyst that comprised Cu nanoparticles encapsulated inside the nanochannels of carbon nanotubes (Cu@CNTs) was designed and prepared. As a result of the interaction of Cu species with the electron‐deficient interior surface of the CNTs, calcination could realize the autoreduction of copper oxide directly with CNTs as the reductant. In the hydrogenation of dimethyl oxalate (DMO), the autoreduced Cu@CNTs catalyst, which did not need to be prereduced, exhibited an excellent catalytic activity, high target product selectivity, and high catalytic efficiency. Furthermore, the effect of the calcination temperature on the autoreduction degree of Cu@CNTs and the product selectivity in DMO hydrogenation were investigated in detail. The results showed that the autoreduction degree could be tuned easily by changing the calcination temperature, and the highest selectivity of ethanol could be obtained over the catalyst calcined at 500 °C. The findings obtained will inspire the development of other autoreduced catalysts, the reduction degree and catalytic performance of which can be tuned as desired.

Analysis of non-silica catalytic system for selective hydrogenation of dimethyl oxalate

Analysis of non-silica catalytic system for selective hydrogenation of dimethyl oxalate

A Fe5C2 nanocatalyst for the preferential synthesis of ethanol via dimethyl oxalate hydrogenation.

A Fe-based catalyst exhibits extremely high selectivity (89.6%) besides excellent catalytic activity in gas-phase dimethyl oxalate hydrogenation. The ethanol formation occurs via hydrogenation of methyl acetate instead of ethylene glycol over the active species Fe5C2.

Synthesis of Cu–Mg/ZnO catalysts and catalysis in dimethyl oxalate hydrogenation to ethylene glycol: enhanced catalytic behavior in the presence of a Mg2+ dopant

Mg2+ doped nanoscale Cu–Mg/ZnO catalysts prepared by the co-precipitation method have been systematically characterized focusing on the amount of Mg2+ ions incorporated.

Efficient tuning of surface copper species of Cu/SiO2 catalyst for hydrogenation of dimethyl oxalate to ethylene glycol

The chemoselective synthesis of ethylene glycol (EG) from the hydrogenation of dimethyl oxalate (DMO) derived from syngas is an attractive technology in the modern chemical industry. This work reported a novel hydrolysis precipitation (HP) method to efficiently tune the active copper species of Cu/SiO2 catalysts for DMO hydrogenation. Characterization techniques such as N2 physical adsorption, X-ray diffraction, H2 temperature programmed reduction, N2O titration, Fourier-transform infrared spectra, transmission electron microscopy, and X-ray photoelectron spectroscopy were employed to reveal the origin of the catalytic performances. Compared to the ammonia evaporation (AE) method, the HP method presented remarkable higher dispersion of copper species and large ratio of Cu+/(Cu++Cu0) on the catalyst surface, resulting in a superior catalytic performance in the hydrogenation of DMO to EG. Moreover, the amount of Cu0 and Cu+ sites on catalyst surface is dramatically affected by copper loading, and the catalyst with 30% copper showed the highest catalytic activity with a space time yield of 1.74gEG/(gcat·h) at 463K. Meanwhile, the positive correlation between Cu+ surface area and space time yield of EG suggests that the amount Cu+ is the key factor for hydrogenation of DMO to EG on the as-prepared Cu/SiO2 catalyst. The formation of more Cu+ species in the catalyst would enhance the activation of CO group in DMO and significantly improve the catalytic performances in DMO hydrogenation.

Effect of Cu-doping on the structure and performance of molybdenum carbide catalyst for low-temperature hydrogenation of dimethyl oxalate to ethanol

Several copper-doped molybdenum carbide (Cu–Mo2C) nanomaterials for the hydrogenation of dimethyl oxalate (DMO) to ethanol at low temperature (e.g., 473K) have been developed through a facile solid-state pyrolysis method. Characterization techniques including X-ray diffraction, scanning/transmission electron microscopy, N2-physisorption, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy were employed to reveal the morphology, structure and properties of the synthesized nanomaterials. The characterization and reaction results suggest that the incorporation of copper species in Mo2C plays a crucial role in modifying the morphologic structure of Cu–Mo2C as well as tuning the electronic state of Mo active sites, resulting in an important enhancement in the catalytic performance. Moreover, a strong synergistic effect between Cu and Mo2C is observed in DMO hydrogenation. Accordingly, the 67.2% yield of ethanol can be attained at a low temperature of 473K over the Cu–Mo2C nanomaterials with a suitable atom ratio (e.g., Cu:Mo=0.03:1), which are higher than those obtained by using a pure Mo2C (e.g., 13.7%) under the same reaction conditions. The Cu-doped Mo2C nanomaterials also display excellent catalytic stability during the hydrogenation of DMO to ethanol for longer than 300h.