Dimethyl Carbonate Formation Research Articles

One-Pot, Metal-Free Synthesis of Dimethyl Carbonate from CO2 at Room Temperature

Herein, we report on the metal-free, one-pot synthesis of industrially important dimethyl carbonate (DMC) from molecular CO2 under ambient conditions. In this process, initially the CO2 was chemisorbed through the formation of a switchable ionic liquid (SIL), [DBUH] [CH3CO3], by the interaction of CO2 with an equivalent mixture of organic superbase 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) and methanol. The obtained SIL further reacted with methyl iodide (CH3I) to form DMC. The synthesis was carried out in both dimethyl sulfoxide (DMSO) and methanol. Methanol is preferred, as it not only served as a reagent and solvent in CO2 capture and DMC synthesis, but it also assisted in controlling the side reactions between chemical species such as CH3I and [DBUH]+ cation and increased the yield of DMC. Hence, the use of methanol avoided the loss of captured CO2 and favored the formation of DMC with high selectivity. Under the applied reaction conditions, 89% of the captured CO2 was converted to DMC. DBU was obtained, achieving 86% recovery of its salts formed during the synthesis. Most importantly, in this report we describe a simple and renewable solvent-based process for a metal-free approach to DMC synthesis under industrially feasible reaction conditions.

Fabrication of Few-Layer Graphene-Supported Copper Catalysts Using a Lithium-Promoted Thermal Exfoliation Method for Methanol Oxidative Carbonylation.

Exfoliation of graphene oxide (GO) via thermal expansion is regarded as the most promising approach to obtain few-layer graphene (FLG) in bulk. Herein, we introduce an efficient strategy for improving the exfoliation process by adding a tiny amount of lithium nitrate in the precursors, which significantly enhances the removal of oxygen-containing functional groups and produces 1-2 layer graphene. FLG-supported highly dispersed Cu nanoparticles (NPs, ≈4.2 nm) can be further synthesized through exfoliating the mixture of GO, lithium nitrate, and copper(II) nitrate, which displayed superior catalytic activity and stability in the synthesis of dimethyl carbonate (DMC) using liquid methanol oxidative carbonylation. The characterization results demonstrate that during the thermal expansion process, lithium nitrate was decomposed to Li2O and immediately reacted with CO2 released by the decomposition of GO to form stable Li2CO3, which promotes efficient charge transfer and produces Cuδ+ (0 < δ < 1) species in the Cu/Li-PGO catalyst. Density functional theory calculations prove that the presence of Cuδ+ markedly facilitates CO adsorption over the resulting catalyst and causes a decrease of the energy barrier of the rate-limiting step for DMC formation (CO insertion). These findings give a theoretical explanation of the enhanced catalytic performance of the Cu/Li-PGO catalyst. The present work provides a simple and practical avenue to the exfoliation of graphene and the dispersions of metal NPs on graphene sheets.

Теоретическое исследование получения диметилкарбоната алкоголизом мочевины

Using the density functional method М06, the mechanisms of non-catalytic reactions of transesterification of urea with methanol with the formation of dimethyl carbonate, as well as in catalysis with zinc oxide and acetate, were studied. The transesterification proceeds stepwise with the intermediate formation of methyl carbamate. The non-catalytic process of transesterification of urea with methanol proceeds by the mechanism of nucleophilic SN2 substitution and is accompanied by the formation of pre-reaction complexes, which through synchronous transition states turn into post-reaction complexes, decomposing into ammonia and methyl carbamate in the first stage and dimethyl carbonate in the second. It has been established that methanol associates can take part in these reactions. Their participation is preferable both kinetically and thermodynamically. An analysis of the equilibrium constants of the reaction of urea with methanol at various temperatures showed that in a wide temperature range their values remain large in the first stage – the formation of methyl carbamate and become significantly reversible in the second – the conversion of methyl carbamate to dimethyl carbonate. Reactions involving acetate and zinc oxide proceed through the same stages as non-catalytic interactions. In the case of zinc acetate catalyzed reactions, if methanol monomer is involved in the reaction, the reaction of formation of methyl carbamate has a lower activation barrier compared to the reaction of conversion of methyl carbamate to dimethyl carbonate. If a methanol dimer is involved in the reaction, both reactions have a practically equal activation barrier. In the case of zinc oxide catalyzed interactions, reactions involving a methanol dimer were not detected. The participation of the catalyst leads to a significant decrease in activation barriers, and a more significant decrease occurs in the case of catalysis with zinc oxide. The reason for the different catalytic activity, in our opinion, is the difference in the charges on the urea carbon atom in the pre-reaction complexes.

CO direct esterification to dimethyl oxalate and dimethyl carbonate: the key functional motifs for catalytic selectivity.

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.

Gas phase synthesis of dimethyl carbonate from CO2 and CH3OH over Cu-Ni/AC. A kinetic study

The catalytic activity for dimethyl carbonate formation from carbon dioxide and methanol over mono and bimetallic Cu:Ni supported on activated carbon is presented. Bimetallic catalysts exhibit higher catalytic activity than the monometallic samples, being Cu:Ni-2:1 (molar ratio) the best catalyst; X-Ray diffraction, transmission electron microscopy, and metal dispersion analysis provided insight into the improved activity. In situ FT-IR experiments were conducted to investigate the mechanism of formation of dimethyl carbonate from methanol and carbon dioxide over Cu-Ni:2-1. The kinetics of the direct synthesis of dimethyl carbonate in gas phase over Cu:Ni-2:1 supported on activated carbon catalyst was experimentally investigated at 12 bar and temperatures between 90 oC and 130 oC, varying the partial pressures of CO2 and methanol. Experimental kinetic data were consistent with a Langmuir–Hinshelwood model that included carbon dioxide and methanol adsorption on catalyst actives sites (Cu, Ni and Cu-Ni), and the reaction of adsorbed CO2 with methoxi species as the rate determining step. The estimated apparent activation energy was 94.2 kJ mol-1.

Dopant-tuned stabilization of intermediates promotes electrosynthesis of valuable C3 products

The upgrading of CO2/CO feedstocks to higher-value chemicals via energy-efficient electrochemical processes enables carbon utilization and renewable energy storage. Substantial progress has been made to improve performance at the cathodic side; whereas less progress has been made on improving anodic electro-oxidation reactions to generate value. Here we report the efficient electroproduction of value-added multi-carbon dimethyl carbonate (DMC) from CO and methanol via oxidative carbonylation. We find that, compared to pure palladium controls, boron-doped palladium (Pd-B) tunes the binding strength of intermediates along this reaction pathway and favors DMC formation. We implement this doping strategy and report the selective electrosynthesis of DMC experimentally. We achieve a DMC Faradaic efficiency of 83 ± 5%, fully a 3x increase in performance compared to the corresponding pure Pd electrocatalyst.

Metal-organic frameworks MOF-808-X as highly efficient catalysts for direct synthesis of dimethyl carbonate from CO2 and methanol

A series of metal-organic frameworks MOF-808-X (6-connected) were synthesized by regulating the ZrOCl2·8H2O/1,3,5-benzenetricarboxylic acid (BTC) molar ratio (X) and tested for the direct synthesis of dimethyl carbonate (DMC) from CO2 and CH3OH with 1,1,1-trimethoxymethane (TMM) as a dehydrating agent. The effect of the ZrOCl2·8H2O/BTC molar ratio on the physicochemical properties and catalytic performance of MOF-808-X was investigated. Results showed that a proper ZrOCl2·8H2O/BTC molar ratio during MOF-808-X synthesis was fairly important to reduce the redundant BTC or zirconium clusters trapped in the micropores of MOF-808-X. MOF-808-4, with almost no redundant BTC or zirconium clusters trapped in the micropores, exhibited the largest surface area, micropore size, and the number of acidic-basic sites, and consequently showed the best activity among all MOF-808-X, with the highest DMC yield of 21.5% under the optimal reaction conditions. Moreover, benefiting from the larger micropore size, MOF-808-4 outperformed our previously reported UiO-66-24 (12-connected), which had even more acidic-basic sites and larger surface area than MOF-808-4, mainly because the larger micropore size of MOF-808-4 provided higher accessibility for the reactant to the active sites located in the micropores. Furthermore, a possible reaction mechanism over MOF-808-4 was proposed based on the in situ FT-IR results. The effects of different reaction parameters on DMC formation and the reusability of MOF-808-X were also studied.

Improvement of dimethyl carbonate formation via methanol carbonation over vanadium-doped Cu–Ni/AC catalyst

In present study, Cu–Ni/AC and V-doped Cu–Ni/AC were prepared using an impregnation and co-impregnation methods respectively for dimethyl carbonation (DMC) formation from CH3OH carbonation at various temperatures (110, 170, and 220°C) and CO2/N2 volumetric flow ratios (1/4, 1/7, and 1/9). Effects of vanadium addition on Cu–Ni/AC intrinsic properties and catalytic performances were investigated. Decrease of Cu–Ni/AC surface acidity with vanadium addition was found with NH3–temperature programmed desorption (NH3–TPD) at 25–450°C. Furthermore, the valence shifts of metallic atoms in catalysts were found by X–ray absorption near–edge structure/extended X–ray absorption fine structure (XANES/EXAFS). Optimal reaction conditions (170°C and CO2/N2 = 1/7) with the highest CH3OH conversion (8.1%), DMC selectivity (93.2%), and DMC yield (7.5%) were confirmed in a fixed-bed column reactor. Linear regressions of the pseudo-first-order, pseudo-second-order, and third-order models referred that the largest CH3OH consumption rate constant (15.56 × 10−3 1/min, 9.29 L/mol-min), turnover number (TON = 17.89), and turnover frequency (TOF = 3.73 × 10−2 1/min) of DMC formation were acquired with V-doped Cu–Ni/AC at optimal reaction conditions. A reaction mechanism over Cu–Ni/AC or V-doped Cu–Ni/AC active sites was proposed.

Preparation and characterization of H3PW12O40/ZrO2 catalyst for carbonation of methanol into dimethyl carbonate

A H3PW12O40/ZrO2 catalyst for effective dimethyl carbonate (DMC) formation via methanol carbonation was prepared using the sol–gel method. X-ray photoelectron spectra showed that reactive and dominant (63%) W(VI) species, in WO3 or H2WO4, enhanced the catalytic performances of the supported ZrO2. The mesoporous structure of H3PW12O40/ZrO2 was identified by nitrogen adsorption–desorption isotherms. In particular, partial sintering of catalyst particles in the duration of methanol carbonation caused a decrease in the Brunauer–Emmett–Teller surface area of the catalyst from 39 to 19 m2/g. The strong acidity of H3PW12O40/ZrO2 was confirmed by the desorption peak observed at 415 °C in NH3 temperature-programmed desorption curve. At various reaction temperatures (T = 110, 170, and 220 °C) and CO2/N2 volumetric flow rate ratios (CO2/N2 = 1/4, 1/7, and 1/9), the calculated catalytic performances showed that the optimal methanol conversion, DMC selectivity, and DMC yield were 4.45, 89.93, and 4.00%, respectively, when T = 170 °C and CO2/N2 = 1/7. Furthermore, linear regression of the pseudo-first-order model and Arrhenius equation deduced the optimal rate constant (4.24 × 10−3 min−1) and activation energy (Ea = 15.54 kJ/mol) at 170 °C with CO2/N2 = 1/7 which were favorable for DMC formation.

Spectroscopic Investigation of the Electrosynthesis of Diphenyl Carbonate from CO and Phenol on Gold Electrodes.

In this work, we study the synthesis of diphenyl carbonate (DPC) from phenol and CO on gold electrodes studied by means of in situ Fourier transform infrared spectroscopy (FTIR). The results show that, on gold electrodes, the formation of DPC is observed at potentials as low as 0.4 V vs Ag/AgCl, together with the formation of dimethyl carbonate (DMC) from the carbonylation of methanol that was used as a solvent. The spectroelectrochemical results also suggest that the formation of DPC occurs via the replacement of the methoxy groups from DMC with phenoxy groups from phenol and not directly by the carbonylation of phenol. Although this transesterification process is known to occur with heterogeneous catalysts, it has not been reported under electrochemical conditions. These are interesting findings, since the direct DPC production by carbonylation of phenol to DPC is usually performed with Pd-based catalysts. With this reaction scheme of transesterification happening under electrochemical conditions, other non-Pd catalysts could be used as well for one-step DPC production from phenol and CO. These findings give important mechanistic insights into this reaction and open up possibilities to an alternative process for the production of DPC.

Insight into the formation mechanism and kinetics for the oxidative carbonylation of methanol to dimethyl carbonate over CuO catalyst: Effects of Cu valence state and solvent environment

The formation mechanism and kinetics of dimethyl carbonate (DMC) via the oxidative carbonylation of methanol over Cu(II) catalyst have been investigated using density functional theory calculations under gas phase and solvent conditions. The results show that the preferred pathway of DMC formation in the gas phase is that via CO insertion into (CH3O)2 species, which is more favorable in kinetics than that via CO insertion into CH3O; the rate-limiting step of DMC formation is CO insertion into (CH3O)2. Meanwhile, the kinetic results of DMC formation in the liquid phase show that the solvent can improve the catalytic activity of Cu(II) catalyst towards DMC formation in a liquid-phase slurry, especially in water. Moreover, the comparisons among different valence state Cu catalysts for the most favorable pathway of DMC formation indicate that Cu valence state has a significant effect on the formation mechanism of DMC. The calculated results can provide a clue to finely tune the catalytic activity of DMC formation over Cu-based catalyst using the valence state and solvent environments under the realistic conditions.

The preparation and efficacy of SrO/CeO2 catalysts for the production of dimethyl carbonate by transesterification of ethylene carbonate

The need for eco-friendly fuels has given a fillip to search for new molecules and their cost-effective synthesis. A series of ceria-strontium (CexSr1−xO2; x = 0 to 1) catalysts were prepared by a citric acid assisted sol–gel method. These catalysts were characterized by BET, XRD, SEM-EDAX, ICP-MS, FTIR, NH3-TPD and CO2-TPD techniques and tested for the synthesis of dimethyl carbonate (DMC) in a batch reactor for the transesterification of ethylene carbonate (EC). The activity of the synthesized catalysts was found to be closely related to basic and acidic sites, and the surface area of the catalysts. The catalyst, Ce0.6Sr0.4, showed highest basicity and acidity, and was found to be most effective in the formation of DMC from transesterification of EC. Reactions were carried out by varying the particle size (50–800 μm) and agitation speed (200–600 rpm) for minimizing the internal mass transfer resistance and the external mass transfer resistance, respectively. Further, Ce0.6Sr0.4 catalyst was used to optimize the reaction conditions such as methanol/EC molar ratio (in the range of 4–12), catalyst dose (in the range of 2–5 wt% of EC), reaction time (in the range of 2–6 h) and temperature (in the range of 100–180 °C) for DMC yield and EC conversion. At the optimum conditions of methanol/EC molar ratio of 8, 3 wt% of catalyst, 5 h reaction time and 150 °C temperature, the DMC selectivity was 87% and EC conversion of 82%, with a reaction rate of ∼0.547 mol/L.h (with respect to EC). The reusability of the Ce0.6Sr0.4 catalyst for EC conversion with turn-over frequency and DMC selectivity were also studied.

Nitrogen-doped graphene supported copper catalysts for methanol oxidative carbonylation: Enhancement of catalytic activity and stability by nitrogen species

Nitrogen-doped graphene (NG) has recently attracted much interest because of its ability to fix the metal nanoparticles (NPs). In this study, NG materials with a nitrogen content of 4.5–7.6 wt% were prepared by hydrothermal method and then used to support Cu catalysts for dimethyl carbonate (DMC) synthesis via the oxidative carbonylation of methanol. The Cu/NG catalysts showed significantly enhanced catalytic activity and stability as compared with copper/reduced graphene oxide (rGO) catalyst. The characterization results show that the enhancing effect of nitrogen doping can be attributed to the decrease in size of Cu NPs and the increase in density of carrier for efficient charge transfer. Density functional theory calculations gave further evidence that the energy barrier for the rate-limiting step for DMC formation (CO insertion) is 89.6 to 67.5 kJ/mol, and that the energies of binding between Cu and the substrate on Cu/rGO and Cu/NG catalysts are 723.1 and 922.7 kJ/mol, respectively.

Phosphate Functionalization of CeO2–ZrO2 Solid Solutions for the Catalytic Formation of Dimethyl Carbonate from Methanol and Carbon Dioxide

AbstractPhosphate surface groups on CeO2–ZrO2 solid solutions were generated by treating Ce–Zr–hydroxide precursors with phosphoric acid. In the catalytic formation of dimethyl carbonate (DMC) from methanol and CO2, the performance of the P‐modified samples was markedly affected relative to that of the unmodified ones: Phosphate treatment caused remarkable changes in the phase composition, acid–base properties, and the ability to form monodentate methoxy intermediates. The DMC yield (1.6 %) was successfully improved from 0.24 to 1.6 % by phosphate modification of CeO2–ZrO2 (Ce/Zr=4.7, P/Zr=0.13) and by performing the reaction at 170 °C and 6.5 MPa for 1 h.

Synthesis of dimethyl carbonate on single Cu atom embedded in N-doped graphene: Effect of nitrogen species

The synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of methanol on atomic Cu supported on N-doped graphene (Cu1/NG) was explored by density-functional theory. The configurations with which the Cu atom is anchored to pyridinic- (Cu/PNG), graphitic- (Cu/GNG) and amino-N (Cu/ANG) doped graphene have been systematically investigated and compared with Cu-doped monovacancy graphene (Cu/MG) and pristine graphene (Cu/PG). The binding energy of the Cu atom was found to decrease in the order Cu/GNG>Cu/ANG>Cu/MG>Cu/PNG>Cu/PG. On Cu1/NG, DMC can be formed via CO insertion into CH3O to form CH3OCO, which then reacts with additional methoxide. The barrier energies of the rate-limiting reaction of CO insertion into methoxide on Cu/PNG, Cu/GNG, Cu/MG, and Cu/ANG surfaces have been found to be 31.0, 52.1, 73.5, and 92.0kJ/mol, respectively. And the corresponding reaction energies are −38.2, −51.3, −44.6, and −63.4kJ/mol, respectively. The activity of the Cu1/NG catalysts increases in the order Cu/PNG<Cu/GNG<Cu/MG<Cu/ANG. To summarize, the presence of pyridinic- and graphitic-N in Cu1/NG catalysts is beneficial to the oxidative carbonylation of methanol, while amino-N has a negative effect on DMC formation.

Spectro-Electrochemical Examination of the Formation of Dimethyl Carbonate from CO and Methanol at Different Electrode Materials.

In this work, we report a fundamental mechanistic study of the electrochemical oxidative carbonylation of methanol with CO for the synthesis of dimethyl carbonate on metallic electrodes at low overpotentials. For the first time, the reaction was shown to take place on the metallic catalysts without need of oxidized metals or additives. Moreover, in-situ spectroelectrochemical techniques were applied to this electrosynthesis reaction in order to reveal the reaction intermediates and to shed light into the reaction mechanism. Fourier transformed infrared spectroscopy was used with different electrode materials (Au, Pd, Pt, and Ag) to assess the effect of the electrode material on the reaction and the dependence of products and intermediates on the applied potentials. It was observed that the dimethyl carbonate is only formed when the electrode is able to decompose/oxidize MeOH to form (adsorbed) methoxy groups that can further react with CO to dimethyl carbonate. Furthermore, the electrode needs to adsorb CO not too strongly; otherwise, further reaction will be inhibited because of surface poisoning by CO.

Ordered mesoporous silica-carbon-supported copper catalyst as an efficient and stable catalyst for catalytic oxidative carbonylation

Ordered mesoporous silica-carbon (MSC) nanocomposites with homogeneously distributed networks were synthesized by the triconstituent co-assembly method and used as supports of Cu catalysts for dimethyl carbonate (DMC) synthesis. The introduced silica contributes to the considerably increased pore size (∼5.8nm), the enhanced metal-support interaction and high dispersion of Cu nanoparticles (∼3.8nm) confined in the mesopores. An improved catalytic performance of Cu/MSC is achieved, reaching a DMC selectivity up to 90% at a methanol conversion of 1.5%, and a stable performance during five recycling runs. On the other hand, the benchmark Cu/MC catalyst undergoes a dramatic decrease of methanol conversion, from 1.3 to 1.0%, accompanied by a 27% reduction of DMC space-time yield (STYDMC). The mechanism through which the hybrid carrier affects the catalytic performance is analyzed using DFT calculations. The results show that the binding energy of Cu on MSC is greatly increased while the energy barrier to CO insertion for DMC formation is reduced evidently, thus enhancing the metal-support interaction and, in turn, the catalytic performance.

Density-functional theory study of dimethyl carbonate synthesis by methanol oxidative carbonylation on single-atom Cu1/graphene catalyst

The mechanism for dimethyl carbonate (DMC) synthesis by oxidation carbonylation of methanol on a single-atom Cu1/graphene catalyst was investigated by density-functional theory calculations. Carbon vacancies in graphene can significantly enhance the interaction between Cu atoms and graphene supports, and provide an increased transfer of electrons from Cu atoms to the graphene sheet. Compared with Cu-doped divacancy graphene (Cu/DG), Cu-doped monovacancy graphene (Cu/MG) provides a stronger interaction between adsorbents and the catalyst surface. Among the reaction processes over Cu1/graphene catalysts, CO insertion into methoxide was more favorable than dimethoxide. The rate-limiting step on the Cu/DG surface is the carbomethoxide reaction with methoxide, which is exothermic by 164.6kJmol−1 and has an activation barrier of 190.9kJmol−1 energy. Compared with that on the Cu crystal surface, Cu4 and Cu3Rh clusters, and the Cu2O(111) surface, the rate-determining step for DMC formation on Cu/MG, which is CO insertion into methoxide, needs to overcome the lowest barrier of 73.5kJmol−1 and is exothermic by 44.6kJmol−1. Therefore, Cu/MG was beneficial to the formation of DMC as a single-atom catalyst.

(n‐Bu2Sn)2O(CO3): An active, robust and recyclable organotin(IV) for the direct synthesis of linear organic carbonates from carbon dioxide and alcohols

Organotin(IV) compounds are known to promote the direct synthesis of organic carbonates from carbon dioxide and alcohols. In the past, structural studies have highlighted that the carbonato moiety is a recurring ligand of tin species collected during CO2 pressurized reactions. In a mimetic approach and in order to achieve an available and recyclable precursor, the title compound (n‐Bu2Sn)2O(CO3) (1) was prepared in a single step by reacting commercial di‐n‐butyltin dichloride with an aqueous solution of sodium carbonate. Compound 1 was characterized using infrared spectroscopy and thermogravimetric and elemental analyses. Multinuclear NMR investigations in solution were also conducted. Compound 1 was then evaluated for the direct carbonation of alcohols (methanol, ethanol, n‐butanol and isopropanol) under CO2 pressure. Recycling experiments were performed showing the efficient reuse of 1 without loss of activity. Furthermore, the infrared fingerprint of 1 was preserved even after several runs demonstrating a good stability. The effects of pressure and of reaction time on dimethyl carbonate formation were also studied.

Synthesis and characterization of H3PW12O40/Ce0.1Ti0.9O2 for dimethyl carbonate formation via Methanol carbonation

Ce0.1Ti0.9O2 and H3PW12O40/Ce0.1Ti0.9O2 catalysts were synthesized with a sol–gel method to form dimethyl carbonate (DMC) at reaction temperatures T = 110, 170, and 220 °C and volumetric flow-rate ratios CO2/N2 = 1/4, 1/7, and 1/9. The zeolite-like properties of H3PW12O40/Ce0.1Ti0.9O2 with an organized Keggin heteropolyacid structure were demonstrated from X-ray diffraction patterns and Fourier transform infrared spectra. 31P nuclear magnetic resonance spectra indicated that the Keggin heteropolyacid structure was formed through the addition of heteropoly acid (H3PW12O40). The bond lengths between titanium (Ti(IV)) and its adjacent atoms in the first shell (TiO) of Ce0.1Ti0.9O2 and H3PW12O40/Ce0.1Ti0.9O2 were 1.90 and 1.86 Å, respectively, confirmed with EXAFS spectra. At 170 °C and CO2/N2 = 1/7, the optimal methanol conversion (5.5%), DMC selectivity (91.4%), and DMC yield (5.0%) of H3PW12O40/Ce0.1Ti0.9O2 were greater than those of Ce0.1Ti0.9O2. Linear regressions of the pseudo-first-order model indicated that the largest rate constant (4.16 × 10−3 min−1), turnover number (TON = 29.07), and turnover frequency (TOF = 4.85 × 10−2 min−1) of DMC formation were obtained with H3PW12O40/Ce0.1Ti0.9O2 at 170 °C and CO2/N2 = 1/7. A reaction mechanism induced by oxygen vacancies over the surfaces of Ce0.1Ti0.9O2 and H3PW12O40/Ce0.1Ti0.9O2 is proposed to describe the formation of DMC.