Tuning the cross-linked structure of basic poly(ionic liquid)to develop an efficient catalyst for the conversion of vinyl carbonate to dimethyl carbonate

Dimethyl carbonate(DMC)is a crucial chemical raw material widely used in organic synthesis,lithiumion battery electrolytes,and various other fields.The current primary industrial process employs a conventional sodium methoxide basic catalyst to produce DMC through the transesterification reaction between vinyl carbonate and methanol.However,the utilization of this catalyst presents several challenges during the process,including equipment corrosion,the generation of solid waste,susceptibility to deactivation,and complexities in separation and recovery.To address these limitations,a series of alkaline poly(ionic liquid)s,i.e.[DVBPIL][PHO],[DVCPIL][PHO],and[TBVPIL][PHO],with different crosslinking degrees and structures,were synthesized through the construction of cross-linked polymeric monomers and functionalization.These poly(ionic liquid)s exhibit cross-linked structures and controllable cationic and anionic characteristics.Research was conducted to investigate the effect of the cross-linking degree and structure on the catalytic performance of transesterification in synthesizing DMC.It was discovered that the appropriate cross-linking degree and structure of the[DVCPIL][PHO]catalyst resulted in a DMC yield of up to 80.6%.Furthermore,this catalyst material exhibited good stability,maintaining its catalytic activity after repeated use five times without significant changes.The results of this study demonstrate the potential for using alkaline poly(ionic liquid)s as a highly efficient and sustainable alternative to traditional catalysts for the transesterification synthesis of DMC.

Mechanism study on the influence of surface properties on the synthesis of dimethyl carbonate from CO_(2)and methanol over ceria catalysts

The direct synthesis of dimethyl carbonate(DMC)from CO_(2)and methanol has attracted much attention as an environmentally benign and alternative route for conventional routes.Herein,a series of cerium oxide catalysts with various textural features and surface properties were prepared by the one-pot synthesis method for the direct DMC synthesis from CO_(2)and methanol,and the structure-performance relationship was investigated in detail.Characterization results revealed that both of surface acid-base properties and the oxygen vacancies contents decreased with the rising crystallinity at increasingly higher calcination temperature accompanied by an unexpectedly volcano-shaped trend of DMC yield observed on the catalysts.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)studies indicated that the adsorption rate of methanol is slower than that of CO_(2)and the methanol activation state largely influences the formation of key intermediate.Although the enhanced surface acidity-basicity and oxygen vacancies brought by low-temperature calcination could facilitate the activation of CO_(2),the presence of excess strongly basic sites on low-crystallinity sample was detrimental to DMC synthesis due to the preferred formation of unreactive mono/polydentate carbonates as well as the further impediment of methanol activation.Moreover,with the use of 2-cyanopyridine as a dehydration reagent,the DMC synthesis was found to be both influenced by the promotion from the rapid in situ removal of water and the inhibition from the competitive adsorption of hydration products on the same active sites.

Deactivation mechanism of CaO in a flow type dimethyl carbonate synthesis process

It is well known that calcium oxide (CaO) has better catalytic efficiency than most heterogeneous catalysts in many transesterification reactions. However, the gradual deactivation problem prevents its large-scale application in industry. In this paper, the deactivation mechanism of CaO in a fixed-bed reactor is investigated based on the transesterification reaction of propylene carbonate and methanol. The leaching amount of CaO during the reaction was estimated by the concentration of Ca in the products. The pretreated and recovered catalysts were characterized by FT-IR, XRD, TG-MS and SEM-EDS. It is evident from experiments and characterization that the deactivation process of CaO is accompanied by the leaching of calcium species and the generation of CaCO3, which are also verified by DFT calculations. At high temperature and high weight hourly space velocity, the deactivation was attributed to the formation of dense CaCO3 shell, which prevents the contact between the feedstock and the active species inside.

CaF_2-doped ZrO_2:A base catalyst for synthesis of dimethyl carbonate

The effect of CaF2-doped ZrO2 catalyst for the synthesis of dimethyl carbonate （DMC） was studied by X-ray diffraction （XRD）, CO2-temperature programmed desorption （TPD）, Raman spectra, and X-ray photoelectron spectroscopy （XPS）. Catalytic performance was evaluated in the bath and distillation reactors. Results showed that the CaF2/ZrO2 catalysts had activity and stability for DMC synthesis.

Fixation of CO_2 by electrocatalytic reduction to synthesis of dimethyl carbonate in ionic liquid using effective silver-coated nanoporous copper composites

With high surface area,open porosity and high efficiency,a catalyst was prepared and firstly employed in electrocatalytic reduction of CO2 and electrosynthesis of dimethyl carbonate（DMC）.The electrochemical property for electrocatalytic reduction of CO2 in ionic liquid was studied by cyclic voltammogram（CV）.The effects of various reaction variables like temperature,working potential and cathode materials on the electrocatalytic performance were also investigated.80%yield of DMC was obtained under the optimal reaction conditions.

One-pot Synthesis of Dimethyl Carbonate in the Presence of a Two-component Catalyst

The one-pot synthesis of dimethyl carbonate（DMC） with co-production of propy-lene carbonate（PC） and propylene glycol（PG） from propylene oxide（ PO）, carbon dioxide and methanol as the starting materials was investigated. The catalyst adopted here was a mixture of tetrabutyl ammonium bromide and sodium methoxide. It was found that un- der the reaction conditions of t = 150 ℃, p =3-4 MPa and 2 h, the PO conversion could reach 100%, the DMC, PC and the PG selectivities were 49. 7%, 42. 7% and 49. 8%, respectively, and the selectivity of by-products was below 10%.

Critical temperatures and pressures of reacting mixture in synthesis of dimethyl carbonate with methanol and carbon dioxide

Critical temperatures and pressures of nominal reacting mixture in synthesis of dimethyl carbonate （DMC） from methanol and carbon dioxide （quaternary mixture of carbon dioxide ＋ methanol ＋ water ＋ DMC） were measured using a high-pressure view cell. The results suggested that the critical properties of the reacting mixture depended on the reaction extent as well as its initial composition （initial ratio of carbon dioxide to methanol）. Such information is essential for determining the reaction conditions when one intends to carry out the synthesis of DMC with CO2 and methanol under supercritical conditions.

Synthesis of Dimethyl Carbonate from Methanol and Carbon Dioxide Catalyzed by Potassium Hydroxide under Mild Conditions

The synthesis of dimethyl carbonate （DMC） from methanol and carbon dioxide using potassium hydroxide as catalyst in the presence of CH3I and the effect of ionic liquid on the reaction were investigated. The results showed that KOH is an effective catalyst; the high selectivity and raised yield of DMC formation under mild conditions were achieved. However, the addition of the ionic liquid, l-ethyl-3-methylimidazolium bromide （emimBr）, can evidently accelerate the conversion of methanol and yield of the product.

Metal-organic frameworks MOF-808-X as highly efficient catalysts for direct synthesis of dimethyl carbonate from CO_2 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.

Studies on the Simultaneous Synthesis of Dimethyl Carbonate and Poly(ethylene terephthalate): I. Catalytic Activity of Metal Acetate in Transesterification of Ethylene Carbonate with Dimethyl Terephthalate

A novel direct method for preparation of dimethyl carbonate and poly（ethylene terephthalate） from ethylene carbonate and dimethyl terephthalate has been demonstrated in the presence of metal acetate catalysts, lithium acetate dihydrate showed highest catalytic activity with 47.9% yield of dimethyl carbonate. This method was a green chemical process.

Synthesis of methyl N-phenyl carbamate from dimethyl carbonate and 1,3-diphenyl urea under mild conditions

Synthesis of methyl N-phenyl carbamate from dimethyl carbonate and 1,3-diphenyl urea was investigated under atmospheric pressure. The results showed that homogenous catalyst sodium methoxide had the excellent activity to efficiently catalyze the synthesis of methyl N-phenyl carbamate under atmospheric pressure.

Process design and economic optimization for the indirect synthesis of dimethyl carbonate from urea and methanol

Much attention has been paid for the synthesis of dimethyl carbonate(DMC) by urea indirect alcoholysis method, which had not been actually industrialized by now. The rigorous full process model was then necessary to optimize the process with heat integration. In this paper, a full process was designed and optimized for the DMC synthesis by urea indirect alcoholysis method based on Aspen Plus software.The technological analysis was developed to find how the process was influenced by the three main recycled materials of methanol, 1,2-propylene glycol(PG) and mixture of DMC–methanol. Simultaneously,the thermal optimization was taken into account for energy saving and the optimized process was proposed with heat integration. Moreover, the economic evaluation was implemented for the optimized process with total annualized cost(TAC) and cost of product(COP) according to the plant investment and operations. It was found that the 11.6% decrease in TAC was obtained for the optimized process compared to the original designed process. The COP analysis showed that the process was economically efficient for the production of DMC from urea and methanol.

Direct Synthesis of Dimethyl Carbonate from CO_2 and CH_3OH Using 0.4nm Molecular Sieve Supported Cu-Ni Bimetal Catalyst

The 0.4 nm molecular sieve supported Cu-Ni bimetal catalysts for direct synthesis of dimethyl carbonate (DMC) from CO 2 and CH 3 OH were prepared and investigated. The synthesized catalysts were fully characterized by BET, XRD (X-ray diffraction), TPR (temperature programmed reduction), IR (infra-red adsorption), NH 3-TPD (temperature programmed desorption) and CO 2-TPD (temperature programmed desorption) techniques. The results showed that the surface area of catalysts decreased with increasing metal content, and the metals as well as Cu-Ni alloy co-existed on the reduced catalyst surface. There existed interaction between metal and carrier, and moreover, metal particles affected obviously the acidity and basicity of carrier. The large amount of basic sites facilitated the activation of methanol to methoxyl species and their subsequent reaction with activated carbon dioxide. The catalysts were evaluated in a continuous tubular fixed-bed micro-gaseous reactor and the catalyst with bimetal loading of 20% (by mass) had best catalytic activities. Under the conditions of 393 K, 1.1 MPa, 5 h and gas space velocity of 510 h 1 , the selectivity and yield of DMC were higher than 86.0 % and 5.0 %, respectively.

Carbamate Synthesis from Aromatic Amines and Dimethyl Carbonate Using Lead Acetate as Catalyst

Carbamates are important intermediates in the syntheses of pesticides, herbicides, drugs, polyurethane-based polymers, and other fine and commodity chemicals.

Dimethyl carbonate synthesis via transesterification catalyzed by quaternary ammonium salt functionalized chitosan

A quaternary ammonium salt covalently linked to chitosan was first used as a catalyst for dimethyl carbonate （DMC） synthesis by the transesterification of propylene carbonate （PC） with methanol. The effects of various reaction variables like reaction time, temperature and pressure on the catalytic performance were also investigated. 54% DMC yield and 71% PC conversion were obtained under the optimal reaction conditions. Notably, the catalyst was able to be reused with retention of high catalytic activity and selectivity. Consequently, the process presented here has great potential for industrial application due to its advantages such as stability, easy preparation from renewable biopolymer, and simple separation from products.

Synthesis of dimethyl carbonate by gas-phase oxidative carbonylation of methanol in the presence of solid catalyst I. Catalyst preparation and catalytic Properties

The gas-phase synthesis of dimethyl carbonate (DMC) from methanol, carbon monoxide and oXygen has here Studied in a flow system at atomspheric Pressure. A series of Catalyst used in this reaCtion have been prepared and evaluated. The influence of trivared carbon supporters, alkaline metal Promoters and operation conditions on DMC opthesis reaction has been discussed. Under the conditions of 130℃, CO/O2=1 .96, SV=3340h-1, the space-time yield (STY) of DMC over PdCl2-CuCl2-CH3COOK/ac. catalyst is 217g/l-cat h,which is higher than what is published in the literatUre so far.

Solid base catalysts derived from Ca-M-Al(M = Mg, La, Ce, Y) layered double hydroxides for dimethyl carbonate synthesis by transesterification of methanol with propylene carbonate

Composite solid base catalysts derived from Ca‐M‐Al(M=Mg,La,Ce,Y)layered double hydroxides(LDH)were synthesized,characterized and applied to the transesterification of methanol with propylene carbonate.X‐ray diffraction analyses of the catalysts show that all of the catalysts were in the form of composite oxides.Compared with the Ca‐Al LDH catalyst,the specific surface areas and pore volumes of the catalysts were increased with the introduction of Mg,La or Ce.The catalytic performance of these catalysts increases in the order of Ca‐Y‐Al<Ca‐Al<Ca‐Ce‐Al<Ca‐La‐Al<Ca‐Mg‐Al,which is consistent with the total surface basic amounts of these materials and the formation of especially strong basic sites following modification with Mg and La.The Ca‐Mg‐Al catalyst shows the highest(Ca+Mg):Al atomic ratio,indicating that it likely contains more unsaturated O2?ions,providing it with the highest concentration of very strong basic sites.The recyclability of these catalysts is improved following the addition of Mg,La,Ce or Y,with the Ca‐Mg‐Al maintaining a high level of activity after ten recycling trials.X‐ray diffraction analyses of fresh and used Ca‐Mg‐Al demonstrate that this catalyst is exceptionally stable,which could be of value in practical applications related to heterogeneous catalysis.

Highly active Pd containing EMT zeolite catalyst for indirect oxidative carbonylation of methanol to dimethyl carbonate

Palladium containing EMT zeolite catalyst(Pd/EMT) was prepared and used for the indirect oxidative carbonylation of methanol to dimethyl carbonate(DMC).The EMT zeolite was employed as a new catalyst support and compared with the conventional Pd containing FAU zeolite catalyst(Pd/FAU).The Pd/EMT in contrast to the Pd/FAU catalyst exhibited high intrinsic activity with the turnover frequency of 0.25 s^(-1) vs.0.11 s^(-1).The Pd/EMT catalyst showed high CO conversion of 82% and DMC selectivity of 79%,that maintained for at least 130 h,while the activity of the Pd/FAU catalyst rapidly deteriorated within 12 h.The enhanced interactions between Pd and EMT zeolite inhibited the sintering of palladium clusters and maintained the Pd2+ active sites in the Pd/EMT catalyst.The stabilization of the mono-dispersed Pd clusters within the EMT zeolite is paramount to the excellent performance of the catalyst for the indirect oxidative carbonylation of methanol to DMC.

Simultaneous Synthesis of Dimethyl Carbonate and Poly（ethylene terephthalate） Using Alkali Metals as Catalysts

Dimethyl carbonate （DMC） and poly（ethylene terephthalate） was simultaneously synthesized by the transesterification of ethylene carbonate （EC） with dimethyl terephthalate （DMT） in this paper. This reaction is an excellent green chemical process without poisonous substance. Various alkali metals were used as the catalysts. The results showed alkali metals had catalytic activity in a certain extent. The effect of reaction condition was also studied. When the reaction was carded out under the following conditions： the reaction temperature 250℃, molar ratio of EC to DMT 3 ： 1, reaction time 3h, and catalyst amount 0.004 （molar ratio to DMT）, the yield of DMC was 68.9%.

Synthesis of Dimethyl Carbonate from CO_2, Methanol, and Epoxides Using Re(CO)_5Cl/K_2CO_3 as Catalyst System

Over the past few years, dimethyl carbonate （DMC） has been proven to be an efficient methylating, methoxylating, and methoxycarbonylating agent in organic syntheses, in which DMC is used to replace the toxic methyl halides, dimethyl sulfate or carbon monoxide, and so forth. Furthermore, DMC has been used in the syntheses of polycarbonates and polyurethane to develop the nonphosgene routes Therefore, DMC has become one of the most important compounds in the development of green synthetic chemistry.