A highly efficient La-modified ZnAl-LDO catalyst and its performance in the synthesis of dimethyl carbonate from methyl carbamate and methanol

In this paper,the highly efficient ZnAlLa layered double oxide(ZnAlLa-LDO)catalyst was evaluated and used in methyl carbamate(MC)alcoholysis synthesis of dimethyl carbonate.Under optimal conditions,the MC conversion was 33.5% and the dimethyl carbonate(DMC)selectivity was up to 92,4% at 443 K and in 9 h.The prepared catalysts were well characterized to investigate the effect on the catalytic performance and reaction catalysis mechanism.The experimental results show that the addition of La adjusted the structure and chemical properties of ZnAl composite oxide and that the synergistic effect among Zn,Al and La play a key role in adjusting the acid-base properties and stability of the catalyst,which definitely improved the DMC selectivity and catalytic stability.Based on the proposed reaction mechanism,two kinetic models of the catalytic reaction were established and modified:LangmuirHinshelwood and power-rate law kinetic model.The good agreement between kinetic models and experimental data showed that the power-rate law kinetic model based on the elementary reactions is a suitable model for providing a theoretical basis.The pre-exponential factor and activation energy of the main reaction are 5.77×10^(7)and 77.60 kJ·mol^(-1),respectively.

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.

Effect of dimethyl carbonate on the behavior of water confined in carbon nanotube

The dehydration of water by dimethyl carbonate(DMC)is of great significance for its application in electrochemistry and oil industry.With the rapid development of nanomaterial,one-dimensional(e.g.carbon nanotube(CNT))and two-dimensional(e.g.lamellar graphene)materials have been widely used for molecular sieving.In this work,the molecular behavior of dimethyl carbonate/water mixture confined in CNT with varying diameters was studied based on molecular dynamics simulation.Due to different van der Waals interactions for the components in the mixtures with the solid surface,DMC molecules are preferentially adsorbed on the inner surface of the pore wall and formed an adsorption layer.Comparing with the pure water molecules confined in CNT,the adsorption DMC layer shows notable effect on the local compositions and microstructures of water molecules under nanoconfinement,which may result in different water mobility.Our analysis shows that the surface-induced DMC molecules can destroy the hydrogen bonding network of water molecules and result in an uniform and dispersed distribution of water molecules in the tube.These clear molecular understandings can be useful in material design for membrane separation.

Study on Spray Characteristics of Dimethyl Carbonate Blended Fuel in IC Engines

The spray characteristics of the blended fuel composed of biodiesel and dimethyl carbonate were compared with those of biodiesel and diesel.The macroscopic spray characteristic parameters including spray tip penetration,maximum spray width,average spray cone angle,and peak tip velocity were used to evaluate the spray characteristics of the blended fuel.The results showed that the spray tip penetration of blended fuel was lower than that of biodiesel,while the spray cone angle and maximum spray width of blended fuel were both larger than that of biodiesel.On the basis of the Hiroyasu and Arai mathematical model combined with the actual working conditions of this experiment,including physical parameters such as the viscosity and density of the fuel,a correct model of spray penetration was established,and the experimental results were compared.

Continuous dimethyl carbonate synthesis from CO_(2) and methanol over Bi_(x)Ce_(1-x)O_(δ) monoliths:Effect of bismuth doping on population of oxygen vacancies,activity,and reaction pathway

We evaluated bismuth doped cerium oxide catalysts for the continuous synthesis of dimethyl carbonate(DMC)from methanol and carbon dioxide in the absence of a dehydrating agent.Bi_(x)Ce_(1-x)O_(δ)nanocomposites of various compositions(x=0.06-0.24)were coated on a ceramic honeycomb and their structural and catalytic properties were examined.The incorporation of Bi species into the CeO_(2) lattice facilitated controlling of the surface population of oxygen vacancies,which is shown to play a crucial role in the mechanism of this reaction and is an important parameter for the design of ceria-based catalysts.The DMC production rate of the Bi_(x)Ce_(1-x)O_(δ) catalysts was found to be strongly enhanced with increasing Ov concentration.The concentration of oxygen vacancies exhibited a maximum for Bi_(0.12)Ce_(0.88)O_(δ),which afforded the highest DMC production rate.Long-term tests showed stable activity and selectivity of this catalyst over 45 h on-stream at 140°C and a gas-hourly space velocity of 2,880 mL·g_(cat)^(-1)·h^(-1).In-situ modulation excitation diffuse reflection Fourier transform infrared spectroscopy and first-principle calculations indicate that the DMC synthesis occurs through reaction of a bidentate carbonate intermediate with the activated methoxy(-OCH_(3))species.The activation of C0_(2) to form the bidentate carbonate intermediate on the oxygen vacancy sites is identified as highest energy barrier in the reaction pathway and thus is likely the rate-determining step.

An in situ infrared study of dimethyl carbonate synthesis from carbon dioxide and methanol over well-shaped CeO2

The mechanism of dimethyl carbonate(DMC) formation from CO_2 and methanol is investigated using three well-shaped CeO_2 catalysts, nanorod, nanocube and octahedron, which are packed with different crystal planes. In situ Fourier Transform Infrared Spectroscopy(FTIR) is employed to probe each reaction step in the DMC synthesis. The number of –OH groups and the species of CO_2 adsorptions on ceria surface have significant influence on the activity of ceria with different morphologies. Rod-ceria has favorable catalytic activity because of the large amount of –OH groups and the formation of bidentate carbonate species.

Novel eco-efficient reactive distillation process for dimethyl carbonate production by indirect alcoholysis of urea

Dimethyl carbonate is an eco-friendly essential chemical that can be sustainably produced from CO_(2),which is available from carbon capture activities or can even be captured from the air.The rapid increase in dimethyl carbonate demand is driven by the fast growth of polycarbonates,solvent,pharmaceutical,and lithium-ion battery industries.Dimethyl carbonate can be produced from CO_(2)through various chemical pathways,but the most convenient route reported is the indirect alcoholysis of urea.Previous research used techniques such as heat integration and reactive distillation to reduce the energy use and costs,but the use of an excess of methanol in the trans-esterification step led to an energy intensive extractive distillation required to break the dimethyl carbonate-methanol azeotrope.This work shows that the production of dimethyl carbonate by indirect alcoholysis of urea can be improved by using an excess of propylene carbonate(instead of an excess of methanol),a neat feat that we showed it requires only 2.64 kW·h·kg^(-1) dimethyl carbonate in a reaction-separation-recycle process,and a reactive distillation column that effectively replaces two conventional distillation columns and the reactor for dimethyl carbonate synthesis.Therefore,less equipment is required,the methanol-dimethyl carbonate azeotrope does not need to be recycled,and the overall savings are higher.Moreover,we propose the use of a reactive distillation column in a heat integrated process to obtain high purity dimethyl carbonate(>99.8 wt-%).The energy requirement is reduced by heat integration to just 1.25 kW·h·kg^(-1) dimethyl carbonate,which is about 52%lower than the reaction-separation-recycle process.To benefit from the energy savings,the dynamics and control of the process are provided for10%changes in the nominal rate of 32 ktpy dimethyl carbonate,and for uncertainties in reaction kinetics.

Synthesis of cyclic carbonates and dimethyl carbonate using CO_(2) as a building block catalyzed by MOF-5/KI and MOF-5/KI/K_(2)CO_(3)

The synthesis of cyclic carbonates or dimethyl carbonate(DMC)using CO_(2) as a building block is a very interesting topic.In this work,we found that the metalorganic framework-5(MOF-5)/KI was an active and a selective catalytic system for the synthesis of cyclic carbonates from CO_(2) and epoxides,and MOF-5/KI/K_(2)CO_(3) was efficient for the preparation of DMC from CO_(2),propylene,and methanol by a sequential route.The impacts of temperature,pressure,and reaction time length on the reactions were investigated,and the mechanism of the reactions is proposed on the basis of the experimental results.

A review on transesterification of propylene carbonate and methanol for dimethyl carbonate synthesis

Dimethyl carbonate(DMC)is widely applied in various fields according to its outstanding physico-chemical properties,especially as a solvent in electrolyte of lithium-ion batteries.More than 90%DMC in China is industrially produced from the propylene carbonate(PC)and methanol(MeOH)route because it is an environmentally friendly and highly efficient process.This review summarizes different DMC production technologies,homogeneous and heterogeneous catalysts,catalytic mechanisms,reaction kinetics and engineering,with particular focus on the relationship between catalyst preparation and catalytic performances.The advantages and disadvantages of various catalysts are categorically compared.Homogeneous catalysts are highly efficient but prone to deactivate and are difficult to separate.Heterogeneous catalysts are easy to separate and have the promising future in industrial application,but their low catalytic efficiency is still the critical bottleneck.From process aspect,the catalytic distillation technology would be promising to overcome the efficiency problem of solid catalysts.

Efficient synthesis of dimethyl carbonate via transesterification of ethylene carbonate catalyzed by swelling poly(ionic liquid)s

The synthesis of dimethyl carbonate(DMC)via transesterification of ethylene carbonate(EC)and methanol(MeOH)was an environmental and practical strategy.Herein,poly(ionic liquid)s(PILs)with swelling abilities were synthesized by free radical copolymerization of N-vinylimidazolium ionic liquids,sodium 4-vinylbenzoate and cross-linker(1,8-triethylene glycoldiyl-3,3'-divinylimidazolium bromide([(EG)_(3)-DVIm]Br_(2)).The swelling abilities of PILs in various solvents were measured,and PILs could swell in methanol(MeOH).The swelling ability of PILs in MeOH could be modulated by changing the cross-linker content and chain length of 3-alkyl-substituents on imidazolium.The swollen state of PILs in MeOH presented a porous cross-linked network structure observed by the cryo-scanning electron microscope(cryo-SEM).The swelling PILs were used to catalyze the transesterification of ethylene carbonate(EC)and MeOH to prepare the DMC,and the catalytic activities was correlated with the swelling abilities of PILs.The PIL with 3-butyl-substituent and 2.5 mol%cross-linker(poly[VBIm-VBA-DVIm]-2.5%)had the highest swelling ratio(Q=12.4(g/g))in MeOH and EC mixed solvents and exhibited excellent catalytic activities,which was similar to corresponding homogeneous ionic liquid.Furthermore,the catalyst could be reused up to seven runs without any considerable loss of its initial activity.

Direct synthesis of dimethyl carbonate over rare earth oxide supported catalyst

Solid base catalysts for the direct synthesis of dimethyl carbonate(DMC)from carbon dioxide,methanol,and propylene oxide were prepared by loading KCl and K_(2)CO_(3) on the surface of La_(2)O_(3),Y_(2)O_(3),CeO2 and Nd_(2)O_(3).The catalysts were characterized by thermogravimetric analysis(TGA)and X-ray diffraction(XRD)techniques.The catalytic activities were efficiently influenced by the preparation conditions.The optimal loading amount of K_(2)CO_(3) is 17.6%(mass)for KCl-K_(2)CO_(3)/Y_(2)O_(3) and 22.2%for other catalysts.Supports affected the activity of catalyst.KCl-K_(2)CO_(3)/Nd_(2)O_(3) exhibited the highest activity.The activity of KCl-K_(2)CO_(3)/Y_(2)O_(3) increased with the increase of calcination temperature in the range of 800℃–900℃.The formation of KYO2,Y_(3)O_(4)Cl or YOX species probably promoted the catalysts.

Performance, emission and combustion characteristics of DI diesel engine running on blends of honne oil/diesel fuel/kerosene/DMC

Honne oil(tamanu)(H),a non-edible vegetable oil is native for northwards of Northern Marianas islands and the Ryukyu Islands in southern Japan and westward throughout Polynesia.It has remained as an untapped new possible source of alternative fuel that can be used as diesel engine fuel.Literature pertaining to use of vegetable oil in diesel engine with kerosene and dimethyl carbonate(DMC)is scarce.The present research is aimed to investigate experimentally the performance,exhaust emission and combustion characteristics of a direct injection(DI)diesel engine,typically used in agricultural sector,over the entire load range,when fuelled with neat diesel(ND)and blends of diesel fuel(D)/DMC/H/kerosene(K).DMC/D/H/K blends have a potential to improve the performance and emissions and to be an alternative to ND.Experiments have been conducted when fuelled with H20(20%H+80%D),HK(20%H+40%K+40%D)and HKD5(20%H+40%K+35D+5%DMC)to HKD15 in steps of 5%DMC keeping H and K percentages constant.The emissions(CO,HC and smoke density(SD))of fuel blend HKD15 are found to be lowest,with SD dropping significantly.The NOx level is slightly higher with HKD5 to HKD15 as compared to ND.The brake thermal efficiency of HKD5 to HKD15 is same and it is higher than that of ND.There is a good trade off between NOx and SD.Peak cylinder pressure and premixed combustion phase increases as DMC content increase.

Non-equilibrium model for catalytic distillation process

A new improved tri-diagonal method was developed for the non-equilibrium stage model of the catalytic distillation by coupling consumptive reaction coefficient.The reactions in the distillation column were divided into generative reaction and consumptive reac-tion.The non-equilibrium stage model was introduced for the catalytic distillation process of the dimethyl car-bonate(DMC)synthesis by urea methanolysis over solid based catalyst,and the improved tri-diagonal method was used to solve the model equations.Comparison of pre-dicted results with experiment data shows that the mean relative error of the yield of DMC was 3.78%under dif-ferent conditions such as different operating pressures and reaction temperatures.The improved tri-diagonal matrix method could avoid the negative values of the liquid com-positions during the calculations and restrain the fluc-tuation of compositions by slowing down the variations of the values in the iteration.The modeling results show that the improved tri-diagonal method was appropriate for system containing a wide range of boiling point com-ponents and a different rate of reactions.