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Effects of dimethyl ether and ethanol additions on soot transition in ethylene counterflow diffusion flames

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Science China(Technological Sciences) 2024年第4期67卷 1094-1112页

作者： GUO LinGe YING YaoYao CHEN Chen ZHAO Xuan LIU Dong MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing 210094China Advanced Combustion Laboratory School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing 210094China

This paper investigates the effect of blending dimethyl ether(DME)and ethanol on the soot transition periods in ethylene counterflow diffusion flames by using a novel optical diagnostic method.The soot critical transition point in different conditions is identified experimentally and numerically.Two kinds of flames are carried out to gain the soot critical transition point in counterflow diffusion flames by changing oxygen fraction(Xo)and changing volume flow rates of fuel and oxidizer(Qv).The red-green-blue(RGB)ratio method is used to precisely identify the soot critical transition point,and chemical kinetic simulations are performed to analyze the detailed reaction paths.The results show that compared to the ethylene flame,the soot critical transition point occurs at a higher Xoand a lower Qvwhen DME or ethanol is blended.The addition of DME and ethanol can inhibit soot formation,due to the degree of soot formation reaction being lower than the degree of the oxidation reaction in the blending flames.

关键词： optical diagnosis sooting tendency counterflow diffusion flame dimethyl ether ethanol

Harnessing dimethyl ether and methyl formate fuels for direct electrochemical energy conversion

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能源化学:英文版 2023年第8期83卷 454-464,I0012页

作者： Medhanie Gebremedhin Gebru Radhey Shyam Yadav Hanan Teller Haya Kornweitz Palaniappan Subramanian Alex Schechter Department of Chemical Science Ariel UniversityAriel 40700Israel New Technologies-Research Centre(NTC).University of West Bohemia Pilsen 30100Czech Republic

In this work,the oxidation of a mixture of dimethyl ether(DME) and methyl formate(MF) was studied in both an aqueous electrochemical cell and a vapor-fed polymer electrolyte membrane fuel cell(PEMFC)utilizing a multi-metallic alloy catalyst,Pt_(3)Pd_(3)Sn_(2)/C,discovered earlier by us.The current obtained during the bulk oxidation of a DME-saturated 1 M MF was higher than the summation of the currents provided by the two fuels separately,suggesting the cooperative effect of mixing these fuels.A significant increase in the anodic charge was realized during oxidative stripping of a pre-adsorbed DME+MF mixture as compared to DME or MF individually.This is ascribed to greater utilization of specific catalytic sites on account of the relatively lower adsorption energy of the dual-molecules than of the sum of the individual molecules as confirmed by the density fu nctional theory(DFT) calculations.Fuel cell polarization was also conducted using a Pt_(3)Pd_(3)Sn_(2)/C(anode) and Pt/C(cathode) catalysts-coated membrane(CCM).The enhanced surface coverage and active site utilization resulted in providing a higher peak power density by the DME+MF mixture-fed fuel cell(123 mW cm^(-2)at 0.45 V) than with DME(84mW cm^(-2)at 0.35 V) or MF(28 mW cm^(-2)at 0.2 V) at the same total anode hydrocarbon flow rate,temperature,and ambient pressure.

关键词： dimethyl ether Methyl formate Fuel cell Electrocatalysis Multi-metallic alloy

Inhibition Effects of CH_(4)/CH_(3)OH on dimethyl ether Cool Flames

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Journal of Thermal Science 2023年第6期32卷 2284-2296页

作者： ZHOU Xun ZHANG Rui YANG Shenghua LIU Dong Key Laboratory of Thermal Control of Electronic Equipment Ministry of Industry and Information TechnologyNanjing210094China Advanced Combustion Laboratory School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing210094China

CH_(4)/DME mixtures can be used for engines and gas turbines,and have already been studied for many years.However,DME has a strong cool flame phenomenon,which will greatly influence the ignition and combustion characteristics of following hot flames.Therefore,the cool flame characteristics of CH_(4)/DME mixture are very important for their utilization.Recently,the inhibition effect of CH_(4)on DME cool flames has been discovered,but the mechanisms of the inhibition effects lack further verification and research.In this study,the inhibition effects were investigated via both experiments and simulations.In order to validate the inhibition effects,a comparison fuel of CH_(3)OH/DME was also used in this study.The extinction limits,flame temperatures and combustion products of the cool flames of the CH_(4)/DME and CH_(3)OH/DME mixtures were measured using a counterflow burner,and the reaction paths and heat release rate were derived from the HPMech-v3.3.The results indicate that CH_(4)and CH_(3)OH will both inhibit the cool flame of DME via competing with DME for OH and O radicals,and CH_(3)OH has stronger inhibition effects than CH_(4),because it is more competitive and produces more CH2O,which inhibits the oxidation of DME.The HPMech-v3.3 closely agrees with the experimental data,but still needs to be improved.

关键词： cool flame dimethyl ether methane methanol non-premixed counterflow flame

Importance of metal location in M-H zeolite for synergistically catalyzing dimethyl ether carbonylation

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Chinese Journal of Chemical Engineering 2022年第1期35卷 350-357页

作者： Shiyue Li Shouying Huang Kai Cai Ying Li Jing Lv Xinbin Ma Key Laboratory for Green Chemical Technology of Ministry of Education Collaborative Innovation Center of Chemical Science and EngineeringSchool of Chemical Engineering and TechnologyTianjin UniversityTianjin 300350China

Mordenite(MOR)has shown great potential to catalyze dimethyl ether(DME)carbonylation to methyl acetate(MA)in industry.The synergy between metal species and Brønsted acid sites accelerates DME conversion.Here we designed and prepared two catalysts with different Ag locations by seed-directed growth method and two-step impregnation method(named as Ag@HMOR and Ag/HMOR-out,respectively),to explain the effect of Ag location on catalytic performance.The results of TEM,XPS,CO-IR and UV–Vis showed that Ag species mainly presented as Ag^(0) species over both Ag@HMOR and Ag/HMOR-out.Meanwhile,Ag^(0) species mainly located in the micropores of Ag@HMOR,while as for Ag/HMOR-out,Ag^(0) mainly existed on external surface.After comparing the performance of the catalysts with different Ag positions,we confirmed that the Ag^(0) species encapsulated in the channels of HMOR promoted the DME carbonylation,which revealed the importance of spatial adjacency on the acid-metal catalysts.

关键词： dimethyl ether Carbonylation Silver modification Metal location

Temperature Dependence of Laminar Burning Velocity in Ammonia/dimethyl ether-air Premixed Flames

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Journal of Thermal Science 2022年第1期31卷 189-197页

作者： CAI Tao ZHAO Dan Department of Mechanical Engineering College of EngineeringUniversity of CanterburyChristchurch 8041New Zealand

The combustion of ammonia(NH3)has attracted wide interest in fuel vehicle engines,marine engines,and power generators to mitigate carbon dioxide emissions.Unfortunately,the relatively low laminar flame speed presents a technical barrier for this renewable fuel to be used in practice.This work is concerned with numerical examining the effects of elevating inlet temperature on the laminar burning velocity of NH3/air flames with various contents of dimethyl ether(DME)using ID freely propagating flame calculations,and to shed light on the flame enhancement mechanism.For this,the mechanism is first validated by comparing the numerical predictions with experimental data.Results show that increasing the inlet temperature has a positive effect on the laminar burning velocity of pure NH3/DME/air flames.It is revealed that elevating inlet temperature contributes to a higher adiabatic flame temperature,which is beneficial to the overall chemical reaction rate.Furthermore,the thermal diffusivity of the binary mixture is observed to increase substantially as well.Further kinetic and sensitivities analyses reveal that the inlet temperature has a minimal effect on the reaction pathway,leading to the relative importance of the dominant chain branching over terminating reaction steps to be varied negligibly.The present work confirms that the flame speed enhancement with increasing inlet temperature is primarily the synergetic result of the thermal and diffusion effects,rather than the chemical effect.

关键词： ammonia dimethyl ether laminar burning velocity temperature dependence kinetic analyses

Cu-embedded porous Al_(2)O_(3) bifunctional catalyst derived from metal–organic framework for syngas-to-dimethyl ether

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Chinese Chemical Letters 2022年第6期33卷 2906-2910页

作者： Yongle Guo Lu Feng Yuefeng Liu Zhongkui Zhao State Key Laboratory of Fine Chemicals Department of Catalysis Chemistry and EngineeringSchool of Chemical EngineeringDalian University of TechnologyDalian 116024China Dalian National Laboratory for Clean Energy(DNL) Dalian Institute of Chemical PhysicsChinese Academy of ScienceDalian 116023China Zhang Dayu School of Chemistry Dalian University of TechnologyDalian 116024China

dimethyl ether(DME),as a promising alternative to diesel fuel and liquefied petroleum gas,has attracted considerable attention in catalysis domain.The catalytic direct synthesis of DME from syngas is an upand-coming route but remains a challenge.In this work,we firstly prepared a Cu-embedded porous Al_(2)O_(3)bifunctional catalyst(Cu@Al_(2)O_(3)-dp)by filling Cu-1,3,5-benzenetricarboxylate metal–organic framework(Cu-BTC MOF)with Al(OH)_(3) followed by a two-step calcination process(400℃for 4 h and 600℃for1 h),exhibiting excellent catalytic performance for direct synthesis of DME from syngas.Cu@Al_(2)O_(3)-dp catalyst demonstrates much higher CO conversion(25.7%vs.15.4%)and extremely higher DME selectivity(90.4%vs.63.9%)with the increased catalytic stability compared to the supported Cu catalyst on MOF-derived porous Al_(2)O_(3)(Cu/Al_(2)O_(3))prepared by incipient wetness impregnation method,ascribed to the unique embedding-type structure,promoted Cu dispersion and stronger metal-support interaction.This work not only provides an efficient syngas-to-DME catalyst,but also paves a new way for designing highly-efficient core-shell bifunctional catalysts for diverse consecutive reactions.

关键词： dimethyl ether CO hydrogenation Bifunctional catalyst Embedding-type structure Metal–organic framework

Shaped binderless ZSM-11 zeolite catalyst prepared via a dry-gel conversion method:Characterization and application for alkylation of benzene with dimethyl ether

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Journal of Energy Chemistry 2017年第3期26卷 380-389页

作者： Wanshuo Zhang Shuang Zhang Wenjie Xin Hui Liu Yongchen Shang Xiangxue Zhu Shenglin Liu Longya Xu College of Chemistry and Chemical Engineering Harbin Normal University State Key Laboratory of Catalysis Dalian Institute of Chemical PhysicsChinese Academy of Sciences Research and Development Center Sinochem Quanzhou Petrochemical Co.Ltd.

Shaped binderless ZSM-11 zeolite catalysts were synthesized via a dry-gel conversion technique from 70ZSM-11/30 SiO;mix extrudates. 1,6-hexanediamine combined with tetrabutylammonium bromide was proved to be the best structure directing agent for the synthesis of the binderless ZSM-11 catalyst, without adding other alkaline materials. The 70HZSM-11/30 SiO;mix serials materials crystallized for different times were detected by X-ray diffraction（XRD）, nuclear magnetic resonance（NMR）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, scanning transmission electron microscopy–energy dispersive spectroscopy（STEM–EDS） techniques, and so on. In order to investigate the possible crystallization mechanism, the textural and structural properties of 70HZSM-11/30 SiO;mix serials samples were further characterized by N;adsorption–desorption. Acid properties were determined by temperature-programed desorption of NH;（NH;-TPD） and pyridine adsorption-infrared（Py-IR） measurements. In the alkylation of benzene with dimethyl ether, the serials catalysts exhibited different benzene conversions. 70HZSM-11/30 SiO;mix showed the lowest benzene conversion while sample 70HZSM-11/30 SiO;mix-6.5h synthesized only for 6.5h displayed a higher benzene conversion, even higher than the value over 70HZSM-11/30Al;O;mix. Extending the crystallization time, the obtained samples displayed the increased benzene conversion in general under the same reaction conditions. In the end, the relation of physicochemical properties with the reaction performance was investigated.

关键词： Shaped binderless ZSM-11 Crystallization mechanism Mechanical strength Acidity Alkylation dimethyl ether

A density functional theory study on the mechanism of dimethyl ether carbonylation over heteropolyacids catalyst

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Frontiers of Chemical Science and Engineering 2021年第2期15卷 319-329页

作者： Kai Cai Ying Li Hongbao Shen Zaizhe Cheng Shouying Huang Yue Wang Xinbin Ma Key Laboratory for Green Chemical Technology of Ministry of Education Collaborative Innovation Center of Chemical Science and EngineeringSchool of Chemical Engineering and TechnologyTianjin UniversityTianjin 300350China

dimethyl ether(DME)carbonylation is considered as a key step for a promising route to produce ethanol from syngas.Heteropolyacids(HPAs)are proved to be efficient catalysts for DME carbonylation.In this work,the reaction mechanism of DME carbonylation was studied theoretically by using density functional theory calculations on two typical HPA models(HPW,HSiW).The whole process consists of three stages:DME dissociative adsorption,insertion of CO into methoxyl group and formation of product methyl acetate.The activation barriers of all possible elementary steps,especially two possible paths for CO insertion were calculated to obtain the most favorable reaction mechanism and rate-limiting step.Furthermore,the effect of the acid strength of Brønsted acid sites on reactivity was studied by comparing the activation barriers over HPW and HSiW with different acid strength,which was determined by calculating the deprotonation energy,Mulliken population analyses and adsorption energies of pyridine.

关键词： dimethyl ether carbonylation mechanism heteropolyacids density functional theory

The effect of FER zeolite acid sites in methanol-to-dimethyl-ether catalytic dehydration

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Journal of Energy Chemistry 2017年第3期26卷 406-415页

作者： Enrico Catizzone Alfredo Aloise Massimo Migliori Girolamo Giordano Department of Environmental and Chemical Engineering University of CalabriaVia P.BucciCubo 42aI-87036 RendeCSItaly

In this paper, the effect of acidity of zeolites with FER framework was studied in the methanol dehydration to dimethyl ether reaction, by comparing catalysts with different Si/Al ratios(namely 8, 30 and60). The aim of this work was to investigate how the acid sites concentration, strength, distribution and typology(Br?nsted and Lewis) affect methanol conversion, DME selectivity and coke formation. It was found that the aluminium content affects slightly acid sites strength whilst a relevant effect on acid sites concentration and distribution(Br?nsted/Lewis) was observed as 24% of Lewis sites were found on Alrichest samples, whilst less than 10% of Lewis acid sites were observed on FER at higher Si/Al ratio. All the investigated catalyst samples showed a selectivity toward DME always greater than 0.9 and samples with the lowest Si/Al ratio exhibit the best performances in terms of methanol conversion, approaching the theoretical equilibrium value(around 0.85) at temperatures below 200 °C. Turnover-frequency analysis suggests that this result seems to be related not only to the higher amount of acid sites but also that the presence of Lewis acid sites may play a significant role in converting methanol. On the other hand, the presence of Lewis acid sites, combined with a high acidity, promote the formation of by-products(mainly methane) and coke deposition during the reaction. As final evidence, all the investigated catalysts exhibit very high resistance to deactivation by coke deposition, over 60 h continuous test, and a GC–MS analysis of the coke deposited on the catalyst surface reveals tetra-methyl benzene as main component.

关键词： Methanol dehydration dimethyl ether Lewis acid sites FER zeolite Coke formation