• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Study of selective hydrogenation of biodiesel in a DBD plasma reactor

    2021-09-10 09:26:50WeidongZHAO趙衛(wèi)東ChaoHUA華超XiaoyinZHANG張瀟尹XiaolongQI戚小龍KiatsiriroatTANONGKIATandJunfengWANG王軍鋒
    Plasma Science and Technology 2021年9期
    關(guān)鍵詞:衛(wèi)東小龍

    Weidong ZHAO (趙衛(wèi)東),Chao HUA (華超),Xiaoyin ZHANG (張瀟尹),Xiaolong QI(戚小龍),Kiatsiriroat TANONGKIAT and Junfeng WANG(王軍鋒)

    1 School of Automotive and Traffic Engineering,Jiangsu University,Zhenjiang 212013,People’s Republic of China

    2 Department of Mechanical Engineering,Faculty of Engineering,Chiang Mai University,Chiang Mai 50200,Thailand

    3 School of Energy and Power Engineering,Jiangsu University,Zhenjiang 212013,People’s Republic of China

    Abstract In order to achieve the selective hydrogenation of biodiesel at room temperature and under normal pressure,we researched the upgrading of soybean biodiesel using a dielectric-barrier discharge (DBD) reaction system.Using Raney-Ni as the hydrogenation catalyst,the effects of the operating parameters on the hydrogenation depth and the selectivity of biodiesel were systematically analyzed.The results show that the polyunsaturated components in soybean methyl ester were reduced by 57.04%,and that the polyunsaturated components were hydrogenated to monounsaturated components with a selectivity of 77.75%.Based on the gas chromatography and mass spectrometry(GC-MS)test results,we established a kinetic model for biodiesel hydrogenation.A comparison of the calculated and experimental results shows that the hydrogenation of the biodiesel can be described by a quasi first-order reaction model.The calculated reaction rate constants indicate that under DBD plasma reaction conditions,the hydrogenation of biodiesel has high selectivity for the formation of monounsaturated components.

    Keywords: biodiesel,selectivity,hydrogenation,dielectric-barrier discharge,oxidation stability,saturation

    1.Introduction

    Biodiesel prepared by transesterification contains a large number of polyunsaturated components,resulting in poor oxidation stability and a low cetane number.Oxidation and polymerization are likely to occur,resulting in high molecular polymers and precipitates which are not conducive to storage,and can easily cause blockages of the engine oil circuit.On the other hand,the lower cetane number is also an obstacle to improving engine fuel economy and emission performance,so it is necessary to upgrade biodiesel.

    The oxidation stability and cetane number of biodiesel could be greatly improved by the selective hydrogenation of polyunsaturated fatty acid esters to monounsaturated fatty acid esters,while not reducing low-temperature fluidity too much,and better lubrication performance could simultaneously be obtained; in doing so,the quality of biodiesel could be improved,and hydrogen consumption and cost could be reduced.Therefore,the selective hydrogenation of polyunsaturated fatty acid esters has become the main technical solution for upgrading biodiesel.

    Rajkumaraet al[1] studied the physicochemical properties of hydrogenated biodiesel–diesel blends and their NOxemissions characteristics when applied to turbodiesel; the results showed that B20 blended fuel can significantly reduce NOxemissions.Nikolaouet al[2] conducted a selective catalytic hydrogenation of sunflower-oil biodiesel.Under reaction conditions of 50 bar of hydrogen pressure and a temperature of 90°C,deep hydrogenation of polyunsaturated fatty acid esters was achieved,but a large number of trans oleates and stearates with high condensation points were produced,which seriously reduced the low-temperature fluidity of the biodiesel; similar problems and results were reported in references [3,4].

    In summary,the feasibility of using selective hydrogenation to improve the quality of biodiesel has been confirmed,but the massive production of fully saturated and trans fatty acid esters caused by the high hydrogen pressures of traditional thermodynamic reaction conditions is the main problem that needs to be solved.It is therefore necessary to explore biodiesel hydrogenation methods that require mild reaction conditions,in order to improve the controllability of biodiesel hydrogenation depth and selectivity.

    A gas-phase reactant can be ionized by an electric field and transformed into a non-thermal plasma which contains large number of highly reactive active particles,such as excited molecules,free radicals,positive ions,negative ions,and highenergy electrons,so that chemical reactions can be initiated under mild conditions.In addition,the ionization degree and energy level of the gas-phase reactants can be changed by adjusting the working voltage,so as to realize control of the chemical reaction rate and path.Due to its low energy consumption,easy operation,and high efficiency,discharge plasma reaction technology has been widely used in material preparation,surface modification,and plasma cleaning[5–11].Recently,its application has gradually been extended to the field of oxygen-containing-compound hydrogenation,and the advantages of easy control of the reaction depth and selectivity have been further reflected in this research [12–16].

    Normally,non-thermal plasmas have been produced by gas discharges; the commonly used discharge forms include coronal discharge,glow discharge,spark discharge,and dielectric-barrier discharge.The energy of free electrons generated by dielectric-barrier discharge is in the range of 1–10 eV,which is suitable for breaking most chemical bonds[17–22],and the discharge can be stable and uniformly distributed in the discharge zone,so dielectric-barrier discharge is the preferred choice for non-thermal plasma generation.

    Yin [23] and Dai [24] verified the feasibility of highly selective hydrogenation of unsaturated fatty acid esters in a DBD reactor under normal pressure and at room temperature,achieving the selective hydrogenation of linolenic acid esters and linoleic acid esters in C18 enoate; the hydrogenation selectivity reached 83.5%.Liuet al[25]studied the conversion of anisole and guaiacol to benzene and toluene in a DBD reactor.They found that DBD can effectively decompose H2into active atomic hydrogen,which can effectively promote the hydrogenolysis reaction of the Caro–OR bond,and that the high selective conversion of anisole and guaiacol can be realized at room temperature by combining a hydrogen plasma with a Ni-Mo/SiO2catalyst.These applications and studies indicated the potential of efficiently achieving the selective hydrogenation of biodiesel using a discharge plasma reaction.

    Figure 1.Schematic diagram of the DBD hydrogenation reactor.(1-inner electrode,2-gas inlet,3-outer electrode,4-discharge tube,5-reaction vessel,6-catalyst,7-SME outlet pipe,8-SME intake pipe).

    Table 1.Components and contents of biodiesel.

    In order to solve the problems that exist in current biodiesel upgrading,we propose a technical solution for the selective hydrogenation of biodiesel at room temperature and atmospheric pressure based on a DBD plasma reaction.Using soybean biodiesel as the raw material and hydrogen as the hydrogen donor,we conducted research into the selective hydrogenation of biodiesel.We expect that this research will provide an experimental and theoretical reference for biodiesel upgrading.

    2.Experimental details

    2.1.Preparation of biodiesel

    According to the preparation process described in [26],the biodiesel to be used in the experiment was prepared by the transesterification of soybean oil and methanol with NaOH as a catalyst,which is called soybean methyl ester (SME).The components and component percentages of the biodiesel obtained are shown in table 1.

    2.2.Experimental system and procedure

    A coaxial cylindrical DBD hydrogenation reactor was designed,as shown in figure 1,for biodiesel upgrading.

    Figure 2.Experimental DBD selective catalytic hydrogenation system and layout.(1-gas cylinder,2-pressure-reducing valve,3-glass rotor flow meter,4-measuring cylinder,5-micro-peristaltic pump,6-DBD reactor,7-AC high-voltage power supply,8-oscilloscope).

    The device consists of a reaction vessel and a discharge tube.The reaction vessel is a quartz glass tube with a length of 300 mm and an inner diameter of 20 mm.The bottom and top of the vessel are equipped with an inlet and outlet pipe,respectively,with inner diameters of 8 mm,to circulate biodiesel into and out of the reactor during the reaction.The discharge tube is designed to be a coaxial cylindrical structure,with an inner diameter of 8 mm,a wall thickness of 1.5 mm and a length of 100 mm.An intake branch pipe with an inner diameter of 8 mm and a length of 40 mm is set perpendicular to the discharge area to supply hydrogen into the discharge area during the reaction.The inner electrode is a solid copper screw rod with a length of 100 mm,a diameter of 3.5 mm,and a pitch of 0.6 mm.An aluminum foil 0.3 mm thick,used as an outer electrode,is wrapped around the outer surface of the discharge tube.The high-voltage terminal of the power supply is connected to the inner electrode,and the outer electrode is grounded.

    A schematic diagram of the experimental DBD selective catalytic hydrogenation system is shown in figure 2.

    Raney-Ni (with a particle diameter of 0.1 mm,a specific surface area of 131 m2g?1,and a pore volume of 0.20 ml g?1)was selected as the hydrogenation catalyst,due to its high activity at low temperatures and large specific surface area [27–33].

    After the system was built,we first opened the upper cap of the reactor and added the catalyst (3 wt.% of SME),then closed the upper cap.Next,200 ml(183 g)of prepared SME was poured into a measuring cylinder,the micro-peristaltic pump was turned on,and the flow rate was adjusted in the range of 0–50 ml min?1.SME was pumped into the oil inlet at the bottom of the reactor,and then flowed out from the oil outlet at the top of the reactor.The oil circulated from bottom to top,combined with the agitating action of the gas bubbles,enhancing mass transfer between the gas,liquid,and solid phases.A mixture of 40 vol.% H2and 60 vol.% He (Beijing Huayuan Gas Chemical Co.Ltd) was adopted as the hydrogen donor.We opened the gas cylinder and adjusted the gas flow rate through a pressure-reducing valve and the glass rotor flow meter in the range of 0–50 ml min?1,so that the mixture of H2and He gas entered the reactor from the inlet branch pipe.After the gas flow rate was stabilized,we turned on the AC high-voltage power supply (Model: CTP-2000S,Nanjing Suman Electronics Co.,Ltd) and the digital oscilloscope and adjusted the working voltage and operating frequency in the range of 10.61–21.21 kV and 5–30 kHz,respectively,to start the DBD reaction system.

    Figure 3.Effects of the working voltage on the depth and hydrogenation selectivity of SME.

    Under the conditions of a room temperature of 25°C and 0.1 MPa of hydrogen pressure,hydrogen was ionized by the dielectric-barrier discharge,passed into the mixture of SME and Raney-Ni catalyst,and reacted with unsaturated fatty acid esters in the SME on the active sites of the catalyst.After the reaction was completed,the obtained solid-liquid mixture was filtered,and the liquid phase,i.e.the target product,partially hydrogenated soybean methyl ester (PHSME),was collected.

    2.3.Experimental design for selective biodiesel hydrogenation

    The working voltage,gas flow rate,SME circulation flow rate,and reaction time were selected as influencing factors,and single-factor experiments were conducted to investigate the effect of each factor on the depth and selectivity of SME hydrogenation.The ranges of the working voltage,gas flow rate,SME circulation flow rate and reaction time were 10.61–21.21 kV,10–40 ml min?1,0–60 ml min?1,0.5–2 h,respectively.

    2.4.GC-MS detection method

    The PHSME samples were analyzed by a gas chromatography mass spectrometer (GC-MS,model: Agilent 6890N-5973,USA),equipped with a HP-5MS (30 m×0.25 mm×0.25 μm) capillary column.The carrier gas was high-purity He (99.999%),and the carrier gas flow rate was 1.0 ml min?1.The injection port temperature was 280°C and the solvent delay time was 3 min.The ion source temperature and transmission line temperature of the mass spectrometer were set to 230 °C and 250 °C,respectively.The ionization potential of the EI ionization source was 70 eV,the scanning mass range was 30.00–550.00 amu,and the scanning time was set to 1 s.The temperature program was set to an initial temperature of 150 °C,held for 1 min,and then raised to 300 °C at a rate of 5 °C min?1,then held for 11 min.

    3.Results and discussion

    3.1.Effects of working parameters on the depth and selectivity of hydrogenation

    The unsaturation degree of biodiesel is usually evaluated using the iodine value.The higher the iodine value,the higher the contents of unsaturated components in biodiesel and the worse the oxidation stability.Therefore,the iodine value reduction rate can be used to evaluate the hydrogenation depth of SME [34].

    The compositions and relative contents of the PHSME samples obtained by experiment were determined by GC-MS analysis and classified according to the saturation of fatty acid esters.The hydrogenation selectivity of a fully saturated fatty acid ester is defined asSF,as shown in equation (1):

    In equation (1),ΔWCn:0is the mass fraction increment of the fully saturated fatty acid ester after hydrogenation (as a percentage) and ΔWCn:2is the mass fraction increment of the polyunsaturated fatty acid ester after hydrogenation (as a percentage).

    The hydrogenation selectivity of the monounsaturated fatty acid esters produced is defined asSL,as shown in equation (2):

    in equation (2),ΔWCn:1is the mass fraction increment of the monounsaturated fatty acid ester after hydrogenation (as a percentage) and ΔWCn:2is the mass fraction increment of the polyunsaturated fatty acid ester after hydrogenation (as a percentage).

    3.1.1.Working voltage.Figures 3(a) and (b) show the influences of the working voltage on the depth and hydrogenation selectivity of SME for a gas flow rate of 30 ml min?1,a SME circulation flow rate of 40 ml min?1,and a reaction time of 90 min.

    Figure 4.Effects of the SME circulation flow rate on the depth and hydrogenation selectivity of SME.

    As shown in figure 3(a),with an increase in the working voltage from 10.61 kV to 17.68 kV,the hydrogenation depth gradually increased and reached a maximum value of 52.8% at 17.68 kV.When the working voltage was continuously increased to 21.21 kV,the change in the hydrogenation depth was insignificant.The reason for this is that as the voltage increased,the hydrogen ionization degree gradually reached a maximum value,as did the amount of active hydrogen in the discharge tube [35].

    Figure 3(b) indicates that the working voltage has a significant effect on the hydrogenation selectivity of SME.When the working voltage was increased from 10.61 kV to 17.68 kV,SLincreased and reached a maximum value of 76.75%at a working voltage of 17.68 kV,whileSFdecreased and reached a minimum value of 23.25%at a working voltage of 17.68 kV.When the working voltage was higher than 17.68 kV,SLbegan to decrease andSFincreased.

    3.1.2.SME circulation flow rate.Figures 4(a) and (b) show the influences of the SME circulation flow rate on the depth and hydrogenation selectivity of SME for a working voltage of 17.68 kV,a gas flow rate of 30 ml min?1,and a reaction time of 90 min.

    As shown in figure 4(a),as the SME circulation flow rate increased to 40 ml min?1,the hydrogenation depth of SME increased,and the maximum reduction in the iodine value was 53.3%.This is because the flow of the liquid phase caused the SME at the bottom of the reactor to be pumped to the upper end.Due to the disturbance of the liquid phase,the fine Raney-Ni catalyst particles were more uniformly dispersed,enhancing the mass transfer between the gas,liquid,and solid phases,and thereby increasing the rate of SME hydrogenation.When the SME circulation flow rate was greater than 40 ml min?1,the rate of decrease in the iodine value did not change significantly,indicating that the enhancement of mass transfer due to the SME circulation flow rate was limited.

    As shown in figure 4(b),when the liquid phase did not circulate,SFwas slightly higher thanSL.When the SME circulation flow rate increased to about 40 ml min?1,SLrose to the highest value of 89.48%,andSLdecreased to the lowest value of 10.52%,indicating that the polyunsaturated components were mainly converted into monounsaturated components.As the circulation flow rate continued to increase,bothSLandSFtended to be stable.Liquid-phase circulation was the main means of enhancing the interphase mass transfer in this discharge reaction system; therefore,we draw the conclusion that enhancing the interphase mass transfer of the discharge reaction system can effectively improve the selectivity of monounsaturated fatty acid esters;a similar conclusion was reported in reference [36].

    3.1.3.Gas flow rate.Figures 5(a) and (b) show the influences of the gas flow rate on the depth and hydrogenation selectivity of SME for a working voltage of 17.68 kV,an SME circulation flow rate of 40 ml min?1,and a reaction time of 90 min.

    As shown in figure 5(a),as the gas flow rate increased from 10 ml min?1to 34 ml min?1,the rate of decrease of the iodine value of the SME increased from 47.0% to 52.8%.The reason for this is that when the gas flow rate increased,more hydrogen was ionized in the discharge zone per unit time,thereby providing more active hydrogen for the hydrogenation reaction;the depth of hydrogenation was then increased.While the gas flow rate was continuously increased,the rate of decrease of the iodine value showed a downward trend.This is because the residence time of hydrogen molecules in the discharge zone was too short and the collision probability of high-energy electrons and ground-state molecules was reduced;meanwhile,the excited-state molecules were more likely quenched by excessive gas renewal,so that the amount of active hydrogen available for SME hydrogenation was reduced,and therefore the hydrogenation depth was also reduced [37].

    Figure 5.Effects of the gas flow rate on the depth and hydrogenation selectivity of SME.

    Figure 6.Effect of the reaction time on the depth and hydrogenation selectivity of SME.

    Figure 5(b) shows the effect of gas flow rate on the hydrogenation selectivity of SME.With an increase in the gas flow rate,SLwas always greater thanSF.SLfirst increased and then fell and reached its highest value of 76.33%at a gas flow rate of 30 ml min?1.SFshowed the opposite trend,reaching a minimum of 23.67%at a gas flow rate of 30 ml min?1;when the gas flow continued to increase,SLshowed a reducing trend andSFbegan to increase.When the gas flow rate increased,the absolute number of highly reactive hydrogen atoms generated per unit time increased,but an excessive gas renewal rate caused a decrease in the residence time of the gas in the discharge zone,and then a decrease in the concentration of hydrogen atoms.It can be inferred that increasing the number of active hydrogen atoms is advantageous for increasing the selectivity of the monounsaturated fatty acid ester formation and suppressing the selectivity of the fully saturated fatty acid ester formation.

    3.1.4.Reaction time.Figures 6(a) and (b) show the influences of the reaction time on the depth and hydrogenation selectivity of SME for a working voltage of 17.68 kV,a gas flow rate of 30 ml min?1,and an SME circulation flow rate of 40 ml min?1.

    As shown in figure 6(a),as the reaction time was prolonged,the rate of decrease of the iodine value of SME gradually increased to 53.0%and then remained stable after 1.5 h.Appropriately extending the reaction time was advantageous for increasing the probability of collisions between the hydrogen plasma and unsaturated C=C bonds,and the hydrogenation reaction was also performed more fully.However,continuously prolonging the reaction time was not obviously beneficial to the hydrogenation depth,because the hydrogenation reaction between the hydrogen plasma and the SME tended to be saturated;that is,under the specific discharge reaction conditions described herein,the collision probability of the hydrogen plasma with unsaturatedcarbon bonds reached a maximum value [38].Therefore,the reaction time should be controlled from the viewpoint of improving the hydrogen utilization rate and reducing energy consumption.

    Table 2.Main composition and relative contents of SME and PHSME.

    As shown in figure 6(b),at the initial stage of the hydrogenation reaction(0–0.6 h),SLwas negative andSFwas more than 100%,indicating that the number of monounsaturated components produced by hydrogenation was less than the number of monounsaturated components converted to fully saturated components.In the middle stage of the hydrogenation reaction (0.6–1.5 h),with an increase in the reaction time,SLincreased sharply,whileSFdecreased.Where the two curves intersect,SL>SF,indicating that the polyunsaturated components in SME were mainly converted into monounsaturated components.At the end of the hydrogenation reaction (1.5–2.0 h),SFincreased slightly,indicating that some of the monounsaturated components were converted into fully saturated components,and that the hydrogenation reaction proceeded to deep hydrogenation.Due to the higher melting point of fully saturated fatty acids,although an increase in their content is beneficial for improving the oxidation stability of biodiesel,the lowtemperature fluidity of biodiesel is then deteriorated.Therefore,to improve the overall quality of biodiesel,the deep hydrogenation reaction of monounsaturated fatty acid ester should be inhibited by controlling the reaction time.

    3.2.Analysis of the hydrogenation depth and selectivity of biodiesel

    According to the single-factor experimental results,the preferred operating parameter combination was determined,that is,a working voltage of 17.68 kV,a gas flow rate of 30 ml min?1,a SME circulation flow rate of 40 ml min?1,and a reaction time of 1.5 h.With the preferred operating parameter combination,three groups of biodiesel hydrogenation experiments were carried out.The SME and PHSME were analyzed by GC-MS; the main components of the SME and PHSME are shown in table 2.

    The relative contents of saturated,monounsaturated,and polyunsaturated components in PHSME,as calculated from table 2,changed from 8.91%,27.04%,and 64.06% to 17.10%,55.45%,and 27.52%,respectively.The conversion rate of the polyunsaturated components reached 57.04% and the hydrogenation selectivity of the monounsaturated components produced was 77.75%.

    Xia[39]and Yuan[40]conducted research into biodiesel upgrading using Raney-Ni as the catalyst.Their polyunsaturated disintegration rates were 100% and 75.74% at 85°C,and the hydrogenation selectivities of the monounsaturated components were 67.89% and 26.12%,respectively.

    Compared with biodiesel upgraded under traditional thermodynamic reaction conditions,the 57.04% conversion rate of the polyunsaturated components described here is lower,but the 77.75% selectivity of the monounsaturated components produced is higher.The reduced catalytic activity of Raney-Ni at room temperature may be the main reason for the lower conversion rate of the polyunsaturated components.

    The overall quality of the biodiesel produced under gasphase discharge reaction conditions could be further improved by moderately raising the reaction temperature to enhance the activity of the catalyst,and optimizing the design of the hydrogenation reactor to enhance the interphase mass transfer.

    3.3.Mechanism of biodiesel hydrogenation under discharge reaction conditions

    3.3.1.Main types of biodiesel hydrogenation reaction.The formation of atomic hydrogen with high reaction activity is of great significance for the hydrogenation of SME.Under the action of an electric field,there are five main types of ionization and excitation processes of H2,namely excitation,de-excitation,ionization,recombination,and elastic collision[41].Inelastic collisions are the main reason for the ionization of hydrogen.Strong inelastic collisions between hydrogen molecules and high-energy electrons produce a hydrogen plasma containing hydrogen radicals,positive and negative ions,and excited atoms.The reaction forms include the electron ionization reaction,the electron–neutral molecular reaction,the electron–ion reaction,the electron excitation reaction,the electron–neutral particle reaction,the positive ion–negative ion reaction,etc.The main inelastic collision reaction processes are shown in table 3.

    In the hydrogenation process,a small amount of water(visible to the naked eye)and an acid substance(based on the GC-MS test results) were produced.It could be inferred that there are additional reactions of unsaturated C=C,hydrodeoxidation,and carbon chain addition taking place.Their chemical reaction formulas are as follows:

    (1) Adsorption of active hydrogen on Raney-Ni

    (2) Addition reaction of unsaturated C=C (C18:1,C18:2and C19:2)

    (3) Hydrodecarboxyl reaction (C18:0,C18:2)

    (4) Carbon chain addition reaction (C18:0,C18:1)

    3.3.2.Kinetic model for biodiesel hydrogenation.According to the results of the GC-MS analysis,and referring to relevant research results[29],it is inferred that the main hydrogenation pathways of SME on the Raney-Ni catalyst and the discharge reaction conditions are as shown in figure 7.

    In figure 7,c1,c2,c3,c4,andc5are the mass fractions of C18:2,C18:1,C18:0,C20:0,and C20:1,respectively;k1,k2,k3,andk4are the rate constants of the respective hydrogenation steps.Assuming that the catalytic hydrogenation of SME over the Raney-Ni catalyst is a kind of quasi first-order reaction,then the hydrogenation processes shown in figure 7 can be described by kinetic equations (7)–(11).

    The hydrogenation rate constantsk1,k2,k3andk4can be calculated according to the GC-MS test data.According to the initial mass fraction of each component of SME and the mass fractions of the PHSME components after 90 min of reaction (table 2),it can be calculated thatk1=0.0167 min?1,k2=0.0059 min?1,k3=0.0043 min?1,andk4=0.0128 min?1.The mass fractions of C18:2,C18:1,C18:0 and C20:1 at other reaction times can be calculated using the kinetic equations above.

    Figure 8 shows the calculated and experimental values of the mass fractions of C18:0,C18:1,C20:1,and C18:2.It can be seen that the calculated results are basically consistent withthe experimental values,which proves that the hydrogenation of SME on the Raney-Ni catalyst can be described by a quasi first-order reaction model.

    Table 3.Major ionization and excitation processes of H2 [42].

    Figure 7.Hydrogenation process of SME on Raney-Ni.

    The reaction rate constants obey the relationk1>k4>k2>k3,indicating that the conversion rate of C18:2 to C18:1 is faster than that of C18:1 to C18:0.It can be deduced from this that the hydrogenation rate of polyunsaturated fatty acid ester is faster than that of monounsaturated fatty acid ester,which is beneficial for increasing the content of monounsaturated components.

    The hydrogenation selectivity of each component can be described by the ratio of the reaction rate constants.The ratio ofk1tok2,that is,S1=k1/k2=2.83,which indicates that the formation rate of C18:1 by C18:2 hydrogenation is 2.83 times that of C18:0 from C18:1.C18:1 has two conversion methods;one is that the carbon chain length increases but the number of unsaturated carbon bonds remains the same,resulting in conversion into C20:1; the other conversion path is deep hydrogenation to the fully saturated component C18:0.The ratio ofk4tok2isS2=k4/k2=2.17,which indicates that the conversion from C18:1 to C20:1 has a higher probability and that deep hydrogenation can be avoided.Some of the C18:0 components were converted to C20:0 due to carbon chain growth,and the selectivity coefficientS3=k2/k3=1.37,indicating that the formation rate of C18:0 from C18:1 hydrogenation is 1.37 times that of C20:0 from C18:0.

    Figure 8.Comparison of the experimental and calculated values of the C18:2,C18:1,and C18:0 mass fractions of PHSME with reaction time.

    In conclusion,in the discharge reaction system,the hydrogenation rate of polyunsaturated fatty acid esters is larger than that of monounsaturated fatty acid esters,and it has good selectivity for the formation of monounsaturated products,which is very beneficial for the comprehensive quality improvement of biodiesel.

    4.Conclusions

    A DBD hydrogenation reaction system was constructed to achieve the selective hydrogenation of biodiesel at low temperatures and under normal pressure,using soybean methyl ester as the raw material and Raney-Ni as the catalyst.Research into biodiesel upgrading was carried out,and the main conclusions are as follows:

    (1) The hydrogenation depth of biodiesel first increased and then decreased with an increase in the gas flow rate; it increased and then remained stable with an increase in the working voltage,the SME circulation flow rate and the reaction time.With an increase in the working voltage,gas flow rate,and reaction time,the hydrogenation selectivity of the monounsaturated components produced showed a trend of first increasing and then declining; it first increased and then remained stable with an increase of the SME circulation flow rate.With the preferred operating parameter combination,the polyunsaturated components in SME were reduced by 57.04% and hydrogenated to monounsaturated components with a selectivity of 77.75%.

    (2) The hydrogenation reaction of SME can be described by a quasi first-order reaction model.The calculated reaction rate constants indicate that under DBD reaction conditions,the hydrogenation of biodiesel has high selectivity for the formation of monounsaturated components.

    Acknowledgments

    This work was supported by National Natural Science Foundation of China (No.51761145011),the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),and the Jiangsu University Senior Talent Fund Project (No.12811020026).

    猜你喜歡
    衛(wèi)東小龍
    《小龍的假日》
    El regreso del dragón
    Nanosecond laser preheating effect on ablation morphology and plasma emission in collinear dual-pulse laser-induced breakdown spectroscopy
    小小小小龍
    祝衛(wèi)東
    愛打噴嚏的小河馬
    劉小龍
    風(fēng)中的祈禱詞
    詩(shī)選刊(2015年4期)2015-10-26 08:45:28
    種心情
    POWER, DESIRE, AND VIOLENCE
    漢語世界(2014年4期)2014-02-27 01:19:23
    免费观看人在逋| 国产淫片久久久久久久久| а√天堂www在线а√下载| 精品不卡国产一区二区三区| 国产精品不卡视频一区二区| 国产在视频线在精品| 国产在视频线在精品| 男人狂女人下面高潮的视频| 麻豆国产av国片精品| 午夜激情福利司机影院| 国产麻豆成人av免费视频| 成人av在线播放网站| 国产精华一区二区三区| or卡值多少钱| 亚洲国产欧美人成| 成人特级av手机在线观看| 成人二区视频| 很黄的视频免费| 一级黄片播放器| 桃色一区二区三区在线观看| 日本黄色片子视频| 亚洲一区高清亚洲精品| 国产69精品久久久久777片| 中文在线观看免费www的网站| 91在线观看av| 永久网站在线| 黄色女人牲交| 免费搜索国产男女视频| 日韩亚洲欧美综合| 在线看三级毛片| 久久久久久久久久久丰满 | 乱码一卡2卡4卡精品| 欧美一级a爱片免费观看看| 看黄色毛片网站| 精品久久久久久久人妻蜜臀av| 国内精品一区二区在线观看| 在线观看av片永久免费下载| 日本精品一区二区三区蜜桃| 高清毛片免费观看视频网站| 欧美高清性xxxxhd video| 午夜视频国产福利| 在线观看免费视频日本深夜| 国内揄拍国产精品人妻在线| 国产国拍精品亚洲av在线观看| 俄罗斯特黄特色一大片| 韩国av在线不卡| 精品久久久噜噜| 婷婷亚洲欧美| 午夜影院日韩av| 国产亚洲91精品色在线| 久久久久久久精品吃奶| 免费观看的影片在线观看| 在线播放国产精品三级| 久久久久国产精品人妻aⅴ院| 999久久久精品免费观看国产| 亚洲乱码一区二区免费版| 亚洲熟妇中文字幕五十中出| 99热这里只有是精品在线观看| 国产高潮美女av| 黄色日韩在线| 国产乱人视频| 亚洲欧美日韩无卡精品| 熟女电影av网| 干丝袜人妻中文字幕| 69av精品久久久久久| 久久午夜福利片| 久久久久久久精品吃奶| 国产亚洲av嫩草精品影院| 麻豆精品久久久久久蜜桃| 欧美中文日本在线观看视频| 欧美极品一区二区三区四区| 久久久久精品国产欧美久久久| 午夜精品一区二区三区免费看| 真实男女啪啪啪动态图| 国产av麻豆久久久久久久| 亚洲国产色片| 久久国内精品自在自线图片| 麻豆国产av国片精品| 美女高潮的动态| 九九爱精品视频在线观看| 亚洲在线自拍视频| 国产色爽女视频免费观看| 啦啦啦观看免费观看视频高清| 国产精品不卡视频一区二区| 看免费成人av毛片| 伦理电影大哥的女人| 三级男女做爰猛烈吃奶摸视频| 中文字幕av成人在线电影| 3wmmmm亚洲av在线观看| 色综合亚洲欧美另类图片| 日本精品一区二区三区蜜桃| 淫秽高清视频在线观看| 国产伦人伦偷精品视频| 免费人成视频x8x8入口观看| 高清毛片免费观看视频网站| 97热精品久久久久久| 99在线视频只有这里精品首页| 久久久久性生活片| 成人鲁丝片一二三区免费| 午夜激情欧美在线| 午夜福利成人在线免费观看| 男女那种视频在线观看| 日韩一区二区视频免费看| 色5月婷婷丁香| 人妻制服诱惑在线中文字幕| 国语自产精品视频在线第100页| 亚洲第一区二区三区不卡| 99国产极品粉嫩在线观看| 色噜噜av男人的天堂激情| 国产精品免费一区二区三区在线| 国产精品爽爽va在线观看网站| а√天堂www在线а√下载| 日本 欧美在线| 美女cb高潮喷水在线观看| 一进一出抽搐动态| 成人鲁丝片一二三区免费| 日本在线视频免费播放| 免费在线观看日本一区| 中文资源天堂在线| 国产精品一区二区三区四区免费观看 | 国产av在哪里看| 久久久久久久久久黄片| 国产男靠女视频免费网站| 国产精品福利在线免费观看| 午夜影院日韩av| 国产精品福利在线免费观看| 国产精品福利在线免费观看| 五月伊人婷婷丁香| 国产精品久久久久久精品电影| 床上黄色一级片| 免费看美女性在线毛片视频| 一边摸一边抽搐一进一小说| 女人十人毛片免费观看3o分钟| 精品久久久久久久末码| 麻豆成人午夜福利视频| 一级av片app| 日韩欧美国产在线观看| 精品久久久久久久人妻蜜臀av| 久久久久国产精品人妻aⅴ院| 精品福利观看| 国产乱人视频| 在线观看一区二区三区| 精品久久久久久,| 人妻夜夜爽99麻豆av| 如何舔出高潮| 亚洲av中文字字幕乱码综合| 欧美不卡视频在线免费观看| 亚洲第一区二区三区不卡| 久久这里只有精品中国| 久久久久久久久久黄片| 天天躁日日操中文字幕| 日本欧美国产在线视频| 欧美xxxx性猛交bbbb| 亚洲一区高清亚洲精品| 亚洲天堂国产精品一区在线| 伦精品一区二区三区| 嫩草影视91久久| 欧美日韩精品成人综合77777| 精品午夜福利在线看| 免费人成视频x8x8入口观看| 97超级碰碰碰精品色视频在线观看| 色尼玛亚洲综合影院| 成年免费大片在线观看| 成人亚洲精品av一区二区| 联通29元200g的流量卡| 日韩欧美在线乱码| 成人高潮视频无遮挡免费网站| 一级黄片播放器| 亚洲精品乱码久久久v下载方式| 亚洲欧美日韩高清在线视频| 在线国产一区二区在线| 国产精品1区2区在线观看.| 日韩国内少妇激情av| 最近最新中文字幕大全电影3| 搡女人真爽免费视频火全软件 | 成人精品一区二区免费| 婷婷亚洲欧美| 美女大奶头视频| 搡女人真爽免费视频火全软件 | 欧美日韩精品成人综合77777| 亚洲av免费在线观看| 亚洲av熟女| 国产精品美女特级片免费视频播放器| 欧美极品一区二区三区四区| 中文字幕免费在线视频6| 在线播放国产精品三级| 特级一级黄色大片| 欧美日韩黄片免| 色噜噜av男人的天堂激情| 噜噜噜噜噜久久久久久91| 男插女下体视频免费在线播放| 亚洲一区高清亚洲精品| 欧美潮喷喷水| h日本视频在线播放| 日韩人妻高清精品专区| 3wmmmm亚洲av在线观看| 色综合站精品国产| 91久久精品国产一区二区三区| 久久午夜福利片| 国产成人aa在线观看| 国产大屁股一区二区在线视频| 国产伦在线观看视频一区| 亚洲专区中文字幕在线| 免费观看在线日韩| 精品人妻1区二区| 国产伦精品一区二区三区视频9| 日日撸夜夜添| 亚洲国产精品sss在线观看| 一进一出好大好爽视频| 露出奶头的视频| АⅤ资源中文在线天堂| 一夜夜www| 久久天躁狠狠躁夜夜2o2o| 麻豆成人午夜福利视频| 国产单亲对白刺激| 91麻豆av在线| 啦啦啦观看免费观看视频高清| 在线观看舔阴道视频| 老熟妇仑乱视频hdxx| 亚洲 国产 在线| 久久亚洲精品不卡| 久久久成人免费电影| 亚洲av美国av| 亚洲无线在线观看| 嫁个100分男人电影在线观看| 成人鲁丝片一二三区免费| 欧美极品一区二区三区四区| 色哟哟哟哟哟哟| 99久久精品一区二区三区| 国产成人一区二区在线| 中文资源天堂在线| 永久网站在线| 日本五十路高清| 男女下面进入的视频免费午夜| 超碰av人人做人人爽久久| 麻豆国产av国片精品| 成熟少妇高潮喷水视频| 国产精品电影一区二区三区| 变态另类成人亚洲欧美熟女| 国产午夜精品久久久久久一区二区三区 | 欧美+亚洲+日韩+国产| 男女做爰动态图高潮gif福利片| 极品教师在线免费播放| 1024手机看黄色片| 非洲黑人性xxxx精品又粗又长| 免费观看精品视频网站| 国产乱人伦免费视频| 91av网一区二区| 国产一区二区在线观看日韩| 欧美精品国产亚洲| 我要看日韩黄色一级片| 成年人黄色毛片网站| 欧美中文日本在线观看视频| 午夜久久久久精精品| 色5月婷婷丁香| 一区二区三区高清视频在线| 国产不卡一卡二| 在线观看66精品国产| 91久久精品电影网| 有码 亚洲区| 成年人黄色毛片网站| 九九爱精品视频在线观看| 日韩国内少妇激情av| 无遮挡黄片免费观看| 国产精品精品国产色婷婷| 国产中年淑女户外野战色| 一本精品99久久精品77| 欧美激情久久久久久爽电影| 午夜福利18| 天堂√8在线中文| 禁无遮挡网站| 精品一区二区三区av网在线观看| 一级黄色大片毛片| 日本成人三级电影网站| 久久精品夜夜夜夜夜久久蜜豆| 午夜亚洲福利在线播放| bbb黄色大片| 亚洲三级黄色毛片| 日本黄色视频三级网站网址| 97碰自拍视频| 精品久久久久久久久av| videossex国产| 亚洲avbb在线观看| 国产精品99久久久久久久久| 亚洲自拍偷在线| 天天躁日日操中文字幕| 国产高清三级在线| 我的老师免费观看完整版| 国产精品三级大全| 少妇人妻精品综合一区二区 | 国产精品久久久久久亚洲av鲁大| 男女之事视频高清在线观看| 九九爱精品视频在线观看| 久久精品91蜜桃| 舔av片在线| 成熟少妇高潮喷水视频| 欧美日韩综合久久久久久 | 狂野欧美白嫩少妇大欣赏| 亚洲中文日韩欧美视频| 午夜免费成人在线视频| 99国产精品一区二区蜜桃av| 久久精品国产鲁丝片午夜精品 | 精品欧美国产一区二区三| 色5月婷婷丁香| 精品国产三级普通话版| 一本久久中文字幕| av专区在线播放| 2021天堂中文幕一二区在线观| 99国产精品一区二区蜜桃av| 老女人水多毛片| 日韩欧美国产一区二区入口| 女人十人毛片免费观看3o分钟| 99久久成人亚洲精品观看| 麻豆久久精品国产亚洲av| 有码 亚洲区| 天美传媒精品一区二区| 三级毛片av免费| 亚洲av中文字字幕乱码综合| 91午夜精品亚洲一区二区三区 | 一级毛片久久久久久久久女| 很黄的视频免费| 久久久久久久久中文| 又粗又爽又猛毛片免费看| 国产精品日韩av在线免费观看| 精品一区二区三区视频在线| 国产人妻一区二区三区在| 级片在线观看| 国产亚洲精品久久久久久毛片| 亚洲精品成人久久久久久| 精品乱码久久久久久99久播| 俺也久久电影网| 内地一区二区视频在线| 婷婷亚洲欧美| 国产老妇女一区| 亚洲精品色激情综合| 午夜精品久久久久久毛片777| 午夜精品一区二区三区免费看| 又紧又爽又黄一区二区| 村上凉子中文字幕在线| 免费看美女性在线毛片视频| 日本黄色片子视频| 在线播放无遮挡| 欧美日本亚洲视频在线播放| 亚洲精品色激情综合| 乱系列少妇在线播放| 国产在视频线在精品| 国内精品美女久久久久久| 亚洲精品粉嫩美女一区| 精品人妻熟女av久视频| 中文字幕av在线有码专区| 久久久午夜欧美精品| 丰满乱子伦码专区| 美女 人体艺术 gogo| 欧美+日韩+精品| 精品久久久久久,| 亚洲欧美日韩卡通动漫| 日本在线视频免费播放| 久久精品91蜜桃| 九九热线精品视视频播放| 亚洲人成伊人成综合网2020| 中文字幕高清在线视频| 男女啪啪激烈高潮av片| 超碰av人人做人人爽久久| 毛片一级片免费看久久久久 | 久99久视频精品免费| 日韩,欧美,国产一区二区三区 | 久9热在线精品视频| 亚洲国产日韩欧美精品在线观看| 18禁黄网站禁片免费观看直播| 久久中文看片网| 成人av在线播放网站| a级一级毛片免费在线观看| ponron亚洲| 欧美日韩乱码在线| 中文字幕免费在线视频6| .国产精品久久| 美女高潮喷水抽搐中文字幕| 午夜爱爱视频在线播放| 又黄又爽又刺激的免费视频.| 两人在一起打扑克的视频| 内射极品少妇av片p| 日本黄大片高清| 狠狠狠狠99中文字幕| 久久国产精品人妻蜜桃| 国产午夜福利久久久久久| 国产精品爽爽va在线观看网站| 日本撒尿小便嘘嘘汇集6| 老司机深夜福利视频在线观看| 婷婷色综合大香蕉| 日韩欧美精品免费久久| 欧美潮喷喷水| 亚洲精品在线观看二区| 亚洲av一区综合| 色尼玛亚洲综合影院| 久久精品91蜜桃| 国产精品自产拍在线观看55亚洲| 欧美丝袜亚洲另类 | a级一级毛片免费在线观看| 国产老妇女一区| АⅤ资源中文在线天堂| 欧美中文日本在线观看视频| 亚洲性久久影院| 精品久久久久久,| 日本 欧美在线| 一本一本综合久久| 日韩欧美在线乱码| 午夜福利在线在线| 久久人人爽人人爽人人片va| 成人av在线播放网站| 天天一区二区日本电影三级| 精华霜和精华液先用哪个| 一区二区三区免费毛片| 免费观看精品视频网站| 亚洲av中文av极速乱 | 免费不卡的大黄色大毛片视频在线观看 | 国内精品久久久久精免费| 午夜免费成人在线视频| 两个人视频免费观看高清| 国产在视频线在精品| 一进一出抽搐gif免费好疼| 国产精品爽爽va在线观看网站| 97超级碰碰碰精品色视频在线观看| 亚洲精华国产精华液的使用体验 | 国产精品一区二区免费欧美| 精品国内亚洲2022精品成人| 久久国产乱子免费精品| 嫩草影院入口| 欧美人与善性xxx| 麻豆国产97在线/欧美| 直男gayav资源| 日日啪夜夜撸| 中国美女看黄片| 久久精品国产亚洲av涩爱 | 别揉我奶头 嗯啊视频| 亚洲 国产 在线| 毛片一级片免费看久久久久 | 久久久午夜欧美精品| 高清毛片免费观看视频网站| 人妻制服诱惑在线中文字幕| АⅤ资源中文在线天堂| 欧美日韩亚洲国产一区二区在线观看| 欧美+亚洲+日韩+国产| 一本久久中文字幕| 欧美日韩国产亚洲二区| АⅤ资源中文在线天堂| 久久精品国产鲁丝片午夜精品 | 黄片wwwwww| 久久久成人免费电影| aaaaa片日本免费| 亚洲精品一卡2卡三卡4卡5卡| 久久久久久久午夜电影| 精品久久久久久成人av| 免费在线观看影片大全网站| 久久久久久久午夜电影| 尤物成人国产欧美一区二区三区| 亚洲av中文av极速乱 | 欧美绝顶高潮抽搐喷水| 色哟哟·www| 亚洲不卡免费看| 日韩精品青青久久久久久| 欧美黑人巨大hd| 国产精品不卡视频一区二区| 天堂动漫精品| 国产69精品久久久久777片| 91久久精品电影网| 给我免费播放毛片高清在线观看| 亚洲欧美日韩东京热| 女生性感内裤真人,穿戴方法视频| 国产av一区在线观看免费| 波多野结衣高清无吗| 日韩亚洲欧美综合| 欧美区成人在线视频| 男女之事视频高清在线观看| 国产欧美日韩精品一区二区| 国产精品av视频在线免费观看| 欧美色欧美亚洲另类二区| 可以在线观看的亚洲视频| 在线观看舔阴道视频| 香蕉av资源在线| 中出人妻视频一区二区| av.在线天堂| 最近中文字幕高清免费大全6 | 国产午夜福利久久久久久| 男女之事视频高清在线观看| 99精品在免费线老司机午夜| 国产伦精品一区二区三区视频9| 女的被弄到高潮叫床怎么办 | 亚洲av免费高清在线观看| 赤兔流量卡办理| 女生性感内裤真人,穿戴方法视频| 欧美色视频一区免费| 白带黄色成豆腐渣| 国产精品爽爽va在线观看网站| 联通29元200g的流量卡| 男女做爰动态图高潮gif福利片| 99热6这里只有精品| ponron亚洲| 午夜老司机福利剧场| 国产精品乱码一区二三区的特点| 亚洲av日韩精品久久久久久密| 国产高清三级在线| 亚洲自拍偷在线| 成人av在线播放网站| 久久久久久九九精品二区国产| 久久国内精品自在自线图片| 欧美激情久久久久久爽电影| 床上黄色一级片| 观看免费一级毛片| 久久精品夜夜夜夜夜久久蜜豆| 国产视频内射| 久久久久久九九精品二区国产| 免费观看的影片在线观看| 看免费成人av毛片| 有码 亚洲区| 精品一区二区三区av网在线观看| 久久亚洲精品不卡| 国产精品久久电影中文字幕| 国产男靠女视频免费网站| 久久久色成人| 亚洲av五月六月丁香网| 国内毛片毛片毛片毛片毛片| 日韩在线高清观看一区二区三区 | 国产真实乱freesex| 国语自产精品视频在线第100页| 一级毛片久久久久久久久女| 国产伦在线观看视频一区| 久久久久久大精品| 亚洲在线自拍视频| www.色视频.com| 欧美日韩亚洲国产一区二区在线观看| 国产爱豆传媒在线观看| 午夜精品久久久久久毛片777| 中国美白少妇内射xxxbb| 久久人人爽人人爽人人片va| 亚洲在线自拍视频| 美女高潮喷水抽搐中文字幕| 乱码一卡2卡4卡精品| 国产免费av片在线观看野外av| 一卡2卡三卡四卡精品乱码亚洲| 亚洲欧美日韩无卡精品| 99在线视频只有这里精品首页| 亚洲一区二区三区色噜噜| 免费观看的影片在线观看| 欧美三级亚洲精品| videossex国产| .国产精品久久| 中亚洲国语对白在线视频| 欧美日韩国产亚洲二区| 亚洲av日韩精品久久久久久密| 日韩欧美在线乱码| 精品久久久久久久久av| 欧美潮喷喷水| 天堂动漫精品| 最近最新中文字幕大全电影3| 久久久久久久久大av| 成熟少妇高潮喷水视频| 一区福利在线观看| 欧美极品一区二区三区四区| 18禁黄网站禁片免费观看直播| 免费黄网站久久成人精品| 精品国产三级普通话版| 免费黄网站久久成人精品| 日本 av在线| 美女高潮的动态| 人人妻人人澡欧美一区二区| 性欧美人与动物交配| 亚洲乱码一区二区免费版| 亚洲av不卡在线观看| 国产真实伦视频高清在线观看 | 国产真实伦视频高清在线观看 | 日日啪夜夜撸| 国产视频内射| 日本与韩国留学比较| 最新在线观看一区二区三区| 99国产极品粉嫩在线观看| 免费看av在线观看网站| 亚洲真实伦在线观看| 美女 人体艺术 gogo| 午夜影院日韩av| 国产视频内射| www日本黄色视频网| 老司机午夜福利在线观看视频| 少妇人妻一区二区三区视频| 欧美色欧美亚洲另类二区| 无遮挡黄片免费观看| 校园春色视频在线观看| 久久精品国产自在天天线| 日本撒尿小便嘘嘘汇集6| 亚洲自拍偷在线| 99热6这里只有精品| 22中文网久久字幕| 日韩 亚洲 欧美在线| 大型黄色视频在线免费观看| 免费在线观看成人毛片| 午夜免费成人在线视频| 久久精品国产亚洲网站| 国产精品久久久久久亚洲av鲁大| 亚洲人与动物交配视频| 久久热精品热| 最新在线观看一区二区三区| 国产精品无大码| 性插视频无遮挡在线免费观看| 国产精品一区二区三区四区免费观看 | 国产乱人视频| 国产中年淑女户外野战色| 村上凉子中文字幕在线| 一级av片app| 久久亚洲精品不卡| 国产在视频线在精品| 亚洲一级一片aⅴ在线观看| 看片在线看免费视频| 国产精品自产拍在线观看55亚洲| 国产免费男女视频| 亚洲aⅴ乱码一区二区在线播放| av天堂中文字幕网|