• <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 ?

    Conversion of Methane by Steam Reforming Using Dielectric-barrier Discharge*

    2009-05-15 00:25:58ZhangXu張旭WangBaowei王保偉LiuYongwei劉永衛(wèi)andXuGenhui許根慧
    關(guān)鍵詞:張旭

    Zhang Xu (張旭), Wang Baowei (王保偉), Liu Yongwei (劉永衛(wèi)) and Xu Genhui (許根慧)

    ?

    Conversion of Methane by Steam Reforming Using Dielectric-barrier Discharge*

    Zhang Xu (張旭), Wang Baowei (王保偉)**, Liu Yongwei (劉永衛(wèi)) and Xu Genhui (許根慧)

    Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering Technology, Tianjin University, Tianjin 300072, China

    Conversion of methane by steam reforming was carried out by means of dielectric-barrier discharge. A systemic procedure was employed to determine the suitable experimental conditions. It was found that one of the plasma generators can match the system best. A higher power input can always bring a higher conversion, but the selectivity to C2H6decreased from 52.48% to 39.43% as the power increased from 20W to 49W. When discharge distance was 4 mm, selectivities to almost all main products reached the max. The inner electrode made of stainless steel and the outer electrode with aluminum foil were one of the best options which can obviously enhance the conversion of methane. A larger flow rate always resulted in a lower conversion of methane. In the most time, 19.93% steam promoted conversion of methane.

    methane, steam, dielectric-barrier discharge, plasma

    1 Introduction

    Methane or natural gas is widely applied in industry to obtain hydrogen or synthesis gas as source materials for the production of raw chemicals [1-6]. Although the steam reforming process has been industrially used to produce synthesis gas from methane recently, there are still problems waiting for being solved [7]. Efforts had been devoted on the catalysts applied in the methane steam reforming [8-12]. Considering the advantages of plasma, many articles also emerged in the field of conversion of methane by using plasma [13-15]. Pati?o. [7] firstly used radio frequency glow discharge to carry out the non-oxidative coupling of CH4/H2mixtures and studied the reforming of methane with CO2, O2, and steam plasma with the same system to produce higher hydrocarbons. Bo. [16] investigated the influence of feed gases proportion on the performance of gliding arc discharge plasma assisted methane reforming with carbon dioxide process, which can effectively convert the reagents into synthesis gas with C2H4and C2H2as the main hydrocarbon compounds. Li. [17] compared the performance of the non-thermal plasma generated by four different electric discharge techniques in the conversion of methane and found that ethane is the major C2product in the dielectric-barrier discharge (DBD) processes. Considerable studies had also been done by our team [18-21]. On the basis of these works, effects of more detail factors, including the match of reactor with plasma generators, discharge frequency, input power, discharge distance, different electrode and source gas were studied in this paper.

    Figure 1 Schematic diagram of DBD reactor

    2 Experimental

    Figure 1 shows the plasma rector which consists of a quartz tube (with a outer diameter of 10mm and a inner diameter of 6 mm, if not mentioned specially), a metal stick (with a diameter of 3 mm, if not mentioned specially) inside it as the inner electrode and a metal foil or net (with a length of 90 mm) around it as the outer electrode. Fig. 2 shows the schematic diagram of the reaction and analysis system. Methane controlled by mass flow controllers (D07-7A/ZMM) was introduced and passed a bottle which was immersed in a water bath and filled with water to carry and mix with steam. The plasma was generated by a high-voltage generator. After reaction and condensation to remove water, the gases from the reactor were analyzed by gas chromatogram (FULI9790II) online. All experiments were carried out at room temperature and atmospheric pressure.

    Figure 2 Flow chart of the experiment 1—CH4; 2—water bath; 3—reactor; 4—condensator; 5—gas chromatogram; 6—flowmeter; 7—plasma generator

    Methane conversion and product selectivity are defined as follows:

    3 Results and Discussion

    3.1 Effect of plasma generators

    Four plasma generators were examined in the same conditions in the experiments. The parameters and the results are listed in Table 1 and Fig. 3, respectively. It is shown that when plasma generator 4 was used, not only the conversion of CH4but also the selectivities to H2and C2H4were highest. The difference of other selectivities was not very obvious and the yields reached the max for all the products. It was declared that plasma generator 4 can match to the reactor best. The reason is that the reactor of DBD is a capacitor in fact and the plasma generator is a circuitry, which includes adjustable capacitor and inductance. The reactor and the plasma generator can produce acceptor resonance or current resonance when the characteristic of the electrical apparatus of reactor matches with the plasma generator, resulting in the highest energy efficiency. At the same time, the appropriate discharge voltage and frequency are needed for conversion of methane and steam. The plasma generator 4 was chosen in the following works.

    Table 1 Parameter of plasma generator

    3.2 Effect of input power

    The input power, which can influence the conversion and product distribution, was tested as one important factor. From Fig. 4 (a), it is shown that as the power increased from 20 W to 49 W, CH4conversion gradually increased when others conditions were constant. The density of free radicals, which is responsible to the reaction rate, increased with the power of plasma. The increasing power leads to an increase in the temperature and density of electrons. Thus, the activity of plasma is enhanced, which accelerates the breakage of the bond of CH4, and finally improves the conversion of CH4.

    The distribution variation shown in Fig. 4 (b) suggests that as the input power increased, the selectivities to H2and C2H4rise from 31.12% to 41.29% and from 4.24% to 7.18%, respectively, but the selectivity to C2H6decreased from 52.62% to 41.29%. The selectivity to CO was less than 4% in all ranges. The change could be attributed to the increasing of the conversion. When more CH4was active in this process, more H? and CH3? were emerged to form more H2and abundant C2H6. However, the larger power also made it likely to transform CH3? to CH2? and H?, which further led to the change of the selectivities to C2H4and H2. After calculation, it is found that a larger power brought a higher yield for every product.

    3.3 Effect of discharge distance

    In order to investigate the effect of discharge distance, the experiments were conducted by changing the diameters of inner electrodes and quartz tubes. The diameters, thickness of tube and discharge distances are shown in Table 2.

    Table 2 Diameters of electrodes and discharge distance

    Figure 5 suggests that the conversion of CH4was reduced from 16.42% to 7.13% by increasing the diameter of the reactor, which directly decreased the average energy carried by elections and the intensity of electric field in the discharge area. All selectivities came through the process of increasing and then decreasing and most of them reached the max when the distance was 4 mm. But as the range of conversion was more obvious, the trends of the yields were as the same as the conversion.

    3.4 Effect of different electrode

    Inner electrodes made of red copper, brass, aluminum and stainless steel were examined with the outer and inner diameters of quartz tube changed to 12 mm and 10 mm, respectively. The results are shown in Table 3. The conversion of CH4varied with the material of electrodes in the following order: stainless steel>red copper>brass>aluminum. Also, the lowest selectivity to H2and highest selectivity to C2H6were obtained when aluminum inner electrode was used and the variety of selectivities was reverse for red copper inner electrode. The differences may be attributed to the catalytic effect of the different metals. In the reaction, the temperature of electrode directly contacted with CH4and steam could reach 200°C and play an important role beside of transferring electron.

    Table 3 Effect of inner electrode on methane conversion and the selectivities of the products (P40 W, steam concentration19.93%,?40 ml·min-1)

    Two kinds of outer electrodes,.., aluminum foil and iron net were examined in the experiment. The results are listed in Table 4. It clearly shows that the former one was better in the activity and selectivity to H2but worse in the selectivities to C2H6and C3H8. Because both of these electrodes did not contact with the gases, there was no catalytic influence. Perhaps compared with the iron net with a lot of meshes, the larger area helped the foil to make a uniform and stable electric field, which led to the higher conversion. However, the net is likely more propitious to focus the energy and form longer hydrocarbons.

    Table 4 Effect of outer electrode on methane conversion and the selectivities of products (P30 W,?40 ml·min-1)

    3.5 Effect of flow rate and steam proportion

    The flow rate and steam proportion were also studied. The influence of steam proportion was not well-regulated. As a whole, when the proportion was 19.93%, the highest conversion was obtained. Fig. 6 shows that the conversion of CH4decreased with the flow rate. It can be explained by the fact that the increase in flow rate leads to the decrease of the residence time. As the power is constant, the number of high-energy electron remains in a stable level, which leads to the average energy of CH4receives declines and results in less chance for the molecule to be excited and the reduction of the conversion.

    The influences of the two factors in the selectivities were listed in Tables 5 (a) and (b) which took the situations of steam proportion were 0 and 19.93% as examples. It is not surprising that when steam was not introduced into the reaction system, there was no CO formation because of absence of O element. The results shown in Table 4 indicate that the variation of selectivities to C2H4and C2H6was as same as discussed above.

    Table 5 (a) Effect of flow rate on product selectivities (pure CH4)

    Table 5 (b) Effect of flow rate on product selectivities (with 19.93% steam concentration)

    4 Conclusions

    Conversion of methane by steam reforming was accomplished by means of DBD and the effects of several factors were discussed. By using plasma generator which can match the reactor, higher yields could be obtained. Higher conversion of methane could be obtained by using higher input power and smaller discharge distance. The electrodes made of stainless steel and aluminum foil with 19.93% steam proportion were favorable for the reaction.

    1 Jasiński, M., Dors, M., Mizeraczyk, J., “Production of hydrogenmethane reforming using atmospheric pressure microwave plasma”,., 181 (1), 41-45 (2008)

    2 Dong, X.F., Zhang, H., Lin, W. M., “Preparation and characterization of a perovskite-type mixed conducting SrFe0.6Cu0.3Ti0.1O3-δmembrane for partial oxidation of methane to syngas”,...., 16 (3), 411-415 (2008).

    3 Wei, W.S., Xu, J., Fang, D.W., Bao, X.J., “Catalytic partial oxidation of methane with air to syngas in a pilot-plant-scale spouted bed reactor”,...., 11 (6), 643-648 (2003).

    4 Xu, J., Wei, W.S., Bao, X.J., “Thermodynamic study on the catalytic partial oxidation of methane to syngas”,...., 10 (1), 56-62 (2002).

    5 Quincoses, C.E., Gonzalez, M.G., “Kinetic study on CO2reforming of methane”,...., 9 (2), 190-195 (2001).

    6 Wu, S.F., Beum, T.H., Yang, J.I., Kim, J.N., “The characteristics of a sorption-enhanced steam-methane reaction for the production of hydrogen using CO2sorbent”,...., 13 (1), 43-47 (2005).

    7 Pati?o, P., Pérez, Y., Caetano, M., “Coupling and reforming of methane by means of low pressure radio-frequency plasma”,, 84 (16), 2008-2014 (2005).

    8 Xu, J.H., Yeung, C.M.Y., Ni, J., Meunier, F., Acerbi, N., Fowles, M., Tsang, S.C., “Methane steam reforming for hydrogen production using low water-ratios without carbon formation over ceria coated Ni catalysts”,.., 345 (2), 119-127 (2008).

    9 Profeti, L.P.R., Ticianelli, E.A., Assaf, E.M., “Co/Al2O3catalysts promoted with noble metals for production of hydrogen by methane steam reforming”,, 87 (10/11), 2076-2081 (2008).

    10 Ma, Y., Xu, Y., Demura, M., “Catalytic stability of Ni3Al powder for methane steam reforming”,.., 80 (1/2), 15-23 (2008).

    11 Maluf, S.S., Assaf, E.M., “Ni catalysts with Mo promoter for methane steam reforming”,, 88 (9), 1547-1553 (2009).

    12 Yoshida, K., Begum, N., Ito, S., Tomishige, K., “Oxidative steam reforming of methane over Ni/α-Al2O3modified with trace noble metals”,.., 358 (2), 186-192 (2009).

    13 Nozaki, T., Hattori, A., Okazaki, K., “Partial oxidation of methane using a microscale non-equilibrium plasma reactor”,., 98 (4), 607-616 (2004).

    14 He, J.X., Han, Y.Y., Gao, A.H., Zhou Y.S., Lu Z.G., “Investigation on methane decomposition and the formation of C2hydrocarbons in DC discharge plasma by emission spectroscopy”,...., 12 (1), 149-151 (2004).

    15 Wang, Y., Liu, C.J., Zhang, Y.P., “Plasma methane conversion in the presence of dimethyl ether using dielectric-barrier discharge”,, 19 (3), 877-881 (2005).

    16 Bo, Z., Yan, J.H., Li, X.D., Chi, Y., Cen, K.F., “Plasma assisted dry methane reforming using gliding arc gas discharge: Effect of feed gases proportion”,.., 33 (20), 5545-5553 (2008).

    17 Li, X.S., Zhu, A.M., Wang, K.J., Xu, Y., Song, Z.M., “Methane conversion to C2hydrocarbons and hydrogen in atmospheric non-thermal plasma generated by different electric discharge techniques”,., 98 (4), 617-624 (2004).

    18 Wang, B.W., Yang, E.C., Xu, G.H., Hao, J.K., “Theoretical study of reaction paths and transition states on conversion methane into C2hydrocarbons through plasma”,...., 15 (1), 44-50 (2007).

    19 Wang, B.W., Xu, G.H., Sun, H.W., “Distribution of electrical field energy for conversion of methane to C2hydrocarbonsdissymmetrical electric field enhanced plasma”,, 15 (2), 115-121 (2006).

    20 Wang, B.W., Yang, K.H., Xu, G.H., “Effect of cooling methods on methane conversiondielectric-barrier discharges”,, 10 (5), 575-580 (2008).

    21 Wang, B.W., Zhang, X., Liu, Y.W., Xu, G.H., “Conversion of CH4, steam and O2to syngas and hydrocarbonsdielectric barrier discharge”,, 18 (1), 94-97 (2009).

    2009-01-12,

    2009-06-26.

    the National Natural Science Foundation of China (20606023, 20490203).

    ** To whom correspondence should be addressed. E-mail: wangbw@tju.edu.cn

    猜你喜歡
    張旭
    THE TIME DECAY RATES OF THE CLASSICAL SOLUTION TO THE POISSON-NERNST-PLANCK-FOURIER EQUATIONS IN R3*
    《古詩(shī)四帖》與晚明鑒藏家的“張旭”概念
    書(shū)法家肚子痛
    Effects of Froude number and geometry on water entry of a 2-D ellipse *
    The Three-Pion Decays of the a1(1260)?
    張旭典藏欣賞
    寶藏(2017年10期)2018-01-03 01:53:02
    『脫發(fā)』的大樹(shù)
    淺談氧化還原反應(yīng)的實(shí)際應(yīng)用
    許淇·中國(guó)畫(huà)《張旭》
    散文詩(shī)(2017年2期)2017-06-05 15:11:09
    打針
    久久精品国产99精品国产亚洲性色 | 最近最新中文字幕大全免费视频| АⅤ资源中文在线天堂| 好男人电影高清在线观看| 久久精品亚洲熟妇少妇任你| 亚洲avbb在线观看| 久久香蕉激情| 老汉色av国产亚洲站长工具| 97碰自拍视频| 中文字幕高清在线视频| 在线av久久热| 性色av乱码一区二区三区2| 在线观看免费视频网站a站| 国产精品1区2区在线观看.| 多毛熟女@视频| 午夜精品久久久久久毛片777| 90打野战视频偷拍视频| 好男人电影高清在线观看| 国产成+人综合+亚洲专区| 国产亚洲欧美精品永久| a在线观看视频网站| 久久精品aⅴ一区二区三区四区| 亚洲人成网站在线播放欧美日韩| 一区二区三区国产精品乱码| 久久午夜综合久久蜜桃| 可以免费在线观看a视频的电影网站| 欧美激情 高清一区二区三区| 亚洲精品国产区一区二| 最近最新中文字幕大全电影3 | av电影中文网址| 18禁裸乳无遮挡免费网站照片 | 很黄的视频免费| 性色av乱码一区二区三区2| www.自偷自拍.com| 国产亚洲精品av在线| 色av中文字幕| 好男人在线观看高清免费视频 | 欧美av亚洲av综合av国产av| 又黄又粗又硬又大视频| 欧美最黄视频在线播放免费| 又大又爽又粗| 亚洲av电影在线进入| 日韩欧美一区二区三区在线观看| 国产xxxxx性猛交| 99国产极品粉嫩在线观看| 黑人巨大精品欧美一区二区mp4| av天堂久久9| 午夜免费激情av| 俄罗斯特黄特色一大片| 日韩欧美一区视频在线观看| 国产高清视频在线播放一区| 亚洲一区二区三区不卡视频| www.熟女人妻精品国产| 免费在线观看黄色视频的| 欧美成人一区二区免费高清观看 | 欧美色欧美亚洲另类二区 | 欧美国产日韩亚洲一区| 久久午夜亚洲精品久久| 久久久久久久精品吃奶| videosex国产| 日韩欧美一区二区三区在线观看| 日本欧美视频一区| 久久国产精品影院| 超碰成人久久| 麻豆一二三区av精品| 天堂影院成人在线观看| 亚洲第一电影网av| 国产精品秋霞免费鲁丝片| 久久久久久久久久久久大奶| 国产一区二区三区在线臀色熟女| 国产主播在线观看一区二区| 天天躁狠狠躁夜夜躁狠狠躁| 成人特级黄色片久久久久久久| 国产亚洲精品av在线| 自拍欧美九色日韩亚洲蝌蚪91| 久久精品成人免费网站| а√天堂www在线а√下载| 亚洲精品国产精品久久久不卡| 男女做爰动态图高潮gif福利片 | 男人舔女人下体高潮全视频| 少妇粗大呻吟视频| 亚洲午夜精品一区,二区,三区| 成人永久免费在线观看视频| 国产日韩一区二区三区精品不卡| 国产亚洲av嫩草精品影院| а√天堂www在线а√下载| 国产一区二区在线av高清观看| 美女大奶头视频| 波多野结衣av一区二区av| 一区二区三区激情视频| 亚洲午夜理论影院| 两个人看的免费小视频| www国产在线视频色| 男人的好看免费观看在线视频 | 国产片内射在线| 极品人妻少妇av视频| 桃红色精品国产亚洲av| 日本免费a在线| 亚洲熟妇熟女久久| 丰满的人妻完整版| 天天躁狠狠躁夜夜躁狠狠躁| 久久欧美精品欧美久久欧美| 亚洲 欧美 日韩 在线 免费| 久久香蕉精品热| 一本综合久久免费| 看片在线看免费视频| 亚洲天堂国产精品一区在线| 熟女少妇亚洲综合色aaa.| а√天堂www在线а√下载| 亚洲无线在线观看| 十八禁网站免费在线| 国产精品一区二区三区四区久久 | 国产精品 欧美亚洲| 国产精品亚洲av一区麻豆| 黄片大片在线免费观看| 99国产精品一区二区蜜桃av| av视频在线观看入口| 久久人妻福利社区极品人妻图片| 色综合站精品国产| 久久久久久大精品| 久久中文字幕人妻熟女| 免费搜索国产男女视频| 一级片免费观看大全| 叶爱在线成人免费视频播放| 久久精品影院6| 亚洲成人国产一区在线观看| 女性生殖器流出的白浆| 一进一出好大好爽视频| 久久狼人影院| 午夜福利18| 亚洲国产精品sss在线观看| 美女午夜性视频免费| 国产精品香港三级国产av潘金莲| 精品国产一区二区三区四区第35| 美女高潮喷水抽搐中文字幕| 婷婷六月久久综合丁香| 国产av在哪里看| 欧美久久黑人一区二区| 亚洲情色 制服丝袜| 亚洲精品国产一区二区精华液| aaaaa片日本免费| 99精品久久久久人妻精品| 男人操女人黄网站| 欧美乱妇无乱码| 一区在线观看完整版| 别揉我奶头~嗯~啊~动态视频| 日本一区二区免费在线视频| 国产成人av教育| 免费在线观看黄色视频的| 亚洲人成电影免费在线| 欧美日韩福利视频一区二区| 亚洲五月婷婷丁香| 久久九九热精品免费| 丝袜人妻中文字幕| 在线观看午夜福利视频| a级毛片在线看网站| 一级片免费观看大全| 久久久久国内视频| 高清毛片免费观看视频网站| 18禁裸乳无遮挡免费网站照片 | 精品福利观看| 午夜激情av网站| 又紧又爽又黄一区二区| 亚洲av五月六月丁香网| 国产精品1区2区在线观看.| 亚洲午夜精品一区,二区,三区| 亚洲最大成人中文| 日韩精品中文字幕看吧| 国语自产精品视频在线第100页| 国产精品国产高清国产av| 变态另类成人亚洲欧美熟女 | 俄罗斯特黄特色一大片| 国产伦人伦偷精品视频| 国产高清有码在线观看视频 | 国产极品粉嫩免费观看在线| 在线观看日韩欧美| 女警被强在线播放| 日韩有码中文字幕| 久久这里只有精品19| 18禁黄网站禁片午夜丰满| 热99re8久久精品国产| 午夜老司机福利片| 国产精品久久视频播放| 长腿黑丝高跟| 99在线人妻在线中文字幕| 久久精品国产亚洲av香蕉五月| 色哟哟哟哟哟哟| 亚洲午夜精品一区,二区,三区| 精品久久久久久久人妻蜜臀av | 国产亚洲av高清不卡| 亚洲欧美激情在线| 在线观看www视频免费| 亚洲成人久久性| 日韩精品青青久久久久久| 亚洲美女黄片视频| 久久久国产欧美日韩av| 一级a爱片免费观看的视频| 国产又色又爽无遮挡免费看| 国产精品香港三级国产av潘金莲| 黄色女人牲交| 亚洲第一青青草原| 变态另类丝袜制服| 天天添夜夜摸| 国产亚洲精品久久久久5区| av视频在线观看入口| 亚洲精品久久国产高清桃花| 大香蕉久久成人网| 黄色片一级片一级黄色片| 性少妇av在线| 欧美中文综合在线视频| 淫妇啪啪啪对白视频| 一区二区三区国产精品乱码| 老司机深夜福利视频在线观看| 国语自产精品视频在线第100页| 女人被躁到高潮嗷嗷叫费观| 午夜福利欧美成人| 国产黄a三级三级三级人| 免费观看人在逋| 99riav亚洲国产免费| 国产麻豆成人av免费视频| 亚洲一区中文字幕在线| 少妇 在线观看| 此物有八面人人有两片| av在线播放免费不卡| 成人免费观看视频高清| 免费看美女性在线毛片视频| 日韩av在线大香蕉| 免费看十八禁软件| 99精品久久久久人妻精品| 欧美日韩一级在线毛片| x7x7x7水蜜桃| 成人国语在线视频| 久久热在线av| 91在线观看av| 美女国产高潮福利片在线看| 精品不卡国产一区二区三区| 纯流量卡能插随身wifi吗| 黑人巨大精品欧美一区二区蜜桃| 97人妻精品一区二区三区麻豆 | 色尼玛亚洲综合影院| 久久国产亚洲av麻豆专区| 亚洲一区中文字幕在线| 老熟妇仑乱视频hdxx| 久久狼人影院| 国产成年人精品一区二区| 国产成人精品在线电影| 午夜福利在线观看吧| 久久香蕉激情| 日韩大尺度精品在线看网址 | 一a级毛片在线观看| 亚洲av美国av| 亚洲七黄色美女视频| 国产精华一区二区三区| 在线观看免费午夜福利视频| 亚洲一区高清亚洲精品| www.熟女人妻精品国产| 国产99久久九九免费精品| 又黄又粗又硬又大视频| 国产精品免费视频内射| 久久欧美精品欧美久久欧美| 美女免费视频网站| 国产私拍福利视频在线观看| АⅤ资源中文在线天堂| 叶爱在线成人免费视频播放| 日本a在线网址| 母亲3免费完整高清在线观看| 夜夜爽天天搞| 久久性视频一级片| 日韩有码中文字幕| 桃色一区二区三区在线观看| 精品日产1卡2卡| 91大片在线观看| 免费一级毛片在线播放高清视频 | 欧美黑人欧美精品刺激| 午夜福利免费观看在线| 老鸭窝网址在线观看| 午夜精品久久久久久毛片777| 成年女人毛片免费观看观看9| 国产片内射在线| 亚洲国产欧美网| 黄色成人免费大全| 亚洲专区中文字幕在线| 欧美老熟妇乱子伦牲交| videosex国产| 在线观看午夜福利视频| 黄色片一级片一级黄色片| www.www免费av| 精品一区二区三区四区五区乱码| 欧美大码av| 在线十欧美十亚洲十日本专区| 18禁观看日本| 国产av一区二区精品久久| 免费高清在线观看日韩| 久久久久国内视频| 成年女人毛片免费观看观看9| 国产在线精品亚洲第一网站| 亚洲av五月六月丁香网| 波多野结衣高清无吗| 99国产精品免费福利视频| 一个人观看的视频www高清免费观看 | 久久久久久久久免费视频了| 日韩国内少妇激情av| 999久久久国产精品视频| 国产熟女午夜一区二区三区| 无人区码免费观看不卡| 99久久综合精品五月天人人| 午夜成年电影在线免费观看| 亚洲av片天天在线观看| 亚洲精品中文字幕在线视频| 国产高清激情床上av| 90打野战视频偷拍视频| 午夜福利视频1000在线观看 | 午夜精品国产一区二区电影| 90打野战视频偷拍视频| 久久久精品国产亚洲av高清涩受| 国内精品久久久久精免费| 欧美亚洲日本最大视频资源| 他把我摸到了高潮在线观看| 给我免费播放毛片高清在线观看| 高清在线国产一区| 老熟妇乱子伦视频在线观看| avwww免费| 日本 欧美在线| 91大片在线观看| 国产亚洲av高清不卡| 一进一出好大好爽视频| 久久久国产成人精品二区| 免费在线观看日本一区| 欧美不卡视频在线免费观看 | 久久午夜亚洲精品久久| 伦理电影免费视频| 一边摸一边抽搐一进一出视频| 亚洲精品一区av在线观看| av有码第一页| 欧美成狂野欧美在线观看| 午夜成年电影在线免费观看| 老司机深夜福利视频在线观看| 波多野结衣高清无吗| 免费高清视频大片| 国产色视频综合| 中文字幕最新亚洲高清| 精品福利观看| 国产精品,欧美在线| 一本久久中文字幕| 成人18禁高潮啪啪吃奶动态图| 国产视频一区二区在线看| 宅男免费午夜| 午夜福利视频1000在线观看 | 国产真人三级小视频在线观看| 丝袜美腿诱惑在线| 国产亚洲欧美98| 一本大道久久a久久精品| 嫩草影视91久久| 国产黄a三级三级三级人| 好男人在线观看高清免费视频 | 精品欧美一区二区三区在线| 国产精品国产高清国产av| 天天躁狠狠躁夜夜躁狠狠躁| 免费看美女性在线毛片视频| 国产亚洲欧美98| 国产乱人伦免费视频| 日韩欧美一区视频在线观看| 夜夜爽天天搞| 成人18禁高潮啪啪吃奶动态图| 国产99白浆流出| www.999成人在线观看| 午夜精品久久久久久毛片777| 亚洲精品av麻豆狂野| 欧美日本亚洲视频在线播放| 视频区欧美日本亚洲| 美女 人体艺术 gogo| 一本综合久久免费| 国产主播在线观看一区二区| 91国产中文字幕| 国内精品久久久久精免费| 免费在线观看影片大全网站| 国产一区二区三区综合在线观看| 在线观看免费午夜福利视频| 91九色精品人成在线观看| 国产三级在线视频| 亚洲黑人精品在线| 午夜久久久久精精品| 少妇 在线观看| 国产亚洲欧美在线一区二区| 十分钟在线观看高清视频www| 欧美乱色亚洲激情| 少妇被粗大的猛进出69影院| 在线观看免费日韩欧美大片| 啦啦啦韩国在线观看视频| 亚洲少妇的诱惑av| 狠狠狠狠99中文字幕| 亚洲天堂国产精品一区在线| 激情视频va一区二区三区| 亚洲第一青青草原| 中文字幕人妻熟女乱码| 一级毛片精品| 嫩草影视91久久| 黄色视频,在线免费观看| 欧美丝袜亚洲另类 | 国产主播在线观看一区二区| 啪啪无遮挡十八禁网站| 欧美日韩亚洲国产一区二区在线观看| 日韩精品中文字幕看吧| 久热这里只有精品99| 欧美成人一区二区免费高清观看 | 亚洲男人的天堂狠狠| 亚洲精品在线美女| 极品教师在线免费播放| 精品久久蜜臀av无| 又紧又爽又黄一区二区| 久久久久久大精品| www国产在线视频色| 亚洲欧美日韩另类电影网站| 亚洲成av片中文字幕在线观看| 最新在线观看一区二区三区| 激情在线观看视频在线高清| 亚洲av成人av| 两人在一起打扑克的视频| 成人国产综合亚洲| 变态另类丝袜制服| 熟女少妇亚洲综合色aaa.| 亚洲五月色婷婷综合| 黄色视频不卡| 免费在线观看亚洲国产| 国产精品国产高清国产av| 在线免费观看的www视频| 亚洲人成电影免费在线| 熟妇人妻久久中文字幕3abv| av欧美777| 国产欧美日韩综合在线一区二区| 国产亚洲精品一区二区www| 一a级毛片在线观看| 好男人在线观看高清免费视频 | 欧美久久黑人一区二区| 欧美+亚洲+日韩+国产| av超薄肉色丝袜交足视频| 日日夜夜操网爽| av天堂在线播放| 亚洲五月天丁香| 国产激情欧美一区二区| av在线天堂中文字幕| 他把我摸到了高潮在线观看| 99香蕉大伊视频| 超碰成人久久| 国产精品九九99| av天堂久久9| 人人妻人人澡欧美一区二区 | 久久影院123| 午夜福利高清视频| 两个人视频免费观看高清| 国产日韩一区二区三区精品不卡| 老熟妇仑乱视频hdxx| 欧美日韩乱码在线| 黑人欧美特级aaaaaa片| 涩涩av久久男人的天堂| 1024视频免费在线观看| 黑人操中国人逼视频| 黄片小视频在线播放| 夜夜夜夜夜久久久久| 亚洲精品中文字幕在线视频| 满18在线观看网站| 可以在线观看毛片的网站| 精品久久久久久,| 午夜精品在线福利| 欧美精品啪啪一区二区三区| 欧美日韩中文字幕国产精品一区二区三区 | 一级,二级,三级黄色视频| 午夜福利影视在线免费观看| 国产91精品成人一区二区三区| 性少妇av在线| 亚洲电影在线观看av| 精品免费久久久久久久清纯| 夜夜躁狠狠躁天天躁| 男人舔女人下体高潮全视频| 欧美日韩一级在线毛片| 少妇 在线观看| 91av网站免费观看| 日韩大尺度精品在线看网址 | 中文字幕人妻熟女乱码| 手机成人av网站| videosex国产| 黄色丝袜av网址大全| 日韩欧美国产一区二区入口| 老鸭窝网址在线观看| 国产成人精品久久二区二区免费| 两个人免费观看高清视频| 黄色片一级片一级黄色片| 在线观看66精品国产| 精品久久久久久久毛片微露脸| 在线播放国产精品三级| 伊人久久大香线蕉亚洲五| av网站免费在线观看视频| 中文字幕久久专区| 男人舔女人下体高潮全视频| 欧美日韩福利视频一区二区| 亚洲一区中文字幕在线| 国产精品av久久久久免费| 国产1区2区3区精品| 欧美午夜高清在线| 精品久久蜜臀av无| 国产精品影院久久| 波多野结衣一区麻豆| 欧美不卡视频在线免费观看 | 久久国产亚洲av麻豆专区| 一进一出好大好爽视频| 欧美丝袜亚洲另类 | 久久天躁狠狠躁夜夜2o2o| 国产亚洲精品综合一区在线观看 | 国产精品 欧美亚洲| 亚洲美女黄片视频| 男人操女人黄网站| 国产精品免费视频内射| 18禁美女被吸乳视频| 一级毛片精品| 在线免费观看的www视频| 国产激情久久老熟女| 久久国产乱子伦精品免费另类| 亚洲精品久久国产高清桃花| 两性午夜刺激爽爽歪歪视频在线观看 | 国产亚洲精品久久久久5区| 亚洲色图综合在线观看| 国产精品久久久久久精品电影 | 成年女人毛片免费观看观看9| 午夜福利高清视频| 桃红色精品国产亚洲av| 欧美日韩精品网址| 午夜亚洲福利在线播放| 在线观看舔阴道视频| 亚洲熟妇熟女久久| 久久人妻av系列| 亚洲精品久久成人aⅴ小说| 成人国语在线视频| 男人舔女人的私密视频| 国产亚洲av嫩草精品影院| 老司机在亚洲福利影院| 亚洲欧美一区二区三区黑人| av电影中文网址| 成人免费观看视频高清| av天堂久久9| 男女做爰动态图高潮gif福利片 | 黄片播放在线免费| 亚洲精品久久成人aⅴ小说| 国产精品亚洲av一区麻豆| 久久人人97超碰香蕉20202| 黄片大片在线免费观看| 手机成人av网站| 美女高潮到喷水免费观看| 我的亚洲天堂| 99热只有精品国产| 天堂影院成人在线观看| 亚洲片人在线观看| 91麻豆av在线| 亚洲国产精品sss在线观看| 免费在线观看亚洲国产| 999久久久国产精品视频| 久9热在线精品视频| 久久婷婷成人综合色麻豆| 久久午夜亚洲精品久久| 亚洲国产高清在线一区二区三 | 黑人巨大精品欧美一区二区蜜桃| 亚洲色图 男人天堂 中文字幕| 国产视频一区二区在线看| 久久天躁狠狠躁夜夜2o2o| 国产精品99久久99久久久不卡| 国产精品久久久久久人妻精品电影| 成人精品一区二区免费| 日韩三级视频一区二区三区| 午夜日韩欧美国产| 久久人妻福利社区极品人妻图片| 国产亚洲精品一区二区www| 俄罗斯特黄特色一大片| 亚洲av成人一区二区三| 国产一区二区三区在线臀色熟女| 久久国产亚洲av麻豆专区| 色综合站精品国产| 久久 成人 亚洲| 久久久久久久午夜电影| 一级毛片精品| 久久香蕉国产精品| 一级毛片高清免费大全| 亚洲精品粉嫩美女一区| 日日夜夜操网爽| 国产欧美日韩精品亚洲av| 国产aⅴ精品一区二区三区波| 国产免费av片在线观看野外av| 老汉色∧v一级毛片| 国产欧美日韩一区二区精品| 亚洲av成人不卡在线观看播放网| 操美女的视频在线观看| 日本欧美视频一区| 成人18禁在线播放| 深夜精品福利| 亚洲中文日韩欧美视频| 欧美日韩乱码在线| 九色亚洲精品在线播放| 如日韩欧美国产精品一区二区三区| 每晚都被弄得嗷嗷叫到高潮| 日本撒尿小便嘘嘘汇集6| 国产又色又爽无遮挡免费看| 九色国产91popny在线| 久久久久久国产a免费观看| 中文字幕精品免费在线观看视频| 一级片免费观看大全| 亚洲精品中文字幕在线视频| 99久久精品国产亚洲精品| 在线观看免费视频网站a站| 我的亚洲天堂| 99国产综合亚洲精品| 国产精品一区二区精品视频观看| 香蕉国产在线看| 大型黄色视频在线免费观看| 成年女人毛片免费观看观看9| 免费在线观看完整版高清| 女性被躁到高潮视频| 亚洲欧美激情综合另类|