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1、基于汽车氢燃料的有机液体氢化物贮氢技术.MCH的随车脱氢反应及其催化剂研究陈进富吴芳云朱亚杰(石油大学，北京102200)文摘：MCH随车脱氢作为一种非稳态的、反应条件苛刻的过程，要求其脱氢催化剂具有良好的低温活性和高温稳定性，现有的脱氢催化剂尚难满足其要求。对碱改性工业3861催化剂的研究表明：碱性氧化物能有效地改善催化剂的脱氢性能，Pt-Sn-K(0.4%)r-AlO3催化剂的稳定性较工业3861催化剂可提高8倍以上，但低温活性尚需继续提高；在常压、WHSV6h1、300400、纯MCH进料时，MCH的有效贮氢量为2.786.12；空速与催化剂脱氢活性无明显依赖关系，这为实现随车脱氢反应器
2、的小型化提供了可能性。关键词：随车脱氢，有机液体氢化物贮氢，脱氢催化剂，有效贮氢量，氢燃料0引言利用甲基环己烷(MCH)-甲苯(TOL)-氢(H)的一对可逆化学反应贮氢的MTH贮氢技术，大致可分为两种应用情形：一是固定式应用，即通过建立固定的脱氢装置以实现寄存氢的释放。如未来“氢经济”时代的大规模氢能发电，即可设想通过固定装置脱氢，供氢燃料电池发电使用，可以预见，这种释氢方式采用现有工业脱氢技术也是容易实现的。二是移动式应用，如氢能汽车。正是这种应用方式，赋予了该贮氢技术新的任务，提出了新的要求和挑战。瑞士的M.Taube等人1，2已开发出两代(MTH-和MTH-)随车供氢氢燃料汽车。结果表明
3、，利用MCH随车脱氢供汽车氢燃料，在技术上是可行的，但现有的脱氢催化剂尚难以满足随车脱氢的需要，主要表现在催化剂的低温活性较差，高温稳定性又欠佳两方面。MTH随车供氢系统主要有以下特点：(1)随车脱氢反应的能量由尾气废热源提供。研究表明，维持脱氢反应器高转化率(MCH释氢效果更佳)所需能量仅靠尾气提供尚不足够，解决的方案一是燃烧少量的甲苯，二是分流脱氢反应器产生的氢气并燃烧供能。(2)随车脱氢反应器存在明显的轴向温度分布和径向温度分布并有较显著的温度波动。MTH-型试验汽车轴向中心温度为320480。(3)MCH随车脱氢反应是无氢循环的初始非临氢反应。脱氢反应的不稳定性(反应过程是非稳态的)和
4、反应条件的苛刻化对脱氢催化剂提出了更严格的要求。强调催化剂的高温稳定性和低温脱氢活性对提高MTH贮氢技术在随车供氢燃料应用方面的有效性是极其重要的。1实验部分1.1催化剂实验采用工业3861重整催化剂及作者对3861催化剂的碱改性催化剂。催化剂的改性包括氧化态3861催化剂的除氯处理3和Li、K、Ba、Mg对除氯催化剂的改性处理。基础催化剂3861的物性数据见表1。表1工业3861催化剂的物性数据物性Pt(wt.%)Sn(wt.%)Cl(wt.%)比表面(mg)孔体积(mlg)堆比重(gml)粒度(mm)数据0.360.311.22000.60.61.22.01.2活性评价 催化剂活性评价在微
5、反-色谱实验装置上进行(见图1)；脱氢反应放大实验在自制的管式反应器(14mm，L350mm)内进行(见图2)。催化剂活性以MCH的脱氢转化率表示。图1研究MCH脱氢反应的微反-色谱实验装置1氢气瓶2氮气瓶3减压阀4干燥器5流量调节阀6流量计7截止阀8微量泵9压力表10反应器11加热炉12六通阀13色谱议14积分仪15冷凝器16空气压缩机17流量控制器18预热器2实验结果与讨论2.1工业Pt-Snr-AlO催化剂的非临氢反应MCH随车脱氢时，易于实现的过程是采用纯MCH(氢载体)进料，这意味着反应体系存在无氢循环，它是一个初始非临氢的反应过程。含Cl和除Cl的Pt-Snr-AlO催化剂非临氢反
6、应实验结果如图3所示。反应条件为：400，0.12MPa，空速WHSV14h1，NMCH（mol比）31。图3Pt-Snr-AlO催化剂非临氢反应实验结果图4除Cl催化剂在高温下的脱氢性能500或550，0.12MPa，WHSV6h1，NMCH31（mol）由图3可知，在无氢循环的苛刻随车脱氢反应条件下，工业Pt-Snr-AlO催化剂的MCH脱氢稳定性是难以令人满意的。在上述反应条件下，含Cl催化剂的稳定活性仅为6h，除Cl催化剂稳定性虽有所提高，但增幅不大，反应12.0h后其活性已开始下降。一般认为，Cl的存在提供了催化剂的表面酸中心，Cl含量越大，其表面酸中心越多，酸量越大；催化剂结焦失活
7、速度与表面酸中心数量及强度有密切关系。因此，对于MCH随车脱氢催化剂，除去氯离子，减少酸中心数量，降低酸强度是有利的。这与见诸文献的小分子烃类脱氢催化剂的研究结果相一致4。图4所示是除Cl催化剂在更高的反应温度(500和550)条件下的脱氢性能。汽车尾气温度高达7775，实测的随车脱氢反应器轴向中心温度也可达480(意味着反应器管壁温度会更高)，因此考察催化剂在500左右的脱氢性能是有意义的。图4的结果表明，仅靠除Cl提高催化剂稳定性是不够的，远不能满足实际随车脱氢操作的需要。2.2碱改性Pt-Snr-AlO催化剂的脱氢性能作者的研究表明，碱金属氧化物LiO、KO和碱土金属氧化物BaO、MgO
8、能有效地改进工业除氯Pt-Snr-AlO的脱氢性能。碱含量(以金属单质计)为0.4wt%的改性催化剂低温脱氢活性(350)和高温稳定性(500)实验结果列于表2。由表2可知，在500的高温反应条件下，碱金属Li和K具有较好的抗失活能力，其改性催化剂维持反应初活性(x01.0)及活性降为x0.8的反应时间明显长于Ba、Mg改性催化剂；另一方面，在350反应时，K、Mg、Ba改性催化剂有较好的低温脱氢活性，其活性分别为0.73、0.75和0.76，400反应时K改性催化剂的活性可达0.99。这表明适量K改性工业Pt-Snr-AlO可获得较好的低温脱氢活性和良好的高温稳定性。表2加量0.4%的碱改性
9、催化剂脱氢性能 反应温度脱氢初活性xxx的最大反应时间(min)x08x的反应时间(min)()LiKMgBaLiKMgBaLiKMgBa3500.610.730.750.764000.920.990.990.99待添加的隐藏文字内容25001.01.01.01.0420420606042051012590x为MCH脱氢转化率，x为脱氢反应的初活性图5所示是Pt-Sn-K(0.4%)r-AlO催化剂的温度与MCH转化率关系的实验结果。实验条件为300500、0.12MPa、WHSV6h1、纯MCH进料。可见，催化剂在400以上反应时，MCH基本可完全释放出寄存的氢，在300、350、380反应
10、时可分别释放理论贮氢量(6.18wt.%)的45、73和90，即在300400随车脱氢时，其有效贮氢量为2.786.12。如何更进一步提高300左右的低温脱氢活性，有待继续研究。图5反应温度对MCH脱氢转化率的影响图6空速对改性催化剂脱氢性能的影响适宜的随车脱氢催化剂应能在较大的空速下保持良好的活性和稳定性，以实现脱氢反应器的小型化并使其具有产生足量氢气的能力。图6所示是在400、0.12MPa、WHSV214h1、纯MCH或NMCH31进料的条件下，Pt-Sn-K（04）r-AlO催化剂的脱氢活性随空速变化的实验结果。可见，当WHSV8h1时，MCH脱氢转化率随空速变化甚小；当空速为814h
11、1，随空速增加，两种进料方式的脱氢转化率均有所下降且以纯MCH进料降幅稍大。但总的来看，在较大的空速范围内，催化剂的活性变化不显著。这说明随车脱氢反应器可望采用较大的空速操作，它为减少脱氢反应器体积、降低催化剂用量、实现随车脱氢反应器的小型化提供了可能性。2.3Pt-Sn-Kr-AlO催化剂的单管放大实验及稳定性考察图7MCH脱氢单管放大实验结果单管放大实验装置如图2所示。反应物MCH经微量泵准确计量后由反应管预热段加热至250，气态反应物MCH随即进入反应器(内装Pt-Sn-K催化剂或Pt-Sn催化剂各9.0g，其重量为微反的60倍，反应管两端以石英砂充填，3060目的催化剂填充于反应器中部
12、)，反应后的产物经冷凝器冷凝，液体产物收集，气体产物由皂泡流量计计量后放空。图7所示是Pt-Sn-K（04）r-AlO和工业3861催化剂在常压、400、WHSV6h1反应条件下的放大实验对比结果。由图7可知，改性催化剂在至少100h内其脱氢转化率和产氢速率可基本不变，实验测得的转化率和产氢速率分别为0.92、62.4mlHg(cat)*min(均为平均值)。而工业3861催化剂维持相同转化率或产氢速率的时间仅为12h。可见，改性催化剂的稳定性可至少提高8倍(10012833)。3结论(1)MCH随车脱氢是一个非稳态、无氢循环的过程，适宜的催化剂应具有高温稳定性好，低温活性又高的特点。(2)碱
13、改性3861催化剂的高温稳定性有明显提高。Pt-Sn-K（04）r-AlO催化剂在常压、400、WHSV6h1、纯MCH进料时其稳定性较3861催化剂至少可提高8倍；但300左右的低温活性仍有待继续改善。在其它条件相同，温度为300400时，其有效贮氢量为2.786.12wt.%。(3)在空速WHSV14h1的范围内，Pt-Sn-K改性催化剂活性与空速无显著依赖关系，这为实现随车脱氢反应器的小型化提供了可能性。参考文献1Jain I P，Taube M.Int J Hydrogen Energy，1988，13（1）：15-232Schucan T H and Taube MProc6th W
14、orld Hydrogen Energy Conf，1986，8268303潘韫，杨锡尧，庞礼催化学报，1989，10(1)：7-124USP5344805，19945TaubeMandTaubePProc3thWorldHydrogenEnergyConf，1980，10771085HYDROGENSTORAGEOFORGANICLIQUIDHYDRIDEBASEDONFUELFORHYDROGENVEHICLESONBOARDMCHDEHYDROGENATIONCONSIDERINGOFTHEENVIRONMENT ITSCATALYSTChenJinfuWuFangyunZhuYajie
15、(UniversityofPetroleum，Beijing102200）Abstract：This paper deals with MCH dehydrogenation process considering of the environment on board based on hydrogen fuel for vehiclesBecause MCH dehydrogenation on board is an transient process（for example，temperature distribution fluctuation）and is operated wit
16、hout the addition of hydrogen to the feed of MCH，the dehydrogenation catalysts on board exist the drawbacks of low activity during 300350 and low stability at about 500at presentAuthors study results show that alkali metal oxides（K2O and LiO）and alkali-earth metal oxides （BaO and MgO） which modify 3
17、861 industry catalyst can effectively improve the catalysts stabilityThe stability of Pt-Sn-K（04）r-AlO catalyst is at least 8 times more than that of 3861 industry catalyst in the reaction conditions：400，WHSV6h1，atmosphere pressure，pure MCH feedBut the low temperature activity of the modification ca
18、talyst needs to be further improvedThe amount of hydrogen storage is 2.786.12wt.% at the temperature range 300400Keywords：dehydrogenationonboard，hydrogenstorageoforganicliguid hydride，dehydrogenationcatalyst，amountofhydrogenstorage，hydrogenfuelEditors note: Judson Jones is a meteorologist, journalis
19、t and photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio and through the crackling static from space hear the faint beeps of the
20、 worlds first satellite - Sputnik. I also missed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I was fascinated with what goes on in the sky, and when NASA pulled the plug on the shuttle program I was
21、heartbroken. Yet the privatized space race has renewed my childhood dreams to reach for the stars.As a meteorologist, Ive still seen many important weather and space events, but right now, if you were sitting next to me, youd hear my foot tapping rapidly under my desk. Im anxious for the next one: a
22、 space capsule hanging from a crane in the New Mexico desert.Its like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall from the edge of space - live.The (lack of) air up there Watch man jump from 9
23、6,000 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in a vertical straight line we would be go for launch.I feel this mission was cre
24、ated for me because I am also a journalist and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgartner, must have that same feeling, at a level I will never reach. However, it di
25、d not stop me from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thicker than a dry cleaning bag, scraped the ground I knew it was over.How claustro
26、phobia almost grounded supersonic skydiverWith each twist, you could see the wrinkles of disappointment on the face of the current record holder and capcom (capsule communications), Col. Joe Kittinger. He hung his head low in mission control as he told Baumgartner the disappointing news: Mission abo
27、rted.The supersonic descent could happen as early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move t
28、hrough the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere
29、. As he crosses the boundary layer (called the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, Fearless Felix will unclip. He will roll back the door.Then, I would assume, he will slowly step out o
30、nto something resembling an Olympic diving platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so despite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving
31、 into the shallow end.Skydiver preps for the big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to
32、 stop him completely.If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy his 270-square-foot (25-square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).In
33、order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned, it wont. Baumgartner still will free fall at a speed that would cause you and
34、 me to pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
