化工系外文翻译

1、焦炉煤气在活性碳作用下干燥重整合成甲摘要焦炉煤气在以活性炭为催化剂进行干燥重整已经被研究用来生产合适的甲醇合 成气，这项工作的主要目的是研究焦炉煤气中氢数量对焦炉煤气干燥重整的影响, 以及其它条件的影响，利如温度和体积空速的影响。结果发现，反向水煤气变换 （RWGS）反应的发生是由于焦炉煤气中氢的存在，而且它对反应的影响随着温度 的降低过程而增加。这种情可能引起的焦炉煤气中的氢组成的变化，并由此预计。 这种反应可以在约1000度的高温下生产适合用于合成甲醇的合成气。结果还发 现，空速的增加对水煤气变换反应有利。此外，活性炭被证明是最适合焦炉煤气 生产合成甲醇的合成气的催化剂。关键词：焦炉煤气;

2、干重整，合成气，甲醇1 简介合成气是大多数氢产品和各种有机物的生产原料，它主要由氢气和一氧化碳组成, 它基本上产自天然气和石油，但有限的化石燃料的供应和应对气候变化以及温室 气体（GHG）的排放，加强了对生产的替代工艺，如生物质气化1或沼气重整研 究3。焦炉气体（焦炉煤气），它可以被认为是焦化厂的副产品，主要由氢气（55-60%）,甲烷（23-27%），氧化碳（5-8%）和 N2 （3-5%），以及其他碳 氢化合物，其中硫化氢和氨的比例小。这种气体大部分是用作炼焦炉和钢铁厂的 燃料，但往往对过剩焦炉煤气的使用不能使用这种方式，所以通常放散燃烧，这 也引起了环境污染的问题和如何解决环境的问题 4

3、-9。对于多余的焦炉煤气如 何处理，我们可以通过氢分离手段加以利用或通过部分氧化 8,10,11蒸汽重整 7,12,14,15或干燥重整4,5,16来生产合成气 12,13，生。这样生产的合成气可 以反过来用于不同其他有机合成产品，主要是甲醇。虽然大多数研究者都集中在 焦炉煤气水蒸汽转化法的研究，在过去的几年焦炉煤气干燥重整也已经被深入的 研究4,5,16。由于它提供了比水蒸汽重整更理想的反应条件和环境，如二氧化 碳消耗的能源或节能，有着许多优势。另一个重要的优势在于焦炉煤气干燥重整 的好处是获得了氢气和一氧化碳的比率约2的合成气，这是一个理想中合成甲醇 的合成气的比率17,18图中所示只有一

4、个步是提供甲烷和二氧化碳反应时的化 学计量条件。从图1中可以看出，这个过程可以被视为一种方法，即二氧化碳的 部分再循环、部分参加反应“，在理论上甲醇燃烧时会产生一半的二氧化碳。 这项技术的研究的前景是深远的，由于汽车燃料对甲醇的需求，和氢燃料电池或 生物柴油的原料量的迅速增加19。这项工作主要目的是对焦炉煤气的干燥重整的研究，以生产合适的原料气 H2/C0作为合成甲醇的合成气。焦炉煤气干燥重整中的活性炭，已被证明是一个 对甲烷干燥重整有效的催化剂。氢气数量是影响焦炉煤气干燥重整和其它反应条 件，如温度或空速度，是目前研究重心。2实验焦炉煤气的干燥重整是在常压下固定床石英反应器及其在电毛皮纳采激

5、烈。 在催化剂床中的反应温度进行监测，并通过一个K型热电偶手段控制。商业活性 炭具有高比表面积（Filtracarb FY5）,表1中列出了其主要特点，它可以被用 来作焦炉煤气干燥重整的催化剂。在前一次实验中，甲烷和二氧化碳在原料中的比例为1：1，在余下的实验 当中，增加了氢气的量以便研究对甲烷在干燥重整过程中存在的影响。氢气除了 引起三元混合气体的组成变化，其中氢气占53%、甲烷和二氧化碳各占23%, 为了使H2/CH4的比率在焦炉气特性的范围内，所以干燥重整中甲烷和二氧化碳 的反应的条件应控制在反应的化学计量值的范围之内，对于焦炉煤气中的CO的 影响已超出目前的范围这项工作，将在适当时候研

6、究。为了评估对焦炉煤气干 重整温度的影响，试验完成了大气压力下的三个不同 温度（800, 900，和1000C 型）下的反应，此外，在以上3个不同的反应下，每小时的总体积空速，体积空 速每小时（0.75，1,和 1.5Lg-1 h-1，它代表了 0.16，0.22， 0.32 Lg-1 h-1 r 的甲烷含量，VHSVCH ）进行研究后，发现如空速增加则会减少了催化剂床层的CH 4质量。干燥重整反应中碳催化剂在石英反应器内进行，该系统是用氮气冲洗（流 量为15分钟60mLmin率），然后加热到预先设定的反应温度。该产品在Tedlar 气体样品采集实验期间定期袋。由于在实验中形成一些蒸汽，冷凝器

7、置于反应器 后以防止水流入袋。样品的分析在长瓦里安-3800用热导检测器和装备色谱分 析仪（80/100 Hayesep Q和 80/100 Molesieve 13X 型）串联。第二格是由一名 为二氧化碳和碳氢化合物分析六通阀通过。甲烷和二氧化碳的转化率和H2的选择性分别计算后确定所生产的水量和出 水口流量，通过关于非线性方程组的牛顿迭代法的一个程序和使用微软Excel 的规划求解工具进行计算，并在5%误差收盘质量平衡。使氢的选择性，（如 轻烃，C2,或水），甲烷转化为氢气或其它物种数量最大。参数按质量标准按照 式1-3进行计算：出甲烷，二氧化碳和氢气在反应器入口处和出口处的摩尔分子 质量。

8、3结果与讨论在我们之前的试验中20，对干燥重整的甲烷与二氧化碳（反应1）通过对 活性炭FY5进行了研究（见图2）。对该干燥重整反应中二氧化碳作用进行讨论。 实验进行了 6小时以上的时间，在反应在温度为800r和常压下进行甲烷和二氧化碳在空速为0.16Lg-ih-1小时（共0.32Lg -1 h -1VSHV）转化率超过40%。如果反应过程进行采用三元混合气体，（GTM）在三元气体中的氢的存在， 有两种不同的现象可能发生：（i）均衡转移到反应物（见反应1），产生较低甲 烷和二氧化碳，（ii）以及反向水煤气变换反应（RWGS）发生（反应2）造成在 CO2转化的增加和水的形成16,21,22。这两种

9、作用的结果会降低氢化物的产量。这两种现象都是发生在温度为800度时气体混合物的干燥重整，并导致了 甲烷和从甲烷干重整造成二氧化碳转换的变化。正如图3所示，甲烷转化降至 40%以下开始的反应，反应6小时后达到20%左右。仔细的观察，在减少可能 由于初始不稳定的第一分钟。此外，二氧化碳转化率比在干燥的甲烷重整（图2）, 这表明RWGS比对的平衡转移效应的影响更大。在冷凝器收集的大量水，约占8vol% 反应的产品，这个也是由其他研究者报告的建议16。除了降低氢气的产量和改 变H2/C0比，水也会阻碍甲醇合成，因为它会使铜催化剂的失能的影响23。温度的影响图4显示了在900C时的三元混合气体干燥重组反

10、应。可以看出，此时甲烷 转化率大于50%,在整个反应实验中可以看出，这个转化率是800C时测试所达 不到的，CO2的转化率也高于它在800C的。由于RWGS反应（反应2）小于甲 烷干重整（反应1）吸热，反应温度的增加提高了干燥改革吸热，便出现了较高 的甲烷转化率，因此，会产生更多的氢，而水则会减少。实际上，随着CO2转 化率的增加，会使干燥重整反应增强，而不是RWGS反应，因为反应所需的水量， 在近3次的实验明中显低于800C时的。其他可能的解释是甲烷水蒸在高温度下 进行重整（反应3）。但是，这个机制似乎不太可能，因为它会导致甲烷和二氧化碳的转换而没 有发生类似的增量，在图4中可以看到。然而，

11、RWGS反应（反应2）和蒸汽重 整反应（反应3）引起的干重整反应（反应1），这使得难以区分此种反应遵循什 么样的规律。图5显示了在1000C时所进行的测试的转换结果。反应温度的增加同时也增加 了转换结果，多达80%的甲烷和95%的二氧化碳的实验后6小时。此外，在1000C 时没有水的生产。所以，在此温度下工作，它有可能避免水煤气变换的发生，最大限度 地利用氢。3.2空速的影响的体积空速在900C和1000C研究空速对反应过程的影响。在800C温度，因为在空速 增加而导致转换物的进一步减少20和水的形成，这将使它很难研究的空速变化 和对反应进程的影响。三元混合气体在900C时采用三种不同的空速（

12、分别是0.75，1，1.5Lg-1 h-1小时下进行干燥重整反应，图6所示反应的结果。可以看出，甲烷和二氧化 碳的转换是受空速变化的影响。因此，转换率的影响在于空速变化，转换率随着 空速增加而降低。随着水煤气变换反应空速增加。反应器中二氧化碳浓度的也增 加。由于存在较高氢气的含量，二氧化碳可能是限制水煤气变换反应的物种。因 此，二氧化碳的转换应避免高的转换，以防止水煤气变换的副反应。图7显示了通过在1000C和0.75Lg-ih-1和1.50Lg-1 h-1时两次测试，出现了两种不同的结果。正如上文所述，在反应条件为0.75Lg-1 h-1 1000C时不产生 水。当空速增加到1.50Lg -

13、1 h -1小时，则会产生一些水，由于干重整反应转化减 少而造成的二氧化碳浓度增加。然而，水收集不到产品总额的1vol%，因为在 1000 C二氧化碳转化率不够高，尽管空速的增加。3.3 合成气分析为了确定在甲烷转化为氢气时有多少氢气的生成以及其他物种，有必要对其 选择性进行评估（式（3）。表2所示为每一个实验H2的选择性。在800C时 氢气的选择性最低，主要是氢气与二氧化碳发生反应，并生成大量的水。在这个 温度下观察到低的选择性，不仅仅是因为氢的产量低，而且原料中含氢量少也占 一部分原因。水产量较低在900C或1000C时，此时氢气选择性达到较高值，超过90%，没有水的产生（1000C和0.

14、75Lg-1 h-1），因为碳氢化合物在反应过和中的产量（少于 1）比例微不足道，可以消耗这部分氢。很显然，在空速的增 加必会对选择性产生影响，由于在水产生的增加。因此，在温度一定时，空速增 加则选择性下降，这种下降在900C时比1000C更为明显比.要确定合成气是否适用于生产甲醇，在干燥重整反应过程后要记录 H2/CO 比以便 进行比较得到合适的气气比。甲醇合成适宜的H2/C0比为2（反应4）2 17,18。这两种蒸汽和甲烷干重整引起的比率大大高于或远低于此值（即， 3例在蒸汽重 整和干燥重整中的实验1）。因此，必须要包含反应进程的其他反应条件，以调 节适合用于生产甲醇的合成气 17。然而，

15、在焦炉煤气氢的存在使干燥重整只 须一步就可能达到接近适用于合成甲醇的 H2/CO 比率。 H2/CO 比虽然是最常用 的因素来评价一个合成气的成分，但是有些人建议，在原料气中二氧化碳的影响 也应考虑对甲醇合成阶段的影响6,17,24， 25甲醇合成反应（反应 4）。二氧 化碳可以与氢气发生反应生成甲醇和水（反应5），它有助于保持了催化剂的活 性。氢气，二氧化碳和一氧化碳在合成甲醇的原料气中的比例关系及R参数，其 定义如下是指：17,24,25其中氢气，二氧化碳，和一氧化碳的摩尔数是在甲醇 中每一个合成阶段。为了优化其反应过程中，参数R必须等于或略低于2 17,24,25高。如果R 值需小于2，

16、它会导致在甲醇合成期间副产品量的增加，而当值大于2时，有必 要增加甲醇合成阶段甲醇的回收率，由于反应过和中氢过剩，这使得反应过程效 率变低和合成成本高。表2显示了干H2/CO比率和R参数在不同的温度和空速的情况下的GTM干燥 重整实验。可以看出，在800C，尽管二氧化碳的转化率大大超过了甲烷转化率，H2/CO 比率大于3。这是由于强烈的影响，原料气中的氢转换时，此参数是最低的。这 种影响会随着转换的增加而降低（900 C and 1000C型）。此外，即使甲烷和二 氧化碳的转换有很大的不同（900C），但H2/CO摩尔比接近2,这是最合适的 甲醇合成的比率。至于R参数，在800C进行的实验产生

17、合成气值不适合用于甲醇合成。这可 能是由于低转换率造成的，从而导致在生成大量的二氧化碳。在900C和1000C 时其值略高于2,它可被视为用于甲醇生产的合成气可以接受的R值。在空速变化既影响H2/CO比和R参数。空速的增加作为H2/CO比的增加，由 于减少了转换。这种情况可能会导致H2/CO比的降低，由于转换时甲烷比二氧化 碳损失高，即在生产氢比减少有限公司生产的大。然而，由于在这两个转换的降 低,氢气在原料气中的影响增加，这就会引起H2/CO摩尔比的变化.相反的趋势，可观察到的H2/C0比率，因为当空速增加时则参数R减小，由于生产的合成气中 有大量的二氧化碳存在。4结论这项工作的主要目标是研

18、究了活性炭焦炉气的干重整，以生产适用于合成甲醇的 合成气，对焦炉煤气中氢含量在干燥重整反应中对反应进程的影响进行了研究， 研究发现氢的最明显的影响是对反相水煤气变换反应的影响最大。在800C时， 在这种情况下，转换率比较低，导致了焦炉煤气中的氢部分消耗和水的产生。因 此所产生的合成气H2/CO比值较高和R参数较低，这对合成甲醇条件来说不合 适。随着温度的增加，则转换率也随之变大，甲烷和二氧化碳的转化率会别达到 80%和95%。因此水的产量下降，在1000C时则完全没有水的产生，当反应进 程采用较低空速时。这种情况下便会引起H2/CO值降低，R参数增加，从而能 够生产出适合用于生产甲醇的合成气，

19、即H2/CO比为2.2,和R的参数为2.13， 此时H2的选择性高（高达90%）。空速对反应过程的影响是相反的，因为空速 增加时则会导致转换率的降低和产水量的增加。在这种情况下，H2/CO比值的 增加，R参数减小，因而值过高和过低的分别的生产甲醇。因此，可以得出结论认为，在（1000C ）和VHSVs不高于1.5Lg-1 h-1时，活性炭为焦炉煤气干燥 重整生产甲醇的最佳催化剂。Dry reforming of coke oven gases over activated carbon to produce syngas formethanol synthesisabstractThedry

20、reforming of cokeoven gases(COG) over an activated carbon used as catalyst has been studied inorder toproduce asyngas suitable formethanol synthesis. The primary aim of this workwas tostudy theinfluence of the high amount of hydrogen present in the COG on the process of dry reforming, as well asthe

21、influence of other operation conditions, such us temperature and volumetric hourly space velocity(VHSV). It was found that the reverse water gas shift (RWGS) reaction takes place due to the hydrogenpresent in the COG, and that its influence on the process increases as the temperature decreases. This

22、 situation may give rise to the consumption of the hydrogen present in the COG, and the consequent formation of a syngas which is inappropriate for the synthesis of methanol. This reaction can be avoided byworking at high temperatures (about 1000 C) in order to produce a syngas that is suitable for

23、methanolsynthesis. It was also found that the RWGS reaction is favoured by an increase in the VHSV . In addition,the active carbon FY5 was proven to be an adequate catalyst for the production of syngasfrom COG.Keywords:Coke oven gasDry reformingSyngasMethanol1. IntroductionSynthesis gas, or simply s

24、yngas, is a raw material for the largescale production of hydrogen and a wide variety of organic products, consisting mainly of hydrogen and carbon monoxide 1,2.It is basically produced from natural gas and oil, but the limitedsupply of fossil fuels and the fight against climate change andgreenhouse

25、 gas (GHG) emissions have intensified the search foralternative processes of production, such as biomass gasification1 or biogas reforming 3.Coke oven gases (COG), which can be considered a byproduct ofcoking plants, consist mainly of H2 (55 60%), CH4 (23 27%), CO(5 8%) and N2 (3 5%), along with oth

26、er hydrocarbons, H2S andNH3 in small proportions. Most of this gas is used as fuel in thecoke ovens and other processes of the steel plant, but very oftenthe excess of COG cannot be used in this way and so it is burntin torches. But this gives rise to environmental problems that urgently need to be

27、solved 4 9. An alternative option for the excessCOG is for it to be valorized by means of hydrogen separation8,10,11 or syngas production through partial oxidation 12,13,steam reforming 7,12,14,15 or dry reforming 4,5,16. The syngasthus produced can in turn be used for the synthesis of differentothe

28、r organic products, mainly methanol. Although most authorshave concentrated their attention on the steam reforming of COG7,12,14,15,inthe lastfewyearsthedryreformingofCOGhasalsobeen investigated 4,5,16, due to the numerous advantages that itoffers compared to steam reforming, such as the saving of e

29、nergyor CO2 consumption. Another important advantage of the dryreforming of COG is the possibility of obtaining a syngas with aH2/CO ratio of about 2, which is the ideal proportion for methanolsynthesis 17,18, in only one step provided the process is carriedoutunderstoichiometricconditionsofCH4 andC

30、O2.Ascanbeseenin Fig. 1, the process can be considered as a way of partial recycling”ofCO2 since it consumes, at least theoretically, half of theCO2 producedwhen methanolis burnt.The prospects for thistechnology are far-reaching, since the demand for methanol for vehiclefuel,asasourceofhydrogenforfu

31、elcellsorbiodieselproductionisrapidly increasing 19.Themainobjectiveofthisworkistoinvestigatethedryreforming of COG in order to produce a syngas with a ratio of H2/CO suitable for methanol production. The dry reforming of COG is carriedoutoveranactivatedcarbon,whichhasbeenproventobeaneffectivecataly

32、stforthedr yreformingofmethane20.Theinfluenceofthelargehydrogenamountwhichispresentinth eCOGontheprocess of dry reforming and other operating conditions, such as temperature or space velocity, are studied.2. ExperimentalThe dry reforming of COG was carried out in a fixed-bed quartzreactor under atmo

33、spheric pressure and heated in an electric furnace. The reaction temperature in the middle of the catalyst bedwas monitored and controlled by means of a type KA commercial activated carbon with a high surface area (FiltracarbFY5),whosemaincharacteristicsare shownin Table1,was usedascatalyst.In the f

34、irst test, CH4 and CO2 were fed in at a ratio of 1:1. In therest of the experiments, H2 was added in order to study the effectof the presence of H2 in the feed stream on the process of dryreforming of methane. The addition of H2 gave rise to a gaseousternary mixture (GTM) composed of 54% H2, 23% CH4

35、 and 23%CO2 (vol.%), in order that the H2/CH4 ratio was within the rangecharacteristic of COG (22.7). The CH4 and C02 were kept understoichiometric conditions for the dry reforming of the methane.The influence of the CO present in the COG is beyond the scopeof this work and will be studied in due co

36、urse.In order to assesstheinfluenceoftemperatureonthedryreformingoftheCOG,testswere performed at atmospheric pressure and at three differenttemperatures (800, 900, and 1000C). In addition, tests at threedifferent total volumetric hourly space velocities, VHSV (0.75,l,and 1.5Lg -1 h -1, which represe

37、nt 0.16, 0.22, and 0.32 Lg -1 h-1 for the methane respectively, VHSVCH ) were carried out with theaim of studying the effect of this variable upon the process andthe composition of the products. The VHSV was increased byreducing the mass of the catalyst bed.Dry reforming reactions were performed in

38、a quartz reactorcharged with the carbon catalyst, which had previously been driedover night at 110 C. Before starting the reaction, the system wasflushed with N2 (flow rate of 60mLmin for 15min) and then,heated up to a pre-set operating temperature. The gas productwas collected in Tedlar sample bags

39、 periodically during theexperiment. Due to the formation of steam insomeoftheexperiments,acondenserwasplacedafterthereactorinordertopreventwaterfromreachingt hebags.ThesampleswereanalyzedinaVarian CP-3800 gas-chromatograph equipped with a thermal conductivity detector TCD and two columns (an 80/100

40、Hayesep Q and an80/100 Molesieve 13X) connected in series. The second columnwasbypassedbyasix-portvalvefortheanalysisofCO2 andhydrocarbons (PC2).The CH4 and CO2 conversions and the selectivity to H2 were calculated after determining the amount of water produced and thecomposition of the outlet strea

41、m by means of an iterative procedure based on the Newton method for non-lineal equations andusing the Solver Microsoft Excel tool, and closing mass balanceswithin a5% error margin. Selectivity to hydrogen gives anapproximate idea of the amount of methanetransformed into H2or into other species (such

42、 as light hydrocarbons, C2, or water).The parameters were calculated according to Eqs. (1) -3): where CH4in,CO2in and H2in, are moles of each gas at the inlet ofthe reactor and CH4 out,CO2 out and H2 out are moles of each gas atthe outlet.CHg con version (%) CHg con version (%) = 100 yC03 ccnversion

43、 (% = 100 xH2 selectivity, S (%) - 100 xCH4 in CH4 cutCHin COj cutQ)g inH2 C1jt Hj inQ)2 - 匚出s匸比諒一3 ResuIts and discussionIn a previous work by our group 20, the reformingof CH4 withCO2 (Reaction 1) carried out over the activated carbon FY5 wasstudied (see Fig. 2). A possible mechanism for the dry r

44、eformingreactionand the role of CO2 introduced were discussed. The experiments were conducted over a period of 6h, at 800C and atmosphericpressure, under stoichiometric conditions of the methaneand carbon dioxide and at a VHSVCH of 0.16Lg -1 h -1 (total VSHVof0.32Lg -1 h -1 )andconversionsofmorethan

45、40%wereachieved.匚H“ 十匚一 2內十丄匚0, = 247.3 kJ/mol(Reaaknl)If the process is carried out introducing the GTM, i.e., in thepresence ofhydrogeninthe feed, two different phenomena maytake place: (i) the equilibrium is shifted to thereactants (see Reac-tion 1), which results in lower CH4 and CO2 conversions

46、, and (ii)the reverse water gas shift reaction (RWGS) occurs (Reaction 2),giving rise to an increase in CO2 conversion and the formation ofwater 16,21,22. Both effects result in a decrease in hydrogenproduction.H2 + C02 H2D + C0, AH = 41 卫 kJ /mol(Reaction)Tjt)k! 1Milii chemical diaraCTtrtsnc? and r

47、extural properdei M Ttie acttvj rH cartwn F5,PLDjeirkUce ALUlyii wl%)UlEiouif dLdly山M OiLiLAstrV口皿阻i赃皿产cNSObH/C6.72.B3U917Q505CU(13D.OGLw 呼 rwcoinpiKihinn ct the-eMprcsscd 2s vjt.% irf mhal化3iEh3NjJ3弧伽Ni539.7925-40些D5咅ah.41012.77Z?11 1Rnd5jd5TcKrurai prDiwrtlffi勾口 l讦闾叫如(cm3/F0250.34032叫B佃0.Z5Dry 斶Is

48、.CMLuldLud的di血阳盘.N0左MLgTiwni gpcdhc perp s/cHunwSpcclhc vol u me of m icrjpDn?5 pores ofin rtrnal width 2 nmjiSwciric boiumeEsmall mlrnjaoR-ttoorw witu an inrcrnai width0.7nml.LJW. iSerriiu-dex er uf./f ne f20 tO) jcgs?wFig.乙 cHji arxl CQj CHMivcrslons for itic dry refer Fig.乙 cHji arxl CQj CHMivcrs

49、lons for itic dry refer m ln cr 网 at BOO T. HTime mini)FI& 4. CH4nd CO2 ccrwereiorts for rtie dry nefoLiYiine ot tlw GTM WJ C. Cl-U co2-1.*HSVc出-0.I6LE- h.VH5V-D.75Lf1 Ir1 and 1 atm.Both phenomena occurred in the case of the dry reforming of the GTM at 800 C, and led to changes in the CH4 and CO2 co

50、nversions resulting from the dry reforming of CH4. As can be seen in Fig. 3, methane conversion fell to below 40% from the very beginning of the reaction, reaching values of about 20% after 6h of reaction. The sharp decreasing observed during the first minutes maybe due to initial instabilities. In

51、addition, carbon dioxide conversion was higher than in the case of the dry reforming of methan(Fig. 2), which suggests that RWGS had more influence on the process than the effect of the shift of the equilibrium. The large amount of water collected in the condenser, representing about8vol.% of the pr

52、oducts of the reaction, reinforces this suggestionwhich has also been reported by otherauthors 16. Besides reducing H2 production and changing the H2/CO ratio, water could also obstruct the synthesis of methanol, since it has a deactivating effect on the Cu catalyst 23.Effect of the temperatureFig.

53、4 shows the dry reforming of the GTM at 900C. As can be seen, CH4 conversion is higher than 50% throughout the experiment, a level of conversion never reached in tests carried out at 800C. CO2 conversion is also higher than it is at 800C. Since the RWGS reaction (Reaction 2) is less endothermic than

54、 the dry reforming of methane (Reaction 1), an increase in the operating temperature enhances dry reforming, giving rise to a higher methane conversion and, therefore, greaterhydrogen production, whereas the production of water is reduced. In actual fact, the increase in CO2 conversion may have been

55、 due to anenhancement of The dry reforming reaction,and not to the RWGS reaction,since the amount of water collected was nearly three times lower than that in the experiment at 800C.Other possible explanation to these results is that at higher temperatures the steam reforming of methane (Reaction 3)

56、 can occur, i.e. the water produced in the RWGS could react with the methane.However, this mechanism seems less probable since it would lead to similar increments in both CH4 and CO2 conversions which did not take place,as can be seen in Fig. 4.Nevertheless,the sum of RWGS reaction (Reaction 2) and

57、steam reforming reaction (Reaction 3) gives rise to the dry reforming reaction (Reaction 1), which makes difficult to distinguish the path followed by the reaction.Fig.5 shows the conversion results corresponding to the test carried out at 1000C. This increment in temperature results in an increase

58、in the conversions, up to 80% for CH4 and 95% for CO2 after 6h of experimentation.Moreover,no production of water was detected at 1000C. Therefore, by working at this temperature, it is possible to avoid the occurrence of RWGS, and so maximize the production of hydrogen.Effect of the volumetric hour

59、ly space velocity (VHSV)The effect of the VHSV on the process was studied at 900C and 1000C.The temperature of 800C was discarded since an increase in VHSV would lead to a further decrease in conversions 20 and to the formation of more water, which would make it difficult to study the effect of the

60、variation of VHSV and its influence on the process.10020160邕 UQmEA 匚口04010020160邕 UQmEA 匚口0402同3 o30亠 CH出-O-CO2060120160240300360Time (mln)Fig. 3. Fig. 3. (IL jnd.CO. cMivrhiflns for Itie y refornungnf tlw CT何 Jl HCunC,匸 匚6 = I, VHSV - 0.16 L E1 tiVHSV = 05 Lfi- hf Jnd 1 JtfTLPig. 1 CIL Jhnd tOjCMwr