甲醇氧化重整制氢工艺条件的研究

在Cr-Zn氧化物催化剂上考察了各种工艺条件对甲醇氧化重整(POX)制氢过程的影响.正交实验表明:对甲醇的转化率、氢气的选择率、氢产率和产物中CO、CO2的浓度影响显著程度为反应温度>氧醇比>水醇比.该催化剂无需预还原可直接使用,反应压力选择在0.3～0.5 MPa,合适的反应温度为650～700 K,氧醇比0.15～0.20,水醇比约1.0.     

用于PEMFC的丙烷自热重整制氢操作条件优化研究

Autothermal reforming （ATR） is one of the leading methods for hydrogen production from hydrocarbons. Liquefied petroleum gas, with propane as the main component, is a promising fuel for on-board hydrogen producing systems in fuel cell vehicles and for domestic fuel cell power generation devices. In this article, propane ATR process is studied and operation conditions are optimized with PRO/Ⅱ from SIMSCI for proton exchange membrane fuel cell application. In the ATR system including water gas shift and preferential oxidation, heat in the hot streams and cold streams is controlled to be in balance. Different operation conditions are studied and drawn in contour plots. The region for ATR reforming with the highest efficiency can thus be identified. One operation point was chosen with the following process parameters： feed temperature for the ATR reactor is 425℃, steam to carbon ratio S/C is 2.08, air stoichiometry is 0.256. Thermal efficiency for the integrated system is calculated to be as high as 84.0 % with 38.27 % H2 and 3.2μl·L^-1 CO in the product gas.     

甲醇自热重整制氢整体催化剂的制备

将整体催化剂应用于甲醇自热重整制氢体系。以堇青石蜂窝陶瓷为载体,对催化剂的活性组分和载体涂层进行了筛选,同时采用一种特殊的热涂方法制备出一次担载量高,活性和稳定性好,无须预还原处理的甲醇自热重整整体催化剂。采用XRD、SEM-EDAX等表征方法对催化剂进行表征,评价结果表明,与浸渍法相比,采用热涂法制备的ZnO-Cr_2O_3/CeO_2-ZrO_2整体催化剂(B型)具有良好的活性和稳定性。     

丙烷自热重整制氢

以丙烷为主要成分的液化石油气(LPG)是一种有希望作为燃料电池车车载制氢系统的燃料。本文利用SIMSCI公司的PRO/Ⅱ软件对丙烷的自热重整制氢过程进行了研究,结果显示,空气比率是一个重要的参数,会对热效率产生敏感的影响。对于一套其他参数,存在一个最优的空气比率值,而且随着操作压力增加和操作温度的降低而降低。虽然汽碳比率对热效率影响不大,但是对产物气中氢气和一氧化碳的含量影响较大。通过对操作条件的分析,绘成了不同操作条件下的最优热效率图,可对重整系统的整合分析起到指导作用。     

仿蜂巢微通道分叉结构的甲醇重整制氢

针对甲醇蒸汽的微通道重整催化反应过程,建立了三维稳态多组分传输反应模型;利用数值模拟分析,分别研究了平行阵列微通道和仿蜂巢分叉微通道在Zn_Cr/CeO₂/ZrO₂催化剂下的反应情况。通过双速率模型考察这两种流道中操作条件对甲醇蒸汽重整制氢输运规律的影响,发现这两种微通道反应器均可促进甲醇转化率和氢气产率的提高。与常规平行微通道的比较发现,仿蜂巢分叉微通道内反应气流动所需的泵功较小;在相同的加热面积下所能吸收的热量更大,而且更有利于反应器内温度的均匀分布,从而提高甲醇的转化率、减小出口CO的含量。研究结果表明,仿蜂巢分叉微通道结构具有较好的重整制氢综合性能,并可改善氢气产出的品质。     

低温甲醇水重整制氢催化剂研究进展

甲醇具有结构简单、含氢量高、产能大等优点,利用甲醇与水蒸气进行重整是一种节能高效的现场制氢方式。甲醇水蒸气重整(MSR)与燃料电池联用能够实现多场景应用,但由于反应温度较高(250~300℃),存在启动速度较慢、副产CO含量较高和热效率较低等问题。低温甲醇水重整(LT-Methanol Water Reforming, LT-MWR)包括低温甲醇水蒸气重整(LT-MSR)与液相甲醇水重整(Aqueous-phase Reforming of Methanol, APRM),反应通常在200℃以下进行,同时保持较高的反应活性,进而能够减少预热时间、减弱副反应发生,且能与燃料电池实现更强的热耦合。本工作首先介绍了商用催化剂优异的性能与存在的缺陷,然后对低温甲醇水重整制氢催化剂,诸如Cu基催化剂、贵金属催化剂与光协同催化剂的研究进展进行了回顾。归纳了低温铜基催化剂的改性策略,包括合成方法、结构设计与元素掺杂。对国内外商用CuZnAlOx催化剂结构与性能的测试表明,其转化率高和稳定性好,存在的缺陷是价格较贵且在低温区催化活性急剧下降。Cu基催化剂活性受温度影响较大,在低温区活性很低,但通过适当的改性能够实现其应用价值,其改性策略包括合成方法、结构设计与元素掺杂。贵金属催化剂低温下活性较高,但存在价格昂贵、合成复杂等缺点。光协同催化剂则是在光照条件下进行催化重整,尚处于研究阶段。对于Cu基催化剂,合成方法的改进能够大大改善催化剂的微观混合程度与可重现性。适当的结构设计可提升催化剂的比表面积与热稳定性。元素掺杂则能够提升活性组分的分散度,修饰催化剂表面结构。三种改性策略能够有效提升Cu基催化剂低温下甲醇重整制氢的性能,在保持较高活性的同时,降低CO副产物的含量。展望了低温甲醇水重整制氢催化剂的发展前景和挑战,对催化剂的开发与应用有指导意义。     

柴油自热重整制氢反应及反应器

设计了带预热段的绝热管式反应器(A型)和带喷嘴及预热段的绝热管式反应器(B型),设计了相应流程并组建了柴油自热重整制氢装置,以直馏柴油为原料,研究了2种反应器内的柴油自热重整制氢反应行为。研究结果表明:2种结构的反应器均能用于柴油自热重整制氢,采用带喷嘴的绝热管式反应器可以确保雾化及气化效果良好,柴油热裂解生成甲烷的反应有助于柴油制氢过程。     

甲醇重整气为燃料的质子交换膜燃料电池

进行了甲醇重整气与燃料电池的联合试验。与PEMFC配套的甲醇制氢氢源系统运行稳定,出口氢浓度为43-45%,CO含量为0-6ppm,压力控制在0.22~0.25MPa(表压)。单对电池氢的利用率可达到83%,电池排氢浓度为12%以下。不同氢源下PEMFC性能从高到底的顺序为纯氢、甲醇重整气、配气。单电池试验表明,微量的甲醇或二甲醚对电池未发现明显的影响。     

甲醇水蒸汽重整制氢催化剂制备的研究

针对燃料电池用氢制备用于甲醇水蒸汽重整制氢的Cu/Zn/Al系列催化剂,研究催化剂组成、制备方法对催化剂性能的影响。利用热分析和X射线衍射等分析手段对催化剂前驱体和焙烧后催化剂样品进行分析和表征。结果表明,铜基催化剂对甲醇水蒸汽重整制氢反应有较好的活性和选择性,合适的组成是Cu、Zn和Al的原子质量百分比为45∶45∶10和47.5∶47.5∶5,210 ℃反应转化率达到100%;并流共沉淀法和热分解法制备的催化剂都具有较好的催化性能。     

甲烷自热重整催化剂的研究进展

简要介绍了甲烷自热制合成气的研究进展,重点从催化剂活性组分、载体、助剂方面介绍了自热重整反应常用的负载型金属催化剂,指出了联合活性组分和功能型载体是大规模自热重整制氢的发展热点.     

Characterization of CuMn-spinel catalyst for methanol steam reforming

CuMn-spinel oxide (CuMn(S)) and non-spinel CuMn (CuMn(NS)) oxide have been obtained by calcining the same precursor at 900 °C and 300 °C, respectively. CuMn(S) was composed of Cu_1.5Mn_1.5O₄ spinel and Mn₃O₄, while CuMn(NS) consisted of CuO and Mn₃O₄. XRD, EXAFS, and TEM measurements of the samples reduced in hydrogen revealed that both CuMn(S) and CuMn(NS) were reduced to Cu metal dispersed on MnO and that the particle size of Cu metal from the CuMn(S) was smaller than that from CuMn(NS). In methanol steam reforming, the spinel derived catalyst showed higher activity than the non-spinel due to the higher dispersion of the Cu metal.     

Method of catalyst coating in micro-reactors for methanol steam reforming

Micro-channels of silicon-based micro-reactors were successfully coated with deionized (DI) water-based Cu–ZnO–Al₂O₃ catalyst slurry by a fill-and-dry coating method, applicable to pre-assembled micro-reactors, for steam reforming of methanol. The 10–20 μm thick catalyst layers could be formed on the inner walls of the micro-channels after the micro-channels were fully filled with catalyst slurry, because the catalyst particles in the slurry cohered to the walls of micro-channels by surface tension during drying and calcinations. The adhesion between the catalyst layer and silicon surface was improved by pre-coating the micro-channels with an alumina adhesion layer. The addition of polyvinyl alcohol (PVA) in the alumina sol resulted in better adhesion of the alumina layer at the corners of the channels. The critical minimum thickness of the alumina layer for catalyst coating was 0.15 μm. The highest catalytic activity without loss of intrinsic catalytic activity was obtained using 1:5 (catalyst to solvent) DI water-based catalyst layers coated by fill-and-dry coating. The maximum H₂ production rate was 85 ccm with 1650 ppm of CO measured at 300 °C using a methanol feed rate of 9 ml/h.     

Prediction of catalyst stability in naphtha reforming

A method to predict catalyst activity (RON) and selectivity (ηc5⁺, liquid yield) of naphtha-reforming catalysts during normal operation is described. It involves performing experiments at normal operational conditions and testing accelerated deactivation. These last experiments have a severe intermediate period at lower pressure. Carbon formation is related to time and the decrease in RON and ηc5⁺ is related to carbon at normal operation. The accelerated deactivation produces a similar coke to the one at normal conditions for an equal amount of coke. Therefore for each time at normal conditions there is a corresponding pressure in the accelerated deactivation test. Power law-equations fit the data well and combining them results in the following relations: P = at^b; Δ_NRON = cP^d; Δ_Nηc5⁺ = eP^f. The coefficients a, b, c, d, e and f depend on the catalyst and are calculated from four or six experiments (half at normal conditions and half accelerated deactivation tests); b, d and f bare negative. The value of pressure for the time at which it is desired to predict catalyst activity and selectivity is calculated from the first equation. This value when applied to the second and third equations gives the activity and selectivity, respectively, that the catalyst will have after time t.     

共沉淀法制备Cu-Mn-Al尖晶石催化剂用于甲醇水蒸气重整制氢

以硝酸铜、硝酸铝和硝酸锰为原料,用共沉淀法制备了Cu-Mn-Al尖晶石固溶体催化剂,用于甲醇水蒸气重整制氢反应.采用BET、H2-TPR、XRD、SEM、XPS等方法对催化剂进行了表征,考察了Mn的添加比例(CuMnxAl4–x,x=0～0.5)对催化剂物理化学性质、形貌及催化性能的影响.结果表明,Mn添加比例不同,催化剂的比表面积、还原性能以及表面化学性质发生改变,随着Mn比例从0增大到0.5(以Cu的物质的量为基准,下同),CuAl尖晶石粒径增大、比表面积下降,并且更难被还原.催化剂的催化性能在x=0.25时最佳,在260℃、0.3 MPa、n(H2O):n(CH3OH)=1:1、质量空速(WHSV)为3.0 g-feed/(g-cat·h)的反应条件下,最高甲醇转化率为91.7％,连续运行150 h后甲醇转化率降至78.8％,均明显高于未含Mn的CuAl尖晶石催化剂.     

催化活性分布对甲醇水蒸气重整制氢的影响

为了强化微通道中甲醇水蒸气重整制氢,考察了催化表面活性分布对该反应过程的影响。利用计算流体力学软件FLUENT中的通用有限速率模型对微通道中甲醇水蒸气重整进行了二维数值研究。计算表明,在相同的反应条件下,通过微通道壁面上催化活性的合理分布可以提高反应器出口甲醇的转化率,这一效果在低进口温度和高速度下更为明显,在进口温度为453 K、进口速度为1.0 m/s下转化率最大提高46%。合理的活性分布应是进口处活性较低,沿着反应通道活性逐渐增加。这种催化活性分布还可降低反应通道中的冷点温差。     

A novel alumina catalyst support with high thermal stability derived from silica-modified alumina aerogel

A new alumina catalyst support with high thermal stability was synthesized. The high thermal stability was achieved through the synergetic effect of silica addition and the ultra-low bulk density (aerogel). The amount of silica was varied from 2.5 to 10 wt% and 5 wt% was found to be most effective for suppressing phase transformation; the θ phase remained even after heating at 1400°C for 1 h. The surface areas of the present alumina with 5 wt% silica were 86 and 36 m²/g after heating at 1300 and at 1400°C, respectively. This revised version was published online in November 2006 with corrections to the Cover Date.     

Spinel CuFe2O4: a precursor for copper catalyst with high thermal stability and activity

Spinel CuFe₂O₄ has been studied as a precursor for copper catalyst. The spinel CuFe₂O₄ was effectively formed on the SiO₂ by calcination in air at 800 °C with the atomic ratio of Fe/Cu = 2. The spinel CuFe₂O₄ on the SiO₂ was reduced to fine dispersion of Cu and Fe₃O₄ particles by the H₂ reduction at 240 °C. After H₂ reduction at 600 °C, sintering of Cu particles over the CuFe₂O₄/SiO₂ (Fe/Cu = 2) was inhibited significantly, while fatal sintering of Cu particles over the Cu/SiO₂ (Fe/Cu = 0) occurred. The CuFe₂O₄/SiO₂ catalyst exhibited much higher activity and thermal stability for steam reforming of methanol (SRM), compared with the Cu/SiO₂ catalyst. The spinel CuFe₂O₄ on the SiO₂ can be regenerated after an intentional sintering treatment by calcination in air at 800 °C where the activity is also restored completely. Based on these findings, we propose that spinel CuFe₂O₄ is an effective precursor for a high performance copper catalyst in which the immiscible interaction between Cu and Fe (or Fe oxide) plays an important role in the stabilization of Cu particles.     

Pt-Re催化剂重整高温F-T合成石脑油的催化性

选用SB粉制得γ-Al₂O₃载体,采用共浸渍法制备Pt-Re催化剂,并对其进行BET、XRD、NH₃-TPD、H₂-TPR和ICP表征。以高温F-T合成石脑油为原料,在反应温度500 ℃、反应压力1.0 MPa、空速2.0 h^-1和氢油体积比1 000条件下,考察Pt-Re催化剂的重整活性及其稳定性。结果表明,Pt-Re催化剂能高效催化重整高温F-T合成石脑油,240 h重整过程中,高温F-T合成石脑油液体收率79.89%,芳烃质量分数61.60%,直链烷烃质量分数降低了28.15%,重整转化率达200.53%,研究法辛烷值提高35个单位,表明Pt-Re催化剂能有效催化重整高温F-T合成石脑油,使之转化为汽油调和组分成为可能。     

甲醇水蒸汽重整制氢反应的热力学分析

针对甲醇水蒸汽重整制氢反应体系,通过理论计算研究了化学平衡常数随温度的变化规律,指出该反应适宜的反应温度。选取自行开发的CuZnZrAlO催化剂作为研究对象,比较了反应体系中理论平衡组成和实际组成之间的差别,研究了体系中两个独立反应——甲醇分解和水蒸汽变换的反应进度受温度影响的敏感度。通过比较实际反应性能和理论平衡极限的差别,为CuZnZrAlO催化剂的进一步改进提供了研究方向。