用抗硫催化剂生产甲烷的方法

该法使特别含有CO、H、硫化物的混合物与含有一种金属(钼、钒、钨、钴或镍)的、放在氧化铯载体上的抗硫催化剂接触反应。反应予250～650℃,5～140巴下进行。该法的优点是能有选择性地、有效地制取甲烷。     

铂基催化剂快速部分催化氧化甲烷的研究

以Al 2O 3为载体,采用浸渍法制备Pt/Al 2O 3催化剂,通过测量重整反应过程中催化剂的温度分布情况,研究了改变甲烷快速部分氧化重整反应中反应条件(反应气体预混合温度、N 2体积比例、CH 4/O 2比)对反应物的转化率及产物选择性的影响。研究发现,催化剂床层温度的上升可以促进CH 4的转化,使H 2和CO的选择性升高且H 2与CO的物质的量的比(简称H 2/CO比,依此类推)升高。N 2体积比例及CH 4/O 2比的升高,会降低催化剂床层温度,进一步造成CH 4的转化率和H 2/CO比降低,但与仅降低混合气预热温度不同的是,提高N 2体积比例及CH 4/O 2比会造成H 2和CO的选择性升高,这可能是催化剂表面的活性氧导致的。通过对甲烷在Pt催化剂上的反应机理进行了初步讨论,认为甲烷的快速部分催化氧化反应为多种反应路径共存,不同的反应条件下各种反应路径所占比例会发生变化。     

载镍橄榄石催化剂对棉秆热解的影响

为了揭示催化剂对生物质热解过程的影响,文章以新疆棉秆为原料,研究了橄榄石及载镍橄榄石(NiO-olivine)对棉秆热解产物的影响规律,并对其物理、化学性质进行表征。研究结果表明:催化剂对生物质热解起到双重作用,一方面,促进半焦的进一步热解,提高生物质热解过程中碳的转化率和原料的利用率,另一方面,对热解焦油的裂解具有较好的催化作用,促进了焦油和甲烷的裂解/重整反应,从而提高了气体产率,H2含量提高一倍。生物质热解过程中,催化剂表面的NiO被热解气还原形成单质Ni充当活性中心;随着热解温度的升高,催化剂的催化效果更加明显;随着NiO负载量的增加,催化剂的催化活性不断增强,当负载量大于7%时,催化剂的自还原消耗大量的热解气导致产气中的H2和CO含量大幅度降低,CO2和H2O含量增加。该研究结果有助于深入了解镍基催化剂对生物质热解的影响机制,为生物质催化气化提供参考依据。     

基于Ni/Al2O3整体式催化剂的生物质气化合成气甲烷化研究

以生物质气化模拟合成气H2/CO/N2为原料气,以堇青石蜂窝陶瓷为基体制备Ni/Al2O3整体式催化剂,通过扫描电镜(SEM)、比表面积(BET)、X射线衍射(XRD)、程序升温反应法(TPR)、热重分析(TG)等表征分析手段,考察催化剂制备方法(浸渍法和溶胶-凝胶法)、温度(250~550℃)及空速GHSV(6000~14000 mL/(g·h))对催化剂甲烷化性能的影响。结果表明:浸渍法制备的Ni/Al2O3催化剂(DIP-Ni/Al2O3)与溶胶-凝胶法制备的Ni/Al2O3催化剂(SGNi/Al2O3)相比,前者甲烷化性能较好。在H2、CO、N2物质的量之比为3∶1∶1且空速为10000 mL/(g·h)条件下,浸渍法制备的Ni/Al2O3催化剂在400℃时甲烷化性能最佳,且该条件下CO转化率为98.6%,CH4选择性为90.9%。当H2、CO、N2物质的量之比为3∶1∶1且温度为400℃时,在实验空速范围内,浸渍法制备的Ni/Al2O3催化剂CO转化率和CH4选择性均基本稳定在90%,甲烷化性能较好。     

煤制天然气过程催化甲烷化的数值模拟

两步法煤制天然气的第一步反应主要生产粗煤气CO和 H2,调整CO与 H2的比值后进行甲烷化反应。在计算软件HSC中分别控制反应温度、压力和CO与H2比例,计算了甲烷化产物变化规律,得到第二步甲烷化反应最适条件是1．8 M Pa、700℃;通过在计算软件FL U EN T 中进行一步对催化甲烷化反应的模拟,0．1 M Pa、720℃时的催化甲烷化即可达到无催化高压条件的甲烷摩尔产率,甲烷化产率最高时对应的n（H2）∶ n（C O ）比值为1．8。     

甲烷快速部分氧化重整试验研究

采用常规浸渍法制备了Rh/α-Al2O3催化剂,建立了甲烷快速部分氧化重整试验体系。通过控制变量法,考察了甲烷快速部分氧化重整反应中反应条件参数(CH4/O2、反应气体预混合温度、空速)变化对反应物的转化率、反应产物及分布的影响。试验结果表明,在试验条件下,CH4的转化率始终大于85%,O2转化率接近100%,CO的选择性为85%左右,H2的选择性为40%～60%。反应过程大致为催化剂入口处的部分氧化反应和下游的水蒸气重整,大部分的CO由部分氧化产生,而H2的产生受水蒸气重整反应的影响较大;随着反应温度的上升,CH4的转化率上升,CO,H2的选择性也上升;随着空速的增大,H2的选择性减小,表明甲烷催化部分氧化反应是一个受传质控制的反应。     

生物质合成气的化学当量比调整

针对生物质气化气中硫化物少、V（H2／CO）低和V（CO2）高的特点，采用气化炉内铁系高温变换催化剂和气化炉外钛促进的钴钼耐硫催化剂进行水煤气变换调整H2／CO比，添加部分沼气重整过量CO2，对生物质合成气化学当量比调整进行了实验研究。结果表明：气化炉内铁系催化剂调整效果不明显；在高温低硫的生物质气化气中，钛促进的钴钼耐硫催化剂具有较高的变换活性，CO转化率达到80％以上，合成气H2／CO比在1-8范围内可调；在V（CH4，CO2）=1、常压、750℃和镍基催化剂作用下沼气重整过量CO2，制备出宽V（H2／CO）、V（CO2）和V（CH4）均低于5％（摩尔百分比）的合成气；通过水煤气变换过程结合沼气重整过程，可依据目的产物合成的要求，制备合适化学当量比、高碳转化率的生物质合成气。     

CO_2/CH_4重整镍基碳纤维催化剂的制备与性能研究

为研制高性能的甲烷二氧化碳重整催化剂,采用静电纺丝法制备了镍基原纤维经预氧化、炭化后的原位镍基碳纤维催化剂和浸渍法制备的浸渍镍基碳纤维催化剂.通过SEM、H_2-TPR、重整反应分析了两种制备方法下催化剂结构及性能的变化,结果表明,原位镍基碳纤维催化剂较浸渍法所得催化剂保持了更好的纤维结构及金属分散性.并且,原位碳纤维的镍含量只有浸渍碳纤维的5%,,当温度大于900,℃以后,其转化率明显高于浸渍镍基碳纤维.在850,℃进行两种催化剂的寿命评价得出的结果显示,浸渍法所得镍基碳纤维催化剂在50,min内表现出失活,而原位法所得镍基碳纤维催化剂在200,min时仍然保持活性.     

浅谈高纯氮气中微量CO、CH4、CO2的测定

气相色谱法是快速、准确、灵敏的分析高纯氮气中微量CO、CH4、CO2最有效方法.此方法采用化学转化法使CO、CO2和H2在镍催化剂作用下转化为CH4,然后经过高灵敏度FID检测器检测,外标峰高(或面积)进行定量.其最低检测浓度为1PPM.     

甲烷三重整制合成气热力学分析

甲烷三重整反应(TRM,Tri-reforming of methane)具有过程能效高、合成气H2/CO适宜和较低催化剂积炭的优点。采用平衡常数法对TRM反应制合成气进行了热力学分析,研究了反应温度、压力及反应原料进气组分对重整特性的影响。结果表明:温度在1073K以上时TRM反应表现出很好的效果,温度升高有利于转化率的提高;但是压力的升高不利于反应正向进行。氧气含量增加,将使甲烷和二氧化碳转化率分别升至95%以上和降至10%以下,但是H2/CO值维持在1.5附近;水蒸气和二氧化碳含量增加,甲烷转化率升高,二氧化碳转化率降低,而且H2/CO值在1.4～2.1之间变化,前者使之升高,后者使之降低。     

Activity and stability enhancement of Ni-MCM-41 catalysts by Rh incorporation for hydrogen from dry reforming of methane

Ni incorporated and Ni–Rh incorporated bimetallic MCM-41 like mesoporous catalysts, which were synthesized following a one-pot hydrothermal procedure, showed very high activity in dry reforming of methane. Among the Ni incorporated catalysts, Ni-MCM-41-V, with a Ni/Si ratio of 0.19, showed the best catalytic performance. Rh incorporation into this catalyst by the one-pot procedure improved both activity and time on stream stability of the catalyst. However, Rh incorporation by impregnation caused instabilities due to coke formation, after about 11 h of reaction time. Occurrence of reverse water gas shift reaction caused higher CO selectivity than H₂ selectivity, with the Ni incorporated catalysts. Rh incorporation into these catalysts decreased the relative significance of reverse water gas shift reaction, with respect to dry reforming reaction.     

H2-rich syngas production from biogas reforming: Overcoming coking and sintering using bimetallic Ni-based catalysts

Dry reforming of methane is a very appealing catalytic route biogas (mainly composed by greenhouse gases: carbon dioxide and methane) conversion into added value syngas, which could be further upgraded to produce liquid fuels and added value chemicals. However, the major culprits of this reaction are coking and active phase sintering that result in catalysts deactivation. Herein we have developed a highly stable bimetallic Ni–Rh catalyst supported on mixed CeO₂–Al₂O₃ oxide using low-noble metal loadings. The addition of small amounts of rhodium to nickel catalysts prevents coke formation and improves sintering resistance, achieving high conversions over extended reaction times hence resulting in promising catalysts for biogas upgrading.     

Water-gas shift of reformate streams over mono-metallic PGM catalysts

Mono-metallic Pt and Rh catalysts supported on both CeO₂ and TiO₂ were prepared and tested for water-gas shift activity in a Flowrence, high throughput reactor system. The feed composition mimicked a typical fuel processor, steam methane reformer outlet stream. The Pt/CeO₂ catalyst showed the best metal activity of ～3.8 E-07 moles CO converted·gPt^-1 s^-1, at a Pt loading of 0.5 wt%, activity decreasing with increasing metal loading. Furthermore, the Pt/CeO₂ catalyst produced almost no methane while the Rh based catalysts led to substantial methanation.     

CNT-based catalysts for H2 production by ethanol reforming

Hydrogen production by steam reforming of ethanol (SRE) was studied using steam-to-ethanol ratio of 3:1, between the temperature range of 150–450 °C over metal and metal oxide nanoparticle catalysts (Ni, Co, Pt and Rh) supported on carbon nanotubes (CNTs) and compared to a commercial catalyst (Ni/Al₂O₃). The aim was to find out the suitability of CNTs supports with metal nanoparticles for the SRE reactions at low temperatures. The idea to develop CNT-based catalysts that have high selectivity for H₂ is one of the driving forces for this study. The catalytic performance was evaluated in terms of ethanol conversion, product gas composition, hydrogen yield and selectivity to hydrogen. The Co/CNT and Ni/CNT catalysts were found to have the highest activity and selectivity towards hydrogen formation among the catalysts studied. Almost complete ethanol conversion is achieved over the Ni/CNT catalyst at 400 °C. The highest hydrogen yield of 2.5 is, however, obtained over the Co/CNT catalyst at 450 °C. The formation of CO and CH₄ was very low over the Co/CNT catalyst compared to all the other tested catalysts. The Pt and Rh CNT-based catalysts were found to have low activity and selectivity in the SRE reaction. Hydrogen production via steam reforming of ethanol at low temperatures using especially Co/CNT catalyst has thus potential in the future in e.g. the fuel cell applications.     

Autothermal reforming of methane over Ni catalysts supported on nanocrystalline MgO with high surface area and plated-like shape

Autothermal reforming of methane (ATRM), combination of partial oxidation and steam reforming was performed over MgO supported Ni catalysts. The preparation of MgO via surfactant-assisted precipitation method led to obtain a nanocrystalline carrier for nickel catalysts. The results demonstrated that methane conversion is significantly increased with increasing the Ni content (5, 7, 10 and 15%Ni) and methane conversion of 15%Ni/MgO was higher than that of other catalysts with lower Ni loading in all operation temperatures.In addition, increasing the system operation temperatures led to decrease in H₂/CO due to the fact that water-gas shift reaction was thermodynamically unfavorable at elevated temperatures. This catalyst also exhibited stable catalytic performance during 50 h time on stream. Furthermore, the influences of varying GHSV and feed ratio on activity of 15%Ni/MgO catalyst were investigated.     

Reforming of a model sulfur-free biogas on Ni catalysts supported on Mg(Al)O derived from hydrotalcite precursors: Effect of La and Rh addition

Ni catalysts supported on calcined Mg–Al hydrotalcite, Mg(Al)O, were prepared and the effect of the addition of La and/or Rh was tested in the performance of the catalysts in the dry reforming of methane with excess of methane in the feed, simulating a model sulfur-free biogas. The effect of adding synthetic air was assessed. The catalysts were characterized by surface area (BET), XRD, TPR and XPD. The results showed the reconstruction of the hydrotalcite structure during the Ni(NO₃) impregnation, with the segregation of the lanthanum. In the catalyst without Rh and La, Ni showed a strong interaction with the support Mg(Al)O, showing high reduction temperatures in TPR test. The addition of Rh and La increased the amount of reducible Ni species and facilitated the reduction of the species interacting strongly with the support which resulted in high rates of carbon deposition. The NiMgAl catalyst presented the strong Ni-support interactions and the best performance with low carbon deposition at both conditions of reaction. The NiMgAl catalyst did not present deactivation during 24 h of stability testing in the oxidative reforming of a model biogas.     

Production of syngas from carbon dioxide reforming of methane by using LaNixFe1−xO3 perovskite type catalysts

A series of bulk and supported LaNixFe1-xO3 catalysts were synthesized, characterized and studied for dry reforming of methane (DRM) reaction. The catalysts were synthesized using sol-gel, incipient wetness impregnation (IWI) and co-precipitation methods. The catalysts were characterized by BET, XRD, FE-SEM, H2-TPR, and FTIR spectroscopy. A specific type of perovskite phase was obtained while changing the ratio of Ni to Fe for the synthesis of LaNixFe1-xO3 perovskite catalyst. The addition of supports increased the dispersion of perovskite phase, surface area and pore volume of the bulk perovskite catalysts. The support silica destroyed the perovskite features of the catalysts at higher calcinations temperature. The most active catalyst was found to be 40LaNi0.75Fe0.25O3/SiO2 calcined at 973 K for the DRM reaction with ratio of CH4:CO2:N2 as 1:1:2. The highest conversion corresponded to the catalyst calcined at 1073 K. However, the highest products yields and selectivity obtained while the catalyst was calcined at 773 K for 1 h. Thus, the choice of Ni to Fe ratio, support, method of synthesis and catalyst calcination temperature were crucial factors while synthesizing and designing a perovskite catalyst for dry reforming of methane reaction.     

Catalytic activity of SBA-15 supported Ni catalyst in CH4 dry reforming: Effect of Al,Zr, and Ti co-impregnation and Al incorporation to SBA-15

In this study, the catalytic activity of the mesoporous SBA-15 supported Ni–Al, Ni–Zr, and Ni–Ti catalysts prepared by an impregnation method were investigated in dry reforming of methane. In addition, Al incorporated SBA-15 (Al–SBA-15) materials used as catalyst support were synthesized following a one-pot hydrothermal route in three different conditions: synthesis in the presence of only HCl, only NaCl, and both HCl and NaCl (denoted as A, S, and B, respectively). All catalysts were characterized by XRD, N₂ adsorption-desorption isotherms, ICP-OES, DRIFTS, SEM, TEM-EDX and TGA techniques before and/or after reaction tests. Among Al, Zr, and Ti impregnated catalysts, Ni–Al impregnated catalyst showed the highest activity in dry reforming of methane. According to activity test results, Al–SBA-15 supported Ni catalyst prepared by the one-pot hydrothermal route in the presence of both HCl and NaCl showed the best catalytic activity with high methane (81%) and carbon dioxide conversion (88%) values at 750 °C. The highest H₂ and CO selectivity values were obtained with the same catalyst with an H₂/CO molar ratio of 0.80. Therefore, these results showed that partial Al (0.11%) incorporated into the structure of SBA-15 was sufficient to improve the catalytic activity of the catalyst in dry reforming of methane.     

Complete removal of carbon monoxide in hydrogen-rich gas stream through methanation over supported metal catalysts

Complete removal of CO by methanation in H₂-rich gas stream was performed over different metal catalysts. Ni/ZrO₂ and Ru/TiO₂ were the most effective catalysts for complete removal of CO through the methanation. These catalysts can decrease a concentration of CO from 0.5% to $\text{20}\text{ppm}$ in the gases formed by the steam reforming of methane with a significantly low conversion of CO₂ into methane. Catalytic activities of supported Ni and Ru strongly depended on the type of supports, i.e. ZrO₂ for Ni and TiO₂ for Ru are suitable supports for the methanation of CO. The effect of catalytic supports on methanation of CO could be explained by particles sizes of Ni and Ru metal. Catalytic activity of supported Ru catalysts for the complete removal of CO through methanation became higher as particle sizes of Ru metal became smaller, while Ni metal particles with relatively larger diameters were effective for the reaction.     

Anti-sintering mesoporous Ni–Pd bimetallic catalysts for hydrogen production via dry reforming of methane

In this work, a series of mesoporous silica supported nickel or nickel-palladium catalysts were synthesized and performed in dry reforming of methane (DRM) reaction for producing syngas. Compared with the monometallic catalyst, the Ni–Pd bimetallic catalysts, especially synthesized by the OA-assisted route, exhibited promising yields of H₂ and CO in the catalytic DRM reaction, achieved at 63% and 69% over NiPd-SP-OA bimetallic catalyst at the reaction temperature of 700 °C, respectively. TEM image results confirmed that no obvious sintering phenomenon happened on spent NiPd-SP-OA bimetallic catalyst within 1550 min time-on-stream reaction. Based on the results of XRD, XPS and H₂-TPR, it could be known that the superior catalytic performance on NiPd-SP-OA catalyst were main ascribed to the smaller-sized Ni nanoparticles with a uniform metal dispersion and a larger fraction of exposed active sites (Ni⁰).