甲烷化梅花状催化剂CFD计算及改进

对合成气甲烷化反应体系进行CFD（计算流体动力学）计算,并对模型提出合理的改进。通过建立合理的甲烷化梅花状催化剂颗粒三维模型进行计算,并验证了模型的有效性。结果表明：甲烷化反应内扩散阻力很大,CO在催化剂表面与内部存在明显的浓度差。且H₂与CO扩散速率不同,导致催化剂内部的氢碳比很高,内部的反应条件与催化剂表面相比发生改变,使用单一的动力学方程无法准确描述实际的反应过程。因此,提出对催化剂的不同区域分别讨论,根据催化剂内CO含量的变化将两种不同的动力学方程分别应用在催化剂的不同区域。计算后发现采用两种动力学控制下催化剂内甲烷化反应的平均反应速率加快,反应进行的程度变大,更加接近实际过程,提高了计算的精确性。     

流化床甲烷化基础与应用最新进展

由于CO甲烷化的快速表面反应、强放热特性,相比固定床,采用小颗粒催化剂的流化床甲烷化技术在反应活性和催化剂稳定性方面具有明显的技术优势。从高耐磨催化剂、流化床反应器及其创新、短流程两段甲烷化技术构建及其验证等方面总结了流化床甲烷化技术开发的最新进展。优化催化剂前体制备方法、调变催化剂组成可获得具有较高骨架强度和均匀性的催化剂一次微粒,进而通过优化的喷雾造粒工艺和填充黏结剂,制备出具有可调变粒度分布、高强度和高球形度的流化床用粉末催化剂,但其黏结剂的添加明显影响催化剂的低温活性。通过改性如Al₂O₃和FCC催化剂的球形颗粒,进而负载活性组分,开发了制备高活性、磨损指数小于1.5的流化床甲烷化Ni基催化剂的另一种技术方法。实验室研究证实了流化床甲烷化反应速率极快,在分布板上数毫米处即可实现可能的最高转化率,且在转化率和催化剂稳定性方面明显优于固定床,不仅由于流态化催化剂床层温度均匀,而且催化剂在床层内不停循环,加快了颗粒表面的更新。增大空速和表观气速,流化床的催化剂床层膨胀,反应气体与催化剂颗粒表面间的有效接触面积增加,使得流化床甲烷化对空速和表观气速的可调范围大。操作在更高气速条件的输送床甲烷化避免了操作气速的上限限制,可大幅降低反应器尺寸,有效提高单位截面的原料气负荷能力。输送床甲烷化可采用高热导率的催化剂颗粒传递反应热,相对于气体移热效率高、能力大。流化床甲烷化已在生物废弃物利用和焦炉煤气甲烷化方面开展了侧线示范,形成了相对多段绝热固定床工艺更简单的短流程两段甲烷化新工艺。     

受平衡约束的平行反应体系的催化剂粒内反应-扩散过程模拟

以甲烷化体系为例，研究了受平衡约束的平行反应的催化剂粒内状态。采用正交配置法求解催化剂的一维、二维反应－扩散非等温模型。模拟结果表明，由于甲烷化反应与变换反应交互作用，导致变换反应在催化剂粒内正、逆反应均存在。内扩散效率因子不能准确描述催化剂内表面利用率，应考虑粒内参数分布。     

助剂对煤基合成气甲烷化反应用镍基催化剂的促进作用

助剂促进的合成气甲烷化反应用镍基催化剂具有反应活性高、使用寿命长以及甲烷选择性高等优点,被广泛应用于煤基合成气甲烷化制替代天然气反应中。本文重点介绍了贵金属、碱土金属、稀土金属以及过渡金属助剂等对活性镍基催化剂的分散度、还原度、双金属合金协同效应、镍基催化剂结构稳定性及其对合成气甲烷化反应速率和产物选择性的影响。较系统地分析了这些助剂改性镍基催化剂的作用机制。提出了非贵金属助剂以及复合助剂将是合成气甲烷化用镍基催化剂助剂研发的发展方向,旨在为煤基合成气制替代天然气甲烷化催化剂的研发提供借鉴和参考。     

Promotion effect of Re additive on the bifunctional Ni catalysts for methanation coupling with water gas shift of biogas: Insights from activation energy

The cheap manganese sand was first modified by H₂O₂ and was further creatively utilized as Ni-based catalyst support. In order to enhance the catalytic performance, Re was added into the Ni-based catalyst and the promotion effect of Re on the methanation coupling with water gas shift of biogas was investigated from the perspective of activation energy. It was found that CH₄ and CO₂ formation rates, which separately represented the reaction rate of methanation and water gas shift, were both enhanced after Re addition compared to non-added catalyst. Two kinetics models including empirical model and K-model were employed and from the results of calculation, it showed that Re selectively decreased the activation energy of methanation reaction and had little impact on the activation energy of water gas shift. The increased CO₂ formation rate was owing to the assistance of accelerated H₂O production from methanation rather than the activation energy change in water gas shift.     

煤制天然气甲烷化催化剂及机理的研究进展

煤制天然气技术是将高碳能源转化为富氢、低碳能源的有效途径,发展以煤为原料、将合成气通过甲烷化反应制备天然气是今后煤清洁利用的重要途径。介绍了国内外煤制天然气的研究现状和甲烷化反应在煤制天然气中的应用。阐述了近年来CO、CO₂甲烷化催化剂中几种常见的氧化物负载型Ni基催化剂载体(Al₂O₃、ZrO₂、SiO₂、TiO₂)和催化剂助剂的制备方法以及化学结构特点,分析了一些新型催化剂载体（MWCNT、SiC、LaFeO₃）、贵金属催化剂、非晶态合金催化剂、钙钛矿催化剂的研究现状和制备方法对催化剂催化性能的影响。分别对因高温烧结、催化剂中毒和催化剂积炭在工业上引起的甲烷化催化剂失活进行分析,并提出催化剂的改进方法。阐述CO甲烷化反应的次甲基机理、表面碳机理和变换-甲院化反应机理;近年来CO₂甲烷化反应机理尽管一直存在分歧,但在催化过程中生成含碳中间物种的理论已被认同。今后甲烷化催化剂的研究方向包括开发新型甲烷化催化剂（低温催化剂、催化剂掺杂改性）、新型复合载体、抗硫催化剂（钼、钨催化剂）以及开发甲烷化新工艺和进一步深入探索甲烷化反应机理。     

基于甲烷化反应的催化剂颗粒设计与过程强化

甲烷化反应过程的主要问题是“烧结”和“积炭”。基于甲烷化反应的强放热、减分子特性和对反应机理的认识,从催化剂与反应器的匹配性角度,论述了当前的主要甲烷化工艺、甲烷化催化剂、甲烷化反应及过程强化方法。流化床技术可有效防止催化剂的积炭和烧结,从与流化床反应器匹配的催化剂结构设计源头出发,制备具有耐磨损、易流化、低密度的高活性甲烷化催化剂,是流化床甲烷化发展的一个重要途径。     

DTC合成气甲烷化催化剂的工业化应用

大唐国际化工技术研究院有限公司自主研发的DTC合成气甲烷化催化剂在内蒙古大唐国际克什克腾煤制天然气有限责任公司甲烷化装置上实现了高负荷长周期稳定运行,为国内合成气甲烷化催化剂的首次工业化应用。介绍DTC合成气甲烷化催化剂基本性质与特点,详细介绍其工业化应用情况,并与同类型进口催化剂进行对比。工业运行结果表明,DTC合成气甲烷化催化剂活性高,抗破碎粉化能力强,预期寿命长,完全满足工业装置使用要求。     

焦炉煤气甲烷化研究进展

对国内外的焦炉煤气甲烷化技术发展概况进行了综述,分析、比较了各项技术的工艺流程与特点;进一步介绍了目前国内外甲烷化技术采用的催化剂,概括了催化剂活性组分、助剂及载体对甲烷化催化剂性能的影响,提出甲烷化技术及甲烷化催化剂的研究方向。     

Effect of hydrogen sulphide on the deactivation of alumina-supported ruthenium methanation catalysts

The deactivation of a 0.5% ruthenium-alumina catalyst for the methanation reaction has been studied at 250 and 400 °C in the absence and presence of small concentrations of hydrogen sulphide (H₂S). The adequacy of a suggested mechanistic model for the methanation reaction has been confirmed and the model has been applied to the deactivation in the absence of H₂S, which is significantly improved with respect to an empirical methanation rate equation. The effect of the presence of 10 mg dm^?3 H₂S in the reactant stream on the catalyst deactivation rate has also been investigated.     

METH-108H型甲烷化催化剂还原探讨

介绍了赤天化股份公司对METH-108H型甲烷化催化剂还原的情况。还原在高空速,高一氧化碳浓度下进行,还原温度高,时间短,效果好。要保证METH-108H型甲烷化催化剂得到深度还原,利用高变气控制一氧化碳浓度是关键。     

Performance of Ni/Nano-ZrO2catalysts for CO preferential methanation简

Large surface areas nano-scale zirconia was prepared by the self-assembly route and was employed as support in nickel catalysts for the CO selective methanation. The effects of Ni loading and the catalyst calcination temperature on the performance of the catalyst for CO selective methanation reaction were investigated. The cata- lysts were characterized by Brunauer-Emmett-Teller （BET）, transmission electron microscope （TEM）, X-ray dif- fraction （XRD） and temperature-programmed reduction （TPR）. The results showed that the as-synthesized Ni/nano-ZrO2 catalysts presented high activity for CO methanation due to the interaction between Ni active particle and nano zir- conia support. The selectivity for the CO methanation influenced significantly by the particle size of the active Ni species. The exorbitant calcination resulted in the conglomeration of dispersive Ni particles and led to the decrease of CO methanation selectivity. Among the catalysts studied, the 7.5% （by mass） Ni/ZrO2 catalyst calcinated at 500℃ was the most effective for the CO selective methanation. It can preferentially catalyze the CO methanation with a higher 99% conversion in the CO/CO2 competitive methanation system over the temperature range of 260-280℃, while keeping the CO2 conversion relatively low.     

The reactivity of adsorbed carbon on vanadium promoted rhodium catalysts

The hydrogenation reactivity of surface carbon deposited by CO decomposition was investigated for a rhodium-vanadium catalyst. It appeared that the rate of methanation of reactive surface carbon is decreased by vanadium. The reactivity towards C₂+ hydrocarbons is enhanced by vanadium. The relation between stronger adsorbed carbon atoms and the formation of higher hydrocarbons is discussed. ASED calculations support the proposal that changes in metal-carbon bond strength have a significantly larger effect on the rate of methanation than on carbon chain growth.     

Research progress of coal-based high temperature methanation catalyst for synthetic natural gas

随着人们生活水平提高和工业日益快速增长的需求,对天然气的需求越来越大,在较长时间内出现供不应求的局面。煤制天然气是煤经气化、合成气变换、净化以及甲烷化形成的过程,其中高温甲烷化催化剂的研究与开发备受关注。本文首先对高温甲烷化催化剂国内外发展概况进行了综述,并对高温催化剂的组成及其失活原因进行了分析,失活原因主要包括：硫中毒、烧结和析碳,最后提出高温甲烷化催化剂的研究方向,旨在为高温甲烷化催化剂的研发提供借鉴与参考。     

Effect of Catalyst Preparation on Catalytic Activity: VI. Chemical Structures on Nickel/Alumina Catalysts: their Impact on the Rate-Determining Step in the Hydrogenation of Carbon Monoxide

Titration of the carbon pool subsequent to steady-state reaction of hydrogen and carbon monoxide over Ni/Al₂O₃ catalysts in conjunction with temperature-programmed surface reaction studies has been performed to assess the impact of nickel speciation on the rate-determining step in the methanation reaction. Mass balances for the desorption products reveal significant differences that depend on the weight loading of the catalyst. Low-weight loading catalysts prepared by incipient wetness consist of NiAl₂O₄ reactive centers as revealed by electron spectroscopy for chemical analysis and carbon monoxide temperature-programmed reaction experiments. Data are presented which support the hypothesis the rate of methanation is controlled by the rate of surface-bound carbon monoxide dissociation over the catalysts. On the other hand, high-weight loading catalysts prepared by this method consist of “particle-like” nickel. Over these catalysts, the rate of methanation is found to be controlled by the rate of hydrogenation of CH_x. It is proposed that variation in catalyst preparation procedures can account for the wide-spread controversy in the determination of rate-determining step for methanation over Ni/Al₂O₃ catalysts.     

焦炉煤气甲烷化催化剂的性能研究

针对传统甲烷化催化剂在高碳原料气中耐热性和抗积碳性差的缺点,开发了适用于焦炉煤气甲烷化制SNG的新型甲烷化催化剂。考察了催化剂制备方法、助剂、氢碳比及反应温度对催化剂活性的影响,并对催化剂进行了500 h稳定性考察。结果表明,该催化剂具有优异的低温活性,添加助剂的催化剂具有良好的耐高温和抗积碳能力,在800℃氢气气氛40 h后,CO2转化率仍〉99.0%,说明催化剂具有稳定活性。     

Synthesis of Nanocrystalline CeO2 with High Surface Area by the Taguchi Method and its Application in Methanation

Mesoporous nanocrystalline cerium(IV) oxide (CeO₂) with high surface area was synthesized by precipitation using a cationic surfactant and employed as support for a nickel catalyst in CO methanation. The preparation factors of CeO₂ were optimized by the Taguchi method to achieve a sample with high surface area. The obtained results reveal that the sample prepared under optimized conditions has a mesoporous structure with high surface area and crystallite size. The addition of a surfactant significantly influences the structural properties of CeO₂ and improves the specific surface area. The optimized sample was employed as support for a nickel catalyst in CO methanation reaction. The prepared catalyst possessed a high activity compared to a commercial methanation catalyst.     

MONOLITHIC-SUPPORTED NICKEL CATALYSTS: I. METHANATION ACTIVITY RELATIVE TO PELLET CATALYSTS

The catalytic activity and selectivity of pellet and monolithic supported Ni/A1₂O₃ for methanation of carbon monoxide were investigated to determine the role of support geometry in catalyst performance. Turnover numbers, CO conversion versus temperature data, and product distributions were measured at space velocities from 15,000 to 50,000 hr^-1 and pressures of 140 to 2500 kPa. The data show that monolithic supported nickel is significantly more active and selective for methane production at both low and high CO conversions compared to nickel catalysts beads and pellets. Monolithic supported methanation catalysts apparently operate with a higher effectiveness and rate of mass transfer than do catalyst beads or pellets. Because of its superior activity, selectivity and tow pressure drop at high space velocities, monolithic nickel may be the ideal catalyst for use in a high throughput recycle methanator     

前驱体对Ru/CeO_2-ZrO_2-Al_2O_3催化剂CO选择性甲烷化的影响

以CeO_2-ZrO_2-Al_2O_3复合氧化物为载体,采用分步等体积浸渍法制备了不同Ru负载量及不同Ru前驱体的催化剂,并考察了这些因素对催化剂CO选择性甲烷化活性及为燃料电池供氢操作温度窗口的影响。结果表明,Ru负载量为1%的催化剂具有较好的CO选择性甲烷化活性及最宽的操作温度窗口;以Ru(NO)(NO_3)_3为前驱体制备的催化剂,Ru金属分散度较差,低温CO甲烷化活性较低,高温CO甲烷化选择性较差,操作温度窗口仅为15℃;以RuCl_3·xH_2O为前驱体制备的催化剂具有良好的CO选择性、甲烷化活性及60℃操作温度窗口,且水洗除氯操作对催化剂性能影响不明显。     

新型焦炉气甲烷化催化剂的性能研究

针对传统甲烷化催化剂在水煤气或焦炉煤气等高碳含量原料气甲烷化过程中耐热性和抗积炭性差等缺点,开发出适用于焦炉气、水煤气甲烷化制合成天然气（SNG）的新型W907甲烷化催化剂。考察了催化剂还原温度、反应压力、空速、反应温度及水气分压对反应活性的影响,同时对该催化剂进行了连续220 h稳定性考察。结果表明,催化剂在较宽的空...