CeO2中晶格氧直接部分氧化甲烷制取合成气的研究

介绍了一种合成气制取的新方法-熔融盐中用晶格氧直接部分氧化甲烷制取合成气技术,对该技术的概念进行了阐述.以CeO2为氧载体,对反应过程进行了热力学分析,结果表明以CeO2中晶格氧直接部分氧化甲烷制合成气是可行的.在固定床石英反应器中对非熔融盐体系下的氧载体进行了性能评价,并用XRD技术进行了氧载体的表征.在750～900 ℃温度范围内,分别对(0.462×104)/h,(0.924×104)/h,(1.386×104)/h三种空速进行了实验,同时对产物气中n(H2)/n(CO)进行了考察,结果表明,(0.924×104)/h的空速和900 ℃的温度比较适于合成气的制取,失去晶格氧的CeO2-x有着很好的氧再生能力.     

甲烷部分氧化的热力学模拟研究

甲烷部分氧化制备合成气对于提高天然气的利用价值具有重要的意义。甲烷部分氧化反应是一个非常复杂的反应体系。反应涉及部分氧化（主反应）、燃烧、重整、水煤气变换、积炭等。使用Aspen Plus和HSC Chemistry软件对甲烷部分氧化制备合成气过程进行热力学模拟计算。考察了温度、压力和CH4/O2比对CH4转化率、氢和CO选择性的影响。同时对甲烷部分氧化反应热力学平衡产物组成和积炭副反应进行了热力学计算分析。研究结果表明,随反应温度的升高,压力的减小,CH4的转化率和CO与H2的选择性均呈上升趋势。反应温度在300℃时就有相当多的积炭生成,在550℃积炭量达到最大,随后又随温度上升,积炭量逐渐减少,在900℃以上无积炭产生。     

甲烷部分氧化催化剂上的积碳研究进展

积碳是影响甲烷转化制合成气的催化剂性能的重要因素.在阐述甲烷催化部分氧化过程反应机理和催化剂体系的基础上,重点论述了甲烷催化部分氧化的催化剂失活与积碳的关系及影响催化剂的积碳因素.认为提高催化剂抗积碳性能的关键在于活性组分和负载量的改变、助剂的添加、载体的调控和制备方法的改进和储氧材料的使用,并对晶格氧催化甲烷部分氧化制合成气技术提出了展望,认为该技术具有良好的工业化应用前景.     

焦炉煤气催化部分氧化转化的实验研究

用部分氧化转化法进行了焦炉煤气中甲烷的重整转化实验,分别考虑了（CO2＋H2O）／CH4比例、反应温度丁及配氧量三个因素对甲烷转化率的影响。研究结果表明：焦炉煤气中甲烷重整转化的最佳动力学条件是（CO2＋H2O）／CH4=1．1～1.3、反应温度T=1223-1323K、配氧量O2=6％左右,CH4的转化率大于95％。     

煤-氧-水蒸气-焦炉气联合气化制备直接还原气

进行煤-氧-水蒸气-焦炉气联合气化制备直接还原气或液态燃料合成气的工艺概念设计，并对其关键技术进行热态模拟的基础研究。结果表明，借用高炉炼铁系统可望实现煤-氧-水蒸气-焦炉气联合气化制备H2／CO可调、有效成分H2 CO大于95％的富氢还原气或化工合成气，为解决直接还原炼铁以及液态燃料合成的原料气指出了一条可能的途径。     

Mn/W催化剂上甲烷氧化偶联反应机理的Monte Carlo模拟

通过对Mn-Na2WO4/SiO2催化剂的甲烷氧化偶联反应机理进行初步研究,以Mn/W双金属活性中心为基础,分析了CH4和O2共进料氧化偶联制C2烃的反应模型,并采用Monte Carlo方法对该反应的微观过程进行模拟,在与实验相近的条件下,得到了较准确的模拟结果.在模拟实验中,考察了活性位规模和原料气组成对反应结果的影响以及反应过程中表面吸附物种的变化规律.结果表明:活性位规模增大将减缓表面反应的速度,而不同进料烷氧比将对甲烷转化率以及C2烃收率产生影响;同时在对表面吸附物种的考察中发现,反应末期催化剂催化活性不高与晶格氧的补充不足有关,而C2H6和C2H4的反应更多地发生在气相主体.     

气基竖炉工况焦炉煤气甲烷改质行为试验

 利用焦炉煤气+气基竖炉生产优质海绵铁,可延伸焦化行业产业链,同时可促进中国废钢/海绵铁—电炉短流程发展,改变钢铁行业能源、产品结构。针对典型焦炉煤气,通过基础性试验研究了在气基竖炉工况下,温度、H2O和CO2配比,高温海绵铁载体对焦炉煤气中甲烷改质行为的影响。研究结果表明,提高温度有利于焦炉煤气中甲烷的改质反应,1000℃时改质后有效还原气体体积分数最高可达80%;热态海绵铁对焦炉煤气改质有催化促进作用,可提高CO2参与改质反应比例至84.9%、H2O参与反应比例至100%;CO2配入体积分数2%～6%、H2O配入体积分数4%～10%为促进甲烷改质反应的适宜范围。     

熔融钒渣添加碱性添加剂吹氧氧化行为研究

熔融钒渣直接氧化提钒中碱性添加剂的主要作用是与氧化钒结合生成可溶性钒酸盐,以便后续湿法浸出。以Na2CO3和CaO为例,通过理论分析和实验室实验着重研究了碱性添加剂对转炉熔融钒渣吹氧氧化行为的影响。结合后续的湿法浸出实验研究熟料中钒的氧化状态以及其与钒浸出的关系,利用X射线光电子能谱仪(XPS)对钒渣熟料中钒的价态含量进行分析。理论分析表明熔融钒渣中的钒氧化成高价在热力学和动力学上均存在一定限制,强制供纯氧和添加碱性添加剂有利于促进钒的氧化。实验结果发现,无添加剂条件下,熔渣中钒的氧化率极限约在80%,Na2CO3和CaO的存在有助于促进熔渣中钒的氧化。随着Na2CO3和CaO含量的增加,钒的氧化率与酸浸出率有增加的趋势,区别为钠法中钒的氧化率与水浸率协同增加,而钙法中,当钒氧化率为65%时酸浸率的峰值出现,钙化熟料中CaV2O5比Ca2V2O7更容易用酸浸出。     

硫化钠对铝酸钠种分母液蒸发排盐的影响

研究了硫化钠对拜耳法铝酸钠种分母液蒸发排盐的影响。结果表明:铝酸钠溶液深度蒸发排盐渣中主要存在Na2CO3·H2O和NaAlO2·1.25H2O;当苛性碱质量浓度(NK)为300~310g/L时,碳酸钠能有效析出且不导致NaAlO2析出过高;随硫化钠添加量增加,Na2CO3、硫盐和NaAlO2析出率提高,排盐率提高且均在60%以上,硫化钠质量浓度(NS)为4g/L时排盐效果最佳;将硫质量浓度(NS)为4.5g/L的铝酸钠溶液蒸发至苛性碱质量浓度(NK)为310g/L时,排盐渣中存在Na2CO3·H2O、NaAlO2·1.25H2O、Na2S、Na2S2O3、Na2SO3及Na2CO3·Na2SO3,同时,约有7%和4%的S2-分别被氧化为S2+和S4+,而亚硫酸钠与碳酸钠更容易结晶形成复盐Na2CO3·Na2SO3而析出;碳酸钠和各价态硫化合物交互作用,影响蒸发排盐效果。     

Ni/Al_2O_3及La改性Ni/Al_2O_3催化CO浆态床甲烷化性能

采用等体积浸渍法制备了Ni/Al2O3及La改性的Ni-La/Al2O3催化剂,并考察了其浆态床CO甲烷化反应性能。借助XRD、H2-TPR、CO-TPD、H2-TPD等对催化剂进行了表征。结果表明,La助剂改性制备的Ni-La/Al2O3催化剂较Ni/Al2O3催化剂具有更高的CO甲烷化活性,La助剂的添加促进了Ni物种在载体表面的分散,降低了还原温度,增强了催化剂对CO和H2的吸附能力。La助剂的添加次序对甲烷化活性影响较大,采用共浸渍法制备的催化剂具有最佳的甲烷化活性,CO转化率达到96.3%,CH4选择性和时空收率分别达到87.1%和179.6 m L·kg-1·h-1,优于先浸渍Ni后浸渍La或先浸渍La后浸渍Ni制备的催化剂。     

Preparation and characterization of Ce_1-xNi_xO₂ as oxygen carrier for selective oxidation methane to syngas in absence of gaseous oxygen

A citric acid complex method was employed to prepare Ce/Ni mixed oxides with various Ce/Ni ratios useful for selective oxidation methane to syngas in the absence of gaseous oxygen,and the catalytic activity measurement was investigated in a fixed bed reactor at 800 oC.The prepared oxygen carriers were characterized by various characterization techniques such as TG-DSC,XRD and TPR.The results of TG-DSC indicated that the Ce1-xNixO2 precursor generated a stable phase after the heat-treatment at temperatures above 800 oC.The XRD characterization suggested that some Ce-Ni solid solution was formed when Ni2+ ions was incorporated into the lattice of CeO2,and it led to the generation of O-vacancy which could improve the oxygen mobility in the lattice of oxygen carriers.It was found that Ce0.8Ni0.2O2 gave the highest activity in the selective oxidation methane to syngas reaction,and the average methane conversion,CO and H2 selectivity reached to 82.31%,82.41% and 87.64%,respectively.The reason could be not only attributed to the fitting amount of NiO dispersed on the CeO2 surface and bulk but also to actual lattice oxygen amount increased in oxygen carrier.     

Preparation and characterization of Ce-Fe-Zr-O(x)/MgO complex oxides for selective oxidation of methane to synthesize gas

A series of Ce-Fe-Zr-O(x)/MgO(x denotes the mass fraction of Ce-Fe-Zr-O,x=10%,15%,20%,25%,30%) complex oxide oxygen carriers for selective oxidation of methane to synthesis gas were prepared by the co-precipitation method.The catalysts were characterized by means of X-ray diffraction and H2-TPR.The XRD measurements showed that MgFeO4 particles were formed and Fe2O3 particles well dispersed on the oxygen carriers.The reactions between methane diluted by argon(10% CH4) and oxygen carriers were investigated.Suitable content of CeO2/Fe2O3/ZrO2 mixed oxides could promote the reaction between methane and oxygen carriers.There are mainly two kinds of oxygen of carriers:surface lattice oxygen which had higher activity but lower selectivity,and bulk lattice oxygen which had lower activity but higher selectivity.Among all the catalysts,Ce-Fe-Zr-O(20%)/MgO exhibited the best catalytic performance.The conversion of the methane was above 56%,and the selectivity of the H2 and CO were both above 93%,the ratio of H2/CO was stable and approached to 2 for a long time.     

Catalytic performance of cerium iron complex oxides for partial oxidation of methane to synthesis gas

The cerium iron complex oxides oxygen carrier was prepared by the co-precipitation method. The reactions between methane and lattice oxygen from the complex oxides were investigated in a fixed micro-reactor system. The reduced oxygen carder could be re-oxidized by air and its initial state could be restored. The characterizations of the oxygen carders were studied using XRD, O2-TPD, and H2-TPR. The results showed that the bulk lattice oxygen of CeO2-Fe2O3 was found to be suitable for the partial oxidation of methane to synthesis gas. There were two kinds of oxygen species on the oxygen carrier： the stronger oxygen species that was responsible for the complete oxidation of methane, and the weaker oxygen species （bulk lattice oxygen） that was responsible for the selective oxidation of methane to CO and H2 at a higher temperature. Then, the lost bulk lattice oxygen could be selectively supplemented by air re-oxidation at an appropriate reaction condition. CeFeO3 appeared on the oxygen carrier after 10 successive redox cycles, however, it was not bad for the selectivity of CO and H2.     

Preparation and characterization of Ce1-x NixO2 as oxygen carrier for selective oxidation methane to syngas in absence of gaseous oxygen

A citric acid complex method was employed to prepare Ce/Ni mixed oxides with various Ce/Ni ratios useful for selective oxidation methane to syngas in the absence of gaseous oxygen, and the catalytic activity measurement was investigated in a fixed bed reactor at 800 °C. The prepared oxygen carriers were characterized by various characterization techniques such as TG-DSC, XRD and TPR. The results of TG-DSC indicated that the Ce_1-xNi_xO₂ precursor generated a stable phase after the heat-treatment at temperatures above 800 °C. The XRD characterization suggested that some Ce-Ni solid solution was formed when Ni²⁺ ions was incorporated into the lattice of CeO₂, and it led to the generation of O-vacancy which could improve the oxygen mobility in the lattice of oxygen carriers. It was found that Ce_0.8Ni_0.2O₂ gave the highest activity in the selective oxidation methane to syngas reaction, and the average methane conversion, CO and H₂ selectivity reached to 82.31%, 82.41% and 87.64%, respectively. The reason could be not only attributed to the fitting amount of NiO dispersed on the CeO₂ surface and bulk but also to actual lattice oxygen amount increased in oxygen carrier.     

Effect of calcination temperature and reaction conditions on methane partial oxidation using lanthanum-based perovskite as oxygen donor

We investigated the effect of calcination temperature, reaction temperature, and different amounts of replenished lattice oxygen on the partial oxidation of methane （POM） to synthesis gas using perovskite-type LaFeO3 oxide as oxygen donor instead of gaseous oxygen, which was prepared by the sol-gel method, and the oxides were characterized by XRD, TG/DTA, and BET. The results indicated that the particle size increased with the calcination temperature increasing, while BET and CH4 conversion declined with the calcination temperature increasing using LaFeO3 oxide as oxygen donor in the absence of gaseous oxygen. CO selectivity remained at a high level such as above 92%, and increased slightly as the calcination temperature increased. Exposure of LaFeO3 oxides to methane atmosphere enhanced the oxygen migration of in the bulk with time online owing to the loss of lattice oxygen and reduction of the oxidative stated Fe ion simultaneously, The high reaction temperature was favorable to the migration of oxygen species from the bulk toward the surface for the synthesis gas production with high CO selectivity. The product distribution and evolution for POM by sequential redox reaction was determined by amounts of replenished lattice oxygen with gaseous oxygen. The optimal process should decline the total oxidation of methane, and increase the selectivity of partial oxidation of methane.     

Stoichiometry of methane oxidation in the methane-oxidizing strain M 102 under the influence of various CH4/O2 mixtures

In laboratory-scale experiments with growing cells of the obligate methane-oxidizing strain M 102, an overall molar gas turnover ratio of the order given below could be postulated: 1 CH4+1--1.2 O2=0.3 CO2+water. Expectations that the optimal gas mixture of methane and oxygen should lie within the range of this stoichiometric consumption ratio have been verified in fermenter 5 1 batch culture experiments. The optimal range of methane-oxygen mixture, found under the experimental conditions described, is based on the estimated growth parameters as generation and doubling times, yield coefficients related to methane and oxygen, and the efficiency of methane metabolism as indicated in the absolute amounts of CH4, O2, and CO2 turned over. The mentioned stoichiometric relation of 1 CH4:1--1.202 did not change with varying the composition, i.e. the partial pressures of CH4 and O2 introduced as a mixture to the cells. The efficiency of methane oxidation was obviously influenced and decreased markedly when deviating from the broad optimal range of CH4/O2 mixtures. With non-growing cells, on the other hand, the stoichiometric relation showed a considerable shift (1:1.4--1.8 CH4:O2) with a clear tendency towards more O2 consumption. The oxidation potential of growing cells, seems then to have a linear interdependence to the substrate concentrations, i.e. partial pressures.     

Partial Oxidation of Methane to Syngas over Monolithic Ni/γ-Al2O3 Catalyst——Effects of Rare Earths and Other Basic Promoters

A series of monolithic Ni/γ-Al2O3 catalysts with and without basic promoters (Na, Sr, La, Ce) were prepared. Partial oxidation of methane (POM) to syngas was carried out in a continuous-flow, fixed-bed reactor. The influences of reaction conditions, including temperature, CH4/O2 ratio and space velocity, on the performance of the catalyst were investigated. The results show that at a high space velocity of 1×105 h-1, optimal CH4 conversion can be obtained. Effects of promoters such as Na, Sr, Ce, La were also investigated, and the catalyst samples were characterized by means of temperature-programmed reduction and XRD techniques. XRD suggests that the addition of promoters has no influence on the crystal structure of Ni/γ-Al2O3 catalyst. The results show that the addition of a small amount of promoters improves the reducibility and activity of the catalyst. The side reaction CH4 2 O2→CO2 H2O, is fully restrained and 100% H2 selectivity is achieved when Ce and La are used as promoters, respectively.     

Preparation and characterization of Ce1-xFexO2 complex oxides and its catalytic activity for methane selective oxidation

A series of Ce1-xFexO2 （x=0, 0.2, 0.4, 0.6, 0.8, 1） complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane and lattice oxygen from the complex oxides were investigated. The characteristic results revealed that the combination of Ce and Fe oxide in the catalysts could lower the temperature necessary to reduce the cerium oxide. The catalytic activity for selective CH4 oxidation was strongly influenced by dropped Fe species. Adding the appropriate amount of Fe2O3 to CeO2 could promote the action between CH4 and CeO2. Dispersed Fe2O3 first returned to the original state and would then virtually form the Fe species on the catalyst, which could be considered as the active site for selective CH4 oxidation. The appearance of carbon formation was significant and the oxidation of carbon appeared to be the rate-determining step; the amounts of surface reducible oxygen species in CeO2 were also relevant to the activity. Among all the catalysts, Ce0.6Fe0.402 exhibited the best activity, which converted 94.52% of CH4 at 900 ℃.     

Effect of water vapor on the CO and CH4 catalytic oxidation over CeO2-Mox (M=Cu,Mn,Fe,Co,and Ni) mixed oxide

CeO2-MOx (M=Cu, Mn, Fe, Co, and Ni) mixed oxide catalysts were prepared by a citric acid complexation-combustion method. CeO2-MOx solid solutions could be formed with M cations doping into CeO2 lattice, while NiO and Co3O4 phases were detected on the surface of CeO2-NiO and CeO2-Co3O4 by Raman spectroscopy. The presence of M in CeO2 could obviously promote its catalytic activity for CH4 catalytic combustion and CO oxidation. Among the prepared samples, CeO2-CuO exhibited the best performance for CO oxidatio...