Ni-Mn/Al_2O_3催化剂在浆态床中CO甲烷化催化性能

采用共浸渍法制备了Ni-Mn/Al2O3催化剂,考察了助剂Mn的含量对催化剂结构及浆态床CO甲烷化性能的影响。采用XRD、H2-TPR、BET、TEM、H2-化学吸附等表征对催化剂进行了测试分析,结果表明,Mn助剂的引入能够促进Ni物种在载体表面的分散,减弱Ni物种与载体的相互作用,降低催化剂的还原温度,提高催化剂的比表面积,减小活性金属Ni的晶粒尺寸。随着Mn含量的增加,Ni-Mn/Al2O3催化剂的甲烷化性能先升后降,其中以Mn含量为4%(质量分数)时的催化甲烷化性能最佳,添加过量的Mn导致活性组分Ni被部分覆盖,催化甲烷化性能下降。通过对16Ni4Mn/Al2O3催化剂样品的浆态床反应温度及反应压力的研究发现,当反应温度为280℃、反应压力为1.5 MPa时,催化剂样品16Ni4Mn/Al2O3的CO转化率及CH4选择性分别达到96.2%和88.8%。     

耐硫甲烷化反应的研究进展

耐硫甲烷化工艺对含硫气氛和低H₂/CO比均有良好的适应性,是甲烷化技术发展的重要方向。其中Mo基催化剂是研究最为广泛的耐硫甲烷化催化剂。重点介绍了Al₂O₃、ZrO₂、CeO₂和CeO₂-Al₂O₃载体以及CoO、NiO助剂对Mo基催化剂耐硫甲烷化性能的影响;分析了催化剂的硫化机理以及CoO、NiO助剂和CeO₂载体在硫化过程中的作用,指出硫化温度是影响催化剂的物种分布和催化性能的重要因素;阐述了耐硫甲烷化反应的机理;对甲烷化催化剂的研究方向进行展望。     

CeO2-Al2O3复合载体负载Ni基催化剂催化COx共甲烷化性能

通过浸渍沉淀法分别制备Ni/Al₂O₃、Ni/CeO₂和Ni/CeO₂-Al₂O₃催化剂，并对其分别进行不同CO/CO₂比例下COx共甲烷化性能评价。发现Ni/Al₂O₃催化剂催化CO转化为CH4的能力明显高于Ni/CeO₂，而催化CO₂甲烷化的性能则相反。采用Ni/CeO₂-Al₂O₃催化剂，可以在提高CO转化率的同时而不降低CO₂转化率。结合BET、XRD、TPR、TPD和原位红外等各种表征手段，发现CeO₂掺杂虽然降低了催化剂的比表面积和金属Ni的分散度，但却可明显提高其吸附活化CO₂的能力，这主要是由于具有较高含量氧空位的CeO₂的掺杂可以提高载体表面碱性位，促使共甲烷过程中CO_...     

Ni/Al2O3催化剂对高纯HCl中微量CO2甲烷化反应的催化性能

用浸渍法制备了以Al₂O₃为载体、Ni为活性组分的Ni/Al₂O₃二氧化碳甲烷化催化剂,在等温固定床反应器中研究了在Ni/Al₂O₃催化剂作用下,高纯氯化氢中微量CO₂甲烷化反应效果,并考察了温度、压力、氯化氢体积空速以及H₂/CO₂摩尔比对CO₂转化率的影响,同时研究了催化剂活性、稳定性及其再生性能。结果表明,在温度为250℃、压力为4.0 MPa、氯化氢空速为100 h^-1、H₂/CO₂摩尔比为500:1条件下,CO₂甲烷化反应效果最好,其转化率可达到90%左右,对于高纯氯化氢中微量CO₂的脱除起到很好的效果;催化剂在温度高于300℃时,反应不久后会迅速失活;催化剂再生性能只能部分恢复到新鲜水平。     

基于MCM-41的镍基甲烷化催化剂活性与稳定性

采用浸渍法分别以MCM-41,Al₂O₃和SiO₂ 为载体制备了不同镍负载量的甲烷化催化剂,并在连续流动固定床反应装置上对其甲烷化催化活性进行了评价。研究结果表明,与Ni/Al₂O₃和Ni/SiO₂相比,相同镍负载量的Ni/MCM-41催化剂具有更好的催化活性。同时研究了Ni含量对于Ni/MCM-41催化剂催化活性的影响,发现随着Ni含量的增加,CO转化率和CH₄收率逐渐升高,并且在Ni含量大于10%（质量分数）以后趋于稳定。在n（H₂）：n（CO）=3：1、反应压力1.5 MPa、反应温度350℃及质量空速12000 ml·h^-1·g^-1的反应条件下,10%Ni/MCM-41催化剂CH₄选择性达到94.9%,CO转化率接近100%。在100 h催化活性稳定性试验中,10%Ni/MCM-41催化活性无明显下降,表现出良好的催化活性稳定性。采用X射线衍射（XRD）、氮气物理吸附（BET）、热重分析（TG）及氢气程序升温还原（H₂-TPR）等技术手段对催化剂进行了表征,结果表明Ni颗粒大小是影响Ni/MCM-41催化剂催化活性的主要因素。     

CeO2助剂对Ni基催化剂甲烷化性能的影响

甲烷化工艺是煤制天然气的关键技术,甲烷化催化剂则是甲烷化技术的核心。Ni基催化剂具有活性高、选择性好和价格低廉等优点,但易积炭,积炭堵塞催化剂孔道,覆盖表面金属活性位,导致催化剂失活。稀土类金属氧化物（如CeO₂、La₂O₃等）对Ni基催化剂的活性、稳定性、抗积炭性能以及活性组分的分散有明显的促进作用。采用共沉淀法制备了CeO₂-La₂O₃复合氧化物载体,负载Ni后用于CO甲烷化反应,利用N2物理吸附、XRD、H₂-TPR、XPS和TG等对催化剂结构进行表征。结果表明,Ni/CeO₂-La₂O₃中CeO₂的添加主要发挥了电子助剂的作用,CeO₂的存在提高了催化剂表面Ni0周围的电子密度,促进Ni物种的还原,同时还能提高催化剂的抗积炭能力,使催化剂表现出更好的甲烷化活性与稳定性。在V（H₂）∶V（CO）=1、反应温度450 ℃、空速24 000 h^-1和常压下,Ni/CeO₂-La₂O₃催化剂的CO转化率达82.7%。     

ZrO2-Al2O3复合载体负载Ni基催化剂COx甲烷化性能

采用浸渍和粉末压片的方法制备了两种ZrO₂-Al₂O₃复合载体并用于负载Ni基催化剂，并利用氮气等温物理吸附、X射线粉末衍射（XRD）、H₂程序升温还原（H₂-TPR）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）等分析手段对催化剂物化性质进行表征，考察了ZrO₂-Al₂O₃复合载体制备方法及ZrO₂的引入对Ni基催化剂在CO、CO₂和CO-CO₂共存的3种体系下甲烷化反应活性的影响。材料表征和活性测试结果表明，在CO甲烷化体系中，与单一Al₂O₃载体相比，引入ZrO₂的复合载体能有效提高催化剂中Ni物种的分散度从而增强CO甲烷化过程中催化剂活性，且粉末压片法较浸渍法制备的复合载体能有效提高催化剂的还原度，降低还原温度，但前者会大大降低催化剂的比表面积；在CO₂甲烷化体系中，当载体形貌和制备方法相同时，载体的变化对催化剂活性的影响较小，CO₂转化率主要受到制备方法不同引起的物理性质如比表面积变化的影响；在CO-CO₂共存体系中，由于CO在竞争吸附中比CO₂更容易占据活性位点，所以呈现出优先进行CO甲烷化再进行CO₂甲烷化、CO₂的含量先增多后减少的规律。     

新型合成气甲烷化催化剂La2O3-ZrO2-Ni/Al2O3的制备与性能

针对常规合成气甲烷化催化剂高热结构稳定性差、活性低、适应性差等不足,本文创新地引用稀土金属氧化物La₂O₃复配过渡金属氧化物ZrO₂作为多功能复合助剂,利用反向沉淀法制备了新型合成气甲烷化催化剂La₂O₃-ZrO₂-Ni/Al₂O₃,同时制备催化剂Cr₂O₃-Ni/Al₂O₃作为参照组。采用X射线衍射（XRD）、透射电子显微镜（TEM）表征了催化剂的微观结构,并利用N₂吸附仪（BET）测量催化剂经高温水热处理前后的微孔结构参数,以考察催化剂的高热结构稳定性。结合国内某大型煤制天然气项目工艺特征和运行实践,应用Aspen Plus软件模拟了四段甲烷化工艺理论平衡值。基于自主固定床合成气甲烷化评价实验装置,考察了反应压力、空速和原料气H₂O(g)含量等因素对La₂O₃-ZrO₂-Ni/Al₂O₃催化性能的影响,并开展了1000h长周期寿命评价实验。结果表明,La₂O₃-ZrO₂-Ni/Al₂O₃比Cr₂O₃-Ni/Al₂O₃具有更优的高热结构稳定性;可使CO和CO₂反应达到或接近催化剂床层出口温度下的理论平衡状态,呈现显著的宽温活性;活性组分NiO晶粒尺寸介于7~10nm,分散度较高;对反应压力、空速和原料气H₂O(g)含量的变化不敏感,具有良好的操作弹性;1000h反应后仍能保持较高的活性和稳定性。     

二氧化碳甲烷化催化剂的研究进展

CO₂催化加氢甲烷化反应是温室气体CO₂资源化利用的有效途径之一。本文回顾了CO₂催化加氢甲烷化催化剂的研究现状, 其中Ni基催化剂是研究最为广泛的CO₂甲烷化催化剂。重点介绍了Al₂O₃、SiO₂和La₂O₃载体及CeO₂和La₂O₃助剂等对Ni基催化剂CO₂甲烷化性能的影响, 阐述了载体的结构、电子性能、化学性能和助剂等对Ni基催化剂CO₂甲烷化性能的影响。结合几种非Ni基CO₂甲烷化催化剂的对比研究发现, 具有有序介孔结构的Co基催化剂也表现出了优越的CO₂甲烷化性能。由此表明, 催化剂新颖的结构也是影响CO₂甲烷化性能的重要因素, 通过催化剂结构、组成等的调变, 能实现CO₂低温高效甲烷化, 为CO₂甲烷化工业化进程奠定基础。     

丁酮和甲醛羟醛缩合与催化加氢制备甲基异丙基酮的研究

以Al₂O₃为载体,采用等体积浸渍法制备了Ni/Al₂O₃,利用XRD、N₂物理吸附、H₂-TPR和NH₃-TPD对Ni/Al₂O₃进行表征,并考察了其催化丁酮和甲醛羟醛缩合(aldol)反应产物脱水加氢制备甲基异丙基酮(MIPK)的反应性能。结果表明,在醛酮摩尔比为1.1、反应温度为50℃和反应时间为4 h的条件下,5%三乙胺催化丁酮和甲醛交叉aldol反应的转化率为61.5%,目标产物选择性超过90%;以此反应液为原料,Ni/Al₂O₃在240℃、0.1 MPa H₂和0.5 h^-1空速条件下能够实现80%的MIPK选择性和50%的MIPK收率。此外,Ni/Al₂O₃催化剂具有较高的结构稳定性,在脱水加氢反应中未出现明显的Ni粒子聚集。丁酮和甲醛羟醛缩合和催...     

载体对镍基催化剂顺酐液相加氢性能的影响

分别以ZrO₂、SiO₂与Al₂O₃为载体,采用等体积浸渍法制备了Ni质量分数为15%的催化剂,考察了其催化顺酐液相加氢性能,并利用BET、XRD、H₂-TPR以及TPO-MS等表征手段对催化剂进行了详细表征。结果表明,随载体不同各催化剂的加氢活性及选择性存在较大差异,Ni/Al₂O₃催化剂的C=C键加氢活性最高,但其几乎没有C=O加氢活性,催化顺酐加氢主产物为丁二酸酐。Ni/ZrO₂催化剂具有最高的C=O加氢活性,催化顺酐加氢主产物为γ-丁内酯,在反应温度为483 K,氢气压力为5 MPa的条件下反应8 h时,Ni/ZrO₂催化剂的γ-丁内酯选择性达79.20%。催化剂的套用实验表明,Ni/ZrO₂与Ni/SiO₂催化剂具有高的使用稳定性,Ni/Al₂O₃催化剂则在套用过程中快速失活。顺酐加氢至γ-丁内酯的中间产物--丁二酸酐与催化剂间的相互作用是影响催化剂加氢选择性及使用稳定性的主要原因。     

Coke study on MgO-promoted Ni/Al2O3 catalyst in combined H2O and CO2 reforming of methane for gas to liquid (GTL) process

MgO-promoted Ni/Al₂O₃ catalysts have been investigated with respect to catalytic activity and coke formation in combined steam and carbon dioxide reforming of methane (CSCRM) to develop a highly active and stable catalyst for gas to liquid (GTL) processes. Ni/Al₂O₃ catalysts were promoted through varying the MgO content by the incipient wetness method. X-ray diffraction (XRD), BET surface area, H₂-temperature programmed reduction (TPR), H₂-chemisorption and CO₂-temperature programmed desorption (TPD) were used to observe the characteristics of the prepared catalysts. The coke formation and amount in used catalysts were examined by SEM and TGA, respectively. H₂/CO ratio of 2 was achieved in CSCRM by controlling the feed H₂O/CO₂ ratio. The catalysts prepared with 20 wt.% MgO exhibit the highest catalytic performance and have high coke resistance in CSCRM. MgO promotion forms MgAl₂O₄ spinel phase, which is stable at high temperatures and effectively prevents coke formation by increasing the CO₂ adsorption due to the increase in base strength on the surface of catalyst.     

Design of a novel bifunctional catalyst IrFe/Al2O3 for preferential CO oxidation

In this study, a novel bifunctional catalyst IrFe/Al₂O₃, which is very active and selective for preferential oxidation of CO under H₂-rich atmosphere, has been developed. When the molar ratio of Fe/Ir was 5/1, the IrFe/Al₂O₃ catalyst performed best, with CO conversion of 68% and oxygen selectivity towards CO₂ formation of 86.8% attained at 100 °C. It has also been found that the impregnation sequence of Ir and Fe species on the Al₂O₃ support had a remarkable effect on the catalytic performance; the activity decreased following the order of IrFe/Al₂O₃ > co-IrFe/Al₂O₃ > FeIr/Al₂O₃. The three catalysts were characterized by XRD, H₂-TPR, FT-IR and microcalorimetry. The results demonstrated that when Ir was supported on the pre-formed Fe/Al₂O₃, the resulting structure (IrFe/Al₂O₃) allowed more metallic Ir sites exposed on the surface and accessible for CO adsorption, while did not interfere with the O₂ activation on the FeO_x species. Thus, a bifunctional catalytic mechanism has been proposed where CO adsorbed on Ir sites and O₂ adsorbed on FeO_x sites; the reaction may take place at the interface of Ir and FeO_x or via a spill-over process.     

MnOx/Pt/Al2O3 catalysts for CO oxidation in H2-rich streams

The catalytic activity of Pt on alumina catalysts, with and without MnO_x incorporated to the catalyst formulation, for CO oxidation in H₂-free as well as in H₂-rich stream (PROX) has been studied in the temperature range of 25–250 °C. The effect of catalyst preparation (by successive impregnation or by co-impregnation of Mn and Pt) and Mn content in the catalyst performance has been studied. A low Mn content (2 wt.%) has been found not to improve the catalyst activity compared to the base catalyst. However, catalysts prepared by successive impregnation with 8 and 15 wt.% Mn have shown a lower operation temperature for maximum CO conversion than the base catalyst with an enhanced catalyst activity at low temperatures with respect to Pt/Al₂O₃. A maximum CO conversion of 89.8%, with selectivity of 44.9% and CO yield of 40.3% could be reached over a catalyst with 15 wt.% Mn operating at 139 °C and λ = 2. The effect of the presence of 5 vol.% CO₂ and 5 vol.% H₂O in the feedstream on catalysts performance has also been studied and discussed. The presence of CO₂ in the feedstream enhances the catalytic performance of all the studied catalysts at high temperature, whereas the presence of steam inhibits catalysts with higher MnO_x content.     

Mg、La助剂在镍基甲烷化催化剂中的协同作用

采用浸渍法制备Ni/Al2O3、La-Ni/Al2O3、Mg-Ni/Al2O3和Mg-La-Ni/Al2O3催化剂,讨论Mg和Ni两种助剂的协同作用,通过N2低温吸附、H2-TPR、XRD和SEM等表征方法对4种催化剂进行分析。结果表明,La助剂有利于削弱NiO与载体间的相互作用,降低催化剂中γ-NiO含量,但形成活性较低的α-NiO。Mg能够抑制催化剂中NiAl2O4尖晶石的形成,但Mg的添加会导致催化剂孔道堵塞,使NiO在催化剂表面团聚。Mg能够与NiO形成固溶体,在Mg的协同作用下,可抑制La-Ni/Al2O3催化剂中α-NiO的生成。La能够促进NiO分散,克服Mg-Ni/Al2O3催化剂孔道堵塞的缺陷。活性评价实验结果表明,添加不同助剂的催化剂在不同温度区域的活性不同,La-Ni/Al2O3催化剂低温活性较好,Mg-Ni/Al2O3催化剂高温活性较好,而在Mg和La两种助剂的协同作用下,Mg-La-Ni/Al2O3催化剂活性最高。     

Pt/TiO_2催化二甲醚部分氧化重整制氢

二甲醚是一种理想的氢载体,可用于解决氢的储存和运输。以Pt/TiO_2为部分氧化催化剂,结合Ni/Al_2O_3重整催化剂,考察钛前驱体和焙烧温度对二甲醚部分氧化重整制氢反应的影响。结果表明,以Ti(C4H9O)4为原料制备的TiO_2为金红石相,Ti(SO4)2或Ti O(OH)2为原料制备的TiO_2为锐钛矿相;以Ti(C4H9O)4为原料制备的Pt/TiO_2-E催化剂催化性能略好,转化率接近100%,H2收率约90%,表明金红石相TiO_2负载的Pt催化剂略佳;以Ti(SO4)2为原料制备的Pt/TiO_2-S催化剂500℃焙烧可获得金红石相TiO_2。与Pt/Al_2O_3催化剂相比,Pt/TiO_2催化剂具有更好的催化性能,H2收率超过90%,而Pt/Al_2O_3催化剂H2收率约80%。     

Development of Ni catalysts for tar removal by steam gasification of biomass

Catalytic performance of Ni/CeO₂/Al₂O₃ catalysts prepared by a co-impregnation and a sequential impregnation method in steam gasification of real biomass (cedar wood) was investigated. Especially, Ni/CeO₂/Al₂O₃ catalysts prepared by the co-impregnation method exhibited higher performance than Ni/Al₂O₃ and Ni/CeO₂/Al₂O₃ prepared by the sequential impregnation method, and the catalysts gave lower yields of coke and tar, and higher yields of gaseous products. The Ni/CeO₂/Al₂O₃ catalysts were characterized by thermogravimetric analysis, temperature-programmed reduction with H₂, transmission electron microscopy and extended X-ray absorption fine structure, and the results suggested that the interaction between Ni and CeO₂ became stronger by the co-impregnation method than that by sequential method. Judging from both results of catalytic performance and catalyst characterization, it is found that the intimate interaction between Ni and CeO₂ can play very important role on the steam gasification of biomass.     

A comparative study of the water-gas shift activity of Pt catalysts supported on single (MOx) and composite (MOx/Al2O3, MOx/TiO2) metal oxide carriers

The water-gas shift (WGS) activity of platinum catalysts dispersed on a variety of single metal oxides as well as on composite MO_x/Al₂O₃ and MO_x/TiO₂ supports (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, La, Ce, Nd, Sm, Eu, Gd, Ho, Er, Tm) has been investigated in the temperature range of 150–500 °C, using a feed composition consisting of 3% CO an 10% H₂O. For Pt catalysts supported on single metal oxides, it has been found that both the apparent activation energy of the reaction and the intrinsic rate depend strongly on the nature of the support. In particular, specific activity of Pt at 250 °C is 1–2 orders of magnitude higher when supported on “reducible” compared to “irreducible” metal oxides. For composite Pt/MO_x/Al₂O₃ and Pt/MO_x/TiO₂ catalysts, it is shown that the presence of MO_x results in a shift of the CO conversion curve toward lower reaction temperatures, compared to that obtained for Pt/Al₂O₃ or Pt/TiO₂, respectively. The specific reaction rate is in most cases higher for composite catalysts and varies in a manner which depends on the nature, loading, and primary crystallite size of dispersed MO_x. Results are explained by considering that reducibility of small oxide particles increases with decreasing crystallite size, thereby resulting in enhanced WGS activity. Therefore, evidence is provided that the metal oxide support is directly involved in the WGS reaction mechanism and determines to a significant extent the catalytic performance of supported noble metal catalysts. Results of catalytic performance tests obtained under realistic feed composition, consisting of 3% CO, 10% H₂O, 20% H₂ and 6% CO₂, showed that certain composite Pt/MO_x/Al₂O₃ and Pt/MO_x/TiO₂ catalysts are promising candidates for the development of active WGS catalysts suitable for fuel cell applications.     

碱金属K、Li对Ru/γ-Al_2O_3催化剂上CO选择性氧化的助催化作用

以Ru为活性组分,碱金属氧化物K2O和Li2O为助剂,采用浸渍法制备Ru/γ-Al2O3、Ru1K10Oy/Al2O3和Ru1Li10Oy/Al2O3催化剂,对制备的催化剂进行TPR、XRD和SEM表征,采用固定床石英反应器考察催化剂的CO氧化性能。结果表明,碱金属助剂的引入对Ru/γ-Al2O3的催化性能有一定影响,K2O和Li2O的掺杂,显著降低Ru/γ-Al2O3催化剂上CO选择性氧化温度。Ru1K10Oy/Al2O3和Ru1Li10Oy/Al2O3催化剂低温具有较高的CO转化率和选择性,随着反应温度的升高,提高CO转化率的同时,存在更多的氢气消耗,导致CO选择性降低。     

Partial oxidation of methane to synthesis gas over iridium–nickel bimetallic catalysts

Partial oxidation of methane to synthesis gas was carried out using supported iridium–nickel bimetallic catalysts, in order to reduce loading levels of iridium and nickel, and to avoid carbon deposition on nickel-based catalysts by adding iridium. The performance of supported iridium–nickel bimetallic catalysts in synthesis gas formation depended strongly upon the support materials. La₂O₃ gave the best performance among the support materials tested. Ir(0.25 wt%)–Ni(0.5 wt%)/La₂O₃ afforded 36% conversion of methane (CH₄/O₂=5) to give CO and H₂ with the selectivities of above 90% at 800°C, and those at 600°C were 25.3% conversion of methane and CO and H₂ selectivities of about 80%, respectively. Reduced monometallic Ir(0.25 wt%)/La₂O₃ and Ni(0.5 wt%)/La₂O₃ catalysts did not produce synthesis gas at 600°C. A higher conversion of methane was obtained by synergistic effects. The product concentrations of CO, H₂, and CO₂, and CH₄ conversion were maintained in high values, even increasing the space velocity of feed gas over Ir–Ni/La₂O₃ catalyst, indicating that rapid reaction takes place. As a by-product, a small amount of carbon deposition was observed, but carbon formation decreased with increasing the space velocity. On the other hand, with reduced monometallic Ni(10 wt%)/La₂O₃ catalyst, yield of synthesis gas and carbon decreased with increasing the space velocity.