高稳定性Ni/SBA-15催化剂的结构特征及其对二氧化碳重整甲烷反应的催化性能

 采用浸渍法制备了Ni含量为2.5%～20%的系列Ni/SBA-15催化剂,在常压连续流动固定床反应器上考察了催化剂对二氧化碳重整甲烷制合成气的催化性能,并用X射线衍射和N2吸附法研究了Ni/SBA-15催化剂的结构特征. 结果表明, Ni/SBA-15催化剂具有很高的CH4和CO2转化率, 12.5%Ni/SBA-15催化剂在800 ℃反应600 h后活性没有明显下降,但反应710 h后CH4的转化率下降了约50%, CO2的转化率下降了约25%. 其活性下降的主要原因是催化剂积炭. 在高温条件下反应时, SBA-15的介孔结构也没有遭到破坏,分子筛的孔壁能有效阻止活性组分Ni的团聚. SBA-15孔中组装一定量的Ni活性组分后,除了SBA-15的介孔外,还会形成另外一种较小的孔,但这不影响SBA-15的有序介孔结构,只是其孔径、孔容和BET比表面积降低.     

高效甲醇水蒸气重整制氢的SBA-15改性的Cu/ZnO/Al2O3催化剂

以介孔SBA-15为结构助剂, 制备出用于甲醇水蒸气重整制氢的新型高效氧化硅掺杂的Cu/ZnO/Al₂O₃催化剂, 并与传统Cu/ZnO/Al₂O₃催化剂在相同条件下的催化性能进行了比较. 结果表明, 添加适量介孔SBA-15可显著提高催化剂的催化活性和选择性, 在大幅度提高甲醇转化率的同时有效降低了重整产气中CO的含量. 原位XRD分析证实适量介孔SBA-15的添加对传统Cu/ZnO/Al₂O₃催化剂的微结构性质可产生重要的调控作用, 从而大大改善其催化活性和制氢选择性.     

Effect of O2 and H2O on the tri-reforming of the simulated biogas to syngas over Ni-based SBA-15 catalysts

A series of Ni/SBA-15 catalysts with Ni contents from 7.5 wt% to 15 wt% were prepared by impregnation method. The effect of O2 and H2O on the combined reforming of the simulated biogas to syngas was investigated in a continuous flow fixed-bed micro-reactor. The stability of the catalyst was tested at 800 ℃. The results indicated that 10 wt%Ni/SBA-15 catalyst exhibited the highest catalytic activities for the combined reforming of the simulated biogas to syngas. Under the reaction conditions of the feed gas molar ratios CH4/CO2/O2/H2O = 2/1/0.6/0.6, GHSV = 24000 ml•g{cat}-1\cdoth-1 and the reaction temperatureT = 800 ℃, the conversions of CH4 and CO2 were 92.8% and 76.3%, respectively, and the yields of CO and H2 were 99.0% and 82.0%, respectively. The catalytic activities of the catalyst did not decrease obviously after 100 h reaction time on stream.     

CeO2/Ni/Mo/SBA-15甲烷二氧化碳重整催化剂的表征和催化性能

考察了CeO2修饰及未修饰的Ni/Mo/SBA- 15催化剂在CH4-CO2重整上的催化性能并采用N2吸脱附、CO2程序升温脱附、H2程序升温还原、傅里叶红外光谱、X射线衍射、扫描电子显微镜和X射线光电子能谱对催化剂进行了表征.结果表明,在常压,800C条件下,经过100 h在线评价后,Ni/Mo/SBA- 15和CeOz/Ni/Mo/SBA- 15催化剂仍具有高的反应活性和规整的六方介孔结构,其中CeO2修饰的CeO2/Ni/Mo/SBA-15催化剂表面没有积炭形成,表明CeO2的加入促进了Ni物种在SBA-15介孔分子筛表面的分散,从而阻止了Ce/Ni/Mo/SBA- 15催化剂上Ni的烧     

基于改性Ni/γ-Al_2O_3催化剂的电催化甲烷水蒸气重整的研究

提出了电催化作用下甲烷水蒸气催化重整的新工艺。基于工业常规Ni基催化剂,采用等体积浸渍法,以Ni为活性组分,γ-Al_2O_3为载体,MgO、CaO为助剂,制备了Ni/γ-Al_2O_3、Ni-MgO/γ-Al_2O_3和Ni-CaO/γ-Al_2O_3催化剂,考察了电流强度、重整温度、水蒸气与甲烷的物质的量比(水碳比,S/C)对不同催化剂的CH_4转化率、H_2产率、CO选择性和催化剂稳定性的影响。结果表明,电催化工艺有着良好的普适性,电流的引入能够提升CH_4转化率、增加H_2产率,尤其在低温下电流的促进作用显著。在三种催化剂中,Ni-CaO/γ-Al_2O_3催化效果最佳,在电流为4.5 A、S/C为3、重整温度为700℃时,CH_4转化率就高达95%以上。稳定性测试表明,电流的通入还能显著提高催化剂的稳定性,延缓催化剂的积炭失活。通过对催化剂的分析表征,发现电流的通入提升了催化剂中NiO的还原程度,同时抑制了反应过程中NiC_x向石墨炭的转化,从而可延缓催化剂因积炭覆盖反应活性位点而造成的失活。     

Effect of MgO promoter on Ni-based SBA-15 catalysts for combined steam and carbon dioxide reforming of methane

A series of Ni/SBA-15 catalysts with Ni contents ranging from 5 wt% to 15 wt%, as well as another series of 10%Ni/MgO/SBA-15 catalysts, in which the range of the MgO content was from 1 wt% to 7 wt%, were prepared, and their catalytic performances for the reaction of combined steam and carbon dioxide reforming of methane were investigated in a continuous flow microreactor. The structures of the catalysts were characterized using the XRD, H2-TPR and CO2-TPD techniques. The results indicated that the CO selectivity for this reaction was very close to 100%, and the H2/CO ratio of the product gas could be controlled by changing the H2O/CO2 molar ratio of the feed gas. The simultaneous and plentiful existing of steam and CO2 had a significant influence on the catalytic performance of the 10%Ni/SBA-15 catalyst without modification. After reacting at 850 °C for 120 h over this catalyst, the CH4 conversion dropped from 98% to 85%, and the CO2 conversion decreased from 86% to 53%. However, the 10%Ni/3%MgO/SBA-15 catalyst exhibited a much better catalytic performance, and after reacting for 620 h, the CO2 conversion over this catalyst dropped from 92% to around 77%, while the CH4 conversion was not decreased. Oxidation of the Ni0 species as well as carbon deposition during the reaction were the main reasons for the deactivation of the catalyst without modification. On the other hand, modification by the MgO promoter improved the dispersion of the Ni0 species, and enhanced the CO2 adsorption affinity which in turn depressed the occurring of carbon deposition, and thus retarded the deactivation process.     

助剂MgO、CaO对甲烷水蒸气重整Ni/γ-Al2O3催化性能的影响

采用固定床装置,考察了以共浸方式引入的助剂MgO、CaO对Ni/γ-Al₂O₃催化剂在甲烷水蒸气催化重整中的催化反应性能的影响。结果表明,在H₂O/CH₄/N₂的摩尔比为2.86/1/3.28,GHSV为1800h^－1,反应温度为700℃下,催化剂Ni-CaO/Al₂O₃催化性能最好;反应初期甲烷转化率可达到96.95%、CO选择性可达68.93%、H₂收率可达73.58%。XRD和H₂-TPR结果表明,CaO的存在使催化剂中的活性NiO组分增多,还原性和分散性能较好。利用热分析技术对积炭进行考察发现反应10h后的Ni-CaO/Al₂O₃催化剂上并未出现导致催化剂失活的炭物种。     

Improving Catalytic Stability and Coke Resistance of Ni/Al2O3 Catalysts with Ce Promoter for Relatively Low Temperature Dry Reforming of Methane Reaction

Aseries of Ni catalysts supported on alumina with different Ce contents(1.0%-6.0%, mass fraction) was prepared by the impregnation method and used for dry reforming of methane(DRM) at a relatively low temperature of 650 ^oC. The promotion effect of Ce with different loading amounts on the physicochemical properties of the catalysts was systematically characterized by transmission electron microscopy(TEM), X-ray diffraction(XRD), N₂ adsorption-desorption, thermo elemental IRIS Intrepid inductively coupled plasma atomic emission spectrometer (ICP-AES), UV-visible diffuse reflectance spectroscopy(UV-Vis DRS), Fourier transformation infrared(FTIR) spectra, H₂-temperature programmed reduction(H₂-TPR) analysis, H₂-temperature programmed desorption(H₂-TPD), and the X-ray photoelectron spectroscopy(XPS) techniques. The results indicate that all the catalysts mainly exist in the NiAl₂O₄ phase after being calcined at 750 ^oC with small Ni particle sizes due to the strong metal-support interaction derived from the reduction of the NiAl₂O₄ phase. The Ce-promoted catalysts show better catalytic performance as well as the resistance against sintering of Ni particles and deposition of carbon compared to the Ni/Al₂O₃ catalyst. The Ni-6Ce/Al₂O₃ exhibits the best catalytic stability and coke resistance among the four catalysts studied, which is due to its small Ni nanoparticles sizes, excellent reducibility as well as high amount of active oxygen species. In a 400 h stability test for DRM reaction at 650 ^oC, Ni-6Ce/Al₂O₃ exhibits less coke deposition and small growth of Ni nanoparticles. This work provides a simple way to preparing the Ni-Ce/Al₂O₃ catalyst with enhanced catalytic performance in DRM. The Ni-6Ce/Al₂O₃ catalyst has great potential for industrial application due to its anti-sintering ability and resistance to carbon deposition.     

Nd,Ce和La改性对Ni/SBA-15催化剂在CH4/CO2重整反应中性能的影响

以稀土金属Nd,Ce或La的氧化物为助剂,采用β-环糊精浸渍法对Ni/SBA-15催化剂进行了改性,并运用X射线衍射、N₂吸附-脱附、程序升温还原和热重等手段考察了改性的催化剂在CO₂重整CH₄制合成气反应中的催化性能. 结果表明,Nd等稀土金属氧化物的添加对催化剂孔结构和晶相结构等性质影响不大,但可影响NiO的还原; Nd的添加使NiO与载体之间以Ni-Nd-O形式相互作用,促进了活性组分NiO的还原. 其中,Nd的添加量为5-10 wt%时所制备的催化剂在重整反应中的催化活性最高,且具有很强的抗积碳性能. La和Ce氧化物促进的Ni催化剂也表现出类似的性质和催化性能.     

镧助剂对模拟生物沼气重整制备合成气中Ni/SBA-15催化剂结构和性能的影响

以介孔分子筛SBA-15为载体, 采用浸渍法制备了镍质量分数(w)为12.5%, 并且分别添加质量分数(w)为2.5%的镧、铈、镁、钙、锶等助剂的系列Ni基催化剂. 以CH4/CO2体积比为2:1的模拟生物沼气和适量氧气作为原料气, 在常压固定床反应器上评价了催化剂对模拟生物沼气重整制合成气的反应性能. 采用X射线粉末衍射(XRD)、N2吸附/脱附、透射电子显微镜(TEM)、X射线光电子能谱(XPS)及H2程序升温还原(H2-TPR)等对催化剂的结构进行了表征. 催化活性评价显示, 添加镧助剂的2.5%La/12.5%Ni/SBA-15催化剂比添加铈、镁、钙、锶等助剂的催化剂具有更高的催化活性, 并且具有很好的稳定性. 因此, 文中着重研究了镧助剂对催化剂结构和模拟生物沼气重整制合成气的反应性能的影响. 结果表明, 镧能明显提高Ni/SBA-15催化剂的表面镍含量, 同时还具有很好的抗积炭作用, 在850 ℃的温度下反应820 h没有发现积炭生成, 这些可能是提高催化剂性能和稳定性的重要因素.     

B助剂对Ni2P/SBA-15催化剂结构及其加氢脱硫性能的影响

以介孔分子筛SBA-15为载体, 磷酸氢二铵为磷源, 硝酸镍为镍源, 硼酸为硼源, 采用共浸渍法制备了B-Ni₂P/SBA-15催化剂前驱体, 然后采用程序升温氢气还原法, 制备了n_P/n_Ni=0.8, B含量为0.35%-2.10%(w)的一系列B-Ni₂P/SBA-15催化剂. 用X射线衍射(XRD)、N₂吸附脱附、透射电子显微镜(TEM)和氨气程序升温脱附(NH₃-TPD)等表征技术对催化剂的结构进行了研究, 以1%(w)二苯并噻吩(DBT)/十氢萘溶液为模型化合物, 在微型固定床反应器上对催化剂的加氢脱硫(HDS)性能进行了评价. 结果表明, B-Ni₂P/SBA-15催化剂仍具有介孔结构, Ni₂P为主要的活性物相. 适量B助剂的加入可促使Ni₂P晶粒减小, 催化剂比表面积增加. 此外, 随着B含量的增加, B-Ni₂P/SBA-15催化剂的总酸量也增加. 当反应压力为3.0 MPa, 反应温度由300 ℃升高至360 ℃时, B含量对Ni₂P/SBA-15催化剂活性有明显的影响, B含量为1.40%(w)的B-Ni₂P/SBA-15催化剂加氢脱硫活性最高. B-Ni₂P/SBA-15催化剂上二苯并噻吩的加氢脱硫的反应机理以直接脱硫为主.     

Effect of Cu promoter on Ni-based SBA-15 catalysts for partial oxidation of methane to syngas

A series of Ni/SBA-15 catalysts with 5wt% to 15wt% Ni content as well as a series of 12.5%Ni/Cu/SBA-15 catalysts with 1% to 10% copper content were prepared by the impregnation method. The catalytic performance for partial oxidation of methane was investigated in a continuous flow microreactor under atmospheric pressure. The textural and chemical properties of the catalysts were characterized by XRD, TEM, BET and H2-TPR techniques. The results indicated that the catalysts modified with Cu promoter showed better performance than those without modification. For the 12.5%Ni/2.5%/Cu/SBA-15 catalyst, at 850 ◦C the conversion of CH4 reached 97.9% and the selectivity of CO and H2 reached 98.0% and 96.0%, respectively. In XRD patterns of the Ni/Cu/SBA-15 catalyst with 7.5 to 10% Cu contents there were CuO characteristic peaks beside NiO characteristic peaks. The mesoporous structure of SBA-15 was retained in all of the catalysts. TPR analysis of the catalysts revealed that a strong interaction between Ni, Cu promoter and SBA-15 support may be existed. This interaction enhanced significantly the redox properties of the catalysts resulting in the higher catalytic activity.     

H5PMo10V2O40/SBA-15催化剂的制备及其催化性能

以Keggin型杂多酸H5PMo10V2O40为主体,SBA-15介孔分子筛为载体,利用溶胶-凝胶法制备了不同负载量的H5PM10V2O40/SBA-15负载型催化剂,通过XRD、FTIR、TEM、H2-TPR和N2吸脱附法对样品进行了分析和表征,并将制得的负载型催化剂应用于苯氧化苯酚的反应中,研究了不同条件(温度、时间和催化剂用量等)下的催化性能.研究结果表明:H5PMo10V2O40杂多酸能均匀地分散于SBA-15孔道中且SBA-15的六方介孔结构并未发生改变:较好地解决了活性组分大量溶脱的问题;与H5PMo10V2O40杂多酸相比,H5PMo10V2O40/SBA-15催化剂在苯氧化为苯酚的反应中具有更高的转化率和更好的选择性,当反应温度为70℃,催化剂的使用量为0.25 g,反应时间为2 h和H5PMo10V2O40负载量为60%时苯酚的选择性达到了82.53%.     

Ni2P/SBA-15催化剂的结构及加氢脱硫性能

以硝酸镍为镍源,磷酸氢二铵为磷源,介孔分子筛SBA-15为载体,用共浸渍法制备了含磷化镍前驱体的样品,然后在氢气流中采用程序升温还原法,制备了Ni2P质量分数为5%-40%的Ni2P/SBA-15催化剂.用X射线衍射(XRD)、N2吸附脱附、透射电子显微镜(TEM)、傅立叶变换红外光谱(FTIR)等分析测试技术对催化剂的结构进行了表征,以噻吩和二苯并噻吩(DBT)为模型化合物,在微型同定床反应器上对催化剂的加氧脱硫(HDS)性能进行了评价.结果表明,Ni2P/SBA-15催化剂中SBA-15的介孔结构依然存在,活性组分Ni2P具有良好的分散性,但随Ni2P含量的增加,催化剂的比表面积、孔容和孔径均有明显减小.当反应温度为320℃时,Ni2P含量为15%-25%(w)的催化剂就具有很好的加氢脱硫催化性能;反应温度在360℃以上时,所有催化剂都具有优异的深度脱硫催化性能.Ni2P/SBA-15催化剂对二苯并噻吩的加氢脱硫(HDS)主要以直接脱硫机理(DDS)进行.     

Reforming of CH4 with CO2and O2to produce syngas over CaO modified Ni/SiO2 catalysts in a fluidized bed reactor

Methane reforming by carbon dioxide and oxygen was investigated over 5 wt.%Ni/CaO-SiO₂ catalyst in a fluidized-bed reactor. The catalyst exhibited high activity and good stability at stoichiometric methane, carbon oxide and oxygen feed. Effects of calcium loading, space velocities, reaction temperatures and the feed gas compositions for this combined reaction were investigated. These results indicated that Ni/CaO-SiO₂ is more effective and stable. The catalyst performance, stability, structure, dispersion of nickel and carbon deposition of the modified and unmodified catalysts were investigated by a series of characterization techniques. Results showed that catalysts modified with CaO improved their stability better than the pure nickel-based catalysts. This revised version was published online in June 2006 with corrections to the Cover Date.     

SBA-15的硅烷化对钴基催化剂费-托合成性能的影响

以未硅烷化和硅烷化的SBA-15为载体,采用满孔浸渍法制备了钴基费-托合成催化剂,通过元素分析、N_2吸附-脱附、X射线衍射、H_2程序升温还原、H_2程序升温脱附以及氧滴定等手段对催化剂进行了表征.催化剂的费-托合成活性测试在固定床反应器上进行.研究表明,对于SBA-15硅烷化后制备的催化剂,金属钴与载体之间的相互作用降低,氧化钴的还原度增加.随着三甲基氯硅烷用量的增加,三甲基硅基的表面覆盖度增加,钴的晶粒直径增大.硅烷化后的催化剂的高活性归因于高的还原度.而C_(5+)选择性的增加则归因于钴晶粒直径的增大.     

Ni3Al箔在甲烷重整反应中的催化性能

研究了以冷轧工艺制备的Ni₃Al单晶箔(Ni-24at% Al), 以及表面预处理(873 K下蒸汽氧化后还原处理)后的Ni₃Al箔, 在甲烷重整制氢反应中的催化性能. 首先, 采用逐步升温法研究了873～1173 K下Ni₃Al箔的催化活性与温度的关系; 然后, 采用等温法研究了973 K下Ni₃Al箔的催化稳定性. 根据催化反应和扫描电镜显微观察的结果得出: 未经预处理和经过预处理的Ni₃Al箔, 在反应中均显示出一定的催化活性和稳定性; 表面预处理对Ni₃Al箔的催化活性有显著的增强作用, 原因是经过该预处理后的Ni₃Al箔形成了富Ni表面; Ni₃Al箔在甲烷重整反应的气氛中, Ni原子从Ni₃Al基体向表面的移动, 是维持催化活性的主要原因.     

Pt/CexZr1-xO2 催化剂在含硫合成气中催化水煤气变换反应活性

 采用浸渍法制备了 Pt/Ce_xZr_1-xO₂ 催化剂, 通过 X 射线衍射和程序升温还原等方法对催化剂进行了表征, 并在固定床反应器中评价了催化剂在合成气和含硫合成气中的水煤气变换活性. 结果表明, 铈锆固溶体的氧化还原能力强于 CeO₂, Zr 的掺杂明显改善了 CeO₂ 的孔道结构, 其担载的 Pt 催化剂具有更高的金属分散度, 因而活性更高. 两种催化剂在含硫合成气中的催化活性较无硫合成气中的均有所降低, 且 H₂S 浓度越大, 催化剂活性下降越多, 但这种因吸附硫而引起的失活是可逆的, 即催化剂重新暴露在无 H₂S 重整气的还原性气氛下活性能基本恢复.     

COO-NiO/SBA-15的合成与表征

用组装的方法得到了高负载量、均匀分布的CoO-NiO负载型SBA-15介孔材料,并采用XRD,BET,HRTEM等测试手段对样品进行了分析.结果表明,CoO,NiO双组分氧化物已成功地组装进入了SBA-15的有序孔道,在CoO,NiO组装过程中,CoO,NiO含量(w)分别为0.0691和0.0837时,介孔材料的有序结构没有遭到破坏.     

乙醇水蒸气重整Co/CeO2催化剂

 采用共沉淀法制备了Co/CeO2催化剂并将其应用于乙醇水蒸气重整制氢反应,考察了活性组分含量和焙烧温度对催化剂性能的影响. 结果表明,在原料气水∶乙醇∶N2摩尔比为3∶1∶16, 空速为40 L/(g·h)和反应温度为350～600 ℃的条件下, 经650 ℃焙烧的10%Co/CeO2催化剂对乙醇水蒸气重整制氢反应具有高活性和高选择性. 在500 ℃下进行的40 h稳定性测试中,该催化剂上的乙醇转化率始终接近100%, 反应后气体中的H2含量保持在65%左右. X射线衍射表征结果显示,焙烧后催化剂的主要物相组成为Co3O4和CeO2, 二者之间存在相互作用. Co/CeO2催化剂中钴的主要存在形式包括小晶粒的钴氧化物、大晶粒Co3O4和进入CeO2晶格的钴,Co3O4含量和焙烧温度的改变可影响催化剂中钴的存在形式. 由催化剂中高分散小晶粒的钴氧化物还原所得的金属钴是关键的活性组分.