Dry reforming of methane on active and coke resistant Ni/Y_2Zr_2O_7 catalysts treated by dielectric barrier discharge plasma

In this study, Ni/Y_2Zr_2O_7 catalysts prepared with impregnation method and treated by dielectric barrier discharge plasma(DBD) in different atmospheres have been investigated for methane dry reforming. It is revealed by H_2-TPR that plasma treatment can enhance the interaction between Ni O/Ni particles and the Y_2Zr_2O_7 pyrochlore support. Therefore, catalysts with smaller Ni O and Ni grains sizes, higher metallic Ni active surface areas can be achieved, as evidenced by XRD, TEM and H_2 adsorption-desorption measurements. As a consequence, the plasma-treated catalysts show significantly improved activity, stability and coke resistance, as testified by the TEM and TGA-DSC results. Plasma treatment in H_2/Ar gas mixture is found to be the best condition to prepare Ni/Y_2Zr_2O_7, which can be used to obtain a catalyst with the highest activity, stability and most potent coke resistance. It is believed that the smaller Ni grain size and higher metallic Ni active surface area induced by plasma treatment are the inherent reasons accounting for the promoted reaction performance of the Ni/Y_2Zr_2O_7 pyrochlore catalysts.     

溶剂化金属原子浸渍法制备高分散负载型催化剂(Ⅶ)——Ni-Cu/SiO2双金属催化剂的结构与性能

利用金属蒸气法制备了不同组成的Nj-CujSiO₂双金属催化剂,XRD、TEM和磁性测定表明有Ni-Cu合金形成,合金颗粒的组成不均匀,而且有部分自由的Ni和Cu存在;Ni/Cu摩尔比为1:1催化剂的催化活性大于2:1和3:1的双金属催化剂以及Ni和Cu的单金属催化剂。     

溶剂化金属原子浸渍法制备高分散负载型催化剂——ⅩⅤⅠ.聚合物负载La-Ni和Ni催化剂的性质

应用溶剂化金属原子浸渍(Solvated metal atom impregnation)技术制备了D-72树脂负载的和非负载的La-Ni和Ni催化剂.X-ray diffraction和磁测定结果表明La-Ni催化剂中La和Ni已形成合金.合金和镍颗粒极小,平均直径小于4.0nm.负载催化剂的金属粒度小于非负载催化剂.X-rayphotoelectron spectroscopy结果表明Ni主要以零价态存在,La以金属La和La_2O_3存在.在丙酮和二丙酮醇加氢反应中,D-72负载催化剂的活性均高于对应的非负载催化剂.     

溶剂化金属原子浸渍法制备高分散负载型催化剂——ⅩⅤⅠ.聚合物负载La-Ni和Ni催化剂的性质

 应用溶剂化金属原子浸渍(Solvated metal atom impregnation)技术制备了D-72树脂负载的和非负载的La-Ni和Ni催化剂.X-ray diffraction和磁测定结果表明La-Ni催化剂中La和Ni已形成合金.合金和镍颗粒极小,平均直径小于4.0nm.负载催化剂的金属粒度小于非负载催化剂.X-rayphotoelectron spectroscopy结果表明Ni主要以零价态存在,La以金属La和La₂O₃存在.在丙酮和二丙酮醇加氢反应中,D-72负载催化剂的活性均高于对应的非负载催化剂.     

Methane reforming With CO2 to syngas over CeO2-promoted Ni/Al2O3-ZrO2 catalysts Prepared Via a direct sol-gel process

CeO2-promoted Ni/Al2O3-ZrO2 (Ni/Al2O3-ZrO2-CeO2) catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy (IR), thermal gravimetric analysis (TGA), microscopic analysis, X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts. The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst. The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.     

抗积炭CH_4/CO_2重整用Ni/Al_2O_3催化剂

甲烷转化制备的合成气是合成液体燃料和含氧有机化合物的原料 .甲烷转化制合成气的方法有甲烷蒸汽重整、甲烷部分氧化和甲烷、二氧化碳重整 3种 [1～ 3] .对于 CH4/CO2 重整反应 ,调节进料比可制备出 H2 /CO≤ 1、富含 CO的合成气 ,它适于羰基合成和 F- T合成 .这种方法一方面充分利用碳资源 ,缓解能源危机 ;一方面可减少温室气体的排放 ,改善人类的居住环境 .目前倍受关注 .CH4/CO2 重整制合成气 ,Rh、Ru、Pd、Ir等贵金属有很高的活性和稳定性 [4] .但其价格昂贵 ,高温易流失 ,商业化困难 .Ni基催化剂的活性与贵金属相当 ,但它易积…     

镁铝混合氧化物负载镍催化剂上液化石油气的预重整

采用共沉淀-浸渍法并在较低温度(400～700℃)下焙烧制备了镁铝混合氧化物(MgmAl)负载的Ni催化剂.X射线衍射和程序升温还原结果表明,Ni物种高度分散于催化剂表面,没有形成尖晶石NiAl2O4.在650℃可被还原成金属Ni纳米晶粒,在400℃和较低水/碳摩尔比(S/C=2)条件下表现出较好的催化液化石油气(LP...     

碱金属和碱土金属促进的Ni/SiO2催化剂上甲烷的二氧化碳重整制合成气

Ni/SiO2 catalysts promoted by alkali metals K and Cs or alkaline earth metals Mg, Ca, Sr and Ba were prepared, characterized by H2-TPR and XRD, and used for the production of synthesis gas via methane reforming with CO2. Though K and Cs promoted Ni catalysts could eliminate coke deposition, the reforming activity of these promoted catalysts was decreased heavily. Mg and Ca promoted Ni/SiO2 catalysts exhibited excellent coke resistance ability with minor loss of the reforming activity of Ni/SiO2. Ba showed poor coke resistance ability and small amount of Sr increased the formation of coke. The possible mechanism of these promoters was discussed.     

La2O3对沼气重整制氢催化剂Ni/γ-Al2O3的影响

用浸渍法制备了不同La2O3含量的Ni/La2O3/γ-Al2O3催化剂, 用CH4/CO2体积比为1的混合气体模拟沼气, 考察了La2O3对沼气重整制氢催化剂Ni/γ-Al2O3的结构及催化性能的影响. 运用XRD、H2-TPR、BET及TEM等手段对催化剂进行了表征. 结果表明, La2O3对催化剂Ni/γ-Al2O3的影响主要取决于其含量. 载体中La2O3的添加增强了Ni与Al2O3之间的相互作用. 添加适量的La2O3能使催化剂具有更好的可还原性, 并能增加金属Ni的分散性, 抑制反应过程中Ni的烧结, 提高载体对CO2的吸附能力, 从而改善了催化剂的抗积炭性, 使催化剂具有较好的活性及稳定性. 反之, 过量La2O3的掺杂会使催化剂的抗积炭性及活性下降. 当La2O3含量为6%(w)时, 催化剂中Ni晶粒具有较好的分散性、还原性及抗积炭性, 从而使催化剂具有更好的活性及稳定性.     

甲烷部分氧化制合成气Ni/MgO和Ni-MgO/MgO催化剂的研究

甲烷氧化偶联制乙烷、乙烯以及甲烷选择氧化制甲醇、甲醛等反应 ,因其转化率和收率低 ,故短期内无法实现工业化 .目前 ,工业上应用甲烷蒸汽转化制合成气 ,进而合成氨等化工产品 .甲烷蒸汽转化制的合成气 ,其 H2 /CO≥ 3,不适用于甲醇合成和 F- T合成 .而甲烷部分氧化制的合成气 ,其H2 /CO≤ 2 ,因而最适合用于甲醇合成和 F- T合成 ,故近 1 0年来倍受科学家的关注[1 ,2 ] .在 CH4部分氧化制合成气中 ,钌、铑、钯、铂等贵金属催化剂的活性高、选择性好、稳定性好[1 ] ,但价格昂贵 (负载量以 1 2 %～ 4 0 %为佳 ) ,因而难以实现商品化 .N…     

Liquid Phase Hydrogenation of t,t,c‐1,5,9‐Cyclododecatriene over Ni/MCM‐41 and Ni/SiO2 Catalysts

Ni‐loaded pure siliceous and aluminosilicate MCM‐41 (Ni/MCM‐41) and nickel‐loaded silica (15Ni/SiO₂) were synthesized via wet impregnation and were characterized by various techniques. The H₂ consumption in the TPR analysis was found to be proportional to the Ni amount in the calcined samples. After reduction the average Ni particle sizes of 15Ni/MCM‐41 and 15Ni/SiO₂ were 9–12 and 16 nm, respectively, by means of XRD and TEM measurements. All catalysts owned weak and intermediate Lewis acid sites that increased slightly with increasing the Ni amount and the Al content. In the liquid phase hydrogenation of t,t,c‐1,5,9‐cyclododecatriene over Ni/MCM‐41, the catalytic activity was parallel to the Ni content and enhanced slightly with the acid amount of the catalysts. Consequently, it was proposed that the Ni metallic sites contributed the major effect to the catalytic activity while the Lewis acid sites promoted a small but significant influence on the catalytic performance. It is noteworthy that all 15Ni/MCM‐41 catalysts exhibited remarkably higher activity than that of the conventional 15Ni/SiO₂ catalyst.     

Mo对Ni/ZnO催化乙醇水蒸气重整制氢性能的影响

考察了Mo及温度对Ni/ZnO催化乙醇水蒸气重整制氢的活性、选择性和抗积炭性能的影响。结果表明，773K适量添加Mo能提高Ni/ZnO催化剂的活性和氢气选择性；Ni/ZnO及Ni-Mo/ZnO催化剂的活性随着温度的升高而提高，823K乙醇完全转化；873K时，Mo质量分数为0.83%的Ni-Mo/ZnO催化剂对氢气的选择性最高；添加Mo可以提高Ni/ZnO催化剂的抗积炭能力，从而提高该催化剂的稳定性。程序升温还原（TPR）和X射线衍射（XRD）结果表明，添加Mo有利于Ni氧化物在载体上的分散；减弱氧化态镍物种与载体之间的作用，从而提高了催化剂的活性、选择性和稳定性。     

A study of acidity and coke deposits on NiHZSM-5 catalyst in aromatization

The acidity and coke deposits of HZSM-5 and NiHZSM-5 catalysts were studied in the aromatization using NH₃-TPD, IR and TPD techniques. The results showed that both strong acid and B acid sites decreased quickly at the initial stage of reaction for the two catalysts. The coking and reaction rates also dropped quickly at this stage. Yet it was discovered, that adding Ni into HZSM-5 led to weakening B acid sites and strengthening L acid ones. At the same time, the results revealed that metallic Ni decreases the coking rates and slows down the activity decline rates.     

Ni-Fe/蒙脱土催化剂催化乙醇水蒸气重整制氢的研究

采用浸渍法制备了一系列Ni-Fe/蒙脱土(MMT)催化剂,并应用于乙醇水蒸气重整制氢反应(ESR)。采用X射线衍射(XRD)、N_2吸附脱附分析和H_2-程序升温还原(H_2-TPR)表征手段对催化剂的物理化学性质、还原性能、碳沉积等进行了研究。结果表明,Ni-Fe/MMT催化剂中,Ni、Fe高度分散在载体MMT层间及表面,而且Fe的加入降低了Ni颗粒的粒径,增强了Ni~(2+)与载体的相互作用力。以10Ni5Fe/MMT为催化剂,在反应温度为500℃、水醇比为3∶1、空速为12 h~(-1),反应进行30 h后,乙醇转化率为100%,氢气选择性仍保持72%,副产物CO和CH_4含量明显降低。这是因为催化助剂Fe的引入,一方面,提高了Ni的分散度,使得ESR低温活性较好;另一方面,减小了Ni颗粒粒径,小颗粒的Ni有利于抑制甲烷的生成,并且Fe的加入加强了甲烷重整和水煤气变换反应,提高产物中氢气的选择性。     

Synthesis of Ni2P promoted trimetallic NiMoW/γ-Al2O3 catalysts for diesel oil hydrotreatment

The Ni2P promoted and γ-Al2O3 supported NiMoW sulfide catalyst consisting of 4 wt% Mo, 22 wt% W, 2 wt% Ni and 2.5 wt% Ni2P was synthesized by a co-impregnation method. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, NH3 temperature-programmed desorption (NH3-TPD) and transmission electron microscopy (TEM). The results showed that Ni2P, Ni, Mo and W species were highly dispersed over γ-Al2O3. The hydrodesulfurization (HDS) of dibenzothiophene (DBT) showed that the presence of Ni2P brought a strong promotional effect on the HDS activity, which was further confirmed by the HDS and hydrodenitrogenation (HDN) of diesel oil under industrial conditions. The enhancement in HDN activity and stability by Ni2P addition could be attributed more to the effect of new active sites of Ni2P than that of acidity modification. The as-prepared Ni2P-NiMoW/γ-Al2O3 catalyst showed better hydrotreating performance than NiMoW/γ-Al2O3 and commercial catalysts.     

抽放煤层气（CH4-CO2-Air）制合成气的研究——固溶体的形成对NiO/MgO催化剂性能的影响

采用浸渍法制备了NiO/MgO催化剂，用TPR、XRD、BET、H2(O2)化学吸附等技术对催化剂进行了表征，对催化剂在甲烷空气部分氧化与CO2重整耦合制合成气反应中的催化性能进行了评价。结果表明，在800 ℃焙烧的催化剂中，NiO完全与MgO形成NixMg1－xO固溶体。与低温焙烧的NiO/MgO催化剂相比，虽然NixMg1－xO固溶体催化剂的还原度较低，但可以获得较高的金属分散度和较小的金属粒径，能有效抑制积炭的生成，在反应过程中显示出良好的活性稳定性。对于900 ℃焙烧的催化剂，由于形成了更多难还原的体相固溶体，催化剂的初活性较低。     

STUDIES ON REFORMING NATURAL GAS WITH CARBON DIOXIDE TO PREPARE SYNTHESIS GAS XI. Effect of La2O3 Promoter on Ni/|á-Al2O3 Catalysts

This paper reports the results of our experiments on the activity and stability of La2O3 promoted Ni/|á-Al2O3 catalysts used in reforming natural gas (or methane) with carbon dioxide under atmospheric pressure by using a fixed bed flow reactor and XRD and TPR techniques. It was showed that the activity and stability of Ni/|á-Al2O3 catalysts modified by La2O3 were higher than that of unmodified one, and the optimum content of La2O3 was 2%(wt).     

用MS-PSR技术研究甲烷部分氧化反应的引发过程

借助质谱 程序升温表面反应(MS TPSR)技术研究了NiO/悛睞l2O3、700 ℃ H2还原 后的Ni0/悛睞l2O3和添加Pt的NiO/悛睞l2O3催化剂(分别记为NiO、Ni0和Pt NiO)上甲烷 部分氧化反应(POM)的引发行为.结果表明,在CH4＋O2气氛下NiO和Ni0具有相同的引发行为 , Ni0在反应气氛下首先被氧化为NiO.在低于760 ℃时, CH4和O2在NiO上发生深度氧化反 应生成H2O和CO2,在770 ℃开始逐渐引发POM反应. Pt NiO在520 ℃左右就能引发POM反应 .在流化床反应器中Pt NiO催化剂500 ℃左右引发POM反应,并且具有与Ni0基本相同的反应 性能,因此添加Pt有利于氧化镍还原为Ni0,从而降低了POM反应的引发温度.     

活性炭负载Pt-Ni双金属催化剂上甘油水溶液原位加氢反应性能

采用KBH4液相还原法制备了系列活性炭(AC)负载的Pt-M(M=Fe,Ni,Co,Zn,Cu)双金属催化剂,考察了该系列催化剂对甘油水溶液原位加氢制备1,2-丙二醇反应的催化性能.结果表明,当Pt负载量(质量分数)为2.0%,Pt/Ni质量比为1∶1时,在220℃和1.0 MPa氮气压力下反应8 h,2%Pt-2%Ni/AC催化剂上甘油转化率和1,2-丙二醇选择性分别达到98.7%和60.5%;且在5次重复使用过程中,催化剂保持较高的稳定性.采用氮气物理吸附-脱附实验、X射线衍射(XRD)、透射电子显微镜(TEM)、选区电子衍射(SAED)及X射线光电子能谱(XPS)等对催化剂的结构和形貌进行了表征.结果表明,粒径约为2 nm的纳米颗粒在活性炭载体上均匀分散,纳米粒子中金属多以还原态形式存在,Ni原子进入Pt晶格中形成的Pt-Ni物种使Pt与Ni之间表现出强相互作用力.通过比较Pt/AC,Ni/AC与Pt-Ni/AC双金属催化剂的催化性能,推断Pt能够促进甘油水溶液重整而Ni有利于氢解反应,Pt-Ni金属间协同作用是Pt-Ni/AC催化剂对甘油原位加氢反应具有优良催化性能的重要原因.     

甲烷干重整催化剂Ni/Al2O3表面积炭表征与分析

用蒸发法制备了Ni/Al2O3催化剂及浸渍法制备了Ni/α-Al2O3和Ni/γ-Al2O3催化剂, 并与商品天然气水蒸气重整催化剂Z118Y一起进行了甲烷干重整实验, 考察了各催化剂上表面积炭行为. 通过H2程序升温还原(H2-TPR)、BET(Brunauer-Emmett-Teller)比表面积分析、X射线衍射(XRD)、透射电镜(TEM)、热重-差式扫描量热(TG-DSC)、程序升温氢化(TPH)等表征手段对催化剂表面沉积炭的特性进行了表征. 结果表明, 各催化剂上至少存在三种形式的碳物种: 无定形碳、丝状碳及石墨碳. 由于载体性质不同, 各催化剂上沉积炭的种类及其含量有所差别. Z118Y、Ni/Al2O3及Ni/α-Al2O3催化剂上主要沉积丝状炭, 而Ni/γ-Al2O3催化剂上则主要是石墨碳. Ni/γ-Al2O3催化剂中金属Ni颗粒较小(小于15 nm)、粒径分布范围较窄、分散性较好, 能减少催化剂表面炭的沉积, 有效地抑制丝状碳的生长.