Ni/Al2O3催化甲烷裂解

分别通过浸渍法和共沉淀法制备了不同Ni负载量的Ni/Al2O3催化剂。考察了Ni负载量、制备方法以及反应温度对Ni/Al2O3催化甲烷裂解性能的影响。结果表明,在550℃,浸渍法制备的Ni/Al2O3催化剂,当Ni负载量为20%(质量分数)、Ni金属平均粒径为11.25 nm时,具有最佳的甲烷催化裂解效果,其每摩尔Ni的氢气产量和每克Ni碳产量分别为164 mol和15.30 g。催化剂制备方法对Ni/Al2O3甲烷催化裂解反应有显著影响,相同Ni负载量共沉淀法制备的Ni/Al2O3甲烷催化裂解总体效果要好于浸渍法制备的Ni/Al2O3,而且反应过程中生成的碳纤维较长,管径也较均一。550℃时,共沉淀法制备的Ni负载量为41.2%(质量分数)的Ni/Al2O3催化剂在反应至350 min时,仍保持着30%以上的转化率。     

碱性助剂的添加对Ni/CaO-Al2O3催化剂性能的影响

在CH4、 CO2和O2制合成气的反应中, 通过在Ni/CaO-Al2O3催化剂中添加碱性助剂K2O、 MgO和La2O3, 使催化剂的性能得到了改善. 实验结果表明, MgO和La2O3助剂的添加, 有利于提高催化剂的活性;添加K2O, 却相反. 测得催化剂上积炭量的顺序为: Ni-La2O3/CaO-Al2O3相似文献   

制备方法对La改性的Ni/γAl2O3催化甲烷部分氧化的研究

采用共沉淀法和浸渍法制备La改性的Ni/γAl2O3催化剂，并用于催化甲烷部分氧化反应。共沉淀法制备的催化剂表现出较高的活性和稳定性。空速为80000h－1、800℃时甲烷的转化率接近100％，H2的选择性达99.8％，且在稳定性实验中保持15h活性变化不大。实验采用BET、TPR和XRD说明共沉淀法制备的镍基氧化铝催化剂中，La的加入提高了催化剂的比表面积，有效的抑制了大颗粒NiAl2O4的形成，降低了催化剂活性组分的还原温度，对POM显示出很高的催化活性。     

Pd catalysts supported on modified Zr0.5Al0.5O1.75 used for lean-burn natural gas vehicles exhaust purification

Composite supports Zr0.5Al0.5O1.75 modified by metal oxides,such as La2O3,ZnO,Y2O3 or BaO,were prepared by co-precipitation method,and palladium catalysts supported on the modified composite supports were prepared by impregnation method.Their properties were characterized by X-ray diffraction(XRD),NH3 temperature-programmed desorption(NH3-TPD),H2 temperature-programmed reduction(H2-TPR),N2 adsorption/desorption,and CO-chemisorption.The catalytic activity and the resistance to water poisoning of the prepared Pd catalysts were tested in a simulated exhaust gas from lean-burn natural gas vehicles with and without water vapor.The results demonstrated that the modified supports had an apparent effect on the performance of Pd catalysts,compared with the Pd catalyst supported on the unmodified ZrAl.The addition of ZnO or Y2O3 promoted the conversion of CH4.In the absence of water vapor,Pd/ZnZrAl exhibited the best activity for CH4 conversion with the light-off temperature(T50) of 275℃ and the complete conversion temperature(T90) of 314℃,respectively.However,in the presence of water vapor,Pd/YZrAl was the best one over which the light-off temperature(T50) of methane was 339℃ and the complete conversion temperature(T90) was 371℃.These results indicated that Pd catalyst supported on the modified composite ZrAl support showed excellent catalytic activity at low temperature and high resistance to H2O poisoning for the exhaust purification of lean-burn natural gas vehicles.     

钡改性的Ni/γ- Al2O3催化剂用于甲烷部分氧化的研究

800 ℃、80 000 h－1、CH4/O2/N2=14/7/79下比较了质量分数20%的Ni/γ- Al2O3和Ba改性的Ni/γ- Al2O3催化剂，用于甲烷部分氧化反应的活性和选择性。结果表明，Ba的添加提高了镍基催化剂的活性和稳定性。BET和XRD表明，Ba的加入有利于高温焙烧下抑制大颗粒的Ni Al2O4的形成，保持了高比例的活性镍组分，提高了催化剂催化活性。常压下，xCH4接近100%，sCO、sH2达到92.2%和98.1%，催化剂15 h内活性稍微下降。Ba的加入使Al2O3的晶型转化温度由800 ℃提高到900 ℃，提高了载体的稳定性。     

Effect of CeO2 on the catalytic performance of Ni/Al2O3 for autothermal reforming of methane

The effect of promoter Ce on the catalytic performance of Ni/Al2O3 catalyst for autothermal reforming of methane to hydrogen was investigated. The catalysts were characterized by X-ray diffraction （XRD）, temperature-programmed reduction （TPR）, and X-ray photoelectron spectroscopy （XPS）. The results indicated that the catalytic performance of the catalysts was improved with the addition of Ce. Ni/Ce30Al70Oδ showed the highest CH4 conversion in operation temperatures ranging from 650 ℃ to 850 ℃. At the same time, the decrease in H2/CO ratio with increasing reaction temperature was consistent with the fact that water-gas shift reaction was thermodynamically unfavorable at higher temperatures. The XRD result indicated that adding Ce to Ni/Al2O3 catalyst prevented the formation of NiAl2O4 and facilitated the formation of NiO. The formation of NiO increased the number of active sites, resulting in higher activity. Comparing the TPR profiles of Ni/Ce30Al70Oδ with Ni/Al2O3, it could be clearly observed that with the addition of Ce, the total reduction peak areas in the middle and low temperatures increased. It was most probably that the addition of Ce inhibited the stronger interaction between Ni and Al2O3 to form the phase of NiAl2O4, and favored the formation of the strong interaction between NiO species and CeO2. Therefore, the addition of Ce to the Ni/Al2O3 catalyst increased the active surface that promoted the activity of the catalyst.     

甲烷二氧化碳转化制备富含一氧化碳合成气

研究了甲烷二氧化碳转化反应的热力学特性,计算了反应平衡常数及平衡组成,分析和确定了抑制积碳的生成条件,采用固定床流动和脉冲反应装置研究了Ni/Al_2O_3催化剂对甲烷二氧化碳转化的催化性能。     

Autothermal reforming of methane over Ni catalysts supported over ZrO2-CeO2-Al2O3

Ni catalysts supported on Al2O3, ZrO2-Al2O3, CeO2-Al2O3 and ZrO2-CeO2-Al2O3 were prepared by coprecipitation method, and their catalytic performances for autothermal reforming of methane to hydrogen were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS. The relationship between the structures and catalytic activities of the catalysts was discussed. The results showed that the catalytic activity and stability of the Ni/ZrO2-CeO2-Al2O3 catalyst was better than those of other catalysts with the highest CH4 conversion, H2/CO and H2/COx ratio at 750 ℃. The catalyst showed a little deactivation along the reaction time during its 72 h on stream with the mean deactivation rate of 0.08%/h. The catalytic performance of the Ni/ZrO2-CeO2-Al2O3 catalyst was also affected by reaction temperature, no2 ： nCH4 molar ratio and nH2O ： nCH4 molar ratio. TPR, XRD and XPS measurements indicated that the formation of ZrO2-CeO2 solid solution could improve the dispersion of NiO, and inhibit the formation of NiAl2O3, and thus significantly promoted the catalytic activity of the Ni/ZrO2-CeO2-Al2O3 catalyst.     

制备方法对Ni/MgO/Al2O3催化剂在甲烷与二氧化碳重整反应活性的影响

采用浸渍－还原法制备的Ｎｉ／ＭｇＯ／Ａｌ２Ｏ３在ＣＨ４与ＣＯ２重整制合成气反应中显示出良好的催化性能和一定的抗积炭能力;在１０２３Ｋ下流动反应气氛中连续运转１００ｈ,未见活性下降,ＣＨ４及Ｃ弦均为９０％左右,ＣＯ收率高于９０％,实验还发现,ＣＨ４转化率随着原料气中ＣＯ２浓度的增加而升高,当Ｖ（ＣＯ２）／Ｖ（ＣＨ４）＝２时ＣＨ４转化率可达１００％,通过ＢＥＴ比表面积测定及ＸＲＤ,ＴＥＭ等分析手段,比     

ZrxTixAl1-2xO2的制备及其在三效催化剂上的应用

Zr_0.5Ti_0.5O₂(ZT) and Zr_0.25Ti_0.25Al_0.5O₂(ZTA) mixed oxides were prepared by co-precipitation method and characterized by low temperature adsorption-desorption， XRD and NH₃-TPD. The activity of Pt/Zr_0.5Ti_0.5O₂ and Pt/ Zr_0.5Ti_0.5Al_0.5O₂ catalysts was evaluated using the simulated gases. The results show that ZTA samples exhibit higher specific surface area， larger pore volume and proper surface acidic amount and acidity in comparison with ZT. The results of the catalytic test indicate that Pt/ZT and Pt/ZTA catalysts exhibit excellent low-temperature catalytic activity and lower light-off temperatures of hydrocarbon， carbon monoxide and nitrogen oxides， especially better conversion for nitrogen oxides (NO_x). The addition of Al₂O₃ into ZT enhanced the anti-aging property of Pt/ ZTA catalysts due to the excellent textural， structural， surface acidity and thermal stability.     

CH4,CO2和O2制合成气反应中载体对Ni催化剂抗氧化性能的影响

在ＣＨ４、ＣＯ２ 催化氧化制合成气反应中, Ｎｉ／Ａｌ２Ｏ３ 催化剂在高温下生成ＮｉＡｌ２Ｏ４ 尖晶石,是导致催化剂失活的一个重要因素． 通过向载体（Ａｌ２Ｏ３）中添加各种氧化物, 使得催化剂的抗氧化性能得到改善． 并运用ＴＰＲ、ＸＲＤ对催化剂进行表征, 发现催化剂的抗氧化性顺序为： Ｎｉ／ＣａＯ－Ａｌ２Ｏ３ ＞ Ｎｉ／ＭｇＯ－Ａｌ２Ｏ３ ＞ Ｎｉ／ＣｅＯ２－Ａｌ２Ｏ３ ＞ Ｎｉ／Ｌａ２Ｏ３－Ａｌ２Ｏ３ ＞ Ｎｉ／Ｙ２Ｏ３－Ａｌ２Ｏ３ ＞ Ｎｉ／ＴｉＯ２－Ａｌ２Ｏ３＞ Ｎｉ／Ａｌ２Ｏ３＞ Ｎｉ／Ｆｅ２Ｏ３－Ａｌ２Ｏ３．     

TiO2对Ni/Al2O3催化剂CO甲烷化性能的影响

采用溶胶凝胶法制备了一系列不同TiO₂含量的TiO₂-Al₂O₃复合载体,并通过浸渍法制备了NiO/TiO₂-Al₂O₃催化剂。分别考察了不同TiO₂含量的NiO/TiO₂-Al₂O₃催化剂及反应温度对CO甲烷化催化性能的影响。实验结果表明,当复合载体中TiO₂质量分数为30%,反应温度为350～450 ℃时,催化剂催化活性较高。利用N₂吸附-脱附(BET)、X射线衍射(XRD)及H₂程序升温还原(H₂-TPR)等手段对催化剂物化性能进行了表征。结果表明,加入适量的TiO₂能抑制镍铝尖晶石NiAl₂O₄物种的生成,改善NiO的表面分散性能,避免大晶粒NiO的形成,也改善了催化剂的还原性能,从而提高催化剂的CO甲烷化活性。     

Effect of Transition Metals (Cu, Co and Fe) on the Autothermal Reforming of Methane over Ni/Ce0.2Zr0.1Al0.7Oδ Catalyst

The transition metals (Cu, Co, and Fe) were applied to modify Ni/Ce0.2Zr0.1Al0.7Oδ catalyst.The effects of transition metals on the catalytic properties of Ni/Ce0.2Zr0.1Al0.7Oδ autothermal reforming of methane were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS.Tests in autothermal reforming of methane to hydrogen showed that the addition of transition metals (Cu and Co) significantly increased the activity of catalyst under the conditions of lower reaction temperature,and Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ was found to have the highest conversion of CH4 among all catalysts in the operation temperatures ranging from 923 K to 1023 K. TPR, XRD and XPS measurements indicated that the cubic phases of CexZr1-xO2 solid solution were formed in the preparation process of catalysts.Strong interaction was found to exist between NiO and CexZr1-xO2 solid solution. The addition of Cu improved the dispersion of NiO, inhibited the formation of NiAl2O4, and thus significantly promoted the activity of the catalyst Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ.     

EFFECTS OF RARE EARTH OXIDES ON PERFORMANCES OF Ni/Al_2O_3 CATALYSTS FOR METHANE STEAM REFORMING REACTION

The Catalytic performances for methane steam reforming reaction ofNi/Al_2O_3(commercial), Ni/Al_2O_3 (developed surface )and Ni/Al_2O_3-R_xO_y (R israre earth oxide) Catalysts were investigated by means of X-ray diffraction,TG, SEM/ X-ray analysis, pulse gas chromatography,BET and Mercuryporsiniter techniques. The distribution of rear earth oxides on the supports,themetal-support (additives) interaction and the influence of rare earth oxideadditives on the dispersion of active components,catulytic activities,variationof nickel crystallites size,CO chemisorption,formation of NiAl_2O_4 as well asthe reducibility of the catalysts were examined.The presence of rare earthoxides in the Ni/Al_2O_3 (developed surface) results in great improvement ofstubility through suppressing the growth of Ni crystallites,the oxidation of themetallic Ni and the formation of NiAl_2O_4. The effect of heavy rare earth oxidesis more distinct than that of the light ones.Strong metal support interaction(SMSI) exists in Ni/Al_2O_3- R     

低浓度甲烷甲醇深度氧化Ag/La0.6Sr0.4MnO3催化剂

Ag-modified La0.6Sr0.4MnO3 catalysts were prepared and their catalytic performance for deep oxidation of CH4 and CH3OH at low concentrations were investigated. The results showed that the La0.6Sr0.4MnO3 host catalyst with the perovskite-type nano-crystallite structure displayed considerably high catalytic activity for deep oxidation of CH4 and CH3OH at low concentrations. Ag modification to the La0.6Sr0.4MnO3 host catalyst resulted in significant enhancement of the catalyst activity, making the T95 (the reaction temperature needed for conversion of 95%of CH4 or CH3OH) lowered down to 735K (for CH4) and 421K (for CH3OH) from 813 and 465 K over the Ag-free system under the reaction conditions:0.1MPa,CH4/O2/N2=2/12/86(molar ratio),GHSV=45000 h-1 and CH3OH/O2/N2= 0.2/1.0/98.8 (molar ratio),GHSV=58000 h-1,respectively.The carbon containing product was almost CO2 and the contents of HCHO and CO in the reaction exit gas were both under GC detectable limit in both cases.
The results of spectroscopic characterization indicated that modification by proper amount of Ag-dopant did not change the perovskite structure of the La0.6Sr0.4MnO3 host catalyst as a whole. Interaction of Ag-dopant with the surface of the host catalyst,La0.6Sr0.4MnO3,was in favor of high dispersion of the Ag component at the catalyst surface and led to the oxidation of part of the Mn3+species to Mn4+,resulting in an increase of amounts of the reducible Mnn+ species and a decrease of their reduction temperature. On the other hand, this interaction led also to enhancement of adsorption ability of the catalyst toward O2 at relatively low temperature. High activity of the Ag modified La0.6Sr0.4MnO3 catalyst for CH4 and CH3OH complete oxidation was closely related to high redox-activity of the catalyst and its prominent adsorption-activation ability to O2 at relatively low temperatures.     

Kinetics of hydrogen production of methanol reformation using Cu/ZnO/Al2O3 catalyst

The catalytic performance of methanol reformation using Cu/ZnO/Al2O3 was investigated at low temperature. The operation conditions, such as composition of Cu, Zn, and Al, temperature, molar ratio of H2O/CH3OH, weight hourly space velocity, catalyst weight, and kind and flow rate of carrier gas (helium and air), were evaluated to obtain the optimum reaction condition. The catalysts were prepared by oxalic coprecipitation, coprecipitation, and polyol method. The weight composition of Cu, Zn, and Al prepared by oxalic coprecipitation was 15:15:5 by high-throughput screening of combinatorial chemistry method, which was the best Cu/ZnO/Al2O3 catalyst. The prepared catalysts showed high activity and selectivity towards hydrogen formation. The methanol conversion, production rate, and volumetric percentage of hydrogen using this best catalyst were larger than 95%, 0.65 mol/h x g and 59%, respectively, and the CO volumetric percentage was smaller than 0.22% when the reaction temperature was 240 degrees C. The size and dispersity of copper, and the activity and turnover frequency of the catalyst were calculated as well.     

PROMOTING EFFECT OF RARE EARTH OXIDES ON Ni/Re_xO_y-Al_2O_3 CATALYST FOR PARTIAL OXIDATION OF METHANE TO SYNTHESIS GAS

IntroductionSynthesisgas(HZ CO)isproducedfrommethanemoshybysteamrefonningwhichsuffersfromlimitationssuchasveryhighenergyrequirements,complicatedequipmentandinstallations,highHZ/COproductratioandpoorselectivityforcarbonmonoxide.Recently,manyresearchershave…     

负载型La0.8Sr0.2MnO3燃烧催化剂的载体效应

Combustion catalysts La0.8Sr0.2MnO3 supported on γ-Al2O3, α-Al2O3, cordierite (2MgO•2Al2O3•5SiO2) and ZrO2 were compared. Further investigation was focused on LSM/ γ-Al2O3 catalyst. It was observed that LSM/γ－Al2O3 catalyst loaded with 20% (mass fraction) LSM (La0.8Sr0.2MnO3 or corresponding oxides), heated at 750℃ or above, perovskite-type oxides were found by XRD examination, whereas, the same catalyst loaded with 10% or less LSM, perovskite oxides were absent, calcination temperature about 750℃ is necessary for the formation of perovskite structure in LSM/γ-Al2O3 catalysts. High activity of complete oxidation of xylen will be obtained when perovskite-type oxides.
Investigation of TPR showed that neat LSM or LSM/γ-Al2O3(20%) was reduced by H2-N2 mixed gas. Two degradation processes took place. In the first, reduced temperature peak was about 350 - 450℃. If reduction ended at 400℃, perovskite structure was retained, which may be due to the reduction of Mn3+to Mn2+ on the surface of LSM only. In the second process, perovskite structure was destroied, and La2O3, Mn2O3, Mn - Sr - O oxides could be obtained, which took place in the temperature range 685 - 750℃ and ended at 800℃. This was proved by TPR experiments (Fig. 3, 5) and XRD patterns (Fig. 4)
Catalysts LSM/γ-Al2O3(10% or 20%) heated at 500℃ have only one TPR peak, i. e. lower temperature peak. This is due to the absence of perovskite-type oxides in the catalysts. However, neat LSM or LSM/γ-Al2O3(20%) heated 750℃ or above, not only the first low temperature TPR peak but also the second peak, which is contributed by the perovskite-type oxides in these catalysts appeared. Therefore, the second TPR peak, i. e. the higher temperatue peak is a characteristic peak for perovskite-type oxides in the reduced process. When LSM/ γ-Al2O3 (10%) catalys is heated at 750℃, no perovskite-type oxides were detected by XRD, and the second reduction peak was absent also in TPR process. \
The order of the second reduction peak temperature(characteristic peak of perovskite - type ox- ides) is: neat LSM(750℃）> LSM/γ-Al2O3 20% (685-698℃) -deposited LSM/γ-Al2O3 (698℃) > LSM/γ-Al2O3 15% (677 - 680℃) >(LSM/γ-AL2O3 10% 620 - 630℃, for Mn - Al - O medium oxides on surface). It is correleted with the increasing of the effect of support sequentially.
When LSM/γ-Al2O3 catalysts were heated at 900℃, more stable phase, spinel MnAl2O4 appeared, which could be proved by TPR of model catalyst MnAl2O4/γ-Al2O3.     

镁铝混合氧化物负载镍催化剂的制备及在液化石油气低温重整反应中的催化性能

采用共沉淀-浸渍法制备了不同Ni 含量的 Ni/Mg(Al)O 催化剂并用于液化石油气(LPG)的低温水蒸气重整反应. X 射线衍射和程序升温还原结果表明, 在 800 ℃焙烧的 Ni/Mg(Al)O 催化剂中, NiO 与 MgO 反应生成 Mg-Ni-O 固溶体, 还原后形成金属 Ni 纳米颗粒. 详细研究了 Ni 含量(质量分数)、反应温度和水/碳摩尔比(n_H2O/n_C) 等对催化剂性能的影响. 实验结果表明, 15%Ni/Mg(Al)O 催化剂对 LPG 低温重整反应具有最佳的催化性能. 提高反应温度能显著提高 Ni/Mg(Al)O 催化剂的催化性能. 当n_H2O/n_C=2时, 在400~500 ℃的温度范围使LPG完全转化的最大反应空速从 28900 mL·h^-1·g^-1Cat提高到 86800 mL·h^-1·g^-1Cat. 适当增大水/碳摩尔比有利于 LPG 转化为小分子气体, 但在 LPG 摩尔流量不变的情况下, 反应气中水含量过高会导致 LPG 转化率降低. 反应后催化剂的X射线衍射谱(XRD)和热重分析(TG)结果表明, Ni/Mg(Al)O催化剂优良的催化活性和反应稳定性可归因于催化剂表面Ni晶粒较高的稳定性和抗积炭性能.     

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.