Ni/TPC催化剂的制备、表征及在秸秆热解燃气重整中的应用（英文）

以废弃汽车外轮胎热解后的副产物轮胎热解焦(Tyre pyrolysis char,TPC)为原料,利用均匀沉淀法制备以轮胎焦为载体的负载型Ni/TPC催化剂,采用EDX、SEM、XRD、TG、BET手段对催化剂进行了表征与分析,同时使用管式炉测试了Ni/TPC催化剂在秸秆热解燃气重整中的催化性能,并考察了热解温度、保温时间、镍负载量及催化时间对秸秆热解燃气重整效果的影响。研究结果表明,TPC富含焦和金属,Ni/TPC催化剂分散均匀,热稳定性好,比表面积为62 m2/g。催化剂活性测试显示,Ni/TPC催化剂用于作物秸秆热解燃气重整具有很强的催化活性,可显著提高燃气中可燃气体含量;热解温度在750℃、保温时间10 min、30%的Ni负载量时Ni/TPC催化剂的催化效率最高,连续使用850 min后,燃气中的H_2含量仍相对提高到50%以上,长时间使用后活性结构由Ni_3ZnC_(0.7)转变成FeNi_3,催化活性依然较强且趋于稳定,TPC可以作为良好的新型镍基催化剂载体。     

SiO2和Al2O3负载的Ni基催化剂在甲烷干重整中的催化性能差异

CH₄与CO₂干重整反应对于环境保护和天然气资源的合理利用具有重要意义。SiO₂和Al₂O₃是适用于甲烷干重整反应的两种典型的催化剂载体。为了阐明这两种载体对催化剂性能的影响,本研究采用等体积浸渍法制备了Ni/Al₂O₃和Ni/SiO₂催化剂,并利用BET、TEM、H₂-TPR、XRD、TG和Raman等技术对还原和反应后的催化剂进行了表征。结果表明,由于载体的性质不同,Ni基催化剂在甲烷干重整中的催化性能也不同。Ni/SiO₂催化剂的初始活性较高,但由于其金属-载体相互作用较弱,催化稳定性较差,在800℃下反应15h其催化活性急剧下降;较弱的金属-载体相互作用使得Ni/SiO₂催化剂上的Ni颗粒较大,有利于积炭前驱物种的生成,导致催化剂快速失活。而对于Ni/Al₂O₃催化剂,金属-载体相互作用较强,Ni颗粒较小,但由于Ni与Al₂O₃生成了NiAl_xO_y物种,有效活性位减少,其催化活性相对较低,但催化稳定性较好,干重整反应进行50h其活性保持稳定;Ni与Al₂O₃之间较强的相互作用有利于形成小且稳定的Ni粒子,能减少积炭,因而具有优异的催化稳定性。     

Ni/Zr-MOF催化剂的制备及其在生物质热解中的应用

通过均匀沉淀法制备了以锆-金属有机骨架化合物(Zr-metal organic framework,Zr-MOF)为载体的Ni/Zr-MOF催化剂,并用于湿污泥和秸秆混合催化热解实验。采用元素分析、X射线荧光光谱(XRF)、热重分析(TG)、X射线衍射(XRD)、扫描电镜(SEM)和N_2吸附-脱附等温(BET)对载体和催化剂进行表征分析,通过一系列实验来探讨热解温度、秸秆添加量和Ni负载量对于湿污泥和秸秆混合催化热解制备富氢合成气的影响。结果表明,Zr-MOF载体颗粒均匀呈八面体,比表面积高达805.93 m~2/g,平均孔径为20.14 nm,为介孔结构。Ni/Zr-M OF催化剂具有较高的热稳定性和催化活性。与不添加催化剂相比,使用Ni/Zr-MOF催化剂在500℃下热解,H_2的产量从0.39 mol/kg显著提高到12.65 mol/kg。随着热解温度的升高,催化剂出现团聚现象,同时在反复使用之后其表面产生了少量的积炭,导致催化剂催化活性逐渐降低。因此,Ni/Zr-MOF催化剂适用于生物质低温催化热解。     

载体效应与镍晶粒尺寸对CO2甲烷化低温催化性能的影响

采用等体积浸渍法制备MgO和CeO₂负载的一系列不同镍含量催化剂，对其进行了二氧化碳甲烷化催化性能评价。研究结果表明NiO/CeO₂基催化剂具有优异的低温催化活性，其中80%NiO/CeO₂催化剂，在18 L/(g·h)、H₂/CO₂=4和350℃反应条件下甲烷产率为67%。探究了镍含量对NiO/MgO和NiO/CeO₂催化剂活性的影响，结果表明，随着镍含量增加，二氧化碳转化率、甲烷产率升高，在镍负载量为50%～80%时催化性能最佳。通过X射线衍射(XRD)、氢气程序升温还原(H₂-TPR)、拉曼(Raman)、CO₂-TPD表征探究不同载体和Ni晶粒大小对NiO/MgO,NiO/CeO₂催化剂催化活性的影响。本研究可为设计具有优异低温催化性能的二氧化碳甲烷化催化剂提供参考。     

负载Ni催化剂用于乙二醇蒸汽重整制氢催化性能研究

采用等体积浸渍法和共沉淀法制备了Ni催化剂,在固定床反应器上考察了Ni负载量、焙烧温度、反应温度等因素对乙二醇低温重整制氢反应活性和选择性的影响。应用X射线衍射、氮物理吸附、H₂程序升温还原等技术对负载型Ni催化剂进行了表征。结果表明,共沉淀法制备的Ni/CeO₂催化剂具有较小的NiO颗粒与CeO₂载体颗粒粒径,催化活性较高。添加少量氧化钴到Ni/CeO₂催化剂中可使H₂收率达72.6%,EG转化率达93.1%。在CeO₂中添加Al₂O₃能提高负载Ni催化剂的活性,乙二醇转化率达94.0%,H₂收率达67.0%;但添加SiO₂则使其活性明显变差。     

CO2重整CH4纳米ZrO2负载Ni催化剂的研究(Ⅰ)——与常规载体上Ni催化剂的比较

在Ni负载量相近(约5%)时,比较了由超临界干燥得到的纳米ZrO₂-AS为载体制备的Ni/ZrO₂-AS与几种常规载体(γ-Al₂O₃,TiO₂,SiO₂和ZrO₂-CP)负载的Ni催化剂对CO₂重整CH₄制合成气反应的催化性能.研究结果表明,γ-Al₂O₃,TiO₂,SiO₂和ZrO₂-CP负载Ni催化剂表现出明显的失活过程,而Ni/ZrO₂-AS催化剂在反应200h后活性未下降.“纯ZrO₂-AS”载体本身不仅能催化生成合成气的反应,而且活性稳定.TPO测定结果表明,负载在这种活性ZrO₂-AS载体上的Ni催化剂具有良好的抗积炭能力.     

镍负载量对乙醇水蒸气重整制氢催化性能和催化剂的影响

采用稳态实验对镍负载量对Ni/MgO催化剂在乙醇水蒸气重整反应的影响进行了研究。结果表明，在101.3kPa下，镍负载量越高，催化剂的活性越高。对于催化剂的选择性，存在一个最佳镍负载量为10%Ni/MgO。按选择性从大到小排序，不同镍负载量的催化剂为：10Ni/MgO>15Ni/MgO>12.5Ni/MgO>7.5Ni/MgO≈5Ni/MgO。热分析表明，焙烧过程中不同镍负载量的催化剂镍前体与载体前体之间发生的相互作用不同。XRD和TPR 表征结果显示，催化剂的晶体结构和还原特性也与催化剂上镍的负载量有关。焙烧过程中样品10Ni/MgO上镍前体与载体前体发生了两种相互作用, 并且其氧化态与其他催化剂相比具有特殊的结构和还原性。说明催化剂的选择性不仅受活性相Ni的影响而且受Ni活性相周围环境的影响。     

负载Ni催化剂上低温甘油蒸汽重整制氢

采用等体积浸渍法制备了Al₂O₃、CeO₂、TiO₂及MgO负载Ni催化剂,考察了它们对甘油蒸汽重整制氢反应的催化性能。采用X射线衍射、N₂吸附、透射电镜及H₂程序升温还原等方法对催化剂进行了表征。结果表明,载体对Ni催化剂的活性有显著影响。在400 ℃下Ni/CeO₂的催化活性明显好于其他催化剂,活性次序为Ni/CeO₂> Ni/Al₂O₃ > Ni/TiO₂ ~ Ni/MgO。Ni/CeO₂也具有好的稳定性,反应20 h未见活性下降,甘油转化率70%,氢气收率69.2%。这与CeO₂的本性及其与活性组分的相互作用有关。Al₂O₃具有较大的比表面积与孔体积,有利于CO吸附及甲烷化反应的进行,使得Ni/Al₂O₃催化剂在较高温度下具有很高的甘油转化率85.7%,但H₂选择性较差。由于MgO载体与活性组分强的相互作用而生成NiMgO₂固溶体,导致Ni/MgO低温活性差。     

镍负载量对Ni/MgO(111)催化甲烷二氧化碳重整反应性能影响

研究了MgO(111)负载镍基催化剂催化甲烷二氧化碳重整反应性能,针对镍负载量对反应活性和稳定性的影响进行了探讨。结果表明,随着镍负载量从2%增加到10%,催化剂的活性和稳定性均有所提高,但是当镍负载量进一步增加到20%时,催化剂的活性和稳定性略有下降。利用透射电子显微镜、X射线衍射和H₂吸附脱附等手段对催化剂结构进行了表征,利用热重分析、拉曼光谱和透射电镜等手段对反应后回收的催化剂进行了表征。研究发现,随着镍负载量的增大,活性金属镍的颗粒粒径呈现增长趋势,并且在反应过程中显示出不同的失活方式。2%Ni/MgO(111)催化剂的失活原因主要以Ni粒子的氧化为主,而负载量大于2%的Ni/MgO(111)催化剂的失活原因则是以积炭为主。     

镍基整体式催化剂上生物质粗燃气重整调变的特性研究

采用浸渍法制备了Ni基整体式催化剂,考察了不同条件(温度、时间、空速、水蒸气添加等)对催化剂上生物质粗燃气重整反应性能的影响。结果表明,催化剂在较低温度下(≤500 ℃)只具有CO加氢反应活性,随着反应温度的升高粗燃气重整反应逐渐进行,在800 ℃以上,CH₄和C₂转化率均高达95 %以上,CO₂转化率达到92%,但随着反应空速和水蒸气添加量的增加,CH₄和CO₂等转化率呈现缓慢降低的趋势。此外,通过改变水蒸气添加量可对合成气中H₂/CO体积比在0.85~4.00进行较好调节。结合XRD表征发现,Ni基整体式催化剂中Ni°的生成可较好地促进重整反应的进行。     

Hydrogen Production From Crude Bio-oil and Biomass Char by Electrochemical Catalytic Reforming

We reports an efficient approach for production of hydrogen from crude bio-oil and biomass char in the dual fixed-bed system by using the electrochemical catalytic reforming method. The maximal absolute hydrogen yield reached 110.9 g H₂/kg dry biomass. The product gas was a mixed gas containing 72%H₂, 26%CO₂, 1.9%CO, and a trace amount of CH₄. It was observed that adding biomass char (a by-product of pyrolysis of biomass) could remarkably increase the absolute H₂ yield (about 20%-50%). The higher reforming temperature could enhance the steam reforming reaction of organic compounds in crude bio-oil and the reaction of CO and H₂O. In addition, the CuZn-Al₂O₃ catalyst in the water-gas shift bed could also increase the absolute H₂ yield via shifting CO to CO₂.     

炭包覆氧化铝负载镍催化剂的制备和表征及其催化加氢性能

以炭包覆A12O3(CCA)为载体,采用等体积浸渍法制备了17%Ni/CCA催化剂,采用热重-差示量热扫描、扫描电镜、X射线光电子能谱、N2物理吸附、H2程序升温还原和X射线衍射等手段对样品进行了表征,并用于粗1,4-丁二醇加氢反应中.结果表明,炭的引入显著改变了Al2O3的表面性质、负载Ni的存在形态以及金属.载体间...     

High effects of smoke suppression and char formation of Ni?Mo/Mg(OH)2 for polypropylene

The Ni? Mo/Mg(OH)₂ (NMM) hybrid as an efficient flame retardancy and smoke suppression composite for polypropylene (PP) was synthesized through Ni? Mo co‐precipitation on the surface of Mg(OH)₂ (MH) hexagonal nanosheets. Compared to PP/MH, PP/NMM exhibited excellent smoke suppressing and flame retardancy on the heat release rate, total heat release, smoke production rate, total smoke production, CO production rate and total CO production with the same loading. The reduced hazard of PP/NMM was mainly attributed to the high physical barrier effect of compact char residues on heat, smoke and combustible gas. The mechanism study indicated that multiwalled carbon nanotubes (MWCNTs) generated from the catalytic carbonization of PP by the Ni? Mo compound could play the role of “rebar” to strengthen the char residues, avoid the generation of cracks and form highly compact char layer. Furthermore, MgO could facilitate the production of MWCNTs through changing the pyrolysis process of PP and increasing the reaction time between pyrolysis gas and Ni? Mo compound. Hence, the new Ni? Mo/MH catalyst hybrid may explore the potential for solving the tough problem of the flammability and heavy smoke of the polyolefins system.     

The effects of temperature on product yields and composition of bio-oils in hydropyrolysis of rice husk using nickel-loaded brown coal char catalyst

Hydropyrolysis of rice husk was performed using nickel-loaded Loy Yang brown coal char (Ni/LY) catalyst in a fluidized bed reactor at 500, 550, 600 and 650 °C with an aim to study the influence of catalyst and catalytic hydropyrolysis temperature on product yields and the composition of bio-oil. An inexpensive Ni/LY char was prepared by the ion-exchange method with nickel loading rate of 9 ± 1 wt.%. Nickel particles which dispersed well in Loy Yang brown coal char showed a large specific surface area of Ni/LY char of 350 m²/g. The effects of catalytic activity and hydropyrolysis temperature of rice husk using Ni/LY char were examined at the optimal condition for bio-oil yield (i.e., pyrolysis temperature 500 °C, static bed height 5 cm, and gas flow rate 2 L/min without catalyst). In the presence of catalyst, the oxygen content of bio-oil decreased by about 16% compared with that of non-catalyst. Raising the temperature from 500 to 650 °C reduced the oxygen content of bio-oil from 27.50% to 21.50%. Bio-oil yields decreased while gas yields and water content increased with increasing temperature due to more oxygen being converted into H₂O, CO₂, and CO. The decreasing of the oxygen content contributed to a remarkable increase in the heating value of bio-oil. The characteristics of bio-oil were analyzed by Karl Fischer, GC/MS, GPC, FT-IR, and CHN elemental analysis. The result indicated that the hydropyrolysis of rice husk using Ni/LY char at high temperature can be used to improved the quality of bio-oil to level suitable for a potential liquid fuel and chemical feedstock.     

Steam reforming for syngas production over Ni and Ni-promoted catalysts

In this article, nanocrystalline γ-alumina with high surface area (309 m² g^?1) and mesoporous structure with an average pore size of 4.3 nm was synthesized and employed as a carrier for the synthesis of Ni catalysts in steam reforming of methane. The results revealed that the metal–support interaction decreased by increasing the nickel loading and led to the movement of the T_max of reduction temperature to lower temperatures. The results demonstrated that the synthesized catalysts exhibited high CH₄ conversion and stability and increasing the nickel loading up to 10 wt% improved the CH₄ conversion. The results revealed that the incorporation of MgO in nickel catalyst improved the resistance of the catalyst against carbon deposition and also enhanced the catalytic activity and the 10%Ni–5%MgO–Al₂O₃ catalyst exhibited high stability during 60 h. The high stability of the promoted catalyst was related to the high basicity of the catalyst.

     

Comparison of two preparation methods of supported Li?Ni catalyst on alumina for selective oxidation of methane

Lithium-added nickel catalysts on alumina were prepared for CO₂ reforming of methane by two methods, precipitation and impregnation. Performances of the catalysts were investigated by TG, CO-adsorption and SEM analysis. The catalyst with ratio of Li/Ni=1.0 prepared by precipitation method has high nickel dispersion, catalytic activity and stability for CO₂ reforming of methane.     

Effect of Ni loadings on the activity and coke formation of MgO-modified Ni/Al2O3 nanocatalyst in dry reforming of methane

MgO-modified Ni/Al₂O₃ catalysts with different Ni loadings were prepared and employed in dry reforming of methane (DRM). The effect of Ni loadings on the activity and coke formation of Ni/MgO-Al₂O₃ catalysts were investigated. The synthesized catalysts were characterized by XRD, N₂ adsorption-desorption, SEM, TPO and TPR techniques. The obtained results showed that increasing nickel loading decreased the BET surface area and increased the catalytic activity and amount of deposited carbon. In addition, the effect of gas hourly space velocity (GHSV) and feed ratio were studied.     

CO2 reforming of methane over zirconia-supported nickel catalysts, I. Catalytic specificity

CO₂ reforming of methane is performed over zirconia-supported nickel catalysts. The catalysts show high activity toward CH₄ and CO₂ conversions. Over the high Ni loading catalyst, long-term performances without significant deactivations have been achieved at 1023 K for 30 h and 1123 K for 20 h, respectively. The effects of reduction and calcination temperatures on the catalytic activities are also examined.     

在Ni/HZSM-5催化剂上低温水蒸汽重整生物油制氢

We investigated high catalytic activity of Ni/HZSM-5 catalysts synthesized by the impregna-tion method, which was successfully applied for low-temperature steam reforming of bio-oil. The influences of the catalyst composition, reforming temperature and the molar ratio of steam to carbon fed on the stream reforming process of bio-oil over the Ni/HZSM-5 catalysts were investigated in the reforming reactor. The promoting effects of current passing through the catalyst on the bio-oil reforming were also studied using the electrochemical catalytic re-forming approach. By comparing Ni/HZSM-5 with commonly used Ni/Al₂O₃ catalysts, the Ni₂₀/ZSM catalyst with Ni-loading content of about 20% on the HZSM-5 support showed the highest catalytic activity. Even at 450 oC, the hydrogen yield of about 90% with a near complete conversion of bio-oil was obtained using the Ni₂₀/ZSM catalyst. It was found that the performance of the bio-oil reforming was remarkably enhanced by the HZSM-5 supporter and the current through the catalyst. The features of the Ni/HZSM-5 catalysts were also investigated via X-ray diffraction, inductively coupled plasma and atomic emission spectroscopy, hydrogen temperature-programmed reduction, and Brunauer-Emmett-Teller methods.