Fe-Ca-Ce催化生物质热解制备富氢合成气——以山楂药渣为例

以山楂药渣作为原料,在固定床反应器中研究了热解温度和Fe、Fe-Ca、Fe-Ca-Ce催化剂及负载量对药渣热解的影响规律,并研究了浸渍法和共沉淀法对热解气体产率的影响.研究结果表明,热解温度从500℃升高至700℃,H_(2)由10.40 mL/g升高至27.64 mL/g,当Fe负载量为w=7%时,H_(2)产率由27.64 mL/g增加至46.16 mL/g,在Fe中引入Ca有效提高了H_(2)的产率,Ca的负载量增加至w=2.0%时,H_(2)产率增加至69.53 mL/g.采用共沉淀法制备Fe和Fe-Ca催化剂有利于降低CO_(2)产率,而在Fe-Ca中引入Ce后H_(2)产率从69.53 mL/g减少至50.18 mL/g.

界面效应在锰氧化物修饰的CeO_(2)纳米立方甲苯氧化中的作用

本研究通过水热-浸渍两步法成功制备了不同Mn负载量的二元xMn/Ce(xMnOx/CeO_(2))催化剂,并评估了催化剂在甲苯催化氧化反应中的性能。研究结果表明,引入MnOx能显著提高催化剂的甲苯氧化活性。特别是当Mn负载量为10%(10Mn/Ce)时,在气体空速为60000 mL/(g·h)的条件下,t90(甲苯转化率达到90%时的温度)仅为233℃,显示出最优的甲苯催化氧化活性。这一结果说明,适量加入MnOx能够显著提高催化剂的催化性能。通过X射线衍射(XRD)、拉曼光谱(Raman)、透射电子显微镜(TEM)、程序升温还原(H2-TPR)和X射线光电子能谱(XPS)等表征手段,发现MnOx的加入在MnOx与CeO_(2)之间形成了界面效应,这显著改变了Mn/Ce催化剂的物理化学性质。由于界面效应的作用,不仅提高了10 Mn/Ce催化剂中Ce3+、Mn3+离子的浓度以及氧空位的浓度,而且还降低了催化剂表面Ce−O键强度,使得表面晶格氧更易于参与甲苯的催化氧化,提升了催化剂的氧化还原性能,从而促进了甲苯的催化氧化。本研究不仅成功制备了具有优异甲苯氧化活性的Mn/Ce催化剂,而且揭示了其背后的界面效应机制,为VOCs高效氧化催化剂设计与制备提供了简单有效的方法与思路。

Selective catalytic oxidation of NO with O_2 over Ce-doped MnO_x/TiO_2 catalysts

A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=l/3 and calcined at 300 ℃ shows a superior activity for NO oxidation to NO2. On Ce（1）Mn（3）Ti catalyst, 58% NO conversion was obtained at 200 ℃ and 85% NO conversion at 250 ℃ with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst （48% at 250 ℃）. Characterization results implied that the higher activity of Ce（1）Mn（3）Ti could be attributed to the enrichment of well-dispersed MnO2 on the surface and the abundance of Mn3＋ and Zi3＋ species. The addition of Ce into MnO2/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.

Effect of pretreatment methods on the performance of Cu-Zr-Ce-O catalyst for CO selective oxidation

The Cu-Zr-Ce-O catalysts prepared using the coprecipitation method exhibited better catalytic performance for CO selective oxidation. The Cu-Zr-Ce-O catalysts pretreated with different methods were studied by CO-TPR and XPS techniques. The results showed that the Cu-Zr-Ce-O catalyst pretreated with oxygen exhibited the best catalytic performance and had the widest operating temperature window, with CO conversion above 99% from 160 to 200 ℃. The O2 pretreatment caused an enrichment of the oxygen storaged on the Cu active species and promoted the conversion of adsorbed oxygen into surface lattice oxygen. It also improved the amount of Cu＋/Cu^2＋ ionic pair, and then facilitated the formation of CuO active species on the catalyst for selective CO oxidation.

Evaluation of H2 Influence on the Evolution Mechanism of NOx Storage and Reduction over Pt–Ba–Ce/c-Al2O3 Catalysts

In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) storage and reduction (NSR). The physical and chemical properties of the Pt–Ba–Ce/c- Al2O3 catalysts were studied using a combination of characterization techniques, which showed that PtOx, CeO2, and BaCO3, whose peaks were observed in X-ray diffraction (XRD) spectra, dispersed well on the c-Al2O3, as shown by transmission electron microscope (TEM), and that the difference between Ce3+ and Ce4+, as detected by X-ray photoelectron spectroscopy (XPS), facilitated the migration of active oxygen over the catalyst. In the process of a complete NSR experiment, the NOx storage capability was greatly enhanced in the temperature range of 250–350℃, and reached a maximum value of 315.3μmol·gcat^-1 at 350℃, which was ascribed to the increase in NO2 yield. In a lean and rich cycling experiment, the results showed that NOx storage efficiency and conversion were increased when the time of H2 exposure (i.e., 30, 45, and 60 s) was extended. The maximum NOx conversion of the catalyst reached 83.5% when the duration of the lean and rich phases was 240 and 60 s, respectively. The results revealed that increasing the content of H2 by an appropriate amount was favorable to the NSR mechanism due to increased decomposition of nitrate or nitrite, and the refreshing of trapping sites for the next cycle of NSR.

Characterization and CO Catalytic Oxidation of CuO/Ce-Zr-La-O Catalyst

The Ce-Zr-La-O solid solution was prepared by the sol-gel method. Thestructure and the redox behavior of Ce-Zr-La-O solid solution and CuO/Ce-Zr-La-O catalysts wereinvestigated by using XRD, Raman and TPR techniques. The result shows that the reduction capabilityof Ce_(0.7)Zr_(0.3-y)La_yO solid solution is related to content of La. Appropriate content of La canenhance the redox capability of the solid solution. The oxidation activity of the CuO (6 percent)/Ce_(0.7)Zr_(0.15)La_(0.15)O catalyst is the highest. CuO, which finely dispersed and interacted withthe support, is the site of oxidation activity.

Ce_xTi_(1-x)O_2 Mixed Oxides Supported CuO Catalyst for NO Reduction by CO

Ce x Ti 1- x O 2 mixed oxides of different mole ratios ( x =0, 0.1, 0.2～0.9, 1.0) were prepared by co precipitation of TiCl 4 with Ce(NO 3) 3 and then loaded with different amounts of CuO. The effects of CuO on NO+CO reaction were investigated, and the structure and reductive properties of various CuO/Ce x Ti 1- x O 2 were characterized by the methodologies of BET, TPR and XRD. The results show that different Ce/Ti mole ratios and calcination temperatures induce changes of structure and reductive properties of the Ce x Ti 1- x O 2 mixed oxides. When x =0.1～0.5, amorphous CeTi 2O 6 phase mainly forms at 650 ℃ compared to the formation of CeTi 2O 6 which crystallizes at 800 ℃. When x >0.6, some TiO 2 enters the CeO 2 lattice and a CeO 2 TiO 2 solid solution is formed. The activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 650 ℃ is largely affected by the x values, which is the highest when x =0.3, 0.4 and 0.9. The NO conversion reaches 70% at a reaction temperature of 150 ℃. By comparison, the x values have little effect on the activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 800 ℃ . There are strong interactions between CuO and CeTi 2O 6, i.e., formation of the CeTi 2O 6 phase shifts the CuO reduction peak temperature from 380 to 200 ℃, and CuO, in turn, shifts the CeTi 2O 6 reduction peak temperature from 600 to 300 ℃.

Ce改性Ni/MnO_(x)催化剂用于甲烷干重整的研究

采用氧化还原沉淀法制备了系列xCe(100-x)MnO_(x)(简记为xC(100-x)M,x分别为0、10%、30%、50%、80%、100%)复合氧化物,通过浸渍法负载Ni制备Ni/xC(100-x)M系列催化剂。以CH_(4)干重整反应制合成气为模型反应,研究Ce与Mn质量比对Ni/CeMnO_(x)催化剂活性的影响。结果表明,在Ni/MnO_(x)催化剂中引入Ce助剂,提高了催化剂的比表面积和表面碱性位点数量,改善了催化剂的还原能力。在系列Ni/CeMnO_(x)催化剂中,Ce与Mn质量比对反应活性有着显著的影响,Ce质量分数的增加有利于提高CH_(4)和CO_(2)转化率,在反应温度为700℃和V(CH_(4))/V(CO_(2))=1∶1的条件下,Ni80C20M催化剂的CH_(4)和CO_(2)转化率相对较高,CH_(4)转化率为73.90%,CO_(2)转化率为79.38%。

Ce/HZSM-5和生物质原位改造油页岩:提高页岩油的收率和品质

为进一步提高油页岩的转化效率,缓解我国的原油对外依存度,将藻类水热液化与油页岩原位转化过程耦合,以Ce/HZSM-5为催化剂,利用藻类水热液化产物提升干酪根有机质的转化效率和页岩油的品质,借助SEM、TG、GC-MS和元素分析等对反应前后产物分析表征。实验结果表明,在催化剂和小球藻的共同参与下,水热裂解转化的页岩油产率为6.15%,页岩油品质也有了很大提升。与单纯油页岩水热裂解相比,提质后的页岩油轻组分提高了18.58%和4.04%,重组分含量降低了22.62%。

Ce改性Mn-Fe碳基催化剂低温脱硝性能及抗硫活性研究

以硝酸氧化处理后的椰壳活性炭为原料,负载硝酸锰、硝酸铁和硝酸铈等活性物质,经中低温煅烧制备Ce改性Mn-Fe碳基低温抗硫脱硝催化剂。利用固定床脱硝评价实验装置并结合BET、SEM-Mapping、XPS等表征方法研究其低温脱硝性能及抗硫活性。结果表明,Ce改性Mn-Fe碳基催化剂具有高比表面积,且表面Mn均匀分布,较高的Mn^(4+)、Ce^(3+)和表面吸附氧(O_(α))含量增强了碳基催化剂脱硝及抗硫性能。在130~220℃的脱硝效率高达99%以上;低SO_(2)浓度对催化剂脱硝性能基本无抑制作用,持续反应8 h脱硝效率仍高达88.78%。

Promoter of (Ce-Zr)O_2 Solid Solution Modified by Praseodymia in Three-Way Catalysts

The three way catalysts (TWCs) promoters (Ce Zr)O 2, (Pr Ce Zr)O 2 and (Pr Zr)O 2 were prepared by sol gel like method. They were characterized by XRD, EXAFS and BET surface area determination. The reduction features of the promoters were measured by temperature programmed reduction (TPR) of H 2 to access the potential for the promoters containing praseodymia as oxygen storage component in three way catalyst. The (Pr Zr)O 2 cubic solid solution is formed at high temperature up to 800 ℃, which makes it more reducible than the (Ce Zr)O 2 solid solution. For the (Pr Ce Zr)O 2 samples, the ternary solid solution plays an important role in the reduction process. The performance of the three way catalysts with fully formulated Pt, Pd and Rh is proceeded by using both light off temperature under a stoichiometric gas composition and the conversion of CO, C 3H 6 and NO under changing air/fuel ratio at a constant reaction temperature 400 ℃ . The results indicate that a small amount of praseodymia doping into (Ce Zr)O 2 favors the light off temperature of C 3H 6 and NO, and all the catalysts containing praseodymia obviously exhibits enhanced width of S value for NO conversion at lean region ( S ≥1.00).

Ce-Cu协同作用对Ce-CB/Al_(2)O_(3)催化剂催化甲醛乙炔化性能的影响

采用共沉淀法制备了具有不同Ce质量分数掺杂改性的CuO-Bi_(2)O_(3)/Al_(2)O_(3)催化剂,通过XRD、BET、H2-TPR、SEM、XPS等手段研究了Ce助剂对催化剂结构及其甲醛乙炔化反应性能的影响。结果表明,Ce和Cu的双金属协同作用不仅提高了CuO在催化剂中载体表面的分散度,还促进了CuO的还原活化过程,使得催化剂中的CuO高效转变为乙炔亚铜活性物种,并在反应过程中保持较高的分散度与稳定性。Ce掺杂改性的催化剂表现出更高的催化活性,在Ce5-CB/Al_(2)O_(3)催化剂催化甲醛乙炔化反应中,实现了93.7%的甲醛转化率以及98.1%的1,4-丁炔二醇选择性,且催化剂经历6次循环后催化活性未见明显降低。

Influences of (Ce-Zr-La-Pr)O Contents on Three-Way Catalyst Performances

A series of catalysts with (Ce-Zr-La-Pr)O contents range from 0 to 50% in coating and single-palladium loads on substrates were prepared to study effects of (Ce-Zr-La-Pr)O contents on catalytic activities and durability by contrasting the characteristics of light-off, A/F and catalytic conversions of the fresh catalysts with that of the aged catalysts. The results show that (Ce-Zr-La-Pr)O can enhance the catalysts light-off characteristics, widen A/F windows and increase catalytic conversions at a certain extent through optimizing physical structural and chemical property of the mixed coating. However, (Ce-Zr-La-Pr)O contents influence greatly on the catalysts activities and durability, and the catalysts with contents ranging from 10% to 30% exhibited better integrative properties in all samples, and 10% was the optical content to make the catalyst performance highest in this thesis. It is indicated that an suitable content of (Ce-Zr-La-Pr)O plays an important role in assisting catalysis, enhancing durability and increasing oxygen storage capability.

湿法制备Cu基Mn-Ce改性甲醇重整制氢催化剂及其催化性能研究

为了提升Cu基催化剂的高温稳定性和使用寿命,并研究过渡金属Mn及轻稀土金属Ce对Cu基甲醇重整催化剂的影响,本文采用新型湿法制备了Cu基Mn-Ce改性催化剂,并在气-固相固定床催化反应装置上评价了其甲醇重整制氢的性能。甲醇转化实验结果显示,Cu基Mn-Ce改性催化剂的甲醇转化率达到98.77%,产出的(H2+CO)含量达到92.5%。高温碳化性能对比实验结果表明,相比未改性的催化剂,Mn-Ce改性催化剂的高温稳定性更强,使用寿命更长。高温碳化后,205℃下的甲醇转化率均在40%以上,未改性催化剂的转化率仅为20%左右。催化剂性能评价实验结果表明,催化反应温度与其制氢性能呈正相关,高温下催化剂有更优异的制氢表现。Mn、Ce的加入可以有效提高Cu基催化剂甲醇重整制氢的性能。

Influences of Platinum Precursors and Solution Acidities on REO-Based Catalysts Performances

Important effects exist between precious metals and rare earths oxides in three-way catalyst, especially the coordinated effects. These effects were studied by using H2PtCl6, Pt(NH3)2(NO2)2 and Pt(OH)2(C2H5ONH2)2 as Pt precursors, and the mixed oxide of (Ce-Zr-La-Pr)O as base material to prepare a series of catalysts, and their performances of the catalysts were studied by TPR and CO pulse titration technologies. The results shown that Pt precursors and their solutions pH values influenced the oxygen storage capabilities, the active metal distribution degrees of the catalysts obviously, and every catalyst prepared by different precursors had an optimal pH values. It indicates that the active metals precursors and their solutions acidities have outstanding influences on the catalysts performances for the mutual effects existing between the active metals and the Rare Earth metal oxides, which results from the mate groups of the precursors and the solution acidity.

Ce-Cu复合催化剂用于对硝基苯酚废水处理研究

通过络合法制得Ce-Cu复合催化剂,采用X射线衍射、扫描电子显微镜和程序升温还原对催化剂性能进行了研究,考察了该催化剂用于废水中对硝基苯酚去除性能。结果表明,催化剂中Cu氧化物能很好地溶入CeO2晶格形成表面具有多孔结构的Ce0.86Cu0.14O2固溶体催化剂,催化剂中Cu-O键得到一定程度的削弱,使其可还原性能得到提高而提高了催化剂中氧化物的活性。Ce0.86Cu0.14O2催化剂可将废水中对硝基苯酚的质量浓度由150 mg.L-1降到1.8 mg.L-1左右,对硝基苯酚去除率可达98.8%。

载体对Mn-Ce催化剂低温选择性催化还原脱硝性能的影响

使用3种组成不同的钛白粉作为载体,采用浸渍法制备Mn-Ce/TiO_2,Mn-Ce/TiO_2-SiO_2,Mn-Ce/TiO_2-WO_3催化剂,采用XRD,BET,SEM等方法对催化剂的微观结构及形貌进行表征,探索SiO_2、WO_3的掺加对催化剂脱硝活性和抗硫性能的影响。结果表明:掺加SiO_2、WO_3有助于增大载体的比表面积及催化剂表面活性酸中心数量,催化剂的脱硝活性和抗硫性能得到提高;在空速为10 000 h^(-1)、反应温度为100℃的条件下,Mn-Ce/TiO_2催化剂上NO去除率仅为30%,Mn-Ce/TiO_2-SiO_2和Mn-Ce/TiO_2-WO_3催化剂上NO去除率分别为45%和50%;当反应气中含有150μL/L的SO_2时,在反应温度为150℃、反应时间为270 min的条件下,与不含SO_2时相比,Mn-Ce/TiO_2催化剂上NO去除率从80%降低至40%,Mn-Ce/TiO_2-SiO_2和Mn-Ce/TiO_2-WO_3催化剂上NO去除率从84%降至55%和70%。

SO_2对Mn-Ce/TiO_2低温SCR催化剂的毒化作用研究

考察了SO_2对Mn-Ce/TiO_2低温脱硝催化剂活性的影响,利用XRD、BET、SEM和XPS对其毒化作用的原因进行分析。结果表明,SO_2对催化剂活性有明显的抑制作用,使NO_x去除率由84%降至42%左右。主要是SO_2的加入造成催化剂比表面积减小,孔径为5-10 nm的孔数量减少,且催化剂晶相由锐钛矿型转化成金红石型结构,活性组分MnO_x发生晶化现象,破坏了Mn-Ti间的强相互作用。催化剂理化性质的变化造成吸附态氧转化为晶格氧的路径受阻、MnO_2含量减少和CeO_x储氧功能减弱,并且产生氧阻效应而使NO吸附和解吸受阻,造成催化剂活性降低。同时生成的硫酸铵盐在催化剂表面沉积,覆盖了催化剂表面的Lewis酸性位,使其对NH_3吸附能力减弱。

Ce含量对Ni-Ce/Al_2O_3催化剂结构及浆态床CO甲烷化性能的影响

以γ-Al2O3为载体,采用等体积浸渍法制备了不同Ce含量的Ni-Ce/Al2O3催化剂,并考察了其浆态床CO甲烷化反应性能。借助XRD、BET、H2-TPR及CO-TPD等对催化剂进行了表征分析,研究了催化剂的微观结构与甲烷化性能之间的关系。结果表明,助剂Ce的引入能够加强Ni物种与载体之间的相互作用、增强活性组分Ni对CO的吸附能力。随着Ce含量的升高,Ni物种在载体表面的分散度提高、Ni晶粒粒径减小,催化剂的比表面积及与载体相互作用较强的β-NiO相对含量先升后降。催化剂的浆态床甲烷化活性随Ce含量的升高呈现规律性的变化,CO转化率和CH4时空收率先增加后略有下降,当Ce含量为4%(质量分数)时,催化剂甲烷化活性最佳。

交互正交试验设计在Mn/Ce催化剂制备中的应用

利用交互正交试验设计对柠檬酸络合法制备Mn/Ce复合氧化物催化剂(简称Mn/Ce催化剂)的制备条件进行了优化,重点考察金属配比(Mn∶Ce=7∶3、1∶1、3∶7)、焙烧温度(350℃、500℃、650℃)、焙烧时间(2 h、3.5 h5、h)等3种因素对催化湿式氧化(CWAO)降解正丁酸过程中Mn/Ce催化剂活性的影响。结果表明,金属配比和焙烧温度对催化剂活性有显著影响(置信度p分别为99%和95%),焙烧时间对催化剂活性无显著影响(p=90%),焙烧温度与金属配比之间有显著的交互作用(p=99%),得到的最佳制备条件为:Mn∶Ce=3∶7、焙烧温度500℃和焙烧时间5 h;并对最佳制备条件下得到的Mn/Ce催化剂进行XRD、BET和SEM等表征。