ZrO2-Al2O3复合载体负载Ni基催化剂COx甲烷化性能

采用浸渍和粉末压片的方法制备了两种ZrO₂-Al₂O₃复合载体并用于负载Ni基催化剂，并利用氮气等温物理吸附、X射线粉末衍射（XRD）、H₂程序升温还原（H₂-TPR）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）等分析手段对催化剂物化性质进行表征，考察了ZrO₂-Al₂O₃复合载体制备方法及ZrO₂的引入对Ni基催化剂在CO、CO₂和CO-CO₂共存的3种体系下甲烷化反应活性的影响。材料表征和活性测试结果表明，在CO甲烷化体系中，与单一Al₂O₃载体相比，引入ZrO₂的复合载体能有效提高催化剂中Ni物种的分散度从而增强CO甲烷化过程中催化剂活性，且粉末压片法较浸渍法制备的复合载体能有效提高催化剂的还原度，降低还原温度，但前者会大大降低催化剂的比表面积；在CO₂甲烷化体系中，当载体形貌和制备方法相同时，载体的变化对催化剂活性的影响较小，CO₂转化率主要受到制备方法不同引起的物理性质如比表面积变化的影响；在CO-CO₂共存体系中，由于CO在竞争吸附中比CO₂更容易占据活性位点，所以呈现出优先进行CO甲烷化再进行CO₂甲烷化、CO₂的含量先增多后减少的规律。     

CeO2-Al2O3复合载体负载Ni基催化剂催化COx共甲烷化性能

通过浸渍沉淀法分别制备Ni/Al₂O₃、Ni/CeO₂和Ni/CeO₂-Al₂O₃催化剂，并对其分别进行不同CO/CO₂比例下COx共甲烷化性能评价。发现Ni/Al₂O₃催化剂催化CO转化为CH4的能力明显高于Ni/CeO₂，而催化CO₂甲烷化的性能则相反。采用Ni/CeO₂-Al₂O₃催化剂，可以在提高CO转化率的同时而不降低CO₂转化率。结合BET、XRD、TPR、TPD和原位红外等各种表征手段，发现CeO₂掺杂虽然降低了催化剂的比表面积和金属Ni的分散度，但却可明显提高其吸附活化CO₂的能力，这主要是由于具有较高含量氧空位的CeO₂的掺杂可以提高载体表面碱性位，促使共甲烷过程中CO_...     

金属氧化物催化CO2与甲醇合成碳酸二甲酯的研究进展

CO₂是主要的温室气体。近年来随着工业的大力发展,CO₂的排放量迅猛增加,严重影响着人类的生存环境。将CO₂转化成有价值的化工产品,受到了研究领域的广泛关注。其中将CO₂与产能过剩的甲醇作为原料,生产碳酸二甲酯（DMC）,既能减少CO₂排放,又能产生有价值的绿色产品DMC。本文简述了影响CO₂转化的因素,即受热力学限制和CO₂活化困难;重点介绍了具有酸碱活性中心的金属氧化物ZrO₂、CeO₂以及复合金属氧化物催化剂的催化性能和反应机理,并分析了影响催化活性的主要原因：表面酸碱性能决定了催化活性;进一步分析了催化剂表面的酸碱性来源于Lewis酸碱位和Br?nsted酸性位。对于开发高效的金属氧化物催化剂未来的研究方向提出了展望: 通过调控催化剂的晶相和形貌、增加氧空位和羟基官能团、掺杂碱性或者酸性物种来改变催化剂表面的酸碱性,并且向催化系统中添加脱水剂。最后指出了由于CO₂分子的稳定性很难被活化,需进一步深入研究其活化CO₂的机理,提高CO₂的转化率。     

NaOH改性MnO2/γ-Al2O3催化尿素醇解合成碳酸丙烯酯

采用超声浸渍法制备了MnO₂/γ-Al₂O₃催化剂,并用碱和盐对其进行了改性.采用X射线衍射仪(XRD)、CO₂-TPD对改性后的MnO₂/γ-Al₂O₃催化剂进行了表征,研究了改性后催化剂在尿素醇解合成碳酸丙烯酯(PC)反应中的催化性能.研究结果表明,NaOH改性MnO₂/γ-Al₂O₃催化剂具有最好的催化性能;同时催化剂的焙烧时间、焙烧温度以及NaOH改性量影响催化剂表面碱性活性中心的数量和强度,其中中强碱的增加是改性后催化剂活性提高的主要原因.在NaOH用量为MnO₂质量的10%,400℃焙烧2h后,改性MnO₂/γ-Al₂O₃催化剂表面的中强碱量最大,催化活性最高,PC收率与选择性分别达86.9%、91.8%.     

修饰的CuO/Fe2O3水煤气变换催化剂的性能测试与表征

ZrO₂是一种高熔点金属氧化物,同时具有弱酸性和弱碱性以及氧化性与还原性,具有p型半导体性质,易产生氧空穴,是理想的催化材料。通过添加不同质量分数的ZrO₂(0~5%) 作为助剂,采用分步沉淀法制备系列CuO/Fe₂O₃-ZrO₂催化剂,通过XRD、N₂物理吸附-脱附、H₂-TPR和CO₂-TPD等表征技术,考察ZrO₂助剂对CuO/Fe₂O₃水煤气变换催化剂催化性能的影响。结果表明,适量ZrO₂（质量分数1%）的添加,削弱了CuFe₂O₄中铜铁物种之间的协同作用,增加了催化剂中可被还原的铜物种的数量,形成较多的弱碱性位点,有利于增加活性中心铜的数量,具有较好的水煤气变换反应活性和热稳定性。     

ZrO2添加对MoO3/Al2O3催化剂耐硫甲烷化性能的影响

采用共沉淀法制备了ZrO₂-Al₂O₃复合载体,并进一步制备了MoO₃/ZrO₂-Al₂O₃催化剂,考察了不同ZrO₂质量分数对催化剂结构及其耐硫甲烷化性能的影响。利用N₂物理吸附、X射线衍射、H₂程序升温还原和透射电子显微镜等手段对催化剂的结构进行了表征。结果表明,MoO₃/ZrO₂-Al₂O₃中ZrO₂的添加可以明显削弱MoO₃与载体间的相互作用,促进Mo物种的还原,适量ZrO₂的存在还有助于提高催化剂的比表面积,改善Mo活性相的分散性,使催化剂表现出优异的耐硫甲烷化活性。     

Ni/ZrO2-SiO2催化剂催化乙酰丙酸加氢合成γ-戊内酯

分别以ZrO₂、SiO₂及ZrO₂-SiO₂复合氧化物为载体,采用等体积浸渍法制备了Ni含量为10%（质量分数）的催化剂,考察了其催化乙酰丙酸液相加氢性能。采用N₂-物理吸附、NH₃-TPD、H₂-TPR、XRD、TEM等表征手段对催化剂进行了表征。研究结果表明,在所制备的催化剂上,乙酰丙酸先经C=O加氢生成4-羟基戊酸,后者快速脱水酯化为γ-戊内酯。Ni/ZrO₂-SiO₂催化剂较Ni/ZrO₂与Ni/SiO₂催化剂具有高的金属分散度和丰富的表面酸性中心,表现出高的C=O加氢活性以及优异的乙酰丙酸加氢合成γ-戊内酯性能。在反应温度为200℃,氢气压力4 MPa的反应条件下,乙酰丙酸的转化率达到100%,γ-戊内酯的选择性大于99.9%。     

新型合成气甲烷化催化剂La2O3-ZrO2-Ni/Al2O3的制备与性能

针对常规合成气甲烷化催化剂高热结构稳定性差、活性低、适应性差等不足,本文创新地引用稀土金属氧化物La₂O₃复配过渡金属氧化物ZrO₂作为多功能复合助剂,利用反向沉淀法制备了新型合成气甲烷化催化剂La₂O₃-ZrO₂-Ni/Al₂O₃,同时制备催化剂Cr₂O₃-Ni/Al₂O₃作为参照组。采用X射线衍射（XRD）、透射电子显微镜（TEM）表征了催化剂的微观结构,并利用N₂吸附仪（BET）测量催化剂经高温水热处理前后的微孔结构参数,以考察催化剂的高热结构稳定性。结合国内某大型煤制天然气项目工艺特征和运行实践,应用Aspen Plus软件模拟了四段甲烷化工艺理论平衡值。基于自主固定床合成气甲烷化评价实验装置,考察了反应压力、空速和原料气H₂O(g)含量等因素对La₂O₃-ZrO₂-Ni/Al₂O₃催化性能的影响,并开展了1000h长周期寿命评价实验。结果表明,La₂O₃-ZrO₂-Ni/Al₂O₃比Cr₂O₃-Ni/Al₂O₃具有更优的高热结构稳定性;可使CO和CO₂反应达到或接近催化剂床层出口温度下的理论平衡状态,呈现显著的宽温活性;活性组分NiO晶粒尺寸介于7~10nm,分散度较高;对反应压力、空速和原料气H₂O(g)含量的变化不敏感,具有良好的操作弹性;1000h反应后仍能保持较高的活性和稳定性。     

Ni/Al2O3-SiO2催化剂表面性质及顺酐加氢性能

以Al₂O₃质量分数为10%的Al₂O₃-SiO₂复合氧化物为载体,通过浸渍法制备一系列不同Ni负载量的Ni/Al₂O₃-SiO₂催化剂。运用BET、XRD、H₂-TPR和NH₃-TPD-MS方法研究催化剂表面性质随活性金属Ni负载量的变化规律,探讨催化剂表面性质的变化对其顺酐加氢活性、选择性及催化剂稳定性的影响。结果表明,Ni/Al₂O₃-SiO₂催化剂中的Ni质量分数由5.0%增加至12.5%时,γ-丁内酯收率由7.9%快速增至38.9%,进一步增加Ni质量分数至20.0%,γ-丁内酯收率增加趋于平缓。催化剂中Ni活性物种与催化剂酸性中心的数量是影响催化剂顺酐加氢活性的主要原因。     

不同元素掺杂锰基催化剂的NH3-SCR反应性能研究

为了研究催化剂的酸碱性和氧化还原能力对纯锰氧化物催化剂的NH₃-SCR(选择性催化还原)反应性能影响，选取碱土金属Sr、过渡金属Ce、Fe和非金属Si对纯锰氧化物催化剂进行改性，所有催化剂均采用共沉淀法制取。通过XRD、N₂-BET、NH₃-TPD、XPS和H₂-TPR表征手段对催化剂进行分析。XRD结果表明，实验采用的制备方法制备的锰基催化剂主要物相为Mn₂O₃和Mn₅O₈;N₂-BET结果显示，Ce、Fe、Si₃种元素能有效增加纯锰氧化物的比表面积；NH₃-TPD和XPS结果证明，Ce、Fe、Si的引入使得纯锰氧化物的表面吸附氧(OⅡ)、Mn⁴⁺含量提高，Ce和Si的掺杂增加了催化剂的总酸量，Fe则有效调控了酸性位的分布；H₂-TPR结果表明，除Ce外其余元素均使纯锰氧化物催化剂的氧化还原能力有所减弱...     

CO_2 methanation over TiO_2–Al_2O_3 binary oxides supported Ru catalysts

TiO_2 modified Al_2O_3 binary oxide was prepared by a wet-impregnation method and used as the support for ruthenium catalyst. The catalytic performance of Ru/TiO_2–Al_2O_3catalyst in CO_2 methanation reaction was investigated. Compared with Ru/Al_2O_3 catalyst, the Ru/TiO_2–Al_2O_3catalytic system exhibited a much higher activity in CO_2 methanation reaction. The reaction rate over Ru/TiO_2–Al_2O_3 was 0.59 mol CO_2·(g Ru)1·h-1, 3.1 times higher than that on Ru/Al_2O_3[0.19 mol CO_2·(gRu)-1·h-1]. The effect of TiO_2 content and TiO_2–Al_2O_3calcination temperature on catalytic performance was addressed. The corresponding structures of each catalyst were characterized by means of H_2-TPR, XRD, and TEM. Results indicated that the averaged particle size of the Ru on TiO_2–Al_2O_3support is 2.8 nm, smaller than that on Al_2O_3 support of 4.3 nm. Therefore, we conclude that the improved activity over Ru/TiO_2–Al_2O_3catalyst is originated from the smaller particle size of ruthenium resulting from a strong interaction between Ru and the rutile-TiO_2 support, which hindered the aggregation of Ru nanoparticles.     

TiO2-coated on Al2O3 support prepared by the CVD method for HDS catalysts

Mo---Co or Mo---Ni catalysts supported on alumina (Al₂O₃) have been widely used for hydrodesulfurization (HDS) of heavy petroleum fractions. In order to enhance the catalytic activities for HDS, a composite type support (TiO₂-Al₂O₃) prepared by the chemical vapor deposition (CVD) method has been studied. We found that Mo catalyst supported on TiO₂-Al₂O₃ showed much higher catalytic activity for HDS of dibenzothiophene derivatives than the catalysts supported on Al₂O₃.     

Hydrogen production from steam reforming of methanol over CuO/ZnO/Al2O3 catalysts: Catalytic performance and kinetic modeling

A series of CuO/ZnO/Al_2O_3, CuO/ZnO/ZrO_2/Al_2O_3 and CuO/ZnO/CeO_2/Al_2O_3 catalysts were prepared by coprecipitation and characterized by N_2 adsorption, XRD, TPR, N_2O titration and HRTEM. The catalytic performances of these catalysts for the steam reforming of methanol were evaluated in a laboratory-scale fixed-bed reactor at 0.1 MPa and temperatures between 473 and 543 K. The results showed that the catalytic activity depended greatly on the catalyst reducibility and the specific surface area of Cu. An approximate linear correlation between the catalytic activity and the Cu surface area was found for all catalysts investigated in this study.Compared to CuO/ZnO/Al_2O_3, the ZrO_2-doped CuO/ZnO/Al_2O_3 exhibited higher activity and selectivity to CO,while the CeO_2-doped catalyst displayed lower activity and selectivity. Finally, an intrinsic kinetic study was carried out over a screened CuO/ZnO/CeO_2/Al_2O_3 catalyst in the absence of internal and external mass transfer effects. A good agreement was observed between the model-derived effluent concentrations of CO(CO_2) and the experimental data. The activation energies for the reactions of methanol-steam reforming, water-gas shift and methanol decomposition over CuO/ZnO/CeO_2/Al_2O_3 were 93.1, 85.1 and 116.5 k J·mol~(-1), respectively.     

Ru催化加氢选择性脱除F-T合成水相中的含氧化合物

采用催化加氢技术脱除F-T合成水相中羧酸、醛、醇、酮、酯含氧化合物,考察了Ru/ZrO₂、Ru/TiO₂、Ru/SiO₂和Ru/Al₂O₃ 4种Ru催化剂的反应性能.相对于酸、醇,水中的醛、酮、酯更易被转化.其中Ru/ZrO₂和Ru/TiO₂具有良好的加氢脱羰活性,在200℃、9.8 MPa、3.0 h^-1空速下,酸、醛、醇、酮、酯均转化为C₁～C₆的烷烃,总转化率达92%.同条件下,虽然Ru/Al₂O₃对酸、醛、酮、酯的转化活性较高(>87%),但对醇的转化不到30%,具有选择性转化特点.H₂-TPR和NH₃-TPD结果表明,Ru/Al₂O₃催化剂的金属活性位与载体酸性位的协同作用有利于羧酸的加氢反应,能抑制醇的加氢脱羰活性;而金属-载体相互作用较弱和酸度较低的催化剂有利于羧酸、醇发生加氢脱羰反应.Ru/Al₂O₃催化剂运行500 h后失活,XRD、SEM和N₂-物理吸附表明,载体结构物相和织构性质的改变以及活性组分的流失是导致催化剂失活的主要因素.     

B2O3负载量对MoO3/CeO2-Al2O3耐硫甲烷化性能的影响

考察B₂O₃负载量对于MoO₃/CeO₂-Al₂O₃催化剂对耐硫甲烷化活性的影响,利用BET、XRD、TEM、NH₃-TPD等手段对催化剂进行了表征。结果表明,催化剂的耐硫甲烷化活性随B₂O₃负载量增加呈现先升高后降低的变化规律;当B₂O₃负载量为0.5%时,催化剂的耐硫甲烷化活性最高,CO转化率达到55%。结合表征分析,发现添加B₂O₃会影响催化剂载体的结构和表面酸度,从而影响活性组分的分散程度,进而影响MoO₃/CeO₂-Al₂O₃催化剂的耐硫甲烷化性能。催化剂的晶化程度太高或单位面积上的强酸量太多均不利于甲烷化反应;较好的活性组分分散度有利于催化剂甲烷化活性的提高。     

CuO含量对Pd/Al2O3催化剂乙醇氧化性能的影响

采用浸渍法制备了一系列具有不同CuO含量的Pd-CuO/Al₂O₃催化剂，并将其用于乙醇氧化反应，其结构与性质通过XRD、H₂-TPR和NH₃-TPD等手段进行分析。结果发现，催化剂的活性并不是随着CuO含量的增加而增强，Pd-1.0%CuO/Al₂O₃催化剂表现出最佳的活性，其点火温度和完全转化温度比Pd/Al₂O₃催化剂至少降低了50℃。与Pd/Al₂O₃催化剂相比，含CuO催化剂增强的衍射峰强度以及氢化钯分解峰的消失，说明Pd-Cu合金结构的形成有利于Pd、Cu物种之间的协同作用。对于Pd-1.0%CuO/Al₂O₃催化剂来说，还原峰向低温的移动以及还原峰面积的增大说明该催化剂上氧化性物质更易被还原且数量在增加，这对于氧化反应是十分有利的，新出现的还原峰表示Pd、Cu的相互作用生成了新物种。NH₃-TPD结果中更高含量的低温酸有利于高活性，而且新出现的脱附峰说明形成了新的酸性位点。     

Oxidative dehydrogenation of propane over vanadium oxide based catalysts Effect of support and alkali promoter

The oxidative dehydrogenation of propane was investigated using vanadia type catalysts supported on Al₂O₃, TiO₂, ZrO₂ and MgO. The promotion of V₂O₅/Al₂O₃ catalyst with alkali metals (Li, Na, K) was also attempted. Evaluation of temperature programmed reduction patterns showed that the reducibility of V species is affected by the support acid–base character. The catalytic activity is favored by the V reducibility of the catalyst as it was confirmed from runs conducted at 450–550°C. V₂O₅/TiO₂ catalyst exhibits the highest activity in oxydehydrogenation of propane. The support’s nature also affects the selectivity to propene; V₂O₅ supported on Al₂O₃ catalyst exhibits the highest selectivity. Reaction studies showed that addition of alkali metals decreases the catalytic activity in the order non-doped>Li>Na>K. Propene selectivity significantly increases in the presence of doped catalysts.     

制备条件对Pt/SO42-/ZrO2-Al2O3异构化性能的影响

采用沉淀法制备了Pt/SO₄^2-/ZrO₂-Al₂O₃ (PtSZA)催化剂,考察了氢氧化锆水凝胶干燥速率、锆盐浓度、铂含量、Al₂O₃和SO₄^2-添加顺序等制备条件对PtSZA异构化性能,尤其是低温异构化性能的影响,并用XRD和TG对催化剂进行了表征。结果表明,提高水凝胶的干燥速率降低了PtSZA催化剂中的硫含量,大大提高了催化剂中的单斜相,进而导致了催化剂低温失活加速以及高温活性下降。较低或较高的锆盐浓度劣化了PtSZA的低温异构化稳定性,以0.4~0.6mol/L硝酸氧锆制备的催化剂硫含量和四方相氧化锆含量较高,异构化活性相对较好,Al₂O₃和SO₄^2-添加顺序对PtSZA异构化性能没有明显影响。     

Catalytic activity of PdO/ZrO2 catalyst for methane combustion

Catalytic activity of ZrO₂ supported PdO catalysts for methane combustion has been investigated in comparison with Al₂O₃ supported PdO catalysts. It was found that the drop of catalytic activity owing to decomposition of PdO at a high temperature region (600–900°C) was suppressed by using ZrO₂ support. Temperature-programmed reduction (TPR) measurements of the catalyst with hydrogen revealed that the PdO of PdO/Al₂O₃ catalyst was reduced at the temperature less than 100°C, whereas in PdO/ZrO₂ catalyst the consumption of hydrogen was also observed at 200–300°C. This result indicates that the stable PdO species were present in the PdO/ZrO₂ catalyst. In order to confirm the formation of the solid solution of PdO and ZrO₂, X-ray diffraction (XRD) analyses of the mixtures of ZrO₂ and PdO calcined at 700–900°C in air were carried out. The lattice volume of ZrO₂ in the mixture was larger than that of ZrO₂. Furthermore, the Pd thin film on ZrO₂ substrate was prepared as a model catalyst and the depth profile of the elements in the Pd thin film was measured by Auger electron spectroscopy (AES). It was confirmed that Zr and O as well as Pd were present in the Pd thin film heated at 900°C in air. It was considered that the PdO on ZrO₂ support might be stabilized by the formation of the solid solution of PdO and ZrO₂.