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1.
采用XRD、UV-vis DRS、ESR和微分吸附量热等技术,考察了铬担载量分别为2.5、5和10wt%的CrO x/SiO 2催化剂的结构、表面性质和氧化还原性能。结果表明,催化剂表面上存在多种Cr的氧化态和聚集形式。随着Cr担载量从2.5wt%到10wt%的逐渐增大,催化剂表面占主导地位的Cr物种由CrO 3单体转为多聚CrO 3和Cr 2O 3晶相。在CO 2气氛中催化剂对丙烷转化率和丙烯选择性的大小顺序为2.5wt%CrO x/SiO 2>5wt%CrO x/SiO 2>10wt%CrO x/SiO 2,反应过程中的原位ESR和UV-visDRS测定结果表明,催化剂表面的反应活性中心为Cr 5+,Cr 5+可由催化剂预处理过程中Cr 3+的氧化及丙烷反应过程中CrO 3单体的还原产生,在反应中CO 2可使Cr 3+重新氧化为Cr 5+. 相似文献
2.
The Ni/ZrO 2/SiO 2 aerogels catalysts were synthesized via three different routes: (i) impregnation ZrO 2–SiO 2 composite aerogels with a aqueous solution of Ni(NO 3) 2, (ii) impregnation SiO 2 aerogels with a mixed aqueous solution of Ni(NO 3) 2 and ZrO(NO 3) 2 · 2H 2O, (iii) one-pot sol–gel procedure from precursors Ni(NO 3) 2/ZrO(NO 3) 2 · 2H 2O/Si(OC 2H 5) 4. These catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), ammonia temperature-programmed
desorption (NH 3-TPD), N 2 adsorption–desorption isotherms and Fourier transform infrared (FT-IR). The Liquid-phase hydrogenation of maleic anhydride
(MA) was performed over these catalysts. The results revealed that the different preparation routes result in a difference
between the obtained samples, concerning the crystal structure and composition, surface acidity, mixed level of each component,
texture, and catalytic selectivity. 相似文献
3.
采用热扩散法(TS)和等体积浸渍法制备了MoO 3/SiO 2催化剂用于草酸二甲酯和苯酚酯交换反应.结果表明,热扩散法制备的10%MoO 3/SiO 2-TS催化剂较等体积浸渍法制备的10%MoO 3/SiO 2-C催化剂具有更好的催化性能.运用X射线衍射、Raman光谱、X射线光电子能谱分析、吡啶吸附红外光谱、NH 3程序升温脱附等手段对催化剂进行了表征,发现虽然两种方法制备的催化剂都只有弱Lewis酸中心,钼均以氧化钼单体形式存在,未形成解离和聚合,但是10%MoO 3/SiO 2-TS催化剂较10%MoO 3/SiO 2-C催化剂表面钼含量更高且MoO 3分散得更好.在苯酚用量为0.2mol,10%MoO 3/SiO 2-TS催化剂用量为1.2g,反应温度为180℃,草酸二甲酯与苯酚的摩尔比为2,反应时间为4h的优化条件下,苯酚转化率可达70.9%,甲基苯基草酸酯和草酸二苯酯的收率分别达63.1%和7.7%. 相似文献
4.
以九水合硝酸铝(Al(NO 3) 3·9H 2O)与正硅酸乙酯(TEOS)为前驱盐,采用溶胶-凝胶法制备一系列不同Al 2O 3含量的SiO 2-Al 2O 3复合氧化物,并通过浸渍硝酸氧锆引入ZrO 2,制备ZrO 2/SiO 2-Al 2O 3复合氧化物催化剂,考察催化剂在肉桂醛(CAL)MPV转移加氢中的催化性能,并结合N 2物理吸附、X射线粉末衍射(XRD)、傅里叶变换红外光谱(FTIR)、NH 3-程度升温脱附(NH 3-TPD)、Py-原位红外(Py-IR)等技术,研究催化剂结构、织构以及表面性质与其催化性能间的构效关系.研究表明,所制备的催化剂均以L酸为主,并含有少量B酸中心,这使得加氢产物以肉桂醇(COL)为主,并含有少量1-苯丙烯-2-丙基醚(CPE).Al 2O 3含量不仅影响催化剂表面的酸中心数量,而且对催化剂的织构参数有较大影响.随Al 2O 3含量的增加,催化剂表面L酸与B酸中心均有所增加,而孔径则持续变小,这使得催化反应呈现CAL转化率先增加后减少、目标产物COL选择性先稍有减小后有所增加的趋势.在Si/Al比为2时,催化剂具有最优的催化性能,优化反应条件下,CAL转化率达96%,目标产物COL选择性达90%. 相似文献
5.
通过向SO 2-4 /ZrO 2催化剂中同时引入适量的Pt和Al 2O 3, 制备出了具有较高催化性能和稳定性的Pt-SO 2-4 /ZrO 2-Al 2O 3型固体超强酸催化剂. 以正戊烷异构化反应为探针, 考察了Al含量对催化剂性能的影响; 并采用X射线衍射(XRD)、比表面积测定(BET)、红外(IR)光谱、程序升温还原(TPR)、热重-差热分析(TG-DTA)和氨-程序升温脱附(NH 3-TPD)手段对催化剂进行了表征. 结果表明, Al能够提高ZrO 2的晶化温度, 抑制硫的分解, 增加催化剂的比表面积, 增强硫氧键的结合, 提高催化剂的还原性能, 增加催化剂的酸强度和酸总量. 当Al 2O 3含量(质量分数, w)为5.0%时, Pt-SO 2-4 /ZrO 2-Al 2O 3固体超强酸催化剂的催化活性最好, 在100 h内异戊烷收率可稳定在52.0%以上, 选择性在98.2%以上. 相似文献
6.
对丙三醇和苯胺在Co或Ni促进的Cu/SiO2-Al2O3催化剂上气相合成3-甲基吲哚进行了研究.采用N2吸附、氢气程序升温还原(H2-TPR)、电感耦合等离子体(ICP)发射光谱、X射线衍射(XRD)、透射电子显微镜(TEM)、氨程序升温脱附(NH3-TPD)及热重(TG)分析等技术对催化剂进行了表征.结果表明,向Cu/SiO2-Al2O3催化剂加入钴或镍助剂改善了催化剂的催化性能,钴比镍更加有效.在催化剂Cu-Co/SiO2-Al2O3和Cu-Ni/SiO2-Al2O3上,反应第3 h,3-甲基吲哚收率分别达到47%和45%,而且催化剂经过6次再生收率仍能达到44%和42%.各种表征表明,向Cu/SiO2-Al2O3催化剂加入钴或镍助剂能增强铜和载体之间的相互作用,其结果不仅促进了铜粒子在载体表面的分散度,而且有效减少了反应过程中铜组分的流失.另外,加入钴或镍助剂还能减少催化剂的中强酸中心数,从而提高3-甲基吲哚的选择性,并且抑制积炭的形成.此外,钴助剂还能增加催化剂的弱酸中心数,促进3-甲基吲哚的生成.提出了金属铜与弱酸中心共同促进3-甲基吲哚合成的催化反应机理. 相似文献
7.
采用共沉淀的方法制备了不同Fe 掺杂量的SO 42-/SnO 2-Fe 2O 3固体超强酸催化剂. 利用傅里叶变换红外(FTIR)光谱, 粉末X射线衍射(XRD), N 2吸附-脱附实验(BET), 热重(TG)分析和扫描电镜(SEM)等方法对样品进行了表征. 考察了所得催化剂对4-叔丁基环己酮与乙二醇缩合反应的催化性能. 实验结果表明, 与未经过掺杂改性的SO 42-/SnO 2固体酸催化剂相比, 改性后催化剂的催化性能得到了改善. 研究了以Fe/Sn 摩尔比为0.5的SO 42-/SnO 2-Fe 2O 3固体酸为催化剂, 部分醛酮类化合物与乙二醇及1,2-丙二醇的缩合反应. 考察了反应时间、催化剂用量等因素对反应的影响. 同时, 将所得催化剂应用于环酮Baeyer-Villiger 氧化反应中, 催化剂表现出良好的催化活性, 且催化剂具有一定的循环使用性. 相似文献
8.
采用共沉淀-后浸渍方法制备了表面助剂改性的Cu/ZnO/Al 2O 3 (CZA)甲醇合成催化剂, 在固定床反应器上以合成气为原料分别考察了三种助剂(Zr、Ba和Mn)对CZA催化剂性能的影响; 以Zr为助剂时反应温度的影响; 并进行了催化稳定性试验. 利用粉末X射线衍射(XRD)、低温氮气吸脱附(N 2-sorption)、氧化亚氮(N 2O)反应吸附技术、X射线光电子能谱(XPS)、氢气程序升温吸脱附(H 2-TPD)、扫描电子显微镜(SEM)和高分辨透射电子显微镜(HR-TEM)技术对催化剂进行了表征.结果显示: 以Zr或Ba作为助剂能够明显提高CZA催化剂耐热前后的甲醇时空收率(STY); Mn的引入降低了CZA催化剂的耐热前活性; Zr的引入降低了CZA催化剂最高活性温度点, 增强了CZA催化剂的催化稳定性; 还原态CZA催化剂表面Cu 0和ZnO都能吸附活化氢气, Cu 0与ZnO的强相互作用有利于提高催化剂的性能, 耐热后催化剂性能的降低归因于Cu晶粒的长大. 在实验和表征结果基础上,提出了CZA催化剂上合成气制甲醇的“双向同步催化反应历程”. 相似文献
9.
The acid-base properties of a series of SiO 2-supported NiMoO 4 catalysts were investigated by temperature-programmed desorption of NH 3 and CO 2. Results show that supported catalysts with ca. one monolayer of the active phase are less acidic than the unsupported stoichiometric NiMoO 4. 相似文献
10.
Silica-supported perchloric acid and bisulfate (SiO 2/HClO 4 and SiO 2/KHSO 4) have been developed as reusable green catalysts for nitration of aromatic compounds using NaNO 2 in acetonitrile medium under conventional and solvent-free microwave conditions. The reaction times under microwave irradiation are significantly shorter than conventional method even though the yields obtained in microwave-assisted reactions are comparable with those obtained under reflux conditions. 相似文献
11.
采用两步浸渍法和载体上的原位反应制备了一系列Cs部分取代的Ni-Cs xH 3-xPW 12O 40/SiO 2催化剂,并用N 2吸附比表面积测定(BET)、电感耦合等离子体发射光谱(ICP)、X射线衍射(XRD)、拉曼光谱(Raman)、原位X射线衍射(in situ XRD)、NH 3程序升温脱附(NH 3-TPD)、H 2程序升温还原(H 2-TPR)、H 2程序升温脱附(H 2-TPD)、吡啶吸附傅里叶变换红外(FTIR)光谱等分析测试技术对催化剂进行了表征. 以正癸烷为模型化合物,对催化剂的加氢裂化性能进行了评价. 结果表明,8%Ni-50%Cs 1.5H 1.5PW/SiO 2催化剂具有最高的C 5+收率,明显优于8%Ni-50%H 3PW/SiO 2催化剂和工业催化剂. 随着Cs 在Cs xH 3-xPW中比例的增加,正癸烷的转化率逐渐降低,而C 5+选择性则逐渐提高. 当催化剂具有合适的孔径时,选择性的提高是由于催化剂酸性的减弱,而转化率的降低则是由于催化剂加氢能力的减弱. 相似文献
12.
采用共沉淀法制备了系列铜负载量不同的Cu/Fe 2O 3水煤气变换(WGS)催化剂,并考察了铜负载量对催化剂结构和水煤气变换反应性能的影响. 结果表明,Cu/Fe 2O 3催化剂呈现出良好的水煤气反应性能,当CuO质量分数为20%时,催化剂的WGS性能最优,250 ℃时CO转化率高达97.2%,同时热稳定性也最好. 运用X射线粉末衍射(XRD)、N 2物理吸脱附和H 2程序升温还原(H 2-TPR)等手段对Cu/Fe 2O 3催化剂的物相、织构特征及还原性能进行了表征,结果表明,CuFe 2O 4物种的存在极大地改善了催化剂的还原性能和WGS反应活性. 这是由于CuFe 2O 4特殊的尖晶石结构有利于Cu微晶的稳定;同时,CuFe 2O 4在低温下即被还原为单质铜,有利于促进催化剂体系中电子的转移. 此外,通过(NH 4) 2CO 3溶液处理,研究了独立相CuO对Cu/Fe 2O 3催化剂WGS反应性能的影响,结果发现,独立相CuO的存在,有利于H原子在各组分传递,从而促进催化剂的CuFe 2O 4的还原,改善Cu/Fe 2O 3催化剂的WGS反应性能. 相似文献
13.
采用并流共沉淀方法制备了一系列不同铬含量的Cu/ZrO2/CNTs-NH2催化剂,在固定床反应器上考察铬对催化剂催化CO2加氢合成甲醇反应性能的影响.当铬含量为1%(w),反应温度为260°C,压力为3.0MPa,原料气组成为V(H2):V(CO2):V(N2)=69:23:8,空速为3600 mL·h-1·g-1时,催化剂的促进效果最显著,甲醇收率达7.78%.氮吸附、粉末X射线衍射(XRD)、氢气程序升温脱附(H2-TPR)、X射线光电子能谱(XPS)、二氧化碳程序升温脱附(CO2-TPD)、差热分析(DTA)以及扫描电子显微镜(SEM)等表征结果表明,随着铬含量的增加,铜颗粒的粒径减小,催化剂的比表面积增大.铬的加入一方面提高了铜的分散性,抑制了ZrO2的相变和活性组分的烧结;另一方面提高了CO2的吸附量并促进CO2由弱吸附向强吸附转化,从而提高甲醇的收率;但是当铬含量大于1%时,催化剂表面Cu、Zr的总含量明显下降,降低了CO2的吸附量并且形成了超强CO2吸附物种,抑制了CO2及其中间产物的转化,从而降低了甲醇收率. 相似文献
14.
采用吸附相反应技术制备得到了MnO x/CeO 2/SiO 2催化剂,通过X 射线衍射(XRD)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)、紫外激光拉曼(Raman)等手段对催化剂进行了表征. HRTEM分析表明活性组分MnO x与CeO 2都均匀分布在载体SiO 2表面;XRD分析表明Mn 3O 4特征峰随着CeO 2含量的增加逐渐减小至完全消失,CeO 2的加入降低了MnO x的结晶程度,增加了MnO x的分散性;Raman光谱表明催化剂表面的Mn离子能够进入CeO 2晶格,激发出空穴氧,随着CeO 2负载量的增加,催化剂氧空穴浓度先升高后降低.以NH 3为还原剂,考评催化剂的NO x低温选择性催化还原(SCR)性能,催化剂催化活性随CeO 2负载量增加先升高后降低,与催化剂氧空穴浓度变化规律一致,说明催化剂活性受氧空穴浓度影响,氧空穴浓度升高,催化剂催化活性升高. 相似文献
15.
SiO 2-TiO 2-ZrO 2 and 5Na 2O·95(SiO 2 + TiO 2 + ZrO 2) gels were synthesized and role of Na 2O in gel formation and crystallization behavior of gels were studied. From Si(OC 2H 5) 4, Ti(iso-OC 3H 7) 4, Zr( n-OC 3H 7) 4 and NaOCH 3 solutions in EtOH without H 2O, transparent and opaque gels were obtained. Opaque bulk gels, rich in TiO 2 or ZrO 2 composition in Na 2O containing SiO 2-TiO 2-ZrO 2 system, contain agglomerated spherical particles of diameter small <10 m, in contrast with opaque gels having large particles <30 m in alkali-free SiO 2-TiO 2-ZrO 2 system. Crystallization temperature (Tc) was measured by DTA on dried gels. Compared with the alkali-free SiO 2-TiO 2-ZrO 2 gels, 5 mol% Na 2O containing gels gave lower Tc in SiO 2 rich compositions and higher in TiO 2 rich or ZrO 2 rich compositions. 相似文献
16.
The thermal decomposition of tribochemically activated Al 2(SO 4) 3· xH 2O was studied by TG, DTA and EMF methods. For some of the intermediate solids, X-ray diffraction and IR-spectroscopy were applied to learn more about the reaction mechanism. Thermal and EMF studies confirmed that, even after mechanical activation of Al 2(SO 4) 3· xH 2O, Al 2O(SO 4) 2 is formed as an intermediate. Isothermal kinetic experiments demonstrated that the thermochemical sulphurization of inactivated Al 2(SO 4) 3· xH 2O has an activation energy of 102.2 kJ·mol ?1 in the temperature range 850–890 K. The activation energy for activated Al 2(SO 4) 3· xH 2O in the range 850–890 K is 55.0 kJ·mol ?1. The time of thermal decomposition is almost halved when Al 2(SO 4) 3· xH 2O is activated mechanically. The results permit conclusions concerning the efficiency of the tribochemical activation of Al 2(SO 4) 3· xH 2O and the chemical and kinetic mechanisms of the desulphurization process. 相似文献
17.
The electronic state of platinum supported on SO 4/ZrO 2, SO 4/TiO 2, SO 4/Al 2O 3, and SO 4/SiO 2 systems and on systems unpromoted by sulfur was investigated by diffuse-reflectance IR spectroscopy using CO as the probe
molecule. The introduction of SO 4
2− anions increases the electron deficit on platinum particles. This suppresses the formation of bridging CO complexes with
the metal, leads to the high-frequency shift of absorption maxima of CO adsorbed in the linear form, and stabilizes positively
charged metal species (Pt δ+ and Pt +) during the reduction process. The formation of the positively charged species includes the interaction between the acidic
protons and the metal particles yielding [Pt−H] δ+ adducts. The extent of the influence of the support on the electronic state of the metal increases in the series SO 4/SiO 2<SO 4/Al 2O 3<SO 4/TiO 2<SO 4/ZrO 2 in parallel with an increase in the strength of the acid sites in the system.
Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1094–1099, June, 1998. 相似文献
18.
The data on the thermal decomposition of FeSO4?H2O upon various regimes of heating and gaseous environment prove the formation of intermediate products of the types Fe2O(SO4)2 and FeOHSO4, their stability and amount being determined mainly by temperature and oxygen-reduction potential. This communication aims at presenting results on the synthesis and characterization of Fe2O(SO4)2. The synthesis was carried out using a laboratory thermal equipment operating under isothermal conditions in the temperature range 713–813 K in a gaseous environment either poor in oxygen or containing 100% oxygen. The experimental conditions under which Fe2O(SO4)2 is stable are established. The effect of three basic parameters on the synthesis of Fe2O(SO4)2 is clarified: the oxygen partial pressure, the ratio PH2O/PO2 and the temperature and the mode of heating. Mössbauer spectroscopy and X-ray diffraction data for Fe2O(SO4)2 are presented. 相似文献
19.
Factors (reaction temperature, reaction time, flow rate of oxygen, amount of catalyst, etc.) influencing the catalytic properties of Co 3O 4/SiO 2catalyst in the oxidation octadecan-1-ol to octadecanoic acid were investigated. The catalysts were characterized by means of XRD, FT-IR and N 2-adsorption. The experimental results indicate that under the optimal condition the selectivity to octadecanoic acid reached 97.5 % over 5 % Co 3O 4/SiO 2 catalyst.This revised version was published online in December 2005 with corrections to the Cover Date. 相似文献
20.
采用溶胶-凝胶法和水热法(HTM)合成了Fe 3O 4@SiO 2@TiO 2-Co/rGO复合纳米粒子(磁性光催化剂),通过X射线衍射、扫描电子显微镜及其能量分散光谱和UV-vis漫反射光谱对产物进行了表征分析.研究了Co掺杂量、溶液pH值、亚甲基蓝(MB)溶液初始浓度以及干扰离子(例如Cl -、SO 42-、CO 32-)等因素对MB降解的影响,并对磁性光催化剂的可重复使用性进行了分析.正常实验条件下(pH=7,[MB]=10 mg/L,磁性光催化剂用量=0.1 g/50 mL),150 min内MB最大去除率达到98.24%.干扰离子影响MB降解次序为CO 32- < Cl - < SO 42-,磁性光催化剂重复使用7次MB光降解率仅下降7.07%,新型磁性光催化剂具有良好的MB降解性能和较高的重复使用性能. 相似文献
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