铜锆复合氧化物的结构对其催化选 择还原－氧化氮性 能的影响

用浸渍法和共沉淀法分别制得CuO---ZrO~2复合氧化具物有不同的选择还原NO~x的催化性能,采用XRD,BET,EXAFS和H~2---TPR等手段对样品进行了表征,发现浸渍法制备的样品具有的比表面较大,氧化锆被稳定在四方相。EXAFS实验表明,浸渍法制得样品的铜离子填入氧化锆表面空穴中,并以Cu^2+形式存在;500℃焙条件下用共沉淀法引入的铜离子可部分取代锆离子,在氧化锆体相高度分散形成均匀的无定形固溶体,铜离子在氧化锆体相的高度分散是形成表面弧立铜物种的关键。溶入氧化锆体相的铜离子在取代部位由于局部负电荷而使氧化性降低,是共沉淀法制备样品具有较高催化活性的主要原因。     

不同方法制备的CeO2-ZrO2体系结构研究

采用不同方法制备了几种CeO2-ZrO2二元氧化物体系,并用XRD、BET、XPS等技术研究了各个体系中氧化铈与氧化锆的存在状态.结果表明以773K焙烧过的氧化锆为载体,浸渍Ce(NO3)3溶液制得的CeO2/ZrO2体系中,氧化铈单层分散于氧化锆的表面,分散阈值约为0.03gCeO2/gZrO2.以水合氧化锆为载体,浸渍Ce(NO3)3溶液制得CeO2-ZrO2固溶体,但用此法制备的固溶体样品与用共沉淀法制备的样品不同.共沉淀法得到的是均一固溶体,浸渍法得到的是富锆固溶体和富铈固溶体的混合物;而且浸渍法制备的样品表面Ce/Zr原子比高,热稳定性好.     

铁的添加方式对Cu-Mn/ZrO2合成低碳醇催化剂的影响

采用浸渍和共沉淀两种方法制备了Fe/Cu/Mn/ZrO2催化剂,考察了Fe的添加方式对催化剂反应性能的影响,发现添加方式的不同使催化剂的整体性能有较大的改变,在温和条件下,浸渍法制备的催化剂醇的时空收率可达0.26g/mL*h,其中C2+OH的选择性约为22%,产物以直链醇为主,催化剂的活性和选择性均高于同等Fe浓度的共沉淀催化剂.用EXAFS研究了催化剂的表面状况,发现浸渍法制备催化剂促进了Cu的高度分散,从而提高了催化剂的催化性能.     

MoO3-SnO2相互作用的研究

用沉淀法、浸渍法和机械混合物焙烧法制备了三组MoO_3-SnO_2催化剂。XDR, IR和ESR等研究表明: MoO_3-SnO_2之间存在明显的相互作用, 两组份间发生电子迁移现象, 导致Mo(Ⅵ)→Mo(Ⅴ)的价态变化, 产生pKa≤+3.3的表面酸位和甲醇选择氧化活性位。制备方法对这种相互作用以及样品的催化性能有明显影响。沉淀法所得样品中MoO_3可溶于SnO_2形成固溶体; 浸渍法则可发生钼离子向SnO_2体相的扩散; 机械混合物焙烧法在一定MoO_3含量下, MoO_3可在SnO_2表面形成近似单层分散。红外光谱中950 cm~(-1)的新吸收谱带可归因于表面上Mo(Ⅴ)=0振动。表面Mo(Ⅴ)位可能是催化剂表面酸位和甲醇氧化的活性中心。没有发现催化剂中Sn~(4+)价态有明显变化。     

MoO_3-SnO_2相互作用的研究

用沉淀法、浸渍法和机械混合物焙烧法制备了三组MoO_3-SnO_2催化剂。XDR,IR和ESR等研究表明:MoO_3-SnO_2之间存在明显的相互作用,两组份间发生电子迁移现象,导致Mo(Ⅵ)→Mo(Ⅴ)的价态变化,产生pKa≤+3.3的表面酸位和甲醇选择氧化活性位。制备方法对这种相互作用以及样品的催化性能有明显影响。沉淀法所得样品中MoO_3可溶于SnO_2形成固溶体;浸渍法则可发生钼离子向SnO_2体相的扩散;机械混合物焙烧法在一定MoO_3含量下,MoO_3可在SnO_2表面形成近似单层分散。红外光谱中950cm~(-1)的新吸收谱带可归因于表面上Mo(Ⅴ)=0振动。表面Mo(Ⅴ)位可能是催化剂表面酸位和甲醇氧化的活性中心。没有发现催化剂中Sn~(4+)价态有明显变化。     

MgO-ZrO_2共沉淀体系的结构表征及单层分散现象

用共沉淀法制备了一系列MgO-ZrO2复合氧化物,用XRD、XPS、BET、DTA、EXAFS和TEM等进行了表征.结果表明,500℃与600℃下焙烧得到的MgO-ZrO2复合氧化物,在ZrO2高含量一端,MgO倾向于固溶到ZrO2中,最大固溶量可达到1:1(摩尔比);固溶达到饱和后,MgO开始在固溶体表面分散,并析出单独的MgO晶粒;在MgO高含量端,少量的ZrO2以分散态存在于MgO的表面,并使其表面性质发生较明显的变化.这些结果表明,在共沉淀法制备的MgO-ZrO2样品中,在一定相对含量范围内,会出现一种组分在另一种组分或由两种组分形成的固溶体上的单层分散现象.     

Mo/ZSM-5催化剂体系上NO的选择性催化还原研究

 首先用浸渍法在HZSM－5上负载了不同的金属元素（Mo，Sn和Ni），并比较了它们在含氧条件下对NO分解反应的影响．结果表明，Mo／ZSM－5的催化活性最高．进一步用离子扩散法、浸渍法、物理混合法及合成法制备了四种Mo／ZSM－5样品，并以NH3为还原剂，考察了它们的NO的选择性催化还原反应性能．结果表明，用离子扩散法制得的样品对NO还原反应的催化活性最高，在360℃下，NO转化率可达98％．同时，用XRD，SEM，ICP和EDS等技术对4种样品的体相和表面结构进行了测试．结果表明，用离子扩散法制得的样品，Mo元素在分子筛催化剂的内表面有很好的分散性，导致Mo／ZSM－5具有高的催化活性．这可能是由于Mo元素迁移到分子筛的孔道内，在催化剂表面形成了有利于NO选择性催化还原反应的某种特殊活性结构．     

CuO/Ce0.5Zr0.5O2的结构特征及催化性能表征

以硝酸铈和硝酸锆为原料,采用共沉淀法制备了不同摩尔比(X=0,0.1,0～1.0)的CexZr1-xO2样品.并以Ce0.5Zr0.5O2为载体,采用浸渍法负载不同含量的CuO,用色谱流动法考察其对CO的氧化活性.并用XRD,TPR和BET等技术对CuO/Ce0.5Zr0.5O2各样品进行了表征,结果表明,当CuO负载量为10.0%时,催化剂CO的氧化活性最高;XRD测定表明催化剂氧化活性的高低与铜物种在Ce0.5Zr0.5O2上的分散状态有关;TPR结果亦显示活性的高低与Ce0.5Zr0.5O2上分散较好的铜物种的α还原峰及分散较差的γ还原峰的峰温及形状有关.     

制备方法对Cu-SiO_2催化剂结构及其生物基木糖醇选择氢解性能的影响

生物质基高碳多元糖醇选择氢解制备高附加值的C2、C3小分子多元醇具有重要的科学意义和应用前景.采用常规浸渍法(IM)、沉淀凝胶法(PG)、尿素水解沉积沉淀法(UHDP)、蒸氨沉积沉淀法(AEDP)和异相沉积沉淀法(HTDP)等5种不同方法制备了纳米Cu-Si O2催化剂,通过XRD、XPS、H2-TPR、BET和N2O化学吸附等不同方法对催化剂结构进行了表征,以Ca(OH)2为助剂考察了催化剂在生物基木糖醇选择氢解制备乙二醇和1,2-丙二醇反应中的催化性能.结果显示:制备方法不同Cu-Si O2催化剂的表面和体相组成不同,IM催化剂焙烧样品表面主要以Cu O存在,AEDP和HTDP焙烧样品的表面主要是页硅酸铜,而PG和UHDP焙烧样品的表面Cu O和页硅酸铜共存;IM和UHDP焙烧样品的体相以团聚的大颗粒Cu O为主,PG和HTDP样品以高分散Cu O为主,AEDP样品体相以高分散无定形页硅酸铜存在.受样品中物相组成的影响,不同方法所制备催化剂的分散度按AEDPPGHTDPUHDPIM顺序递减,经H2还原活化后,催化剂中Cu0颗粒尺寸按相反顺序递增.催化剂的木糖醇氢解反应活性和二元醇目标产物选择性受制备方法影响十分明显,均按AEDP、PG、HTDP、UHDP和IM的顺序先增高后降低,以UHDP法制备的Cu颗粒尺寸在12 nm左右的催化剂表现最佳,主要原因是该反应为结构敏感型反应,活性和选择性依赖于Cu颗粒尺寸.     

铁系催化剂上乙苯与CO2氧化脱氢反应

采用浸渍法和溶胶-凝胶法制备了三种含Mg,Fe和Al量相同的Fe2O3-MgO/γ-Al2O3,Fe2O3/MgAl2O4和MgFe0.1Al1.9O4催化剂,在580°C考察了它们催化乙苯与CO2氧化脱氢反应性能,并采用X射线衍射,表面元素分析,H2-程序升温还原和CO2-程序升温脱附等技术对催化剂体相及表面性质进行了表征.结果表明,催化剂制备方法影响Fe物种的存在形态,进而影响催化剂的稳定性和活性.采用浸渍法制备的Fe2O3/MgAl2O4催化剂含有高度分散的Fe2O3活性物种,该物种具有较好的初活性,但是稳定性较差;而采用溶胶-凝胶法制备的MgFe0.1Al1.9O4催化剂中,Fe物种主要以同晶取代的形式存在于尖晶石骨架中,因而具有较高的乙苯与CO2氧化脱氢催化活性和稳定性.     

La2-xSrxCuO4-λ复合氧化物的合成、表征和氨的氧化催化性能的研究

合成了x值不同的La2-xSrxCuO4-λ(x=0~1)系列复合氧化物, 用XRD研究了这一系列氧化物的结构, 结果表明x在0~0.3之间可形成K2NiF4结构单相化合物。用化学分析方法测定了过渡金属Cu的价态及含量, 并计算出复合氧化物中的非计量氧数。用TPD, TPR, TG, XPS, SEM等方法研究了这类复合氧化物的氧化还原性能, 所含氧种及表面形态, 考察了对NH3氧化的催化活性, 并对其催化活性与化学组成及结构的关系进行了讨论。     

溶胶-凝胶和浸渍法制备的铜催化剂在仲丁醇脱氢反应中的研究

采用溶胶-凝胶和浸渍法制备Cu/SiO2催化剂, 研究了不同制备方法对催化剂表面Cu物种的存在状态和其催化性能的影响. 采用BET, XRD, EPR和TPR等手段对催化剂进行了表征, 结果表明, 溶胶-凝胶法可制备高分散铜催化剂, 该催化剂中存在孤立的不可还原的Cu2+和可还原的Cu2+簇两种物种. 浸渍法制备的催化剂中含有可还原的Cu2+簇物种. 反应活性测试结果表明, 不可还原的孤立Cu2+呈高分散状态, 但其对仲丁醇脱氢反应没有活性; 可还原的Cu2+在反应过程中被还原成Cu0, Cu0是反应稳定脱氢的活性中心.     

费-托合成Co/ZrO2-Al2O3催化剂反应性能的研究

以ZrOCl2·6H2O和AlCl3为原料,采用共沉淀方法制得一系列不同ZrO2质量分数的ZrO2-Al2O3混合氧化物载体;并以该混合氧化物为载体,采用初湿浸渍法制得钴质量分数为12％的Co/ZrO2-Al2O3催化剂。XRD、NH3-TPD、TPR和原位IR等表征结果表明,随着混合载体中ZrO2质量分数的增加,载体比表面积先增加后减少,混合载体的平均孔径则小于单一氧化物ZrO2和Al2O3的平均孔径。ZrO2和Al2O3载体混合后会导致氧化物的比表面积和酸性增大并且有新的物相生成。当混合氧化物用作载体时,能够抑制载体表面金属钴的分散,改变催化剂的还原行为,降低催化剂对CO物种的吸附能力。CO加氢反应表明,与单一金属氧化物相比,钴负载ZrO2-Al2O3混合氧化物催化剂的加氢活性和重质烃选择性有所降低。     

铁锰复合氧化物的氧化还原沉淀法制备及其表征

分别采用氧化还原沉淀法和常规共沉淀法制备得到铁锰复合氧化物, 并对样品进行了 Ｘ射线衍射、 Ｂ Ｅ Ｔ比表面积、程序升温还原的初步表征和比较． 结果表明, 与常规共沉淀法制备的样品相比较, 采用氧化还原沉淀法制备的铁锰复合氧化物具有粒径较小、较大的比表面积、铁锰互溶性好、铁锰物种之间的相互作用较强等特点． 作为一种较为新颖的催化剂制备方法, 氧化还原沉淀法利用在高低价可变金属离子之间发生氧化还原反应的同时使之沉淀, 不利于各相单独形成微晶, 有利于不同金属离子的均匀混合． 此种方法对制备高比表面积、含变价过渡金属离子的各类复合氧化物催化剂有其独到之处．     

Comparative Study of the Acidity of Sulphated Zirconia Supported on Alumina Prepared by Sol-Gel and Impregnation Methods

Sulphated and unsulphated alumina-zirconia with atomic ratio Zr/Al = 0.5 were prepared by sol-gel and impregnation methods. The solid prepared by the sol-gel method exhibits the higher specific surface area. The Kelvin probe shows that the value of unsulphated sample is around 400 mV. This value grows up to 1100 mV for sample prepared by impregnation of aerogel alumina by sulphated propoxide zirconium and up to 1450 mV for sulphated alumina-zirconia aerogel catalyst. The modification of the work function is probably due to the charge transfer from the zirconium and aluminium to an oxygen species, responsible for the increase of Lewis acidity. XPS results show that the aluminium and zirconium exist in oxide form as Al₂O₃ and ZrO₂. The sulphur is present as sulphate species in the solids bonded to the Al—Zr—O framework. Furthermore, the oxygen species exist in different types created by the introduction of sulphur in the bulk of solids.Compared to the impregnated catalyst the sol-gel sulphated alumina zirconia exhibits higher activity in the isopropanol dehydration reaction in the temperature range 423 K–523 K.     

Simultaneous removal of ethanol, acetaldehyde and nitrogen oxides over V-Pd/γ-Al_2O_3-TiO_2 catalyst

V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction (XRD), N2 adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS) and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature (<300 ?C) were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ?C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V4+ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4+ and Pd2+ species on the surface, which might be favorable for the formation of active sites.     

Effect of Temperature on Cd2+ Sorption by Mixed Oxides of Iron and Silicon

The current study focuses on the synthesis and sorption properties of two mixed oxides of iron and silicon prepared by physical mixing (M₁) and sequential precipitation methods (M₂). Both the mixed oxides were synthesized from equimolar ratios of Fe(OH)₃ and SiO₂ and characterized for surface area, EDX, XRD and PZC. The surface area, micropore volume and average pore width of the oxide M₁ were higher as compared to the oxide M₂. However, potentiometric titrations revealed that mixed oxide synthesized by this method had a very high capacity towards Cd²⁺ ions as compared to the mixed oxide M₁. Sorption of Cd²⁺ ions at pH 5 on mixed oxide, M₂ was found to increase with temperature in the range 288 to 318 K. Langmuir equation was found applicable to the sorption data with R²>0.99. Entropy (ΔS^?), enthalpy (ΔH^?) and free energy changes (ΔG^?) were calculated which revealed the process to be endothermic and spontaneous in nature.     

Investigation of the Cu-Zr-Y oxides activity in the carbon black catalytic oxidation by differential thermal analysis and temperature programmed reduction

Different copper/zirconium-yttrium catalysts have been tested in carbon black oxidation reaction. Supported mainly on differential thermal analysis and temperature programmed reduction, two different mechanisms have been proposed to explain the catalytic results. In the absence of copper, it has been shown that Zr³⁺ ions and associated anionic vacancies are responsible to the catalytic enhancement observed in the mixed oxides, oxygen species being activated on these sites. Among mixed zirconia-yttria solids, ZrO₂-5 mol%Y₂O₃ is the most active catalyst. Copper impregnation on these oxides leads to the formation of different copper species. Small particles of CuO in low interaction with the support, induce a catalytic improvement due to the highest reducibility of these species. Moreover, in order to be more efficient, CuO species should have some interactions with the support, since impregnated samples are more active than the simple mechanical mixtures.     

CeO2掺杂的Mn/Al催化剂的物化、表面及催化性能

Pure and CeO2-doped Mn/Al mixed oxides were prepared by the wet impregnation method using finely powdered alumina, manganese, and cerium nitrates. The physicochemical, surface, and catalytic properties of the thermally treated solids (at 500, 800, and 900 ℃) were investigated using XRD, nitrogen adsorption at -196 ℃, and hydrogen peroxide decomposition in an aqueous solution at 30 - 50 ℃. The Mn oxidation state changed from Mn4 to Mn2 on increasing the calcination temperature. There were two unique features associated with CeO2 that are of interest. The first was that it favored the dispersion of manganese oxides deposited on the γ-Al2O3 catalyst calcined at 500 ℃. The second was that it enhanced the formation of Mn3O4 species from Mn2O3 deposited initially on the alumina support calcined at 800 and 900 ℃. Consequently, the specific surface area of the Mn/Al mixed oxides calcined at 500 ℃ was increased by increasing the amount of dopant added. An opposite effect was observed by increasing the calcination temperature from 500 to 900 ℃. The doping followed by calcination at different temperatures brought about an increase in the catalytic activity of mixed oxides. Pretreatments did not modify the mechanism of the catalyzed reaction but changed the number of catalytically active sites without changing the nature of these sites.     

Biphasic epoxidation of 1-octene with H2O2 catalyzed by amphiphilic fluorinated Ti-loaded zirconia

A series of amphiphilic fluorinated zirconia containing titanium was prepared by titanium impregnation followed by fluorination and alkylsilylation of zirconium oxide. Physical properties of the resulting samples were characterized by XRD analysis, UV-vis spectroscopy, BET surface area analysis and EDAX analysis. The effects of fluorine and alkylsilane groups on the samples were studied by the epoxidation of 1-octene with aqueous hydrogen peroxide. The epoxidation of alkenes is one of the most important methods of functionalizing simple hydrocarbons. The amphiphilic fluorinated catalysts were more active and more efficient than the conventional titania-silica and zirconia-silica mixed oxides in linear alkene epoxidation; enhanced by the presence of alkylsilane and fluorine groups in the catalysts. Modification with alkylsilane successfully induces the hydrophobic behavior of zirconia which is hydrophilic in nature; whereas fluorine was chosen for its electron-withdrawing effect which further activates the titanium active sites.