Deep Oxidation of Benzene on Pt/V2O5–TiO2 Catalysts

The combustion of benzene was studied on Pt supported on V₂O₅–TiO₂ samples containing different amounts of V₂O₅. Vanadium was highly dispersed as V⁴⁺ for low V₂O₅ loadings, forming a vanadia monolayer on titanium dioxide for a V₂O₅ concentration of about 5%wt. V₂O₅–TiO₂ samples were more active than V₂O₅ and TiO₂ single oxides, and the activity increased with the vanadia content. The platinum dispersion in Pt/V₂O₅–TiO₂ catalysts increased with the V₂O₅ loading but the activity for the deep oxidation of benzene exhibited an opposite trend. Benzene combustion was a structure sensitivity reaction promoted on larger metallic Pt crystallites which were preferentially formed when the V₂O₅ content in the sample was decreased.     

V2O5负载量对V2O5／TiO2催化剂SCR法脱硝的影响

以TiO2载体,采用浸渍法制备了不同V2O5负载量的用于选择性催化还原NOx的V2O5／TiO2催化剂。利用BET,SEM和Ⅺ①,对不同V2O5负载量的催化剂组成、结构、形貌和性能进行了表征,考察不同V2O5负载量对催化剂制备的影响。结果表明制备的催化剂具有较多的中孔和微孔,催化剂中V2O5含量的增加,会降低催化剂的表面积;V2O5含量为2％的V2O5／TiO2催化剂样品比表面积最大,但是其活性非常低;V2O5含量为4％催化剂比表面积较大,NOx脱转化率高;V2O5的负载量小时,V2O5主要以等轴聚合的钒基型式（V3O7和V6O13）存在,这些钒基是催化剂的活性中心;当负载量超过6％,V2O5主要以结晶相存在,占据大量活性位,降低催化效果。     

Effect of V2O5 Loading on Propane Combustion over Pt/V2O5–Al2O3 Catalysts

Propane combustion was studied on Pt(0.4%)/V₂O₅–Al₂O₃ catalysts containing up to 20% V₂O₅. The density, strength and nature of surface acid sites were determined by TPD of NH₃ and FTIR spectra of adsorbed pyridine. The sample acidity increased with the vanadium content, essentially because the addition of vanadium oxide generated Brønsted acid sites. The Pt dispersion as determined by H₂ chemisorption increased with increasing V₂O₅ loading. The sample activity for propane combustion was evaluated through both conversion versus temperature (light-off curves) and kinetically-controlled conversion versus time catalytic tests. The propane combustion turnover rate on Pt/V₂O₅–Al₂O₃ increased with the amount of vanadium, probably because the intrinsic Pt oxidation activity increases with the sample acidity.     

MgO修饰的V2O5-MoO3/TiO2低温SCR催化剂

V系催化剂具有良好的抗中毒能力,广泛应用于燃煤电厂、工业锅炉烟气(固定源)和车辆尾气(移动源)脱硝领域.本文采用水热法制备了V2O5-MoO3/TiO2催化剂,并通过挤出成型得到蜂窝式V2O5-MoO3/TiO2催化剂,通过与共混法相比,发现采用水热法表现出来的较高的低温SCR活性,并研究了MgO的掺杂对V2O5-MoO3/TiO2催化剂性能的影响,发现MgO的掺杂能够降低SO2的转化率.并通过表征发现采用水热反应法得到的V2O5-MoO3/TiO2催化剂能使活性组分高度分散于TiO2载体表面上,具有较高的比表面积,从而使催化剂表现出最佳的低温活性,同时MgO修饰的V2O5-MoO3/TiO2催化剂的抗硫抗水性以及抗碱金属中毒性也做出了研究.     

Oxidative Dehydrogenation of Ethylbenzene to Styrene with CO2 Over V2O5–Sb2O5–CeO2/TiO2–ZrO2 Catalysts

Utilization of CO₂ as a soft oxidant in the oxidative dehydrogenation of ethylbenzene to styrene, a remarkable V₂O₅–Sb₂O₅–CeO₂/TiO₂–ZrO₂ catalyst has been accomplished. Preparation of TiO₂–ZrO₂ support by co-precipitation followed by a single step deposition of V and Ce and Sb as stabilizers yielded a highly active and selective catalyst. Acid–base and redox properties including sustained stability of active species (V⁵⁺) are responsible for high activity of V₂O₅–Sb₂O₅–CeO₂/TiO₂–ZrO₂ catalyst. The redox cycle is related to the dispersed V⁵⁺ and lattice reduced vanadium site in the VSbO₄ phase. The antimony oxide inhibits the easy redox cycle between different vanadia species.     

Characterization and catalytic properties of MoO3–V2O5/Nb2O5 catalysts

The influence of molybdenum oxide on the dispersion of vanadium oxide supported on niobia was investigated. A series of MoO₃–V₂O₅/Nb₂O₅ catalysts with varying MoO₃ content ranging from 1% to 5% (w/w) with fixed V₂O₅ content were prepared by impregnation of previously prepared 5 wt% V₂O₅/Nb₂O₅ with requisite amounts of ammonium molybdate solution. X-ray diffraction patterns indicate the presence of β-(Nb,V)₂O₅ phase with the addition of MoO₃ up to a loading of 3 wt%. Temperature-programmed reduction (TPR) results suggest that the reducibility is decreasing with MoO₃ loading. The results of temperature programmed desorption (TPD) of ammonia suggest that the acidity of the catalysts increased with the addition of MoO₃. The catalytic properties of the catalysts in the ammoxidation of 3-picoline were correlated with the characterization data.     

V2O5-WO3/TiO2-SiO2制备及其选择性催化还原脱硝活性

以硫酸氧钛和硅溶胶为原料,通过共沉淀法制备得到高比表面积的TiO2-SiO2复合氧化物(Ti/Si=1:1atom),并以此复合氧化物为载体用浸渍法制备了V2O5-WO3/TiO2-SiO2脱硝催化剂,考察了催化剂脱硝性能。结果表明,TiO2-SiO2复合氧化物载体出现较多的隧道孔,提高了载体的比表面积,同时Ti元素更易分布在复合氧化物的表面。相比较于纯TiO2,以复合氧化物为载体的V2O5-WO3催化剂表现出更好的活性温度窗口,催化剂表面酸性更强,催化剂对NH3的吸附性能更好,在低的NH3/NO摩尔比情况下(0.8～1.0mol?mol?1),仍然具有较好的脱硝活性,反应温度280～350℃时,脱硝率可达到98%。     

溶胶-凝胶原位合成宽活性温度V2O5/TiO2脱硝催化剂

利用溶胶-凝胶技术原位合成一系列不同V₂O₅担载量的V₂O₅/TiO₂催化剂,通过BET、XRD、NH₃-TPD及紫外-可见光等手段对催化剂进行表征。结果表明：制备的催化剂均具有介孔结构,V₂O₅在TiO₂表面高度分散,且存在3种典型的酸性位。通过选择性催化还原反应对V₂O₅/TiO₂催化剂进行活性评价,结果显示随着V₂O₅含量的增加,NO转化率大于75%的温度窗口向低温方向偏移,含10% （质量分数）V₂O₅的催化剂的NO转化率为80%的温度窗口最宽为200～450℃,240℃时20 h连续实验表现出稳定的抗硫抗水性能。结合紫外-可见光谱分析,揭示了钒掺杂所形成的单聚和低聚钒酸盐为催化剂的活性组分。     

失活V2O5-WO3/TiO2 SCR脱硝催化剂的再生方法

针对模拟钙中毒的商业V_2O_5-WO_3/TiO_2选择性催化还原(SCR)脱硝催化剂,选用络合剂乙二胺四乙酸(EDTA)、表面活性剂十二烷基苯磺酸(LAS)两种清洗剂配合超声波震荡方法对其进行清洗再生,并结合活性测试以及多种表征手段,研究清洗剂浓度及组配方式和清洗时间对钙中毒催化剂的活性恢复及物化性能变化的影响。结果表明:0.01 mol/L的EDTA水溶液辅助超声波震荡清洗30 min取得较好的再生效果,清洗再生后的催化剂脱硝活性在400℃达到85%以上,恢复到新鲜催化剂活性的近90%,并且CaSO_4的去除率达到92%以上,钒和钨的残余率分别为99.4%和98.3%。此外,增加少量的LAS可以微弱地提升CaSO_4的去除率和催化剂的脱硝活性。清洗再生机理研究表明,EDTA可以较好地恢复催化剂的微孔结构、去除表面条带状硫酸钙涂覆层、恢复催化剂表面Lewis酸位以及1 680 cm~(-1)处的Br?nsted酸位。EDTA和LAS均可以有效提高催化剂的氧化还原能力。     

Radiation attenuation properties of Bi2O3–Na2O– V2O5– TiO2–TeO2 glass system using Phy-X / PSD software

The purpose of this work is to investigate the effect of increasing Bi₂O₃ mol% on the radiation shielding parameters of tellurite glass system with the formula Bi₂O₃–Na₂O– V₂O₅– TiO₂–TeO₂ by using Phy-X/PSD computer software between 15 keV and 10 MeV. The results showed that the attenuation factor is very large at 15 keV. The mass attenuation coefficient (μ/ρ) at 15 keV lies within the range of 55.96–67.03 cm²/g for the selected samples. The μ/ρ for the investigated samples at 10 MeV is in the range of 0.0365–0.0392 cm²/g. The results also revealed that the addition of Bi₂O₃ enhances the effective atomic number (Z_eff) and the sample corresponding to the lowest and highest amount of Bi₂O₃ (coded as TeBTi1 and TeBTi6) has the lowest and highest Z_eff. Moreover, Z_eff has high values between 15 keV and 0.1 MeV and the maximum Z_eff occurs at 0.1 MeV (equal to 61.01, 62.67, 64.10, 65.34, 66.44 and 67.41 for TeBTi1– TeBTi6 samples respectively). The half value layer (HVL) increased when the energy changes from 15 keV to 10 MeV and the lowest HVL occurs at 15 keV for the sample coded as TeBTi6 and equal to 0.0025 cm, while the HVL at this energy for TeBTi1 is 0.0056 cm. Also, we calculated the tenth value layer (TVL) for the present system and we found that TVL reduces with the increment of Bi₂O₃ content, and the sample corresponding to 22 and 0 mol% of Bi₂O₃ and TiO₂ respectively namely TeBTi6 possesses the lowest value of TVL, thus has the best radiation attenuation performance in comparison to other selected glasses. Also, we evaluated the effective removal cross-sections of fast neutrons (∑_R) for the investigated glass system and we found that the ∑_R values increase with increase the concentration of Bi₂O₃.     

Fe2O3对V2O5-WO3/TiO2催化剂表面性质及其性能的影响

催化剂是选择性催化还原(SCR)脱硝技术的核心,研究Fe对钒钛系SCR催化剂脱硝活性及SO₂/SO₃转化率的影响具有重要意义。采用等体积浸渍法制备了不同Fe/V质量比的Fe₂O₃-V₂O₅-WO₃/TiO₂催化剂,并进行表征,研究Fe对钒钛系SCR催化剂脱硝活性及SO₂/SO₃转化率的影响,并讨论Fe对于钒钛系SCR催化剂表面性质的影响。结果表明,随着催化剂表面Fe₂O₃含量增加,催化剂的脱硝效率及二氧化硫氧化率均是先上升后下降,当Fe/V质量比为3.0时,催化剂的脱硝效率和二氧化硫氧化率均达到最大值91.78%、1.01%。XPS及H₂-TPR结果表明,随着Fe₂O₃含量增加,催化剂表面钒活性组分的相对含量及V⁴⁺/V⁵⁺比减小,催化剂表面吸附氧(O_α)浓度增加,催化剂的氧化能力增强。NO-TPD结果表明,随着Fe₂O₃含量增加,催化剂表面吸附NO的能力增强。     

Soft chemistry preparation of layered Al0.3V2O5·5H2O

A novel layered compound Al_0.3V₂O₅·5H₂O was successfully prepared and characterized using powder X-ray diffraction, Thermal analysis, scanning and transmission electron microscopes. The new layered Al_0.3V₂O₅·5H₂O has like-nanowires shape and the layered structure was stable until 400 °C. At higher temperature (500 °C), it decomposes to orthorhombic Al_xV₂O₅ and triclinic AlVO₄.     

V2O5/（TiO2-SiO2）脱硝催化剂新型制备工艺及性能研究

将偏钒酸铵和羟丙基甲基纤维素搅拌混溶制备滴胶液,以自制的7孔圆柱蜂窝钛硅复合氧化物为载体,采用滴胶涂覆法制备了V₂O₅/（TiO₂-SiO₂）脱硝催化剂。通过X射线衍射（XRD）、程序升温还原（H₂-TPR）、比表面积分析（BET）和催化剂评价等方法对制备的脱硝催化剂进行分析表征。考察了五氧化二钒在钛硅复合氧化物载体上的分布、五氧化二钒涂覆量等对催化剂性能的影响,并就反应温度、反应空速、氨与一氧化氮物质的量比等条件对脱硝催化剂活性的影响进行了研究。实验结果表明,使用五氧化二钒涂覆量为1.2%（质量分数）的V₂O₅/（TiO₂-SiO₂）脱硝催化剂,在反应温度为320 ℃、空速为10 000 h^-1、氨与一氧化氮物质的量比为1.2条件下进行脱硝活性实验,一氧化氮转化率达到93.0%。经与工业脱硝催化剂对比实验表明,制备的V₂O₅/（TiO₂-SiO₂）脱硝催化剂性能优良,并且降低了钒的使用量,节约了生产成本,减少了环境污染。     

钒酸盐助剂对V2O5/TiO2系SCR再生脱硝催化剂性能的影响

以废旧商业锐钛矿型Ti O2为载体,通过浸渍法制备了4种通过钒酸盐助剂(无水草酸、柠檬酸、氨水、水)再生的V2O5/Ti O2催化剂,并考察不同钒酸盐助剂对4种再生脱硝催化剂的影响。分别对催化剂样品进行XRF、比表面积、孔容、孔径、脱硝效率表征。研究发现,不同的钒酸盐助剂对再生催化剂成品的比表面积、孔容、孔径等影响很小,但对成品的XRF和脱硝效率的影响较为明显,且柠檬酸对于V2O5/Ti O2系SCR催化剂的再生具有更大的优势。     

Ag掺杂V2O5/TiO2催化氧化3-甲基吡啶 脱甲基效应

浸渍法制备了不同Ag掺杂的Ag-V/TiO2催化剂,考察其催化部分氧化3-甲基吡啶脱甲基性能。采用X射线衍射（XRD）,X射线光电子能谱（XPS）,H2程序升温还原（H2-TPR）对催化剂进行了表征。表征表明,Ag的掺杂提高催化剂中表面氧和 4价态的钒物种的含量,有效的加快了催化剂的还原过程,提高了氧化活性。3-甲基吡啶氧化反应表明,Ag掺杂使反应选择性发生根本性变化,主产物由烟酸变成吡啶,选择性84.7%,烟酸几乎不产生。该脱甲基氧化反应的过程是V4 /V5 （O2-）在攻击侧链的C-H键的同时Ag在O2的作用下形成了含有亲电子型氧（O-和O2-）的Agp O活性物种,攻击侧链和苯环相连的C-C键,Ag和V共同作用将侧链的甲基以氧化形成COx的形式脱除。     

水泥窑烟气脱硝催化剂V2O5/TiO2中杂质元素的发射光谱研究

建立了水泥窑烟气脱硝催化剂V2O5/TiO2中杂质元素的分析方法.选择硝酸+氢氟酸为混合消解溶剂,V2O5/TiO2经微波消解后采用电感耦合等离子体发射光谱(ICP-OES)法直接测定其中杂质元素(Na、K、Ca、Mg、As、Zn、Pb).通过对仪器工作参数和待测元素分析谱线的选择,确定了仪器的最优工作条件,详细地研究了基体元素Ti产生的基体效应以及共存元素对待测元素的光谱干扰,利用同步背景扣除技术消除光谱干扰,以In为内标元素并结合基体匹配法消除基体效应.7个元素的检出限为1.72～ 41.60 μg/L,回收率为93.82％ ～ 105.58％,相对标准偏差(RSD)为0.87％～3.43％ (n=11).方法可用于V2O5/TiO2中杂质元素的检测,为水泥窑烟气脱硝催化剂的质量评价提供了新的技术手段.     

V2O5-WO3/TiO2脱硝催化剂机械强度和孔隙率的响应曲面模型

氨气选择性催化还原技术(NH₃-SCR)是目前燃煤电厂消除氮氧化物(NO_x)最有效、最成熟的方法之一,其中催化剂作为技术体系的核心,其成型技术逐渐成为研究热点。本文针对V₂O₅-WO₃/TiO₂蜂窝式脱硝催化剂的成型工艺,通过响应曲面法对其机械强度和孔隙率进行研究,分别得出压制压力和聚甲基丙烯酸甲酯(PMMA)微球添加量对机械强度和孔隙率的显著回归模型。发现一定的压制压力和PMMA微球的添加可以使得压制而成的蜂窝式脱硝催化剂既能保持较高的机械强度,又能维持高的孔隙率。孔径分布及扫描电子显微镜(SEM)结果表明催化剂壁上存在明显的纳米-微米多级孔。活性测试结果显示:催化剂表现出了优良的NO_x转化率及N₂选择性,满足了目前工业脱硝领域的需求。