Mo对平板式V-Mo/Ti脱硝催化剂活性及SO2氧化性能的影响

在工业脱硝催化剂生产线上制备不同MoO₃含量的V-Mo/Ti脱硝催化剂，通过XRF、XRD、N₂吸附-脱附、Raman、H₂-TPR、NH₃-TPD、SO₂-TPD、TG和耐磨强度对催化剂物化性质进行分析。在固定床反应器中考察催化剂的脱硝活性，并研究MoO₃含量对催化剂SO₂氧化性能的影响。结果表明，提高催化剂中MoO₃含量，对催化剂的晶型、孔结构影响较小，对催化剂单板的机械性能有一定的负面影响。相比V-Mo(3)/Ti催化剂，V-Mo(5)/Ti催化剂的酸性变化不大，还原性能提升，具有更好的脱硝活性。当MoO₃含量达到质量分数6.98%时，催化剂的总酸量明显降低，导致脱硝活性下降。提高催化剂中MoO₃含量造成脱硝反应过程中副产物N₂O生成量的增加，但较高的MoO₃含量可以有效减少催化剂对SO₂的吸附，减...     

Cr2O3/TiO2催化剂上铵盐选择性催化还原脱硝研究

因低温NH₃-SCR脱硝面临耐硫性能差、硫酸氢铵中毒等难以克服的问题,构建了采用无机铵盐选择性催化还原脱硝的方法。采用浸渍法制备了Cr₂O₃/TiO₂催化剂,选用草酸铵、硫酸氢铵、磷酸氢二铵、磷酸二氢铵作为还原剂,对氮氧化物进行选择性催化还原反应,并测定了4种铵盐作还原剂的脱硝活性。利用XRD、XPS和原位漫反射红外光谱等表征探究了4种铵盐对催化剂物化性质的影响,并研究了4种铵盐在Cr₂O₃/TiO₂催化剂上的反应与再生过程。结果表明,4种铵盐中的NH⁺₄都可以在Cr₂O₃/TiO₂催化剂上与NO发生反应,除硫酸氢铵因HSO^-₄易与TiO₂结合为Ti(SO₄)₂而不可再生外,其它铵盐皆可再生。     

V2O5-WO3-MoO3/TiO2催化剂在柴油机NH3-SCR系统中的性能

针对柴油机运行工况特点及柴油机尾气成分特点,以工业纯锐钛型二氧化钛、偏钒酸铵、偏钨酸铵、钼酸铵为主要原料制备了颗粒状V₂O₅-WO₃-MoO₃/TiO₂催化剂,以Lister Petter TR1重型直喷式单缸柴油机为依托搭建试验台,研究了在真实柴油机尾气环境下催化剂的脱硝性能。结果表明,柴油机负载增大,催化剂脱硝活性呈现下降趋势。1800 r·min^-1时,脱硝活性最大值87.1%在负载25%、反应温度380℃、空速20000 h^-1、氨氮比1.0处取得。柴油机负载不同,导致催化剂活性温度窗口(脱硝活性>70%)发生较大变化,与负载25%相比,负载50%活性温度窗口减小约60℃。增大柴油机负载可以提高NH₃/N₂O反应起始温度,但是同时会导致高温区间(>400℃)N₂O生成量增大。     

微波热解制备g-Fe2O3催化剂及其SCR脱硝性能

以FeSO₄·7H₂O[Fe(NO₃)₃·9H₂O]为铁源,采用新型微波热解法制备γ-Fe₂O₃[a-Fe₂O₃]催化剂样品,通过XRD、N₂等温吸附-脱附、压汞法等实验手段对催化剂样品晶相、微观孔结构等进行表征;考察两种催化剂样品的NH₃-SCR脱硝性能,通过归一化处理得到两种催化剂在不同温度下的本征脱硝反应速率,同时对比研究了γ-Fe₂O₃与钒系催化剂的脱硝活性;研究氨氮比、氧浓度等运行参数对γ-Fe₂O₃催化剂NH₃-SCR脱硝性能的影响规律,并对其抗硫抗水性能进行考察.结果表明:采用新型微波热解法可得到纯度较高的γ-Fe₂O₃催化剂,其介孔分布合理且大孔数量丰富;同时γ-Fe₂O₃催化剂表现出优于a-Fe₂O₃催化剂的脱硝性能,400℃时最大NO_x转化率达到96%,300、325、350℃下单位面积脱硝速率达到a-Fe₂O₃催化剂的3倍左右;γ-Fe₂O₃催化剂具备优良的抗硫抗水性能,其最佳氨氮比为1、最佳氧体积分数为3.5%.     

四氢糠醇合成吡啶催化剂的制备及工艺研究

研究了四氢糠醇(THFA)与氨气在固定床反应器中合成吡啶的工艺路线,对催化剂进行了考察。以Al₂O₃为基底,分别制备负载Co₃O₄、Cr₂O₃、MoO₃的单一组分催化剂,筛选出催化性能最好的催化剂MoO₃作为主催化剂,混合不同量的Co₃O₄、Cr₂O₃,制备成各种复合催化剂。确定催化剂Cr₂O₃-MoO₃/Al₂O₃催化效果最佳,对其结构进行了表征,并在固定床反应器上对该催化剂催化四氢糠醇合成吡啶的工艺及稳定性进行了研究。最适宜反应条件下,即500 ℃,氨气流量700 mL/min,四氢糠醇进液量0.15 mL/min及常压条件进行时,四氢糠醇转化率达100%,吡啶收率达85.30%。     

杂多酸改性V-Mo/Ti-W催化剂的宽温SCR脱硝性能

采用等体积浸渍法制备了一系列Keggin型杂多酸改性的V-Mo/Ti-W催化剂,并通过X射线衍射（XRD）、BET比表面分析（BET）、NH₃程序升温脱附（NH₃-TPD）、H₂程序升温还原（H₂-TPR）、X射线光电子能谱（XPS）和傅里叶变换红外光谱（FTIR）等表征方法对催化剂物化性质进行了表征分析。各项表征分析结果表明,杂多酸改性后的HPAs-V-Mo/Ti-W催化剂相比于改性前的催化剂,平均孔径尺寸更大,可抑制硫酸氢铵沉积,以提高催化剂抗硫性能;与V-Mo/Ti-W样品相比,改性后的催化剂具有更强的NH₃吸附能力、更好的还原性能和更多的化学吸附氧物种,从而表现出更优异的脱硝性能和N₂选择性。杂多酸改性后的催化剂在200~380℃温度范围内、150000h^-1高空速、高浓度SO₂和H₂O存在的模拟烟气中表现出高 NH₃-SCR活性、优异的抗SO₂性能,并保持几乎100%的N₂选择性,可作为燃煤电厂深度调峰的宽温催化剂,具备良好的工业应用价值。     

Cr2O3/SiO2催化苯酚与碳酸二乙酯邻位烷基化反应

以Cr(NO₃)₃?9H₂O为前体,采用等体积浸渍法制备了一系列不同Cr₂O₃负载量的Cr₂O₃/SiO₂催化剂;在固定床连续微反装置上,考察了Cr₂O₃/SiO₂催化剂对苯酚与碳酸二乙酯邻位烷基化反应的催化性能;采用XRD、NH₃-TPD、CO₂-TPD和吡啶吸附、红外等手段对催化剂进行了表征。实验结果表明,随着Cr₂O₃负载量的增加,苯酚的转化率和邻乙基苯酚的选择性均逐渐增加;当Cr₂O₃负载量达到7.5%时,苯酚的转化率和邻乙基苯酚的选择性均达到最大值,分别为48%和67%。催化剂的表征结果表明,L酸中心是苯酚邻位烷基化反应的活性中心,苯酚转化率和邻乙基苯酚选择性的变化主要是由催化剂的酸、碱中心数目变化引起的。     

CeO2纳米棒负载Co催化CO脱除NOx的机理

以碱法水热合成径向尺寸6～10 nm的CeO₂纳米棒,采用湿法浸渍在纳米棒上负载不同含量的Co氧化物。通过实验探究Co含量改变对脱硝性能的影响原理,实验结果显示浸渍方案为3 g CeO₂∶30 ml 10%（质量分数） 硝酸钴溶液时,脱硝效率最高,在NO与CO摩尔比为1∶5,体积空速为30000 h^-1,无氧状态下,250℃ 即能达到70%以上的效率。采用氮气吸附、XPS、TEM以及XRD测试不同钴含量催化剂的物化性质,与催化性能结果比对分析后得出Co的添加是通过改变催化剂表面的活性官能团来提高效率,其中Co₂O₃对于催化CO与NO_x进行反应具有较高的效率,提高催化剂中Co₂O₃的比重可以将高效率温度段降低,CoO在一定程度上对CO与NO_x反应具有负面作用,而Co₃O₄对低温阶段N₂O选择性影响较大。     

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。     

钇掺杂三氧化二铁催化剂的脱硝性能研究

为提升三氧化二铁(Fe₂O₃)催化剂的脱硝性能,扩展催化剂的活性温度窗口,采用共沉淀法引入助剂钇(Y)元素对Fe₂O₃催化剂进行改性。通过X射线衍射(XRD)、氮气等温吸-脱附(N₂-BET)、X射线光电子能谱(XPS)、氨气程序升温脱附(NH₃-TPD)、氢气程序升温还原(H₂-TPR)等表征方法对样品进行了表征分析。XRD和N₂-BET结果表明,Y的掺杂使催化剂结构发生变化,比表面积增加、孔径减小。XPS和NH₃-TPD结果证明,Y掺杂Fe₂O₃具有更多的表面吸附氧(O_Ⅰ)、Fe²⁺以及更多的酸量。H₂-TPR结果表明,Y的掺杂使催化剂的氧化还原能力略有下降。测试了不同含量Y掺杂的Fe₂O₃催化剂在150～400℃的脱硝性能,其中Fe<...     

Sulphur poisoning of transition metal oxides used as catalysts for methane combustion

Different bulk metal oxides (NiO, CuO, Mn₂O₃, Cr₂O₃ and Co₃O₄) were prepared and tested for the combustion of methane–air lean mixtures (5000 ppmV of CH₄) in presence of SO₂ (40 ppmV). Methane combustion experiments were carried out at ambient pressure, 425 and 625 °C and a space time of 93.3 g h mol_CH4⁻¹. Catalysts aged (60 h on stream) both in absence and in presence of SO₂, were characterised by nitrogen physisorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed desorption (TPD-MS) and infrared spectroscopy (DRIFTS). It was observed that Cr₂O₃ is not deactivated at the studied conditions, whereas all the other materials present fast deactivation in presence of SO₂. Aged catalysts characterisation reveals that the outstanding behaviour of the Cr₂O₃ catalyst is caused by the absence of formation of surface sulphates. By contrast, Mn₂O₃ and Co₃O₄ are more active than Cr₂O₃ for methane oxidation in absence of sulphur species, but they are strongly deactivated in presence of SO₂.

Finally, the performance of the Cr₂O₃ catalysts was compared to the corresponding to Pd/Al₂O₃ catalyst and to a highly sulphur-tolerant perovskite (La_0.9Ce_0.1CoO₃) for the oxidation of methane in a real industrial emission from a coke oven, containing different inorganic gases (NH₃, N₂, H₂, H₂O, CO, CO₂, SO₂ and H₂S). Cr₂O₃ catalyst shows to be also the most stable catalyst for the treatment of these emissions.     

沉淀方式对沉淀法制备Co_3O_4催化N_2O直接分解性能的影响

以Co(NO_3)_2·6H_2O为钴源,K_2CO_3为沉淀剂,采用沉淀法制备Co_3O_4催化剂,用于催化N_2O直接分解反应。利用N_2~-物理吸附、XRD、FT-IR、TEM、TPR和ICP等对其进行表征,考察沉淀方式对Co_3O_4催化剂结构及其催化性能的影响。结果表明,沉淀方式对制备的Co_3O_4催化剂织构性质、物相组成和晶粒尺寸等影响不大,但显著影响其K残留量和还原性能,进而决定催化剂直接催化分解N_2O的催化性能。反加法制得的催化剂中K残留量为1.43%,明显高于正加法,同时催化剂中Co~(3+)较正加法更易还原,因而表现出更高的催化性能。在空速10 000 h~(-1)和N_2O体积分数0.1%的条件下,反加法制备的催化剂可在280℃催化N_2O完全分解,较正加法低20℃。     

Promoting effects of CO2 on dehydrogenation of propane over a SiO2-supported Cr2O3 catalyst

The effects of carbon dioxide on the dehydrogenation of C₃H₈ to produce C₃H₆ were investigated over several Cr₂O₃ catalysts supported on Al₂O₃, active carbon and SiO₂. Carbon dioxide exerted promoting effects only on SiO₂-supported Cr₂O₃ catalysts. The promoting effects of carbon dioxide over a Cr₂O₃/SiO₂ catalyst were to enhance the yield of C₃H₆ and to suppress the catalyst deactivation.     

Niobium oxide as support material for the oxidative dehydrogenation of propane

The ability of using niobium oxide (Nb₂O₅) as a support for preparing surface metal oxide species and testing the catalyst for the ODH of propane was done in the present study. Chromium oxide was used as the representative surface metal oxide species. To test the objective several loadings of Cr₂O₃/Nb₂O₅ were prepared by the incipient wetness impregnation technique. Surface area analysis, Raman, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) spectroscopy and TPR studies were used to characterize the sample. It was observed that surface chromium oxide species are formed similar to those on other oxide supports and similar monolayer coverages were achieved. However, the reduction characteristic (T_max temperature) was different due to the change in the Cr–O–support bond. The ODH of propane over the Cr₂O₃/Nb₂O₅ catalysts revealed that the activity increased up to monolayer coverage and then decreased due to the presence of Cr₂O₃ crystals. Similar observations were seen for the V₂O₅/Nb₂O₅ and MoO₃/Nb₂O₅ catalysts. The turnover frequency (TOF) was independent of coverage for the surface chromium, vanadium and molybdenum oxide species on Nb₂O₅. The constant TOF suggests the structure insensitivity of this type of reaction. The propene selectivities were high and relatively constant for the Cr₂O₃/Nb₂O₅ catalysts revealing the higher yields that can be obtained on this series of catalysts compared to the Cr₂O₃/Al₂O₃ and Cr₂O₃/TiO₂ catalysts. Additional studies involving tungsten and molybdenum oxide additives on 1% Cr₂O₃/Nb₂O₅ reveal the effect of exposed support surface on the propene selectivities.     

Dehydrogenation of light alkanes over oxidized diamond-supported catalysts in the presence of carbon dioxide

Oxidized diamond demonstrated excellent support for the dehydrogenation of light alkanes to alkenes in the presence of CO₂. Oxidized diamond-supported Cr₂O₃ and V₂O₅ catalysts exhibited comparatively higher catalytic activities in the dehydrogenation of lower alkanes in the presence of CO₂. In the dehydrogenation of propane, the oxidized diamond-supported Cr₂O₃ and V₂O₅ catalysts in the presence of CO₂ afforded nearly twofold higher activities than that in the absence of CO₂. The activity of the oxidized diamond-supported V₂O₅ catalyst in the dehydrogenation of propane increased with increasing reaction temperatures. Furthermore, in the dehydrogenation of n-butane and iso-butane, a promoting effect of CO₂ on butane conversion and butenes yields was observed over the oxidized diamond-supported Cr₂O₃ and V₂O₅ catalysts, though the promotion effect was small.

UV-Vis analyses of the fresh and the reacted catalysts in the presence and absence of CO₂ revealed that CO₂ kept the surface V₂O₅ and Cr₂O₃ in a state of oxidation slightly higher than that in the absence of CO₂.     

动物骨源羟磷灰石负载Co3O4用于N2O催化分解

通过焙烧猪骨和鸡骨获得羟磷灰石(nHAP)载体,并采用浸渍法制备Co3O4/nHAP催化剂。采用XRD、N2物理吸附-脱附、FT-IR和H2-TPR等对催化剂进行表征,在连续流动微反装置上考察催化剂催化分解N2O的性能。结果表明,相比于鸡骨源Co3O4/nHAP催化剂,以猪骨源HAP为载体的催化剂因其较大的比表面积以及较小的Co3O4粒径尺寸,提供了更多的活性位点。特别是猪骨源Co3O4/nHAP催化剂中适量的K、Na等元素促进了Co^3+到Co^2+的还原,削弱了Co-O键,使催化剂的催化活性显著提高。     

铈锆固溶体担载的镍催化剂对CO2甲烷化性能研究

采用共沉淀法制备了Ce_xZr_1-xO₂固溶体作为催化剂载体,采用柠檬酸络合法将镍负载于Ce_xZr_1-xO₂载体上得到Ni/Ce_xZr_1-xO₂催化剂,利用X射线衍射（XRD）、N₂吸附-脱附（N₂-BET）、程序升温脱附（TPD）、程序升温还原（TPR）等技术对催化剂进行表征,在常压微型固定床反应器上测试了CO₂甲烷化的性能,考察了n（Ce）/n（Zr）、镍含量对催化性能的影响。研究发现制备的催化剂具有优异的活性,在常压和空速15 000 mL·g^-1·h^-1条件下,反应温度200℃时,12% Ni/Ce_0.25Zr_0.75O₂催化剂（负载量为质量分数,下同）CO₂的转化率达74%,CH₄选择性为100%。12% Ni/Ce_0.25Zr_0.75O₂催化剂300 h的稳定性测试结果显示其具有较高的抗烧结性能。催化剂的优异活性归因于采用了新的负载方法--柠檬酸络合法负载活性组分镍,该法实现了镍的高分散和催化剂的大的比表面积。