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通过对Ce-TiO2催化剂进行SO2+O2气氛下的不同时间的预硫化处理并用于NH3-SCR反应,研究了Ce-TiO2催化剂物化特性随预硫化时间的演变规律,以及预硫化对中低温活性及NH3-SCR反应路径的影响。结果表明Ce-TiO2催化剂表面氧化铈的硫酸化相当迅速,在预硫化处理0.5h后,几乎所有的表面氧化铈都被硫酸盐化形成硫酸铈,随着硫酸化时间的增加到1h和1.5h,Ce-TiO2催化剂上沉积的硫缓慢增加。活性测试表明预硫化后的催化剂对SCR活性的抑制作用随着反应温度的提高而减弱,结合NO-DRIFT、NH3-DRIFT等多种原位表征,结果表明预硫化后低温NH3-SCR活性大幅降低是由于生成硫酸铈后催化剂氧化还原能力大幅削弱,E-R反应路径严重受阻。随着反应温度的升高,SCR活性逐渐不受硫酸铈沉积的影响,一方面,氧化还原性能的提高导致E-R反应路径逐渐恢复;另一方面,硫酸铈的生成促进了NO的活化,增强了L-H反应路径,两者共同导致了预硫化后较高的中温NH3-SCR活性。 相似文献
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STUDY OF Cu-Mu CATALYST FOR THE SYNTHESIS OF METHYL FORMATE AND METHANOL FROM SYNTHESIS GAS 下载免费PDF全文
将一种新型的CuMn催化剂用于由合成气合成甲酸甲酯和甲醇,该催化剂表现出良好的反应活性和甲酸甲酯选择性。考察了反应温度、合成气压力及催化剂制备方法等对合成甲酸甲酯和甲醇的反应活性及选择性的影响。在反应条件下,产物收率最高达60.10g/(L·h),产物甲酸甲酯的选择性很高。用BET、XRD及XPSAuger等测试方法对催化剂的比表面、晶相组成以及铜、锰在催化剂中的价态进行了表征,并探讨了催化剂失活的原因。 相似文献
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应用XRD、ESR、URDS、XPS及XAES等手段研究了CO2加H2合成甲醇Cu-Zn-O催化剂在还原后和反应状态下的表面化学状态。结果表明,在还原及反应状态下,催化剂表面仅能检测到CU^0,而未发现稳定的Cu^2+和Cu^+存在;ZnO被 部分还原产生低价锌Zn^(2-δ)+(0<δ<2)。关联活性测试结果认为:Cu^o/Zn^(2-δ)+O构成CO2加H2合成甲醇反应的活性中心。 相似文献
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利用金属蒸气法制备了三种不同金属重量比的树脂固载及活性炭负载Pd-Cu双金属催化剂。透射电镜(TEM)和X-射线衍射(XRD)测定结果表明催化剂中Pd-Cu已形成合金。合金粒度极小,平均直径小于5mm。树脂固载催化剂金属粒度远小于活性炭负载催化剂的金属粒度。X-射线光电子能谱(XPS)结果表明Pd和Cu均以零价态存在。在4-甲基-3-戊烯-2-酮加氢反应中,树脂固载催化剂的活性和选择性均高于相应的 相似文献
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Cobalt oxide catalysts supported on mesoporous silica (Co3O4/MPS) were prepared, characterized and applied for catalytic oxidation of NO.
Effects of catalyst supports, calcination temperatures, H2O and SO2 on NO conversion were investigated. The samples were also characterized
by BET, XRD, FTIR and TG/DTG. The results suggested that Co3O4/MPS catalyst calcined at 573 K had the smallest crystal particles and
the best surface dispersion. This catalyst had the highest activity and yielded 82% NO conversion at 573 K, at a space velocity of 12000 h−1.
Although the conversion of NO decreased with the introduction of H2O, it could be restored completely after removing residual H2O from
Co3O4/MPS catalyst by heating at 573 K. In the presence of SO2, the oxidation activity decreased and CoSO4 was detected on the catalyst.
The NO conversion decreased to 30.2% in the presence of SO2 and H2O. It could not be restored completely after cutting off H2O and SO2.
The deactivation of the catalyst in the presence of SO2 and H2O was attributed to the formation of cobalt sulfate species. 相似文献
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为了提高MNOx/TiO2催化剂催化氧化NO的活性,在载体TiO2上负载醋酸锰的同时掺杂了一定量的硝酸铈,构成了Ce(1)Mn(3)Ti催化剂,并对催化剂进行XRD、BET和XPS等表征。重点考察了H2O和SO2对催化剂活性的影响,通过FT-IR、SEM和BET等表征手段对毒化前后的催化剂组成及结构进行了分析。结果表明,Ce(1)Mn(3)Ti催化剂具有较好的活性,在空速41 000 h-1、NO体积分数为300×10-6及O2含量10%的条件下,反应温度200℃时NO转化率可达58%,250℃时NO转化率达到最高值85%。单独加入4%H2O使得催化剂活性降低,升高反应温度,H2O对催化剂的影响减弱;同时通入4%H2O和100×10-6SO2,在反应温度250℃时,NO转化率下降并维持在48%左右,停止通入后恢复到61%。H2O和SO2使催化剂活性物种硫酸盐化失活。 相似文献
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磁性纳米固体超强酸的合成、表征及性能 总被引:16,自引:0,他引:16
首次制备了SO42-/Co0.5Fe2.5O4-ZrO2磁性固体超强酸,利用TEM,DTA,XRD和FTIR等手段研究了Co0.5Fe2.5O4磁性基质对ZrO2的粒子大小、晶化温度与结构的影响.考察了磁性固体超强酸的催化性能及催化剂的寿命、回收率和磁性.结果表明,引入Co0.5Fe2.5O4磁性基质不但赋予催化剂以磁性,而且在固体超强酸形成过程中延迟了ZrO2由四方晶相向单斜晶相的转变,有助于稳定样品表面的含硫物种,磁性固体超强酸对酯化反应具有较高的催化活性,可活化再生,并保持磁性. 相似文献
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固体超强酸SO2-4-MoO3-TiO2的制备及其催化酯化性能研究 总被引:4,自引:0,他引:4
In this paper a new solid superacid catalyst SO2-4-MoO3-TiO2 was prepared.The activity of the catalyst in esterification of acetic acid and iso-amyl alcohol was measured and compared with that of SO2-4-TiO2 and MoO3-TiO2.The results showed that SO2-4-MoO3-TiO2 had better catalytic performance than SO2-4-TiO2 and MoO3-TiO2.There was evident coordination between MoO3 and SO2-4 when they coexisted on TiO2. 相似文献
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Superacid catalyst SO42--ZrO2/TiO2 was applied in esterification of Acetic Acid and Butanol. The particle size of ZrO2 in the catalyst was about 12.5 nm. In catalyst preparation conditions, the effect factor order on catalytic activity is H2SO4 concentration > calcination temperature > ZrO2 supported content. The optimum preparation condition is as follows: ZrO2 content 3.5g/g; calcination temperature 600℃, and H2SO4 concentration 0.5mol/L. The catalytic activity is 96.5 vol%.SO42-/MxOy solid superacid is a kind of green catalyst, whose application perspective is bright. In this paper, SO42--ZrO2/TiO2 solid superacid was prepared with nanometer compound carrying method. The acidic strength of catalysts was measured with the following Hammett indicators, 2,4-dinitrofluorobenzene (H0=-14.52) and p-nitrochlorobenzene (H0=-12.70). Catalytic activity was evaluated with esterification reaction of Acetic Acid and Butanol. Reaction temperature was at 105℃, and reaction time was only 1h. The conversion rate of Acetic Acid was analyzed by a gas chromatograph (GC-14C SHIMADZU in Japan)The experimental results showed that H2SO4 concentration had more influences on catalytic activity than other two factors, calcination temperature and ZrO2 supported content. Since sulfur absorbed on the surface of metal oxides is necessary to the acidity of SO42-/MxOy solid superacid,H2SO4 concentration in impregnation solution is needed enough high. But, it can't be too much high,otherwise, Zirconium sulfate formed on the catalyst surface will be harmful influences on catalytic activity. In researched cover, 0.5mol/L H2SO4 concentration is the most suitable, and the catalyst prepared with this concentration has very strong acidity.The optimum preparation condition is as follows: ZrO2 content 3.5g/g; calcination temperature 600℃, and H2SO4 concentration 0.5mol/L. In the catalyst prepared with above conditions, the acidic strength (H0) of the catalyst is smaller than <-14.52, and catalytic activity is 96.5 vol%. When it was re-used in esterification reaction, catalytic activity decreased gradually with re-used times increasing(seen in Table 1). But after catalyst is used repeatedly up to five times, catalytic activity (84.3 vol %)is still higher than that of H2SO4 catalyst.The X-ray diffraction patterns showed that ZrO2 supported in TiO2 belonged tetragonal zirconia phases. Through the calculation of Scherrer formula, the particle size of ZrO2 in the catalyst is about 12.5 nm. After SO42- promoted nanometer ZrO2/TiO2 compound carrier, the diffraction peaks of tetragonal zircoma become broader and the strength weaker. It shows that adding SO4 ions restrains the crystallization of ZrO2, diminishes the size of particles. This might be why SO42--ZrO2/TiO2 has high catalytic activity and stability in acidic catalysis reaction. 相似文献
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固体强酸具有酸强度高 ,不腐蚀设备 ,不污染环境 ,与产物分离方便等特点 ,是一种对环境友好的催化剂。业已发现固体强酸对许多重要的有机反应如烃类异构化、傅克酰基化、傅克烷基化、酯化、缩合、聚合、氧化等具有良好的催化活性 ,可替代传统的浓 H2 SO4 及 Al Cl3、HF等高污染催化剂。在前文 [1]基础上 ,本文通过添加 Cr2 O3、Ce2 O3和 La2 O3对催化剂 S2 O2 - 8/Zr O2 - Al2 O3改进后制备出 S2 O2 - 8/Zr O2 -Al2 O3- M2 O3( M=Cr,Ce,La)系列固体强酸催化剂 ,用对乙酸和正丁醇的酯化转化率评价了催化活性 ,用 XRD、BET、流… 相似文献
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Butyl butyrate is a very important compound, which is transparent liquid and has the pear,apple flavor. Natural exist is in the fruit, such as apple, pear, banana, grape and strawberry, etc.Primarily used for to prepare the edible spice and is also widely used in industrial intermediate product, solvent and synthetic perfumery. Until now, there are many methods to synthesize it.Conventionally H2SO4 was reported, but it causes many problems, such as the erosion of equipment,easily causes the vice-reaction, difficulty for after-treatment, environment pollution etc. A new environmentally friendly catalyst, SO42-/TiO2-La2O3 was prepared. And catalytic activity of catalyst in esterification of n-butanoic acid and n-butyl alcohol with SO42-/TiO2-La2O3 as catalyst has been no report up to now. Therefore, studying on the synthetic catalyst has theoretical and practical significances. The catalytic activity of catalyst in esterification of n-butanoic acid and n-butyl alcohol was measured.In this paper, we fast reported the preparation of SO42-/riO2-La2O3 and discussed the factors influencing the synthesis catalyst. The catalyst rare earth solid superacid SO42-/TiO2-La2O3 was The precipitate was filtered and washed thoroughly with distilled water until chloride ions were free.furnace at 480 ℃ for 3 h, and finally stored in a desiccator until use.The factors influencing the synthesis were discussed and the best conditions were found out. The experiment indicated that this catalyst has the following advantage. The amount of catalyst was little and getting high yield, its product has a good quanlity and is favour of reducing erosion of equipment, avoiding environment pollution. The optimum conditions are: molar ratio of n-butanoic acid to n-butyl alcohol was 1:1.5, the quantity of catalyst was equal to 1.5% of feed stocks, the reaction temperature was 93-114 ℃, and the reaction time was 1.0 h. Rare earth solid superacid SO42-/TiO2-La2O3 is an excellent catalyst for synthetizing butyl butyrate and its yield can reach over 90.0%.A good catalyst should be able to be used repeatedly. The reusing of the catalyst was studied. We found that the catalytic activities of our catalyst are almost unchanged after it had been used five times. From the above results and discussion, we can see that the synthesis of n-butyl butyrate by SO42-/TiO2-La2O3 instead of H2SO4 has a great prospect of application. It has a good applied foreground. 相似文献
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SO2 -4 MxOy 型固体超强酸自问世以来一直受到人们的广泛关注 ,已对其进行了大量的研究。该类催化剂的酸强度高 ,在烷基化、酰基化、裂解、醇脱水、异构化、酯化等反应中有很高的催化活性。最常用的氧化物基体是ZrO2 和TiO2 ,最好的促进剂是SO2 -4 。也有用MoO3作促进剂的[1~3] ,得到相应的超强酸催化剂。作者在SO2 -4 TiO2 超强酸的基础上 ,将MoO3和SO2 -4 同时负载在TiO2基体上 ,得到SO2 -4 MoO3 TiO2 固体超强酸 ,以乙酸异戊酯的合成为探针反应考察了该催化剂的催化酯化活性 ,并与SO2 -4 … 相似文献
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V2O5-CeO2/TiO2催化剂上低温氨选择性催化还原NO的性能 总被引:8,自引:5,他引:3
考察了V2O5-CeO2/TiO2催化剂中V、Ce活性组分的担载量和焙烧温度对催化剂低温催化还原NO活性的影响及其在单独SO2、H2O和两者共存气氛下的抗毒化性能。结果表明,焙烧温度400℃下制备的5V30Ce/TiO2催化剂具有良好的低温催化还原NO活性,空速为10000h-1,165℃时NO转化率达99.2%;500℃以下低焙烧温度时,添加的Ce不与V相互作用,在催化剂表面主要以CeO2形式存在,有利于增大催化剂比表面积,增强V2O5在催化剂上的分散度,提高催化活性。而在500℃以上较高焙烧温度下,Ce与V会形成CeVO4,对活性提高不利。催化剂具有良好的低温抗水中毒性能,但受SO2毒化作用明显,其在SO2、H2O共存气氛下中毒程度较单独SO2下浅。 相似文献
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低温陈化超声波共沉淀法制得SO4^2-/ZrO2-La2O3前驱体,经H2SO4处理,在不同温度下焙烧得到纳米晶催化剂SO4^2-/ZrO2-La2O3;用Hammett指示剂法测定其酸性.用XRD、BET、TEM、IR和XPS对样品进行表征,其催化活性用醋酸和甘油的酯化反应进行了评价.结果表明经超声波搅拌和低温(-15℃)陈化,650℃焙烧4h得到的固体超强酸表现出较高催化活性. 相似文献