Enhanced alkali resistance of CeO2/SO42 −–ZrO2 catalyst in selective catalytic reduction of NOx by ammonia

Ceria catalysts supported on sulfated zirconia showed a remarkable resistance towards alkali metal poisoning in selective catalytic reduction of NO by NH₃. TPD results revealed sulfation treatment of supports produced massive acid sites on the surface of catalysts. Adequate acidity was of importance for the enhanced resistance to alkali metal ions. The introduction of potassium did not affect the crystalline phases and morphology of catalysts, but it could lead to higher surface areas of samples.     

La–Ni modified S2O82−/ZrO2-Al2O3 catalyst in n-pentane hydroisomerization

The La –Ni–S₂O₈²⁻/ZrO₂ –Al₂O₃ (La–Ni–SZA) was prepared and the effect of La and Ni on the structure and isomerization performance of catalyst was investigated. The addition of La could lead to a higher dispersion of metal and more acid sites. The addition of Ni can promote redox performance of catalyst and formation of Lewis acid sites. The highest isopentane yield of 66.5% at a lower reaction temperature of La–Ni–SZA can be attributed to the synergistic interaction between La and Ni.     

制备条件对Pt/SO42-/ZrO2-Al2O3异构化性能的影响

采用沉淀法制备了Pt/SO₄^2-/ZrO₂-Al₂O₃ (PtSZA)催化剂,考察了氢氧化锆水凝胶干燥速率、锆盐浓度、铂含量、Al₂O₃和SO₄^2-添加顺序等制备条件对PtSZA异构化性能,尤其是低温异构化性能的影响,并用XRD和TG对催化剂进行了表征。结果表明,提高水凝胶的干燥速率降低了PtSZA催化剂中的硫含量,大大提高了催化剂中的单斜相,进而导致了催化剂低温失活加速以及高温活性下降。较低或较高的锆盐浓度劣化了PtSZA的低温异构化稳定性,以0.4~0.6mol/L硝酸氧锆制备的催化剂硫含量和四方相氧化锆含量较高,异构化活性相对较好,Al₂O₃和SO₄^2-添加顺序对PtSZA异构化性能没有明显影响。     

复合固体超强酸SO42-/Fe2O3/Al2O3/ZnO/ZrO2催化剂的制备及其催化性能

沉淀法由Fe（NO3）3、Al（NO3）3、Zn（Ac）2、ZrOCl2和H2 SO4制备SO42-/Fe2O3/Al2O3/ZnO/ZrO2催化剂,用于催化合成苯乙酮乙二醇缩酮,研究了醇酮摩尔比、反应时间、带水剂用量、催化剂用量等对产品收率的影响.结果表明,在n（苯乙酮）∶n（乙二醇）=1∶1.2,苯乙酮物质的量为0.2 mol,催化剂的量是反应物料总质量的1.5％,带水剂甲苯20 mL,100～120℃回流反应60 min的条件下,苯乙酮乙二醇缩酮的收率达98.8％.     

活化条件对正己烷在Pt/SO42-/ZrO2-Al2O3上的异构化活性影响

采用浸渍法制备了Pt改性的Pt/SO42/ZrO2-Al2O3（PSZA）催化剂,考察了活化条件对PSZA催化剂正己烷异构化活性的影响,采用程序升温氧化（TPO-MS）、氮气-程序升温处理（TPN-MS）、程序升温还原（TPR-MS）对催化剂进行表征。异构化反应在连续流动的固定床微型反应器中进行。结果表明,200℃以上的高温氮气中活化预处理后的PSZA几乎没有异构化活性;空气气氛中、200～500℃高温条件下活化预处理的PSZA表现出了较高的异构化活性,正己烷初始转化率均在85%以上。在高于300℃的氢气中活化预处理,PSZA表现出较低的异构化活性。空气气氛中预处理除脱水之外,由于氧气的存在对催化剂的表面起到再氧化作用,导致高的异构化活性。氢气气氛中高温活化预处理导致了PSZA上硫物种的损失,进而引起异构化活性的下降。PSZA适宜的预处理条件为：空气气氛、300～500℃活化,250℃氢气中还原。     

SO2 Reactions over γ-Al2O3,Pt/γ-Al2O3,Sn/γ-Al2O3 and Pt–Sn/γ-Al2O3

Platinum and Platinum–tin bimetallic catalysts supported on alumina were prepared by co-impregnation of both metallic precursors on the support and used as catalysts for the oxidation of SO₂. Platinum dispersion was determined by means of H₂–O₂ titration. Tin addition (1 and 2 wt%) only slightly decreased the exposed platinum atoms suggesting that tin is mainly over the support. At temperatures lower than 300 °C, SO₂ did not react with oxygen. Nevertheless, when the temperature was increased, the SO₂ oxidation began. The ignition temperatures for SO₂ oxidation (taken at 50% conversion) were 345 °C for 1% Pt/Al₂O₃ and 520 °C for 1% Pt–2% Sn/Al₂O₃. The strong displacement on activity suggests that tin plays an important role as inhibitor of the SO₂ oxidation reaction.     

SO42-/Fe2O3固体酸催化合成香叶基氯

香叶基氯是一种由异戊二烯为原料合成香料香叶醇的中间体,今以SO42-/Fe2O3固体酸为催化剂,在溶剂环己烷的存在下,异戊二烯与异戊烯氯反应合成了香叶基氯.考察了催化剂制备过程中浸渍H2SO4浓度和焙烧温度对固体酸表面硫含量和反应结果的影响,得到比较好的催化剂制备条件浸渍硫酸浓度和焙烧温度550℃.还考察了反应温度、反应时间、催化剂用量和溶剂环己烷的用量对反应的影响.实验结果表明,当,WCatWC5Hs=130,WC6H12WC5Hs=10.8,在反应温度18℃时反应2h,异戊二烯的转化率为18.3%,生成香叶基氯的选择性可达到75.2%.     

Preparation,catalytic performance and theoretical study of porous sulfated binary metal oxides shell (SO42 −/M1xOy-M2xOy) using pollen grain templates

Porous micro-sized particles of binary metal oxide (SO₄^2 −/M1_xO_y-M2_xO_y) shell were prepared by template-directed synthesis method employing HCl-treated pollen grains. With 150 m²/g high surface area, these solid acids could provide more acid sites and thus obtain better catalytic activity. Using aromatic nitration as the typical reaction, their catalytic performances were evaluated and showed a significant improvement in both conversion and regioselectivity. Then, with chlorobenzene as substrate, theoretical studies were performed to investigate the interaction between transition metals and chlorobenzene. The results showed that the excellent para-selectivity was closely relative to the metal ion in these solid acids.     

Preparation of solid acid catalyst SO42−/TiO2/γ-Al2O3 for esterification: A study on catalytic reaction mechanism and kinetics

In this work, a series of SO₄^2-/TiO₂/γ-Al₂O₃ solid acid catalysts were synthesized by impregnation method, in which nano-TiO₂ was prepared by sol-gel method, and then the nano-TiO₂ sol was loaded on porous γ-Al₂O₃ supporter through impregnation. The structure and property of catalyst were characterized by XRD, N₂-BET, SEM, TEM, XPS, NH₃-TPD, Pyridine-IR and FT-IR. In addition, the catalyst of chelate bidentate coordination acid center model was established. The catalytic performance test was carried out in the esterification of n-butyl alcohol with lauric acid and the catalyst showed excellent activity. The experimental results showed that the medium strength acid sites were more dominant active sites than the strong and weak acid sites for the rapid esterification reaction. Its kinetic behaviors and activation energy were studied for the esterification under the catalytic reaction condition.     

SO42-/Fe2O3-Al2O3-SiO2固体超强酸的制备及催化活性研究

采用化学共沉淀和单因素法制备新型固体超强酸催化剂SO2-4/Fe2O3-Al2O3-SiO2,研究得到催化剂的最佳制备条件为:n(铁)、n(铝)、n(硅)=1∶2∶1,陈化时间6 h,浸渍硫酸浓度0. 75 mol/L,浸渍时间40 min,焙烧温度500 ℃,焙烧时间5 h.用红外光谱对固体酸进行了表征,以乙酸正丁酯的酯化反应对其催化活性进行了初步研究.     

Excess oxygen-vacancy formed by FAST regime of direct-current electric field during flash sintering for 3 mol%–10 mol% Y2O3-doped ZrO2

The amount of excess oxygen vacancies that are generated during FAST regime of direct-current flash sintering was estimated semi-quantitatively for 3 mol%–10 mol% Y₂O₃-doped ZrO₂ (3–10YSZ) using the temperature dependence of the electrical conductivity. For the estimation, the electrical conductivity in the temperature range, where shrinkages are below a few percent, was used to avoid the effect of large microstructural changes on the electric conductivity. For all Y₂O₃ contents except 3YSZ, the amount of excess oxygen vacancies increased above a compact temperature of approximately 840 °C, which depended on Y₂O₃ content, and was highest in 8YSZ. Approximately 0.13% excess oxygen vacancy was generated by direct-current flashing in 8YSZ in the present electric field condition. In contrast, the increase in the excess oxygen vacancies is negligible in 3YSZ. The dependence of the amount of excess oxygen vacancies on the Y₂O₃ content was related possibly to the dependence of the electrode overvoltage on the Y₂O₃ content.     

SO42-/Fe2O3-Al2O3-SiO2固体超强酸的制备及催化活性研究

采用化学共沉淀和单因素法制备新型固体超强酸催化剂SO42/Fe2O3-Al2O3-SiO2,研究得到催化剂的最佳制备条件为:铁、铝、硅物质的量之比1:2:1,陈化时间6h,浸渍硫酸浓度0.75mol/L,浸渍时间40min,焙烧温度500℃,焙烧时间5 h.用红外光谱对固体酸进行了表征,以乙酸正丁酯的酯化反应对其催化活性进行了初步研究.     

SO42-/Fe2O3-Al2O3-TiO2固体超强酸的制备及催化活性研究

采用共沉淀法制备SO42-/FeO3-Al2O3-TiO2固体超强酸.通过正交实验考察了3种金属最佳配比,陈化时间,硫酸浸渍浓度,浸渍时间,焙烧温度,焙烧时间等因素对酸强度的影响.研究表明,SO42-/Fe2O3-Al2O3-TiO2固体超强酸最佳制备条件是:n(Fe):n(AL):n(Ti)=1:2:2,陈化时间3h,浸渍H2SO4浓度1.0mol·L-1,浸渍用量15mL·g-1,浸渍时问20min,焙烧温度500℃,焙烧时间5h.此外,还利用红外光谱对催化剂进行了结构表征,利用酯化反应对其催化活性进行了初步研究.     

Effect of Al Content on the Isomerization Performance of Solid Superacid Pd–S2O82−/ZrO2 –Al2O3

The effect of Al content on the performance of the Pd–S₂O₈²⁻/ZrO₂ –Al₂O₃ solid superacid catalyst was studied using n-pentane isomerization as a probe reaction. The catalysts were also characterized by X-ray diffraction (XRD), Fourier transform Infrared (FTIR), specific surface area measurements (BET), thermogravimetry–differential thermal analysis (TG–DTA), H₂-temperature programmed reduction (TPR) and NH₃ temperature-programmed desorption (NH₃-TPD). The Pd–S₂O₈²⁻/ZrO₂ –Al₂O₃ catalyst made from Al₂O₃ mass fraction of 2.5% exhibited the best performance and its catalytic activity increased by 44.0% compared with Pd–S₂O₈²⁻/ZrO₂. The isopentane yield reached 64.3% at a temperature of 238 °C, a reaction pressure of 2.0 MPa, a space velocity of 1.0 h ^− 1 and a H₂/n-pentane molar ratio of 4.0. No obvious catalyst deactivation was observed within 100 h.     

Isothermal “light-off” during catalytic N2O decomposition over Fe/ZSM-5

The catalytic decomposition of N₂O over Fe/ZSM-5 was studied at pressures up to 1 atm. As the partial pressure of N₂O in the feed to a packed bed reactor was varied, the catalytic activity was observed to abruptly increase at inlet partial pressures above some critical value. This abrupt increase in activity was not due to the reaction exotherm, but is believed to be a kinetic phenomenon. In similar experiments where the temperature was varied the activity did not jump to a higher level. The dual levels of activity were observed for several Fe/ZSM-5 catalysts that spanned a range of SiO₂/Al₂O₃ ratios from 30 to 280, irrespective of whether the iron was introduced into the zeolite by ion exchange or by sublimation of iron chloride. When the inlet partial pressure of N₂O to the packed bed reactor was sufficiently high to cause the catalyst to operate in the high activity regime, the high activity state was sustained throughout the catalyst bed, even though the N₂O partial pressure in the latter part of the bed had dropped below the critical level. Microkinetic modeling shows that this kind of behavior is possible in an isothermal catalytic system. The microkinetic model includes two redox cycles. In one cycle the cation oxidation state alternates between Fe²⁺ and Fe³⁺. In the second, more active redox cycle there is alternation between a surface nitrite and nitrate. The former redox cycle predominates at low partial pressures and the latter at high N₂O partial pressures.     

SO42-/ZrO2-Al2O3催化合成糠酸酯类香料的研究

以固体超强酸SO42-/ZrO2-Al2O3为催化剂合成糠酸酯类香料.通过对催化剂制备的正交试验,优选了催化剂的制备条件;通过正交试验优化了糠酸酯化的条件:以糠酸0.1mol为准,催化剂用量0.6g,酸醇摩尔比1∶3,反应时间4h,并以此条件合成了糠酸甲酯、乙酯、丁酯三种糠酸酯类香料.     

Study on the NO reduction by NH3 on a SO42 −/AC catalyst at low temperature

The selective catalytic reduction (SCR) of NO with NH₃ at low temperature over a novel SO₄^2 −/AC catalyst (activated coke supported sulfate acid) was investigated especially in the presence of SO₂ and H₂O. A higher SCR activity and stability were attributed to the cooperation of the oxygen-containing function group and carbon. SO₂ promoted SCR activity, which was due to the formation of H₂SO₄ on the catalyst surface and adsorbed more NH₃. The capillary condensation of H₂O in the micropores of the catalyst inhibited SCR activity and the reaction of adsorbed NH₃ and NO.     

Thermal stability of nanostructured 13 wt% Al2O3–8 wt% Y2O3–ZrO2 thermal barrier coatings

Nanostructured 13 wt% Al₂O₃–8 wt% Y₂O₃–ZrO₂ (13AlYSZ) coatings were developed by atmospheric plasma spraying (APS). The phase structure and the morphology of the 13AlYSZ coatings were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). It was found that the as-sprayed coatings mainly consisted of tetragonal zirconia, with the Al element solid solution in ZrO₂. Heat treatment at 1100 °C increased the average grain size of the ZrO₂ phase from 61 to 120 nm and decreased the porosity from 23.8 to 18%. The addition of the nano-Al₂O₃ can effectively inhibit the grain growth of the zirconia phase. The mechanism on inhibiting the grain growth of nanostructured 8 wt% Y₂O₃–ZrO₂ thermal barrier coatings has been discussed in detail.     

Exploration of cinnamaldehyde hydrogenation in Co–Pt/γ‐Al2O3 catalytic membrane reactors

The feasibility of Co–Pt/γ‐Al₂O₃ catalytic membrane reactors for cinnamaldehyde hydrogenation has been explored. The results of hydrogenation in four membrane reactors with different configurations indicate that the effect of the gas transport limitation is more important than the liquid diffusion limitation. The membrane with the catalytic layer situated on the gas side shows the highest activity due to the minimized gas transport limitation. This revised version was published online in July 2006 with corrections to the Cover Date.