Enhanced catalytic performance for direct synthesis of dimethyl ether from syngas over a La2O3 modified Cu-ZrO2/γ-Al2O3 hybrid catalyst

A series of hybrid catalysts were made by physically mixing Cu-ZrO 2 and γ-Al 2 O 3,for former it was modified with different loadings of La 2 O 3 prepared by co-precipitation method.The catalysts were characterized by BET,XRD,N 2 O-adsorption,EXAFS,H 2-TPR,NH 3-TPD techniques and evaluated in the synthesis of dimethyl ether from syngas.The results show that La 2 O 3 promoted catalysts displayed a significantly better catalytic performance compared with Cu-ZrO 2 /γ-Al 2 O 3 catalyst in CO conversion and DME selectivity,and the optimum catalytic activity was obtained when the content of La 2 O 3 was 12 wt%.The characterizations reveal that high copper dispersion,facile reducibility of copper particles and appropriate amount of acidic sites are responsible for the superior catalytic performance.     

NiO在γ-Al2O3及 TiO2/γ-Al2O3载体上的表面存在状态

本文采用LRS,XRD,UV－DRS考查了γ－Al2O3上TiO2的分散容量,分散态Ti^4 离子的配位环境;NiO在经TiO2改性后的γ－Al2O3载体上的分散容量,结果表明,（1)TiO2在γ－Al2O3表面的分散容量约为0．65mmol/100m^2γ－Al2O3,当TiO2含量低于该分散容量时Ti^4 在γ－Al2O3载体表面以嵌入形式呈离子态分布,而含量离于分散容量时还有结晶态的TiO2出现,（2）NiO在TiO2/γ－Al2O3载体表面的分散容量约为1．1mmol/100m^2γ－Al2O3,比之在γ－A2O3载体表面的分散容量（1．5mmol/100m^2γ－Al2O3）要低,这是由于γ-AlO3表面上部分空位被Ti^4 离子占据,用表面相互作用的“嵌入模型”（Incorporation Model)讨论的这些结果。     

Dehydrogenation of Isobutane Over V2O5/γ-Al2O3 Catalyst

The effect of the type of the support and the amount of V₂O₅ loading on the activity of V₂O₅/γ-Al₂O₃ catalyst for the dehydrogenation of isobutane have been investigated. Based on the experimental results of TPR, XRD and ESR spectroscopy, it is suggested that there are strong interactions between vanadia and carrier and that the V⁴⁺ species on the surface is the active site of V₂O₅/γ-Al₂O₃ for this reaction. This revised version was published online in June 2006 with corrections to the Cover Date.     

沉淀法结合超临界CO2干燥制备纳米γ-Al2O3

纳米γ-Al2O3具备多孔性、高比表面积、良好的吸附性、热稳定性和表面酸性[1,2],用作吸附剂和催化剂(及其载体),是催化剂载体领域应用最为广泛的品种[3～6].制备纳米氧化铝的方法有很多,大致可分为固相法、液相法、气相法等.     

γ-Al2O3表面原位合成Ni-Al-CO3LDHs研究

Ni-Al-CO₃LDHs/γ-Al₂O₃have been prepared using an in-situ synthesis technique. NH₃·H₂O was chosen as activation agent of Al on the γ-Al₂O₃surface as well as precipitant. Ni-Al-CO₃LDHs/γ-Al₂O₃was synthesized by controlling the reaction conditions such as temperature, concentration of Ni²⁺ and initial pH. The crystalline structure, chemical composition and porous structure were characterized by means of XRD, FT-IR, TG-DTA, ²⁷Al MAS-NMR and N₂ adsorption-desorption. The resulting sample of Ni-Al-CO₃LDHs/γ-Al₂O₃possesses higher specific area and narrower pore distribution, in which Ni-Al-CO₃LDHs are located on the surface of γ-Al₂O₃and share the same Al-O bonds with the γ-Al₂O₃lattice. Finally a possible structural model was proposed to account for the porous characters of Ni-Al-CO₃LDHs/γ-Al₂O₃.     

New alternatives for high specific area γ-Al2O3 synthesis

-Al₂O₃ was synthesized from trisec-butoxide by the sol-gel method. pH was varied during reaction and solvents of different polarity were used. Solids with specific areas, greater than 200 m²/g, were obtained, which depend directly on the reaction parameters.

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-Al₂O₃ - -. . pH . , 200 ²/ .

     

Influence of MgO loading on the structure and catalytic performance of Pd/γ-Al2O3, I. Effect of interaction between MgO and γ-Al2O3

The influence of MgO dispersed on -Al₂O₃ in different amounts on the structure and performances of Pd/-Al₂O₃ catalysts has been studied by means of XRD, H₂–O₂ titration, BET and catalytic activity test for CO oxidation. It was found that introduction of MgO enhanced greatly the CO oxidation activity of catalyst. It seems that the enhanced activity stems from the stronger interaction between MgO and -Al₂O₃ at a given temperature (e.g. 450 °C).     

CeO2/γ-Al2O3复合材料制备及其光催化性能研究

以Ce(NO₃)₃·6H₂O及Al(NO₃)₃·9H₂O为原料,NH₄HCO₃为造孔剂,以沉淀法制备了具有介孔结构的CeO₂/γ-Al₂O₃光催化材料。研究了不同NH₄∶Al及Ce∶Al摩尔比等条件下制备CeO₂/γ-Al₂O₃样品的光催化性能。结果表明,所制备CeO₂/γ-Al₂O₃复合材料具有优异的光催化性能,最佳NH₄∶Al及Ce∶Al摩尔比分别为1及0.2,该条件下制备的样品BET比表面积为94.4642 m²·g^-1,孔径为5.8565 nm,对亚甲基蓝(MB)的光催化降解率可达93.59%,动力学常数k为0.0218 m...     

CuMnCeLa-O/γ-Al2O3催化剂助燃脱硝性能研究

采用等体积浸渍法制备了Cu Mn-O/γ-Al_2O_3、Cu Mn Ce-O/γ-Al_2O_3和Cu Mn Ce La-O/γ-Al_2O_3催化剂.用XRD、BET、SEM、XPS和H_2-TPR技术对其物相和表面性质进行了表征.在连续固定床微反装置上评价了催化剂的CO+O_2和CO+NO反应性能.结果表明,催化剂样品中观测不到Cu O、Mn O_x、Ce O_2和La_2O_3的XRD晶相峰,活性组分在γ-Al_2O_3载体表面呈高度分散状态.Ce、La的引入对催化剂的比表面积、孔容和孔径分布影响不大.SEM谱图中未观测到活性组分的形貌,金属氧化物在载体表面均匀分布.Ce~(3+)!Ce~(4+)之间的可变价转换,引起Cu Mn Ce-O/γ-Al_2O_3催化剂表相Cu O中具有非完整结构的[Cu~(2+)_(1-x)Cu_x~+][O_(1-2)1_x□1_(2x)]增多,Cu~+/Cu~(2+)比例增大,表相氧空位增多,H_2-TPR还原峰温度向低温区偏移.Ce~(4+)、La~(3+)之间不平衡电荷以及共生过程中Cu-Mn-Ce-La-O之间的强相互作用,加大了Cu O和Mn O_x结构的不完整性,导致Cu Mn Ce La-O/γ-Al_2O_3催化剂样品表相产生更多的Cu~+、Mn~(2+)、Mn~(3+)和氧空位,相应的H_2-TPR还原峰温度进一步向低温区偏移.催化氧化CO和CO催化还原NO实验结果表明,在反应空速20 000 h~(-1),350℃反应温度下,Cu Mn Ce La-O/γ-Al_2O_3催化剂CO催化还原NO反应的CO转化率达到88.2%,NO转化率达到了96.1%,表现出了较好的氧化还原活性.     

La2O3对Ni-Mo/γ-Al2O3催化剂CO和CO2甲烷化的影响

采用浸渍法制备了一系列Ni-Mo-La/γ-Al     

Comparing the deactivation behaviour of Co/CNT and Co/γ-Al2O3 nano catalysts in Fischer-Tropsch synthesis

An extensive study of Fischer-Tropsch (FT) synthesis on cobalt nano particles supported on γ-alumina and carbon nanotubes (CNTs) catalysts is reported.20 wt% of cobalt is loaded on the supports by impregnation method.The deactivation of the two catalysts was studied at 220 C,2 MPa and 2.7 L/h feed flow rate using a fixed bed micro-reactor.The calcined fresh and used catalysts were characterized extensively and different sources of catalyst deactivation were identified.Formation of cobalt-support mixed oxides in the form of xCoO yAl2O3 and cobalt aluminates formation were the main sources of the Co/γ-Al2O3 catalyst deactivation.However sintering and cluster growth of cobalt nano particles are the main sources of the Co/CNTs catalyst deactivation.In the case of the Co/γ-Al2O3 catalyst,after 720 h on stream of continuous FT synthesis the average cobalt nano particles diameter increased from 15.9 to 18.4 nm,whereas,under the same reaction conditions the average cobalt nano particles diameter of the Co/CNTs increased from 11.2 to 17.8 nm.Although,the initial FT activity of the Co/CNTs was 26% higher than that of the Co/γ-Al2O3,the FT activity over the Co/CNTs after 720 h on stream decreased by 49% and that over the Co/γ-Al2O3 by 32%.For the Co/γ-Al2O3 catalyst 6.7% of total activity loss and for the Co/CNTs catalyst 11.6% of total activity loss cannot be recovered after regeneration of the catalyst at the same conditions of the first regeneration step.It is concluded that using CNTs as cobalt catalyst support is beneficial in carbon utilization as compared to γ-Al2O3 support,but the Co/CNTs catalyst is more susceptible for deactivation.     

低温等离子体协助B2O3/γ-Al2O3 选择催化还原NO（英文）

研究了低温等离子体协助催化条件下甲烷选择性催化还原NO反应(SCR).反应气体经等离子体活化后,生成NO2,HCHO,CH3NO和CH3NO2等活性更高的中间产物.程序升温表面反应表明,这些中间产物可在等离子体后置催化装置上进一步反应,从而使NOx还原为N2.在考察的一系列催化剂(包括γ-Al2O3,Ag/γ-Al2O3,B2O3/γ-Al2O3,Ga2O3/γ-Al2O3,In2O3/γ-Al2O3等)中,B2O3/γ-Al2O3表现出最好的催化活性.当反应温度为300oC时,NOx转化率达到最高.与γ-Al2O3催化剂相比,在10wt%B2O3/γ-Al2O3催化剂上,300oC时,NOx转化为N2的转化率从33.4%提高至51.0%.催化剂的酸性对于经等离子体活化后的反应气体在催化剂上的SCR反应起到重要作用.同时,催化剂上吸附态NOx对于NOx的转化也起到一定作用.     

Effect of Fe-modified α-Al2O3 on the properties of Pd/α-Al2O3 catalysts in selective acetylene hydrogenation

The use of nanocrystalline Fe-modified α-Al₂O₃ prepared by sol–gel and solvothermal method as supports for Pd catalysts resulted in an improved catalyst performance in selective acetylene hydrogenation. Moreover, the amount of coke deposits was reduced due to lower acidity of the Fe-modified α-Al₂O₃ supports.     

钙改性对γ-Al2O3的高温热稳定性的影响

研究了以Ca(NO3)2浸渍改性对γ-Al2O3的高温热稳定性的影响.考察了Ca的添加量及高温(1273K、1373K)处理后的表面性质和稳定性.BET比表面积和XRD结果表明,高温下Ca物种的引入明显地抑制了氧化铝比表面积的损失和α相变,提高了其耐热性.探讨了Al2O3烧结动力学,高温动力学研究表明,Ca的高温稳定作用主要是抑制焙烧过程中最初1h内的烧结和α相变.     

γ-Al2O3颗粒溶液浸润过程的原位磁共振成像

在催化剂的制备过程中,常采用浸渍法将金属或活性相负载到多孔固体载体上以获得高性能的负载型催化剂;在浸渍过程中溶剂对载体的浸润能力和效果对负载活性组分的分布和状态至关重要,进而会影响催化剂的催化性能.本文利用磁共振成像(MRI)技术开展了溶剂对γ-Al₂O₃颗粒浸润过程的原位研究.评估了自旋回波(SE)、梯度回波(GRE)和超短时间回波(UTE) 3种不同MRI序列的成像效果,发现UTE序列在观测短横向弛豫时间(T₂)值的¹H MRI信号方面展现出优越的性能,应用小激发角和短恢复时间(TR)可以获得比SE和GRE序列更高时间分辨率(<1 min)的动态图像.利用UTE序列对γ-Al₂O₃在不同极性溶剂中的浸渍过程进行了原位监测,发现极性溶剂水和甲醇均表现出典型的自由扩散过程,即溶剂从颗粒的外缘逐渐扩散到其中心直至饱和;非极性溶剂环己烷展现了不同的浸润行为,γ-Al₂O₃颗粒的整体¹H M...     

Role of support nature （γ-Al2O3 and SiO2-Al2O3） on the performances of rhenium oxide catalysts in the metathesis of ethylene and 2-pentene

The metathesis of ethylene and 2-pentene was studied as an alternative route for propylene production over Re2O7/γ-Al2O3 and Re2O7/SiO2-Al2O3 catalysts. Both NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR) results showed that Re2O7/SiO2-Al2O3 exhibited stronger acidity and weaker metal-support interaction than Re2O7/γ-Al2O3. At 35 60℃, isomerization free metathesis was observed only over Re2O7/γ-Al2O3, suggesting that the formation of metal-carbene metathesis active sites required only weak acidity. Our results suggest that on the Re2O7/SiO2-Al2O3, hydrido-rhenium species ([Re]-H) were formed in addition to the metathesis active sites, resulting in the isomerization of the initial 1-butene product into 2-butenes. A subsequent secondary metathesis reaction between these 2-butenes and the excess ethylene could explain the enhanced yields of propylene observed. The results demonstrate the potential for high yield of propylene from alternative feedstocks.     

磺酸功能化纳米γ-Al2O3催化下合成硫醚类化合物

在磺酸功能化纳米γ-Al2O3催化下,以硫醇或硫酚和醇类化合物为原料,在室温、无溶剂条件下,高收率地实现了一系列硫醚类化合物的合成,产物结构经1H NMR,13C NMR和元素分析进行了表征.     

Method for Metal Dispersion Measurements on Pt-Sn/γ -Al2O3

An easy, inexpensive method for metal dispersion measurements in Pt-Sn/γ -Al₂O₃ catalysts is proposed. The method is based in avoiding Sn oxidation during catalyst evacuation. This revised version was published online in June 2006 with corrections to the Cover Date.     

CO预处理对CuO/γ-Al2O3催化剂性能的影响

采用XRD，TPR，CO吸附in-situ IR，CO氧化反应等对CuO/γ-Al₂O₃催化剂经CO处理前后的结构、组成和催化性能进行了研究。结果表明，经CO在250 ℃下处理1 h后CuO/γ-Al₂O₃催化剂中出现了分散态Cu⁺物种，该物种的产生使催化剂的活性明显提高。     

Hydrogenation of 2-ethylanthraquinone over Pd/Zro2-γ-Al2O3 catalyst

A ZrO₂-γ-Al₂O₃ supported Pd catalyst was prepared and characterized by XRD, XPS, H₂-TPR and TEM techniques. The catalytic activity was evaluated in the liquid-phase hydrogenation of 2-ethylanthraquinone. Comparing with Pd/γ-Al₂O₃, it showed high catalytic activity.