B2O3对Ag/TiO2-Al2O3吸附剂的柴油吸附脱硫性能影响

采用浸渍法制备了不同B₂O₃负载量(e.g. 5%~20% (w))的Ag/TiO₂-B₂O₃-Al₂O₃吸附剂。以含硫量为245.36mg(S)/L 的商业柴油作为考察对象,常温常压下采用静态评价进行吸附脱硫性能研究。结果表明,B₂O₃改性后的Ag/TiO₂-Al₂O₃吸附剂的柴油吸附脱硫活性有了较大提高,当B₂O₃的负载量为15%时,吸附剂的吸附脱硫活性最高,2%Ag/4%TiO₂-15%B₂O₃-Al₂O₃ (w)的饱和吸附硫容达到2.36mg(S)/g 吸附剂。这对于未经预处理的商业柴油而言,吸附脱硫活性已经达到较高水平。采用N₂物理吸附、O₂化学吸附、X射线衍射(XRD)、NH₃程序升温脱附(NH₃-TPD)、傅里叶红外光谱(FT-IR spectra)、¹¹B核磁共振(¹¹B-NMR)等表征手段对不同负载量B₂O₃改性Ag/TiO₂-Al₂O₃吸附剂的织构性质、晶相结构和表面酸性的影响进行研究。关联活性测试和表征结果发现,吸附剂的吸附脱硫活性主要与吸附剂的表面弱酸性有关,而B₂O₃改性在吸附剂表面引入了较多的四配位的BO₄物种,能显著增加吸附剂表面弱酸性位点数量,提高吸附剂的吸附脱硫活性。     

Nb2O5在t-ZrO2表面的分散状态与Brønsted 酸特征

以草酸铌为前驱物,四方相氧化锆（t-ZrO₂）为载体,通过浸渍法制备不同负载量的Nb₂O₅/t-ZrO₂催化剂.采用粉末X射线衍射（XRD）、激光拉曼光谱（LRS）、紫外-可见漫反射光谱（UV-Vis DRS）等技术对t-ZrO₂表面Nb₂O₃分散状态进行表征;采用异丁烯（IB）与异丁醛（IBA）缩合生成2,5-二甲基-2,4-己二烯（DMHD）反应评价不同负载量的Nb₂O₅/t-ZrO₂的催化性能,采用吡啶吸附红外（Py-IR）光谱表征催化剂Bronsted酸中心特征.结果表明,由XRD定量相分析方法测定的Nb₂O₅在t-ZrO₂表面单层分散容量与"嵌入模型"预测值接近.Nb₂O₅/t-ZrO₂表面Bronsted酸中心特征与Nb₂O₅聚集状态密切相关.     

复合载体TiO2-Al2O3的制备及其对Ni-Mo-S负载型催化剂加氢脱氧性能的影响

采用共沉淀法制备出复合载体TiO₂-Al₂O₃,用N₂-吸附、XRD和吡啶吸附红外光谱等手段进行表征。采用原位硫化法制备Ni-Mo-S/TiO₂-Al₂O₃负载型催化剂,以苯酚为模型化合物研究其加氢脱氧催化性能。主要研究铝源和沉淀剂对TiO₂-Al₂O₃复合载体性能的影响以及其作为载体对Ni-Mo-S/TiO₂-Al₂O₃催化苯酚加氢脱氧反应的影响。结果表明,以氯化铝为铝源制备的复合载体具有较大的孔容和孔径,孔容达1.12cm³/g,孔径达18.0nm;以硫酸铝为铝源和以碳酸氢铵为沉淀剂制备的复合载体具有较大的比表面积,高达295m²/g;氨水沉淀制备的复合载体具有较多的L酸;以硫酸铝为铝源制备的复合载体形成少量的B酸。TiO₂-Al₂O₃作为载体影响Ni-Mo-S/TiO₂-Al₂O₃负载型催化剂加氢脱氧性能的主要因素是载体的酸性和载体的比表面积。在300℃,4.0MPa条件下Ni-Mo-S/TiO₂-Al₂O₃催化苯酚的转化率达81.9%,产物中无氧化合物的总选择性达100%,脱氧率达79.4%。     

CO2重整CH4纳米ZrO2负载Ni催化剂的研究(Ⅰ)——与常规载体上Ni催化剂的比较

在Ni负载量相近(约5%)时,比较了由超临界干燥得到的纳米ZrO₂-AS为载体制备的Ni/ZrO₂-AS与几种常规载体(γ-Al₂O₃,TiO₂,SiO₂和ZrO₂-CP)负载的Ni催化剂对CO₂重整CH₄制合成气反应的催化性能.研究结果表明,γ-Al₂O₃,TiO₂,SiO₂和ZrO₂-CP负载Ni催化剂表现出明显的失活过程,而Ni/ZrO₂-AS催化剂在反应200h后活性未下降.“纯ZrO₂-AS”载体本身不仅能催化生成合成气的反应,而且活性稳定.TPO测定结果表明,负载在这种活性ZrO₂-AS载体上的Ni催化剂具有良好的抗积炭能力.     

B-TS-1分子筛的合成及其催化氧化性能

通过将杂原子B引入钛硅-1（TS-1）分子筛对其进行改性,并研究其催化氧化性能。结果发现,B-TS-1明显延长了环己酮氨肟化反应运行寿命。结合氨肟化体系催化剂失活主要原因以及反应体系H₂O₂反应路径,分析表明,H₂O₂是控制TS-1/H₂O₂氨肟化体系副反应发生的关键,并且有机副产物是导致催化剂堵孔失活的重要原因。本文提出B-TS-1能有效控制体系H₂O₂残留,从而进一步抑制副反应发生与积碳生成以延长催化剂寿命。结合Al-TS-1的催化特性,发现同时引入适量B、Al的B/Al-TS-1具有进一步提高环己酮肟化反应稳定性的作用。     

Bi4B2O9晶体及其熔体结构的高温原位拉曼光谱研究

利用密度泛函理论计算了Bi₄B₂O₉晶体的常温拉曼光谱, 并通过与实验拉曼光谱对比, 对其振动模式进行了归属. 利用高温原位拉曼光谱研究了Bi₄B₂O₉从常温到750 ℃升温过程中微结构的变化. 随着温度的升高, 晶体的平均键长变长, 键角分布变宽, 熔化后晶体中的BiO₄和BiO₅多面体解体, BO₃构型则保持三配位不变. 运用量子化学从头算法模拟了Bi₄B₂O₉的熔体结构并与实验拉曼光谱进行了对比分析, 发现在Bi₄B₂O₉熔体中B原子团簇为孤立的BO₃构型, Bi ³⁺游离于BO₃之间, 并结合未参与形成BO₃的O原子起到平衡电荷的作用.     

负载催化剂SmMn2O5/γ-Al2O3负载量对NO氧化的影响

贵金属催化剂对NO_x催化氧化具有优异的催化性能,但催化剂成本较高,而负载型催化剂及非贵金属催化剂受到了广泛的关注。 本文中采用水热法和浸渍法分别制备了SmMn₂O₅纯相催化剂和SmMn₂O₅/γ-Al₂O₃负载催化剂,探索了活性成分SmMn₂O₅含量对NO催化氧化的影响。 对负载SmMn₂O₅不同质量分数(5%~100%)的复合催化剂进行了扫描电子显微镜、比表面积、孔径分布、程序升温还原和程序升温脱附的表征以及NO催化氧化的研究。 当SmMn₂O₅负载量小于50%(35%、25%、15%、5%)时,负载量为25%的催化剂显示出最低的燃点温度(260 ℃),继续增加负载量到50%和75%,与负载25%的复合催化剂相比,起燃温度降低10 ℃,仅高于纯相催化剂40 ℃。 该探索对于SmMn₂O₅催化剂的有效利用将具有一定的指导作用,并为负载型非贵金属催化剂的设计提供一定的思路。     

γ-Al2O3对SCR脱硝催化剂V2O5-WO3/TiO2的改性研究

采用溶胶凝胶法制备了不同γ-Al₂O₃含量的钛铝复合载体,以此为载体采用浸渍法负载V₂O₅和WO₃制备了一系列催化剂。采用X射线衍射(XRD)、比表面积测定(BET)、程序升温还原(H₂-TPR)、高分辨率透射电子显微镜(HRTEM)等表征技术对催化剂表面形态进行分析,同时在模拟氨气选择性催化还原NO(NH₃-SCR)的反应条件下,对催化剂的脱硝反应活性和SO₂抗中毒进行考察。结果发现,TiO₂和γ-Al₂O₃之间的协同作用使得V₂O₅-WO₃/TiO₂-γ-Al₂O₃催化剂的脱硝效率及活性窗口明显优于单一载体制备的催化剂,表现出了良好的热稳定性和抗SO₂毒化能力,特别是V₂O₅-WO₃/TiO₂-15% γ-Al₂O₃在310~460 ℃,NO的转化率均在80%以上,反应窗口最宽。各种表征结果表明,TiO₂-γ-Al₂O₃复合载体中γ-Al₂O₃高度分散在TiO₂上,复合载体具有较大的比表面积,同时具有较强的还原能力。     

五氧化二钒/铈改性二氧化钛催化甲醇高选择性氧化制备二甲氧基甲烷

通过溶剂热法制备Ce掺杂的TiO₂,利用等体积浸渍法制得一系列V₂O₅/Ce-TiO₂催化剂,并用于甲醇选择性氧化制二甲氧基甲烷(DMM)。 采用XRD、UV-Vis、 H₂-TPR、NH₃-TPD等技术手段对催化剂进行了表征。 结果表明,Ce掺杂改性后的TiO₂负载V₂O₅更有利于催化剂表面钒氧物种的分散,且钒氧物种主要以孤立的和聚合态的形式存在,没有形成V₂O₅晶相结构。 Ce掺杂改性后,改变了TiO₂载体与钒氧物种间的作用力,Ce掺杂量越大,钒氧物种的还原温度逐渐向高温移动,使得催化剂的氧化还原能力减弱。 Ce改性的TiO₂负载V₂O₅,Ce的改性量对催化剂的酸性质几乎没有影响,但是催化剂的酸性却随着V₂O₅负载量的增大而逐渐减弱。 当Ce和Ti的摩尔比为0.01,V₂O₅的负载量为10%所得催化剂10V/1Ce-TiO₂具有较为适宜的氧化还原性和酸性,在反应温度160 ℃时,甲醇的转化率为39.6%,DMM的选择性高达99.9%。     

TiO2/Bi2O3纳米复合体的制备及可见光催化产氢性能

首先采用相分离的水解-溶剂热法制备了Bi₂O₃纳米粒子,然后利用简单的湿化学法在Bi₂O₃表面负载不同比例的TiO₂纳米颗粒,进而得到TiO₂/Bi₂O₃纳米复合体。通过气氛调控的表面光电压谱(SPS)等测试表明,表面负载适量的TiO₂后能够提高Bi₂O₃光生电荷分离。可见光催化产氢和降解污染物测试结果进一步证明,表面负载适量的TiO₂后可显著提高其可见光催化活性,其中Ti/Bi摩尔比为7%时具有最高的光催化活性。这主要归因于TiO₂具有较为合适的导带能级位置,可以接收Bi₂O₃在可见光激发下所产生的高能级电子,从而抑制光生电子-空穴对复合,并且维持了高能级电子较高的还原能力。     

改性钛锆复合氧化物催化环己酮肟气相Beckmann重 排反应

制备了经SO4^2-,PO4^3-,MoO3,WO3和B2O3改性的钛锆复合氧化物(TiO2-ZrO2)催化剂,并用常压连续流动固定床微型反应器考察了它们对环己酮肟气相Beckmann重排反应制己内酰胺的催化性能。结果表明,在反应温度300℃时,B2O3/TiO2-ZrO2具有较高的己内酰胺选择性(97.0%)和收率(96.7%),且明显高于B2O3/TiO2和B2O3/ZrO2催化剂,用N2吸附和NH3-TPD,CO2-TPD等方法对催化剂的经表面积、孔容、孔分布和表面酸、碱性分别进行了测定,讨论了这些物化性能对催化剂活性、选择性和稳定性的影响。     

The Effect of Platinum on Stability of the B2O3/TiO2-ZrO2 Catalyst for Beckmann Rearrangement of Cyclohexanone Oxime

It has been well illustrated that the rapid catalyst deactivation with time is the most serious limitation of vapor phase approach to the production of ε-caprolactam from cyclohexanone oxime (CHO) (Scheme 1), and is a common problem with all catalyst typ…     

Preparation of tantalum-pillared magadiite and its catalytic performance in Beckmann rearrangement

Vapor phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam has been carried out using tantalum-pillared magadiites (Ta-magadiites) with different surface areas as catalysts. The Ta-magadiite catalysts of relatively large surface areas showed high catalytic activities, due to a large number of active sites. For the Ta-magadiite catalyst of the largest surface area, the oxime conversion reached 99.1%, with 97.5% of lactam selectivity. FT-IR and NH₃-TPD results demonstrated that the new hydroxyl groups and a large amount of acidic sites generated by Ta pillaring into the magadiite interlayer were responsible for the high catalytic performance of Ta-magadiite catalyst.     

The Catalysis of Vapor-Phase Beckmann Rearrangement for the Production of ε-Caprolactam

Recently, Sumitomo Chemical Co., Ltd. developed the vapor-phase Beckmann rearrangement process for the production of -caprolactam. In the process, cyclohexanone oxime is rearranged into -caprolactam using a zeolite as a catalyst instead of sulfuric acid. EniChem in Italy developed the ammoximation process that involves the direct production of cyclohexanone oxime without producing any ammonium sulfate. Sumitomo Chemical Co., Ltd. has commercialized the combined process of vapor-phase Beckmann rearrangement and ammoximation in 2003.In this paper, the authors focus on some aspects of the vapor-phase Beckmann rearrangement catalysis. A solid catalyst that is mainly composed of a high-silica MFI zeolite (Silicalite-1) has been developed for the vapor-phase Beckmann rearrangement. This catalyst does not possess acidity that can be detected by ammonia TPD. Methanol fed into the reactor with cyclohexanone oxime improves the yield of caprolactam. Methanol reacts with terminal silanols on the zeolite surface and converts them to methoxyl groups. The modification of the catalyst by methanol has an important role for the Beckmann rearrangement reaction.Nest silanols located just inside the pore mouth of the MFI zeolite are supposed to be the active sites of the catalyst. We propose that the coordination between the NOH group of cyclohexanone oxime molecule and the nest silanols through hydrogen bonding is responsible for the reaction. The reaction mechanism of Beckmann rearrangement under vapor-phase conditions is the same as in the liquid phase, namely, the alkyl group in anti-position against the hydroxyl group of the oxime migrates to the nitrogen atom's position.     

A novel task-specific ionic liquid for Beckmann rearrangement: a simple and effective way for product separation

Under mild conditions and without any additional organic solvents, Beckmann rearrangement of ketoximes was performed in a novel task-specific ionic liquid consisting sulfonyl chloride. Especially for the conversion of cyclohexanone oxime to ε-caprolactam, ε-caprolactam has good solubility in water while the task-specific ionic liquid is immiscible with water, therefore, ε-caprolactam could be easily separated from the reaction system by water extraction.     

A Facile Beckmann Rearrangement of Oximes with AlCl3 in the Solid State

Abstract

A facile and efficient synthetic procedure, for Beckmann rearrangement of oximes with AlCl₃ in the absence of solvent is developed. We have been able to convert cyclohexanone oxime to ?-caprolactam in a quantitative yield.     

Integrated Theoretical and Empirical Studies for Probing Substrate–Framework Interactions in Hierarchical Catalysts

Soft templating with siliceous surfactant is an established protocol for the synthesis of hierarchically porous silicoaluminophosphates (HP SAPOs) with improved mass transport properties. Motivated by the enhanced performance of HP SAPOs in the Beckmann rearrangement of cyclohexanone oxime to the nylon 6 precursor ϵ-caprolactam, an integrated theoretical and empirical study was carried out to investigate the catalytic potential of the siliceous mesopore network. Inelastic neutron scattering (INS) studies, in particular, provided unique insight into the substrate-framework interactions in HP (Si)AlPOs and allowed reactive species to be studied independent of the catalyst matrix. The spectroscopic (INS, FTIR spectroscopy, MAS NMR spectroscopy) and computational analyses revealed that in the organosilane-templated SAPO, the interconnectivity of micro- and mesopores permits cooperativity between their respective silanol and Brønsted acid sites that facilitates the protonation of cyclohexanone oxime in a physical mixture at ambient temperature.     

钛锆复合氧化物载体的制备、物化性质及在催化反应中的应用

 TiO2-ZrO2复合氧化物具有比TiO2和ZrO2更高的比表面积、更好的热稳定性和更强的表面酸碱性,作为催化剂载体已引起很大的研究兴趣并得到了重要的应用. 本文主要介绍了TiO2-ZrO2复合氧化物载体的制备方法以及织构、结构和表面酸碱性等物化性质,并对其在催化反应中的应用进行了综述.     

Al柱层状钛铌酸盐的制备

本文采用分步交换法,首次将[Al~1~3O~4(OH)~2~4(H~2O)~1~2]^7^+Keggin离子交换进入到层状金属钛铌酸盐(KTiNbO~5)的层间.通过焙烧,制备了以Al~2O~3 为柱的层状金属化合物.该化合物具有较高的热稳定性(>500℃)和比较大的层间距(d=1.34nm,500℃)     

Catalyzed Beckmann rearrangement of cyclohexanone oxime in heterogeneous liquid/solid system: Part 2: Influence of acid catalysts and organic promoters

The influence of some transition metal oxide promoters in the catalyzed Beckmann rearrangement of cyclohexanone oxime was studied by preparing several heterogeneous H₂SO₄/M/SiO₂ catalysts using SiO₂ as support and H₂SO₄ as acid source. A definite effect of each metal has been observed and the best results have been obtained with Cr-, Zr- and Zn-oxides based promoter, which have shown an improved selectivity towards -caprolactam formation if compared to the H₂SO₄/SiO₂ catalytic system. Moreover, the influence of some organic promoters on the reaction pathway was investigated. Acetic and trifluoroacetic anhydrides gave the best results, even if only the latter allowed the rearrangement even without solid acid catalysts. The transacetylation of the cyclohexanone oxime by using the acetyl caprolactam, which is the product of rearrangement of the acetyl cyclohexanone oxime, was studied for developing a step wise catalytic cycle. Finally, some preliminary results on a homogeneous organic catalyzed process are reported.