以RuCl3为前驱体的无氯Ru/Al2O3氨合成催化剂的制备

用等体积浸渍法制备了一种以RuCl₃作为钌母体，分别以γ-Al₂O₃和δ,θ-Al₂O₃为载体的负载型无氯Ru/Al₂O₃氨合成催化剂。该催化剂用水合肼还原，以Sm(NO)₃和Ba(NO₃)₂作助剂。催化剂各组分n(Ru)∶n(Ba)∶n(Sm)=1∶0.55∶1.6。用N₂物理吸附、XRD、XRF和CO化学吸附等方法对载体和催化剂进行表征。结果表明，以δ,θ-Al₂O₃为载体的催化剂，其氨合成活性高于以γ-Al₂O₃为载体的催化剂的活性；用水合肼还原并用热碱液和纯水洗涤的催化剂不残留Cl^-，Ru金属分散度高，其氨合成活性与用无氯钌前驱体制备并用H2还原的催化剂的活性相当，在压力10.0 MPa，空速10 000 h^-1的反应条件下，475 ℃转化率为81.2%，在500 ℃时转化率可以达到100%。而用H₂还原以RuCl₃作为钌母体的Ru/Al₂O₃催化剂时，因还原后催化剂上有Cl^-残留，其催化活性较低。     

Highly efficient subnanometer Ru-based catalyst for ammonia synthesis via an associative mechanism

The industrial manufacture of ammonia (NH₃) using Fe-based catalyst works under rigorous conditions. For the goal of carbon-neutrality, it is highly desired to develop advanced catalyst for NH₃ synthesis at mild conditions to reduce energy consumption and CO₂ emissions. However, the main challenge of NH₃ synthesis at mild conditions lies in the dissociation of steady NN triple bond. In this work, we report the design of subnanometer Ru clusters (0.8 nm) anchored on the hollow N-doped carbon spheres catalyst (Ru-SNCs), which effectively promotes the NH₃ synthesis at mild conditions via an associative route. The NH₃ synthesis rate over Ru-SNCs (0.49% (mass) Ru) reaches up to 11.7 mmol NH₃·(g cat)^-1·h^-1 at 400 ℃ and 3 MPa, which is superior to that of 8.3 mmol NH₃·(g cat)^-1·h^-1 over Ru nanoparticle catalyst (1.20% (mass) Ru). Various characterizations show that the N₂H₄ species are the main intermediates for NH₃ synthesis on Ru-SNCs catalyst. It demonstrates that Ru-SNCs catalyst can follow an associative route for N₂ activation, which circumvents the direct dissociation of N₂ and results in highly efficient NH₃ synthesis at mild conditions.     

Carbon-supported Ru catalyst with lithium promoter for ammonia synthesis

The electronegativity of Li is much higher than that of Na or K, but the ammonia synthesis activities of Li-promoted Ru/AC catalysts were comparable to the values of Ru catalyst promoted with K, which were much higher than those over Ru catalyst with Na promoter. The presence of Li increased the catalytic activity by changing the chemisorption properties such as hydrogen adsorption and nitrogen adsorption for carbon-supported Ru catalysts, rather than affecting the sizes of Ru particles or the electron density of Ru metal.     

The temperature-programmed desorption of N2 from a Ru/MgO catalyst used for ammonia synthesis

The temperature-programmed desorption (TPD) of N₂ from a Ru/MgO catalyst used for ammonia synthesis was studied in a microreactor flow system operating at atmospheric pressure. Saturation with chemisorbed atomic nitrogen (N-*) was achieved by exposure to N₂ at 573 K for 14 h and subsequent cooling in N₂ to room temperature. With a heating rate of 5 K/min in He, a narrow and fairly symmetric N₂ TPD peak at about 640 K results. From experiments with varying heating rates a preexponential factor A_des = 1.5×10¹⁰ molecules/(site s) and an activation energy E_des = 158 kJ/mol was derived assuming secondorder desorption. This rate constant of desorption is in good agreement with results obtained with a Ru(0001) single crystal surface in ultra-high vacuum (UHV). The rate of dissociative chemisorption was determined by varying the N₂ exposure conditions. Determination of the coverage of N-^* was based on the integration of the subsequently recorded N₂ TPD traces yielding A_ads = 2×10^–6 (Pa s)^–1 and E_ads = 27 kJ/mol. The corresponding sticking coefficient of about 10^–14 at 300 K is in agreement with the inertness of Ru(0001) in UHV towards dissociative chemisorption of N₂. However, if the whole catalytic surface were in this state, then the resulting rate of N₂ dissociation would be several orders of magnitude lower than the observed rate of NH₃ formation. Hence only a small fraction of the total Rumetal surface area of Ru/MgO seems to be highly active dominating the rate of ammonia formation.     

Ru/Al2O3催化剂表面分形分析

利用静态氮吸附仪在-196.15 ℃液氮气氛中,测定Ru/Al2O3催化剂的比表面积以及孔结构参数,研究了催化剂的孔容-孔径分布和吸附-脱附等温线。基于FHH多层吸附模型,利用全吸附数据计算出Ru/Al2O3催化剂的表面分形维数。结果表明,3种Ru/Al2O3催化剂的表面分形维数均约2.4,分形维数与比表面积和总孔体积无直接关联。     

活性炭负载钌催化剂上氨合成反应动力学研究

在固定床反应器中对Ba-Ru-K/AC催化剂在相应的工业条件下［温度(350~450) ℃,压力10 MPa,V(H₂)∶V(N₂)=1.0、1.5、2.0、2.5和3.0,空速(60 000~180 000) h^－1］,进行了系列动力学测试。采用改进的Temkin动力学方程对实验数据进行拟合,考虑到H₂和NH₃的吸附对催化剂作用的阻碍效应,优化得到动力学模型参数n、α、w₁和w₂分别为1、0.15、0.5和1.4。结果表明,在Temkin方程中加入H₂和NH₃的吸附项能够获得可靠的动力学模型,用Arrhenius和Van’t Hoff方程对动力学和热力学参数k、K_H2和K_NH3进行线性拟合,得到氨合成反应的活化能为90.2 kJ·mol^－1,远低于铁基催化剂,说明Ru上N₂的解离吸附活化能垒远低于传统磁铁矿基催化剂和维氏体基催化剂。H₂的吸附热为76.2 kJ·mol^－1,证明Ba-Ru-K/AC催化剂上H₂的吸附较强烈,对N₂的吸附有强烈的抑制作用。改进的Temkin动力学方程能应用于使用Ru/C催化剂的氨合成反应器的设计和操作。     

活性炭表面改性对钌基氨合成催化剂的影响

研究了活性炭经HNO₃进行表面改性后对Ru/AC催化剂的影响。利用表面官能团滴定、N₂物理吸附和CO化学吸附方法对催化剂进行表征,并对催化剂进行氨合成活性评价。结果表明,活性炭经适量的HNO₃改性处理后,中孔有所增加,更主要的是增加了表面羧基,使活性炭的亲水性得到提高,从而提高了以水溶液浸渍法制备的Ru/AC催化剂的活性以及Ru的分散度;但过量HNO₃的改性处理会使活性炭表面不稳定基团增加,这些不稳定基团会降低Ru/AC催化剂的活性以及Ru的分散度。用5 mol·L^-1的HNO₃进行改性处理可以达到最优的效果。     

反应条件对钌催化剂和铁催化剂的氨合成性能影响

Activated carbon-supported Ru-based catalyst and A301 iron catalyst were prepared,and the influences of reaction temperature,space velocity,pressure,and H2/N2 ratio on performance of iron catalyst coupled with Ru catalyst in series for ammonia synthesis were investigated.The activity tests were also performed on the single Ru and Fe catalysts as comparison.Results showed that the activity of the Ru catalyst for ammonia synthesis was higher than that of the iron catalyst by 33.5%-37.6% under the reaction conditions:375-400 °C,10 MPa,10000 h-1,H2︰N2 3,and the Ru catalyst also had better thermal stability when treated at 475 °C for 20 h.The outlet ammonia concentration using Fe-Ru catalyst was increased by 45.6%-63.5% than that of the single-iron catalyst at low tem-perature (375-400 °C),and the outlet ammonia concentration increased with increasing Ru catalyst loading.     

FCC汽油选择性加氢脱硫催化剂Ru/Al_2O_3的研究

以900℃焙烧的Al_2O_3为载体,用浸渍法制备了蛋壳型Ru催化剂,Ru的负载质量分数为3%,并对催化剂进行了BET和XRD表征。催化剂活性评价在高压微反装置上进行,以FCC汽油为原料,评价前催化剂预硫化。结果表明,400℃高温焙烧会造成Ru的烧结,不焙烧(仅120℃干燥6h)的催化剂具有较高活性,对于FCC汽油的选择性加氢脱硫,在300℃、2.0MPa、空速2h~(-1)和氢油体积比=200:1条件下,FCC汽油的加氢脱硫率达66.4%,烯烃加氢饱和率达24.7%,选择性因子仅为3.8。单组分Ru催化剂用于FCC汽油的加氢脱硫时有一定的选择性,但结果不理想。     

Introducing trace Co to molybdenum carbide catalyst for efficient ammonia synthesis

Development of the cost-effective catalysts with excellent catalytic performance is highly demanded for ammonia synthesis, and the strong adsorption of ammonia greatly hinders the design of cost-effective and high-performance ammonia synthesis catalysts. Herein, we report that the addition of a small amount of Co species (0.1 wt%) into Mo₂C catalyst, which can provide electrons to Mo₂C, not only leads to improvement of the adsorption and migration of hydrogen, but also facilitates the adsorption and desorption of ammonia. Consequently, Mo₂C catalyst with 0.1 wt%Co offers a 40% higher ammonia synthesis activity and a lower negative reaction order with respect to NH₃ in comparison to Mo₂C. This work stresses the importance of the minor components in improving the ammonia synthesis activity by accelerating the migration of reactants over the catalyst surface and the escape of products from the catalyst.     

A facile,efficacious and reusable Sm2O3/ZrO2 catalyst for the novel synthesis of functionalized 1,4-dihydropyridine derivatives

An efficient four component/one-pot protocol was developed for synthesis of novel functionalized 1,4-dihydropyridines at room temperature by a reaction of malononitrile, substituted aldehydes, dimethylacetylenedicarboxylate and 4-fluoroaniline in ethanol and using Sm₂O₃/ZrO₂ as catalyst. All reactions were completed in < 20 min. The structures of all the new compounds were confirmed by different spectral analyses. The catalyst, Sm₂O₃/ZrO₂ was synthesized and characterized by various techniques including powder X-ray diffraction, N₂ adsorption/desorption, scanning electron microscopy, and transmission electron microscopy analysis. The key advantages of this process are good to high yields (87 to 96%), short reaction times, easy work-up, reusability and no chromatographic purification.     

An efficient novel regeneration method for Ca-poisoning V2O5-WO3/TiO2 catalyst

Ca poisoning and regeneration on V₂O₅-WO₃/TiO₂ catalysts for selective catalytic reduction of NOx was investigated based on the changes of activity, structure, reducibility, acidity and reaction details. It is found that high contents of CaO can lead to CaWO₄ formation and thus passivate bulk tungsten species and surface acid sites of fresh catalyst. Additionally, reactable surface oxygen species and reducibility are also greatly suppressed by CaO species. However, unlike previous regeneration method, HEDP showed exclusive and excellent removal rate of CaO without large active ingredients loss, which had a better prospect of industrial application.     

Activity and stability of Cu/ZnO/Al2O3 catalyst promoted with B2O3 for methanol synthesis

The addition of B₂O₃ to a Cu/ZnO/Al₂O₃ catalyst increased the activity of the catalyst for methanol synthesis after an induction period during the reaction. The stability of the B₂O₃-containing Cu/ZnO/Al₂O₃ catalyst was greatly improved by the addition of a small amount of colloidal silica to the catalyst. This revised version was published online in July 2006 with corrections to the Cover Date.     

沉淀剂对Ru/MgO-CeO2氨合成催化剂催化性能的影响

以K<,2>RuO<,4>为钌前驱体,通过共沉淀法制备了Ru/MgO-CeO<,2>氨合成催化剂.考察了5种不同沉淀剂对Ru/MgO-CeO<,2>催化剂的结构和性能的影响,并运用X射线衍射(XRD)、CO吸附、N<,2>物理吸附和H<,2>程序升温还原(H<,2>-TPR)等技术对催化剂进行了表征,讨论了沉淀剂对氨合...     

Highly active Mo/Al2O3 hydrodesulfurization catalyst presulfided with ammonium thiosulfate

Ammonium thiosulfate ((NH₄)₂S₂O₃) was used as an ex situ sulfiding agent to pretreat Mo/Al₂O₃ catalyst through impregnation. After H₂ activation, Mo/Al₂O₃ presulfided with (NH₄)₂S₂O₃ exhibits much higher catalytic activity in thiophene hydrodesulfurization (HDS) than Mo/Al₂O₃ in situ sulfided by dimethyl disulfide. Through (NH₄)₂S₂O₃ presulfidation, Al₂O₃ support is modified by sulfate groups, leading to a decrease of interaction between Mo and support; this promotes the formation of multi-layer type II MoS₂ that contributes to the high HDS activity of the ex situ presulfided Mo/Al₂O₃ catalyst.     

Nitrogen-doped reduced graphene oxide/Fe2O3 hybrid as efficient catalyst for ammonium nitrate

In this investigation, we successfully synthesized a hybrid material, N-rGO@Fe₂O₃, via a one-step hydrothermal process, comprising nitrogen-doped reduced graphene oxide and α-Fe₂O₃. Thorough characterization using diverse analytical methods validated its structure. Employing this hybrid composite as a catalyst, we studied its efficacy in the catalytic thermal decomposition of ammonium nitrate (AN). The N-rGO@Fe₂O₃/AN composite was prepared using a recurrent spray coating method with 3 % mass of the hybrid material. Thermo-gravimetric (TG) and differential scanning calorimetric (DSC) analyses were employed to investigate the catalytic effect. Computational assessment of Arrhenius parameters was conducted through isoconversional kinetic approaches. Results from the kinetic analysis allowed the determination of the critical ignition temperature. Furthermore, calorific values for pure AN and N-rGO@Fe₂O₃/AN were measured using an oxygen calorimetric bombe, revealing a 41 % reduction in activation energy barrier and a lowering of the critical ignition temperature from 292 °C to 283 °C upon incorporation of the hybrid material. Notably, the surface modification of AN with N-rGO@Fe₂O₃ resulted in an increase of 1440 J/g in the observed calorific values. These findings highlight the potential of N-rGO@Fe₂O₃ as an effective catalyst, offering promising implications for applications in enhancing ammonium nitrate thermal decomposition.     

焙烧温度对Ru/Ba-Mg(Al)O4氨合成催化剂性能影响

采用超声-沉淀-强静电吸附法制备了化学性质比较稳定的掺钡纳米镁铝复合氧化物Ba-Mg(Al)O₄,并以其为载体、Ru₃(CO)₁₂为活性组分前驱体,制备了一系列钌基氨合成催化剂。通过场发射扫描电镜、X射线衍射和N2物理吸附等表征手段,重点考察了焙烧温度对载体的物相组成和表面织构的影响。结果表明,随着焙烧温度的升高,制备的载体比表面积逐渐下降,表面碱性增强。当载体焙烧温度为780 ℃时,制备的负载型Ru/Ba-Mg(Al)O₄催化剂表现出较高的催化活性,在425 ℃、10 MPa和10 000 h^-1条件下,出口氨浓度达到49.17 mmol·(g·h)^-1。     

载体焙烧温度对Ni/CuO-ZrO_2-CeO_2-Al_2O_3催化剂在甲烷自热重整制氢反应中催化性能的影响

采用浸渍-共沉淀法制备Ni/CuO-ZrO_2-CeO_2-Al_2O_3催化剂,Ni负载质量分数为10%。在固定床微反装置考察载体焙烧温度(600℃=、700℃、800℃和900℃)对Ni/CuO-ZrO_2-CeO_2-Al_2O_3催化剂在甲烷自热重整制氢反应中催化性能的影响。结果表明,载体焙烧温度800℃制备的催化剂活性较好。由XRD和TPR分析可知,随着焙烧温度的升高,各衍射峰的峰强度增强,峰尖锐,说明随着焙烧温度的升高,催化剂中各氧化物晶粒增大。焙烧温度800℃的Ni/CuO-ZrO_2-CeO_2-Al_2O_3催化剂的NiO峰强度较小,说明在该催化剂上NiO以高度分散的状态存在于催化剂表面。     

固体超强酸S2O2-8/ZrO2-CeO2催化合成乳酸丁酯的研究

以固体超强酸S2O2-8/ZrO2-CeO2为催化剂,乳酸和正丁醇为原料合成乳酸丁酯.考察了催化剂的用量,反应物的配比、反应时间、反应温度、催化剂重复使用等因素对反应的影响.结果表明,催化合成乳酸丁酯的最佳条件为:n(丁醇):n(乳酸)=3.0:1.0,w(S2O2-8/ZrO2-CeO2)=12.0%(相对于乳酸),温度145℃,反应2.0 h,乳酸的醇化率达96.6%,催化剂可重复多次使用.     

Magnetically separable Fe3O4/graphene oxide nanocomposite: An efficient heterogenous catalyst for spirooxindole derivatives synthesis

Heterocyclic compounds such as spirooxindole, with five rings containing nitrogen, have an important role in the realm of medicine. This study aims to synthesize the spirooxindole derivative compounds using Fe₃O₄/graphene oxide (GO) nanocomposite as the catalyst. The GO sample was synthesized by Hummers' method, followed by the insertion of Fe₃O₄ into the graphene oxide layers by the co-precipitation method. Both XRD and FTIR analyses reveal that GO and Fe₃O₄/GO samples have been successfully formed. SEM-EDX micrograph supported by TEM image indicates that the Fe₃O₄ nanoparticles in the composite have excellent dispersibility, attributable to the existence of the GO sheets. The evaluation of the ability of Fe₃O₄/GO as a catalyst in the synthesis of spirooxindole derivatives was carried out by the one-pot three-component method. The reaction yield shows that Fe₃O₄/GO was a suitable and reusable catalyst in this reaction.