钌基氨合成催化剂氢氮吸附性能的研究

The effects of promoters K, Ba, Sm on the chemisorption and desorption of hydrogen and nitrogen, dispersion of metallic Ru and catalytic activity of active carbon (AC) supported ruthenium catalyst for ammonia synthesis have been studied by means of pulse chromatography, temperature-programmed desorption, and activity test. Promoters K, Ba and Sm increased the activity of Ru/AC catalysts for ammonia synthesis significantly, and particularly, potassium exhibited the best promotion on the activity because of the strong electronic donation to metallic Ru. Much higher activity can be obtained for Ru/AC catalyst with binary or triple promoters. The activity of Ru/AC catalyst is dependent on the adsorption of hydrogen and nitrogen. The high activity of catalyst could be ascribed to strong dissociation of nitrogen on the catalyst surface. Strong adsorption of hydrogen would inhibit the adsorption of nitrogen, resulted in decrease of the catalytic activity. Ru/AC catalyst promoted by Sm2O3 shows the best dispers     

Effect of Chlorine on the Chemisorptive Properties and Ammonia Synthesis Activity of Alumina-Supported Ru Catalysts

Abstract  

A series of Ru/Al₂O₃ catalysts were prepared to study the effect of the amount and the origin of residual chlorine on chemisorptive property and the ammonia synthesis activity. The catalysts were characterized by X-ray fluorescence, CO chemisorption, transmission Electron Microscopy, X-ray photoelectron spectroscopy, hydrogen temperature-programmed desorption, hydrogen temperature-programmed reduction. It is found that the presence of chlorine had a limited impact on Ru particle size. Residual chlorine originated from RuCl₃ would not influence on Ru 3d_5/2 binding energy, but chlorine from HCl solution significantly increased Ru 3d_5/2 binding energy. Regardless of their source, the presence of chlorine severely reduced the amount of hydrogen species corresponding to the desorption peak at medium temperature. The inhibition effect of chlorine on hydrogen adsorption was more strong for Ru catalyst with residual chlorine from the RuCl₃ precursor. With a similar amount of residual chlorine, the catalysts with chlorine originated from the RuCl₃ precursor showed much lower catalytic activity than those prepared by impregnation of HCl. These results suggest that chlorine mainly affects the catalytic properties of alumina supported Ru catalysts for ammonia synthesis by selective site blocking.     

助剂对苯加氢Ru系催化剂催化性能的影响

以三氯化钌(RuCl3)、硫酸锌(ZnSO4)和硫酸亚铁(FeSO4)为原料,采用共沉淀法制备Ru-Zn及Ru-Fe-Zn催化剂,研究了苯选择加氢制环己烯过程中助剂Zn和Zn/Fe对Ru系催化剂催化加氢性能的影响,并利用透射电镜等对催化剂进行表征。结果表明:Ru-Zn催化剂粒子清晰较为分散,Ru-Fe-Zn催化剂粒径变大,比表面积变小;Ru系催化剂中加入助剂Zn,Ru/Zn摩尔比为7时,环己烯选择性较高,加入第三组分Fe,Zn/Fe摩尔比为10,环己烯选择性进一步提高;Ru-Fe-Zn催化剂具有很好的催化活性和稳定性,苯转化率达54.9%,环己烯选择性达81.8%。     

Influence factors on activity of Ru–Zn catalysts in selective hydrogenation of benzene

Selective hydrogenation of benzene is an atom economic green route to produce cyclohexene. The control of Zn species is the key to the catalytic performance of Ru–Zn catalysts. The influences of ZnO crystals on selective hydrogenation of benzene were explored. A series of Ru–Zn catalysts with different Zn contents and ZnO morphologies were prepared by changing the amount of NaOH in the co-precipitation process. The catalysts were characterized by N_2 physisorption, X-ray powder diffraction(XRD), inductively coupled plasma optical emission spectrometer(ICP-OES), scanning electron microscope(SEM), temperature-programmed reduction(H_2-TPR)and Malvern laser particle size analyzer. It is found that with increasing the amount of NaOH, the Zn content first increased then decreased, and the ZnO crystals changed from relatively thicker pyramidal-shaped crystals to slimmer needle-shaped crystals. The catalyst had the highest Zn content(22.1%) and strongest interaction between ZnO crystals and Ru particles at pH 10.6 of the solution after reduction. As a result, it had the lowest activity. The activity of Ru–Zn catalysts is affected by both the Zn content and the interaction between ZnO crystals and Ru particles. The effect of reduction time was also investigated. Prolonging the reduction time caused no significant growth of ZnO crystals but the aggregation of catalyst particles and growth of Ru nanocrystals, thus resulting in the decrease of catalytic activity.     

助剂对钌基氨合成催化剂活性的作用研究

利用等体积浸渍法制备了活性炭负载钌基氨合成催化剂,考察了助剂Ba、K、Sm对催化活性的影响,探讨了其改善活性的调变规律。用TPD技术研究了氮在系列催化剂上的脱附行为。研究结果表明,助剂Ba、K、Sm的加入显著地提高了催化剂的活性,多助剂催化剂的活性明显优于单助剂催化剂。稀土金属氧化物Sm2O3除具有助催作用外,还有助于催化剂的热稳定性及钌的分散。在钌基氨合成催化反应中,N2 分子的活化离解是速控步骤。氮的脱附活化能愈低,催化活性愈高,其脱附活化能次序为Ru>Ru-Sm>Ru-K>Ru-Ba>Ru-Sm-K>Ru-Sm-Ba>Ru-Ba-K>Ru-Sm-Ba-K。     

Influence of ethylene glycol,ethanol and formic acid on platinum and ruthenium electrodeposition on carbon support material

Carbon supported Pt–Ru catalysts were prepared by potentiostatic deposition at −0.5 V from H₂PtCl₆ + RuCl₃ in H₂SO₄ solution in the presence of ethylene glycol (EG), ethanol (EtOH) and formic acid (HCOOH) as stabilizing agents. The active surface area of the Pt–Ru catalyst was determined by Cu-UPD. The highest value was obtained with HCOOH added, followed by EtOH, and EG. SEM and AFM images showed that the mean particle size of the Pt–Ru nanoparticles was three or four times smaller in the presence of a stabilizer. Electrocatalytic activity measurements indicated that the most active electrode for methanol electrooxidation was obtained with EtOH as additive, followed by EG. The electrode prepared with HCOOH additive gave lower catalytic activity than that without stabilizing agent.     

The promoting effect of Pb on carbon supported Pt and Pt/Ru catalysts for electro-oxidation of ethanol

Carbon supported Pt/Pb and Pt/Ru/Pb catalysts were prepared by deposition of Pb on commercial Pt and Pt/Ru catalysts, respectively. It was found that after addition of Pb, the catalytic activity of Pt and Pt/Ru for ethanol oxidation increased greatly, especially at high potentials. It has been shown that decorating commercial Pt and Pt/Ru catalysts with Pb is a simple and effective way to prepare carbon supported Pt/Pb and Pt/Ru/Pb catalysts for ethanol oxidation. The physical properties of the catalysts were characterized by XRD, EDX and TEM, and it was found that no Pt/Pb and Pt/Ru/Pb alloys were formed.     

Hydroformylation of 1-hexene for oxygenate fuels via promoted cobalt/active carbon catalysts at low-pressure

The hydroformylation of 1-hexene was catalyzed with active carbon-supported cobalt catalysts under the low syngas pressure. Small amount of Pt, Pd and Ru, added as promoters in Co/AC, led to a great improvement of catalytic activity for hydroformylation of 1-hexene. The promotional effect of Ru for Co/AC catalyst was the best in this study as the highest activity and selectivity for oxygenate formation. Meanwhile, the activity of 1-hexene hydroformylation increased with increasing Ru loading. Ru added was bulk-rich in the active carbon supported cobalt particles, showing very low surface Ru density. This kind of unbalanced alloy formation determined the highest performance of Ru added Co/AC catalyst, via small particles but high reduction degree, keeping more CO in non-dissociative state and lowering surface hydrogen pressure.     

Effect of Ru Nanoparticle Size on Hydrogenation of Soybean Oil

Four Ru nanoparticles of different mean sizes from 1.13 to 17.22 nm were prepared and used as catalysts for the selective hydrogenation of polyunsaturated soybean oil at 353 K and initial pressure of 1.5 MPa. The catalyst with the smallest mean size (1.13 nm) had the lowest activity, the activity increased as the mean size increased to 3.10 nm, then decreased with further increase in the mean particle size. The cis–trans isomerization rate decreased with the increase in particle size.     

以KMnO4改性炭黑为载体的Pd-Ni催化剂的制备和性能

以不同浓度的KMnO4溶液预处理的炭黑为载体，通过沉淀共还原法合成了3种Pd1Ni1/ACx (x=3,5,7)催化剂，并将3种催化剂与商业Pd/C催化剂进行了性能对比。用XPS、ICP、XRD和TEM对催化剂了进行表征。结果表明：Pd1Ni1/AC5的Pd负载量（质量分数，下同）最大（3.66%），Pd晶粒的平均粒径最小（4.71 nm），且均匀地分布在KMnO4氧化处理后的碳载体上，活性位点较多；XRD显示，3种Pd1Ni1/ACx催化剂中的Ni均以无定形存在。在电化学性能测试中，3种催化剂均表现出比商业Pd/C更好的电化学稳定性和存活率；其中，Pd1Ni1/AC5电化学活性表面积达62.21 m2/gPd，且乙醇催化活性为1797.85 A/gPd。     

Novel inexpensive transition metal phosphide catalysts for upgrading of pyrolysis oil via hydrodeoxygenation

Supported molybdenum/molybdenum‐phosphides as inexpensive catalysts for bio‐oil hydrodeoxygenation (HDO) were in‐house prepared using different support materials, i.e., Al₂O₃, activated carbon (AC), MgAl₂O₄, and Mg₆Al₂(CO₃)(OH)₁₆. The HDO activity of these catalysts were investigated using a 100 mL bench‐scale reactor operating at 300°C with an initial hydrogen pressure of 50 bar for 3 h with a pyrolysis oil (PO). The catalytic efficiencies for bio‐oil HDO for the catalysts were compared with the expensive but commercially available Ru/C catalyst. Addition of small amount of P to the Mo catalysts supported on either AC and Al₂O₃ led to increased degree of deoxygenation (DOD) and oil yield compared with those without P. MoP supported on AC (MoP/AC) demonstrated bio‐oil HDO activity comparable to the Ru/C catalyst. Furthermore, three AC‐supported metal phosphides for PO HDO were compared under the same conditions, and they were found to follow the order of NiP/AC > CoP/AC > MoP/AC. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3664–3672, 2016     

Characterizations of Ru/ZnO catalysts with different Ru contents for selective hydrogenation of crotonaldehyde

Ru catalysts supported on ZnO with different Ru contents were prepared by an impregnation method and were applied to the vapor-phase selective hydrogenation of crotonaldehyde. The catalysts were characterized by X-ray powder diffraction (XRD), NH₃ temperature-programmed desorption (NH₃-TPD), transmission electron microscopy (TEM) and temperature-programmed oxidation (TPO). It was found that with increasing Ru contents in the Ru/ZnO catalysts, the activity (TOF), surface acidity amount and deactivation rate increased and the selectivity to crotyl alcohol increased first and then decreased. The 3Ru/ZnO catalyst showed the highest selectivity to crotyl alcohol (up to 88.0%) for the hydrogenation of crotonaldehyde. The initial TOF values of the catalysts depended on the strength of surface acidity and the Ru particle sizes. The more Lewis acid sites made catalysts deactivate more easily. It was assumed that the deactivation was due to the formation of organic compounds deposition and poison effect of CO strongly adsorbed on the Ru atoms.     

Influence of Citric Acid on Size Distribution of Ru Particles and the Catalytic Activities of the Ru/AC Catalysts

Citric acid (CA) was used to modify graphited activated carbon (AC) for improving size distribution of Ru particles and catalytic activity of the Ru/AC catalyst. The influence of CA on the texture of AC and Ru/AC, Ru distribution and catalytic activity were investigated. TEM, TGA, TPD-MS, CO pulse chemisorption and N₂ physisorption indicate that CA modified AC creates more functional groups and thus more homogeneous dispersion of Ru nanoparticles. TEM images show most of the Ru particles were ca. 2–2.5 nm for the CA4 + Ru4/AC catalyst. The increase of ammonia synthesis activity for Ru–Ba–K/AC catalyst is more than 16% when the content of CA in AC is 4 wt.% at 673 K and 10,000 h^?1.     

Nd修饰的PtSn/C催化剂对乙醇的电催化氧化性能

利用浸渍还原法,以甲酸为还原剂制备了PtSnNd/C和PtSn/C纳米催化剂。XRD测量了催化剂的粒径和晶格参数,循环伏安法和计时电流法测试了催化剂对乙醇的催化氧化性能。结果表明,添加Nd可以明显提高PtSn/C催化剂对乙醇的电催化氧化活性,峰电流密度增大了86%。     

抑制碳负载钌基氨合成催化剂甲烷化的研究

The effects of promoters K, Ba, Sm on the resistance to carbon-methanation and catalytic activity of ruthenium supported on active carbon (Ru/AC) for ammonia synthesis have been studied by means of TG-DTG (thermalgravity-differential thermalgravity), temperature-programmed desorption, and activity test. Promoters Ba,K, and Sm increased the activity of Ru/AC catalysts for ammonia synthesis significantly. Much higher activity can be reached for Ru/AC catalyst with bi- or tri-promoters. Indeed, the triply promoted catalyst showed the highest activity, coupled to a surprisingly high resistance to methanation. The ability of resistance of promoter to methanation of Ru/AC catalyst is dependent on the adsorption intensity of hydrogen. The strong adsorption of hydrogen would enhance methanation and impact the adsorption of nitrogen, which results in the decrease of catalytic activity.     

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。     

Lattice oxide ion-transfer effect demonstrated in the selective oxidation of propene over silica-supported bismuth molybdate catalysts

Silica-supported bismuth molybdate catalysts were prepared by impregnation in a highly dispersed state and by coprecipitation in a largely crystallized state. Their catalytic behavior was investigated in the oxidation of propene to acrolein. The highly dispersed bismuth molybdate catalysts on silica were found to be intrinsically active but poorly selective to acrolein. When we increased the loading amount the oxidation activity drastically increased. The poor acrolein selectivity of this catalyst was improved by continuous use in the catalytic oxidation for making the particle size of the dispersed bismuth molybdate larger. The catalytic activity and selectivity were little influenced by the loading amount in the cases of the coprecipitated catalysts. The results demonstrate that, for the activity and selectivity, bismuth molybdate catalysts need to be of a certain particle size which can provide sufficient lattice oxide ions during the catalytic redox cycle.     

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.     

硝酸改性对活性炭结构及钌炭催化性能的影响

运用H2脉冲化学吸附、N2低温吸附技术和TPR-MS联用技术研究了酸改性的活性炭（AC）的结构性质,考察了酸处理对活性炭载体物理结构和化学性质的影响。研究表明,酸处理可以显著增加活性炭表面含氧官能团数量,经过改性的活性炭用于制备前驱体RuCl3／AC,Ru组分与含氧官能团之间存在明显的相互作用。酸改性对活性组分Ru的分散度及有效Ru比表面有较大影响,导致了Ru／AC用于催化丁酮加氢活性的显著改善。     

Selective liquid-phase hydrogenation of maleic anhydride to succinic anhydride on biosynthesized Ru-based catalysts

Ru-based catalysts, supported on activated carbon and carbon nanotubes, were synthesized by a simple and eco-friendly bioreduction method and tested in the liquid-phase hydrogenation of maleic anhydride. Over 2.0% Ru/AC, succinic anhydride was produced with a maximum yield of 99.2% without further hydrogenation to γ-butyrolactone. Well-defined spherical shapes with uniform small size of Ru nanoparticles and the residual plant biomass were responsible for the excellent catalytic activities and stabilities.