Hydrodechlorinative dimerization of 1,1,1-trifluorohaloethanes over Ru/SiO2 catalyst

The hydrodechlorination of CCl₃-CF₃ (CFC-113a) was studied over silica-supported metal catalysts. Pd/SiO₂ and Pt/SiO₂ catalysts showed high activity for the replacement reaction of the chlorine atoms in CFC-113a with hydrogen. On the other hand, Ru/SiO₂ selectively catalyzed the dimerization and gave CF₃-CC1=CC1-CF₃ and CF₃-CCl₂-CC1₂-CF₃. CHC1₂-CF₃ (HCFC-123) and CC1₂F-CF₃ (CFC-114a) also dimerized into the corresponding C₄-dimers over the catalyst. The reactivity of CF₃-having haloethanes on the Ru/SiO₂ decreased in the order of CFC-113a > HCFC-123 > CFC-114aHCFC-124. The selectivity of dimerization decreased with decreasing the reactivity of substrates.     

Conversion of CCl2F2 (CFC-12) in the presence and absence of H2 on sol–gel derived Pd/Al2O3 catalysts

Conversion of CCl₂F₂ in the presence (hydrogenolysis) and absence of hydrogen was investigated on Al₂O₃, AlF₃ and Pd/Al₂O₃ xerogel and aerogel catalysts. CCl₂F₂ was found to form CClF₃ and CCl₃F on Al₂O₃ and AlF₃ in the presence and absence of hydrogen as well as on the Pd/Al₂O₃ catalysts in the absence of hydrogen. Overall activity increased during the hydrogenolysis reactions at 230°C as a function of time which was paralleled by a significant increase in the yield of CClF₃ formed through a Cl/F-exchange reaction. X-ray diffraction patterns of the spent catalyst recovered after 3 h of hydrogenolysis confirmed the presence of Pd(C) (Pd–carbon solid solution) and AlF₃ phases on Pd/Al₂O₃ catalysts indicated that the carbon incorporation into the Pd lattice and the transformation of Al₂O₃ to AlF₃ starts at the initial stage of the reaction. It was concluded that AlF₃ is responsible for the Cl/F-exchange reactions. CH₄, a complete hydrogenation product, is formed during hydrogenolysis. Another route for its formation is the reaction between hydrogen in the gas phase and the interstitial carbon.     

Effect of the aluminium fluoride phase for the Cl/F exchange reactions in CCl2F2 (CFC-12) and CHClF2 (HCFC-22)

Two different aluminium trifluorides (-AlF₃ and γ-AlF₃) of high-area have been prepared, characterised by XRPD, N₂ physisorption, IR, X-ray fluorescence, TPD and SEM techniques, and tested for the Cl/F exchange reaction of CCl₂F₂ (CFC-12) and CHClF₂ (HCFC-22) in the gas phase.

Catalyst -AlF₃ is more active than catalyst γ-AlF₃ for both reactions. This is due to both its higher amount of Lewis acid sites, as deduced from ammonia-TPD and pyridine FT-IR studies, and its higher TOF values, which favours the Cl/F exchange in CFC and HCFC compounds. The main products obtained are those which result from the exchange of one chlorine by one fluorine, CClF₃ and CHF₃ for the exchange reaction of CCl₂F₂ and CHClF₂, respectively.     

Decomposition of CCl2F2 over metal sulfate catalysts

Activity for hydrolysis of CCl₂F₂ (CFC12) on various metal sulfate was investigated. Zr(SO₄)₂ was found to be the most active while FeSO₄, Cr₂(SO₄)₃, Al₂(SO₄)₃, La₂(SO₄)₃ and Ce₂(SO₄)₃ had intermediate activity. MnSO₄, CoSO₄, and MgSO₄ showed low activity and SrSO₄, CaSO₄, and BaSO₄ had even less activity. The major carbon containing product was CO₂ and small amount of CClF₃ and CO were formed over several sulfates. The crystal structure of the sulfates was stable during decomposition of CCl₂F₂, and the conversion reached a steady state after initial decrease at 275 °C over Zr(SO₄)₂ catalyst. The concentration of surface hydroxyl was larger than that over AlPO₄-based catalysts and a reaction mechanism similar to that over AlPO₄-based catalysts was proposed.     

Relationship between the structure of Ru/CeO2 catalysts and their activity in the catalytic ozonation of succinic acid aqueous solutions

Two Ru/CeO₂ catalysts were used for the study of the catalytic ozonation of aqueous solutions of succinic acid (SA). These catalysts were prepared either by impregnation (I) or by acid exchange (AE). The objectives were (1) to determine the efficiency towards the oxidation of the organic molecule in relation to the catalysts characterization, and (2) to examine the modifications of the structure induced by ozonation. For each catalyst, two experimental conditions of catalyst and succinic acid concentrations were studied. The diluted conditions ([SA]₀=1 mM, weight_cata=0.8 g/l) were applied for the study of the behavior of the catalysts during successive uses. The efficiency was also studied for higher initial concentrations ([SA]₀=5 mM, weight_cata=3.2 g/l). Under both conditions the best efficiency was obtained with the impregnated catalyst.

Transmission electronic microscopy analyses indicated that before ozonation of SA, ruthenium was distributed within the whole volume of the grain of CeO₂ for the AE catalyst, and included only in an external layer for the I catalyst. The size of the particles determined by X-ray diffraction (XRD) was around 3.5 nm for Ru and in the range 10–75 nm for CeO₂. In most cases, the catalytic ozonation induced Ru sintering with the formation of clusters. After four successive ozonation experiments the AE catalyst efficiency was significantly decreased and the structure totally disorganized.     

Performance and characterization of Ru/Al2O3 and Ru/SiO2 catalysts modified with Mn for Fischer–Tropsch synthesis

Mn effect and characterization on γ-Al₂O₃-, -Al₂O₃- and SiO₂-supported Ru catalysts were investigated for Fischer–Tropsch synthesis under pressurized conditions. In the slurry phase Fischer–Tropsch reaction, γ-Al₂O₃ catalysts showed higher performance on CO conversion and C₅⁺ selectivity than -Al₂O₃ and SiO₂ catalysts. Moreover, Ru/Mn/γ-Al₂O₃ exhibited high resistance to catalyst deactivation and other catalysts were deactivated during the reaction. From characterization results on XRD, TPR, TEM, XPS and pore distribution, Ru particles were clearly observed over the catalysts, and γ-Al₂O₃ catalysts showed a moderate pore and particle size such as 8 nm, where -Al₂O₃ and SiO₂ showed highly dispersed ruthenium particles. The addition of Mn to γ-Al₂O₃ enhanced the removal of chloride from RuCl₃, which can lead to the formation of metallic Ru with moderate particle size, which would be an active site for Fischer–Tropsch reaction. Concomitantly, manganese chloride is formed. These schemes can be assigned to the stable nature of Ru/Mn/γ-Al₂O₃ catalyst.     

合成方法对Ru-Zn/ZrO2苯部分加氢催化剂的影响

分别采用水热-共沉淀法和机械混合法制备Ru-Zn/ZrO2催化剂,并用于苯部分加氢制环己烯反应体系.通过XRD、SEM、TEM等对催化剂的组成、结构和形貌进行表征,对比不同方法合成的催化剂对苯部分加氢反应的影响.结果表明,水热-共沉淀法制备的Ru-Zn/ZrO2催化剂上的Ru分散度高,晶粒尺寸小,催化剂表面苯加氢位点多...     

Investigation of carbonaceous compounds deposited on NiMo catalyst used for ultra-deep hydrodesulfurization of gas oil by means of temperature-programmed oxidation and Raman spectroscopy

NiMo/Al₂O₃ catalyst used for ultra-deep HDS of several gas oils at various conditions was characterized by both temperature-programmed oxidation combined with mass spectroscopy (TPO–MS) and/or gas chromatography (TPO–GC), and Raman spectroscopy to make clear how the catalyst was deactivated. TPO–MS showed the presence of carbonaceous compounds containing H and N atoms on the used catalysts. TPO–GC showed that the combustive property of the carbonaceous compounds sensitively changes depending on the HDS reaction conditions and the position of the catalyst charged in the HDS reactor. A curve fitting analysis of TPO–GC profiles indicated that the carbonaceous compounds combusted below 680 K during TPO were observed on all the spent catalysts examined here whereas more refractory carbonaceous compound (combusted at around 690 K during TPO) was observed on the catalyst that had experienced severe HDS reaction conditions. More refractory carbonaceous compound was preferentially observed on the catalyst charged near the outlet of the HDS reactor. Raman spectra of the carbonaceous compounds indicated that the carbonaceous compounds combusted below 680 K during TPO has an amorphous-like structure whereas the refractory carbonaceous compound has a graphite-like one. Raman spectra also indicated that the graphite-like carbonaceous compound possesses a greater lateral size than the amorphous-like one, implying that the refractory carbonaceous compound can cover the catalyst surface more effectively. The carbonaceous compound having a graphite-like structure is one of main reasons for the catalyst deactivation. It is suggested that the precursor for this type of carbonaceous compound is not formed directly from the feed, but indirectly formed during the HDS of gas oil, because of its preferential deposition on the catalyst charged near the outlet of the HDS reactor.     

Selective hydrogenation of benzene to cyclohexene catalyzed by Ru supported catalysts: Influence of the alkali promoters on kinetics, selectivity and yield

The selective hydrogenation of benzene to cyclohexene in the presence of Ru supported catalysts has been investigated in a tetraphase slurry reactor at 423 K, at 5 MPa of pressure, in the presence of two liquid phases: benzene and an aqueous solution of ZnSO₄ (0.6 mol l⁻¹). A study of the influence of the transport phenomena on the reactivity of the catalyst has been carried out. But no correlation between Carberry and Wheeler–Weisz numbers and the selectivity of the catalysts has been found. The main features of the catalysts are the strong dependence between the catalysts preparation procedure and their activity and selectivity. The best results have been observed with Ru/ZrO₂ catalysts. The influence of the bases employed in the precipitation of the catalysts precursor has also been investigated. KOH is the most effective, yield of 41% and initial selectivity of 80% of cyclohexene has been observed.     

Liquid phase methanol reforming with water over silica supported Pt–Ru catalysts

The mechanism of the liquid phase methanol reforming reaction over silica supported Pt–Ru catalyst was investigated by kinetic studies, employing a pyrex glass reactor with reflux condensers connected to a closed gas circulation system under ambient pressure. The rate of H₂ formation over Pt–Ru/SiO₂ catalysts was more than 20 times faster than that over Pt/SiO₂ catalysts with high selectivity for CO₂ (72.3%), indicating a marked addition effect of Ru. In the case of HCHO–H₂O reaction over Pt–Ru/SiO₂, the H₂ formation rate was five times larger than that in the CH₃OH–H₂O reaction but selectivity to CO₂ was only 4%. On the contrary, in the HCOOCH₃–H₂O and HCOOH–H₂O reactions, both high activity and selectivity were observed over Pt–Ru/SiO₂. These results clearly indicate that the CO₂ formation does not proceed via HCHO decomposition and following water gas shift reaction. We propose the following pathway for liquid phase methanol reforming reaction over Pt–Ru/SiO₂; a partly dehydrogenated methanol (CH₂OH^*) is the initial reaction intermediate, from which H₂ and CO₂ are formed through HCOOCH₃ and HCOOH as the successive reaction intermediates.     

预处理对Ru/Al_2O_3催化马来酸二甲酯加氢影响

采用吸附-沉淀法制备负载Ru质量分数为1.0%的Ru/Al_2O_3催化剂,以马来酸二甲酯催化加氢合成丁二酸二甲酯为探针反应,详细考察预处理条件对Ru/Al_2O_3催化剂加氢性能的影响,并对其进行XRD、TEM和H2-TPR表征。结果表明,焙烧温度越高,催化剂催化活性越低;直接还原活化所得催化剂活性高于空气中焙烧后还原活化所得催化剂。以甲醇为溶剂,在70℃和1.0 MPa条件下,直接还原活化所得Ru/Al_2O_3催化剂上马来酸二甲酯转化率达100%,丁二酸二甲酯选择性约100%。相同时间内,空气焙烧后还原活化所得Ru/Al_2O_3催化剂上马来酸二甲酯转化率接近25%,继续延长反应时间,马来酸二甲酯转化率几乎不变。经高温焙烧还原后,活性组分Ru烧结;直接还原活化后,活性组分Ru高度分散。     

Development of an in-situ H2 reduction and moderate oxidation method for 3,5-dimethylpyridine hydrogenation in trickle bed reactor

The Ru/C catalyst prepared by impregnation method was used for hydrogenation of 3,5-dimethylpyridine in a trickle bed reactor. Under the same reduction conditions (300 °C in H₂), the catalytic activity of the non-in-situ reduced Ru/C-n catalyst was higher than that of the in-situ reduced Ru/C-y catalyst. Therefore, an in-situ H₂ reduction and moderate oxidation method was developed to increase the catalyst activity. Moreover, the influence of oxidation temperature on the developed method was investigated. The catalysts were characterized by Brunauer–Emmett–Teller method, hydrogen temperature programmed reduction H₂-TPR, hydrogen temperature-programmed dispersion (H₂-TPD), X-ray diffraction, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, O₂ chemisorption and oxygen temperature-programmed dispersion (O₂-TPD) analyses. The results showed that there existed an optimal Ru/RuO_x ratio for the catalyst, and the highest 3,5-dimethylpyridine conversion was obtained for the Ru/C-i1 catalyst prepared by in-situ H₂ reduction and moderate oxidation (oxidized at 100 °C). Excessive oxidation (200 °C) resulted in a significant decrease in the Ru/RuO_x ratio of the in-situ H₂ reduction and moderate oxidized Ru/C-i2 catalyst, the interaction between RuO_x species and the support changed, and the hard-to-reduce RuO_x species was formed, leading to a significant decrease in catalyst activity. The developed in-situ H₂ reduction and moderate oxidation method eliminated the step of the non-in-situ reduction of catalyst outside the trickle bed reactor.     

Ru催化加氢选择性脱除F-T合成水相中的含氧化合物

采用催化加氢技术脱除F-T合成水相中羧酸、醛、醇、酮、酯含氧化合物,考察了Ru/ZrO₂、Ru/TiO₂、Ru/SiO₂和Ru/Al₂O₃ 4种Ru催化剂的反应性能.相对于酸、醇,水中的醛、酮、酯更易被转化.其中Ru/ZrO₂和Ru/TiO₂具有良好的加氢脱羰活性,在200℃、9.8 MPa、3.0 h^-1空速下,酸、醛、醇、酮、酯均转化为C₁～C₆的烷烃,总转化率达92%.同条件下,虽然Ru/Al₂O₃对酸、醛、酮、酯的转化活性较高(>87%),但对醇的转化不到30%,具有选择性转化特点.H₂-TPR和NH₃-TPD结果表明,Ru/Al₂O₃催化剂的金属活性位与载体酸性位的协同作用有利于羧酸的加氢反应,能抑制醇的加氢脱羰活性;而金属-载体相互作用较弱和酸度较低的催化剂有利于羧酸、醇发生加氢脱羰反应.Ru/Al₂O₃催化剂运行500 h后失活,XRD、SEM和N₂-物理吸附表明,载体结构物相和织构性质的改变以及活性组分的流失是导致催化剂失活的主要因素.     

Hydrogenation of naphthalene on NiMo- Ni- and Ru/Al2O3 catalysts: Langmuir–Hinshelwood kinetic modelling

The importance of the hydrodearomatisation (HDA) is increasing together with tightening legislation of fuel quality and exhaust emissions. The present study focuses on hydrogenation (HYD) kinetics of the model aromatic compound naphthalene, found in typical diesel fraction, in n-hexadecane over a NiMo (nickel molybdenum), Ni (nickel) and Ru (ruthenium) supported on trilobe alumina (Al₂O₃) catalysts. Kinetic reaction expressions based on the mechanistic Langmuir–Hinshelwood (L–H) model were derived and tested by regressing the experimental data that translated the effect of both naphthalene and hydrogen concentration at a constant temperature (523.15 and 573.15 K over the NiMo catalyst and at 373.15 K over the Ni and Ru/Al₂O₃ catalysts) on the initial reaction rate. The L–H equation, giving an adequate fit to the experimental data with physically meaningful parameters, suggested a competitive adsorption between hydrogen and naphthalene over the presulphided NiMo catalyst and a non-competitive adsorption between these two reactants over the prereduced Ni and Ru/Al₂O₃ catalysts. In addition, the adsorption constant values indicated that the prereduced Ru catalyst was a much more active catalyst towards naphthalene HYD than the prereduced Ni/Al₂O₃ or the presulphided NiMo/Al₂O₃ catalyst.     

Hydrogenation of CO2 over sprayed Ru/TiO2 fine particles and strong metal–support interaction

Ru/TiO₂ catalysts were prepared by spray reaction (SPR) and conventional impregnation (IMP) methods. The catalytic activities of SPR fine particles were much higher than those of IMP catalysts for CO₂ hydrogenation. A high temperature reduction greatly promoted the activity of SPR catalyst. A model of surface structure was proposed which exhibits the enhancement of decoration and the formation of more boundaries over spr-Ru/TiO₂. The high activity of SPR catalyst is attributed to the occurrence of new active sites at the metal–support perimeters and not any SMSI phenomenon. EXAFS reveals that the Ru atom was interacting with TiO₂ by oxygen atom so strongly on the SPR catalysts that a part of the Ru atoms, located near the internal interface between Ru particles and TiO₂ support, existed as Ruⁿ⁺ (n<4) cations even if SPR catalyst was subjected to a high temperature reduction. These Ruⁿ⁺ cations are responsible for the inhibition of SMSI formation over SPR catalysts.     

Pd/C催化剂上CFC-12加氢脱氯生成HFC-32的研究

通过浸渍法制备了Pd/C催化剂,研究了其CFC-12加氢脱氯生成HFC-32性能,考察并优了载体种类及负载量等因素对催化剂性能的影响。在最优催化剂的基础上,得出最佳反应条件为:CFC-12∶H2=1∶4(摩尔比)、总空速为600 mL·g-1(catal.)h-1、反应温度为523 K时。在此反应条件下,CFC-12转化率可达53.4%,对HFC-32选择性为61.5%。并研究了催化剂的稳定性,发现720 h后,催化剂活性方开始下降。     

Low-temperature hydrodechlorination of chlorobenzenes on platinum-supported alumina catalysts

Hydrodechlorination of chlorobenzenes on platinum (Pt)-supported γ-alumina and alumina Lewis superacid (AmLSA) catalysts was carried out at room temperature and ambient pressure using a fixed bed flow reactor and a semi-batch reactor. Both the catalysts indicated good activity for the hydrodechlorination, but the former was superior to the latter. The hydrodechlorinations of reactants C₆H_6−xCl_x (x=1, 2, 3) proceeded step-wisely to benzene and then cyclohexane via C₆H_6−yCl_y (y=x−1). The reactions seem to be promoted by the contribution of spillover hydrogen formed on the Pt-supported catalysts. The catalysts deactivated with reaction time and the amount of chlorine that accumulated on the Pt-supported γ-alumina catalyst in the hydrodechlorination of 1,4-dichlorobenzene for 3 h was near to that estimated from the converted reactant molecules. When the deactivated catalysts were treated in a stream of hydrogen above 503 K, the original activity was completely restored, but the deactivation phenomenon with reaction time was observed again.     

氨分解制氢棒状La x Ce1-x O y 负载Ru催化剂

氨分解得到的H₂不含CO _x 、SO _x 、NO _x 等有害物质,是其他所有含碳资源为原料制氢所不能比拟的。本文采用无模板水热法制备了一系列棒状载体,并采用沉积沉淀法制备了Ru/La _x Ce_1-x O _y 催化剂,考察了制备方法、催化剂组成对性能的影响,并通过扫描电镜（SEM）、X射线衍射（XRD）、BET、H₂-程序升温还原（TPR）和CO₂-程序升温脱附（TPD）进行了表征。结果表明,La₂O₃掺杂量为40%的Ru/La_0.4Ce_0.6O_1.8催化剂在常压、7800h^-1、450℃下氨分解转化率为98%。该催化剂活性高归因于部分还原的CeO_2-x 对Ru的供电子性能和Ru/La_0.4Ce_0.6O_1.8催化剂表面的强碱性增加了对Ru活性位的给电子能力。同时考察了K₂O含量的影响,最优的催化剂为Ru-2%K/La_0.4Ce_0.6O_1.8,在400℃、7800h^-1氨气转化率可以达到93%。结果表明Ru-2%K/La_0.4Ce_0.6O_1.8可以作为一种新型高效氨分解催化剂,为工业化应用提供了可能,具有良好的发展前景。     

Textural properties evolution of Ir and Ru supported on alumina catalysts during hydrazine decomposition in satellite thruster

Ir/Al₂O₃, Ru/Al₂O₃, and Ir-Ru/Al₂O₃ catalysts with total metallic contents of 30% in mass were prepared by an incipient wetness method. The characterization of these materials, before and after their use for hydrazine decomposition in a satellite thruster, was performed by measurement techniques of specific surface area, volume and pores size distribution, H₂ chemisorption, TEM and basic chemical analysis. An average decrease of 11% in the BET surface area was observed, independent of the catalyst composition. The total specific pore volume remained unchanged because the volume reduction in the size range diameters between 1.0 and 10 nm was compensated by the increase in the diameters size range between 10 and 100 nm. A reduction of the H₂ quantity adsorbed on the Ir/Al₂O₃ catalyst can be explained by the metal loss through erosion as well as by its partial occlusion within the pores of the alumina support. On the other hand, catalysts containing Ru showed an increase of H₂ chemisorbed amount, attributed to a more complete reduction of this material after hydrazine decomposition, in spite of the erosion and occlusion losses. Such observations were confirmed by TEM, which showed a great stability of the distributions of the metallic particle sizes in all catalysts.