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.     

The cooperation effect of Ni and Pt in the hydrogenation of acetic acid

The catalytic hydrogenation of carboxylic acid to alcohols is one of the important strategies for the conversion of biomass.Herein,a series of Ni-doped PtSn catalysts were prepared,characterized and studied in the hydrogenation of acetic acid.The Ni dopant has a strong interaction with Pt,which promotes the hydrogen adsorption,providing an activated hydrogen-rich environment for the hydrogenation.Meanwhile,the presence of Ni also improves the Pt dispersion,giving more accessible active sites for hydrogen activation.The cooperation of Pt and Ni significantly promotes the catalytic activity of the hydrogenation of acetic acid to ethanol.As a result,the catalyst with 0.1%Ni exhibits the best reaction activity,and its space time yield is twice as that of the PtSn/SiO2 catalyst.It provides a meaningful instruction on the catalyst design for the carboxylic acid hydrogenation.     

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.     

Cobalt catalysts for Fischer–Tropsch synthesis: The effect of support,precipitant and pH value

In this report,Co-based catalysts supported on ZnO,Al_2O_3 and ZrO_2 as well as the ZrO_2 derived from different precipitants and different pH values were prepared by co-precipitation method.Their catalytic Fischer–Tropsch synthesis(FTS)performance was investigated in a fixed-bed reactor.The results revealed that Co catalyst supported on ZrO_2 exhibited better FTS catalytic performance than that supported on ZnO or Al_2O_3.For the Co/ZrO_2catalyst,different precipitants showed the following an activity order of NaOHNa_2CO_3NH_4OH,and the best pH value is 13.The catalysts were characterized by N_2adsorption–desorption,XRF,XRD,H_2-TPR,H_2-TPD and TEM.It was found that the main factor affecting the CO conversion of the catalyst was the amounts of low-temperature active adsorption sites.Moreover,the selectivity of C_5~+hydrocarbons had a positive relationship with the peak temperature of the weak hydrogen adsorption sites.The higher the peak temperature,the higher the C_5~+selectivity is.     

负载型钴铜双金属氮化物催化氨分解研究

Co and Mo bimetallic nitrides supported on Mg（Al）O, MgO and γ-Al2O3 were prepared in temperatureprogrammed reactions with NH3. The surface morphology, chemical composition and catalytic activity for NH3 decomposition on the supported Co and Mo bimetallic nitrides were studied by X-ray diffractometer （XRD）, NH3 temperature-programmed desorption and mass spectrometer （NH3-TPD-MS）, temperature-programmed desorption and mass spectrometer （TPD-MS）, H2 temperature-programmed surface reaction （H2-TPSR） and activity test. The phases of Co3Mo3N and MoN could be formed on Mg（Al）O, MgO and Al2O3 during the nitridation, and they might be more uniformly dispersed on Mg（Al）O and MgO than on γ-Al2O3. Transition metallic nitrides are generally considered as potential catalysts for hydrogen-involving reactions due to the entrance of hydrogen atoms into subsurface and the lattice of metallic nitrides. The diffusion of nitrogen in the bulk and the structure transformation of Co and Mo nitride compounds occur during NH3-TPD, but the supported Co and Mo bimetallic nitrides are not easily reduced at H2 atmosphere. Co3Mo3N/Mg（Al）O catalyst exhibits the highest activity, while Co3Mo3N/Al2O3 exhibits the lowest activity for NH3 decomposition. Furthermore, the catalytic activity of Co and Mo bimetallic nitrides is not only much higher than that of supported single metallic nitride, but also highly dependent upon the surface acidity and BET surface area of support.     

CO_2 methanation over TiO_2–Al_2O_3 binary oxides supported Ru catalysts

TiO_2 modified Al_2O_3 binary oxide was prepared by a wet-impregnation method and used as the support for ruthenium catalyst. The catalytic performance of Ru/TiO_2–Al_2O_3catalyst in CO_2 methanation reaction was investigated. Compared with Ru/Al_2O_3 catalyst, the Ru/TiO_2–Al_2O_3catalytic system exhibited a much higher activity in CO_2 methanation reaction. The reaction rate over Ru/TiO_2–Al_2O_3 was 0.59 mol CO_2·(g Ru)1·h-1, 3.1 times higher than that on Ru/Al_2O_3[0.19 mol CO_2·(gRu)-1·h-1]. The effect of TiO_2 content and TiO_2–Al_2O_3calcination temperature on catalytic performance was addressed. The corresponding structures of each catalyst were characterized by means of H_2-TPR, XRD, and TEM. Results indicated that the averaged particle size of the Ru on TiO_2–Al_2O_3support is 2.8 nm, smaller than that on Al_2O_3 support of 4.3 nm. Therefore, we conclude that the improved activity over Ru/TiO_2–Al_2O_3catalyst is originated from the smaller particle size of ruthenium resulting from a strong interaction between Ru and the rutile-TiO_2 support, which hindered the aggregation of Ru nanoparticles.     

超临界氨合成

Ammonia synthesis at supercritical conditions was first studied over iron and active carbonsupported ruthenium catalysts in a fixed-bed reactor. The influences of 15 kinds of different supercritical media, such as alkanes of C7-C13, 1, 2, 3, 4-tetrahydronaphthalene, cis-decalin, o-xylene,ethylbenzene, quinolin, n-hexane and aniline etc. and reaction conditions (catalyst, temperature, space velocity, particial pressure of media) on ammonia at supercritical condition were investigated.Supercritical medium was decomposed under reaction conditions over Fe and Ru/AC catalysts. The decomposition products deactivated the catalysts. Alkane decomposed the least, and the rate of deactivation was the slowest. Therefore alklane was a relatively good medium. The decomposion of supercritical medium was the key for the deactivation of catalysts. Another important reason for the decrease of ammonia concentration was that the effective pressure of syngas decreased because of the presence of supercritical media. The active temperature of catalyst was the decisive factor in supercritical ammonia synthesis. Supercritical catalytic reaction was viable only at a lower temperature. Ammonia ynthesis at supercritical conditions is possible if a catalyst with active temperature lower than 573 K could e developed and the decomposition of supercritical media could be prevented.     

The effect of copper valence on catalytic combustion of styrene over the copper based catalysts in the absence and presence of water vapor☆

Catalysts Cu Ox/γ-Al_2O_3-IH and Cu Ox/γ-Al_2O_3-IM were prepared, characterized, and tested for styrene combustion in the absence and presence of water vapor. The effect of copper valence of the catalysts on the catalytic activity for styrene combustion was discussed using the theory of hard soft acids and bases(HSAB).The results showed that the existence of water vapor in feed stream inhibited the catalytic activity for styrene combustion due to the competition adsorption of water molecule. HSAB theory confirmed that the local soft acidity of the catalyst Cu Ox/γ-Al_2O_3-IH was much stronger than that of the catalyst Cu Ox/γ-Al_2O_3-IM because of the higher content of soft acid Cu+on its surface, which increased the adsorption ability toward soft base of styrene and reduced the adsorption toward hard base of water vapor, and thus increased the catalytic activity for styrene combustion and weakened the negative influence of water vapor.     

Ni-mediated Liquid Phase Reduction of Carbonyl Compounds in the Presence of Atmospheric Hydrogen

An efficient reduction system of benzaldehyde with hydrogen under ambient pressure was developed using facile NiO catalyst. The non-aromatic solvents such as cyclohexane, tetrahydrofuran （THF） and n-hexane, and the additive with strong basicity e.g. KOH, were necessary for smooth conversion of the substrate. That the catalyst can be recovered and reused for nine times without loss of catalytic activity indicates that this catalyst is a recyclable one for benzaldehyde reduction.     

载体对镍催化剂催化间二硝基苯加氢制间苯二胺反应性能的影响

The hydrogenation of m-dinitrobenzene to m-phenylenediamine in liquid phase was studied with the nickel catalysts supported on SiO2, TiO2, γ-Al2O3, MgO and diatomite carders. Based on the experiments of X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, temperature-programmed reduction （TPR）, temperature-programmed desorption of hydrogen （H2-TPD） and activity evaluation, the physico-chemical and catalytic properties of the catalysts were investigated. Among the catalysts tested, the SiO2 supported nickel catalyst showed the highest activity and selectivity towards m-phenylenediamine, over which 97.3% m-dinitrobenzene conversion and 95.1% m-phenylenediamine yield were obtained at 373K under hydrogen pressure of 2.6MPa after reaction for 6 h when using ethanol as solvent. Although TiO2 and diatomite supported nickel catalysts also presented high activity, they had lower selectivity towards m-phenylenediamine. As for γ-Al2O3 and MgO supported catalysts were almost inactive for the object reaction. It was shown that both the activity and selectivity of the catalysts were strongly depended on the interaction between nickel and the support. The higher activities of Ni/SiO2, Ni/TiO2 and Ni/diatomite could be attributed to the weaker metal-support interaction, on which Ni species presented as crystallized Ni metal particles. On the other hand, there existed strong metal-support interaction in Ni/MgO and Ni γ-Al2O3, which causes these catalysts more difficult to be reduced and the availability of Ni active sites decreased, resulting in their low 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 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.     

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.     

助剂对活性炭负载钴催化剂氨合成活性的影响

采用四槽高压连续流动反应器研究了添加助剂Ba、K和Sm对活性炭负载钴催化剂氨合成活性的影响,结果发现,添加助剂Ba、K和Sm可以提高催化剂的氨合成活性,其中,Ba的促进效果最好,Ba与Co物质的量比为0.3时,催化活性最高。在Ba-Co/AC催化剂中,助剂Sm的加入降低了催化剂的氨合成活性,而少量K助剂(K与Co物质的量比为0.25～0.5)可以提高其催化性能,在10 MPa、10 000 h^-1和450 ℃条件下,双助剂催化剂的氨合成活性可达120 mmol·(g·h）^-1,进一步增加K的量,其氨合成活性下降。     

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.     

Ammonia synthesis on magnesia supported ruthenium catalysts with mesoporous structure

Mesoporous Ru/MgO catalysts for ammonia synthesis were prepared by sol–gel method with concurrently decomposing Ru carbonyl complex. The catalytic properties were characterized mainly by means of nitrogen adsorption isotherm, hydrogen chemisorption, X-ray diffraction, and transmission electron microscopy. The detailed observation of decarbonylation behavior on the catalysts prepared under various conditions revealed that the carbonyl complex acted as an effervescent reagent to form a mesoporous structure with radius of 1–9 nm on MgO support. Furthermore, both specific surface area and metal dispersion tended to increase with increasing the Ru carbonyl complex concentration. The best ammonia formation rate was consequently observed on the Ru/MgO catalyst (Ru: 7.1 wt%) with high surface area (290 m²/g) of this series.     

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。     

表面活性剂辅助溶胶-凝胶法制备掺Ba纳米MgO及其负载钌基氨合成催化剂

在表面活性剂聚乙二醇（PEG）、聚丙烯酸钠（PAAS）、聚乙烯醇（PVA）的辅助下,采用溶胶-凝胶法制备了一系列掺Ba纳米MgO及其负载的氨合成Ru催化剂。并采用场发射扫描电镜、X射线粉末衍射、N2物理吸附-脱附、X射线能谱仪对样品进行表征。结果表明：表面活性剂的添加可改善掺Ba纳米MgO的织构性质和表面性质,并增强钡、镁之间的相互作用,促使了钡在载体中的分散。其中,在10 MPa、425 ℃、10000 h－1的测试条件下,添加5%的PAAS时制得的2%Ru/Ba-MgO催化剂出口氨生成速率达65.9 mmol/(g?h)。     

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...