Hydrodechlorination of 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113) over supported ruthenium and other noble metal catalysts

The hydrodechlorination of CCl₂F–CClF₂ (CFC-113) was studied using silica- and activated carbon-supported Ru, Rh, Pd, and Pt catalysts. The activity of the catalysts changed with time-on-stream. Ru was most stable among the four noble metals and gave a simple product distribution yielding CClF=CF₂ (CFC-1113) and CHClF–CClF₂ (HCFC-123a) as main products. Over silica-supported Ru, CFC-1113 yield decreased gradually with time-on-stream but HCFC-123a yield did not change throughout the reaction, suggesting that these products were formed on different sites of Ru. XRD studies and temperature-programmed reduction of the spent catalyst revealed that the deactivation was caused by halogen-containing carbonaceous species accumulated on the Ru surface during the reaction. The carbonaceous species seemed to be formed on the active site for CFC-1113 formation. Because CFC-1113 selectivity was higher over the catalyst having higher Ru dispersion, it was assumed that the hydrodechlorination of CFC-113 is structure-sensitive and CFC-1113 formation is promoted by Ru having highly unsaturated coordination sphere.     

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。     

Methanation of carbon dioxide over Ru/Titania at room temperature: explorations for a photoassisted catalytic reaction

The methanation of CO₂ has been investigated over a special Ru/TiO₂ catalyst suggested by Thampi, Kiwi and Graetzel [4]. This paper deals with the analysis of the material and the investigation of the reported photoenhancement of the activity. The catalyst is characterised by in situ UV-VIS spectroscopy and by XPS. Conversion experiments at atmospheric pressure were carried out with and without UV light irradiation. The irradiation increases the conversion significantly. From various experiments it can be shown, however, that this effect is due to a thermal effect and does not involve an intrinsic photochemical step. Localised Ti³⁺ states sensitise the support to convert visible light into heat resulting in the observed increase in conversion.     

Plasma catalytic methane conversion over sol–gel derived Ru/TiO2 catalyst in a dielectric-barrier discharge reactor

Plasma catalytic methane conversion was carried out in the presence of sol–gel derived Ru/TiO₂ catalysts within a dielectric-barrier discharge (DBD) reactor. Plasma-assisted reduction (PAR) was applied to reduce the prepared Ru/TiO₂ catalysts in DBD reactor, and most of the catalysts were successively reduced by PAR within 15 min. The highest methane conversion was obtained when 5 wt% Ru/TiO₂ catalysts were used after calcination at 400 °C. The selectivities of light alkanes (C₂H₆, C₃H₈, C₄H₁₀) were highly increased when Ru/TiO₂ catalysts were used in DBD reactor.     

Partial oxidation of methane over ruthenium catalysts

The catalytic partial oxidation of methane with oxygen to produce synthesis gas was studied under a wide range of conditions over supported ruthenium catalysts. The microreador results demonstrated the high activity of ruthenium catalysts for this reaction. A catalyst having as little as 0.015% (w/w) Ru on Al₂O₃ gave a higher synthesis gas selectivity than a catalyst having 5% Ni on SiO₂. XANES measurements for fresh and used catalyst samples confirmed that ruthenium is reduced from ruthenium dioxide to ruthenium metal early during the experiments. Ruthenium metal is thus the active element for the methane partial oxidation reaction.     

Oxidative methane conversion to carbon monoxide and hydrogen at low reactor wall temperatures over ruthenium supported on silica

Oxidative methane conversion to carbon monoxide and hydrogen is catalyzed over ruthenium supported on silica at reactor wall temperatures as low as 400° C when the flow rate of reactants (methane and oxygen) is significantly high. The conversion of methane and the yields of carbon monoxide and hydrogen increase with increase in the flow rate of the reactants while oxygen is always completely consumed. Addition of carbon dioxide to the reactant flow can increase the yield of carbon monoxide in the reaction, suggesting that carbon dioxide functions as an oxidant and the actual surface temperature of the catalyst is sufficiently high that thermal conversion of methane via carbon dioxide and water can take place.     

Influence of Pd Precursor and Method of Preparation on Hydrodechlorination Activity of Alumina Supported Palladium Catalysts

A series of alumina supported Pd catalysts were prepared by the novel deposition-precipitation method adopting the chloride precursor (DP-Cl) of Pd and varying the metal content from 0.25 to 1.0 wt%. The catalytic properties of prepared catalysts were studied by various characterization techniques such as N₂ adsorption, CO chemisorption, TPR, XRD, XPS, and TEM techniques. The activity and stability of the catalysts were evaluated for the gas phase hydrodechlorination (HDC) of chlorobenzene operating at atmospheric pressure. At 1 wt% of Pd the catalyst showed higher chlorobenzene conversion with good stability when tested for a period of 25 h, whereas the other catalysts exhibited a loss in activity with time. In order to elucidate the exceptional activity and stability of this catalyst, a few more catalysts with 1 wt% Pd were prepared by impregnation technique and also using a non-chloride precursor, palladium nitrate. The 1 wt% DP-Cl catalyst again was found to be the best among the others. The activity and stability of the DP-Cl catalyst was also found to be superior to two low-dispersed catalysts, each with 10 wt% Pd, prepared by conventional impregnation method using the chloride and nitrate as the precursors. The characterization results reveal that the high activity and stability of the DP-Cl catalyst is related to the formation of electron deficient Pd species and its stabilization in the octahedral vacancies of alumina.     

Ru/Na-H-ZSM-5双功能催化剂催化对苯二酚加氢

采用浸渍沉淀法制备了Ru/Na-H-ZSM-5系双功能催化剂,利用XRD、SEM、TEM、FT-IR及电泳仪等对催化剂结构、晶形外貌、孔道特点及表面电性进行测试,并在釜式反应器中进行催化性能评价。结果表明,Ru/Na-H-ZSM-5双功能催化剂用量0.5 g,反应压力3.0 MPa,反应温度130℃,反应时间3.0 h和Ru负载质量分数3.0%的条件下,对苯二酚转化率可达98.9%,目标产物1,4-环己二醇选择性达到85.2%。催化剂Ru/Na-H-ZSM-5用于对苯二酚加氢制备1,4-环己二醇反应活性组分Ru是关键所在,而分子筛结构以及电负性对于其反应有重要影响。     

Ru／C催化剂上硝基苯与苯甲醇“一锅法”合成N-亚苄基苯胺的研究

采用软模板法制备出多孔碳材料,以此为载体采用浸渍法制备了Ru／C催化剂,用于硝基苯与苯甲醇“一锅法”合成N-亚苄基苯胺中。利用XRD、SEM、TEM等方法对催化剂进行了表征。考察了Ru负载量对催化剂催化性能的影响,并对反应条件进行了优化。结果表明,Ru负载量为5．0wt％时Ru／C催化剂具有最佳的催化活性和选择性。在实验优化条件下反应22h,硝基苯转化率为100％,N-亚苄基苯胺选择性可达94．1％。     

溶剂对Pd/C催化四氯化碳液相加氢反应的影响

考察了活性组分、载体、Pd含量及溶剂对四氯化碳液相催化加氢转化为氯仿反应的影响。实验结果表明，质量分数0.5%的Pd/C是四氯化碳液相催化转化的较优催化剂。溶剂对该反应的速率和产品分布有显著影响，在正庚烷、甲苯和甲醇3种溶剂中，甲醇最利于提高Pd/C催化剂的活性，且四氯化碳转化的平均反应速率随着甲醇含量的增加呈现先增大后减小的趋势，氯仿的选择性随着甲醇含量的增加有所降低。当甲醇和四氯化碳的体积比为2∶1时，四氯化碳转化速率最高。甲醇和四氯化碳的体积比为1∶10时，氯仿的选择性达90%。     

Ru/CNTs催化合成1,4-环己二胺工艺及反应机理

以碳纳米管为载体制备Ru/CNTs催化剂,系统考察反应温度、反应压力、反应时间、催化剂用量、溶剂种类、助剂和催化剂重复使用性能等对催化对苯二胺合成1,4-环己二胺的影响,同时对催化反应机理进行探讨。结果发现,反应为串联反应,较高的反应温度、反应压力、催化剂用量和较长的反应时间利于提高转化率,但过高的反应温度、反应压力和过长的反应时间会导致副反应发生,产物收率下降。适宜的反应条件为:反应温度120℃,反应压力6 MPa,反应时间3 h,对苯二胺10 g,40 mL异丙醇作溶剂,助剂氢氧化锂添加量0.1 g,5%Ru/CNTs催化剂用量0.5 g,此条件下,对苯二胺转化率100%,1,4-环己二胺收率93.87%,催化剂重复使用11次后仍保持较高活性。     

The oxidative dehydrogenation of ethane with CO2 over Mo2C/SiO2 catalyst

Mo₂C prepared on SiO₂ was found to be an effective catalyst for the dehydrogenation of ethane to produce ethylene in the presence of CO₂. The selectivity to ethylene at 850–923 K was 90–95% at an ethane conversion of 8–30%. With the increase of the temperature the dry reforming of ethane became also a significant process. It is assumed that the Mo oxycarbide formed in the reaction between CO₂ and Mo₂C plays an important role in the activation of ethane. This revised version was published online in July 2006 with corrections to the Cover Date.     

Catalytic hydrogenation of carbon monoxide over silica-supported Ir-Mo-Rh catalyst

We present here some results on Ir-Mo-Rh metallic catalysts for the synthesis of C₂-C₄ alcohols from syngas. It was found that Ir-Mo-Rh supported on silica containing small amounts of Rh exhibited much higher activity for CO hydrogenation than Ir-Mo bimetallic catalyst. The selectivity to various alcohols did not change very much upon the addition of Rh. The activity was greatly affected by the impregnation procedure of the metals in the catalyst preparation.     

Methanol synthesis from carbon dioxide at atmospheric pressure over Cu/ZnO catalyst. Role of methoxide species formed on ZnO support

Methanol synthesis from CO₂ and H₂ was carried out over a Cu/ZnO catalyst (Cu/Zn = 3/7) at atmospheric pressure, and the surface species formed were analyzed by diffuse reflectance FT-IR spectroscopy and temperature programmed desorption method. Two types of formate species and zinc methoxide were formed in the course of the reaction. Zinc methoxide was readily hydrolyzed to methanol. H₂O formed through the reverse water gas shift reaction was suggested to be involved in the hydrolysis of zinc methoxide.     

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。     

Co-decorated carbon nanotube-supported Co–Mo–K sulfide catalyst for higher alcohol synthesis

Using chemical reduction-deposition method, a type of metallic cobalt-decorated multi-walled carbon nanotubes, noted as y%(mass percentage)Co/MWCNTs, was prepared. TEM, SEM and XRD measurements demonstrated that the metallic cobalt was evenly coated on the MWCNT substrate, with granule-diameter of the Co _x ⁰ -crystallites of 5–8 nm. Using the y%Co/MWCNTs as support, a type of supported Co–Mo–K sulfide catalysts, noted as x%(Co _i Mo _j K _k )/(y%Co/MWCNTs), for higher alcohol synthesis (HAS) was developed. It was experimentally shown that using the Co-modified MWCNTs in place of simple MWCNTs or activated carbon (AC) as the catalyst support led to a significant increase in activity of CO hydrogenation conversion and improvement in the selective formation of C₂₊-alcohols. Under the reaction condition of 5.0 MPa, 613 K, CO/H₂/N₂ = 45/45/10 (v/v) and GHSV = 3600 ml_STPh⁻¹ g _−cat. ⁻¹ , the observed STY of C_1–4-alcohols reached 154.1 mgh⁻¹g _−cat. ⁻¹ at 12.6% conversion of CO over the 11.6%(Co₁Mo₁K_0.6)/(6.4%Co/MWCNTs) catalyst, which was 1.76 and 2.33 times as high as that (87.7 and 66.1 mgh⁻¹g _−cat. ⁻¹ ) of the reference systems supported by simple MWCNTs and AC respectively. Ethanol became the predominant product of the CO hydrogenation, with carbon-based selectivity ratio of C_2–4-alcohols to CH₃OH reaching 3.6 in the products. It was experimentally found that using the Co-modified MWCNTs in place of simple MWCNTs or AC as the catalyst support caused little change in the apparent activation energy for the conversion of CO, but led to a slight increase in the molar percentage of catalytically active Mo-species (Mo⁴⁺) in the total Mo-amount at the surface of the functioning catalyst. Based upon the results of TPD investigation, it could be inferred that, under the reaction condition of HAS, there existed a considerably larger amount of adsorbed H-species and CO-species on the functioning catalyst, thus in favour of increasing the rate of a series of surface hydrogenation reactions in HAS.     

Formation of carbon nanotubes from the carbon monoxide disproportionation reaction over Co/Al2O3 and Co/SiO2 catalysts

The ammonia method has been successfully used for preparing thermostable and well dispersed alumina‐supported catalysts with a surface average size of cobalt particle D _{s= 5.7} nm. The disproportionation reaction of CO over this Co/Al₂O₃ catalyst and a similar Co/SiO₂ catalyst leads to the formation of carbon nanotubes demonstrating the same morphology. The amount of nanotubes over Co/Al₂O₃, however, is much larger than that obtained over Co/SiO₂, because of a faster ageing in the latter solid. Similar support effects have already been reported for other catalytic reactions involving carbon oxides. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pd/C催化剂催化邻硝基苯胺加氢制备邻苯二胺

卤代芳胺是重要的有机中间体,广泛应用于合成染料、农药、医药、香料及橡胶助剂等。卤代芳香硝基化合物通过液相催化加氢制备卤代芳胺的技术以其环境友好、产品质量稳定和工艺先进而受到重视。用负载型贵金属催化剂催化芳香硝基化合物选择加氢制备相应的芳胺有广泛的应用价值。采用邻硝基苯胺为原料,Pd/C为催化剂,低压催化加氢还原合成邻苯二胺,考察不同溶剂、反应压力、反应温度和反应时间对产物收率的影响。结果表明,在甲醇为溶剂、反应温度100 ℃、反应压力0.8 MPa和反应时间100 min条件下,邻苯二胺平均收率为97%。与传统硫化碱还原或铁粉化学法还原工艺相比,以甲醇为溶剂,Pd/C催化剂催化加氢法在减少废水和降低成本等方面有较大优势。     

Ru/AlOOH催化丙酸甲酯加氢反应研究

采用浸渍、水热还原的方法制备了Ru/A lOOH催化剂,进行了XRD表征。以水作溶剂,考察了该催化剂对丙酸甲酯的催化加氢性能。结果表明,催化剂中金属以Ru0存在,并且很好的分散在载体A lOOH上;反应时间、温度、氢气压力和溶剂体积对丙酸甲酯加氢转化率和目标产物丙醇选择性都有很大的影响。在180℃、氢压5 MPa条件下,反应10 h,丙酸甲酯的转化率达到85.9%,丙醇的选择性为94.0%。