氮化碳负载钯催化剂催化苯酚加氢制环己酮

为了开发苯酚加氢制环己酮高效催化剂,将脲在550 ℃高温聚合,制备了片层状氮化碳催化剂载体g-CN;负载钯纳米粒子后,得到Pd/g-CN催化剂。采用红外光谱、X射线粉末衍射、透射电镜和X射线光电子能谱对催化剂进行表征。将Pd/g-CN催化剂用于催化苯酚水相加氢,考察了不同载体和反应温度对催化性能的影响,并对催化剂重复使用性能进行研究。结果表明,载体g-CN含有大量的含N基团,能有效稳定金属纳米粒子,从而获得粒径较小、分散较好的Pd纳米粒子;同时,g-CN具有较强碱性,有利于苯酚的吸附,可提高苯酚的反应速率和环己酮选择性。采用负载Pd质量分数2%的Pd/g-CN催化剂,在反应温度80 ℃、反应压力0.1 MPa、n(Pd)∶n(苯酚)=0.02、苯酚1 mmol、水3 mL和反应时间3 h条件下,苯酚可完全转化,环己酮选择性高达99%。Pd/g-CN催化剂制备工艺简单,原料价廉,催化性能优异。     

Wrinkled mesoporous carbon supported Pd nanoparticles for hydrogenation and aerobic oxidation reactions

Wrinkled mesoporous silica (WMS) was employed as a hard template to synthesize a carbon replica. The resulting carbon materials, wrinkled mesoporous carbon (WMC), retained the main structural features from the WMS, which has conical pores that radiate from the center of the spherical particle to the outer surface in all directions resulting in wrinkled shaped pore walls. This WMC material was used as a catalyst support for Pd nanoparticles. The Pd on WMC catalyst showed superior performance over commercial Pd on activated carbon for both styrene hydrogenation and the aerobic oxidation of benzyl alcohol.     

Nb2O5 promoted Pd/AC catalyst for selective phenol hydrogenation to cyclohexanone

Phenol hydrogenation is a green route to prepare cyclohexanone, an intermediate for the production of nylon 66 and nylon 6. The development of high-performance catalysts still keeps a great challenge. Herein, the activated carbon (AC) was modified with an acidic material Nb₂O₅ to adjust the microstructure and surface properties of AC, and the influences of the calcination temperature and Nb₂O₅ content on the catalytic performance of the Pd/AC-Nb₂O₅ catalysts for the phenol hydrogenation to cyclohexanone were investigated. The Nb₂O₅ with proper content can be highly uniformly distributed on the AC surface, enhancing the acidity of the Pd/AC-Nb₂O₅ catalysts with comparable specific surface area and Pd dispersion, thereby improving the catalytic activity. The hybrid Pd/AC-10Nb₂O₅-500 catalyst exhibits the synergistic effect between the Pd nanoparticles and AC-10Nb₂O₅, which enhances the catalytic activity for the hydrogenation of phenol. Furthermore, the as-prepared Pd/AC-10Nb₂O₅-500 catalyst shows good reusability during 7 reaction cycles.     

Enhanced liquid phase catalytic hydrodechlorination of 2,4-dichlorophenol over mesoporous carbon supported Pd catalysts

Supported Pd catalysts on ordered mesoporous carbon (OMC) and activated carbon (AC) were prepared and their catalytic behavior for the liquid phase catalytic hydrodechlorination (HDC) of 2,4-dichlorophenol was investigated. In comparison with Pd/AC, Pd particles of Pd/OMC were effectively confined in the mesopores of OMC, resulting in high Pd dispersion and Pd²⁺ content. Accordingly, Pd/OMC exhibited higher catalytic activity than Pd/AC. Moreover, increasing catalyst reduction temperature lowered the catalytic activities and favored stepwise HDC of 2,4-dichlorophenol.     

Electrocatalysis over Pd catalysts: A very efficient alternative to catalytic hydrogenation of cyclohexanone

Electrocatalytic reaction was examined as an alternative method for the catalytic hydrogenation of cyclohexanone over Pd catalysts. The behavior of Pd/alumina catalyst and finely divided Pd catalyst in the electrocatalytic and catalytic hydrogenation of cyclohexanone in aqueous solution were investigated as a comparative study. The role of the pH of the solution was studied both in electrocatalytic and catalytic hydrogenation over Pd/alumina catalyst using acetic acid as a supporting electrolyte. High current yields were obtained for the electrocatalytic process, whereas, as expected from the literature, the catalytic hydrogenation was inefficient.     

中孔碳负载铂催化剂制备及其催化3,4-二氯硝基苯加氢反应

以糠醇为碳源,在酸性中孔模板剂MSU-S上缩合,合成具有中孔结构碳材料(MC),通过浸渍法合成Pt/MC催化剂。采用XRD、BET、SEM和TEM等手段对MC和Pt/MC进行表征,MC富含中孔,有效分散Pt纳米粒子并在反应过程中稳定Pt。研究Pt/MC对3,4-二氯硝基苯催化加氢反应的催化性能,在3,4-二氯硝基苯 1 mmol、催化剂用量100 mg、乙醇5 mL、反应温度30 ℃、常压氢气和反应时间6 h条件下,3,4-二氯硝基苯转化率达100%,3,4-二氯苯胺选择性达99.7%,Pt/MC重复使用5次,催化性能保持不变。     

Pd/C催化硝基环己烷氢化制备环己酮肟

以Pd/C为催化剂,溶剂存在下硝基环己烷氢化制备环己酮肟.考察了溶剂种类、催化剂用量、反应时间、反应温度等因素对催化剂性能的影响.结果表明,溶剂的种类对硝基环己烷氢化产物的选择性有很大影响,乙二胺是该反应的合适溶剂.在催化剂与硝基环己烷摩尔比为1∶100、反应温度95 ℃的条件下,反应6 h后的硝基环己烷转化率可达100%,环己酮肟选择性可达84.2%.对硝基环己烷在碱性溶剂中氢化的反应机理作了初步探讨.     

碳纳米管负载镍基催化剂上乙炔选择性加氢

分别采用浸渍法、化学还原法和超声辅助的浸渍-化学还原法,制备晶态Ni/CNTs、非晶态NiB和NiB/CNTs催化剂,对非晶态NiB/CNTs催化剂热处理使其晶化.表征了催化剂,并考察催化剂的乙炔选择性加氢性能.结果表明非晶态NiB/CNTs合金的催化性能优于晶态Ni/CNTs以及晶化NiB/CNTs催化剂的性能,其在乙炔选择性加氢反应中有较好的稳定性,连续使用650 min后乙炔转化率达80%以上.乙烷选择性随反应进行逐渐下降,最终趋于7.5%;乙烯选择性随反应进行逐渐上升,最终趋于55%.     

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%。     

负载型Pd/SBA—15催化剂催化性能研究

将负载型催化剂Pd/SBA—15用于催化邻氯硝基苯加氢。考察了反应温度、催化剂用量对Pd/SBA—15催化性能的影响,并考察了催化剂的使用寿命。实验结果表明,Pd/SBA—15催化剂表现出很好的催化性能,有望应用于工业生产。     

Selective hydrogenation of cinnamaldehyde over reduced graphene oxide supported Pt catalyst

Highly dispersed platinum nanoparticles (NPs) were fabricated on the surface of few-layered reduced graphene oxide (Pt/RGO) via direct ethylene glycol reduction of PtCl₆^2 − in aqueous solution. This well-defined Pt/RGO catalyst was highly selective and active for the hydrogenation of cinnamaldehyde (CAL) to corresponding cinnamyl alcohol (COL) under mild conditions. It was found that the selectivity of COL remained 85.3% at 97.8% CAL conversion in ethanol. These results could be ascribed to the well dispersed Pt NPs on RGO sheets, well dispersion of Pt/RGO in ethanol and ethanol can inhibit the generation of acetals.     

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.     

Hydrogenation of phenol to cyclohexanone over Pd/MgO

Hydrogenation of phenol to cyclohexanone has been investigated in the temperature range 160–250°C on a series of Pd/MgO catalysts. At 160°C the orders of reaction were found on all catalysts to be about ?1 with respect to phenol and about + 1 with respect to hydrogen. On the basis of the kinetic results it is suggested that the rate determining step is the surface reaction between phenol and hydrogen adsorbed on the catalyst. An increase in the reaction temperature decreases the rate of reaction. This has been explained through a change of the orders of reaction which increase with temperature. Palladium dispersion does not influence the reaction mechanism. The specific activity was found to be independent of palladium particle size.     

Hydrogenolysis of sorbitol to glycols over carbon nanofiber supported ruthenium catalyst

Sorbitol hydrogenolysis was carried out over a carbon nanofiber supported ruthenium catalyst prepared by incipient wetness impregnation. The carbon nanofiber supported ruthenium catalyst was shown to have an attracting behavior when compared with a commercial activated carbon supported ruthenium catalyst, especially in terms of selectivity to glycols. The preferable hydrogen partial pressure for sorbitol hydrogenolysis was ca. 8.0 MPa, lower than that usually reported in previous works. Slightly soluble calcium hydroxide, which was used as a basic promoter, remarkably increased the selectivity to glycols, as compared with the soluble sodium hydroxide. The variation of product selectivity with catalyst amount indicated that glycerol was the initial C3 polyol product while propylene glycol was derived from glycerol. The parametric investigation was further focused on the intrinsic features of sorbitol hydrogenolysis.     

活性炭负载磷钨酸催化合成环己酮乙二醇缩酮的研究

用活性炭负载磷钨酸催化合成环己酮乙二醇缩酮,考察了催化剂的用量、反应温度、反应时间、酮醇物质的量比及带水剂等因素对反应的影响,实验表明,在n( 环己酮)∶n(乙二醇)=1∶1.8,催化剂用量为反应物料总质量分数的0.84%、环己烷为带水剂和反应时间30 min条件下,环己酮乙二醇缩酮的收率可达88.73%。催化剂可重复使用。     

选择性催化加氢合成3,4-二氯苯胺的Pd/C催化剂研究

研究了Pd/C催化剂表面金属钯平均粒径对3,4-二氯硝基苯催化加氢反应选择性的影响，发现金属钯平均粒径越大，脱氯副反应越不明显，加氢选择性越高。采用浓硝酸预处理的活性炭负载钯催化剂虽然能够增大表面金属钯平均粒径，粒径分布却较宽，不利于加氢选择性的提高。使用饱和EDTA·2Na溶液预处理活性炭后，在钯负载量降低的情况下，可以达到活性炭载体表面金属钯大粒径、狭窄的分布，实现了在不添加脱氯抑制剂的情况下高选择性合成3,4-二氯苯胺。     

Selective hydrogenation of 4-isobutylacetophenone over a sodium-promoted Pd/C catalyst

The effect of sodium promotion on the selective hydrogenation of 4-isobutylacetophenone, 4-IBAP, was investigated over a Pd/C catalyst. A precipitation and deposition method was used to prepare the catalyst, and sodium was promoted on the Pd/C catalyst via post-impregnation while varying the sodium content. The sodium-promoted Pd/C catalyst resulted in a significantly improved yield greater than 96% of the desired product, 1-(4-isobutylphenyl) ethanol (4-IBPE), compared with the non-patented literature results under a mild hydrogenation condition. A detailed hydrogenation network over the Pd/C catalyst was suggested. The reaction mechanism for the yield and selectivity enhancement of 4-IBPE induced-by the promoted Pd/C was elucidated in relation to the geometric and electronic effects of reactant molecules in the microporous support depending on the reaction steps.     

TiO2负载Pd-Fe催化间硝基三氟甲苯常压加氢反应动力学

研究了TiO2负载Pd-Fe催化间硝基三氟甲苯的常压加氢反应,考察了反应温度和催化剂质量浓度对加氢反应的影响,建立了加氢反应的动力学方程。结果表明:在间硝基三氟甲苯初始浓度0.125 mol/L,催化剂质量浓度0.32 g/L,氢气压力0.1 MPa,,323.2 K和2.5 h条件下,间硝基三氟甲苯转化率达到99.2%。通过拟合实验数据,加氢反应对间硝基三氟甲苯浓度表现为1级,对催化剂质量浓度表现为0.464级,反应活化能为22 728.0 J/mol。由动力学方程回算得到的间硝基三氟甲苯浓度与实验值能较好地吻合。     

Hydrocracking of waste lubricant into gasoline fraction over CoMo catalyst supported on mesoporous carbon from bovine bone gelatin

The hydrocracking of waste lubricant into gasoline fraction was carried out using CoMo catalyst supported on mesoporous carbon. The carbon was synthesized using bovine bone gelatin and SBA-15 as a template. The metals were loaded onto the carbon by wet impregnation method. The total metal content of catalyst was prepared into two different amounts which were labelled as CoMo/MCG1 and CoMo/MCG2. Catalytic activity and selectivity were evaluated in hydrocracking of waste lubricant at 450, 475, and 500 °C, and lubricant/catalyst weight ratio of 50, 100, 200, 300, and 400. The result revealed that acidity and specific surface area of the catalyst played an important role in determining the catalytic performance in the hydrocracking of waste lubricant. The highest percentage of gasoline fraction was 58.09%, produced by hydrocracking of waste lubricant at 475 °C and lubricant/catalyst weight ratio of 300 using CoMo/MCG2 catalyst.     

Effect of hydrogen spillover on the hydrogenation of 1-hexene over diluted carbon molecular sieve supported Pt catalyst

Pt supported on a carbon molecular sieve (Pt/CMS) was prepared by pyrolysis of polyfurfuryl alcohol containing pre-reduced Pt particles. The catalysts were characterized by hydrogen chemisorption, XRD, N₂ adsorption/desorption and TEM. Hydrogen chemisorption showed that not all the Pt particles were exposed to H₂ molecules. Oxidation treatment made Pt particles more accessible to H₂. Catalyst activity was evaluated by hydrogenation of 1-hexene. Hydrogen spillover was demonstrated by diluting Pt/CMS with activated carbon or hydrogen type zeolite Y. The initial conversion of 1-hexene was increased from 86.5% to 98.5% and to 100% when Pt/CMS was diluted with activated carbon and hydrogen type zeolite, respectively. The high initial conversion was sustained for 6 h in the presence of diluents while the conversion decreased quickly for Pt/CMS alone.