Pt-Au/TiO2 在对氯硝基苯催化加氢反应中的催化性能

采用尿素沉积-沉淀方法制备Pt-Au/TiO2催化剂,考察了第二金属Pt的加入以及反应条件对由对氯硝基苯加氢制对氯苯胺的影响.结果表明,少量Pt的加入极大的提高了Au/TiO2催化剂的活性,当Pt-Au/TiO2催化剂中Pt含量为0.02%时,在50 ℃、1.0 MPa氢气条件下反应1 h,对氯硝基苯即被100%转化为对氯苯胺.     

负载型镍催化剂用于催化加氢制备对氯苯胺

以KT-02新型Ni/SiO2为催化剂,催化对氯硝基苯加氢制备对氯苯胺,考察了反应条件如温度、压力、搅拌速度及催化剂加入量等因素对反应的影响,并对催化剂进行了套用实验。结果表明,以甲醇为溶剂,加入10%催化剂和适量脱氯抑制剂三乙醇胺,在90℃、2.0 MPa氢气条件下反应8 h,对氯硝基苯转化率大于99%,对氯苯胺的选择性大于97%,脱氯反应得到有效抑制。本催化剂可套用8次以上。     

焙烧条件对Pt-Fe/AC催化对氯硝基苯加氢性能的影响

考察了焙烧条件对活性炭负载Pt-Fe催化对氯硝基苯选择加氢制对氯苯胺反应性能的影响,同时用X射线衍射、透射电子显微镜和X射线光电子能谱表征了该催化剂的结构。结果表明,焙烧气氛和焙烧温度对催化剂性能影响显著,在空气气氛中200℃下焙烧的Pt-Fe/AC具有较高的催化对氯硝基苯选择加氢制对氯苯胺反应性能。在对氯硝基苯/催化剂质量比为50∶1、30℃、1.0 MPa氢气条件下反应90 min,对氯硝基苯即被100%转化为对氯苯胺。     

焙烧条件对Pt-Fe/AC催化对氯硝基苯加氢性能的影响

考察了焙烧条件对活性炭负载Pt-Fe催化对氯硝基苯选择加氢制对氯苯胺反应性能的影响,同时用X射线衍射、透射电子显微镜和X射线光电子能谱表征了该催化剂的结构。结果表明,焙烧气氛和焙烧温度对催化剂性能影响显著,在空气气氛中200℃下焙烧的Pt-Fe/AC具有较高的催化对氯硝基苯选择加氢制对氯苯胺反应性能。在对氯硝基苯/催化剂质量比为50∶1、30℃、1.0 MPa氢气条件下反应90 min,对氯硝基苯即被100%转化为对氯苯胺。     

负载型Ni-Cr-B非晶态合金催化对氯硝基苯加氢制备对氯苯胺

提出一种以负载型Ni-Cr-B非晶态合金催化对氯硝基苯加氢制备对氯苯胺的工艺。通过正交实验考察反应温度、反应时间、反应压力和催化剂用量对对氯苯胺收率的影响。最优工艺条件为:反应温度60℃,反应时间4 h,反应压力1.2 MPa,催化剂用量占对氯硝基苯质量的8%。在此优化条件下,催化剂重复使用4次,对氯硝基苯转化率为99.9%,对氯苯胺选择性为99.9%,对氯苯胺平均收率为99.8%。     

载体处理对Pt/C催化剂的选择性加氢性能影响

研究了活性炭处理方式对以其为载体制备的铂炭催化剂性能的影响,以对氯硝基苯催化加氢制备对氯苯胺反应为模型反应对催化剂的性能进行评价。结果表明,经过处理的活性炭制备的铂炭在对氯硝基苯加氢反应中表现出的催化性能更高,5%NaOH在80℃下处理2 h的活性炭可以达到最佳效果,所制备的Pt/C催化剂重复使用4次,对氯苯胺收率在99%以上,脱氯率在0.3%以下。     

温和条件下Pt/MSU-S催化氯代硝基苯选择性加氢研究

采用乙醇还原法制备负载型Pt/MSU-S催化剂,采用X射线衍射、透射电镜、N2吸附-脱附对催化剂进行了表征。TEM表明,质量分数为0.5%的Pt在MSU-S载体上高度分散,Pt粒径在5 nm左右,无团聚现象。在常压反应温度30℃下分别考察了Pt/MSU-S催化剂对邻位、间位和对位氯代硝基苯催化加氢性能的影响,反应3 h,底物转化率为100%,邻氯苯胺的选择性达到96%,间氯苯胺和对氯苯胺的选择性达到98%。催化剂重复使用5次后仍然有很高催化活性和选择性。     

Pt-Fe/CNTs催化对氯硝基苯选择加氢的研究

基于乙醇分子易被碳纳米管容纳,分别用H_2PtCl_6和Fe(NO_3)_3的乙醇溶液和先乙醇吸附饱和后再用H_2PtCl_6和Fe(NO_3)_3水溶液浸渍碳纳米管,将0.3%Pt-4%Fe负载于碳纳米管内和管外,考察了其催化对氯硝基苯选择加氢制备对氯苯胺性能,并采用TEM、XRD、XPS等对其结构进行了表征。结果表明,碳纳米管内负载0.3%Pt-4%Fe(0.3%Pt-4%Fe/in-CNTs)对催化对氯硝基苯加氢制备对氯苯胺具有优异性能。乙醇为溶剂、较高的H_2压力和反应温度对0.3%Pt-4%Fe/in-CNTs催化对氯硝基苯加氢制备对氯苯胺有利。催化剂与对氯硝基苯质量比1∶50,30℃和1 MPa H_2条件下反应50 min,p-CAN收率达100%,并且催化剂重复使用3次,活性无明显下降。     

Pt/C催化剂的制备及其在对氯苯胺合成中的应用

采用浸渍法制备Pt/C催化剂，考查了催化剂中Pt含量，催化剂还原温度以及第二金属的加入对由对氯硝基苯合成对氯苯胺的影响。结果表明，Pt/C催化剂中Pt含量为2％，还原温度500 ℃效果最佳，加入第二金属后氯苯胺的选择性高达99%以上。通过XRD、SEM和BET等方法对催化剂的失活进行初步探讨，分析发现，失活催化剂的Pt晶粒明显长大、载体形貌发生变化和比表面积变小等是导致催化剂失活的重要因素。     

复合催化剂催化水合肼还原对氯硝基苯制备对氯苯胺

研究了在FeCl3 ·6H2 O -AlCl3 ·6H2 O复合催化剂存在下 ,催化水合肼还原对氯硝基苯制备对氯苯胺。结果表明 ,FeCl3 ·6H2 O -AlCl3 ·6H2 O复合催化剂具有良好的催化活性和选择性 ,并经实验得到了用乙醇作为溶剂时的最佳反应条件 :还原对氯硝基苯 3.2 g(0 .0 2mol) ,催化剂组成是 0 .5g活性炭、m(FeCl3 ·6H2 O) :m(AlCl3 ·6H2 O)=1∶1,用量均为 0 .2 g ;物料配比为n(对氯硝基苯 )∶n(水合肼 ) =1.0∶2 .0 ;反应温度为 70℃ ;反应时间 2h ;对氯硝基苯的转化率可达 10 0 % ,对氯苯胺的选择性大于 99%。     

三苯基膦稳定的负载钌纳米粒子上对氯硝基苯的选择加氢反应

制备了γ-Al2O3负载的三苯基膦稳定的钌纳米粒子（PPh₃-Ru/Al₂O₃）催化剂,并进行了XRD 和XPS表征。将其用于对氯硝基苯的选择加氢反应,考察了反应压力、温度和时间对催化性能的影响。结果表明,在60 ℃、氢压2 MPa、反应21 h和对氯硝基苯几乎完全转化的条件下,实现了产品对氯苯胺99.7%的选择性。分析表明,脱氯反应的抑制是取得产品高选择性的主要原因,阐明了该催化剂如何有效抑制脱氯反应的发生。     

高分散度Ru/C选择性催化对氯硝基苯加氢制备对氯苯胺

研究了高分散度Ru/C在对氯硝基苯(p-CNB)加氢制备对氯苯胺(p-CAN)反应中的催化性能,考察了Ru负载量、溶剂种类、底物浓度、反应温度和压力等反应条件对反应的影响。结果表明,反应条件只影响p-CNB的加氢速率,但对p-CAN的选择性没有影响,p-CNB 100%转化时,p-CAN的选择性100%,没有脱氯副反应发生。催化剂的高活性和高选择性与纳米Ru在活性炭上的高分散度及催化剂的表面碱性有关。p-CNB浓度低于0.96mol/L时,还原反应对p-CNB宏观表现为零级反应。催化剂连续套用30次活性保持稳定。     

High halogenated nitrobenzene hydrogenation selectivity over nano Ir particles

The selective hydrogenation of halogenated nitrobenzene over noble metal catalysts (Pd,Pt,and It) has attracted much attention owing to its high efficiency and environmental friendliness.However,the effect of size on the catalytic performance varies among different metal catalysts.In this study,sub-nano (＜3 nm) Ir and Pd particles were prepared,and their catalytic properties for hydrogenation of halogenated nitrobenzene were evaluated.Results show that high selectivity (＞99％) was achieved over small Ir nanoparticles,in which the selectivity over the Pd with same size was much lower than that on lr nanoparticles.Meanwhile,Ir and Pd have different hydrogen consumption rates and reaction rates.Density functional theory calculations showed that p-chloronitrobenzene (CNB) has different adsorption properties on Ir and Pd.The distance between oxygen (cholorine) and Ir is much shorter (longer) than that between oxygen and Pd.The reaction barriers of dechlorination ofp-CNB and p-chloroaniline over different Ir models are much larger than those on Pd.Especially,lower coordination of lr leads to larger barriers of dechlorination reaction.These theoretical results explain the difference between Ir and Pd on hydrogenation of halogenated nitrobenzene.     

Pt/γ-Al2O3 catalytic membranes vs. Pt on γ-Al2O3 powders in the selective hydrogenation of p-chloronitrobenzene

The catalytic activity of Pt/γ-Al₂O₃ membrane reactors, prepared using mesitylene solvated platinum atoms as source of active Pt particles, has been compared with that of analogously obtained Pt/γ-Al₂O₃ powders in the liquid phase hydrogenation of p-chloronitrobenzene. A largely different behaviour has been observed, the membrane reactor acting as a H₂ richer system. This revised version was published online in July 2006 with corrections to the Cover Date.     

Catalytic Performance of Pt Metal Particles at the Tips of Carbon Nanotubes

Abstract  

The catalytic performance of Pt metal at the tips of carbon nanotubes (CNT@Pt), which was prepared by ethylene decomposition over Pt/MgO, was compared with that of Pt metal on the outer surface of CNT (Pt/CNT). CNT@Pt showed excellent catalytic performance toward the hydrogenation of α, β-unsaturated aldehydes to unsaturated alcohols, which was similar to that of Pt/CNT and resulted from a strong interaction between Pt metal and the CNT.     

Sn~(4+)修饰的PEG-Pd催化氯代硝基苯选择性加氢反应

考察了PEG-Pd(PEG:聚乙二醇,Pd 0.2%)催化剂催化对氯硝基苯的加氢反应中,添加第二金属组分以及Sn4+含量对反应的影响。结果表明,添加一定量的Sn4+对反应选择性有着显著的影响。不添加Sn4+离子,会有严重的脱氯反应发生;加入Sn4+离子后,在Sn与Pd的摩尔比为0.8,温度60℃,氢压1.0 MPa的条件下,经过60 min反应,对氯硝基苯转化率为99.6%,而对氯苯胺选择性由不加Sn4+离子时的68.5%上升到96.1%。对取代位置不同的其它氯代硝基苯,该催化体系同样表现出很高的催化活性和氯代苯胺选择性。     

Sn^4＋修饰的PEG-Pd催化氯代硝基苯选择性加氢反应

考察了PEG-Pd（PEG：聚乙二醇,Pd 0.2%）催化剂催化对氯硝基苯的加氢反应中,添加第二金属组分以及Sn^4＋含量对反应的影响。结果表明,添加一定量的Sn^4＋对反应选择性有着显著的影响。不添加Sn^4＋离子,会有严重的脱氯反应发生;加入Sn^4＋离子后,在Sn与Pd的摩尔比为0.8,温度60℃,氢压1.0 MPa的条件下,经过60 min反应,对氯硝基苯转化率为99.6%,而对氯苯胺选择性由不加Sn^4＋离子时的68.5%上升到96.1%。对取代位置不同的其它氯代硝基苯,该催化体系同样表现出很高的催化活性和氯代苯胺选择性。     

Platinum group metals as catalysts in enantioselective 1-phenylpropane-1,2-dione hydrogenation

Different γ-Al₂O₃ supported Ir, Pd, Ru, Rh and Pt catalysts were tested in enantioselective 1-phenylpropane-1,2-dione hydrogenation using cinchona alkaloid modifiers. Activity and enantioselectivity over Ir and Ru catalysts were low. Pd catalyst was active in the hydrogenation of 1-phenylpropane-1,2-dione, however, the enantioselectivity over this catalyst was almost negligible. Over Pd hydrogenation proceeded mainly via hydrogenation of the C₁O₁ carbonyl group, which is attached to the phenyl ring. Hydrogenation over Pd did not proceed in the second hydrogenation step via an enol form as found for ethyl pyruvate hydrogenation over Pd. The structure-selectivity relationship and solvent effects are similar over Pt and Rh in the first hydrogenation step. However, in the second hydrogenation step of hydroxyketones to diols large mechanistical differences between Pt and Rh were observed. Although the activity over Rh catalysts was lower than over Pt after optimization the best result obtained with Rh/γ-Al₂O₃ (5754 Lancaster) was 60% ee in toluene at maximum yield of 28%, which makes Rh a promising metal for enantioselective hydrogenation.