烷基苯酚加氢用Pd/C催化剂性能研究

采用浸渍法制备不同助剂改性的Pd/C催化剂,并与未添加助剂的Pd/C催化剂对比,考察不同助剂对苯酚加氢制备环己酮用Pd/C催化剂性能影响。结果表明,助剂Zn对催化剂活性和选择性影响较小,助剂Mg、Fe、Co使烷基苯酚加氢用Pd/C催化剂活性和选择性均有所提升,且以CoCl2为Co源,质量含量为2.0%Co修饰的Pd/C催化剂效果较优,催化剂重复使用性能良好。     

Ba修饰的Pd/C催化剂催化2,6-二氯吡啶加氢脱氯性能

采用浸渍法制备系列不同助剂修饰的Pd/C催化剂,并考察不同助剂对2,6-二氯吡啶加氢脱氯性能的影响。结果表明,助剂Sn使催化剂活性明显下降,Fe、Mg对催化剂活性影响不大,少量Ba的修饰可以提高Pd/C催化剂活性。Ba质量分数为1.0%时,2,6-二氯吡啶完全转化,催化剂可多次重复使用。     

CO偶联合成草酸二甲酯催化剂研究

采用浸渍法制备CO偶联制备草酸二甲酯用负载型Pd催化剂,考察载体、浸渍方法、Pd含量、助剂对Pd催化剂性能的影响。根据傅里叶变换红外光谱研究Pd/α-Al_2O_3负载型催化剂上CO偶联制草酸二甲酯的反应机理。结果表明,采用α-Al_2O_3载体,Pd质量分数4‰,掺杂助剂Cu的蛋壳型的Pd/α-Al_2O_3催化剂上,草酸二甲酯时空收率达到735.7 g·(L·h)~(-1)。     

铜、钡对单钯型汽车尾气净化催化剂性能影响研究

制备了Pd/Ni/La-Ce-Al、Pd/cu/Ni La-Ce-Al、Pd/Ba/Ni-La-Ce-A1 3 种类型的汽车尾气净化催化剂,考察了3种催化剂对CO、C3H8和NO氧化还原活性.研究结果表明,铜不适合作为Pd/Ni/La-ce-Al催化剂的助剂;钡是提高Pd/Ni/La-Ce-Al催化剂性能特别是改善其NO还原性能的良好助剂.     

助剂对Pd/AC催化剂催化三氟氯乙烯加氢脱氯的影响

采用等体积浸渍法制备了Cu-Pd/AC和K-Pd/AC催化剂,分别考察了Cu和K助剂添加量对三氟氯乙烯加氢脱氯生成三氟乙烯的反应性能的影响,并采用N_2-物理吸附、X射线粉末衍射(XRD)测试、透射电镜(TEM)和H_2-程序升温还原(TPR)等对催化剂进行表征。结果表明:加入助剂Cu,其与Pd形成Pd-Cu合金,抑制催化剂的加氢性能,从而降低催化剂反应活性;加入助剂K,其改变了Pd的电子结构,增强了Pd的电子云密度,使Pd活化H的能力增强,从而提高催化剂的活性。助剂K质量分数为3%的催化剂,在250℃下,具有较好的催化活性,三氟氯乙烯的转化率可达90%左右,三氟乙烯的选择性可达85%左右。     

Al、K和Ca助剂对FeSi催化剂的CO2加氢反应性能影响

对于CO₂合成烃,采用SiO₂作Fe基催化剂强度增强剂,利用Al、K和Ca促进催化剂的CO₂加氢反应性能。Al可以增加Fe基催化剂的强酸性位,提高C₅⁺烃选择性,K能增加Fe基催化剂表面碱性,增强CO₂吸附和加氢反应,Ca助剂可以提高Fe基催化剂碱性,采用共沉淀法制备FeSi催化剂母体,利用浸渍法添加Al、K和Ca助剂,考察Al、K和Ca助剂对FeSi 催化剂的CO₂加氢性能影响。结果表明,3种助剂被单独添加时,均引起催化剂比表面积减小和CO₂转化率降低,Ca助剂具有扩孔作用;同时添加3种助剂时,每种助剂的含量变化均引起催化剂性能改变,Al、K和Ca助剂添加质量分数分别为7%、5%和0.25%时,催化剂合成烃的性能较佳,通过配合调整Al和K的添加量,可以进一步提高催化剂的CO₂加氢性能。在提高烃收率方面,Ca的促进作用优于K。     

Pd-Pt-Ce/Al_2O_3催化剂在VOC净化处理中的催化性能

采用浸渍法制备Pd-Pt-Ce/Al_2O_3催化剂,考察贵金属Pd和Pt负载量、助剂种类及负载量、空速对催化甲苯燃烧活性的影响。结果表明,适宜的贵金属负载量和助剂可极大提高Pd-Pt/Al_2O_3催化剂活性,当Pd和Pt质量分数分别为0.05%和0.005%、助剂Ce质量分数为1%时,Pd-Pt-Ce/Al_2O_3催化剂在低温条件下表现出较好的催化性能。空速对催化剂的催化活性影响较为明显,适宜的空速低于20 000 h-1。     

Pd-M(Ce、Ca、Fe)/γ-Al_2O_3催化2,5-二氢呋喃加氢性能

通过分步浸渍法制备了Pd含量为0.3%,M含量为3.0%的Pd-M(M=Ce、Ca、Fe)/γ-Al_2O_3催化剂,采用XRD、N_2物理吸附-脱附、H_2-TPR、H_2-TPD和Py-IR等对催化剂进行表征,并研究了助剂对Pd/γ-Al_2O_3催化剂催化2,5-二氢呋喃加氢性能的影响。结果表明,在Pd/γ-Al_2O_3催化剂中引入助剂,降低了Pd与金属相互作用,同时减少了表面暴露L酸位点;促进了2,5-二氢呋喃加氢转化为四氢呋喃,抑制了异构化产物2,3-二氢呋喃的产生。特别是Fe的引入,与Pd之间的协同作用,使CC双键在Pd表面吸附增强,2,5-二氢呋喃转化率大幅提高。该催化剂在反应温度30℃,氢压0.5 MPa和反应时间1 h的加氢条件下,2,5-二氢呋喃转化率达到94.25%,目标产物四氢呋喃选择性达到99.97%。     

Pd/Al2O3液相选择加氢催化剂抗硫性能研究

研究了助剂对Pd/Al2O3催化剂裂化汽油液相选择加氢活性及其抗硫性能的影响。着重探讨了Co助剂的作用规律。结果表明，助剂对Pd/Al2O3催化剂的加氢活性有不同影响，其中加入Ag、Cu和Co助剂时，可以提高催化剂加氢活性，而Co助剂的提高最为明显，通过对催化剂进行XPS和反应后催化剂硫含量的分析，表明Co助剂改善Pd/Al2O3催化剂液相加氢活性的作用有两方面，一是与Pd金属产生电子相互作用，改变其电子状态，减弱对硫化物的吸附；二是Co具有吸硫作用，使部分硫化物吸附在助剂Co上，从而减少了在活性中心Pd上的吸附，导致Pd－Co/Al2O3催化剂具有良好的液相选择加氢活性。     

助剂对Pd/γ-Al2O3催化剂一步法合成二甲醚反应稳定性的影响

采用浸渍法制备了一系列不同助剂下的负载型Pd/γ-Al₂O₃催化剂,考察了助剂类型对Pd/γ-Al₂O₃催化剂一步法合成二甲醚（STD）反应稳定性的影响规律;采用氮吸附、XRD、H₂-TPR及TG等多种表征手段考察了稳定性试验前后以及烧炭再生后催化剂的表面物化性质及结构变化。结果表明,助剂成分对Pd/γ-Al₂O₃催化剂的STD反应稳定性影响显著。相比Pd/γ-Al₂O₃催化剂,添加CeO₂可以提高Pd在γ-Al₂O₃表面的分散度,但会覆盖表面的部分酸性位,一定程度上提高了催化剂的活性和稳定性,但仍存在Pd烧结和积炭现象;添加复合助剂CeO₂-ZrO₂后形成的Ce-O-Zr固熔晶面能显著促进Pd均匀分散,提高催化剂的抗积炭能力和抗烧结能力,催化剂的活性和稳定性更高;经SO₄^2-改性后Pd/γ-Al₂O₃催化剂会因为表面积炭加剧和表面硫流失严重,中强酸酸性位减少而快速失活。CeO₂-ZrO₂-Pd/γ-Al₂O₃催化剂经历20h的稳定性试验后CO转化率仍保持59%以上,二甲醚选择性65%以上,烧炭再生后催化活性恢复至新鲜催化剂的91.83%。     

蒽醌加氢钯催化剂载体改性研究

针对Pd/Al2O3催化剂载体的改性进行研究,将1 000℃焙烧后的氧化铝粉末与未焙烧的活性氧化铝粉末按不同比例混合和焙烧制备载体,采用等体积浸渍法制得负载Pd的Pd/Al2O3催化剂。采用XRD、BET、NH3-TPD和HOT对载体以及催化剂进行表征,并考察催化剂的蒽醌加氢性能。结果表明,提高载体中焙烧后氧化铝粉末的比例,导致载体中γ-Al2O3减少和δ-Al2O3增多,载体酸性降低,Pd分散度变大,从而提高了催化剂氢化效率。当焙烧后氧化铝质量分数为40%时,分散度和活性表面积达到最大,晶粒度最小,氢化效率最高,催化活性最佳。     

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.     

Pd/Al2O3催化剂的制备及其在对氨基苯酚合成中的应用

用等体积浸渍法制备了Pd/Al2O3催化剂。采用ICP、XRD、HRTEM和XPS等对催化剂的组成和形貌进行表征。结果表明，Pd粒子均匀分布在Al₂O₃的表面，粒径约为5 nm。在对硝基苯酚催化加氢制备对氨基苯酚的反应中，对催化剂的催化性能进行了考察。Pd/Al₂O₃催化剂的催化活性随着Pd负载量的增大而增大；其与市售的骨架镍、纳米镍以及2%Pd/C相比，显现了优异的催化活性；Pd/Al₂O₃具有高的催化选择性；Pd/Al2O3的催化活性稳定性明显优于骨架镍；随着使用次数的增加，Pd/Al₂O₃的催化活性有所降低，这可能是因为Pd粒子的团聚。     

Vapour phase hydrogenation of phenol over Pd/C catalysts: A relationship between dispersion,metal area and hydrogenation activity

A series of palladium supported on activated carbon catalysts, with Pd varying from 0.5 to 6.0 wt%, were prepared via wet impregnation method using PdCl₂ · xH₂O as a precursor salt. The dried samples were further reduced at 573 K in hydrogen and characterized by CO adsorption at room temperature in order to determine the dispersion, metal area and particle size. The catalysts were tested for vapour phase phenol hydrogenation in a fixed-bed all glass micro-reactor at a reaction temperature of 453 K under normal atmospheric pressure. The decrease in metal surface area as well as dispersion with corresponding increase in turn-over frequency (TOF) against palladium loadings suggest the unusual inverse relationship that exist between Pd dispersion and phenol hydrogenation activity over Pd/carbon catalysts. The stability of TOF at larger crystallite size indicates that phenol hydrogenation is less sensitive reaction especially beyond 3 wt% of Pd content. It is evident from the results that structural properties of the catalysts strongly influence the availability of Pd atoms on the surface for CO chemisorption and hence for phenol hydrogenation. A comparison between selectivity and product yield of the reaction against overall phenol conversion indicates that changes in reaction selectivity for cyclohexanone or cyclohexanol is independent of phenol conversion level and either of the product is not formed at the cost of another. The stability of the catalysts with reaction time suggests that coke formation on the surface of the catalyst is less significant and the formation of cyclohexanone remains almost total even at higher reaction temperatures.     

Phenol hydrogenation to cyclohexanone over palladium nanoparticles loaded on charming activated carbon adjusted by facile heat treatment

Selective phenol hydrogenation is a green approach to produce cyclohexanone. It still remains a big challenge to prepare efficient supports of the catalysts for the phenol hydrogenation via a simple and cost-effective approach. Herein, a facile approach was developed, i.e., direct calcination of activated carbon (AC) under argon at high temperature, to improve its structure and surface properties. The modified AC materials were supported with Pd nanoparticles (NPs) to fabricate the Pd/C catalysts. The as-prepared Pd/C600 catalyst exhibits superior catalytic performance in the phenol hydrogenation, and its turnover frequency (TOF) value is 199.2 h^-1, 1.31 times to that of Pd/C-raw. The Pd/C600 catalyst presents both better hydrophobicity and more structural defects, contributing to the improved dispersibility in the reaction solution (phenol-cyclohexane), the better Pd dispersion and the smaller Pd size, which result in the enhancement of the catalytic performance. Furthermore, the as-prepared Pd/C600 catalyst shows a good recyclability.     

非晶态Pd-B/Al2O3催化剂用于邻氯硝基苯加氢合成邻氯苯胺的研究

用化学还原法制得了Pd-B/Al2O3非晶态催化剂,并用于邻氯硝基苯液相加氢反应的研究.采用XRD、SEM、SAED等技术手段对催化剂进行了表征,表明Pd-B以超细颗粒的形式分散在载体上,并且明确了催化剂的非晶态性质、结构形态等.以邻氯硝基苯液相加氢为目标反应,对所制备催化剂的催化性能进行系统评价.在反应温度90℃、氢气压力1.0MPa的反应条件下,邻氯硝基苯的转化率达99.9%,邻氯苯胺的选择性达98.0%;在不加脱卤抑制剂的情况下,脱卤率小于2%,表明负载Pd系非晶态催化剂具有较好的邻氯硝基苯加氢活性及良好的选择性,优于Pd基晶态催化剂和Ni基晶态催化剂.从催化剂的微观结构、金属-载体相互作用、活性组分在载体表面的几何效应和电子效应等方面对非晶态催化剂响影响邻氯硝基苯加氢性能进行了讨论和解释.     

Highly selective hydrogenation of phenol and derivatives over Pd catalysts supported on SiO2 and γ-Al2O3 in aqueous media

Pd/Al₂O₃ and Pd/SiO₂ catalysts containing Pd nanoparticles in the size range of 3–13 nm were prepared and investigated in direct selective hydrogenation of phenol to cyclohexanone. Catalysts with 3 nm Pd nanoparticles present highly active and promoted the selective formation of cyclohexanone under atmospheric pressure of hydrogen in aqueous media without additives. Conversion of 99% and a selectivity higher than 99% were achieved within 3 h at 333 K. The generality of Pd/Al₂O₃ catalyst with 3 nm Pd nanoparticles for this reaction was demonstrated by selective hydrogenation of other hydroxylated aromatic compounds with similar performance.     

Phenol hydrogenation to cyclohexanone over palladium nanoparticles loaded on charming activated carbon adjusted by facile heat treatment

Selective phenol hydrogenation is a green approach to produce cyclohexanone. It still remains a big challenge to prepare efficient supports of the catalysts for the phenol hydrogenation via a simple and cost-effective approach. Herein, a facile approach was developed, i.e., direct calcination of activated carbon (AC) under argon at high temperature, to improve its structure and surface properties. The modified AC materials were supported with Pd nanoparticles (NPs) to fabricate the Pd/C catalysts. The as-prepared Pd/C600 catalyst exhibits superior catalytic performance in the phenol hydrogenation, and its turnover frequency (TOF) value is 199.2 h⁻¹, 1.31 times to that of Pd/C-raw. The Pd/C600 catalyst presents both better hydrophobicity and more structural defects, contributing to the improved dispersibility in the reaction solution (phenol-cyclohexane), the better Pd dispersion and the smaller Pd size, which result in the enhancement of the catalytic performance. Furthermore, the as-prepared Pd/C600 catalyst shows a good recyclability.     

PdAg、PdAu合金纳米晶的制备及其催化性能研究

采用硼氢化钠一步还原法,首先得到PdAg和PdAu双金属合金纳米颗粒.利用XRD、TEM以及紫外可见光光谱技术对其进行了表征分析.结果表明,PdAg和PdAu两种合金都具有纳米颗粒分散均匀且颗粒尺寸小等优点.随后采用胶体沉积法将两种合金均匀地负载到Al2O3上,成功获得PdAg/Al2O3和PdAu/Al2O3两种金属纳米催化剂.在邻氯硝基苯加氢反应中,与Pd/Al2O3纳米催化剂相比,PdAg/Al2O3催化剂显示出95.5％的选择性,而PdAu/AI2O3催化剂的选择性高达98.7％,这可能归因于Pd与Ag或Au金属间的协同效应.     

选择加氢催化剂载体氧化铝的改性及其工业应用(Ⅱ)

采用浸渍法制备稀土元素和／或碱金属改性的氧化铝加氢催化剂载体,考察了助剂稀土和碱金属的加入对氧化铝热稳定性、表面酸度的影响以及改性载体对活性组分Pd分散度的影响。采用BET法测定催化剂的比表面积,吸附一脱附法测试催化剂的表面物性,在工业装置上进行催化剂应用试验。结果表明,加入改性组分的氧化铝载体制成催化剂,其活性、选择性均有较大提高。