Regeneration of Pd/Al2O3 catalysts used for tetrachloroethylene hydrodechlorination

The deactivation of the Pd/Al₂O₃ catalyst used for the hydrodechlorination of tetrachloroethylene (TTCE) is caused by both the carbonaceous deposits and by the hydrogen chloride produced in the reaction. In this work, several regeneration procedures have been tested, concluding that the best procedure is the leaching with ammonia, followed by calcinations and reduction. This procedure leads to an important recovery of the initial activity. The catalyst regenerated with this treatment is even less prone to deactivation that the fresh catalyst.     

Liquid-phase hydrodechlorination of polychloroaromatic compounds in the presence of Pd-promoted nickel catalysts

Liquid phase hydrodechlorination of chlorobenzene, 1,2,4-trichlorobenzene, hexachlorobenzene, polychlorinated biphenyls in the ethanol-containing solution, on Me⁰/C (where Me⁰-Pd, Ni or bimetallic Ni−Pd; C-carbon material “Sibunit”) with H₂ have been studied at 20–70°C and P_{H 2}=1–50 atm. Pd and Pd-promoted Ni catalysts exhibit the highest activity. Kinetic studies show hydrodechlorination of these compounds to be a consecutive reaction, which under the conditions described may produce less chlorinated compounds.     

Catalytic hydrodechlorination of chlorobenzene in liquide phase

Catalytic hydrodechlorination of chlorobenzene (CB) was carried out in the liquid phase in a mixture of methanol/water (MeOH/H₂O) at 30°C and 2kg/cm² pressure. The reaction orders with respect to CB and H₂ pressure were one and zero, respectively. Addition of NH₄OH in the reaction produces a decrease in the activity (TOF). Solvent effect shows the following order of activity: H₂O>MeOH/H₂O>EtOH/H₂O>MeOH.     

Making the liquid-phase catalytic hydrodechlorination of pce over Pd/C safer

Summary The hydrodechlorination of tetrachloroethylene in methanol (MeOH) over palladium catalysts on activated carbon (Pd/C) at 20°C and atmospheric pressure was rendered safer by using ethanol (EtOH), isopropanol (IPA) or water-alcohol mixtures as solvents. Adding water to MeOH was better than using EtOH or IPA since it resulted in a faster reaction and better stability of Pd/C, which could also be completely reactivated.     

金属钯纳米颗粒/氮化钛复合材料对水中2,4-二氯苯酚的电催化氢化脱氯（英文）

随着社会经济的快速发展,含氯有机物,特别是含氯苯系物,在农业、化工和医药等领域的使用量逐年增多,而使用过程中不合理的排放和控制致使含氯苯系物对生态环境,特别是水体环境的污染日趋严重.含氯苯系物具有高致毒致癌性,易生物富集,且很难被完全降解矿化,已被国家环保局认定为优先控制污染物.常规的废水处理工艺,如吸附、氧化及生物降解等,效率不高,且具有二次污染风险.电催化氢化脱氯技术是一种新型特别针对废水中含氯有机污染物的处理工艺,是通过在阴极电解还原水,原位生成原子态氢,以进攻苯环上C.Cl键,通过C.Cl键断裂H原子取代,使含氯苯系物完全转化为苯系物,达到去毒去害化的目的,近年来越来越受到研究者的关注.在整个电催化氢化脱氯技术中,高效稳定的电催化剂合成是关键,决定着脱氯效率、脱氯动力学、产物选择性及能量的利用率.本文报道了一种简易、无需添加任何表面活性剂的湿式还原法制备金属钯/氮化钛(Pd/TiN)和金属钯/碳(Pd/C)复合材料.在该复合材料中,金属钯颗粒具有均一的纳米尺寸(约5.0 nm)和球状形貌,且均匀分布在TiN和C载体上.作为针对水体中代表性含氯苯系物2,4-二氯苯酚的电催化氢化脱氯反应催化剂,Pd/TiN所展现的活性和稳定性均优于TiN和Pd/C,这源于TiN载体的促进作用.当TiN与Pd复合时,相应形成的Pd-TiN界面可改变Pd表面的电子结构,进一步优化Pd产活性氢及其吸附活化2,4-二氯苯酚的性能,因而其催化氢化脱氯活性增加.阴极工作电压是该催化反应中一个重要操作参数,决定了电催化氢化脱氯的效率和最终产物的构成.实验表明,.0.80 V vs Ag/AgCl是最佳操作电压,此时2,4-二氯苯酚的电催化氢化脱氯效率最高,可达到93.27%,且可实现最大程度的2,4-二氯苯酚向苯酚转化.脱氯反应路径研究发现,在Pd/TiN催化剂上2,4-二氯苯酚脱氯反应路径为2,4-二氯苯酚→对位一氯苯酚,邻位一氯苯酚→苯酚,但Pd/TiN对邻位和对位的C.Cl键断裂基本没有选择性.本文提供了一种新的有效调控Pd材料电催化氢化脱氯性能的方法,可望用于其他氢化反应体系的高效催化剂的设计合成,同时可推动电催化氢化脱氯技术在环境污染修复中的应用.     

Photocatalytic decomposition of tetrachloroethylene in the gas phase with titanium dioxide as catalyst

The gas phase photocatalytic destruction of tetrachloroethylene (PCE) was investigated by using an in situ photocatalytic reactor with FT-IR analysis in batch mode. The main products of PCE degradation are CO₂ and COCl₂, with trichloroacetylchloride as an intermediate. It was found that the rate of PCE degradation and the appearance of products in the gas phase are highly dependent on their adsorption properties on the surface of the catalyst, besides other reaction conditions, such as the intensity of irradiation and the composition of the reaction mixture.     

4-硝基二苯胺和4-亚硝基二苯胺钠催化加氢制4-氨基二苯胺 Ⅰ.溶剂对加氢反应的影响

用Pd—M/C催化剂(M为非贵金属),对工业原料4-硝基二苯胺及4-亚硝基二苯胺钠催化加氢制4-氨基二苯胺,其活性和选择性都较好。本文报导了在常压加氢中添加各种溶剂对反应的影响,并建议采用苯胺溶剂较适宜。     

Tandem catalytic condensation and hydrogenation processes in ionic liquids

A domino reaction composed of a Knoevenagel condensation combined with a simultaneous catalytic hydrogenation is reported in an ionic liquid solvent under mild conditions (298-363 K and 300 kPa). No interference between the catalysts (Pd/C and amine acetate salt) of the two diverse steps was monitored. The product could be neatly extracted by diethyl ether and the solvent containing the catalysts could be recycled and reused five times without any loss in activity or selectivity. The same methodology in a common organic solvent such as DMA resulted in significant competing parallel hydrogenation of the aldehyde to alcohol.     

Pd-Co/C催化剂上葡萄糖的催化氧化反应

Pd-Co/C催化剂上葡萄糖的催化氧化反应     

电感耦合等离子体发射光谱(ICP-OES)法同时测定活性炭中铝、钴、镉、铜、铁、镁、锰、钠、磷、硫10种元素

提出了使用ICP-OES同时测定活性炭中Al、Co、Cr、Cu、Fe、Mg、Mn、Na、P和S的分析方法。采用高氯酸和硝酸处理样品,以硝酸作为测定介质,在选定的仪器工作条件下直接测定。各元素的测定检出限为0.002～0.012μg/mL,相对标准偏差(RSD,n=6)为0.32%～1.83%。对样品进行加标回收试验,回收率在92.1%～108.4%之间。实验表明:方法不仅具有较高的灵敏度和较低的检出限,而且快速、准确,能够满足活性炭和以活性炭为载体的催化剂杂质元素分析的要求。     

Palladium nanoparticles supported on cucurbit[6]uril: an efficient heterogeneous catalyst for the Suzuki reaction under mild conditions

A new NC palladacycle was synthesized and supported on cucurbit[6]uril (CB[6]). The CB[6]‐supported palladium was used as an efficient nanocatalyst for the Suzuki reaction. In these reactions various aryl halides were reacted with arylboronic acids in H₂O–EtOH at both room temperature and 40 °C. The obtained Pd nanocatalyst exhibited excellent reactivity and stability in C ? C bond formation, which confirms that the catalyst is a completely active heterogeneous species. The Pd nanocatalyst was characterized using X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. Copyright © 2014 John Wiley & Sons, Ltd.     

甘氨酸在DMF/水和乙醇/水混合溶剂中的焓对相互作用

利用LKB2277生物活性检测仪对298.15K时甘;氨酸在纯水,DBF/水和乙醇/水混合溶剂DBF(或乙醇的质量分数为0.05~0.45,以10%递增)中的稀释焓进行了测定,并利用维里展开式法关联得到焓对相互作用系数值.结果表明,焓对相互作用系数h~2与溶剂的结构性质密切相关.在DBF/水混合物溶剂中,h~2随DBF含量的增加而变得更负;而在乙醇/水混合溶剂中,h~2与乙醇含量近似呈抛物线型关系,在乙醇质量分数为0.25时h~2达到一个极小值。     

芳香氨基酮选择性还原反应的研究

非均相催化剂(钯碳催化剂)一般会将芳香酮彻底还原至亚甲基产物,而不易得到苄醇类的中间还原产物.本文报道一系列氨基酮用钯碳催化剂催化氢化的结果,随酮底物含有不同种类的氨基而得到不同的氢化产物(亚甲基产物或二级醇产物),部分则不发生还原反应;分析讨论了底物所含氨基对产物的影响及其机理.结果表明,这是一个制备胺基芳香仲醇的有效方法.     

Synthesis of Xenbucin using Suzuki reaction catalyzed by Pd/C in water

Xenbucin 1, an analgesic drug, was synthesized in 4 steps using two different routes. The biaryl fragment could successfully be produced via a Pd/C catalysed Suzuki coupling in water using sodium tetraphenylborate as a phenylation reagent. Overall yields of the routes were 36% and 59%, respectively.      

Comparative study on electrochemical degradation of 4-chlorophenol by different Pd/C gas diffusion electrodes

Pd/C catalyst used for the Pd/C gas diffusion cathodes was prepared by hydrogen reduction method and formaldehyde reduction method, and characterized by X-ray diffraction (XRD), transmission elec- trode microcopy (TEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) tech- niques. The electrochemical degradation of 4-chlorophenol was investigated in the diaphragm elec- trolysis system, aerating firstly with hydrogen gas then with air, using three different kinds of gas dif- fusion cathode. The results indicated that the self-made Pd/C gas diffusion cathode can not only re- ductively dechlorinate 4-chlorophenols by aerating hydrogen gas, but also accelerate the two-electron reduction of O2 to hydrogen peroxide (H2O2) by aerating air. Therefore, the removal efficiency of 4-chlorophenol by using Pd/C gas diffusion cathode is better than that of the C/PTFE gas diffusion cathode (no catalyst). The catalytic activity of Pd/C catalyst prepared by hydrogen reduction method is higher than that prepared by formaldehyde reduction method. The stability of the Pd/C gas diffusion cathodes is good. Therefore, both the removal efficiency and the dechlorination degree of 4-chlorophenol reached about 100% after 60 min, and the removal efficiency of 4-chlorophenol in terms of chemical oxygen demand (COD) in the cathodic compartment reached 87.4% after 120 min.     

Selective Hydrogenation of Aromatic Aminoketones by Pd/C Catalysis

We report an alternative hydrogenation of aromatic aminoketones by heterogeneous catalyst of palladium on carbon (Pd/C) in which nitro, in particular carbonyl groups in the ketones, could be selectively transformed to corresponding amino ketone, secondary alcohol, or methylene compound.     

室温CO催化氧化反应动力学的研究

本文采用无梯度反应器,考察了纳米金催化剂以及其它商品化的催化CO氧化催化剂,在不同CO浓度下催化CO氧化反应的转化率和反应速率,证明在CO初始浓度从ppm到pct数量级范围内,纳米金催化剂具有最好的催化CO室温转化的能力.     

水相中Pd/C催化的杂环芳卤的还原偶联反应研究

在H₂O-alcohol体系中通过Pd/C催化的还原偶联反应由杂环芳卤高收率的得到了二芳基化合物. 该方法操作简单, 环境友好, Pd/C可重复使用, 无需相转移催化剂也能得到较高收率. 讨论了醇、碱的种类和用量以及不同底物对反应收率的影响.     

Synthesis and catalytic performance on methanol conversion of NiAPSO-34 crystals (II): catalytic performance under various reaction conditions

This work has been focused on the catalytic performance for methanol conversion of NiAPSO-34 catalysts which had been synthesized by various preparation methods. The deposited coke during the hydrocarbon transformation was analyzed by temperature-programmed oxidation (TPO) method. For a catalyst with small acid sites and sharp particle size distribution, the catalytic activity and selectivity to ethylene increased compared with other catalysts. It could be confirmed that the catalysts having different acidic densities on external surface and internal surface represented different catalytic activities. Furthermore, it was elucidated that amount of coke formation was strongly related to acidic density on the external crystal surface. On the other hand, catalytic performances under various reaction conditions were exhibited variously and the deposited coke amount was also various. In particular, a surprising result was that the catalytic performance was not changed on the revived catalyst by thermal treatment at 600°C for 3 h.     

钯-膦-酸体系催化烯烃氢酯基化反应研究进展

烯烃氢酯基化反应是羰基合成领域的重要分支之一,长期以来一直备受关注。目前已发展了钯基、铑基、钴基、钌基等众多催化体系,其中钯-膦-酸催化体系因具有反应条件温和、底物普适性良好、催化性能优异等优点而得到最广泛、最深入的研究。因此,我们对均相、非均相的钯-膦-酸催化体系在烯烃氢酯基化反应中的研究应用进行了简要综述,并对催化机理、催化剂组成和性能进行讨论,最后指出稳定性高、可回收性好的非均相钯-膦-酸催化体系将是该领域的研究重点。