Pd/Fe双金属对1,2,4-三氯苯的催化脱氯

采用Pd/Fe双金属体系对1,2,4-三氯苯（1,2,4-TCB）进行了快速催化还原脱氯的研究.结果表明,在钯的催化作用下,零价铁对1,2,4-TCB有较好的还原脱氯效率.当Pd/Fe双金属的钯化氯为0.06%时,催化剂用量为1g/40mL,反应1h后TCB的脱氯率可达99%.反应速率随钯化氯的提高而增加.反应在Pd/Fe表面进行,符合准一级反应,反应速率常数为0.0837min-1.TCB在催化脱氯的过程中先脱氯成为DCB,再依次脱氯为氯苯和苯.     

零价铁对土壤中六氯乙烷还原脱氯研究

本文研究了常温常压下Fe^0及其负载贵金属的多组分体系及其他反应条件对土壤中六氯乙烷还原脱氯效率的影响。实验证明：Fe^0及其负载Pd、Pt、Rh多组分金属体系对六氯乙烷都有还原脱氯作用,Pd、Pt、Rh之间不存在协同催化还原脱氯效应;反应初始pH呈酸性时有利于脱氯反应进行;加入甲醇能够提高六氯乙烷在土壤溶液中的溶解度,但不能有效提高其在土壤中的还原脱氯率;甲酸铵是Fe^0体系对六氯乙烷还原脱氯的良好助剂,当甲酸铵加入量为400mg时,用Fe^0还原六氯乙烷脱氯率可以提高59％左右;相同实验条件下,用Pd／Fe还原六氯乙烷的脱氯率可以提高77％左右。文中对零价铁还原脱氯反应机理和助剂甲酸铵的作用机理作了初步探讨。     

零价金属对氯代有机物还原脱氯的研究进展

对零价金属及双金属体系在还原氯代有机物中的应用做了综述,展望了零价金属还原脱氯降解氯代有机物研究领域的发展前景.     

Ni/Fe双金属降解CCl4、CHCl3和CH2Cl2的试验

在批试验条件下研究了Ni/Fe双金属对CCl4(CT)、CHCl3(TCM)和CH2Cl2(DCM)的还原性脱氯性能。结果表明:(1)Ni/Fe双金属可有效对CT和TCM脱氯,但对DCM没有脱氯效果;(2)Ni/Fe双金属对CT和TCM的降解反应均符合准一级反应动力学方程;(3)在相似的反应条件下,Ni/Fe双金属对CT和TCM的脱氯效果好于Fe0,且脱氯速度与Ni/Fe质量比在一定数值范围内成正比;(4)对CT和TCM脱氯的反应速率常数kSA相差10.98～16.60倍,说明Ni/Fe双金属对氯代程度高的CT脱氯快于对氯代程度低的TCM;(5)Ni/Fe双金属对CT脱氯过程产生TCM,不产生DCM,且随着反应时间的继续,产生的TCM也继续被降解;而Ni/Fe双金属对TCM脱氯并不逐级产生DCM;Fe0对CT脱氯不仅产生TCM,也产生DCM。     

Fe/Cu催化还原法处理氯代有机物的机理分析

研究了多种氯代有机物在铁、铜二金属体系中的还原脱氯处理效果,着重分析了氯代有机物还原脱氯处理中的机理问题,探讨了还原脱氯反应的基本原理、还原脱氯反应中pH值的变化、出水中Fe2 浓度的变化以及有机物结构性质对还原脱氯反应的影响。     

氯代烷烃在Fe/Cu二相金属体系中的催化还原脱氯研究

以氯代甲烷系列为例研究了多种氯代烷烃在Fe／Cu二相金属体系中的还原脱氯反应．分析了氯代有机物结构性质对还原脱氯反应的影响和规律性,以及反应过程中pH的变化．并探讨了氯代烷烃在金属还原作用下的还原脱氯机理。     

纳米级Co/Fe双金属催化剂对废水脱氯的研究

采用化学还原法制备了纳米级Co/Fe双金属催化剂,对其催化水溶液中四氯化碳还原脱氯性能进行了考察,并与废铁屑催化性能进行了对比。同时,考察了反应条件对脱氯性能的影响。结果表明,采用化学还原法制备的纳米级Co/Fe双金属催化剂具有较高的比表面积和表面反应活性,对四氯化碳的脱氯效果优于废铁屑。搅拌转速、反应温度和脱氯时间对脱氯效率有促进作用。     

Pd/Fe双金属体系对1,2,4-三氯苯脱氯机理探讨

在重水和水作溶剂下,采用Pd/Fe双金属体系在常温常压下对1,2,4-TCB的脱氯机理进行了研究.结果表明,TCB脱氯是逐步完成的;TCB在催化脱氯过程中先脱氯成为DCBs,再依次脱氯为氯苯和苯;重水作溶剂,用氘示踪可推知为了整个脱氯反应的速度和完成度,脱氯中间产物1,2-DCB含量会明显大于1,3-DCB和1,4-DCB,以便在下一阶段脱氯反应中可以更快的脱氯.     

氯代有机物在铁、铜双金属体系中的还原脱氯研究

本文研究了多种氯代有机物在铁、铜双金属体系中的还原脱氯处理效果,着重分析了氯代有机物在还原脱氯处理中的机理问题,探讨了还原脱氯反应的基本原理、还原脱氯反应中pH值的变化以及有机物结构性质对还原脱氯反应的影响。     

Ni-Fe双金属对氯代苯酚催化还原脱氯的试验

分别采用Ni-Fe双金属体系和单一零价铁对氯代有机物2,4-二氯苯酚、2-氯苯酚和4-氯苯酚进行了催化还原脱氯的研究。结果表明:单一零价铁能够对氯代苯酚还原脱氯,但效率不高,通常在10%～25%。在镍的催化作用下,零价铁对氯代苯酚的还原脱氯效率大大提高。当零价铁加入量为60 g/L,硫酸镍为0.6 g/L,初始氯代苯酚的质量浓度在25 mg/L左右,反应初始pH值控制在偏酸性的条件下,还原脱氯效率可达到70%以上。氯代苯酚降解的准一级速率常数和降解率满足以下规律:4-氯苯酚大于2-氯苯酚大于2,4-二氯苯酚。     

Pd/Fe对-二氯苯的催化脱氯及其动力学

o-Dichlorobenzene (o-DCB) was dechlorinated by Pd/Fe powder in water through catalytic reduction. The dechlorination reaction is believed to take place on the surface site of the catalyst via a pseudo-first-order reaction. The final reduction product of o-DCB is benzene. The dechlorination rate increases with the increase of bulk loading of palladium due to the increase of both the surface loading of palladium and the total surface area. Dechlorination efficiency accounts for 90% at Pd/Fe mass ratio 0.02% and metal to solution ratio about 53.3g-L-1 in 120 minutes. Dechlorination is affected by the reaction temperature, pH, Pd/Fe ratio and the addition of Pd/Fe. Ea is found to be 102.5kJ.mol-1 in the temperature ra,nge of 287-313K.     

Catalytic hydrodechlorination of hexachlorobenzene on carbon supported Pd-Ni bimetallic catalysts

The study of the catalytic activity of carbon supported Pd-Ni catalysts for the hydrodechlorination of hexachlorobenzene was carried out in the liquid phase. The degree of dechlorination was found proportional to the surface Pd concentration, which is enhanced by the segregation of this element at the surface of the bimetallic particles.

It is also shown that isolated Pd atoms located at the surface of Ni rich bimetallic particles are more active than those lying in larger ensembles.

Finally bimetallic Pd-Ni catalysts containing only between 20 and 50 Pd atom%, although less active than pure Pd, lead to 75% of useful compounds, i.e. benzene, mono and dichlorobenzene.     

纳米钯金铁三金属催化剂的制备及其对三氯乙烯的降解

在乙醇-水体系中利用硼氢化物液相还原法合成纳米铁颗粒,通过化学沉淀法将钯金粒子负载于纳米铁表面,得到纳米钯金铁(Pd-Au@Fe)三金属催化剂复合材料,采用TEM, EDS和XPS对其进行表征. 结果表明,与纳米单金属Fe0及双金属Pd@Fe相比,三金属催化剂对三氯乙烯(TCE)具有更高的降解能力. 保持催化剂加量1.4 g/L, Pd/Fe为0.35%(w), Au/Fe为1.0%(w)时,其降解15 mg/L TCE的速度最快,5 min时去除率为88.21%,表观速率常数为0.311 min-1,是相同Pd含量下Pd@Fe双金属催化剂的3.6倍. 随降解反应持续,Pd-Au@Fe的乙烯乙烷生成率及乙烯加氢转换乙烷速率均远高于双金属Pd@Fe.     

Treatment of chlorinated organic contaminants with nanoscale bimetallic particles

Nanoscale bimetallic particles (Pd/Fe, Pd/Zn, Pt/Fe, Ni/Fe) have been synthesized in the laboratory for treatment of chlorinated organic pollutants. Specific surface areas of the nanoscale particles are tens of times larger than those of commercially available microscale metal particles. Rapid and complete dechlorination of several chlorinated organic solvents and chlorinated aromatic compounds was achieved by using the nanoscale bimetallic particles. Evidence observed suggests that within the bimetallic complex, one metal (Fe, Zn) serves primarily as electron donor while the other as catalyst (Pd, Pt). Surface-area-normalized reactivity constants are about 100 times higher than those of microscale iron particles. Production of chlorinated byproducts, frequently reported in studies with iron particles, is notably reduced due to the presence of catalyst. The nano-particle technology offers great opportunities for both fundamental research and technological applications in environmental engineering and science.     

纳米晶Pd修饰p-Si电极的制备及其光电析氢性能

在半导体p型Si上化学沉积金属Pd,制备了纳米晶Pd修饰p-Si电极.控制化学沉积的时间,可得到不同沉积量和不同尺度的Pd颗粒,沉积时间为20 min时,Pd颗粒的直径约为80 nm.XRD测试结果表明,Pd颗粒的平均晶粒尺寸为7.37 nm.重点研究了Pd/p-Si电极在光照前后的催化析氢性能.光照下Pd/p-Si电极的析氢过电位较无光照减小约250 mV,比半导体Si减小约450 mV（电流密度为2.5 mA•cm^-2时）.电化学交流阻抗谱（EIS）表明,光照下Pd/p-Si电极的电化学析氢反应电阻由未光照的593.12 Ω•cm2降低至442.20Ω•cm²,光照下的析氢反应速率明显增加.     

MCM-41 supported PdNi catalysts for dry reforming of methane

A series of bimetallic PdNi catalysts supported on mesoporous MCM-41 with different Ni content (Ni/Si ratio of 0.2–0.4) was synthesized. The effect of Pd addition to Ni-containing catalysts as well as the effect of the Ni content on the surface and catalytic properties of the catalysts was studied. The samples were characterized using various techniques, such as energy-dispersive X-ray spectroscopy, N₂ adsorption–desorption isotherms, X-ray diffraction, thermogravimetric and differential analyses, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy and temperature-programmed reduction. Reforming of methane with carbon dioxide was used as a test reaction. The results indicated that the addition of a small amount of Pd (0.5%) to Ni-containing catalysts leads to formation of small nano-sized, easy reducible NiO particles. Agglomeration of NiO as well as of metallic nickel phase over PdNi samples increased with increasing the Ni content. Formation of filamentous carbon over surface of spent monometallic Ni and bimetallic PdNi catalyst was observed. In spite of filamentous carbon deposition, the catalytic activity and stability of bimetallic PdNi catalysts are higher than those of monometallic Ni one. Within bimetallic system, the PdNi catalyst with Ni/Si ratio of 0.3 revealed the best performance and stability caused by presence of small nickel particles well dispersed on the catalyst surface.     

Pt/Ni wet impregnated over Al incorporated mesoporous silicates: a highly efficient catalyst for anisole hydrodeoxygenation

This work reports, formation of benzene from anisole via hydrodeoxygenation process using vapour phase fixed bed reactor. The surface properties of bimetallic catalysts such as textural properties, acidic, and Pt/Ni dispersion has established by various characterization techniques. The reaction was carried out at 370 and 420 °C with space velocity 3.3 & 6.6 h^??1, over acidic and non-acidic supported mono and bimetallic catalysts. The optimum conversion and selectivity was observed at 420 °C and WHSV?=?3.3 h^??1 for all mono and bimetallic catalysts. Pt/Ni/Al-SBA-15 acidic bimetallic catalyst shows maximum anisole conversion 59% with benzene selectivity 37% under atmospheric pressure, due to the more acidic centres and high dispersion of Pt/Ni species on the bimetallic catalyst, enhance the anisole conversion; this was proved by NH₃-TPD and HR-TEM analysis. The acidic Pt/Ni bimetallic catalyst shows higher anisole conversion as compared to the mono metallic Pt/Ni catalysts and it works predominantly through demethylation and hydrogenolysis reaction pathway.     

Bimetallic gold/palladium catalysts for the selective liquid phase oxidation of glycerol

A new methodology for the preparation of single phase bimetallic Au–Pd on activated carbon (AC) has been recently developed and now used for preparing Au/Pd catalysts at different atomic ratio. The bimetallic catalysts have been tested in the liquid phase oxidation on glycerol in water using oxygen as the oxidant and compared with monometallic Au and Pd catalysts. We observed that strong synergistic effect is present in a large range of Au/Pd ratio, being maximized for Au₉₀–Pd₁₀ composition. Gold-rich composition showed an increased durability compared to palladium-rich alloy.     

Electrochemical and structural characterization of carbon-supported Pt-Pd bimetallic electrocatalysts prepared by electroless deposition

Electrochemical and structural characteristics of various Pt-Pd/C bimetallic catalysts prepared by electroless deposition (ED) methods have been investigated. Structural analysis was conducted by X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDS). Monometallic Pt or Pd particles were not detected by EDS, indicating the ED methodology formed only bimetallic particles. The size of the Pt-Pd bimetallic particles was smaller than those of a commercially available Pt/C catalyst. The morphology of the Pt on Pd/C catalysts was identified and corresponded to Pd particles partially encapsulated by Pt.The electrochemical characteristics of the lowest Pd loading catalyst (7.0% Pt on 0.5% Pd/C) for the oxygen reduction reaction (ORR) have been investigated by the rotating ring disk electrode technique. The electrochemical activity was equal or lower than the commercially available Pt/C catalyst; however, the amount of hydrogen peroxide observed at the ring was reduced by the Pd, suggesting that such a catalyst has the potential to decrease ionomer degradation in applications. The Pt on Pd/C catalysts also show a higher tolerance to ripening induced by potential cycling. Therefore, catalyst suitability cannot be judged solely by its initial performance; information related to specific degradation mechanisms is also needed for a more complete assessment.