钯/铁双金属对水中氯苯的催化脱氯研究

钯/铁双金属能有效地进行氯苯的催化脱氯.实验考察了钯化率、氯苯水溶液初始pH、钯/铁投加量、反应温度等参数对氯苯脱氯效果的影响.实验结果表明,把钯作为催化剂明显加速了氯苯还原脱氯反应,并且脱氯率随着钯化率增加而增加.在温和条件下(室温、常压、低钯化率(0.005%)),5h内氯苯脱氯率达45%以上.在钯/铁双金属表面,氯苯的脱氯符合准一级反应.速率常数为0.0071min-1,用钯/铁表面积校正后的速率常数为8.0×10-3L·m-2·h-1.

钯/铁双金属对土壤中2,2′,3,4,4′,5,5′-七氯联苯的催化脱氯研究

采用Fe0还原、钯催化法对土壤中2,2′,3,4,4′,5,5′-七氯联苯的的还原特性进行了实验研究.结果表明,Pd/Fe双金属能有效地进行2,2′,3,4,4′,5,5′-七氯联苯的催化脱氯.在钯化率为0.05%、钯/铁加入量1 g、初始pH为5.6、反应时间5 d的条件下,钯/铁双金属对土壤中2,2′,3,4,4′,5,5′-七氯联苯去除率达54%.实验还考察了钯化率、初始pH、反应时间、钯/铁投加量、2,2′,3,4,4′,5,5′-七氯联苯初始浓度等参数对2,2′,3,4,4′,5,5′-七氯联苯脱氯效果的影响.研究表明,较高的钯化率、钯/铁加入量,较低的2,2′,3,4,4′,5,5′-七氯联苯初始浓度及弱酸性等条件更有利于Pd/Fe对2,2′,3,4,4′,5,5′-七氯联苯的还原脱氯.在Pd/Fe双金属表面,2,2′,3,4,4′,5,5′-七氯联苯的脱氯符合一级动力学反应,反应速率常数为0.014 2/h,其半衰期为49 h.利用实验数据,对钯/铁双金属作用下的2,2′,3,4,4′,5,5′-七氯联苯还原脱氯的反应机制也进行了分析.

纳米钯/铁双金属颗粒对一氯乙酸的脱氯

为了提高零价铁对氯代有机物还原脱氯的性能,采用还原沉淀法制备了纳米钯/铁双金属颗粒.利用X射线衍射(XRD)、X射线荧光光谱(XRF)、扫描电子显微镜(SEM)、透射电镜(TEM)、以及BET-N2比表面积法对纳米钯/铁双金属颗粒进行了表征.结果表明,制备的纳米钯/铁双金属颗粒中Fe主要以α-Fe0形式存在.纳米钯/铁双金属颗粒的直径约为30～50nm,比表面积约51m2/g.纳米钯/铁双金属颗粒对一氯乙酸还原脱氯的脱氯率是还原铁粉和纳米铁粉对一氯乙酸还原脱氯的脱氯率的7.9倍和1.7倍.

纳米钯/铁双金属对2,4-二氯酚的还原脱氯研究

应用改进液相还原法合成纳米Pd/Fe双金属颗粒并对2,4-二氯酚进行还原脱氯,探讨双金属颗粒的钯负载率和初始pH值对脱氯效率的影响.结果表明,合成的纳米钯/铁颗粒分散均匀,平均粒径为50 nm.纳米Pd/Fe双金属颗粒对2,4-二氯酚的脱氯反应符合拟一级反应动力学方程.量子化学计算与还原脱氯实验均表明,分子中氯原子的化学环境对还原脱氯过程具有明显影响.

Pd/Fe双金属对水中m-二氯苯的催化脱氯

Pd/Fe bimetallic catalysts were synthesized via chemical deposition and used to treat m-DCB.Batch experiments demonstrated that the Pd/Fe bimetallic particles could effectively dechlorinate m-DCB.The dechlorination efficiency reached 90% at a Pd/Fe loading ratio of 0.02% (mass) and metal to solution ratio 4g∶75ml in 90 min.Dechlorination was affected by several factors such as reaction temperature, pH, Pd/Fe ratio, and the induction of Pd/Fe catalysts.Chlorobenzene represents the partially stable dechlorinated intermediate in the generation of the final product (i.e., benzene), while part of m-DCB was dechlorinated to benzene directly.The dechlorination reaction was believed to take place mainly on the active surface sites of the Pd/Fe bimetallic particles via a pseudo-first order reaction, and the activation energy of this reaction was found to be 96.6 kJ·mol -1 .

金属催化还原技术对p-二氯苯的脱氯

研究了Pd/Fe双金属体系对 p 二氯苯 (p DCB)的快速催化还原脱氯处理 .结果表明 ,在Pd的催化作用下 ,零价Fe对p DCB具有较好的还原脱氯效率 .当Pd/Fe双金属的钯化率为 0 0 2 % ,催化还原剂的用量为 4 g/ 75mL ,反应 90min p DCB脱氯率达到 90 %以上 ;p DCB的脱氯效率与溶液初始pH值、反应温度、钯化率、Pd/Fe投加量等因素有关 ;p DCB在催化还原脱氯过程中先生成氯苯 。

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0.0837m in-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。

Environmentally benign and economic synthesis of covalent triazine-based frameworks

Covalent triazine-based frameworks（CTFs） are important microporous materials with a wide range of applications.Here,we demonstrate an environmentally benign and economic synthetic pathway to CTFs.The monomers used for CTFs,aromatic nitriles,were obtained by cyanation using nontoxic potassium hexacyanoferrate（Ⅱ） in place of commonly used toxic cyanides.Then,the CTFs were synthesized by trimerization of the corresponding cyano monomers in molten zinc chloride.A series of CTFs was synthesized,and the highest Brunauer-Emmett-Teller surface area measured in this series was 2404 m^2/g.Among the synthesized CTFs,CTF_（DCP） exhibited excellent CO_2 adsorption properties,with a CO_2 uptake of 225 mg/g at 0℃.

Pd-M-TiO_(2)(M=Mn,Cu,Ce and Fe)as passive NO_(x) adsorber(PNA)at low temperature

A series of transition metal Mn,Cu,Ce and Fe were loaded on TiO_(2) by sol-gel method with noble metal Pd as promotor for the application of passive NO_(x) absorber.Experiments on adsorption and desorption of NO_(x) were conducted and characterization methods such as X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM)and in situ Fourier transform infrared spectroscopy(in situ DRIFTS)were involved.The experimental results show that Mn-contained catalysts,Mn-Ti and Pd-Mn-Ti,performed excellent NO_(x) adsorbing ability and appropriate desorption temperature window.On the other hand,Ce-and Cu-contained samples were not suitable for the purpose of PNA.In addition to the low adsorption capacity,these two series of catalysts released massive amount of NO below 150℃.Characterization results indicated that Pd was highly dispersed on all catalysts.The loading of Pd lowered not only the valence states of transition metals but surface oxygen percentage as well.From in situ DRIFTS tests,the Pd had little influence on the types of adsorbed substances for Mn,Ce and Cu series.However,the storage forms of NO_(x) were obviously different on Pd-Fe-Ti and Fe-Ti.