Pd/TiO2催化剂对三氯生的催化加氢脱氯研究
Catalytic hydrodechlorination of triclosan over Pd/TiO2
-
摘要: 采用沉淀-沉积法制备不同载体的Pd负载型催化剂，采用透射电镜（TEM）、X-射线衍射（XRD）和电感耦合等离子体发射光谱（ICP-AES）对材料进行表征；并以所得材料为催化剂对三氯生（TCS）的催化加氢脱氯反应进行了研究.结果表明，Pd/TiO2型催化剂在TCS加氢脱氯反应中具有较好的效果，反应活性随着Pd负载量的提高而增强.当反应物初始浓度为0.016 mmol·L-1，pH值为10，催化剂0.36% Pd/TiO2用量为20 mg时，TCS在70 min可以完成脱氯过程.碱性条件下，pH的升高不利于反应的进行.当催化剂用量在15-25 mg时，催化剂质量标化的反应初活性没有明显变化，表明催化反应过程不受传质阻力的影响.当反应物初始浓度在0.009-0.02 mmol·L-1时，反应初活性随浓度的提高显著增加，但进一步增加反应物的浓度时初活性没有明显提高，因此，TCS在Pd/TiO2催化剂上的脱氯行为符合Langmuir-Hinshelwood模型，表明TCS的加氢脱氯受表面吸附所控制.催化反应的过程中生成多种脱氯中间产物，反应的最终产物为2-羟基二苯醚.Abstract: Supported palladium catalysts were prepared by the deposition-precipitation method,and were characterized by TEM, XRD and ICP-AES. The liquid phase catalytic hydrodechlorination of triclosan (TCS) over the catalysts was investigated. Pd/TiO2catalysts showed good catalytic performance in hydrodechlorination process, and the catalytic activity increased with Pd loading. At initial TCS concentration of 0.016 mmol·L-1, pH 10 and catalyst dosage of 50 mg, complete hydrodechlorination of TCS was achieved within 70 min. Under alkaline conditions, increasing pH hindered the reaction. The initial activity normalized by catalysts mass was found to be nearly identical when the amount of catalyst used varied within 15-25 mg, indicative of the absence of mass transport limitations. Finally, the initial activity was markedly enhanced with the initial concentration of TCS when the concentration was in the range of 0.009-0.02 mmol·L-1. While it remained constant with higher initial concentration, reflecting that the catalytic hydrodechlorination of TCS over Pd/TiO2 followed the Langmuir-Hinshelwood model, and the catalytic hydrodechlorination was controlled by TCS adsorption. During the catalytic hydrodechlorination process of TCS, many intermediate products were formed, and the final product was 2-phenoxyphenol.
-
Key words:
- Pd/TiO2 /
- triclosan /
- hydrodechlorination /
- deposition-precipitation
-
-
[1] PERENCEVICH E N, WONG M T, HARRIS A D.National and regional assessment of the antibacterial soap market:A step toward determining the impact of prevalent antibacterial soaps[J]. American Journal of Infection Control, 2001, 29(5):281-283. [2] ZHAO J L, ZHANG Q Q, CHEN F, et al. Evaluation of triclosan and triclocarban at river basin scale using monitoring and modeling tools:Implications for controlling of urban domestic sewage discharge[J]. Water Research, 2013,47(1):395-405. [3] United States Environmental Protection Agency. Estimating Exposure to Dioxin-Like Compounds[R]. Washington D C:Office of Water, Office of Science and Technology, 1994. [4] MENOUTIS J, PARISI A I. Testing for dioxin and furan contamination in triclosan[J].Cosmetics and Toiletries, 2002, 117(10):75-78. [5] LATCH D E, PACKER J L, ARNOLD W A, et al. Photochemical conversion of triclosan to 2,8-dichlorodibenzo-p-dioxin in aqueous solution[J]. Journal of Photochemistry and PhotobiologyA:Chemistry, 2003, 158(1):63-66. [6] RULE K L, EBBETT V R, VIKESLAND P J. Formation of chloroform and chlorinated organics by free-chlorinemediated oxidation of triclosan[J]. Environmental Science & Technology,2005, 39(9):3176-3185. [7] SON H S, KHIM J, ZOH K D. Degradation of triclosan in the combined reaction of Fe2+and UV-C:Comparison with the Fenton and photolytic reactions[J]. Environmental Progress & Sustainable Energy, 2010,29(4):415-420. [8] KIM Y M, MURUGESAN K, SCHMIDT S, et al. Triclosan susceptibility and cometabolism A comparison for three aerobic pollutant-degrading bacteria[J]. Bioresource Technology, 2011, 102(3):2206-2212. [9] BEHERA S K, OH S Y, PARK H S. Sorption of triclosan onto activated carbon, kaolinite and montmorillonite:Effects of pH, ionic strength, and humic acid[J]. Journal of Hazardous Materials, 2010, 179(1):684-691. [10] VLADIMIR I KOVALCHUK, JULIE L D'ITRI. Catalytic chemistry of chloro and chlorofluorocarbon dehalogenation:From macroscopic observation to molecular level understanding[J].Applied Catalysis A:General, 2004, 271:13-25. [11] XIAC H,LIU Y,ZHOU S W,et al.The Pd-catalyzed hydrodechlorination of chlorophenols in aqueous solutions under mild conditions:A promising approach to practical use in wastewater[J].Journal of Hazardous materials,2009,169:1029-1033. [12] YUAN G, KEANE M A. Role of base addition in the liquid-phase hydrodechlorination of 2, 4-dichlorophenol over Pd/Al2O3 and Pd/C[J].Journal of Catalysis,2004, 225(2):510-522. [13] PANAGIOTOPOULOU P,KONDARIDES D I. Effect of morphologicalcharacteristics of TiO2-supported noble metal catalysts on theiractivity for the water-gas shift reaction[J].Journal of Catalysis,2004,225(2):327-336. [14] WANG M,GUO D J,LI H L. High activity of novel Pd/TiO2 nanotube catalysts for methanol electro-oxidation[J].Journal ofSolid State Chemistry,2005,178(6):1996-2000. [15] WOJCIESZAK R,GENET M J,ELOY P,et al. Determination of thesize of supported Pd nanoparticles by X-ray photoelectronspectroscopy. Comparison with X-ray diffraction,transmissionelectron microscopy,and H2 chemisorption methods[J].Journal of Physical Chemistry C,2010,114(39):16677-16684. [16] YUAN G,KEANE M A.Liquid phase catalytic hydrodechlorinationof 2,4-dichlorophenol over carbon supported palladium:Anevaluation of transport limitations[J].Chemical Engineering Science,2003,58(2):257-267. [17] 刘冬,周娟,万玉秋,等.碳纳米管负载Pd基催化剂对水中2,4-二氯酚的催化加氢脱氯[J].环境化学,2013,32(3):351-357. LIU D, ZHOU J,WAN Y Q.Catalytic hydrodechlorination of 2,4-dichlorophenolover carbon nanotube supported Pd catalysts[J].Environmental Chemistry,2013,32(3):351-357(in Chinese).
[18] ILINITCH O M, CUPERUS F P, NOSOVA L V, et al. Catalytic membrane in reduction of aqueous nitrates:Operational principles and catalytic performance[J]. Catalysis Today, 2000, 56:137-145. [19] YUAN G, KEANE M A. Aqueous-phase hydrodechlorination of 2,4-dichlorophenol over Pd/Al2O3:Reaction under controlled pH[J].Industrial and Engineering Chemistry Research, 2007,46(3):705-715. [20] GUMY D,GIRADO S A,RENGIFO J, et al. Effect of suspended TiO2 physicochemical characteristics on benzene derivatives photocatalytic degradation[J].Applied Catalysis B:Environmental, 2008,78(1-2):19-29. [21] KOSMULSKI M.pH-dependent surface charging and points of zero charge. Ⅳ. Update and new approach[J].Journal of Colloid Interface Science, 2009, 337(2):439-448. [22] MOGYORÓSI K,BALÁZA N,SRANKÓ D F, et al. The effect of particle shape on the activity of nanocrystalline TiO2photocatalysts in phenol decomposition. Part 3:The importance of surface quality[J]. Applied Catalysis B:Environmental, 2010, 96(3-4):577-585. -
点击查看大图
计量
- 文章访问数: 1242
- HTML全文浏览数: 1166
- PDF下载数: 424
- 施引文献: 0
下载:
