Catalytic reduction of chlorobenzenes with Pd/Fe nanoparticles: reactive sites, catalyst stability, particle aging, and regeneration.
Monochlorobenzene (MCB), dichlorobenzenes (DCBs), and 1,2,4-trichlorobenzene (124TCB) dechlorination experiments in water were carried out with freshly synthesized Pd/Fe particles. The pre- and postreacted Pd/Fe samples were characterized by applying various analytical techniques (XRD, SEM, TEM, and XPS). Chlorinated benzenes could be completely reduced by the Pd/Fe to benzene and the reaction followed the pseudo-first-order kinetics. The reaction rates followed the order TCB < DCBs < MCB, while among the DCBs the order was 1,4-dichlorobenzene >1,3-dichlorobenzene > or = 1,2-dichlorobenzene. Insignificant reactions were observed with the unpalladized iron, suggesting that Pd was the only reactive site in the Pd/Fe particles. The aged Pd/Fe particles exhibited significant decrease in its dechlorination reactivity. The loss of Pd/Fe reactivity could be due to Pd dislodgment from the aged Pd/Fe particles and Pd islets encapsulation by the iron oxides film developed over aging period. Reactivity of the aged Pd/Fe could be only partially restored after HCI treatment, while regeneration with the NaBH4 reduction method could not restore its activity, although zerovalent state of the iron was reinstated.
School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Republic of Singapore.
Bao-Wei
BW
Zhu
Teik-Thye
TT
Lim
D001894:Borohydrides / Q000737:chemistry; D002384:Catalysis; D002713:Chlorine / Q000737:chemistry; D002722:Chlorobenzenes / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
D001894:Borohydrides; D002722:Chlorobenzenes; D014874:Water Pollutants, Chemical; D002713:Chlorine; D010165:Palladium; C025364:sodium borohydride; D007501:Iron