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.
Zhu
Bao-Wei
BW
School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Republic of Singapore.
Lim
Teik-Thye
TT
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