TY - JOUR
T1 - Use of unsupported and silica supported molybdenum carbide to treat chloroarene gas streams
AU - de Lucas Consuegra, Antonio
AU - Patterson, Patricia M.
AU - Keane, Mark A.
PY - 2006/6/6
Y1 - 2006/6/6
N2 - The gas phase catalytic hydrodechlorination (HDC) of mono- and di-chlorobenzenes (423 K = T = 593 K) over unsupported and silica supported Mo carbide (Mo2C) is presented as a viable means of detoxifying Cl-containing gas streams for the recovery/reuse of valuable chemical feedstock. The action of Mo2C/SiO2 is compared with MoO3/SiO2 and Ni/SiO2 (an established HDC catalyst). The pre- and post-HDC catalyst samples have been characterized in terms of BET area, TG-MS, TPR, TEM, SEM, H2 chemisorption/TPD and XRD analysis. Molybdenum carbide was prepared via a two step temperature programmed synthesis where MoO3 was first subjected to a nitridation in NH3 followed by carbidization in a CH4/H2 mixture to yield a face-centred cubic (a-Mo2C) structure characterized by a platelet morphology. Pseudo-first order kinetic analysis was used to obtain chlorobenzene HDC rate constants and the associated temperature dependences yielded apparent activation energies that decreased in the order MoO3/SiO2 (80 ± 5 kJ mol-1) ˜ MoO3 (78 ± 8 kJ mol-1) > Ni/SiO2 (62 ± 3 kJ mol-1) ˜ a-Mo2C (56 ± 6 kJ mol-1) ˜ a-Mo2C/SiO2 (53 ± 3 kJ mol-1). HDC activity was lower for the dechlorination of the dichlorobenzene reactants where steric hindrance influenced chloro-isomer reactivity. Supporting a-Mo2C on silica served to elevate HDC performance, but under identical reaction conditions, Ni/SiO2 consistently delivered a higher initial HDC activity. Nevertheless, the decline in HDC performance with time-on-stream for Ni/SiO2 was such that activity converged with that of a-Mo2C/SiO2 after three reaction cycles. A temporal loss of HDC activity (less extreme for the carbides) was observed for each catalyst that was studied and is linked to a disruption to supply of surface active hydrogen as a result of prolonged Cl/catalyst interaction. © 2006 Elsevier B.V. All rights reserved.
AB - The gas phase catalytic hydrodechlorination (HDC) of mono- and di-chlorobenzenes (423 K = T = 593 K) over unsupported and silica supported Mo carbide (Mo2C) is presented as a viable means of detoxifying Cl-containing gas streams for the recovery/reuse of valuable chemical feedstock. The action of Mo2C/SiO2 is compared with MoO3/SiO2 and Ni/SiO2 (an established HDC catalyst). The pre- and post-HDC catalyst samples have been characterized in terms of BET area, TG-MS, TPR, TEM, SEM, H2 chemisorption/TPD and XRD analysis. Molybdenum carbide was prepared via a two step temperature programmed synthesis where MoO3 was first subjected to a nitridation in NH3 followed by carbidization in a CH4/H2 mixture to yield a face-centred cubic (a-Mo2C) structure characterized by a platelet morphology. Pseudo-first order kinetic analysis was used to obtain chlorobenzene HDC rate constants and the associated temperature dependences yielded apparent activation energies that decreased in the order MoO3/SiO2 (80 ± 5 kJ mol-1) ˜ MoO3 (78 ± 8 kJ mol-1) > Ni/SiO2 (62 ± 3 kJ mol-1) ˜ a-Mo2C (56 ± 6 kJ mol-1) ˜ a-Mo2C/SiO2 (53 ± 3 kJ mol-1). HDC activity was lower for the dechlorination of the dichlorobenzene reactants where steric hindrance influenced chloro-isomer reactivity. Supporting a-Mo2C on silica served to elevate HDC performance, but under identical reaction conditions, Ni/SiO2 consistently delivered a higher initial HDC activity. Nevertheless, the decline in HDC performance with time-on-stream for Ni/SiO2 was such that activity converged with that of a-Mo2C/SiO2 after three reaction cycles. A temporal loss of HDC activity (less extreme for the carbides) was observed for each catalyst that was studied and is linked to a disruption to supply of surface active hydrogen as a result of prolonged Cl/catalyst interaction. © 2006 Elsevier B.V. All rights reserved.
KW - Chlorobenzene(s)
KW - Hydrodechlorination
KW - Molybdenum carbide
KW - Nickel/silica
UR - http://www.scopus.com/inward/record.url?scp=33747768643&partnerID=8YFLogxK
U2 - 10.1016/j.apcatb.2006.02.006
DO - 10.1016/j.apcatb.2006.02.006
M3 - Article
SN - 0926-3373
VL - 65
SP - 227
EP - 239
JO - Applied Catalysis B: Environmental
JF - Applied Catalysis B: Environmental
IS - 3-4
ER -