Effect of substituents on the hydrodechlorination reactivity of para-substituted chlorobenzenes

Effect of surface acid groups associated with amorphous and structured carbon on the catalytic hydrodechlorination of chlorobenzenes

“…In the gas phase HDC of CB, DCB and trichlorobenzene (TCB) over alumina supported Pt, Hashimoto et al 60 observed that the conversion of TCB was lower than that of DCB and CB, which were equivalent. In liquid phase applications, Aramendia et al 64 recorded a lower DCB HDC rate compared with CB, whereas Konuma et al 65 observed the reverse. Some consensus is, however, emerging in the literature2, 63, 66, 67 that gas phase HDC over Ni catalysts proceeds via an electrophilic mechanism involving a carbocation (arenium ion) intermediate as the transition complex in the rate determining step where an additional Cl substituent (as opposed to hydrogen) serves to deactivate the ring for electrophilic attack via inductive effects.…”

Complete hydrodechlorination of chlorobenzene and its derivatives over supported nickel catalysts under liquid phase conditions

“…In the gas phase reaction of substituted chlorobenzenes over a supported Ni/g-Al 2 O 3 catalyst [17], Suzdorf et al [19] observed a correlation between reaction rates and the donor-properties of the substituents. Konuma and Kameda [11] hydrogenolyzed chlorobenzenes para-substituted such groups as amino, methoxy, methyl, chloro, acetoxy and nitrile over Pd/AC catalyst in liquid phase, and found that the reactivities are accelerated by the presence of both electron-donating groups and electronwithdrawing groups. Aramendia et al [3] have sorted out the hydrodechlorination reactivity of para-substituted chlorobenzenes over Pd/AlPO 4 -SiO 2 catalysts using the Taft equation but not with the simple Hammett equation.…”

“…Noble metal catalysts, like Pd, Rh, Pt, on various supports are active for the reaction under mild conditions [2][3][4][5][6][7][8][9]. Chlorobenzene and its derivatives were hydrodechlorinated on Pd/C catalyst in a flow system [10], and Pd/AlPO 4 -SiO 2 [3] and Pd/C catalysts [11] in liquid phase, but few of these catalysts are introduced to large-scale applications because of high cost of these catalysts [12,13]. Transition metal catalysts, such as Ni, NiMo on g-alumina, silica or carbon composite [14][15][16][17][18][19][20][21] required high temperature (>473 K) or high hydrogen pressure (2 MPa) [14,15] to reach significant activity in the gas phase dechlorination process.…”

Copper and Nickel Modified MCM-41 An Efficient Catalyst for Hydrodehalogenation of Chlorobenzene at Room Temperature

“…Noble metal catalysts, like Pd, Rh, and Pt on various supports, are active for the reaction under mild conditions. − Chlorobenzene and its derivatives were hydrodechlorinated on Pd/C catalyst in a flow system; Pd/AlPO 4 −SiO 2 and Pd/C catalysts , were tested in liquid phase. A few of these catalysts are introduced to large-scale applications because of their high cost. , Transition metal catalysts, such as Ni, Ni−Mo on γ-alumina, or silica or carbon composite, − required high temperature (>473 K) or high hydrogen pressure (2 MPa) to reach significant activity in the gas phase dechlorination process.…”