Hydrodechlorination and oligomerization of carbon tetrachloride over nickel Y zeolites

Journal Article · Fri Jan 01 04:00:00 EST 1982 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(82)90017-3· OSTI ID:6803675

Weiss, A H ^[1]; Valinski, S; Antoshin, G V

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1. Worcester Polytechnic Inst., MA

A pulsed microreactor was used to study the reaction of carbon tetrachloride with hydrogen at 370/sup 0/C over NiNaY, NiCuNaY, NiCrNaY, NiCoNaY, and CuNaY. Nickel was present at about 30 wt%. Activity was in the above order when catalysts were incompletely reduced at 370/sup 0/C. Ni/sup 0/ in NiCoY was measured to be 40% of the total Ni by X-ray photoelectron spectroscopy. Upon complete reduction at 530/sup 0/C, NiCoNaY became the most active and most selective catalyst for production of 1,1,1,2-tetrachloroethane (I). The highly specific conversion of CCl/sub 4/-0.40 mole Cl/sub 3/CCH/sub 2/Cl/mole CCl/sub 4/ at 80-100% conversion - is postulated to proceed by a free-radical mechanism initiated by H/sub 2/ dissociation on the metal H/sub 2/ reverse arrow..-->.. 2Hin equilibrium, followed by hydrodechlorination propagation reactions such as CCl/sub 4/ +.H..-->...CCl/sub 3/ + HCl, CH/sub 2/Cl/sub 2/ + .H..-->...CH/sub 2/Cl + HC1 and oligomerization termination reactions such as .CCl/sub 3/ + .CH/sub 2/Cl..-->..Cl/sub 3/CCH/sub 2/Cl. Catalyst activity and selectivity to I correlated with the order of Ni diffusion out of the supercages. Outside, on the crystallite, hydrogen from the gas stream is readily available, and hydrodechlorination is favored by excess hydrogen. Inside the supercage there should exist a relative deficiency of hydrogen, and oligomerization could be favored. That the latter process proceeds inside the supercage is evidenced by the abrupt deactivation of the catalysts after a highly active initial period. The deactivation would be related both to HCl generation and to formation of higher-molecular-weight oligomers inside the zeolite. In the absence of metal, NaY is inactive. It is probable that the Ni/sup 0/ inside and outside the supercage is not of a different nature, but the proportions in effect tailor the catalyst selectivity. Such a remarkable selectivity to Cl/sub 3/CCH/sub 2/Cl was not anticipated.

• OSTI ID: 6803675
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 74:1; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
CARBON TETRACHLORIDE
CATALYTIC EFFECTS
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
DATA
DECHLORINATION
ELEMENTS
EXPERIMENTAL DATA
HALOGENATED ALIPHATIC HYDROCARBONS
HIGH TEMPERATURE
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
METALS
MINERALS
NICKEL
NUMERICAL DATA
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
RADICALS
REDUCTION
TRANSITION ELEMENTS
YTTRIUM
ZEOLITES