Xn:Harmful;
127-18-4Relevant articles and documents
A novel method of CCl4 disposal by disproportionation with CH4 over Pt on various supports
Bae, Jong Wook,Lee, Jae Sung,Lee, Kyung Hee,Lee, Byeongno,Yang, Duck Joo
, p. 264 - 265 (2001)
In disproportionation of CCl4 with CH4 into CH3Cl and CHCl3, platinum supported on SrCO3, SiO2, MgO and MgAl2O4 showed stable activity and high selectivities around 700 K, providing a novel disposal method of ozone-depleting CCl4.
Mechanistic modeling of the wall reactions in the pyrolysis of pentachloroethane
Huybrechts,Daniels,Van Assche,Van Mele
, p. 322 - 330 (2002)
The thermal dehydrochlorination C2HCl5 → C2Cl4 + HCl has been studied in a static system between 565 and 645 K at pressures ranging from 5 to 21 torr. The course of the reaction was followed by measuring the pressure rise in the conditioned quartz reaction vessel and by analyzing the products by gas chromatography. The observed experimental results and data from the literature for flow systems can be explained quantitatively in terms of a radical reaction model involving heterogeneous chain initiation and termination steps. The rate constants have been deduced for reactions of Cl, Cl2, and C2HCl5 over reactor walls covered with a pyrolytic carbon film and for reactions of adsorbed Cl atoms.
Influence of amine buffers on carbon tetrachloride reductive dechlorination by the iron oxide magnetite
Danielsen, Karlin M.,Gland, John L.,Hayes, Kim F.
, p. 756 - 763 (2005)
The influence of amine buffers on carbon tetrachloride (CCI4) reductive dechlorination by the iron oxide magnetite (FeIIFe II2O4) was examined in batch reactors. A baseline was provided by monitoring the reaction in a magnetite suspension containing NaCl as a background electrolyte at pH 8.9. The baseline reaction rate constant was measured at 7.1 × 10-5 ± 6.3 × 10-6 L m-2 h-1. Carbon monoxide (CO) was the dominant reaction product at 82% followed by chloroform (CHCI3) at 5.2%. In the presence of 0.01 M tris-(deuteroxymethyl) aminomethane (TRIS d), the reaction rate constant nearly tripled to 2.1 × 10 -4 ± 6.5 × 10-6 L m-2 h -1 but only increased the CHCI3 yield to 11% and did not cause any statistically significant changes to the CO yield. Reactions in the presence of triethylammonium (TEAd) (0.01 M) increased the rate constant by 17% to 8.6 × 10-5 ± 8.1 × 10 -6 L m-2 h-1 but only increased the CHCI 3 yield to 8.8% while leaving the CO yield unchanged. The same concentration of N,N,N′,N′-tetraethylethylenediamine (TEEN) increased the reaction rate constant by 18% to 8.7 × 10-5 ± 4.8 × 10-6 L m-2 h-1 but enhanced the CHCI3 yield to 34% at the expense of the CO yield that dropped to 35%. Previous work has shown that CHCI3 can be generated either through hydrogen abstraction by a trichloromethyl radical ( .CCI3), or through proton abstraction by the trichlorocarbanion (-:CCI3). These two possible hydrogenolysis pathways were examined in the presence of deuterated buffers. Deuterium tracking experiments revealed that proton abstraction by the trichlorocarbanion was the dominant hydrogenolysis mechanism in the magnetite-buffered TRISd and TEAd systems. The only buffer that had minimal influence on both the reaction rate and product distribution was TEAd. These results indicate that buffers should be prescreened and demonstrated to have minimal impact on reaction rates and product distributions prior to use. Alternatively, it may be preferable, to utilize the buffer capacity of the solids to avoid organic buffer interactions entirely.
Novel photocatalytic mechanisms for CHCl3, CHBr3, and CCl3CO2 degradation and the fate of photogenerated trihalomethyl radicals on TiO2
Choi, Wonyong,Hoffmann, Michael R.
, p. 89 - 95 (1997)
The photocatalytic degradation of CHCl3, CHBr3, CCl4, and CCl3CO2- is investigated in aqueous TiO2 suspensions. A common intermediate, the trihalomethyl radical, is involved in the degradation of each substrate except for CCl3CO2-, CHCl3 and CHBr3 are degraded into carbon monoxide and halide ions in the absence of dissolved oxygen. The anoxic degradation proceeds through a dihalocarbene intermediate, which is produced by sequential reactions of the haloform molecule with a valence band hole and a conduction band electron. Carbon dioxide and halide ion are formed as the primary products during CHCl3 degradation in the presence of oxygen. Under these conditions, the trihalomethyl radicals react rapidly with dioxygen. At pH > 11, degradation of the haloforms is enhanced dramatically. This enhancement is ascribed to photoenhanced hydrolysis. The secondary reactions of the trichloromethyl radical generated during CCl4 photolysis is strongly influenced by the nature of the electron donors. Both ·CCl3 and Cl- production increase substantially when 2-propanol is present as an electron donor. A new photocatalytic mechanism for CCl3CO2- degradation, which involves the formation of a dichlorocarbene intermediate, is proposed.
Dynamic behaviour of chlorofluoroethanes at fluorinated chromia aerogels and fluorinated zinc(II) or magnesium(II) doped chromia aerogels
Bozorgzadeh, Hamid,Kemnitz, Erhard,Nickkho-Amiry, Mahmood,Skapin, Toma?,Winfield, John M.
, p. 83 - 92 (2003)
The preparation and characterisation of two series of fluorinated chromia aerogel materials, lightly doped with zinc(II) or magnesium(II), are described. They behave as heterogeneous catalysts for transformations of 1,1,2-trichlorotrifluoroethane under HF
Generation of radical species in surface reactions of chlorohydrocarbons and chlorocarbons with fluorinated gallium(III) oxide or indium(III) oxide
Thomson
, p. 1881 - 1885 (1998)
The reactions of C1 and C2 chlorohydrocarbons and chlorocarbons have been studied with the Lewis acid catalysts fluorinated gallium(III) oxide and fluorinated indium(III) oxide, respectively. Product analysis shows chlorine-for-fluorine exchange reactions together with the formation of 2-methylpropane and its chlorinated analogues 2-chloromethyl-1,3-dichloropropane and 2-chloromethyl-1,2,3-trichloropropane. Reactivities of the chlorohydrocarbon probe molecules show fluorinated gallium(III) oxide to be a stronger Lewis acid than fluorinated indium(III) oxide. The formation of the symmetrical butyl compounds is consistent with the generation of surface radical species and is also consistent with a 1,2-migration mechanism operating within radical moieties at the Lewis acid surface.
Chlorination and dehydrochlorination reactions relevant to the manufacture of trichloroethene and tetrachloroethene: Part 1. Reaction pathways
Sutherland, Iain W.,Hamilton, Neil G.,Dudman, Christopher C.,Jones, Peter,Lennon, David,Winfield, John M.
, p. 1 - 11 (2011)
Factors which affect the selectivity of the chlorination of 1,2-dichloroethane and the associated dehydrochlorination reactions have been examined using approximate thermodynamic calculations, equilibrium measurements, and a continuous flow micro-reactor. There is a balance between surface and gas-phase chemistry within the system. Heterogeneous catalysis is not necessary to effect dehydrochlorination of 1,1,2,2-tetrachloroethane to trichloroethene but an attapulgite-supported copper(II) chloride catalyst favours formation of pentachloroethane and its dehydrochlorination product, tetrachloroethene. The latter is the thermodynamic minimum of the system. Below 473 K and with long reaction times (2 h, batch reactor), radical chlorination to form pentachloroethane is dominant. Above 573 K and under flow conditions, free radical dehydrochlorination to form trichloroethene becomes dominant. Heterogeneous chlorination under flow conditions provides a route to pentachloroethane and thence tetrachloroethene. High conversions favour the formation of oligomeric products.
Hydrodechlorination of Tetrachloromethane over Supported Pt Catalysts
Kim, Sang Y.,Choi, Hyun C.,Yanga, O B.,Lee, Kyung H.,Lee, Jae S.,Kim, Young G.
, p. 2169 - 2170 (1995)
In the selective hydrodechlorination of tetrachloromethane to chloroform, long catalytic life as well as high selectivity to chloroform is achieved over a platinum catalyst supported on MgO.
The pyrolysis of CCl4 and C2Cl6 in the gas phase. Mechanistic modeling by thermodynamic and kinetic parameter estimation
Huybrechts,Narmon,Van Mele
, p. 27 - 36 (1996)
A detailed radical reaction mechanism is proposed to describe the thermal reactions of CCl4 and C2Cl6 in the gas phase quantitatively. A consistent set of activation energies and preexponential factors for all elementary reactions, in combination with enthalpies of formation and entropies for all species involved, is computer optimized to fit experimental pressure-rise curves and concentration profiles. For this purpose new experimental results on the pyrolysis of CCl4 are used, together with published kinetic data on the pyrolysis of C2Cl6 (in the absence and in the presence of Cl2).
A homoleptic tetravalent cerium silylamide
Crozier, Alan R.,Bienfait, Andre M.,Maichle-Moessmer, Caecilia,Toernroos, Karl W.,Anwander, Reiner
, p. 87 - 89 (2013)
Treatment of Ce[N(SiHMe2)2]3(thf) 2 with the chlorinating agents PhICl2, Ph3CCl or C2Cl6 gave the homoleptic Ce(iv) silylamide Ce[N(SiHMe2)2]4. When performed in the absence of donating (solvent) molecules, the trivalent cluster Ce 5[N(SiHMe2)2]8Cl7 was isolated.
