- Kinetics of tetrachloromethane fluorination by hydrogen fluoride in the presence of antimony pentachloride
-
Contradictory information concerning the kinetics of tetrachloromethane fluorination by anhydrous hydrogen fluoride in the presence of antimony pentachloride has been explained. The present studies were performed using a stainless steel autoclave. The exchange of the first chlorine atom was carried out in the temperature range of 35-95°C, with the molar ratio of HF/CCl4 varied within the range of 1.2-1.7 and at a constant molar ratio of SbCl5/Cl2 equal to 1.9. The degree of conversion of CCl4 to CCl3F and the reaction rate constant as a function of temperature fit to an Arrhenius straight line. The Arrhenius constants (pre-exponential factor) and the activation energy were determined. Studies concerning the exchange of the second chlorine atom, i.e. the conversion of CCl3F to CCl2F2 have been performed. The results of kinetic investigations were created in the same way. Based on these results it was found that the Arrhenius equation is fulfilled also in the second stage of the fluorination. The same slope of the straight lines confirms that the fluorination stages proceed according to the same mechanism with the same activation energy but with different pre-exponential factors. Several kinetic problems associated with the performance of the reactor can be solved on the basis of the equations derived. However, knowledge of CCl4 conversion as a function of time, temperature, catalyst concentration and the type of the reaction is required for this purpose. Such calculations enable the selection of the optimal process parameters.
- Meissner, Egbert,Milchert, Eugeniusz
-
-
Read Online
- Interaction of trichloromethane and tetrachloromethane with nitrogen trifluoride
-
Interaction of nitrogen trifluoride with trichloromethane and tetrachloromethane at temperatures in the range from 20 to 200°C and pressures of up to 6.0 MPa in the gas and liquid phases was studied.
- Mukhortov,Pashkevich,Blinov,Kambur,Kambur,Petrov,Kurapova
-
scheme or table
p. 420 - 426
(2011/08/04)
-
- PROCESSES FOR THE SYNTHESIS OF 3-CHLOROPERFLUORO-2-PENTENE, OCTAFLUORO-2-PENTYNE, AND 1,1,1,4,4,5,5,5-OCTAFLUORO-2-PENTENE
-
Disclosed is a process comprising reacting CF3CF2CCI2CF2CF3 (CFC-41 -10mca) with hydrogen in the presence of a dehalogenation catalyst to produce CF3CF2CCI=CFCF3 (CFC-1419myx). Also disclosed herein is a process comprising reacting CF3CF2CCI=CFCF3 (CFC- 1419myx) with hydrogen in the presence of a dehalogenation catalyst to produce CF3CF2C≡CCF3 (octafluoro-2-pentyne). Also disclosed herein is a process comprising reacting CF3CF2CCI2CF2CF3 (CFC-41 -10mca) with hydrogen in the presence of a dehalogenation catalyst to produce CF3CF2C≡CCF3 (octafluoro-2-pentyne). In addition, a process for reacting CF3CF2C≡CCF3, in a pressure vessel, with a Lindlar catalyst and hydrogen to produce CF3CF2CH=CHCF3 (1,1,1,4,4,5,5,5-octafluoro-2- pentene) is disclosed.
- -
-
Page/Page column 14
(2009/07/18)
-
- Method for the preparation of high surface area metal fluorides
-
The present invention is related to a method for preparing an amorphous metal fluoride of the formula MX+FX-δ comprising the steps of a) providing a precursor, whereby the precursor comprises a structure having a formula of Mx+F(x-δ)-yBy; and b) reacting the precursor with a fluorinating agent generating the amorphous metal flouride having a formula of Mx+Fx-δ, whereby M is selected from the group comprising metals of the second, third and fourth main group and any subgroup of the periodic table, B is a coordinately bound group; x is any integer of 2 or 3; y is any integer between 1 and 3; δ is 0 to 0.1; and x?δ>y.
- -
-
Page/Page column 8
(2010/10/20)
-
- Decomposition of dichlorodifluoromethane with simultaneous halogen fixation by vanadium oxide supported on magnesium oxide
-
Dichlorodifluoromethane (CCl2F2, 1% in He) decomposition with simultaneous halogen fixation by vanadium oxide supported on magnesium oxide was studied at 723 K in a flow apparatus. The pretreatment condition and vanadium loading of supported vanadium oxide samples affected the CCl2F2 decomposition efficiency. Through characterization studies (XRD, IR, Raman, and XPS) and reference experiments, Mg 3(VO4)2 was revealed to be the active species to initiate CCl2F2 decomposition, leading to MgF 2, MgCl2, and CO2 formation. The model experiments also suggested a detailed mechanism that VOCl3 was formed from Mg3(VO4)2 by a reaction with CCl 2F2 or the major intermediate compound CCl4, and that VOCl3 reacted with MgO to regenerate Mg3(VO 4)2 and to promote chlorine fixation as MgCl2.
- Tamai, Tsukasa,Inazu, Koji,Aika, Ken-Ichi
-
p. 1565 - 1574
(2007/10/03)
-
- Enhanced dichlorodifluoromethane decomposition with selective fluorine absorption by acidic fluoriated magnesinm oxide
-
CCl2F2 decomposition with simultaneous halogen absorption by partially fluorinated MgO (MgF2-MgO) was studied, focusing on the effects of the acidity of the surface. CCl2F 2 decomposition by MgF2-MgO was greatly promoted by fluorination of MgO at 10 mol% or higher. CCl2F2 decomposition was not a catalytic process over MgF2-MgO but basically a selective fluorine absorption reaction with MgO to form MgF2. Chlorine was released in the form of CCl4 regardless of reaction temperature and degree of fluorination of MgO due to low reactivity to CCl 4. NH3-TPD and pyridine adsorption experiments were carried out to characterize the acid sites on MgF2-MgO samples. The amount of acid sites became maximum for 10% MgF2-MgO and the strength of acid sites increased as fluorination proceeded. CCl2F2 decomposition was revealed to be initiated by Lewis acid sites on MgF 2-MgO formed by CCl2F2 decomposition as well as by fluorination with hydrofluoric acid aqueous solution. Thus, formation of the Lewis acid sites was considered to be the key step for efficient CCl 2F2 decomposition with selective fluorine absorption.
- Tamai, Tsukasa,Inazu, Koji,Aika, Ken-Ichi
-
p. 1239 - 1247
(2007/10/03)
-
- The radiation chemistry of acyclic hydrofluoro and perhalogenated ether and hydrocarbon compounds
-
The radiolytic stability of some hydrofluoroethers and hydrofluorocarbons was investigated and compared with those of perfluoropolyethers (PFPEs) and the CCl2FCClF2 (CFC 113). The experimental results indicate that stability depends mainly on the relative abundance of hydrogen atoms in the molecule; however, a significant role is played also by the chemical structure (i.e. the relative positions of the hydrogen atoms in the molecule). As a result, molecules containing hydrogen atoms as -OCF2H chain ends show a higher stability compared with the other hydrofluoro compounds. Based on the analysis of the end products and on the nature of radicals detected by EPR, radiolysis mechanisms are proposed and discussed. Due to their high dipole moments the hydrofluoro compounds and CCl2FCClF2 degrade mainly through an ionic mechanism.
- Marchionni, Giuseppe,Guarda,Buttafava,Faucitano, Antonio
-
p. 153 - 162
(2007/10/03)
-
- Transient puffs of trace organic emissions from a batch-fed waste propellant incinerator
-
Emissions data have been obtained from a waste propellant incinerator. The incinerator is a dual fixed hearth, controlled air incinerator equipped with acid gas and particulate scrubbing. Puffing has been evident in this waste propellant incinerator by spikes in the CO concentration. Transient puffs of organics may travel down the combustion chambers and lead to stack emissions. The major conclusions from this study are that (1) transient puffs are formed due to the semi-batch feed nature of the combustion process (causing a local oxygen deficiency) and high water content of the desensitized propellant; (2) in batch-fed combustors, puffs can contribute to most of the organic emissions (which are relatively low) measured with US EPA sampling and analytical methods; (3) it is estimated that batch-fed combustion contributes up to 7-18 times more emissions than steady-state combustion will generate; (4) by applying dispersion analyses to determine the amount of oxygen deficiency in the flame zone, the combustion zone concentration of CO during batch-fed operation could be as high as 160,000 ppm, compared to a measured peak stack concentration of 1200 ppm CO; and (5) an organic sample is collected and averaged over at least a 2-h period that smooths out the transient peaks of organics emissions during batch-fed operation. For emissions that are associated with long-term potential health impacts, this is an appropriate sampling method. However, if a compound has a short-term potential health impact, it may be important to measure the time-resolved emissions of the compound.
- Hart, John R.
-
p. 559 - 569
(2007/10/03)
-
- The fluoromethyl ether sevoflurane as a fluoride source in halogen-exchange reactions 1
-
Fluoromethyl 2,2,2-trifluoro-1-(trifluoromethyl) ethyl ether (sevoflurane), fluoromethyl 1,1,2,3,3,3-hexafluoropropyl ether, and fluoromethyl 1,2,2,2-tetrafluoroethyl ether are found to be selective fluoride donors in some halogen-exchange reactions. For example, treatment of a mixture of a polychlorinated substrate and one equivalent of sevoflurane with a catalytic amount of antimony pentachloride gives a monofluorinated product and one equivalent of chloromethyl 2,2,2-trifluoro-1-(trifluoromethyl) ethyl ether as by-product.
- Rozov, Leonid A.,Lessor, Ralph A.,Kudzma, Linas V.,Ramig, Keith
-
-
- Generation of radical species in surface reactions of chlorohydrocarbons and chlorocarbons with fluorinated gallium(III) oxide or indium(III) oxide
-
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.
- Thomson
-
p. 1881 - 1885
(2007/10/03)
-
- Substituent effects and threshold energies for the unimolecular elimination of HCl (DCl) and HF (DF) from chemically activated CFCl2CH3 and CFCl2CD3
-
Combination of CFCl2 and methyl-d0 and -d3 radicals form CFCl2CH3-d0 and -d3 with 100 and 101 kcal/mol of internal energy, respectively. An upper limit for the rate constant ratio of disproportionation to combination, kd/kc, for Cl transfer is 0.07 ± 0.03 for collision of two CFCl2 radicals and 0.015 ± 0.005 for CH3 and CFCl2 radicals. The chemically activated CFCl2CH3 undergoes 1,2-dehydrochlorination and 1,2-dehydrofluorination with rate constants of 3.9 × 109 and 4.9 × 107 s-1, respectively. For CFCl2CD3 the rate constants are 8.7 × 108 s-1 for loss of DCl and 1.1 × 107 s-1 for DF. The kinetic isotope effect is 4.4 ± 0.9 for HCl/DCl and appears to be identical for HF/DF. Threshold energies are 54 kcal/mol for loss of HCl and 68 kcal/mol for HF; the E0's for the deuterated channels are 1.4 kcal/mol higher. Comparison of these threshold energies with other haloethanes suggests that for HF and HCl elimination the transition states are developing charges of different signs on the carbon containing the departing halogen and that chlorine and fluorine substituents exert similar inductive effects.
- McDoniel, J. Bridget,Holmes, Bert E.
-
p. 3044 - 3050
(2007/10/03)
-
- Dismutation of CFC-12 to CFC-13 over Chromia-Alumina Catalyst
-
Selective transformation of CCl2F2 (CFC-12) to fluorine-rich CClF3 (CFC-13) in the absence of HF over a chromia-alumina catalyst has been achieved.
- Venugopal, A.,Rao, K. S. Rama,Prased, P. S. Sai,Rao, P. Kanta
-
p. 2377 - 2378
(2007/10/03)
-
- Room-temperature Catalytic Fluorination of C1 and C2 Chlorocarbons and Chlorohydrocarbons on Fluorinated Fe3O4 and Co3O4
-
A study of the room-temperature reactions of a series of C1 and C2 chlorohydrocarbon and chlorocarbon substrate molecules with fluorinated iron(II,III) oxide and cobalt(II,III) oxide has been conducted.The results show that fluorinated iron(II,III) oxide exhibits an ability to incorporate fluorine into the following substrates in the order: Cl2C=CCl2 > H2C=CCl2 > CH3CCl3 > CHCl3 > CH2Cl2 > CH2ClCCl3 > CCl4 > CHCl2CHCl2.The fluorinated cobalt(II,III) oxide gave the reactivity series CHCl3 > CCl4 > H2C=CCl2 > CHCl2CHCl2 > CH2Cl2 > CH3CCl3 > CCl2CCl2 > CH2ClCl3.Reactions of C1 chlorohydrocarbon or chlorocarbon probe molecules with fluorinated Fe3O4 gave predominately C1 chlorofluorohydrocarbon and chlorofluorocarbon products, respectively, whereas fluorinated cobalt(II,III) oxide produced predominately C2 chlorofluorohydrocarbon and chlorofluorocarbons.For fluorinated Co3O4 the distribution of C2 products obtained from C1 chlorohydrocarbon precursor molecules is consistent with the formation of radical intermediates at strong Lewis acid surfaces.C2 chlorohydrocarbons exhibit a fluorine for chlorine (F-for-Cl) exchange reaction through the catalytic dehydrochlorination of the substrate to the alkenic intermediate.The F-for-Cl exchange process was dependent upon the ability of the substrate material to undergo dehydrochlorination; the inability of a substrate to undergo dehydrochlorination results in the fluorination process proceeding through the formation of chlorocarbon or chlorohydrocarbon radical intermediates.
- Thomson, James
-
p. 3585 - 3590
(2007/10/02)
-
- The reactions of xenon difluoride with "inert" solvents
-
The reactions of XeF2 with a variety of organic solvents are dscribed.XeF2 is found to undergo both hydrogen-and chlorine-fluorine exchange over a relatively short timescale with chloroform, dichloromethane and dibromomethane.XeF2 reacts very slowly with tetrachloromethane and fluorotrichloromethane, although the addition of a catalitic amount of Hf increases the rate of reaction considerably.XeF2 dissolves in acetonitrile with negligible reaction to the extent of 2.25 mol kg-1.
- Dukat, Wolfgang W.,Holloway, John H.,Hope, Eric G.,Townson, Paul J.,Powell, Richard L.
-
p. 293 - 296
(2007/10/02)
-
- Zur Kinetik des heterogenen Halogenaustausches zwischen Kaliumfluoroferraten und gasfoermigem CCl4
-
The reaction of solid KFeF4 respectively K3FeF6 with gaseous CCl4 was investigated under differential conditions.From temperature- and partial pressure dependence of the specific rate of reaction the kinetical parameters have been determined (ΔH(excit.)KFeF4 = 25.7 kJ/mol; ΔH(excit.)K3FeF6 = 40.1 kJ/mol) and the kinetic laws have been estimated.The chemical reactivity of the fluoroferrates is correlated with that of alkaline fluorides up to one dimension lower.A change in the mechanism leads to a new increase of the rate of reaction because there is now an activation of CCl4 by the reaction products for example FeCl3
- Kemnitz, E.,Hass, D.
-
p. 937 - 944
(2007/10/02)
-
- Zur Kinetik des heterogenen Halogenaustausches zwischen Alkalifluoriden und gasfoermigem CCl4
-
The Reaction IF>s + g to ICl>s + g (M = Li, Na, K) was investigated under differential conditions.The specific rates of reaction (rsp) were determined from r/t-curves.The partial pressure dependence of rsp indicates a marked influence of sorption equilibria to the stage chemical reaction.The formed solid product layer controls the further reaction enormously.For the stage of the pure chemical reaction, the values of activation enthalpy were determined and correlated with thermodynamic values like ionic distance or lattice enthalpies of the alkaline metal fluorides.
- Kemnitz, E.,Hass, D.
-
p. 1131 - 1136
(2007/10/02)
-
- BEITRAEGE ZUR CHEMIE DER SCHEFELHALOGENIDE 15. DICHLOR-FLUOR-TRIFLUOROMETHYLSULFURAN, CF3SCl2F
-
The preparation of the sulfurane CF3SCl2F is reported.Upon sublimation of the sulfonium salt CF3SCl2+AsF6- the compounds CF3SCl2F and AsF5 coexist in the gaseous phase.After trapping AsF5 as KAsF6 extremely instable CF3SCl2F is isolated and characterised by IR-, Raman- and 19F-NMR-spectroscopy.
- Minkwitz, Rolf,Nass, Ulrike
-
p. 393 - 398
(2007/10/02)
-
- SUBSTITUTIVE AROMATIC FLUORINATION WITH CHLORINE PENTAFLUORIDE
-
In contrast to limited substitutive fluorination of aromatics with halogen fluorides such as ClF, ClF3, BrF3 and IF5, fluorination is the predominant reaction path with ClF5.Under non-catalytic liquid phase conditions, benzene was converted to fluorobenzene (54percent yield) and chlorobenzene (37percent yield), respectively.For a heterocyclic substrate, i.e. 2,4,6-trifluoropyrimidine, sunstitutive fluorination predominated over chlorination.Three possible fluorination mechanisms are discussed.A transition complex of ClF5 with benzene is favored.Enhanced exchange fluorination of CCl4 was effected with ClF5 (CF2Cl2 >> CFCl3 > CF3Cl) as compared with ClF3 (CFCl3 >> CF2Cl2)
- Boudakian, Max M.,Hyde, Gene A.
-
p. 435 - 446
(2007/10/02)
-
- REACTIONS OF CHLORINE MONOFLUORIDE. SUBSTITUTION OF CHLORINE ATOMS BY FLUORINE IN CHLORINE-SUBSTITUTED ALKANES AND ESTERS
-
In anhydrous hydrogen fluoride under mild conditions chlorine monofluoride selectively substitutes the chlorine atoms in chlorine-substituted alkanes and esters by fluorine with the formation of high yields of the corresponding fluorides.The presence of an alkoxycarbonyl group or difluoromethylene group at the α position to the CHCl group deactivates the chlorine atom, and substitution by fluorine does not occur.In chloroalkanes, from which elimination of the chloride ion leads to sufficiently stable carbocations, substitution by fluorine can be realized in the absence of hydrogen fluoride at temperatures between -20 and -60 deg C.The fluorinating capacity of chlorine monofluoride is increased in the presence of catalytic amounts (3-5percent) of antimony pentachloride.Here the reaction is less selective than in hydrogen fluoride.In certain cases substitution is accompanied by hydride transfers.
- Chuvatkin, N. N.,Panteleeva, I. Yu.,Boguslavskaya, L. S.
-
p. 821 - 827
(2007/10/02)
-
- PREPARATION OF HALO-F-METHANES VIA POTASSIUM FLUORIDE-HALOGEN CLEAVAGE OF HALO-F-METHYLPHOSPHONIUM SALTS
-
Treatment of halo-F-methylphosphonium salts with potassium fluoride and halogen (I2, Br2, ICl, IBr) gives modest yields of halo-F-methanes.This method of preparation augments the classical Hunsdiecker approach to these materials.
- Burton, D. J.,Shin-Ya, S.,Kesling, H.S.
-
-
- DISPROPORTIONATION OF CF3Cl CATALYZED BY AL2O3*Cr2O3
-
A mixed oxide of Al2O3 and Cr2O3 (Al2O3*Cr2O3) showed catalytic activity higher than that of Al2O3 or Cr2O3 in the disproportionation of CF3Cl.Maximum conversion (>30percent) was obtained when the reaction was carried out over the mixed oxide (atomic ratio of Cr/Al:1/9) at 450 deg C.
- Okazaki, Susumu,Eriguchi, Hideki
-
p. 891 - 894
(2007/10/02)
-