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Priority 1989-12-22 • Filed 1990-12-13 • Granted 1995-02-15 • Published 1995-02-15

Background of the Invention.
• [0003]
  There are references in the literature concerning several methods for reducing the halogen content of a range of organohalogenated compounds. Nevertheless, the majority are impractical and of no commercial interest because of their excessive sophistication.
• [0004]
  As a result of the declining market for carbon tetrachloride, there is a growing excess of this product. In view of this situation, researchers are trying to revalue this product by searching for methods allowing it to be used as a raw material for the manufacture of chloroform, the market demand for which is, on the contrary, growing.
• [0005]
  Thus, the Dow Chemical Co. U.S. patent 2,886,605 of 1959 teaches a method of hydrodehalogenation of polyhalogenated hydrocarbons, using a cuprous chloride catalyst in a fluidized bed. The greatest drawback of this method for commercial exploitation is that it is run at so high temperatures (350^oC to 550^oC) that such an abundant carbonization occurs that it becomes necessary continuously or very frequently to regenerate the catalyst.
• [0006]
  Another Dow Chemical Co. patent (U.S. 3,579,596 of 1971) teaches a process for producing chloroform from gas phase carbon tetrachloride, using a fixed catalyst bed of platinum on a substrate. This method, nevertheless, suffers from serious limitations, such as:
• a) the need to use excessively high amounts of hydrogen relative to stoichiometry encourages the production of methane and, furthermore, extraordinarily hinders the recovery of the reaction products.
• b) The reaction is highly exothermic (H = -22.70 kcal/mol, at 400 K, for a 100% theoretical selectivity of chloroform production), making it very hard to control the temperature. According to trials carried out by the inventors, hot spots are formed in the catalyst in the gas phase process, encouraging the formation of free radicals which, in turn, give rise to the formation of heavy polychlorinated compounds. When these are deposited on the catalyst surface they almost immediately and irreversibly deactivate it.
Description of the Invention.
• [0007]
  Example 2.-
  • [0036]
    This Example relates to the preparation of chloroform (CHCl₃).
  • [0037]
    2,072 g of liquid carbon tetrachloride were charged into a stainless steel tubular reactor, 1.25 m high x 4 cm inside diameter, without mechanical stirring, and 24.89 g of catalyst prepared as per Example 1 were added. After purging the air, the hydrogen flow was opened and was adjusted to give permanently 1 l/min H₂ in the exhaust. The hydrogen was fed in through the bottom of the reactor, was diffused through a perforated plate and, further to being used as reactant, it was also used to stir the liquid and the solid. The reactor was heated to 160^oC and the pressure was adjusted to 3,000 kPa. After one hour (t = 1 hour) an 86.6% carbon tetrachloride conversion to chloroform, with a 77.6% molar selectivity (S) was obtained, representing a productivity rate (P) of 2,762 kg CHCl₃/hour per kg palladium.
  • [0038]
    The selectivity (S) is defined as the number of moles of carbon tetrachloride converted into product, divided by the total number of moles of carbon tetrachloride reacted multiplied by 100.
  • [0039]
    The main by-products obtained were:
  • hexachloroethane, with selectivity: S(C₂Cl₆) = 1.2%.
  • tetrachloroethylene, with selectivity: S(C₂Cl₄) = 14.8%
  • methane, with selectivity: S(CH₄) = 3.9%.
  • [0040]
    The complements to 100 of the selectivity sums correspond to small amounts of other by-products, such as ethane, trichloroethane, pentachloroethane and traces of others.

US2095240A 1937-10-12 Chloroform manufacture