The method of vapor-phase hydrodechlorination of carbon tetrachloride

 

(57) Abstract:

The invention relates to the production of chlorinated derivatives of methane, ethane, ethylene catalytic hydrochloridebuy of carbon tetrachloride. The process is conducted in the vapor phase using a platinum catalyst on the carrier. As a carrier of the active component - platinum use of diamond-like substance. Selectivity for compounds C2above is 2 to 8 times compared with known methods. table 1.

The invention relates to a method of catalytic hydrodechlorination of chlorinated organic compounds. More specifically, it relates to a method of hydrodechlorination of carbon tetrachloride on platinum catalysts, representing the deposited platinum.

Products hydrodechlorination of carbon tetrachloride on platinum catalysts are compounds C1mainly chloroform and methane, and connections C2mainly chlorinated derivatives of ethylene and ethane. Known methods of hydrodechlorination of carbon tetrachloride, for example, US patent 3 579 596, US atent 5 146 013, US patent 5 081 097), are characterized by a significantly higher selectivity for compounds C1, Cano close to 100%, and in the patent (US patent 5 081 097), selected as a prototype, the catalyst is platinum on alumina, this figure is reduced to only 80%, i.e., the selectivity of the formation of compounds C2does not exceed 20%.

The aim of the present invention is to provide a method for hydrodechlorination of carbon tetrachloride on platinum catalysts, providing higher in comparison with the known methods, the selectivity of the formation of compounds C2having a practical interest. The objective is achieved by deposition of platinum on a carrier of diamond-like substances (RF patent 2051093, BI, 1995 No. 36, S. 201), providing the necessary degree of oxidation of the catalyst surface and dispersion of platinum.

As a diamond-like substance used diamond nanopowder (A. M. Staver, A. I. the Lyamkin, N. In. Gubareva, E. A. Petrov. The way to obtain diamonds. Auth. mon. THE USSR, N 1165007 (01. 07. 82), A. I. the Lyamkin and other Receiving diamonds from explosives. DAN SSSR, 1988, I. 302, No. 3, S. 611-613), resulting from the detonation of explosive mixtures of TNT with RDX in a 1: 1 ratio in the blast chamber filled with carbon dioxide. The nanopowder separated from the condensed carbon is Alenia non-diamond forms of carbon and metallic impurities.

Physico-chemical properties of diamond-like substances characterized by a set of analytical techniques, including x-ray analysis, spectroscopy Raman scattering, spectroscopy electron paramagnetic resonance, mass spectrometry and electron microprobe elemental analysis, infrared spectroscopy. The samples represent carbon dielectric material with a crystalline structure of diamond. The average crystallite size of 4 nm. The specific surface of the powder - 280 m2/, Content of non-diamond forms of carbon not more than 5 wt.%. The composition of the diamond-like substance composed of oxygen up to 10%, the nitrogen and hydrogen to 1%, other impurities - a total of up to 2%. Its main differences from other diamond-like carbon substances subject to the specifics of the detonation synthesis and lie in the small size of the crystals, defects in their structure and the presence of surface functional cover defining surface activity, in particular, tightly-coupled surface groups, C-O, which are stable up to temperatures of 700oC.

The catalyst was prepared by mixing nanopowder of diamond-like substance with an aqueous solution of charitablecardonation the behaviour of the catalyst was carried out on running cellophane glass installation. The reactor was heated in an air thermostat. Before the beginning of experiments freshly loaded catalyst was reduced by hydrogen directly in the reactor at 450oC.

Hydrogen was purified using a palladium membrane. Carbon tetrachloride was filed in the installation, saturating them with hydrogen in the saturator.

Analysis of the reaction products was carried out by the methods of gas chromatography and volumetric titration.

Example 1. 15 g Nanopowder slaboionizovannogo diamond-like substances (broadened line on the radiograph when d = 0,205 nm, the average crystallite size of 3.8 nm, broadened line 1328 cm-1in the spectra of CU) containing point defects and dislocations (intense singlet with g-factor 2.00 and H = 8 GS in the spectrum EPR) and surface CO-group with a characteristic frequency of vibration of C= O bond (intensive line 1880 cm-1in the IR spectra, the concentration of group - 8 wt.% oxygen), were mixed in a mortar with 25 ml 0,0069 molar aqueous solution hloristovodorodnykh acid (platinum concentration of 2.34 g/l) to form a paste. The resulting paste was extrudible through the metal syringe with a diameter of Spinneret 3 mm extrudates were dried in air at room temperature for 20 h, and then in susil the Torah - 0.39 wt.%.

Example 2. 7,89 g (15 cm3) Of the catalyst prepared as described in example 1 were loaded into eraksoy reactor (diameter 20 mm) with a Central pocket for thermocouples (diameter 4 mm) was heated in a stream of hydrogen (5 nl/h), 450oC and kept under these conditions for 4 hours and Then the reactor was cooled to 150oC and reduced total flow of hydrogen to 4.2 nl/h In this part of the hydrogen (1,68 nl/h) on the way to the reactor was saturated vapors of carbon tetrachloride (of 0.6 nl/h).

The reaction mixture was 4.2 nl/h of hydrogen and 0.6 nl/h of carbon tetrachloride was carried out at 150 and 80oC. the Results of these tests are shown in table.

Example 3. For comparative tests of the preparation of the catalyst used well-known carrier - aluminum oxide with a specific surface area of 200 m2/g immediately before use calcined in air at 550oC for half an hour.

13,62 g of a Carrier in the form of extrudates with a diameter of 3 mm was soaked in water holding capacity of 2.2 N. hydrochloric acid solution hloristovodorodnykh acid (platinum concentration 0,0038 g/ml). The impregnated pellets were kept in closed containers within four days. Then four hours was dried in a drying Cabinet at 130ooC and expenses of the initial reactants, hydrogen and carbon tetrachloride - 4,2 and 0.6 nl/h, respectively. The results presented in the table.

From the comparison of the results in examples 2 and 3, it follows that the proposed method significantly (2-8 times) to increase the selectivity of the process for compounds C2.

The method of vapor-phase hydrodechlorination of carbon tetrachloride in the presence of platinum catalyst on a carrier, characterized in that as the carrier of the use of diamond-like substance.

 

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