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Ind. Eng. Chem. Res. 1996, 35, 3290-3294
Technological Parameters in the Synthesis of 1,1,1-Trichloroethane from Vinylidene Chloride Eugeniusz Milchert,* Waldemar Goc, Jolanta Stefan ´ ska, and Waldemar Paz´ dzioch Department of Organic Technology, Technical University of Szczecin, Pułaskiego 10, Pl 70-322 Szczecin, Poland
The optimum parameters in the synthesis of 1,1,1-trichloroethane during the reaction between vinylidene chloride and hydrogen chloride are as follows: temperature, 22 °C; catalyst (FeCl3) concentration, 0.3% by weight;, equimolar ratio of raw materials; VDC flow rate, 0.22-0.23 cm3 cm-3 h-1. Changing these parameters does not result in considerable change in the product yield. Introduction During the production of vinyl chloride the waste fraction is formed at the stage of ethylene chlorination and 1,2-dichloroethane pyrolysis. The fraction called “heavy” contains mainly 1,2-dichloroethane and significant amounts of 1,1,2-trichloroethane. The following composition seems to be typical (% by weight): 1,2dichloroethane, 68; 1,1,2-trichloroethane, 24; perchloroethylene, 4; tetrachloroethane, 3; pentachloroethane, 1. The simplest way of processing this fraction is by chlorinolysis to tetrachloroethylene and tetrachloromethane:
3CH2ClCH2Cl + 11Cl2 f 2CCl2dCCl2 + 2CCl4 + 12HCl 6CHCl2CH2Cl + 25Cl2 f 4CCl2dCCl2 + 4CCl4 + 18HCl 1,1,2-Trichloroethane is advantageously used by conversion to vinylidene chloride (VDC):
CHCl2CH2Cl f CCl2dCH2 + HCl Considerable amounts of vinylidene chloride are used in production of 1,1,1-trichloroethane (111-TCE, Vogt, 1962):
CCl2dCH2 + HCl f CCl3CH3 Synthetic methods to produce 1,1,1-trichloroethane and applications of this compound have been discussed in papers by Milchert et al. (1992). Several methods of 111-TCE synthesis in the reaction between VDC and HCl have been described in the patent literature. In these methods the addition was carried out in the presence of AlCl3 as catalyst and nitrobenzene (Campbell et al., 1962; Nishihara et al., 1973). Baggs (1977) described the catalytic activity of simple secondary, tertiary, and quaternary ammonium hydroxides. The processes were carried out at ambient temperature or at 35 °C (Stephan and Richtzenhain, 1966) maintaining FeCl3 catalyst suspended using the HCl stream. The application of a chloro derivative of higher boiling temperature such as 1,1,2-trichloroethane or perchloroethylene elongated the durability of FeCl3 as a catalyst and made it possible to carry out the process below 75 °C and under an atmospheric pressure (Lobunez and Berkowitz, 1969). The literature review indicates that the synthesis at ambient or raised temperature, in the S0888-5885(95)00185-0 CCC: $12.00
Figure 1. Scheme of the equipment for 1,1,1-trichloroethane synthesis: (1) reactor, (2) product receiver, (3) thermometer, (4) distillation head, (5) water condenser, (6) brine condenser, (7) dryer with CaCl2, (8) packed scrubber, (9) flow meter, (10) piston pump.
presence of FeCl3 and reaction product as a solvent, appears to be the most advantageous. The thermodynamic properties of 111-TCE and reaction thermodynamics have also been known (Rubin et al., 1944). The production of 111-TCE based on reacting VDC with hydrogen chloride has been applied in industry, but the influence of reaction parameters on the course of this synthesis has not yet been described and the optimum parameters have not yet been determined. Experimental Section Analytical Control. The composition of 111-TCE and VDC was determined by a gas chromatography method. The determinations were carried out using a Chrom 5 apparatus, equipped with a steel column 3 m × 4 mm filled with 15% by weight SE 30 on Chromosorb W AW DMCS 80/100 mesh connected with an identical © 1996 American Chemical Society
Ind. Eng. Chem. Res., Vol. 35, No. 10, 1996 3291
Figure 2. Influence of raw materials flow rate: temperature 25 °C; catalyst concentration, 0.3% by weight; VDC:HCl molar ratio, 1:1; (O) 1,1,1-trichloroethane yield; (4) nonreacted vinylidene chloride in relation to the amount introduced.
column filled with 10% by weight FFAP on Chromosorb W AW DMCS 80/100 mesh. The FID detector employed nitrogen as the carrier gas at 28 cm3/min, and the injection chamber and detector temperatures were 200 °C. The oven temperature was 50 °C for 10 min and then increased at a rate of 5 °C/min to 150 °C and held at 150 °C for 12 min. Hydrogen chloride in the aqueous layer was determined by acid-base titration. Methods of Synthesis. Each experiment was carried out in a continuous manner. A determined amount of 111-TCE and catalyst (FeCl3) was introduced into the tube reactor having a capacity of 0.5 dm3 and an inside diameter of 3 cm (Figure 1). The hydrogen chloride absorber was sprinkled with water. The reactor temperature was set. The flows of cooling streams and raw materials hydrogen chloride and VDC were started. On finishing the experiment, the content of the reactor was collected in the flask and combined with product from the receiver. The product (approximately 150 cm3) was shaken in a separatory funnel with 50 cm3 of water. After the aqueous and organic layers had been separated, the layers were weighed and analyzed by gas chromatography. The experiments were carried out at an equimolar VDC to hydrogen chloride ratio. It is known (Campbell et al., 1962; Vogt, 1962) that a deficiency in hydrogen chloride lowers the conversion of VDC to 111-TCE. The excess of hydrogen chloride increases the losses in volatile VDC and makes the recycling of hydrogen chloride into the reactor necessary. The yield of 111-TCE was calculated in relation to VDC introduced to the reactor. Additionally, the fraction of nonreacted VDC in relation to that introduced to the reactor was calculated. The selectivity of the 111TCE synthesis in relation to VDC used in all experiments was 100%. Raw Materials. Vinylidene chloride, 99.9%, was obtained from Department of Organic Technology,
Technical University of Szczecin; VDC was distilled prior to each synthesis in order to separate hydroquinone monomethyl ether (stabilizer). Hydrogen chloride from a steel cylinder, 99.9% by weight, was the product of Bohumin Chemical Plant, Czech Republic. 1,1,1-Trichloroethane, 99.8% by weight, from LobaChemie, Austria, was used as the reaction medium. Anhydrous ferric chloride, 98% pure, was obtained from Alfa Products, Germany. Results and Discussion Preliminary Tests. A series of syntheses of 111TCE was performed in order to determine the influence of the flow rate of VDC and hydrogen chloride on its yield. The experiments were carried out by maintaining the following reaction conditions: temperature, 25 °C; atmospheric pressure; VDC to hydrogen chloride molar ratio, 1 to 1.00-1.02; FeCl3 concentration in the reaction medium, 0.3% by weight. The duration of the experiments was from 4.2 to 8 h, depending on the feeding flow rate. The lower the raw materials flow rate, the longer the duration of the experiment. The experimental results are gathered in Figure 2. The results show that for the VDC flow rate over the range of 0.0300.254 cm3 cm-3 h-1 the yield of 111-TCE remains almost constant with a simultaneous negligible increase in the nonreacted VDC amount in relation to that introduced into the reactor. The losses of VDC are also negligible. The increase in raw materials flow rate above 0.254 cm3 cm-3 h-1 causes the decrease in 111-TCE yield and an increase in VDC losses. The stream of hydrogen chloride carries away a significant amount of VDC. The content of VDC in the product in relation to raw material introduced increases insignificantly. Another series of 111-TCE syntheses was performed over the temperature range of 15-30 °C. The other parameters of the syntheses were as follows: VDC flow rate, 0.227 cm3 cm-3 h-1; FeCl3 concentration, 0.3% by
3292 Ind. Eng. Chem. Res., Vol. 35, No. 10, 1996
Figure 3. Influence of temperature: VDC flow rate, 0.227 cm3 cm-3 h-1; catalyst concentration, 0.3% by weight; VDC:HCl molar ratio, 1:1, (O) 1,1,1-trichloroethane yield; (4) nonreacted vinylidene chloride in relation to the amount introduced. Table 1. Levels of the Examined Factors level basic higher lower star higher star lower
Table 2. Design Matrix and Experimental Results
coded temp flow rate of vdc catalyst concn factor (°C) (x1) cm3 cm-3 h-1 (x2) (% by weight) (x3) 0 +1 -1 +1.215 -1.215
28.00 38.00 18.00 40.15 15.85
0.158 0.237 0.079 0.254 0.062
1.65 2.76 0.54 3.00 0.30
weight; VDC:HCl molar ratio, 1:1; reaction duration, approximately 6 h. These investigations (Figure 3) indicate that changing the reaction temperature over the range from 15 to 25 °C causes a small increase in the yield of 111-TCE, with a slight maximum at 22 °C. Over the temperature range under investigation, the content of nonreacted VDC in the product remains unchanged. The decrease in 111-TCE yield with the temperature increase to 30 °C is caused by the lower conversion of VDC. Simultaneously, an increase in the VDC content in the product and in balance losses is observed. The decrease in yield with the temperature increasesin the first placespoints to significant lowering of the hydrogen chloride concentration in the liquid phase. Over the catalyst concentration range of 0.3-3.0% by weight, the yield of 111-TCE does not change and is 95% mole (VDC flow rate, 0.227 cm3 cm-3 h-1; temperature, 20 °C). At concentrations below 0.3% by weight the yield decreases and at 0.05% by weight is 81% mole. Since the high yield has been achieved under the atmospheric pressure, the examination of the process under the raised pressure was not necessary. Optimization Methods. The preliminary investigations were the basis for the evaluation of changes in parameters and process optimization. The maximum yield of 111-TCE with respect to VDC introduced was assumed as an optimization criterion. Yield optimization experiments were based on a second-order orthogonal design matrix (Achnazarowa and Kafarow, 1982). Table 1 shows ranges over which the essential param-
experiment no.
z1
z2
z3
Y
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
18.00 38.00 18.00 38.00 18.00 38.00 18.00 38.00 40.15 15.85 28.00 28.00 28.00 28.00 28.00
0.079 0.079 0.237 0.237 0.079 0.079 0.237 0.237 0.158 0.158 0.254 0.062 0.158 0.158 0.158
0.54 0.54 0.54 0.54 2.76 2.76 2.76 2.76 1.65 1.65 1.65 1.65 3.00 0.30 1.65
90.05 84.38 98.71 93.60 95.01 85.87 97.65 94.29 88.96 96.30 96.92 88.57 93.43 92.06 92.74
eters were changed. These are given in coded and natural form. The design matrix and the results of the experiments (Y yield) are shown in Table 2. The coefficients of the regression equation for the yields were expressed by a second-order polynomial. They were calculated by applying the least-squares method: k
y* ) b0 +
k
k
bixi + ∑bijxixj + ∑biixi2 ∑ i)1 i
