Isobaric vapor-liquid equilibrium for methyldichlorosilane-dimethyldichlorosilane-benzene system

Isobaric vapor-liquid equilibrium for methyldichlorosilane-dimethyldichlorosilane-benzene system 1 2 first-author †E-mail:qiuzm@ncu.edu.cn †E-mail:qiuzm@ncu.edu.cn qiuzm@ncu.edu.cn 1 3 3 1 1 School of Environmental Science and Engineering, Nanchang University, Nanchang 330029, China School of Environmental Science and Engineering, Nanchang University, Nanchang 330029, China Key Laboratory of Poyang Lake Ecology and Bio-resource Utilization, Nanchang University, Nanchang 330029, China Key Laboratory of Poyang Lake Ecology and Bio-resource Utilization, Nanchang University, Nanchang 330029, China Editorial Department of Journal of Nanchang University, Nanchang 330029, China Editorial Department of Journal of Nanchang University, Nanchang 330029, China The elucidation of vapor-liquid equilibrium (VLE) of the halogenated silane was necessary for the production of silicon derivatives, especially for methylvinyldichlorosilane, due to the lack of the relevant reports. Isobaric VLE for the system methyldichlorosilane-dimethyldichlorosilane-benzene and isobaric VLE of the three binary systems were measured with a new pump-ebulliometer at the pressure of 101.325 kPa. These binary compositions of the equilibrium vapor were calculated according to the Q function of molar excess Gibbs energy by the indirect method and the resulted VLE data agreed well with the thermodynamic consistency. Moreover, the experimental data were correlated with the Wilson, NRTL, Margules and van Laar equations by means of the least-squares fit, the acquired optimal interaction parameters were fitted to experimental vapor-liquid equilibrium data for binary systems. The binary parameters of Wilson equation were also used to calculate the bubble point temperature and the vapor phase composition for the ternary mixtures without any additional adjustment. The predicted vapor-liquid equilibrium for the ternary system was in a good agreement with the experimental results. The VLE of binary and multilateral systems provided essential theory for the production of the halogenated silane. Ebulliometer Vapor-liquid equilibrium Methyldichlorosilane Dimethyldichlorosilane Benzene INTRODUCTION 1 Vapor-liquid equilibrium (VLE) data are very important in the design and operation of separation processes in the chemical industry. Such information can be obtained experimentally or estimated by using generalized methods for calculation of the properties of mixtures. For ideal system, it is relatively easy to estimate vapor-liquid equilibrium. However, most systems of industrial interest show deviations from the ideal behavior. The methyldichlorosilane-dimethyldichlorosilane-benzene and constituent binary system are of importance in the production of halogen silanes, while VLE data on these systems are very scarce in the literature. Only in the past several years did some researchers (Ana et al., 1995 1995 ; Sacarescu et al., 1995 1995 ; Wu and Cai, 1997 1997 ; Xie et al., 1998 1998 ) begin to study isobaric vapor-liquid equilibrium of multicomponent systems containing halogenated silane. Yu et al.( 2000 2000 ; 2003a 2003a ; 2003b 2003b ) and Qiu et al.( 2005 2005 ) also have done some works on this problem. In order to provide some necessary basic data on silicon derivatives, these systems are selected for study. The VLE data are measured by the total pressure-temperature-liquid composition ( pTx ) method. In this study, the VLE data are determined at 101.325 kPa for methyldichlorosilane-dimethyldichlorosilane-benzene and constituent binary system. The results calculated by the activity coefficient models agreed well with the experimental data. EXPERIMENTAL DETAILS 1 Materials 2 Methyldichlorosilane, dimethyldichlorosilane and benzene were obtained from Xinhuo Chemical Factory, Jiangxi, China. All the chemicals were purified by distillation in a laboratory column to a purity of more than 99.5% as verified by gas chromatography (GC) analysis. Methyldichlorosilane and dimethyldichlorosilane and benzene should be purified just before measurement because they easily react with water when exposed to the air. Comparison between some measured data and data in literature is given in Table 1 1 . 2 Component 2 Boiling point (K) Lit. Exp. Methyldichlorosilane 314.15 (Dean, 2003 2003 ) 314.41 Dimethyldichlorosilane 343.15 (Dean, 2003 2003 ) 343.46 Benzene 353.15 (Dean, 2003 2003 ) 353.16 Apparatus and procedure 2 A new type of magnetic pump-ebulliometer described in detail by Qiu et al.( 1995 1995 ) was used for measuring the boiling points with different liquid phase compositions (Qiu et al., 1997 1997 ). The apparatus was an all-glass dynamic recirculation still with total volume of about 1.00×10 −4 m 3 . During the run, the still was submerged in a constant temperature bath at about 3 °C below the equilibrium boiling point. The atmospheric pressure, P , was measured by a Fortin-type mercury barometer. Since the barometric pressure changed slightly, the experimental temperatures were automatically corrected to that at 101.325 kPa. The equilibrium temperature, T , was measured using a standard mercury thermometer with accuracy of 0.1 K. In each experiment, a known mass of the material was introduced from the injector into the still and heated at a fixed pressure of 101.325 kPa by an automatic pressure regulation system. Liquid compositions component, x i , were added into the still. Vapor compositions, y i , were calculated from the experimental pTx data by an indirect method (Qiu et al., 1994 1994 ) based on the Q function (the function of molar excess Gibbs energy) and had rigorous thermodynamic consistency (Hu, 1982 1982 ). RESULTS AND DISCUSSION 1 At low and moderate pressures, the pointing factor is negligible, so the equilibrium relation is as follows $$Py_i \hat \varphi _i {\text{ = }}P_i^s \varphi _i^s x_i \gamma _i$$ , where y i is the mole fraction of component i in the vapor phase, $$\hat \varphi _i$$ is the fugacity coefficient of component i in the vapor phase, P is the total pressure, γ i is the activity coefficient of component i in the liquid phase, x i is the mole fraction of component i in the liquid phase, φ i s is the pure component fugacity coefficient at saturation, and P i s is the vapor pressure of pure component i at saturation. The coefficients $$\hat \varphi _i$$ and φ i s were evaluated using the second virial coefficient equation, respectively. The vapor pressure of pure component, P i s is calculated by the Antoine equation. The critical data and Antoine constants of the pure component are given in Table 2 2 . A , B , C : Antoine constants; T c : Critical temperature; P c : Critical pressure; V c : Critical volume Component A B C T c (K) P c (kPa) V c (×10 −6 m 3 /mol) Methyldichlorosilane (Rugina and Sacarescu, 1992 1992 ) 7.0484 1179 242 475 3901.1 290 Dimethyldichlorosilane (Rugina and Sacarescu, 1992 1992 ) 7.1435 1328 241 520 3485.6 350 Benzene (Dean, 2003 2003 ) 6.90565 1211.033 220.79 562.05 4895 255 The experimental data were correlated using the Wilson, NRTL, Margules and van Laar equations. The optimal interaction parameters were obtained by minimization of the objective function F (Qiu et al., 1994 1994 ) by means of the least-squares fit. $$F{\text{ = }}\sum {\left| {\ln (\gamma _1 )_{{\text{cal}}} - f_1 (\bar a_i )} \right|_k^2 } {\text{ + }}\sum {\left| {\ln (\gamma _2 )_{{\text{cal}}} - f_2 (\bar a_i )} \right|_k^2 }$$ , where γ 1 , γ 2 are the activity coefficients of component 1 and component 2 in the liquid phase, a i ̄ is model interaction parameter, f 1 , f 2 are model equation calculated the activity coefficients of component 1 and component 2, respectively. k is the inflexion point to calculate. The binary systems VLE data were used to plot the three graphs in Fig. 1 1 . • Calculated vapor phase points; – Calculated temperature curve; ◦ Experimental temperature data The model interaction parameters of liquid activity coefficient and the absolute average deviations are listed in Table 3 3 (in the preceding page) showing that the deviations of Wilson, NRTL, Margules equations are reasonably small, especially that of the Wilson equation, while the deviation of the van Laar equation is a little bigger. So the activity coefficient models are suitable for representing the binary experimental data. The binary interaction parameters of the Wilson model given in Table 3 3 were used to predict the VLE data of the ternary system. The results were satisfactory. The VLE data of the ternary system and the average deviation in the bubble temperatures are listed in Table 4 4 . d t =∑| T − T mod |/ N d y =∑| y cal − y mod |/ N N : Number of data points; T mod : Calculated bubble point from model (K); y cal : Calculated vapor phase mole fraction from pTx ; y mol : Calculated vapor phase mole fraction from model Equation Parameters and deviations Methyldichlorosilane (1)+dimethyldichlorosilane (2) Methyldichlorosilane (1)+benzene (2) Dimethyldichloroslane (1)+benzene (2) Wilson A −120.1 −62.8 −22.4 B 0.1 1.2 0.005 d t * * 0.14 0.27 0.05 d y ** ** 0.0089 0.0039 0.0052 NRTL A −0.1 −65.6 −42.2 B −148.7 1.1 0.8 A ij 0.3 0.27 0.3 d t 0.15 0.26 0.05 d y 0.0081 0.004 0.0053 Margules A −0.41 −0.1 −0.117 B −0.12 −0.13 −0.01 d t 0.5 0.27 0.11 d y 0.0042 0.0042 0.0037 van Laar A 0.0001 0.0001 0.0001 B 0.05 0.01 0.02 d t 1.34 0.49 0.34 d y 0.0157 0.0046 0.0061 d t =∑| T exp − T mod |/ N T mod : Calculated bubble point from model; T exp : Experimenta boiling point; x 1 , x 2 , x 3 : Liquid-phase mole fraction of (1) (2) (3); y 1,cal , y 2,cal , y 3,cal : Calculated vapor-phase mole fraction of (1) (2) (3) from pTx ; N : Number of data point No. T mod (K) T exp (K) x 1 x 2 x 3 y 1,cal y 2,cal y 3,cal 1 330.92 331.93 0.3144 0.6058 0.0798 0.5392 0.4200 0.0408 2 331.75 332.28 0.2979 0.5740 0.1281 0.5235 0.4093 0.0672 3 333.15 333.79 0.2715 0.5232 0.2053 0.4968 0.3907 0.1125 4 333.76 334.41 0.2602 0.5013 0.2385 0.4847 0.3821 0.1332 5 334.52 334.88 0.2467 0.4753 0.2780 0.4696 0.3715 0.1589 6 335.35 335.50 0.2323 0.4476 0.3201 0.4529 0.3595 0.1877 7 336.04 336.05 0.2207 0.4253 0.3540 0.4388 0.3493 0.2119 8 336.61 336.77 0.2114 0.4074 0.3812 0.4271 0.3408 0.2321 9 347.04 346.20 0.0236 0.3777 0.5987 0.0655 0.4305 0.5040 10 346.15 345.60 0.0388 0.3718 0.5894 0.1047 0.4130 0.4823 11 344.03 344.47 0.0766 0.3572 0.5662 0.1932 0.3733 0.4335 12 342.07 342.21 0.1138 0.3428 0.5434 0.2700 0.3388 0.3912 13 341.04 340.68 0.1342 0.3349 0.5309 0.3085 0.3214 0.3701 14 339.96 339.34 0.1564 0.3263 0.5173 0.3478 0.3037 0.3485 15 338.35 338.82 0.1906 0.3131 0.4963 0.4037 0.2784 0.3179 16 337.34 337.97 0.2131 0.3044 0.4825 0.4377 0.2630 0.2994 17 336.12 336.43 0.2411 0.2935 0.4654 0.4773 0.2449 0.2778 18 335.29 335.23 0.2609 0.2859 0.4532 0.5036 0.2329 0.2635 19 334.42 334.17 0.2820 0.2777 0.4403 0.5303 0.2207 0.2490 20 334.04 333.47 0.2915 0.2741 0.4344 0.5419 0.2154 0.2427 21 325.93 325.95 0.5502 0.0370 0.4128 0.8001 0.0232 0.1767 22 326.31 326.49 0.5333 0.0665 0.4002 0.7844 0.0422 0.1734 23 326.36 327.34 0.5307 0.0711 0.3982 0.7820 0.0451 0.1729 24 326.94 327.71 0.5051 0.1158 0.3791 0.7577 0.0745 0.1679 25 327.33 327.56 0.4884 0.1452 0.3664 0.7414 0.0943 0.1643 26 327.71 328.04 0.4720 0.1738 0.3542 0.7252 0.1139 0.1610 27 327.93 328.16 0.4630 0.1895 0.3475 0.7161 0.1248 0.1591 28 328.22 328.51 0.4511 0.2104 0.3385 0.7040 0.1395 0.1565 29 328.55 329.02 0.4374 0.2343 0.3283 0.6899 0.1566 0.1535 9 Deviations: d t =0.42; d t (max)=1.01 CONCLUSION 1 VLE of the ternary system of methyldichlorosilane-dimethyldichlorosilane-benzene and constituent binary systems were measured at 101.325 kPa. 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