r, = income in year], dollars R = total worth of enterprise s = salvage value, dollars S, = total sales in year j t = taxrate I ' = utility W = present worth, dollars u o = present worth of venture assuming no failures, dollars w i = present worth of venture assuming failure i, dollars W = initial worth of enterprise, dollars x = decision \. ariable XI = time at which plant constructed. years 1 2 = capacity of plant 3 = technological coefficient z = standard normal variate z r = value of autoregressive process at current time z t + & = value of autoregressive process k years from the present
Grepk Letters = randomshock &,32 = constants 6 , = constant defined by eq 15 q = autocorrelation coefficient (L
p(k,k + J ) = correlation coefficient for values at years k and ( k + j ) u( ) = standard deviation of bracketed quantity a2( ) = variance of bracketed quantity $ = weightingfactor Literature Cited Box, G . , Jenkins, G . , "Time Series Analyses, Forecasting and Control." pp 7-10, 127-144, 158-160, Holden-Day, San Francisco, 1970. Dubey. S. D., Nav. Res. Logis. Quart., 14, 69 (1967) Freund, R . J . , Econometrica, 24, 253 (1956) Gottfried. B., Weisman, J.. "Introduction to Optimization Theory," pp 418-429, 517-522, Prentice-Hall. Englewood Cliffs, N.J.. 1973. Guthrie, K . M.. Chem. Eng., (March 1969). Happel. J , , Chem. Eng. Progr., 15, 533 (1955). Mapstone, G . , Chem. Eng., 80 (111, 126 ( M a y 1973). U S . Tariff Commission, Report on Synthetic Organic Chemicals, 19601970, U.S. Govt. Printing Office, 1971. Weibull, W., d. Appl. Mechan., 18, 293 (1951 j . Weisman. J.. Holzman, A . , lnd. Eng. Chem., Process Des. Develop.. 11, 386 (1972). Weisman, J., Wood, C., Rivlin. L., Chem. Eng. Progr. Symp. Ser.. 61 (55). 50 (1965). Williams, H., Holmes, R. D . , Fruehauf, F.V., U.S. Patent 1.911.717 (1942).
Receivedfor review February 15, 1974 Accepted June 27, 1974
Process for Synthesizing Tetrachlorobisphenol A Using Aluminum Chloride Catalyst Koji lkeda and Yoshiro Sekine* Departmenf of Chemistry. School of Science and Engineering. Waseda University. Nishi-Ohkubo. Shinjuku-ku. Tokyo. Japan
Aluminum chloride can catalyze chlorination of bisphenol A (BPA) selectively in acetic acid solution. Effects of temperature and concentrations of BPA, chlorine, and the catalyst were investigated with bench-scale experiments. Highly pure tetrachlorobisphenol A (TCBPA) was synthesized under these conditions: flow rate of chlorine, 0.25-0.60 I./min mol of BPA; concentration of BPA, 10%; that of catalyst over 1%; and reaction temperature, 30-33°C. The reaction was clearly divided into inhibited and uninhibited steps and could be explained with a selective, successive reaction model. The composition of intermediates was dependent entirely on the dimensionless reaction time, and the selective synthesis of dichlorobisphenol A (DCBPA) and TCBPA was possible with the catalyst. Pilot-scale experiments were studied under recycling of the mother liquor. No special difficulties arose on the scale-up. Highly pure TCBPA was obtained by controlling the water content in the mother liquor below 5 6 % during the oDeration time.
Introduction Attention has heen directed to chlorinated bisphenol A, such as dichlorobisphenol A (DCBPA), tetrachlorobispheno1 A (TCBPA) etc., as monomers which improve heat resistance. mechanical properties, nonflammability, and resistance to chemicals of polycarbonate (Jackson and Cadwell. 1967; Perepelkin and Kozlov, 1968; Schnell. 1964), epoxy (Kakiuchi. 1964; Lee and Nevill. 1967), and phenoxy resins (Lee, et a / , 1967). TCBPA can be formed by successive chlorine substitution at the 3, 3', 5 , and 5' positions of bisphenol A (BPA), but as the chlorination proceeds further, some perchlorinated products mav be obtained. In the prior arts of TCBPA synthesis (Deutsche Solvay Co., 1958; K h o , et al , 1967), some intermediate and perchlorinated products are naturally present in TCBPA. Therefore, the purity and the yield of TCBPA are markedly lowered. Consequently, 58
Ind.
Eng. Chem., Process Des. Develop., Vol. 1 4 , No. 1, 1975
manufacturing of the monomer of high purity to cause minimum coloration of the final resin product requires very complicated purification procosses and therefore is very expensive. The process patented to Dow Chemical Co. (1966) may be an excellent one when the disadvantages mentioned above are eliminated, but the formation of intermediates has not been discussed, and only very few reports on the effective industrial methods of DCBPA production have been published. In studying the chlorination of BPA in glacial acetic acid by using ordinary liquid-phase chlorination catalysts, authors have found that an aluminum chloride has catalyzed the selective formation of reaction intermediates and, inhibiting the formation of perchlorinated compounds, has been very effective in the production of TCBPA of high purity. Thus, for the purpose of industrialization of this process, several factors which can affect the reaction have been initially studied with a bench-scale
reactor. Next, TCBPA of high purity has been produced by a semicontinuous operation by using a pilot plant with re-use of the mother liquor by recycling. In this paper, the more profitable industrial synthetic method for chlorinated BPA monomers will be reported. Experimental Section Experiments with a Bench-Scale Apparatus. In a 10-1. reactor equipped with a stirrer were placed the prescribed quantities of glacial acetic acid, BPA. and anhydrous aluminum chloride, and the temperature of the mixture was kept constant by controlling the temperature of the cooling water. Then, under continuous stirring (300 rpm), chlorine gas of a constant speed, measured with an orifice meter, was bubbled into the reactor through a gas distributor. The reaction mixture was analyzed by gas chromatography successively in the course of the reaction to obtain the time dependence of relative concentrations of the reaction intrmediates, and the reaction conditions were investigated. When the BP.4 disappeared and the intermediates were converted almost completely to TCBPA, the reaction was stopped and, with the purpose of studying the crystallizability of TCBPA, the reaction mixture was cooled to 15°C under stirring to crystallize TCBPA; the mixture was then centrifuged. The TCBPA obtained was washed with water, filtered, dried, and the melting point and the crystallization yield were measured. Experiments with a Pilot-Scale Apparatus. Into a 200-1. glass-lined, stirred tank reactor were fed the prescribed quantities of BPA. anhydrous aluminum chloride (2% based on BPA), and glacial acetic acid. Chlorine gas was bubbled into the reactor a t a constant flow rate (23 l./min) through a rotameter and a distributor. The amount of chlorine gas used was in the range of 4.2 to 4.6 mol/mol of BPA. Under constant stirring 1150 rpm), the reaction temperature was kept a t 32 f 0.5.C with a thermistor recording regulator by passing hot or cold water through a coil inside the reactor. After the reaction was completed, nitrogen gas was passed to replace the remaining HC1. Then the contents were transferred into a 150.1. glass-lined closed tvpe crystallization tank and were crystallized forcedly by cooling them down to 15°C under stirring for 3 hr. The crude TCBPA obtained (including 30 to 35% of acetic acid) was washed with water through a washing tower (made of vinyl chloride, 15 cm in diameter, 120 cm in length, provided with a porous resin plate having pores of 50 p diameter a t the bottom) and after being centrifuged was dried with hot air a t 60°C. To the filtrate obtained by centrifugal separation was added fresh glacial acetic acid to restore the original weight of the solvent, and predescribed amounts of BPA and the catalyst (2%) were added, and again chlorinated; in this way, so-called "recycling of the mother liquor process" was repeated. Materials. Commercial BPA was twice recrystallized from xylene; mp 155-157"C. Glacial acetic acid was dried with phosphorus pentoxide, distilled, and the 116.5-117°C fraction was used. Anhydrous aluminum chloride of guaranteed reagent of super grade was used as a catalyst. Analysis of the Reaction Products a n d the Water Content of the Mother Liquor. The reaction products and the water content of the mother liquor were determined by gas chromatography under conditions given in Table I. All the determinations were carried out by the half-width method by making the absolute calibration curves based on the internal standard method. Results and Discussion Characteristics of the Chlorination of BPA Catalyzed by Aluminum Chloride. Preliminary experiments were
Table I . Conditions of Gas Chromatographic AnalysisL Analytical condition Column packing
Column length
(and diameter)
For chlorinated
For water content
BPA'
Celite 545. Celite 545, MLved l i q u i d Apiezon L phase of grease 20'6, a n d Apiezon L polycarbonate grease 2 0 ' ~ . a n d 1 5 ' ~ 6. 0 to 80 senacir acid 6 ' r . me s 11 60 t n 80 mesh 200 cm ( 5 mni). 80 cm (4 mml. made of glass made of stainless steel
Column tempera- 260'C ture 20 mt 'min Flow rate of c a r r i e r gas (He)
80 C
40- 60 ml 'min
Yanagimoto Seisakusho Model GCG - 5501' was used. Yanagimoto Seisakusho Model GCG - 2 was used. Under these analvtical conditions. isomer5 of chlorinated compounds cannot be separated. b u t the authors did not attempt to separate them. because their rates of chlorination were considered to be little different from each other. (1
carried out with 0.1-570 catalyst or without it under these conditions: the flow rate of chlorine was kept constant, and the concentration of BPA and reaction temperature was varied within the ranges of 5--1590 and 17-55"C, respectively (see also the explanation under Figure 1). The results of these preliminary experiments indicated that the reaction pattern in the presence of a catalyst was considerably different from that in the absence of a catalyst. Namely, as shown in Figure 1-11, in the case of no catalyst. the progression of a typical successive reaction was observed as soon as the chlorination started and a mixture of reaction intermediates was formed unselectively and, moreover. TCBPA, formed in the course of the reaction, was chlorinated further to produce perchloro compounds in the later period of the reaction. On the contrarv. as an example is shown in Figure 1-1, in the presence of an aluminum chloride catalyst. the formation of trichloro-BPA and other more chlorinated compounds was inhibited until the concentration of DCBPA. formed through monochloro-BPA from BPA. reached a maximum. Other reaction intermediates were also formed successively and selectively in a similar manner and, finally, pure TCBPA was obtained while the formation of perchloro compounds was inhibited. In this way, it was indicated that this successive reaction could proceed selectively in the presence of aluminum chloride. The results showed that the suitable reaction conditions were: concentrations of BPA and the catalyst, 10% and over 170,respectively. and the reaction temperature, 30-33°C. Also, effects of the presence of excess chlorine. ultraviolet irradiation. and water content of the reacting solution were investigated. It was found that these factors could promote the formation of perchloro compounds and must be avoided. I t is considered that the chlorination of aromatic coinpounds is one of electrophilic substitution reactions: the aromatic compound in solution may, a t first. react rapidly with a chlorine molecule to form a benzenoid complex ( T complex) and then splitting of a chlorine ion from the comlex caused by the electrophilic property of the catalyst may occur (formation of u comples). The step of the u complex formation may be much slower than that of the T complex formation, and consequently the former may be rate-determining (March, 1968; Norman and Taylor, Ind.
Eng. Chem., Process Des. Develop., Vol.
14, No. 1, 1975
59
P
Under each condition, when the formation of TCBPA (determined by gas chromatography) reached about 10070, the reaction was stopped, and TCBPA was crystallized. The mean yield of TCBPA crystallized was about 60%, but as described below, the total yield of it became considerably higher, by applying a process with recycling of the mother liquor. In this process, highly pure TCBPA, having a melting point close to that given in the literature, 133-134" (Christopher and Fox, 1962), was obtained and can be used immediately as a monomer for polymerization. As described above, the reaction rate of this chlorination depends chiefly on the concentration of T complex in the liquid phase. In the present case, the chlorine, which is continuously bubbled into the solution a t a constant low rate in a small quantity, reacts with the BPA and the catalyst, present in relatively large quantities, to form an equimolar benzenoid complex and the concentration of BPA decreases gradually. Thus, it is quite probable that under each reaction condition, the reaction is first order in the concentration of BPA; if so, the reaction process could easily be analyzed. The effect of the concentration of chlorine will be examined later. Thus, following model of the chlorination reaction, in which TCBPA is produced seemingly through three inrermediates successively and TCBPA formed can also react with chlorine under some conditions to form perchloro compounds as given by eq 1. is adopted
t\
BPA Kcaction t i m e , hr
Figure 1 . Time dependence of relative concentrations of intermediate products: 0 , BPA; A , monochloro-BPh: X , DCBPA: 0 , trichloro-BPA; A , TCBPA; perchloro compounds. Reaction conditions: acetic acid. 300 ml; BPA, 35 g; reaction temperature, 30°C; concentration of' catalyst, 4%; stirring velocity, 300 rpm; flow rate of Clz. 81.6 ml/min (AICla); 84.66 ml/min (no catalyst).
o,
1965; Shiba, 1965; Stock. 1968). Thus, overall, one molecule each of the aromatic compound. chlorine. and the catalyst may participate in the reaction (Stock, 1968). In pther words. if' chlorine is bubbled into the solution, held in an isothermal state in the presence of a sufficient amount of the catalyst. under vigorous stirring, at such a constant flow rate that unreacted chlorine cannot be observed in the exhaust gas, chlorine is immediately absorbed to form a T complex with an equimolar aromatic compound. Therefore, no pronounced effects of diffusion at the interface can be observed. For this reason. many chlorination reactions. such as chlorination of benzene, can be treated in practice as pseudo-first-order reactions ( 6 t a and Murayama. 1957; Smith, 1956: Wiegandt. 1951). For the catalvtic chlorination of BPA. the results of preliminary experiments show the presence of sufficiently large quantities of the catalyst with respect to the amount of chlorine bubbled and. in fact, the effect of the catalyst was not conspicuous when the catalyst concentration was more than 1%. The effects of the change in the rate of stirring from 200 to ,500 rpm on the time dependence of the concentrations of reaction intermediates and on the time necessary to complete the chlorination were also not remarkable. Therefore. it is considered that the effect of diffusion may be small and the rate-determining step may be the formation of the CT complex also in this case. Discussion on the Results of Bench-Scale Experiments on the Basis of Selective-Successive Reaction Model. Based on the results of the investigation described above, bench-scale experiments were carried out with a stirred tank reaction under conditions given in Table 11. 60
Ind. Eng. Chem., Process Des. Develop., Vol. 14, No. 1, 1975
co
k1
monochloro-BPA C1
trichloro-BPA
k4
TCBPA
-% DCBPA
e3 -+
CZ k5
-+
perchloro-BPA ( I )
c3 Cd C5 where CO, CI,CZ, C3, Cq, and C5 are concentrations of BPA, monochloro-BPA, DCBPA, trichloro-BPA, TCBPA, and perchloro-BPA, respectively, and k l , k z , k3, hq, and k5 are rate constants of corresponding stages of the reaction, respectively. Then, rate equations can be expressed as dC,/dt
= -klCo
(2)
dC,/dt = k5C, (7) Actually, as described above. the concentration of the reactants must depend on that of benzenoid complex. Therefore, h, (i = 1-5) in the above equations may be a function of Clz concentration. By solving eq 2 to 7 by Laplace transformation in both cases of BPA only and BPA with all intermediates being present, the concentration of each intermediate can be obtained. For simplification, let T = k l t and K , = k , / k l , where T is a dimensionless reaction time or a reaction time parameter and K , is a relative rate constant. Also, let the rate constant in each inhibited step be represented by k , ' , and K,' = k , ' / k l . Based on the experiments given in Table 11, log CO/ Co'O' was plotted against reaction time t. where Co'o' and CO are the initial concentration and the concentration a t time t of BPA, respectively, and an approximately
Table 11. Reaction Conditions and Results of Bench-Scale Experimentsa Relative C1, flow rate 1. /min mol of BPA
c1, No.
flow rate, 1. /min
BPA-feed, mol
TCBPA product Reaction time, min
Crystallized,
Formed,
%#
0 IC
Melting point, "C
3.84 0.391 360 96.9 66.2 132.7-135.3 3.84 0.30 450 99.0 62.0 132.0- 135.0 3 1.15 1.91 0.603 333 98.8 ... ... 4 1.15 3.95 0.291 470 98.6 53.4 131.9- 134.6 5 1.15 2.56 0.449 333 98.9 49.7 132.0- 134.7 1.5 6.09 0.246 480 98.2 61.4 131.3- 133.6 6 7c 1.15 3.84 0.30 445 95.2 47.9 133.2-135.1 8' 0.85 3.22 0.264 470 96.6 58.3 131.6-134.0 a Concentration of AICIB.2% based on BPA; reaction temperature, 32 & 0.5"C except no. 7 and 8. bDetermined by gas chromatography. Reaction temperature, 38°C. Reaction temperature. 28°C. 1 2
1.5
1.15
Table 111. Relative Rate Constant of Each Stepa
3,
7 I
~
Relative rate constant Reaction step
h',
lis'
K,
K,'
K,j K ,
1.3 0.03 . . . 0.02 . . . 0 Step where formation of more than t r i chlorinated BPA a r e inhibited (2) T = 2.75-4 1.3 . . . 1.2 0.02 . . . 0 Step where formation of more than tetra chlorinated BPA a r e inhibited ( 3 ) T = 4-7 1.3 . . . 1.2 . . . 1.8 0 Step where formation of TCBPA is not inhibited a Note: relative rate constant K , = k , / k l , K,' = h , ' / k l . (1) T = 0-2.75
straight line was observed. This fact suggests that the results obtained by treating this reaction as first order in the concentration of BPA are in fairly good agreement with experimental results of each reaction conditions. Thus, the rate constant of the decrease of BPA was obtained from t h e slope of the log Co/Co(O] us. t curve. By plotting h l against the relative flow rate of chlorine (l./min mol of BPA), a n approximately straight line was obtained, as shown in Figure 2 . The effect of chlorine concentration can be explained as follows. The value e l z / BPA may be considered as the ratio of BPA which reacts with chlorine bubbled into the solution a t a constant rate t o form the complex to that present in the solution. Therefore, the value of (concentration of BPA in the solution) times (Clp/BPA) may indicate the concentration of the complex formed, and K1 must be proportional to the concentration of the complex. From the rate equation of the decrease of BPA, CO = Co'O' exp(-r), it is expected that all plots of Co/C0'O1 u s 7 must be on the same curve regardless of t h e reaction conditions. Actually all experimental results given in Table I1 were on the same curve as shown in Figure 3. Also, the concentration of each intermediate Cp to Cq can be plotted against the reaction time parameter on the same curve corresponding t o each intermediate product, independently on their reaction conditions. Therefore, it was elucidated t h a t the parameter 7 can be used for characterizing the formation of intermediates and t h a t the distribution of all products is determined by T. To obtain
1
0.1
1
1
0.2
1
I
0.3 0.4 0.5 CI, {BPA,1 m i n mol
,
0.6
Figure 2. Relation between rate constant of BPA consumption k i and relative flow rate of chlorine (l./min mol of BPA).
T
Figure 3. Relation between relative concentrations of intermediate compounds and reaction time parameter 7 (comparison of calculated results with experimental results): -, BPA; - - -. nionochloro-BPA; - -, DCBPA: - - - - -, trichloro-BPA; -, TCBPA; 0 , no. 1; X , no. 2; A , no. 3; 0 ,no. 4; 0 , no. 5 ; X , no. 6.
the rate of formation of each intermediate product, by using concentration equations obtained from eq 2 to 7 , each relative rate constant K , and K,' was calculated by means of the trial and error method successively from the curves on which the experimental plots lie. The results are given in Table 111. Since the curves in Figure 3, which represent the relation between the concentrations of intermediates, calculated from their relative constants shown in Table 111, and T are relatively in good conformity with t h e experimental Ind. Eng. Chem.. Process Des. Develop., Vol. 14, No. 1 , 1975
61
Table IV. Results of Recycling Experiments ~~
Analytical results of mother liquor No. of times ok
Water content,
recycling
";
0 1 2
3 4 5
0
1.8 2.8 3.7 4.6 6.3
Relative C1, flow rate, 1. /min mol of BPA
TCBPA Yield,
0.327 0.417 0.413
59.8 67.1 71.8
0.417
75.5
0.427 0.442
78.2 80.5
9
TetrachloroBPA. 2'
...
... ... ...
0.5
2.2 2.0
... ... ... 98.9 97.8 97
DichloroBPA, 'L
133.3-135.0 132.9- 135.0 132.8- 134.9 132.1- 134.9 131.3-134.6 130.4-133.8
...
results, it may be also conceivable that the chlorination model of BPA mentioned above can represent the catalyzed chlorination of BPA fairly well, within the experimental conditions of this study. However, a t the final stage of the formation of each reaction product, the conformity is not so good. The reasons for this nonconformity are first, insufficient accuracy of analysis, and second, the assumption on first-order reactions for treating the reaction under conditions having low concentrations. As can be seen from Table 111, the pattern of this catalytic chlorination, including inhibited steps of formation of tri- and tetrachlorinated compounds, is very interesting. In step ( l ) ,the formation of DCBPA is about 1.3 times faster than that of monochloro-BPA, and the rate of formation of trichloro-BPA, being strongly inhibited, is about li40 that of following uninhibited steps. Consequently, in this step, relatively pure DCBPA having maximum concentration of 0.80 to 0.85 can be obtained. In step ( 2 ) , the formation of TCBPA is still inhibited, and the rate of formation is only about 1/90 that of following uninhibited step. However, the rate of formation of trichloro-BPA is comparable with that of DCBPA. Consequently, the maximum concentration of trichloro-BPA formed cannot exceed 0.60-0.63, and the isolation of trichloro-BPA is more difficult than that of DCBPA in the former step. In step ( 3 ) , the formation of TCBPA is not inhibited, and the relative rate of its formation K4 is larger than that of each other intermediate. Perchloro products also cannot be detected in this step, and the rate constant of their formation may be almost zero. Consequently, when the reaction time parameter does not exceed 7, only TCBPA can be produced ultimately. In this way, it was ascertained that TCBPA was synthesized in the presence of the aluminum chloride catalyst apparently through three steps, and also that DCBPA and TCBPA were obtained in fairly high purity. To study the effect of the reaction temperature, experiments were carried out at 28, 33, and 38"C, and k l , k z , k 3 , and h4 were calculated in a manner simiiar to that described above. The results are shown in Figure 4. From these results, the activation energy of each reaction was calculated. The activation energy of DCBPA formation from BPA through monochloro-BPA (E1 = 2.23 kcal/mol, E2 = 2.48 kcal/mol) is relatively small, while those of trichloro-BPA formation from DCBPA (E3 = 5.75 kcal/mol) and TCBPA formation from trichloro-BPA (E4 = 4.92 kcal/mol) are about two times larger. This suggests that the distribution of the products and also the selectivity of the catalyst are affected by the reaction temperature. Based on the above description, it is conceivable that, by the regulation of several reaction conditions, even in such a complicated reaction, factors affecting the reaction 62
Tri chloroBPA. $C
Melting point, "C
Ind. Eng. Chem., Process Des. Develop., Vol. 14, No. 1, 1975
.,.
... ...
1.1
Perchloro- Cl,/BPA BPA, g~ molar ratio
... ... ... ...
4.39 4.27 4.26 4.25 4.28 4.30
... 0.5
-1
-
,I
2 I1
1
3 22
I
3 24
326 3 28 1 T ' X10'
3 30
3 32
Figure 1. Relation between rate constant li and reaction temper-
ature T can be elucidated and the behavior of reaction intermediates of this successive reaction can be revealed. These results may be useful for the process control and the scaleup of the process. Actually, this procedure was used effectively for the analyses of the experiments with a pilot plant described later, and may also be applicable to an industrial plant. An Approach to Industrialization of the Process by Use of a Pilot-Scale Apparatus. As can he seen from Table 11, a fair amount of TCBPA still remains in the mother liquor separated from TCBPA afer chlorination. Therefore, it is very important for the industrial synthesis of TCBPA to take the effective use and the recovery of acetic acid into consideration. Thus, it may be necessary to apply a mother liquor recycling system. In this process, it is expected that, owing to the hydroscopic propertv of glacial acetic acid, the water content of the mother liquor may increase successively in the course of recycling and must affect the reaction strongly. For this reason, in the experiments with a pilot-scale apparatus, special attention was paid to the effect of the water content. In the following experiments, the initial feed was 157.5 kg of glacial acetic acid with 17.5 kg of BPA (10% concentration) and a t recycling of the mother liquor, 11 kg of BPA was fed. In the experiment with 0% water, the selective formation of TCBPA was observed, similar to curves in Figure 3. This discloses the feasibility of scaling up from the bench scale without changing the reaction conditions. As shown in Figure 5 , in the experiment with 1.6% water content, the formation of some quantities of trichloroBPA was observed a t the earlier stage of the reaction, but
Figure 6. Relation between relative concentrations of intermediate products and T : -. water content '7.65%: - - -. water content 9.5%; 0 , BPA: A , monochloro-BPA: X , DCBPA: 0 , trichloroBPA; A ,TCBPA;Q perchloro-BP. T
Figure 5 . Relation between relative concentrations of intermediate products and i:-. water content 1 . 6 7 ~ -; - -. water content 4.7570; 0 . BPA; A . monochloro-BPA: X . DCBPA: 0 , trichloroBPA: A ,TCBPA.
the selectivity of the catalyst was only slightly diminished. In the case of 4.75% water content, the formation of trichloro-BPA was already observed a t the beginning of the reaction, but only TCBPA was obtained a t the end of the reaction, where the dimensionless time r was 7. As this value of T agreed with that of the bench-scale reaction: it may be clear that the effect of water content on the selectivity of the catalyst may be small until the water content reaches this point. On the contrary. in the case of 7.65% water content, as shown in Figure 6. the inhibiting action of the catalyst on the formation of trichloro-BPA was almost lost. and perchloro compounds were also formed in the course of the reaction and the reaction completed a t T = 8.57. These facts may indicate that the selective formation of each intermediate become more and more difficult with an increase of the water content. In the case of 9.570 water content. perchloro compounds being formed already a t the beginning of the reaction and the selectivity of the catalyst being lost, the aspect of the reaction was similar t o that without catalyst. As such, it was found that when the water content exceeded 5-6'70, the purity of TCBPA was remarkably affected. Relative rate constants of respective intermediates calculated from Figures 5 and 6 are shown in Figure 7. As shown in Figures 5 and 6, the increase of h l and Kz causes the reaction of BPX t o be completed sooner, but causes the reaction time parameter to increase. Meanwhile, as Ks and K4 are smaller than the former. the rates of formation of trichloro-BPA and TCBPA are also small, and consequently. the completion of the successive reaction may be retarded, and the intermediates may remain in TCBPA formed. Moreover, with a n increase of Ks' and K4'. the formation of trichloro-BPA and TCBPA was increased from the beginning of the reaction. and the aspect of the reaction approaches more and more closely the typical successive reaction without catalyst. These facts can be also elucidated by the lowering of the selectivity of the products calculated from the ratios of the relative. rate constants. As the relative rate constant of perchloro compounds Kg may be about 0.01 a t 7.65 and 9.5% water content, it is conceivable that only when the water content exceeds 5 6 % the formation of perchloro compounds may increase and may be the main origin of the yellow coloring of TCRPA. In consideration of' the increase of the water content in the course of practical operations, recycling experiments were carried out under the following conditions: the initial
i,
().--~ -
~
.
~
~
.
~
~
0
lOP/
.
10 .\llsol~llefl \ \ : I t e r , ' ,
Figure 7 . Relation between relative rate constant and ivater con-
tent. feed was 160 kg of glacial acetic acid and 22 kg (12% concentration) of BPA and the feed of BPA in the course of recycling was 14 kg. The results are given in Table IV. Up to the fourth recycling, the water content was kept below 5%; TCBPA. the melting point of which was very close t o that in literature, was obtained and was expected to used as a raw material for the synthesis of resins of light color. As the results of the fifth recycling. where the water content was 6.3. showed, small amounts of perchloro compounds were detected in the mother liquor: thereby the melting point of TCBPA was lowered and the total yield of it was about 80%. In this study. owing t o the insufficient prevention of the increase of the water content for t h e convenience of the operation techniques, the recycling had to be limited to only five times. However. in industrial operations. additional recycling times are possible because of the more adequate prevention of the increase of' water content in closed systems. such as continuous chlorination processes and closed centrifuges. Moreover, a s good results were obtained experimentally even under conditions of the concentration of BPA in the initial fee$ being 15% (concentration close to the solubility of BPA in acetic acid) and that during recycling 11.570, it may be conceivable that. in the industrial scale. the recycling process under conditions of concentrations of BPA-feed being about 12% in both the initial and the recycling periods may be useful. Conclusions In the synthesis of TCBPA by chlorination of BPA in a n Ind. Eng. Chern., Process Des. Develop., Vo'l. 14, No. 1, 1975
63
acetic acid solution catalyzed by aluminum chloride, the successive reaction can proceed selectively, differing from the reaction without a catalyst. Under conditions of a bench-scale reactor, stirring being used, the relative flow rate of chlorine being 0.25 to 0.60, the concentration of BPA feed lo%, that of the catalyst more than 170,and the reaction temperature 30 to 33°C. the selectivity of the catalyst for the formation of DCBPA and TCBPA was very high. The reaction apparently proceeded through three stages and TCBPA of high purity could be synthesized. By assuming a selective, successive reaction model based on the reaction of pseudo-first order in the BPA concentration, the relative rate constant of each intermediate was calculated by the trial and error method. It was ascertained that the reaction could be obviously separated into inhibited and uninhibited steps. the distribution of intermediates was dependent entirely on the dimensionless reaction time T , and the selective synthesis of DCBPA or TCBPA was possible by using an aluminum chloride catalyst. The activation energy of the step to form DCBPA from BPA through monochloro-BPA is remarkably different from that to form trichloro-BPA or TCBPA, and the selectivity of the catalyst decreases with a rise of temperature. It was also confirmed that with a pilot-scale apparatus under recycling of the mother liquor, the aspect of the reaction process can be represented in a similar manner, no special difficulties on the scaleup arose, and the products of comparable quality to that with a bench-scale apparatus could be obtained. The same analytical technique was applied effectively. However, the water content of the
mother liquor is an important factor of the reaction, and
by recycling the mother liquor containing less than 5-67'' water, TCBPA of high purity containing few impurities, which cause the coloring and the lowering of the melting point of the final product, can be produced industrially. Literature Cited Christopher, W . F., Fox, P. W., "Polycarbonates." p 163, Reinhold, New York. N . Y . , 1962. Deutsch Solvay-Werk Co., French Patent 1,180,194 (Dec 19, 1958). Dow Chem. Co.. Japanese Patent 478,333 (July 30. 1966). Jackson, W . J . , Cadweil, J. R . . J . Appl. Polym. Sci.. 11, 243 (1967). Kakiuchi. H., "Epoxy Zyusi no Sei26 to Qy6," p 102, Kdbunshi Kagaku Kankbkai, Kyoto, Japan, 1964. Kdno, K . . inui. K.. Numata, S.,(to Mitsubishi Gasu Kagaku Co.), Japanese Patent 489.475.~ (Feb 20. 1967) Lee, H.. Neville, K . . "Handbook of Epoxy Resin." pp 4-8, McGraw-Hili. New York, N.Y.. 1967. Lee, H., Stoffey. D . , Neville, K . , "New Linear Poiymers." p 24, McGrawHili, New York, N.Y., 1967. March. J., "Advanced Organic chemistry: Reaction, Mechanisms, and Structure," p 376, McGraw-Hill, New York, N.Y., 1968. Norman, R . 0. C., Taylor. R., "Electrophilic Substitution in Benzenoid Compounds." Elsevier. New York. N.Y., 1965. Ota. N., Murayama, H., Kogyo Kagaku Zasshi. 60,417 (1957). Perepelkin. A. N . , Kozlov. P. V . . Vysokornol. Soyed.. A10 ( 1 ) . 1 5 (1968). Schnell, H , "Chemistry and Physics of Polycarbonates," p 105. lnterscience, New York, N.Y.. 1964. Shiba. T . , "Syokubai Kagaku Kbza." Vol. 9, p 6, Chijinshokan. Tokyo, 1965. Smith, J. M.. "Chemical Engineering Kinetics. ' p 62, McGraw-Hili, New York, N.Y., 1956. Stock, L. M., "Aromatic Substitution Reaction," Prentice-Hali, Engiewood Cliffs. N.J.. 1968; (Uchino, N., Sakakibara, Y . . "Hokosoku Chikan Hannd." p 32. Kagaku DBjin, Kyoto. Japan, 1972). Wiegandt, H . F.. Ind. Eng. Chem.. 43. 2167 (1951). ~~~
Received forreuieu' N o v e m b e r 1, 1972 Accepted S e p t e m b e r 3 . 1974
Synthesis Gas from Bovine Wastes James E. Halligan,* Karl L. Herzog, and Harry W . Parker Department of Chemical €ngineering. Texas Tech University Lubbock. Texas 79409
The potential of a process to convert cattle feedlot manure to ammonia synthesis gas was investigated by designing, constructing, and operating a fluidized-bed reactor system. Significant yields of synthesis gas were obtained when this system was fed a mixture of manure, air, steam, and a very small stream of carbon dioxide. This synthesis gas was deemed to be suitable for subsequent conversion to anhydrous ammonia using existing technology.
Introduction Approximately 25 million head of feedlot cattle are marketed annually to supply the beef demands of the United States (Uvacek, 1972). The most negative aspect of the production of this commodity is the accumulation of the animal waste, particularly the manure, which can harm the environment through the watershed and the atmosphere (Hart, 1972). When cattle are fattened by grazing, the large area of land involved dilutes the effects of pollution, but this is not so at the feedlot. Land spreading, still the most used method of manure management, cannot be economically attractive when large quantities of manure must be trucked any distance to achieve dilution. The frequent result is large piles of manure beside the feedlots (Whetstone, et a / , 1973). 64
Ind. Eng. Chem., Process Des. Develop., VOI. 1 4 , NO. 1, 1975
The trend toward large feedlots is particularly evident on the High Plains of Texas where in the Hereford-Dimmitt area the estimated capacity of 30 lots is in excess of 800,000 head (SWPS, 1973). Such large numbers of cattle require that many thousands of acres be in grain crops which in turn require substantial amounts of fertilizers such as anhydrous ammonia. Therefore, large ammonia plants are not uncommon in the vicinity of extensive fed cattle operations. Halligan and Sweazy (1972) have compared previously proposed conversions of solid waste to methane (Feldmann, 1972) and to oil (Appell, et a / , 1971) with their own concept of producing ammonia synthesis gas from cattle manure. Due to its relative simplicity and its obvious consistency with the economy of cattle feedlot areas,
