Ind. Eng. C h e m . Res. 1987, 26, 356-359
356
sociates of Scientific Systems, Inc., is gratefully appreciated. Nomenclature C = controlled variable d = disturbance d , = feedback signal D = control algorithm F = filter transfer function G = impulse-response-type transfer function G, = IMC controller G , = process transfer function h = impulse response coefficients I = identity matrix k = element of process gain inverse matrix k = process gain inverse matrix K = process gain matrix K , = process steady-state gain m, M = manipulated variables N = number of samples P = closed-loop transfer function matrix Q = open-loop transfer function matrix t = time z = z-transform operator Greek Symbols LY = SMPC tuning parameter(s) Subscripts
p = process n = sampling instants
Literature Cited Arulalan, G. R.; Deshpande, P. B. Proceedings of the American Control Conference, Seattle, 1986. Arulalan, G. R.; Deshpande, P. B. Hydrocarbon Process. 1986b, 6. 51. Cutler, C. R.; Ramaker, B. L.; Brosilow, C. B. Proceedings of the Joint Automatic Control Conference, New York, 1980; Paper WP-8. Deshpande, P. B. Distillation Dynamics and Control; Instrument Society of America: Research Triangle Park, NC, 1985; p 471. Deshpande, P. B., Ed. Multivariable Cgntrol Methods; Instrument Society of America: Research Triangle Park, NC, 1987; in press. Deshpande, P. B.; Ash, R. H. Elements of Computer Process Control with Advanced Control Applications; Instrument Society of America: Research Triangle Park, NC, 1981; Prentice-Hall: Englewood Cliffs, NJ, 1983. Garcia, C. E.; Morari, M. Ind. Eng. Chem. Process Des. Deu. 1982, 21(2),308. Garcia, C. E.; Morari, M. I n d . Eng. Chem. Process Des. Dec. 1985a, 24(2),472. Garcia, C. E.; Morari, M. Ind. Eng. Chem. Process Des. Dec. 1985b, 24(2),484. Kuo, B. C. Multivariable Control Systems; Wiley: New York. 1983; p 81. Ralston, P. A. S.; Watson, K. R.; Deshpande, P. B. Ind. Eng. Chem. Process Des. Dev. 1985, 24(4), 1132. Ray, W. H., private communication, University of Wisconsin, 1983. Richalet, J. A.; Rault, A.; Testud, J. D.; Papon, J. Automatica 1978, 14, 413. Tu, F. C. Y.; Tsing, J. Y. H. In Technol. 1979, May, 1. Wood, R. K.; Berry, M. W. Chem. Eng. Sci. 1973, 28, 1707.
Received f o r review August 26, 1985 Revised m a n u s c r i p t received February 18, 1986 A c c e p t e d August 4, 1986
Superscripts = pertaining to model
-
Solubility of Radon in Selected Perfluorocarbon Compounds and Water Christopher Lewis,+*Philip K. Hopke,*+I*and James J. StukeltsL I n s t i t u t e f o r E n v i r o n m e n t a l S t u d i e s , N u c l e a r Engineering Program, D e p a r t m e n t o f Ciuil Engineering, a n d D e p a r t m e n t of Mechanical Engineering, U n i v e r s i t y of Illinois, U r b a n a , Illinois 61801
T h e solubility of radon in a series of perfluorocarbon compounds has been measured in the temperature range 5-40 "C. From the resulting data, a Hildebrand solubility parameter for radon of 8.42 f 0.11 ~ m - was ~ /determined. ~ In order to provide reliable values of these parameters for radon in water, measurements were made for deionized, medium-hardness, and high-hardness water. T h e thermodynamic functions, AGO, AH", AS", and AC,", characterizing the solubilization process have also been determined. Recently there has been renewed interest in radon and radon daughter properties. A model developed by Harley and Pasternak (1981) suggests that from 20% to 100% of the spontaneous lung cancers in the environment may be attributable to radon and its daughters. The US Environmental Protection Agency tentatively proposed standards governing radioactive releases from certain activities (Federal Register, 1983) and has recently set final standards for radon emission (Federal Register, 1985a,b). These activities will initially include uranium mines. In their discussion of these standards, the EPA states that there is a "lack of suitable control technology to capture
* Author to whom correspondence should be addressed.
Institute for Environmental Studies. Nuclear Engineering Program. f Department of Civil Engineering. Department of Mechanical Engineering.
radon-222 being vented from mines", and thus they felt that an emission standard was therefore not feasible. The availability of such technology may be useful. Of greater utility would be the removal of radon from the ventilation streams that could substantially reduce the total air flow needed in uranium mines to meet current occupational radiation exposure limits. These circumstances provide the impetus for the development of techniques to reduce airborne radon concentrations from uranium mine effluents and possibly from other large volume airstreams. Hopke et al. (1984) reviewed the mechanisms available for removal of radon from large-volume airstreams. They suggested that conventional packed bed scrubbers could pr&e useful if an appropriate nonaqueous solvent could be identified. The characteristics of such a solvent previously identified by A.D. Little Inc. (1975) include (1)high radon solubility, (2) low vapor pressure at operating temperature, (3) nonflammable and nontoxic, (4)chemically
0888-5885/87/2626-0356$01.50/0 8 1987 American Chemical Society
Ind. Eng. Chem. Res., Vol. 26, No. 2, 1987 357 unreactive, and (5) low viscosity. Hopke et al. furthermore Table I. Solubility Parameters and Molar Volumes of Solvents Tested suggested the possible use of perflorinated carbon compounds as candidate solvents. The use of perfluorocarbon solubility molar vol, compounds as artificial blood formulations has been exparameter, cm3/mol comDds (calicm3)1/2 -tensively investigated (Reiss and Leblanc, 1978; Wesseler et al., 1977; Lawson et al., 1978). These compounds tend 5.70" FC43 356 5.85" FC72 202 to be nonreactive, nonflammable, and nontoxic. They also 5.59" FC75 239 have low vapor pressures, and many are commercially 5.91" FC71 233 available a t reasonable costs. 5.80a 224 FC84 The solubility of radon in perfluorocarbon compounds 5.70" 247 FC104 could be estimated by using regular solution theory 6.48 perfluoro-1-methyldecalin 266 (Hildebrand et al., 1970). However, it is necessary to know 6.11 perfluoromethylcyclohexane 195 6.95 perfluorooctyl iodide 248 the solubility parameters, 6, for both the solvent and solute. 7.12 ethyl perfluorooctanoate 261 There are very few determinations of radon solubility in 1.14 ethyl heptafluorobutyrate 169 the literature, and most of the data were summarized by 1,3-bis(trifluoromethyl)benzene 8.00 155 Taylor and Hildebrand in 1923. There are only two more 8.11 hexafluorobenzene 115 recent reports, and the existing data have been compiled 7.72 octafluorotoluene 142 by Clever (1979). The prior measurements of radon sol. 5.70 Fomblin-L fluorinated fluid 969 23.40 18 deionized water ubility have yielded quite different values of the radon 23.40 18 medium-hardness water solubility parameter. The value found in the CRC 23.40 high-hardness water 18 Handbook of Solubility Parameters and Other Cohesion Parameters (Barton, 1973) is 6.8 ~ m - ~ Prausnitz /~. a Values estimated by using argon and krypton solubility data by the 3M Company. and Shair (1961) calculated a value of 8.4 ~ m - ~ / ~ furnished . Thus, to resolve these questions, the solubility of radon 15 I in perfluorocarbon compounds has been measured and the Lussboum 8 value of the radon solubility parameter determined. The P u - s c h . ' 958 + tsolubility data have also been used to calc!late the ther+ T h I s Work Z modynamic functions, hii, AS, A@, and ACp for the disLL ++ solution process over the temperature range 5-40 "C. In 10addition, because of the uncertainties in the existing values U LL of radon solubility in water, these measurements were also w 0 made for deionized, medium-hardness, and high-hardness water in the temperature range 5-60 "C. i+
O
Experimental Section The radon solubility measuring system was similar to that used by Nussbaum and Hursch (1958) to measure radon solubility in fatty acids and triglycerides. A 200-mL equilibration vessel with high-vacuum stopcocks at each end was used. Pure nitrogen was passed through the equilibration vessel for 30 min to assure that the compound became saturated with nitrogen. Radon-laden nitrogen was then introduced into the vessel a t a concentration of approximately 20 pCi/Li. The vessel was then sealed and put into a shaking water bath to maintain a constant temperature during the dissolution process. The vessel was left in the water bath for 2 h to assure that thermal equilibrium was reached. Samples of both the gas and the compound were then removed into evacuated 1-mL sample bottles. The activity of the radon in each of the samples was determined by measuring the y-ray activity of one of its daughters, 214Bi,once it is in radioactive equilibrium with the radon. The y-detection system consisted of a 4-in. by 4-in. thallium-activated sodium iodide scintillation [NaI(Tl)] detector, with a 7/s-in.-diameter by 2-in.-deep well. The detector was connected to a standard set of nuclear instrumentation modules. Samples were counted long enough to obtain a t least 10000 counts (i.e., at least 1% counting precision). The solvents were purchased at the highest purity available from commercial sources except for the FC solvents that were provided by the 3M Company. The deionized water was from an ultrapure deionizing system to give >15 mR/cm resistivity water. The medium- and high-hardness water were prepared to have hardness numbers of 150 and 350, respectively. They were prepared by dissolving CaC12and MgC12in deionized water such that the medium-hardness water contained 33.0 mg/L of Ca2+and 16.5 mg/L of Mg2+,while the high-hardness
m
0
++ +
5: I ! O;
f+ +
, +-
5
15
20 25 SOLUBILITY PARFMETER Figure 1. Variation of radon solubility with the solubility parameter of the solvents tested a t 25 "C. IO
water contained 76.8 mg/L of Ca2+and 38.4 mg/L of Mg2+.
Results Where available, solubility parameters and partial molar volumes were obtained from the literature (Barton, 1983). The solubility parameters for a number of perfluorocarbons were estimated by using the method developed by Lawson and co-workers (1978, 1980). The molar volumes were estimated from the ratio of molecular weight to the density a t 25 "C. Details of these calculations are given by Lewis (1984). The solvents and their parameters are given in Table I. The radon solubilities, in terms of the Ostwald coefficient, were then determined experimentally for temperatures between 5 and 40 "C. To test the measurement system, the solubility of radon in toluene (6 = 8.90) was measured at 20 and 25 "C. Values of the Ostwald coefficients of 12.9 and 10.3, respectively, were obtained and they compare quite well with those tabulated by Clever (1979). For water the temperature range was expanded to 60 "C. The results are given in Table 11. A plot of the Ostwald coefficients at 25 "C against the solute solubility parameter is shown in Figure 1. In this figure, the data for 25 "C presented in Table I1 are plotted along with our measured values for toluene and chloroform. In addition, values from Nussbaum and Hursch for short chain carboxylic acids are also plotted to cover the region
358 Ind. Eng. Chem. Res., Vol. 26, No. 2 , 1987 Table 11. Ostwald Coefficients of Various Solvents at Different Temperatures temperature, "C compound 5 10 15 20 25 30 35 FC43 3.07 2.82 2.53 2.30 2.25 2.14 2.11 FC72 3.86 3.73 3.53 3.19 3.01 2.83 2.79 FC75 3.41 3.21 3.06 2.76 2.72 2.52 2.56 FC77 3.46 3.19 3.13 3.08 3.09 2.77 2.49 FC84 3.36 3.31 3.14 2.99 2.97 2.75 2.94 FC104 3.38 3.12 3.19 2.66 2.88 2.75 2.75 perfluoro- 1-methyldecalin 3.16 3.00 2.96 2.86 2.73 2.61 2.54 perfluoromethylcyclohexane 4.15 4.01 3.79 3.61 3.21 2.87 3.20 5.65 4.71 4.38 4.22 4.12 3.66 3.40 ethyl perfluorooctanoate a 5.35 5.09 5.05 4.46 a a perfluorooctyl iodide 6.13 5.54 5.74 5.48 5.32 5.07 4.93 ethyl heptafluorobutyrate 1,3-bis(trifluoromethyl)benzene 7.84 7.64 7.45 6.49 6.17 6.09 5.74 hexafluorobenzene 12.55 11.89 11.23 9.05 10.20 9.96 9.65 7.15 6.68 6.96 6.30 6.18 5.86 5.71 octafluorotoluene Fomblin-L fluorinated fluid 2.55 2.38 2.41 2.21 2.13 2.06 1.92 0.394 0.372 0.285 0.272 0.232 0.202 0.183 deionized water medium-hardness water 0.410 0.328 0.315 0.216 0.214 0.191 0.187 0.456 0.387 0.281 0.216 0.210 0.170 0.163 high-hardness water
40
45
50
b 2.27 2.20 b 2.30 b 2.26 b b 3.97 b b b b b 0.161 0.161 0.141
b b b b b b b b b b b b b b b 0.145 0.158 0.137
b b b b b b b b b b b b b b b 0.130 0.138 0.122
55
60
b b b b b b b b
b b b b b b b b
b
b b
b b b b b b 0.118 0.130 0.104
b b b b b 0.100 0.120 0.115
Perfluorooctyl iodide is solid at these temperatures. *Solubility was not tested at this temperature.
Table 111. Fitting Parameters for Theoretical Solubility Eauation compound A B FC43 -0.76f 0.23 1.15f 0.45 -0.87f 0.24 0.84f 0.45 FC72 -0.95f 0.22 -0.46f 0.46 FC75 -0.89f 0.24 -0.03f 0.48 FC77 0.27f 0.41 -0.86f 0.22 FC84 -0.90$: 0.38 -0.94f 0.20 FC104 -0.90f 0.19 -0.32f 0.37 perfluoro-1-methyldecalin -0.90f 0.20 -0.27 f 0.40 perfluoromethylcyclohexane -0.79If: 0.21 0.28f 0.46 ethyl perfluorooctanoate -0.79f 0.36 0.17f 0.82 perfluorooctyl iodide -0.90f 0.27 -1.08f 0.53 ethyl heptafluorobutyrate -0.73f 0.25 0.63f 0.47 1,3bis(trifluoromethy1) benzene -0.77f 0.26 0.17f 0.50 hexafluorobenzene octafluorotoluene -0.84f 0.19 -0.33f 0.36 Fomblin-L fluorinated fluid -0.63f 0.17 0.01 f 0.34 -2.00f 0.19 deionized water 0.95f 0.34 -2.01f 0.16 medium-hardness water 0.23f 0.27 high-hardness water -2.02f 0.19 1.37f 0.34
10 5 6 I15. The best fit to the regular solution theory model yields a radon solubility parameter of 8.42 f 0.11. The experimental solubility measurements obtained from this experiment were used to calculatg the thermodynamic functions, AGlo, AS,", and AC,,, describing the dissolution process. The mole fraction solubility can be fit a t the various temperatures with an equation of the form (Clever, 1979) In x 2 = A B/(T/100K) + C In (T/100K) + D(T/100K) (1)
mlo,
+
The parameters, A, B, C, and D, for each of the perfluorocarbon compounds are given in Table 111. The thermodynamic functions, A G I O , m?,A&", and ACpol,can be written for the transfer of the gas from the vapor phase at 1-atm partial pressure to the hypothetical solution phase of unit mole fraction as AGlo = -RAT - lOORB - RCT In (T/100K) - RDl?/lOOK ( 2 ) AS," = RA + RC In (T/lOOK) + RC + 2RDT/100K (3) AFT," = -100RB + RCT + RDl?/lOOK (4) AC,", = RC + 2RDT/100K (5) Conclusion These results confirm Prausnitz and Shair's value for the radon solubility parameter. Therefore, solubility
C
D
-2.20f 0.20 -2.23f 0.20 -1.99f 0.19 -2.04f 0.20 -2.12f 0.19 -1.90f 0.17 -1.99f 0.16 -2.02f 0.17 -1.94f 0.18 -1.84f 0.30 -1.76f 0.23 -2.04f 0.21 -1.89f 0.22 -1.91 f 0.16 -1.68f 0.15 -3.96f 0.15 -3.88 f 0.13 -4.09f 0.16
-0.21 f 0.07 -0.23 f 0.07 -0.13f 0.07 -0.16f 0.07 -0.19f 0.07 -0.09 f 0.06 -0.14f 0.06 -0.14f 0.06 -0.11f 0.06 -0.09f 0.11 -0.04f 0.08 -0.15f 0.08 -0.09f 0.08 -0.10f 0.06 -0.02f 0.05 -0.91f 0.05 -0.84f 0.04 -0.92f 0.05
theory predicts the best solvents to be those with solubility parameters around 8.4. Of the fluorochemicals tested, hexafluorobenzene ( 6 = 8.11) and 1,3-bis(trifluoromethyllbenzene (6 = 8.00) are the best choices as potential radon scrubber fluids from the standpoint of radon solubility in compounds with the other characteristics that the perfluorocarbons possess. Acknowledgment
Although the information described in this article has been funded in part by the US Environmental Protection Agency under assistance agreement EPA Cooperative Agreement CR 806819 to the Advanced Environmental Control Technology Research Center, it has not been subjected to the Agency's required peer and administrative review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. We express our appreciation to the Minnesota Mining and Manufacturing Company for providing samples of their FC solvents for testing. Literature Cited A.D. Little, Inc. US Bureau of Mines Report OFR 60-75, 1975. Barton, A. F. M. Handbook of Solubility Parameters and Other Cohesion Parameters; CRC: Boca Raton, FL, 1983. Clever, L. H., ed. Krypton, X e n o n and Radon-Gas Solubilities; Solubility Data Series 2;Pergamon: New York, 1979;Vol. 18.
Ind. Eng. Chem. Res. 1987,26, 359-365 Federal Register, National Emission Standards for Hazardous Air Pollutants; Standard for Radionuclides, 4815076-15091, April 6, 1983. Federal Register, National Emission Standards for Hazardous Air Pollutants; Standard for Radon-222 Emissions from Underground Uranium Mines, 507280-7287, Feb 21, 1985a. Federal Register, National Emission Standards for Hazardous Air Pollutants, Standard for Radon-222 Emissions from Underground Uranium Mines, 5015386-15394, April 17, 198513. Harley, N. H.; Pasternak, B. S. Health Phys. 1981, 40, 307-316. Hildebrand, J. H.; Prausnitz, J. M.; Scott, R. L. Regular and Related Solutions; Van Nostrand: New York, 1970; pp 111-141. Hopke, P. K.; Leong, K. H.; Stukel, J. J. University of Illinois Report AECTRC 84-6, March 1984; Advanced Environmental Control Technology Research Center.
359
Lawson, D. D. Appl. Energy 1980,6, 241-255. Lawson, D. D.; Maacanin, J.; Sherer, K. V.; Terranova, T. F.; Ingham, J. D. J. Fluorine Chem. 1978,12, 221-236. Lewis, C. MS Thesis, University of Illinois, Urbana, 1984. Nussbaum, E.; Hursch, J. B. J . Phys. Chem. 1958, 62, 81-84. Prausnitz, J. M.; Shair, F. H. AZChEJ. 1961, 6, 682-687. Reiss, J. G.; Leblanc, M. Angew. Chem. 1978, 17, 621-700. Taylor, N. W.; Hildebrand, J. H. J. Am. Chem. SOC.1923, 45, 682-694. Wesseler, E. P.; Iltis, R.; Clarke, L. C., Jr. J . Fluorine Chem. 1977, 9, 137-146.
Received for review August 2, 1985 Accepted August 14, 1986
Thermal Chemistry Pathways of Substituted Anisoles Antti I. Vuori and Johan B-son Bredenberg* Department of Chemistry, Helsinki University of Technology, SF-02150 Espoo 15, Finland
The thermolyses of 0-,m-, and p-hydroxyanisoles and 0-,m-, and p-methoxyanisoles have been studied under an inert atmosphere. Experiments were made both with neat compounds and in the presence of tetralin a t the molar ratio 1:l. T h e reaction temperature was varied from 623 t o 673 K and the reaction time from 0.25 t o 7.0 h. The major products formed from all three hydroxyanisoles were the correspondingly substituted dihydroxybenzenes and cresols. The 0-and p-methoxyanisoles gave a product pattern of the same type, while m-methoxyanisole gave more ring-methylated products with two oxygen atoms. The formation of anisole by direct demethoxylation was significant for all three methoxyanisoles. The presence of a hydroxyl group seemed to prevent this demethoxylation in substituted anisoles. T h e reactivity of the lignin-related o-hydroxyanisole (guaiacol) was much higher than the reactivity of all the other model compounds studied. The reaction rates of all compounds were decreased by tetralin. It also prevented the formation of higher products, except for experiments with p-hydroxyanisole a t 673 K. One of the major components of biomass is lignin. It is produced in large amounts during wood pulping, but the main part of it is simply burnt since, on one hand, no large scale use has been found and, on the other, the pulping process requires energy. The need to evaporate large amounts of water before combustion makes the energy balance less favorable. The possibility of using biomass as a chemical feedstock has in recent years attracted increasing attention, and there should be some possibilities to use part of the lignin as a raw material for more valuable products (Deglise and Lede, 1982; Kringstad, 1980; Parkhurst et al., 1980). The first reaction step in any chemical conversion process of lignin is thermal rupture to smaller molecular units (Avni et al., 1983; Parkhurst et al., 1980). Only the products thus formed are small enough to react with a heterogeneous catalyst to the ultimate products. This behavior corresponds to that found for coal. Thermal reactions of lignin are usually very complicated. This makes the interpretation of experimental results from thermal reactions of lignin quite difficult (Connors et al., 1980; Iatridis and Gavalas, 1979; Jegers and Klein, 1985). Hence, the study of suitable lignin-related model compounds can be of great use in the interpretation of the results. Application of the results of model compound studies on more complicated structures must, however, always be done with care since the reactions of macromolecular structures are not necessarily well represented by simple model compounds as has been noted in connection with coal (McMillen et al., 1981). Thermolyses of hydroxy-, methoxy-, and methyl-sub0888-5885/87/2626-0359$01.50/0
Table I. Experimental D a t a substituted reaction anisole temp, K o-OH, neat 623 648 673 623 with tetralin 648 623 m-OH, neat 648 673 648 with tetralin 673 648 p-OH, neat 673 648 with tetralin 673 648 o-OCH,, neat 673 623 with tetralin 648 673 623 m-OCH,, neat 648 673 648 with tetralin 673 648 p-OCH,, neat 673 with tetralin 623 648 673
reaction time, h 0.6, 1.0, 2.0 0.5, 1.0, 2.0, 3.0 1.0, 2.0 0.75, 1.0, 2.0, 3.0, 4.0 0.5, 0.5, 1.0, 2.0, 2.0, 3.0, 4.0, 4.0 2.0, 3.0, 4.0 1.0, 1.0, 2.0, 2.0, 3.0, 4.0 1.0, 1.0, 2.0, 4.0, 4.0 0.5, 1.0, 2.0, 3.0, 4.0, 4.0 0.5, 1.0, 2.0, 2.0, 3.0, 4.0 1.0, 2.0, 4.0 0.5, 2.0 0.5, 1.0, 2.0, 2.0, 3.0, 4.0, 4.0 0.5, 1.0, 2.0, 2.0, 3.0, 4.0 1.0, 2.0, 4.0 0.25, 0.5, 2.0 1.33, 2.0, 4.0, 5.0, 7.0 1.0, 1.0, 2.0, 3.0, 4.0 0.5, 1.0, 1.0, 1.5, 2.0 2.0, 3.0, 4.0 1.0, 1.0, 2.0, 4.0 1.0, 2.0, 2.0, 4.0 1.0, 2.0, 2.0, 3.0, 4.0 0.5, 1.0, 1.5, 2.0, 2.0 1.0, 2.0, 4.0 0.25, 0.5, 2.0 1.33, 2.0, 4.0, 5.0, 7.0 10, 1.0, 2.0, 3.0, 4.0 0.5, 1.0, 1.0, 1.5, 2.0
stituted anisoles in the presence of tetralin have been studied earlier by Bredenberg and Ceylan (1983). Their 0 1987 American Chemical Society
