Ind. Eng. Chem. Prod. Res. Dev. 1982, 21, 82-87
a2
40
t 1
4
6
8
Solids Concantratfin NI Dilulad PIC, %
Figure 3. Effect of solids concentration on trypsin inhibitor (TI) accountability in diluted potato juice concentrate (PJC).
effect of pH on the permeate and retentate fractions. The loss of TI to the permeate was approximately 10% greater at pH 7 and over 25% higher at pH 5. Recovery of T I in the retentate fraction was highest at pH 3.5. Effect of Solids Concentration. All the preceding experiments had been run at 2% solids concentration in the PJC. In the interest of keeping the number of pilot plant runs to a minimum for processing the main bulk of the PJC, it would appear desirable to utilize a higher solids concentration. Experiments were run in which the solids concentration was increased to 5 and 8% (Figure 3). At 5 % , the T I accountability decreased to about 70%, and to about 60% at 8%. It appeared that 2% solids concentration was close to ideal. However, we found that we could operate at 3% solids concentrations with only negligible loss of TI activity. This study has shown that non-TI protein can be separated as an acid curd at pH 3.5, and the low-molecularweight components in the whey can be removed in the permeate by passing over a 1K ultrafiltration module. The resulting TI-rich retentate, which contained approximately 90% of the TI originally present in the PJC, can then be
freeze-dried for incorporation into diets for the long-term feeding trials. Acknowledgment Alkaloid analyses were run by S. Osmon, Eastern Regional Research Center in SEA-AR, USDA, Philadelphia, PA. All other analyses were made by L. T. Black, J. D. Glover, K. A. Rennick, and K. M. MacDonald. Pilot-plant experiments were run by R. L. Brown. Technical advice on potato trypsin inhibitor properties was given by C. A. Ryan, Washington State University, Pullman, WA. Literature Cited American 011 Chemists’ Society, “otflclaland Tentatlve Methods of Analysis”, Vol. I, 2nd ed.; The sodety, Champaign, IL, 1964 (Revised to 1976). Baker, E. C.; Mustakas, G. C. J . Am. OHChem. SOC. 1973, 50. 137. Baker, E. C.; Mustakas, G. C.; Moosemllier, M. D.; Bagby, E. B. J . Appl. P m m . Scl. 1979, 24. 135. Becker, H. C.; MiIner, R. T.; Nagel, R. H. Cere81 Chem. 1940, 77, 447. Bryant, J.: Gren, T. R.; Gurusaddaiah, T.; Ryan, C. A. Biochemlstty 1976,
.-
- . .-.
1.5 , R A l A
Fkpatrick, T. J.; Osrnan, S. F. Am. Potato J . 1974, 51, 318. Gerry, R. W. Poult. SC/. 1977, 56, 1947. Hamerstrand, G. E.; Black. L. T.; Qlover, J. D. Cererrl Chem. 1981, 56, 42. Hass, G. M.; Venketakrlshnan, R; Ryan, C. A. frog. Natl. Acad. Sei. 1976, .73. - , 1974. .- . .. Kakade, M. L.; Rackis. J. J.; McGhee, J. E.; Puski, G. Cereal Chem. 1974, 51, 376. Kakade, M. L.; Shnons, N.; Liener. I . E. CerealChem. 1989, 46. 518. Liener, I . E.; Kakade, M. L. “Protease Inhibitors” In “Toxlc Constituents of Plant Foodstuffs”, Liener, I . E., Ed.; Academic Press; New Yo& 1980. Melville, J. C.; Ryan, C. A. J . Blol. Chem. 1972, 247, 3445. Porter, W. L.; Siciliano, J.; Krullck, S.; Heisler, E. G. Membrane Sei. Techno/. 1970, 220. Rackis, J. J.; McGhee, J. E.; Booth. A. N. Cereal Chem. 1975, 52, 85. Ryan, C. A.; Hass, G. M.; Kuhn, R. W. J . Blol. Chem. 1974, 249, 5495.
Received for review August 21, 1981 Accepted November 6, 1981 Presented at the 181st National Meeting of the American Chemical Society, Atlanta, GA, Mar 29-Apr 3,1981. The mention of firm names or trade products does not imply that they are endorsed by the U.S.Department of Agriculture over other firms or similar products not mentioned.
Alcohol from Membrane Processed Concentrated Cheese Whey K. RaJagopalanand F. V. Koslkowskl’ Department of Food Sclence, Cornell University, Ithaca, New York 14853
A fermentable whey substrate in the form of a high solids permeate was obtained by reconstituting spraydried whey powder to 36% total solids fdlowed by ultrafiltration to separate the protein. The high solus permeate was demineralized to permit rapid yeast growth. The final permeate with 24% lactose and at pH 4.8 gave high yields of alcohol rapidly upon inoculation with lactose fermenting yeasts. One yeast species, K/tyvermyces riagik NRRL Y 2415 yielded 108.8 g of ethanolll, giving 84.3% of the theoretical maximum. Batch ethanol productivity was 3.2 g/(L h). The cost analysis of the ultrafiltration-fermentation process is highly favorable, if evaporation instead of the widely used reverse osmosis is employed for preconcentration of whey.
Introduction Whey is the greenish yellow serum that separates from the curds during conventional cheesemaking or casein manufacture. Its efficient utilization is a major concern to cheese producers. In a recent survey, 25 of 26 New York state cheese manufacturers considered cheese whey a liability without proper end use (Switzenbaum, 1981). Production of any cheese or casein results in approximately 9 kg of liquid whey/kg of the final product. Whey contains more than 50% of the total solids present in milk 0196-4321 I8211 221-0O82$01.25/0
used for cheesemaking and includes lactose, soluble proteins, and salts. Whey has a high biological oxygen demand of about 30000 to 4OOOO mg/L (Gillies, 1974),which makes its discharge into streams undesirable and usually unlawful. In 1980, approximately 15 billion kg of liquid whey and 400 million kg of whey powder were produced. However, there is a limited market for the disposal of whey, whether dried or fluid, and the pollution abatement laws in the United States are forcing cheese producers to find alter0 1982 American Chemical Society
Ind. Eng. Chem. Prod. Res. Dev., Vol. 21, No. 1, 1982 83
native processes for more effective utilization of whey. Recovery of lactose from such dilute solutions is not economically viable because the lactose market is relatively static and lactose cannot compete with other sugars available at relatively lower costs. Nutritionally, the most valuable whey component is protein (Demott, 1972; Wingerd et al., 1972; Humphreys, 1977), and various technologies are being applied to the production of whey protein concentrates (WPC). Industrial processes using ultrafiltration (UF), gel filtration (GF), polyphosphate complexing, and heat-pH precipitation have been reported (Walker, 1970; Wingerd, 1971; Davis, 1972; Morr, 1976; Mann, 1977). Fermentation of whey leading to alcohol also has been studied. Engel (1952) and Yang et al. (1975) reported on the alcoholic fermentation of heat deproteinized 5% lactose whey. Yo0 and Mattick (1969) studied the rate of ethanol production by Saccharomyces fragilis in lactose and reconstituted whey. They observed that fermentation rates were low when the initial concentration of lactose was over 5%, and ethanol levels of lO%(v/v) were attainable only by adding 16% sucrose to 5% lactose whey. Kosikowski and Wzorek (1977) developed a process for making wine containing 12.2% alcohol from lactose permeates during 7-14 days using Kluyveromyces fragilis adapted to high (24%) lactose concentrations by Gawel and Kosikowski (1978). Later, Burgess and Kelly (1979) employed Candida pseudotropicalis and two strains of Kluyveromyces fragilis and reported complete conversion in 15% lactose whey permeates supplemented with urea and yeast extract. Similarly, Moulin et al. (1980) showed conversion efficiencies of about 70% after 48 h when whey permeates containing 24% lactose were fermented. The objective of the present work was to recover the major whey components, improve alcohol production rates in concentrated whey permeates, and identify the factors limiting the fermentation rates when concentrated whey permeates were converted into alcohol either for fuel or for human consumption.
Experimental Section Materials and Methods. Spray-dried whey was reconstituted to 36% total solids with tap water and ultrafiitered in an Abcor 22s Model (Abcor Inc., Cambridge, MA) unit with high flux membranes (HFM) and a molecular weight cutoff of 20000 daltons. The permeate having 3.7% ash was demineralized in an Ionics Stackpack Electrodialysis (Ionics Inc., Watertown, MA) unit to 0.8% ash level to permit rapid yeast growth. Kluyveromyces fragilis NRRL Y 2415 yeast culture was maintained at 30 OC and transferred into fresh concentrated whey permeates every 15 days. Batch cultivation of aerobically grown yeasts was done with skim milk permeate (obtained by ultrafiltration of skim milk) as substrate and the cells were grown rapidly at 30 OC under aerobic conditions by sparging compressed air at 0.227 wm. The working volume was 80% in a 5-gal plastic container. Cells were harvested after 2 days by centrifuging in a Model B-20 refrigerated centrifuge (International Equipment Co., Needham Heights, MA) at 2000g and 30 OC for 20 min and then transferred to 1.8-L Erlenmeyer flasks containing acid whey permeates pasteurized earlier a t 72.8 OC for 15 s. The working volume was 70% and the flasks were incubated in a rotary shaker (New Brunswick Scientific Co., Edison, NJ) and agitated at 200 rpm under aerobic conditions, to help yeast proliferation. After 2 h the flasks were fitted with water traps to maintain anaerobic conditions and incubated at 30 OC without agitation. Inoculum levels were 1,3,5, and 10 g
Table I. Composition of Spray Dried Whey Powdera
component
acid whey powder, %
lactose protein fat ash titratable acidity total solids
68.5 11.0
0.6 11-12 4.2 95.0
sweet whey powder, %
75.0 13.0 0.8
7.3 0.2 96.5
a Kosikowski, F. V. 'Cheese and Fermented Milk Foods', 2nd ed., 2nd printing; 1978, p 450.
Table 11. ComDosition of Protein Concentrate component % lactose protein ( N x 6.38) fat ash total solids
20.87 15.6 0.234 1.91 39.0
wet weight of cells per 100 mL of substrate in duplicate flasks. The number of cells per gram of centrifuged mass was determined by plate count using potato dextrose agar (APHA, 1978). Dry cell weight was determined by centrifuging a known volume of the fermenting medium at 2000g in an IEC centrifuge for 20 min and washing the cells with distilled water. The washed solids and the first supernatent were dried in an oven at 100 "C for 16-20 h or until constant weight was achieved (Mallette, 1969) and reported as dry cell weight and total solids, respectively. Ash content was obtained by ashing samples in a muffle oven at 550 O F until constant weight was achieved (AOAC, 1980). Nitrogen was measured by the Kjeldahl procedure (AOAC, 1980),except that CuS04was substituted for HgO as catalyst. Lactose was determined in an automatic Enzymax TM analyzer (Leeds and Northrup, North Wales,
PA). For determination of ethanol concentrations, 100-mL samples were centrifuged at 2000g and 30 "C for 20 min and the supernatents were subjected to the distillation and hydrometric procedure of Amerine and Ough (1974). Results and Discussion Ultrafiltration of Concentrated Whey. Ultrafiltration of acid whey powder (Table I) yielded a high protein concentrate (WPC) and a permeate essentially free of proteins. A typical composition of the resulting protein concentrate which could be used as a protein supplement is shown in Table 11. The functional applications of whey proteins are primarily dependent on their water solubility and hydrophobic characteristics. Because ultrafiltration concentrates the whey proteins without the use of high heat, the resulting product will contain these proteins in an undenatured state. Thus their valuable native functional properties will be retained intact. Recent reports indicate that digestibilities are high with lyophilized ultrafiltered and spray-dried ultrafiltered whey protein concentrates (Fors u m and Hambraeus, 1977). It was also reported that the available lysine in UF concentrate was considerably higher than the FA0 recommended content of 340 mg/g of nitrogen. Again, as compared to 17.4 g of whole egg protein, and 28.4 g cow's milk protein, only 14.5 g of WPC containing 45% protein on a dry basis will meet the daily requirements of essential amino acids (Delaney, 1972). The major component of the permeate is lactose, Table 111. Recovery of lactose by crystallization or other processes from large amounts of permeates is not economical
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Table 111. Composition of Concentrated Sweet Whey Permeate after Demineralization
INITIAL CELL CONCENTRATION WET BASIS
component
%
24.0
lactose protein ( N x 6.38) fat ash titratable acidity total solids
or 12.6 g wet weight. Here, the inoculum employed corresponds to about 80% of the theoretical amount of cells that can be produced during the fermentation of 24% lactose solution and therefore the cells from one batch can be used as inoculum for the next batch. Concentration changes of dissolved solids, alcohol, and yeast cells during the progress of the fermentation when 10 g wet weight of cells was used as inoculum are shown in Figure 2. Conversion efficiency was 84.3% of the theoretical maximum (0.54 g ethanol/g of lactose) after 34 h at 30 "C. Thereafter, no change in substrate concentration occurred. The alcohol concentration decreased slightly because apparently the yeasts utilized the ethanol which was formed in the absence of a minimum concentration of lactose, a point in agreement with Mahmoud (1980). Volumetric rates of alcohol production vs. fermentation time are shown in Figure 3. The plot indicates two regions where rates of product formation, substrate utilization, and growth attain high values. They are separated by a lag phase indicating a period of readjustment between utilization of two different substrates, possibly glucose and galactose. The first portion of the curve closely follows the Type I classification of fermentation patterns (Gaden, 1955), based on alcohol production by yeasts growing on glucose. Productivity in the batch process is defined as the ratio of final product concentration and the time from inoculation to the delivery of the product (Gaden, 1955). Productivity in whey fermentation was 3.2 g of ethanol/(L h). The maximum specific growth rate was approximately 0.06 h-l, corresponding to a doubling time of 11.6 h, and the maximum specific ethanol formation rate was 0.205
TIME (hours)
Figure 1. Change in alcohol concentration with the progress of fermentation.
because of a limited market for lactose. Kinetics of Alcohol Production. The concentration of alcohol during fermentation is shown in Figure 1. Ten grams of wet biomass weight contained 9 X 10s cells, which indicated that a high concentration of cells was required in the inoculum to obtain rapid rates. At lower inoculum levels corresponding to 9 X lo6 cells per milliliter of the initial medium, a long lag phase appeared despite use of a Kluyveromyces fragilis strain adapted to sugar. The growth curve in each case exhibited a diauxic stepwise growth pattern. The diauxic behavior of yeasts growing on lactose is due to the catabolite repression by high intracellular concentration of glucose and the fact that the galactose pathway enzymes all are on the same operon inducible only by phosphorylated galactose (Douglas and Pelroy, 1963; Stanier et al., 1976). Maximum cell concentration of 10 g wet weight of cells employed corresponds to 1.9 g dry weight of cells. Under anaerobic conditions, the theoretical amount of dry cells that can be produced from 24% lactose solution is 2.4 g
n
1.47 0 0.8 0.5-0.8 27.56
ll.&
95 19
Dry Cell Weight
/
/ - 38
200-
._0 4-
F a, C
._ -34
s u (I)
.0
-k C
4-
E 4.
ar C
-30
w
8 -a,
0
100-
- 26
V 0
20 I
I
I
I
I
I
I
I
I
4
8
12
16
20
24
28
32
36
I 1
- 22 - 20 40
TIME (hours)
Figure 2. Changes in total solids, alcohol, and dry cell weight concentrations with the progress of fermentation at initial cell concentration of 19 g dry wt/L.
Ind. Eng. Chem. Prod. Res. Dev., Vol. 701
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I
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85
VOLUMETRIC RATES
TIME (hours) Figure 3. Rate of change of alcohol, substrate, and growth (initial dry cell concentration 19 g/L).
0 Sp alcohol productILIi late
0 Sp
substrate utilization rate Sp growth rate
TIME (hours)
Figure 4. Specific rates of ethanol production, substrate utilization, and growth (initial dry cell concentration in the medium 19 g/L).
SALTS
L 3 1:,s
147” HLCOtiO. ( V I V I = !3 > tics (lush ETWOL)
Figure 5. Processing sequence in dried whey to alcohol conversion plant. Numbers on the right indicate typical yield of fractions and their components.
h-l (Figure 4). These data eliminate high growth rates as a necessary condition for whey alcohol production and it appears that high initial cell numbers are essential for high rates of alcohol production. Cost Analysis for Whey Alcohol Plant. The yield data for a process involving dried whey ultrafiltration, demineralization, and fermentation are shown in Figure 5. The overall costs of a process involving ultrafiltration, demineralization, and alcohol fermentation are dictated by several factors, such as the amount of preconcentration of whey prior to ultrafiltration, the use of diafiltration (washing with water), and ethanol productivity. However, it is now known (De Boer et al., 1977) that preconcentration of 5% lactose whey to 25% total solids level increases the capacity.of the ultrafiltration unit by 50 to 100% (expressed as kilograms of dry product per square meter
86
Ind. Eng. Chem. Prod. Res. Dev., Vol. 21, No. 1, 1982
f----l
Table IV. Cost Analysis For Whey Alcohol Plant (U.S.Dollars (1980)) planta A
4TCS
Figure 6. Process flow diagram for conversion of 5% lactose whey to produce spray-dried whey protein concentrate and azeotropic alcohol.
of membrane area per hour), In addition, application of diafiitration after ultrafiltration will enhance the product quality and improve the economy of the process (Goudedranche et al., 1976; Hiddink, et al., 1976). Further, the cost calculations will depend upon whether the preconcentration is carried out by reverse osmosis or evaporation or a combination of both. At present, the cost of reverse osmosis at a concentration factor of 2 is favorable when compared with those of evaporation, and a concentration ratio of 4 favors evaporation over reverse osmosis. A model scheme for utilization of whey using a combination of membrane processes, evaporation, and fermentation is shown in Figure 6. Such an operation will lead to savings in energy by avoiding drying, and also all of the components of whey will be effectively utilized. However, the elimination of reverse osmosis will reduce the cost of the retentate (WPC), because at a concentration factor of 6, reverse osmosis is not as economical as evaporation. The cost of UF concentrate obtained after initial reverse osmosis concentration was approximately $355 per ton in 1980 (Muller, 1979). The cost estimates of a plant handling 130 m3 of 5% lactose whey per day is listed in Table IV. The costs of standard equipment were obtained from texts on cost analysis (Peters and Timmerhaus, 1968; Vilbrandt and Dryden, 1959) and adjusted to 1980 costs using the Marshall-Stevens cost index and the CE plant index. Capital and operating costs for ultrafiltration and demineralization were obtained from manufacturers in the US. It is seen that the breakeven production cost of high protein concentrate or retentate has to be $202.98 per ton for plant A, utilizing concentrated whey aa the starting material for ultrafiltration, whereas it has to be $245.30 per ton for plant B, utilizing dried whey as the starting material, as shown in Table IV. The selling price of 99.5% ethanol is fixed at $1.30 per gallon to make it competitive with that obtained from other sources. The return on investment for ultrafiltration-fermentation plants using concentrated whey and dried whey will be approximately 42% and 20%, respectively, if the retentate selling price is $300 per ton. It is to be noted that the cost figures shown above do not take into account the savings incurred by not adopting the conventional waste treatment processes. In 1980, the cost of treatment was approximately $0.69 per lb of BOD (EPA, 1978). Hence the savings in using membrane processes and fermentation will be 1.99 million dollars per year, even if it is assumed that only 90% BOD is reduced by fermentation processes. The present work shows that whey can be effectively
B
Equipment Costs evaporator (2000 ft2 58608.45 73260.50 heating surface area) ultrafiltration unit 93.5 mz 127 875.00 127875.00 fermentors 21 013.84 21 013.84 ( 3 x 5000 lb) cooling tower (cap. 1830.36 1830.36 2.88 x l o 7 Btu/d) demineralizer 39 220.00 39220.00 centrifuge ( 2 0 gpm) 3922.00 3 922.00 distillation unit 49 823.76 49823.76 spray dryer 30098.14 (a) subtotal
302 293.41
347043.60
Installation piping, wiring (30%of (a)) 90688.02 104113.08 buildings (10%of (a)) 30 229.34 34704.36 land (5%of (a)) 15114.67 17352.18 (b) direct costs contingencies (25%of (b))
438 325.44 503 213.22 109 581.36 125 803.31
fixed costs (FCI)
547 906.80 629016.53
Production Costs UF membrane replacement 3 345.38 electricity 20000.00 cleaning, sanitizing 3 914.00 cooling 1500.00 steam costs 11 2 561.90 wages (30%FCI) 164372.04 demineralization costs 360000.00 maintenance 15783.50 depreciation, taxes etc. 54790.68 (10% FCI) whey drying costs electrodialysis membrane 3 914.10 replacement 740181.60
3345.38 20000.00 3914.00 1500.00 150 377.68 188 704.96 360000.00 12722.97 62 901.65 32000.00 3914.10 839380.74
Annual Sales Costs for Breakeven alcohol 203 373.46 U.S. gal 264 385.49 264 385.49 (at 1.30 $/gal) retentate (25%protein 202.98 245.30 DWB) or conc. (2344.04 tons) if retentate selling price is 300 $/ton, return on investment
42%
20%
a Processing steps. Plant A: whey -, concentration to 36%T.S. -, ultrafiltration + permeate electrodialysis -+ fermentations -+ distillation; Plant B: whey + concentration to 45%T.S. + dried whey + reconstitution to 36% T.S. -+ ultrafiltration permeate electrodialysis fermentation + distillation --f
--f
-+
-+
processed to recover a high protein concentrate and a permeate suitable for alcohol production. Three major parameters play important roles in the conversion of high lactose whey permeates into alcohol. They are ash, lactose, and initial yeast levels. With partially demineralized whey permeates, rapid conversion of whey lactose to ethanol was possible. Specific lactose fermenting alcohol tolerant strains of Kluyveromyces fragilis were used for this purpose. The major rate-limiting step is probably galactose utilization. Potentially, fermentation rates could be increased further by developing mutants containing a constitutive enzyme system for galactose pathway enzymes. Conversely, by developing strains of K . fragilis capable of tolerating high ash levels, the demineralization step might be eliminated.
Ind. Eng. Chem. hod. Res. Dev. 1982, 21, 87-93
Literature Cited Amerlne, M. A.; Ough, C. S. “Wine and Must Analysis”; Wlley: New York, 1974; p 33. A.O.A.C. "Official Methods of Analysis”, 13th ed.; Assoclatlon of Offlclal Analytkal Chemists: Washlngton, D.C., 1980;p 15. A.P.H.A. “Standard Methods for the Examlnatlon of Dairy Products”; Marth, E. H., Ed.; 14th ed.; Washlngton, D.C., 1978 p 159. Burgess, K. J.; Kelly, J. Ir. J. Food Sei. T & d . 1979, 3 , 1. Davls, J. C. Chem. Eng. 1972, 79, 114. De Boer, R.; De Wlt, J. N.; Hlddink, J. J. Soc. De@ Technd. 1977, 30, 112. Delaney, R. A. M. Fm Food Res. 1972, 3 , 112. Demott, B. J. FoodRod. Dev. 1972, 24, 86. Douglas, H. C.; Pelroy, 0. Blochem. Blophys. Acfa 1965, 68, 155. Engel, E. R. Brltlsh Patent 669894,1952. EPA. “Analysis of Operations and Maintenance Costs for Munlclpal Waste Water Treatment Systems”; US. Environmental Protectlon Agency: Washlngton, D.C., 1978 No. 430/9-77-105,34. Forsum, E.; Hambraeus, L. J. D ab Sei. 1977, 60, 370. Gaden, E. L., Jr. Chem. Ind. 1955, 154. Gawel, J.; Koslkowskl, F. V. J. FoodSci. 1978, 43, 1417. Glllles, M. T. “Whey Processing and Utlllzatlonfconomic and Technical Aspects”; Noyce Data Corpn.: 1974; 42. Goudabanche. H.; Maubols, J. L.; Van Opstal, C.; Plot, M. Rev. Lek. Fr. 1076, M.345, 521. HkMhk, J.; DeBoer, R.; Nooy, P. F. C. Zulvdzichf. 1976, 68, 1126. Humphreys, M. Roc. 50th Jubilee Conference, N.Z. SOC. Dalry Scl. and Technol., Palmerston North, New Zealand,1977. Koslkowskl, F. V.; Wzorek, W. J. Dab Sei. 1077, 60, l9S2. Mahmoud, M. M. Ph.D Thesis, Cormell Universtly, Ithaca, NY, 1980. MaHette, M. F. “Methods In Mlcroblology”; Nonls, J. R., Ribbons, D. W., Ed.; Academic Press: London and New York. 1969 Vol. 1, p 521.
87
Mann, F. M. Proc. 50th Jubilee Conference, N.Z. SOC.Dairy Scl. Technol.. Palmerston North, New Zealand, 1977. Morr, C. V. Food Technd. 1976, 30, 18. Moulin, 0.;GuHlaume, M.; Galzy, P. Bktech. Bloeng. 1980, 22, 1277. Muller, L. L. N.Z. J . Daky Scl. Techno/.1979, 7 4 , 121. Peters, M. S.;Tlmmehaus, K. D. “Plant Deslgn and Economics for Chemical Englneers”; Mc(3rawSIIII: New York, I968 pp 109,572. Stanler, R.: Adelberg, E. A.; Ingraham, J. “The Microbial World”. 4th ed.; PrentlceHall, Inc.: Englewood Cllffs. N.J., 1976; p 256. Swhenbaum, M. S. Clarkson College of Technology, Potsdam, NY, 1981, private communication. Vllhndt. F. C.; Dryden, C. E. “Chemical Engineering Plant Design”; McGrawHIII: New York. 1959;pp 194-248. Walker, Y. Procsedings,, 18th Internatlonal Dalry Congress, 1970, lE, 327. Wlngerd, W. H. J . DakySd. 1971, 52, 1234. Wlngerd, W. H.; Saperstein, S.; Lutwak, L. Food Technol. 1972, 24, 758. Yang, H. Y.; Bodyfen, F. W.; Berggren, K. E.; Larson. P. K. Proceedings, 6th Natlonal Symposkrm on Food Process Wastes, US. EnvironmentalProtection Agency: Washlngton, D.C., 1975;p 180. Yoo, 8. W.; Mattlck, J. F. J. Daky Sei. 1969, 52, 900.
Received for review May 22, 1981 Accepted November 3, 1981
This paper was presented at the 181st National Meeting of the American Chemical Society, Atlanta, Ga., April 1981, Division of Agricultural and Food Chemistry. This research was supported in part by a grant from Dairy Research Inc., Fbsemont, Ill. 60018.
Kinetic Equation for the Chloromethylation of Benzene with Trioxane and Hydrogen Chloride Using Zinc Chloride as a Catalyst L. Gutlirrez Jodra, A. Romero Salvador, and V. Muiioz Andr6s’ Dpfo. de Fiilcc-Qdmlca de los PIOcesos Industrkles, Facultad de Ciencias Odmicas, UniversMad Complutense de Madrkj, Madrkl-3, Spain
A reaction mechanism is proposed for the chloromethyiatkmreaction of benzene with trioxane and hydrogen chloride using ZnCi, as a catalyst. The experimental data fit the following kinetic equation based on the proposed mechanism: dCp/dt = kpCc[l - (CA/CW)], where Cp is the concentration of benzyl chloride at time t , k p is the specific rate constant for formation of benzyl chloride, Cc is the concentration of catalyst, zinc chloride, CA is the concentration of water, and Cw is the maximum concentration of water permitting the catalytic formatiin of benzyl chloride.
Chloromethylation reactions can be carried out by use of formaldehyde (formalin) and its polymers (trioxane, paraformaldehyde) or chloromethylated compounds (mono- and dichloromethyl ethers). In most cases, it is assumed that molecules of two or more carbon atoms split to give a fragment containing a single carbon atom which reacts with the aromatic nucleus, introducing a chloromethyl group. Formalin in an acid medium (Tepnetsina et al., 1967) and paraformaldehyde in an aqueous medium (Budniv et al., 1971; Shein et al., 1967; Farverov, 1968) have been used with a protonated acid as catalyst. In these conditions, the disappearance of formaldehyde is proportional to the reagent concentration (Llushim et at., 1971) and to the proton concentration (Mironov et al., 1970, 1971). The proposed reaction mechanism (Brown and Kelson, 1953; Mironov et al., 1966; Ogata and Okano,1956) is based on the attack of the aromatic nucleus by the hydroxymethyl cation. The compound formed is the corresponding al-
cohol, which reacts in hydrochloric acid to give the chloromethyl derivative. Studies carried out with metal halides as catalysts (Llushim et al., 1970) were based on results obtained with protonating acids. The hydroxymethyl cation or a protonated chloromethyl alcohol (Olah and Yu, 1975) have been proposed as intermediates. On the other hand, formaldehyde derivatives may be also converted into dichloromethyl ethers. Thus, dichloromethyl ether has been obtained from paraformaldehyde, trioxane, or formalin using an acid catalyst (Buc, 1956, Matejiceek and Furacka, 1966; Kaska and Matejiceek, 1965; Frantisech et al., 1969; Alvarez and Rosen, 1976),dichloromethoxymethane from formaldehyde also using an acid catalyst (Head, 1963),and a mixture of both products on treating paraformaldehyde with hydrogen chloride (Stapp, 1969, 1970). These reactions have not been studied sufficiently and the intermediate compounds formed are unknown.
01964321/82/1221-0087$01.25/0 0 1982 American Chemical Society
