INDUSTRIAL AND ENGINEERING CHEMISTRY
June 1951
time. Of these compounds, the most effective were the alkyl amines of molecular weight in the neighborhood of 200 t o 250. The effect Of compounds is to be due to their adsorption by the asphaltenes t o have the nonpolar portions of the molecules act as stabilizing agents and decrease the rate of aggregation of the particles. ACKNOWLEDGMENT
Appreciation is expressed t o the members of the laboratory staff for carrying out the tests and t o the management of the Lion Oil Go. for permission t o publish results of this study. LITERATURE CITED (1) Am. Soc. Testing Materials, Method D 88-44. (2) Ibid., D 130-50T. (3) Ibid., D 217-48. (4) Bradley, T. F., U.5, Patent 2,347,626 (April 25, 1944).
( 5 ) Eckert, G.
1423
w.,
and Weetman, Bruce, IND. ENQ.CHEM.,39, 1512 (1947)., (6) Fisher, H. C., Ibid., 16,509 (1924). (7) Knowles, E. C., and McCoy, F. C . , U. S. Patent 2,415,697 (Feb. 11, 1947). (8) Marc, Henri, and Greider, H. W., I b d . , 2,188204 (Jan. 23, 1940). (9)Marissens. E., ING. CXIM..29. No. 167. 1-4 (1947). (10) Oliensis, G . L., Proc. An. SOC.Testing MatekaZs, 4 1 , 1108 (1941). (11) Swanson, J. M., J. Phys. Chem., 46, 141 (1942). ENQ. (12) Traxler, R. N., Schweyer, H. E., and Romberg, J. W., IND. CHEM., 36,823 (1944). (13) Uranov, S. A., Orlova, E. N., and Pneva, L. A., BmZZ. O h e m Opyt. Lakokrasoch. Prom., 1939, No. 8 , 22-3. (14) Winterhrn, H. F., and Eckert, G. W., Im. ENG.CHEM., 33, 1286 (1941). RECEIVED October 9, 1950. Presented before the Divisions of Colloid, Gas apd Fuel and Petroleum Chemistry Symposium on the Nature of Bituminous CEEMICAL QocImY, Materida, at the 118th Meeting of the AMERICAN Chicago, Ill.
Kinetics of the Uncatalyzed Reactions between Resorcinol and Formaldehvde J
R. A. V. RAFF AND B. H. SILVERMAN' Mellon I n s t i t u t e , Pittsburgh, Pa.
e
.
Because resorcinol and particularly its condensation products with formaldehyde have found ever-increasing application in the past few years, a sounder and more scientific basis for these reactions is warranted, and a systematic study of the kinetics of the resorcinol-formaldehyde condensation was undertaken. Experiments are described in which this reaction is studied in dioxane, without a catalyst, at various temperatures, and for different mole ratios of resorcinol to formaldehyde. The apparent first order of the reaction, the energy of activation (around 19 kg.-cal.), and the temperature coefficient (around 2.3/10° C.) were found to remain
constant as the uncatalyzed resorcinol-formaldehydecondensation progresses, and practically independent of the resorcinol-formaldehyderatio. Resorcinol has considerably higher reactivity compared with phenol and alkylated monophenols. As no kinetic data for the very slow, uncatalyzed phenol-formaldehyde reaction are available, and the present study deals with the uncatalyzed resorcinol-formaldehyde reaction only, a comparison between resorcinol and phenol in their kinetica was possible in only a few instances. The data presented should lead to a better understanding of the reaction between phenols, as well as resorcinol and formaldehyde.
THEpr
and again pointed out in 1924 by Zamparo (2%). The formation of colloidal resin suspensions from formaldehyde and resorcinol and their flocculation by ions were described by Engeldinger (10)in 1936. However, apparently the only real kinetic study of the resorcinol-formaldehyde reaction, carried out on a rather limited scale, was reported by Dubrisay and Papault ( 9 ) in 1942 and 1945. These authors condensed resorcinol with formaldehyde in the presence of sodium hydroxide a t 18"and a t 40" C., and determined the viscosity and the amount of free resorcinol in the solution. The results were considered to be in agreement with a reaction mechanism involving the formation of 0- and p-phenol alcohols, their combination to substituted dihydroxydiphenylmethanes, and the condensation of these compounds to networks. No further kinetic study of the reaction of resorcinol with formaldehyde was published until 1949, when Sprung and Gladstone (86) reported that the reaction of 0-methyl01 phenol (saligenin) with resorcinol to trihydroxydiphenylmethane is of second order, regardless of the presence of catalyst (triethanolamine) or diluent (pinacol). The curing reaction of resorcinol-formaldehyde condensation products was the subject of several investigations. Boutaric and Engeldinger (3)in 1938,carried out dilatometric measurements on curing resorcinol-formaldehyde resins, without relating them t o the kinetics of the cross-linking reaction. A most important discovery was made in 1946 when Aero Research, Ltd., in Duxford, England (1) reported that the gelation time on heating a fusible resorcinol-formaldehyde resin with additional formaldehyde is dependent on the p H of the curing mixture
o ~ e 8 8 ewhich ~ take place when phenol reacts with formaldehyde have been thoroughly investigated, and it is now commonly accepted that this reaction takes place in three steps {isogel theory of Houwink (14)J which have been studied and explained qualitatively and structurally (6,16, 33). Kinetic investigations of the phenol-formaldehyde reaction are scarce, although some significant research was reported in recent years, particularly by Nordlander (19), Megson (18),Jones ( l a ) , and Sprung (86,86). In several instances, investigators (7, 11, 26) considered the condensation reaction of phenol itself with formaldehyde as too complex to be understood without preliminary studies on phenols in which some of the three reactive positions (ortho, meta, para) were blocked by substituents, and which would not be capable of such diversified reactions. On the other hand, it is known that the entry of a substituent in meta position to the phenol group, enhances still further the reactivity of the phenol. This is particularly true in the case of resorcinol, where two hydroxyl groups are in meta position to one another, thus possessing three doubly wtivated ring positions as against three singly activated positions in phenol. The complexity of the phenomena involved in the condensation of resorcinol with formaldehyde, where even intermediate phenol-alcohols and resols are, if a t all (8, do), stable only a t temperatures of 5' C. or lower, obviously did not encourage studies of a kinetic nature. The eaae with which resorcinol and formaldehyde react to form condensation products, was described f i s t in 1892 by Caro (4) 1
Present address, Heyden Chemical Corp., Garfield, N. J.
Vol. 43, No. 6
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
1424
products with formaldehyde have found ever-increasing applications in the last few years, a sounder and more scientific basis for these reactions is warranted, and a systematic study of the kinetics of the resorcinol-formaldehyde condensation was undertaken. Because this work is still in progress, the paper presented here deals only 15 ith thr kinetics of the uncatalyzed condensation reaction. ONE-STEP EXPERIMENT§
P/A = 1 'I I
-
€00
1200
i0L
I800
,
2400
P / P . I 1;
300
600
900
I
1200
The condensations reported in the following section were carried out on solutions of resorcinol (Koppers U.S.P. 99.81% pure) in dioxane (Eastman, uninhibited, redistilled) and water, to which the calculated amounts of aqueous formaldehyde solutions, prepared by distilling of Fisher's C.P. 37% formaldehyde over calcium carbonate under nitrogen (8), were added. The charges were prepared uniformly in such a way that, despite variations in t,he chosen mole ratio of resorcinol t,o formaldehyde the conibined weights of resorcinol plus formaldehyde (as C&O) represent 40% of the total weight of the solutions. The mixtures further contain 26.7% dioxane, chosen as the solvent for the forming condensates, and 33.3% water, mostly introduced as part of the aqueous formaldehyde solution. These solutions reacted in a resin flask kept in a constant temperat'ure bath. The four openings of the lid of the reaclion vessel v-ere equipped with stirrer, reflux condenser, thermometer, and sampling device. For the experiments carried out a t 90" C. a glass cooling coil was inserted to aid in dispersing the heat of the exothermic reaction. Samples were removed a t proper intervals by suction, and analyzed (6) for free formaldehyde, density, refractive index, pR, viscosity, and water precipi t a bi1it)y. The pl1 values did not indicate any trend over lhe reaction period, nor were they observed to depend on the reaction temperature, They did, however, depend on the resorcinol-formaldehyde ratio ( P / A )as follows: for 1 to 0.5, the p H average was 3.87; for 1to 1: 3.93; arid for 1 to 1.5,4.09.
TIME, MINUTES
Figure 1.
Log of t h e Unreacted Formaldehjde Concentration us. T i m e
in a way quite different from phenol-formaldehyde resins. Geliition was found to be slowest a t a pII of 3 to 4; a t p H values of less than 3 there is a reaction catalyzed by hydrogen ions; a t pH values greater than 3, hydroxyl ions. It is this latter reaction which enables neutral cold-setting resins to be formed from resorcinol, but not from phenol, and Rhodes ( $ 2 ) connects the technical development of the resorcinol adhesives to the increasing knowledge of the effect of the p H on their reactivity. The dependence of the gelation time of a resorcinol-formaldehyde resin on temperature is discussed by Shipley ($4) and by Olson and coworkers ( 2 1 ) with particular reference to their practical application. From a more theoretical viewpoint, Fineman and Puddington (12) studied the cure of resorcinol-fornialdehyde rcsins by measuring electrical resistance and density. The observed increase in electrical resistance during curing was explained by the assumpt,ion that increasing cross bonding trnds to restrict the mobility of the ions within the resin. Likewise, it !vas assumed that cross bonding caused t,he resin molecules to be more closely oriented, occupying an increasingly smaller volume until the cross linkage was complete. However, as far as the interpretation of the eleetrical resist,ance measurements is concerned, Vim-eg and W. Knappe ( 2 7 ) only recently concluded from similar measurement,s that a cross-linking resin behaves in its electrical properties differently from its mechanical and optical properties. After the mechanical and optical skeleton of t,he resin is establishetl, many carriers for the electrical current are left,, Tvhich arc only s l o ~ l y built into the macromolecules of the cured resin. I n view of this status of the present knowledge of t,he kinetics of the resorcinol-formaldehyde reaction, it is felt that the available kinetic data are neither sufficient nor so linked t,ogether as to allow a proper understanding of this reaction. However, since resorcinol and particularly it,s condcnsation
> 40
20 I
I
0 25 0 50 0 75 Mol Forrnoldehyde Reacted per Mol Resorcinol
c
IO0
Figure 2. Yiscosity and Water Precipitability vs. Reacted Mole of Formaldehyde per Mole of Resorcinol
The logarithms of the concentrations of unreacted formaldehyde in moles per liter are plotted against times in minutes and presented in Figure 1for the various series carried out a t different resorcinol-formaldehyde ratios and temperatures. Straight lines obtained in all experiments suggest that first order reactions are involved. From the data for unreacted moles of formaldehyde versus time, first order reaction-velocity constants were calculated, with the results shown in Table I. DISCUSSION OF RSSVLTS. It is not easy t,o compare the data obtained on the uncatalyzed resorcinol-formaldehyde reaction with the known kinetics of the phenol-formaldehyde condensation, because pract,ically all of the latt,er work was carried out under the influence of catalysts. However, the catalyzed condensation of phenol and formaldehyde is generally assumed to be of first order, approaching, according to Kordlander (19), second order only a t very low catalyst concentrat,ions. Cont'rary to the results shown
INDUSTRIAL AND ENGINEERING CHEMISTRY
June 1951
TABLE I. REACTION-VELOCITY CONSTANTS P/A" 1:0.5
Temp., C. 60 90 40 1: 1 60 90 60 1: 1 . 5 90 ,?/A, resoroinol-formaldehyde mole ratio.
4
KI 19.2 X 20.6 X 15.1 X 10.5 x 9.44 x 5.32 x 6.84 x
10-4 10-8 10-6 10-4 10-a
10-4 10-3
in Table I, Jones ( 1 6 )reported the order of the catalyzed phenolformaldehyde reaction t o decrease from the second, and to approach first order, if the reaction temperature decreases. Jones explains this by assuming that the initially formed monophenol alcohols react a t lower temperatures with formaldehyde, rather than with phenol, to form dialcohols. Yanagita (28) who found the ammonia-catalyzed condensation of phenol and formaldehyde, at 80" and 90" C., to be of first order, explained this by the fact that the hydroxybenzyl alcohol produced in the early stages behaved toward formaldehyde like phenol itself, so that the effective concentration of phenol did not change, As far ~8 a comparison of the velocity constants themselves is concerned, Sprung ( 2 5 )has reported data for phenol and substituted monophenols, when reacting 1 mole of the phenol with 0.87 mole of paraformaldehyde a t 98 O C. in the presence of 0.0241 mole of triethanolamine per mole of phenol, but in the absence of any solvent. These constants are shown in Table 11, where they are compared with the value obtained on the uncatalyzed reaction of resorcinol with formaldehyde a t 90 C., for a resorcinol-formaldehyde ratio of 1 to 0.5 and in the presence of water and dioxane, as taken from Table I.
1425
Based upon the reaction-velocity constants given in Table I, the temperature coefficients for the resorcinol-formaldehyde condensation, for an assumed increase by lo", were calculated and are given in Table IV. They are independent of the mole ratio of the reactants.
TABLE Iv. TEMPERATURE COEFFICIENTS INCREASE OF 10" PIA 1:0.5 1: 1 1:1.5
Reaction Temp., " C . 60' ua. 90' 40° u6. 6O0 40' us. 90' 60' us. 90' 60° us. 90"
FOR A TEMPERbTURE
Temperature Coefficients 2.20 2.64 2.50 2.07 2.35
The average temperature coefficient reported by Sprung (26) for the catalyzed reaction of m-cresol with formaldehyde, using 0.0241 mole of triethanolamine per mole of cresol, is somewhat lower-namely 1.71 per 10"C. When plotting the viscosities in centipoises, as obtained under the various reaction conditions, against the moles of formaldehyde reacted per mole of resorcinol, curves as shown in Figure 2 are obtained. For the resorcinol-formaldehyde ratios of I to 0.5 and of 1 to 1.5, the points obtained at different temperatures tend to fall on the same curves. For the resorcinol-formaldehyde ratio of 1 to 1, however, the curve shows three branches a t the later stage of condensation depending on the temperature. In all the cases, a period of only slight increase in viscosity (addition reaction) is followed by an increasingly steep increase (condensation and cross-linking reactions) until gelling takes place. The increase in viscosity starts a t a smaller molecular amount of reacted formaldehyde, the lower the mole ratio of formaldehyde present in the unreacted mixture Obviously, the viscosity in the case of a resorcinol-formaldehyde ratio of 1 to 0.5 cannot rise above a TABLE11. COMPARISON OF REACTION-VELOCITY CONSTANTS certain point, owing to the limited amount of formaldehyde present. However, even then some cross linking appears to have Comparative Rate Phenol taken place. Further, although no actual gelling takes place in Reaction Taken as Phenol Conditions K1 Unity the reaction mixture, its miscibility with water becomes limited. 6 30 X 10-9 7.75 3,5-xylenol Water precipitability for the mixtures with a resorcinol-form2 33 x 10-2 2 88 m-Cresol .33 X .88 aldehyde ratio of 1 t o 1 and of 1 to 1.5 sets in a t higher viscosi1 . 21 2 1 x 10-2 1 . 49 49 2,3,5-trimethylphenoI I, 2.3.5-trimethvl~henol 8 11 x 10-8 Phenol -a 1 . 00 00 ties and after more formaldehyde has reacted, than in the case of a 3,4-xylenoi \11 Catalyzed, 6 . 7733 X 10-8 0.83 2,5-xylenol no solvent 5 . 7 0 X 10-3 0.71 ratio of 1 to 0.5. 2 87 x 10-3 0.35 Table V compares the viscosities corresponding to an arbitrarI 2 . 7 2 X 101; 0.34 10-s 2.11 x 10-2 o-Cresol 0.26 ily chosen water precipitability of 2.5. If the water precipitabil-1 0.16 J 1 . 3 0 X 10-8 2,d-xyIenol ity is taken as a measure for the degree of cross linking, the results Uncatalyzed, 2 . 0 6 X 10 - 2 2.54 Resorcinol shown in Table V indicate that a change of the resorcinol-formalIn solution dehyde ratio from 1 to 1.5 to 1 to 0.5, as well as lower temperatures, cause larger but less cross-linked, initial condensation prodApparently the velocity constant for the uncatalyzed resorcinolucts to be formed up to the point where cross linking becomes formaldehyde reaction in solution at 90 " C. is still larger than the more predominant one for phenol at 98" C., the latter obtained in the absence of solvents and under the influence of a fairly large amount of an alT A B L E V. ~ I S C O S l T I E SCORRESPONDING TO A WATER PRECIPITAkaline catalyst. The reaction-velocity constant for the uncataBILITY OF 2.5 Viscosity lyzed resorcinol-formaldehyde condensation may be several orders P/A Temp., C . Cp. a t 25O 'C. of magnitude greater than that of the uncatalyzed phenol-formal1:0.5 60 Above 15 0 dehyde condensation. 90 15.9 1: 1 40 24.1 Using the Arrhenius equation, energies of activation were cal60 17.8 90 14 7 culated from the reaction-velocity constants as shown in Table 1:1.5 60 15.0 111. These values are in good agreement with some reported on 90 13.9 phenol ( 17, 26) and on p-cresol ( 8 ) ,wherever there is any possibility of comparison. Similar observations regarding the relation between reaction temperature and water precipitability are reported on phenolformaldehyde condensates. Finn and Rogers ( I S ) used the TABLE 111. ENERGIES OF ACTIVATION cloud point-i.e., the temperature at which turbidity occurs on Energies of cooling in a reaction mixture of phenol and aqueous formaldeReaction Activation, Kg.-Cal. Temp., C . P/A hyde-as a measure for the extent to which the reaction has pro1:0.5 60° va. 90" 18.8 ceeded. They found that the initial cloud point is higher when 20.3 40' va. 60' 1: 1 40° ~8.90" 18.9 the initial condensation has taken place a t a lower temperature 17.7 60' v6. 90" than when the condensation is kept at a higher temperature 1:1.5 60° 8 8 . BOa 20.6 throughout. O
GziL
-*
A
O
~~
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
1426
TWO-STEP EXPERIMENTS
As it seemed important to investigate how variations in the reaction conditions in the earlier stages of the resorcinol-formaldehyde reaction reflect upon the behavior in later stages, the following experiments were carried out. Resorcinol-formaldehyde mixtures with a resorcinol-formaldehyde ratio of 1 to 0.5 were reacted to practical completion at 60" and 90" C., respective1 and then dehydrated under water ump vacuum a t about 60" The resins obtained through confensation at 60" C. were harder and more brittle than those prepared at 90" C., as would be expected from the data in Table V. These resins were redissolved in dioxane, and for each niole of the resin an additional mole of formaldehyde was added in aqueous solution. The composition of the reaction mixture was finally the same as that for the resorcinol-formaldehyde ratio of 1 to 1.5. These mixtures were reacted a t 60" and 90" C. Samples were taken during the runs and analyzed as previously described,
8
The logarithms of the concentrations of the unreacted formaldehyde in mole per liter are plotted against times in minutes in Figure 3. As before, the reaction is most probably of first order.
Vol. 43, No. 6
Lomakin and Guseva (17') claim a decrease of the activation energy for the catalyzed phenol-formaldehyde reaction from 20 0 kg.-cal. before layering, to 15.0 or 16.0 kg.-cal. after layering. The temperature coefficients for a temperature increase of 10O, for the second-step experirncnts, as given in Table VIII, are also quite similar to the ones previously reported in Table IV for the various resorcinol-formaldehyde ratios. Therefore, it may be assumed that the temperature coefficient for the uncatalyzed resorcinol-formaldehyde reaction neither depends on the mole ratio of the reactants, nor changes as the reaction progresses.
TABLEVII.
ENERGIES O F a C T I V A T I O N FOR
EXPERIMENTS
SECOND-fhIP
Reaction temp. in Firstandsecondstepsus. 60",f)0', u s , 60°, 60°, u s . 90°, 6 O o , u a . go", 60", 1's. first and second steps 60'. 90' 90°, 90' 60°, SOo 90°, 90' First order, energies of activation, kg.-cal. 19.1 19.4 19.3 19.6
TABLE VIII.
TEMPERATURE COEFFICIENTS FOR A TEMPERATURE 10" FOR SEC0NI)'STEP EXPERIMENT5
INCREASE O F
- Step
o-First
Reaction temp. in First and second steps us. first and second steps
60: Second - S t e p 60'
60c,CIO*, 60°, 90'
a
K1
20
c8.
GO", 60'. us. 90°, 6 0 ° . OS. 90°, 6 0 * , P.S. HOo, 90' 60'. SOo goo, 90' 2.23 2.24 2.27
*-First. Step 60: Second -Step 90.
-
300
900
600
,
10
1200
I
i 8
-
5 ,I
-
Step go', Second -Step 60" First Step 90: Second Step 90.
o First
-
~
I
I
300
Figure 3.
900
600 TIME, MINUTES
1200
It has already been shown that the relationship between viscosity and water precipitability indicates that larger, but less cross-linked condensation products are formed, if the condensation temperature is decreased. This, however, holds true only for &e initial stages of the reaction, as the two-step experiments have indicated, where the temperature in the first step is of deciding influence. Figure 4 shows this slight dependency of the water prccipitability-viscosity relationship on tho reaction temperature to diminish and soon to disappear completely as the reaction progresses beyond the initial stages. The increase in the rate of cross linking ie bound to render any initially existing differences in particle size more and more indistinguishable.
Log of the Unreacted Formaldehyde Concentration vs. Time Second-step reactions
-1st step 60' - 2nd - p s1 step 90" - 2nd 0 1st step 60" - 2nd A -Ist sleD 90'- 2nd
F 0
DISCUSSION OF RESULTS.The calculated first order reactionvelocity constants for these second-step experiments are given in Table VI. They increase with increasing temperature in tshe first stage, if the second step is carried out at 90" C., but decrease with increasing temperature in the first stage, if the second step is carried out at 60 O C.
TABLE VI.
n 2 p - 4
REACTION-VELOCITY CONSTANTS FOR SECOSD-~TEP
Reaction temp. in First step, O C. Second step, C .
Kl
n
.-.-a
$rep 60' step 60' step 90' step 90"
EXPERIMENTS 6.99
60 60
x
90 10-4 6.58
60
x io--'
7.45
Figure 4. 60 90
x
Water Precipitability z's. Viscosity
HQ
10-3 7 . 7 3
90
x
10-3
When pairing these constants, energies of activation may be calculated as shown in Table VII. Since these values are about the same as the ones reported previously in Table I11 for the various resorcinol-formaldehyde ratios, it may be assumed that the energy of activation neither depends on the mole ratio of the reactants nor changes as the reaction proceeds. Such results are in accordance with the findings of Sprung (255) who reports the somewhat lower activation energy of 15.8 kg.-cal. for the catalyzed phenol-formaldehyde reaction to remain the same from addition to condensation step. On the other hand,
GENERAL CONCLUSIONS
The reported uncatalyxed resorcinol-formaldehyde experiments have shown the considerably higher reactivity of resorcinol as compared to phenol and alkylated monophenols. As no kinetic data for the very slow, uncatalyzed, phenol-formaldehyde reaction are available, a comparison between resorcinol and phenol in their kinetics was possible only in a few isolated instances. The uncatalyzed resorcinol-formaldehyde reaction was found to be of first order for different resorcinol-formaldehyde ratios and under changing temperature conditions. Both energy of activation and temperature coefficient were found to remain constant as the reaction progresses, and independent of the resorcinol-formaldehyde ratio.
lune 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
In continuation of these kinetic studies, the influence of catalysts and different pH conditions on the resorcinol-formaldehyde reaction is presently under investigation, and resorcinol may be expected to react basically different from phenol. ACKNOWLEDGMENT
The authors gratefully acknowledge the support of this work by the Koppers Co., Inc., through its multiple fellowship on special resins and its permission t o publish this paper. LITERATURE CITED
1
(1) Aero Research, Ltd., Duxford, England, Sci. and Tech. Memo 1-47 (December 1946). (2) Boehm, T., and Parlasca, N., Arch. Pharm., 270,168 (1932). (3) Boutaric, A., and Engeldinger, M., Compt. rend., 206, 1488 (1938). (4) Caro, N.,Ber., 25,939 (1892). (5) Carswell, T.S.,“Phenoplasts,” New York, Interscience PublishBrs, Inc., 1947. (6) D’Alelio, G. F., “ExperimentaI Plastics and Synthetic Resins,” New York, John Wiley & Sons, 1946. (7) Dostal, H., Marks, H., and Raff,R., IND.ENG.CHEM.,29,595 (1937). {8) Dostal, H., and Raff, R., 2.physik. Chem., 32B,117 (1936). (9) Dubrisay, R., and Papault, R., Compt. rend., 215, 348 (1942); Inds. Plastics, 1, 132 (1945). (10) Engeldinger, M., Compt. rend., 202,842,1854 (1936). (11) Euler, H.V.,et ai., 2.physik. Chem., 189A,109 (1941); 2.ang e m Chem., 54,458(1941).
1427
(12) Fineman, M. N.,and Puddington, I. E., Can. J . Research, 258, 101 (1947);IND. ENQ.CHEM.,39,1288 (1947). (13) Finn, S. R., and Rogers, L. R., J . SOC.Chem. Ind., 67,51 (1948). (14) Houwink, R., Ibid., 55, 247 (1936); Trans. Faraday Soc., 32, 122, 131 (1936). (15) Hultsch, K.,“Chemie der Pheolharse,” Berlin, Springer-Verlag, 1950. (16)Jones, T. T.,J . SOC. Chem. Ind., 65,264 (1946). (17) Lomakin, B. A.,and Guseva, V. I., Plastichestic Massy, Sbornik. 2, 111, 281 (1937). (18) Megson, N. J. L., J . SOC.Chem. Ind., 57, 189 (1938); 58, 131 (1939). (19) Nordlander, B. W., Oil, Paint Drug Reptr., 130,I, No. 11, 3,27 (1936). (20) Novotny, E.E., and Stokes, J. S., U. S.Patent 1,776,366(Sept. 23,1930). (21) Olson, W. C.,et al., U.S. Dept. Agr. Forest Service, Forest Products Lab. Rept., 1531,1532,1537, 1565,1568 (1946-1948). (22) Rhodes, P. H., Modern Plastics, 24,145,238 (1947). (23)Robitschek, P., “Phenolic Resins,” London, Iliffe and Sons, Ltd., 1950. (24) Shipley, R. L.,Plastics (Chicago),4,No. 1, 58,60,62 (1946). (25) Sprung, M. M., J . Am. Chem. SOC.,63,334(1941). (26) Sprung, M. M., and Gladstone, M. T., J. Am. Chem. SOC.,71, 2907 (1949). (27)Vieweg, R., and Knappe, W., Kunststoffe, 39,279 (1949). (28) Yanagita, M., J . SOC.Chem. I n d . Japan, 45,1297 (1942). (29) Zamparo, A.,Boll. chim. farm., 63,161 (1924). RECEIVED September 9, 1950. Presented before the Division of Paint, VarCHIOMnish, and Plastics Chemistry at the 118th Meeting of the AMERICAN ICAL SOCIETY, Chicago, Ill.
Catalytic Hydrogenolvsis of Wood U
EARL G. HALLONQUIST Plywood Research Foundation, Tacoma, Wash.
*
-
Hydrogenation has shown considerable promise as a means of obtaining useful chemical products by the controlled decomposition of wood. The present investigation was carried out to explore the possibilities of hydrogenolysis (concomitant hydrogenation and hydrolysis) in converting wood to distillable liquids. Optimum yields of slightly more than 50% of the weight of the wood were obtained as nonaqueous distillable liquids by this method. Nickel catalysts were the most effective, and yields varied considerably, depending on the amount of catalyst used and the time and temperature of reaction. The quantities of gas and water formed, and the amount of unreacted material remaining, were determined for various conditions. The ultimate feasibility of the conversion of lignocellulose to chemicals and oils is of continuing scientific and industrial interest, and the information contained in this report should indicate the possibilities for wood liquefaction by methods involving hydrogenolysis.
V
ARIOUS investigations into the catalytic hydrogenation of
wood have been carried out in recent years. Some of these have had as their object the production of hydrocarbons and liquid fuels from wood by methods similar t o those employed for coal (10-12, 16). I n other cases hydrogenation was effected using a suitable catalyst and a solvent or carrier such as alcohol (S), dioxane ( 1 , 9,IS), or dilute aqueous alkali (7,8, 14). Hydroxyl compounds such as ethylene glycol, glycerol (6),and various cyclohexanols ( 4 , 5 , 9 )have been identified in the reaction products of these hydrogenations of wood. This report gives the results of a study of the hydrogenation of wood in water (here referred t o as the hydrogenolysis of wood). The work described was carried on primarily t o determine the
effect of type and amount of catalyst on the quantity of distillable products obtained from this reaction. No attempt was made t o identify these distillables except by classification into rough boiling point ranges. Water was used as the diluent and carrier in order t o avoid any suspicion of products‘being obtained from sources other than the wood. An effort was made t o determine also the amounts of gas and water formed during the hydrogenolysis, the unreacted material remaining, and the hydrogen absorbed. APPARATUS AND PROCEDURE
A n American Instrument Co. shaker-type reaction bomb having a capacity of 2500 ml. was used for this work. The quantities of wood or other material was varied from 35 to 150 grams, with the catalyst ranging from 0 to 50 grams. The liquid carrier (water) was maintained generally a t 1200 ml. The maximum temperature range was 250” to 290” C. and the initial hydrogen pressure 1800 pounds per square inch. The time of reaction a t the maximum temperature varied from 0 to 8 hours. After completion of the hydrogenolysis and cooling of the bomb, the contents were removed and filtered to separate the catalyst and unreacted material from the liquids. The catalyst and unreacted material were washed with 100 grams of water. I n some preliminary runs the combined aqueous solutions were subjected to fractional distillation a t atmospheric pressure. Considerable darkening of the solution occurred, and the amount of material boiling lower than water which was recovered was only 1or 2yo of the weight of the original raw material. I n order to expedite the results, and to avoid decomposition, the atmospheric fractionation for low boiling material was eliminated. The water was removed under reduced pressure a t 25” to 28” C., using a nitrogen source for the boiling capillary, and a short packed column. A sharp break always occurred between the last of the water fraction and the next highest boiling material, no distillate being obtained up to about 50” C. a t 17 to 23 mm. The liquid remaining after removal of the water was transferred to a flask of suitable size, and the distillation was continued a t 17 to 23 mm. for material boiling up to 150” C., and a t 2 to 5 mm. for higher
