Behavior of Liquid Hydrocarbons with White Fuming Nitric Acid C. H. TRENTi
&I. J. ZUCROW
Yurdue University Rocket Laboratory and Engineering Experiment Station, Lafuyette, Ind.
PROBLEAI encountered in the development of liquid propellant rocket engines is that of obtaining a basic understanding of the ignition processes for the various bipropellant combinations. Liquid bipropellant systems fall into two (:lasses: those which ignite spontaneously upon mutual contact, a t ambient temperature and pressure, termed hypergolic systems; and those which do not ignite upon cont,act, a t iLmbient temperature and pressure, called nonhypergolic systems. The latt,er must be provided with an ignition system to initiate conibust,ion. From the standpoint, of aviilability, cost, and general logistics, hydrocarbon fuels derived from petroleum possess many advantages as the fuel component. in a bipropellant system. For cxample, in the assisted take-off (-4TO) of jet-propelled aircraft it is highly desirable t o use the same fuel for the rocket AT0 unit and the turbojet engine for propelling the aircraft. One of the fuels currently specified for jet-propelled aircraft' is JP-3 which iF a hydrocarbon fuel endowed with physical properties common to both gasoline and kerosene. JP-3 is not hypergolic n-ith either of the common oxidizing agents, liquid oxygen or white fuming nitric acid ( S V F S S ) , and present to the rocket engineer the problem of reliably igniting these propellant combinations. TO ICE EATH AND A survey of the literature OSCILLOGRAPH disclosed that the combustion of hydrocarbons with nitric acid as the oxidizAL I ing agent has not been previously studied. Therefore, it is the purpose of this paper t o present the results of an experimental study of the combustion behavior of a number of p u r e h y d r o c a r b o n compounds with white fuming nitric acid under conditions simulating those found in an actual rocket motor. When nitric acid in concentrations exceeding 90% is added rapidly t o unsaturated hydrocarbons, a vigorous, highly exothermic reaction occurs, the violence reaching almost explosive proportions especially with the polyolefins and acetylenic hydrocarbons. The preliminary inquiry into the reaction of liquid hydrocarbons with nitric acid indicated that T/C 1 Present address. Aerojet Engineering Corp., .42U5a, Calif.
during their reaction the temperature rkes quickly to a maximum .i.aluc. If it is assumed that' the rate of heat evolut.iori is proportional t o the rate of reaction, the time interval, At (seconds), between the initial contact of the two liquids and the inaximuni temperature produced should serve as a useful criterion for comparing the relative rlttes of the liquid phase reaction between difierent hydrocarbons and nitric acid. The value of the maximum temperature attained during the time interval, At, is proportional to the t'hermal energy developed. I t would appear, therefore, that' the magnitudes of the aforementioned quantities might give an indication of the suitability of a hydrocarbon, from a n ease of ignition standpoint, as the fuel component in a hj-drocarbon-x-hite fuming nitric acid rocket propellant. Thc ten-carbon-atom chain \vas selected as representative of turated and unsaturated hydrocarbons present in jet engine fuel. Ellis (2) and Sachanen ( 1 6 )list hydrocarbons which have been isolatcd from various petroleum stocks. From those listings suit'able liquid alicyclic and aromatic hydrocarbons Twre chosen t80 represent t,he naphthenic and aromat,ic conbent of .JP-3. I n all, 20 hydrocarbon compounds were reacted a-ith anhydrous niIS cm H g tric acid. The apparatus N2 PRESS employed for measuring the time required t o attain the maximum reaction temperature is illustrated in Figure 1 and the data obtained are presented in Table I. The molar nitric acid to hydrocarbon ratio was held G-.-WATER LEVEL-. constant a t 3/1 and the total volume of reactants in all cases was 5.39 ml. 0 EXPERIMENTAL WFNA
Figure 1. Apparatus for Measuring Rate of Temperature Rise
2668
DETERTEXPERATURE HISTORY. Because of the vigor of the reaction between olefinic and acetylenic hydrocarbons with anhydrous nitric acid, the stirred flow reactor designed by Rand and Hammett ( I S ) could not be adapted to measuring the temperature rise during such a chemical reaction. Therefore, a special apparatus was designed for thifi purpose. Figure 1 illustrates schematically the apparatw developed. -4PPARATUS FOR
XINING
INDUSTRIAL AND ENGINEERING CHEMISTRY
November 1952
2669
The reactor, C, was constructed from a borosilicate glass 24/40 tapered ground joint. The thermocouple, F , rectangular in shape, was sealed into the wall of the reactor 5 mm. from the bottom and extended 2 mm. into t h e interior. The thermocouple was fabricated from No. 26 platinum and platinum-10% rhodium wire. The rectangular junction, 0.236 inch long, 0.088 inch wide, and 0,0099 inch thick, was located so t h a t the stirred liquid flowed parallel to t h e plane of the thermoelement. The stirring mechanism found to give the most reproducible data consisted of a stainless steel propeller, B , with blades set for downward displacement. The propeller was housed in a stainless steel cylinder, A , and rotated a t more than 6000 r.p.m. The cylinder, A , was held in place by stainless steel springs which pressed against the wall of the reactor and were mounted on t h e I n operation the top of t h e stirrer housin liquid is forced downwar3 through t h e stirrer housing and upward, helically, around t h e thermocouple, F . B y injecting t h e second liquid through t h e delivery tube, E, directed toward the center of the stirrer housing, satisfactory mixing of t h e two liquids is accomplished before t h e mixFigure 2. Time-Temperature Curve for Reaction between 1-Decene and ture reaches t h e thermocouple. 97.68% Nitric Acid The nitric acid was stored in the tank, D. To initiate t h e reaction t h e nitric acid was forced into the reactor through delivery tube E by means of nitrogen pressure applied at the top of tank D. The end of tube Figure 2 presents the type of record obtained with the oscilloE consisted of an orifice 0.157 inch in diameter. By using t h e graph. same orifice diameter and the same nitrogen pressure of 15 em. of The time-temperature measuring apparatus calibrated mercury, a constant average flow rate for the introduction of nitric acid could be maintained. The flow of nitrogen into tank D utilizing the reaction between 1-decene and 93.27% nitric acid, was controlled by a 24-volt solenoid valve. The molar oxidizer-to-fuel ratio of the reactants was 10.7 and The apparatus assembled in Figure 1 was immersed in a thermothe total volume of liquids amounted to 8,2 ml. The time to stat t o the level, G. maximum temperature was measured at 0.77 second with a n THERhrocouPLE A N D INSTRUMENTCALIBRATION. The theraverage deviation of a single measurement from the mean of mocouple for sensing the temperature variations was calibrated 0.86% for six determinations. by standard methods in conjunction with a recording ConsoliTYPICAL DETERMINATION. The operation of the time-temdated oscillograph. The latter is a n instrument which measures perature apparatus can be illustrated by the description of a small changes in electromotive force by means of a sensitive single determination of the temperature history for the reaction D'Arsonval-type galvanometer. An optical system allows the between 1-decene and anhydrous nitric acid. fluctuations of the galvanometer t o be recorded on a moving strip The stirring mechanism, A and B , is inserted into the reactor of photographic paper. A timirig trace, calibrated to read in and the latter filled with 3.2 ml. of freshly distilled 1-decene. The hundredths of a second and synchronized with the paper speed, remainder of the apparatus of Figure 1 is assembled, placed in a is also superimposed on the moving strip of photographic paper. constant temperature bath, and brought to the desired temperature. The anhydrous nitric acid used for these runs was stored in the solid state at -78" C. t o prevent decomposition. During the time the reactor is reaching the desired temperature, the solid TABLE I. SUMMARY OF TIME-TEMPERATURE DATAFOR HYDRO- nitric acid (2.19 ml.) is thawed in the dark and its container is CARBONS REACTED WITH ANHYDROUS NITRIC ACID^ then placed in the thermostat. After the nitric acid is uniMixture Initial Max. Increase Time to Ratio, Temp,, T;mp., in Temp., Max. Temp., formly a t the desired temperature, it is poured into the vessel, Hydrocarbon O/Fb ' C. C. C. At, Sec.cvd D,and the nitrogen pressure line is attached. The stirring motor ALIPHATIC HYDROCARBONS is started and allowed t o reach 7200 r.p.m.; angular velocity 1-Decene 3 25 127.5 102.5 0.16 was measured with a General Radio Strobatac. After reaching 1,3-Decadiene 3 25 170. 145 0.305 3-Methyl-3-nonene 3 25 128.5 103.5 0.32 the proper stirring speed, the oscillograph record is started and 1.9-Decadiene ' 3 25 166 141 0.535 No reaction %-Decane 3 25 the switch controlling the solenoid valve is closed, thus allowing ALICYCLIC HYDROCARBONS the flow of nitrogen t o force the nitric acid from D into the reactor 3 25 Spout. comb. 0.04 Dicyclopentadiene and initiate the reaction. After all noxious fumes have been 3 25 110 85 0.24 Cyclohexene swept from the hood, the stirrer is stopped and the apparatus is 3 25 71 46 2.48 Methylcyclohexane 80 55 2.55 Ethylcyclohexane 3 25 dissembled and cleaned, 53 28 17 Cyclohexane 3 25 The record of t h e temperature changes is obtained by developAROMATIC HYDROCARBONS ment of the exposed oscillograph paper. 25 92.5 67.5 Benzene 3 0.10
.
25 95.5 70.5 Toluene 3 0.12 25 85 0.12 110 a-Methylnaphthalene 3 25 76 +Xylene 3 101 0.133 122 97 25 Mesitylene 3 0.163 25 112 87 p-Cymene 3 0.176 25 3 101 125 Ethylbenzene 0.273 99.5 25 Cumene 3 124.5 0.352 25 396 421 Indene 3 3.17 a Analysis of "0s: 100.24% "Os, 0% N o t , 0 % HaO. b Expressed as ratio of moles of "Os to moles of hydrocarbon. c Time reauired for reaction t o proceed from entry of acid to maximum temperature. d The data for each hydrocarbon is the average of at least three,determinations, where necessary additional determinations were made until the desired precision was obtained.
APPARATUS FOR DETERMINING R/IINIMUM IGNITION TEMPERATURE. The apparatus employed to determine t h e minimum ignition temperature consisted of P block fabricated from a piece of pure aluminum 3 inches in diameter and 8 inches long. il V-shaped groove 2.5 inches wide was milled into the top of the block. The groove had a slant of '/4 inch so t h a t the liquids sprayed onto the block would flow slowly along the axis of the groove. The block was heated by two 110-volt, 500-watt immersion heaters placed in holes drilled into the block l / 4 inch from the surface of t h e groove. The temperature of t h e block could be varied and, at the desired temperature, maintained within 1 5 ' C. by means of an electronic temperature controller. The
2670
INDUSTRIAL AND ENGINEERING CHEMISTRY
temperature of the block wm measured by a 0 O to 650' C. partial immersion thermometer placed in a hole drilled into the block to a depth corresponding t o the immersion point of the thermometer. The heat losses from the aluminum block were decreased by insulation with magnesite pipe insulation. 0; 0.2c
w
v)
c
a 0.15
13
G
a
w n
H w
t-
0.10
5
Vol. 44, No. 11
l,%DECADIENE. This compound was synthesized following the method of Fournier ( 4 ) ; boiling point 170.5' t o 172" C. (763 mm.); di5 0.774; n g 1.441; -+IDcalculated 47.4, found 47.1. ANHYDROUS NITRIC ACID. ilnhydrous, nitrogen dioxidefree nitric acid was prepared by the distillation under reduced pressure of the nitric acid formed by the interaction of potassium nitrate and concentrated sulfuric acid ( 3 , 9). The distillate collected was further purified by a series of fractional crystallizations. The fraction possessing the freezing point of -41.6' C. analyzed 100.2% nitric acid. The second fraction recovered had a freezing point of -67.4' C. and analyzed 89.4% nitric acid. Immediately after purification, the absolute nitric acid was placed in a borosilicate, ground-glass stoppered bottle and stored in the solid state a t -78" C. until ready for use. Kitric acids possessing concentrations intermediate between 100 and 89.4% were obtained by blending absolute nitric acid with 89,4% nitric acid in the proper proportions.
r
DISCUSSION OF RESULTS
X
9
0.05
+
0 W
3 +
o O
I
e
3
4
5
Table I shows that the presence of unsaturation in a hydrocarbon molecule has a marked effect upon its rate of energy release when reacted with nitric acid. For example, n-decane gave no measurable temperature rise over a period of time in excess of 2 minutes, whereas 1-decene produced a temperature of 127.5' C. in 0.18 second. The reactions of diolefin hydro-
NUMBER OF METHYL GROUPS 3.0
Figure 3. Variation A t with Number of Methyl Groups Attached to Benzene Ring
-
The hydrocarbon and nitric acid to be tested were stored in borosilicate glass vessels. The liquids were sprayed onto the heated block through small glass nozzles arranged so t h a t the liquid s t r e a m impinged a short distance above the surface of the block. Air pressure was used to force t h e liquids out of the stoiage vessels and t o spray them onto the heated block.
REAGXXTS. Most of the hydrocarbon compounds used in the experiments were reagent grade chemicals obtained from commercial sources. All compounds were redistilled through a Todd rectifying column prior to use. DECY CY NE. 1-Decyne was synthesized by a procedure analogous t o that outlined by Jacobs(1); boiling point 73.5" to 74" C. (19 mm.); d23 0.794; ng 1.423; fi.rO calculated 46.4, found 44.3. The of Lauer and Gender (IO) ~,~-DECADIY X Eprocedure . was followed for the synthes? of 1,g-decadiyne; boiling point 71.5' t o 73' C. (11 mm.); d;' 0.8156; n:; 1.448; &In calculated 44.38, found 43.98 ~ , ~ - D E C A D I E NhE .satisfactory conversion ( 50yo) of 1,9decadiyne to 1,9-decadiene was obtained by reducing 1,9-decadiyne with metallic sodium and ammonium sulfate in liquid ammonia according to a procedure used by I-Ienne and Greenlee (8) for the preparation of 1,6-heptadiene. -4 2-liter, 3-necked flask equipped with a Herschberg stirrer and a dry-ice reflux condenser was filled mith 1 liter of anhydrous liquid ammonia and 7 5 gram& of ammonium sulfate, added with stirring. To this mixture was added 26.5 grains of l,9-decadiyne. Sodium metal was added until the blue color of dissolved sodium spread throughout the solution. The end point corresponds t o the theoretical amount of sodium required for the reduction; the sodium added amounted to 22 grams. The mixture was allowed to stir for an additional hour a t which time 200 ml. of saturated ammonium chloride solution were added followed by 200 ml. of water. The organic layer was separated, washed with water, concentrated hydrochloric acid, saturated sodium bicarbonate solution, water, and finally dried over anhydrous calcium chloride. The organic layer was rectified under reduced pressure yielding 13.5 grams of 1,g-decadiene; boiling point 67" C. (20 mm.); c1io 0.7534; nD 1.430; M D calculated 47.45, found 47.32.
5
2
EX
.g 1.0 0
I-
w
3
I-
0.5
0
89
90
95
100
PER CENT NITRIC ACID Figure 4. Variation of A t with Nitric Acid Concentratioii
carbons, such as 1,g-decadiene and 1,3-decadiene, gave higher maximum temperatures than 1-decene but the times required to reach the maximum temperatures were considerably longer. The substitution of a methyl group for one hydrogen atom of a double bond contained within the molecule retards the reaction rate with nitric acid. Thus for 3-methyl-3-noneneJ the time interval, At, is twice that for 1-decene. For the aliphatic hydrocarbons investigated, t>herelative rates of reaction with anhydrous nitric acid are, in the order of increasing rate, n-decane < l,9-decadiene < 3-methyl-3-nonene < 1,3-decadiene < 1-decene. The above order does not hold, however, for nitric acids of lower concen-
November 1952
INDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y
2671
trations. When reacted with 93.27y0 nitric acid, the relative rates become n-decane < 1-decene < 1,9-decadiene < 1,a-decadiene. The relative rates of reactivity for the aromatic hydrocarbons investigated present an anomaly. Normally the presence of methyl groups attached t o the benzene ring facilitate substitution in the ring. For example, under the ordinary experimental conditions for aromatic nitration, toluene is nitrated 14 times
Indene is also hypergolic with anhydrous nitric acid and p r e sents a n interesting comparison t o dicyclopentadiene. Indene when treated with anhydrous nitric acid undergoes a rapid primary temperature rise, requiring 0.26 second t o reach 129' C. The temperature continues t o rise at a slower rate until it reaches 421' C. During the latter interval spontaneous combustion is initiated. The ignition delay for indene, estimated from its timetemperature curve, is approximately 1 to 2 seconds. The EFFECT OF NITRICACIDCONCENTRATION. time t o maximum temperature and the maximum temperature attained are affected by the concentration of the nitric acid. The value of At increases and consequently the rate of reaction decreases with a decrease in nitric acid concentration. Measurements were made for a number of aliphatic hydrocarbons when treated with 93.27% nitric acid and these data are presented in Table 11. I n contrast to the data obtained with anhydrous nitric acid, the relative rates of temperature rise fall more nearly in the expected order, Figure 5. Time-Temperature Curve for Reaction between 1-Decene that of the most unsaturated compound being the and 95.2570 Nitric Acid most rapid. Among the aliphatic hydrocarbons the
early with the number of methyl groups (Figure 3). The maximum reaction temperatures fall in the expected order, mesitylene giving the highest temperature and benzene the lowest. However, as a group the aromatic hydrocarbons produce lower maximum wmperaturos than the aliphatic hydrocarbons. There are two compounds listed in Table I which merit special attention: dicyclopentadiene and indene. Of the hydrocarbons investigated, dicyclo-
T
v
*
TJ J
a
I,
I1
A-,t
4At.
pentadiene is the most reactive member of a class of Figure 6. Time-Temperature Curve for Reaction between 1-Decene unsaturated bicyclic hydrocarbons which are sponand 89.44% Nitric Acid taneously inflammable (hypergolic) with anhydrous nitric acid. The other members of that class are apinene and &pinene. The reaction between dicyclopentadiene temperature curve is a smooth curve. Figure 2 shows that with and nitric acid is so violent that it was not possible to determine a concentration of 97% the curve possesses a point of inflection, its temperature history with the available apparatus. Apparently, Tz,and Figures 5 and 6 show that for concentrations of 95% and the increase in pressure during the reaction was so rapid that the less the time-temperature curves possess two such points of inthermocouple responded abnormally. In runs immediately preflection. These points of inflection are believed t o indicate that ceding and following the attempted determination, calibrations the reaction between 1-decene and nitric acid probably occurs as showed that the thermocouple functioned properly. During the a series of consecutive, exothermic chemical changes, each reacexperiments with dicyclopentadiene, however, the thermocouple tion possessing it different rate and requiring a different temperaactually indicated a below-zero temperature. ture for its activation. An alternative method was employed to determine the reacThe presence of nitrogen dioxide in concentrations of less than tivity of dicyclopentadiene. Gunn ( 6 ) has developed an elec0.7% in concentrated nitric acid apparently exerts no significant tronic instrument for measuring the time interval between the effect upon the rate of temperature rise for 1-decene. In coninstant two hypergolic liquids come into contact to the instant centrations exceeding 1%, however, dissolved nitrogen dioxide visible radiation is emitted by their reaction; that time interval increases the rate considerably. For example, the reaction beis commonly termed the ignition delay. Measurements gave tween l-decene and 95.86% nitric acid containing 3.36% nitrogen an ignition delay of 0.032 second for dicyclopentadiene reacted dioxide reaches its maximum temperature in 0.21 second, whereas with anhydrous nitric acid a t ambient temperature. the same reaction with nitric acid of an equivalent concentration
2672
'10 DICYCLQPENTADIENE IN N-DECANE
Figure 7. Variation of Minimum Ignition Temperature with Per Cent of Dicpclopentadiel~ein n-Decane
but free of dissolved oxides requires 0.38 second to reach the same maximum temperature. A more striking example of the effect of high concentrations of nitrogen dioxide is the reaction between l-decene and a red fuming nitric acid which conhained 68.6% nitric acid, 28.7% nitrogen dioxide, and 2.67% water. T h a t reaction required only 0.30 second to reach its maximum temperature, whereas the same reaction with an equivalent nitrogen dioxide-free acid would exhibit a At considerably larger than 2.5 second. NATUREOF THE REACTIOX.Kone of the reactions reported herein n w e analyzed for the products formed since such analyses mould probably not yield any conclusive data regarding the course of the reaction. The study of the reaction between nitric acid and olefins has been reported by various investigators ( 7 , 12, 16,
17). The conclusion reached by Michael and Carlson ( 1 2 ) is that pure nitric acid in carbon tetrachloride solution a t -20" C. adds to the double bond as H-ON02. The addition of nitrogen tetroxide t o olefins has been shon-n to yield a mixture of nitrated products ( 1 1 ) . In view of these facts, the uncontrolled reaction betmen unsaturated hydrocarbons and nitric acid must be complex. It does not seem unreasonable to assume that the initial exothermic reaction responsible for the first portion of the time-temperature curve for 1-decene (Figure 2) should be the addition of H-ONOz to the double bond. I t is also significant to note that the initial portion of the time-temperature curve (Figures 5 and 6) is the portion most sensitive to changes iri nitric acid concentration. MISI~JM IGNTION TmmmmvRE. The minimum ignition temperature ( N I T ) of a hydrocarbon--nitric acid mixture was employed as the third criterion t o study the liquid phase reaction betmcn nitric acid and hT-drocnrbons. The minimum ignition temperature was determined by causing individual streams of nitric acid and hydrocarbon t o impinge on an aluminum block heated to a temperature sufficientlyhigh to produce combustion. The minimum ignition temperature is here defined as the lowest tempeiature of the aluminum block that would initiate corntiustion. To determine the interdependence betn een the minimum ignition temperature, rate of temperature rise, and maximum temperature produced, a number of hydrocarbon mixtures were preparcd hp blending pure hydrocarbons of different molecular structure. Data on the minimum ignition temperature and the temperature history for these mixture? and several pui e hvdrocarbons are presented in Table 111. I n the earlp phases of the research discussed in this paper, the hypotheyis m-as formulated that hydrocarbon compounds that exhibited rapid rates of temperature rise to high temperatures might he either hypergolic or, a t leayt, readilv ignited with a small rxpenditure of external energv From that hypothesis, onc might infer that those hydrocarbons giving the most rapid rates of temperature rise to the higheit temperatur es would require the least amount of external energy to initiatc combustion. This hrpothecis has been found to be valid only in certain casrs. If one considers hydrocarbon mixtures containing different percentages of the same components, the niixturr possessing the fastest rate of temperature rise and the highest maximum temperature gives the lowrat minimum ignition temperatui e The aforementioned hrpothesis doeq not applv, homwer, t o
Initial
Temp.,
c.
Hydrocarbon
TABLE 11. SCMMARY O F TIME-TEMPERATURE DATA FOR CARBONS RE.4CTED WITH 93.27% NITRICi!lCIDa Hydrocarbon
Mixture Ratio, O/F
Initial Tzmp., C.
hiax. Temp., O C.
Temp. Increase,
C.
HYDRO-
A t , f3ec.b
ALIPrIATIC H B D R O C A R B O S ~ 10.7 27 109 82 0.166 10.7 30 116 86 0.17 10.7 30 I24 94 0.197 10.7 28 120 92 0.475 10.7 25 105 80 0.77 10.7 28 N o irnmed. reaction ALICYCLICHYDROCARBONS a-Pinene 10.7 30 113 83 0.095 Dicyclopentadiene 10.7 30 128 98 0.107 &Pinene 10.7 30 122 92 0.152 10.7 27 126 Dipentene 98 0.18 a Analysis of nitric acid: 93.27% "03. 0.62% NOz, 6.l;% HzO. b Time resuired for reaction t o proceed from entry of acid t o maximum temperature. C Hypergolic. d Curve possessed twoslopes: T'71' C At 0.34sec. e Curve possessed two slopes: T' 66' C . , dt, 0.67 sec.
1-Decyne 1 3-Decadiene 1'9-Decadiyne C 1:Q-Decadiened 1-Decenee n-Decane
Vol. 44, No. 11
INDUSTRIAL AND ENGINEERING CHEMISTRY
90% l.Decene-lO% pentadiene 80% l-Decene-20% pentadiene 70 % 1-Decene-30 % pentadiene 767n n-Decane-25%
dicyclodicyclodicyclodicyclo-
SOYo 1-Decene-207" indene 65% l-Decene-16% 0-xyIene-l6% a-methylna~hthalene 65% n-Decane-35% dicyclopentadiene Mesitylene 1-Decene p-Cymene n-Decane SO% l-Decene-20%
decadiene 5
1,9-
Analysis of nitric acid:
"08
Ser.
h1,in . Ignition Temp., O C.
Maw.
Temp.,
c.
4t,
25
15:
0 155
213
25
l59,5
0 17
I 82
25
164
0.15
143
25
115
0.32
154
25
118
0 1.5
85
25 25
128 121
0.12 0.165
8 240
25
121
0.15
271
25 25 25 25 25
119 122 127.5 112 No ;e?+n
0.15 0.163 0.16 0.176 at
85 398 a02 3Q3 340
25
163
0.25
281
- a - c,.
99.l'%, NOz 0.39%, H20 0.51 70.
November 1952
INDUSTRIAL AND ENGINEERING CHEMISTRY
mixtures of either different aliphatic or different aromatic hydrocarbons. For example, the hydrocarbons listed in the second section of Table I11 require approximately the same time interval t o reach the same maximum temperature when reacted with anhydrous nitric acid but their minimum ignition temperatures are markedly different. It is probable that the differences are related t o the combined effects of the thermal instability and the concentration of the most unstable chemical compounds formed during the reaction. The importance of the concentration of the unstable intermediate is deduced from a comparison of the minimum ignition temperatures for mixtures of n-decane and dicyclopentadiene; the latter compound forms very unstable compounds with nitric acid. To ignite n-decane and nitric acid required a block temperature of 340’ C. before combustion occurred, whereas mixtures of 25 and 35% dicyclopentadiene were ignited a t 154’ and 85’ C., respectively. Figure 7 presents the minimum ignition temperature as a function of per cent dicyclopentadiene. B y means of the curve the minimum ignition temperature for a mixture of 45% dicyclopentadiene was predicted t o be 12’ C.; the observed temperature was 8’ C. The correlation between minimum ignition temperature and ’the thermal instability of the reaction intermediates closely parallels the conclusions of Reutenaur (1.4) who studied the spontaneous ignition behavior in air of several hydrocarbons. ACKNOWLEDGMENT
The authors wish t o acknowledge Project Squid, the Office of Naval Research, and the Office of Air Research whose financial support made this work possible.
2673
LITERATURE CITED
Adams, R., ed., “Organic Reactions,” Vol. 5, p. 48, New York, John Wiley & Sons, 1949. Ellis, Carleton, “The Chemistry of Petroleum Derivatives,” Vol. 2, pp. 31-6, 140-5, New York, Reinhold Publishing Corp., 1945. Forsythe, W. R., and Giauque, W. F., J . Am. Chem. Soc., 64, 48 (1942).
Fournier, I$., Bull scc. chim. France, 13, 884 (1895). Gilman, H., “Organic Chemistry, An Advanced Treatise,” Vol. 1, p. 204, New York, John Wiley & Sons, 1945. Gunn, 8.V., M.S. thesis, Purdue University, 1949. Haitinger, Ann., 193, 366 (1878). Henne, A. L., and Greenlee, K. W., J . Am. Chem. Soc., 65, 2020 (1943).
Kuster, F. W., and Munch, S., 2. anorg. Chem., 43, 350 (1905). Lauer, W. M., and Gender, W. J., J . Am. Chem. Soc., 67, 1174 (1945).
Levy, N., Scaife, C. W., and Wilder-Smith, A. E , J. Chem. SOC.. 1948,52.
Michael, H., and Csrlson, G. H., J . Am. Chem. Soc., 57, 1268 (1935).
Rand, M. J., and Hammett, L. P., Ibid., 72, 287 (1950). Reutenaur, G., Pubs. sci. et. tech. direction inds. aeronaut. (France),Bull. services tech., No. 177,93 pp. (1942).
Sachanen, A. N., “The Chemical Constituents of Petroleum,” pp. 197-274, New York, Reinhold Publishing Corp., 1945. Wieland, H., and Rahn, F., Ber., 54, 1770 (1921). Wieland, H., and Sakellarious, E., Ibid., 53, 201 (1920). RECEIVED for review February 26, 1952.
ACCEPTED July 9, 1952.
Resin Forming Reactions of
Furfural and Phenol LLOYD H . BROWN The Quaker Oats Co.,Merchandise Mart Plaza, Chicago 5 4 , I l l . OST of t h e work t h a t has been published on the reactions of phenol and furfural has been confined to the patent literature; as such, it is concerned primarily with t h e preparation of specific resins (3, 7 ) . A few attempts have been made to isolate intermediate reaction products and to describe t h e course of t h e reaction ( 1 , 4 ,6). The purpose of this work has been to investigate some of the variables involved and to describe their effects in terms of yield and properties of t h e reaction products obtained. I n making resins from phenol and furfural one must accept t h e fact t h a t furfural is a slower reacting aldehyde than formaldehyde. Also, our work has thus far been confined t o alk‘aline catalysts. Even so, it is possible to prepare most of t h e types of resins which can be made from phenol and formaldehyde, such as both one and two step resins and intermediate types. Some of these resins possess unusual properties, such as (in t h e Novolak series) oil solubility and acid reactivity. REACTIONS IN AQUEOUS SOLUTIONS
T h e variables which affect t h e rate of reaction in aqueous systems and which have been explored in this work are: the furfural-phenol ratio, catalyst concentration, and amount of water. Strong alkaline catalysts are required to obtain high .yields in a reasonable time a t reflux temperatures. Alkaline
earth hydroxides and alkali carbonates are too weak; ammonium hydroxide is also too weak, and in addition, it reacts with t h e furfural to form hydrofuramide. Sodium hydroxide is the preferred catalyst, and it is needed in such high concentrations as to appear to be a reactant. Figure 1 shows the rate of reaction with 5 and 10% sodium hydroxide based on the phenol in a system containing an amount of water equal t o t h e volume of phenol. Indications are t h a t increasing t h e catalyst concentration above 10% sodium hydroxide increases the reaction rate still further; however, t h e effect is not as pronounced as it is below 10%.
EXPERIMENTAL. Two moles of furfural are refluxed with one mole of phenol, in the presence of 5 or 10% sodium hydroxide based on the phenol, in an amount of water equal t o the phenol. Zero time refers t o the moment the system reaches reflux. At intervals thereafter, samples are withdrawn, neutralized, and tested for nonvolatile solids. T h e reaction rate is also affected by the concentration of furfural (Figure 2). T h e rate increases with increasing proportions of furfural to phenol. EXPERIMENTAL. These reactions are run as described with 10% sodium hydroxide: 10-ml. samples are removed a t intervals, diluted with methanol, and neutralized t o p H 5 ( p H meter) with 1N hydrochloric acid. After diluting t o 200 ml. with methanol, 2 ml. aliquots are tested for furfural using the sodium bisulfite method ( 2 ) . The curves are not corrected for furfural consumed
