INDUSTRIAL AND ENGINEERING CHEMISTRY
1364
may be due in part to the lower p H in solutions of more silicates, the actual ratio of silica to sodium oxide seems to be very important. A high sodium oxide activity is desirable in most industrial metal cleaning, and for this reason podium metasilicate is the most widely used of the silicates. I n some cases, hon-ever, and especially where the cleaning practice iq likely to impqse or encounter conditions outside the safe washing area, i t is necessary to use a more siliceous silicate. For example, in the reclaiming of rejected lithographed tinned iron sheets, it is customary to use a highly siliceous liquid silicate. Occasionally a highly siliceous detergent in powdered form is desired. This demand may often be met by using one of the powlered hydrous siliceous silicates. The protection of a more siliceouq silicate, together with the rapid solubility of the metasilicate, can he secured by a novel way. A dry mixture is prepared containing sodium
T'OL. 27, NO. 11
metasilicate and a less alkaline substance such as sodium acid phosphate. The mixture dissolves readily in water, hut part of the sodium of the metasilicate is taken up by the phosphate. The resultant solution has a lower p H than i t would have had in the ahsence of the phosphate and behaves toward metals like a more siliceous silicate; that ib, the safe range of temperature, sodicm oxide concentration, and immersion time is greater than as if sodium metasilicate alone had been used. A1mo.t any ea-ily soluble substance capable of taking up the sxlium ion may be used, provided its presence in the solution doe? not interfere with the Tl-ork t o be done. To date, NaHC03, Sa2COs2SaIIC03 2H20, Sa2B407lOHrO, S a 2 H P 0 4 , and SaH2POlH.0 have given good results. d further study of this subject is under way and will he reported from time to time. RECEITED S l a y 8, 1933
Polvrnerization of Ethylene J
4
Under High Pressures in the Presence of V. K. IPATIEFF
AND
HERMAN PINES
Phosphoric Acid
Universal Oil Products Company, Riverside, Ill.
QT
H I S article describes the polymerization of ethylene a t 250", 280", 300°, and 330" C. under a n initial ethylene pressure of 50 and 65 atmospheres. I n spite of the wide range of the temperature used, the character of the reaction remains the same, and, as can be seen from the analysis of the gases after the reaction, there is no noticeable cracking of the products. The residual gases always contained some unreacted ethylene, some isobutane, a small amount of hydrogen, and a negligible quantity of other gases such as propane and butane. It was established that the percentage yield and the composition of corresponding fractions remained practically the same, whether the polymerization of ethylene took place without refilling or whether ethylene was pumped into the
apparatus two or more times, and the process was repeated in the same bomb. The polymerization of ethylene beginning at 250" C. gives the same hydrocarbon groups-olefins, paraffins, naphthenes, and aromatic hydrocarbons; an increase in the aromatic content is accompanied by an increase in the paraffin content of the lighter fractions, especially isobutane, the amount of which reaches 18.8 per cent at 330" C.
lpparatus and Procedure The apparatus consisted of an electrically heated, 3-liter Ipatieff rotating autoclave provided with a pressure gage, a valve, a thermocouple well, and Pyrex liner (to prevent corrosion of the steel walls by phosphoric acid). The autoclave was charged with 200 grams of 90 per cent phosphoric acid, ethylene was added up to 50 kg. per sq. cm. pressure, and then it was heated a t the desired temperature for S hours. Whenever -it was necessary to obtain a larger quantity of polymers, the procedure was The polymerization of ethylene under high pressures in the presence repeated several times, and after of 90 per cent phosphoric acid was studied for the first time. Catalytic cooling the bomb, ethylene was again pumped in up to a pressure polymerization of ethylene yields a mixture of paraffinic, olefinic, naphof 50 kg. per sq. em. thenic, and aromatic hydrocarbons. Thermal polymerization of e thylAfter the bomb had cooled to room temperature, the gases were ene under similar conditions does not yield aromatic hydrocarbons. passed through two traps in series The high-pressure catalytic polymerization of ethylene yields isobutane, maintained a t -78" C. by a mixture of solid carbon dioxide and the percentage of which increases with the temperature of polymerizaacetone, and the noncondensable tion. From 250' to 330' C. it varies from 2.5 to 18.8 per cent by weight gases were collected in a gas holder over saturated salt solution. The of the ethylene which reacted. bomb was heated to 40' in order Analysis of the gases at different temperatures permits us to assume to distill o f f all of the gases dissolved by the liquid formed durthat cracking does not take place to any appreciable extent. A mechaing the reaction. nism of ethylene polymerization is suggested. A portion of the condensable gases was subjected to fractional
KOVEMBER, 1935
INDUSTRIAL AND ENGINEERING CHEMISTRY
distillation using (t low-temperature Podbielniak fractional distillation column (4). Another portion of the condensable gases was analyzed by an absorption gas analysis of the Orsat type. The combination of the two methods permits accurate determination of the composition of the gases. The liquid product was separated from the phosphoric acid, washed first with a 15 per cent solution of sodium hydroxide and then with distilled water, dried over calcium chloride, ancl later fractionally distilled.' Index of refraction and bromine number were determined on most of the fractions.
TABLE I. Fraction so.
B. P.
1 40-110 110-225 3 225-300 4 300-340 Bottoms and loss
Method of Analysis 1. The olefin content was determined with 96 per cent sulfuric acid at 0" C. by t,reatment of one volume of the different fractions from the product with two volumes of the acid. ' The mixture was cautiously shaken for 15 to 20 minutes, and then the olefin-free layer was separated from the sulfuric acid at once since, with longer standing, higher polymeric compounds n-ould be liberated from the sulfuric acid layer and pass into the olefinfree layer. The hydrocarbon layer was then washed, dried, and distilled. 2. The degree of unsaturation Fyas shown by the determination of the bromine numbers of the different fractions. [The bromine number and the treatment with 96 per cent sulfuric acid gave comparative data ;as to the amount of olefinic hydrocarbons present in each fract,ion. In view of the fact that no aromatic hydrocarbons were present in the fractions boiling up to 200" C., the treatment with sulfuric acid gave a reliable indication as to the amount of olefinic hydrocarbons present. The higher boiling fractions contained both olefinic and aromatic hydrocarbons, but under the experimental conditions (at 0" C.) the high-boiling aromatic hydrocarbons were not alkylated with the high-boiling olefinic hydrocarbons in the presence of 96 per cent sulfuric acid at a temperature of 0" C. Therefore, the sulfuric acid treatment could be used as a method of separating olefinic hydrocarbons from the other types of hydrocarbons. ] 3. The aromatic hydrocarbon content of the different fractions was determined by treating them with fuming sulfuric acid (15 per cent sulfur trioxide). One volume of the fraction w s treated with two volumes of the sulfuric acid at 0 ' C. Sometimes this treatment had to he repeated in order to remove the last trace of aromatics. 4. The different fractions wereselectively hydrogenated a t 220" C. in the presence of nickel oxide under an initial h sure of 100 atmospheres, using cyclohexane as a sol temperature only the olefinic hydrocarbons were hydrogenated. 5. Hydrogenation was conducted also at 330" C. under pressure in order to convert the aromatic into hydroaromatic hydrocarbons. 6. Carbon and hydrogen analysis was made on each fraction before and after the treatments mentioned. 7. The naphthenes were identified by passing them over heated pallndinized asbestos ( 2 )a t 300" C. by which treatment the naphthenes were dehydrogenated into aromatic hydrocarbons. Polymerization of Ethylene at 2.50' C. Fraction No.
Sixty atmospheres of ethylene were introduced 1 into the high-pressure apparatus, and the glass 2 tube inserted into the bomb was filled n i t h 200 3 4 grams of 90 per cent phosphoric acid. The time 5 of reaction was 24 hours. The bomb Tvas cooled, the gases were collected, and 162 grams of liquid polymers were formed. Analysis of the gases condensable a t -78" C. shon-ed that the isobutane formed amounted to 2.5 per cent by weight of the ethylene which entered into the reaction. Analysis of the gases noncondensable a t -73" C. gave the following results: ethylene, 93.7 per cent; ethane, 5 3 ; hydrogen, 0.5. A 150-gram portion of the liquid polymers was subjected to distillation with a dephlegmator. The data obtained are given in Table I. T h e liquid product was separated into t w o fractions. T h e fraction boiling u p t o 170' C . was distilled on a high-temperature Podbielniak distilling apparatus. -4 Vigreux column (30 b y 1.75 em.) surrounded b y a n evacua t e d jacket was used for t h e distillation of t h e higher boiling fractions. T h e reflux ratio was 6 : 1.
OK
Weight Grams 56 39 40 10 5
c.
POLYMERIZ~4TIoNAT 250"
percentage
c. 2
D.4T.k
1365
of Total Product
P~~~~~~~~~ .iction on Remaining Hydrocarof cns a t d . Hydrocarbons
bons a f t e r Reinoval of Unsatd. Hydrocarbons o f : KMnOd S i t r a t i n g mixt.
3' 28
37 536 27 7 3
None Sone None
31
Sone \-cry weak
.Energetic
. ...
, . .
I n order to separate the unsaturated hydrocarbons, fractions 1 , 2 , and 3 were subjected to the 96 per cent sulfuric acid treatment a t 0" C., the remaining hydrocarbons of each fraction did not react with a permanganate solution and they distilled within the same boiling range as the original fraction. This shows the complete removal of the olefinb. The hydrocarbons of the third fraction reacted very energetically with the nitrating mixture. The index of refraction of the third fraction was nz: = 1.5030. After careful treatment of the third fraction with fuming sulfuric acid (15 per cent d f u r trioxide) a t 0" C. (this treatment was carried out after the 96 per cent sulfuric acid treatment), about 75 per cent of the hydrocarbons dissolved in the acid ; the remaining hydrocarbons no longer reacted with the nitrating rtiixture and could have consisted only of naphthenes and paraffins. The hydrocarbons which dissolved in the fuming d f u r i c acid must have been aromatic, All these conclusions about the character of the product were entirely confirmed by a thorough investigation of all fractions obtained on polymerization of ethylene a t higher temperatures, as will be seen later.
Polymerization of Ethylene at 280' C. A glass tube containing 200 grams of 90 per cent phosphoric acid was inserted into the bomb, and ethylenp was added up to a pressure of 60 atmospheres. The heating was continued for 8 hours and ethylene was pumped in twice. The analysis of the gas gave: ethylene, !33 per cent; C,H2,+2, 6 (index of paraffins, 3.3); hydrogen 1. Liquid polymers in the amount of 433 grams m r e subjected to distillation with a dephlegmator; the data obtained are summarized in Table 11. ~_____
TABLE 11.
D.kT.4 O S
Percentage Total B.P. Weight Product C. Grams 40-110 134 31 110-225 143 33 225-314 110 25 26 6.0 314-325 Bottoms 10 2 5 Losses 10 2.5
POLYYERIZlTION AT 280" Refractive ---Hydrocarbon Index. Ole- P a r a f nL5 fins fins
7 0 7 0 1.3890 1.4380 1.4910 1 5119 1.5234
....
21
23
79
..
, ,
0
, .
..
.. ..
0 0
77
c.
Content--NaphAromatics thenes
70
70
0
0 0 Present Present Present
.
,
Present Present Present
..
.
....
The analysis of the first fraction showed that it consists mostly of paraffinic hydrocarbons and that the reinaiiiing portion is olefins. In the second fraction x e also find naphthenes. The higher fractions, beginning with t'he fourth, contain aromatic hydrocarbons. The niethod of determining the naphthencs and the proof of the presence of ariiniat.ic hydrocarbons as well as the method of quantitative determination will be found in the description of polymerization a t 300" to 330" C.
Polymerization of Ethylene at 300° C. Ethylene was admitted tWice into the high-pressure apparatus. Five hundred grams of a liquid product were ob-
1366
INDUSTRIAL AND ENGINEERIXG CHEMISTRY
per cent; and nz: = 1.5155. It did not react with a permanganate solution. The fact that the hydrogen content of the product before and after the treatment with sulfuric acid was practically the same supports the supposition that, in this case, we do not have open-chain olefins but probably cyclic hydrocarbons with double bonds in the side chains. This fraction, boiling a t 270" to 290" C., vigorously reacted with a nitrating mixture and, therefore, undoubtedly contained aromatic hydrocarbons. I n order to remove these hydrocarbons, the fraction was treated with fuming sulfuric acid a t 0" C. The product obtained did not react with a nitrating mixture, and its analysis gave the following results: molecular'weight, 233; boiling point, 260" to 280" C.; nz: = 1.4790; carbon, 86.97 per cent; and hydrogen, 13.40 per cent. The remaining hydrocarbons represent a mixture probably of mono- and dicylic naphthenes. I n order to verify the results obtained, hydrogenation of various fractions under pressure in the presence of nickel oxide a t 220" C. was made. The data are given in Table VI. The carbon-hydrogen content of the fraction boiling a t 160" to 225" C., after the removal of olefins and after hydrogenation at 250" to 270" C., was practically the same. The hydrogenated higher boiling fractions were stable toward the pernianganate solution but reacted gently with the nitrating mixture and therefore must have contained a small quantity of aromatic hydrocarbons.2 For this reason after hydrogenation all fractions were treated with fuming sulfuric acid until there was no reaction with the nitrating mixture. The analysia of the hydrogenated hydrocarbons shows that in this case we have a mixture of mono- and polycyclic naphthenes.
tained. The analysis of the product gave results similar to those obtained in the foregoing experiment. The distillation of the product with a dephlegmator gave the results s h o m in Table 111. AT 300" C TABLE 111. DATAO N POLYMERIZ~TION
Fraction
R. P
NO.
O L '
6 7 8
Percentage of T o t a l Product
Weight Grams
310-335 335-360 Bottoms
20 19 16
4 1 3 8 3 3
An analysis of the fractions is given Tables I V and V. Table IV indicates that the paraffinic hydrocarbons have already disappeared in the fraction boiling a t 160" to 22.5" C. in which the aromatic hydrocarbons have just begun to appear, and that the amount of the latter increases in the higher boiling fractions. Investigations showed t h a t naphthenes begin t o appear only in the second fraction. I n order to prove their presence in the second fraction and t o make a quantitative determination, the product of polymerization boiling a t 120" to 140" C. was subjected to dehydrogenation with palladium according to the method of Zelinsky (6). The product obtained (boiling point, 120" to 130" C.) did not react with a permanganate solution but vigorously reacted with a nitrating mixture and gave a crystalline trinitro compound (melting point, 155" to 160" C.) which corresponded to one of the aromatic hydrocarbons with formula CsHlo. Fuming sulfuric acid dis-olved approximately 20 per cent of the aromatic hydrocarbons.
Polymerization of Ethylene at 330' C.
TABLE IV. ANALYSISOF FRACTIONS Fractions
c.
Analysis
%
Refractive Index. ?I.;
Density, d,",
%
Olefins
%
Paraf- Xaphfins thenes
%
VOL. 27, NO. 11
%
The polymerization of ethylene a t this temperature was carried out in two ways: (1) by pumping ethylene int,o the bomb once and (2) by pumping ethylene six times. The latter experiment will Arobe described first, and then the results of the matics former experiment will be given. By comparing % the data obtained in both cases it can easily be seen that the character of the reaction is essen4 36 tially the same. 70
14.76a 1.4205 .... 33 10 57 85.50 110-160 1.4535 ,, , , 24 .. 72 14.38a 160-225 85.39 225-270 87.90 12.14 1.5005 0.8802 27b . . 37 1.5090 .,.. 20b .. 10 11.78 87.85 270-310 1.5215 .,. , 28b .. 10 62 11.79 310-335 88.01 1.5310 ... 25b , . 10 65 88.44 11.50 335-360 Analysis of fraction a f t e r removal of olefins with 96 per cent sulfuric acid. b Fractions boiling above 225' C. contain, according t o all d a t a , cyclical hydrocarbons with a side chain containing a double bond. Q
WITH SULFURIC ACID TABLE V. ANALYSISAFTER TREATMENT AND FUMING& SCLFCRIC ACID
B. P. of FracFractions
tion a f t e r Treatment
Analysis a f t e r Removal of Olefins a n d Aromatic Hydrocarbons
110-160 140-160 85.50 160-225 200-210 85 80 225-270 215-240 86.59 270-310 250-270 86.54 310-335 270-290 86.97 335-360 .,.,, , . . a F i f t e e n per cent sulfur trioxide.
14.76 14.32 13.50 13.60 13.40
...
Refractive Index, n 2,5 1.4320 1.4375 1.4675 1.4705 1.4790 , . . .
Density, M o l . d$" Weight 0.7623 0.7876 0.8493 0 8620
.... ., .
118 175 216 237
..
293
I n order to decide whether fractions boiling above 225" C. contain olefins or aromatic hydrocarbons and naphthenes with double bonds in side chains, the following experiment was carried out: From the fraction boiling a t 270" to 310" C. there was separated a fraction boiling a t 280" to 290" C.: carbon, 88.03 per cent; hydrogen, 11.87 per cent; and nzi = 1.5080. After treating the fraction twice with 96 per cent sulfuric acid a t 0" C., a product boiling a t 270" to 290" was obtained: carbon, 88.33 per cent; hydrogen, 11.90
The Pyrex liner of a 3-liter autoclave was charged with 200 grams of 90 per cent phosphoric acid, and ethylene was added to a gage pressure of 50 atmospheres. I t was heated at 330" C. for 5 to 6 hours, after which it was cooled and more ethylene was introduced; this procedure was repeated six times until the desired amount of liquid product, had been ohtained. At the end of the experiment, after the bomb had cooled to room temperature, the gas was passed through two traps cooled by solid carbon dioxide-acetone, the noncondensable gas being collected in a gas holder over brine. The bomb was heated to 40" C. in order to remove dissolved gas from the liquid product. The condensable gas was separated into fractions by low-temperature Podbielniak distillation, and each fraction xas separately analyzed for olefin content by absorption (isobutylene by 63 per cent sulfuric acid, propene and higher olefins by 87 per cent sulfuric acid, ethylene by bromine). This combination of distillation and absorption permits more accurate determination of gas composition than either method alone. The condensable gas was 98 per cent isobutane and 2 per cent n-butene. The weight of isobutane corresponded to an 18.8 per cent yield based on the ethylene which underivent reaction.
There were obtained 14.1 liters of gases noncondensable a t -78" C., consisting of 47.8 per cent ethylene, 25.3 hydrogen, 26.8 paraffins with an index of 2 . On calculating the number of moles of gases which were formed on polymerization of 2 For complete hydrogenation i t is necessary t o use higher temperatures, u p t o 330' C. (see section on hydrogenation of product of polymerization a t 330").
NOVEMBER, 1935
INDUSTRIAL AND ENGINEERING CHEMISTRY
22.5 moles of ethylene, the folloxing approximate figures were obtained: isobutane. 2 moles; hydrogen, 0.16; ethylene, 0.3; paraffins,0.23; and n-butene, 0.07 mole. As can be seen from the gas analysis, there was practically no cracking. Table VI1 presents distillation data on the liquid product and characteristics of the various cuts. The data obtained from the polymerization of ethylene when the latter was pumped into the same bomb only once a t the initial ethylene pressure of 65 atmospheres, is given in Table T'III. The time of heating was 9 hours. The gas obtained condensed a t -78" C. It weighed 33 grams and contained 26.8 grams of isobutane, 4 grams of higher paraffins, and 2 grams of propane. The noncondensable gas in the amount of 38 liters consisted of 98.1 per cent ethylene and 1.9 per cent butane and propane. A thorough investigation of all the fractions of the product obtained with repeated additions of ethylene was carried out, and in addition check determinations of the olefin and aromatic contents of the product obtained on single introduction of ethylene were a150 made. The fractions boiling u p to 84" C. were entirely paraffinic as shown by their negative response to 2 per cent permanganate solution and by their ratios of carbon to hydrogen. The cut boiling a t 140" to 155" C. contained 10 per cent of paraffins, 25 of olefins, and 65 of naphthenes. The naphthenic content decreased with rise in boiling point, becoming zero in the fraction boiling a t 285" to 241" C. Paraffins were absent in the fraction boiling a t 225" to 241 O C. The aromatic content increased with rise in boiling point, the cut boiling a t 285" to 300" C. being essentially aromatic. The olefin content corresponding to the volume decrease occasioned by shaking with 96 per cent sulfuric acid a t 0 " C. agreed with that calculated from the bromine number. After treatment with 96 per cent sulfuric acid, the various fraction, were shaken with funiing sulfuric acid at 0" C., and the volume decrease was assumed to correspond to aromatic hydrocarbons. (Distillation after each sulfuric acid treatment showed the boiling range to be about the same as before acid treatment.) Additional information was furnished by the carbonhydrogen ratios before and after the sulfuric acid treatments. Finally, the various fractions were subjected to two selective hydrogenations a t superatmospheric pressure in the presence of nickel oxide. Carbon-hydrogen ratios were determined for initial material and for the products from each of the two hydrogenations. The change in the carbon-hydrogen ratio due to sulfuric acid treatment and to stepwise hydrogenation agreed with the values predicted from the hydrocarbon composition determined by bromine number and sulfuric acid treatment. Illustrative data are presented in Table IX. T h e product from the first hydrogenation was stable to permanganate solution, but it reacted with nitrating mixture. The product from the second hydrogenation did not react with nitrat-
1367
TABLE VI. HYDROGENATION OF FR.4CTIOX.S 3 . P. of ractions after lydrojnation
160-225 85.39 14 38 1 4535 160-220 225-270 87.90 12.14 1.5005 250-260 270-310 87.85 11.78 1.5090 250-270
Reiractire Index, Denrity, Mol. nz,? d-4Weight
Analysis
...
14.40 1.4150 0 7623 13.97 0 8413 85.90 13.90 1:iSio ...
85.80 85 95
2ig
TABLE VII. PROPERTIES OF THE ETHYLENE POLYMER Fraction B. P. No. (757 M m , )
Weight Grams Per cent
e. - 12
1 2 3
8
- 12-24.5 24.5-30.0 30.0-30.5 30.5-32.5 32,5-37,4 37.4-59.0 59 .O-60.5
16
70.0-84.0 84-95 95-110 110-125 125-140 140-155 155-170
4
5 6
7
60.5-70.0
9 10 11 12 13 14 15 17 18 19 20 21 22 23 24 25 26 27 28 29 30
170-185
185-205 205-225 225-241 241-250 250-263 263-276 276-285 285-300 160-174a 174-185" 185-200a 200-2lo=
118.0 6.9 12 2 6.9 6.6
6.3 12.8 39.0 36.2 16.5 14.0 16.0 12.5 11.0 16.0
18.8 1.1 1.8 1.1 1.1 1.1
18.8 19.9 21.7 22.8 23.9 25.0
2.0 6.0
27.0
5.5 2 5 2.2
25 2.0 1.7
2.5 1.9
12.0
13.0 l5,O 11.5 29.0 32.0 28 5 27.0 33 0 41.5 14.0 14.0 14.0 10.0 20.0
2.0
2.3 1.8 4.0 5.0 4.4 4.2 5.2 6.4 2.1 2.1 2.1
Bromine
rota1 Per Cent Over
33.0 38 5 41.0 43.2 45.7 47.7 49.4 51.9 53.8 55.8 5s.1 59.9 63.9 68.9 73.3 77.5 82.7 89.1 91.2 92.9 95.1 96.6 99.6
Analysie Found
KO.
%b c
% H
..
.. ..
.. .. ..
, . . .
3
....
..
.... .... ....
..
..
, .
16:4
'2
84:2
15:s
84:s
15:o
6 8
9 14
..
16
..
23 33 37
..
.. ..
8i:i
12:9
.. ..
32
, .
..
20
88.4
, .
13 8 7
86:3 88.8
ii:s
6 6
88:4 ..
11.5
11.6
..
.. .. .. ..
11.4
1.5 Residue 3.0 .. a T h e product n-as distilled under S mm. oi pressure
ny
,.
.. .. ..
83:6
..
Refractive Index,
Found
.... , . . .
...
I
1.3785 1.3822 1.3911 1,4025 1.4111 1,4222 1.4325 1.4415 1.4520 1.4678 1.4852 1,4978 1.5061 1.5120 1,5170 1.5220 1.5255 1.5309 1.5378 1.5483 1.5616
. I
TABLE 1'111. DATAON POLYMERIZ.4TION O F ETHYLENE WH EX PUMPED ONLYONCEINTO BOMB Fraction
B. P .
NO.
Weight Grams
c. Isobutane
26.8 48.5 19.5 24.5 4.0 63 21 7
27-66 66-126 126-190 190-225 225-300 300-350
Bottoms
TABLE Ix. Fraction No.
B.P. O
1 2
3
Reiractive Index,
nV
L
....
12.7
1.3682 1.3968 1.4372
22.5
9.1 11.5 1.9 30.0 10.0 3.3
D.kT.4 ON VARIOUS
:
I 5054 I ,5264
TREATMEXTS
Initial Material Mol. Bromine Denrity, Refractive Weighto No. dz6 Index, 5n\
Analyses Found %(; % H 87.1 12.9 88.4 11.6 88.3 11.6
c.
175-225 241-250 285-300
At 200-2200 Fraction No. d26 n;2
7 -
Percentage of T o t a l Product
165
182 224
c.
30 13 6
0.8298 0.8899 0.9202
-
1.4655 1.5061 1.5255
After Hydrogenation Analyses found
Fraction so. d5 :
4 t 330" C % .5
-----. Analyses found
% C % H %C % H 1 .... 1.4400 85.8 14 2 1 .... .... 2 .... 1.4840 8 7 . 2 12.5 2 0.8312 1.4568 85:8 1411 3 0,9101 1.5140 88.0 11.9 3 0.8584 1.4780 8 6 . 1 13.9 A f t e r Sulfuric Acid a t 0' C 7 96% Sulfuric Acid-15% Fuming Sulfuric AcidFraction Analyses Fraction -4nalyees NO. dz5 ng found NO. ;5 naJ found % C % H '%C % H 1 .. 1 4570 86 5 13.4 1 . ... 1.4761 85.8 14.3 2 .. 1.5062 88.2 11.8 2 , , .. 1.4752 86.8 13.3 3 .. 1.5205 88.4 11.7 3 , . . , 1.4790 8 6 . 9 13.4 a Molecular weights were determined b y t h e cryoscopic method in benzene solution.
1368
INDUSTRIAL AND ENGINEERING CHEMISTRY
ing mixture and its carbon-hydrogen ratio corresponded to that of the naphthenes, C,H,,.
Thermal Polymerization of Ethylene I n order t o show the difference existing between the polymerization of ethylene in the presence and absence of phosphoric acid, a thermal polymerization of ethylene was carried out a t 330". This experiment was made in one of the same apparatus and under similar conditions as those used for the catalytic polymerization of ethylene a t 330' C. Ethylene (64 atmospheres) was pumped in three times and the total time of reaction was 29 hours. After the reaction, 5 grams of gas condensable a t -78" C. was obtained l\-hich consisted of 70 per cent butanes and butenes, 25 per cent propane and propene, and 5 per cent higher hydrocarbons. Seventy-five liters of gas noncondensable a t -78" C. were obtained, consisting of 92 per cent ethylene, 6.5 paraffins, and 1.5 hydrogen. The polymers were subjected to the Podbielniak distillation, and the results are shown in Table X. They are similar to results obtained by one of the authors ( 3 ) . An inspection of the data obtained clearly brings out the wide differences in the polymerization of ethylene with and without the influence of phosphoric acid. The composition of the product of polymerization by hydrocarbon groups follows : 8 per cent p a r a m s , 68 olefins, and 24 naphthenes; there was a total absence of aromatic hydrocarbons and a very large amount of high-boiling fractions, only 24 per cent of the prod-
VOL. 27, NO. 11
on the other hand, appear in the fractions distilling a t 225' C. and higher. The unsaturated hydrocarbons are present with one exception in all fractions; no olefinic hydrocarbons were found in the product boiling below 60" obtained from the polymerization of ethylene at 330". The naphthenic hydrocarbons are present in the fractions boiling above 110" C, The most interesting fact about catalytic polymerization of ethylene is the formation of isobutane, the percentage of which increases with the temperature of polymerization. A t 250' C., 2.5 per cent by weight of isobutane was formed, based on the weight of ethylene which entered the reaction. At 330' C., 18.8 per cent by weight of the ethylene reacting was converted into isobutane. The effect of temperature of polymerization u p m the boiling range of the product formed is given in the following table: Total Product at Polymerization Temp. o f : 250' C . 280' C. 300' C 330' C. = c. Per cent b y weight 37 31 42 46O 1. Below 110 26 33 20 14 2. 110-225 27 23 26 29 3. 225-300 10 13 12 11 4. Above 300 18.8 per cent of the total product is isobutane. Boiling Range
4
The distillation curve of the fraction boiling above 225" C. is almost the same in all the experiments; the percentage of the product distilling between 110" and 225' C.is the smallest when the temperature of polymerization is 330" C. The difference between the polymerization of ethylene in the presence and absence of phosPOLYMERIZATION OF ETHYLENE AT 330" C. phoric acid consi&s in the presence of aromatic TABLE X. THERMAL Weight Total Refraoand paraffinic hydrocarbons in the f o r m e r , of Per- Brotive whereas no traces of aromatics and only small Fraction B . P. Frac- centage mine Index, Ole- Density, Mol. No. (758 Mm.) tion Over No. .y fins ay Weight Analysis quantities of paraffinic were discovered in the ' C . Grams % %C %H latter. It appears that the phosphoric acid acts 1 36-60 11.0 2.1 117 1.3879 60 ....... here also as a hydrogenation and dehydrogenation 2 60-75 9.2 3.9 113 1.3883 60 0.6716 85 84:70 l5:65 3 (5-90 5.4 4.9 105 1.3980 55 . . . . . . . . . . . . . catalyst. . . . . . . . . . . . . . 4 5 115-135 90-115 18.2 5.0 5 9. , 83 88 81 1.4099 1.4136 55 56 T h e t h e r m a 1 polymerization in comparison . . . . . . . . . . . . . 6 135-155 21.0 13.3 70 1.4205 55 0 . 7 3 ~ 1 127 85.17 14.96 with the catalytic polymerization yields higher . . . . . . . . . . . . . 8 7 155-175 175-195 18.8 10.5 17.1 19.1 61 66 1.4272 1.4338 53 58 boiling hydrocarbons. . . . . . . . . . . . . . 9 195-205 4 . 0 19.9 . . . . . . . . . . . . . . . . . . . . . 10 205-225 20.0 24 0 58 1.4443 61 . . . . . . . . . . . . . Mechanism of Ethvlene Polvmerization 1.4469 63 0.7940 194 85.69 14.35 37.5 31.2 52 11 225-245 .... ... ... ... 1.4511 76 12 245-260 23.0 35.3 58 I n order to explain the presence of the differ1.4544 70 0.8060 211 . . . ... 34.5 41.9 53 13 260-270 ent types of hydrocarbons in the product obtained . . . . ... . . . ... 1.4591 74 14 155-170@ 17.0 45.1 55 1.4610 70 .... ... . . . ... 15 170-190a 23.5 49.6 43 from the polymerization of ethylene, the following 0,8289 299 85.68 14.17 1.4632 56 16 19(t;207a 42.5 57.7 30 mechanism of the reaction is suggested: ... ... 17 207-220" 23.0 62.1 28 1.4663 .. ... 1.4661 . . 18 22&235a 18.0 65.5 26 630 85:98 ii:is .. , . 67 19 389 190.0 99.9 17 1. The first step in the reaction is the formation The product was distilled under 15 mm. of pressuire. of ethvl phosphates. This fact was proved by a speciai ex'periment on the action of ethylene uider pressure on orthophosphoric acids. At 180" C. and under an initial pressure of ethylene of 50 atmospheres a rapid uct boiling u p to 225" C. The absence of aromatic hydroabsorption of ethylene began to take place. When the pressure carbons was evidenced by the figures obtained on organic remained constant the experiment was discontinued and the prodanalysis of the product, and also by the fact that after the 96 uct of the reaction was examined. The monoethyl ester of phosphoric acid which was formed was converted into a barium salt, per cent sulfuric acid treatment of the fractions there was a the analysis of which corresponded to the formula: product obtained which did not react with a nitrating mixture. For a further proof a method of hydrogenation a t 220" C. in Calculated, % Found, % P 11.9 12.1 the presence of nickel oxide was applied to fractions 11,16,and Bl3 52.5 53.3 19. The products obtained analyzed as follows: 2. Ethyl phosphates, being unstable a t higher temperatures, Fraction % % .- C . _H decompose t o give ethylene polymers and naphthenes. 11 85.16 14 SO 16 86.58 14 48 1 nitrating mixture, no reaction 3. Na hthenic hydrocarbons dehydrogenate to form aro19 85.76 14 30) matic hylrocarbons. 4. Olefin hydrocarbons are hydrogenated to paraffins b the These data show that we have chiefly naphthenic hydrocarhydrogen resulting from the dehydrogenation of the naphtzenes bons. to aromatics. 0
Discussion of Results The polymerization of ethylene in the presence of phosphoric acid, within the temperature range studied (250" to 330" C.), yields a mixture of paraffinic, olefinic, naphthenic, and aromatic hydrocarbons. The concentration of paraffins is the greatest in the lowest boiling fractions; the aromatics,
The last two reactions take place simultaneously; since the hydrogen is in the nascent state, it reacts with the olefins (molecular hydrogen under the same conditions does not react with olefins). The formation of paraffin and aromatic hydrocarbons is due to intermolecular hydrogenation-dehydrogenation reactions.
NOVEMBER, 1935
INDUSTRIAL AND ENGINEERING CHEMISTRY
Mechanism of Isobutane Formation The first product of the polymerization of ethylene must be 1- or 2-butylene, which on hydrogenation should give nbutane. Undoubtedly, under the experimental conditions, a n isomerization of 1- or 2-butene into isobutene ( 2 ) occurs, and the latter, on hydrogenation, gives isobutane. Experiments in connection with this reaction have shown that nbutane does not isomerize into isobutane in the presence of phosphoric acid. The possibility for 1-butene to isomerize into isobutene was shown in the following experiment: Pure 1-butene was heated to 330" C. with phosphoric acid in the presence of hydrogen, the initial pressure of the latter being 100 atmospheres. After heating for 12 hours, a liquid polymer and a gas were obtained, and the latter was subjected to an analysis according to Podbielniak. This gas which was condensable a t -78" C. consisted of 50 per cent isobutane, a small quantity
1369
of n-butane and the unreacted n-butene. The amount of isobutane formed represented 6 per cent of the reacted butene.
Acknowledgment The authors wish to express their thanks to R. C. Wackher for making the carbon and hydrogen analyses and determinations of density and molecular weight.
Literature Cited (1) Francis, A. W., IND. ENQ.CHEM.,18, 621 (1920). (2) Ipatieff, V. N., Ber., 36, 2003 (1903); Ipatieff and Huhn, W., Ibid., 36, 2014 (1903); Ipatieff and Sdaitovecky, Ibid., 40 1827 (1907). (3) Ipatieff, V. N., Ibid., 44, 2978 (1911). EKG.CHEM.,Anal. Ed., 5, 172 (1933). (4) Podbielniak, W., IND. (5) Zelinsky, N. D., and Borissoff, P., Ber., 57, 2060 (1924).
RECEIVED January 21, 1935
Natural Resins for the Varnish Industry of its satisfactory performance, is said to have delayed the development of porcelain. C. L. MANTELL, C. H. ALLEN, AND K. R.I. SPRINKEL
Source of Supply and Origin
American Gum Importers' Association, Inc., New York, N. Y.
HE use of the natural resins, either b y themselves or a s a constituent of coating materials for decorative and protective purposes, has been practiced from very early times. It is believed that the Egyptians used natural resins of the balsam type to varnish their mummy cases. It is probable that the natural resin was smeared on. Evidence exists that the Incas of South America employed natural resins for embalming. The properties of resins were known to the Carthaginians, the Phoenicians, and the earliest Greeks. Evidence exists in the form of varnished objects several thousand years old and in excellent condition, that natural resins skillfully applied can yield finishes of outstanding durability. The natural lacquers, which are tree exudations, on Chinese and Japanese carriages, armor, bridges, and temples have withstood long periods of weathering in severe climates. Lacquered tableware, because
T
GUMTREE,SHOWING METHOD OF TAPPING AND TYPEOF NATIVE WITH GUM SPE.4R TAKEN NEAR LENKEON LAKE TOWOETI, CELEBES
I n our present chemical age with its emphasis on synthetic products, there is a tendency to deride raw materials from natural sources. There is a feeling that natural varnish resins are collected by ignorant savages from the ground and limbs of trees in tropical forests, and brought to the market by wily traders operating in an unorganized manner. The actual facts certainlydo not bear out or substantiate any of these impressions. The natural resin business is world wide in its organization; it is conducted in a systematic and organized manner as far as the collection, grading, sorting, preparation for market, and distribution of the product are concerned. It is fully as well set up as a going business as the collection of rubber, the development of naval stores, the production of coconut and palm oils, or the preparation of sugar. The natural resin business is stable and ready to meet any demands made on it. It is not subject to decreasing supplies o r v a n i s h i n g sources of material. I t s art in varnish making is old, well established, and free from patent restrictions and the attenda n t difficulties of such influences. The natural resins are forest products rather than synthetic materials prepared from
