INDUSTRIAL AND ENGINEERING CHEMISTRY
762
to be using a 3.5 per cent retirement rate, which at 3 per cent interest requires a useful life of 21 years. To chemical engineers who often use from 5 to 20 per cent depreciation rates and thus retire investments in 16 to 4.5 years, a depreciation rate retiring an investment in 26.5 years may appear unreasonable. It can only be ointed out that the parts of a gas plant not renewed frequentg under routine maintenance do indeed have a long life. Gasholders with over 50 years of service are to be found in many places, and the same is true of other types of simple equipment used in gas plants. The general opinion evidently prevails in the gas industry that an average life of 20 to 30 years may be assumed for gas plant equipment. In the present estimate an average life of 26.5 years has been assumed and a liberal allowance made for current maintenance. 7. The allowance for taxes is another item difficult to determine in this type of estimate. If the statistics for the manufactured gas industry for 1937 be used, the tax item is 1.96 per cent of the- lant investment. In one large city plant the property tax is Enown to be approximately 1.3 per cent on full plant value, to which must be added the taxes based on employment pay rolls, etc. In estimating the cost of gas in the holder, it is
VOL. 32, NO. 6
common practice to include only property taxes and taxes based directly on pay roll; items such as interest on depreciated investment, licenses, income taxes, etc., are included with the other numerous ones which must be added to the holder cost of gas in order to arrive a t a permissible domestic rate for gas. Since the purpose of the present estimate is only to arrive a t a gas-inthe-holder cost which may be compared with corresponding costs by other processes, a tax of 2 per cent of total investment has been used to correspond with the 1.96 per cent shown in the statistics of the gas industry. As stated above, this does not include taxes based on income or any of the other necessary expenses incurred in supplying gas to the ultimate consumer.
Literature Cited (1) Hoopes, W., U. S. Patents 1,366,457-8 (Jan. 25, 1921) ; Duchesne, M. H., French Patent 682,347 (Oct. 13, 1924). (2) MoKee, B. F., U. S. Patents 1,282,445 (Oct. 22, 1918); Stevens, Harold, Ibid., 1,938,121-4 (Dec. 5 , 1933). (3) Walker, H. S., Gaa Age-Record, 70, 27-30 (1932). (4) White, C. E., U. S. Pat,ents 935,344 (Sept. 28, 1909); Berglof, A., Ibid., 1,085,096 (Jan. 20, 1914); Fueler, H. F., Ibid., 1,286,577 (Dec. 3, 1918).
Destructive Hydrogenation of
High=Molecular= Weight Polymers Isobutene Polymer, Butadiene Polymer, and Natural Rubber VLADIMIR N. LPATIEFF AND RAYMOND E. SCHAAD Universal Oil Products Company, Riverside, Ill.
Destructive hydrogenation of rubberlike isobutene polymers produced only paraffinic hydrocarbons and thus showed that the original rubberlike polymers probably had long aliphatic carbon chains. Destructive hydrogenation of butadiene thermal rubber and of natural rubber gave only naphthenic hydrocarbons. Hydrogenation of isoprene yielded isopentane as well as cyclic hydropolymers.
ESTRUCTIVE hydrogenation under pressure in the
D
presence of nickel oxide and molybdenum oxide has been used (2) to show the presence of naphthenic hydrocarbons in high-boiling olefin polymer. It was of interest t o apply this tool to other hydrocarbons having large molecules, especially rubber and synthetic rubberlike polymers. The destructive hydrogenation of isobutene polymer yielded paraffinic hydrocarbons only, including isobutane in the gases. Butadiene polymer, on the other hand, gave only naphthenic products, chiefly ethylcyclohexane and a dicyclic hydrocarbon. Similarly, natural rubber yielded naphthenes only, with p-methylisopropylcyclohexane as the major constituent of the lower boiling portion of the product. Isoprene,
under the conditions used for the destructive hydrogenation of the rubber, yielded isopentane and an unsaturated naphthene (i. e., a hydropolymer of isoprene) which was converted into p-methylisopropylcyclohexane by further hydrogenation. Discussion of the relation of these results to the structures of the polymeric substances hydrogenated is re8erved for a future publication of further work now in progress undertaken to aid in the proper interpretation of the above indicated experiments.
Apparatus and Procedure The destructive hydrogenations were carried out in electrically heated, rotating autoclaves (450- and 3515-cc. capacity) of the Ipatieff type made of stainless steel (17-19 per cent chromium and 7.0-9.5 per cent nickel). Equal weights of the rubberlike polymer or rubber (cut into small pieces) and solvent, and black nickel oxide (Baker's) equivalent t o 10 per cent of the weight of the polymer were placed in the autoclave in the order named. The autoclave was closed, the air was swept from it by hydrogen, and it was charged with hydrogen t o an initial pressure of 100 kg. per sq. em. at 25" C. and then heated a t 250" for 4 to 12 hours (an additional 1.5 to 2.0 hours usually being required to reach the desired operating temperature). After the heating, the autoclave was permitted to cool, the gases were released through a trap cooled by solid carbon dioxide and acetone, and the noncondenaable gases were collected in a gas holder over salt water. The head was then removed from the autoclave, and the liquid product and solvent were taken from the bomb by means of a pipet and filtered to remove the catalyst. The solvent was removed and the product was separated by fractional distillation.
INDUSTRIAL AND EKGINEERING CHEMISTRY
JUNE, 1940
TABLE
Fraction No. 1
2 3 4
5
6 Bottoms
I. DESTRUCTIVELY HYDROGENATED ISOBUTENE
Boiling RangeC. (mm. H g ) C. (760 mm.)
7 -
102-126 (750) 126-149 (750) 50-75 (10) 75-95 (10) 95-125 (11) 125-151 (10)
.. , , . . ..
..... 1661197 197-222 222-258 258-293
....
Dist. % by Wt: per Fraction 19.0 7 8 10 0 2 1 4 0
51.3
7
1.3970 1 405s 1 4278 1 4270 1.4438 1 4461 ,...
Noncondensable Gas, Vole Olefins (total by Br) 0 1 Oxygen 0 9 CO
Hydrogen Paraffins Nitrogen Index of paraffins
POLYMER
Mol. wt.
Destructive Hydrogenation of Isobutene Polymer in Presence of Black Nickel Oxide White rubberlike polymer which was hydrogenated destructively in this work was obtained by polymerizing isobutene in liquid propane solution in the presence of aluminum chloride and hydrogen chloride. For example, 10 grams of resublimed anhydrous aluminum chloride were covered by liquid propane in a 500-cc. three-neck flask fitted with a motor-driven stirrer and surrounded by a bath of solid carbon dioxide and acetone a t -78" C. Temperatures within the flask were measured by a thermocouple inserted in a glass well which extended almost to the bottom of the flask. Then 230 cc. of a solution of 21.5 mole per cent isobutene in propane and 1.5 grams of gaseous hydrogen chloride were added gradually during a period of 1.5 hours to the stirred mixture of aluminum chloride and propane, maintained at approximately - 75" C. After all the isobutene-propane solution was added, the total propane solution, later found to contain 8.5 mole per cent isobutene and 3.2 grams of heavy oil, was decanted from a gummy product and from admixed aluminum chloride which had become slightly yellow during use. Then ice water and cold ammonium hydroxide solution, added carefully to the aluminum chloride residue and gummy product, decomposed the aluminum chloride and left 12.6 grams of white rubberlike polymer material of the nature of that formed in larger scale polymerizations and used as starting material in the present destructive hydrogenation tests. This white rubberlike polymer was cut into small pieces and hydrogenated by the above procedure, using 100 cc. of npentane as solvent with 50 grams of the rubberlike polymer. Gases condensable a t -78" C. and totaling 44 per cent by weight of the polymer charged and the noncondensable gases (2.5 weight per cent) had the following analyses: Condensable Gas, Mole % Propene 0 3 Propane 7.9 Isobutene 0 0 n-Butene 0 9 Isobutane 73 4 n-Pentane (the solvent) 17.5
763
0 81 9 5 1
0 0 3 7 67
After removal of the solvent, the liquid products were distilled by the high-temperature Podbielniak method (4)and separated into fractions with the properties shown in Table I. The analyses and properties indicate that fraction 1 consists of octanes, fraction 4 of dodecanes, fractions 5 and 6 of hexadecanes, and the bottoms of hydrocarbons with an approximate formula C44H90 (molecular weight 618). According to these analyses and properties, these products are entirely paraffinic.
Destructive Hydrogenation of Butadiene Thermal Rubber Rubberlike polymers formed by heating butadiene a t 150"C. under 40 atmospheres initial pressure and freed by vacuum distillation from oils boiling below 300" C. were subjected to destructive hydrogenation. A test a t 100" C. caused no decomposition, but during 6 hours a t 250" C. part of the rubbery polymers was converted into liquid products which were stable to nitrating mixture. The residue of unidecomposed
0.7030 0.7231 0 0 0 0
:7730 7926 8110 8744
C 81.00 84 45 85.05 84.80 84. 80 84 90 85.04
117 123
17i 200 212 625
Found
8ah-d. for CnHl C Hn+2
H 15 65 15.44 15.12 14.98 1.5 05 14 96 14.62
15.76
84.24 , . .
...
Si160 8 4 80
1s:io
8S:iO
1i:60
15.20
polymers was more stable than the original polymer, as 11.0 grams of this residue yielded only 1 cc. of liquid products after further destructive hydrogenation for 8 hours at 240-250" C. under 100 kg. per sq. cm. hydrogen pressure in the presence
AUTOCLAVE ASSEMBLY (FURNACE TOP
C S E D I N DESTRUCTIVE HYDROGENATION R E M O V E D TO S H O W .kUTOCLAVE)
of 1 gram of black nickel oxide. Distillation of the total liquid products obtained a t 250" C. gave the fractions with properties indicated in Table 11. Fractions 2 and 3, which had the physical properties of ethylcyclohexane, were combined and dehydrogenated over platinized alumina a t 250" C. The 3.8 cc. of composite with n2j of 1.4360 yielded 3.7 cc. of dehydrogenation product with nz: of 1.4403 and 735 cc. of gas analyzing 97 per cent hydrogen. The dehydrogenated liquid was converted into a diacetamino derivative (3) melting a t 224-225" C. and corresponding to that of ethylbenzene formed from ethylcyclohexane, a product of the destructive hydrogenation of the rubbery butadiene polymer. TABLE 11. DESTRCCTIVELY HYDROGENATED BTTADIEXE POLYMER Fraction NO.
Boiling Ranse a t 750 Mm., C.
1 2 3 4 5 6"
124-130 130-135 135-145 145-230 230-295
Dist. Vol. yo per Fraction 9.6
23.7
25.7 9.6
n y 1,4083 1.4325 1.4367 1.4617
11.4 1.4771 295-310 7.1 1.4605 Bottoms ... 11.9 1A850 Per cent analysis: found, C 86.20, H 13.81; calculated for CUHJO, C 86.10,
H 13.60.
~~
~
Fraction 6 was saturated, as shown by its stability to both potassium permanganate solution and to nitrating mixture. Its analysis corresponded to that of a naphthenic hydrocarbon with two rings. These results show the products from the destructive hydrogenation of butadiene rubber to be naphthenic hydrocarbons with one or two rings.
INDUSTRIAL AND ENGINEERING CHEMISTRY
764
VOL. 32, NO. 6
TABLE 111. DESTRUCTIVELY HYDROQBNATED PALECREPERUBBER Dist. Fraction KO.
1
2 3 4 5 6 7 8 9 10 11 12
Boiling Range Mm. e Hg
c.
97-110 110-127 127-156 156-163 163-171 171-182 182-193 60-67 67-88 88-93 93-115 115-143
747 747 747 747 747 747 747 8 8
Bottoms (black, viscous)
1 1 6
VOl.
Nor2al B. P., C.
..... ..... .....
..... ..... ..... .....
182-192 192-217 217-270 270-301 301-293
Decomp.
%per Fraction
nv
2.4 2.1 3.8 3.7 7.2 8.9 1.3 8.9 7.1 3.7 3.8 6.3 40.8
1.4258 1.4335 1.4410 1.4463 1.4520 1.4598 1.4662 1,4771 1,4864 1,4950 1.4977 1,5043
Br.
No.
d:'
.... 0.7723
..
49 51 53 54
0.7847 0.8013 0.8119
.... ..... ... .... ....
.. ..
C
H
86:26
l3:68
86:29 86.86
13:b 12.87
... ...
... ...
.. ....
....
(by differenoe)'
Analysis Found, %
73 59
..
'
... ... ... ... ... ...
... ... ... ... ... ...
TABLEIV. PROPERTIES OF COMPLETELY HYDROQENATED PRODUCTS FROM DESTRUCTIVE HYDROGENATION OF RUBBER 7
Product from Crepe Sheet Crepe Crepe Sheet
,------Boiling RangC. (mm. Hg)' C. (760 mm.) n'D" 125-155 (751) 167-169.5 (744) 171-190(750) 90-100 (0.6) 149-160(1.0
..... ..... ..... 277-290
343-356
1.4251 1.4402 1.4449 1.4786 1.4859
d:'
Mol. Wt.
--FoundC
0.7602 0.7993 0.8109 0.8832 0.8957
112 143 146 234 335
85.23 85.43 85.69 86.87 85.88
Destructive Hydrogenation of Rubber in Presence of Black Nickel Oxide Both smoked sheet and pale crepe rubber yielded similar unsaturated destructive hydrogenation products containing 40 to 50 per cent of liquids boiling below 300" C. The remainder consisted of higher boiling liquid or viscous products. Afkr removal of the cyclohexane solvent, the product obtained from pale crepe rubber was separated by high-temperature Podbielniak distillation into fractions with the properties shown in Table 111. No isopentane was detected in the solvent removed from any of these destructive hydrogenation products of rubber. Destructive hydrogenation products of both pale crepe and smoked sheet rubber were hydrogenated t o completion a t low temperatures (up to 150" C.) in the presence of a nickelkieselguhr catalyst (1) with the results listed in Table IV. These data show that only naphthenic and polycyclic hydrocarbons were formed by the destructive hydrogenation of rubber. The completely hydrogenated fraction with 167-170 " C. boiling range obtained from the destructive hydrogenation products of both smoked sheet and pale crepe rubber had a density, refractive index, molecular weight, and carbon and hydrogen content in complete agreement with the best values reported in the literature for these properties of p-methylisopropylcyclohexane (p-menthane) . Further proof of the presence of p-methylisopropylcyclohexane in the products from both smoked sheet and pale crepe rubber was obtained by dehydrogenating the 167-190 O C. fractions a t 250' C. over platinum supported by activated alumina. Gases obtained consisted of 96 per cent hydrogen. After dehydrogenation the liquid products were brominated a t room temperature in the presence of aluminum powder and iodine, and yielded white needles which, after recrystallization from benzene, had a melting point of 276-278" C. These crystals were the same as those obtained similarly from pcymene or from the dehydrogenation product formed from completely hydrogenated dipentene; the latter had B boiling point of 169-170" C. and naz of 1.4402. These crystals were pentabromotoluene formed by cleavage of a n isopropyl group from p-cymene during the bromination. Analysis of this bromide was as follows: Calculated for CHaC&rb: Br, 82.0; molecular weight, 487. Calculated for CHaCar, (isoCIH7): Br, 71.2; molecular weight, 450. Found: Br, 80.58, 81.15; molecular weight, 505.
Analysis, % ' -Calcd.Formula C 14.47 CaHls 85.65 14.51 CaHnt 8 5 . 6 5 14.35 CloHo 8 5 . 6 5 13.10 CiiHa 8 7 . 0 5 13.04 CI~HII 87.10
--.
H
H 14.35 14.35 14.35 12.96 12.90
Further evidence of p-cymene in these dehydrogenation products was the p-toluic acid (melting point 177-179" C.) formed by oxidation with dilute nitric acid (1.0 cc. hydrocarbon refluxed for 12 hours with 15 cc. concentrated nitric acid in 25 cc. water). Accordingly it is concluded that the completely hydrogenated 167-190' C. fraction obtained from rubber contained p-methylisopropylcyclohexane.
Hydrogenation of Isoprene Isoprene in cyclohexane under 100 atmospheres of hydrogen pressure a t 250" C. in the presence of 10 per cent by weight of black nickel oxide yielded 32 per cent by weight of isopentane and 68 per cent of hydropolymerized isoprene boiling from 155' to 190" C. as indicated in Table V. TABLE V. Fraction NO.
1
2 3 4" 5
Bottoms
PRODUCTS FROM HYDROGENATION OF ISOPRBNX IN CYCLOHEXANB SOLUTION Dist. yo by Wt. Boiling Point, O
c.
29-31 31-155 155-166 166-175 175-190
.....
of Total Product
and Solvent 16.5 55.0 4.0 8.6 3.2 7.0
n
so
....
....
1.4447 1.4500 1.4529 1.4739
d a o 0.8099; mol. wt., 143. Per cent analysis: found, C 86.51, H 13.55; calcu&tkd for Cl,Hls, C 86.8, H 13.2. 4
Redistillation of fraction 1 by the low-temperature Podbiehiak method (6) showed it to contain 7.6 per cent butanes and 92.4 per cent isopentane. The liquid products boiling from 155" to 190" C. were unsaturated and consisted of incompletely hydrogenated isoprene dimers which were converted into methane by further hydrogenation,
Acknowledgment The authors wish to thank G. L. Hervert for assistance with the experimental work and R. W. Moehl for the combustion analyses, density, and molecular weight determinations.
Literature Cited (1) Ipatieff and Corson. IND.ENQ.CHEM.,30, 1039 (1938). (2) Ipatieff and Pines, J. Org. Chum., 1, 464 (1936). (3) Ipatieff and Schmerling, J . Am. Cham. soc., 59, 1056 (1937). (4) Podbielniak, IND. ENQ.CHEY.,Anal. Ed., 5, 119,135 (1933). (5) Ibid., 5, 172 (1933).
