GASOLINE FROM
ETHYLENE BY CATALYTIC POLYMERIZATION V. N. IPATIEFF
The charging stock was ethylene of 98 per cent purity, the 2 per cent impurity being mainly ethane. The exit gas was mostly ethylene (about 70 er cent), together with ethane butenes, isobutane, higher hygocarbons, and a small amount of hydrogen (about 0.3 per cent by volume). The production of liquid polymer ranged from 0.01 to 0.03 gallon per hour per pound of cataIyst, depending on the operating conditions. The theoretical yields are shown in Figure 2. In calculating the contact times, the free space in the catalyst charge was taken as 63 per cent, the arithmetical mean of the inlet and outlet rates was used as the gas rate, and deviations from the perfect gas laws were neglected.
B. B. CORSON Universal Oil Products Company, Riverside, 111. AND
HIS paper describes the properties of gasoline obtained by the catalytic polymerization of ethvlene. Ethylene was polymerized in the presence of commercial "solid phosphoric acid" catalyst (1) in a small pilot plant with continuous flow. This investigation was made under conditions approximating commercial operation for gasoline production, whereas the previous study of this reaction by Ipatieff and Pines ( 3 ) , using liquid phosphoric acid as catalyst and long contact time, was concerned only with the chemical composition of the liquid product. Under the conditions employed, polymerization was not the only reaction, as was evident from the nature of the product. which contained not only polymeric olefins but also paraffins (aliphatic and cyclic) and aromatic hydrocarbons. Cyclization, dehydrogenation, hydrogenation, and isomerization also -took place. Such polymerization the authors propose to call "conjunct polymerization" in order to differentiate from pure polymerization. It is assumed that a master reaction-in this case, pplymerization-furnishes the energy necessary for other reactions.
Catalytic polymerization of ethylene in the presence of commercial "solid phosphoric acid" catalyst yields 4.7 gallons of 82 octane number (C. F. R. motor method) gasoline per thousand cubic feet of ethylene charged (total liquid yield, 7 to 8 gallons). The operating pressure was 520 pounds per square inch gage pressure. T w o temperatures were employed, 565" Weight and 615" F. (296" and 324" C.). balances were calculated for two sets of conditions: A, 520 pounds per square inch, 565" F. (296" C.), 1400 seconds contact time; and B y 520 pounds per square inch, 615" F. (324" C.), and 200 seconds. These conditions showed the following conversions : A, recovered ethylene 13.7 per cent, butene 0.7, isobutane 11.6, liquid polymer 73.7 ; B, recovered ethylene 18.0 per cent, butene 0.8, isobutane 6.4, liquid polymer 74.5. The liquid polymer contained paraffins, cycloparaffins, olefins, and aromatics.
Pilot Plant, Charging Stock, and Method of Calculation The pilot plant (Figure 1) consisted of a vertical catalyst tower, charged with solid catalyst, followed by a stabilizer. The catalyst tube was welded inside a larger tube which was filled with a 50:50 mixture of lead and tin; this metal bath was incased in an electrical heater. Polymerization was carried out at 520 pounds per square inch gage pressure. The pressure of the incoming ethylene was controlled by an automatic valve, and the pressure on the exit gas from the polymerizer was lowered to the stabilizing pressure of 50 pounds by another automatic valve. The bottom temperature of the stabilizer was held at 150' F. (66' C . ) , the top at 70" F. (21' C . ) . The boiler section of the stabilizer was an electrically heated Jerguson gage glass. Polymer was continuously withdrawn so as to maintain a constant liquid level in the stabilizer. 860
JULY, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
Polymerization of Ethylene and Characteristics of Ethylene Polymer Gasoline Table I presents run data obtained under' three sets of operating conditions. Increasing the temperature 50" F. [from 565" to 615" F. (296" to 324" C.)]almost doubled the rate of polymer production. Polymer yields are reported o n the basis of once-through operation. Recirculation would raise the liquid yield to 90 per cent and better since the only nonpolymerizable material in the exit gas was isobutane-6 to 12 per cent, depending on the operating conditions (Table
IV) .
TABLE I. RUNDATAON ETHYLENE POLYMERIZATION AND PROPERTIES OF CRUDE LIQUIDPOLYMER A
B
C
288 520 565 296
192 520 615 324
264 520 615 324
1.5 790
2.5 420
3.4 320
73
72
65
8.0 4.7
7.9 4.7
7.1 4.6
48.8
48.7
48.8
8.8
8.3
8.1
Operating conditions: Hours on test Gage pressure, lb./sq. in. Temp., O F. Temp O C. Inlet '&as rate, cu. ft./hr./lb. of catalysts
Contact time, sec. Ethylene polymerization, conversion to liquid polymer, % Ga1./1000 cu. ft. of gas: Liquid polymer Gasoline b Pro erties of crude liquid polymer: O A. P. I. at 60°F. (15.6' C.) Reid vapor pressure at 100' F. (38' C . ) , lb.
&.,
--c.
100-cc. A. S. T. 41. Distillation
,---A --
'C.
O F .
99
37
108
118 134 165 209 272 352 409 462 512 597 639 644
48 67 74 98 133 178 209 239 267 314 337 340
O F .
Initial b . 8 . . Fer cent istilled over: 5 10 20 30
40
50
60 70 ..
*7
c.
7--
F.
a
42
111
44
132 56 145 63 177 81 212 100 267 131 169 400 204 453 234 503 262 577 303 631 333 635 335
142 158 188 220 261 314 364 411 466 534 591 625
70 87 104 127 157 184 211 241 279 311 329
-
61
--
80 90 95 End point 5 Apparent density of catalyst, 0.9. b Initial boiling point, ca. 106' F. 41' C.): end point 400' F. (204' C.): Reid vapor pressure at 100' F. (38' ca. 6.5 pounds.
L.),
The effects of temperature and contact time are shown in Figure 3 which represents the A. S. T. M. distillation curves of crude liquid polymer obtained under different operating conditions. It is evident that increase in severity of the polymerizing conditions increased the amount of higher boiling material, and vice versa. Difference in degree of stabilization is probably responsible for the shape of the first portion of the distillation curves. Table I1 presents characteristics Qf 400" F. (204" C.) end point, steam-distilled gasoline from a composite of the crude polymer produced under the various conditions described in this paper (Figure 4). Distillation data for the bottoms from steam distillation are included. Color and gum were satisfactory, and the octane number was 82 (same as crude polymer). The induction period of the uninhibited distillate was only 100 minutes, but 0.025 per cent of inhibitor raised it to 1600. Distillation characteristics of the crude ethylene polymer are further illustrated by the Podbielniak distillation data (together with the operating conditions of pressure, temperature, and contact time) listed in Table I11 and presented graphically in Figure 5 . The less severe polymerizing conditions favored the production of a simpler product as shown by the more pronounced plateaus in curve E. The same tendency had been previously observed in the polymerization of isobutene (a). The plateau a t 150" F. (66" C.) corresponds
86 1
INDUSTRIAL AND ENGINEERING CHEMISTRY
862
TABLE 11. PROPERTIES OF STEAM-DISTILLED ETHYLENE POLYMER SteamDistd. Polymer 67.4 0.711 30+ 26 ' 10
