Symposium on Utilization of Gaseous Hydrocarbons Presented before the Division of Petroleum Chemistry at the 82nd Meeting of the American Chemical Society, Buffalo, N. Y., August 31 to September 4, 1931.
G
ASEOUS hydrocarbons present an excellent potential source of raw material for chemical manufacture. Everyone is cognizant of this fact but few appreciate why this potential source does not become a real source. At least two important reasons can be given for this failure to utilize our gaseous hydrocarbons. First, most chemical reactions involving gaseous hydrocarbons take place with an evolution of heat. It is difficult to obtain the necessary heat transfer in order to maintain proper temperature conditions. Proper temperature conditions or the confining of the reaction temperature within narrow limits arc absolutely necessary in order to produce the pure products desired, instead of a complex mixture. A second reason is evident when we consider that even though there is no great evolution of heat in certain reactions involving gaseous hydrocarbons, nevertheless there is great difficulty in operating these reactions under what might be considered reasonable equilibrium conditions. This is probably due to the fact that reasonable equilibrium conditions necessitate reactions a t very high temperatures and high pressures. Satisfactory equipment t o meet such conditions has only recently been developed.
Lately there has been an attempt on the part of investigators in this general field to utilize pure organic compounds rather than mixtures. This is apparently a step in the right direction as shown by the increase of interesting results obtained in this field. It is believed that the papers in this symposium will clearly substantiate the statements made above. One peculiar economic feature of the general problem should be noted. The present large use for hydrocarbons is as motor fuel; approximately 20 billion gallons are produced per year in this country. The next largest use for these hydrocarbons that has been proposed is in the production of solvents with only 200 million gallons per year possible consumption. Between the two uses there should be developed a third field before the oil refineries can afford t o spend the large sums necessary to utilize the hydrocarbon gases. Two possibilities have recently appeared. One is the use of hydrocarbons in the manufacture of synthetic resins to be used in paints, varnishes, lacquers, and plastics The other is the use of hydrocarbon gases in the manufacture of new synthetic textiles-for example, the polymers of glycol sebacate. D. B. KEYES,Chairman
Partial Oxidation of Hydrocarbons Catalyzed by Oxides of Nitrogen C . H. BIBB,Oxidation Products Company, Jersey City, N . J .
T H E O X I D A l I O N of methane to formaldeof heating; form of r e a c t i o n hyde and methanol has been involved in most of the c h a m b e r ; and the nature of of nitrogen to catalyze work sf the past. However, considerable quanthe hydrocarbon all have prothe p a r t i a l o x i d a t i o n nounced effects on the r e s u l t s Of hydrocarbons with air has tities of formaldehyde can be obtained f r o m obtained. principally been described propane and other hydrocarbons by the process, i n a r t i c l e s b y L~~~~ a n d S o u k u p (s), S m i t h a n d and, as has been described, phenol is the prinOXIDATIONOF NATURAL Milner ( 4 ) , a n d Bibb and cipal oxidation product when benzene is used. GAS L u c a s (8); and in P a t e n t s I n this article, operative conditions of a f e w In addition t o the simplest t o t h e a u t h o r ('1. The runs are described which show better yields on m e t h o d of partially oxidizing process con si s t s e s s e n t i a l l y i n m i x i n g a i r and a gaseous the hydrocarbons and oxides of nitrogen to t h e hydrocarbons of n a t u r a l hvdrocarbon t o g e t h e r with a formaldehyde than have heretofore been pubgas, which c o n s i s t s in only a single pass of the gaseous mixr e l a t i v e l y s m i l l amount of Zished. ture through the reaction zone oxides of nitrogen, heating the mixture to a reaction temperature which may vary between and the condensation of the oxidation products, the tail 500" and 900' C., cooling the mixture, and condensing out gases were oxidized successively four times. I n another the aqueous solution formed from the fixed gases. The series of experiments the recycle principle was used whereby fixed or exit gases may be processed again for additional the tail gases from the condensation apparatus were conoxidation products by mixing with more air, with or with- veyed back to the inlet of the reaction zone and reoxidized. out the further addition of nitrogen oxides, or they may be I n some experiments the recycle rate was over fifteen times recycled in the original heating chamber. The proportions the amount of input into the system. A bleed-off of the of hydrocarbon, air,, and nitrogen oxides; temperature; gases was, of course, necessary in order to maintain constant velocity of the gases through the reaction zone, or the time pressure.
T
HE u s e of t h e oxides
10
INDUSTRIAL AND ENGINEERING CHEMISTRY
January, 1932
FOUR-PASS TREATMENT
SINGLE-PASS TREATNENT Using the first unit of a four-pass system as an illustration of a single pass, the apparatus set-up was as follows: .4n air blower supplied air under slight pressure which was conducted through a drying chamber filled with anhydrous calcium chloride and then through an orifice meter to measure the rate of flow. From the meter the air was bubbled through 66 per cent nitric acid contained in a flask immersed in a constant-temperature water bath, the temperature of the bath determining the amount of acid picked up by the air. From the acid flask the air was lead to a tee where it was mixed with metered natural gas delivered from a gasometer. The gaseous mixture was then passed through the reaction zone, which consisted of a chrome-nickel steel tube of 2.2 cm. inside diameter, heated for 25 cm. of length in an electric furnace with automatic temperature control. The gases from the reaction zone were immediately conducted to a 60-cm. aluminum condenser where an aqueous solution of formaldehyde and methanol collected. The gases were finally scrubbed in a glass tower filled with beads, down the inside of which mater was allowed to trickle, the gases going in a t the bottom and out a t the top. The formaldehyde in both Condensate and tower washings was analyzed by the hydrogen peroxide method. The natural gas used had the following composition, in per cent by volume: Methane Ethane Illurninants Carbon dioxide Oxygen Nitrogen
11
In the run just described, three more furnaces and reaction tubes were attached to the apparatus with a condenser and scrubber for each furnace so that, after each time the gaseous mixture n-as passed through a reaction zone, it was cooled by the condenser and scrubbed with water. Thus, four condensates and four tower washings were obtained. At the inlet of each of the three additional reaction tubes, an air connection was made, and air, metered and charged with the vapors of nitric acid, was forced into the main gas stream, thus supplying the last three reaction zones with auxiliary air and nitrogen dioxide. One conutant-temperature water bath held all four acid flasks. The last three reaction tubes were of silica (2 cm. diameter) and were heated for 45 em. of length in automatically controlled electric furnaces. The data of a 2-hour run with the four reaction zones in series are shown in Table I, and the condensates in Table 11. T ~ B LI.E RESULTS OF 2 - H o n RUN h-atural-gas flow, cc./min. Air flow No. 1 unit, cc./min. .iir flow No. 2 unit, cc./min. Air flow No. 3 unit, cc./min. Air flow No. 4 unit, cc./min. Temp. of all furnaces ' C. Temp. of acid bath, C. Total natural gas used. liters Total air used, liters Total 6 6 7 , nitric acid used, grams
80.40 16.55 0.60 0.10 0.45 1.90
3100 7250 3550 3550 3550 735 22 372 2148 32.0
T.4BLE 11. CONDENSATE DATA VOL.
UNIT CONDENSATE SP. Grc.5
CHaO
470
CC.
The amount of nitric acid consumed was found by weighing the acid flask before and after the experiment, making correction for any change in the acid concentration due to the passage of the air. Thermal decomposition of the acid traveling through the reaction zone formed the oxides of nitrogen which catalyzed the partial oxidation of the hydrocarbons. In some of the runs silica tubes were used instead of the chrome-nickel steel ones. KO differences in catalysis were noted, but the rate of heat transfer mas greater with the latter. It has been found that, in operating a reaction tube of chrome-nickel steel on a large scale for nianufacturing oxidized oil a t temperatures above 600" C., such alloys do not materially change after operation of more than 7000 hours. For the purpose of computing yields of the process a t 760 mm. pressure and 0" C. temperature, thermometers and pressure gages were placed in the gas and air meters, and the room temperature and barometric pressure were taken during each run. Thirty-one hundred cubic centimeters of natural gas and 7250 cc. of air per minute were passed through this apparatus, the air bubbling through 66 per cent nitric acid a t 22" C. just before it mixed with the natural gas. The temperature of the furnace or the outside of the reaction tube was held a t 735" C. during the run, which was continued for 2 hours. Forty-eight cubic centimeters of condensate (specific gravity 1.052 a t 15" C., and containing 16.83 per cent formaldehyde) were collected from the condenser, and 228 cc. of a weak formaldehyde solution, testing 1.005 specific gravity and 3.0 per cent formaldehyde, were taken from the tower washer. The amount of 66 per cent acid used was 13.5 grams, and the total gas used was 372 liters. The total formaldehyde produced was 15.37 grams. This is equivalent to 41.3 grams of formaldehyde per 1000 liters, or 6.42 pounds of 40 per cent formaldehyde per 1000 cubic feet of natural gas. The ratio of nitrogen dioxide to formaldehyde by weight is 1:2.36, or 1 pound of nitrogen dioxide to 5.9 pounds of 40 per cent formaldehyde.
1 2
48 94 67.5 62.5
3
4 .z
1.052 1.019 1.030 1.023
Grama 8.49 6.94 6.07 4.98
16 83 7.25 8.74 7 80
At 15' C.
Tower washings (1265 cc.) which were collected from the four washing towers had a specific gravity of 1.003 and tested 1.53 per cent, giving 19.41 g r a m of formaldehyde. Thus a total of 45.89 grams of formaldehyde were obtained. This is equal t o 123.3 grams of formaldehyde per 1000 liters, or 19.1 pounds of 40 per cent formaldehyde per 1000 cubic feet of natural gas. The ratio by weight of nitrogen dioxide to formaldehyde is therefore 1:2.97, or 1 pound of nitrogen dioxide gives 7.42 pounds of 40 per cent formaldehyde.
EXPERIMEKT WITH PROFANE A run was made on the first unit of the apparatus described, using a gas containing about 90 per cent propane instead of natural gas; results are s h o m in Table 111. TABLE 111. RESULTSIVITH Time of run, hours Rate of gas flow cc./min. R a t e of air flow,'cc / p i n . Temp. of acid bath, C Temp. of furnace, C. Total pro ane used, liters Total acicfused, grams Vol. of condensate, cc. S gr of condensate a t 15' C Hz0 'in condensate. 7 '" Vol. of tower wash, cc CHz0 in tower wash, yo Total formaldehyde produced, grains
2'
PROP.4n.E
2
1700 8500 25 770 204 11.2 96.5 1.043 15.4 1105 0.96
26.1
From these data it is found that 127.9 grams of formaldehyde are produced per 1000 liters of propane for just a single pass through the reaction zone. This is equal to 19.8 pounds of 40 per cent formaldehyde per 1000 cubic feet. The weight of nitrogen dioxide to formaldehyde here is 1:4.83, or 1 pound of nitrogen dioxide gives 12.07 pounds of 40 per cent formaldehyde.
I N I3 1:. It 1 h
lated from tlie rc?aet.imzone t h m i g h t h o com!erts
