March 10, 1933
INDUSTRIAL
AND
ENGINEERING
CHEMISTRY
63
Organic Compounds from Coke-Oven Gas C. H. S. TUPHOLME, 3 2 , Russel Hill, Purley, Surrey, England W I T H THE DEVELOPMENT in synthetic ammonia processes and the interest being shown in the possibilities of hydrogénation, coke-oven gas, until quite lately, it is feared, regarded as more or less of a by-product, has become quite valuable. In Britain, comparatively little work, outside of the well-known Billingham plant of Imperial Chemical Industries, has been done to utilize coke-oven gas except for fuel, either alone or in admixture with manufactured gas. On the Continent, however, quite a number of plants are employing coke-oven gas for the production of organic compounds, and some brief details of the more interesting European plants were described by Osterrieth and Deschamps in a discussion before the British Institute of Fuel on January 11. The Claude and Linde processes are too well known t o merit extended description. At the plant of the Société Γ Air Liquide, for example, a plant is installed for treating 350;OO0 cu. ft. of purified coke-oven gas per hour. The accompanying sketch is a simplified diagram of the process adopted. This plant consists essentially of a nest of tubes, in which compressed coke-oven gas is cooled in contact with gas expanded after fractionation. As the compressed gas cools, condensates are formed at certain points. First, the liquefaction of ethylene and similar products occurs. After that, gases are liquefied which consist principally of methane, and finally, gases rich in carbon monoxide and nitro gen are obtained. Tne evaporation of these liquids at low pres sure cools the coke-oven gas sufficiently to condense the heaviest constituents, so that ultimately only hydrogen, containing a little carbon monoxide and nitrogen, remains in the gaseous phase. It is sufficient to wash the hydrogen with liquid nitrogen, as first demonstrated by Professor Maxted, of Cambridge Uni versity, in order to remove the remaining carbon monoxide. The purified hydrogen passes to an expansion engine driving a com pressor, after which it is heated again to atmospheric tempera tures by the compressed coke-oven gas in the liquefaction plant. At first the expanded gases, other than hydrogen, were returned through one and the same pipe line as rich gas, which was valued only on a calorific power basis. With the perfection of the liquefaction plants, gases were obtained as by-products whose composition made them eminently suitable for the synthesis of compounds other than ammonia. The original coke-oven gas upon analysis showed the following composition: H 2 , 61 per cent; CH 4 , 24 per cent; C n H 2 n, 2 per cent; and CO, δ per cent. From this gas are obtained hourly 218,500 cu, ft. of H 2 , containing 11 per cent N 2 ; 4410 cu. ft. of gas containing 33 per cent CO, 40 per cent N 2 , 10 per cent CH 4 , and 17 per cent H 2 + 0 2 ; 135,700 cu. ft. of gas containing 60 per cent CH 4 , 13 per cent H 2 , 12 per cent CO, and 2 per cent of other gases; 8820 cu. ft. of gas, rich in ethylene, containing 60 per cent olefins and 35 per cent C2H6. Like all gases derived from coke-oven gas which has had only a preliminary purification, these gases contain sulfur and other impurities which may be harmful to catalysts. As they are, however, eminently suitable as raw materials for t h e synthesis of organic products, work undertaken on these gases led t o the de velopment of new manufacturing processes using somewhat im pure raw materials. The gas rich in CO coming from the hydrogen piano is diluted with hydrogen, and the mixture has the following composition: CO, 8 per cent; N 2 , 18 per cent; H 2 , 71.5 per cent; and CH 4 , 2.5 per cent. Of this mixture 176,500 cu. ft. are obtained from 350,000 cu. ft. of coke-oven gas, and 208,750 cu. ft. of H 2 remain for ammonia synthesis by the usual process. T h e efficiency of conversion of the CO to methanol is about 80 per cent, the un converted CO being transformed into CH 4 in the purifier tube, preceding the ammonia synthesis. Several other industrial installations were then described by Osterrieth and Deschamps. The Gesellschaft fur Kohlentechnik at Dortmund-Ewing uses purified coke-oven gas as its raw material in order t o obtain mix tures rich in hydrogen, the production of pure hydrogen being the main objective. A mixture of hydrogen and nitrogen (3H2 + N Î ) for ammonia synthesis is produced incidentally. T h e process developed by this concern converts all the C H 4 with water vapor, any CO formed being converted into CO2 and then removed by absorption. The Société Courrières Kuhlmann has had the synthesis of methanol in view and produces a mixture of 33 per cent CO and 66 per cent H2. Coke-oven gas is used as the raw material, and conversion is obtained by the endothermic reaction CH 4 + H 2 0 = CO + 3H 2 The Société d'Ougrée-Marihaye, according to Osterrieth and Deschamps, produces economically a gas which is suitable for the successive synthesis of methanol and ammonia. At first a gas rich in methane, obtained from the hydrogen plant, was used; later purified coke-oven gas was employed so that the liquefaction could be omitted.
I t is necessary at Ougrée to produce a gas in chemical equilibrium having a CO content of 10 to 12 per cent. Several reasons require such a composition: first, the desire t o obtain an appreciable yield of methanol, without causing the production of ammonia to suffer; second, the fact that the higher the concentration of CO, the lower t h e Na content and consequently the greater the addition of 0 2 to the air used. The reaction is strongly exothermic, and excess of inert gases facilitates tiie removal of the heat liberated and eliminates side reactions and other drawbacks caused by the packing of the tubes. NoC0MR
OAZ. C0MP
C£H4
CH4
APPAREIL A HYDROGENE-PRINCIPE DE FONCTIONNEMENT The cracking plant used by this concern is very simple, i t consists essentially of a reaction chamber made of fire brick, where the purified and preheated coke-oven gas, after the addition of water vapor, is burnt in contact with air charged with O», after which it enters a metal heat interchanger at a high temperature. As the gas still contains some CH 4 at the outlet of the reaction chamber, it passes over a suitable catalyst when still at a high temperature, whereby the conversion is completed. After passage through the heat interchanges the gas is scrubbed and stored in a holder. As a result of the catalyst employed, it is possible to reduce the reaction temperatures to about 800° C , s o that heat interchanges constructed of special metal can b e used, which work continuously and eliminate completely the risk of explosion. The plant functions perfectly and works for more than 1000 hours without requiring inspection or replacement of the catalyst. The process of the Société d'Ougrée-Marihaye produces a cracked gas entirely free from small carbon particles, which can be used immediately for t b e synthesis. T h e gas contains less than one per cent CH 4 and a quantity of CO, easily adj usted by the addition of a small supplementary plant, which converts all or part of the CO into C0 2 , s o that the same plant can be used for the production of gas (N 2 + 3H 2 ) for the ammonia syathesis» The removal of the CO a takes place in the main compressor plant, between two stages of the final compressors. The residual gas from the synthesis returns to the cracking chambers and is used again. At the plant of the Société Franco-Belge d'Ougrée. g a s rich in CH 4 is preheated to a temperature of 800° C. in t h e presence of water vapor, before being admitted to the reaction chamber. The part played by the water vapor is that of preventing the formation of carbon, both during the preheating stage and the pyrolysis. The high instantaneous temperatures which are necessary for the conversion of methane into acetylene are obtained by the injection of a predetermined quantity of O* into the reaction chamber, where i t combines with a part of th.e CH 4 , forming C 0 2 and CO. Under these conditions the process operates with the volumetric velocity to t h e order of ΙΟΟ,ΟΟυ, so that at a temperature of about 1600° C. a gas up to 8 per cent of acetylene is obtained. From 35 to 40 per cent of the methane is thus converted into acetylene, and practically ail of the remain ing methane is converted into carbon dioxide, carbon monoxide, and hydrogen. After the extraction of acetylene and carbon monoxide by the usual methods, a gas is available which can be used directly for the synthesis of methanol. In the practical application of the process, serious difficulties had to be overcome, arising from the high temperatures used. Heat interchangers and reaction chambers had to b e constructed of suitable material, and systematic studies undertaken. As regards the employment of gas rich in ethylene, th.e Com pagnie de Béthune has carried out much original research work on the absorption efficiency, prevention of pitch formation, and regulation of temperatures. The process as it exists in practice consists of three successive operations. First, there i s the absorption of the gas, which is (Continued on page 70)
70
NEWS
E R I E SECTION C E L E B R A T E S T E N T H THE
ERIE
SECTION
of
the
EDITION
ANNIVERSARY
AMERICAN CHEMICAL
SOCIETY
celebrated its tenth anniversary, February 2 1 , with a birthday party a t the University Club in Erie. Thirty-five members attended the dinner and about thirty more joined t h e group later for the entertainment. Paul H. Henkel, of t h e Continental Rubber Co., who was the first chairman of the section, told of t h e development of the organization from the days of the old Erie Chemists' Club until its affiliation with the AMERICAN CHEMICAL SOCIETY ten years
ago. A group of Erie chemists who realized t h e value of fellowship and the exchange of ideas among members of t h e profession, sent out a call for an organization meeting t o be held June 28, 1922. Fourteen men attended and nine more were interested but could not come. These men formed t h e Erie Chemists' Club as a temporary expedient until the requirements for a section charter could be met. As an indication of the value they placed on the association, they assessed themselves six dollars apiece for dues. The club met throughout t h e summer of 1922. The petition for a charter was presented a t the 1923 spring meeting of the AMERICAN CHEMICAL SOCIETY in New
Haven,
and
the Erie Section was established with the following first officers: Chairman, Paul H. Henkel; Vice Chair?na7i, Bjarne Johnsen; Secretary-Treasurer, M. A. KrimmeL The birthday entertainment continued as a burlesque of the regular type of meeting, with W . F. Reichert, of the Viscose Co., Meadville, acting as chairman, and H. V. Strong as secretary. The distinguished speaker of t h e evening was Professor Vacuum, assisted by Herr Tonic of the University of Pinaud. These parts were played by Ralph Eisenberg and George Eacey, students at the Pitt Center. The subject of their discourse was "Water, the Colorless, Tasteless, Odorless Liquid." Many amazing demonstrations of these properties were presented, but no one was injured. The gathering then adjourned to t h e bowling alleys, pool table, and other amusements. Exhibits of t h e products of the Erie chemical industries were interestingly displayed and explained by representatives of the Hammermill Paper Co., Continental Rubber Co., Perry Furnace Co., American Cyanamid and Chemical Co., H . F. Watson Mills, General Electric Co., Metric Metal Works, Keystone Laboratories, and Evans Laboratories. The concluding event w a s the cutting of the large birthday cake by R. E . Lee, of Allegheny College, and the serving of a buffet supper. "Science N e w s of the Week" is broadcast every Wednesday a t 8 P. M. by the Erie Section over Station W L B W , Erie. We hope you listen in.
Vol. 11, N o . 5 Dow
SCRIP
W H E N THE bank holiday was initiated recently in Michigan, the D o w Chemical Co. sougïit to relieve the otherwise bad credit situation in Midland hy preparing to issue its own scrip to employees. We reproduce here a token of JDowmetal, „ 0> ^ „ ^ oN\ J guaranteed b y the company to b e re&&• - J ^ deemable by them on or before March 1, 1933, at 2 0 cents. Howe-ver, before the issuance of t h e token r the local bank was able to make suL
