Mar.,
1920
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Original Material Crude Benzoic Air-dried Material Acid Per Per cent cent 41.2 3.5
Moisture. . . . . . . . . . . . Acidity expressed as benzoic acid. ............ 5 2 . 1 Totalchlorine . . . . . . . . . . 4.45 Monochtorobenzoic acid, from total chlorine minus side-chain chlorine 14. l Benzoic acid by di5erence, total acidity minus monochlorobenzoic acid 6 8 . 0 Chlorine in side-chain. . . 1.25
79.0 5.46
79'
TABLE111-ANALYTICALDATA Run 2 (Made Run 1 (Made with crude material) with crude material) Run 3 (Made with air-dried material) ChamChamChambers 2, ChamChambers 3 ChamChamChamResidue ber 1 3, and 4 Residue ber 1 ber 2 and 4 Residue her 2 ber 3 ber 1 Per Per Per Per Per Per Per Per Per Per Per cent cent cent cent cent cent cent cent cent cent cent
...............
.......................................
97.2 1.48
93.5 1.51
56.6 8.28
.....
......................................
97.4 1.49
...............
.................... ....................
maintain a temperature gradient in a remarkably constant manner, t h e moving stream of gases losing its heat gradually on passing through t h e orifices. The drop in temperature is sharp at t h e screens. The screens, or orifices, afford condensing surfaces, greatly facilitating t h e formation of large crystals. Though t h e screens have every appearance of acting as sieves, this is not their function, for t h e large size of t h e mesh prohibits such action. The crystallization seems t o be due t o t h e sudden drop of temperat u r e of t h e gases on passing through t h e orifices, t h e metal screens acting as conductors of heat. It is reasonable t o expect a large scale apparatus t o produce better results t h a n t h e small laboratory experiments, since sublimations in general are better conducted on a large scale. It is t o be noted t h a t t h e product obtained in R u n 3, Chamber 2 , from a very impure crude benzoic acid, was almost free of chloro-derivatives and a very pure benzoic acid resulted, t h e principal foreign substance present being about 4 per cent of water. THE MANUFACTURE OF PHENOL IN A CONTINUOUS HIGH PRESSURE AUTOCLAVE By Kirk Brown CONDENSITE CO. O F AMERICA, BLOOMFIELD. N. J . Received September 9. 1919
Although condensite, a phenolic condensation product, and halowax, a chlorine substitution product, are t h e best known inventions of t h e late J. W. Aylsworth, they were b u t two of many that he produced in his short b u t fruitful life. The last work t o which Aylsworth addressed himself before his untimely death in 1917 was t h e development of a continuous high pressure autoc1ave.l Although many chemical reactions can be carried o u t with a great economy of time and material if conducted under high pressure and temperature, very little work of this character has been done except i n laboratories on account of t h e difficulty and expense of producing, and t h e danger of operating, apparatus of t h e usual design involving t h e use of high temperatures and of pressures u p t o several thousand pounds per square inch. DESCRIPTION O F AUTOCLAVE
The Aylsworth continuous autoclave consists essentially of a heated coil through which t h e reacting fluids are forced by means of pumps. The practicability of this apparatus depends very largely on t h e 'U.S . Patent 1,213,143.
2
94.7 2 53
95.5 1.02
65.0 8.49
95.1 1.65
95.5 0.34
95.5 0.34
60.9 7.92
........................................ ........................................ heating medium in which t h e reacting coil is immersed. If a liquid is used t h a t must be p u t under pressure in. order t o attain t h e desired temperature, t h e apparatus. must be heavily constructed a n d will cost correspondingly, and not be free from danger of explosion.. Fusible metals can be used b u t have certain objectionable features, as have hot gases or vapor. A satisfactory medium should readily transmit heat b y conduction; should be thinly fluid a t t h e temperatures. of operation so t h a t it will circulate freely, t h u s transmitting heat b y convection; should have a boiling point higher t h a n t h e temperature t o which the. reacting materials are t o be subjected, so t h a t i t need not be used under pressure; and should not attack metals, volatilize readily, or decompose. Nitrite of soda was found t o fulfill these conditions, its melting point being 415' F., and its boiling point 7 3 4 O F. According t o t h e description given in t h e literature, this substance decomposes a t temperatures. above its melting point, b u t baths have been maintained continuously a t and above t h e boiling point for a number of weeks without t h e least evidence of decomposition. M A N U F A C T U R E O F PHENOL
In t h e manufacture of phenol from chlorobenzene i n this autoclave, one t a n k contained t h e chlorobenzene and another t h e sodium hydroxide solution; t h e pump had two plungers of such relative size as t o feed t h e required quantity of each of these liquids. This arrangement permitted t h e use of different packings, rubber for t h e alkali solution and leather for t h e chlorobenzene, thus avoiding t h e difficulty of providing a packing t h a t would be attacked b y neither. The reacting ingredients, under a pressure of 2 5 0 0 , t o 3000 lbs. per sq. in., were forced through a coil of extra heavy hydraulic pipe which was maintained a t a temperature of 700' F. by a b a t h of nitrite of soda. The sodium phenylate thus formed was permitted t o pass from t h e coil by a needle valve, the opening of which was so regulated as t o maintain t h e proper pressure in t h e coil. This was only a question of proportion between t h e capacity of t h e pump and t h e area of t h e opening of t h e needle valve, and the t i m e of passage through t h e coil of t h e reacting ingredients.. From the coil, t h e sodium phenylate passed directly t o a condenser where i t was condensed; i t was t h e n acidified with hydrochloric acid and t h e resultant crude phenol distilled. The writer has seen crude phenol produced in this manner in 1 5 min., t h e reaction proper taking b u t a fraction of t h a t time. The entire process is simplicity itself; t h e apparatus
280
T B E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
much less in size and cost, a n d in space occupied, t h a n t h a t necessary in a n y other system used in t h e manufacture of phenol, a n d doubtless this s,,atement applies with equal force t o t h e manufacture of many other substances. Crude diphenyl ether, for example, was produced in t h e same manner a n d in almost t h e same time. At the time of Aylsworth's death, development work on the production of phenol had not proceeded far enough to say with certainty what proportion t h e final product would bear t o the materials used, b u t there is little waste involved, for t h e unreacted materials can be recovered and again passed through the apparatus, a n d their quantity controlled b y t h e time they are under reacting conditions, and this in t u r n by t h e size of t h e apparatus and t h e proportionate time used. Theoretically, one pound of benzene should produce one pound of phenol. Moreover, the salt required t o prepare t h e electrolytic chlorine used in t h e reaction is again formed, and could be recovered. Possibly, also, t h e hydrogen used in t h e electrolytic process might be used t o furnish p a r t of t h e heat for the reaction. A I O O per cent production, cf course, is not possible, as there are unavoidable wastes in t h e electrolytic process a n d in t h e chlorination of t h e benzene, and also a very small loss in t h e conversion of chlorobenzene t o phenol. C O M P A R I S O N OF METHODS
Many methods of synthetic phenol manufacture have been developed.' A brief description of one method is given herewith for comparison with t h e Aylsworth process. T h e ordinary method is as follows: I-A mixture of sulfuric acid and benzene is allowed to react for 18 or 2 0 hrs. Benzenesulfonic acid is formed to the extent of about 60 per cent of the sulfuric acid taken. By the addition of oleum, containing 25 per cent sulfuric anhydride, to the diluted acid, more benzene is sulfonated, giving a total efficiency of about 80 per cent of the total sulfuric acid. 2-The benzenesulfonic acid is separated from excess sulfuric acid by treatment with lime. After filtering from calcium sulfate, the calcium benzenesulfonate is converted into the sodium salt by treatment with sodium carbonate. A considerable loss of the sodium salt occurs in the removal of calcium carbonate in a filter press. 3-The sodium benzenesulfonate is next evaporated to dryness, usually with multiple-effect evaporators. 4-It is then converted to sodium phenylate by fusion with an excess (about 75 per cent) of the theoretical molecular proportions of caustic soda. This excess is generally wasted, though it can be recovered economically when caustic is high in price by an elaborate apparatus, as described further on. 5-The fused mass is entirely dissolved in water and the solution is neutralized with acid, and allowed to stand while the phenol separates out. The latter is drawn off and distilled, and the balance of the solution (containing some phenol) is thrown away, but the sulfite of soda may be recovered i f desired. Losses occur in distillation.
The Aylsworth
method consists
Of
the
steps: 1 Mer.
12,
No. 3
I-Chlorobenzene a n d caustic soda react t o produce sodium phenylate a n d salt. 2-The sodium phenylate a n d salt are neutralized with hydrochloric acid a n d t h e crude phenol and salt solution allowed t o separate by settling. 3-By blowing steam through the salt solution a n additional quantity of phenol is recovered. T h e difference in t h e two methods is evident a t a glance a n d as each step is carried o u t in a different unit of apparatus, t h e smaller size of t h e plant as a whole in t h e case of the Aylsworth method is also apparent. Not only is there less apparatus, b u t in nearly each instance t h e units of t h e Aylsworth apparatus are smaller because of the greater rapidity with which t h e work is done, t h u s making possible important economies in time, labor, floor space, capital investment, etc.; a cheaper acid is used a n d only about 5 per cent of t h e quantity, and about 40 per cent of t h e amount of caustic soda.
AN ELECTRIC HEATER FOR THE COAL-TAR NAPHTHA DISTILLATION TEST By J. Bennett Hill and Richard B. Chillas H. W. JAYNB LABORATORY, THBBARRBTT Co., FRANKFORD, PHILADBLPHIA, PA. Received October 29, 1919
T h e control of t h e plant operation of fractional distillation processes, particularly in t h e distillation of coal-tar naphthas, is generally carried out by observing t h e distillation range of samples of t h e distillate taken as it runs off t h e still. For this purpose the commonly used method is the distillation test, somewhat similar t o t h e petroleum distillation method, a n d recently fully described by Weiss.' On account of t h e fact t h a t this method requires t h e use of a gas flame, which in a benzol plant would be out of t h e question on account of t h e fire risk, i t is necessary t o send t h e samples t o t h e laboratory t o be tested. I t would generally be not only much more convenient but also more economical t o have them made on t h e spot. I n order t o avoid t h e risk of t h e flame, we have used a steam heater t o a considerable extent in our benzol plant in carrying out the distillation tests. This device was, however, open t o two objections: first, t h a t t h e heating conditions of t h e flask were so decidedly different from those obtained with gas heating t h a t the results were different, and, second, t h a t only low boiling liquids could be tested. This paper describes a n electric heating method which eliminates t h e fire risk a n d a t t h e same time gives results identical with those obtained in t h e laboratory, using a gas flame. Another type of electrical heater for distillation tests has recently been developed by t h e Bureau of Mines,2 t h e idea of this being, however, t o provide a cleaner a n d more nearly uniform heat rather t h a n t o cut down fire risk. A heater such as this with exposed hot wires could not be used in a building where inflammable vapors are present. T h e heater selected for this work was a n electrically 1
Chem. Eng., 13 (lbls), 686-690; 15 (1916). 185-192.
Vol.
2
THISJOURNAL, 10 (1918), 1006. E.W.Dean, Ibid., 10 (L918),823.
