470 



THE INDIA RUBBER WORLD 



[June 1, 1916. 



Now that fries of s 

 hensol is partii-uLirly li 

 tcrly of Ihc Satural F\ 

 Pennsylvaiiiii. 



The Commercial Production of Benzol. 



olz'ciits used 

 ncly and i/i/, 

 r<- Prolcrtiz;- 



uhbcr industry have i:rcatly advanced, the follawin:^ account 



It is summarised from a co>nfrehensive article by J. Alben 



ition." The illustrations are from flants erected by the H . 



of the manufacture of 

 Robinson, in the "Quar- 

 Kopt>ers Co., Pittsburgh, 



BENZOL recovery, from coal gas residuals of gas works and 

 the liy-product coke ovens, has become a great industry new 

 to this country, on a scale of real commercial importance. 

 The recovery of the valuable by-products, such as tar and other 

 residuals, and the extraction from the gas itself of ammonia 

 and benzol has proved a source iif great revenue to the coal 



Battery of 56 Koppers By-Product Coke Ovens. 



gas producer, and this business has become a very important 

 agent for the conservation of a great natural resource. 



Owing to the custom of candle power standard, instead of the 

 scientific method of heat value standard, most of the benzol 

 recovered at the present time is from by-product coke-oven gas. 



COAL TAR. 



Coal tar is the oily mixture which separates from the gases 

 formed in the destructive distillation of coal. The raw tar is 

 composed of light oils, pyridine bases, phenols, naphthalene, 

 anthracene, heavy oils, pitch ; also materials insoluble in benzene, 

 such as free carbon, water, ammonia and dissolved constituents 

 of the gas. It varies greatly in composition, and may be di- 

 vided into retort gas tar and oven gas tar. 



Retort Gas Tar. — The retort gas tar is obtained as a con- 

 densation product in the hydraulic mains, scrubbers or con- 

 densers in the manufacture of coal gas for illuminating purposes. 



Oven Gas Tar.— This material is obtained in the distillation 

 of coal in retort or by-product coke ovens. It is similar to gas 

 tar, but is more fluid. It contains more of the hydrocarbons, 

 and considerably less free carbon. 



One ton of good gas coal yields about 10,000 cubic feet of 

 gas, 1,400 pounds of coke, and 120 pounds, or 20 gallons, of 

 tar. Not over 2 per cent of this tar consists of benzol, while 

 2 gallons of benzol may be recovered from the gas given ofif 

 from the same amount of coal. It is estimated that benzol is 

 now being produced at the rate of 15,000,000 gallons a year in 

 the large steel works alone, an amount five times greater than 

 before the war. 



Pure benzol, or benzene, has the formula C.H«. A similar 

 product of the same formula is found in crude petroleum, and 

 is known as benzine. The distinction in spelling should be noted. 



Commercially, benzol is known as 50 per cent, 90 per cent and 

 100 per cent benzol, these consisting mainly of benzene and 

 toluene, with small amounts of xylene. This percentage does 

 not indicate the comparative purity of the materials, but merely 



the amount distilling at 212 degrees F. The lower boiling benzols 



have the following approximate composition : 



Benzols. 100% 90% 50% 



Beiuere 94—97% 80—85% 40— 507c 



Toluene 2—6% 10—20% 30—60% 



Xylene 0—1% 0-5% 0—25% 



In general, the use of all grades of benzol has been for sol- 

 vents. They are excellent solvents for gums, resins, greases, 

 rubber, etc., and it is mainly upon the wide and varied solvent 

 power of benzol that their commercial utilization has rested. 



The present impetus has been given the industry for the pro- 

 duction of explosives. Aniline oil and synthetic carbolic acid 

 have been manufactured in this country in a small way for 

 technical purposes. 



It is thought that benzol will find a. ready market as an auto- 

 mobile fuel after the war. Experiments for automobile purposes 

 show that benzol has a motive power about 25 per cent better 

 than gasolene ; consequently it would have that advantage at 

 the same price. With the present immense production of benzol, 

 the cost has been reduced so that it could actually be produced 



now, and sold at the same price as gasolene if it were necessary 

 to do so. The use of gasolene for automobile fuel is so large 

 (100,000,000 gallons per year) that it is with difficulty that the 

 oil companies are able to produce enough to meet the demand. 

 METHODS OF RECOVERY OF DENZOL. 

 The recovery of benzol, etc., from gas is carried out in two 

 principal steps : Scrubbing or washing, and extracting or re- 

 covering. 



