248 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1947 



the crude. Heavy hydrocarbons are low in hydrogen-carbon ratio; 

 gasoline is relatively high in this same ratio. The conversion, there- 

 fore, necessitates the throwing out of carbon (coke) as a means of 

 adjustment of this ratio. Catalytic coking, as contrasted with thermal 

 coking, results in less coke "throw-out" for a given conversion, pos- 

 sibly due to the fact that gasolines of relatively high aromatic content 

 have a lower hydrogen-carbon ratio than nonaromatic gasolines, and 

 lower carbon "throw-out" would suffice for the adjustment in hydro- 

 gen-carbon ratio necessitated by this type of conversion. 



Figure 4 is taken directly from the above-mentioned paper.^ This 

 scheme starts with crude petroleum and presents some of the various 

 courses which might be charted in converting this crude oil to gaso- 

 line as the major product, the shaded circles representing positions 

 in a stepwise examination where a stop is made to review ways and 

 means before taking the next step. 



A quick review of this chart shows that the first step for most of 

 the operations in refining crude oil to high octane gasoline, is that in 

 which the hydrocarbon fractions existing in the crude oil as received 

 are changed in molecular structure from chemically stable hydrocar- 

 bons to materials which are chemically reactive and are thus suscepti- 

 ble to synthesis into highly branched chain materials which have been 

 found to have the higher antiknock values. Upon completion of what- 

 ever synthesis methods are used, either thermal cracking, thermal or 

 catalytic dehydrogenation, polymerization, or alkylation the materials 

 thus produced may be satisfactory for blending into motor fuel directly 

 as such, or may require further treatment such as hydrogenation or 

 desulfurization. 



COMBAT-GRADE AVIATION GASOLINE 



In 1939 very few plants were operating dehydrogenation, polymeri- 

 zation, alkylation, or hydrogenation units. During the war the re- 

 quirements for combat-grade aviation gasoline posed a problem in 

 large-scale production of isopentane, iso-octane and the other trimeth- 

 ylpentanes, alkylated aromatics, and carefully fractionated and pre- 

 pared catalytic base stocks to be blended into finished fuel. It was 

 only by tailormaking the fuel in this fashion that the characteristics 

 required by the modern aviation engine could be met completely. The 

 fuel had to be 100 octane under normal cruising conditions, it had to 

 be chemically stable under storage conditions in all parts of the world, 

 and it had to respond with an apparent antiknock value considerably 

 in excess of 100 to permit a heavily loaded plane to take off with maxi- 

 mum power at top supercharge boost pressure and rich mixture 

 conditions. 



» Petroleum-ization — 1940. 



