Gasoline from catalytic cracking

Table II. Aviation Gasoline from Catalytic Cracking and Treating...

The main feedstock for catalytic reforming is heavy gasoline (80 to 180°C) available from primary distillation. If necessary, reforming also converts byproduct gasoline from processes such as visbreaking, coking, hydroconversion and heart cuts from catalytic cracking. 

The isoprene monomer is not readily available from direct cracking processes. Several routes are employed for its synthesis. One route begins with the extraction of isoamylene fractions from catalytically cracked gasoline streams. Isoprene is produced by subsequent catalytic dehydrogenation. 

With the application of DMMC-1 catalyst, the propylene yield is 17.80 wt%, which is higher by 2.43% as compared with the MMC-2 catalyst. The light ends yield increases by 0.64%, and the coke yield decreases by 0.56 wt%. Furthermore, the olefin content of gasoline decreases by 4.5 v%. Thus the worldwide leading position of DCC in propylene production from catalytic cracking has been advanced further. 

Feed stock for the first sulfuric acid alkylation units consisted mainly of butylenes and isobutane obtained originally from thermal cracking and later from catalytic cracking processes. Isobutane was derived from refinery sources and from natural gasoline processing. Isomerization of normal butane to make isobutane was also quite prevalent. Later the olefinic part of the feed stock was expanded to include propylene and amylenes in some cases. When ethylene was required in large quantities for the production of ethylbenzene, propane and butanes were cracked, and later naphtha and gas oils were cracked. This was especially practiced in European countries where the cracking of propane has not been economic. 

A. R. Songip, T. Masuda, H. Kuwahara, and K. Hashimoto, Production of high quality gasoline by catalytic cracking over rare-earth metal exchanged y-type zeolites of heavy oil from waste plastics. Energy and Fuels, 8, 136 (1994). 

Alkylation is a synthetic process in which lower alkenes (from catalytic cracking) are reacted in an acid medium (sulphuric or hydrofluoric acid) with small branched alkanes to produce Cg to Cg branched alkanes. These are probably the most desirable constituents of a gasoline, with good knock resistance and with fewer undesirable properties, such as tendencies to... 

Any mercaptans boiling below 80°C are also readily dissolved in alkaline solutions (Eq. 18.32). A common process for the removal of dissolved mercaptans of this kind, especially from catalytically cracked gasoline and liquefied petroleum gas, is the Universal Oil Products (UOP) Merox process that also uses caustic soda for extraction. In this process, however, the mercaptans are then oxidized to disulfides using air assisted by a metal complex catalyst dissolved in the caustic soda (Eq. 18.34). 

There are two main sources of propylene production— refinery and chemical. The former is derived from catalytic cracking and is used mainly for refinery purposes—i.e., polymer gasoline and alkylate. The latter is derived from ethylene plants and is marketed mainly for petrochemical usage. In both cases, the propylene is a by-product and not a directly manufactured product. In 1963 Davis (19) described propylene as the bargain olefin at 2.25 cents/lb and predicted no shortage in sight. He pointed out that 1962 total domestic refinery derived propylene capacity was 17.1 billion lbs annually, and chemically derived propylene was 3.4 billion lbs annually. All of the propylene cannot be recovered economically. Davis estimated that available propylene amounted to 17 billion lbs, of which chemical uses constituted... 

Isopentane is available in large amounts in C, cuts from catalytic cracking (see Section 2-3.1), and can be produced by n-pentane isomerization. However, since it is widely sought after for the manufacture of gasolines due to its high octane number, this raw material is difficult to secure and costly for petrochemicals. 

BPD plant which came on stream in April, 1937. The successful operation of these plants led Sun and Socony-Vacuum to build more than ten plants during the next four years, and for Houdry Process Corp. (HPC) to license to other companies. During the first two years of WWII about 90% of the aviation gasoline was obtained from catalytic cracking in 24 Houdry plants charging a total of 330,000 barrels a day. By 1944, there were 29 units in operation, with a capacity of 375,000 barrels a day, and by 1947 there were 37 licensed units. 

Table 3.18 Composition of a gasoline fraction from catalytic cracking on aluminum oxide and zeolite catalysts...

About 95% of toluene is obtained from the refinery catalytic reforming of naphtha feedstocks in what are called reformers. About 5% is obtained from pyrolysis gasoline from steam cracking of hydrocarbons associated with ethylene and propylene. 

In the 1970 s, heavy fuel came mainly from atmospheric distillation residue. Nowadays a very large proportion of this product is vacuum distilled and the distillate obtained is fed to conversion units such as catalytic cracking, visbreaking and cokers. These produce lighter products —gas and gasoline— but also very heavy components, that are viscous and have high contaminant levels, that are subsequently incorporated in the fuels. 

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