Octanal alkylation

Alkylation is used in mariy petroleum refineries to react unsaturated butylenes with isobutane to form high octane iso-octane (alkylate). The reaction is carried out in a two hquid-phase system sutfuric acid/tiydrocarbon. 

The additional advantage of this process is the possibility of the utilization of the alcohol products. fcrf-BuOH (and MTBE, its methyl ether) is used as a gasoline additive. It can be dehydrated to yield isobutylene, which is used to produce high-octane alkylates (see Section 5.5.1). 1-Phenylethanol is dehydrated to styrene over Ti02 on alumina.919... 

Pyridinium poly(hydrogen fluoride) (PPHF), which serves as an HF equivalent catalyst with decreased volatility,159 showed similar characteristics in liquid CO2.158 Other liquid amine poly (hydrogen fluoride) complexes with high (22 1) HF/amine ratios are also effective catalysts in the alkylation of isobutane with butenes and, at the same time, also act as ionic liquid solvents.160 Likewise the solid poly(ethyleneimine)/ HF and poly(4-vinylpyridinium)/HF (1 24) complexes have proved to be efficient catalysts affording excellent yields of high-octane alkylates with research octane numbers up to 94. 

SP-Isoether [SnamProgetti] A process for making an Ao-octane alkylate on a plant designed to make methyl /-butyl ether. It is based on the selective dimerization of isobutylene, followed by hydrogenation to Ao-octanc. Developed by Snamprogetti in 2000. See also Nexoctane. 

One possible advantage of the HF process in propylene/ butylene alkylation is the production of isobutylene from isobutane effected by the hydride-ion transfer to propylene. Isobutylene is the C4 olefinic isomer which produces a significantly higher octane alkylate with HF. This shift, however, converts as much as 22% of the propylene to propane and is a debit. 

Some normal butane is also produced from butylenes but this is estimated at only 4-6%. The higher octane isobutylene alkylate and a claimed yield increase must be contrasted with normal paraffin production from olefins and a higher isobutane requirement. The typical mixed 03 = 704= feed can be made to produce a high octane alkylate with either acid catalyst by the optimization of other variables. The highest alkylate octane numbers reported are produced with sulfuric acid catalyst, alkylating with a typical cat cracker butylene olefin. 

If the octane number of the blend is not high enough, it may be raised by increasing the proportion of high octane alkylate, catalytically reformed product, or aromatics in the blend [27]. Or an antiknock compound may be added to accomplish the same thing inexpensively. Use of tetraethyl, or tetra-methyl lead with other additives, has been discontinued in Canada and the United States for two decades and are now almost phased out in most other areas. When these additives were in common use in leaded gasolines, it took... 

Contact times of over 5 min do not affect the yield, and the octane number is at a slight maximum at a contact time of 15 min. An acid strength of 87.5 per cent gives the maximum octane alkylate, but the balance of the acid phase should be organic. A water content of less than 2 per cent is not very harmful, but octanes are replaced by heavier and lower hydrocarbons as the water content builds up. Fluorine content and olefin content in the alkylate build up in the presence of excess water. 

Owing to the uncertainty in the MTBE market, many new projects are being placed on hold. Some of the existing plants are being modified to produce an alternate product such as alkylate (typically the mixture of branched octanes). Alkylate can be an ideal gasoline blendstock as it has high octane and paraffinic nature. A re-... 

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