Motor fuel alkylation

The potential advantages of LPG concern essentially the environmental aspects. LPG s are simple mixtures of 3- and 4-carbon-atom hydrocarbons with few contaminants (very low sulfur content). LPG s contain no noxious additives such as lead and their exhaust emissions have little or no toxicity because aromatics are absent. This type of fuel also benefits often enough from a lower taxation. In spite of that, the use of LPG motor fuel remains static in France, if not on a slightly downward trend. There are several reasons for this situation little interest from automobile manufacturers, reluctance on the part of automobile customers, competition in the refining industry for other uses of and fractions, (alkylation, etherification, direct addition into the gasoline pool). However, in 1993 this subject seems to have received more interest (Hublin et al., 1993). 

Refiners will turn to reformulated motor fuels where the octane number will be increased by alkylate or oxygenated compounds. It has indeed been shown for a long time that oxygenated compounds, alcohols, ethers and ketones Improved the octane number of hydrocarbon-based blends (Whitcomb, 1975). 

Sulfuric Acid All lation. The H2SO4 alkylation process was developed during the late 1930s. In the late 1980s, the H2SO4 process accounted for about 50% of the motor fuel alkylate produced worldwide. 

Propjiene [115-07-17, CH2CH=CH2, is perhaps the oldest petrochemical feedstock and is one of the principal light olefins (1) (see Feedstocks). It is used widely as an alkylation (qv) or polymer—ga soline feedstock for octane improvement (see Gasoline and other motor fuels). In addition, large quantities of propylene are used ia plastics as polypropylene, and ia chemicals, eg, acrylonitrile (qv), propylene oxide (qv), 2-propanol, and cumene (qv) (see Olefin POLYMERS,polypropylene Propyl ALCOHOLS). Propylene is produced primarily as a by-product of petroleum (qv) refining and of ethylene (qv) production by steam pyrolysis. 

Although benzene prices have escalated in recent years, a concurrent need for butenes for use in alkylates for motor fuel has also increased and butane prices have also escalated. As a result, a search for alternative feedstocks began and Amoco Chemical Co. commercialized a process in 1977 to produce maleic anhydride from butane. A plant in JoHet came on-stream in 1977 with a capacity of 27,000 t/yr (135,136). No new plants have been built in the United States based on butenes since the commercialization of butane to maleic anhydride technology. In Europe and particularly in Japan, however, where butane is in short supply and needs for butenes as alkylation feed are also much less, butenes may become the dominant feedstock (see Maleic anhydride). 

The term alkylation generally is applied to the acid catalyzed reaction hetween isohutane and various light olefins, and the product is known as the alkylate. Alkylates are the best of all possible motor fuels, having both excellent stability and a high octane number. 

The primary source of lead in the environment has historically been anthropogenic emissions to the atmosphere. In 1984, combustion of leaded gasoline was responsible for approximately 90% of all anthropogenic lead emissions. EPA phased out the use of lead alkyls in gasoline, however, and by 1990, auto emissions accounted for only 33% of the annual lead emissions (EPA 1996h). Use of lead additives in motor fuels was totally banned after December 31, 1995 (EPA 1996f). The ban went into effect on February 2, 1996. Atmospheric deposition is the largest source of lead found in soils. Lead is transferred... 

Another near future objective is to ensure development of technology that enables production of motor-fuel substitutes fhom non petroleum sources. The production of methanol-higher alcohols mixtures fhom natural gas,via syngas, remains a priority objective to obtain octane boosters capable of replacing lead alkyls and to allow the use of additional low-priced methanol. 

Commercial polymerization was once used only for converting the olefins from cracked gases into motor fuel. However, it is rapidly becoming very important in the production of such petrochemicals as heptene, propylene dimer, trimer, tetramer and pentamer and the alkylated aromatics such as ethylbenzene, isopropylbenzene, cymene, and butyl-benzenes. This list may be expected to grow as new uses are found for the heavier olefins. 

Roeseler, C., 2003, UOP AlkyleneTM process for motor fuel alkylation, in Meyers, R. (ed), Handbook of Petroleum Refining Processes, 3rd edn, McGraw-Hill, New York, USA... 

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