Methyl tert-butyl ether , octane

The other large-scale ethanol user is the USA, where ethanol has been used to increase the octane rating of gasoline, to decrease carbon monoxide emissions, and, more recently, to replace MTBE (methyl tert-butyl ether) in reformulated gasoline. Ethanol production in the USA grew from about 0.6 billion liters in 1980 to... 

Mixed C4 olefins (primarily iC4) are isolated from a mixed C olefin and paraffin stream. Two different liquid adsorption high-purity C olefin processes exist the C4 Olex process for producing isobutylene (iCf ) and the Sorbutene process for producing butene-1. Isobutylene has been used in alcohol synthesis and the production of methyl tert-butyl ether (MTBE) and isooctane, both of which improve octane of gasoHne. Commercial 1-butene is used in the manufacture of both hnear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE)., polypropylene, polybutene, butylene oxide and the C4 solvents secondary butyl alcohol (SBA) and methyl ethyl ketone (MEK). While the C4 Olex process has been commercially demonstrated, the Sorbutene process has only been demonstrated on a pilot scale. 

Butane isomerization is usually carried out to have a source of isobutane which is often reacted with C3-C5 olefins to produce alkylate, a high octane blending gasoline [13]. An additional use for isobutane was to feed dehydrogenation units to make isobutene for methyl tert-butyl ether (MTBE) production, but since the phaseout of MTBE as an oxygenate additive for gasoline, this process has decHned in importance. Zeolitic catalysts have not yet been used industriaUy for this transformation though they have been heavily studied (Table 12.1). 

Olefins, unlike paraffins, do not show significant gains in octane number with skeletal isomerization (see Table 14.2). As a result, olefin isomerization is not a useful octane boosting strategy. However, tertiary olefins (olefins with three alkyl substituents on the double bond), do react fairly readily with olefins to form ethers, which do have good octane numbers-for example, methyl tert-butyl ether (MTBE). 

Isomerization. Isomerization is a catalytic process which converts normal paraffins to isoparaffins. The feed is usually light virgin naphtha and the catalyst platinum on an alumina or Zeolite base. Octanes may be increased by over 30 numbers when normal pentane and normal hexane are isomerized. Another beneficial reaction that occurs is that any benzene in the feed is converted to cyclohexane. Although isomerization produces high quality blendstocks, it is also used to produce feeds for alkylation and etherification processes. Normal butane, which is generally in excess in the refinery slate because of RVP concerns, can be isomerized and then converted to alkylate or to methyl tert-butyl ether (MTBE) with a small increase in octane and a large decrease in RVP. 

For instance, methyl tert-butyl ether (MTBE) used worldwide as an octane improver in gasoline is produced at a still growing global capacity of approx. 8 million mt/yr using sulfonated resins as catalysts (ref. 1). 

Methyl f erf-butyl ether (MTBE, C5H120), a substance used as an octane booster in gasoline, can be made by reaction of isobutylene (C4H8) with methanol (CH40). What is the percent yield of the reaction if 32.8 g of methyl tert-butyl ether is obtained from reaction of 26.3 g of isobutylene with sufficient methanol ... 

Aqueous samples are extracted with methylene chloride using a separatory funnel or a continuous liquid-liquid extractor. Solid samples are extracted with methylene chloride-acetone mixture (1 1) by either sonication or Soxhlett extraction. The methylene chloride extract should be finally exchanged to hexane or iso-octane or methyl tert-butyl ether. The latter solvents should be mixed with acetone during solvent exchange. The extracts should then be cleaned up by Florisil. Often Florisil cleanup reduces the percent recovery of analyte to less than 85%. A preliminary screening of the extract should, therefore, be done to determine the presence of interference and the necessity of florisil cleanup. Gel permeation cleanup also lowers the analyte recovery and thus is not recommended. If a FPD is used in the GC analysis, the presence of elemental sulfur can mask the analyte peaks. In such a case, sulfur cleanup should be performed. Sample extraction and cleanup procedures are described in Chapter 1.5. 

The use of a fuel with a high octane rating is essential in preventing detonation. The quality of the fuel is controlled by the ratio in which different components are blended, and by addition of additives such as methyl tert-butyl ether (MTBE). Although aromatics and olefins increase the octane number, environmental... 

The octane number (.R + M/2) of such reformates is typically in the range of 88.9—94.5, depending on severity of the reforming operation. Toluene itself has a blending octane number of 103—106, which, as shown in Table 19, is exceeded only by oxygenated compounds such as methyl tert-butyl ether, ethanol, and methanol. 

Fig. 1. Ultraviolet absorption of solvents (HPLC grade unless otherwise stated). A, acetonitrile (far-UV grade) B, methyl tert-butyl ether C, acetonitrile D, 1-chlorobutane E, methylene chloride F, acetic acid (AR grade) G, ethyl acetate H, acetone I, hexane J, iso-octane K, methanol L, tetrahydro-furan M, chloroform N, diethylamine (ARgrade).

The importance of isobutylene in the petrochemical industry is well recognized. Isobutylene is used on a large scale for the production of (i) methacrolein by direct oxidation, (ii) polyisobutylene by polymerization, (iii) synthetic rubber (a copolymer of isobutylene and isoprene), and (iv) methyl tert-butyl ether (MTBE, a gasoline octane-number enhancer) by reaction with methanol. 

Because of the reformulated gasoline program introduced by the U.S. government to amend the Clean Air Act in 1990 to reduce emissions from vehicles, oxygenates such as MTBE, ethyl-tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME) were favored as some of the components to increase the octane number of gasoline. In 2002, there were over 60 MTBE units and 10 TAME units worldwide. Methyl-tert-butyl ether is now phased out in California and possibly banned in the United States nationwide because of its discovery in groundwater. Nevertheless, the experience gained from the successful application of CD for the production of... 

At present, glycerol alkyl ethers, especially GTBEs, are of particular interest, because the higher ethers (h-GTBEs) can be used as octane boosters in automotive fuels analogously to methyl tert-butyl ether (MTBE), but they do not exhibit the same environmental problems. Glycerol can be converted with isobutene [47-49] or with tert-butanol [50] to the desired fuel additives (Scheme 3.6). When using on tert-butanol, water is a by-product and must be removed. 

The light alkenes (propene, butene and pentene) are important feedstocks for alkylation, oligomerization and the synthesis of ethers (refs. 1,2). MTBE (methyl tert-butyl ether) and TAME (tert-amyl methyl ether) have research octane numbers of 118 and 112 respectively. These premium blend stocks are synthesised by reaction of methanol with isobutene or isopentene (refs. 3,4). The reaction with methanol is selective towards the branched alkenes so that a mixture may be treated and the straight chain alkenes recovered for other processing such as alkylation. 

Application The Snamprogetti Etherification Technology allows producing high-octane oxygenates compounds such as methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), tert-amyl ethyl ether (TAEE) and etherified light cracked naphtha (ELCN). 

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