Typical light ends

The zinc oxide component of the catalyst serves to maintain the activity and surface area of the copper sites, and additionally helps to reduce light ends by-product formation. Selectivity is better than 99%, with typical impurities being ethers, esters, aldehydes, ketones, higher alcohols, and waxes. The alumina portion of the catalyst primarily serves as a support. 

Equipment. A three-neck distillation flask was used as a reactor. In a typical run, the flask was charged with waste oil and demetallizing reagents. The content was agitated and heated by a mechanical stirrer and heating mantle respectively. The reaction was carried out at atmospheric pressure, and water vapor and light ends were condensed and collected during the process. Oil was filtered immediately after the reaction by means of a vacuum filteration system, or allowed to settle down at constant temperature for a sedimentation study. 

After the condensed crude methanol is recovered in the high-pressure separator, it is sent to a methanol purification column. Typically, methanol purification requires two columns, one to remove the light ends (mainly by-products generated in the methanol synthesis reactor such as dimethyl ether and dissolved gases) and another to separate methanol and water and any other by-products with a lower volatility than methanol. Specification-grade methanol (greater than 99.85 wl% methanol) is recovered as the overhead product of the heavy ends column and sent to storage. 

Figure 5 is a diagram of a typical delayed coker, including the distillation tower and light ends section. The feedstock is preheated using some of the heavy and light gas-oil product streams. It then enters the lower portion of the fractionation tower, above the point where the product vapors from the coke drums enter the tower. This introduction of the... 

Depending on the feed composition, Saipem offers different possible processing schemes. In a typical configuration, the feed is sent to the first column (1) where the heavy hydrocarbons (mainly n-butane and butene-2) are removed as the bottom stream. In the second column, (2) the butene-1 is recovered at the bottom and the light ends (mainly isobutane) are removed as overhead stream. 

The flowsheet in Fig. 4.2 shows a typical distillation system which may be used to describe the process reactions and main characteristics of the equipment used. In addition to dimethyl ether, methyl formiate, acetone and hydrocarbons up to about Cg, the low boilers in a broader sense include also that part of the gases dissolved in the raw methanol which is not expelled when this is flashed into an interim storage tank. This flashing operation is normally performed at pressures between 5-10 bar in order to keep methanol losses down, but frequently also in order to ensiure that the raw methanol can be transferred to the light ends column without using a pump. 

There are two fresh feedstreams. One is methanol. The other is a mixture of C5 components that contains reactive isoamylenes plus other C5 paraffins, naphthenes, and olefins. This C5 stream typically comes from a petroleum refinery light-ends unit that separates light hydrocarbon components generated in catalytic cracking into various streams. Because the boiling points of aU of the C5 components are quite similar, it is uneconomical to separate out the isoamylene reactants from the other C5s. The C5 fresh feedstream contains 24 mol% reactive isoamylenes. The remaining components are pentanes and pentene (largely isopentane), which are inert in the TAME reaction. 

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