Light ethylene production

Butadiene is obtained mainly as a coproduct with other light olefins from steam cracking units for ethylene production. Other sources of butadiene are the catalytic dehydrogenation of butanes and butenes, and dehydration of 1,4-butanediol. Butadiene is a colorless gas with a mild aromatic odor. Its specific gravity is 0.6211 at 20°C and its boiling temperature is -4.4°C. The U.S. production of butadiene reached 4.1 billion pounds in 1997 and it was the 36th highest-volume chemical. ... 

The dramatic increase in 6-MM content--90 to 270 fold in two samples--was unexpected. 6-MM is a potent antifungal agent (4) and one of the most important carrot phytoalexins. Usually 6-MM, one of the components that contributes to the bitterness of stored carrots ( O), is not detected in fresh carrots, but develops during storage. Biosynthetic studies indicate that 6-MM is synthesized via the acetate pathway and its production is stimulated by ethylene (. Thus, UV light may trigger ethylene production in carrots which in turn leads to 6-MM accumulation. 

The light hydrocarbons produce only minor amounts of by-products, while naphtha and heavier feeds produce substantial quantities of propylene, butadiene, and aromatics. Thus, while in the United States these products are obtained generally from other routes at present, in Europe and Japan ethylene production serves as a major source of these chemicals. As discussed in greater detail later, by-product outlet considerations can play an important role in feedstock selection, and by-product realizations can have a major effect on the ethylene production economics. 

Table III gives a range of the possible feedstocks that can be used to produce ethylene and the kinds and amounts of by-products that can be made from them. For our purposes we have selected a constant basis of 1 billion lbs/year ethylene production. The feedstocks illustrated in Table III include ethane, propane, n-butane, a full range naphtha, a light gas oil, and a heavy gas oil. The yields reflect high severity conditions with recycle cracking of ethane in all cases. For propane feed, propane recycle cracking has been included as well.

At current price levels, heavier feeds in the United States are not competitive with light hydrocarbon feeds. With U.S. naphtha at 1.6 /lb (10 /gal), the ethylene production costs from this feed ranges about 40-70% higher than costs associated with lighter feeds, assuming premium by-product values. The differences are even greater with fuel byproduct values prevailing. 

The current unattractiveness of heavier feeds in the United States notwithstanding, ethylene can be made more cheaply from 1.1 /lb heavy gas oil than from 1.6 /lb naphtha even though a gas oil plant is more expensive and requires more feed. This applies for both premium and fuel by-product cases. Even so, ethylene production costs with gas oil feed are about 25-50% higher than costs with light hydrocarbon feeds. 

Figure 3 presents the effect of feed price on ethylene production costs in a billion lb/yr European plant for naphtha, light gas oil, and heavy gas oil feedstocks based on premium by-product valuations. 

Thus, at today s naphtha prices and by-product markets, pyrolysis of light vacuum gas oil appears closely competitive with naphtha for ethylene production. 

Figure 5. Breakeven prices for light gas oil feed vs. naphtha feed in Europe (1000 MM Ibs/yr ethylene production premium and fuel value by-products)...

In Europe, cracking of either light vacuum gas oil or naphtha give very comparable ethylene production costs at current price levels. This holds for either premium or fuel value by-products. 

Knowledge of the complete reaction pathway for ethylene production and the characteristics of the enzymes systems involved, should shed light on the control and regulation of ethylene production and perhaps also its relationship to other hormones. 

There is often no single feedstock choice, since feedstock costs frequently vary erratically over a period of several years. A general guide to the influence of feedstock on capital investment of the entire pyrolysis for ethylene production is shown in Fig. 7. Net raw material costs for an ethylene plant often account for about 50-60% of the production costs, depending on whether the feedstock is a light material such as ethane or a heavier material such as naphtha. 

Reactor effluent is chilled and light-ends are separated from the C2-hydrocarbons. The demethanizer overhead is processed for ethylene recovery while the bottoms is sent to ethylene/ethane separation. An open heat-pump splitter is applied, thus sending ethylene product to the gas pipeline from the discharge of the ethylene-refrigerant compressor. 

Predicted ethylene yields by the generalized correlation are illustrated in Figure 9. The data shown are from two light naphthas which differ only in their iso/normal paraffin ratios. The data illustrate not only the greater ethylene yield potential of the lower iso/normal paraffin ratio feed, but also the enhancement of ethylene production at shorter residence-time operation. As can be seen, the model quantitatively predicts the data. 

To achieve the required quantity of steam cracker charge, the severity of this H-Oil operation would be set to provide more light products than shown in the simple desulfurization case in Table X. A typical yield structure might be that shown in Table XI. This severity could be set to match the desired ratio between low sulfur fuel production and ethylene production. 

Description The SUPERFLEX process is a proprietary technology patented by ARCO Chemical Technology, Inc. (now LyondellBasell) and exclusively offered worldwide for license by KBR. It uses a fluidized catalytic reactor system with a proprietary catalyst to convert low-value feedstocks to predominantly propylene and ethylene products. The catalyst is very robust thus, no feed pretreatment is required for typical contaminants such as sulfur, water, oxygenates or nitrogen. Attractive feedstocks include C4 and C5 olefin-rich streams from ethylene plants, FCC naphthas or C4S, thermally cracked naphthas from visbreakers or cokers, BTX or MTBE raffinates, olefin-rich streams removed from motor gasolines, and Fischer-Tropsch light liquids. 

Yields The MTO process consumes 3 tons of methanol feed per ton of light olefin (ethylene + propylene) produced. The weight ratio of propylene product to ethylene product can be selected within the range of 0.8 to 1.3. When combined with OCP, the Advanced MTO process consumes 2.6 tons of methanol feed per ton of light olefin (ethylene + propylene) produced. The weight ratio of propylene product to ethylene product for Advanced MTO can be selected within the range of 1.2 to 1.8. 

Kellogg Brown Root LLC Propylene Light (C to CJ hydrocarbon olefins-containing streams The SUPERFLEX process uses a fluidized catalytic reactor system with a proprietary catalyst to convert low-value feedstocks to predominately propylene and ethylene products 3 2006... 

Ott, S., 1993. The influence of light on the ethylene production by lichens. In Feige, G.B., Lumbsh, H.T. (Eds.), Phytochemistry and Chemotaxonomy of Lichenized Ascomycetes - A Festchrift in Honour of Siegfried Huneck. Bibl. Licheno. 53, Cramen, Berlin and Stuttgart, pp. 185-190. 

In many side-drawoff columns, the side draw is very small compared to the other product streams. This is a common situation when the side stream serves to remove an intermediate impurity (Sec. 13.7). In many other side-drawoff columns, distillate is withdrawn as a side product a few trays below the top of the column, leaving an upper "pasteurizing section for separating light ends as a small vent stream. Common examples are an ethylene plant Cg splitter, where small quantities of methane are "pasteurized out of the ethylene product, and an alcohol still, where "heads are pasteurized out of the alcohol product. The reverse situation has the bottom product drawn as a vapor side product a few trays above the bottom, leaving a small heavy end stream to exit from the bottom. 

In an extension of our work on vicinal glycol esters described in Section 2.2., we have demonstrated an alternative process scheme for making ethylene-rich light olefins (69). The first stage is CO hydrogenation in the presence of an aliphatic carboxylic acid coreactant this yields the corresponding ethyl and propyl esters as a major product fraction (eq. 6 and 21). Pyrolysis of the intermediate ethyl and propyl esters would yield ethylene and propylene. 

In light-grown hypocotyls of dwarf watermelon seedlings benzyladenine (BA) enhances ethylene production and promotes cell elongation (Loy and Pollard 1977). Prevention of BA-induced ethylene production prevents BA-induced elongation, an indication that ethylene is necessary for BA-induced growth promotion. 

Craker LE, Abeles FB, Shropshire W (1973) Light-induced ethylene production in Sorghum. Plant Physiol 51 1082-1083... 

Kohler K-H, Dorfler M, Goring H (1980) The influence of light on the cytokinin content of Amaranthus seedlings. Biol Plant 22 128-134 Kondo K, Watanable A, Imaseki H (1975) Relationships in actions of indoleacetic acid, benzyladenine and abscisic acid in ethylene production. Plant Cell Physiol 16 1001-1007... 

Lau 0-L, John WW, Yang SF (1977 b) Inactivity of oxidation products of lAA to stimulate ethylene production in mungbean hypocotyls. Plant Physiol 59 Suppl, p 11 Lawson VR, Weintraub RL (1975) Interactions of microtubule disorganizers, plant hormones, and red light in wheat coleoptile segment growth. Plant Physiol 55 1062-1066 Lee BO(1961) Effect of Line tin on the fertility of some strains of Neurospora crassa. Nature 192 288... 

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