Steam cracking of naphtha

The term naphtha is used to denote a petroleum cut whose lightest components have ih e carbon atoms, and whose end boiling point may be as high as about 20(Kr. According to their distillarion temperatures, a disdncdon is drawn between short naphthas, whose 

Feedstock Western Europe United States Japan World 

111 Ethand (Brazil, India) and coal-derived gases(Pdand, South Africa).  

Products I i j i Ethane Propane Butane 1 i Medium range Naphtha Atmospheric gas oil Vacuum gas oil 

The values given ve obtained at very high severity alter recycling to the furnaces of ethane and or propane that is nnconvenol or formed in pyrolysis. 

CjH5 Recycle Without With Without With Without With 

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Butylene yield Gas oil Residue Delayed coking Elexicoking Steam cracking of naphtha... 

Butadiene yields ranging from 2 to 7 weight percent on feed (usually 4 to 5j are expected in the steam cracking of naphthas and gas oils. This is generally 35 to 45 percent of the total yield of C4 s. 

Small olefins, notably ethylene (ethene), propene, and butene, form the building blocks of the petrochemical industry. These molecules originate among others from the FCC process, but they are also manufactured by the steam cracking of naphtha. A wealth of reactions is based on olefins. As examples, we discuss here the epoxida-tion of ethylene and the partial oxidation of propylene, as well as the polymerization of ethylene and propylene. 

Besides ethylene and propylene, the steam cracking of naphtha and catalytic cracking in the refinery produce appreciable amounts of C4 compounds. This C4 stream includes butane, isobutane, 1-butene (butylene), cis- and trans-2-hutene, isobutene (isobutylene), and butadiene. The C4 hydrocarbons can be used to alkylate gasoline. Of these, only butadiene and isobutylene appear in the top 50 chemicals as separate pure chemicals. The other C4 hydrocarbons have specific uses but are not as important as butadiene and isobutylene. A typical composition of a C4 stream from steam cracking of naphtha is given in Table 8.3. 

These processes are specifically designed for ethylene production but they also yield C4 hydrocarbons as coproducts. The amount of C4 compounds produced depends on the feedstock, the cracking method, and cracking severity. Steam cracking of naphtha provides better yields than does catalytic cracking of gas oil. With more severe steam cracking both butenes and overall C4 productions decrease, whereas the relative amount of 1,3-butadiene increases. Overall C4 yields of 4-6% may be achieved. 

The steam cracking of naphtha and catalytic cracking in the refinery produce the C4 stream, which includes butane, 1-butene (butylene), cis- and trans-2-butene, isobutylene, and butadiene. 

Steam cracker tar (SCT) is a by-product from the steam cracking of naphtha or gas oils to produce ethylene. The characteristics and yield of SCT is dependent on the feed characteristics, the plant design and severity of cracking,... 

Application To directly recover styrene from raw pyrolysis gasoline derived from steam cracking of naphtha, gas oils and NGLs using the GT-Styrene process. 

This table, points out the low production of propylene in comparison with the steam cracking of naphtha, the high coproduction of acetylene ranging up to nearly 150 kg t ofethyiene instead of the 15 kg/t observed in naphtha steam cracking, and the substantial formation of fuel oil and tars. 

Ftg. 2.12. Steam cracking of naphtha. Effect of pyrolysis tube geometry on olefin yields. 

The differences that still exist between butadiene supply sources. In different gec ra-phic areas, are now tending to disappear gradually for economic reasons. Current world availabilities of butadiene essentially origiaate in the treatment of C cuts produced by the steam cracking of naphtha or gas oil. The only exception is the United States, where the dehydrogenation of n-bucane and n-buteoes is still in practice although... 

Components that are produced in high yield by side reactions. Some examples include propylene, butylenes, and butadiene, all of which are byproducts of ethylene from steam cracking of naphtha feed. Orthoxylene and metaxylene are byproducts of paraxylene manufacture by catalytic reforming of naphtha. 

By use of an overall steady-state material balance determine whether or not the petrochemical process indicated in Fig. P2.1 has been properly formulated. The block diagrams represent the steam cracking of naphtha into various products, and all flows are on an annual basis (i.e., per year),... 

Figure 3 shows the production capacity profile for an Australian ethylene plant. The plant based on steam cracking of naphtha was expanded in three stages following its initial construction. Capacity growth can be seen to follow a learning curve that is consistent with a model proposed by Malloy ... 

H-Oil unit are processed for sulfur recovery and then sent for separation through the gas recovery facilities associated with the steam cracker. Remaining unconverted residue from the H-Oil operation is used as a fuel oil component for plant fuel. Ethylene is manufactured by steam cracking of ethane, propane, naphtha, and distillate, and products from these operations are separated in conventional gas recovery facilities. Hydrogen for H-Oil is partially supplied by by-product recovery from steam cracker and H-Oil off-gases supplemented by steam reforming of methane. The heavy oils produced in steam cracking of naphtha and distillate are blended with the H-Oil residue to yield plant fuel. 

Application GT-Styrene is an extractive distillation process that directly recovers styrene from the raw pyrolysis gasoline derived from the steam cracking of naphtha, gasoils and natural gas liquids (NGLs). The produced styrene is high purity and suitable for polymerization at a very attractive cost compared to conventional styrene production routes. The process is economically attractive for pygas feeds containing more than 15,000 tpy of styrene. 

GTC Technology Styrene Pygas Cg cut Extractive distillation process that directly recovers styrene from the raw pyrolysis gasoline derived from the steam cracking of naphtha, gasoils and NGL 3 2009... 

Lower olefins are today produced by steam cracking of naphtha, LSR or other paraffinic feeds. Hie actual methanol price does not allow the methanol to olefins process to compete economically. However, if methanol will become more available firom natural gas transforming routes, then there is a great chance for that process to become commercial. 

The current world production of ethene and propene is mainly covered by the petrochemical route based on steam cracking, that is, thermal pyrolysis of petroleum liquids (naphtha, gas oils) and natural gas condensates, that is, ethane, propane, etc. [13-15]. A schematic stoichiometry is given in Eq. (5.2). As an alternative, ethanol can be converted via catalytic dehydration to ethene, as shown in Eq. (5.3) [16]. For steam cracking of naphtha, the reaction stoichiometry gives a maximum product yield of nearly 100 wt%, whereas ethanol conversion can lead only to maximum yields of 61 wt%. 

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