Polyethylene steam cracking

Petroleum resins are low molecular weight thermoplastic hydrocarbon resins synthesized from steam cracked petroleum distillates. These resins are differentiated from higher molecular weight polymers such as polyethylene and polypropylene, which are produced from essentially pure monomers. Petroleum resin feedstocks are composed of various reactive and nonreactive aliphatic and aromatic components. The resins are usually classified as C-5... 

IFP Process for 1-Butene from Ethylene. 1-Butene is widely used as a comonomer in the production of polyethylene, accounting for over 107,000 t in 1992 and 40% of the total comonomer used. About 60% of the 1-butene produced comes from steam cracking and fluid catalytic cracker effluents (10). This 1-butene is typically produced from by-product raffinate from methyl tert-huty ether production. The recovery of 1-butene from these streams is typically expensive and requires the use of large plants to be economical. Institut Francais du Petrole (IFP) has developed and patented the Alphabutol process which produces 1-butene by selectively dimerizing ethylene. 

The most important olefins used for the production of petrochemicals are ethylene, propylene, the butylenes, and isoprene. These olefins are usually coproduced with ethylene by steam cracking ethane, LPG, liquid petroleum fractions, and residues. Olefins are characterized by their higher reactivities compared to paraffinic hydrocarbons. They can easily react with inexpensive reagents such as water, oxygen, hydrochloric acid, and chlorine to form valuable chemicals. Olefins can even add to themselves to produce important polymers such as polyethylene and polypropylene. Ethylene is the most important olefin for producing petrochemicals, and therefore, many sources have been sought for its production. The following discusses briefly, the properties of these olefmic intermediates. 

The three isomers constituting n-hutenes are 1-hutene, cis-2-hutene, and trans-2-hutene. This gas mixture is usually obtained from the olefinic C4 fraction of catalytic cracking and steam cracking processes after separation of isobutene (Chapter 2). The mixture of isomers may be used directly for reactions that are common for the three isomers and produce the same intermediates and hence the same products. Alternatively, the mixture may be separated into two streams, one constituted of 1-butene and the other of cis-and trans-2-butene mixture. Each stream produces specific chemicals. Approximately 70% of 1-butene is used as a comonomer with ethylene to produce linear low-density polyethylene (LLDPE). Another use of 1-butene is for the synthesis of butylene oxide. The rest is used with the 2-butenes to produce other chemicals. n-Butene could also be isomerized to isobutene. ... 

Steam cracking of various petroleum fractions is gaining widespread use for the production of olefins. These olefins are produced essentially for use as feed stock for numerous petrochemical processes, but the by-product butylenes and propylenes are sometimes used as feed stock for aviation and motor alkylation units. Ethylene is the most important of the olefins produced from this type of cracking, and propylene is second in importance. These two olefins are normally charged to either alkylation or polymerization units for the production of petrochemicals or petrochemical intermediates. Polyethylene and propylene dimers, trimers, tetramers, and penta-mers are some of the more important polymers produced, while ethybenzene, dodecylbenzene, cumene, diisopropylbenzene, and alkylated... 

The olefins ethylene and propylene are highly important synthetic chemicals in the petrochemical industry. Large quantities of such chemicals are used as feedstock in the production of polyethylene, polypropylene, and so on [31]. The prime source of lower olefins is the olefin-paraffin mixtures from steam cracking or fluid catalytic cracking in the refining process [32]. Such mixtures are intrinsically difficult to... 

Olefins such as ethylene and propylene are produced in the petrochemical industry by steam cracking of paraffins, followed by repeated compression and distillation to separate the complex vapor mixtures. Ethylene is used to create ethylene oxide, and polyethylene, while propylene is the second highest volume petrochemical feedstock after ethylene and is used for the production of a wide variety of polymers. 

Feedstocks are usually either cat cracker bottoms from a petroleum cracking unit or tars from steam cracking for polyethylene production. Coal tars are commonly used as feedstocks to produce carbon black in China. 

The feed to a steam cracker is a mixture of steam with either LPG (liquefied petroleum gas a mixture of primarily ethane, propane, and butane) or a heavier petroleum fraction, such as naphtha or gas oil. A large number of individual reactions take place. The feed hydrocarbons are cracked to smaller molecules and are dehydrogenated to produce olefins. The reactor operates at about 850 °C and the residence time typically is less than 1 s. Steam cracking is a homogeneous (non-catalytic) reaction. Steam crackers produce monomers that form the building blocks for important, high volume polymers such as polyethylene and polypropylene. 

Chemical intermediates are listed first in Table 1.1. These are the chemicals that are used to synthesize other chemicals, and are generally not sold to the public. For example, ethlyene is an intermediate produced from hydrocarbons by cracking natural gas derived ethane or petroleum derived gas oil, either thermally using steam or catalytically. Ethlyene is then used to produce polyethylene (45%), a polymer and ethlyene oxide (10%), vinyl chloride (15%), styrene (10%), and... 

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