Cracking of dicyclopentadiene

ENB is normally prepared in a two-step process (Scheme 9.5). The first step involves in situ cracking of dicyclopentadiene to cyclopentadiene, and... 

Cyclopentadiene was prepared by thermal cracking of dicyclopentadiene available from the Aldrich Chemical Company, Inc., following the literature procedure.6... 

The cracking of dicyclopentadiene without dedicated equipment was pursued in the usual manner in the discovery setting without incident, and the team assumed that scale-up would be outsourced to a specialized facility. 

Cyclopentadiene is obtained by the thermal cracking of dicyclopentadiene (3a,4,7,7a-tetrahydro-4,7-methanoindene). Dicyclopentadiene is slowly distilled through a short fractionating column, collecting only that which refluxes below 44°. (Cyclopentadiene boils at 42.5°, dicyclopentadiene at 170°.) This cyclopentadiene must be used within 2 or 3 hours or stored at —78° until use, because slow dimerization occurs at room temperature. 

Solutions of NaC5H5 in tetrahydrofuran are available commercially. Alternatively, NaC5H5 can be prepared in the laboratory by cracking of dicyclopentadiene, followed by reduction ... 

In the cracking of dicyclopentadiene, why is it necessary to distill the product very slowly ... 

Cracking of dicyclopentadiene (Diels-Alder dimer of cyclopentadiene). This is an example of a retro Diels-Alder reaction. 

Cracking of dicyclopentadiene on scale would require dedicated, specialized equipment and high thermal input (250-300°C). 

Cyclopentene is a relatively inexpensive compound which is obtained by thermal cracking of dicyclopentadiene and further hydrogenation. Its polymerization has been widely studied ... 

The cracking of dicyclopentadiene should be performed by fhe insfrucfor or laboratory assisfant. If a flame is used for fhis, be sure fhaf fhere are no leaks in fhe sysfem, because bofh cyclopentadiene and fhe dimer are highly flammable. The procedure provides enough cyclopenfadiene for abouf 50 sfudents. 

Gyclopentadiene/Dicyclopentadiene-Based Petroleum Resins. 1,3-Cyclopentadiene (CPD) is just one of the numerous compounds produced by the steam cracking of petroleum distillates. Due to the fact that DCPD is polymerized relatively easily under thermal conditions without added catalyst, resins produced from cycloaHphatic dienes have become a significant focus of the hydrocarbon resin industry. 

Elastomers. Ethylene—propylene terpolymer (diene monomer) elastomers (EPDM) use a variety of third monomers during polymerization (see Elastomers, ethyiene-propylene-diene rubber). Ethyhdenenorbomene (ENB) is the most important of these monomers and requires dicyclopentadiene as a precursor. ENB is synthesized in a two step preparation, ie, a Diels-Alder reaction of CPD (via cracking of DCPD) with butadiene to yield 5-vinylbicyclo[2.2.1]-hept-2-ene [3048-64-4] (7) where the external double bond is then isomerized catalyticaHy toward the ring yielding 5-ethyhdenebicyclo[2.2.1]-hept-2-ene [16219-75-3] (ENB) (8) (60). 

Ethylene and propylene are produced primarily by the cracking of naphtha. They also are available from the fractionation of natural gas. Ethylidene norbornene is produced by reacting butadiene with cyclopentadiene. 1,4 Hexadiene is produced from butadiene and ethylene. Dicyclopentadiene is obtained as a by-product from the cracking of heavy feedstocks to produce ethylene. 

During the last years ROMP has been developed to generate self-healing polymers. In these polymers droplets of dicyclopentadiene and of Grubbs-catalyst are incorporated. When the polymer cracks the droplets burst open, the catalyst comes into contact with the monomer and the plastic ideally heals itself [111]. This methodology is still far from application but it does indicate the power of ROMP. 

Sulfur can be fully plasticized by using the modifiers dipentene, styrene, and dicyclopentadiene. Sulfur can be plasticized with dicyclo-pentadiene at two minimum concentrations, as indicated in Table III 13% at reaction temperatures of < 140°C and 6% at reaction temperatures > 140 °C. This effect probably results from cracking of the dicyclopentadiene dimer molecule, which doubles the molecules available for reaction. The higher percentage dicyclopentadiene mixture was initially flexible. Upon aging, both plasticized materials became brittle. The reaction is exothermic and very difficult to control above 140 °C. When uncontrolled, extreme viscosity increases were encountered. 

The cheapness of dicyclopentadiene (DCPD), obtained as a byproduct from the cracking of oil, makes it an attractive candidate for the production of materials by metathesis polymerization. Its ROMP has been extensively studied and two companies, BFGoodrich and Hercules, have commercialized the corresponding polymer under the tradenames Telene and Metton respectively [34, 35]. Recently, a part of BFGoodrich and APT (Advanced Polymer Technologies) formed a joint venture to produce some related products, especially poly-DCPD. This company has... 

Dicyclopentadiene is obtained as a byproduct from the cracking of heavy feedstocks to produce ethylene. 

Aliphatic C-5—C-6. Aliphatic feedstreams are typically composed of C-5 and C-6 paraffins, olefins, and diolefins, the main reactive components being piperylenes cis-[1574-41 -0] and /n j -l,3-pentadiene [2004-70-8f). Other main compounds iaclude substituted C-5 and C-6 olefins such as cyclopentene [142-29-OJ, 2-methyl-2-butene [513-35-9] and 2-methyl-2-pentene [625-27-4J. Isoprene and cyclopentadiene maybe present ia small to moderate quaatities (2—10%). Most steam cracking operatioas are desigaed to remove and purify isoprene from the C-5—C-6 fraction for applications ia mbbers and thermoplastic elastomers. Cyclopentadiene is typically dimerized to dicyclopentadiene (DCPD) and removed from C-5 olefin—diolefin feedstreams duriag fractionation (19). 

Cycloaliphatic Diene CPD—DCPD. Cycloatiphatic diene-based hydrocarbon resias are typically produced from the thermal or catalytic polymerization of cyclopeatadieae (CPD) and dicyclopentadiene (DCPD). Upon controlled heating, CPD may be dimerized to DCPD or cracked back to the monomer. The heat of cracking for DCPD is 24.6 kJ / mol (5.88 kcal/mol). In steam cracking processes, CPD is removed from C-5 and... 

The purity of a dicyclopentadiene stream may be expressed in terms of DCPD itself or in terms of available CPD monomer. Both analyses are deterrnined by gas chromatography (gc). The first analysis is capillary gc on a nonpolar column. The data from the analysis can be used to calculate the available CPD, assuming that all the DCPD and CPD codimers crack completely. In the second analysis the sample is charged to the gc equipment under temperature conditions (injection port 400°C) that cause essentially complete reaction of the dimers to monomers. 

Several different companies have greened various steps of the process. In VNB production by-products come from competing Diels-Alder reactions and polymerization, largely of cyclopentadiene. The reaction is usually carried out in a continuous tube reactor, but this results in fouling, due to polymerization, at the front end, where the dicyclopentadiene is cracked to cyclopentadiene at temperatures over 175 °C. Whilst fouling does not have a very significant effect on yield, over time it builds up. 

Dicyclopentadiene is the Diels-Alder reaction dimer of cyclopentadiene. It is the thermodynamically stable form of cyclopentadiene at room temperature, and is also a byproduct in the olefin cracking process. Industrially, it is isolated by distillation, and currently is readily available in North America. 

Cyclopentadiene is a product of petroleum cracking. It dimerizes exothermically in a Diels-Alder reaction to dicyclopentadiene, which is a convenient form for storage and transport. Dicyclopentadiene plus cyclopentadiene demand in the United States amounted to 270 million lb in 1998. 

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