Steam cracking Composition

Typical steam cracking feedstock composition and yields. 

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. 

Typical Olefinic Feed Compositions Obtained from Steam Cracking of Propane and... 

The pyrolysis experiments were conducted in an electrically heated, once-through tubular flow reactor, designed to simulate the time-temperature history experienced in commercial steam-cracking operations. Reactor effluent compositions were ascertained by gas chromatograph and mass spectrometer analyses. Material and hydrogen balances could always be effected, with typical closures of 98 2 wt %. 

Dicyclopentadiene (DCPD) is usually recovered as a high value product from the byproduct pyrolysis gasoline stream that is generated in steam cracking furnaces (see Ethylene and Propylene by Steam Cracking ). U.S. 6,258,989 (to Phillips Petroleum) gives a typical pyrolysis gasoline composition and describes a suitable... 

Steam cracking of ethane is the most widely used process for making ethylene. U.S. 6,578,378 (to Technip-Coflexip) gives a typical ethane cracker product composition and describes an improved separation process for ethylene recovery. U.S. 5,990,370 (to BP) gives yields for ethane, propane, and mixtures. U.S. 5,271,827 (to Stone Webster) gives details of furnace design and yields for a naphtha feed. Several other separation schemes for ethylene and propylene recovery are described in the literature. Estimate the cost of production for a new steam cracking facility that produces 1 million metric tons per year of ethylene and 600,000 metric tons per year of propylene. What feedstock would you recommend ... 

Figure 2. Exit gas composition from steam cracking of propane in quartz reactor with steel (Sandvik 15RelO) as the foil material after 10 min on stream. Conditions temperature range, 800-870°C feed gas composition, 29 mol% C3Ha, 32% HtO, and 39% N3 and total feed rate, 0.42 L gas/min.

Content of carbon oxides in the exit gas from steam cracking of propane in different reactors. Composition of the feed ... 

Figure 5. Exit gas composition from steam cracking of propane. Comparisons between prereduced and preoxidized systems. Conditions as in Figure 4.

Kltleha steam cracking, effluent composition (% Wt of feedstock)... 

This integrated technology is suitable for revamps of ethylene plants, as well as grassroots applications. The figure shows a maximum integration scenario for an HO FCC and steam cracking. The level of integration is a function of contaminant levels, HO FCC effluent gas composition and other capital reduction considerations. 

Mixed C4 streams, containing butadiene, butenes, and butanes, are co-produced in steam-cracking processes. These streams contain valuable components, which can be either processed in situ or extracted purely. A typical composition of a steam-cracker C4 cut is shown in Fig. 3.1. Maximizing its value is a major objective for most petrochemical companies. Therefore, a variety of techniques exists for upgrading the C4 streams by removal of pure C4 components and conversion of low-value streams to higher-value products. 

Table 24-8. Composition of a Cs Fraction from the Steam Cracking of...

Table 3.24 Composition of pyrolysis products from steam cracking various feedstock materials...

The two most important sources of aromatics from steam cracking are pyrolysis gasoline and pyrolysis tar. The composition of typical pyrolysis gasoline from cracking is shown in Table 3.25. 

Table 3.26 Composition of pyrolysis tar from naphtha steam cracking...

An analysis of the typical by-products in the C4 stream derived from cracking a full-range Middle East naphtha is given in Table 3. The range reflects composition at medium and high severity during steam cracking. 

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