Catalytic cracking steam cracker

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. 

Figure 7.7b shows the essential features of a refinery catalytic cracker. Large molar mass hydrocarbon molecules are made to crack into smaller hydrocarbon molecules in the presence of a solid catalyst. The liquid hydrocarbon feed is atomized as it enters the catalytic cracking reactor and is mixed with the catalyst particles being carried by a flow of steam or light hydrocarbon gas. The mixture is carried up the riser and the reaction is essentially complete at the top of the riser. However, the reaction is accompanied by the deposition of carbon (coke) on the surface of the catalyst. The catalyst is separated from the gaseous products at the top of the reactor. The gaseous products leave the reactor... 

Q Catalytic Cracking for Integration of Refinery and Steam Crackers... 

Figure 3.35 shows a process flow diagram of Phillips MTBE/ETBE/TAME process. This process is often called the Phillips Etherification Process. The reaction section (1,2) which receives methanol and isobutene concentrate, contains an ion exchange resin. The isobutene concentrate may be mixed olefins from a Fluid Catalytic Cracking Unit (FCCU) or steam cracker or from the on-purpose dehydration of isobutene (Phillips STAR process). High purity MTBE (99 wt%) is removed as a bottoms product from the MTBE fractionator (3). AH of the unreacted methanol is taken overhead, sent to a methanol... 

We have seen that by 1973 catalytic cracking will only satisfy 2 to 4 billion lbs/year of a projected 11 billion lb/year propylene demand. Most of the balance will be produced as a by-product of ethylene manufacture. Shifting from ethane and propane to heavier stocks such as n-butane and gas oil will satisfy propylene needs. Some propylene will also be produced from isobutane steam crackers as an isobutylene co-product. 

Application Advanced Pygas Upgrading (APU) is a catalytic process technology developed by SK Corp. and is exclusively offered by Axens to convert pyrolysis (ex steam cracking) gasoline to a superior steam-cracker feed (LPG), and benzene, toluene and xylene (BTX) aromatics. 

Feed Olefinic C4 streams from steam cracker or fluid catalytic cracking (FCC) units can be used as feedstock for the recovery of butene-1. 

Feed C, streams from steam cracker, fluid catalytic cracking unit (FCCU)... 

Apart from the oxidation of organic molecules, the catalytic pyrolysis of waste tires to light olefins using mesoporous material containing metals was also performed. Generally, the production of light olefins has been derived mostly from steam crackers and refinery fluid catalytic cracking units. Moreover, their demand... 

Reactors for Non-catalytic Single-Phase Systems Classical reactors for single-phase reactions are stirred tank reactors for liquids (Figure 4.10.3) and flow tubes for fluids in all aggregation states. Ethylene and propylene synthesis from naphtha by thermal cracking in the presence of steam is a good example for a tubular reactor (Section 6.6). The tubes of a steam cracker have an internal diameter of 10 cm and... 

Propylene is also a product of the steam-cracking process (up to 15 wt% of the steam cracker product mix. Section 6.6). In addition, it is obtained by catalytic dehydrogenation of propane (Section 5.3.1) and as a by-product of the FCC process (Section 6.7.2). The technical relevance of propylene as a feedstock for the synthesis of industrial chemical processes has ever increased since the 1960s. The increasing value of propylene can be realized from the fact that propylene was seen in former times as an undesirable by-product of the steam-cracking process and as such it was... 

The feedstocks will t3 ically be low value refinery or petrochemical streams, such as steam cracker by-products rich in C4 s, which have poor propylene selectivity when recycled to the steam cracker. The feedstock can include raffinates, catalytic cracked naphtha, coker naphtha, steam cracker pyrolysis gasoline, as well as synthetic chemical streams containing sufficient amounts of C4-C7 olefins. Dienes, sulfur, nitrogen and oxygenates in the feeds are preferably selectively hydrotreated prior to the conversion process. However, feeds with low levels of dienes, sulfur, nitrogen, metal compounds and oxygenates can be processed directly from FCC units, cokers or steam crackers without any pretreatment. 

The catalytic cracker is one of the largest producers of "sour water" in the refinery. This sulfur-containing water forms in the steam strippers and overhead accumulators on the product fractionators. The major by-products resulting from catalytic cracking operations are oil, sulfides, phenols, ammonia, and cyanide. 

MTBE is produced by reacting methanol with isobutene. Isobutene is contained in the C4 stream from steam crackers and from fluid catalytic cracking m the crude oil-refining process. However, isobutene has been in short supply in many locations. The use of raw materials other than isobutene for MTBE production has been actively sought. Figure 2 describes the reaction network for MTBE production. Isobutene can be made by dehydration of i-butyl alcohol, isomerization of -butenes [73], and isomerization and dehydrogenation of n-butane [74, 75]. t-Butanol can also react with methanol to form MTBE over acid alumina, silica, clay, or zeolite in one step [7678]. t-Butanol is readily available by oxidation of isobutane or, in the future, from syngas. The C4 fraction from the methanol-to-olefins process may be used for MTBE production, and the C5 fraction may be used to make TAME. It is also conceivable that these... 

More than 90% of today s petrochemicals are produced from refineiy products. Most are based on the use of C2-C4 olefins and aromatics finm hydrocarbon steam cracking units, which are even more closely linked to refineries. In North America, the feedstock for steam cracker units have generally been ethane, propane, or LPG. As a result, most of the propylene and aromatics have been provided by FCC units and catalytic reformers. In maity other parts of the world where naphtha feed has been more readily available, suppUes of propylene and aromatics have been produced directly by steam cracking. When necessary, the catalytic dehydrogenation of paraffins or dealkylation of toluene can balance the supply of olefins or benzene. In Table 7.2 some of the catalytic processes that convert olefins and benzene from a steam cracker into basic petrochemicals for the modem chemical industry are shown. 

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