Naphtha cracker

Compounds considered carcinogenic that may be present in air emissions include benzene, butadiene, 1,2-dichloroethane, and vinyl chloride. A typical naphtha cracker at a petrochemical complex may release annually about 2,500 metric tons of alkenes, such as propylenes and ethylene, in producing 500,000 metric tons of ethylene. Boilers, process heaters, flares, and other process equipment (which in some cases may include catalyst regenerators) are responsible for the emission of PM (particulate matter), carbon monoxide, nitrogen oxides (200 tpy), based on 500,000 tpy of ethylene capacity, and sulfur oxides (600 tpy). 

A typical C4 hydrocarbon stream coming from a gas oil or naphtha cracker, like that shown in the last chapter in Figure 5-4, might have the following composition ... 

C3 5 feeds or LPG typically come either from the field or from naphtha crackers and FCC units. Hydrogenation to minimize dienes is required to limit severe... 

Hydroformylation of Other Lower Olefins and Dienes - Lower olefins such as 1-butene or 1,3-butadiene are hydroformylated with acceptable rates using Rh/tppts catalysts according to the RCH/RP process. Hoechst AG Werk Ruhrchemie has developed an attractive new process350 for the hydroformylation of raffinate II, a mixture of 1-butene, cis- and /rbutane derived from the C4 stream of naphtha crackers (after removal of 1,3-butadiene... 

Mitsubishi Kasei introduced a process to manufacture isononyl alcohol, an important PVC (polyvinyl chloride) plasticizer, via the hydroformylation of octenes (a mixture of isomers produced by dimerization of the C4 cut of naphtha cracker or FCC processes).95 First a nonmodified rhodium complex exhibiting high activity and selectivity in the formation of the branched aldehyde is used. After the oxo reaction, before separation of the catalyst, triphenylphosphine is added to the reaction mixture and the recovered rhodium-triphenylphosphine is oxidized under controlled conditions. The resulting rhodium-triphenylphosphine oxide with an activity and selectivity similar to those of the original complex, is recycled and used again to produce isononanal. 

In the process based on n-butane feedstock, vanadium phosphorous oxides (V-P-O) catalysts are mainly used.1010-1012 Processes for the oxidation of low-cost C4 fraction from naphtha cracker consisting mainly of butenes have also been developed.1013,1014 In contrast with benzene oxidation where two carbon atoms are lost in the form of ethylene no carbon is lost in the oxidation of C4 hydrocarbons ... 

Most polymer products are offered for recycling in the form of mixed plastic waste (MPW). Compressed gases as solvents may offer advantages compared with liquid solvents in the necessary separations (e.g., to collect families of polymers out of MPW) because such solvents are easy to recover and, furthermore, they make it possible to use pressure as an additional separation parameter or to remove the organic additives of the polymers. Finally, MPW may be added as a polymer solution in a compressed gas to a feed of a Naphtha cracker, and thus be recycled to base chemicals. 

For ethylene, similar data could be constructed from either an average of ethylene producers in this geography or on-site naphtha crackers. In certain cases, databases exist for certain commonly used compounds. In other cases, data are unavailable and estimates have to be made. In case of plants that produce more than one product, the total emissions are allocated proportionally to their sales. 

The Middle East should exploit every ton of stranded gas available. The heavy investments in crackers (primarily ethane) and downstream products (mostly polymers) already under way will bring the region close to this level. Iran s NPC is building the two largest crackers in the world in the Pars Special Economic Energy Zone, one of which is a naphtha cracker that will also produce 900,000 t/year of propylene. SABIC, meanwhile, is planning the start-up of its 1.3 mmt/year cracker by 2009 in Yanbu, Saudi Arabia and a joint venture between Chevron... 

Some parts of the production process are better located domestically. Naphtha crackers, for example, may as well be located in China, as naphtha could be imported from the Middle East cheaply. It could also be made using CTL technology, if that becomes competitive or is subsidized by the government. 

Consumers can also negotiate with feedstock suppliers on upfront payments or payment terms under which they pay a higher price than the lowest market price at the trough, but pay lower prices when product prices spike. An interesting application of this is the potential for an ethane cracker operator to convert the economics of its cracker to those of a virtual naphtha cracker, by paying an integrated gas producer-processor a price for ethane indexed to naphtha-based ethylene production costs. 

Maleic anhydride is widely used in polyester resins, agricultural chemicals and lube additives. The growth rate of its production is currently 7-9 percent per year world-wide. In the U.S. the expected consumption by 1983 is 223,000 tons per year ( 5). Conventionally, the production of maleic anhydride via heterogeneous catalytic oxidation of benzene is performed in fixed bed reactors. Rapid increase in benzene prizes and tight benzene-emission control standards caused intense investigations in alternative feedstocks like n-butenes (6), butane ( 5) and the C,-fraction of naphtha crackers (7). As for these alternative feedstocks... 

In the following the synthesis of maleic anhydride in the fluidized bed will be described for two different feedstocks i.e. benzene and C -fractions of naphtha crackers, respectively. 

The C,-fraction of naphtha crackers is used as a feedstock in the Mitsubishi fluid bed process for the production of maleic anhydride. This process was commercialized in 1970. Many data related to this process including the catalyst screening, laboratory experiments, pilot plant design, reactor behaviour and the development of higher selectivity catalysts may be found in the patent literature (12-17).The patents thus give a nearly complete picture of the scale-up process. The data have been used in the present investigation to test the fluid bed reactor model. 

Calculated and experimental maleic anhydride yields for the three fluid bed reactors involved in the scale-up of the Mitsubishi process are shown together in Figure 7. The yield value for the 45 cm dia. reactor was used to determine the reaction rate constant k, but the calculations for the 15 cm dia. bed and for the laboratory reactor with 4 cm diameter were performed without any parameter fitting. The calculation for the 15 cm bed is surprisingly close to the measurement whereas there is some deviation between theory and experiment on the laboratory scale the reason of which ist not quite clear. It should be noted however that in the laboratory reactor 1-butene was used as feed while on the pilot scale C -fractions of the naphtha cracker i.e. mixtures of various hydrocarbons were used. 

In the present paper Werther s two-phase model has been applied to the synthesis of maleic anhydride as an example of a complex reaction system. Based on experimental data found in the literature two process routes were investigated. For the synthesis of MA with benzene as a feedstock as well as for the synthesis with C -fractions of naphtha crackers as feedstocks the model is shown to be able to describe the behaviour of the fluid bed reactor. In particular the changes in hydrodynamics in the course of the reactor scale-up are considered in the present model. Thus the model allows to describe the behaviour of the fluidized bed reactor on different scales. The model may therefore be helpful in the development of industrial fluidized bed processes. 

An alternate course, which was not pursued, would be to operate the reformer at less severe conditions where naphthene conversions are high but where isomerization and hydrocracking are less. The resultant reformate could be extracted with raffinate going to a naphtha cracker for olefin production while the extract is hydrodealkylated. 

Other catalytic reactions carried out in fluidized-bed reactors are the oxidation of naphthalene to phthalic anhydride [2, 6, 80] the ammoxidation of isobutane to mcthacrylonitrilc [2] the synthesis of maleic anhydride from the naphtha cracker C4 fraction (Mitsubishi process [81, 82]) or from n-butane (ALMA process [83], [84]) the reaction of acetylene with acetic acid to vinyl acetate [2] the oxychlorination of ethylene to 1,2-di-chloroethane [2, 6, 85, 86] the chlorination of methane [2], the reaction of phenol with methanol to cresol and 2,6-xylenol [2, 87] the reaction of methanol to gasoline... 

Zeolites are used in separation processes for extracting p-xylene and m-xylene at high purity and recovery. There are zeolitic processes for converting C3-C7 paraffins into aromatics. In addition, zeolitic processes can co-produce aromatics and chemical-grade light olefins, or co-produce superior feedstocks for catalytic reformers and naphtha crackers. 

Foley T.D., Greer D.W. and Pujado P.R., MaxEne Process Increased Ethylene Yield in Naphtha Crackers (AIChE Spring National Meeting, Houston, 2001). 

Economics Ethylene yields vary between 25%, 35%, 45% and 83% for gas oils, naphtha, LPG and ethane respectively. The related specific energy consumption range is 6,000/5,400/4,600 and 3,800 kcal/kg ethylene. Typical installation costs for a world-scale ISBL gas (naphtha) cracker on a Gulf Coast basis are 500 (750) US /ton installed ethylene capacity. 

Application The MaxEne process increases the ethylene yield from naphtha crackers by raising the concentration of normal paraffins (n-paraffins) in the naphtha-cracker feed. The MaxEne process is the newest application of UOP s Sorbex technology. The process uses adsorptive separation to separate C5-Cn naphtha into a rich n-paraffins stream and a stream depleted of n-paraffins. 

Extract This stream contains n-paraffin and a liquid desorbent. Naphtha, rich in n-paraffin, is recovered by fractionation (3) and is sent to the naphtha cracker. 

Yields Product yields are dependent on feedstock composition. The process provides propylene/ethylene production at ratios of nearly 4 1. Case studies of olefin cracking integration with naphtha crackers have shown 30% higher propylene production compared to conventional naphtha-cracker processing. 

MaxEne A process for increasing the yield of propylene from naphtha crackers without increasing that of propylene. A version of the Sorbex process is used to separate the normal paraffins from the branched paraffins before the cracker. Developed and offered by UOP in 2000, but not reported to have been licensed by 2005. 

Economics For increase in naphtha-cracker ethylene production from 247,000 mtpy to 330,000 mtpy, based on U.S. Gulf Coast ... 

JSR Corp. Butadiene monomer BD C4 fraction from naphtha cracker Extractive distillation at lower temperature, no compressor, popcorn-free and low energy consumption 3 1997... 

JSR Corp. Isoprene monomer (IP) C5 fraction from naphtha cracker Low investment cost, energy efficient and low production costs 1 1986... 

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