Steam cracking of propane

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

The effect of surfaces on the gaseous and solid products of the steam cracking of propane has been studied. The chemical nature of the surface near the reactor inlet has a significant effect on the reaction products while the surface near the exit does not. The material of the reactor tube appears to catalyze gas phase reactions as well as coke formation and gasification. Pretreatment of the reactor tube alters the chemical nature of the surface and, as a result, alters the effect of the material on the reaction products. 

The present studies were initiated in order to investigate the effect of the reactor surface on the product distribution and on the tendency for coke formation during the steam cracking of propane in a tubular reactor. Attention has been focused on correlating various effects which can arise in the system. Previous studies of the pyrolysis of propane has been reviewed recently (17, 18), and the findings of the present work are related to these studies later in this paper. 

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.

Figure 3. Coke formation during steam cracking of propane in the quartz reactor at 850°C on foils made from different materials. Key O, steel V, Co A. Mo , Cu and 0, quartz. Conversion of C3HB — 98%. Feed gas as in Figure 2.

Figure 7. Coke formation during steam cracking of propane at 840°C on a steel foil (Sandvik ISRelO) in a preoxidized steel reactor. The reactor surface and the foil were preoxidized for 95 min using 46% Ot in Nt at 840°C. Conversion of C3Hs 89%. Feed gas as in Figure 4.

Figure 9. Coke formation during steam cracking of propane at 850°C on steel foils (Sandvik 15RelO) in a preoxidized quartz reactor.

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

Using the quartz liner, coke formation on the foils was substantially less and so were the difference between the coke formation of preoxidized and prereduced foils. Quartz has been found to be catalytically inert and any effect on steam-cracking of propane should not and does not reflect the chemical nature of the surface. Gaseous and solid products obtained in the quartz reactor are shown in Figures 2, 3 and 9. The gas phase product spectrum is typical of a quartz reactor (Figure 2) and is unaffected by the foil material. The initial rate of coke formation on the foil depends on the foil material, but the rate of coke formation on all foils appears to approach a value similar to that for coke formation on coke. 

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

Like ethylene, propylene (propene) is a reactive alkene that can be obtained from refinery gas streams, especially those from cracking processes. The main source of propylene, however, is steam cracking of hydrocarbons, where it is coproduced with ethylene. There is no special process for propylene production except the dehydrogenation of propane. 

Propylene is manufactured by steam cracking of hydrocarbons as discussed under ethylene. The best feedstocks are propane, naphtha, or gas oil, depending on price and availability. About 50-75% of the propylene is consumed by the petroleum refining industry for alkylation and polymerization of propylene to oligomers that are added to gasoline. A smaller amount is made by steam cracking to give pure propylene for chemical manufacture. 

Table 8.1 shows the stochastic model solution for the petrochemical system. The solution indicated the selection of 22 processes with a slightly different configuration and production capacities from the deterministic case, Table 4.2 in Chapter 4. For example, acetic acid was produced by direct oxidation of n-butylenes instead of the air oxidation of acetaldehyde. Furthermore, ethylene was produced by pyrolysis of ethane instead of steam cracking of ethane-propane (50-50 wt%). These changes, as well as the different production capacities obtained, illustrate the effect of the uncertainty in process yield, raw material and product prices, and lower product... 

Metal granules also have been found in cokes formed or deposited on iron, cobalt, and nickel foils in experiments using methane, propane, propylene, and butadiene (7-10). Platelet-type coke, whose properties match those of graphite also was produced in some cases. Lahaye et al. (11) investigated the steam cracking of cyclohexane, toluene, and n-hexane over quartz, electrode graphite, and refractory steel. They report that heavy hydrocarbon species form in the gas phase, condense into liquid droplets which then strike the solid surface, and finally react on the solid surfaces to produce carbonaceous products. The liquid droplets wet and spread out on certain surfaces better than on others. 

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 ... 

Propylene, or propene by lUPAC (International Union of Pure and Applied Chemistry) nomenclature, is probably the oldest petrochemical feedstock, employed as it was in the early processes to isopropanol. It is produced by the cracking of propane or higher hydrocarbons in the presence of steam... 

H-Oil unit are processed for sulfur recovery and then sent for separation through the gas recovery facilities associated with the steam cracker. Remaining unconverted residue from the H-Oil operation is used as a fuel oil component for plant fuel. Ethylene is manufactured by steam cracking of ethane, propane, naphtha, and distillate, and products from these operations are separated in conventional gas recovery facilities. Hydrogen for H-Oil is partially supplied by by-product recovery from steam cracker and H-Oil off-gases supplemented by steam reforming of methane. The heavy oils produced in steam cracking of naphtha and distillate are blended with the H-Oil residue to yield plant fuel. 

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