Middle temperature pyrolysis

Steam cracking (or middle temperature pyrolysis ) converts alkanes and refinery cuts [e.g., ethane, light fuels (naphtha)] into a mixture of saturated and unsaturated hydrocarbons, with ethylene, propylene, butenes, butadiene, benzene, and toluene being the most valuable products. 

The steam cracker process - sometimes in the literature also referred to as middle temperature pyrolysis process - forms the heart of modern petrochemistry. The process converts a crude oil distillation cut into a mixture of reactive small molecules that can be purified and later used to produce a wide variety of base chemicals. It is fair to state that modem petrochemistry has developed around the steam cracker process and operates today largely as a result of the characteristic product distribution provided by the steam cracker. 

In the Smuda process the pyrolysis reactor temperature is 350°C and the operating pressure is 4-5 psi. The pyrolysis gases from the pyrolysis vessel are sent directly to a distillation column. The distillation column has a typical temperature profile as follows top 140°C, Sulzer 250Y middle 322°C, Sulzer 350Y and bottom 331°C. 

Carbon coating can be achieved using pyrolysis of hydrocarbons at elevated temperatures [69]. Figure 2 shows a device used for carbon coating via hydrocarbon pyrolysis. In the example described here, an alumina-washcoated monolith is covered with carbon by pyrolysis of cyclohexene. A gas mixture of cyclohexene in nitrogen is passing the reactor at a certain flow rate. The monolith block to be coated is placed in the middle of the heated tubular reactor. The reaction takes place at 873-973 K, and the amount of carbon deposited can be controlled by the temperature and the time on stream. Up to 3-10 wt% carbon can be homogeneously coated onto the monolith in this way. It appears that the surface area of the carbon-coated alumina-washcoated cordierite monolith is of... 

Figure 14.7. Typical XRD and EDAX data as a function of pyrolysis temperature (under Ar) for the smeltable RF-MOx systems in the native aerogel (top), xerogel (middle), and X-aerogel (bottom) forms. Case shown RF-SnO to.

Figure 14.9. XRD data of RF-CrO - as a function of the pyrolysis (Ar) temperature. Top native aerogel middle xerogel bottom X-aerogel.

Kuwait Crude. Kuwait crude, one of the typical Middle East crude oils, was subjected to the pyrolysis. The experimental conditions covered the ranges of temperature 700 900°C, of residence time 0.2 l sec, and of steam dilution ratio 0.5 2 by weight to crude oil. These operating variables were examined relative to their effect on the yields of olefins and aromatics. 

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