Temperature cracking

Cracking temperatures are somewhat less than those observed with thermal pyrolysis. Most of these catalysts affect the initiation of pyrolysis reactions and increase the overall reaction rate of feed decomposition (85). AppHcabiUty of this process to ethane cracking is questionable since equiUbrium of ethane to ethylene and hydrogen is not altered by a catalyst, and hence selectivity to olefins at lower catalyst temperatures may be inferior to that of conventional thermal cracking. SuitabiUty of this process for heavy feeds like condensates and gas oils has yet to be demonstrated. 

Certain environments containing nitrate, cyanide, carbonate, amines, ammonia or strong caustic, due to the risk of stress corrosion cracking. Temperature is an important factor in assessment of each cracking environment ... 

The coil heat transfer coefficient had a value of 0.1159 and a x2 statistic of 27.8. This value suggests that a gross error is present. Some clues can be found from examination of the residuals of the balances. They are presented in Table 7. There appears to be a problem with the balances for coils 2 and 3 their residuals are different from the others (especially coil 2). The reconciled value for the coil 2 cracking temperature is also significantly different from the measured value, thus suggesting an abnormal situation associated with both coils 2 and 3. 

These results would be satisfactory, but for the arbitrary nature of the adjustment to the coil 2 cracking temperature. The gross error could also be eliminated by adjusting either the flow rates through the coil 2 and 3 or the inlet temperature to the radiant zone (crossover temperature) for coil 2. As it happens, the best reduction in... 

The EB entering the styrene plant is generally heated to the threshold cracking temperature (about 1100°F) in a heat exchanger The counter flow in the exchanger is the effluent from the second stage reactor, as shown... 

This type of reactor aims to challenge fast fluidization with its 1 to 10 second gas residence time as the prime reactor for the catalytic cracking of petroleum. The claim is that the higher cracking temperature and shorter residence time will give a very different—and better—distribution of reaction products. 

Removal of naphtha and distillate fractions from the crude oil under atmospheric pressure distillation requires charge temperatures to be maintained below the cracking temperature of the crude oil components. This temperature will vary but can typically range from 750°F to 800°F (398.9°C to 426.7°C). Occasionally, even lower temperatures may be required. Above these temperatures, crude oil components can begin to thermally crack and foul processing equipment. 

Table VI. Effect of Cracking Temperature in Fluid Catalytic Cracking Using Silica-Alumina Catalyst...

The major industrial source of ethylene and propylene is the pyrolysis (thermal cracking) of hydrocarbons.137-139 Since there is an increase in the number of moles during cracking, low partial pressure favors alkene formation. Pyrolysis, therefore, is carried out in the presence of steam (steam cracking), which also reduces coke formation. Cracking temperature and residence time are used to control product distribution. 

BERGIUS PROCESS. Formation of petroleum-like hydrocarbons by hydrogenation of coal at high temperatures and pressures (e.g.. 450 C and 300 atm) with or without catalysts production of toluene by subjecting aromatic naphthas to cracking temperatures at 100 atm with a lovt partial pressure of hydrogen in the presence of a catalyst. 

The aromatic ring is considered fairly stable at moderate cracking temperatures (350-500°C, 660-930°F). Alkyl aromatics, like the alkyl naphthenes, are more prone to dealkylation than to ring destruction. However, ring destruction of the benzene derivatives occurs above 500°C (930°F), but condensed aromatics may undergo ring destruction at somewhat lower temperatures (450°C, 840°F). 

Cracking temperature the temperature (350°C 660°F) at which the rate of thermal decomposition of petroleum constituents becomes significant. 

Figure 2 shows the effect of cracking temperature at 2 s vapor residence time on the yields of BTX, benzene, and ethylene from Linby coal (A), coal extract (B), and anthracene oil (C). 

Figure 2. Effect of cracking temperature on yields from unhydrogenated coal-derived materials top, Linby coal middle, anthracene oil extract of Linby coal bottom, anthracene oil carbonizer temperature, 873 K vapor residence time, 2 s ...

Figure 3. Effect of cracking temperature on yields from further hydrogenated extracts D1 (top) and El (bottom) (X) BTX, (A) ethylene, (O) benzene vapor residence time, 0.4 s nitrogen diluent...

Figure 4. Variation of yields with hydrocarbon type P = paraffin (n-undecane), N = naphthalene (cis/trans decalin), HA = hydroaromatic (tetralin), A = aromatic (mesitylene) cracking temperature, 1133 K vapor residence time, 1 s...

Cracking temperature and vapor residence time were the most important parameters controlling the cracking reactions. Within the range of conditions tested, other variables such as type and area of cracking surface, the vapor concentration of the feedstock and presence of steam made little difference to the yields of BTX and ethylene. Steam is used as a diluent and... 

Assuming that cumene vapor at cracking temperature behaves as a... 

The plot of at versus poison compounds loading Is shown In Figure 3. It shows that ot is linearly dependent on the pyridine loading and independent of the cracking temperature. The parameter, at, can be expressed for pyridine poisoning as follows ... 

The reactant mixture then enters the tubular reactor or the radiant coil at the cross-over temperature generally above 1000° F. It is rapidly heated to the cracking temperature by radiant heat supplied by burners in the combustion chamber. The gas leaving the reactor enters the transfer line exchanger where it is rapidly quenched to avoid decomposition of valuable products. 

---