Quartz reactor, coke formation

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 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.

It is seen that coke formation on the sample of foil is dependent on the material of the tubular reactor as is the product gas composition. With the steel reactor, preoxidation leads to a substantial increase in the coke formation on the steel foil (Figures 6 and 7). The effect of preoxidation is even more pronounced with Ni as the foil material (Figure 8). On the other hand, preoxidation does not lead to a high rate of coke formation on the steel foil if a quartz liner is used in the tubular reactor (Figure 9). 

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

The second broad grouping of papers (Chapters 13-17) describes useful design modifications for commercial plants. Surface reactions resulting in both the formation of coke and carbon oxides, and the destruction of olefins and other desired products are described. In quartz or Vycor glass reactors, however, such surface reactions are relatively unimportant and often have not been considered. Yet such reactions can be most significant in metal reactors when steam is used as a diluent of the entering feedstock. Data obtained in metal reactors are of value to the designer of plant equipment. 

---