An ultraviolet Raman spectroscopic study of coke formation in methanol to hydrocarbons conversion over zeolite H-MFI

Towards real-time spectroscopic process control for the dehydrogenation of propane over supported chromium oxide catalysts

“…Based on Raman characteristics of different coke species reported by Chua and Stair (2003) assignments for the two most dominant types of coke observed can be made. Since the position and shape of bands shift as a function of temperature, it is most convenient to use the Raman spectra shown in Fig.…”

“…Especially, if the catalyst reaches a high temperature during coke combustion, this migration occurs more rapidly. Raman spectroscopy is an excellent method to track the different types of coke as they are being deposited on the catalyst (Chua and Stair, 2003). The advantage of using both UV-Vis and Raman spectroscopy simultaneously is that they provide complimentary information: electronic for UV-Vis and vibrational for Raman.…”

Characterisation of coking activity during supercritical hydrocarbon pyrolysis

“…The same type of coke has been analysed downstream the process in a reduced section, which shows that this coke does not stick to the wall. So that, it could have been mostly produced in the fluid flow and not on the reactor surface, which would be the result of catalytic reactions [40] [42] [43]. Thus, this coke is assumed to be a mix of pyrolytic and asphaltic ones because these ones have been respectively found in the hottest part of the reactor, near the furnace middle, and also near the furnace outlet, where the temperature is decreasing near 600 K. The high concentration of Nickel and Chromium in the stainless steel should favour the production of catalytic coke.…”

“…The surface roughness effect is not studied in this paper even if it is known that the coke formation depends on the open porosity of the material [40] [42] [51]. Furthermore, it appears that the carbon deposit rate found in various studies of the literature could not be extrapolated to our case.…”

“…Various parameters can influence the coke formation : the temperature [28] [40], the pressure [42], the physical state of the fluid [36] [41], the material nature of the reactor [28], the residence time in the process [28] [42] [40], the dilution and the pyrolysis rate [28], the flow turbulence [32], the presence of dissolved impurities [43], the presence of colder parts in the process [32]- [34] and the combined effect of applied heat flux and residence time [44]. It has to be noticed that for some rare specific cases, a moderate heat flux applied on the fluid could provide more carbon deposit than high temperature if the fluid is not completely evaporated [43].…”