(201c) In-Situ Evaluation of the Concentration of 1-Hexene in a Laboratory-Scale Fluid Catalytic Cracking (FCC)

In-situ evaluation of the
concentration of 1-hexene in a laboratory-scale Fluid Catalytic Cracking (FCC)

Juan Lacayo, Sebastián López, David Soto, Alejandro
Molina.

jglacayol@unal.edu.co, selopezgo@unal.edu.co, dasotog@unal.edu.co, amolinao@unal.edu.co.

Bioprocesos y Flujos Reactivos, Facultad de Minas,
Universidad Nacional de Colombia - Sede Medellín, Carrera 80 # 65-223,
Medellín, Colombia

Presenting author: Alejandro Molina.

Abstract:
The
concentration of 1-hexene at conditions similar to those observed in FCC
industrial units was determined in situ with an optical technique. Experiments
were carried out in a laboratory-scale (internal diameter = 1.3 cm and 110 cm
of length), semi-continuous downer reactor that allows optical access through
fused quartz walls. Equilibrated FCC catalyst with a mean particle size of 84
µm was injected to the reactor at a rate of 30 g/min to a flow (300 - 3000
sccm) of 1-hexene that entered the system as a vapor at 373 K. The estimated
catalyst to oil ratio was between 20 - 70. The light source was a helium-neon
laser (2.0 mW minimum) operating at 2949.9 cm^-1 (3.39 µm). The laser
beam traversed the reactor and was modulated with an optical chopper operating
at 500 Hz. A PbSe photodetector was coupled to a data acquisition system and
the amount of light absorbed was quantified as fractional transmission (I/Io).
Figure 1 presents a schematic of the reaction setup. Estimated residence times
for particles and gas were between 2 - 5 and 8 - 25 seconds, respectively. The
experiments were carried out in the range at temperatures varying between 373 K
and 673 K and at 0.85 atm.

Figure
2 shows the variation of I/Io with the concentration of 1-hexene. The
comparison is made for experiments in the absence and presence of the catalyst
and at 373 K, 523 K, and 673 K. In the catalyst-free experiments, the fact that
the variation of I/Io is not linear suggests that at high 1-hexene
concentration the path becomes optically thick and linearity is lost. In the
presence of particles, I/Io increases as the value of Io decreases due to light
absorption by the particles. Nevertheless, a good linear correlation (r²=0.9774)
was found at all temperatures. Figure 2 also marks concentrations of
experimental setups [1,2] used for the characterization of FCC systems. The
fact that  I/Io linearly correlates with the 1-hexene concentration at
conditions similar to those used to characterize FCC and in the presence of
catalyst gives confidence that this system can be used to measure the advance
of the FCC reaction in industrial FCC units for process control applications
and in the development of new petroleum refining technologies.

Keywords: Fluid catalytic cracking,
downer reactor, in situ measurement.

References

[1] Corma, A.,
Martı́nez, C., Melo, F. V., Sauvanaud, L., & Carriat, J. Y.
(2002). A new continuous laboratory reactor for the study of catalytic
cracking. Applied Catalysis A: General, 232(1-2), 247-263.

[2] Bryden, K., Weatherbee,
G., & Habib, E. T. (2013). Flexible pilot plant technology for evaluation
of unconventional feedstocks and processes. Catalagram, 113,
3-21.