35
645
635
30
625
25
615
20
605
595
RX inlet temp Conversion
15
585
10
575
0
20
40
60
80
Cycle length, hours
Figure 2 Reactor temperature vs conversion – LSR feed
for the cycle. Butylene yield decreases by 0.5 wt% for each 10°C reactor temperature as the temperature is increased to maintain conversion as the cycle length progresses. • Methane and ethane: Methane and ethane selectivity decreases gradually in direct proportion as the olefin yields increase over the first 24 hours of the cycle. The methane yield increases by about 1.0 wt% and the ethane selectivity by about 0.75 wt% for each 10°C reactor temperature as the temperature is increased to maintain conversion as the cycle length progresses. • Propane, normal butane, and isobutane: The C₃ and C₄ paraffin selectivities all decline as the catalyst ages during the catalyst cycle. The paraffin selectivities decrease at the expense of the light olefin selectivities. The propylene and butylene yields increase to an asymptotic value over the first 20-30 hours of the cycle, while the ethylene selectivity increases by about 0.5 wt% for each 10°C reactor temperature
increase. Interestingly, the normal butane yield is most sensi- tive to reactor temperature increases, with an approximate 0.5 wt% selectivity decline for each 10°C increase. • Coke: A significant element of the Gasolfin catalyst is the very low coke yield of the system. The coke yield for both the paraffinic and olefinic components of the feedstocks is sig- nificantly less than 0.5 wt%. The low coke yield permits the catalyst to be operated in a fixed catalyst bed mode. Patents exist to protect this element of the technology. Table 2 presents the feed qualities and yield selectivities for the feeds employed while designing the Gasolfin cata- lyst system. Gasolfin has recently converted three feedstocks (LSR, FRN, and HCN) from an Asian refiner seeking maximum pro- pylene. These feeds were converted across a single batch of Gasolfin catalyst deactivated to simulate a mid-catalyst life age. The LSR and FRN feeds were cracked at an initial reactor inlet temperature of 600°C and a 550°C reactor inlet temperature for the FCC naphtha. The reactor temperature was increased once the conversion had reduced by 25%. The reactor temperature gradually increased as the catalyst deactivated. Each cycle was terminated when the reactor temperature reached 620°C. The cycle length for each feed was three to four days. Table 3 provides the feed composition, while Figure 2 provides the conversion for the LSR feed, and Figure 3 pro - vides the propylene yield for the FRN feed. Figure 2 indicates the effect of reactor temperature on
Refiner feed properties
Feed analysis
LSR
FRN
FCC
PIONA (wt%) Total iso paraffins
36.9 46.2
36.2 38.5
32.7
Total normal paraffins
7.0 8.2
Total N-olefins Total I-olefins Total di-olefins
– – –
–
0.2
15.1
–
0.0 8.4 3.2
Total saturated naphthenes Total unsaturated naphthenes
14.6
14.9
–
–
Total aromatics
2.3
10.3
25.5
Total
100.0
100.0 100.0
27 28 29 30 31 32 33 36 35 34 37
Carbon number (wt%) Butanes (C4)
0.5
3.9
1.0
Pentanes (C5) Hexanes (C6) Helptanes (C7) Octanes (C8) Nonanes (C9) Decanes (C10) Undecanes (C11) Dodecanes (C12)
38.5 59.9
19.1 24.9 23.5 20.0
23.3 20.6 16.2 15.2 11.8
1.1
– – – – –
5.6 0.0 1.0 2.1
7.1 3.8 1.1
0
20
40
60
80
100
Total
100.0
100.0 100.0
Cycle length, hours
Figure 3 Propylene selectivity – FRN feed
Table 3
47
Catalysis 2024
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