The_Catalyst_Review_February_2024 - 9

SPECIAL FEATURE
Methane and Ethane. The methane and ethane selectivity
decreases gradually in direct proportion as the olefin yields
increase over the course of 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. Notably, the normal butane yield is
most sensitive to reactor temperature increases with an approximate
0.5 wt% selectivity decline for each 10 °C increase.
Coke. Low coke yield is a requirement for a fixed-bed operation.
The initial cracking studies performed by Gasolfin produced a
coke yield too high for a fixed bed operation as observed by cycle
lengths of a few hours up to about 12 hours. After substantial
work, Gasolfin has developed a catalyst system with coke yields
averaging less than 0.25 wt% permitting cycle lengths of 100-120
hours (4-5 days) yet delivering the activity required to convert low
molecular weight paraffins such as normal and isopentane. This
catalytic breakthrough is protected by several patents and trade
secrets. Table 2 presents the feed qualities and yield selectivities
for the feeds employed while designing the Gasolfin catalyst
system.
Pentane Hexane
PIONA (wt%)
Total Iso Paraffins
Total Normal Paraffins
Total N-Olefins
Total I-Olefins
Total Di Olefins
Total Saturated Naphthenes
Total Unsaturated Naphthenes
Total Aromatics
Total
Carbon Number (wt%)
Butanes (C4)
Pentanes (C5)
Hexanes (C6)
Helptanes (C7)
Octanes (C8)
Nonanes (C9)
Decanes (C10)
Undecanes (C11)
Total
Yield Selectivities (wt%)
Conversion
Hydrogen
Methane
Ethane
Ethylene
Propane
Propylene
Isobutane
Normal butane
Butylene
Total olefin
42.3
48.9
1.7
1.3
0.3
2.0
0.1
3.4
100.0
1.0
88.8
7.2
1.7
0.8
0.3
--100.0
35.2
0.8
7.8
10.1
19.2
5.4
32.1
0.8
7.6
16.1
67.4
2.5
97.1
---0.4
--100.0
LSR
36.9
46.2
---14.7
-2.3
100.0
-0.1
99.8
0.1
----100.0
34.2
0.7
1.5
9.5
7.1
12.3
39.8
0.9
4.5
23.7
70.7
0.5
38.5
59.9
1.1
----100.0
30.9
0.6
7.8
10.4
16.5
8.6
34.3
1.0
2.8
18.0
68.8
Table
2. Gasolfin yield selectivities.
Source: Author
FRN
36.2
38.5
0.1
--14.9
-10.3
100.0
3.9
19.1
24.9
23.5
20.0
5.6
0.0
3.0
100.0
35.2
0.8
5.6
7.3
12.6
8.4
31.9
2.8
11.2
19.4
63.9
Pyrolysis
14.9
16.9
16.8
17.3
2.2
15.7
10.4
5.8
100.0
8.6
78.6
8.4
4.5
----100.0
35.3
0.5
3.7
6.0
17.3
10.0
34.6
2.2
5.7
20.1
72.0
FCC
30.9
4.1
11.6
19.4
0.3
7.4
4.2
22.4
100.0
1.2
25.2
22.8
19.5
17.4
10.0
3.6
0.4
100.0
36.1
0.4
1.5
2.2
11.7
4.7
46.0
0.9
2.8
29.7
87.5
Chart
4. Typical butylene selectivities for various feedstocks.
Source: Author
Inovacat recently converted three feedstocks, LSR, FRN
and HCN, from an Asian refiner seeking maximum
propylene. These feeds were converted across a single
batch of Gasolfin catalyst deactivated to simulate a midcatalyst
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 was 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 Chart 5
provides the conversion for the LSR feed and Chart 6
provides the propylene yield for the FRN feed.
Chart 5 indicates the effect of reactor temperature
on conversion for LSR naphtha. The cycle was initiated
at 600 °C. The reactor temperature was increased
by 10 °C after 48 hours followed by a second 10 °C
increase after 63 hours. The conversion increased by
3.7 wt% for each 10 °C temperature increase. The rate
of conversion loss was -0.15 wt%/hr after 48 hours at
Chart 3. Typical ethylene selectivities for various feedstocks.
Source: Author
The Catalyst Review
February 2024
9
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