Gasolfin yield selectivities
Butane
Pentane
Hexane
LSR
FRN
FCC
Pyrolysis
PIONA (wt%) Total iso paraffins
8.0
42.3 48.9
2.5
46.0 49.0
41.9 23.7
30.9
14.9 16.9 16.8 17.3
Total normal paraffins
92.0
97.1
4.1
Total N-olefins Total I-olefins Total di olefins
– – – – – –
1.7 1.3 0.3 2.0 0.1 3.4
– – –
– – –
– – –
11.6 19.4
0.3 7.4 4.2
2.2
Total saturated naphthenes Total unsaturated naphthenes
0.4
4.3
21.3
15.7 10.4
– –
–
–
Total aromatics
0.7
13.2
22.4
5.8
Total
100.0
100.0
100.0
100.0
100.0
100.0
100.0
Carbon number (wt%) Butanes (C4)
100.0
1.0
–
6.6
– –
1.2
8.6
Pentanes (C5) Hexanes (C6) Helptanes (C7) Octanes (C8) Nonanes (C9) Decanes (C10) Undecanes (C11)
– – – – – – –
88.8
0.1
56.7 35.3
25.2 22.8 19.5 17.4 10.0
78.6
7.2 1.7 0.8 0.3
99.8
2.1
8.4 4.5
0.1
1.4
20.3 26.4 32.0 15.7
– – – –
– – – –
– – – –
– –
3.6 0.4
3.5
Total
100.0
100.0
100.0
100.0
100.0
100.0
100.0
Yield selectivities (wt%) Conversion
37.6
35.2
34.2
38.5
32.2
36.1
35.3
Hydrogen Methane
1.0
0.8 7.8
0.7 1.5 9.5 7.1
0,7 6.0
0.7 2.4 3.8
0.4 1.5 2.2
0.5 3.7 6.0
10.5 20.9 27.2
Ethane
10.1 19.2
10.0 15.3 14.3 30.1
Ethylene Propane Propylene Isobutane
15.8
11.7
17.3 10.0 34.6
8.3
5.4
12.3 39.8
7.3
4.7
32.1
32.1
40.5
46.0
– – –
0.8 7.6
0.9 4.5
2.5 4.7
1.4 4.7
0.9 2.8
2.2 5.7
Normal butane
Butylene Recycle
16.1 64.8 67.4
23.7 65.8 70.7
16.4 61.5 61.9
23.5 67.8 79.7
29.7 63.9 87.5
20.1 64.7 72.0
62.4 59.3
Total olefin
Table 2
recommended that sulphur be removed prior to the Gasolfin unit for polymer-grade propylene production. Removal of mercaptan and disulphide sulphur is recommended when processing cracked naphthas. Thiophene and benzothi- ophene are removed with the aromatics in the aromatic extraction step. The catalyst is also not affected by moisture but is temporarily impacted by the presence of nitrogen. The higher nitrogen contents of cracked naphthas, such as FCC naphtha or coker naphtha, are compensated for by increas- ing reactor catalyst loading. Nitrogen is released during regeneration, and sodium is a permanent poison. Yield selectivities Two important terms are ‘conversion’ and ‘yield selectivity’. Conversion is defined as ‘100 – recycle’. The targeted con - version is 35 wt% for maximum propylene yield. An addi- tional term related to conversion is ‘single pass conversion’. Single-pass conversion is defined as the conversion the reactor feed experiences after one pass through the reactor. The terms ‘conversion’ and ‘single pass conversion’ are used interchangeably within the Gasolfin technology. Yield selectivity is defined as ‘100 X (product yield conver - sion)’. The yield selectivity is the final yield for any product
after feed extinction. For example, the propylene yield selec- tivity of 35 wt% implies that the catalyst will convert the feedstock with a final yield of 35 wt% propylene at the exit of the unit, with further elaboration as follows: • Propylene: The propylene selectivity ranges from 30 to 46 wt%, depending upon feed composition. The propyl- ene yield increases by 3-5 wt% for the first 24 hours of a given cycle. The product yield asymptotically approaches the average value for the cycle. The propylene yield remains constant as the reactor temperature is increased to maintain conversion as the cycle length progresses. • Ethylene: The ethylene selectivity averaged 16.3 wt% with a low of 7.1 wt% for hexane cracking and a high of 27.2 wt% while cracking butane. The ethylene yield increases gradually across the cycle length by 2-3 wt%. Ethylene yield increases by 1.0 wt% for each 10°C reactor temperature as the temperature is increased to maintain conversion as the cycle length progresses. • Butylene: The butylene selectivity ranges from 16 to 30 wt%. The butylene yield increases as the average molecular weight of the feed increases. The butylene yield increases by about 3.0 wt% for the first 24 hours of a given cycle. The product yield asymptotically approaches the average value
46
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