The Hydroformylation of Short-chain Olefins in a Venezuelan Refinery’s Naphtha Cut
Table 2: Main Products Obtained in the Hydroformylation of the Olefins Present in a Light Naphtha Cut Products
2-Methylbutanal 3-Methylbutanal
Cyclopentanecarboxaldehyde 2-Ethylbutanal
2-Methylpentanal Hexanal
2,3-Dimethylpentanal 2,4-Dimethylpentanal 2-Methylhexanal 3-Methylhexanal 4-Methylhexanal 5-Methylhexanal Heptanal
2-Ethylhexanal Octanal
Conversion (%) l/b Ratio
Molar Distribution (%) Over time* 0 hours 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0
4 hours 1.02 0.25 0.28 0.06 0.48 2.33 0.00 0.04 0.11 0.01 0.01 0.03 0.22 0.04 0.00 17
0.00 1.38 1.08
8 hours 2.53 0.53 0.44 0.11 0.69 3.87 0.00 0.08 0.17 0.03 0.03 0.05 0.38 0.05 0.00 35
12 hours 24 hours 2.97 1.11 0.54 0.23 3.96 4.93 0.15 0.19 0.32 0.06 0.07 0.32 0.39 0.07 0.03 50
4.57 2.25 0.86 0.38 8.70 5.10 0.21 0.27 0.87 0.16 0.27 0.75 0.55 0.10 0.09 67
0.64 0.43 *Molar percentage present in the total naphtha mixture. Conditions: T = 70ºC; substrate catalyst (S/C) 200/1; l/b ratio = linear-to-branched ratio.
36 hours 50 hours 5.51 3.13 0.95 0.48
5.65 3.26 0.96 0.54
11.39 5.59 0.28 0.46 1.51 0.28 0.28 0.83 0.79 0.13 0.11 81
0.33
11.75 6.67 0.37 1.11 1.65 0.90 0.60 1.24 0.87 0.27 0.24 93
0.37
72 hours 5.54 3.19 0.93 0.69
11.93 6.78 0.53 1.16 1.87 0.92 0.79 1.44 1.20 0.30 0.44 96
0.39
78 hours 5.50 3.17 0.93 0.68
11.89 6.76 0.58 1.13 1.86 0.92 0.79 1.45 1.21 0.31 0.42 96
0.39
Figure 1: Reaction Profile of the Biphasic Hydroformylation of Olefins Present in Venezuelan Naphtha without a High-pressure Reservoir
100
10 20 30 40 50 60 70 80 90
0 0 4 8 1216202428323640
Reaction time (hours) 44 48 52 56 60 64 68 72 76 80
Figure 2: Reaction Profile of the Biphasic Hydroformylation of Olefins Present in Venezuelan Naphtha with a High-pressure Reservoir
100
10 20 30 40 50 60 70 80 90
0 0 4 8 1216202428323640
Reaction time (hours) 44 48 52 56 60 64 68 72 76 80
14
Chromatographic analysis showed that the light naphtha cut used in the experiments consisted of olefins (42%), paraffins (31%), naphthens (19%) and aromatics (7%).
The olefins present in the naphtha cut were also classified according to their chain length as C5 (5%), C6 (56%) and C7 (39%). Finally, the olefin content was classified as presented in Table 1 according to steric hindrance.
This olefin distribution was favourable for the hydroformylation process, since nearly 55% of the olafins were mono- and di-substituted. In the authors’ experience, these substituted forms reacted rapidly under the best operational conditions. However, the presence of so many sterically hindered olefins (45%) slowed down the reaction times required to achieve high conversion into aldehydes.
Reactor Charged Once
In these experiments, the reactor was charged once to the working pressure of syn-gas (825 psi) and the reaction ran without the use of a high-pressure reservoir. A reaction profile of the biphasic hydroformylation of the olefins present in naphtha is shown in Figure 1. Here the conversion refers to the molar percentage of the total olefins that react to form aldehydes at a given time. All of the other components of the light naphtha cut acted as solvents for the biphasic reaction.
The total olefin conversion reached high values after 48 hours of reaction, which is an extremely long period compared with the times obtained in previous studies with the same catalyst using 1-hexene as a model molecule.7
competition between the different substrates for the active sites of the catalyst. The percentage conversion continued to rise until it reached a maximum of 96% after 72 hours of reaction time.
Table 2 lists the major aldehydes produced. An analysis of these shows that the linear-to-branched ratio (l/b) varies from 1.39 at four hours to 0.39 at 78 hours of reaction time. This is evidence of a noticeable tendency towards the formation of branched aldehydes. This is very attractive from a petrochemical point of view, since branched products
HYDROCARBON WORLD – VOLUME 6 ISSUE 1
This behaviour corroborated the complexity of
Total olefin conversion (%)
Total olefin conversion (%)
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