Nominal Gas-to-oil (Nm /m )
250
500
40
Mean (i-C = yield (wt%)) (Catalyst=CoMo) Mean (i-C yield (wt%)) (Catalyst=CoMo) Mean (i-C = yield (wt%)) (Catalyst=NiW) Mean (i-C yield (wt%)) (Catalyst=NiW) Mean (i-C = yield (wt%)) (Catalyst=NiMo) Mean (i-C yield (wt%)) (Catalyst NiMo)
30
20
10
0
40
30
20
10
0
150 160 170 180
230 240 190 200 210 220
150
160
170
180
190
200
210
220
230
240
Temperature [T] (˚C)
Figure 9 Product yields of isobutene and isobutane resulting from the decomposition of TBPS over CoMo, NiMo, and NiW catalysts at PH2 = 60 bar (Run02)
Conclusion The study aimed to investigate the decomposition profile of TBPS, a sulphiding agent, in hydroprocessing catalysts. The presence of a catalyst significantly facilitated the decom - position of TBPS into sulphur-containing and non-sul - phur-containing species. The type of catalyst employed exhibited a discernible impact on the decomposition of TBPS. The CoMo catalyst facilitated a faster decomposition rate compared to the NiMo and NiW catalysts. Notably, sig - nificant differences were observed in the decomposition of C4 mercaptans and H₂S, indicating that the catalyst type played a crucial role in the C-S bond cleavage step, leading to the formation of isobutene and H2S species. The thermal decomposition of TBPS started at around 170°C and increased with temperature. At tempera - tures below 200°C, TBPS remained mostly unconverted or decomposed into non-volatile sulphur components. However, in the presence of a catalyst, TBPS began to decompose at lower temperatures, indicating the catalytic effect on its decomposition. The relatively weak S-S bonds in TBPS facilitated its breakdown, leading to the formation of tert-butyl mercaptan, which then underwent further decomposition into H₂S and isobutene. These findings
align with previous studies that reported a decomposition temperature of approximately 160°C for TBPS. The decomposition of TBPS increased as the temperature rose, with nearly complete conversion observed at 240°C. H₂S was the primary by-product of TBPS decomposition, with a maximum yield observed around 230°C. The influence of temperature and LHSV on the product distribution fol - lowed expected trends. At a given temperature, the fraction of unconverted TBPS was higher at higher LHSV (shorter contact times), while the trends in product evolution shifted to higher temperatures in reactors operating at higher LHSV. Furthermore, various factors were found to influence the decomposition of TBPS and the formation of H2S, C4 mer- captans, isobutene, and isobutane. The H2 partial pressure, gas-to-oil ratio, LHSV, and temperature all exhibited varying degrees of influence on the product distribution. The H2 par- tial pressure showed a weak effect on TBPS decomposition and the formation of H₂S, C4 mercaptans, isobutene, and isobutane, with some dependence on the catalyst type. The gas-to-oil ratio also had a weak effect on TBPS decomposition and the formation of H₂S and C4 mercap- tans, except for the NiW catalyst at PH2 = 60 bar and tem - peratures above 200°C. The LHSV demonstrated a weak
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PTQ Q4 2024
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