PTQ Q4 2024 Issue

Nominal Gas-to-oil (Nm/m)

250

500

Mean (SZ54 yield (wt%)) (Catalyst=CoMo) Mean (SZ54 yield (wt%)) (Catalyst=NiMo) Mean (SZ54 yield (wt%)) (Catalyst=NiW) Mean (HS yield (wt%)) (Catalyst=CoMo) Mean (HS yield (wt%)) (Catalyst=NiMo) Mean (HS yield (wt%)) (Catalyst=NiW) Mean (C mercaptans yield (wt%)) (Catalyst=NiW) Mean (C mercaptans yield (wt%)) (Catalyst=CoMo) Mean (C mercaptans yield (wt%)) (Catalyst NiMo)

150

170

190

210

230

150

170

190

210

230

Temperature (˚C)

Figure 7 Product yields resulting from the decomposition of TBPS over CoMo, NiMo, and NiW catalysts at PH2 = 60 bar (Run02)

influence of temperature and LHSV on product distribution followed expected trends. The results also indicated that C4 mercaptans and isobutene acted as intermediate reaction products, with C4 mercaptans likely serving as intermedi - ates in the formation of isobutene. Overall, the findings pro - vided valuable insights into the decomposition behaviour of TBPS and its interaction with NiMo catalysts in naphtha hydrotreatment processes. Decomposition of TBPS over CoMo, NiMo, and NiW catalysts used in diesel hydrotreating Decomposition of TBPS over CoMo, NiMo, and NiW cata - lysts was investigated in Run02 and Run03, and the result - ing product distribution of sulphur and non-sulphur species vs temperature is illustrated in Figure 7 . The data is grouped by LHSV and gas-to-oil ratio, with a specific focus on the condition at LHSV = 0.5 and gas-to-oil ratio = 500 in the first quadrant from Run02. Notably, the observed trends were consistent across various LHSV and gas-to-oil ratios, allowing us to concentrate on this representative condition. The presence of a catalyst significantly facilitated the decomposition of TBPS into both sulphur-containing and non-sulphur-containing species, confirming the findings

from Run01 and closely aligning with those of Run03. In the first quadrant, at the lowest temperature of 150°C, approximately 85% of TBPS decomposed, with tert-butyl mercaptan constituting around 55% of the product yields and H₂S accounting for approximately 30%. The notable abundance of C₄ mercaptans can be attributed to the rela - tively weak S-S bonds present in TBPS, which easily break under the test conditions. Consistent with the results obtained in Run01, the decom - position of TBPS increased as the temperature rose, with nearly complete conversion observed at 240°C. Within the temperature range of 150-210°C, C₄ mercaptans under - went rapid decomposition, leading to the formation of H₂S, which reached its peak concentration above 220°C. Similar to the findings in Run01, C₄ mercaptans acted as intermedi - ate reaction products in the decomposition of TBPS to H₂S. Interestingly, the LHSV and gas-to-oil ratio had a mild impact on product distribution. Regardless of catalyst type, at fixed temperature and LHSV, an increase in the gas-to-oil ratio from 250 to 500 resulted in a minor effect on the yield of unconverted TBPS but had a more pronounced influence on the C₄ mercaptans yield. This observation can be attributed to the larger volumetric flow rate of gas, leading to shorter

PTQ Q4 2024