PTQ Q4 2026 Issue

Quality of the light naphtha

60.00 50.00 52.00 54.00 56.00 58.00 62.00 64.00

Light naphtha

Period 1

Period 2 -25.8% -81.7% -19.7% +12.2% +15.1%

Total sulphur, ppm Mercaptans, ppm Thiophenes, ppm

Base Base Base Base Base 59% 41%

Benzothiophenes, ppm

FBP naphtha, °F

Sulphur < FBP wt% Sulphur > FBP wt%

97%

Table 2

reflects an inefficiency in the separation of the fractions, associated with the degradation of vapour-liquid contact in the upper section of the fractionator due to deposit build-up. This operational deterioration favours the carryover of heavier hydrocarbons into the light naphtha stream, affecting both the product quality and the process selectivity. In con- trast, during the second period, a significant improvement in sulphur distribution is observed. Despite the increase in the naphtha FBP, the fraction of sulphur present above this point decreases drastically, falling from 41% to just 3%. This behaviour is consistent with a recovery in the per- formance of the fractionation system, allowing for a more efficient separation between the light and heavy naphtha streams (see Figure 3 ). Additionally, this improvement in separation efficiency allowed for an increase in light naphtha yield, achieving volume increases of up to 5%, demonstrat- ing the direct impact of deposit removal on the overall per- formance of the unit. Conclusions The results of this study show that the formation of ammo- nium chloride (NH₄Cl) salts in the main fractionator of FCC units should not be treated solely as an operational problem, but as a systemic phenomenon directly related to the chlo- ride balance of the system. First operating period: Operation under severe salt fouling. During the first period, the unit had a recurring history of fouling in the fractionator overhead, characterised by the build-up of salt deposits that directly affected operational stability. This condition required: • Continuous use of salt dispersants, with an accumulated cost exceeding $700 million (COP). • Frequent washing with water in the top system, weekly for ΔP control. • Feed reduction during interventions, impacting operational continuity. • Increased frequency of failures in mechanical seals of pumping equipment, with average repair costs around $45 million (COP) and upgrade costs close to $140 million (COP) per event. From a process performance standpoint, sulphur speci- ation studies showed clear inefficiency in the separation zone between heavy naphtha and light naphtha, with sul- phur compounds being carried over to the fractionator over- head. This behaviour is consistent with the degradation of

Figure 3 Naphtha performance

vapour-liquid contact caused by the presence of deposits on the tower internals. In terms of chloride balance, this period was characterised by an open behaviour, with chloride output exceeding the input from the feed, indicating the existence of additional sources within the system. This scenario coincided with operation using a catalyst formulated with a chlorinated sol-alumina-based binder, whose contribution to the sys- tem’s chloride inventory became evident from the compara- tive analysis of the operating data. Second operating period: Elimination of the phenomenon and sustained stability. The transition to the second period, after replacing the catalyst with a technology free of chlorin- ated compounds, marked a substantial change in the unit’s behaviour. From this moment on, immediate and sustained operational improvements were observed: • Complete elimination of the need for continuous injection of salt dispersants. • Elimination of the periodic washes in the fractionator overhead. • Progressive reduction and stabilisation of the differential pressure (ΔP). • Improvement in the reliability of rotating equipment, with a reduction in failures associated with salts. • Sustained operation without evidence of deposit build-up. It is worth highlighting that this condition was not tem- porary. Operation free of salt build-up in the fractionator overhead system has been consistently maintained to date (2026), confirming the stability of the new operating state achieved and the resolution of the root cause of the problem. From the process perspective, a clear recovery of fraction- ation efficiency was observed. Light naphtha showed an increase in its FBP, accompanied by a sulphur distribution consistent with effective separation, eliminating the carry- over of heavy compounds to the overhead. Additionally, the improvement in separation efficiency allowed for an increase in the volumetric yield of light naphtha by up to 5%, reflect- ing a direct impact on the unit’s profitability. Operational implications and lessons learned This study shows that the strategies traditionally used in the industry, such as dispersants, frequent washes, or

PTQ Q4 2026