active sites from nitrogen to meet the refiner’s FCC unit product yields, selectivity, and operations. Hydrodearomatisation (HDA) activity The aromatics content in Figure 6 is represented for both the feed and the products specific to all the catalyst con - figurations tested at 370°C/80 barg (condition 4). Excel rejuvenated catalysts as standalone have exhibited equal performance in terms of aromatic saturation in comparison to their parent fresh, reaching about 35 wt% as mono aro - matics for all catalyst configurations. Aromatic compounds are not easily cracked in an FCC unit, and the limited amount of cracking achieved can produce a large amount of coke, deactivating the active site of the FCC zeolite catalyst. Excel rejuvenated cata - lysts exhibit a high degree of poly-nuclear aromatic (PNA) saturation to promote conversion in the FCC into more valuable products compared with fresh. Figures 7 and 8 show volume swell efficiencies and com - pare, side-by-side, Excel and fresh catalyst at two different pressures. The term ‘volume swell’ refers to liquid volume increase when the product density and boiling range are lowered as a result of the hydrotreating process. This is induced by different reactions, such as HDS and HDN, but more importantly, the saturation of poly-aromatics and mono-aromatics. Figures 7 and 8 quantify the volume swell by comparing the liquid product density with the feed density. Both Excel rejuvenated catalysts and fresh catalysts enable about 102.4% of volume swell to be achieved at 80 barg/375°C, whereas the volume swell enables 102.8% to be achieved at the same temperature but at a higher pressure (120 barg). This slightly higher volume swell can be explained by the fact that HDN and, more importantly, aromatic satura - tion (ASAT) are enhanced at a higher partial pressure of H₂. In Figures 9 and 10 , Excel rejuvenated catalyst exhibited a similar C₅+ yield compared to their parent fresh, namely
40
Feed
Fresh 2 Excel 1 Excel 2 Excel 3 Fresh 3 Fresh 1
30
20
10
0
Mono- aromatics
Di-aromatics Tri-aromatics Tetra-aromatics
Figure 6 Aromatics content for catalyst configurations tested at 80 barg and 370°C
• Effect of H₂ partial pressure on HDN is more significant than HDS. It can be explained by the fact that hydrogena - tion of an N-containing ring occurs prior to C-N bond scis - sion over conventional catalysts • The HDN rate can be affected by the equilibrium of N-ring hydrogenation because N-ring hydrogenation occurs before nitrogen removal (hydrogenolysis). In marked contrast, HDS does not always require hydroge - nation. HDS can proceed via two possible mechanisms: (1) ring hydrogenation followed by hydrogenolysis or (2) direct hydrogenolysis. That is the reason why HDN reac - tions have been enhanced when pressure increased from 80 to 120 barg • Excel rejuvenated NiMo catalyst exhibited higher HDN activity compared to its fresh (and other fresh) or Excel rejuvenated CoMo/NiCoMo catalysts: 120 ppmwt nitrogen for Excel vs 160 ppmwt for fresh at 120 barg and 375°C • The rejuvenated catalyst will protect FCC zeolite catalyst
104
104
0.92
0.92
103
103
0.91
0.91
102
102
0.9
0.9
101
101
0.89
100
0.89
100
90
0.88
90
0.88
30 31 32 33 34 35 36 37 38
16 17 18 19 20 21 22 23 24
TOS [day]
TOS [day]
Density: Fresh 1 Density: Fresh 2 Density: Excel 1 Density: Excel 2 Density: Excel 3 Density: Fresh 3
Volume gain: Fresh 1 Volume gain: Fresh 2 Volume gain: Excel 1 Volume gain: Excel 2 Volume gain: Excel 3 Volume gain: Fresh 3
Density: Fresh 1 Density: Fresh 2 Density: Excel 1 Density: Excel 2 Density: Excel 3 Density: Fresh 3
Volume gain: Fresh 1 Volume gain: Fresh 2 Volume gain: Excel 1 Volume gain: Excel 2 Volume gain: Excel 3 Volume gain: Fresh 3
Figure 7 Volume gain for catalyst configurations tested at 80 barg
Figure 8 Volume gain for catalyst configurations tested at 120 barg
74
PTQ Q4 2022
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