CATALYST IN OIL AND GAS INDUSTRY

CHUNG KEN VUIA98753KB/4

Zeolite in Hydrodesulphurization

ZEOLITES AS CATALYST

Crystalline, hydrated, microporous aluminosilicate mineral

Network of tetrahedral of aluminate and silicate ions, linked by sharing oxygen atoms

Contains alkaline earth metals and water trapped in the cavities

High boiling point, largely insoluble in water or inorganic solvent, non-flammable and non-oxidize in air

Used vastly in petrochemical processes: Fluid catalytic cracking Hydrodesulphurization Isomerization

Molecular structure of ZSM-5Source: Clements et al. 2010

Structures of four selected zeolites (from top to bottom: faujasite or zeolites X, Y; zeolite ZSM-12; zeolite ZSM-5 or silicalite-1; zeolite Theta-1 or ZSM-22) and their micropore systems and dimensions

Source: Weitkamp 2000

HYDRODESULPHURIZATION (HDS)

• Desulfurization can be performed via two parallel pathways: Direct desulfurization pathway (DDS) Hydrogenization pathway (HYD)

• Compounds containing sulphur undergo a catalytic reaction with hydrogen to form the corresponding hydrocarbon and hydrogen sulphide (El Kady et al. 2010)

Two distinctive HDS process pathways of 4,6-dimethyldibenzothiopheneSource: Oyama et al. 2012

HYDRODESULPHURIZATION (HDS)

HDS helps to eliminate sulphur to achieve desirable low-sulphur diesel fuel

Commercial HDS catalyst: Mo or W supported on γ-alumina, promoted by either Co or Ni

1. El Kady et al. investigate the use of CoMo/γ-alumina on HDS The differences between equilibrium deposition filtration (EDF)

and incipient wetness impregnation (IWI)

Temperature (°C)

kS (h-1) kA (h-1)

EDF IWI EDF IWI

340 2.480 2.050 0.874 0.570

360 3.230 2.500 1.180 0.777

380 3.800 3.190 1.360 1.000

400 4.500 4.180 1.280 0.860

Rate constants for HDS and hydrodearomatization (HAD) of HGO at various reaction temperatures at P = 50 bar and LHSV = 1.5 h-1

Source: El Kady et al. 2010

While alumina catalyst alone can demonstrate high activity for hydrogenation, HDS and hydrodenitrogenation (HDN), the acidity property is insufficient to promote hydrocracking and isomerisation.

2. Nakano et al. suggested the combination of USY-zeolite with γ-alumina Physical mix of zeolite and γ-alumina may be unfavoured due to

over-cracking and coke formation Coating of alumina on zeolite particle

HYDRODESULPHURIZATION (HDS)

T (°C) CZ-1 CZ-5 AZ LX6kS

(h-1)S (ppm) kS

(h-1)S (ppm) kS

(h-1)S (ppm) kS

(h-1)S (ppm)

330 25.8 113.3 17.4 228.3 24.7 122.0 14.9 300.5345 71.0 16.7 46.9 37.0 63.8 20.5 37.9 55.4360 144.0 4.2 94.9 9.5 131.8 5.0 93.4 9.8

Table 2 Performances of catalysts in dual-bed configuration for HDS of HGO at different temperatures under operating conditions of P = 6 MPa and LHSV = 1.0 h-1

Source: Nakano et al. 2013