Catalytic
decomposition of pyrolysis fuel oils (PFO) for selective
production of hydrogen without any significant formation of greenhouse
gas (CO2 and CH4) was investigated using ferrierite
(FER) zeolites with different Si/Al molar ratios. The hydrogen production
rate based on the feed moles of PFO was maximized on the FER having
a Si/Al molar ratio of 10.4, and the hydrogen production rate on the
FER zeolites was well correlated with their amounts of strong acid
sites which easily form the active coke intermediates. In situ generated
crystalline coke precursors on the acidic FER(10) surfaces having
larger amounts of defect sites further played an important role as
catalytic active sites for PFO decomposition and reforming reaction
of CH4 generated as a main byproduct. The crystalline phases
of the encapsulated graphitic carbon layers formed on the outer surfaces
of the FER zeolites were strongly affected by their original acidic
strengths, which simultaneously altered a steady-state hydrogen production
rate with different product distributions of liquid-phase polycyclic
aromatic components. Less amounts of amorphous polyaromatic chemicals
were formed on the most active FER(10) by easy decomposition reactions
of the cracked intermediates from PFO. Although the initial activity
of catalytic PFO decomposition was well correlated with the number
of acidic sites of FER zeolites, the steady-state production rate
of pure hydrogen was significantly affected by the newly formed surface
coke properties on the carbon-encapsulated FER such as its crystallinity
and number of defect sites. The FER(10) showed a higher catalytic
activity for PFO decomposition due to its abundant strong acidic sites
and newly formed active graphitic carbon layers for a further CH4 reforming reaction.