105
resid can be cracked is an important consideration in the design of resid catalysts,
among others. Resid feeds are generally characterized by their high amount of contaminant metals and high carbon to hydrogen ratio, which yields copious amount of
coke and dry gas when processed. Hydrotreating the feed before processing helps
but requires significant capital and operation cost. Polyaromatic compounds in the
feed, which remain unsaturated in the hydrotreating process, oligomerize to form
refractory compounds, which end up as coke. Vanadium and nickel contaminants
catalyze hydrogenation reactions, which increase the dry gas yield. Hence, catalyst
coke selectivity is another important catalyst performance characteristic. Higher
coke yield translates to higher dense bed temperature in the regenerator, which further lowers cat/oil ratio and conversion and can damage the catalyst or even the
unit’s metallurgy itself. Resid processing units are hence normally equipped with
catalyst coolers and multiple stages of regeneration. Catalyst stability at high temperatures and metal trapping characteristics are ensured by rare-earth stabilization
of zeolite and rare-earth-based vanadium traps. Feedstock properties along with the
dominant bottom-cracking mechanisms characteristic of the feed must also be considered when designing zeolite and matrix activity. Resistance to less common catalyst poisons such as iron is more critical for resid processing. Iron contaminants
alter the average bulk density of catalyst, thereby affecting fluidization, and also
adsorb onto the catalyst’s surface forming nodules. These nodules intensify the
attrition between catalyst particles and generate plenty of fines, which severely
influence units’ smooth running. A dense layer formed on the catalyst’s surface after
iron contamination, and the dense layer stops reactants to diffuse to inner structures
of the catalyst.
9 Summary
Fluid catalytic cracking (FCC) is a versatile process that can process a wide variety
of feeds at a wide range of operating conditions to obtain the required yield and
maximize the refinery’s profit. The profitability of any FCC unit relies largely on the
properties of the catalyst. Any and all limitations in the unit’s design can be supplemented by using the appropriate catalyst additives. There have been numerous
developments in the field of process design, operation, separation, catalyst design,
and synthesis; however, research has not come to a standstill. With the gradual shift
of the energy market toward alternate energy, the relevance of FCC has been shifted
from a refinery to the petrochemical complex. FCC can greatly contribute to the
ongoing integration of refineries to petrochemical complexes and help to maintain
the relevance of oil refining companies in the years to come.
Acknowledgments The authors thank the BPCL management for their encouragement and permission to publish this chapter.
Recent Developments in FCC Process and Catalysts
resid can be cracked is an important consideration in the design of resid catalysts,
among others. Resid feeds are generally characterized by their high amount of contaminant metals and high carbon to hydrogen ratio, which yields copious amount of
coke and dry gas when processed. Hydrotreating the feed before processing helps
but requires significant capital and operation cost. Polyaromatic compounds in the
feed, which remain unsaturated in the hydrotreating process, oligomerize to form
refractory compounds, which end up as coke. Vanadium and nickel contaminants
catalyze hydrogenation reactions, which increase the dry gas yield. Hence, catalyst
coke selectivity is another important catalyst performance characteristic. Higher
coke yield translates to higher dense bed temperature in the regenerator, which further lowers cat/oil ratio and conversion and can damage the catalyst or even the
unit’s metallurgy itself. Resid processing units are hence normally equipped with
catalyst coolers and multiple stages of regeneration. Catalyst stability at high temperatures and metal trapping characteristics are ensured by rare-earth stabilization
of zeolite and rare-earth-based vanadium traps. Feedstock properties along with the
dominant bottom-cracking mechanisms characteristic of the feed must also be considered when designing zeolite and matrix activity. Resistance to less common catalyst poisons such as iron is more critical for resid processing. Iron contaminants
alter the average bulk density of catalyst, thereby affecting fluidization, and also
adsorb onto the catalyst’s surface forming nodules. These nodules intensify the
attrition between catalyst particles and generate plenty of fines, which severely
influence units’ smooth running. A dense layer formed on the catalyst’s surface after
iron contamination, and the dense layer stops reactants to diffuse to inner structures
of the catalyst.
9 Summary
Fluid catalytic cracking (FCC) is a versatile process that can process a wide variety
of feeds at a wide range of operating conditions to obtain the required yield and
maximize the refinery’s profit. The profitability of any FCC unit relies largely on the
properties of the catalyst. Any and all limitations in the unit’s design can be supplemented by using the appropriate catalyst additives. There have been numerous
developments in the field of process design, operation, separation, catalyst design,
and synthesis; however, research has not come to a standstill. With the gradual shift
of the energy market toward alternate energy, the relevance of FCC has been shifted
from a refinery to the petrochemical complex. FCC can greatly contribute to the
ongoing integration of refineries to petrochemical complexes and help to maintain
the relevance of oil refining companies in the years to come.
Acknowledgments The authors thank the BPCL management for their encouragement and permission to publish this chapter.
Recent Developments in FCC Process and Catalysts