3
advancements in the area of hydrotreating/hydrodesulfurization of petroleum fractions with respect to the nature of active phase and support material.
2 Chemistry of Deep Hydrotreating/Hydrodesulfurization
The chemistry of petroleum hydroprocessing has been extensively studied and
reported in the literature. Hydroprocessing involves a combination of hydrotreating
and hydrocracking reactions. During the hydrotreating process, predominant reactions are removal of heteroatoms and saturation of unsaturated hydrocarbons (olefins and aromatics) with minimal hydrocracking of the feedstock. During the
hydrocracking process, cracking reactions occur predominantly in addition to
hydrotreating reactions resulting in significant conversion of the feedstock into
high-quality lighter fractions. Catalysts play an important role during hydrotreating
of petroleum fractions in controlling the rate of certain chemical reactions. The
chemical reactions involved in the hydrotreating process are of two types: desirable
and undesirable reactions (Table 1). Desirable reactions are those that help the main
purpose of the hydrotreating process, while undesirable reactions are those that
result in the loss of valuable components of feed or decrease of catalyst activity.
Hydrodesulfurization refers to the removal of organic sulfur from various hydrocarbon fractions. There are a wide variety of organic sulfur compounds present in
various petroleum fractions, which include mercaptans, sulfides, disulfides, and
thiophene derivatives. Mercaptans, sulfides, and disulfides are aliphatic sulfur compounds. Other thiophenic sulfur compounds can be broadly grouped into the following three categories:
1. Thiophenes.
2. Benzothiophenes.
3. Dibenzothiophenes.
It is easier to remove sulfur from compounds such as mercaptans, sulfides, and
disulfides. However, it is increasingly difficult to remove sulfur from aromatic sulfur compounds such as thiophenes, benzothiophenes, dibenzothiophenes, and substituted dibenzothiophenes during the hydrotreating process. Thiophenes are the
easiest to desulfurize compared to benzothiophenes and dibenzothiophenes. It is
Table 1 Desirable and undesirable reactions during hydrotreating of petroleum fractions
Desirable reactions
Undesirable reactions
Hydrodesulfurization
Hydrocracking
Hydrodenitrogenation (HDN)
Coking
Hydrodeoxygenation
Saturation of olefinic compounds
Hydrogenation of aromatic compounds
Hydrodemetallization (HDM)
Recent Advances in Hydrotreating/Hydrodesulfurization Catalysts: Part I: Nature…
advancements in the area of hydrotreating/hydrodesulfurization of petroleum fractions with respect to the nature of active phase and support material.
2 Chemistry of Deep Hydrotreating/Hydrodesulfurization
The chemistry of petroleum hydroprocessing has been extensively studied and
reported in the literature. Hydroprocessing involves a combination of hydrotreating
and hydrocracking reactions. During the hydrotreating process, predominant reactions are removal of heteroatoms and saturation of unsaturated hydrocarbons (olefins and aromatics) with minimal hydrocracking of the feedstock. During the
hydrocracking process, cracking reactions occur predominantly in addition to
hydrotreating reactions resulting in significant conversion of the feedstock into
high-quality lighter fractions. Catalysts play an important role during hydrotreating
of petroleum fractions in controlling the rate of certain chemical reactions. The
chemical reactions involved in the hydrotreating process are of two types: desirable
and undesirable reactions (Table 1). Desirable reactions are those that help the main
purpose of the hydrotreating process, while undesirable reactions are those that
result in the loss of valuable components of feed or decrease of catalyst activity.
Hydrodesulfurization refers to the removal of organic sulfur from various hydrocarbon fractions. There are a wide variety of organic sulfur compounds present in
various petroleum fractions, which include mercaptans, sulfides, disulfides, and
thiophene derivatives. Mercaptans, sulfides, and disulfides are aliphatic sulfur compounds. Other thiophenic sulfur compounds can be broadly grouped into the following three categories:
1. Thiophenes.
2. Benzothiophenes.
3. Dibenzothiophenes.
It is easier to remove sulfur from compounds such as mercaptans, sulfides, and
disulfides. However, it is increasingly difficult to remove sulfur from aromatic sulfur compounds such as thiophenes, benzothiophenes, dibenzothiophenes, and substituted dibenzothiophenes during the hydrotreating process. Thiophenes are the
easiest to desulfurize compared to benzothiophenes and dibenzothiophenes. It is
Table 1 Desirable and undesirable reactions during hydrotreating of petroleum fractions
Desirable reactions
Undesirable reactions
Hydrodesulfurization
Hydrocracking
Hydrodenitrogenation (HDN)
Coking
Hydrodeoxygenation
Saturation of olefinic compounds
Hydrogenation of aromatic compounds
Hydrodemetallization (HDM)
Recent Advances in Hydrotreating/Hydrodesulfurization Catalysts: Part I: Nature…