Another important trend is that unit capacity continues to increase which provides higher efficiency via economy of scale. CCR reforming unit capacities range
from 5,000 to 100,000 B/D, with unit capacity trending higher beginning after the
year 2000. The average unit capacity as of 2014 is approximately 23,000 B/D.
Reforming Reactions
In BTX production, the objective is to transform paraffins and naphthenes into
benzene, toluene, and xylenes with minimal cracking to light gases. The yield of
desired product is the percentage of feed converted to aromatics. In motor fuel
applications, the objective is to greatly increase the octane value which is accomplished via aromatization of paraffins and naphthenes, isomerization of the paraffins
into higher octane branched species, and the removal of low octane paraffins by
cracking to gaseous products. The yield is defined as liquid product with five or
more carbons (C 5 + reformate). This section will describe the main reactions in
reforming.
Reaction Sites
Typical reforming catalysts consist of platinum with additional metals as modifiers
or attenuators supported on chlorided alumina. In these bifunctional catalysts,
separate and distinct reactions occur on the platinum sites and on the acidic
chlorided alumina sites. The platinum sites primarily perform dehydrogenation
and hydrogenolysis (C-C scission), while the acidic alumina sites mainly perform
isomerization, cyclization, and hydrocracking.
Naphthene Reactions
The conversion of naphthenes to aromatics is one of the key reactions on reforming
catalysts. Naphtha feeds contain both five-member and six-member naphthene
rings such as cyclopentanes, substituted cyclopentanes, cyclohexanes, and
substituted cyclohexanes. The six carbon ring cyclohexanes, for example, can be
directly dehydrogenated to produce aromatics and hydrogen on platinum sites. This
is a very fast reaction which produces significant endotherms in the lead reactors
due to the large amount of naphthenes typically in the naphtha feed.
R
R
+ 3 H 2
However, the five-member ring cyclopentanes must be hydroisomerized to give
a cyclohexane intermediate prior to dehydrogenation to aromatics.
Catalytic Reforming in Petroleum Processing
243
from 5,000 to 100,000 B/D, with unit capacity trending higher beginning after the
year 2000. The average unit capacity as of 2014 is approximately 23,000 B/D.
Reforming Reactions
In BTX production, the objective is to transform paraffins and naphthenes into
benzene, toluene, and xylenes with minimal cracking to light gases. The yield of
desired product is the percentage of feed converted to aromatics. In motor fuel
applications, the objective is to greatly increase the octane value which is accomplished via aromatization of paraffins and naphthenes, isomerization of the paraffins
into higher octane branched species, and the removal of low octane paraffins by
cracking to gaseous products. The yield is defined as liquid product with five or
more carbons (C 5 + reformate). This section will describe the main reactions in
reforming.
Reaction Sites
Typical reforming catalysts consist of platinum with additional metals as modifiers
or attenuators supported on chlorided alumina. In these bifunctional catalysts,
separate and distinct reactions occur on the platinum sites and on the acidic
chlorided alumina sites. The platinum sites primarily perform dehydrogenation
and hydrogenolysis (C-C scission), while the acidic alumina sites mainly perform
isomerization, cyclization, and hydrocracking.
Naphthene Reactions
The conversion of naphthenes to aromatics is one of the key reactions on reforming
catalysts. Naphtha feeds contain both five-member and six-member naphthene
rings such as cyclopentanes, substituted cyclopentanes, cyclohexanes, and
substituted cyclohexanes. The six carbon ring cyclohexanes, for example, can be
directly dehydrogenated to produce aromatics and hydrogen on platinum sites. This
is a very fast reaction which produces significant endotherms in the lead reactors
due to the large amount of naphthenes typically in the naphtha feed.
R
R
+ 3 H 2
However, the five-member ring cyclopentanes must be hydroisomerized to give
a cyclohexane intermediate prior to dehydrogenation to aromatics.
Catalytic Reforming in Petroleum Processing
243