CHM 4155 UO INEOS Group Company Major Chemical Products Questions
CHM4155 Assignment – Fall 2022
Due date: your assignment must be submitted before 18h00 on November 11
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1. (10 points) CHOOSE FROM ONE OF THE FOLLOWING:
Infographics are a convenient method to efficiently convey information in a visually
appealing format. Create a one-page (or one-slide) infographic for future students in this
course explaining the difference between thermal cracking and catalytic cracking, and
how these two reactions fit into the overall petroleum refining process. You may generate
your infographic digitally or by hand, and it will be graded on the quality of the content
as well as its visual appeal. For inspiration, here is an infographic illustrating the
differences between gasoline and diesel fuels (you can find many other examples of
excellent chemistry-related infographics at this website):
The Chemistry of Petrol & The Tetraethyl Lead Story
Don't use plagiarized sources. Get Your Custom Essay onCHM 4155 UO INEOS Group Company Major Chemical Products QuestionsJust from $13/Page
————- OR ————The Chemical & Engineering News article below lists the Top 50 chemical manufacturers in
the world, for 2022 (note: you may need to be logged into uOttawa’s wifi to gain access
to this site):
https://pubs.acs.org/doi/10.1021/cen-10026-cover
Let’s pretend you have just been hired as a scientific consultant at a financial investment
firm. Your boss wants to expand into investing in the chemical industry and has asked
you to investigate the options available. Choose one of the companies listed and do some
research into their business. Write a page (~1000 words) for your boss, summarizing the
main points about the company and their chemical manufacturing. Your summary may
include:
• A description of the company’s major chemical products
• A brief history of the company, and their development over time
• Any strengths or weaknesses, including R&D
• The current stock price, and its recent market behaviour
• The company’s location(s), and location of customers; global implications
• + any other interesting/pertinent info you feel your boss should know before
investing
Your goal is not to persuade your boss into investing into your chosen company; instead,
your objective is to provide concise information so that your boss may make an informed
initial decision about whether further investigation is warranted.
2. (5 points) The C-H bonds highlighted below show very similar BDE’s; nevertheless,
one is weaker than the other. Identify the weaker bond, and explain your choice, using
resonance structures to support your answer.
Ha
Hb
3. The following reactions show propagation cycle for the combustion of methane:
CH4 + •OH
•CH3 + H2O
•CH3 + O2
CH3OO•
CH3OO•
CH2O + •OH
CH2O + •OH
•CHO + H2O
•CHO + O2
HC(O)OO•
HC(O)OO•
CO2 + •OH
a. (6 points) Draw an electron-pushing mechanism for each step. Identify each
step in the cycle (e.g., thermolysis, atom transfer, etc.)
b. (4 points) The first step is the rate-determining step of the process, with a
rate constant of 7.84×109 M–1•s–1 at 2200 K and 5.10×109 M–1•s–1 at 1900 K.
Determine the activation energy and pre-exponential factor for this
reaction, in the appropriate units.
c. (2 points) Estimate the enthalpy change of the rate-determining step using
BDE values (as precisely as possible, cite your sources).
d. (2 points) Estimate the enthalpy change of the rate-determining step using
enthalpy of formation values (cite your sources). Compare with your answer
from part c.
e. (2 points) draw a representative reaction profile diagram for the ratedetermining step. Label your diagram thoroughly and try to be as precise
as possible.
f. (5 points) Methane is burned in a Bunsen burner. As the ports of the burner
are opened, the colour of the flame changes from orange to blue, and the
temperature of the flame increases. Explain these observations.
4. The reaction shown below is known as the Reppe Process and is a historical method
for the production of acrylic acid (an important monomer we will see later this
semester) from acetylene.
HC
CH
+ CO + H2O
HNi(CO)2X
X = halogen
O
OH
a. (8 points) Draw a catalytic cycle for this process, using a format similar to
those shown throughout Chapter 7 (hint: this reaction is very similar to
olefin hydroformylation). Identify each step in the cycle (i.e., oxidative
addition, reductive elimination, etc.) and the oxidation state of the metal
centre.
b. (2 points) The modern version of the Reppe Process uses a different catalyst
and ethylene instead of acetylene as the starting material. Give at least two
reasons for this switch.
c. (4 points) In a 200 L reaction vessel at 450 K, 250 bars of acetylene, 240 bars
of CO and 25.5 kg of steam are allowed to react, and 72.8 kg of acrylic acid
are formed. What was the yield of the reaction?
5. Find and read the following article (J. Chem. Ed. 1979, 56 (7), p465) to answer the
following questions:
a. (1 point) What consumer demand originally drove investigation into
petroleum refining?
b. (1 point) Why was early petroleum refining so dangerous?
c. (2 points) What is RON and MON? How are these related to the value of
octane number you see at the gas pump?
d. (1 point) According to the article, branched alkenes have high octane
numbers but make poor gasoline. Why?
e. (1 point) Environmental regulations were not the initial reason why
unleaded gasoline was introduced to the market in the early 1970’s. What
was the actual reason?
f. (4 points) Being from 1979, this paper is quite dated. Find a fact and/or
prediction made in the article that has since been shown to be false and
provide a corrected update. In your answer, include a specific quote from
the article and cite any sources you use in your correction.
Petroleum Chemistry
by Doris Kolb
Illinois Central College
East Peoria, IL 61635
in cooperation with
Kenneth E. Kolb
Downloaded via QUEEN’S UNIV on November 1, 2022 at 19:08:13 (UTC).
See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
Bradley University
Peoria, IL 61625
The chemistry of petroleum is a subject often ignored in
standard chemistry courses. This is unfortunate because the
petroleum refinery is one of the most important chemical
plants in the world. About half of our energy needs in the
United States are currently being met by petroleum products
(gasoline, diesel fuel, furnace oil, petroleum gases, etc.) and
a major segment of our chemical industry depends for its raw
materials on petrochemicals (ethene, propene, butenes, benzene, toluene, xylenes, etc.). To overlook petroleum is to miss
out on some of the most significant facets of contemporary
chemistry.
History
Exactly how it originated no one knows. We believe petroleum to be of marine origin derived from living matter that
existed perhaps as long as 500 million years ago. Radioactive
dating indicates that even the newest oil deposits are at least
50 million years old. Present theory holds that crude oil was
produced through the action of anaerobic microbes lowering
the oxygen and nitrogen content of what had been living organic matter.
The earliest records we have of man using petroleum go
back to about 3000 B.C. At that time seepages of asphaltic
bitumen were collected in Mesopotamia for waterproofing
ships and canals, for paving roads, for making bricks for
building (by mixing with sand and fibers), and for use as a
general purpose “glue”. These uses continued in the Middle
East until about 600 B.C. when those lands were subjugated,
first by the Persians and then by the Greeks. The Greeks, who
had plenty of stone and wood for building, apparently were
not interested in this black sticky tar. Thus petroleum was
largely neglected by ancient Greece, and its use was not passed
on to the Romans and the rest of western Europe.
Interest in petroleum did survive among the Arabs, however, and by 1000 A.D. they were distilling crude oil to obtain
kerosene for burning in order to produce light. During the
destruction of Cairo in 1077 A.D. kerosene was used to fuel the
fire. Arab and Mongol armies both appear to have used a type
of petroleum fed flame thrower in their wars around 1200, but
there seems to have been little, if any, technological carry-over
to Europe.
With the discovery of the western hemisphere and the
opening of the New World, there was renewed interest in the
use of petroleum, since it was both available and needed. Its
first major use was as caulking material for the big wooden
sailing ships. Cuban asphalt deposits became important for
the necessary job of periodic recaulking. The Cuban natives
had long used petroleum, not only as a caulking compound but
also as a liniment for sore muscles and cuts, and even as a kind
of chewing gum.
The Age of Illumination
By the beginning of the 19th century the uses of petroleum
were still rather trivial, but the industrial revolution had
begun and urban areas were expanding. Though working
hours were long and many workers were exploited, the overall
standard of living started to rise. There was a need for better
lighting as the cities continued to grow and became more ac-
tive in the evening. In London some illumination was obtained
from bottled gas produced by thermal cracking of fish and
whale oil. (It was from this cracked gas that Faraday discovered benzene in 1825.) In America, night time illumination
came mainly from the fireplace and from bowls of animal fat
or fish oil burning by means of wicks.
During the period 1830-50 several new illuminating fuels
were
developed. Camphene from turpentine (obtained by
steam distilling pine tree stumps) was used in this country as
fuel for lanterns. Candles made from refined lard began to be
produced industrially. In Europe the production of coke for
reducing iron ore resulted in large quantities of by-product
coal oil. This oil, a mixture of hydrocarbons, was also found
to be well suited for use as fuel in lanterns.
In America the increased demand for illuminating fuels
caused Benjamin Sifliman at Yale University to study the
composition of petroleum. He found that crude oil could be
distilled to give as much as 50% of a material similar to coal
oil and thus useful for lighting. To satisfy the demand for more
lighting fuel, Edwin Drake drilled the first oil well at Titusville, Pennsylvania, in 1859. The oil was distilled to produce
a fraction of hydrocarbons with about 9 to 18 carbons per
molecule (called kerosene) for use as illuminating fuel. The
more volatile fraction containing compounds of 5 to 8 carbons
(called naphtha) found limited use as a solvent, especially for
paints. Often there was not much need for the naphtha, so the
excess was simply dumped into the rivers (which occasionally
caught fire!), an early example of industrial pollution. The
heavy higher boiling oils were used for lubrication in place of
animal and vegetable oils, which tended to be less stable. The
material left after distillation, the asphaltic tar, was used for
paving streets and waterproofing roofs. From 1859 until the
20th century the production of kerosene for lighting and oils
for lubrication remained the major uses of petroleum.
Impact of Autos and Electric Lights
The beginning of the 20th century was a turning point in
the history of petroleum. By 1900 two new technologies had
appeared that would have a drastic effect not only on the petroleum industry but on the whole of modern society. These
were the electric light and the gasoline powered automobile.
Since gasoline was a mixture of hydrocarbons of 5 to 12 carbons, gasoline was essentially just another name for the often
surplus naphtha. The petroleum refiners could now sell kerosene for lighting and naphtha, or gasoline, for motor fuel.
However, demand for gasoline soon began to sky-rocket along
with production of automobiles. While a gallon of kerosene
might suffice in a household for a week or more, a gallon of
gasoline could be burned in minutes. By 1910 there was a large
demand for naphtha and a surplus of kerosene, not only because kerosene was used at a moderate rate but also because
the electric light was replacing the kerosene lantern in the
cities.
During the first decade of the 20th century several American companies established laboratories for research. In 1910
at the Standard Oil Co. (Indiana) William Burton initiated
a study to increase the amount of gasoline available from a
barrel of crude oil. Since kerosene had become a surplus maVolume 56, Number 7, July 1979 / 465
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terial, his approach was to try to convert it to gasoline. The
kerosene molecules were approximately twice the size of
gasoline molecules, so perhaps they could be “cracked” into
smaller molecules. Burton and his coworkers developed a
process for subjecting the kerosene distillate to high temperatures (600-700°C) and cracking the molecules into
smaller fragments. An idealized equation is shown here for
cracking a 16 carbon molecule into two smaller ones with 8
carbons each.
700°C
ClfiH;)4 -*
s
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0
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D
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C8H16 + CgHig
Notice that one of the products is an alkene and the other an
alkane. (Such a cracking process actually gives a mixture of
alkanes and alkenes, not just two as shown here.) The product
hydrocarbons containing 5 to 12 carbons are useful as gasoline,.
while small molecules such as methane, ethene, and propene
can be used as fuel to reach the temperatures needed for
cracking.
Thermal cracking had become a commercial process by
1913. So great had the demand for gasoline become that soon
other oil companies were also using the Burton thermal
cracking process. The original process was carried out in crude
pressure-cooker type reactors. They had riveted seams that
would often leak when they were heated. Workmen who
tended these leaking reactors (which sometimes exploded) had
a grimy, dangerous job. During the 1920’s the batch operation
was gradually replaced by one involving thermal treatment
of the oil as it flowed through pipes. Not only was this new
process continuous, but it also had the advantage of giving less
coke formation. The inventor of this improved continuous
process was C. P. Dubbs, whose full name happened to be
Carbon Petroleum Dubbs.
S
The Octane Scale
C
By 1920 the gasoline powered car, typified by Ford’s model
T, was becoming part of the American culture. No longer was
the car a plaything of the few; it was a practical means of
transportation for many. It soon became clear that all gasoline
was not equal in quality. Some gasolines seemed to cause excessive engine noise. Chemists found that gasoline produced
considerable preignition or “knock” if it contained mainly
straight chain alkanes, such as hexane (C6H14), heptane
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(C7Hi6), and octane (08H18). Even the lowest compression
engine would audibly knock when gasoline made up of these
straight chain alkanes was used. However, branched chain
alkanes had a greatly diminished tendency to knock. While
normal octane was a very poor motor fuel, a branched isomer,
2,2,4-tri-methylpentane (“isooctane”), was found to have
excellent combustion properties. It was postulated that
branched alkanes burned in a more controllable manner than
the straight chain compounds in an engine. An arbitrary
gasoline rating scale was set up with isooctane assigned a
rating of 100 and normal heptane given a rating of 0.
pression engines, especially for airplanes, later made it necessary to extend the octane number scale beyond 100.) While
the octane number scale is not a perfect means for rating
gasoline quality, it remains the single best rating scale.
Petroleum refiners sometimes speak in terms of “research”
octane number (RON) and sometimes of “motor” octane
number (MON). RON values are obtained by testing fuel in
a single cylinder engine with variable compression ratio at 600
rpm, with inlet air at 52° C and a modest spark advance. MON
values are obtained at 900 rpm, with inlet air at 149°C and a
larger spark advance. Before 1973 RON values were the ones
usually quoted to the public, but since 1973 the octane values
posted on station pumps have been RON-MON averages. The
average value better relates to the actual performance of the
gasoline in an automobile engine. Concurrently with the introduction of this new average scale, refiners also lowered the
octane quality of their gasolines by about two units. As a result
some motorists began noticing knocking noises in their engines, even though they thought they were using the same
gasoline they had always used.
(RON-MON)
Since 1973
RON-MON Average
Before 1973
RON
Premium
Regular
(Advertised)
(MON)
average
(Posted on pumps)
100
94
(94)
(88)
(97)
(91)
95
89
Diesel fuel does not have the same requirements as gasoline,
spontaneous ignition being desired in a diesel engine.
Diesel oil consists of C15-C25 molecules with minimal
branching, since straight chain hydrocarbons are preferred
for diesel use. A cetane scale is used to rate diesel fuels, with
cetane values of 100 and 0 having been arbitrarily assigned to
cetane (n-hexadecane) and a-methylnaphthalene.
more
(TI;,CH2CH2CH2OH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2(TH:)’
cetane
(cetane no.
=
100)
a-methylnaphthalene
(cetane no. = 0)
Just as with the octane scale for gasoline, the cetane number
of a fuel is determined by comparing its performance in a
single cylinder variable compression engine with mixtures of
these reference fuels. The higher the octane number of a fuel,
the lower its cetane number will tend to be. A fuel with an
octane number of 80 would have a cetane number of about
20.
Addition of Lead Compounds
CH:l—CH,—CH,—CH,-CH2— CH2— CH.
normal heptane (octane no. 0)
;h3
CH;—C—CH,—CH— CH
CH;
H:.
iso-octane (octane no. 100)
If a gasoline had the same knocking characteristics as a 50/50
volume percent mixture of heptane and isooctane, it was said
to have an “octane number” of 50. If it gave the same performance
as a 25/75 mixture of heptane and isooctane, it was
rated as “75 octane”. (The development of very high com466 / Journal of Chemical Education
In the 1920’s petroleum refiners became interested in using
additives to increase the octane rating of gasoline. Thomas
Midgley had found that the addition of heavy metal compounds to gasoline would decrease its tendency to knock. After
much research he and his coworkers concluded that tetraethyl
lead, Pb(C2H5)4, was an ideal additive. It was a covalent
compound, soluble in gasoline, and it gave a considerable increase in octane number. At first the lead compound was
added at the gas station, but because of its toxicity it was later
added at the refinery, along with a dye to indicate that the
gasoline contained lead. The addition of lead, as both tetraethyl and tetramethyl derivatives, was so successful in
raising octane number that its use increased each year. By the
1950’s most gasolines were “leaded”, containing about 2.4 g
of lead per gallon. For a typical gasoline the lead additive
boosted the octane number by 7 to 9 units.
In order to remove spent lead from the engine, a mixture
of 1,2-dichloroethane and 1,2-dibromoethane must also be
added to leaded gasoline. These organic compounds supply
halogens that convert the lead metal to volatile lead halides,
which then become part of the auto exhaust gas. The “ethyl
fluid’’ added to gasoline (about 3 ml per gallon) contains about
60% of the lead compound, roughly 40% of the mixed organic
halides, and a little solvent, dye, and stabilizer. In 1967 the
production of tetraethyl lead in the U.S. was 685 million
pounds. Virtually alt of it went into gasoline, and the lead
eventually was sent into the atmosphere. The toxicity of airborne lead from automobile exhaust gas has been a subject of’
serious concern in recent years.
Before 1970 there was very little unleaded gasoline on the
market, but by 1974 all gas stations were offering it. In fact,
no-lead fuel had become a necessity for most new cars because
of their catalytic converters (designed to lower the amounts
of carbon monoxide and unburned hydrocarbons in auto exhaust gas, so as to meet the clean air standards set by the
Environmental Protection Agency). Since lead poisons the
catalyst in these converters, and since most new cars have
them and cannot use leaded fuel, the demand for no-lead
gasoline is rapidly increasing. Current federal regulations call
for a phasing out of all leaded gasoline during the 1980’s.
Lead additives are the least expensive means for raising
gasoline octane number. Their removal will necessitate an
increase in certain refinery processes, such as catalytic reforming and alkylation, which also increase octane number
but at greater cost. This need for more refinery processing will
result in increases both in the price of gasoline and in the energy required to produce it. For the past several years another
additive, methylcyclopentadienyl manganese tricarbonyl
(MMT), has been used as an antiknock agent in unleaded
gasoline, but its use has now been ruled out because it is a
potential health hazard. Recently methyl t-butyl ether
(i.e., cyclohexanes are more abundant than cyclopentanes, which
in turn much more abundant than other ring systems).
are
5) The amount of aromatic hydrocarbons varies widely, depending
on the source of the crude oil. Sometimes aromatic content is
insignificant, but certain crude oils contain substantial quantities of alkylbenzenes.
In one research project 234 different hydrocarbons were found
to be present in a single sample of crude oil. It is this complex
mixture that is fed into pipelines to be separated and improved by the methods of refinery processing,
The major processes used in a modern refinery are discussed
–
below.
Crude Oil Distillation
After the crude oil is washed, it is then vaporized and sent
through fractionating towers, where the oil is separated into
fractions of hydrocarbons with similar boiling point and molecular size. There are usually about five major fractions, their
amounts and exact composition depending on the particular
crude oil being used. With the exception of the dissolved gases
(methane, ethane, and propane) pure compounds are seldom
separated by distilling crude oil. The following distribution
of products is rather typical. There is considerable variat ion
Volume
Percent
1-2%
Carbon Atoms
Boiling
Point (°C)
(approx, range)
400
>C25
(H
has shown promise as an octane number enhancer, and it is
already being used by several companies with government
approval.
Modern Refining Processes
During the past. 40 years a number of petroleum refining
processes have been developed to increase the quantity and
quality of gasoline, and also to produce the basic petrochemicals (methane, ethene, propene, butenes, benzene, toluene,
and the xylenes). Petrochemicals currently amount to less
than 5% of refinery output; however, they are a highly important group of products, providing the basic raw materials
for a major portion of the chemical industry. But it is gasoline
that remains the refinery’s primary reason for being. Impetus
for development of several basic refining processes was the
demand for high octane fuel for airplanes during World War
II and then for the higher compression engines of post-war
automobiles.
As obtained from the well petroleum is a dark, viscous liquid
usually containing dissolved inorganic salts and naphthenic
acids. These latter materials are removed by water (or caustic
water) washing, leaving a mixture that is mainly hydrocarbons
with the following general composition:
1)
Straight chain alkanes are most abundant, just as the alkyl
groups in fats and oils are mainly straight chains. (This supports
the theory that petroleum is derived from fats and oils of prehistoric living matter.)
2) Odd numbered carbon compounds are most, prominent, pre-
sumably as a result of decarboxylation of even numbered fatty
acids.
3) Among the methyl branched compounds, 2-methyl alkanes
predominate.
4) Cycloalkanes present are those predicted by thermodynamics
lubricating oil
residual oil
paraffin wax
asphalt (tar)
in the composition of crude oils from different sources. Middle
East petroleum, for example, is usually very rich in lower
boiling hydrocarbons, while Mexican crude oil tends to be high
in heavy oils‘and residuals. The residual oil is normally vacuum distilled to produce more gas oil and a heavy oil (C20–C70)
suitable for lubricating oil after the straight, chain paraffin wax
has been removed. The undistiilable bottom material is a
heavy tar suitable for paving and coating uses.
Catalytic Cracking
Unlike the distillation process, which is a simple physical
separation, most petroleum refining processes involve
chemical reactions. In the cracking process the reaction involves splitting larger molecules into smaller ones by breaking
carbon to carbon covalent bonds.
catalyst
large molecules — >*
500°C
(kerosene range)
alkanes 4- aikeries
(gasoline range)
The thermal cracking process of the 1920’s was largely replaced by catalytic processes during the 30’s and 40’s. Today
more
than a third of all crude oil is ultimately subjected to
cracking. The catalyst most used today is silica-alumina (SiOg,
ALO;t), often containing nickel or tungsten and used in the
presence of a hydrogen atmosphere. The silica-alumina promotes scission of carbon-carbon bonds, preferentially those
near
the middle of the chain, since they are weakest. The
process is also called “hydrocracking” because it occurs in a
hydrogen atmosphere, and it is sometimes called “fluid
cracking” when a fluidized catalyst bed is used (the finely
divided solid catalyst being kept in a fluid-like state by the
upward moving stream of gas). Catalytic cracking occurs at
a lower temperature (500°C) than thermal cracking, and it
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produces fewer small molecules and much less coke. The ad-
dition of Ni or W plus H2 has two advantages: (1) alkenes,
which are gum-formers, are hydrogenated to alkanes, and (2)
sulfur and nitrogen, which are potential air pollutants, are
removed as H2S and NH3.
Although thermal cracking is no longer important for
making gasoline, a type of severe thermal cracking called
“steam cracking” is the major process for producing the alkene
petrochemicals—ethene, propene, and the butenes. The use
of steam in this high temperature (about 800°C) process reduces the partial pressure of the hydrocarbons in the system,
which favors a greater yield of gaseous products, the volatile
alkenes, and also reduces coke formation.
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Catalytic Reforming
The catalytic reforming process can convert a 6-9 carbon
naphtha fraction of modest octane number (about 60) to
material of very high octane (100-110). This dramatic increase
in octane number results from the conversion of alkanes and
cycloalkanes to aromatic compounds (benzene and alkylbenzenes) all of which have octane numbers greater than 100.
The product, called reformate, often contains more than 60%
aromatics. In the following example
0
N
CH3CH2CH2CH2CH2CH2CH3 5oo°c
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since alkylation is an effective means for increasing octane
number. In the context of petroleum refining, alkylation
means the combination of an alkene (such as propene, a butene, or a pentene) with isobutane (2-methylpropane).
H,C=CH—CH:J + CH:J—CH—CH;J
in,
CH,—CH—CH—CH,—CH
=
mosphere of hydrogen. Many of the newer catalyst systems
are bimetallic, containing in addition to platinum a metal such
as rhenium, which promotes aromatization of cyclohexanes
to benzene. Typically a catalytic reformer operates around
500°C and 20 atm. With appropriate regeneration the platinum catalyst can be used for a decade or longer. This process
was first commercialized during World War II to make high
octane fuel for airplanes. It also provided toluene for making
trinitrotoluene (TNT) explosives. Since 1952 reformate has
become the major source of benzene, toluene, and the xylenes
(BTX) for the chemical industry, although this represents a
small use as compared with gasoline. (The original commercial
source for these aromatics was coal tar, which can supply only
about 10% of the current demand.
Besides producing high octane gasoline and BTX petrochemicals, catalytic reforming also produces large amounts
of by-product hydrogen. The rapid growth of the ammonia
fertilizer business during the 1950’s was the direct result of
this process. Needing to find a use for all their by-product
hydrogen, refiners started building plants to combine it with
nitrogen from the air to make ammonia by the Haber process.
400″C
Polymerization
Another way to produce gasoline from smaller molecules
is to polymerize an alkene such as propene. Perhaps oligomerize is a more accurate term, since the products are dimers,
trimers, and tetramers rather than long chain polymers. The
formation of the propene trimer is shown here
3CH,-CH=CH,
acid cat.
cat.
-j-*-
CH,
CH:,
The catalyst used is an acid such as H2S04 or HaP04. The
polymerization of propene actually yields a mixture of
branched alkenes of the molecular formulas C^H, C9H18, and
C12H24. These compounds have good octane numbers, but
because they are alkenes they form gum upon standing, and
so they must be hydrogenated in order to give stable gasoline.
For about ten years, starting in the late 1940’s, propene tetramer
was used in large volume to alkylate benzene for making
alkylbenzene sulfonate (ABS) detergents. These ABS products dominated the synthetic detergent market until their
resistance to biodegradation started causing environmental
problems. It was the branched structure of the propene tetramer that was causing the trouble. Today’s heavy duty synthetic detergents are still mainly of the ABS type, but now
they are based on linear alkylbenzene sulfonates, which are
•>,
biodegradable.
Isomerization
The isomerization process converts straight chain hydrocarbons to branched mixtures. Although isomerization is a
highly important reaction in refining processes (such as catalytic cracking and reforming), as a separate process isomerization is of minor importance in a modern oil refinery.
Probably its main use today is for converting n-butane to
isobutane, which is reacted with an alkene in the alkylation
process.
C02 + 4H2
Alkylation
The alkylation process, although not as important as catalytic cracking or reforming, is a useful process for converting
468 / Journal of Chemical Education
CH:,-CH—OH,—CH—CH=CH —CH;J
2NH3
Many petroleum companies went into large-scale ammonia
manufacture, hoping to convince farmers that they should
apply ammonia directly to their fields as fertilizer. Needless
to say, they were highly successful. Soon the mounting demand for ammonia fertilizers, along with expanded refinery
uses for hydrogen (e.g., hydrocracking and hydrotreating),
created a need for hydrogen far in excess of what the catalytic
reformers could supply. Today much of that needed hydrogen
is obtained by steam reforming of natural gas or naphtha.
CH4 + 2H20
CH,
Thus propene with isobutane produces a mixture of branched
heptanes. The heptane one might at first expect, 2,2-dimethylpentane, is not produced, since the reaction involves
carbonium ions that give rearranged molecules. Alkylation
is usually catalyzed by HF or H2S04 and yields an alkane
mixture in the 90 octane range.
much more
N2 + 3H2
CH
acid
catalyst
+4H
(octane no.
0)
normal heptane is converted to toluene, resulting in a phenomenal increase of 103 octane units. The major catalyst for
catalytic reforming is platinum on silica-alumina. One popular
trade-marked process is called Platforming. The operation
is also called “hydroforming”, since it is carried out in an at=
A
C6H5CH3
toluene
103)
(octane no.
n-heptane
gaseous hydrocarbons to gasoline. Alkylation has been used
in petroleum refineries since the late 1930’s. Today its role is
growing as lead additives are being phased out of gasoline,
;h„
CH,—CH,—CH,—CH:,
CH*—CH—CH,
The catalyst often used is a complex of platinum on alumina
to diminish, just as it already has in the U.S. Thus we must
establish an active energy policy during the next decade to
ensure
a smooth transition as oil and gas are replaced by other
energy sources. Energy conservation measures, although important, can only give us a little more time. We need to develop
new energy sources.
In the 21st century our limited supplies of oil and gas will
for organic chemicals,
become more treasured as sources
especially for making fibers, plastics, and synthetic rubber.
The role of coal will be greatly expanded. Not only will coal
substitute directly for oil and gas as fuel, but coal will also be
converted to gas and oil. The conversion will probably be accomplished by some modification of the Fischer-Tropsch
process or the Bergius process. The Fischer-Tropsch process
reacts coal with steam to make producer’s gas (CO + H2), then
catalytically combines these small molecules to give hydrocarbons. In the Bergius process finely powdered coal is hydrogenated to liquid hydrocarbons by breaking up the
multi-ring systems present in coal. Both approaches still need
considerable research and development, and the plant investment will be enormous, so this synthetic oil and gas. will
be quite expensive. But it will be needed. There will probably
be some oil extracted from tar sands and shale, but this oil will
also be much more costly than the oil we merely pump out of
wells. The conversion of plant and animal wastes to hydrocarbons will probably also contribute to our supplies of synthetic gas and oil. In a longer time frame, living green plants
may become a source for hydrocarbon oils, to be made into
new natural rubbers and other organic materials. Even though
other energy sources will be supplying most of the world’s
energy needs in the 21st century, oil and gas (both natural and
synthetic) will remain the primary sources for organic chemicals and synthetic organic materials.
plus aluminum chloride, which promotes isomerization at
temperatures as low as 100°C. Mixtures of pentanes and
hexanes can also be isomerized to increase their octane rating
from 66-70 to the high 90’s.
Hydrogen Treating
Since 1960 the fastest growing refining process has been
catalytic hydrogenation. Just as cracking done in a hydrogen
atmosphere gives less tar formation, hydrogenated feed materials can generally be used to avoid undesirable side reactions. Treatment with hydrogen can remove double bonds and
get rid of nitrogen and sulfur. Since these two elements are
poisons for certain catalysts, hydrogen treatment results in
longer catalyst life. Nitrogen and sulfur compounds are undesirable in fuels because they produce oxides that are irritating air pollutants. The sulfur compounds, which are usually
mercaptans, also have disagreeable odors which can give
gasoline an unpleasant smell. Removal of double bonds avoids
the problems of gum and varnish formation.
Current Petroleum Use
For the past several decades oil and gas have accounted for
almost 3/4 of the U.S. energy supply. Energy sources in the
U.S. for 1970 and 1978 were:
Oil
Gas
Coal
Hydroelectric
Nuclear
1970
45%
33%
1978
49%
25%
18%
4%
18%
4%
4%
