Paraffins. Chemistry and Technology

899 Pages·1968·15.44 MB·English

by  F. Asinger and H. M. E. Steiner (Auth.)

PARAFFINS
CHEMISTRY AND TECHNOLOGY
BY
F. ASINGER
TRANSLATED BY
B.J. HAZZARD
EDITED BY
H. M. E. STEINER
PERGAMON PRESS
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English edition copyright © 1968
Pergamon Press Ltd.
First English edition 1968
This is a translation based on the German book
Chemie und Technologie der Paraffinkohlenwasserstoffe,
published in 1962 by Akademie-Verlag,
which has been brought up to date by the author
Library of Congress Catalog Card No. 65-16851
08 002340 1
MADE IN GREAT BRITAIN
PREFACE TO THE ENGLISH EDITION
The present book, the first edition of which was published by the Akademie -
Verlag GmbH, Berlin, in 1956, and an unchanged reprint of which of the
first edition was necessary in 1959, has been revised, in 1962, for translation
into English.
The number of literature references has been considerably increased,
since many friends of the German edition and colleagues have again and
again expressed the desire for a maximum number of references to the original
literature.
The section on the hydrogénation of coal and the chapter on the Fischer-
Tropsch synthesis have purposely been neither shortened nor omitted, since
it is perhaps the last time that both processes will be treated in a single
monograph such as the present one. In the era of the molecular sieve process
and the urea extractive crystallization process, neither of the two procedures
mentioned will ever again acquire importance for the manufacture of paraffinic
hydrocarbons that can be used as raw materials for the chemical industry.
A later work is frequently referred to in the text. This relates to the book
Chemie und Technologie der Monoolefine which is being published in English
under the title Olefins, Chemistry and Technology by Pergamon Press.
At this point I should like to thank Akademie-Verlag and Pergamon
Press for attending to the English edition and for the care with which the
printing and preparation of the figures has been carried out. I should also
like to thank my assistant Dr. Kurt Halcour for his assistance in reading
and checking the German manuscript.
Aachen, Autumn 1965 F. ASINGER
PREFACE TO THE FIRST GERMAN EDITION
The present book was not written with the object of an in any way ex-
haustive treatment of the extensive field of the chemistry and technology
of the paraffinic hydrocarbons. It deals primarily in more detail with the
fundamentals of those methods and processes for the manufacture and
chemical treatment of the paraffinic hydrocarbons which are either already
being carried out industrially today or which are within the range of technical
possibilities provided by the present state of knowledge and experience.
In this way, the technical man will perhaps be put in a position in which
he can rapidly obtain an insight into this field of science.
The book is directed primarily to the chemist involved in research and
development. In addition, it will give the advanced student a picture of
the many-sided possibilities of the use of the paraffinic hydrocarbons,
which were long regarded as extraordinarily unreactive. It will show that
the paraffinic hydrocarbons are incorrectly named, since they are capable
of undergoing reactions which the aromatics cannot take part in at all,
and that they undergo reactions which until recently appeared to be restricted
to the aromatics, although in a different form, even more readily and under
milder conditions than the latter.
In a special chapter an attempt is made for the first time to give a com-
prehensive account of the results of investigations in the field of the sub-
stitution ratios in the paraffinic hydrocarbons. In the last few years, many
old ideas have been recognized to be incorrect and much has been elucidated.
Nevertheless, some results have still to be refined and confirmed.
Numerous literature references refer the particularly interested reader
to the original papers.
Reference is frequently made in the text to a later work. This is the
book Chemie und Technologie der Monoolejine which is in course of prepa-
ration. *
The author would be very grateful to all technical readers for pointing
out. any errors, and for advice and suggestions.
Leuna-Halle, Autumn 1955 F. ASINGEK
* To be published in English as Olefins,, Chemistry and Technology.
INTRODUCTION
THE PRODUCTION AND CHEMICAL UTILIZATION
OF THE PARAFFINIC HYDROCARBONS
Up to about the turn of the century, aliphatic compounds played a minor
role in the synthetic organic chemical industry. At that time it was the
well-known constituents of coal tar, such as benzene, toluene, phenol, and
naphthalene, which were processed primarily. From these the most diverse
intermediate and finished products were manufactured. In the refined form
of dyestuffs and pharmaceutical products they exemplified the successes of
scientific research and of technical chemistry. After the first world war,
the development of the petroleum industry over the whole world, but
particularly in the United States, was extremely vigorous. Because of
the ever-increasing consumption of gasoline, the construction of new cracking
plants became urgent. Under these conditions, the necessity arose for
subjecting the lower gaseous aliphatic hydrocarbons produced in these
plants to at least a partial chemical upgrading and not merely to make use
of their heating power, as previously.
This point of view led to an ever-increasing study of the aliphatic hydro-
carbons. This had been begun primarily by Russian workers in the middle
of the nineteenth century and had been continued for a long time with very
great success. Later, the centre of gravity, particularly in the technical
field, gradually shifted to the United States, where the chemical study of
petroleum derivatives began on a grand scale in about 1925.
In other countries, this new field was first substantially neglected. This
is to be ascribed partially to the complete lack of petroleum and the consequent
lower interest in its chemical processing. The expensive processing methods
of aliphatic chemistry also played a role. In Germany, a need for the chemical
treatment of paraffinic hydrocarbons arose only with the technical introduc-
tion of coal hydrogénation and the FISCHER-TROPSCH hydrocarbon synthesis,
since the necessary starting materials became available only with the devel-
opment of these processes.
Before this time, the organic chemical industry worked almost exclusively
with such aliphatic compounds as were obtained from the animal and plant
kingdoms. These were the higher-molecular-weight fatty acids and alcohols,
which were readily obtainable from fats and waxes, together with glycerol,
carbohydrates, cellulose, starch, sugar, and, finally, proteins.
ρ ι
2 PARAFFINS, CHEMISTRY AND TECHNOLOGY
The aliphatic hydrocarbons abundantly present in petroleum were not
used directly for chemical processing, although they were extraordinarily
cheap raw materials. There are two reasons for this. Petroleum is an ex-
tremely complicated mixture of hydrocarbons differing very greatly according
to its origin. Even today, its higher-molecular-weight components have been
comparatively little investigated. Moreover, petroleum hydrocarbons react
with the usual chemicals applied to aromatic hydrocarbons comparatively
poorly and, in addition, non-uniformly. This is the reason why for a long
period petroleum acquired no particular interest for the synthetic industry.
Consequently, it is understandable that the gaseous representatives of
the aliphatic hydrocarbons were the first to be chemically treated and utilized,
since they are more uniform to start with. Further, because of the com-
paratively large differences in their boiling points, they can easily be separated
by distillation under pressure into definite individual compounds. Again,
it is understandable that within this group of gaseous aliphatic hydrocarbons
it was the most reactive — namely the olefins —- which were used first.
The lower paraffinie hydrocarbons remained, as before, practically unused,
apart from the chlorination of methane and pentane. Only in 1930 were
comparatively extensive attempts begun to use the lower homologues of
methane, as well as synthetic starting materials. Attempts to utilize the
higher-molecular-weight paraffins are only of quite recent date, with the
exception of the production of fatty acids by oxidation of paraffins. The
reason for this was, in the first place, the attempt to make soaps, sulphonates,
alkyl sulphates, etc., which play an extremely important, if generally too
little valued, role in detergent, emulsion, textile, and flotation technology.
It was desired to replace their preparation from fats in order to reserve the
latter entirely for human nutrition.
However, the higher aliphatic hydrocarbons cannot be obtained from
petroleum in the purity and uniformity necessary for chemical treatment.
Uniform individual materials can be obtained from coal tar easily by
fractional distillation and, if necessary, subsequent crystallization. In the
case of petroleum, because of its complicated composition, this does not
lead to the desired result. Even the isolation of a fraction covering a range
of compounds of 10-20 carbon atoms is not sufficient for the purposes of
chemical processing. In such fractions the straight-chain hydrocarbons
required in the first place are mixed with isoparaffins of various degrees
of branching, with naphthenes, and with aromatic compounds, the contents
of these compounds in these fractions varying greatly according to the origin
of the oil. In all cases, however, such constituents are a great nuisance.
It is true that such mixtures can be separated into aromatic-rich and
paraffinic-rich components by means of selective solvents such as liquid
sulphur dioxide — e.g. by the EDELEANU process. Nevertheless, in most
cases the paraffins are still too impure to be used satisfactorily for chemical
processing. Not even hydrocarbon mixtures from the paraffin-based Pennsyl-
vanian oils can compete with uniform straight-chain normal paraffins.
Meanwhile, it has recently become possible to separate straight-chain paraf finie
INTRODUCTION 3
hydrocarbons in very pure form from petroleum oils and fractions of petroleum
oils by means of the so-called extractive crystallization process. Whether
this process can make available to industry higher-molecular-weight
paraffinic hydrocarbons in a form suitable for chemical treatment cannot
be decided at the present time.
In the field of the chemical treatment of higher paraffinic hydrocarbons
with 10-20 carbon atoms in the molecule, a fundamental change took place
when RUHECHEMIE A. G. succeeded in developing the FISCHER-TROPSCH
hydrocarbon synthesis process on the large scale. As is well known, the
synthesis rests on the catalytic hydrogénation of oxides of carbon at normal
or slightly increased pressures (10 atm) over a cobalt catalyst activated with
thorium oxide; it yields the aliphatic hydrocarbons in an unbroken series
with astonishing purity.
The crude product of the FISCHER-TROPSCH synthesis is generally separated
into three large fractions :
1. 40-180 °C, Kogasin I, boiling range of gasoline,
2. 180-320 °C, Kogasin II, boiling range of middle oil,
3. Above 320 °C, "Paraffingatsch" [slack wax], which is sent almost
exclusively to the paraffin oxidation process for the production of soap
fatty acids.
Kogasin II contains the mixture of paraffinic hydrocarbons with 10-20
carbon atoms which is so interesting in many respects. It still contains an
average of 10 per cent of compounds absorbable by phosphorus pentoxide-
sulphuric acid — in the first place, olefins and oxygen-containing compounds.
They are hydrogenated by reduction over sulphide catalysts, such as nickel
sulphide-tungsten sulphide, at 300-350 °C and 200 atm to give saturated
hydrocarbons. In this way, a completely saturated water-clear mixture of
paraffinic hydrocarbons of various chain lengths is obtained which possesses
a mean degree of branching of 15-20 per cent. This hydrocarbon mixture
is an ideal starting material for the chemical treatment of the higher paraffins.
Today, the most modern plants for the synthesis of hydrocarbons by the
hydrogénation of carbon monoxide work with iron instead of cobalt as catalyst
and under pressure (10-25 atm). The new heavy-duty synthesis process
of the RUHRCHEMIE-LURGI consortium with a fixed iron catalyst or the
RHEINPREXJSSEN company's process with an iron catalyst suspended in oil
(KÖLBEL), with their possibilities of directing the synthesis with respect
to the composition of the product, permit the preparation of any desired
molecular size.
While coal-tar chemistry is built on raw materials which are available in
relatively limited quantities, such as the aromatic hydrocarbons benzene,
toluene, naphthalene, and anthracene, together with phenol, cresol, etc.,
unlimited amounts of hydrocarbons are available to the aliphatic chemical
industry. The basic material of aromatic chemistry — coal tar — is far
surpassed in amount by the basic materials of the modern aliphatic chemical
industry — petroleum and the products of the FISCHER-TROPSCH synthesis.
ι
4 PARAFFINS, CHEMISTRY AND TECHNOLOGY
Consequently, the chemical and technical processing of the aliphatic hydro-
carbons have today reached enormous proportions. The production of
special gasolines, solvents and plasticizers, plastics, synthetic soaps, textile
auxiliaries, and emulsifiers has already far overtaken the aromatic industry
and is close to surpassing the heavy inorganic chemical industry.
Today there are five different processes which can be carried out industrially
for the utilization of paraffinic hydrocarbons :
1. Oxidation,
2. Chlorination,
3. Nitration,
4. Sulphochlorination, and
5. Sulphoxidation.
Hitherto, the oxidation of paraffins has, apart from a few plants for the
oxidation of natural gas, been operated industrially in the first place with
paraffin wax in order to obtain fatty acids from this mixture of hydrocarbons
with 20-25 carbon atoms. In the oxidation of paraffins, fatty acids of various
molecular weights are obtained, through the breaking of the carbon chains.
The crude fatty acid mixtures are separated by distillation into three large
fractions and a residue :
1. Fore-run fatty acids with 5-11 carbon atoms,
2. Soap fatty acids with 12-18 carbon atoms, and
3. Residual fatty acids with more than 18 carbon atoms.
The soap fatty acids can in all cases successfully replace the higher saturated
fatty acids of animal and vegetable fats. At an early stage the unavoidable
formation of fore-run fatty acids raised doubt about the economic feasibility
for the oxidation of paraffins, since it was at first not known how to utilize
them. Today, however, they are much sought after, since they can be con-
verted by catalytic hydrogénation into primary alcohols which are very
important constituents of plasticizers.
Chlorination is the oldest substitution process of paraffins. It takes place
very smoothly and leaves the carbon skeleton unchanged. In comparison
with the paraffins, the alkyl chlorides possess an increased reactivity. Con-
sequently, work was carried out on halogenation at quite an early period
in the hope of transforming the paraffinic hydrocarbons, which were con-
sidered very unreactive at that time, into attackable compounds. Practical
results of this work were the preparation of the amyl alcohols (Pentasols)
by the chlorination of technical pentane and saponification of the amyl
chlorides, and the production of methylene chloride and ethyl chloride
by the chlorination of methane and ethane.
Today the nitration of the paraffinic hydrocarbons can be carried out
smoothly on the technical scale in the case of the lower and higher molecular
weight members. Since the nitroparaffins are at least as reactive as the
aromatic nitro compounds, although in a different manner, they offer the
most diverse possibilities for industrially important syntheses in the aliphatic
series.
INTRODUCTION 5
By sulphochlorination is understood the combined action of sulphur
dioxide and chlorine on paraffinic hydrocarbons under the influence of
ultraviolet light. Under these conditions, aliphatic sulphonyl chlorides are
formed which, because of their reactivity, can be converted in many different
ways. Sulphochlorination is a typical chain reaction. It has already fertilized
the field of the chemical utilization of paraffinic hydrocarbons to an extra-
ordinary degree and is still undergoing intensive development. Sulphochlorin-
ation and sulphoxidation are, on the other hand, not possible with aromatic
hydrocarbons; on the contrary, they are actually inhibited by aromatic
compounds. These reactions are therefore a typical example of the fact
that the paraffins may under certain circumstances be more reactive than
the aromatic hydrocarbons.
In sulphoxidation, sulphur dioxide and oxygen react with paraffinic
hydrocarbons under ultraviolet irradiation or in the presence of peroxides
to form aliphatic sulphonic acids. Direct sulphonation with sulphuric acid,
as in the case of the aromatic compounds, is not possible with paraffins.
Sulphoxidation may compensate for this defect.
In practice, all the processes just mentioned for the utilization of paraffinic
hydrocarbons are chain reactions and are subject to the same rules of isomer
distribution.
In the coming years, there will probably be an even further substantial
broadening of the possibilities of production of the aliphatic chemical paraffin
industry. The necessary conditions for this have been recognized in the
synthetic preparation of paraffinic hydrocarbons from coal, natural gas,
and petroleum, and in the technical methods for the substitution of paraffinic
hydrocarbons and in the conversion of the paraffin derivatives. Thus new
valuable intermediates and finished products will be manufactured from
paraffins.
If the present book should make a small contribution to the achievement
of these aims, its purpose would be satisfactorily fulfilled.
CHAPTER 1
THE PRODUCTION AND MANUFACTURE
OF THE PARAFFINIC HYDROCARBONS
I. INTRODUCTION
The paraffinic hydrocarbons necessary for all the reactions which will be
described below encompass the whole spectrum of the saturated aliphatic
hydrocarbons from methane up to about triacontane.
At the present time, natural gas and petroleum are still available in nature
in large amounts for the production of paraffinic hydrocarbons.
From both these sources, low-molecular-weight normally gaseous or very low-
boiling paraffinic hydrocarbons, such as methane, ethane, propane, the butanes,
and the pentanes, can be isolated, preferably in the individual state. But
petroleum also yields the high-molecular-weight representatives of the type of
paraffin wax and microerystalline wax — that is, hydrocarbon mixtures with
about 20 to 25 carbon atoms and more.
The intermediate molecular sizes with 10-20 carbon atoms from decane to
eicosane could not, until recently, be obtained from petroleum with the purity
which must generally be demanded for further treatment by chemical methods.
The low-molecular-weight components of petroleum, such as are present in
the waste gases of petroleum distillation plants and in natural gas, can easily be
separated because of the large difference in the boiling points of the individual
members.
Table 1 gives some physical constants of the most important low-molecular-
weight paraffinic hydrocarbons. It can be seen from this that separation of the
individual representatives by fractional distillation is easily possible.
TABLE 1. Physical properties of the lower paraffinic hydrocarbons
Paraffinic Boiling Melting Crit. Crit. press,
hydrocarbon Mol. wt. point, °C point, °C temp., °C atm
Methane 1603 -161-5 -182-6 - 82-5 45-7
Ethane 30-06 - 8-86 -183-5 32-5 48-8
Propane 44-06 - 42-3 -188-0 97-0 45-0
n-Butane 58-08 - 0-5 -138-5 1520 35-7
Isobutane 58-08 - 12-0 -159-6 134-5 36-5
n-Pentane 72-09 361 -129-0 197-2
Isopentane 72-09 28-0 -159-0 187-7