U.S. patent application number 14/375077 was filed with the patent office on 2014-11-20 for process for reducing fouling in the processing of liquid hydrocarbons.
This patent application is currently assigned to CLARIANT FINANCE (BVI) LIMITED. The applicant listed for this patent is Clariant International Ltd.. Invention is credited to Dominko Andrin, Michael Feustel, Matthias Krull.
Application Number | 20140338254 14/375077 |
Document ID | / |
Family ID | 47630247 |
Filed Date | 2014-11-20 |
United States Patent
Application |
20140338254 |
Kind Code |
A1 |
Feustel; Michael ; et
al. |
November 20, 2014 |
Process For Reducing Fouling In The Processing Of Liquid
Hydrocarbons
Abstract
The present invention relates to the use of a polyester which
bears hydroxyl groups and is preparable by polycondensation of a
polyol containing two primary OH groups and at least one secondary
OH group with a dicarboxylic acid or anhydride thereof or ester
thereof bearing a C.sub.16- to C.sub.400-alkyl radical or a
C.sub.16- to C.sub.400-alkenyl radical as an antifoulant in the
thermal treatment of liquid hydrocarbon media in the temperature
range from 100 to 550 DEG C.
Inventors: |
Feustel; Michael;
(Koengernheim, DE) ; Andrin; Dominko; (Schwalbach
am Taunus, DE) ; Krull; Matthias; (Harxheim,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Clariant International Ltd. |
Muttenz |
|
CH |
|
|
Assignee: |
CLARIANT FINANCE (BVI)
LIMITED
Tortola
VG
|
Family ID: |
47630247 |
Appl. No.: |
14/375077 |
Filed: |
January 29, 2013 |
PCT Filed: |
January 29, 2013 |
PCT NO: |
PCT/EP2013/000254 |
371 Date: |
July 28, 2014 |
Current U.S.
Class: |
44/398 |
Current CPC
Class: |
C10G 9/16 20130101; C10G
75/04 20130101; C10L 1/1983 20130101 |
Class at
Publication: |
44/398 |
International
Class: |
C10G 75/04 20060101
C10G075/04; C10L 1/198 20060101 C10L001/198 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2012 |
DE |
10 2012 001 821.5 |
Mar 10, 2012 |
DE |
10 2012 004 882.3 |
Claims
1. The use of a polyester which bears hydroxyl groups and is
preparable by polycondensation of a polyol containing two primary
OH groups and at least one secondary OH group with a dicarboxylic
acid or anhydride thereof or ester thereof which bears a C.sub.16-
to C.sub.400-alkyl radical or a C.sub.16- to C.sub.400-alkenyl
radical as an antifoulant in the thermal treatment of liquid
hydrocarbon media within the temperature range from 100 to
550.degree. C.
2. The use as claimed in claim 1, wherein the OH number of the
polyester is at least 40 mg KOH/g.
3. The use as claimed in claim 1 and/or 2, wherein the dicarboxylic
acid or anhydride thereof or ester thereof bears a C.sub.16- to
C.sub.40-alkyl radical or a C.sub.16- to C.sub.40-alkenyl
radical.
4. The use as claimed in claim 3, wherein the dicarboxylic acid is
a C.sub.16- to C.sub.40-alkyl- or C.sub.16- to
C.sub.40-alk(en)ylsuccinic acid or anhydride thereof.
5. The use as claimed in one or more of claims 1 to 4, wherein the
alkyl or alkenyl radical of the dicarboxylic acid or anhydride
thereof or ester thereof contains 18 to 36 carbon atoms.
6. The use as claimed in one or more of claims 3 to 5, wherein the
alkyl or alkenyl radical derives from an .alpha.-olefin.
7. The use as claimed in claim 1 and/or 2, wherein the dicarboxylic
acid or anhydride thereof or ester thereof bears a C.sub.41- to
C.sub.400-alkyl radical or a C.sub.41- to C.sub.400-alkenyl
radical.
8. The use as claimed in claim 7, wherein the alkyl or alkenyl
radical of the dicarboxylic acid is branched.
9. The use as claimed in claim 7 and/or 8, wherein the alkyl or
alkenyl radical derives from a polyolefin.
10. The use as claimed in claim 9, wherein the polyolefin derives
from an olefin having 3 to 6 carbon atoms.
11. The use as claimed in claim 10, wherein the polyolefin is
poly(isobutene).
12. The use as claimed in one or more of claims 1 to 11, wherein
the polyol is of monomeric structure, and comprises three to 10
carbon atoms and 1 to 6 secondary OH groups, but not more than one
OH group per carbon atom.
13. The use as claimed in one or more of claims 1 to 11, wherein
the polyol is of polymeric structure and comprises six to 150
carbon atoms and two to 50 secondary OH groups, but not more than
one OH group per carbon atom.
14. The use as claimed in one or more of claims 1 to 11, wherein
the polyol is selected from glycerol and oligomers thereof having 2
to 10 monomer units.
15. The use as claimed in one or more of claims 1 to 14, wherein
the polyester corresponds to the structural formula (A)
##STR00004## in which one of the R.sup.1 to R.sup.4 radicals is a
C.sub.16-C.sub.400-alkyl or -alkenyl radical and the other R.sup.1
to R.sup.4 radicals are each independently hydrogen or an alkyl
radical having 1 to 3 carbon atoms, R.sup.5 is a C--C single bond
or an alkylene radical having 1 to 6 carbon atoms, R.sup.16 is a
hydrocarbyl group which bears at least one hydroxyl group and has 3
to 10 carbon atoms, n is a number from 1 to 100, m is a number from
3 to 250, p is 0 or 1, and q is 0 or 1.
16. The use as claimed in claim 15, wherein one of the R.sup.1 to
R.sup.4 radicals is a linear C.sub.16-C.sub.40-alkyl or -alkenyl
radical.
17. The use as claimed in claim 15, wherein one of the R.sup.1 to
R.sup.4 radicals is a C.sub.41-C.sub.400-alkyl or -alkenyl
radical.
18. The use as claimed in claim 9, wherein R.sup.16 is a radical of
the formula (2)
--(CH.sub.2).sub.r--(CH(OH)).sub.t--(CH.sub.2).sub.s-- (2) in which
t is a number from 1 to 6, r, s are each independently a number
from 1 to 9 and t+r+s is a number from 3 to 10.
19. The use as claimed in one or more of claims 1 to 18, wherein
the polyester is nitrogen-free.
20. The use as claimed in one or more of claims 1 to 19, wherein
the molecular weight of the polyester is between 2000 g/mol and 100
000 g/mol.
21. The use as claimed in one or more of claims 1 to 20, wherein
the liquid hydrocarbon medium is crude oil or a fraction obtainable
from crude oil.
22. The use as claimed in one or more of, claims 1 to 21, wherein
the liquid hydrocarbon medium is a petrochemical or a hydrocarbon
used as a heat carrier.
23. The use as claimed in one or more of claims 1 to 22, wherein
the liquid hydrocarbon medium is of biogenic origin.
24. The use as claimed in one or more of claims 1 to 23, wherein
the use is effected at temperatures between 200 and 550.degree.
C.
25. A method for reducing fouling in a liquid hydrocarbon medium
during the heat treatment of the medium at temperatures between 100
and 550.degree. C., in which the polyester bearing hydroxyl groups
as defined in one or more of claims 1 to 20 is added to the liquid
hydrocarbon before and/or during the thermal treatment.
26. A method for increasing the service life of plants for thermal
treatment of hydrocarbons, in which the polyester bearing hydroxyl
groups as defined in one or more of claims 1 to 20 is added to the
hydrocarbon media to be processed before and/or during the thermal
treatment.
27. The method as claimed in claim 25 or 26, which proceeds at
temperatures of 200 to 550.degree. C.
Description
[0001] The present invention relates to a process for reducing
fouling by liquid hydrocarbons during the processing thereof at
relatively high temperatures, for example in refinery
operations.
[0002] In the course of processing, hydrocarbons such as crude oil
and intermediates in mineral oil processing, for example, but also
petrochemicals and petrochemical intermediates, are generally
heated to temperatures between 100.degree. C. and 550.degree. C.,
frequently between 200.degree. C. and 550.degree. C. In heating and
heat exchange systems too, hydrocarbons used as heat carriers are
exposed to such temperatures. In virtually all these cases,
hydrocarbons used form unwanted breakdown products or by-products
at elevated temperatures, which can separate out and accumulate at
the hot surfaces of the heat transferers. The formation of these
deposits is generally attributed to the presence of comparatively
unstable compounds, for example oxidized and/or oxidizable
hydrocarbons and olefinically unsaturated compounds, but this is
also blamed on high molecular weight organic compounds and
inorganic impurities. In specific cases, the extraneous substances
which separate out and accumulate may even already be present in
the raw material or precursor to be processed. In the specific case
of mineral oil distillation, the crude oils used for that purpose
generally comprise constituents which lead to deposits, for example
alkali metal and alkaline earth metal salts, compounds or complexes
containing transition metals, for example iron sulfide or
porphyrins, sulfur compounds, for example mercaptans, nitrogen
compounds, for example pyrroles, compounds containing carbonyl
groups or carboxyl groups, and polycyclic aromatics, for example
asphaltenes and/or coke particles. In addition, the hydrocarbons
used for processing virtually always contain small amounts of
dissolved oxygen.
[0003] The deposits which form in the course of processing of the
hydrocarbons at elevated temperatures and settle out on the
surfaces in contact with the liquid are referred to as fouling.
They form particularly on the hot insides of pipes, machines or
heat exchangers.
[0004] These deposits in the processes mentioned gradually reduce
the bore of pipelines and vessels, which impairs both the process
throughput and heat transfer. Often, the deposits even block filter
screens, valves and traps, and as a result cause plant shutdowns
for cleaning and maintenance. In all cases, these deposits are
additionally unwanted by-products which reduce the yield of target
product and hence lower the economic viability of the plant. In the
case of heat exchange systems, the deposits form an insulating
layer on the surfaces present, which restricts heat transfer.
Consequently, the deposits necessitate frequent shutdowns of the
plants for cleaning and in some cases even replacement thereof.
Accordingly, these deposits are highly undesirable in industry.
[0005] The above-described deposits are usually higher molecular
weight materials, the consistency of which may range from tar
through rubber and "popcorn" to coke. The composition thereof may
differ in nature and in many cases defies any detailed analysis.
They often contain a combination of carbonaceous phases which are
coke-like in nature, polymers and/or condensates which are formed
from the hydrocarbons or impurities present therein by various
mechanisms. Further deposit constituents are frequently salts
composed primarily of magnesium chloride, calcium chloride and
sodium chloride. The formation of polymers and/or condensates is
attributed to catalysis by metal compounds, for example compounds
of copper or iron, which are present as impurities in the
hydrocarbons to be processed. Metal compounds of this kind can, for
example, accelerate the hydrocarbon oxidation rate by promoting
degenerative chain branching. The free radicals formed can in turn
trigger oxidation and polymerization reactions, which leads to the
formation of resins and sediments. Often, relatively inert
carbonaceous deposits are enclosed by more adhesive condensates or
polymers.
[0006] Fouling deposits are equally encountered in the
petrochemical field, where petrochemicals are either produced or
purified. The deposits in this environment are primarily polymeric
in nature and have a severe effect on the economic viability of the
petrochemical operation. The petrochemical operations include, for
example, the preparation of ethylene or propylene, or else the
purification of chlorinated hydrocarbons. Fouling is also observed
in the processing of biogenic raw materials, for example in the
processing of fatty acids and derivatives thereof, for example
fatty acid esters.
[0007] To prevent the formation of deposits, oil-soluble, polar
nitrogen compounds are used in many cases. These are predominantly
reaction products of alkyl- or alkenylsuccinic acids or anhydrides
thereof with polyamines, which are optionally derivatized
further.
[0008] For instance, U.S. Pat. No. 3,271,295 discloses reaction
products of alk(en)ylsuccinic anhydrides with polyamines for
prevention of deposits on metal surfaces in heat transferers in
mineral oil refining.
[0009] WO-2011/014215 discloses the use of mono- and bisimides
formed from polyamines and C.sub.10- to C.sub.800-alkyl- or
-alkenylsuccinic anhydrides for prevention of deposits in plants
for mineral oil refining.
[0010] U.S. Pat. No. 5,342,505 discloses the use of reaction
products formed from poly(alkenyl)succinimides with epoxyalkanols
as antifoulants in liquid hydrocarbons during the processing
thereof at elevated temperatures
[0011] U.S. Pat. No. 5,171,420 discloses reaction products formed
from alkenylsuccinic anhydrides, polyols, amines bearing hydroxyl
groups, polyalkylenesuccinimides and polyoxyalkyleneamines for
prevention of deposits in the course of heating of liquid
hydrocarbons. In the preferred embodiments, which are demonstrated
by examples, polyfunctional reagents which lead to highly branched
structures are used.
[0012] The reaction products of dicarboxylic acids with polyamines
typically have a relatively low molecular weight, since
dicarboxylic acids, when condensed with primary amines, react
preferentially to give imides and form only minor proportions, if
any, of diamides. Typically, the condensation is restricted to the
reaction of the primary amino groups of the polyamine with one
dicarboxylic acid each, such that the result is typically molecular
weights of not more than 3000 g/mol. Higher molecular weight
compounds, which are desirable for the efficient reduction of
fouling, are thus not obtainable in this way.
[0013] In addition, it is desirable from an economic point of view
to use additives having a minimum nitrogen content. As a result,
any increase in the nitrogen content of the products obtained in
the thermal treatment of liquid hydrocarbons and any occurrence of
by-products and residues can be avoided. Both in the thermal
treatment of liquid hydrocarbons themselves and in the subsequent
further use of the products, by-products and residues obtained, an
elevated content of nitrogen compounds can lead to unwanted
by-products and conversion products. For example, the combustion
thereof forms nitrogen oxides.
[0014] There have been no descriptions to date of higher molecular
weight oligomeric or even polymeric compounds and more particularly
of higher molecular weight oligomeric or even polymeric
nitrogen-free compounds for reduction of fouling by liquid
hydrocarbons during the processing thereof at relatively high
temperatures.
[0015] Higher molecular weight and additionally nitrogen-free
condensates of alkenylsuccinic acids are obtainable only by
condensation with polyols, but these have been used to date only in
entirely different applications.
[0016] For instance, EP-0809623 discloses oligomeric and polymeric
bisesters of alkyl- or alkenyldicarboxylic acid derivatives and
polyalcohols, and the use thereof as solubilizers, emulsifiers
and/or wash-active substances. Preferred polyalcohols are glycerol
and oligomeric glycerols.
[0017] WO-2008/059234 discloses oligo- and polyesters based on
alk(en)ylsuccinic anhydrides and polyols having at least 3 hydroxyl
groups and the use thereof as emulsifiers. These polymers are
additionally useful in the oilfield as foaming agents in foam
drilling fluids, as kinetic gas hydrate inhibitors and as
lubricants in aqueous drilling fluids.
[0018] U.S. Pat. No. 4,216,114 discloses condensation products of
C.sub.9-18-alkyl- or -alkenylsuccinic anhydrides with water-soluble
polyalkylene glycols and polyols having at least 3 OH groups and
the use thereof for splitting water-in-oil emulsions.
[0019] U.S. Pat. No. 3,447,916 discloses condensation polymers of
alkenylsuccinic anhydrides, polyols and fatty acids for lowering
the pour point of hydrocarbon oils. In these polymers, the hydroxyl
groups of the polyol are very substantially esterified.
[0020] DE-A-1920849 discloses condensation polymers of
alkenylsuccinic anhydrides, polyols having at least 4 OH groups and
fatty acids for lowering the pour point of hydrocarbon oils.
Preferably, the stoichiometry of the reactants used for the
condensation is selected such that the number of moles of OH groups
and carboxylic groups is the same, meaning that there is
substantially complete esterification.
[0021] WO-2011/076338 discloses low-temperature additives for
middle distillates comprising polycondensates of a polyol
containing two primary OH groups and at least one secondary OH
group with a dicarboxylic acid or anhydride thereof or ester
thereof bearing a C.sub.16- to C.sub.40-alkyl radical or a
C.sub.16- to C.sub.40-alkenyl radical.
[0022] The additives used according to the prior art for
suppression or at least for reduction of fouling often show
deficits in the efficacy thereof.
[0023] Consequently, there is a need for additives for more
efficient suppression or at least for reduction of the formation of
sparingly soluble deposits on the apparatus walls in the thermal
treatment of hydrocarbons, for example in processing and purifying
plants, and also in heat exchange systems. These should preferably
be nitrogen-free. Specifically, this need exists in the
distillation of crude oils and in the further processing of the
mineral oil distillation fractions which remain in distillation
processes.
[0024] It has been found that, surprisingly, specific
polycondensates of dicarboxylic acids or dicarboxylic anhydrides
bearing C.sub.16-C.sub.400-alkyl radicals or
C.sub.16-C.sub.400-alkenyl radicals and polyols having two primary
and at least one secondary OH group achieve the stated objects. It
has been found that higher molecular weight condensates having an
essentially linear polymer backbone are particularly useful.
[0025] The invention accordingly provides for the use of a
polyester which bears hydroxyl groups and is preparable by
polycondensation of a polyol containing two primary OH groups and
at least one secondary OH group with a dicarboxylic acid or
anhydride thereof or ester thereof which bears a C.sub.16- to
C.sub.400-alkyl radical or a C.sub.16- to C.sub.400-alkenyl radical
as an antifoulant in the thermal treatment of liquid hydrocarbon
media within the temperature range from 100 to 550.degree. C.
[0026] The present invention further provides a method for reducing
fouling in a liquid hydrocarbon medium during the thermal treatment
of the medium at temperatures between 100 and 550.degree. C., in
which a polyester which bears hydroxyl groups and is preparable by
polycondensation of a polyol containing two primary OH groups and
at least one secondary OH group with a dicarboxylic acid or
anhydride thereof or ester thereof which bears a C.sub.16- to
C.sub.400-alkyl radical or a C.sub.16- to C.sub.400-alkenyl radical
is added to the liquid hydrocarbon before and/or during the thermal
treatment.
[0027] The invention further provides a method for increasing the
service life of plants for thermal treatment of liquid hydrocarbon
media within the temperature range from 100 to 550.degree. C., in
which a polyester which bears hydroxyl groups and is preparable by
polycondensation of a polyol containing two primary OH groups and
at least one secondary OH group with a dicarboxylic acid or
anhydride thereof or ester thereof which bears a C.sub.16- to
C.sub.400-alkyl radical or a C.sub.16- to C.sub.400-alkenyl radical
is added to a liquid hydrocarbon medium to be processed in the
plant before and/or during the thermal treatment.
[0028] The polyester bearing hydroxyl groups is generally obtained
by the polycondensation of a dicarboxylic acid bearing a C.sub.16-
to C.sub.400-alkyl radical or -alkenyl radical, also referred to
collectively hereinafter as C.sub.16-C.sub.400-alk(en)yl radical,
with the primary hydroxyl groups of the polyol. It is preferable
that the secondary OH groups remain essentially unesterified. The
preferred structure of the polyester bearing hydroxyl groups can
thus be represented, for example, by formula (A):
##STR00001##
in which [0029] one of the R.sup.1 to R.sup.4 radicals is a
C.sub.16-C.sub.400-alkyl or -alkenyl radical and [0030] the other
R.sup.1 to R.sup.4 radicals are each independently hydrogen or an
alkyl radical having 1 to 3 carbon atoms, [0031] R.sup.5 is a C--C
bond or an alkylene radical having 1 to 6 carbon atoms, [0032]
R.sup.16 is a hydrocarbyl group which bears at least one hydroxyl
group and has 3 to 10 carbon atoms, [0033] n is a number from 1 to
100, [0034] m is a number from 3 to 250, [0035] p is 0 or 1, and
[0036] q is 0 or 1.
[0037] Preferred dicarboxylic acids which bear
C.sub.16-C.sub.400-alkyl- and/or -alkenyl radicals and are suitable
for preparation of the polyesters A) bearing hydroxyl groups
correspond to the formula (1)
##STR00002##
in which [0038] one of the R.sup.1 to R.sup.4 radicals is a
C.sub.16-C.sub.400-alkyl or -alkenyl radical and [0039] the other
R.sup.1 to R.sup.4 radicals are each independently hydrogen or an
alkyl radical having 1 to 3 carbon atoms, and [0040] R.sup.5 is a
C--C bond or an alkylene radical having 1 to 6 carbon atoms.
[0041] More preferably, one of the R.sup.1 to R.sup.4 radicals is a
C.sub.16-C.sub.400-alkyl- or -alkenyl radical, one is a methyl
group and the rest are hydrogen. In a specific embodiment, one of
the R.sup.1 to R.sup.4 radicals is a C.sub.16-C.sub.400-alkyl- or
-alkenyl radical and the others are hydrogen. In a particularly
preferred embodiment, R.sup.5 is a C--C single bond. More
particularly, one of the R.sup.1 to R.sup.4 radicals is a
C.sub.16-C.sub.400-alkyl- or -alkenyl radical, the other R.sup.1 to
R.sup.4 radicals are hydrogen and R.sup.5 is a C--C single
bond.
[0042] The dicarboxylic acids or anhydrides thereof bearing alkyl-
and/or -alkenyl radicals can be prepared by known processes. For
example, they can be prepared by heating ethylenically unsaturated
dicarboxylic acids with olefins or with chloroalkanes. Preference
is given to the thermal addition of olefins onto ethylenically
unsaturated dicarboxylic acids or anhydrides thereof ("ene
reaction"), which is typically conducted at temperatures between
100 and 250.degree. C. The dicarboxylic acids and dicarboxylic
anhydrides bearing alkenyl radicals which are formed can be
hydrogenated to dicarboxylic acids and dicarboxylic anhydrides
bearing alkyl radicals. Dicarboxylic acids and anhydrides thereof
preferred for the reaction with olefins are maleic acid and more
preferably maleic anhydride. Additionally suitable are itaconic
acid, citraconic acid and anhydrides thereof, and the esters of the
aforementioned acids, especially those with lower
C.sub.1-C.sub.8-alcohols, for example methanol, ethanol, propanol
and butanol.
[0043] In a first preferred embodiment, one of the R.sup.1 to
R.sup.4 radicals is a linear C.sub.16-C.sub.40-alkyl- or -alkenyl
radical. For the preparation of such dicarboxylic acids or
anhydrides thereof bearing alk(en)yl radicals, preference is given
to using olefins having 16 to 40 carbon atoms and especially having
18 to 36 carbon atoms, for example having 19 to 32 carbon atoms. In
a particularly preferred embodiment, mixtures of olefins having
different chain lengths are used. Preference is given to using
mixtures of olefins having 18 to 36 carbon atoms, for example
mixtures of olefins in the C.sub.20-C.sub.22, C.sub.20-C.sub.24,
C.sub.24-C.sub.28, C.sub.26-C.sub.28, C.sub.30-C.sub.36 range.
Olefin mixtures may also comprise minor proportions of shorter-
and/or longer-chain olefins compared to the range specified, for
example hexene, heptene, octene, nonene, decene, undecene,
dodecene, tetradecene and/or olefins having more than 40 carbon
atoms. Preferably, the proportion of the shorter- and longer-chain
olefins in the olefin mixture is, however, not more than 10% by
weight. More particularly, it is between 0.1 and 8% by weight, for
example between 1 and 5% by weight.
[0044] Olefins particularly preferred for the preparation of the
dicarboxylic acids or anhydrides thereof bearing
C.sub.16-C.sub.40-alk(en)yl radicals have a linear or at least
substantially linear alkyl chain. "Linear or substantially linear"
is understood to mean that at least 50% by weight, preferably 70 to
99% by weight, especially 75 to 95% by weight, for example 80 to
90% by weight, of the olefins have a linear component having 16 to
40 carbon atoms and especially having 18 to 36 carbon atoms, for
example having 19 to 32 carbon atoms. In a specific embodiment,
.alpha.-olefins, wherein the C.dbd.C double bond is at the chain
end, are used. Particularly useful olefins have been found to be
technical grade alkene mixtures. These contain preferably at least
50% by weight, more preferably 60 to 99% by weight and especially
70 to 95% by weight, for example 75 to 90% by weight, of terminal
double bonds (.alpha.-olefins). In addition, they may contain up to
50% by weight, preferably 1 to 40% by weight and especially 5 to
30% by weight, for example 10 to 25% by weight, of olefins having
an internal double bond, for example having vinylidene double bonds
having the structural element R.sup.17--CH.dbd.C(CH.sub.3).sub.2
where R.sup.17 is an alkyl radical having 12 to 36 carbon atoms and
especially having 14 to 32 carbon atoms, for example having 15 to
28 carbon atoms. In addition, minor amounts of secondary components
present for technical reasons, for example paraffins, may be
present, but preferably not more than 5% by weight. Particular
preference is given to olefin mixtures containing at least 75% by
weight of linear .alpha.-olefins having a carbon chain length in
the range from C.sub.20 to C.sub.24.
[0045] In a further preferred embodiment, one of the R.sup.1 to
R.sup.4 radicals is a C.sub.41-C.sub.400-alkyl- or -alkenyl radical
and especially a C.sub.50- to C.sub.300-alkyl or -alkenyl radical,
for example a C.sub.55- to C.sub.200-alkyl- or -alkenyl radical.
Preferably, this alk(en)yl radical is branched. Additionally
preferably, these C.sub.41-C.sub.400-alk(en)yl radicals derive from
polyolefins preparable by polymerization of monoolefins having 3 to
6 and especially having 3, 4 or 5 carbon atoms. Particularly
preferred monoolefins as base structures for the polyolefins are
propylene and isobutene, which give rise to poly(propylene) and
poly(isobutene) as polyolefins. Preferred polyolefins have an
alkylvinylidene content of at least 50 mol %, particularly of at
least 70 mol % and especially at least 80 mol %, for example at
least 85 mol %. "Alkylvinylidene content" is understood to mean the
content in the polyolefins of structural units which result from
compounds of the formula (3):
##STR00003##
in which R.sup.6 or R.sup.7 is methyl, ethyl or propyl and
especially methyl and the other group is an oligomer of the
C.sub.3-C.sub.6-olefin. The alkylvinylidene content can be
determined, for example, by means of .sup.1H NMR spectroscopy. The
number of carbon atoms in the polyolefin is between 41 and 400. In
a preferred embodiment of the invention, the number of carbon atoms
is between 50 and 3000 and especially between 55 and 200. The
parent polyolefins of the C.sub.41-C.sub.400-alkyl- or -alkenyl
radical are obtainable, for example, by ionic polymerization and
are available as commercial products (e.g. Glissopal.RTM.,
polyisobutenes from BASF with different alkylvinylidene content and
molecular weight). Also suitable in accordance with the invention
are mixtures of various polyolefins, in which case these may
differ, for example, in terms of the parent monomers, the molecular
weights and/or the alkylvinylidene content.
[0046] Preferred polyesters bearing hydroxyl groups are preparable
by reaction of alkyl- or alkenylsuccinic acids and/or anhydrides
thereof bearing a C.sub.16-C.sub.400-alkyl- or -alkenyl radical
with polyols bearing two primary and at least one secondary
hydroxyl group.
[0047] Preferred polyols may be monomeric, oligomeric or polymeric
in terms of structure. Polymers and oligomers are referred to
collectively as polymers. R.sup.16 in formula A) is preferably a
radical of the formula (2)
--(CH.sub.2).sub.r--(CH(OH)).sub.t--(CH.sub.2).sub.s-- (2)
in which t is a number from 1 to 6, r and s are each independently
a number from 1 to 9 and t+r+s is a number from 3 to 10.
[0048] In monomeric polyols, n in formula A) is 1. Preferred
monomeric polyols have three to 10 and especially four to six
carbon atoms. They additionally have at least one and preferably 1
to 6, for example 2 to 4, secondary OH groups, but not more than
one OH group per carbon atom. Suitable monomeric polyols are, for
example, glycerol, 1,2,4-butanetriol, 1,2,6-trihydroxyhexane, and
also reduced carbohydrates and mixtures thereof. Reduced
carbohydrates are understood here to mean polyols which derive from
carbohydrates and bear two primary and two or more secondary OH
groups. Particularly preferred reduced carbohydrates have 4 to 6
carbon atoms. Examples of reduced carbohydrates are erythritol,
threitol, adonitol, arabitol, xylitol, dulcitol, mannitol and
sorbitol. A particularly preferred monomeric polyol is
glycerol.
[0049] In polymeric polyols, n in formula A) is a number from 2 to
100, preferably a number from 2 to 50, more preferably a number
from 3 to 25 and especially a number from 4 to 20. Preferred
polymeric polyols have six to 150, especially eight to 100 and
particularly nine to 50 carbon atoms. They bear at least one,
preferably two to 50 and especially three to 15 secondary OH
groups, but not more than one OH group per carbon atom. Polymeric
polyols suitable in accordance with the invention are preparable,
for example, by polycondensation of polyols having two primary and
at least one secondary OH group. A preferred polymeric polyol is
poly(glycerol). "Poly(glycerol)" is especially understood to mean
structures derivable by polycondensation from glycerol. The
condensation level of poly(glycerols) preferred in accordance with
the invention is between 2 and 50, more preferably between 3 and 25
and especially between 4 and 20, for example between 5 and 15.
[0050] The preparation of poly(glycerol) is known in the prior art.
It can be prepared, for example, via addition of
2,3-epoxy-1-propanol (glycide) onto glycerol. In addition,
poly(glycerol) can be prepared by polycondensation, as known per
se, of glycerol. The reaction temperature in the polycondensation
is generally between 150 and 300.degree. C., preferably between 200
and 250.degree. C. The polycondensation of glycerol is normally
conducted at atmospheric pressure. Catalyzing acids include, for
example, HCl, H.sub.2SO.sub.4, organic sulfonic acids or
H.sub.3PO.sub.4; catalyzing bases include, for example, NaOH or
KOH. The catalysts are added to the reaction mixture preferably in
amounts of 0.01 to 10% by weight, more preferably 0.1 to 5% by
weight, based on the weight of the reaction mixture. The
polycondensation of glycerol can be conducted without solvent, or
else in the presence of solvent. If the polycondensation is
effected in the presence of solvent, the proportion thereof in the
reaction mixture is preferably 0.1 to 70% by weight, for example 10
to 60% by weight. Preferred organic solvents here are the solvents
also used and preferred for the condensation of the dicarboxylic
acid, anhydride thereof or ester thereof bearing alk(en)yl radicals
with the polyol. The polycondensation of glycerol generally takes 3
to 10 hours. This process is also applicable mutatis mutandis to
the polycondensation of other polyols.
[0051] The dicarboxylic acid, anhydride thereof or ester thereof
bearing alk(en)yl radicals are converted to the polyester bearing
hydroxyl groups preferably in a molar ratio of 1:2 to 2:1, more
preferably in a molar ratio of 1:1.5 to 1.5:1 and especially in a
molar ratio of 1:1.2 to 1.2:1, for example in a equimolar ratio.
More preferably, the conversion is effected with an excess of
polyol. In this context, molar excesses of 1 to 10 mol % and
especially 1.5 to 5 mol % based on the amount of dicarboxylic acid
used have been found to be particularly useful.
[0052] The polycondensation of the dicarboxylic acid, anhydride
thereof or ester thereof bearing alkyl radicals with the polyol is
effected preferably by heating C.sub.16-C.sub.400-alkyl- or
-alkenyl-substituted dicarboxylic acid or the anhydride or ester
thereof together with the polyol to temperatures above 100.degree.
C. and preferably to temperatures between 120 and 320.degree. C.,
for example to temperatures between 150 and 290.degree. C. For
adjustment of the molecular weight, which is important for the
efficacy of the polyester bearing hydroxyl groups, it is typically
necessary to remove the water of reaction or the alcohol of
reaction, which can be effected, for example, by distillative
removal. Azeotropic removal by means of suitable organic solvents
is also suitable for this purpose. Preferred solvents for the
polycondensation of the dicarboxylic acid, anhydride thereof or
ester thereof bearing alk(en)yl radicals with the polyol are
relatively high-boiling, low-viscosity solvents. Particularly
preferred solvents are aliphatic and aromatic hydrocarbons and
mixtures thereof. Aliphatic hydrocarbons preferred as solvents have
9 to 20 carbon atoms and especially 10 to 16 carbon atoms. They may
be linear, branched and/or cyclic. They are preferably saturated or
at least substantially saturated. Aromatic hydrocarbons preferred
as solvents have 7 to 20 carbon atoms and especially 8 to 16, for
example 9 to 13, carbon atoms. Preferred aromatic hydrocarbons are
mono-, di-, tri- and polycyclic aromatics. In a preferred
embodiment, these bear one or more, for example two, three, four,
five or more, substituents. In the case of a plurality of
substituents, these may be the same or different. Preferred
substituents are alkyl radicals having 1 to 20 and especially
having 1 to 5 carbon atoms, for example methyl, ethyl, n-propyl,
isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl,
tert-pentyl and neopentyl radical. Examples of suitable aromatics
are alkylbenzenes and alkylnaphthalenes. For example, aliphatic
and/or aromatic hydrocarbons or hydrocarbon mixtures, e.g.
petroleum fractions, kerosene, decane, pentadecane, toluene,
xylene, ethylbenzene or commercial solvent mixtures such as Solvent
Naphtha, Shellsol.RTM. AB, Solvesso.RTM. 150, Solvesso.RTM. 200,
Exxsol.RTM. products, ISOPAR.RTM. products and Shellsol.RTM. D
products, are particularly suitable. As well as the solvents based
on mineral oils, solvents based on renewable raw materials and
synthetic hydrocarbons obtainable, for example, from the
Fischer-Tropsch process, are suitable as solvents. Also suitable
are mixtures of the solvents mentioned. If the polycondensation is
effected in the presence of solvent, the proportion thereof in the
reaction mixture is preferably 1 to 75% by weight and especially 10
to 70% by weight, for example 20 to 60% by weight. The condensation
is preferably conducted without solvent.
[0053] For acceleration of the polycondensation, it has often been
found to be useful to conduct the polycondensation in the presence
of homogeneous catalysts, heterogeneous catalysts or mixtures
thereof. Preferred catalysts here are acidic inorganic,
organometallic or organic catalysts and mixtures of two or more of
these catalysts.
[0054] Acidic inorganic catalysts in the context of the present
invention are, for example, sulfuric acid, phosphoric acid,
phosphonic acid, hypophosphorous acid, aluminum sulfate hydrate,
alum, acidic silica gel and acidic aluminum hydroxide. Additionally
usable as acidic inorganic catalysts are, for example, aluminum
compounds of the formula Al(OR.sup.15).sub.3 and titanates of the
formula Ti(OR.sup.15).sub.4, where the R.sup.15 radicals may each
be the same or different and are each independently selected from
C.sub.1-C.sub.10-alkyl radicals, for example methyl, ethyl,
n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,
n-pentyl, isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl,
isoamyl, n-hexyl, sec-hexyl, n-heptyl, n-octyl, 2-ethylhexyl,
n-nonyl or n-decyl, C.sub.3-C.sub.12-cycloalkyl radicals, for
example cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,
cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl and
cyclododecyl; preference is given to cyclopentyl, cyclohexyl and
cycloheptyl. Preferably, the R.sup.15 radicals in
Al(OR.sup.15).sub.3 and Ti(OR.sup.15).sub.4 are each the same and
are selected from isopropyl, butyl and 2-ethylhexyl.
[0055] Preferred acidic organometallic catalysts are, for example,
selected from dialkyltin oxides (R.sup.15).sub.2SnO where R.sup.15
is as defined above. A particularly preferred representative of
acidic organometallic catalysts is di-n-butyltin oxide,
commercially available as "oxo-tin" or as the Fascat.RTM.
brand.
[0056] Preferred acidic organic catalysts are acidic organic
compounds having, for example, phosphate groups, sulfo groups,
sulfate groups or phosphonic acid groups. Particularly preferred
sulfonic acids contain at least one sulfo group and at least one
saturated or unsaturated, linear, branched and/or cyclic
hydrocarbyl radical having 1 to 40 carbon atoms and preferably
having 3 to 24 carbon atoms. Especially preferred are aromatic
sulfonic acids and specifically alkylaromatic monosulfonic acids
having one or more C.sub.1-C.sub.28-alkyl radicals and especially
those having C.sub.3-C.sub.22-alkyl radicals. Suitable examples are
methanesulfonic acid, butanesulfonic acid, benzenesulfonic acid,
p-toluenesulfonic acid, xylenesulfonic acid, 2-mesitylenesulfonic
acid, 4-ethylbenzenesulfonic acid, isopropylbenzene-sulfonic acid,
4-butylbenzenesulfonic acid, 4-octylbenzenesulfonic acid,
dodecyl-benzenesulfonic acid, didodecylbenzenesulfonic acid and
naphthalenesulfonic acid. It is also possible to use acidic ion
exchangers as acidic organic catalysts, for example poly(styrene)
resins which bear sulfo groups and have been crosslinked with about
2 mol % of divinylbenzene.
[0057] For the performance of the process according to the
invention, particular preference is given to boric acid, phosphoric
acid, polyphosphoric acid and polystyrenesulfonic acids. Especially
preferred are titanates of the formula Ti(OR.sup.15).sub.4 and
specifically titanium tetrabutoxide and titanium
tetraisopropoxide.
[0058] If it is desirable to use acidic inorganic, organometallic
or organic catalysts, according to the invention, 0.01 to 10% by
weight, preferably 0.02 to 2% by weight, of catalyst is used. In a
specific embodiment, the condensation is effected without addition
of catalysts.
[0059] In a preferred embodiment, for adjustment of the molecular
weight, minor amounts of the dicarboxylic acids, anhydrides thereof
or esters thereof bearing alk(en)yl radicals are replaced in the
reaction mixture by C.sub.1- to C.sub.18-monocarboxylic acids,
preferably C.sub.2- to C.sub.16-monocarboxylic acids and especially
C.sub.3- to C.sub.14-monocarboxylic acids, for example C.sub.4- to
C.sub.12-monocarboxylic acids. At the same time, however, not more
than 20 mol % and preferably 0.1 to 10 mol %, for example 0.5 to 5
mol %, of the dicarboxylic acids, anhydrides thereof or esters
thereof bearing alk(en)yl radicals is replaced by one or more
monocarboxylic acids. In addition, minor amounts, for example up to
10 mol % and especially 0.01 to 5 mol % of the alk(en)ylsuccinic
acids or anhydrides thereof may also be replaced by further
dicarboxylic acids, for example succinic acid, glutaric acid,
maleic acid and/or fumaric acid. More preferably, the polyesters
bearing hydroxyl groups are prepared in the absence of
monocarboxylic acids.
[0060] In a further preferred embodiment, for adjustment of the
molecular weight, minor amounts of the polyol are replaced in the
reaction mixture by C.sub.1- to C.sub.30-monoalcohols, preferably
C.sub.2- to C.sub.24-monoalcohols and especially C.sub.3- to
C.sub.18-monoalcohols, for example C.sub.4- to
C.sub.12-monoalcohols. At the same time, preferably not more than
20 mol % and more preferably 0.1 to 10 mol %, for example 0.5 to 5
mol %, of the polyol is replaced by one or more monoalcohols. More
preferably, the polyesters bearing hydroxyl groups are prepared in
the absence of monoalcohols. In addition, the polyol bearing two
primary and at least one secondary hydroxyl groups may also be
replaced by one or more diols in minor amounts of up to 10 mol %,
for example 0.01 to 5 mol %. Preference is given here to diols, for
example ethylene glycol, propylene glycol and/or neopentyl glycol.
More preferably, the polyesters bearing hydroxyl groups are
prepared in the absence of diols.
[0061] In a further preferred embodiment, to increase the molecular
weight, minor amounts of the polyol bearing two primary and at
least one secondary OH group are replaced in the reaction mixture
by polyols having three or more primary OH groups, for example
having four, five, six or more primary OH groups. At the same time,
preferably not more than 10 mol % and more preferably 0.1 to 8 mol
%, for example 0.5 to 4 mol %, of the polyol bearing two primary
and at least one secondary OH group is replaced by a polyol having
three or more primary OH groups. Suitable polyols having three or
more primary OH groups are, for example, trimethylolethane,
trimethylolpropane and pentaerythritol.
[0062] The mean condensation level of the polyesters bearing
hydroxyl groups used in accordance with the invention is preferably
between 4 and 200, more preferably between 5 and 150, especially
between 7 and 100 and particularly between 10 and 70, for example
between 15 and 50, repeat dicarboxylic acid and polyol units. The
condensation level is understood here to mean the sum of m+p+q as
per formula (A). The weight-average molecular weight Mw of the
polyesters bearing hydroxyl groups, determined by means of GPC in
THF against poly(ethylene glycol) standards, is preferably between
2000 g/mol and 600 000 g/mol. In the case of polyesters which
derive from dicarboxylic acids bearing C.sub.16-C.sub.40-alk(en)yl
radicals, it is more preferably between 2000 and 100 000 g/mol and
especially between 3000 and 50 000 g/mol, for example between 4000
and 20 000 g/mol. In the case of polyesters which derive from
dicarboxylic acids bearing C.sub.41-C.sub.400-alk(en)yl radicals,
it is more preferably between 3000 and 500 000 g/mol, particularly
between 5000 and 200 000 g/mol and especially between 8000 and 150
000 g/mol, for example between 10 000 and 100 000 g/mol.
[0063] Preferably, the acid number of the polyesters bearing
hydroxyl groups is less than 40 mg KOH/g and more preferably less
than 30 mg KOH/g, for example less than 20 mg KOH/g. The acid
number can be determined, for example, by titration of the polymer
with alcoholic tetra-n-butylammonium hydroxide solution in
xylene/isopropanol. Additionally preferably, the hydroxyl number of
the polyesters is between 40 and 500 mg KOH/g, more preferably
between 50 and 300 mg KOH/g and especially between 60 and 250 mg
KOH/g. The hydroxyl number can, after reaction of the free OH
groups with isocyanate, be ascertained by means of .sup.1H NMR
spectroscopy, by quantitative determination of the urethane
formed.
[0064] Preferably, the polyesters bearing hydroxyl groups used in
accordance with the invention are nitrogen-free. "Nitrogen-free" is
understood in accordance with the invention to mean that the
nitrogen content thereof is below 1000 ppm by weight and more
preferably below 100 ppm by weight and especially below 10% by
weight, for example below 1 ppm by weight. The nitrogen content can
be determined, for example, according to Kjeldahl.
[0065] The term "liquid hydrocarbon medium", according to the
invention, represents various different mineral oil hydrocarbons
and petrochemicals. For example, mineral oil hydrocarbon feedstocks
including crude oils and fractions obtainable therefrom, for
example naphtha, gasifier fuel, kerosene, diesel, jet fuel, heating
oil, gas oil, vacuum residues inter alia are covered by this
definition. Examples of petrochemicals are olefinic or naphthenic
process streams, aromatic hydrocarbons and derivatives thereof,
ethylene dichloride and ethylene glycol. Likewise covered by the
term "liquid hydrocarbon media" are hydrocarbons used as heat
carriers, for example fused and/or substituted aromatics.
Additionally covered by this definition are biogenic raw materials
and products obtainable from biogenic raw materials by processing,
for example animal and vegetable oils and fats and derivatives
thereof, for example fatty acid alkyl esters. The liquid
hydrocarbon media may also comprise constituents not consisting of
hydrocarbons, for example salts, minerals and organometallic
compounds.
[0066] The polyesters used in accordance with the invention are
added to the liquid hydrocarbon media preferably in amounts of 0.5
to 5000 ppm by weight, more preferably of 1.0 to 1000 ppm by
weight, for example of 2 to 500 ppm by weight. The polyesters may
be dispersed or dissolved in the liquid hydrocarbon medium. They
are preferably dissolved.
[0067] For easier handling, the polyesters used in accordance with
the invention are preferably dissolved or dispersed in a polar or
nonpolar organic solvent and added to the liquid hydrocarbon medium
as a concentrate. Preferred solvents here are the solvents and
solvent mixtures already mentioned as solvents for the condensation
reaction between dicarboxylic acid and polyol. Particular
preference is given to aromatic solvents. Preferably, the
proportion of the polyester in the concentrate is 5 to 95% by
weight, more preferably 10 to 80% by weight and especially 20 to
70% by weight, for example 25 to 60% by weight.
[0068] The polyester is preferably added to the liquid hydrocarbon
medium prior to the thermal treatment thereof. The addition can be
undertaken batchwise, for example into the storage vessel of the
liquid hydrocarbon medium, or continuously into the feed line to
the heat treatment plant. The addition is preferably effected at a
site where the temperature of the liquid hydrocarbon medium is at
least 10.degree. C. and especially at least 20.degree. C., for
example at least 50.degree. C., below the maximum heat treatment
temperature. Especially in the case of hydrocarbon media of
relatively high viscosity, it has often been found to be useful to
promote the mixing of the polyester into the liquid hydrocarbon
medium by means of static or dynamic mixing apparatus.
[0069] Particular advantages are shown by the inventive use of
polyesters bearing hydroxyl groups and by the method that utilizes
them in the processing or treatment of liquid hydrocarbon media
above 100.degree. C., especially between 150 and 500.degree. C. and
particularly between 200.degree. C. and 480.degree. C., for example
between 250.degree. C. and 450.degree. C.
[0070] The polyesters used in accordance with the invention can be
used together with one or more further additives. Preferred further
additives are pour point depressants and demulsifiers, the latter
preferably based on alkoxylated alkylphenol-aldehyde resins.
[0071] The inventive use of polyesters bearing hydroxyl groups in
the thermal treatment of liquid hydrocarbon media leads to a
reduction in fouling superior to the prior art additives and often
also to the substantial and in some cases even complete suppression
thereof. As a result, the energy requirement in the processing of
liquid hydrocarbon is lowered and the throughput of the plant and
the yield of target product are increased.
[0072] The method of the invention is generally suitable for
reducing and often even for suppressing fouling in the processing
of liquid hydrocarbon media at relatively high temperatures. This
lowers the energy requirement of the process and increases the
throughput of the plant and the yield of target product. The
reduction in fouling reduces the frequency of maintenance shutdowns
for removal of deposits and hence increases the plant
availability.
[0073] For instance, the methods of the invention have been used
successfully for reduction of fouling in crude oil distillation, in
the processing of intermediates in mineral oil processing and in
the processing of petrochemicals, and also of petrochemical
intermediates, for example of gases, oils and reforming feedstocks,
chlorinated hydrocarbons and liquid products from olefin plants,
for example of bottoms phases from deethanization. The methods have
likewise been used successfully for reduction and often for
suppression of fouling by hydrocarbons used as heating media on the
`hot side` of heat exchange systems.
[0074] The suitability of the additives used in accordance with the
invention for suppression or at least for reduction of fouling by
liquid hydrocarbons in the course of thermal treatment thereof can
be measured, for example, with commercially available HLPS (Hot
Liquid Process Simulation) systems. In these systems, the oil to be
treated thermally is pumped continuously through a capillary with a
heating element present therein. As a result of fouling, deposits
gradually form on the heating element, which impair heat transfer
and lead to a pressure drop over the capillary. The extent of
fouling can be assessed, for example, via the drop in the
temperature at the outlet of the capillary. A significant drop in
the temperature during the experiment indicates the occurrence of
fouling. Measurements of this kind are generally regarded as a
measure for assessment of the tendency of an oil to fouling in heat
exchangers.
EXAMPLES
[0075] The .alpha.-olefins used were commercially available
mixtures of 1-alkenes or poly(isobutenes) having the compositions
specified. The acid numbers were determined by titration of an
aliquot of the reaction mixture with alcoholic
tetra-n-butylammonium hydroxide solution in xylene/isopropanol. The
hydroxyl numbers were determined, after reacting the free OH groups
of the polymers with isocyanate, by means of .sup.1H NMR
spectroscopy, by quantitative determination of the urethane formed.
The values reported are based on the solvent-free polymers.
[0076] The molecular weights were determined by means of lipophilic
gel permeation chromatography in THF against poly(ethylene glycol)
standards and detection by means of an RI detector.
[0077] Polyesters used: [0078] P1) Copolymer of equimolar
proportions of C.sub.20-24-alkenylsuccinic anhydride (prepared by
thermal condensation of maleic anhydride with technical-grade
C.sub.20-24-olefin containing, as main constituents, 43% C.sub.20-,
35% C.sub.22- and 17% C.sub.24-olefin, with 90% .alpha.-olefins and
7.5% linear internal olefins) and glycerol. The reactants, in the
form of a 50% solution in Shellsol.RTM. AB (aromatic solvent
mixture having a boiling range of about 185-215.degree. C.), were
heated to 150.degree. C. while stirring until the acid number
remained constant. The water which formed was distilled off. The
acid number of the polymer thus prepared was 7.8 mg KOH/g, the
hydroxyl number was 98 mg KOH/g and the weight-average molecular
weight was 6100 g/mol. [0079] P2) Copolymer prepared in analogy to
example P1) from equimolar proportions of
C.sub.20/24-alkenylsuccinic anhydride (prepared by thermal
condensation of maleic anhydride with technical-grade
C.sub.20/24-olefin containing, as main constituents, 43% C.sub.20-,
35% C.sub.22- and 17% C.sub.24-olefin, with 90% .alpha.-olefins and
7.5% linear internal olefins) and poly(glycerol) having a mean
condensation level of 3. The acid number of the polymer was 6.5 mg
KOH/g, the hydroxyl number was 195 mg KOH/g and the weight-average
molecular weight was 8700 g/mol. [0080] P3) Copolymer prepared in
analogy to example P1) from equimolar proportions of
C.sub.26/28-alkenylsuccinic anhydride (prepared by thermal
condensation of maleic anhydride with technical-grade
C.sub.26-28-olefin containing, as main constituents, 57% C.sub.26-,
39% C.sub.28- and 2.5% C.sub.30+-olefin, with 85% .alpha.-olefins,
4% linear internal olefins and 9% branched olefins) and glycerol.
The acid number of the polymer was 10.4 mg KOH/g, the hydroxyl
number was 68 mg KOH/g and the weight-average molecular weight was
9100 g/mol. [0081] P4) Copolymer of C.sub.20/24-alkenylsuccinic
anhydride as per example P1, 0.7 molar equivalent of glycerol and
0.3 molar equivalent of behenic acid. The acid number of the
polymer was 15 mg KOH/g, the hydroxyl number was 32 mg KOH/g and
the weight-average molecular weight was 1800 g/mol. [0082] P5)
Copolymer of equimolar proportions of C.sub.20-24-alkenylsuccinic
anhydride and ethylene glycol in analogy to example P1. The acid
number of the polymer thus prepared was 8.2 mg KOH/g, the hydroxyl
number was 2 mg KOH/g and the weight-average molecular weight was
5700 g/mol (comparative example). [0083] P6)
C.sub.20-24-Alkenylsuccinic anhydride as per example P1, reacted
with 2 molar equivalents of triethylenetetramine. The reactants, in
the form of a 50% solution in Shellsol AB, were heated to
150.degree. C. while stirring until the acid number remained
constant. The water which formed was distilled off. The acid number
of the polymer thus prepared was 10.2 mg KOH/g and the
weight-average molecular weight was 1000 g/mol (comparative
example). [0084] P7) Copolymer prepared in analogy to example P1)
from equimolar proportions of poly(isobutenyl)succinic anhydride
(prepared by thermal condensation of maleic anhydride with
poly(isobutene) having a mean molecular weight Mn of 1000 g/mol and
an alkylvinylidene content of 87 mol %) and glycerol. The acid
number of the polymer was 8.6 mg KOH/g, the hydroxyl number was 47
mg KOH/g and the weight-average molecular weight was 14 000 g/mol.
[0085] P8) Copolymer prepared in analogy to example P1) from
equimolar proportions of poly(isobutenyl)succinic anhydride
(prepared by thermal condensation of maleic anhydride with
poly(isobutene) having a mean molecular weight Mn of 2300 g/mol and
an alkylvinylidene content of 81 mol %) and poly(glycerol) having a
mean condensation level of 5. The acid number of the polymer was
7.8 mg KOH/g, the hydroxyl number was 110 mg KOH/g and the
weight-average molecular weight was 21 000 g/mol.
[0086] The efficacy of the additives in terms of their ability to
prevent or reduce fouling by mineral oils on hot surfaces was
tested with the aid of a modified Hot Liquid Process Simulation
(HLPS) system from Alcor. In the HLPS system, the oil to be
examined was pumped continuously from a stirred and heated
reservoir vessel through an electrically heated heating element
mounted in a stainless steel capillary (=hot capillary), before
being returned to the reservoir vessel. During the experiment, the
maximum oil temperature attained after switching on the heating
(the surface temperature of the heating element was about
400.degree. C.) was firstly registered at the output of the
stainless steel capillary (T1). Secondly, the oil temperature was
registered at the same point after an experimental duration of 5
hours (T2). Since the deposits formed on the heating element as a
result of fouling have low thermal conductivity, the maximum
temperature initially attained correlates indirectly (low initial
temperature T1 implies immediate onset of fouling), and the
difference in the temperatures T2 and T1 directly, with the extent
of fouling.
[0087] For each experiment, about 500 ml of the oil sample to be
examined were introduced into the reservoir vessel and heated to
about 150.degree. C. for better pumpability. The oil was then
pumped at a volume flow rate of 3 ml/min through the stainless
steel capillary which has been provided with a clean heating
element with a bare surface. The heating element was then heated to
a temperature of about 400.degree. C. for test oil 1, about
375.degree. C. for test oil 2 or about 390.degree. C. for test oil
3, and the maximum oil temperature which was then established at
the capillary outlet was noted (T1). After a run time of 5 hours,
the oil temperature that was then present at the end of the
stainless steel capillary (T2) was noted and the experiment was
ended. A high maximum temperature T1 and a low .DELTA.T
(.DELTA.T=T2-T1) indicate low coverage of the surface of the
heating element with insulating deposits and hence effective
suppression of fouling.
[0088] The following test oils were used for the assessment of the
fouling-reducing effect of the additives:
TABLE-US-00001 Test oil 1 2 3 Origin Brazil Malaysia Thailand API
gravity @ 15.degree. C. 25.7 47.2 11.4 [.degree.API] Viscosity
[mPas] 61 5 160 (25.degree. C.) (25.degree. C.) (50.degree. C.)
Density [g/cm.sup.3] 0.900 0.792 0.990 (20.degree. C.) (20.degree.
C.) (16.degree. C.) Pour point [.degree. C.] -27 +18 +33 Asphaltene
content 7.9 3.2 10.3 [% by wt.]
[0089] The viscosity was determined to ASTM D-445, and the density
to DIN EN ISO 12185. The pour point was determined to ASTM D-97.
The asphaltene content was determined to IP 143.
Experimental Results in Test Oil 1
TABLE-US-00002 [0090] Dosage T1 T1 Fouling Measure- Addi- rate (t =
0) (t = 5 h) .DELTA.T reduction ment tive [ppm] [.degree. C.]
[.degree. C.] [.degree. C.] [%] 1 none -- 278 256 22 0 2 P1 5 281
266 15 32 3 P2 5 282 268 14 36 4 P3 5 281 266 15 32 5 P4 5 280 262
18 18 6 (comp.) P5 5 279 257 22 0 7 (comp.) P6 5 280 261 19 14 8 P1
10 283 269 14 36 9 P2 10 285 274 11 50 10 P3 10 283 271 12 45 11 P4
10 281 265 16 27 12 (comp.) P5 10 279 259 20 9 13 (comp.) P6 10 282
264 18 18 14 P1 15 285 274 11 50 15 P2 15 286 278 8 64 16 P3 15 285
275 10 55 17 P4 15 284 270 14 36 18 (comp.) P5 15 280 261 19 14 19
(comp.) P6 15 283 266 17 23
Experimental Results in Test Oil 2
TABLE-US-00003 [0091] Dosage T1 T1 Fouling Measure- Addi- rate (t =
0) (t = 5 h) .DELTA.T reduction ment tive [ppm] [.degree. C.]
[.degree. C.] [.degree. C.] [%] 20 none 0 257 230 27 0 21 P1 10 261
238 23 15 22 P2 10 262 239 23 15 23 P3 10 261 238 23 15 24 P4 10
260 236 24 11 25 (comp.) P5 10 258 231 27 0 26 (comp.) P6 10 260
235 25 7 27 P1 25 263 244 19 30 28 P2 25 263 243 20 26 29 P3 25 262
243 19 30 30 P4 25 261 240 21 22 31 (comp.) P5 25 258 234 24 11
32(comp.) P6 25 262 239 23 15 33 P1 50 264 253 11 59 34 P2 50 265
256 9 67 35 P3 50 263 253 10 63 36 P4 50 261 247 14 48 37 (comp.)
P5 50 260 241 19 30 38 (comp.) P6 50 261 245 16 41
Experimental Results in Test Oil 3
TABLE-US-00004 [0092] Dosage T1 T1 Fouling Measure- Addi- rate (t =
0) (t = 5 h) .DELTA.T reduction ment tive [ppm] [.degree. C.]
[.degree. C.] [.degree. C.] [%] 39 none 0 266 244 22 0 40 P1 10 270
254 16 27 41 P2 10 271 256 15 32 42 (comp.) P5 10 265 244 21 5 43
(comp.) P6 10 268 250 18 18 44 P7 10 271 257 14 36 45 P8 10 273 261
12 45 46 P1 20 272 259 13 41 47 P2 20 272 260 12 45 48 (comp.) P5
20 265 245 20 9 49 (comp.) P6 20 270 253 17 23 50 P7 20 273 262 11
50 51 P8 20 274 264 10 55 52 P1 40 273 262 11 50 53 P2 40 274 264
10 55 54 (comp.) P5 40 266 246 20 9 55 (comp.) P6 40 271 258 13 41
56 P7 40 275 266 9 59 57 P8 40 275 268 7 68
[0093] The decreases in temperature after an experimental duration
of 5 hours observed in the experiments using the method of the
invention are much smaller than in comparative experiments using
other methods or additives. Moreover, higher maximum temperatures
are generally observed at first. Both indicate lower deposits on
the heating element and hence more efficient suppression of fouling
in the case of inventive use of the additives or of the method that
utilizes them. Accordingly, the method of the invention entails
less frequent maintenance of the plant for removal of the deposits
and hence longer service lives of the plant. Since the target oil
temperature is often preset in industrial plants, the method of the
invention additionally leads to saving of energy.
* * * * *