EP0344644A2 - Mineral oil with a modified flow rate - Google Patents

Abstract

Paraffin-containing mineral oils from the group comprising crude oils, vacuum gas oils and residual oils which have improved flow properties, it being common to the mineral oils that paraffin crystallisation starts at a temperature below or equal to 30 degrees C and that they contain 1-10,000 ppm of at least one polymer P, from the class of polyalkyl(meth)acrylates or of polydialkylfumarates whose crystallization starts below 15 degrees C.

Description

Field of the Invention

The invention relates to mineral oils, in particular crude oils, vacuum gas oils or residual oils with improved flow behavior.

State of the art

The cold behavior of petroleum and petroleum products is decisively influenced by the paraffins they contain. The paraffins crystallize on cooling. As a result, the fluidity of the oils is reduced or completely prevented. The paraffins generally dissolve in the oil matrix when heated. The dewaxing of the oils can be used to improve the low-temperature flow properties. The technology has also developed additives, so-called "pour depressants", which already have the "pour point" (= temperature at which the oil is still flowing, cf. DIN 51 597) in concentrations between 0.55 and 1 wt. - Effectively reduce%. Their mode of action was interpreted with the following model: Paraffin-like compounds are built into the growing paraffin crystal surfaces and thus prevent the crystals from growing further and the formation of extensive crystal groups. From an empirical point of view, the mode of action of such pour point improvers appears to be linked to the presence of certain structural elements, namely sufficiently long alkyl groups to grow from nucleation Paraffin crystals to be installed and the presence of side chains or side groups at greater distances to disrupt the crystal growth. (See Ullmanns Encyklopadie der Technische Chemie, 4th edition, volume 20, Verlag Chemie 1981, p. 548 ff).

In practice, in addition to ethylene-vinyl acetate copolymers (EVA copolymers) and long-chain polyalkyl fumarates, mainly polyalkyl acrylates with C₁₈-C₂₄ alkyl radicals have been used as crude oil flow improvers.
At the beginning of the development there should have been the teaching of DE-A 17 70 695 from 1959, which recommends the use of long-chain (C> 12) polyalkyl (meth) acrylates as crude oil flow improvers.

Task and solution

The scarcity of resources leads to an increasing exploitation of oil deposits, the processing of which poses greater technological problems than a few years or decades ago. Some of these problems are related to the overall higher, but different, paraffin content of the individual crude oil sources. It has therefore proven to be increasingly difficult to provide additives which control the properties of the crude oils in the desired sense in at least a representative majority of the deposits. If possible, these additives should be inexpensive to manufacture and should be usable within the framework of the usual technologies. The present invention is therefore based on the object of providing flow improvers for crude oils in the broadest sense, for vacuum gas oils or residual oils places that, in relation to certain characteristics of these oils, reliably meet the requirements for flow improvers for these oils. The temperature-dependent onset of paraffin crystallization in the oils was recognized as such a characteristic. (For the determination methods see A. Ecker in "Petroleum and Coal" Vol. 38 (6) 281 (1985); A. Ecker, Erdöl, Erdgas 101, 154 (1985); CS Moynihan et al. Thermochimica Acta 52, 131 (1982) RL Blaine, NGLI-Spokesman, June 1976).

The paraffins contained in the oils crystallize on cooling while releasing heat. The heat released can be recorded by means of differential thermal analysis (DTA) or preferably differential scanning calorimetry (DSC) as an exothermic peak and thus the start of paraffin crystallization can be correctly determined, while the determinations based on visual observation of the "wax appearance point" or the "cloud point""generally fail with dark products and residues. It has now been found that mineral oils from the group of crude oils, vacuum gas oils and residual oils, in which the start of paraffin crystallization is at a temperature of less than or equal to 30 degrees C. and which have a content of 1 - 10,000 ppm of at least one polymer P - selected from the group of polyalkyl (meth) acrylates or polydialkyl fumarates - their start of crystallization - measured as the cloud point of a 0.1% solution (% by weight) of the polyalkyl (meth) acrylate or polydialkyl fumarate in isooctane according to DIN 51 597 or ASTM D 97-66 is below 15 degrees C, have, improved properties which generally meet the requirements of technology, in particular have improved flow behavior.

In the context of the present invention, the determination of the start of the paraffin crystallization of the mineral oils is expediently carried out by means of "differential scanning calorimetry (DSC)".
(See "Determination Methods" above)
The standard condition used, under which the start of paraffin crystallization at ≦ 30 degrees C was determined, is a cooling rate of the oil sample of 10 ^o K / min.
To determine the start of the crystallization of the polyalkyl (meth) acrylates PI or the polyalkyl difumarates P-II to be used according to the invention, the cloud point of a 0.1% solution (% by weight) of the polymer in isooctane is defined according to DIN 51 597 used.

The polyalkyl (meth) acrylates or polydialkyl fumarates P.

The polyalkyl (meth) acrylates PI to be used according to the invention differ on the basis of the definition made from the customary polyalkylacrylates of the prior art (see above) with C₁₈-C₂₄-alkyl radicals whose association temperature (start of crystallization) is approximately 20 degrees C. The polyalkyl (meth) acrylates required according to the invention with an association temperature <15 degrees C are polymers of esters of acrylic or methacrylic acid with longer-chain alkanols (from C₈ and up to C₄₀), including those with C₁₆-C₂₄-alkyl radicals, but the selection is taken such that said criterion of the association temperature is met. The following selection criteria can be used:
- Polymerization or copolymerization of esters of acrylic acid with alkyl radicals <18 C atoms, in particular 12 to 18 C atoms.
- Polymerization or copolymerization of esters of meth acrylic acid instead of acrylic acid, especially with C12 - C40 alkyl radicals.
- Copolymerization with monomers that are not capable of side chain crystallization, in particular with alkyl radicals <C10 or branched alkyl radicals with C3 to C40.

For example, the following types of polymers meet the above condition:
Poly tallow fat acrylate (C16 - C18 alkyl acrylate) = PI-1
Polybehenyl methacrylate (C18-C24 alkyl methacrylate) = PI-2
Copolymer of behenyl acrylate (C18-C24 alkyl acrylate) and isodecyl acrylate = PI-3.
The molecular weights of the polymers PI or P-II are generally in the range from 5,000 to 1,000,000, preferably from 10,000 to 500,000. In general, compliance with the molecular weight range is ensured by using regulators known per se, for example of the sulfur regulator type . (See Th. Völker, H. Rauch-Puntigam, Acryl- und Methacrylverbindungen, Springer-Verlag 1967). Mercaptans such as dodecyl mercaptan in amounts of 0.01 to 2% by weight, based on the monomers, are particularly mentioned. The molecular weights are determined by means of gel permeation chromatography, using polymethyl methacrylate as the calibration substance (see Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Ed Ed. 18, pg. 209 749, J. Wiley 1982).

The polydialkyl fumarates P-II, which are also to be used according to the invention, correspond in terms of their preparation and molecular weight to those used in the prior art (cf. T. Otsu et al., Mem.Fac.Eng., Osaka, City Univ. 23 , 79-91 (1982); Y. Murata et al., Chem. Econom., Eng. Rev. 17 (10) 18-22 (1985).
The alkyl radicals correspond to those customary for the (meth) acrylic acid esters, ie those with up to 40 C atoms, preferably 8-40 C atoms, in particular 18-40 C atoms.
The starting monomers are known per se or they can be prepared in a manner known per se, for example by transesterification of lower (meth) acrylates such as, for example, the methyl or ethyl ester with the higher alcohols. The polymers can be prepared following the radical polymerization processes of the prior art. (See H. Rauch-Puntigam, TH. Völker, Acryl- und Methacrylverbindungen, Springer-Verlag, Berlin 1967). An inert medium is preferred as the polymerization medium, preferably of the mineral oil type itself, for example 100 N oil.
Possible reaction vessels are those which are usually used and which are expediently equipped with a stirrer, heating device, thermometer, reflux condenser and metering line; preferably one works under an inert gas such as carbon dioxide. Furthermore, the usual free radical initiators are preferably peresters, peroxides or azo compounds, for example tert. Butyl perbenzoate, tert. Butyl perpivalate in the usual Concentrations, for example 0.1-5% by weight, preferably 0.3-1% by weight, based on the total amount of monomers. In general, the process is started at elevated temperature, preferably from 60 degrees C, in particular at 70 ± 5, whereupon initiator is added and the temperature reaches a peak which can be above 80 degrees C, for example 140 ± 10 degrees C. If necessary, a temperature range suitable for postpolymerization can be achieved by heating and / or adding initiator. In general, the polymerization is completed in about 5 hours.

The mineral oils

The mineral oils or mineral oil products, the properties of which, in particular their temperature-dependent dilution behavior, are improved by the present invention, are by definition those in which the start of paraffin crystallization is at a temperature of less than / equal to 30 degrees C.
For the purposes of the present invention, the mineral oils to be used according to the invention are understood to mean, for example:
- Raw oils
- Vacuum gas oils with a boiling point of 320 to 500 degrees C at normal pressure (true boiling point)
- Residual oils (distillation residues that would distill over 350 degrees C).
(See Winnacker-Küchler, Chemische Technologie, Volume 5, 4th edition, Carl Hanser Verlag, Munich 1981).
The following are therefore not included: mineral oils or petroleum products with the start of paraffin crystallization at a temperature greater than 30 degrees C.
The use of paraffin crystallization (CP) as a function of the temperature is an important parameter for the mineral oil provenances or the petroleum products in question, the determination of which is carried out routinely by a person skilled in the art. As already mentioned, the preferred determination method is the DSC.

According to the definition, the mineral oils in the polymers P are 1 - 10,000, preferably 50 to 2,000 ppm, in adaptation to the provenances, whose diligence properties need to be improved.

Implementation of the invention

After the polymerization, the polymers P can advantageously be diluted with a suitable compatible solvent, for example a hydrocarbon such as xylene, toluene, kerosene, SHELLSOL®. The solution thus obtained can then be used in the preparation of the mineral oil mixtures. In special cases, this solution can be added to the crude oil directly at the probe head or in the pipeline.
The polymers P are mixed, preferably in the form of the solutions mentioned, the mineral oils such as crude oils, Vacuum gas oils or residual oils expediently at an elevated temperature, for example at 40 to about 80 degrees C.
The effect of the flow-improving additives is retained over the period that is normally required. In addition to the polymers P according to the invention, there is generally no need for any further addition of flow improvers.

Beneficial effects

As already explained, it is important in the current difficult raw material situation to have the right additive for the right petroleum provenance or the right petroleum product.
In particular, the idea was not very encouraging that there was nothing else but to find out the suitable additive for each provenance using "Trial and Error". It can therefore be regarded as extremely valuable that the present invention provides criteria for the applicability of specific additives and the characterization of such suitable additives. Even if the polymers P to be used according to the invention only have the same good effect as additives of the prior art, this would nevertheless be a considerable improvement because of the much cheaper raw material base and the clearly better cost situation compared to, for example, the C18-C24 polyacrylic acid esters mean.
In fact, at least in a number of examined crude oils (which meet the required criterion demonstrate a better quality effect. This effect is all the more astonishing since the polymers P are little or not at all effective in crude oils with temperatures at the start of paraffin crystallization higher than 30 degrees C.

EXAMPLES A. Determination of the start of crystallization of the polymers P (cloud point) / visual

The determination is based on DIN 51 597 or ASTM D 97-66:
A 0.1% by weight solution of the polyalkyl (meth) acrylate or the polydialkyl fumarate P in isooctane is prepared at 80 ° C. and transferred to a sample vessel with a jacket vessel. The solution is cooled by placing it in a temperature-controlled cooling bath. At intervals of 1 degree C, a check is carried out to see whether the solution becomes cloudy. Upon the occurrence of the very first light haze of the onset of crystallization of the polymers is reached.

B. Determination of the start of crystallization of the mineral oils / DSC (see also DIN 51 005).

The measurement is started at 80 - 100 degrees C. The cooling rate is 10 K / min. The start of crystallization is the temperature at which the exothermic peak begins, the so-called "onset" temperature.

C. Determination of the fixed point of the mineral oil mixtures according to the invention (based on DIN 51 597 or ASTM D 97-66)

In deviation from the DIN standard, the sample was taken from the cold bath at intervals of 1 degree C and opened Flowability checked. The fixed points are the temperatures at which the oil stops flowing. The automatic measuring device from Herzog, Lauda (Federal Republic of Germany) can advantageously be used.

D. Preparation of the Polymers P.

100 N oil is understood to mean a base oil with a viscosity of 4 mm² / sec at 100 degrees C, as is customary in public circles.
The viscosity η sp / _c is determined in accordance with DIN 1342 or 51 562 in chloroform at 20 degrees C.
The cloud point (CP) determination was given above.

Example 1: Production of poly tallow fat acrylate P-I-1

85 kg of tallow fat acrylate (C16-18 acrylate), 15 kg of 100 N oil and 0.425 kg of dodecyl mercaptan are placed in a 150 l kettle. The mixture is degassed by adding CO₂ ice and then heated to 70 degrees C. Then 0.425 kg of t-butyl perpivalate are added. The temperature rises to 148 degrees Celsius. 1 and 2 hours after reaching the temperature peak, 0.17 kg of dodecyl mercaptan and 0.085 kg of t-butyl perbenzoate are added at 130 degrees C. The polymerization is complete after 5 hours. Mw (GPC, PMMA calibration) = 118,000 g / mol ηsp / c (CHCl₃, 20 degrees C) = 21 ml / g EP (0.1% in isooctane) = +10 degrees C.

Example 2: Production of polybehenyl methacrylate P-I-2

30 kg of behenyl methacrylate (C18-24 methacrylate), 30 kg of 100 N oil and 0.60 kg of dodecyl mercaptan are placed in a 100 l stirred kettle. After degassing the mixture with CO₂ ice, the mixture is heated to 70 ° C. and 0.60 kg of t-butyl perpivalate are added. 2 hours after the temperature peak of 96.5 degrees C is reached, the temperature is raised to 130 degrees C and 0.03 kg of dodecyl mercaptan and 0.06 kg of t-butyl perbenzoate are added. The polymerization is complete after 5 hours. Mw (GPC, Pmma calibration) = 24,300 g / mol η sp / c (CHCl₃, 20 degrees C) = 11 ml / g CP (0.1% in isooctane) = -2 degrees C.

Example 3: Preparation of a copolymer of behenyl and isodecyl acrylate P-I-3

30 kg of 100 N oil, 21 kg of behenyl acrylate (C18-24 acrylate) and 9 kg of isodecyl acrylate are placed in a 100 l stirred kettle. After adding 0.60 kg of dodecyl mercaptan, degassed with CO₂ ice and then to 70 degrees C. warmed up. The polymerization is initiated by adding 0.12 kg of t-butyl perpivalate. After the temperature peak of 83 degrees C has been reached, the mixture is heated to 130 degrees C and polymerized by adding 0.03 kg of dodecyl mercaptan and 0.06 kg of t-butyl perbenzoate. The post-polymerization is complete after 3 hours. Mw (GPC, PMMA calibration) = 24,900 g / mol η sp / c (CHCl₃, 20 degrees C) = 10.1 ml / g CP (0.1% in isooctane) = +1.5 degrees C.

Example 4 (comparison): Preparation of polybehenyl acrylate V-I-1

51 kg of behenyl acrylate (C18-24 acrylate, 9 kg of 100 N oil and 0.051 kg of dodecyl mercaptan) are placed in a 100 l stirred kettle, degassed with CO₂ ice and heated to 70 ° C. Then 0.191 kg of t-butyl perpivalate and 0.115 kg of t-butyl perbenzoate were added to start the polymerization 1 hour after the temperature peak of 134 ° C. had been reached, 0.077 kg of dodecyl mercaptan and 0.051 kg of t-butyl perbenzoate were added and the mixture was post-polymerized at 130 ° C. for 3 hours. Mw (GPC, PMMA calibration) = 560,000 g / mol η sp / c (CHCl₃, 20 degrees C) = 48 ml / g CP (0.1% isooctane) = 19.5 degrees C.

Example 5 (comparison): Preparation of polybehenyl acrylate V-I-2

45 kg of behenyl acrylate, 45 kg of 100 N oil and 0.675 kg of dodecyl mercaptan are placed in a 150 l stirred kettle and degassed with CO₂ ice. After heating to 70 degrees C, 0.18 kg of t-butyl perpivalate are added. After the temperature peak of 120 degrees C is reached, the temperature is raised to 130 degrees C and 0.045 kg of dodecyl mercaptan and 0.09 kg of t-butyl peroctoate are added. The polymerization is complete after 5 hours. Mw (GPC, PMMA, calibration) = 23,200 g / mol η sp / c (CHCl₃, 20 degrees C) = 11 ml / g CP (0.1% in isooctane) = 20.5 degrees C.

E. Examples of effects Examples 6-11:

The polymers PI-1 to PI-4 and VI-1 and VI-2 were added as a 10% stock solution in xylene to the crude oils at 80 degrees C. All dosages relate to polymer. The fixed points were determined in accordance with DIN 51 597 using an automatic measuring device from Herzog, Lauda. The start of paraffin crystallization (CP) of the crude oils was determined by means of DSC at a cooling rate of 10 K / min.

Example 6:

Australian crude oil, 43.8% n-alkane content, CP = 25 degrees C. Benchmark without addition + 21 1000 ppm PI-1 + 11 1000 ppm PI-2 + 12 1000 ppm PI-3 + 13 1000 ppm PI-1: PI-2 = 1: 1 + 12 1000 ppm VI-1 + 15 1000 ppm VI-2 + 16

Example 7:

Pakistani crude oil, 34.3% n-alkane content, CP = 22 degrees C. Benchmark Additional quantity 100 ppm 500 ppm PI-1 + 12 + 7 PI-2 + 9 + 7 PI-3 + 8 + 6 VI-2 + 18 +16 without addition +21

Example 8:

South German crude oil, 22.7% n-alkane content, CP = 29 degrees C. Benchmark Additional quantity 100 200 500 1000 ppm PI-1 + 13 +9 +6 +4 PI-2 +7 +4 PI-3 +9 +7 VI-2 + 15 +11 +8 +5 without addition +21

Example 9:

Pakistani crude oil, 25.3% n-alkane content, CP = 24 degrees C. Benchmark without addition + 21 100 ppm PI-1 + 7 100 ppm PI-2 + 3 100 ppm PI-3 + 4th 100 ppm VI-1 + 12 100 ppm VI-2 + 12

Example 10 (comparison):

In contrast to Examples 6 - 9, North Sea crude oil with an n-alkane content of 14.7% has a CP of 47 degrees C, i.e. greater than 30 degrees C. Benchmark without addition + 27 + 1000 ppm PI-1 + 26 + 1000 ppm PI-2 + 27 + 1000 ppm PI-3 + 27 + 1000 ppm VI-2 ± 0

Example 11 (comparison):

Bombay High Crude, n-alkane content 22.6%, CP = 38 degrees C, also greater than 30 degrees C. Benchmark without addition + 30 + 150 ppm PI-1 + 30 + 150 ppm PI-2 + 30 + 150 ppm PI-3 + 30 + 150 ppm VI-1 + 9 + 150 ppm VI-2 + 11

Example 12 (comparison):

African crude oil with 10.6% n-alkane content, CP = 35 degrees C. Benchmark without addition + 24 + 250 ppm PI-1 + 20 + 250 ppm PI-2 + 21 + 250 ppm VI-1 + 10

Example 13:

North German vacuum gas oil, 2.2% n-alkane content, CP = 12 degrees C. Benchmark without addition + 19 1,000 ppm PI-1 - 2nd 1,000 ppm PI-2 - 5th 1,000 ppm PI-3 - 5th 1,000 ppm PI-1: PI-2 = 1: 1 - 2nd 1,000 ppm PI-1: PI-3 = 1: 1 - 3rd 1,000 ppm PI-2: PI-3 = 1: 1 - 5th 1,000 ppm VI-1 + 2 1,000 ppm VI-2 + 5

Claims (3)

1. Paraffin-containing mineral oils from the group of crude oils, vacuum gas oils and residual oils, which have improved flow properties,
characterized,
that the mineral oils have in common that the start of the paraffin crystallization is at a temperature of less than or equal to 30 degrees C and that they contain 1 - 10,000 ppm of at least one polymer P, selected from the class of the polyalkyl (meth) acrylates or the polydialkyl fumarates possess whose crystallization start is below 15 degrees C. 2. Mineral oils according to claim 1, characterized in that the determination of the paraffin crystallization by means of differential scanning calorimetry (DSC) is carried out at a cooling rate of 10 K / min. 3. Mineral oils according to claims 1 and 2, characterized in that the start of the crystallization of the polymer P is determined as a "cloud point" of a 0.1% solution of the polymer in isooctane according to DIN 51 597.