CA2020104A1

CA2020104A1 - Process for improving the fluidity of mineral oils and mineral oil distillates

Info

Publication number: CA2020104A1
Application number: CA002020104A
Authority: CA
Inventors: Wolfgang Payer; Werner Reimann
Original assignee: Individual
Current assignee: Hoechst AG; Veolia WTS USA Inc
Priority date: 1989-06-29
Filing date: 1990-06-28
Publication date: 1990-12-30
Also published as: EP0405270A1; DE3921279A1; AU624965B2; KR910001004A; AU5791090A; ES2054152T3; ATE82587T1; JPH0339385A; ZA904894B; DE59000480D1; JPH0768505B2; EP0405270B1; KR930011928B1

Abstract

Abstract of the Disclosure Addition of a mixture of an ethylene/vinyl acetate copolymer and an ethylene/vinyl acetate/N-vinyl-pyrrolidone terpolymer to mineral oils and mineral oil distillates whereby fluidity thereof i improved.

Description

Process for Improving the Fluidity of ~lineral Oils and Mineral Oil Distillate The present invention relates to a process for improving the fluidity of mineral oils and mineral oil distillates by the addition of mixtures of ethylene/vinyl acetate copolymers and ethylene/vinyl acetate/N-vinyl-pyrrolidone terpolymers.

Background of the Invention Depending on the provenance, mineral oils and mineral oil distillates contain varying quantities of dissolved paraffin, which precipitates at low temperatures in the form of plate-like crystals, with which the oils are still occluded. This impairs the fluidity of mineral oils and mineral oil distillates considerably. For example, in the case of diesel fuel, this leads to blockage of filters, so that the fuel supply to the combustion units, such as internal-combustion engines or jet engines, takes place irregularly or is completely interrupted. Likewise, faults can arise in the transportation of fuel oils in combustion plants, if such wax precipitation occurs due to low temperatures. A]so, the transportation of middle distillates through pipelines over relatively long distances can be impaired in winter for the same reason.

2~20~ ~

To control the precipitation of paraffin wax, additives which modify the size and shape of paraffin crystals, are introduced into the mineral oils and mineral oil distillates, in particular to the so-called middle distillates, so that the middle distillates remain fluid even at low temperatures. The economically most important pour point depressants and flow improvers for mineral oils and mineral oil distillates are copolymers of ethylene with esters of vinyl alcohol, in particular \vj with vinyl acetate. Such copolymers and their use are described, for example, in DE-C 1,914,756 and DE-A
2,515,805. Eronl Published Japanese Patent Application 58/80,386, abstracted in C.A. 99 (1983), 215519, it is known to use terpolymers of ethylene, vinyl acetate, and N-vinyl-2-pyrrolidone as flow improvers.

In practice it has been found that the effectiveness of these copolymers as flow improvers depen~s on the properties of the mineral oils and mineral oil distillates whose fluidity is to be increased. In the case of middle distillates, for example, the fluidity is affected, inter alia, by the total n-paraffin content and the content of n-paraffins of certain chain lengths.
The content and distribution of paraffin are determined by the proportions of light, medium-heavy and heavy distillate fractions of which the middle distillate is composed, and by the crude oil provenance.

202~1~4 It is therefore understandable that the ethylene/vinyl acetate copolymers, in spite of their excellent suitability for increasing the fluidity, do not always show the desired effect. In such cases, the problem is overcome by adding them in large quantities or by mixing the mineral oil or the mineral oil distillate with low-boiling hydrocarbons.

Another possibility of increasing the effectiveness of flow improvers is to use additive combinations. Thus, in DE-A-2,639,672, mixtures of polymers having an ethylene backbone and copolymers of C2- to C50-olefins are described. These, it is taught, can lead to a synergistic improvement of the flow properties of distillate hydrocarbon oils in the cold.

According to U.S. Patent 3,660,057, mixtures of an ethylene/vinyl acetate copolymer and a solid hydrocarbon, which is free of n-paraffins, are used as flow improvers. Mixtures which are composed of an ethylene-containing polymer, beeswax, ozocerite and/or a long-chain alpha-olefin are disclosed in U.S. Patent 4,019,878 as flow improvers for crude oil middle distillates.

202~4 Even though the known substances and substances mixtures have, in many cases, improved (sometimes even greatly) the fluidity of mineral oils and mineral oil distillates of various provenances and compositions at low temperatures, there is, nevertheless, a lack of additives having a versatile applica~ility ideally a universal applicability.

Summary of the Invention It is, therefore, an object of the present Invention to provide additives which have an even wider range of application as compared with the known flow improvers. They should also increase the fluidity of even those oils with which the known additives show only a slight effect or none at all.

The invention is a process for improving the fluidity of mineral oils and mineral oil distillates. It comprises adding mixtures of an ethylene/vinyl acetate copolymer and an ethylene/vinyl acetate/N-vinyl-pyrrolidone terpolymer to the mineral oils or mineral oil distillates.

Surprisingly, it has been found that the process according to the invention effectively suppresses the precipitation of paraffins from mineral oils and mineral oil distillates and holds paraffin crystals which may 2~20~04 have precipitated in suspension. The additives used according to the novel process thus counteract a rise in the viscosity of the hydrocarbon mixtures due to falling temperatures; they also lower the pour point. The claimed procedure has proved suitable for improving the f]uidity of mineral oils and distillation products thereof, independently of their qualitative and quantitative composition. It is of particular importance that the two components interact with each other synergistically. The effectiveness of the polymer mixture is thus 8reater than the sum of the effectiveness of its constituents.

Detailed Description of the Invention The ethylene/vinyl acetate copolymers used accordislg to the invention contain 20 to 40% by weight of vinyl acetate. Copolymers Wit}l 25 to 35% by weight of vinyl acetate have proved particularly suitable. Their viscosity, measured in accordance with DIN 53 019 in a rotary viscometer (made by Haake) at 140C, is 30 to lO00 mPa.s, preferably 30 to 250 mPa.s.

Per 100 CH2 groups, they contain l to lO
(preferably 2 to 7) CH3 groups, other than those originating from the acetate radical of the vinyl acetate, in the side chains. The determination of the number of CH3 groups is carried out by H-NMR
spectroscopy.

202~104 The preparation of the ethylene/vinyl acetate copolymers is known. It can be carried out, for example, by polymerization of the monomer mixture at pressures fronl 5 to 15 ~Pa, at temperatures from 70 to 150C, S and in the presence of initiators forming free radicals.
The reaction medium can be an organic solvent or suspending agent such as toluene.

The ethylene/vinyl acetate/N-vinylpyrrolidone terpolymers used as the second constituent of the flow improver mixture contain 15 to 50% by weight, in particular 20 to 35% by weight, of vinyl acetate and 0.5 to 10% by weight, in particular 1.0 to 5.0% by weight, of N-vinylpyrrolidone. Their viscosity, measured in the same way as in the case of the ethylene/vinyl acetate copolymers, is 100 to 5000 mPa.s and especially 150 to 1500 mPa.s.

The production of ethylene/vinyl acetate/N-vinylpyrrolidone terpolymers is known. It is carried out, for example, in autoclaves by polymerization of the monomer mixture at pressures above 5 ~Pa, temperatures above 60C, and in the presence of initiators which form free radicals. ~rganic solvents which dissolve ~ 5% by weight of ethylene are used as the reaction medium. ~ethanol, t-butanol, benzene, and dioxane are suitable (cf. FR 1,392,354).

2~2~104 The weight ratio of the two polyrners in the additive mixture can be varied within wide limits. It has proved suitable to use the ethylene/vinyl acetate copolymer and ethylene/vinyl acetate/N-vinylpyrrolidone terpolymer in a weight ratio from 1:1 to lOO:l. Mixtures which contain copolymer and terpolymer in a weight ratio from 3:1 to 20 : l are preferred.

The process according to the invention improves the fluidity of both mineral oils and mineral oil distillates. The term mineral oils is here to be understood as meaning especially crude oils and distillation residues, such as heavy fuel oil.
Hydrocarbon fractions having a boiling point between about 150 and 400C are designated as mineral oil distillates. lhese include, for example, petroleum, light fuel oils and diesel fuels. The middle distillates such as fuel oil EL and diesel oil are of particular importance.

The mixture of the two polymers is added to the mineral oils or mineral oil distillates in the form of solutions which contain 20 to 70% by weight, relative to the solution, of the polymers. Suitable solvents are aliphatic or aromatic hydrocarbons or hydrocarbon mixtures, for example, naphtha fractions. Kerosene is particularly suitable. The ~uantity of polymer, relative to mineral oil or mineral oil fractions, shoula amount to 0.001 to 2 and preferably 0.005 to 0.5% by weight.

2~20104 The polymer mixtures can be used alone or also together with other additives, for example, with other pour point depressants, dewaxing auxiliaries, corrosion inhibitors, antioxidants, sludge inhibitors, additives for lowering the cloud point, and the like.

The process according to the invention is explained in more detail by the illustrative examples which follow. Examples 1 to 4 relate to the process according to the invention. Examples S to 7 reproduce the results of comparative tests, which are obtained with the use of ethylene/vinyl acetate copolymers alone (Examples 5 and 6) and of an ethylene/vinyl acetate/N-vinylpyrrolidone terpolymer alone (Example 7).

The effectiveness of the fluidity improvement processes investigated is described by reference to the "cold filter plugging test" (CFPP test). The test is carried out in accordance with ~IN 51 428. It has also been published in J. of the Inst. of Petr., Vol. 52, June 1966, pages 173 to 185.

Three middle distillates, Ml, ~2 and M3, were used for testing. They are characterized by the characteristics as set forth in Table 1.

FROM:~IERMP~ ~ MU5ERLI~N TO: al9 770 a847 JUN 27, 1990 12:34PM P.02 202~104 f~

~x~lnp~ es 1 ~o 8:
.

In ~l~c cxanlp1es ~ih~cll ~ollow, tlle polylllcrs ~hs'ra~2erizcd l~low are used alone or as .2 nlixturc.

A. Al~ e~lly1ene/villyl. ~ce~ate co~o1ymcr ll~lv~ng a n ~ vlnyl aceta~e content of 30.5~ ~Dy wci~ and a viscosity o 3~ mPa.s ~t 140C.
', t)~.~
. An c~hylelle/vlnyl ace~ate c.~po1ynlcr l)avilll~ a viny1 ac,etate con~en~ ~ 29.8~ ~y welg~)~ and vis¢~sity o~ 80 ~nl~a.s at 140 C. An etl)ylene~virly1 aceta~e/N-viny1~yrro1idoll( terpo1ylner haYi12~ a v1l)y1 ~ceta~c ~ollten~ of 23.2~ by wclgll~ asld an N-viny1pyr~ olle cont'crlt of 1.4% by woi,gl~ alld ~ vis~os;~y o 23~ Inl~a.s at 1~~.
, .

'I`he vinyl acc~ate con~ent o~ ~he ~o1yol~rs is dc~cl~mincd by ~l2c pyrolysis nlethod. 170r t]lis pur~s~, 200 mg o tlle polynler aro~ heated witll 3~V mg o~ purc po1yethy1e~le in a ~yrolysis flask ~or 5 minu~es at ~50~ and the cr~ckillg ~ses are co11ccted in a round-bot~omed 250 m1 ~lask. The ~ccti~ acid ~orllled is ~eactcd witl~ an Nal/~03 solution and tlle iodine released is titra~cd with Na25~03 so1u~ion. Tl~e .,.
1 . ' .~...... . .
g 2~2~

N-vinylpyrrolidone content in the polymer is calculated from the nitrogen content of the polymer, determined by the Dumas method.

Table 2 contains data on the effectiveness of the process accordin~ to the invention for improving the fluidity of mineral oils and mineral oil distillates.

-- ~02~104 Table 1: Cl~IaLterictics of the test oilc .

Cloud point (C) (~csc~nLing to DIN 51 597) +1 -2.2 +3 CEFP (C) _5 -4 -2 . __ _ Pour point (C) -6 -15 _9 Wax ~e tfny~oature (C) -4.0 -6.0 -3.0 n-PAraffin cortent (%) 41 _ 37 ~ ic (C) Initi~l boi~ poLnt 176 184 190 20 % _ 217 234 90 % _ 350 350 Final ~oi 1 i ng poLnt 381 377 373 Table 2: Effectiveness of the polymer nixt~res Ex- Co~pcsition ConDen- CFPP( C) --ample (palts by wt. )(ppm) _ ~ 1~ 2 M 3 1 85 A + 15 C 575 - 8 -11 _ ll2os -17 -17 250 -20 l -14 _ ..
2 95 B ~ 5 C 755 - 75 -17 - 2 _ ... _ 3 90 B + 10 C 50 - 5 - 4 - 2 250 -17 _ 4 85 B + 15 C 755 - 95 -13 - 2 ll 125 -18 -18 250 -17 -12 .

202010~

Table 2: Conti~

Ex~ osi~ OE~P(C) .
al!ple (parts }~ wt. ) (1~) M 1 N 2 X 3 5 lC0 A 0 ~ 5 ~ _ 4 ~ _ 2 _15 ~ 1005 210~o 2~ lOOC 1~0 ~~ ~_9 :' ' '':~ . ;, ' . .' ', --- - ' ! . ,, ' : . , , ,`' , '.' ~' ~' '.''' ' . . . ' ' ' . ' ' ' ' . ' , . ' ' : '.
,' ;'''' ,.',. ",' ' ' .
. . ':' . ' ., .' ' :, '. , '

Claims

1. A process for improving the fluidity of mineral oils and mineral oil distillates comprising adding mixtures of an ethylene/vinyl acetate copolymer and an ethylene/vinyl acetate/N-vinylpyrrolidone terpolymer to the mineral oils or mineral oil distillates.

2. The process of Claim 1 wherein said copolymer contains 20% to 40% by weight of vinyl acetate.

3. The process of Claim 2 wherein said copolymer contains 25% to 35% by weight of vinyl acetate.

4. The process of Claim 1 wherein said copolymer has a viscosity, measured at 140°C, of 30 to 1000 mPa.

5. The process of Claim 4 wherein said viscosity is 30 to 250 mPa.

6. The process of Claim 1 wherein said copolymer contains 1 to 10 CH3 groups, excluding those originating from the acetate radical of said vinyl acetate, per 100 CH2 groups.

7. The process of Claim 6 wherein said copolymer contains 2 to 7 CH3 groups, excluding those originating from the acetate radical of said vinyl acetate, per 100 CH2 groups.

8. The process of Claim 1 wherein said terpolymer contains 15% to 50% by weight of vinyl acetate and 0.5% to 10% by weight of N-vinylpyrrolidone.

9. The process of Claim 8 wherein said terpolymer contains 20% to 35% by weight of vinyl acetate and 1.0% to 5.0% by weight of N-vinylpyrrolidone.

10. The process of Claim 1 wherein said terpolymer has a viscosity, measured at 140°C, of 100 to 5000 mPa.

11. The process of Claim 10 wherein said viscosity is 150 to 1500 mPa.

12. The process of Claim 1 wherein the ratio of said copolymer to said terpolymer is 1:1 to 100:1.

13. The process of Claim 12 wherein said ratio is 3:1 to 20:1.

14. The process of Claim 1 wherein the boiling point of said mineral oils and distillates is 150° to 400°C.

15. The process of Claim 1 wherein said mixtures are added in the form of solutions.

16. The process of Claim 15 wherein said mixtures are 20% to 70% of said solutions.

17. The process of Claim 15 wherein said solutions comprise said mixtures in a solvent selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons, and blends thereof.

18. The process of Claim 17 wherein said solvent is selected from the group consisting of naphtha and kerosene.

19. The process of Claim 1 wherein said mixture is present in an amount of 0.001% to 2.0% by weight based on said mineral oils and said distillates.

20. The process of Claim 19 wherein said amount is 0.005% to 0.5%.

21. The process of Claim 1 wherein said copolymer contains 20% to 40% by weight of vinyl acetate, has a viscosity, measured at 140°C, of 30 to 1000 mPa, and has 1 to 10 CH3 groups, excluding those originating from the acetate radicals of said vinyl acetate, per 100 CH2 groups, said terpolymer contains 15% to 20% by weight of vinyl acetate and 0.5% to 10% by weight of N-vinylpyrrolidone, and has a viscosity, measured at 140°C 9 of 100 to 5000 mPa, the ratio of said copolymer to said terpolymer is 1:1 to 100:1, and said mineral oil and distillate contains 0.001%
to 2.0% by weight of said mixture.

22. The process of Claim 1 wherein said copolymer contains 25% to 35% by weight of vinyl acetate, has a viscosity, measured at 140°C, of 30 to 250 mPa, and has 2 to 7 CH3 groups, excluding those originating from the acid radicals of said vinyl acetate, per 100 CH2 groups, said terpolymer contains 20% to 35% by weight of vinyl acetate and 1.0% to 5.0% by weight of N-vinylpyrrolidone, and has a viscosity, measured at 140°C, of 150 to 150 mPa, the ratio of said copolymer to said terpolymer is 3:1 to 20:1, and said mineral oil and distillate contains 0.005%
to 0.5% by weight of said mixture.

23. The mineral oil and distillate which is the product of the method of Claim 1 wherein there is 0.001% to 2.0% of said mixture in said mineral oil and distillate.