HU190423B - Process for improving with polymer additives the cold shut characteristics of oils used in fuel oil thermal equipments - Google Patents

Abstract

The process according to the invention is characterized by determining, on the basis of the composition of the mid-oil distillates of the petroleum-type mineral oil, the linearity factor to be given to the given central distillate and the addition of 0.01% to 0.51% of polyethylene to the middle distillate, the pressure of which is The relationship between (P, bar) and temperature (t, 'C) is 1.4PP = C where C = 159 ± 20 and polymerization at 120-220 ° C, preferably 130-180 ° C, 0.1 to 3%, preferably 0.3 to 1% by weight of the reaction mixture, preferably in the presence of a peroxide compound or azo compound. -1-

Description

The present invention relates to a process for improving the cold-flow properties of oils for use in oil-fired caloric equipment with polymer additives.

More particularly, the present invention relates to a process for improving the cold flow properties, i.e., the pour point and filterability limit, of gas oil-type petroleum middle distillates with oil-soluble polyethylene additives. The present invention provides an opportunity to use, for a given middle distillate composition, an additive having the appropriate properties which, when added to a particular middle distillate, has a favorable effect on the operation of the caloric equipment.

It is known that in order to meet the growing demand for diesel and household fuel oil, the refining industry is also forced to process distillates with a higher end-point and a higher content of paraffin. Of course, middle distillates in the wider or higher boiling range must continue to meet the quality requirements for Diesel and Household Fuel Oil (hereinafter referred to as "Diesel" or "Fuel Oil"). The task is even more difficult when it comes to producing products of the same quality by processing mineral oils of different origins. In the case of the products in question, the standard value of the freezing point is primarily a problem due to the increase in the end-point and the paraffin content.

The use of these products at low temperatures is made difficult by the increase in their viscosity and their possible freezing. In particular, middle distillates derived from paraffinic mixed base oils tend to be paraffin-precipitated in winter, which makes it difficult or even impossible to use in normal operation.

The so-called "cold temperature flow properties" or "Káltefliessverhalten" of the cooled oil in the storage tanks change, making the oil difficult to pump due to the separation of paraffin or, in the case of pipeline clogging, not at all. Thus, the cooling of the oil in the tank interferes with the operation of the service wells or the fueling of the vehicles. Oil transport usually disappears completely at the freezing point temperature.

Diesel engines can experience malfunctions at even higher temperatures, ranging from the point of failure to the freezing point *, and even with some oils, the point of failure is critical in this regard. Because of the paraffin removal at these breakpoints, these oils can already clog the engine fuel filter at temperatures above the freezing point. This phenomenon can be mitigated to some extent by appropriate design solutions (for example, the filter is placed near the motor, etc.), but only plugging during operation can be avoided. In the case of clogging of the fuel line and / or the filter, cold induction becomes impossible, even with high cetane and volatile oils.

Apart from the chemical transformation of the fractions, the only way to satisfy the increasing quantitative demands is to raise the end point. The same effect results in the addition of higher boiling point paraffinic distillates, but clearly has the disadvantage of increasing the freezing point.

In the art, two major methods are used to overcome the problems outlined;

(a) middle distillates are blended with lower freezing point fractions, or

(b) additives that improve cold-flow properties are used.

Blending of petroleum with gas oil and fuel oil [method (a)] is a commonly used but uneconomic solution. The required amount of kerosene can reach 30%, which increases the price of oil, diminishes some of its quality parameters, and at the same time withdraws a significant amount of kerosene stock, which is rapidly growing in demand.

A known method for solving the problem is to use flow enhancers [method b]. The importance of this is generally seen in the fact that it is possible to make greater use of distillation residues and to increase the amount of middle distillates by mixing higher boiling fractions. The mixing of cheap residues and middle distillates makes it economical to use the additive also in fuel oils. At the same time, the additive also makes refineries more flexible and the choice of the right additive can result in actual quality improvements.

In the presence of antifreezing and / or flow enhancing additives, paraffinic precipitation begins at the cloud point, as in unmixed oils and usually the temperature of the cloud point does not change. Thus, the additive does not affect the onset of paraffin release nor does it alter the amount of excellent paraffin. However, it significantly alters the size and shape of the excellent paraffin crystals, thereby giving the oil good flow properties at lower temperatures and lowering its pour point. Gondermann, H.-Giere, Η. H .: Chem.-ZTG. 97, 462 (1973); Agius, P.J., - Brod,

M.-Miller, Η. N .: 8 '* World Petrol. Congr., 1971. Moscow, Proc. 5, 17: Kahsnitz, R .: Dieselkraftstoffe, In: "Minerale Verwendung, Produktion". 2nd edition Bd. 1. 678-705 (1969)].

Many types of additives have been developed and, of course, different types of additives alter the excellent structure of paraffin and the cold flow properties of the oil to varying degrees. Further, different types of middle distillates react to varying degrees even with the same quality and amount of additives.

When selecting an additive for a particular oil composition, it should be borne in mind that there is no general purpose additive that can be used for products of different origins and can compensate for equipment failures. Because the effectiveness of an additive in a given oil depends on many factors, the selection of the right additive requires great care.

With respect to the structure of the flow enhancer component, several authors emphasize that it must necessarily contain paraffin-sized straight chain moieties (20-40 carbon atoms-21).

190,423) and large, bulky groups between them. Extensive groups are classified into two types in the literature [French Patent No. 2,143,791 (1973); Feldman, N. (Esso Rés. Eng. Co.); 79, 81413-A],

1. of a non-polar nature (eg aromatic hydrocarbons),

2. they are polar (mainly containing halogen and oxygen). Examples include octadecyl toluene, sorbitan stearates, pentaerythritol tetrasstearate.

Molecular weight also plays an important role in ensuring or regulating solubility in oil and should also be consistent with the molecular weight of the additive: high molecular weight additives can be used in heavier oils [Trubac, K .: Ropa a Uhlie 16, (7) 381 (1974)]. Other literature for middle distillates [Samoylov, S.M.-Monastursky, V.N .: Him. Technol. Topliv Maszel 18, (2) 60 (1973)], generally, the polymeric additives have an average molecular weight of not more than 5000. In contrast, there are also literature sources, U.S. Patent No. 3,638,349 (1972); Wisotsky, M. J.-Miller, Η. N., (Esso Rés. Eng. Co.); C. A. 76, 143 211-z.], Reported that ethylene / vinyl acetate copolymers exhibited a better pour point reduction effect with a relatively high (~ 9000) average molecular weight polymer than with a lower (2000) molecular weight. The flow enhancer component (with a large group) is generally below 500 molecular weight.

With respect to polymers, those skilled in the art believe that narrow fractions are more effective than those with a broad molecular weight distribution (see Vesely, V., Ropa a Uhlie 16, (9) 499 (1974), and German Patent Publication No. 1,963,826). Biswell, Ch. B-Johnston, Th. E. (du Pont de Nemours Co.), CA 73.47286-v], U.S. Patent No. 3,341,309 (1967); S. (Esso Rés. Eng. Co.); CA 68, 23 319-d], for example, the average molecular weight of terpolymer of ethylene (vinyl acetate) dilauryl fumarate is stated to be in the range 2600-2900. are no longer effective.

No. 3,524,732. U.S. Pat. No. 4,123,198, discloses a copolymer of ethylene-propylene having a molecular weight of 2000-6000.

Most of the additives are thus ethylene copolymers; The use of ethylene homopolymers is hardly mentioned in the literature. There are several reasons for this. One of them is theoretical: ethylene monomers can easily form long carbon chains for incorporation into paraffin crystals, but not bulky or polar branches.

Another reason is that, according to experience (U.S. Patent No. 3,048,479), the use of polyethylene additives in some gas oils has been excellent, but in others it has yielded only insignificant results. So far, no clear explanation for this phenomenon has been found and it has not been possible to relate it to the conditions of polymerization.

British Patent 848,777 seeks to establish a relationship between the structure and efficiency of hydrocarbon polymer additives. Branches Index (BI) is taken into account and found to be only good additives having 3-5 carbon atoms, preferably 4 carbon atoms, in the side chain on a polymethylene chain of 100 carbon atoms. This is accomplished by homopolymerization of ethylene or copolymerization of ethylene-propylene. The production process is not described; nor do they provide a way of taking into account the properties of each of the middle distillates of a given composition and of improving it in the particular case.

The object of the process according to the invention is that in each case, an additive which has the most favorable effect on the cold flow properties of the middle distillate of a given composition can be safely determined and produced to facilitate the operation of oil-fired calorific equipment.

The polyethylene has been discovered by us as an additive in a molecular property that enables the additive against hitherto can not be calculated in advance, the effect is uncertain ²⁰ that is predetermined for the particular distillate how additive must be used.

In developing the process of the invention, experiments were conducted on various parameters to produce polyethylene additives, and the effect of these products on the pour point and filterability limit of gas oil added to them in 0.1 ponds was investigated. Polymerization experiments were carried out in an autoclave using the following method: In a 109 ml autoclave, 10-60 g of benzene and 0.02-0.5 g of peroxide such as di-tert-butyl peroxide were charged. The autoclave was purged with nitrogen followed by ethylene and finally charged with ethylene to give the desired pressure at the polymerization temperature. The autoclave was then sealed and heated to the reaction temperature, generally 120-180 ° C, for 5-50 minutes.

The temperature of the autoclave was maintained to within ± 1 C at that temperature until the reaction time was reached. Upon completion of the polymerization, the reaction mixture was cooled and the product was isolated from the liquid phase by evaporation.

Figure 1 illustrates how the effect of the products on the cold flow property of gas oil 1 is changed when polymerization is carried out at 150 'Con and different starting pressures. For this and the following experiments, I and II are shown. Table 1 shows the typical data for the different types of diesel fuel designated as "D".

In our investigations the gas oil pour point was determined according to MSz 11 721-64 and the filtration effect temperature according to MSz 0 960 122-76.

Table 1

Characteristics of the types of gas oil used in the tests

Quality features ]. fuel oil II. fuel oil Density / 20'C for 0.835 0,838 Viscosity at 20 ° C cSt 5.05 4.66 Viscosity at 20 ° C 'E 1.4 1.36 ₆₅ Viscosity / 50 ° C cSt - 2.46

Continuation of Table 1

Quality features Gasoline I. II. fuel oil Viscosity at 50 ° C 'E - 1.16 cloud point 'C + 8 -7 Pour Point 'C -1 -12 Flash point (M) 'C 76 106 Flash point (PM) 'C 68 72 sulfur content % 0.69 0.95 Acidity mg KOH / 100 ml Engler distillation test: 3.4 1.9 Starting Boiling point 'C 175 194 5 vol% overlap. 'C 192 210 10 vol% overlap. 'C 202 232 20 vol% overlap. • C 219 244 30 vol% overlap. 'C 236 253 40 vol% overlap. 'C 251 262 50 vol% overlap. 'C 270 273 60 vol% overlap. 'C 292 285 70 vol% overlap. 'C 314 302 80 vol% overlap. 'C 342 317 90% vol. • C 368 336 95% vol. 'C 387 348 Végforrpont 'C 394 357 the rest % 3.0 2.2 cetane 54 54 Color UNION 2.5 1 Iodine value g / lOOg 0.35 filterability 'C -7 + 7

Referring to Figure 1, it can be clearly seen that the product obtained under reduced pressure reduces the filtration limit of gas oil I by 6 ° C and increases its freezing point by 3 ° C. Thus, the extreme situation is that the composition has a pour point greater than the filterability limit. By increasing the initial pressure of the synthesis, the product's boiling point first improves rapidly and then decreases again. The effect of lowering the pour point or the filterability limit is not related to each other. The effect of additives prepared at different temperatures with the same amount of ethylene was investigated. This is illustrated in Figure 2 for Diesel I. The figure shows that lower temperature (145-150'C) substances deteriorate, while higher temperature (155-160'C) substances improve the boiling point of Diesel I.

However, changes in the filterability limit tend to be completely opposite.

Based on the above two experiments, it was found that the effect of the polyethylene additive cannot be related to the basic parameters of polyethylene synthesis investigated separately, therefore, new experiments were performed to link the efficacy of the additive with other conditions.

As already mentioned, the average molecular weight plays a crucial role in the efficacy of the additive as generally noted. FIG.

shows the pour point and filtration limit of the oil as a function of the average molecular weight of the additive. It is evident that the M _n = 800-2600 _ efficiency range and average molecular lasúly ^s between any correlation can not be detected. An approx. 1000 average molecular weight products can reduce the freezing point of gas oil by 10-15 'C or increase it by 4'C; and filterability. No limit changes associated with ⁰ molecular weight.

It is also known that thinner polymer fractions with a lower degree of polydispersity are more effective than those with a broader molecular weight distribution.

This observation appears to be supported by the following Table 2, which shows that the effect of the additive decreases with increasing degree of polydispersity of the products.

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Table 2

Change in the freezing point of the product II. gas oil as a function of average molecular weight and degree of polydispersity

Mn Mw / Mn Dp, 'C CFPP, 'C 1036 1.65 20 6 1168 1.81 18 6 1558 1.91 16 6

However, given that the molecular weight is also increasing, the reduction in the effect of the additive cannot be clearly attributed to the expense of the wider polymer fraction. The situation is further complicated by the comparison presented in Table 3; from which it can be seen that, with additives having the same average molecular weight, the freezing point-reducing effect increases dramatically with a smaller increase in polydispersity.

Examination pour point-lowering effect As Table 3 ⁴⁵ Average molecular weights and different products polidiszperzitásfokú gas oil I

50 Mn Mw / Mn Dp, 'C CFPP, 'C 1385 1.82 9 6 1366 2.01 16 6

From the trends shown in Tables 2 and 3, it can be concluded that neither the average molecular weight nor the degree of polydispersity of the product is representative of the efficacy within the range studied.

This finding was also confirmed by the results obtained by fractionating the products. The results of such an experiment are summarized in Table 4 .__

490,423,.

additive Gasoline I. II. fuel oil factions Mn L Dp, 'C CFPP, 'C Dp, 'C CFPP, 'C Average 858 3.74 -5 -8 -3 -5 1 2598 5.33 -11 -8 -4 - 5 2 1430 5.03 -9 -9 -2 -6 3 1507 4.1 -10 -7 -8 -6 4 1279 3.71 -8 - 7 -6 -8 5 1542 3.82 -3 -8 - 4 -6 6 1179 4.0 -2 -9 -2 -4 7 574 2.83 -1 -5 -1 -4

During the experiment, the reaction mixture was not evaporated but the polymer was isolated by fractional precipitation by the addition of methanol. In addition to an average sample, seven more polymer fractions were obtained. The separation resulted not only in molecular weight but also in structural separation. The molecular weights of the fractions show a slight fluctuation in solubility but tend to decrease. To characterize the structure, a linearity factor was introduced, which is the quotient of the polymer HNMR integrals below 0.9 ppm and above 0.9 ppm. This value, which can be quickly verified even under operating conditions, is a rough approximation of the ratio of —CH ₂ - and —CH ₁ groups in the polymer. Its value increases with increasing pressure and decreases with increasing temperature. If the linearity factor is high, the polymer has long, unbranched methylene chains, while polymers with low linearity factor have a "spiny" structure with many branches.

From Table 4 it is striking that Fractions 1 and 2 are for Diesel I and Fractions 3 and 4 are for Diesel II. gas oil gave better results. These differences cannot be attributed to the average molecular weight, since the effect of the additive is hardly changed between 1400 and 2600, however, fractions 2 and 3 show a dramatic difference in the effect of the additive even with a slight change in molecular weight.

The results are much more correlated with the value of the linearity factor and this correlation is well understood. Fractions with a higher linearity factor and less branching are more effective in gas oil I with longer paraffin molecules, whereas fractions with a lower linearity factor have higher efficiency in II. gas oil.

This finding is illustrated by the following example: a polyethylene having an average molecular weight of 1036 and having a linearity factor of 3.5 g is shown in Example II. it reduces the pour point of gas oil by 22 'C, while it increases the freezing point of gas oil I by 4 ° C.

Thus, in accordance with the present invention, we have discovered a molecular property of an additive that can be used to determine the composition of the additive in a gas oil. In other words, before producing the additive, it is possible to decide on the linearity factor of the additive for a given diesel.

Thus, the effect of the additive can be designed with knowledge of the field of application and the additive can be manufactured according to the needs.

In the production of additives was the surprising observation that the beneficial additives production of two key parameters - pressure and temperature - to each other and depend on these parameters vary only within a very narrow range ^25. The values of pressure (P, bar) and temperature (t, 'C) are given by 1.41 - P = C, where C = 159 ± 20.

The linearity factor of the product has been shown to increase with the increase in pressure and can be selected depending on the properties of the additive 30 gas oil.

The process of improving the cold flow properties of oils for use in oil-fired thermal equipment according to the present invention is thus to add to the middle distillate 35 a polyethylene as an additive in an amount of 0.01-0.5% by weight. t, 'C) was 1.41 - P = C - where C = 159 ± 20 - and the polymerization was initiated at 40 120-220' C, preferably 130-180 'C, preferably peroxide or azo compound - in his presence.

The initiators used in the polymerization are known per se and, as is customary in such re45 operations, are selected by aligning the synthesis temperature with the decomposition temperature of the initiator. The initiator is present in an amount of 0.1 to 3%, preferably 0.3%, based on the weight of the reaction mixture.

The following examples illustrate the process of the invention.

Example 1 55

To a 109 ml autoclave were added 25 g of benzene and 0.2 g of di-tert-butyl peroxide. The autoclave was purged with air and charged with nitrogen followed by ethylene and charged with ethylene qq to bring the reaction mixture to 72 bar when heated to 155 ° C (C = 159-14). The autoclave valve is then closed and heated to 155 ° C for 20-30 minutes by placing the autoclave in a nodal autoclave heater jacket. This temperature is maintained at ₆₅ until the pressure drops to 50 bar. EC5

-5. 190423. At 2, the autoclave is cooled, the pressure blown off, and the polymer isolated by vacuum evaporation. Yield:

3.1 g of polyethylene. The product, when added at a concentration of 0.1%, reduces the freezing point of Diesel I by 14 'C. /

Example 2

Following the procedure described in Example 1, the polymerization was carried out at an initial pressure of 91 bar at 150 ° C (C = 159-40). The experimental conditions are outside the preferred parameter range. The product reduces the freezing point of Diesel Oil I under the conditions described in Example 1 by only 7 'C.

Example 3

The experiment described in Example 1 is repeated, except that the reaction is carried out at a starting pressure of 72 bar and at 165 ° C (C = 159 ± 0). The linearity factor of the product is 7.2. The product, when added at a concentration of 0.1%, reduces the freezing point of Diesel I by 16 ° C. The effect of the additive was compared with the known ethylene copolymer type EXXON additives. The results are shown in Table 5.

Table 5

Results of Addition of Diesel Oil with Import Additives and Experimental Product Prepared in Example 3

Clearing Cure- Filterable Statement limit, 'C it was given point, 'C point, 'C I. Diesel Oil ' + 8 -1 + 7 + 0.1 sX ECA 841 + 8 0 + 2 + 0.1 sX ECA 5217 + 6 -12 + 3 +0.1 sX ECA 5920 + 9 -23 0 + 0.1 sX Paradyne + 8 -3 + 4 +0.1 sX Example 3 rinti product + 7 -16 +1

Example 4

Polymerize according to the method described in Example 1. tion is repeated with ^five got filled (C = 159 + 11) 2.5 g, m.p. 150 ° C and 40 bar initial pressure (the linearity factor = 3.5).

See Table 6 for a comparison of product efficacy with commercial product.

Table 6

II. results of the addition of diesel with imported additives and the experimental products prepared in Example 4

additive cloud point, 'C Dermedés- point, 'C Filterable Statement limit, 'C II. fuel oil -7 -12 -7 + 0.1 sX ECA 841 -4 -16 -12 + 0.1 sX ECA 5217 -5 - 16th - 11 + 0.1 sX ECA 5920 - 7 -33 -21 +0.1 sX Paradyne 20 -7 -18 -11 + 0.1 sX Example 4 according to -7 -32 -13

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Claims (1)

A method for improving the cold-flow properties of oils for use in oil-fired caloric equipment with polymer additives, characterized by __ determining the linearity coefficient of polyethylene to be added to the middle distillate by the composition of gas oil-type petroleum distillates ³⁵ , and Polyethylene is added in an amount of 5% by weight, for which the relationship between pressure (P, ⁴ θ bar) and temperature (t, 'C) is as follows: 1.41-P = C - where C = 159 ± 20 - and the polymerization is initiated at a temperature of 120 to 220 ° C, preferably 130 to 180 ° C, 0.1 to 3%, preferably 0.3 to 1% by weight based on the weight of the reaction mixture, preferably a peroxide compound or an azo compound - in his presence.