DE1097605B - Process for dewaxing hydrocarbon oils - Google Patents

Description

Process for dewaxing hydrocarbon oils In dewaxing of hydrocarbon oils by adduct formation with urea occur in technical Operation by agglomeration of urea adducts on disturbances, which result in blockages the agitators, pumps and lines. It has been shown that these disorders appear whenever the adduct formation has not been completed, when So in addition to the already fully reacted adduct parts, those with still feasible Urea are present. The mixture of these two adduct forms is sticky and greasy and cakes. This baking ability does not occur when the adduct has reacted completely.

The urea adduct formation is known to be a time reaction, i. H., The beginning and the end do not coincide almost at the same time as with instantaneous reactions, rather, it extends over a relatively long period of time. The adduct-happy Paraffins almost spontaneously form adducts, while the more sluggish ones only gradually react with urea. In the course of this implementation, those already mentioned above occur greasy and sticky intermediate states.

The aim of the invention is to switch off these intermediate states and to terminate the adduct formation more quickly. For this it was necessary to combine the urea in a specially activated form to use.

It has now been found that for the urea in dispersed form There is a special temperature range in which the urea is activated Shape is present. If the urea is used in this form for dewaxing, so the adduct formation is terminated in a short time, and the sticky and greasy ones Adduct phases are switched off.

The temperature range according to the invention is characterized by a lower temperature at which the urea is no longer out of the urea dispersant system sedimented, and an upper temperature at which the system urea dispersant falls apart almost suddenly. The lower temperature is called educational that the upper one referred to as the demixing temperature.

These temperatures are determined in the following way: A saturated Urea solution is produced at any higher temperature and with stirring mixed with a suitable organic dispersant. Then either directly, e.g. B. by evaporation of the added dispersant, or indirectly chilled. First, urea falls out of the urea solution-dispersant system out and sedimented. This sedimentation process stops at a very specific temperature on, no urea sediments from the urea solution-dispersant system more, and the system can continue to cool down unchanged. In practical operation will the z. B. at 80 ° C saturated urea solution, which is obtained at - .. 85 ° C, cooled down by adding excess methylene chloride and stirring. Even here urea initially precipitates from the urea solution-methylene chloride system and sedimented. With further cooling, this sedimentation process hears from one certain temperature on; the urea is in a milky dispersion before, which can be cooled further unchanged.

The temperature at which the sedimentation process ends is the so-called formation temperature, formation temperature because it is at this temperature the formation of the highly active, no longer sedimenting state occurs.

If the system in this state is now gradually warmed up, so at a certain temperature the separation of the system occurs almost suddenly in urea solution and methylene chloride. This temperature is the so-called Demixing temperature.

In order to achieve this highly active dispersion state, the urea both in an aqueous solution and in the dry state. Preferably aqueous solutions which are saturated in urea at 55 to 80 ° C are used, because they arise in continuous operation.

All organic substances come in as dispersants Question in which urea or urea and water can be dispersed. very Halogenated hydrocarbons which contain both a Halogen as well as various halogens can contain, so mixed halogenated are, such as B. the chlorofluorocarbons. Ketones and aliphatic were also found Hydrocarbons (as long as the latter do not adduct in the adduct formation area) as favorable, esters, ethers, aliphatic amines can also be used.

In the preparation of the highly active dispersion, the stirring has to be considered an influence when this dispersion only gradually increases with slow stirring Intensive stirring, on the other hand, sets in much more quickly.

The highly active state according to the invention therefore exists for everyone resulting systems, e.g. B. for the system dry urea in methylene chloride or in acetone or in octane and, for the corresponding systems, with aqueous urea solutions.

Once the formation temperature has been determined, the highly active one needs Urea dispersion of course not by cooling a hotter, still sedimenting one Urea dispersion to be produced. Rather, it is easily possible this state by mixing together urea, optionally water, and the To achieve dispersant at the relevant formation temperature.

However, if a hot urea solution is produced during operation, this is the case the way described above for determining the temperature range also at the same time easiest way to produce the highly active urea dispersion.

The temperature range according to the invention depends on the type and amount of the dispersant and the concentration of the aqueous uranium solution. The table below shows that, with the same dispersant and the same ratio of urea solution to dispersant, the formation temperature increases when the saturation temperatures of the aqueous urea solution also increase. (Experiments 1, 2, 4, 7 and 9 as well as 12 and 13.) On the other hand, when the same dispersant and the same saturation temperature of the aqueous urea solution are used, the formation temperature decreases with an increasing ratio of "urea solution to dispersant" (experiments 3, 4, 5 and 6 ). When using dry urea, the formation temperature depends on the type of dispersant, but apparently not the demixing temperature (experiments 14 and 15). The demixing temperature, on the other hand, is almost dependent on the ratio of urea solution to dispersion medium. It depends to a small extent on the saturation temperature of the aqueous urea solution. Saturation temperature ratio of the aqueous urea formation dissolving No 'urea solution dispersant solution to di-temperature temperature o C dispersant o C ° C 1 55 methylene chloride 1: 5 -E- 8 +25 2 60 the same 1: 5 + 11 +28 3 70 same as 1.6 +14 +34 4 70 the same 1: 5 +17 +34 5 70 the same 1: 2.5 +23 +34 6 70 the same 1: 1.6 +27 +34 7 80 the same 1: 5 +23 +34 8 80 the same 1: 3.5 +29 +34 9 95 the same - 1: 5 +28 +34 10 70 ethylene chloride-1,2 1: 5 -20 + 5 11 70 acetone 1: 5 + 10 +30 12 80 octane 1: 5 0 +31 13 105 octane 1: 5 +15 +31 14 dry urea methylene chloride 1: 5 + 5 +34 15 dry urea octane 1: 5 +23 +34 The highly active urea dispersion obtained in the manner described can be added to the oil to be dewaxed at all customary adduct formation temperatures. It is therefore not necessary to use them only in the range between the formation and demixing temperature; It is stable below the demixing temperature and can therefore be used at all adduct formation temperatures which are also below the demixing temperature. Frequently, however, it is also possible to use them when the adduct formation is carried out above the demixing temperature, because the reaction of the highly dispersed urea with the paraffins takes place faster than the conversion of the fine, dispersed phase into correspondingly coarser crystals.

The highly active urea dispersion is obtained in continuous operation in the following manner: The adduct separated from the adduct formation mixture is heated to about 70 ° C by heating it indirectly and blowing steam in at the same time. The adduct decomposes in the process; an upper layer of paraffins is formed and a lower layer made of the urea solution diluted due to the addition of steam. This is concentrated in a thickener to a saturation of --- 80 ° C and left keep it at a temperature of -85 ° C to prevent it from freezing on the way.

This concentrated aqueous urea solution is mixed with vigorously Stir in about 5 parts of methylene chloride. At first, methylene chloride evaporates against the atmosphere, afterwards, when applying a vacuum, until it reaches the formation temperature the highly active urea solution adjusts from - 29'C.

The shortening of the adduct formation time when using the highly active urea dispersion compared to a normal dispersion results from Examples 1 and 2. Example 1 1 part of urea solution (saturation 70 ° C) is mixed with 5 parts of methylene chloride at + 17 ° C with stirring and the thus obtained highly active dispersion added to a spindle oil distillate at + 30 ° C. The initial pour point of -i- 14 ° C fell in the course of 30 minutes as follows after 1 minute to -4'C, after 3 minutes to -16 ° C, after 5 minutes to - 23'C, after 7 minutes to - 28 ° C, after 9 minutes to - 28 ° C, after 12 minutes to - 28 ° C, after 15 minutes to - 28 ° C, after 20 minutes to - 28 ° C, after 30 minutes to - 28 ° C. The final stick point of -28'C is reached after an adduct formation time of 7 minutes. Example 2 Concentration of the urea solution, ratio of urea solution to methylene chloride, spindle oil distillate and adduct formation temperature are the same as in Example 1. The only difference is that the urea dispersion is produced at the adduct formation temperature itself, i.e. at -30 ° C, and therefore easily sediments . When this dispersion was added to the spindle oil distillate, the initial pour point of -f- WC fell as follows: after 1 minute to + 14 ° C, after 3 minutes to - + - 6 ° C, after 5 minutes to - 6 ° C, after 7 minutes to -14 WC, after 9 minutes to -15'C, after 12 minutes to -17'C, after 15 minutes to -20'C, after 20 minutes to -21'C, after 30 minutes to -21'C. The final stick point of −28 ° C., which was present in example 1 after an adduct formation time of 7 minutes, is not reached here even after an adduct formation time of 30 minutes.

Claims (3)

PATENT CLAIMS: 1. Process for dewaxing hydrocarbon oils by means of adducts of urea and paraffins, characterized in that the urea, optionally in aqueous solution, is converted into a dispersion state by stirring in a non-adduct-forming solvent, which is dependent on the concentration and amount of the Urea solution and the type of oil dissolver and which is stable between a lower formation temperature, below which the urea no longer sediments out of the dispersion, and an upper demixing temperature, at which the dispersion breaks up almost instantaneously, and is used in this form during adduct formation. 2. The method according to claim 1, characterized in that that as dispersants halogenated hydrocarbons, ketones or aliphatic hydrocarbons which do not form adducts under the working conditions are used. 3. Procedure according to claim 1 and 2, characterized in that the state of dispersion is such is obtained that the hot urea solution leaving the thickener with a Stirred excess of dispersant, initially under atmospheric pressure and later cooled to the formation temperature under vacuum.