EP0728175B1 - Process for dechlorination of a spent oil fraction - Google Patents

Abstract

PCT No. PCT/FR95/01162 Sec. 371 Date May 13, 1996 Sec. 102(e) Date May 13, 1996 PCT Filed Sep. 11, 1995 PCT Pub. No. WO96/08546 PCT Pub. Date Mar. 21, 1996The present invention relates to a process for dechlorinating a spent lubricating oil fraction, optionally mixed with another hydrocarbon stock. Upstream of the recycling operation in refining the spent oil, the latter is subjected to a dechlorination operation at least partially by passing it on a bed of particles (6) of a composition which neutralizes by absorption and containing, as active compound capable of fixing the chlorine, at least one metal oxide and/or at least one metal hydroxide.

Description

The present invention relates to a dechlorination process a fraction of used oil.

We know that the used lubricating oils recovered in garages or service stations, represent very large tonnages, which, for France, rise for example at 100,000 tonnes, even 120,000 tonnes per year.

We have therefore always sought to avoid discharge of these used oils, which could constitute an important factor of pollution and, currently, these oils are usually subjected to a treatment of regeneration.

However, this treatment is expensive because the oils spent have a high content of various metals and chlorine, and regenerated oils are practically also expensive than new oils from refineries.

We also know, from DE-A-1 594 531, a process for processing used lubricating oils containing especially chlorine fixed on organic compounds. This process involves subjecting these oils to treatment at hot, by mixing with hydrated metal oxides, like calcium hydroxide, which has the effect of clotting suspended matter, retaining substances active like chlorine.

This process is however a complex implementation to an industrial scale.

We were therefore led to consider other uses for these used oils, for example as fuel, especially in cement factories, but in this application also, the presence of significant chlorine contents (about 400 to 2,000 ppm) is problematic.

It has therefore been proposed to recycle these refineries used oils, to subject them to distillation, possibly mixed with other fillers, in order to recover at least a fraction of the compounds of interest they contain.  

The preliminary tests carried out for this purpose by the Applicants have however shown that in such a use, the chlorine compounds in used oil again poses serious problems. These compounds are, in fact, organic chlorides, coming additives for oils, which generally include chlorinated compounds, in particular chlorinated polyisobutenes. During a distillation operation, even at a temperature relatively low, especially in the presence of steam of water, the molecules of these chlorine compounds break and   give rise, in particular, to hydrochloric acid, which has a marked corrosive effect on the installations of refining.

The present invention therefore aims to reduce the content of used oils chlorine at a rate compatible with recycling operations in refinery of these oils and she proposes, for this purpose, to use composite products solids, capable of fixing chlorinated ions, already known in the technical for other applications and under conditions different use.

In fact, already used in industry, particulate compositions called "chlorine traps", based on alumina or metal oxides or metal hydroxides such as CaO, Na ₂ O, K ₂ O, MgO, as well as the corresponding hydroxides, for eliminating the chlorine present in the liquid or gaseous flows of process units, in particular in reforming or isomerization units.

These compositions generally have a dimension particles of the order of 0.5 to 3 mm and they neutralize usually chlorine by adsorption. They are generally used at room temperature or order, at most 100 ° C and atmospheric pressure, and they usually retain about 15% of the chlorine present in the charges processed.

The Applicant has established that such chlorine traps are particularly well suited for an operation of partial dechlorination of used oils, upstream of any recycling operation in a refinery, in particular a vacuum distillation, and that, unexpectedly, their chlorine binding power increases significantly with the temperature of the treated oils, the chlorine trap can retain at least 40% of the chlorine present in the treated oil at a temperature between 300 and 400 ° C and at pressure atmospheric.

As we will see below, we can naturally operate at different temperatures and / or pressures.

However, this amount of chlorine greater than 40% represents   roughly the fraction of chlorine compounds that break down in a used oil recycling operation or which distill in a fractionation column under used oil vacuum, leading to acid formation hydrochloric, and the invention therefore proposes, in a simple manner, subjecting used oil to dechlorination upstream of any recycling operation.

The invention therefore relates to a method of dechlorination of a fraction of used lubricating oil, possibly mixed with another charge hydrocarbon, this process being characterized in that, in upstream of an oil refinery recycling operation used, the used oil is subjected to a dechlorination operation at least partial by passing over a bed of particles of an adsorption neutralizing composition containing, as active compound capable of fixing chlorine at least one oxide of a metal belonging to groups I and II of the Periodic classification and / or at least one hydroxide of a metal belonging to groups I and II of the Classification Periodic.

Preferably, the active compound of the composition neutralizing will be an oxide of calcium, magnesium, sodium or potassium, or a calcium hydroxide, magnesium, sodium or potassium. Calcium oxide and calcium hydroxide are active compounds even more preferred.

Preferably, the dechlorination phase will be carried out under conditions such that at least 40% and, preferably, 60% of the amount of chlorine present in the used oil is retained by the neutralizing composition by adsorption. These conditions are, for example, the following: a temperature of at least 150 ° C and, preferably, of the order of 400 ° C, an hourly space velocity of the used oil of 0.5 h ^-1 ( volume of used oil, per volume of adsorbent and per hour) and a pressure substantially equal to atmospheric pressure.

Implementation at temperatures and / or different pressures also comes under the invention.  

In a preferred embodiment of the invention, prior to the dechlorination operation, the used oil will be subjected to a distillation phase atmospheric at a temperature of 300 to 400 ° C in sight to remove the water and the light solvents it contains, and the dechlorination operation will be carried out on the used oil from this atmospheric distillation, possibly after reheating of this oil, by example by heat exchange, to increase the efficiency of dechlorination.

The used oil thus dechlorinated can then be subjected, for example, to vacuum distillation, preferably mixed with another filler, such as residue from atmospheric distillation, with a view to separating into particular vacuum diesel, vacuum distillate and a bituminous vacuum residue, without forming, as it is usual at this stage, hydrochloric acid responsible marked corrosion in the installations.

Naturally, distillation operations atmospheric and vacuum fractionation or others operations on the residue thus dechlorinated will be carried out in serial and continuous.

As indicated above, the compositions of dechlorination used in the process of the invention are well known in the art and generally contain at least 25% by weight of active compound. They are marketed, for example, under the names TRAP'IT sales by Catalysts and Chemicals Europe, SELEXSORB HCl by ALCOA, and DISCOVERY ALUMINAS by the Dycat International Company.

The preferred composition for the implementation of the invention is that marketed under the name TRAP'IT, which contains, in% by weight, from 23.0 to 27.0% of CaO, constituting the active product, and from 43 to 53.0% of oxide of zinc, serving as a support, the complement to 100% being consisting of a binder.

This composition has, in general, an apparent specific mass of 0.720 to 0.800 cm ^{3 /} g, a pore volume of 0.35 to 0.45 cm ³ / g and a specific surface of at least 22 m ² / g. It is usually in the form of rods with a diameter of 1.2 to 1.8 mm and a length of about 4.0 to 12.0 mm.

La figure 1 est un schéma général illustrant cette forme de mise en oeuvre du procédé ;

La figure 2 est un diagramme illustrant l'accroissement du taux de déchloration, exprimé en %, en fonction de la température, exprimée en °C.

An embodiment of the invention will be described below, by way of nonlimiting example, with reference to the accompanying drawings. In these drawings:

Figure 1 is a general diagram illustrating this form of implementation of the method;

FIG. 2 is a diagram illustrating the increase in the dechlorination rate, expressed in%, as a function of the temperature, expressed in ° C.

In the embodiment of the invention illustrated in FIG. 1, the used oil to be treated, arriving via the line 1, is first topped, by atmospheric distillation, in a column 2. The water present in the used oil (4 to 10% by weight) is discharged at the top of the column via line 3, while the light solvents are evacuated via line 4.

The topped oil, discharged at the bottom of the column, by the line 5, at a temperature of 300 to 400 ° C, contains the most often around 500 ppm chlorine. It then crosses a flask 6 containing the particulate composition used as a chlorine trap. If you want to perform the dechlorination of oil at a higher temperature, a heat exchanger 7 can be arranged on line 5 in upstream of the flask 6. The chlorine trap contained in the tank 6 retains about 60% of the chlorine present in the oil used, and the treated oil, which contains only about 200 ppm of chlorine, is evacuated by a line 8 towards a vacuum distillation column 9, in which it is introduced, for example, with a residue of atmospheric distillation arriving via line 10.

The chlorine content of the treated oil is compatible with the conditions of vacuum distillation, which is takes place without any particular risk of corrosion due to formation of hydrochloric acid in column 9.

• en tête de colonne, par la ligne 11, un gas-oil sous vide ;
• à un niveau intermédiaire, par la ligne 12, un distillat sous vide,
• en fond de colonne, par la ligne 13, un résidu sous vide, utilisable comme bitume.

From it are evacuated in the usual way:

• at the top of the column, by line 11, a vacuum diesel oil;
• at an intermediate level, via line 12, a vacuum distillate,
• at the bottom of the column, by line 13, a vacuum residue, usable as bitumen.

Example 1 which follows relates to an application of the method according to the invention using the device of the figure 1, it being understood that other forms of implementation are within the scope of the invention. Example 2 illustrates improved dechlorination of treated oil as the treatment temperature rises dechlorination.

Example 1

• masse volumique : 909,9 kg/m³,
• teneur en chlore total : 1036 ppm,

This example relates to the treatment, in the device of FIG. 1, of a used oil having the following characteristics:

• density: 909.9 kg / m ³ ,
• total chlorine content: 1036 ppm,

température transfert : 360°C,

pression atmosphérique.

This oil is subjected in column 1 to atmospheric distillation under the following conditions:

transfer temperature: 360 ° C,

atmospheric pressure.

3.7% of water is collected, in% by weight, via line 3 and, via line 4, 5.5% of light chlorinated solvents.

The topped used oil, collected at the bottom of the column by line 5, at a temperature of 360 ° C., contains 325 ppm of chlorine. It is subjected to this temperature of 320 ° C., in the flask 6, to a dechlorination operation, by treatment with the composition called TRAP'IT (registered trademark), the composition of which was given above. The flask 6 contains 15m ³ of TRAP'IT and the dechlorination treatment is carried out at an hourly space velocity of the treated oil of 0.5 h ^-1 .

The oil leaving balloon 6 via line 8 does not contain more than 123 ppm by weight of chlorine and 62% of the chlorine present in the oil at the inlet of balloon 6 have therefore been fixed and retained by the TRAP'IT composition.

• température de transfert : 400°C
• pression : 5.10³ Pa en tête de colonne.

The oil thus partially dechlorinated is then mixed with an atmospheric distillation residue, in the following proportions 7/100 by weight, and the mixture is introduced into the vacuum distillation tower 9, where it is treated under the following conditions:

• transfer temperature: 400 ° C
• pressure: 5.10 ³ Pa at the top of the column.

2% by weight of vacuum diesel oil, 57% by weight of vacuum distillate and 41% by weight of vacuum residue, having the following characteristics, are collected by lines 11, 12 and 13 respectively: diesel fuel chlorine content <50 ppm, Vacuum distillate chlorine content <3 ppm, Vacuum residue chlorine content 15 ppm.

Measuring the chlorides in the water of condensation, the hydrochloric acid content at the top of column and we see that the dechlorination of used oil reduces the chloride content in the overhead water up to a value below 20 mg / l and the pH is about 5, to avoid any problems.

This example therefore clearly shows the effectiveness of the treatment of used oils, by vacuum fractionation, according to the invention.

After use, the composition of TRAP'IT can be scrapped or regenerated.

Example 2

This example aims to show the interest of driving the dechlorination operation at such a high temperature as possible.

A head of used oil containing 325 ppm of chlorine is treated in a flask containing 15m3 of the TRAP'IT composition, at an hourly space speed of 0.5 h ^-1 . The treatment is carried out at various temperatures and the dechlorination rate is measured each time, that is to say the fraction, expressed in%, of chlorine of the charge retained by the dechlorination composition.

The results obtained are given in Table I below: Dechlorination temperature (° C) Dechlorination rate (%) 40 20.0 130 26.7 280 56.9 300 58.4 320 64.6 340 79.0 400 95

The results obtained have been reported in FIG. 2 and we see that the dechlorination rate increases so quasi-exponential as a function of temperature, which shows the advantage of performing the dechlorination operation at as high a temperature as possible. In order to profitability, we will preferably conduct the dechlorination at about 350 ° C.

The examples above use the TRAP'IT composition, but the composition DYCAT 115 whose characteristics are grouped in Table II below is also suitable perfectly since the results are very similar to those obtained above with TRAP'IT. We can also use soda and potash compositions which have very similar dechlorination properties TRAP'IT and DYCAT 115 compositions.

The composition of DYCAT 115, in% by weight, is given in Table II below. The DYCAT 115 is in the form of spheres of approximately 3 to 5 mm in diameter. COMPOUNDS % in weight Calcium oxide At least 60 Aluminum oxide 8 Manganese oxide 5 Sodium oxide 4.5 Silica 5.0 Lead <0.1 As, Cd Traces

The tests carried out by the Applicant prove that such favorable results are obtained by substituting calcium hydroxide Ca (OH) ₂ for the calcium oxide of these compositions.

The examples above clearly illustrate the advantages of the invention, which allows reuse in refinery, with dechlorination pre-treatment simple and inexpensive, used lubricating oils.

Claims (7)

1. A process for dechlorinating a fraction of used lubricating oil, optionally mixed with another hydrocarbon charge, said process being characterised in that, upstream of a refinery recycling operation for used oil, the used oil undergoes an at least partial dechlorination operation by being passed over a bed of particles of a composition which neutralises by adsorption containing, as active compound intended to fix the chlorine, at least one oxide of a metal from groups I and II of the periodic table and/or at least one hydroxide of a metal from groups I and II of the periodic table.
2. A process according to claim 1, characterised in that the dechlorination stage is carried out under conditions such that at least 40 % and, preferably, approximately 60 % of the chlorine present in the treated used oil is retained by the adsorbent composition.
3. A process according to claim 2, characterised in that the dechlorination stage is carried out at a temperature of at least 150°C and, preferably, of the order of 400°C, and in that the hourly spatial velocity of the charge of used oil is approximately 0.5 h^-1.
4. A process according to any one of claims 1 to 3, characterised in that, prior to the dechlorination operation, the used oil undergoes an atmospheric distillation phase at a temperature of 300 to 400°C intended to remove the water and light solvents contained therein, and in that the dechlorination operation is carried out on the used oil arising from this atmospheric distillation, optionally after reheating this oil.
5. A process according to any one of claims 1 to 4, characterised in that the active compound of the composition which neutralises by adsorption is an oxide of calcium, magnesium, sodium or potassium and, preferably, an oxide of calcium.
6. A process according to any one of claims 1 to 4, characterised in that the active compound of the composition which neutralises by adsorption is a hydroxide of calcium or magnesium or sodium or potassium and, preferably, a hydroxide of calcium.
7. A process according to claim 1, characterised in that, downstream of the dechlorination operation, the dechlorinated used oil undergoes vacuum distillation.