DE102013106439A1 - Process for removing metals from high boiling hydrocarbon fractions - Google Patents

Abstract

The invention relates to a process for removing metal impurities from hydrocarbon fractions, such as are obtained, for example, as a product of the Fischer-Tropsch synthesis using suspended catalyst. According to the invention, water is added to the hydrocarbon fraction to be treated in the molten state at a temperature of at least 180 ° C. with stirring. The metals to be removed are deposited in a separate phase and can be removed from the process, for example by means of filtration.

Description

Field of the invention

The invention relates to a process for the removal of metals from high-boiling hydrocarbon fractions, in particular for the separation of catalyst-derived nickel, cobalt and aluminum impurities from the primary products of a hydrocarbon synthesis, for example by the Fischer-Tropsch process.

State of the art

Hydrocarbons may be obtained as synthesis products from chemical catalytic processes, such as the Fischer-Tropsch process, the bases of which have been extensively described in the literature, e.g. In Ullmann's Encyclopaedia of Industrial Chemistry, Sixth Edition, 1998 Electronic Release, keyword "Coal Liquefaction", Chapter 2.2 "Fischer-Tropsch Synthesis" , A modern process variant represents the conversion of synthesis gas in a suspension of the solid, fine-grained catalyst in the liquid product hydrocarbons (so-called slurry process). In this case, highly active catalysts are used which contain as active components metals, for example cobalt, on a support material, for example aluminum oxide, as described in US Pat U.S. Patent US 4801573 is described. The international patent application WO 98/27181 A1 suggests, in addition to numerous other publications, a method of separating the catalyst suspension from the hydrocarbon product. The product hydrocarbons thus obtained often contain significant amounts of heavy metals. The cause of this undesirable heavy metal contamination are abrasion and corrosion processes on the catalysts used in the synthesis process and / or the container material. However, these methods based on mechanical separation methods are only suitable for the separation of particulate metal contaminants, but not for the separation of chemically bonded in the hydrocarbon phase or finely dispersed or colloidally dissolved metals.

In addition to heavy metal contamination, contamination with the metal of the catalyst support matrix (eg, aluminum) is also observed. The metal contamination described may be disturbing in a further chemical-catalytic reaction of the product hydrocarbons, as these can be effective as a catalyst poison. In addition, heavy metal contamination, irrespective of the substance in which it is contained, poses a potential environmental and health hazard. Especially nickel and cobalt, which are classified as carcinogenic, should be mentioned here. On the other hand, both heavy metals are valuable catalyst building blocks, which should be fed to a recycling process in order to avoid losses.

The German patent DE 1212662 describes a process for treating hydrocarbon oils to remove metallic contaminants that are detrimental to the catalysts used in their conversions. Here it is proposed to treat the contaminated hydrocarbon oils with a solution of hydrogen fluoride in an organic solvent, whereby the metals are converted into a sparingly soluble precipitate, which can be subsequently separated by a mechanical separation method. This avoids the problems described above in the treatment of a two-phase mixture of hydrocarbon phase and aqueous phase. However, a disadvantage is the use of highly reactive, gaseous hydrogen fluoride for the preparation of the treatment solution for reasons of safety at work and handling.

The US Pat. No. 4,518,484 discloses a method of treating metal-containing hydrocarbon feed streams, comprising the steps of: (a) contacting the hydrocarbon feed streams in an extraction zone with at least one hydrocarbon solvent having from 2 to 10 carbon atoms per molecule under supercritical conditions in the presence of an organophosphorus based deplating agent, (b ) Discharging a top product from the extraction zone, which contains the hydrocarbons largely freed from metals, and a bottom product containing the solvent laden with the metals. A disadvantage is the complex process control, in particular the setting of supercritical conditions to consider.

Subject of the patent application DE 102011013470 A1 is a process and means for removing metal contaminants from hydrocarbon fractions, such as those obtained as a product of Fischer-Tropsch synthesis using suspended catalyst. The feed hydrocarbon fraction is treated with a demetallizing agent comprising at least one sulfur source and at least one basic compound under anhydrous conditions. The metals to be removed are obtained as a precipitate, which can be easily separated by a mechanical separation process, for example filtration.

In the international patent application WO 2006/053350 A1 discloses a process for the separation of metal impurities such as aluminum or cobalt from hydrocarbon fractions, in which the hydrocarbon fraction with a aqueous phase at temperatures of at least 160 ° C, typically around 170 ° C, wherein the aqueous phase may optionally comprise an acid, for example an organic acid such as maleic acid. Although it teaches that higher temperatures than those mentioned above can be used, there is no differentiated specification of these higher temperatures and any advantages.

Description of the invention

The present invention is therefore based on the object to provide a simple method for the removal of metal contaminants from high-boiling hydrocarbon fractions, which is characterized by a simple process control, and which can be carried out without the use of substances with high risk potential.

• (a) Bereitstellen der metallhaltigen Kohlenwasserstofffraktion in flüssiger Form,
• (b) Inkontaktbringen der flüssigen, metallhaltigen Kohlenwasserstofffraktion mit einer wasserhaltigen, einen pH-Wert von 7 aufweisenden Flüssigphase bei Temperaturen von mindestens 180°C unter Rühren,
• (c) Beenden des Rührens, Abkühlen und Durchführen einer Phasentrennung, wobei eine leichte, kohlenwasserstoffhaltige Flüssigphase, eine schwere, wasserhaltige Flüssigphase und eine dritte Phase erhalten wird, die zwischen der leichten, kohlenwasserstoffhaltige Flüssigphase und der schweren, wasserhaltigen Flüssigphase angeordnet ist und die Kohlenwasserstoff, Wasser und Metallpartikel umfasst,
• (d) Abtrennen der Metallpartikel als metallhaltiger Niederschlag mit einem mechanischen Trennverfahren von der dritten Phase,
• (e) Trennung der dritten, von Metallen befreiten Phase in eine leichte, kohlenwasserstoffhaltige Flüssigphase und eine schwere, wasserhaltige Flüssigphase, Vereinigung der getrennten Flüssigphasen mit den korrespondierenden, in Verfahrensschritt (c) erhaltenen Flüssigphasen,
• (f) Ausleiten der kohlenwasserstoffhaltigen Flüssigphase als an Metallen abgereicherte Kohlenwasserstofffraktion.

The object of the invention results essentially from the features of claim 1 by a process for producing a metal-poor hydrocarbon fraction, wherein the metals in the hydrocarbon fraction are chemically bound or dispersed in the hydrocarbon fraction in colloidal or finely dispersed form, comprising the following steps:

• (a) providing the metal-containing hydrocarbon fraction in liquid form,
• (b) contacting the liquid, metal-containing hydrocarbon fraction with a water-containing liquid phase having a pH of 7 at temperatures of at least 180 ° C. with stirring,
• (c) terminating the stirring, cooling and phase separation to obtain a light hydrocarbonaceous liquid phase, a heavy hydrous liquid phase and a third phase interposed between the light hydrocarbonaceous liquid phase and the heavy hydrous liquid phase and the hydrocarbon Comprising water and metal particles,
• (d) separating the metal particles as metal-containing precipitate with a mechanical separation process from the third phase,
• (e) separating the third, metal-free phase into a light, hydrocarbon-containing liquid phase and a heavy, aqueous liquid phase, combining the separated liquid phases with the corresponding liquid phases obtained in process step (c),
• (f) discharging the hydrocarbon-containing liquid phase as a metal-depleted hydrocarbon fraction.

Further advantageous embodiments of the method according to the invention will become apparent from the dependent claims.

For the treatment by the process according to the invention, the feed hydrocarbon fraction must be present in liquid form. Waxy hydrocarbons, such as those obtained, for example, as products of the Fischer-Tropsch process, may need to be melted before treatment.

From the prior art, for example the WO 2006/053350 A1 It is known that an aqueous acidic solution causes agglomeration of the metallic impurities in a hydrocarbon fraction. These agglomerated metallic particles are then separated from the hydrocarbon fraction by mechanical separation techniques, such as filtration, sedimentation or decantation. However, it always requires a quantity of an inorganic or organic acid.

Surprisingly, it has been found in the invention that by treating the hydrocarbon fraction with water at temperatures above 180 ° C without additional addition of acid or other chemicals, the metals can be completely removed from the hydrocarbon fraction. The pH of the water used for the treatment of the hydrocarbon fraction by the process according to the invention is around 7, so it is in the neutral range. An adjustment of the pH of the fresh water used is therefore generally not required.

A simple treatment of the contaminated hydrocarbon fraction by intensive mixing with water at temperatures of at least 180 ° C is sufficient to remove metals such as aluminum, nickel and cobalt from the hydrocarbon fraction. The contact of the hydrocarbon fraction to be treated with water at high temperatures apparently causes the agglomeration of the metallic impurities and their collection in a third phase, which forms between the hydrocarbon phase and the aqueous phase, is visually evident and which is simply mechanical, for example by filtration , can be separated. It is particularly advantageous that at the same time all metallic impurities were removed in one step and no additional chemicals are needed. This is surprising in view of the fact that the metal impurities are present not only as particles but also partially chemically bound, homogeneously dissolved or colloidally dispersed.

For certain applications of the invention in the context of integrated system concepts there is a Another advantage is that water may be incurred as a reaction product of a preceding or downstream stage and thus already exists in the process, for example in the production of synthesis gas or the subsequent Fischer-Tropsch synthesis, so that only a minimal or possibly no fresh water flow is needed here , In principle, it seems possible to recirculate the water used, if necessary after treatment.

Furthermore, the use of water according to the invention has, compared to the other methods known to those skilled in the art, the lowest demands on the corrosion resistance of the materials used for the apparatuses used. This leads to significant savings in investment costs.

The temperature plays an important role in carrying out the process according to the invention. While it was not possible at a temperature of 150 ° C, within a reaction time of 1 h to completely separate the metals, in particular the aluminum impurities, at 180 ° C within the scope of the measurement accuracy complete removal of the metals could be achieved.

Further preferred embodiments of the invention

In a preferred embodiment of the invention, the filtration is used in the process step according to claim 1. (d). It is also possible to use the centrifugation or decantation; however, the filtration offers an optimum in terms of effort and achieved separation efficiency.

In a further aspect of the invention, the aqueous liquid phase is recycled after optional treatment by the process step according to claim 1 (b). This achieves the advantages discussed above.

Execution and numerical examples

Further developments, advantages and applications of the invention will become apparent from the following description of non-limiting examples of execution and numerals. All of the described features alone or in any combination form the invention, regardless of their combination in the claims or their back-reference.

General procedure in the experiments

For the experiments described, a weight ratio between hydrocarbon mixture and water of 1: 1 was used. However, the amount of water could probably be reduced so that all metals could be concentrated in a smaller volume. This would lead to further advantages in terms of process economics since the amount of recirculated and possibly treated water would be further reduced. The stirring speed was the same in all experiments and was constantly 350 revolutions per minute. The mixture was stirred constantly from beginning to end. It is also possible to use other, preferably higher, stirring speeds as long as they ensure intensive mixing of the liquid mixture. If necessary, then the required treatment time must be adjusted in order to achieve the desired degree of metal separation. Suitable periods of time may be determined by routine experimentation. All experiments were carried out in an autoclave with an internal volume of 300 ml.

Example 1: Invention

100 g of a hydrocarbon mixture (wax fraction from the Fischer-Tropsch synthesis with a metal content of 351 ppm by weight (aluminum 220 ppm by weight, nickel 109 ppm by weight, cobalt 22 ppm by weight)) were at 85 ° C. melted and placed in an autoclave. The metal content was determined by X-ray fluorescence analysis (RFA) using the method Uniquant 2. 100 g of water were added to the melted wax and the mixture was heated to 180 ° C. with vigorous stirring. The autoclave was under a pressure of 10 bar, absolute. This temperature was held for one hour and then the mixture was cooled to 90 ° C.

Upon completion of the stirring, a gray-green phase formed which contained most of the metals and could be separated by a pleated filter. The filtrate was separated into two liquid phases (water and hydrocarbon).

Analysis of the hydrocarbon fraction showed no detectable concentrations of nickel, cobalt and aluminum. As part of the measurement accuracy, the metal impurities were thus completely removed from the hydrocarbon fraction.

Example 2: Comparative Example

Analogously to Example 1, 100 g of a hydrocarbon mixture (wax fraction from the Fischer-Tropsch synthesis with a metal content of about 351 ppm by weight (aluminum 220 ppm by weight, nickel 109 ppm by weight, cobalt 22 wt ppm )) was melted at 85 ° C and placed in an autoclave. The metal content was determined by X-ray fluorescence analysis (RFA) using the method Uniquant 2. For melted wax 100 g of water were added and the mixture was heated to 150 ° C. with vigorous stirring. The autoclave stood under a pressure of 4.7 bar, absolute. This temperature was maintained for one hour and then the mixture was cooled to 90 ° C.

Upon completion of the stirring, a gray-green phase formed which contained most of the metals and could be separated by a pleated filter. The filtrate was separated into two liquid phases (water and hydrocarbon).

The analysis of the wax showed that only 50% of the metals were removed from the hydrocarbon fraction. In the hydrocarbon fraction, 120 wt. Ppm aluminum, unquantifiable but identifiable traces of cobalt and 54 wt. Ppm nickel were found in the wax. The metal separation in this comparative example was therefore insufficient.

Industrial Applicability

The invention provides a process for the removal of metal contaminants from hydrocarbon fractions which, compared with the processes known in the prior art, is distinguished by its simplicity of apparatus and by the absence of additional, in particular process-foreign, extractants. Furthermore, it is advantageous that only substances with negligible or low hazard potential are used and the use of substances with high hazard potential, such as hydrogen fluoride, is avoided.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4801573 [0002]
• WO 98/27181 A1 [0002]
• DE 1212662 [0004]
• US 4518484 [0005]
• DE 102011013470 A1 [0006]
• WO 2006/053350 A1 [0007, 0012]

Cited non-patent literature

• Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, 1998 Electronic Release, keyword "Coal Liquefaction," Chapter 2.2 "Fischer-Tropsch Synthesis" [0002]

Claims (3)

A process for producing a low-metal hydrocarbon fraction, wherein the metals in the hydrocarbon fraction are chemically bound or dispersed in colloidal or finely dispersed form in the hydrocarbon fraction, comprising the steps of: (a) providing the metal-containing hydrocarbon fraction in liquid form, (b) contacting the liquid, metal-containing hydrocarbon fraction with a water-containing liquid phase having a pH of 7 at temperatures of at least 180 ° C. with stirring, (c) terminating the stirring, cooling and phase separation to obtain a light hydrocarbonaceous liquid phase, a heavy hydrous liquid phase and a third phase interposed between the light hydrocarbonaceous liquid phase and the heavy hydrous liquid phase and the hydrocarbon Comprising water and metal particles, (d) separating the metal particles as metal-containing precipitate with a mechanical separation process from the third phase, (e) separating the third, metal-free phase into a light, hydrocarbon-containing liquid phase and a heavy, aqueous liquid phase, combining the separated liquid phases with the corresponding liquid phases obtained in process step (c), (f) discharging the hydrocarbon-containing liquid phase as a metal-depleted hydrocarbon fraction. A method according to claim 1, characterized in that in step (d) the filtration is used. A method according to claim 1 or 2, characterized in that the aqueous liquid phase is recycled after optional treatment according to process step (b).