WO2015025268A1

WO2015025268A1 - Method for purifying a mixture comprising liquid hydrocarbons, especially btx, and water

Info

Publication number: WO2015025268A1
Application number: PCT/IB2014/063967
Authority: WO
Inventors: Stefan Maurer; Riichiro Kimura; Andrei-Nicolae PARVULESCU; Pedro SA GOMES; Stefan Marx; Lorenz Siggel; Ulrich Müller
Original assignee: Basf Se; Basf China Company Limited
Priority date: 2013-08-22
Filing date: 2014-08-19
Publication date: 2015-02-26
Also published as: AR102017A1

Abstract

The invention relates to a method for purifying a mixture comprising at least one liquid hydro- carbon and water by at least partly separating off the at least one liquid hydrocarbon from the mixture, the method comprising the step of passing the mixture through a sorption agent comprising at least one porous metal-organic framework material, wherein the at least one metal- organic framework material comprises at least one organic compound coordinated to at least one metal ion, wherein the at least one organic compound is based on imidazole, which is unsubstituted or substituted with one or more substituents independently selected from the group consisting of C_1-6 alkyl, phenyl and benzyl. The invention further relates to the use of such metal-organic framework material for purifying the mixture.

Description

Method for purifying a mixture comprising liquid hydrocarbons, especially BTX, and water Description

The present invention relates to a method for purifying a mixture by a sorption agent, wherein the mixture comprises at least one liquid hydrocarbon and water by at least partly separating off the at least one liquid hydrocarbon from the mixture. The invention further relates to the use of such a sorption agent for purifying the mixture.

Mixtures containing liquid hydrocarbons and water often have to be separated of by air stripping, chromatography, rectification procedures known from the prior art.

However a problem is the exhaustive removal of hydrocarbons even after such processes in order to obtain an aqueous phase with no detectable amounts or only traces of impurities in the purified water.

Here the choice of sorption material plays an important role.

Many sorption materials such as inorganic mineral materials [C. Teas, S. Kalligeros, F. Zanikos, S. Stournas, E. Lois, G. Anastopoulos, Investigation of the effectiveness of absorbent materials in oil spills clean up, Desalination 140 (2001 ) 259-264], synthetic materials [X.M. Zhou, C.Z. Chuai, Synthesis and characterization of a novel high-oilabsorbing resin, J. Appl. Polym. Sci. 1 15 (2010) 3321-3325] and natural materials have been widely studied for the removal of hydrophobic material, like hydrocarbons. However, these materials still have limitations such as low oil sorption capacity, limited availability at larger scale, high costs, or poor reusability.

Very recently a porous polymer (covalent porphyrine framework) showing also promising properties towards absorbance of organics was published [X.-S. Wang, J . Liu, J. M. Bonefont, D.-Q. Yuan, P. K. Thallapally, S. Ma, Chem. Commun. 49 (2013) 1533-1535] claiming highest adsorp- tive capacities. This material however relies on highly sensitive Yamamoto coupling to build up the porous framework, making its scale up impossible on an industrial basis.

The take up of liquids using porous metal-organic framework material in general is known from EP 1 702 925 A1 . Also specific metal-organic framework materials are described for the uptake of hydrocarbons and alcohols in H . Wu et al., Chem. Rev. 1 12 (2012), 836-868. Fluorous metal- organic framework material for oil spill cleanup is described in C. Yang et al., J. Am. Chem. Soc. 133 (201 1 ), 18094-18097.

ZIF-8 material is used as sorbent for fast analysis of acidic drugs in environmental water samples (Journal of Chromatography A, 1257 (2012), 19-24). The extraction of polycyclic aromatic hydrocarbons (PAHs) is described by D. Ge et al., Journal of Chromatography A, 1263 (2012), However there is a need for more advanced metal-organic framework materials for the purification of liquids comprising hydrocarbons.

Accordingly an object of the present invention is to provide a method for the purification of a liquid mixture comprising at least one hydrocarbon using a metal-organic framework material (MOF) having at least partly better properties as described above.

The object is achieved by a method for purifying a mixture comprising at least one liquid hydrocarbon and water by at least partly separating off the at least one liquid hydrocarbon from the mixture, the method comprising the step of

(a) passing the mixture through a sorption agent (adsorbent) in at least one adsorption vessel comprising at least one porous metal-organic framework material, wherein the at least one metal-organic framework material comprises at least one organic compound coordinated to at least one metal ion, wherein the at least one organic compound is based on imidazole, which is un- substituted or substituted with one or more substituents independently selected from the group consisting of Ci-6 alkyl, phenyl and benzyl.

The object is further achieved by the use of a sorption agent (adsorbent) in at least one adsorption vessel for purifying a mixture comprising at least one liquid hydrocarbon and water, wherein the sorption agent comprises at least one porous metal-organic framework material, wherein the at least one metal-organic framework material comprises at least one organic compound coordinated to at least one metal ion, wherein the at least one organic compound is based on imidazole, which is unsubstituted or substituted with one or more substituents independently selected from the group consisting of Ci-6 alkyl, phenyl and benzyl.

Surprisingly, it has been found that the porous metal-organic framework material described herein shows exceptional good properties, such as hydrophobicity, defined structure and pore diameter distribution resulting in favorable uptake kinetics towards liquids, high stability towards temperature and moisture.

Below preferred embodiments are described being preferred for both, the method of the present invention as well as the use of the present invention.

In general, in case the term "comprise" or "comprising" is used this also refers to "consisting of. The term "liquid" means the liquid state under standard conditions of 20°C and 1023 mbar.

Preferably, the amount of the at least one liquid hydrocarbon in the mixture is in the range of from 1 *10 ⁷ % by weight to 5 % by weight based on the total weight of the mixture. More preferably, the range is from 2*10⁷ % by weight to 0.5 % by weight based on the total weight of the mixture. Even more preferably, the range is from 2*10 ⁷ % by weight to 0.3 % by weight based on the total weight of the mixture. According to the present invention the sorption agent comprises at least one porous metal- organic framework material. Thus the sorption agent comprises one or more, like two three or four, metal-organic framework materials. However preferably, only one metal-organic framework material is comprised. It is also possible that the sorption material consists of at least one porous metal-organic framework material, i.e. the sorption material is the metal-organic framework material or a mixture of metal-organic framework materials.

The sorption agent can also comprise further sorbent material and/or additives. Suitable sorbent materials are activated charcoal or zeolites.

The porous metal-organic framework material comprises at least one organic compound coordinated to at least one metal ion. The metal-organic framework material can also consist of one or more than one metal ions, where more than one ion can differ from each other by chemical nature and/or charge. Also one or more, like two, three or four, organic compounds are possible. Most preferably, the porous metal-organic framework material consists of one metal ion and one organic compound. Such metal-organic framework material can be prepared according to methods known in the art. Examples can be found in WO 2007/131955 A1 or WO 2013/005160 A1 .

Preferably, the at least one metal ion is selected from the group of metals consisting of copper, iron, aluminum, zinc, magnesium, zirconium, titanium, vanadium, molybdenum, tungsten, indium, calcium, strontium, cobalt, nickel, platinum, rhodium, ruthenium, palladium, scandium, yttrium, a lanthanide, manganese and rhenium. More preferably, the at least one metal ion is Zn²⁺.

According to the present invention the at least one organic compound is based on imidazole, which is unsubstituted or substituted with one or more (preferably one or two, more preferably one) substituents independently selected from the group consisting of Ci-6 alkyl, phenyl and benzyl.

The term Ci-6 alkyl refers to an alkyl chain having one to six carbon atoms. The alkyl group can be straight-chained or branched. Examples are methyl, ethyl, n-propyl, i-propyl, n-butyl, sec- butyl, tert.-butyl, n-pentyl, n-hexyl. Preferred group is methyl and ethyl. Even more preferred is methyl.

In one aspect the imidazole is unsubstituted. In another aspect the imidazole is substituted. Preferred substituents are methyl, ethyl, phenyl, benzyl. More preferred is methyl, ethyl, and benzyl. Even more preferred is methyl. A preferred substitution is in 2-position of the imidazole.

Even more preferred is the at least one organic compound 2-methylimidazole, 2-ethylimidazole, 2-benzylimidazole or a deprotonated form thereof (i.e. the imidazolate).

In a most preferred embodiment the metal-organic framework material is Zn-2- methylimidazolate. The term "based on" means that imidazole, which can also be partly or fully deprotonated (anion), is used. Thus the metal-organic framework material may have all imidazolates in deprotonated form or only part of them.

The liquid can comprise or consist of liquid aliphatic hydrocarbons like hexane, heptane or octane. Further possible hydrocarbons are aromatic hydrocarbons, like benzene or naphthene or aliphatic and aromatic hydrocarbons, like toluene.

However preferably, the mixture comprises at least one of the liquid hydrocarbons selected from the group consisting of benzene, toluene, ethylbenzene and a xylene (o-xylene, m-xylene and/or p-xylene) (BTEX), more preferably BTX. Even more preferred comprises the mixture benzene, toluene and at least one xylene. Even more preferred comprises the mixture benzene, toluene, ethylbenzene and at least one xylene.

The mixture contains at least one liquid hydrocarbon and water. The mixture can also comprise one or more mineral salts. This is especially the case, when the mixture sea water contaminated with liquid hydrocarbons. Also possible as source of the mixture is contaminated water from rivers, lakes or groundwater.

The sorption agent is placed in at least one adsorption vessel. In a preferred embodiment the sorption agent is comprised in one or more adsorption columns (fixed bed column). In a preferred embodiment the sorption agent (adsorbent) is comprised in a single or multiple adsorption vessels arranged in series and/or in parallel.

Preferably, the at least one metal-organic framework material is in form of shaped bodies. This also applies to the complete binder agent. The preparation of shaped bodies is described for example in WO-A 03/102000 or WO-A 2006/050898. Further methods are known in the art. A shaped body can contain further additives or consists of the at least one metal-organic framework material (binder agent).

The conversion step of molding, shaping or forming and the like may be achieved by any method known to an expert to achieve agglomeration of a powder, a suspension or a paste-like mass.

In general, the following main pathways can be discerned: (i) briquetting, i.e. mechanical pressing of the powdery material, with or without binders and/or other additives, (ii) granulating (pelletizing), i.e. compacting of moistened powdery materials by subjecting it to rotating movements, and (iii) sintering, i.e. subjecting the material to be compacted to a thermal treatment.

Specifically, the molding step is preferably performed by using at least one method selected from the following group: briquetting by piston presses, briquetting by roller pressing, binderless briquetting, briquetting with binders, pelletizing, compounding, melting, extruding, co-extruding, spinning, deposition, foaming, spray drying, coating, granulating, in particular spray granulating or granulating according to any process known within the processing of plastics or any combination of at least two of the aforementioned methods.

The molding may be affected by extrusion in conventional extruders, for example such that result in extrudates having a diameter of, usually, from about 1 to about 10 mm, in particular from about 1 ,5 to about 5 mm. Such extrusion apparatuses are described, for example, in Ullmann's Enzylopadie der Technischen Chemie, 4th Edition, Vol. 2, p. 295 et seq., 1972. In addition to the use of an extruder, an extrusion press is preferably also used for molding.

The preferred process of molding is performed at elevated pressure, i.e. by pressing of the MOF containing powder. The pressure may range from atmospheric pressure to several 100 bar. Also elevated temperatures (ranging from room temperature to 300°C) or in a protective atmosphere (noble gases, nitrogen or mixtures thereof) are suitable. Any combination of these conditions is possible as well.

The conditions under which the pressing may be accomplished depend on, e.g. the press, the filling height, the press capacity, and the form of the shaped body.

Preferred shaped bodies are granulates and extrudates.

Preferably, the at least one metal-organic framework material is recycled after step (a). Also the at least one organic liquid can be recycled. Suitable methods for the recycling are known in the art. Recovery can be achieved by thermal swing adsorption.

The sorption agent can be reused when regenerated, or reactivated, preferably by temperature swing, inert or solvent driven displacement purge and elution/desorption cycles, among other methods known from adsorption processes prior art.

Examples

Synthesis of Basolite Z1200 (Zinc-lmidazolate, ZIF-8)

A solution of zink sulfate hepta-hydrate (800 g) in deionized water (2666 g) was prepared. In a separate vessel a second solution was prepared by adding 2-methylimidazole (456 g) to water (2666 g). To the second solution methanol (2222 g) was added within one hour. After allowing the second solution to stir for 1 .25 h solution 1 was added to solution 2 over a period of 1 hour and 10 minutes. During the addition of zinc sulfate solution to the imidazole solution, a white suspension was formed. The resulting suspension was stirred for 1 hour and 15 minutes at 27°C with a stirring speed of 90 min-1. To that suspension NaOH solution (50 wt%, 444 g) was added slowly keeping the temperature below 30°C. After stirring the suspension for another 1 hour and 15 minutes the content of the vessel was released on a filter and washed ten times with deionized water until the conductivity of the filtrate was below 100 (+/- 50) με. For each washing step 1 I of deionized water were used. The water was layered over the material for one hour and afterwards sucked trough the filter cake. The wet filter cake was dried in a circulating air oven for 24h at 120°C. 600 g of Basolite Z1200 were obtained exhibiting a Langmuir surface area of 1804 m²/g.

Experimental Procedure

One-stage (batch) equilibrium experiments were performed to evaluate the loading capacity (adsorbed quantity) of a benzene toluene and xylenes (BTX) mixture, present in a salt water solution, on Basolite Z1200 at room temperature, i.e., specific portions of a problem mixture (M) were allowed to contact with also specific quantities of the adsorbent within closed flasks, in a shaking flask-cabinet, for a considerable long time period at constant temperature.

Example 1 Removal of toluene from a synthetic salt water solution

Basolite Z1200 adsorbent in powder form was dried overnight at approximately 100 °C; - A synthetic mixture (M 1 ) was prepared by adding 0,406 g of toluene, 13,139 g CaCl2*2H₂0, 5,800 g of MgCI₂*6H₂0 and 89,398 g of NaCI to 2,0 kg of demineralized water; the pH value was corrected to 5,5-6,0 with HCI;

200-300 g of the synthetic mixture M 1 was poured into different glass flasks containing different amounts of the adsorbent (see Table 1 ). In addition, 200 g of the synthetic mixture M 1 was poured into a flask without adsorbent, to serve as reference sample (Table 1 ); All the flasks were closed and allowed to reach equilibrium while shaking with a frequency of 175 min ¹ for approximately 70 hours at room temperature;

A 1 -2 g sample was taken from each flask (Exp. E1 .1 to E1.6) thru a 0,45 μιτι syringe filter and analyzed for toluene content by means of gas chromatography. An extra sample was taken from the reference flask by means of a regular syringe (no filter, E1.7), and similarly analyzed for toluene content, to assess the influence of the filtration procedure (see Table

1 )-

Table 1 - Toluene content in the mixture after 70 hours contact with different quantities of Basolite Z1200, room temperature.

Equilibrium concentraToluene load¬

Mixture (M1 ) Basolite Z1200

Exp. tion ing

(mL) (g)

toluene (mg/L) (g/100 g ads)

E1.1 300 0,050 126 27,6

E1.2 300 0,077 94 30,4

E1.3 200 0,102 27 28,4

E1.4 200 0,200 8 16,4

E1.5 200 0,500 <5 >6,7

E1.6 0,000 172 —

E1.7 0,000 177 — From the results in Table 1 , it can be observed that the toluene content from the synthetic mixture M 1 was significantly reduced by action of the adsorbent Basolite Z1200. In particular, the high adsorbent amount flasks (Exp 1 .4 or Exp 1 .5), revealed that it is possible to effectively decrease the toluene concentration, in the salt water solution, from 177 mg/L down to a value lower than 10 mg/L in a single stage.

The calculation of the resulting toluene loading in Basolite Z1200 revealed a rather favorable adsorption equilibrium isotherm, where loading values above 27.5 g of toluene per 100 g adsorbent can be reached for toluene concentration in the analyzed solution as low as 27 mg/L.

Example 2 Removal of Benzene, toluene and xylene (BTX) from a real salt water solution

Basolite Z1200 adsorbent in powder form was dried overnight at approximately 100 °C; A real BTX mixture in salt water (M2) was considered;

300 g of the mixture M2 was poured into different glass flasks containing different amounts of the adsorbent (see Table 2). In addition, a 100 g of the mixture M2 was poured into a flask without adsorbent, to serve as reference sample (Table 2);

All the flasks were closed and allowed to reach equilibrium while shaking with a frequency of 175 min ¹ for approximately 70 hours at room temperature;

A 1 -2 g sample was taken from each flask (Exp. E2.1 to E2.3) thru a 0,45 μιτι syringe filter and analyzed for benzene, toluene and xylene content by means of gas chromatography. An extra sample was taken from the reference flask by means of a regular syringe (no filter, E2.4), and similarly analyzed for BTX content, to assess the influence of the filtration procedure (see Table 2).

Table 2 - BTX content in the mixture after 70 hours contact with different quantities of Basolite Z1200, room temperature.

Mixture Basolite Equilibrium

Exp.

(M2) Z1200 (ng/L) (HQ/L) (HQ/L)

(mL) (g) Benzene Toluene Xylenes

E2.1 300 0,50 680 18 3

E2.2 300 1 ,00 400 5 <2

E2.3 0,000 740 46 3

E2.4 0,000 940 63 3,9

As can be observed in Table 2, with a relatively low amount of Basolite Z1200 (compared to the amount of mixture ) it seems to be possible to remove a considerable amount of BTX from the initial salted mixture (more than 30 % in the 1 g adsorbent per 300 g M2 sample, E2.2).

Claims

Patent Claims

1 . A method for purifying a mixture comprising at least one liquid hydrocarbon and water by at least partly separating off the at least one liquid hydrocarbon from the mixture, the method comprising the step of

(a) passing the mixture through a sorption agent in at least one adsorption vessel comprising at least one porous metal-organic framework material, wherein the at least one metal-organic framework material comprises at least one organic compound coordinated to at least one metal ion, wherein the at least one organic compound is based on imidazole, which is unsubstituted or substituted with one or more substituents independently selected from the group consisting of Ci-6 alkyl, phenyl and benzyl.

2. The method of claim 1 , wherein the amount of the at least one liquid hydrocarbon in the mixture is in the range of from 1 *10 ⁷ % by weight to 5 % by weight based on the total weight of the mixture.

3. The method of claim 1 or 2, wherein the mixture comprises at least one of the liquid hydrocarbons selected from the group consisting of benzene, toluene, ethylbenzene and a xylene.

4. The method of claim 3, wherein the mixture comprises at least benzene, toluene and a xylene.

5. The method of any one of claims 1 to 4, wherein the at least one metal ion is selected from the group of metals consisting of copper, iron, aluminum, zinc, magnesium, zirconium, titanium, vanadium, molybdenum, tungsten, indium, calcium, strontium, cobalt, nickel, platinum, rhodium, ruthenium, palladium, scandium, yttrium, a lanthanide, manganese and rhenium.

6. The method of any one of claims 1 to 5, wherein the at least one metal ion is Zn²⁺.

7. The method of any one of claims 1 to 6, wherein the at least one organic compound is 2- methylimidazole, 2-ethylimidazole, 2-benzylimidazole or a deprotonated form thereof.

8. The method of any one of claims 1 to 7, wherein the at least one porous metal-organic framework material is Zn-2-methylimidazolate.

9. The method of any one of claims 1 to 8, wherein the at least one metal-organic framework material is in form of shaped bodies.

10. The method of any one of claims 1 to 9, wherein the sorption agent consists of the at least one porous metal-organic framework material.

1 1 . The method of any one of claims 1 to 10, wherein the sorption agent is comprised in an adsorption column.

12. The method of any one of claims 1 to 1 1 , wherein the mixture further comprises one or more mineral salts.

13. The method of any one of claims 1 to 12, wherein the at least one metal-organic framework material is recycled after step (a).

14. The method of any one of claims 1 to 13, wherein after step (a) the at least one liquid hydrocarbon is recycled.

15. Use of a sorption agent in at least one adsorption vessel for purifying a mixture comprising at least one liquid hydrocarbon and water, wherein the sorption agent comprises at least one porous metal-organic framework material, wherein the at least one metal-organic framework material comprises at least one organic compound coordinated to at least one metal ion, wherein the at least one organic compound is based on imidazole, which is un- substituted or substituted with one or more substituents independently selected from the group consisting of Ci-6 alkyl, phenyl and benzyl.