WO2014202815A1

WO2014202815A1 - Adsorbent composite material comprising noble metals and a surfactant polymer, synthesis method and use thereof for the desulfurisation of fluids

Info

Publication number: WO2014202815A1
Application number: PCT/ES2014/070504
Authority: WO
Inventors: Ramón PONS PONS; Jordi MORROS CAMPS
Original assignee: Consejo Superior De Investigaciones Científicas (Csic); Recursos Energéticos De Biomasa, S.L.
Priority date: 2013-06-21
Filing date: 2014-06-20
Publication date: 2014-12-24
Also published as: ES2527359A1; ES2527359B1

Abstract

The invention relates to a material with a large specific surface area, consisting of a surfactant polymer and metal nanoparticles. The invention also relates to the synthesis method of said material, and to the use thereof as a desulfurising agent with a high level of efficiency, in fluids containing impurities of sulfurated compounds, especially liquid fuels, and more especially in derivatives of oil and other sources used in the field of energy.

Description

ADSORBENT COMPOSITE MATERIAL THAT INCLUDES NOBLE METALS AND A TENSIOACTIVE POLYMER, SYNTHESIS PROCEDURE AND ITS USE

FOR THE DESULFURATION OF FLUIDS DESCRIPTION

SECTOR AND OBJECT OF THE INVENTION

The present invention is located in the sectors of the oil, energy and environmental industries, since it refers to an adsorbent composite material comprising noble metals in a reduced state and surfactant polymers, its synthesis process and its use for the treatment of sulfur removal in fluids. STATE OF THE TECHNIQUE

In the current context of oil depletion, it is increasingly important to try to use fuels derived from fossil resources as effectively as possible and with the best possible quality. The reduction of sulfur in fuels is a necessary measure to reduce the harmful impact on the quality of the air produced during the combustion of hydrocarbons (gasoline, diesel, jet fuel, heavy fuel, natural gas, etc.). The combustion of sulphurous compounds present as an impurity produces sulfur oxides that are responsible, among other phenomena, for acid rain and the increase of suspended particles. On the other hand, the acidification of gases has irreversible effects on the metal parts of internal combustion engines, especially in the catalytic agents of the emission control system, reducing their catalytic efficiency for the oxidation of carbon monoxide, hydrocarbons and compounds. volatile organic, resulting in higher levels of environmental pollution (Pet. Technol. Q., 2001, 2, 69-73). Likewise, the presence of sulphurous compounds in effluents from other industries is a general problem and whose discharge into the environment can lead to environmental pollution problems parallel to those generated by the combustion of sulfur-containing products as well as industrial safety and human health problems. The obvious concern about the negative impact on health and the environment has sparked an active public debate about energy generation and its environmental derivatives. Thus, legislative initiatives have been agreed for the regulation of the proportion of sulfur present in liquid fuels and the emission limits of polluting gases. Thus, according to European directive 2003/17 / CE the maximum sulfur content in gasoline and diesel for use in road vehicles is 10 mg / kg (10 ppm). Also, the International Maritime Organization (IMO) and the European Union (EU) have established limits to reduce the sulfur content in heavy fuels used in marine engines.

In view of the growing need to reduce the sulfur content of fuels, the industry is devoting more and more efforts to the development of more effective, more sustainable and less dangerous alternative technologies (Catal. Sci. Technol., 201 1, 1 , 23-42). Current technologies for desulfurization of liquid fuels mainly include hydrodesulfurization (HDS), oxidative desulfurization (ODS), catalytic cracking, biodesulfurization and adsorption desulfurization, among others.

The HDS is the most powerful method used in refineries to produce low sulfur gasoline and diesel. This technique is based on the catalytic hydrogenation of the various sulfur compounds present in hydrocarbons. Normally, its range of application is the products of primary distillation and oil cracking with levels above 1000 ppm of sulfur in some cases. Even so, HDS technology has some limitations that do not allow its use in many other fields of application such as fuel cells or heavy fuels. These limitations are mainly due to two factors, the presence of polyaromatic compounds (of three or more rings) that alter the normal functioning of desulfurization (Environ. Sci. Technol. 2008, 42, 1944-1947) and, the presence of compounds thiophenes (thiophene, benzothiophene and dibenzothiophenes among others) very resistant to hydrogenation and requiring more severe conditions (high temperatures and pressures of hydrogen gas) to be eliminated (RSC Advances, 2012, 2, 1700-171 1). These factors prevent, for example, the obtaining of products with ultra low sulfur levels (<10 ppm), a basic requirement for the fuel cell power supply, as well as the use of the HDS in the recovery of heavy fuels for industry, where the proportion of asphaltens is often very high. Another problem presented by the HDS is that secondary reactions such as olefin saturation are also favored during the process, which increases the number of cetans and, in turn, decreases the octane number. This is an ideal feature for diesel engines, if not for the extra increase in capacity and amount of hydrogen needed in the process.

The other techniques, much less used, are being improved and optimized with good results but are not yet applicable on an industrial scale. This is the case of oxidative desulfurization (ODS), a technique based on the oxidation to water-soluble compounds of sulfur compounds that achieves significant reductions, up to two orders of magnitude, in the sulfur content of residual fuels (Energy & Fuels 2000 , 14, 1232-1239). Another case is the biodesulphurization technique, which uses living organisms instead of chemicals as oxidizing agents (Current Opinion in Biotechnology 2000, 1 1: 540-546). However, in both cases, its implementation on an industrial scale still requires great efforts.

Another desulfurization technique is desulfurization by selective adsorption. A priori more sustainable than the previous two since it does not use organic solvents and has a lower energy cost, selective adsorption desulfurization is a technique based on the preferential adsorption of sulfur compounds in porous adsorbent matrices that allow the passage of fuel through the same. While conventional adsorbents (active carbon, silica gel, alumina, etc.) do not achieve very good results, a molecular design of the adsorbent can greatly increase desulfurization yields. An example of this are the zeolites (clay nanoparticles) modified with transition metals (SCIENCE 301, 79, 2003) or with some metallic oxides of Ti, Zn, Mn, etc., which finely divided manage to quantitatively reduce the sulfur in the laboratory (WO2002018517, WO2001032805). This zeolite-based technique still has some drawbacks that seriously hinder its industrial application. One of them is that to be viable the technique is necessary to regenerate the adsorbent. In this case there is a possibility of regeneration, but in each cycle 5% of the desulfurizing capacity is lost. Another drawback of using zeolites in this technique is that their density does not differ much from the density of liquid fluids. This slows the separation of zeolites from the fluid, which in turn slows down each regeneration cycle.

It is also known to use noble metals in reduced states, especially in the form of nanoparticles, as catalysts to increase the desulfurization capacity in any of the known heavy fuel treatment processes (US20100314286).

On the other hand, the techniques conventionally used to achieve the synthesis of nanoparticles of metals in reduced states that have adsorbent capacities, require the combination of various agents to obtain the appropriate results (Adv Coll Int Sci, 2009, 145, 83-96). Thus, for example, the review article Chem. Mater 2013, 25 (9), 1465-1476 indicates the use of a combination of ascorbic acid and cetyl trimethyl ammonium bromide or oleyl amine.

However, and in the knowledge of the inventors, there is no known method of selective adsorption of sulfur in fluid fuels or in any other type of industrial effluents, which uses only noble metals in a reduced state, and which are obtained according to the procedure that here it is protected, in order to achieve the effective reduction of sulfur levels in said fluids, with high sulfur capture yields per gram of adsorbent and, in addition, allowing its regeneration.

EXPLANATION OF THE INVENTION Brief description of the invention

The present invention relates to a composite material, with a high specific surface area and high sulfur selective adsorption capacity, comprising nanoparticles of noble metals in a state of reduced valence that is mostly 0 and molecules of a surfactant polymer, substantially added .

The invention also relates to the synthesis process of said composite material, which comprises the following steps: a) preparing an aqueous cationic solution comprising at least one "noble metal"cation;

b) preparing an aqueous solution comprising at least one surfactant polymer with moderately reducing groups;

c) add the solution of step (a) on the solution of step (b) and allow to react, until reduction of the metal cation, giving rise to the composite material; and d) isolation and stabilization of the composite material of step (c).

Alternatively, the above steps (a), (b) and (c) can be condensed in a single stage (a ^' ) in which the metal cation and polymer are dissolved in a single aqueous solution that is allowed to react until reduction of the metal cation

The invention also relates to the use of the composite material for the removal of sulfur in fluids, especially in fluid fuels, and more especially in petroleum derivatives or other sources dedicated to the field of energy.

Finally, the invention relates to a process for removing sulfur in fluids, which comprises the following steps:

i) contacting the composite material with the fluid fuel to be treated, to produce the desulfurization of the fluid;

ii) separating the desulfurized fluid from the resulting composite material; Y

iii) regenerate at least a portion of the resulting composite material by substantially removing adsorbed sulfur. Detailed description of the invention

The present invention is based on the observation that a composite material, which has a high specific surface area, and which comprises nanoparticles of noble metals and a surfactant polymer, allows reversible interaction with sulfur compounds, which gives it the capacity as adsorbent for its use in desulfurization by selective adsorption of fluids (see Examples 4 to 6), allows its separation of desulfurized fluid and its regeneration through desorption of sulfur compounds (see Example 6). The present invention is also based on the observation that it is the synthesis process of the composite material that uses at least one cation of a noble metal and at least one surfactant polymer containing moderately reducing groups (see Examples 1.1, 1.2 and 1.3), which favors the composite material having the characteristics that define it, and which are: a substantially aggregate state, a reduced valence state that is mostly 0 and a high specific surface.

The technical advantages of the composite material, its synthesis procedure, and its use for the desulfurization of fluid fuels are indicated below:

a) composite material:

- it has a high specific surface area, a high desulfurization capacity and is easily separable from the reaction medium;

b) synthesis procedure:

-It is simple, economical and uses environmentally acceptable solvents and materials;

c) use as a desulfurization agent in fluids:

- allows its use in fluids that have a kinematic viscosity between 0.1 and 1000 cS at 1 pressure atmosphere,

- allows its use to obtain ultra-low levels of sulfur, and work with substrates from 5 ppm to moderately high levels (20,000 ppm) in the fluid to be treated,

- it has a high potential for regenerative capacity in relation to other adsorbents such as zeolites or carbon nanotube based adsorbents,

-allows its regeneration almost unlimitedly through simple treatments, -presents high chemical stability during the regeneration process due to its high surface and internal purity, and

-It presents a low cost and environmental impact.

That is why a first aspect of the invention is a composite material with selective sulfur adsorption capacity, which comprises a percentage by weight of nanoparticles of noble metals in a state of reduced valence that is mostly 0, and a percentage in minor weight of a surfactant polymer, hereinafter composite material of the invention, having a total specific surface area greater than 1 m ² / g and an apparent radius of less than 300 nm. In an embodiment of the first aspect of the invention, the composite material of the invention comprises a percentage by weight of the surfactant polymer over the total weight of the material between 0 and 50% (w / w), and more preferably between 0.1 and 10% (p / p). Said value can be obtained from the thermogravimetric analysis of the dry material.

In another embodiment of the first aspect of the invention, the composite material of the invention comprises noble metal particles of dimensions between 2 and 300 nanometers that are forming aggregates of dimensions between 1 and 10,000 microns together with surfactant polymer molecules.

In another embodiment of the first aspect of the invention, the metal nanoparticles are of noble metals, preferably silver, copper or gold, and more preferably silver.

The term "noble metal" means a metal that has a more positive standard reduction potential than the standard hydrogen reduction potential.

By the term "surfactant polymer" is meant in the present invention covalently linked monomer chains that in their overall structure have hydrophilic regions and hydrophobic regions. Said regions may be a product of the chemical nature of two different monomers (one hydrophilic and one hydrophobic) or the inclusion of modifications on a hydrophilic or hydrophobic polymer. In addition, the surfactant polymers in the present invention contain moderately reducing groups, that is, they have in their chemical structure groups with moderately positive reduction potential, such as, for example, without limiting the hydroxyl or aldehyde group. Examples of surfactant polymers are hydrophobically modified polysaccharides and hydrophobically modified ethoxylated polymers, in particular fructose and hydroxyethylcellulose polymers.

In another embodiment of the first aspect of the invention, the surfactant polymer is a hydrophobically modified polysaccharide, and is preferably hydrophobically modified inulin. In another embodiment of the first aspect of the invention, the composite material of the invention is a powder material or is redispersed in an organic solvent, preferably hydrocarbon type, or in a sulfur-free aliphatic alcohol, or in a mixture of both.

In a preferred embodiment of the first aspect of the invention, the composite material of the invention is redispersed in a proportion between 5 and 95% (w / w), in a hydrocarbon-type organic solvent. In a more preferred embodiment of the first aspect of the invention, the composite material of the invention is redispersed in a hydrocarbon in a proportion between 5 and 50% (w / w), which is preferably n-hexadecane.

A second aspect of the invention constitutes a synthesis process of the composite material of the invention, hereinafter a synthesis process of the invention, comprising the following steps:

to. preparing an aqueous cationic solution comprising at least one noble metal cation;

b. preparing an aqueous solution comprising at least one surfactant polymer with moderately reducing groups;

C. add the solution of step (a) on the solution of step (b) and let it react, preferably at a temperature between 70 and 110 ° C, until reduction of the metal cation, resulting in the formation of the composite material of the invention;

d. insulation and stabilization of the composite material formed in step (c).

Alternatively, the above steps (a), (b) and (c) can be condensed in a single stage (a ') in which the metal cation and polymer are dissolved in a single aqueous solution that is allowed to react until reduction of the metal cation Thus, this patent application also refers to a synthesis process of the composite material of the invention, comprising the following steps:

a ^' , prepare an aqueous solution comprising at least one noble metal cation and at least one surfactant polymer with moderately reducing groups and allow to react, preferably at a temperature between 70 and 110 ° C, up to reduction of the metal cation, resulting in the formation of the composite material of the invention; Y

b ^' . insulation and stabilization of the composite material formed in step (a ^' ). Throughout the present invention, "metallic cation" means any noble metal that allows obtaining a material of reduced valence state that is mostly 0 and an aggregation state corresponding to a finely divided solid. The metal cation may be, by way of indication and not limitation, copper, silver or gold, and preferably silver.

The synthesis process of the invention that is protected, in any of the alternatives described in this patent application, is the first process that uses a surfactant polymer containing moderately reducing groups as a single agent to achieve a triple function: as an agent reducer, as an inducing agent for nanoparticle aggregation and as a protective agent. The use of this polymer allows that the nanoparticles obtained are not individualized, but that they are presented in substantially aggregate form, as indicated by Morros et al. (Soft Matter, 2012, 8, 1 1353) for inulin aggregates. In this way, it is possible to obtain a material that combines a high specific surface (which confers high efficiency and effectiveness), with a secondary aggregation that makes it useful for use as an easily separable adsorbent.

By "reaction crude" is meant an aqueous solution comprising the solutions and compounds of steps (a) and (b), or of step (a '), of the synthesis process of the invention, in which it takes place the reaction from its beginning to the end of it.

The term "reducing agent" means any chemical species that, in contact with the cation of the metal of interest, provides the necessary electrons for its passage to metal, being its standard potential for negative reduction.

By "protective agent" (in English "capping agent") means any chemical species sufficiently related to metal surfaces whose presence in solution produces an adsorbed layer that prevents the growth of the crystal formed by metal atoms. Usually these are surfactants that form a barrier between the particle and the solution cations. In an embodiment of the second aspect of the invention, the metal cation of step (a) or (a ') is chosen from any noble metal that allows obtaining a material of reduced valence state that is mostly 0 and an aggregation state corresponding to a finely divided solid, selected by way of indication and not limiting between, silver cation, copper cation and gold cation and preferably silver cation.

In another embodiment of the second aspect of the invention, the metal cation of step (a) or (a ') is used according to one of the following presentations, soluble salt or solution of the metal in strong oxidizing acid medium and preferably in the form of salt soluble.

In a preferred embodiment of the second aspect of the invention, the metal cation of step (a) or (a ') is a solution of the silver cation.

It will be obvious to the person skilled in the art that any solution that, in the presence or absence of chemical species, such as pH regulating agents, does not precipitate the metal cation, can not be used as a cationic solution, does not form a complex that stabilizes it in its oxidation state making the reduction unfeasible and does not compete with the metal cation for the reducing agent.

In another embodiment of the second aspect of the invention, the metal cation of step (a) or (a ') is diluted in a pH regulating solution that is selected by way of illustration and not limited to citric bicarbonate / carbonate solutions. / citrate, acetic acid / acetate and formic / formate, to obtain a pH value between 2.0 and 8.5. More preferably the solution is acetic / acetate.

In another preferred embodiment of the second aspect of the invention, the surfactant polymer containing moderately reducing groups of step (b) or (a ') is a hydrophobically modified polysaccharide, preferably hydrophobically modified inulin.

For those skilled in the art, it will be apparent that it is possible to use other surfactant polymers containing moderately reducing groups, such as, without limitation, hydrophobically modified hydroxyethylcellulose or ethoxylated polymers. By the term "hydrophobically modified inulin" in the present invention, a copolymer molecule is understood as consisting of a linear skeleton of fructose with average degrees of polymerization comprised between 10 and 100 units of D-fructosyl linked by β bonds [2 → 1 ] and various hydrophobic chains linked by ether, amide or ester bonds.

In another embodiment of the second aspect of the invention, the surfactant polymer containing moderately reducing groups of step (b) or (a ') is dissolved in a pH regulating solution. For illustrative and non-limiting purposes, it is selected from bicarbonate / carbonate, citric / citrate, acetic acid / acetate, and formic / formate solutions, to obtain a pH value between 2.0 and 8.5. More preferably the solution is acetic / acetate. In another embodiment of the second aspect of the invention, the isolation of the composite material obtained in step (d) or (b ^' ) is performed by some technique selected, by way of illustration and not limitation, from among the following, filtration, sedimentation or centrifugation of the reaction crude, preferably centrifugation. In another embodiment of the second aspect of the invention, in the stabilization of the isolated composite material according to step (d) or (b ^' ), some technique selected is used, by way of illustration and not limitation, of the following, drying and / or redispersion of the material obtained. Preferably, the composite material obtained is redispersed in an organic solvent, more preferably hydrocarbons, or in a sulfur-free aliphatic alcohol, or in a mixture of both.

To achieve this redispersion, it is convenient to remove the water with successive washes with an intermediate polarity solvent, preferably isopropyl alcohol, before incorporating the material obtained in the organic solvent.

In another embodiment of the second aspect of the invention, stabilization of the composite material according to step (d) or (b ^' ) is carried out by redispersion in the organic solvent in a proportion between 5 and 95% (p / p). In a preferred embodiment of the second aspect of the invention, the redispersion of the composite material is made in a proportion between 5 and 50% (w / w) and the hydrocarbon-type organic solvent is sulfur-free n-hexadecane. A third aspect of the invention is the use of the composite material of the invention as a high performance desulphurizing agent applicable in fluids containing impurities of sulfur compounds, hereinafter employed by the invention, especially in fluid fuels, and more especially in derivatives of the oil or other sources dedicated to the field of energy.

In the present invention, "fluids containing impurities of sulfur compounds" means liquids or gases that in their chemical composition have significant amounts of sulfur, which by their use or simple existence pose some risk to the environment and / or human health and / or the viability of industrial processes. Some examples of them, without limitation, are fluid fuels, industrial effluents, domestic effluents or sulphurous waters.

By "sulfur" is meant in the present invention sulfur in any form such as, without limitation, elemental sulfur or a sulfur compound usually present in fluid fuels, such as diesel fuel, cracked gasoline, etc. Examples of sulfur that may be present in a process of the present invention include, without limitation, hydrogen sulfide (H ₂ S), carbon disulfide (CS ₂ ) and all the various families of sulfur compounds, which contain sulfur atoms. in its chemical structure, such as mercaptans, sulphides and organic disulfides, thiophenes, benzothiophenes, dibenzothiophenes, alkylthiophenes, alkylbenzothiophenes, and combinations thereof.

By "fluid fuel" is meant in the present invention a compound that combined with oxygen releases energy and can be in the form of a liquid, such as gasoline, kerosene, fuel oil, diesel fuel or diesel; in the form of gas, such as hydrogen, natural gas or liquefied petroleum gases; or as a combination of both. By "industrial effluent" is meant in the present invention an effluent containing sulfur compounds released by industries, especially chemical ones, that may endanger the population by inhalation or ingestion of said compound. By "domestic effluent" is meant in the present invention an effluent containing sulfur compounds released by homes, such as and without limitation, some medications, which may endanger the environment, especially wild flora and fauna. "Sulphurous waters" means in the present invention waterways with sulfur compounds that, due to their proximity to natural sources of sulfur or due to their passage along with any other of the aforementioned effluents, pose a risk to the environment and / or the population The sulfur desulfurization or removal process of the fluid is based on the adsorption of impurities of sulfur compounds in the composite material of the invention.

Thus, a fourth aspect of the invention constitutes the fluid desulphurization process that employs the composite material of the invention, hereinafter fluid desulphurization process of the invention, and which comprises at least the following steps:

i) contacting the composite material of the invention, with the fluid to be treated, to produce the desulfurization of the fluid;

ii) separating the desulfurized fluid from the resulting sulfurized composite material; and iii) regenerating at least a part of the sulfurized composite material by substantially removing adsorbed sulfur, under suitable conditions of pressure, temperature and using a recovery agent.

By "sulfurized composite material" is meant the composite material of the invention that has been used, at least, in a fluid desulfurization treatment.

In an embodiment of the fourth aspect of the invention, the temperature of step (i) is comprised between the melting point of the fluid and 100 ° C. Preferably the temperature is between 0 and 50 ° C. In another embodiment of the fourth aspect of the invention, the pressure of step (i) is between 0.1 bar and 300 bar. Preferably, the pressure is between 0.1 bar and 100 bar, more preferably it is the atmospheric pressure. In another embodiment of the fourth aspect of the invention, the initial concentration of sulfur in the fluid is below 2% (w / w) and a ratio between 1 and 100g of composite material of the invention per gram of sulfur is used. .

The separation of the desulfurized fluid, either liquid or gas, from the sulphide composite material resulting from step (i) can be carried out by any method known to one skilled in the art, referring to liquid-solid, gas-solid separation systems . Suitable examples may be, without limitation, centrifugation, filtration, decantation, sedimentation. Preferably the separation system is by centrifugation.

"Regeneration" means the process by which the impurities of sulfur compounds can be removed from the surface of the sulphide composite material, and thus achieve that said material becomes active again as a desulfurizer. In a preferred embodiment of the fourth aspect of the invention, the regeneration of the sulphided composite material is carried out by treating said material with an inert gas stream, preferably nitrogen, an organic solvent stream, such as dichloromethane, or by heat application in vacuum conditions. The regeneration with an organic solvent stream is carried out at a temperature between 0 and 100 ° C. Regeneration with an inert gas stream or under vacuum is carried out at a temperature between 100 ° C and 750 ° C, preferably between 100 ° C and 300 ° C, and more preferably at 250 ° C. Said regeneration is carried out, for a period of time sufficient to substantially remove adsorbed sulfur which may be between 1 second and 60 minutes.

In another embodiment of the fourth aspect of the invention, the regeneration percentage of the composite material of the invention per cycle (adsorption / desorption) is greater than 95%, preferably greater than 98% and more preferably greater than 99%. Throughout the description and the claims the word comprises and its variants are not intended to exclude other technical characteristics, components or steps. For those skilled in the art, other objects, advantages and features of the invention will be derived partly from the description and partly from the practice of the invention. The following examples and drawings are provided by way of illustration, and are not intended to be limiting of the present invention.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 a. Scanning electron micrograph at 10000X of the composite material of the invention using silver as a metal cation, hereinafter AgNPs, obtained according to the procedure indicated in Example 1.1.

Figure 1 b. Scanning electron micrograph at 100000X of the composite material of the invention using silver as a metal cation, hereinafter AgNPs, obtained according to the procedure indicated in Example 1.1.

Figure 1 c. Scanning electron micrograph at 10000X of the composite material of the invention using gold as a metal cation, hereinafter AuNPs, obtained according to the procedure indicated in Example 1.2.

Figure 1 d. Scanning electron micrograph at 10000X of the composite material of the invention using copper as a metal cation, hereinafter CuNPs, obtained according to the procedure indicated in Example 1.3.

Figure 2. Percentages of sulfur adsorbed as a function of the amount of adsorbent dispersed per gram of commercial fluid fuel, using the AgNPs material according to Example 4.1 and 4.2. The circles and squares represent the values obtained with a dispersion of AgNPs at 8% (w / w) in n-hexadecane and with a dispersion of AgNPs at 40% (w / w) in n-hexadecane, respectively.

Figure 3. Adsorption kinetics at 25 ° C in model fluid. Percentage of sulfur adsorbed as a function of the amount of adsorbent dispersed in a model fluid (1% solution (w / w) of thiophene in n-hexadecane), using the AgNPs material according to Example 5. EMBODIMENT OF THE INVENTION

Several examples are described below that illustrate details of the composite material of the invention, of the synthesis process of the invention, of its use for the removal of sulfur in various fluids and of the process of desulfurization of fluids of the invention, which do not limit without However the present invention.

Analytical techniques The determination of the amount of sulfur present in the model fluids was performed on aliquots by means of high performance liquid chromatography (HPLC) using a Hitachi device, equipped with a UV detector and a Lichro-sphere CN 5 μηι column. The mobile phase used was 50% H ₂ 0, 50% acetonitrile (v / v). The determination of the amount of sulfur present in commercial fluids and the amount and composition of the organic matter of the composite material of the invention, was carried out directly by means of the organic elemental analysis by the microanalysis service of the Institute of Advanced Chemistry of Catalonia and also by the X-ray fluorescence technique using a MinipaU (Panalytical) device equipped with a Rhodium anode.

The determination of the percentage of polymer in the composite material of the invention was determined by thermogravimetric analysis performed in the Microcalorimetry service of the Institute of Advanced Chemistry of Catalonia.

The specific surface determination was calculated from the small angle X-ray scattering curves (SAXS). The equipment used was a HECUS S3-micro coupled to a GENIX-Fox-3D source and a PSD 50 HECUS detector. Samples of the composite material of the invention were analyzed in dodecane dispersion.

Scanning electron micrographs of the composite material of the invention using silver, gold or copper as a metal cation were performed in a HITACHI TM1000 at 15Kv and 10000x. For AgNPs, high resolution observations were also made with a JEOL team in the scientific and technical services of the University of Barcelona. Fourier transform infrared spectroscopy was performed using a 360-FTIR Nicolet Avatar.

The salts of the metal cations were obtained from the supplier Sigma-Aldrich and the hydrophobically modified inulin polymer was obtained, courtesy of the manufacturer, Beneo BBC (Belgium).

A. OBTAINING THE COMPOUND MATERIAL OF THE INVENTION The preparation of the composite material of the invention is described below, using nanoparticles of silver, gold and copper, according to the two alternatives of the synthesis process of the invention, with adsorbent capacity and which hereafter referred to as AgNPs, AuNPs and CuNPs respectively. EXAMPLE 1. Preparation of the composite material of the invention

EXAMPLE 1.1. Preparation of the AgNPs material according to the synthesis method of the invention

20 g of a 12.5% silver nitrate (w / w) solution in a 1.0 M buffer solution (Acetic / Acetate) at pH 5.5 were combined with 20 g of a hydrophobically modified inulin solution (Inutec® SP1) at 10 % (w / w) in a buffer solution (Acetic / Acetate) 1.0 M at pH 5.5. Then, the resulting solution was allowed to react for a period of 12 hours at 85 ° C with constant stirring and protected from light. Subsequently, the reaction crude was centrifuged. The sediment obtained was washed with water a total of 3 times by decantation / centrifugation cycles. Finally, the precipitate formed by substantially aggregated silver nanoparticles was redispersed using sulfur-free n-hexadecane to reach a weight concentration of 8% in hexadecane or dried in an oven at 100 ° C. Analysis of the small angle X-ray scattering (SAXS) revealed a total specific surface area of 75 m ² / g and an apparent radius of 40 nm. By thermogravimetry it was determined that the material, once dried, suffered a weight loss corresponding to 3.25% when heated to 520 ° C under a nitrogen atmosphere. By means of organic elemental analysis it was determined that the material contained 1.8% (w / w) of carbon, 0.25% (w / w) of hydrogen and 0.06% (w / w) of nitrogen. These proportions are in accordance with the presence of reducing polymer, and its oxidation products, used in the synthesis of the material.

Figure 1 shows the scanning electron micrograph of the solid obtained, where it is observed that its surface is composed of nanoparticles in substantially aggregate form smaller than what is obtained by other procedures, which gives an appearance of roughness (determination to 10,000 increases). Figure 1b, with 100,000 increases shows that said roughness is produced by silver nanoparticles.

The analysis by FT-IR in potassium bromide pellet showed characteristic signals of hydrocarbon chains at wave numbers of 2921 cm ^"1 and 2852 cm ^{" 1} , of the carbonyl of the carbamate ester at wave number 1696 cm ^"1 , of alcohol, a broad band centered at 3400 cm ^"1 and another narrower at 1030 cm ^{" 1} and, finally, signals corresponding to carboxylate anions at wave numbers of 1570 cm ^"1 and 1404 cm ^{" 1.} Of all these signals, the latter do not they are present in hydrophobically modified inulin and signal the partial oxidation thereof in the composite material.

The process of the present invention makes it possible to obtain a material comprising nanoparticles of noble metals in substantially aggregate form with a larger adsorbent surface. The control of obtaining these particles depends on the conditions of pH, temperature and especially the reducing agent used.

EXAMPLE 1.2. Preparation of the AuNPs material according to the synthesis method of the invention

0.208 g of gold chloride (III) trihydrate, 0.270 g of hydrophobically modified inulin (Inutec® SP1), 0.5 g of sodium acetate and 5 g of deionized water were weighed. Then, the resulting solution was allowed to react for a period of 12 hours between 90 ° C and 100 ° C with constant agitation and protected from light. Subsequently, the reaction crude was centrifuged. The sediment obtained was washed with water a total of 3 times by decantation / centrifugation cycles. Finally, the precipitate formed by gold nanoparticles in substantially aggregated form was redispersed using sulfur-free n-decane or dried in an oven at 100 ° C. Figure 1 c shows the scanning electron micrograph of the solid obtained where it is observed that its surface is composed of nanoparticles in substantially aggregate form with some roughness. EXAMPLE 1.3. Preparation of the CuNPs material according to the synthesis method of the invention

To 75 g of a dispersion of 6.67% basic copper (II) carbonate (w / w) in water, 3.35 g of formic acid was added (until total carbonate solubilization was reached, and a pH of 3.4). This solution was combined with 77.5 g of a 22% (w / w) aqueous hydrophobically modified inulin solution (Inutec® SP1).

Then, the resulting solution was allowed to react for a period of 12 hours between 90 ° C and 100 ° C with constant agitation and protected from light. Subsequently, the reaction crude was centrifuged. The sediment obtained was washed with water a total of 3 times by decantation / centrifugation cycles. Finally, the precipitate formed by copper nanoparticles in substantially aggregate form was redispersed using sulfur-free n-decane to reach a weight concentration of 8% in decane or dried in an oven at 100 ° C.

Figure 1 d shows the scanning electron micrograph of the solid obtained where it is observed that its surface is composed of nanoparticles in substantially aggregate form with some roughness. B.- FLUID DESULFURATION

Next, several examples of sulfur reduction processes in a commercial fluid fuel, with a sulfur content of 1% (w / w), using different adsorbent systems are described.

EXAMPLE 2. Using precipitated silver in the presence of ascorbic acid

In this case the adsorbent was precipitated silver obtained by precipitation of the metal in the presence of ascorbic acid as a reductant. In a 3 ml vial, 1 g of commercial fluid hydrocarbon, containing 1% (w / w) sulfur, was weighed, and 250 mg of the dry adsorbent material was added. The mixture was homogenized and allowed to react for 24 hours at room temperature. Once the reaction was over, the crude was centrifuged until effective separation of the adsorbent was achieved.

The sulfur content of the supernatant liquid, corresponding to the fluid hydrocarbon, was analyzed by elemental organic analysis. The result obtained was a sulfur content of 0.92% (w / w). The final results are also expressed as a function of the sulfur desulfurizing or adsorption capacity as the mg of sulfur adsorbed per g of adsorbent. Thus, the adsorption capacity of this adsorbent was 3 mg S / g Adsorbent and it was increased to 4 mg S / g Adsorbent when desulfurization was performed in the presence of 10% (v / v) water. EXAMPLE 3. Using commercial micrometric silver

Following the same procedure described in Example 2, but using 250 mg of Sigma-Aldrich commercial micrometric silver scales (10 μηι) as adsorbent material. The results obtained showed an adsorption capacity for this adsorbent of 5 mg S / g Adsorbent.

When the process was performed at 80 ° C the adsorbent capacity was 2 mg S / g.

EXAMPLE 4.Using dispersed AgNPs material at different concentrations

4.1. 8% AgNPs (w / w) in n-hexadecane

The same procedure described in Example 2 was followed, but using a dispersion of substantially aggregated silver nanoparticles (AgNPs) in 8% hexadecane (w / w), obtained according to the procedure set out in Example 1.1. In this case different amounts of adsorbent dispersion (0, 200, 400 and 800 mg) were tested, the fuel weights being respectively: 2.2 g, 2 g, 1.8 g and 1.4 g, to have a final weight of 2.2 g in all cases. The sulfur analyzes before (by deduction) and after (directly) the treatment of the previous samples were carried out after 24 hours of contact and were the following: from 1.00 to 1.00% (w / w), from 0.92 to 0.67% (p / p), from 0.85 to 0.36% (p / p) and from 0.75 to 0.33% (p / p), respectively.

The results of the desulfurization process with the commercial hydrocarbon using a dispersion of substantially added silver nanoparticles (AgNPs) in 8% hexadecane (w / w), showed a maximum adsorption capacity of 347 mg S / g Adsorbent, according results obtained by elementary analysis. The content of S in the sample was reduced from 0.85% to 0.36% (w / w), corresponding to the third case. The results of the percentage of sulfur adsorbed with respect to the initial as a function of the amount of AgNPs are presented in Figure 2. This figure shows an asymptotic curve where a percentage of saturation of the adsorbent is observed around 45% of adsorbed sulfur.

4.2. 40% AgNPs (w / w) in n-hexadecane

The same procedure described in Example 4.1 was followed, but using a dispersion of substantially aggregated silver nanoparticles (AgNPs) in 40% hexadecane (w / w), obtained according to the procedure set out in Example 1.1. In this case different amounts of adsorbent dispersion (0, 200, 400 and 800 mg) were tested, the fuel weights being respectively: 2.2 g, 2 g, 1.8 g and 1.4 g, to have a final weight of 2.2 g in all cases. The sulfur analyzes before (by deduction) and after (directly) the treatment of the previous samples were carried out after 24 hours of contact and were the following: from 1.00 to 1.00% (w / w), from 0.95 to 0.67% (p / p), from 0.90 to 0.58% (p / p) and from 0.82 to 0.38% (p / p), respectively. The results of the fluid desulfurization process of the invention with the commercial hydrocarbon using a dispersion of substantially aggregated silver nanoparticles (AgNPs) in 40% hexadecane (w / w) sulfur showed a maximum adsorption capacity of 46 mg S / g Adsorbent, according to results obtained by elementary analysis. The content of S in the sample was reduced from 0.82% to 0.38% (w / w), corresponding to the fourth case of the series. The percentage results of sulfur adsorbed with respect to the initial as a function of the amount of AgNPs are presented in Figure 2. This figure shows an asymptotic curve where a saturation percentage of the adsorbent is observed around 40% (w / w) of adsorbed sulfur.

As can be seen from the previous examples, the yield as adsorbent and therefore the desulfurization capacity is much higher using the AgNPs material as adsorbent.

Table 1. Maximum adsorbent capacity of silver particles of Examples 2, 3 and 4.

EXAMPLE 5. Using powdered AgNPs in a 1% (w / w) solution of thiophene in hexadecane

To a 1% (w / w) solution of thiophene in hexadecane (2 mL) as a model fluid fuel, 250 mg of powdered AgNPs were added. The mixture was homogenized and allowed to react for 48 hours at room temperature. Once the reaction was over, the crude was centrifuged until effective separation of the adsorbent was achieved. The analysis of the amount of sulfur compound present in the supernatant liquid was carried out at different reaction times up to a total of 48 hours. In this case, high efficiency liquid chromatography (HPLC) coupled to a UV-Vis detector was used to determine the concentration of aliquots at each time. As can be seen in Figure 3, where the kinetics of this process are shown, desulfurization occurred in two stages, a rapid first and a slower one. In the first stage, of 3h, the amount of dissolved sulfur compound was reduced by 40% (w / w), and in the second stage a reduction of 75% with respect to the initial concentration was reached. EXAMPLE 6: Using 40% AgnPs (w / w) in hexadecane in a 0.23% dibenzothiophene solution (w / w) in dodecane as a fluid fuel

The same procedure as described in Example 4 was followed, but in this case 400 mg of 40% dispersion (w / w) of AgNPs in hexadecane was used on 1 mL of a 0.23% solution of dibenzothiophene (DBT) ( p / p) in dodecane as a model fluid fuel and a time of 20 hours.

6.1. Model fluid fuel and original AgNPs dispersion

Freshly prepared samples of the AgNPs material and the 0.23% DBT solution (w / w) were used. A reduction of DBT was observed up to 0.16% (w / w) (a 30% reduction from the initial concentration), regardless of the reaction time (see Table 2).

6.2. Fluid fuel model previously desulfurized and dispersion of original AgNPs

A second desulfurization cycle was performed using the fluid resulting from Example 6.1 after removing the above sulfur adsorbent and 400 mg of a new 40% (w / w) dispersion of AgNPs was added. A reduction of DBT concentration in the supernatant liquid was observed from 0.16% (see Example 6.1) to 0.13% (w / w) (i.e. a reduction from 30% to 45% with respect to the initial concentration, see Table 2).

6.3. Model fluid fuel and regenerated AgNPs dispersion

400 mg of a 40% dispersion (w / w) of regenerated AgNPs on 1 mL of a 0.23% solution of dibenzothiophene (w / w) in hexadecane was used. The regeneration of AgNPs was carried out by 3 successive washes with 5 ml of dichloromethane.

It was observed that the concentration of dissolved DBT in the model fluid was reduced by 30% with respect to the initial concentration (Table 2). This example shows that the AgNPs, once regenerated as indicated in the general procedure, still have a substantially unchanged desulfurizing capacity. Table 2. Capacity of regeneration of the adsorbent power of AgNPs material determined by HPLC in a model fluid based on dodecane and dibenzothiophene as a source of sulfur.

DBT peak area

Time AgNPs new + fuel AgNPs new + fuel model AgNPs regenerated + fuel (min) model 0.23% (p / p) DBT desulfurized 1 time model 0.23% (p / p) DBT

0 7.36 5.22 7.36

1 5.38

5 4.04 5.01

75 5.53

180 5.79

1200 5.22 4.12

Claims

1. Composite material with selective sulfur adsorption capacity, characterized in that it comprises a percentage by weight of nanoparticles of noble metals in a state of reduced valence that is mostly 0, and a percentage by weight of a surfactant polymer, and by which has a total specific surface area greater than 1 m ² / g and an apparent particle radius of less than 300 nm.

2. Composite material according to claim 1, characterized in that the weight percentage of the surfactant polymer is between 0.1 and 10%.

3. Composite material according to any one of claims 1 and 2, characterized in that the noble metal nanoparticles have dimensions between 2 and 300 nanometers and are forming aggregates of dimensions between 1 and 10,000 microns with surfactant polymer molecules.

4. Composite material according to any one of claims 1 to 3, characterized in that the metal nanoparticles are gold, silver or copper.

5. Composite material according to claim 4, characterized in that the metal nanoparticles are silver.

6. Composite material according to any one of claims 1 to 5, characterized in that the surfactant polymer is a hydrophobically modified polysaccharide.

7. Composite material according to claim 6, characterized in that the surfactant polymer is hydrophobically modified inulin.

8. Composite material according to any one of claims 1 to 7, characterized in that it is a powder material or that is redispersed in an organic solvent or in a sulfur-free aliphatic alcohol, or in a mixture of both.

9. Composite material according to claim 8, characterized in that it is redispersed in a hydrocarbon in a proportion between 5 and 50% (w / w).

10. Synthesis process of the composite material according to any one of claims 1 to 9, characterized in that it comprises the following steps:

a) preparing an aqueous cationic solution comprising at least one noble metal cation;

c) add the solution of step (a) to the solution of step (b) and allow to react until reduction of the metal cation resulting in the formation of the composite material; Y

d) isolation and stabilization of the composite material formed in step (c).

1 1. Synthesis process of the composite material according to any one of claims 1 to 9, characterized in that it comprises the following steps:

a ^' . preparing an aqueous solution comprising at least one noble metal cation and at least one surfactant polymer with moderately reducing groups and reacting until reduction of the metal cation, resulting in the formation of the composite material of the invention; Y

b ^' . insulation and stabilization of the composite material formed in step (a ^' ).

12. Method according to any one of claims 10 or 1, characterized in that the noble metal cation of step (a) or (a ') is chosen from a silver cation, a copper cation or a cation of gold.

13. Method according to claim 12, characterized in that the noble metal cation of step (a) or (a ') is a silver cation.

14. Method according to any one of claims 10 to 13, characterized in that the surfactant polymer containing moderately reducing groups of step (b) or (a ') is a hydrophobically modified polysaccharide.

15. Process according to claim 14, characterized in that the surfactant polymer containing moderately reducing groups of step (b) or (a ') is a hydrophobically modified inulin polymer.

16. Method according to any one of claims 10 to 15, characterized in that the composite material, isolated according to step (d) or (b ^' ), is redispersed in a proportion between 5% and 50% (p / p) in a hydrocarbon-type organic solvent, or in a sulfur-free aliphatic alcohol, or in a mixture of both.

17. Use of the composite material according to any one of claims 1 to 9 as a desulfurizing agent in fluids containing impurities of sulfur compounds.

18. Use of the composite material according to claim 17 wherein the fluid is a fluid fuel.

19. Use of the composite material according to claim 18 wherein the fluid fuel is a petroleum derivative.

20. Procedure for removing impurities of sulfur compounds in fluids characterized in that it comprises the following steps:

i) contacting the composite material according to any one of claims 1 to 9 with the fluid to be treated, to produce the desulfurization of the fluid;

ii) separating the desulfurized fluid from the resulting sulfurized composite material; and iii) regenerating at least a part of the sulfur composite material by substantially removing adsorbed sulfur, using a recovery agent.

21. Method according to claim 20, characterized in that in step (i) the temperature is between the melting point of the fluid and 100 ° C and that the pressure is between 0.1 bar and 300 bar.

22. Method according to claim 21, characterized in that the temperature is between 0 and 50 ° C and the pressure is between 0.1 bar and 100 bar.

23. Method according to any one of claims 20 to 22, characterized in that the initial concentration of sulfur in the fluid is below 2% (w / w) and a ratio between 1 and 100 g of adsorbent material is used. per gram of sulfur.

24. Method according to any one of claims 20 and 23, characterized in that in step (ii) a technique selected from centrifugation, filtration, decantation, evaporation and sedimentation is used.

25. Method according to any one of claims 20 to 24, characterized in that in step (iii), a material regeneration treatment is used by passing an organic solvent stream, by passing an inert gas stream, or by vacuum conditions.

26. Method according to claim 25, characterized in that in step (iii) a material regeneration treatment is used by passing an organic solvent stream at a temperature between 0 and 100 ° C, for a period of time comprised between 1 second and 60 minutes.

27. A method according to claim 25, characterized in that in step (iii) a regeneration treatment is used with an inert gas stream or under vacuum at a temperature between 100 and 750 ° C for a period of time between 1 Second and 60 minutes.

28. Procedure according to claim 27, characterized in that the temperature is between 100 and 300 ° C.