ES2352295B1 - PREPARATION PROCEDURE FOR NI-SN ALLOYS NANOPARTICLES AND THEIR USE IN REFORMING REACTIONS. - Google Patents

Abstract

Process for preparing alloy nanoparticles. # The present invention relates to a process for preparing Ni-Sn nanoparticles comprising # - preparing a solution of a nickel carboxylate in which said carboxylate has between 1 and 6 atoms of carbon, and a tin halide in an organic solvent # - add PVP (polyvinyl pyrrolidone) #main stirring until a homogeneous solution is obtained, # - add an inorganic reducing compound, # - reflux, obtaining a colloidal solution, # - add a polar organic solvent to the colloidal solution resulting above, causing the precipitation of a solid, # and the use of said particles in reforming reactions.

Description

Procedure for preparing nanoparticles of Ni-Sn alloys and their use in reforming reactions.

Technical field

The present invention is encompassed in the field of obtaining catalysts for reforming reactions.

Background

Forecasts on fossil fuel reserves, together with the increase in their price and increasingly stringent environmental regulations, have led to the development of processes capable of generating energy without the use of fossil fuels. Within this field, the importance of product reforming reactions such as bioethanol glycerin (byproduct of the biodiesel process) for obtaining synthesis gas is unquestionable.

These are catalytic processes that have been widely studied in recent years and on which it is known which are the most suitable metals to be used as active phases of these reactions on an industrial scale. Both chemical and economic aspects have been taken into account in this selection. The products formed in the reforming reactions are normally controlled by thermodynamics. Low temperatures favor methane formation, while high temperatures are required to obtain high hydrogen productions, which can affect the stability of the catalyst or cause the sintering of the active particles . However, the most important problem, even without solution, is the poisoning of the catalysts by carbonaceous deposits at these temperatures.This problem has been studied among others, by Trimmycol., Which have proposed series of reactions involved in the formation of coke during the methane reforming reaction:

Keep in mind that for chain hydrocarbons longer than methane, the amount of carbon formed will be more important.

In general, it can be said that the dissociation of hydrocarbons on the surface of a catalyst generates very reactive monocarbonic species that can give rise to CO. However, when the concentration of these species becomes very important or slow sugasi fi cation, they can polymerize and emit species that are much more difficult to oxidize and which will eventually block the active particle.

As a possible solution, it is proposed to prevent the formation of these monocarbon species (“carbide”). Since this composition is formed by the interaction of the orbitals 2p of the carbon with the transition metal that acts as an active phase, it has been proposed to modify the catalyst so that the transition metal orbitals are in interaction with some other suitable electronic configuration element in the original catalyst. This could be achieved by doping nickel catalysts (with a great tendency to form coke despite their high activity) with elements such as Sn, Pb, etc. If these dopants arrive alloyed with the reformed active metal, the formation of the “carbide” origin of most important carbonaceous deposits with the reaction time. In this sense, work has been carried out in which bimetallic catalysts have been prepared and the deactivation of the catalyst has been shown to decrease considerably at the cost of a loss of activity (the presence of Coke formation on the catalyst is less (and consequently also the deactivation thereof). However, the activity may decrease if the total amount of metal is kept constant because Sn is less active than nickel).

Taking into account the interest of the reforming processes, the design of catalysts capable of being active, stable and sufficiently cheap to be used on an industrial scale, is a top priority in the current state of the energy sector.

In order for a catalyst to be active, it is necessary that the reagents are adsorbed on the surface with sufficient force so that the average life time of the species allows the reaction. This adsorption force cannot be too large either, since the desorption of the reaction products would be prevented, that is, it would inhibit the reaction the active centers would be blocked.

This fundamental parameter that determines the activity of a catalyst is severely in fl uenced by the size and shape of the metal clusters on the surface. It has been established that the atoms in the corner corners of a metal cluster, with a lower average coordination number than the atoms inside the cluster, are those that have the best properties to give a good activity. This means that the higher the number of metal atoms with low average coordination number in a cluster, the greater the activity of the catalyst. This number is maximized in the case that the active phase is in the form of nanoparticles.

Therefore, it is necessary that the nickel be very active in reforming reactions, but that it presents a great tendency to form carbon. A good solution to the problem would be the synthesis of nanoparticles of Ni alloyed with Sn: the loss of activity due to the presence of this one would be compensated by the presence of nanoparticles and the formation of the "carbide" would be very limited by the alloy of both metals. As a catalytic support, alumina may be suitable if its stability properties are considered.

With the present invention, the synthesis of Ni-Snde-sized nanometric alloys has been achieved, as well as supported Ni-Sn-sized alloys of nanometric size, preferably on γ-alumina. Characterization analyzes have shown that both metals are alloyed, which will bring interesting stability properties to the catalyst in hydrocarbon reforming reactions.

Description of the invention

The present invention describes a process for preparing nanoparticles of a Ni-Sn alloy (Ni3Sn) and of the same nanoparticles supported onγ-Al2O3.

The present invention relates more specifically to a process for the preparation of Ni-Sn nanoparticles, characterized in that it comprises:

-

preparing a solution of a nickel carboxylate in which said carboxylate has between 1 and 6 carbon atoms, and a tin halide in an organic solvent

-

add PVP

-

keep stirring until a homogeneous solution is obtained,

-

add an inorganic reducing compound, preferably NaBH4

-

Reflux obtaining a colloidal solution,

-

add an organic solvent to the resulting colloidal solution, causing precipitation of a solid.

According to particular embodiments, the nickel carboxylate is nickel acetate, the tin halide is tin chloride and the organic solvent is ethylene glycol.

According to additional particular embodiments, the organic solvent solvent is one of 3 to 6 carbon atoms, preferably acetone.

The process according to the present invention may comprise, in addition to the precipitation of the solid, steps of

-

insulation, preferably by centrifugation,

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washing, preferably with one more alcohol and one or more ketones,

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dried, preferably for at least 6 hours 100 ° C.

According to particular embodiments, the isolation is carried out by centrifugation, it is carried out with acetone and dried and the drying is carried out at 100 ° C for 12 hours.

According to a particularly preferred embodiment, the procedure followed for the preparation of the nanoparticles is as follows:

•

Prepare a solution of acetate acetate (0.64g) and tin chloride (0.16g) in ethylene glycol (70mL of ethylene glycol),

•

add the appropriate amount of PVP (this parameter determines the size of the nanoparticles) (tests done for 0,0,5,0,7 and 1 grams),

•

keep stirring until a completely homogeneous solution is obtained,

•

add NaBH4 (0.34 g.) which acts as a reducing agent,

•

It will reflect 200 ° C for 2.5 hours and cool to room temperature,

•

add acetone (25 mL of acetone) to the above colloidal solution, which causes a solid to precipitate,

•

separate the solid by centrifugation,

•

wash several times with acetonayetanoly dry 100 ° C for 12 hours.

According to a variant of the process of the invention, supported nanoparticles of a Ni-Sn alloy are prepared, then adding the preparation of the tin nickel carboxylate solution in an organic solvent, an amount of a support substance, obtaining supported nanoparticles.

A further preferred embodiment of the process is characterized in that it comprises:

-

Prepare a solution of acetatedehyde (0.64g) and tin chloride (0.16g.) in ethylene glycol (70mL of ethylene glycol),

-

add an amount of a support substance, preferably alumina and more preferably, gamma-alumina

(4.2 g. Of γ-Al2O3)

-

add PVP (0.5 g.),

-

keep stirring until a completely homogeneous solution is obtained,

-

add NaBH4 (0.34 g.) which acts as a reducing agent,

-

It will reflect 200 ° C for 2.5 hours and cool to room temperature,

-

add acetone (25 mL of acetone) to the resulting colloidal solution above, causing precipitation

of a solid,

-

separate the solid by centrifugation,

-

wash repeatedly with acetonayetanoly dry 100 ° C for 12 hours.

A second object of the present invention is the use of the particles obtained by the process, in conversion reactions of organic compounds, and preferably in reforming reactions.

The present invention also relates to a method of reforming fuels which comprises contacting a feed with a catalyst constituted by the Ni-Sn nanoparticles obtained by the process described.

Brief description of the fi gures

Figure 1 shows the variation in particle size with the amount of protective agent used in the synthesis. Figure 2 shows the influence that the amount of PVP has on the particles obtained. Figure 3 shows a DRX (X-ray diffraction) diagram of supported NiyNi-Sn catalysts on

alumina after preparation, in which the support has been added for comparison.

Figure 4 shows a DRX of supported NiyNi-Sn catalysts on alumina after reduction. Support has been added to compare.

The present invention is further illustrated by the following example, which is not limiting.

Example

The described procedure has been used by varying the amount of PVP added that acts as a protective agent, it has been found that the size of the nanoparticles obtained varies linearly with the amount of protective agent.

The images of TEM (Transmission Electron Microscopy) also corroborate the formation of nanoparticles and allow them to see the influence that has the amount of PV.For example, in Figure 2, which shows images of nanoparticles prepared with PVP (a) and (b), and without PVP (c) can clearly see that effect.

In addition, the X-ray diffraction of the nanoparticles (supported in this case), show the presence of a Ni-Sn alloy, this being the only phase on the alumina after the catalyst has been reduced (Figures 3 and 4). Taking into account that the reduction is the treatment Before the catalysts normally follow before carrying out a reforming reaction, this indicates that under reaction conditions, only the Ni-Sn alloy is the one that acts as a phase-active agent.

Claims (10)

1. A procedure for the preparation of nanoparticles characterized in that it comprises: - preparing a solution of a nickel carboxylate in which said carboxylate has between 1 and 6 atoms of carbon, and a tin halide in an organic solvent

-

add PVP

-

keep stirring until a homogeneous solution is obtained,

-

add an inorganic reducing compound,

-

to reflux, obtaining a colloidal solution,

-

add an organic solvent to the resulting colloidal solution, causing precipitation

of a solid.

2.

A process for the preparation of nanoparticles according to claim 1, characterized in that the nickel carboxylate is nickel acetate, the tin halide is tin chloride and the organic solvent is ethylene glycol.

3.

A process for the preparation of nanoparticles, according to claim 1, characterized in that the inorganic reducer is NaBH4.

Four.

A process for the preparation of nanoparticles according to claim 1, characterized in that the polar organic solvent is acetone.

5.

A process for the preparation of nanoparticles, according to claim 1, characterized in that it further comprises after precipitation of the solid-isolation,

-washed -dried

6.

A process for the preparation of nanoparticles, according to claim 5, characterized in that the isolation is carried out by centrifugation, the washing is carried out with acetonay ethanoly and the drying is carried out at 100 ° C for 12 hours.

7.

A process for preparing nanoparticles according to any one of the preceding claims, characterized in that it comprises: -preparing a solution of nickel acetate and tin chloride in ethylene glycol, -add PVP, -main stirring until a completely homogeneous solution is obtained, -adding NaBH4 which acts as a reducing agent, it will reflect at 200 ° C for 2.5 hours and cool to room temperature, add acetone to the colloidal solution resulting above, causing the precipitation of a solid,

-separate the solid by centrifugation, - Wash repeatedly with acetonayetanoly and dry 100 ° C for 12 hours. 8. A process for preparing nanoparticles according to any one of the preceding claims, characterized in that it then comprises the preparation of the solution of nickel carboxylate and tin halide in an organic solvent, adding an amount of a support substance, obtaining supported nanoparticles. 9. A nanoparticle preparation process according to claim 8, characterized in that they comprise from:

-

prepare a solution of nickel acetate and tin chloride in ethylene glycol,

-

add an amount of a support substance,

-

add PVP,

-

keep stirring until a completely homogeneous solution is obtained,

-

add NaBH4 that acts as a reducing agent,

-

It will reflect 200 ° C for 2.5 hours and cool to room temperature,

-

add acetone to the resulting colloidal solution above, causing precipitation of a solid,

-

separate the solid by centrifugation,

-

wash repeatedly with acetonayetanoly dry 100 ° C for 12 hours.

SPANISH OFFICE OF THE PATENTS AND BRAND Application no .: 200901299 SPAIN Date of submission of the application: 27.05.2009 Priority Date: REPORT ON THE STATE OF THE TECHNIQUE 51 Int. Cl.: See Additional Sheet RELEVANT DOCUMENTS

Category

Documents cited Claims Affected

X

CABLE, et al., Low-temperature solution synthesis of nanocrystalline binary intermetallic compounds using the polyol process, Chem. Mater., 2005, Vol. 17, p. 6835-6841; summary; sections: " Introduction ", " Experimental Section " and "Results and Discussion"; Table 1, Figure 1. 1-9

TO

BONESI, A., et al., Synthesis and characterization of new electrocatalysts for ethanol oxidation, International Journal of Hydrogen Energy, 2008, Vol. 33, p. 3499-3501; summary and section " 2.1.Catalyst preparation ". 1-9

TO

CHEN, C.-M., et al., Intermetallic catalyst for carbon nanotubes (CNTs) growth by thermal chemical vapor deposition method, Carbon, 2006, Vol. 44, pp. 1808-1820. 1-9

TO

ARAÑA, J., et al., Bimetallic silica-supported catalysts based on Ni-Sn, Pd-Sn, and Pt-Sn as materials in the CO oxidation reaction, Chem. Mater., 1998, Vol. 10, pp. 1333 -1342; summary. 1-9

TO

CARDENAS, G., et al., Synthesis and properties of NiSn colloids using different metal ratios by CLD, Colloid. Polym Sci., 2006, Vol. 284, p. 644-653; summary. 1-9

Category of the documents cited X: of particular relevance Y: of particular relevance combined with other / s of the same category A: reflects the state of the art O: refers to unwritten disclosure P: published between the priority date and the date of priority submission of the application E: previous document, but published after the date of submission of the application

This report has been prepared • for all claims □ for claims no:

Date of realization of the report 23.11.2010

Examiner M. García Poza Page 1/4

REPORT OF THE STATE OF THE TECHNIQUE Application number: 200901299 CLASSIFICATION OBJECT OF THE APPLICATION B22F9 / 24 (01.01.2006) B22F1 / 00 (01.01.2006) C22C19 / 03 (01.01.2006) C10G35 / 06 (01.01.2006) Minimum documentation sought (classification system followed by classification symbols) B22F, C22C, C10G Electronic databases consulted during the search (name of the database and, if possible, search terms used) INVENES, EPODOC, WPI, XPESP, NPL, CAPLUS State of the Art Report Page 2/4  WRITTEN OPINION Application number: 200901299 Date of Completion of Written Opinion: 11.23.2010 Statement

Novelty (Art. 6.1 LP 11/1986)

Claims Claims 8.9 1-7 IF NOT

Inventive activity (Art. 8.1 LP11 / 1986)

Claims Claims 1-9 IF NOT

The application is considered to comply with the industrial application requirement. This requirement was evaluated during the formal and technical examination phase of the application (Article 31.2 Law 11/1986).  Opinion Base.- This opinion has been made on the basis of the patent application as published. State of the Art Report Page 3/4  WRITTEN OPINION Application number: 200901299 1. Documents considered.- The documents belonging to the state of the art taken into consideration for the realization of this opinion are listed below.

Document

Publication or Identification Number publication date

D01

CABLE, et al., Low-temperature solution synthesis of nanocrystalline binary intermetallic compounds using the polyol process, Chem. Mater., 2005, Vol. 17, p. 6835-6841.

D02

BONESI, A., et al., Synthesis and characterization of new electrocatalysts for ethanol oxidation, International Journal of Hydrogen Energy, 2008, Vol. 33, p. 3499-3501.

D03

CHEN, C.-M., et al., Intermetallic catalyst for carbon nanotubes (CNTs) growth by thermal chemical vapor deposition method, Carbon, 2006, Vol. 44, p. 1808-1820.

D04

ARAÑA, J., et al., Bimetallic silica-supported catalysts based on Ni-Sn, Pd-Sn, and Pt-Sn as materials in the CO oxidation reaction, Chem. Mater., 1998, Vol. 10, pp. 1333 -1342.

D05

CARDENAS, G., et al., Synthesis and properties of NiSn colloids using different metal ratios by CLD, Colloid. Polym Sci., 2006, Vol. 284, p. 644-653.

2. Statement motivated according to articles 29.6 and 29.7 of the Regulations for the execution of Law 11/1986, of March 20, on Patents on novelty and inventive activity; quotes and explanations in support of this statement The object of the invention is a process for preparing nanoparticles.

-

Novelty (Art. 6.1 LP):

Document D01 discloses a process for the preparation of nanoparticles comprising preparing a solution of nickel acetate and tin chloride in tetraethylene glycol, adding polyvinyl pyrrolidone, all with stirring, adding NaBH4 as a reducing agent, heating the solution, precipitating the powder. and wash it with ethanol. In view of the information disclosed in D01, the process of the invention as set forth in claims 1 to 7 is not new.

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Inventive activity (Art. 8.1 LP):

The difference between the process of the invention as set forth in claims 8 and 9 and the method disclosed in document D01 is that a support is added to the solution of nickel acetate and tin chloride in order to obtain the nanoparticles on said support. However, the process of obtaining supported nanoparticles on different supports (carbons, in different forms, silica, etc.) is well known to the person skilled in the art (see, for example, document D02 which discloses the synthesis of PtSnNi nanoparticles. supported on carbon, using the polyol-PVP method, as a catalyst for ethanol oxidation). Therefore, in view of the state of the art, the process of the invention, as set out in claims 8 and 9, lacks inventive activity. State of the Art Report Page 4/4