WO2018094683A1

WO2018094683A1 - A process for producing a supported amination catalyst

Info

Publication number: WO2018094683A1
Application number: PCT/CN2016/107222
Authority: WO
Inventors: Lin FANG; Zhen YAN; Barry William Luke Southward; Marc Pera Titus
Original assignee: Rhodia Operations; Le Centre National De La Recherche Scientifique
Priority date: 2016-11-25
Filing date: 2016-11-25
Publication date: 2018-05-31

Abstract

A process for producing a supported amination catalyst,which comprises (i) anoble metal and/or a noble metal compound, (ii) abase metal and/or a base metal compound and (iii) aredox active support. Catalyst produced by the process has higher catalytic activity over those produced by conventional ways.

Description

A process for producing a supported amination catalyst

The present invention concerns a process for producing a supported amination catalyst comprising (i) a noble metal and/or a noble metal compound, (ii) a base metal and/or a base metal compound and (iii) a redox active support.

PRIOR ART

The following discussion of the prior art is provided to place the invention in an appropriate technical context and enable the advantages of it to be more fully understood. It should be appreciated, however, that any discussion of the prior art throughout the specification should not be considered as an express or implied admission that such prior art is widely known or forms part of common general knowledge in the field.

Cerium oxide supporting noble metal catalysts are widely used in amination reaction. WO15054828 and WO16074121 reports amination of alcohols using catalysts comprising palladium or palladium compound supported on cerium oxide. Avelino Corma, et al. Chemistry-A European Journal (2012) , 18 (44) , 14150-14156 discloses reaction ofalcohols and amines using Au/ceria catalyst.

There are also studies focusing on base metal supported by cerium oxide. US4209424 describes an amination catalyst comprising at least one metal selected from nickel, cobalt and copper impregnated on a microporous substrate selected from the group consisting of alumina, silica, thorium oxide and cerium oxide. The catalyst could further contain rhodium as promotor. Specifically, the transition metal content represents 30％-70％based on total weight of catalyst and maximum content of noble metal is 0.1％by weight of rhodium relative to the weight of catalyst.

CN 102403836 teaches a method for preparation of dibenzylamine by reacting benzaldehyde and ammonia by using a catalyst comprising palladium as primary catalyst, and nickel, ruthenium, osmium, iridium, copper or tin as cocatalyst, and titanium, silica, ceria or tin oxide as carrier. The loading of primary catalyst is in the range of 0.1-0.5％. The loading of cocatalyst is in the range of 0.01-0.2％. The catalyst mentioned is formed by conventional one-step process. Specifically, the carrier is immersed in a nitric acid solution and heated to reflux at 100℃for 7 hours. After it is washed to be a neutral solution, at least one cocatalyst chosen from nickel, ruthenium, osmium, iridium, copper or tin is added to the solution, as well as required palladium chloride and sodium hydroxide. The catalyst is then prepared after washing and drying.

Nevertheless, abovementioned amination catalysts are still not ideal as they have the disadvantages of high metal loading, complexity of manufacture or low catalytic activity and/or selectivity.

INVENTION

It is therefore an objective of this invention to provide an improved amination catalyst with desired characteristics such as decreased cost, decreased environmentally impact and higher catalytic activity and/or selectivity and overcome the drawbacks in prior arts.

According to a first aspect, the present invention therefore pertains to a process for producing a supported catalyst comprising (i) a noble metal and/or a noble metal compound, (ii) a base metal and/or a base metal compound and (iii) a redox active support.

The invention also concerns an optimized supported amination catalyst susceptible of being obtained by the process.

The present invention also relates to use of supported amination catalyst susceptible of being obtained by the process for amination reaction of alcohol or aldehyde to produce amines. It is possible to get higher conversion of amines and selectivity of secondary amine by using invented catalyst than using catalyst produced by conventional methods.

Other characteristics, details and advantages of the invention will emerge more fully upon reading the description which follows.

DEFINITIONS

For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are collected here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skill in the art. The terms used herein have the meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth below.

The articles “a” , “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

The term “and/or” includes the meanings “and” , “or” and also all the other possible combinations of the elements connected to this term.

Throughout the description, including the claims, the term "comprising one" should be understood as being synonymous with the term "comprising at least one" , unless otherwise specified, and "between" should be understood as being inclusive of the limits.

It should be noted that in specifying any range of concentration, any particular upper concentration can be associated with anyparticular lower concentration.

It is specified that, in the continuation of the description, unless otherwise indicated, the values at the limits are included in the ranges of values which are given.

As used herein, metals of group IB, IIB, IIIB, IVB, VB, VIB, VIIB and VIIIB are often referred to as transition metals. This group comprises the elements with atomic number 21 to 30 (Sc to Zn) , 39 to 48 (Y to Cd) , 72 to 80 (Hfto Hg) and 104 to 112 (Rfto Cn) .

As used herein, the term “Lanthanides” refer to metals with atomic number 57 to 71.

As used herein, rare earth metal (REM) , is one of a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides, as well as scandium and yttrium. Rare earth elements are cerium (Ce) , dysprosium (Dy) , erbium (Er) , europium (Eu) , gadolinium (Gd) , holmium (Ho) , lanthanum (La) , lutetium (Lu) , neodymium (Nd) , praseodymium (Pr) , promethium (Pm) , samarium (Sm) , scandium (Sc) , terbium (Tb) , thulium (Tm) , ytterbium (Yb) and yttrium (Y) .

As used herein, the term "hydrocarbon group" refers to a group mainly consisting of carbon atoms and hydrogen atoms, which group may be saturated or unsaturated, linear, branched or cyclic, aliphatic or aromatic.

As used herein, the term “alkyl” refers to a monovalent saturated aliphatic (i.e. non-aromatic) acyclic hydrocarbon group which may be linear or branched and does not comprise any carbon-to-carbon double bond or any carbon-to-carbon triple bond. Representative saturated straight chain alkyls include methyl, ethyl, n-propyl, n-butyl, n-pentyl, and the like； while saturated branched alkyls include isopropyl, sec-butyl, isobutyl, tert-butyl, isopentyl, and the like.

As used herein, the term "alkenyl" refers to a monovalent unsaturated aliphatic acyclic hydrocarbon group which may be linear or branched and comprises at least one carbon-to-carbon double bond while it does not comprise any carbon-to-carbon triple bond. Representative unsaturated straight chain alkenyls include ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl and the like.

As used herein, the term "aryl" refers to a monovalent aromatic hydrocarbon group, including bridged ring and/or fused ring systems, containing at least one aromatic ring. Examples of aryl groups include phenyl, naphthyl and the like. The term "arylalkyl" or the term "aralkyl" refers to alkyl substituted with an aryl. The term "arylalkoxy" refers to an alkoxy substituted with aryl.

As used herein, the term "cyclic group" means a closed ring hydrocarbon group that is classified as an alicyclic group, aromatic group, or heterocyclic group. The term "alicyclic group" means a cyclic hydrocarbon group having properties resembling those of aliphatic groups.

As used herein, the term "cycloalkyl" as used herein means cycloalkyl groups containing from 3 to 8 carbon atoms, such as for example cyclohexyl.

As used herein, the term “heterocyclic" as used herein means heterocyclic groups containing up to 6 carbon atoms together with 1 or 2 heteroatoms which are usually selected from O, N and S, such as for example radicals of : oxirane, oxirene, oxetane, oxete, oxetium, oxalane (tetrahydrofurane) , oxole, furane, oxane, pyrane, dioxine, pyranium, oxepane, oxepine, oxocane, oxocinc groups, aziridine, azirine, azirene, azetidine, azetine, azete, azolidine, azoline, azole, azinane, tetrahydropyridine, tetrahydrotetrazine, dihydroazine, azine, azepane, azepine, azocane, dihydroazocine, azocinic groups and thiirane, thiirene, thiethane, thiirene, thietane, thiete, thietium, thiolane, thiole, thiophene, thiane, thiopyrane, thiine, thiinium, thiepane, thiepine, thiocane, thiocinic groups.

"Heterocyclic" may also mean a heterocyclic group fused with a benzene-ring wherein the fused rings contain carbon atoms together with 1 or 2 heteroatom’s which are selected from N, O and S.

As used herein, the terminology " (C_n-C_m) " in reference to an organic group, wherein n and m are each integers, indicates that the group may contain from n carbon atoms to m carbon atoms per group.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is the curves demonstrating the catalytic efficiency of (a) 2wt. ％Pd/CeO₂, (b) 0.5wt. ％Pd-0.5wt. ％Ni/CeO₂ (EX2) and (c) 0.5wt. ％Pd-0.5wt. ％Ni/CeO₂ (EX3) .

Figure 2 is H₂-TPR curves of (a) 0.5wt. ％Pd/CeO₂ (EX1) , (b) 0.5wt. ％Pd-0.5wt. ％Ni/CeO₂ (EX2) and (c) 0.5wt. ％Pd-0.5wt. ％Ni/CeO₂ (EX3) .

DETAILS OF THE INVENTION

The present invention provides a process for producing a supported amination catalyst comprising (i) a noble metal and/or a noble metal compound, (ii) a base metal and/or a base metal compound and (iii) a redox active support, comprising the steps of:

(a) forming a dispersion D₁ comprising the redox active support, the base metal salt or the noble metal salt and a solvent,

(b) drying and/or calcining the dispersion D₁ obtained at step (a) , so as to obtain solid,

(c) optionally reducing the solid obtained at step (b) under a reducing atmosphere,

(d) forming a dispersion D₂ comprising (i) the solid obtained at step (b) or (c) , (ii) the noble metal salt when the base metal salt is comprised in the dispersion D₁ formed at step (a) or the base metal salt when the noble metal salt is comprised in the dispersion D₁ formed at step (a) , and (iii) a solvent,

(e) drying and/or calcining the dispersion D₂ obtained at step (d) ,

(f) optionally reducing the solid obtained at step (e) under a reducing atmosphere.

It should be understood that base metal salt and noble metal salt are separately introduced at step (a) or (d) above mentioned. For example, when base metal salt is mixed with support in step (a) , noble metal salt is mixed at step (d) with solid obtained at step (b) or (c) . When noble metal salt is mixed with the support at step (a) , base metal salt is mixed at step (d) with solid obtained at step (b) or (c) .

In one embodiment, the process for producing a supported amination catalyst comprising (i) a noble metal and/or a noble metal compound, (ii) a base metal and/or a base metal compound and (iii) a redox active support, may comprise the steps of:

(a) forming a dispersion D₁ comprising the redox active support, the base metal salt and a solvent,

(d) forming a dispersion D₂ comprising (i) the solid obtained at step (b) or (c) , (ii) the noble metal salt, and (iii) a solvent,

(e) drying and/or calcining the dispersion D₂ obtained at step (d) ,

Unlike conventional one-step process, the noble metal salt and base metal salt are mixed with support by two steps in present invention. Without wishing to be bound by any theory, the supported amination catalyst prepared by invented process has better catalytic activity as shown in figure 1.

In present invention, the noble metals are metals that are normally valuable and resistant to corrosion and oxidation in moist air. It could be chosen from a group consisting of ruthenium, rhodium, palladium, silver, osmium, iridium, platinum and gold. Palladium and rhodium are preferred among these noble metals.

As opposed to a noble metal, base metal of present invention refers to relatively inexpensive and common metals, which could be chosen from a group consisting of nickel, copper, lead, zinc, iron, aluminium, tin, tungsten, molybdenum, tantalum, cobalt, bismuth, cadmium, titanium, zirconium, antimony, manganese, beryllium, chromium, germanium, vanadium, gallium, hafnium, indium, niobium, rhenium and thallium. Among them, nickel, copper and cobalt are preferable and nickel is more preferable.

Noble metal or base metal comprised in supported amination catalyst is an elementary substance that consists of atoms belonging to a single metal element.

Noble metal compound comprised in supported amination catalyst may be any compound comprising noble metal. Noble metal compound is preferably chosen in the group consisting of: noble metal oxides, salts of noble metal and any combination thereof. Said salts could be chosen in the group consisting of halide, nitrate, nitrite, carbonate, bicarbonate, sulphate, sulphite, thiosulfate, phosphate, phosphite, hypophosphite, formate, acetate and propionate.

Base metal compound comprised in supported amination catalyst may be any compound comprising base metal. Base metal compound is preferably chosen in the group consisting of: base metal oxides, salts of base metal and any combination thereof. Said salts could be chosen in the group consisting ofhalide, nitrate, nitrite, carbonate, bicarbonate, sulphate, sulphite, thiosulfate, phosphate, phosphite, hypophosphite, formate, acetate and propionate.

In one embodiment, the supported amination catalyst might comprise (i) a noble metal and a noble metal compound, (ii) a base metal and a base metal compound and (iii) a redox active support. The molar ratio of noble metal to noble metal compound comprised in supported catalyst might be at least 10: 1. Preferably, the molar ratio of noble metal to noble metal compound might be comprised from 10: 1 to 100: 1. The molar ratio of base metal to base metal compound comprised in supported catalyst might be at least 10: 1. Preferably, the molar ratio of base metal to base metal compound might be comprised from 10: 1 to 100: 1.

In one specific embodiment, the supported catalyst might comprise (i) a noble metal and a noble metal oxide, (ii) a base metal and a base metal oxide and (iii) a redox active support.

In another embodiment, the supported catalyst might comprise (i) a noble metal, (ii) a base metal and (iii) a redox active support.

The loading amount of noble metal element on the support of present invention may be comprised from 0.001％to 5％by weight based on total weight of supported amination catalyst and preferably be comprised from 0.01％to 1％by weight and more preferably from 0.05％to 0.5％. Said noble metal element refers to noble metal comprised in elementary substance and/or compounds.

The loading amount of base metal element on the support of present invention may be comprised from 0.001％to 5％by weight based on total weight of supported amination catalyst and preferably be comprised from 0.01％to 1％by weight and more preferably from 0.05％to 0.5％and most preferably from 0.05％to 0.2％. Said base metal element refers to base metal comprised in elementary substance and/or compounds.

According to present invention, base metal salt or noble metal salt introduced in step (a) or (d) is not particularly limited. Base metal salt or noble metal salt might be inorganic or organic salt.

The inorganic salt introduced in step (a) or (d) could be chosen in the group consisting of halide, nitrate, nitrite, carbonate, bicarbonate, sulphate, sulphite, thiosulfate, phosphate, phosphite and hypophosphite.

The inorganic salt introduced in step (a) or (d) could notably be a metal halide compound. Metal halide compounds comprise typically at least one halogen atom other than astatine and at least one metal atom which is chemically bound to the halogen atom； the electronegativity of the halogen atom other than the astatine atom is obviously higher than the electronegativity of the metal atom.

The halogen atom can be chosen in the group consisting of a fluorine atom (the case being, the halide is a fluoride) , a chlorine atom (the case being, the halide is a chloride) , a bromine atom (the case being, the halide is a bromide) and an iodine atom (the case being, the halide is an iodide) . Preferably, the halogen atom can be a chlorine atom.

The organic salt introduced in step (a) or (d) could notably be chosen in the group consisting of formate, acetate and propionate.

The redox active support of present invention refers to a support having redox ability. Particularly, it could provide a specific synergistic redox coupling between the support and base metal and/or base metal compound and noble metal and/or noble metal compound of the catalyst. The supports are not redox inactive supports e.g. alumina, doped-alumina (notwithstanding instances wherein the alumina is specifically doped with a redox-active material e.g. ceria or the like) , silica, activated carbon, high surface area carbon and graphite powder or similar.

Preferably, the redox active support may comprise at least one transition metal oxide or lanthanide oxide. More preferably, the redox active support may comprise at least one rare earth metal oxide, such as cerium oxide, cerium zirconium oxide, praseodymium oxide and any combination thereof.

Of the various redox active metal oxide supports possible, cerium oxide/ceria based support oxides are especially preferred. The cerium oxide employed, without wishing to limit the scope of the choice of support, in one preferred embodiment of present invention may have following properties:

-a specific surface area comprised from 50 to 300 m²/g, after calcination at 400℃or 10 hours (calcination of cerium oxide alone) ； and

-a weight loss comprised from-2.0 to+7.0％, between a temperature of 350℃and 1000℃ (calcination of cerium oxide alone) , as measured by a Thermal Gravimetric Analysis.

The cerium oxide particles have a specific surface area (SBET) comprised from 50 to 300 m²/g, after calcination at 400℃ for 10 hours (calcination of cerium oxide alone) , preferably comprised from 120 to 300 m²/g. Preferably, cerium oxide particles may have a specific surface area (SBET) comprised from 30 to 65 m²/g, after calcination at 900℃ for 5 hours (calcination of cerium oxide alone) , preferably comprised from 40 to 65 m²/g.

Total pore volume of cerium oxide particles may be comprised from 0.10 to 0.40 ml/g after calcination at 400℃ for 10 hours (calcination of cerium oxide alone) , under air； preferably comprised from 0.12 to 0.28 ml/g. The total pore volume may be measured by N₂ adsorption at 77.4 K at a P/P₀ value of 0.99, where P is the N₂ pressure andP₀ is the saturation vapor pressure of N₂.

Cerium oxide particles may have a S1/S2 ratio comprised from 0.45 to 0.7 taken after calcination at 800℃ for 2 hours (calcination of cerium oxide alone) . Cerium oxide particles may have a S1/S2 ratio comprised from 0.25 to 0.5 taken after calcination at 900℃ for 5 hours (calcination of cerium oxide alone) .

Said S1/S2 ratio is a ratio of the area (S1) defined by a baseline and a TPR curve in a temperature range of 200 to 600℃ to the area (S2) defined by said baseline and said TPR curve in a temperature range of 600 to 1000℃. A higher S1/S2 ratio of a cerium oxide is expected to result in a higher redox characteristic i.e. oxygen absorbing and desorbing capability and hence improved synergy with base and precious metal oxides and thus higher activity. As used herein, the “baseline” means a line segment drawn from the point on the TPR curve corresponding to 200℃ in a parallel to the axis representing temperature, up to 1000℃. The TPR may be performed as described in U.S. Pat No. 7,361,322.

Cerium oxide particles of the present invention provide a weight loss comprised from-1.0 to+6.0％, between a temperature of 350℃ and 1000℃ (calcination of cerium oxide alone) , preferably comprised from-0.5 to+5.0％.

The weight loss could be measured by TGA analysis on a TA SDT Q600 Instrument with 7 mg sample. The sample is heated from ambient temperature to 1000℃ under air with a heating rate of 10℃/min. The weight loss of the samples is calculated as follows.

Weight loss (％) ＝ (A-B) /A*100

A: weight of the sample at 350℃ detected by TG

B: weight of the sample at 1000℃ detected by TG

Cerium oxide support of present invention could be notably obtained by calcination treatment of some commercial products, such as Actalys HSA5, HSA20 from Solvay.

In another preferred embodiment, metal oxide above mentioned used as a redox active support could further comprise a dopant. Said dopant could preferably be chosen in the group consisting of metalloids, transition metals and Lanthanides. Preferable dopant is chosen in the group consisting of aluminium, silicon, lanthanum, praseodymium, zirconium and any combination of these dopants thereof. For specific examples see EP2724776.

The term metalloid is generally designating an element which has properties between those of metals and non-metals. Typically, metalloids have a metallic appearance but are relatively brittle and have a moderate electrical conductivity. The six commonly recognized metalloids are boron, silicon, germanium, arsenic, antimony, and tellurium. Other elements also recognized as metalloids include aluminum, polonium, and astatine. On a standard periodic table all of these elements may be found in a diagonal region of the p-block, extending from boron at one end, to astatine at the other.

Preferred doped metal oxides are doped ceria, doped-ceria-zirconia and doped-praseodymia etc.

In step (a) or (d) of present invention, support or solid should sufficiently contact with salts in a solvent. Method to achieve sufficient contact is not particularly limited and could notably be mixing by a stirrer, such as magnetic stirrer or mechanical stirrer.

The mixing time of step (a) or (d) of present invention might be comprised from 0.1h to 20hrs. Advantageously, the mixing time could be at least 0.5h and preferably be comprised from 0.5h to 10hs and more preferably from 1h to 5hs.

The dispersion of step (a) or (d) might be formed at the temperature comprised from 0℃ to 50℃ and preferably from 20℃ and 30℃. In one embodiment, the dispersion step (a) or (d) could be performed at room temperature.

The drying process of steps (b) or (e) may be employed to remove the solvent introduced in steps (a) or (d) . For example, the drying process could be realized by using a heating source and the heating temperature could be determined based on boiling point of solvent. Still for example, the drying process could be realized by freeze-drying. In this way, by freezing the solution and then reducing the surrounding pressure, the frozen solvent in the solution sublimate directly from the solid phase to the gas phase.

The calcination process of steps (b) or (e) may be employed so that at least part of the salt undergoes a thermal decomposition. For example, metal carbonate would decompose into metal oxide and carbon dioxide after calcination.

In one embodiment, at least 30％of salt is decomposed after calcination. In another embodiment, at most 100％of salt is decomposed after calcination. Preferably, the salt decomposed may be comprised from 80％to 100％and more preferably from 95％to 100％.

The calcination temperature of steps (b) or (e) may be comprised from 300℃ to 1000℃. Preferably, the calcination temperature is from 350℃ to 500℃.

Optionally, the solution might be filtered to get solid before drying and/or calcination process of steps (b) or (e) .

The reducing atmosphere is an atmospheric condition in which oxidation is prevented by removal of oxygen and which may contain actively reducing gases such as hydrogen, carbon monoxide. Hydrogen is preferable for present invention.

It should be understood by the people of ordinary skill in the art that step (f) could be performed in any reaction resulting in a net reducing condition. In one embodiment, solid obtained by step (e) could be reduced in a catalyst preparation process. In another embodiment, step (f) could also be completed during a reaction in which supported amination catalyst is employed. For example, step (f) also could be completed during a direct amination reaction, in which reduction condition is satisfied. Finally, step (f) may also be realized by including a specific organic component in the precursor which undergoes decomposition during calcination to generate a net reducing/oxygen depleted environment e.g. sugar, sugar alcohol etc. for examples see US5856261 and EP0545931.

In present invention, the solvent for base metal salt or noble metal salt is not particularly limited. Preferred solvents are water and some organic solvents, such as alcohols, ether, ester and ketone. A combination of two or more solvents in blend may be used during the reaction of present invention. Base metal salt or noble metal salt could be completely dissolved in the solvent or form a colloid with the solvent.

Concentration of base metal salt in solution of present invention may be comprised from 0.01mol/L to 5mol/L and preferably be comprised from 0.1mol/L to 0.5mol/L.

Concentration of noble metal salt in solution of present invention may be comprised from 0.01mol/L to 5mol/L and preferably be comprised from 0.1mol/L to 0.5mol/L.

The invention also concerns an optimized supported amination catalyst susceptible ofbeing obtained by the process as described above.

Yet this invention also relates to a method for forming an amine, comprising reacting:

-A first reactant having 2-30 carbon atoms and one or two primary hydroxyl or formyl functionalities, with

-A second reactant being NH₃ or a reactant having at least one primary amine functionality,

in the presence of a supported amination catalyst comprising (i) a noble metal and/or a noble metal compound, (ii) a base metal and/or a base metal compound and (iii) a redox active support, which is obtained by a process comprising the steps of:

(a) forming a dispersion D₁ comprisingthe redox active support, the base metal salt or the noble metal salt and a solvent,

(d) forming a dispersion D₂ comprising (i) the solid obtained at step (b) or (c) , (ii) the noble metal salt when the base metal salt is comprised in the dispersion D₁ formed at step (a) or the base metal salt when the noble metal salt is comprised in the dispersion D₁ formed at step (a) , and (iii) asolvent,

(e) drying and/or calcining the dispersion D₂ obtained at step (d) ,

This first reactant may notably be a compound of formula (I) or formula (II) :

R¹ (-OH) _x (I) R¹ (-CHO) _x (II)

Wherein:

-x is 1 or 2

-R¹ is a straight, branched or cyclic C₂-C₃₀hydrocarbon group

R¹ may represent straight, branched or cyclic C₂-C₃₀hydrocarbon group that can be an alkyl, alkenyl, aryl, cycloalkyl or heterocyclic group, eventually comprising one or several heteroatoms such as O, S, F, and N. More preferred groups for R¹ may be for example C₂-C₁₂ straight aliphatic hydrocarbon group, benzyl, furfuryl, and tetrahydrofurfuryl.

In addition, the first reactant may comprise additional functionalities. The additional functionalities may behave as electron donating or electron withdrawing groups as long as their presence does not prevent reaction with the amine to form the imine intermediate. There is no particular limitation on the number of carbon atoms present in the reactant as long as its structure does not prevent the formation of the imine intermediate.

Preferred first reactant of the present invention, such as compounds of formula (I) , is chosen in the group consisting of: n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol and n-decanol, furfuryl alcohol, 2, 5-furandimethanol, 2, 5-tetrahydrofuranedimethanol, benzyl alcohol, 1, 6-hexandiol and 1, 7-heptandiol.

This second reactant may notably be a compound of formula (III) :

R²-NH₂ (III)

Wherein: R² is H or a straight, branched or cyclic hydrocarbon group. R² may represent straight, branched or cyclic hydrocarbon group that can be an alkyl, alkenyl, aryl, cycloalkyl or heterocyclic group, eventually comprising one or several heteroatoms such as O, S, F, and N. Preferred groups for R² may be for example: H, alkyl, phenyl, benzyl, cycloalkyl, and cycloalkene. More preferred groups for R² may be H or alkyl. More preferred groups for R² may be H or C₁-C₅ alkyl.

In addition, the second reactant may comprise additional functionalities. The additional functionalities may behave as electron donating or electron withdrawing groups as long as their presence does not prevent reaction with the amine to form the imine intermediate. There is no particular limitation on the number of carbon atoms present in the reactant as long as its structure does not prevent the formation of the imine intermediate.

Preferred second reactant of the present invention, such as compounds of formula (III) , is chosen in the group consisting of: NH₃, methylamine, ethylamine and propylamine.

The amine produced by the method of present invention could be chosen in the group consisting of primary amine, secondary amine and tertiary amine. Preferably, the amine is a secondary amine.

The amine produced by the method of the present invention may notably be a compound of formula (IV) :

R¹ (-NHR²) _x (IV)

Wherein:

-x is 1 or 2,

-R¹ is a straight, branched or cyclic C₂-C₃₀hydrocarbon group,

-R² is H or a straight, branched or cyclic hydrocarbon group.

R¹ andR²have the same meaning as above defined.

The amine produced by the method of the present invention may notably be a compound of formula (V) :

R¹ ₂NH (V)

Wherein:

-R¹ is a straight, branched or cyclic C₂-C₃₀hydrocarbon group.

R¹has the same meaning as above defined.

Preferred amine produced in present invention, such as compounds of formula (IV) or (V) , is chosen in the group consisting of: n-ethylamine, Di-n-ethylamine, n-propylamine, Di-n-propylamine, n-butylamine, Di-n-butylamine, n-pentylamine, Di-n-pentylamine, n-hexylamine, Di-n-hexylamine, n-heptylamine, Di-n-heptylamine, n-octylamine, Di-n-octylamine, n-nonylamine, Di-n-nonylamine, n-decylamine, Di-n-decylamine, benzylamine, furan-2-ylmethanamine, (tetrahydrofuran-2, 5-diyl) dimethanamine, (furan-2, 5-diyl) dimethanamine, 1, 6-hexamethylenediamine, and 1, 7-heptamethylenediamine.

The method for forming an amine might be performed at a temperature and for a time sufficient for the primary amine, secondary amine or tertiary amine to be produced.

The reaction temperature may be comprised between-100℃ and 280℃, preferably between 0℃ and 200℃. The reaction may be carried out in liquid or gas phase. In liquid phase, the reaction may be performed in the absence or presence of a solvent. The solvent is typically chosen based on its ability to dissolve the reactants.

The solvent may be protic, aprotic or a combination of protic and aprotic solvents. Exemplary solvents include toluene, octane, xylene, benzene, n-butanol, and acetonitrile. In some embodiments the solvent is a non-polar, aprotic solvent such as toluene. Solvents comprising hydroxyl functionalities or amine functionalities may be used as long as the solvent does not participate in the reaction in place of the reactant.

The reactants, with an optional solvent, and the catalyst are typically combined in a reaction vessel and stirred to constitute the reaction mixture. The reaction mixture is typically maintained at the desired reaction temperature under stirring for a time sufficient to form the amines in the desired quantity and yield.

Hydrogen could be optionally introduced into the reaction medium in this invention. When the reaction is performed in liquid phase, NH₃ and H₂ might be mixed and introduced into reaction medium in one embodiment. In gas phase, the reaction may be performed under a pressure comprised between 1 and 100 bars.

The reaction may be carried out in the presence of air but preferably with an inert atmosphere such as N₂, Ar, CO₂. Those atmospheres may be introduced to the reaction mixture solely or in a form of mixture with NH₃ and/or H₂.

The catalyst is typically removed from the reaction mixture using any solid/liquid separation technique such as filtration, centrifugation, and the like or a combination of separation methods. The product may be isolated using standard isolation techniques, such as distillation.

In addition, the catalyst can be reused. If desired, the catalyst can be regenerated by washing with methanol, water or a combination of water and methanol and subjecting the washed catalyst to a temperature of about 100℃ to about 500℃ for about 2 to 24 hours in the presence of oxygen.

Advantageously, by using the supported amination catalyst prepared by invented process, the conversion of first reactant could reach at least 70％. Preferably, the conversion of first reactant may be comprised from 70％to 100％and more preferably from 75％and 90％. The selectivity of secondary amine could reach at least 70％. Preferably, the selectivity of secondary amine may be comprised from 70％to 90％and more preferably from 75％and 85％.

The following examples are included to illustrate embodiments of the invention. Needless to say, the invention is not limited to the described examples.

EXPERIMENTAL PART

EXAMPLE 1: Preparation of supported noble metal catalyst

CeO₂ (Actalys HSA5 from Solvay) was calcined at 300℃ for 2 h. 3 g of such calcined CeO₂ was mixed with an aqueous solution which contains Pd (NO₃) ₂×2H₂O 0.0375 g and H₂O 0.9 g. The mixture was stirred mechanically for 2 h at room temperature. Then it was freeze dried overnight and followed by calcination at 400℃ for 2 h to obtain 0.5 wt. ％Pd/CeO₂. The loading amount is calculatedbased on Pd (NO₃) ₂ introduced.

EXAMPLE 2: Catalyst preparation by conventional process (one step)

CeO₂ (Actalys HSA5 from Solvay) was calcined at 300℃ for 2 h. 3 g of such calcined CeO₂ was mixed with an aqueous solution which contains Ni (NO₃) ₂×6H₂O 0.0739 g, Pd (NO₃) ₂×2H₂O 0.0375 g and H₂O 0.9 g. The mixture was stirred mechanically for 2 h at room temperature. Then it was freeze dried overnight and followed by calcination at 400℃ for 2 h to obtain 0.5 wt. ％Pd-0.5 wt. ％Ni/CeO₂. The loading amount is calculated based on Pd (NO₃) ₂ andNi (NO₃) ₂introduced.

EXAMPLE 3: Catalyst preparation by invented process (two steps)

CeO₂ (Actalys HSA5 from Solvay) was calcined at 300℃ for 2 h. 3 g of such calcined CeO₂ was mixed with an aqueous solution which contains Ni (NO₃) ₂×6H₂O 0.0739 g and H₂O 0.9 g. The mixture was stirred mechanically for 2 h at room temperature. Then it was freeze dried overnight and followed by calcination at 400℃ for 2 h. For the loading of second metal Pd, the resulted Ni/CeO₂ was impregnated in an aqueous solution which contains Pd (NO₃) ₂×2H₂O 0.0375 g and H₂O 0.9 g. The mixture was stirred mechanically for 2 h at room temperature. Then it was freeze dried overnight and followed by calcination at 400℃ for 2 h to obtain 0.5 wt. ％Pd-0.5 wt. ％Ni/CeO₂. The loading amount is calculated based on Pd (NO₃) ₂ and Ni (NO₃) ₂introduced.

EXAMPLE 4: Catalyst preparation by invented process (two steps)

CeO₂ (Actalys HSA5 from Solvay) was calcined at 300℃ for 2 h. 3 g of such calcined CeO₂ was mixed with a aqueous solution which contains Pd (NO₃) ₂×2H₂O 0.0375 g and H₂O 0.9 g. The mixture was stirred mechanically for 2 h at room temperature. Then it was freeze dried overnight and followed calcination at 400℃for 2 h. For the loading of second metal Ni, the resulted Pd/CeO₂ was impregnated in an aqueous solution which contains Ni (NO₃) ₂×6H₂O 0.0739 g and H₂O 0.9 g. The mixture was stirred mechanically for 2 h at room temperature. Then it was freeze dried overnight and followed by calcination at 400℃ for 2 h to obtain 0.5 wt. ％Pd-0.5 wt. ％Ni/CeO₂. The loading amount is calculated based on Pd (NO₃) ₂ and Ni (NO₃) ₂introduced.

H₂-TPR profiles were collected on a Micromeritics AutoChem II2920 system equipped with a quartz U-type tubular reactor and a TCD detector. The TPR method is used to determine the absolute quantity of active oxygen available in the catalyst through its reaction with H₂. In addition the TPR provides a direct measurement of the reactivity of the available oxygen by comparison of the temperature at which the active oxygen undergoes reaction, as indicated by peaks of H₂ consumption versus temperature in the TPR profile, as shown in Figure 2. Thus the lower the temperature of H₂ consumption, the more active the available oxygen is considered to be. Upon this basis it becomes clear that the catalyst prepared by invented process shows a decreased total oxygen capacity but conversely contains oxygen species with the highest activity (low temperature performance) of the three materials and summarized in Table 1. This enhanced activity of oxygen reflects a specific benefit of the invented process and, without wishing to be bound by theory, is ascribed to a specific synergy between the redox active support and the specific coupling of the redox behavior of the Pd-Ni oxide species produced in the two step process of the invention. This is evidenced by the quite different behavior of the conventional Pd-Ni/CeO₂ produced by the one-step/one-pot method which displays an almost identical similar redox performance in terms of temperature and oxygen reactivity to the conventional Pd-CeO₂ ofEX1.

Table 1

EXAMPLE 5: Preparation of supported noble metal catalyst

This example is performed in the same way as Example 1 but with the use of aluminium oxide as the support oxide.

EXAMPLE 6: Catalyst preparation by conventional process (one step)

This example is performed in the same way as Example 2 by using aluminium oxide as the support oxide.

EXAMPLE 7: Catalyst preparation by invented process (two steps)

This example is performed in the same way as Example 3 by using aluminium oxide as the support oxide.

EXAMPLE 8: Synthesis of amines using supported amination catalyst of Example 3

The catalytic reaction in liquid phase was carried out in a sealed 30-mL autoclave. 15 wt％catalyst versus alcohol was placed in the autoclave and then 1-octanol was added in. NH₃ and H₂ were purged into the closed autoclave using high-pressure gas cylinder. The mol ratio is 1-octanol: NH₃: H₂＝1: 5: 2. After 2 h reaction under 180℃, the resulted liquid mixture was analyzed by GC.

COMPARATIVE EXAMPLE 1: Synthesis of amines using supported noble metal catalyst

This example is performed in the same way as Example 8 by using 2 wt. ％Pd/CeO₂ as catalyst. The supported noble metal catalyst is obtained by the same way of Example 1.

COMPARATIVE EXAMPLE 2: Synthesis of amines using supported amination catalyst of Example 2

This example is performed under the conditions described in Example 8 using the supported amination catalyst of Example 2.

From the data summarized in Table 2 and shown in Figure 1, the conventional PdNiCeO₂ material shows decreased 1-octanol conversion c.f. the 2％PdCeO₂, due to the decrease of Pd content from 2％to 0.5 (75％decrease in relative terms) . By contrast, EX3 of the present invention actually provides a significant increase in conversion at the same low level of Pd. This reflects clear benefits in performance and cost. In addition EX3 also provides the lowest total byproduct generation and the highest selectivity towards the secondary amine (di-octylamine) , a further benefit of the described invention.

Table 2

EXAMPLE 9: Synthesis of amines using supported metal catalyst of Example 7 This example is performed under the conditions described in Example 8 using supported metal catalyst of Example 7.

COMPARATIVE EXAMPLE 3: Synthesis of amines using supported metal catalyst of Example 5.

This example is performed under the conditions described in Example 8 using supported metal catalyst of Example 5.

COMPARATIVE EXAMPLE 4: Synthesis of amines using supported metal catalyst of Example 6

This example is performed under the conditions described in Example 8 using supported metal catalyst of Example 6.

The data listed in Table 3 is in stark contrast to that shown in Table 2. Thus in all cases conversion is extremely low, at best 6％and at worst less than 1％, an order of magnitude lower than that seen for the CeO₂ supported catalysts. Thus the critical role of a support with specific synergistic redox characteristics is apparent. Beyond this a minor benefit is observed using the process of the described invention with increase conversion to 6％and improved selectivity to the secondary amine and no selectivity to heptyl cyanide. This is evidence for the intrinsic benefits of the described process but again emphasizes that to achieve the full benefit there must be a synergistic coupling between the catalytic metals and the redox active support.

Table 3

Claims

A process for producing a supported amination catalyst comprising (i) a noble metal and/or a noble metal compound, (ii) a base metal and/or a base metal compound and (iii) a redox active support, comprising the steps of:

(a) forming a dispersion D₁ comprising the redox active support, the base metal salt or the noble metal salt and a solvent,

(b) drying and/or calcining the dispersion D₁ obtained at step (a) , so as to obtain solid,

(c) optionally reducing the solid obtained at step (b) under a reducing atmosphere,

(d) forming a dispersion D₂ comprising (i) the solid obtained at step (b) or (c) , (ii) the noble metal salt when the base metal salt is comprised in the dispersion D₁ formed at step (a) or the base metal salt when the noble metal salt is comprised in the dispersion D₁ formed at step (a) , and (iii) a solvent,

(e) drying and/or calcining the dispersion D₂ obtained at step (d) ,

(f) optionally reducing the solid obtained at step (e) under a reducing atmosphere.
The process according to claim 1, wherein the noble metal comprised in supported catalyst is palladium or rhodium.
The process according to claim 1 or 2, wherein the base metal comprised in supported catalyst is chosen from a group consisting of nickel, copper and cobalt.
The process according to any one of claims 1 to 3, wherein noble metal compound comprised in supported catalyst is chosen in the group consisting of noble metal oxides, salts of noble metal and any combination thereof.
The process according to any one of claims 1 to 4, wherein noble metal compound comprised in supported catalyst is a salt of noble metal chosen in the group consisting of halide, nitrate, nitrite, carbonate, bicarbonate, sulphate, sulphite, thiosulfate, phosphate, phosphite, hypophosphite, formate, acetate and propionate.
The process according to any one of claims 1 to 5, wherein base metal compound comprised in supported catalyst is chosen in the group consisting of base metal oxides, salts of base metal and any combination thereof.
The process according to any one of claims 1 to 6, wherein base metal compound comprised in supported catalyst is a salt of base metal chosen in the group consisting of halide, nitrate, nitrite, carbonate, bicarbonate, sulphate, sulphite, thiosulfate, phosphate, phosphite, hypophosphite, formate, acetate and propionate.
The process according to any one of claims 1 to 7, wherein the redox active support comprises at least one transition metal oxide or lanthanide oxide.
The process according to any one of claims 1 to 8, wherein the redox active support comprises at least one rare earth metal oxide.
The process according to any one of claims 1 to 9, wherein the redox active support is chosen in the group consisting of cerium oxide, cerium zirconium oxide, praseodymium oxide and any combination thereof.
The process according to any one of claims 1 to 10, wherein the redox active support is cerium oxide having following properties:

-a specific surface area comprised from 50 to 300 m²/g, after calcination at 400℃ for 10 hours； and

-a weight loss comprised from -2.0 to +7.0％, between a temperature of 350℃ and 1000℃, as measured by a Thermal Gravimetric Analysis.
The process according to any one of claims 1 to 11, wherein the redox active support further comprises a dopant chosen in the group consisting of aluminum, silicon, zirconium, lanthanum, praseodymium and any combination thereof.
The process according to any one of claims 1 to 12, wherein the supported amination catalyst comprises (i) a noble metal, (ii) a base metal and (iii) a redox active support.
The process according to claim 13, wherein the supported amination catalyst comprises (i) palladium, (ii) nickel and (iii) a redox active support cerium oxide having following properties:

-a specific surface area comprised from 50 to 300 m²/g, after calcination at 400℃ for 10 hours； and

-a weight loss comprised from -2.0 to +7.0％, between a temperature of 350℃ and 1000℃, as measured by a Thermal Gravimetric Analysis.
The process according to any one of claims 1 to 12, wherein the supported amination catalyst comprises (i) a noble metal and a noble metal compound, (ii) a base metal and a base metal compound and (iii) a redox active support.
The process according to claim 15, wherein the supported amination catalyst comprises (i) a noble metal and a noble metal oxide, (ii) a base metal and a base metal oxide and (iii) a redox active support.
The process according to any one of claims 1 to 16, wherein the base metal salt or the noble metal salt introduced in step (a) or (d) is an inorganic salt chosen in the group consisting of halide, nitrate, nitrite, carbonate, bicarbonate, sulphate, sulphite, thiosulfate, phosphate, phosphite and hypophosphite.
The process according to any one of claims 1 to 16, wherein the base metal salt or the noble metal salt introduced in step (a) or (d) is an organic salt chosen in the group consisting of formate, acetate and propionate.
The process according to any one of claims 1 to 18, wherein the loading amount of noble metal element on the support of present invention is comprised from 0.05％ to 0.5％ by weight based on total weigh of supported amination catalyst.
The process according to any one of claims 1 to 19, wherein the loading amount of base metal element on the support of present invention is comprised from 0.05％ to 0.2％ by weight based on total weigh of supported amination catalyst.
The process according to any one of claims 1 to 20, wherein calcination temperature in steps (b) or (e) is comprised from 300℃ to 1000℃.
The process according to any one of claims 1 to 21, wherein the salt decomposed is comprised from 80％ to 100％ after calcination process of steps (b) or (e) .
A supported amination catalyst susceptible of being obtained by the process according to any one of claims 1 to 22.
A method for forming an amine, comprising reacting:

-a first reactant having 2-30 carbon atoms and one or two primary hydroxyl or formyl functionalities, with

-a second reactant being NH₃ or a reactant having at least one primary amine functionality,

in the presence of the supported amination catalyst prepared by the process according to any one of claims 1 to 22.
The method according to claim 24, wherein the amine is a secondary amine.
The method according to claim 24 or 25, wherein first reactant is a compound of formula (I) or formula (II) :

R¹ (-OH) _x (I) R¹ (-CHO) _x (II)

Wherein:

-x is 1 or 2,

-R¹ is a straight, branched or cyclic C₂-C₃₀hydrocarbon group.
The method according to any one of claims of 24 to 26, wherein second reactant is a compound of formula (III) :

R²-NH₂ (III)

wherein: R² is H or a straight, branched or cyclic hydrocarbon group.
The method according to any one of claims of 24 to 27, wherein the amine is a compound of formula (IV) :

R¹ (-NHR²) _x (IV)

wherein:

-x is 1 or 2,

-R¹ is a straight, branched or cyclic C₂-C₃₀hydrocarbon group,

-R² is H or a straight, branched or cyclic hydrocarbon group.
The method according to any one of claims of 24 to 27, wherein the amine is a compound of formula (V) :

R¹ ₂NH (V)

wherein:

-R¹ is a straight, branched or cyclic C₂-C₃₀hydrocarbon group.