ACIDS

The present invention relates to a continuous process for the skeletal isomerization of unsaturated linear fatty acids and/or alkyl esters thereof to their branched counterparts. The invention further relates to novel catalysts useful in said process as well as to uses of such catalysts.

BACKGROUND OF THE INVENTION

Alkyl-branched fatty acids are useful because of their interesting properties for various applications in the field of cosmetics, lubricants, hydraulic fluids or bio-based fuels, such as in the production of soaps, paints and coatings, fabric softeners and fuel additives. An improvement in spreadability and the oxidative and hydrolytic stability of the products produced in admixture with alkyl-branched fatty acids is generally observed. At the same time the viscosity of the alkyl- branched species is decreased and its melting point is lower in comparison with the corresponding linear fatty acids (D. V. Kinsman, J. Am. Oil Chem. Soc. 56 (1979) 823A; U. Biermann, J. O. Metzger, Eur. J. Lipid Sci Technol., 110 (2008), 805-811). Various heterogeneous catalysts containing acidic sites have been explored for the production of such alkyl-branched fatty acids. In one process, for example, clay is used as a catalyst. Clay catalysed isomerization suffers, however, from two main disadvantages. First, a considerable amount of undesired side products containing oligomers, saturated straight chain fatty acids and intermediate dimers is formed. A second disadvantage is that the clay catalyst cannot be reused effectively (e.g. Nakano et al., J. Am. Oil Chem. Soc. 62 (1985) 888).

Zeolites of suitable geometry and with acid sites can permit shape-selective reactions. This means that under appropriate conditions the formation of dimer- or trimer-fatty acids should be obstructed or reduced due to the channels of the catalyst, whereas double bond or skeletal or other intramolecular reactions are favoured. In the prior art zeolite-based catalysis is generally performed in the batch reactor, which makes recycling of the catalyst difficult as the catalyst has to be separated in an elaborate step, regenerated and reused. In such methods a significant decrease in the yield of the catalyst is observable after about only three recycling steps. WO 2012/146909 Al discloses a process for producing monobranched fatty acids. However, in the process described in WO 2012/146909 Al catalysts are used together with organoamine and organophosphine compounds as Lewis bases. The addition of such compounds must be controlled and it may be necessary to continuously add additional Lewis bases which makes the process cumbersome. In contrast, the present invention uses a different and improved composite catalyst not disclosed in WO 2012/146909 Al.

Also, frequently the yield of skeletal isomerized products or the selectivity of the reaction was too low when using prior art catalysts. Thus, all prior art processes are plagued by low yield and/or a high rate of undesirable byproduct formation. Furthermore, there is no effective way of recycling the catalyst.

Accordingly, there is a need for a new process that overcomes these disadvantages, i.e. a process for the preparation of branched fatty acids from straight chain unsaturated fatty acid feedstocks with a high conversion rate, an increased selectivity towards branched monomeric isomers and which employs a durable and reusable catalyst. Furthermore, there is a need for a new catalyst that can be used in such processes and methods of producing such catalyst.

It was therefore an object of the invention to provide novel catalysts which can be used in methods for producing skeletal isomerized fatty acids and/or skeletal isomerized alkyl esters that fulfill the aforementioned demand.

SUMMARY OF THE INVENTION

To solve the aforementioned problems, the present invention provides novel catalysts for the skeletal isomerization of unsaturated fatty acids or unsaturated fatty acid esters. It was surprisingly found that the novel catalysts are sufficiently stable for use in a continuous flow reactor, provide superior product yield and achieve high selectivity in the skeletal isomerization reactions. Furthermore, these catalysts were found suitable to be effectively recyclable.

In particular the invention provides in a first aspect a catalyst for the skeletal isomerization of unsaturated fatty acids or unsaturated fatty acid esters, wherein said catalyst is obtainable by carrying out at least the following steps:

(a) providing a zeolite;

(b) preparing a composition by mixing the zeolite with one or more hydrophilic and water insoluble inorganic binding agent and optionally a liquid;

(c) optionally drying the composition prepared in step (b) to obtain a solid and preferably crushing the solid to obtain fragments thereof;

(d) extruding the composition obtained in step (b) or compacting the solid and/or fragments obtained in step (c) under pressure; and

(e) optionally calcining

(i) the fragments obtained in step (c),

(ii) the extrudate or obtained in step (d); or

(iii) the pressed solid obtained in step (d);

wherein said zeolite in step (a), said solid in step (c) and/or said fragments in step (c) is/are in the respective step contacted with a protic acid or heated to generate Br0nsted acid sites on said zeolite, said solid and/or said fragments.

In a preferred embodiment of the first aspect the catalyst is obtainable by carrying out at least the following steps:

(a) providing a zeolite powder and contacting said zeolite with a protic acid to generate

Br0nsted acid sites on said zeolite powder;

(b) preparing a composition by mixing the zeolite powder in (a) with water and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium;

(c) drying the composition prepared in step (b) to obtain a solid and crushing the solid to obtain fragments thereof;

(d) optionally compacting the fragments obtained in step (c) under pressure; and

(e) calcining the fragments obtained in step (c) or the pressed solid obtained in step (d).

Also provided is in a further aspect a method for producing a catalyst of the invention wherein the method comprises the steps as outlined above. As a further aspect the invention provides a catalyst for the skeletal isomerization of unsaturated fatty acids or unsaturated fatty acid esters, wherein the catalyst comprises a zeolite treated with a protic acid and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium, wherein the zeolite is characterized by a pore diameter of at least 0,4 nm and/or wherein said catalyst has a BET surface of at least 100 m /g.

In yet a further aspect the invention also provides a method of producing a skeletal isomerized fatty acid and/or skeletal isomerized fatty acid ester comprising the steps:

(1) contacting in a reactor in a continuous process at least one unsaturated fatty acid and/or at least one unsaturated fatty acid ester with a catalyst according to the invention;

(2) optionally regenerating the catalyst; and

(3) optionally hydrogenating the skeletal isomerized unsaturated fatty acid and/or unsaturated fatty acid ester.

A further aspect of the invention relates to the use of a catalyst according to the invention for skeletal isomerizing an unsaturated fatty acid and/or unsaturated fatty acid ester in a continuous flow reaction.

DETAILED DESCRIPTION OF THE INVENTION

Before the present invention is described in detail below, it is to be understood that this invention is not limited to the particular methodology, protocols and reagents described herein as these may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention which will be limited only by the appended claims. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.

In the following passages different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

Some documents are cited throughout the text of this specification. Each of the documents cited herein (including all patents, patent applications, scientific publications, manufacturer's specifications, instructions, DIN norms etc.), whether supra or infra, are hereby incorporated by reference in their entirety. Nothing herein is to be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention.

In the following definitions of some chemical terms are provided. These terms will in each instance of its use in the remainder of the specification have the respectively defined meaning and preferred meanings.

As used herein the term "about" in the context of a numerical value preferably means a deviation of +/- 5% of said value. A "zeolite" may be a naturally occurring or a synthetic zeolite. Synthetic zeolites include for example ion-exchanged zeolites. Br0nsted acids are well known in the art and are proton donors. Thus, "Br0nsted acid sites" as used herein are sites on or in the catalyst which can donate protons. A "fatty acid" and "fatty acid ester" can be any "fatty acid" or "fatty acid ester" including technical grade fatty acids and technical grade fatty acid esters, respectively. Preferred embodiments of "fatty acid" and "fatty acid ester" are also described herein. As mentioned, novel catalysts were found which have over conventional catalysts superior qualities. In particular, the catalysts of the invention were found to be sufficiently stable for use in a continuous flow reactor, provide superior product yield and achieve high selectivity in the skeletal isomerization reactions. Furthermore, these catalysts were found suitable to be effectively recyclable.

Thus, one aim of the invention is the production of acidic zeolite-based catalysts, which are suitable for the operation of a process in a continuous tubular reactor.

Thus, the invention provides in a first aspect a catalyst for the skeletal isomerization of unsaturated fatty acids or unsaturated fatty acid esters, wherein said catalyst is obtainable by carrying out at least the following steps:

(a) providing a zeolite powder; (b) preparing a composition by mixing the zeolite with one or more hydrophilic and water insoluble inorganic binding agent and optionally a liquid;

(c) optionally drying the composition prepared in step (b) to obtain a solid and preferably crushing the solid to obtain fragments thereof;

(d) extruding the composition obtained in step (b), compacting under pressure the

composition obtained in step (b) or compacting the solid and/or fragments obtained in step (c) under pressure; and

(e) optionally calcining

(i) the fragments obtained in step (c),

(ii) the extrudate obtained in step (d); or

(iii) the pressed solid obtained in step (d);

wherein said zeolite in step (a), said solid in step (c) and/or said fragments in step (c) is/are in the respective step contacted with a protic acid or heated to generate Br0nsted acid sites on said zeolite, said solid and/or said fragments.

As is evident also from the above outlined first aspect a catalyst of the invention comprises a binding agent. In this regard suitable binding agents preferably do not destroy the acid sites of the zeolite and also do not clog the pores of the zeolites.

For the preparation of the inventive catalysts said zeolite (or preferably a combination of different zeolites) are treated to generate acid sites on the zeolite. This can be achieved by e.g. treating the zeolite with a protic acid or by calcination of the zeolite. If the zeolite is calcined, i.e. treated with heat then the zeolite is preferably an ammonium form of the zeolite. The time point when the acid treatment or heating occurs generally does not matter. As also outlined above, this treatment can occur prior to or also after preparing said mixture comprising said zeolite and said binding agent. When preparing said composition in step (b) it is furthermore an option to include one or more further additives to the composition whereby said additive can be selected from the group consisting of a stabilizer, a thickener, a set-up agent (Stellmittel), a tenside, an emulsifier, a porosity control additive, a dispersing agent and a further binding agent. Possible additives that can be used are for example, polyvinyl alcohol (e.g. M = about 72000) or cellulose derivatives in particular methyl cellulose powder. Also mixtures of such additives for example a mixture of polyvinyl alcohol and methyl cellulose can be used. In addition, the extrusion or compaction of the catalyst composition under pressure has unexpectedly been shown to have a favourable influence on the catalytic properties in the skeletal isomerization catalyst. Thus, if a liquid was used to prepare said composition as outlined in step (b) above it is preferred that the composition is extruded. Alternatively, the composition can also be compacted. Preferably, the composition is dried and then crushed to obtain fragments. These fragments can then be pressure compacted. In a preferred embodiment these fragments are further calcined. The fragments can also be pressure compacted before calcining. It is preferred that the final catalyst product is in the form of granules. Thus, in a preferred embodiment the catalyst of the invention is in the form of granules. In this context it is preferred that in the production process the catalyst is granulated in a last step. The diameter of the granules can be matched to the diameter of the reactor used for the skeletal isomerization reaction. For example, they can be selected to have a diameter which is not exceeding 1/10 of the diameter of the reactor. Selecting a particular size for the particulate catalyst can be achieved for example by sieving. A preferred granule diameter is more than 1 mm.

In a preferred embodiment, the catalyst of the invention is prepared by carrying out at least the following steps:

(a) providing a zeolite and contacting said zeolite with a protic acid to generate Br0nsted acid sites on said zeolite;

(b) preparing a composition by mixing the zeolite in (a) with water and a binding agent

selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium;

(c) drying the composition prepared in step (b) to obtain a solid and crushing the solid to obtain fragments thereof;

(d) optionally compacting the fragments obtained in step (c) under pressure; and

(e) calcining the fragments obtained in step (c) or the pressed fragments obtained in step (d).

In a further preferred embodiment of the catalyst of the invention the production method for obtaining the catalyst comprises at least the following steps:

(a) treating a zeolite powder with hydrochloric acid to generate Br0nsted acid sites on said zeolite;

(b) preparing a composition by mixing the zeolite powder in (a) with water and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium;

(c) drying the composition prepared in step (b) to obtain a solid and crushing the solid to obtain fragments thereof;

(d) optionally compacting the fragments obtained in step (c) under pressure;

(e) calcining the fragments obtained in step (c) or the pressed solid obtained in step (d); and

(f) optionally crushing the calcined pressed solid obtained in step (d).

In yet a further preferred embodiment of the catalyst of the invention the production method for obtaining the catalyst comprises at least the following steps:

(a) treating a zeolite ammonium ferrierite powder with hydrochloric acid to generate

Br0nsted acid sites on said zeolite;

(b) preparing a composition by mixing the treated zeolite powder in (a) with water and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium;

(c) drying the composition prepared in step (b) to obtain a solid and crushing the solid to obtain fragments thereof;

(d) optionally compacting the fragments obtained in step (c) under pressure;

(e) calcining the fragments obtained in step (c) or the pressed solid obtained in step (d); and

(f) optionally crushing the calcined pressed solid obtained in step (d).

Preferably the method of the invention comprises step (d). Zeolites are crystalline microporous aluminosilicates. The zeolites comprise charge balancing cations. As zeolite frameworks are typically negatively charged, the charge balancing cations that can be used

2+ include monovalent cations such as NH ₄ +, H+, Li+ and the like, divalent cations such as Mg , Zn ²⁺ and the like and trivalent cations such as Ln ³⁺ , Y ³⁺ , Fe ³⁺ , Cr ³⁺ and the like. The framework composition of the three-dimensional zeolites may contain other elements in addition to Al and Si, such as, for example, P, Ti, Zr, Mn, and the like. Although any zeolite meeting the purpose of the present invention can be employed, it is preferred that the zeolite used in step (a) is selected from the group consisting of zeolite A, zeolite Beta, zeolite X, zeolite Y, zeolite L, zeolite ZK-5, zeolite ZK-4, zeolite ZSM-5, zeolite ZSM-11, zeolite ZSM-12, zeolite ZSM-20, ZSM-35, zeolite ZSM-23, zeolite mordenite, zeolite ferrierite, silicoaluminophosphates including but not limited to SAPO-11 , SAPO 18, SAPO-34, SAPO 42, SAPO-44 and mixtures thereof. The aforementioned zeolites can in preferred embodiments be combined with the above mentioned cations. The most preferred zeolite that can be used for making a catalyst according to the invention is Zeolite Ammonium Ferrierite Powder, which is commercially available e.g. under the product name CP914C from Zeolyst International, P. O. Box 830, Valley Forge, PA 19482 USA. It is further preferred that the catalyst of the invention comprises a zeolite that is characterized by a pore diameter of at least 0,4 nm and/or that the catalyst of the invention has a BET surface of at least 100 m ² /g.

For preparing a catalyst according to the invention it is most preferred when in step (a) a zeolite powder is used.

The Si/Al ratio of the zeolites can vary depending on the particular zeolite employed. For the purpose of the present invention the S1O2/AI2O ₃ ratio of the zeolite is preferably at least 3: 1 and preferably at least 100: 1. Most preferably the ratio is in the range of from about 5: 1 to about 80: 1.

The purpose of preferred step (a) has already been mentioned above. The contact with the protic acid serves to generate Br0nsted acid sites on said zeolite which are later participating in the catalysis reaction. It is preferred that said contacting with said protic acid is only temporal and thus the protic acid is preferably removed before the so-treated zeolite is further processed. Analogously is it preferred that said solid in step (c) and/or said fragments in step (c) are only temporarily contacted with said protic acid. The removal of excess protic acid can be achieved for example by washing with water. Thus, preferably, the zeolite treated with said protic acid is washed at least once with water.

Further preferred is a catalyst according to the invention, wherein the protic acid is selected from the group consisting of HC1, HNO ₃ , HCIO4, H2SO4 and short-chained aliphatic carboxylic acids.

The purpose of the binding agent used in the invention is to bind to the zeolite and to allow the zeolite to be formed into a composite comprising said zeolite and said binding agent. This composite can then be formed (extruded, compressed and/or crushed) into particles such as pellets or granules. The advantage of these pellets or granules is that they are sufficiently stabile so that they can be filled into a continuous flow reactor. At the same time they are sufficiently large in size such to prevent the reactor from clogging and such to allow a sufficiently high flux through the reactor without that excess pressure has to be applied on the reactants flowing through the reactor. For preferred applications the average granule size of the catalyst of the invention is selected such that a continuous flow reactor can be operated with moderate pressure for example by using gravity for flowing the fatty acid feedstock though the reactor containing the catalyst particles.

A preferred binding agent that can be used to prepare the catalyst of the invention is selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium. A particularly preferred binding agent is hydrophilic fumed silica and most preferably hydrophilic fumed silica with a specific surface area of about 200 m /g and an average primary particle size of 12 nm. This most preferred binding agent is commercially available under the trademark AEROSIL® 200 from Evonik Industries AG. Thus, in one preferred embodiment of the catalyst of the invention the binding agent that is used has a specific surface area of at least 100 m ² /g and an average primary particle sizes of at least 5 nm.

A further particularly preferred binding agent is alumina sol which can preferably be combined with ammonium ferrierite zeolite that has been pre-treated with HC1 to obtain a catalyst of the invention.

A preferred catalyst of the invention is obtainable according to the above described methods wherein in step (b) the mass ratio between the zeolite and the binding agent is in the range of 0.5: 1 to 100:1, preferably in the range of 3: 1 to 50: 1, even more preferably about 3: 1 to about 20: 1 and most preferably about 4: about 1.

As mentioned it was unexpectedly found that the quality of the catalyst can be further increased when the catalyst of the invention was produced in a method comprising a compacting step under pressure. Thus, it is preferred that the fragments obtained in step (c), the composition obtained in step (b) or the solid in step (c) are compacted under pressure. This pressure is

2 2

preferably at least 0.5 t/cm and more preferably at least 2.0 t/cm . Preferably the compaction step is carried out using a pelletizer or preforming tool, for example a tablet press.

If the catalyst is calcined then it is preferred that in step (e) the calcining occurs at a temperature of at least 300°C for at least 1 hour.

In a further aspect the invention provides a method for producing a catalyst for the skeletal isomerization of unsaturated fatty acids or unsaturated fatty acid esters comprising the steps as outlined above.

As a further aspect the invention provides a catalyst for the skeletal isomerization of unsaturated fatty acids or unsaturated fatty acid esters, wherein the catalyst comprises a protic acid treated zeolite and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium, wherein the zeolite is characterized by a pore diameter of at least 0,4 nm and/or wherein said catalyst has a BET surface of at least 100 m ² /g.

In a preferred embodiment of this catalyst the catalyst comprises a zeolite ammonium ferrierite powder that has been treated with a protic acid described herein and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium, wherein the zeolite is characterized by a pore diameter of at least 0,4 nm and/or wherein said catalyst has a BET surface of at least 100 m ² /g.

In a further preferred embodiment of this catalyst the catalyst comprises a zeolite powder that has been treated with a hydrochloric acid and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium, wherein the zeolite is characterized by a pore diameter of at least 0,4 nm and/or wherein said catalyst has a BET surface of at least 100 m /g.

In a further preferred embodiment of this catalyst the catalyst comprises a zeolite ammonium ferrierite powder that has been treated with a hydrochloric acid and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium, wherein the zeolite is characterized by a pore diameter of at least 0,4 nm and/or wherein said catalyst has a BET surface of at least 100 m /g.

In a further preferred embodiment of this catalyst the catalyst comprises a zeolite powder that has been treated with hydrochloric acid and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium.

In a further preferred embodiment of the catalyst of the invention the catalyst comprises a zeolite ammonium ferrierite powder that has been treated with a hydrochloric acid and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium.

In a further preferred embodiment of this catalyst the catalyst comprises a zeolite powder that has been treated with hydrochloric acid and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium; wherein the catalyst has been calcined.

In a further preferred embodiment of the catalyst of the invention the catalyst comprises a zeolite ammonium ferrierite powder that has been treated with a hydrochloric acid and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium; wherein the catalyst has been calcined.

In a further preferred embodiment of this catalyst the catalyst comprises a zeolite powder that has been treated with hydrochloric acid and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium; wherein the catalyst has been pressure compacted and calcined.

In a further preferred embodiment of the catalyst of the invention the catalyst comprises a zeolite ammonium ferrierite powder that has been treated with a hydrochloric acid and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium; wherein the catalyst has been pressure compacted and calcined.

In a further preferred embodiment of this catalyst the catalyst comprises a zeolite powder that has been treated with hydrochloric acid and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium; wherein the catalyst has been pressure compacted, calcined and granulated.

In a further preferred embodiment of the catalyst of the invention the catalyst comprises a zeolite ammonium ferrierite powder that has been treated with a hydrochloric acid and a binding agent selected from the group consisting of fumed silica, fumed metal oxide, silica sol, alumina sol, dispersible amorphous silica, a hydroxide of aluminium and oxide hydroxides of silicon and aluminium; wherein the catalyst has been pressure compacted, calcined and granulated.

In a further preferred embodiment of this catalyst the catalyst comprises a zeolite powder that has been treated with hydrochloric acid and hydrophilic fumed silica as a binding agent.

In a further preferred embodiment of the catalyst of the invention the catalyst comprises a zeolite ammonium ferrierite powder that has been treated with a hydrochloric acid and as a binding agent hydrophilic fumed silica.

In a further preferred embodiment of this catalyst the catalyst comprises a zeolite powder that has been treated with hydrochloric acid and hydrophilic fumed silica as a binding agent; wherein the catalyst has been calcined.

In a further preferred embodiment of the catalyst of the invention the catalyst comprises a zeolite ammonium ferrierite powder that has been treated with a hydrochloric acid and as a binding agent hydrophilic fumed silica; wherein the catalyst has been calcined.

In a further preferred embodiment of this catalyst the catalyst comprises a zeolite powder that has been treated with hydrochloric acid and hydrophilic fumed silica as a binding agent; wherein the catalyst has been pressure compacted and calcined.

In a further preferred embodiment of the catalyst of the invention the catalyst comprises a zeolite ammonium ferrierite powder that has been treated with a hydrochloric acid and as a binding agent hydrophilic fumed silica; wherein the catalyst has been pressure compacted and calcined.

In a further preferred embodiment of this catalyst the catalyst comprises a zeolite powder that has been treated with hydrochloric acid and hydrophilic fumed silica as a binding agent; wherein the catalyst has been pressure compacted, calcined and granulated.

In a further preferred embodiment of the catalyst of the invention the catalyst comprises a zeolite ammonium ferrierite powder that has been treated with a hydrochloric acid and as a binding agent hydrophilic fumed silica; wherein the catalyst has been pressure compacted, calcined and granulated. Preferably the mass ratio between the zeolite and the binding agent is in the range of 0.5: 1 to 100: 1, preferably in the range of 3: 1 to 50: 1, even more preferably about 3: 1 to about 10: 1 and most preferably about 4: about 1. In a further aspect the invention provides a method of producing a skeletal isomerized fatty acid and/or skeletal isomerized fatty acid ester comprising the steps:

(1) contacting in a reactor in a continuous process at least one unsaturated fatty acid and/or at least one unsaturated fatty acid ester with a catalyst according to the invention;

(2) optionally regenerating the catalyst; and

(3) optionally hydrogenating the skeletal isomerized unsaturated fatty acid and/or unsaturated fatty acid ester.

Preferably the catalyst of the invention is in particulate form having an average granule size of about 0.1 - 10 mm and preferably about 0.5-1.0 mm. Generally the granule size depends on the reactor size. For the method of the invention the catalyst of the invention is preferably placed in a fixed bed continuous reactor. This reactor can preferably be controllably heated to adjust the reaction temperature. Feeding the fatty acid or fatty acid ester according to the invention into the reactor is carried out preferably without a solvent e.g. by using a suitable metering device that can be located at the top of the reactor. Preferably on the head of the reactor a device is installed which ensures a uniform distribution of the reactant across the catalyst bed. The flow of the unsaturated fatty acid and/or unsaturated fatty acid ester is typically adjusted to the amount of catalyst present in the reactor. A preferred liquid hourly space velocity for the flow rate that can be used is in the range of 0.1 to 10 h ^"1 and more preferably from 0.5 to 3 h ^" . In a further preferred embodiment the unsaturated fatty acid and/or unsaturated fatty acid ester is flowing over the catalyst at a liquid hourly space velocity (THSV) of between 0.1 to 5 h-1.

It is also preferred that at least step (1) of the method of the invention of producing a skeletal isomerized fatty acid and/or skeletal isomerized fatty acid ester is carried out under protective gas to avoid undesired oxidation reactions that can increase the amounts of by- products generated. Optionally in step (1) also additional compounds which are different from said fatty acid(s) and from said fatty acid ester(s) can be brought in contact with said catalyst.

It is preferred that in the method of the invention of producing a skeletal isomerized fatty acid and/or skeletal isomerized fatty acid ester the reactor is a continuous flow reactor preferably selected from the group consisting of a fixed bed reactor, a trickle-bed reactor, a loop reactor and a fluidized bed reactor.

Preferably said unsaturated fatty acid / unsaturated fatty acid ester used in the method of the invention is a linear C16-C26 carboxylic acid or ester thereof. If more than one unsaturated fatty acid or more than one fatty acid ester is used then it is preferred that a mixture of different carboxylic acids selected from C16-C26 carboxylic acids or respective esters thereof is used in the method of the invention. In this context it is also preferred that monounsaturated linear fatty acids are used in the method of the invention. More preferably C16-C26 monounsaturated linear fatty acids and/or esters thereof are used in the method. Most preferably, the fatty acid used in the method of the invention is or comprises oleic acid. If for example oleic acid or oleic acid ester is used as educt then carrying out the method of the invention will produce a composition comprising inter alia isooleic acid. In step (1) of the method of the invention also a mixture comprising several different unsaturated fatty acids and/or unsaturated fatty acid esters can be contacted with said catalyst. If a mixture is used as educt then this mixture comprises preferably at least 60%, at least 70%, at least 80% or at least 90% by volume of one particular unsaturated fatty acid and/or unsaturated fatty acid ester such as oleic acid or an oleic acid ester. One advantage of the catalysts of the invention is their suitability for use in a continuous process. This facilitates also the recycling of the catalyst, since it is not necessary to remove the catalyst from the reactor. Thus, in a further preferred embodiment the method of the invention comprises the following step:

(2) regenerating the catalyst e.g. by heating the catalyst to at least 200°C and/or by contacting the catalyst with a protic medium in particular with an organic acid (preferably a Cl- C12 carboxylic acid and most preferably formic acid, acetic acid, propionic acid, butyric acid or caprylic acid), a mineral acid, an alcohol and/or water. Preferred alcohols that can be used in this context include methanol, ethanol and isopropylalcohol.

Phosphoric acid is preferably not used for regenerating the catalyst. In one preferred embodiment of step (2) the educt flow is stopped for example when it is detected that the yield of the skeletal isomerized products is reduced. The catalyst bed is then preferably rinsed with a suitable solvent (for example with alcohol) and regenerated by heating the catalyst to a temperature of e.g. about 400-550 °C. In another embodiment the catalyst is regenerated by passing a protic medium such one as mentioned above in the gaseous state through the catalyst bed. Most preferably gaseous acetic acid is used for this purpose. The regenerating media gas can be introduced into the reactor for example by introducing them via the protective gas flow inlet.

The unsaturated skeletal isomerized fatty acids and their esters obtained by carrying out the method of the invention can in a preferred embodiment conveniently be transformed into their saturated equivalents by subsequently carrying out a further step (3) of hydrogenation. Thus, if in one example isooleic acid and isomers thereof are obtained by carrying out the method of the invention then the hydrogenation step (3) will produce isostearic acid and isomers thereof.

In one preferred embodiment of step (3) the skeletal isomerized fatty acid(s) or ester(s) thereof are passed over a second reactor attached to said first reactor comprising the catalyst of the invention, wherein said second reactor comprises a hydrogenation catalyst. Preferably said hydrogenation catalyst comprises an active metal selected from the group consisting of palladium, platinum, ruthenium, rhodium, iridium, nickel and mixtures thereof. Preferably the active metal is deposited on a suitable carrier or used in the case of nickel catalysts as Raney nickel. The amount of active metal is preferably used in the range of 0.1 to 50 wt.-%, more preferably in the range of 0.5 to 20 wt.- % and most preferably in the range of 1 to 10 wt. , based on the total mass of the hydrogenation catalyst. The carrier material is preferably selected from the group consisting of activated carbon, alumina, silica, titanium, zirconia and mixtures thereof. During the hydration reaction simultaneously with the liquid mixture of unsaturated fatty acids or their derivatives hydrogen is passed over the catalyst. Preferably, the hydrogen is passed over the catalyst at a pressure of between 2 and 100 bar and more preferably at between 5 and 50 bar.

In an alternative embodiment the hydrogenation can also be carried out in a discontinuous process for example by contacting the skeletal isomerized products with hydrogen in an autoclave comprising a suitable hydrogenation catalyst such as those described above.

Since after carrying out the method of the invention the final product might comprise side products it is preferred that the method of the invention has the further step

(4) isolating a branched unsaturated fatty acid or a branched saturated fatty acid or esters thereof from the reaction mixture.

Said optional step (4) can be carried out using conventional methods known in the art including but not limited to fractional crystallization without additives or with addition of a wetting agent (see for example textbook "Ullmann's Encyclopedia of Industrial Chemistry", 2012 Wiley- VCH Verlag GmbH & Co. KGaA, Weinheim and in particular the chapter "Fatty Acids"). In a preferred embodiment the method of the invention comprises a distillation step wherein the isomerized fatty acid(s) is/are distilled under reduced pressure (this step is suitable to remove unwanted polymerized fatty acids), a hydrogenation step as outlined above to remove double bonds and/or a crystallization step with a wetting agent (hydrophilization) to purify the final saturated skeletal isomerized product.

A further aspect of the invention relates to the use of a catalyst according to the invention for skeletal isomerizing an unsaturated fatty acid and/or unsaturated fatty acid ester in a continuous flow reaction. Preferably, said unsaturated fatty acid is a linear C16-C26 carboxylic acid or a mixture of different carboxylic acids selected from C16-C26 carboxylic acids or respective esters thereof. More preferably monounsaturated linear fatty acids are used and in particular C16-C26 monounsaturated linear fatty acids and/or esters thereof are used. Most preferably, oleic acid or a composition comprising oleic acid or ester(s) thereof is used in the skeletal isomerization reaction.

Various modifications and variations of the invention will be apparent to those skilled in the art without departing from the scope of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments.

The following examples are merely illustrative of the present invention and should not be construed to limit the scope of the invention as indicated by the appended claims in any way.

EXAMPLES

Example 1 - Synthesis of catalysts

Granulated zeolite catalysts were prepared according to the specifications below:

Method A

20 g of the NH4 ⁺ forms of the denoted zeolites (Zeolyst International; S1O2/AI2O ₃ ratio: mordenite 20 (CBV 21A), ferrierite 20 (CP914C), ZSM-5 23 (CBV 2314)) and 70 ml of IN HC1 were stirred in a round-bottom flask, equipped with an air condenser, at 55 °C for 24 h. Then the mixture was centrifuged and the separated solid was washed thrice each with 30 ml ¾0. Subsequently, it was dried on air. 4 g of this solid was mixed intensively with 1 g Aerosil 200 (Evonik) while 3.91 g H2O was added in several portions (an equivalent multiple of the specified quantities was used for the preparation of the granulated zeolites on a larger scale). The mixture became a slurry after extensive stirring. The slurry was poured on an unglazed ceramic tile and dried overnight. The dried solid mass was scraped off carefully and crushed to granules. Fractions of the desired grain sizes were separated using an appropriate set of sieves.

Method B

4 g of ferrierite (CP914C, Zeolyst International; Si0 ₂ /Al ₂ 0 ₃ ratio: 20), 1 g of Aerosil 200 and 3.91 g H ₂ 0 were intensively stirred until the mixture became a homogeneous slurry. Then the slurry was dried on an unglazed ceramic tile for two days, and the dry material was crushed and sieved carefully. 20 ml of IN HC1 was added to 4.8 g of the obtained granules. The mixture was held without stirring at 55 °C for 24 h. Then it was centrifuged, the liquid was removed and the remaining solid was triply washed with H ₂ 0 and centrifuged again and finally it was air dried.

Method C

The designated zeolites were prepared as outlined above in method A. The freshly so-prepared material was additionally calcined in a tube furnace (temperature ramp from r.t. to 400 °C for 2h, remaining at 400 °C for 4h, cooling down overnight).

Method D

The designated zeolites were prepared as outlined above in method A. Crushed material with grain sizes <0.5 mm was compacted with a press capacity of 2.2 t/cm . The material was then crushed and the sieve fraction from 0.32 to 1.0 mm was isolated and further used for calcination. The calcination of the compacted granules was carried out at 400 ° C in a muffle furnace for 4 h. The granules comprise zeolite and binder (Si0 ₂ , Aerosil 200, particles of about 12 nm). The material is significantly harder than that produced by method A, B or C. Method E

42 g of ferrierite (NH ₄ ⁺ form, CP914C, Zeolyst), 2 g of polyvinyl alcohol (powder, M = 72000, Roth) and 4 g of methyl cellulose (powder, Roth) were placed in a PTFE beaker and were mixed by stirring with a spatula. Then 20 g of silica sol dispersion (Ludox TM-50, 50 % Si0 ₂ , Aldrich) and 40 g of deionized water were added. A paste was formed by vigorous stirring having a consistency that is comparable to that of modeling clay. Then the paste was homogenized by intensive kneading and subsequently transferred into a rod. The prepared mass was packed airtightly and was aged overnight. Then strands of 1 mm diameter were formed using a manually operated mechanical device. First, these strands were dried at room temperature and then at 120 C (3 h). Finally, they were calcined at 400° C for 10 h. The catalyst comprises zeolite and binder (Si0 ₂ , 50 nm particles). The material is significantly harder than that produced by method A, B or C.

Method F

44 g of ferrierite (NH ₄ ⁺ form, CP914C, Zeolyst) 2 g of polyvinyl alcohol (powder, M - 72000, Roth) and 4 g of methyl cellulose (powder, Roth) were placed in a PTFE beaker and were mixed by stirring with a spatula. Then 50 g of alumina dispersion (20% AI2O ₃ , Alfa Aesar) and 15 g of deionized water were added. A paste was formed by vigorous stirring having a consistency that is comparable to that of modeling clay. Then the paste was homogenized by intensive kneading and subsequently transferred into a rod (diameter 2.5 cm, length 10 cm). The prepared mass was packed airtightly and was aged overnight. Then strands of 1 mm diameter were formed using a manually operated mechanical device. First, these strands were dried at room temperature and then at 120° C (3 h). Finally, they were calcined at 400° C for 10 h. The catalyst completed comprises zeolite and binder (AI2O ₃ , 50 nm particles). The material is significantly harder than that produced by method E.

Table 1 shows an overview of the synthesized catalysts:.

Table 1

Method G

A commercially extruded ferrierite from Zeolyst (CP 914C CY (1.6)) was crushed and grain sizes of 0.5-1 mm were selected by sieving and used as catalyst for the skeletal isomerization reaction. Method H

The catalyst granules of 0.5-1 mm obtained according to Method G were further treated with 1 N HC1 at 60 °C for 24 hours, washed neutrally and air-dried.

Method I

The catalyst obtained according to Method H was further calcined at 400 °C for four hours.

Table 2 shows an overview of used granulated commercial and modified commercial catalysts. Table 2

Example 2 - Catalytic skeletal isomerization

The reactions were carried out in a 1 inch continuous fixed-bed reactor equipped with a heating jacket, an internal temperature sensor, inlets for dosing of liquids and gases, and a sampling device. The respective mass of catalyst (grain size 0.5-1.0 mm) outlined in Table 3 was placed in the reactor. The catalyst bed was fixed by a bed of inert granular material. The reactor filled with the catalyst was purged carefully with an inert gas. Oleic acid (technical grade, 90% purity) or fatty acid mixtures were fed with the desired flow rate under exclusion of oxygen. Ongoing sampling at the reactor outlet was done and the samples were analyzed by GC/MS. Additionally, skeletally isomerized products were isolated by distillation. Results of conversion and yield of skeletally isomerized products testing variations with respect to catalysts and reaction conditions are shown in Table 3. Table 3

values are calculated as mol%

Example 3 - Catalyst regeneration

Table 4. Overview of regenerated catalysts

Regeneration by calcination

For catalyst regeneration, feeding was interrupted. The catalyst bed, consisting of catalyst 4c_5.3, was washed carefully with ethanol. Then the catalyst was calcined at 500° C for 4 h. The catalyst was reused (see Table 5, catalyst 4c_5.3 RT).

Regeneration by treatment with an acid

For catalyst regeneration, feeding was interrupted. The catalyst bed was washed carefully with ethanol. Glacial acetic acid was placed in a saturator (30 g, room temperature) and a certain amount was transferred into the gas phase by passage of argon (10 mL/min). The catalyst bed was passed through by this gaseous glacial acetic acid/argon mixture at room temperature for 12 h. The regenerated catalyst was reused (see Table 5, catalyst 4c_5.3 RC).

The effect of the regeneration is demonstrated in the examples in Table 5.

Tabelle 5

* used catalyst 4c_5.3 after 10 h of operating time

Example 4 - Product Purification

Step 1: Preparation

A mixture of isomerized fatty acid from a longer run experiment with the catalyst 4c_5.3 (see table 3) was used for the preparation of Isostearic acid. Step 2: Distillation

400g of the isomerized fatty acid were distilled under reduced pressure (3 mbar, 240°C). 340 g (85%) distillate was achieved; the residue mainly consists of polymerized fatty acids.

Step 3: Hydro genation The distillate was hydrogenated at 230°C under a hydrogen pressure of 20 bar in a stirred batch reactor with the use of 1.5% Ni-catalyst (Pricat 9932, BASF). The product was distilled to remove Ni-soaps. 330 g (97%) product was achieved; the Iodine value was below 2.

Step 4: Crystallization with wetting agent (Hydrophilization)

The distillate was melted to 50°C and an emulsion with 500 ml water, containing 1.2% of MgS04 and 0.4% of Sodium-Laurylsulfate of the same temperature, was formed by stirring. The emulsion is slowly cooled down in one hour under stirring to 10°C. The obtained aqueous dispersion is separated from the upper organic phase by a centrifuge.

The upper phase is dried. 256g (77%, over all steps 64%) of the Isostearic acid is obtained. The acid has an Iodine value below 2 and is a water-clear liquid at room temperature.