DK201500118A1 - Catalyst for induction heated high temperature endothermic reaction - Google Patents

Abstract

The present invention relates to a method for carrying out catalysis of an endothermic chemical reaction in a reactor, where a reactant is brought into contact with a catalyst material arranged to catalyzing the chemical reaction in a given temperature range T, where the catalyst material comprises a ferromagnetic nanoparticle component and a catalytically active, nanoparticle component. The method comprising the steps of: a. Heating the catalyst material by magnetic induction to a reaction temperature above 700 C, preferably within the temperature range from about 700 C to about 900 C; b. Recovering reaction products formed during the catalysis. The invention moreover relates to a catalyst material arranged to catalyze a chemical reaction as well as a reactor comprising catalyst material and a method of preparing a catalyst material.

Description

Title: Catalyst for induction heated high temperature endothermic reaction

FIELD OF THE INVENTION

The invention relates to a method for carrying out catalysis of an endothermic chemical reaction in a reactor. The invention moreover relates to a catalyst material arranged to catalyze a chemical reaction as well as a reactor comprising catalyst material and a method of preparing a catalyst material.

BACKGROUND OF THE INVENTION WO2014 / 162099 describes a method for heterogeneous catalysis of a chemical reaction using, in a reactor, at least one reagent and a catalytic composition that can catalyze the reaction within a given range of temperatures T. At least one reagent is brought in contact with the catalytic composition comprising a ferromagnetic nanoparticulate component of which the surface is formed at least partially by a compound which is a catalyst for the reaction. The nanoparticulate component is heated by means of magnetic induction in order to reach a temperature within the range of temperatures T. The reaction product (s) formed on the surface of the nanoparticulate component are recovered.

In WO2014 / 162099 the range of temperatures T is given to be 300 ° C to 500 ° C (see page 2, lines 32-34). Thus, WO2014 / 162099 describe a catalyst for use in catalysis of chemical reactions within a relatively limited temperature range. One object of the present invention is to provide a method for carrying out endothermal chemical reactions at a reaction temperature above the temperature range indicated in Wo2014 / 162099. Another object of the invention is to provide a catalyst for use in the method of the invention.

DESCRIPTION OF THE INVENTION

One aspect of the invention relates to a method for carrying out catalysis of an endothermic chemical reaction in a reactor, where a reactant is brought into contact with a catalyst material arranged to catalyze the chemical reaction at a given temperature range T, where the catalyst material comprises a ferromagnetic nanoparticle component and a catalytically active component on a support. The method comprises the steps of: a. Heating the catalyst material by magnetic induction to a reaction temperature above 700 ° C, preferably within the temperature range from about 700 ° C to about 900 ° C; b. Recovering reaction products formed during the catalysis.

In one embodiment, the heating of the catalyst material is carried out by providing a magnetic field of less than 1 Tesla and having a frequency between 0.5 and 100kHz, within the reactor. The frequency of the magnetic field may be between 500 and 1000 Hz.

In one embodiment, the chemical reaction is a steam reforming reaction.

In one embodiment, the chemical reaction is a cyanide reaction

In one embodiment, the ferromagnetic nanoparticle component of the catalyst material comprises Cobalt and the catalytically active component comprises Nickel.

Another aspect of the invention relates to a catalyst material arranged to catalyze a chemical reaction. The catalyst material comprises a ferromagnetic nanoparticle component and a catalytically active nanoparticle component on a support, said ferromagnetic nanoparticle component comprises Cobalt and said catalytically active nanoparticle component comprising Nickel.

In one embodiment, the catalyst material support comprises one or more of the following compositions: MgAl204

CaAl2O4, ZrO2, MgO, and / or La2O3,

In one embodiment, the catalytically active nanoparticle component further comprises one or more of the elements of the group of: Fe, Sm, Nb, Sn and Zn.

In one embodiment, the catalyst material is arranged to catalyze a steam reforming reaction taking place at a temperature above 700 ° C.

In one embodiment, the Curie temperature, Tc, of the catalyst material is about 700 ° C or above.

In one embodiment, the size of the ferromagnetic nanoparticle component is up to 400 nm, while the average size of the catalytically active nanoparticle component is about 10-25 nm.

In one embodiment, about 50 weight% or more of the ferromagnetic nanoparticle component is in the form of particles of size larger than 100 nm.

Yet another aspect of the invention relates to a reactor comprising a reformer, wherein the reformer comprises catalyst material arranged to catalyze a chemical reaction. The catalyst material comprises a ferromagnetic nanoparticle component and a catalytically active, nanoparticle component, and the reformer is at least partially surrounded by an induction coil arranged to be energized by a power source for supplying alternating current. The induction coil, when energized by said power source, is arranged to inductively heat said catalyst material by an alternating magnetic field produced by said induction coil to a reaction temperature above 700 ° C.

Yet another aspect of the invention relates to a method of preparing a catalyst material according to the invention.

This method includes the steps of:

a. Impregnating the support with Co (NO3) 2 * 6H2O b. Drying

c. Impregnating the support with Ni (NO3) 2 * 6H2O i.e. Drying and Calcining. f. Reduction.

In one embodiment, the method of preparing a catalyst material further comprises a step of calcining between the step b) of drying and step c) of impregnating.

In one embodiment, the method of preparing a catalyst material, further, between steps d and e, comprises the steps of: Impregnating the support with a solution comprising one or more of the elements of the group: Fe, Sm, Nb, Sn and Zn; followed by drying, and optionally calcining.

Induction heating is interesting in connection with reforming as heat transfer will often be the limiting factor in a traditional tubular reformer. With induction it is possible to deliver heat directly to the catalyst. Additionally induction heating offers a fast heating mechanism, which makes starting a reforming plant relative fast.

Today, the decentralized market for hydrogen is often dependent on expensive distribution and storage of hydrogen. As an alternative to this, induction heated reform is envisioned as a small scale hydrogen production technology potentially with fast startup for ad hoc hydrogen production and a heating system based on electricity instead of a fired hot box. A typical steam reforming process will be performed at a temperature of about 900 ° C due to thermodynamic constraints of the endothermic reaction. Facilitating this process with catalyst induction heating would require that the catalyst is sufficiently active for the reforming reaction and at the same time susceptible to induction heating.

Finding active materials for steam reforming has already been investigated in the literature and can be briefly summarized by the density functional theory (DFT) work done by Jones et al (G. Jones, J. G. Jakobsen, SS Shim, J. Kleis, MP Andersson, J. Rossmeisl, F. Abild-Pedersen, T. Bligaard, S. Helveg, B. Hinnemann, J. R. Rostrup-Nielsen, I. Chorkendorff, J. Sehested, J. K. Nørskov, First principles calculations and experimental insight into methane steam reforming over transition metal catalysts, Journal of Catalysis, 259 (2008) 147-160). The most active candidates are Ru, Rh, Ni, and Ir, decreasing in activity in that order.

To make the catalyst susceptible to induction heating, it is favorable if the material is ferromagnetic (or ferrimag-netic / antiferromagnetic). The magnetic properties are very dependent on temperature because the thermal vibration of atoms increases with temperature. Over a given temperature the thermal energy will be sufficiently large to overcome the cooperative ordering of the magnetic moments which means that a ferromagnetic material will become paramagnetic. The temperature of this transition is material dependent and is known as the Curie temperature. In practice this is seen as a sudden drop in the saturation magnetization of a material as a function of temperature. As an example, nickel has a Curie temperature of 354 ° C.

Similar to the Curie temperature, also antiferromagnetic materials will become paramagnetic at elevated temperatures. This temperature is defined as the Néel temperature.

To have good induction heating in reforming conditions material selection, the limited to materials with Cu-rie / Néel temperatures will be higher than the operating conditions in the order of 900 ° C. Most elements cannot maintain a magnetic moment on their own at temperatures above 100 ° C. only

Ni, Fe, and Co can be used for higher temperature application, with Curie temperatures of 354 ° C, 770 ° C, and 1115 ° C, respectively.

Compounds containing one or several of the different (anti) ferromagnetic elements will usually have a Curie temperature somewhere in between the Curie temperatures of the bulk compounds. For example, the Curie temperature of a Co-Ni alloy will be between 354 ° C and 1115 ° C.

The Curie temperature will additionally be influenced by the size of the crystal lattice of the ferromagnetic material, as small structures are more sensitive to fluctuations of the magnetic spins of the individual atoms (see e.g. Curie-Weiss law, University of Cambridge, 2013).

Induction heating of materials will be aided by a high magnetic hysteresis loss, which is material specific. Generally materials are distinguished between soft and hard magnets. Soft magnets have high permeability and low coercivi ty. This makes magnetization and demagnetization easy, which means that the hysteresis loop curve will be small. Hard magnets are more suitable for induction heating as these are characterized by having a high coercivi ty and a high magnetic flux saturation. The high coercivity of these materials means that they are difficult to demagnetize and therefore all permanent magnetic materials are by definition hard magnets.

Additionally, the Joule heating contribution will also favor large particles for efficient induction heating, such as this scale with d2, where d is the diameter of the particles. Thus, large particles will generally be favored for induction heating.

In general, the highest magnetic hysteresis heating is achieved with magnetic materials based on combinations of rare earth elements such as Nd, Sm, etc. and the materials with high Curie temperatures, Ni, Fe, and Co. However, the low Curie / Néel temperature of the rare earth metals generally means that hard magnetic materials end up having a low effective Curie temperature. Alnico type permanent magnets are therefore one of the best choices for high temperature application today.

Hard magnetic materials are normally referred to as bulk materials; their known properties are normally indicated for bulk materials, but these could very likely change when transferred to a supported catalytic system.

In summary, a catalyst for induction heated reforming should fulfill the following criteria: • Sufficient catalytic activity for the reforming reaction. o Materials such as Ru, Rh, Ni, and Ir are among the best to achieve high activity. • A Curie temperature above 700 ° C and ideally above 900 ° C. o Only Co as a pure element can achieve this, but alloys with Co are also a possibility. • High hysteresis heating. o Hard magnetic materials are needed for this. A catalyst for induction heated reform should at least contain some cobalt to enable inductive heating at high temperatures. However, the steam reforming activity of cobalt has previously been shown to be low. A candidate for induction heated reform could therefore be a system based on both Co and Ni. Alloys of Co and Ni have previously shown decent activity for reforming (see N. Fischer, B. Clapham, T. Feltes, E. van Steen, M. Claeys, "Size-Dependent Phase Transformation of Catalytically Active Nanoparticles Captured In Situ", Angew Chem. Int. Ed., 53 (2014) 1342-1345). Such an alloy should probably contain in the order of 60% Co of the total loading to maintain a sufficiently high Curie temperature.

To maximize the hysteresis loss, it could be an inspiration to look at the Alnico system, which is a hard magnetic material. These magnets contain Co, Ni, and Al, which seems suitable for the production of a reforming catalyst. A range of Co-Ni based catalysts were produced. A standard MgA1204 carrier was used. Magnetic properties were studied as a function of temperature using an in situ magnetometer. The magnetic set-up uses a Weiss extraction method to determine total magnetization of a material / catalyst under operating conditions.

Determination of the Curie temperature can additionally or alternatively be done on the basis of a drop test.

The catalyst may be characterized by Co and Ni loading and metal particle size. The metal particle size may e.g. be determined by X-ray Diffraction (XRD) analysis or Scanning Electron Microscope (SEM) analysis.

Aged and new versions of the same catalyst sample have been investigated by SEM. The analysis showed that sintering had taken place during the aging process, with particle sizes varying between 50 and 400 nm. Moreover, it seems that sintering of Co is more pronounced than sintering of Ni.

The activity of aged Ni-Co catalyst was also compared to the activity of a fresh Ni-Co catalyst. This showed a certain degree of deactivation, up to more than 50%. During aging, the particle size had increased from about 20 nm in the fresh catalyst to up to 40 nm in the aged catalyst. This seems to correspond to a known development in particle size.

When the activity of the catalyst is determined as a function of nickel loading, it is seen that the activity of the Ni-Co catalyst scales to some extent with the nickel loading, at least in the interval from 0 to 6 wt% Ni.

For the different samples of catalyst, it was found that the Curie temperature was higher than 700 ° C, even in the case of a Co content of about 2 wt%.

In conclusion, a catalyst for induction heated reforming where the heat for the reaction is delivered directly to the active phase of the catalyst has to fulfill several aspects: it should be sufficiently active for the reforming reactions, it should be ferromagnetic at temperatures of up to about 900 ° C and therefore have a sufficiently high Curie temperature, and the hysteresis loss should be high to avoid high frequencies in the magnetic field and to make the catalyst bed compact. A Ni-Co alloy supported on MgA1204 meets these criteria.

On the basis of activity measurements on a range of Ni-Co / MgA1204 catalysts, it was concluded that the best procedure for production of Ni-Co catalysts was sequential impregnation of the active metals with calcination in between each impregnation.

The presence of nickel on the catalyst was pivotal for the steam reforming activity; in that catalyst impregnated with cobalt alone is practically inactive.

Contrary to the steam reforming activity, cobalt was found pivotal for magnetic properties of the NiCo catalysts. Impregnation with any amount of Co was found to give a Curie temperature above 700 ° C. Additionally, the hysteresis loss was found to scale practically linear with the cobalt content on the catalyst, being 8.8 mJ / g for a catalyst with 10 wt% Co.

On the basis of the magnetic characterization it was determined that induction by a magnetic field of up to 0.5 T at a frequency in the low end of the kHz regime could be sufficient to supply the required energy for steam reforming. Using a low frequency for the induction field could make the induction heating more selective and thereby limit undesirable heating of the surroundings by Joule heating by eddy currents and residual heating.

Overall, it is concluded that Ni-Co based catalysts and reformers containing Ni-Co based catalysts are suitable for induction heated reforming. The catalytic effect for steam reforming is in practice attributed to cobalt and the magnetic properties.

All in all, the invention relates to the following aspects: 1. A method for carrying out catalysis of an endothermic chemical reaction in a reactor, where a reactant is brought into contact with a catalyst material arranged to catalyze the chemical reaction at a given temperature range T, where the catalyst material comprises a ferromagnetic nanoparticle component and a catalytically active component on a support, the method comprising the steps of: a. Heating the catalyst material by magnetic induction to a reaction temperature above 700 ° C, preferably within the temperature range from about 700 ° C to about 900 ° C; b. Recovering reaction products formed during the catalysis. 2. A method of aspect 1 wherein the heating of the catalyst material is carried out by providing a magnetic field of less than 0.5 Tesla and having a frequency between 0.5 and 100kHz, within the reactor. 3. A method of aspect 2 wherein the frequency of the magnetic field is between 500 and 1000 Hz. 4. A method of any of the aspects 1 to 3, wherein the chemical reaction is a steam reforming reaction. 5. A method of any of the aspects 1 to 4, wherein the chemical reaction is a cyanide reaction (CH4 + NH3 -► HCN + 3H2). 6. A method of aspect 1 wherein the ferromagnetic nanoparticle component comprises Cobalt and the catalytically active component comprises Nickel. A catalyst material arranged to catalyze a chemical reaction, wherein the catalyst material comprises a ferromagnetic nanoparticle component and a catalytically active nanoparticle component on a support, said ferromagnetic nanoparticle component comprising Cobalt and said catalytically active nanoparticle component comprising Nickel. 8. A catalyst material of aspect 7, wherein the support comprises one or more of the following compositions:

MgAl204 CaAl204, Zr02, MgO, and / or La2C> 3, 9. A catalyst material of any of the aspects 7 or 8, the catalytically active nanoparticle component further comprises one or more of the elements of the group of: Fe, Sm , Nb, Sn and Zn. 10. A catalyst material of any of the aspects 7 to 9, said catalyst material being arranged to catalyze a steam reforming reaction taking place at a temperature above 700 ° C. 11. A catalyst material of any of the aspects 7 to 10, where the Curie temperature, Tc, is about 700 ° C or above. 12. A catalyst material of any of the aspects 7 to 11, wherein the size of the ferromagnetic nanoparticle component is up to 400 nm, while the average size of the catalytically active, nanoparticle component is about 10-25 nm. 13. A catalyst material of any of the aspects 7 to 12, about 50 weight! or more of the ferromagnetic nanoparticle component is in the form of particles of size larger than 100 nm. A reactor comprising a reformer, said reformer comprising catalyst material arranged to catalyze a chemical reaction, said catalyst material comprising a ferromagnetic nanoparticle component and a catalytically active, nanoparticle component, wherein the reformer is arranged at least partly by an induction coil to be energized by a power source for supplying alternating current, said induction coil, when energized by said power source, is arranged to inductively heat said catalyst material by an alternating magnetic field produced by said induction coil to a reaction temperature above 700 ° C. A method of preparing a catalyst material of any of the aspects 7 to 13, comprising the steps of: a. Impregnating the support with a Co containing solution, e.g. Co (NO3) 2 * 6H20 b. Drying c. Impregnating the support with an NI containing solution, e.g. Ni (NO3) 2 * 6H20 d. Drying or Calcining. f. Reduction. A method of preparing a catalyst material of aspect 15, further comprising a step of calcining between the step b) of drying and step c) of impregnating. 17. A method of preparing a catalyst material of any of the aspects 15 or 16, further, between steps d and e, comprising the steps of: - Impregnating the support with a solution comprising one or more of the elements of the group: Fe , Sm, Nb, Sn and Zn, - followed by drying, and optionally calcining. 18. Use of the method of any of the aspects 1 to 6 for producing H2.

Claims (10)

1. A method for carrying out catalysis of an endothermic chemical reaction in a reactor, where a reactant is brought into contact with a catalyst material arranged to catalyzing the chemical reaction in a given temperature range T, where the catalyst material comprises a ferromagnetic nanoparticle component and a catalytically active component on a support, the method comprising the steps of: a. Heating the catalyst material by magnetic induction to a reaction temperature above 700°C, preferably within the temperature range from about 700°C to about 900°C; b. Recovering reaction products formed during the catalysis .

2. A method according to claim 1, wherein the frequency of the magnetic field is between 500 and 1000 Hz.

3. A method according to any of the claims 1 or 2, wherein the chemical reaction is a steam reforming reaction.

4. A method according to claim 1, wherein the ferromagnetic nanoparticle component comprises Cobalt and the catalytically active component comprises Nickel.

5. A catalyst material arranged to catalyze a chemical reaction, where the catalyst material comprises a ferromagnetic nanoparticle component and a catalytically active nanoparticle component on a support, wherein said ferromagnetic nanoparticle component comprises Cobalt and said catalytically active nanoparticle component comprises Nickel.

6. A catalyst material according to claim 5, wherein the catalytically active nanoparticle component further comprises one or more of the elements from the group of: Fe, Sm, Nb, Sn and Zn.

7. A catalyst material according to claim 5 or 6, wherein the Curie temperature, Tc, is about 700°C or above.

8. A reactor comprising a reformer, said reformer comprising catalyst material arranged to catalyze a chemical reaction, said catalyst material comprising a ferromagnetic nanoparticle component and a catalytically active, nanoparticle component, wherein the reformer is at least partly surrounded by an induction coil arranged to be energized by a power source for supplying alternating current, wherein said induction coil, when energized by said power source, is arranged to inductively heat said catalyst material by an alternating magnetic field produced by said induction coil to a reaction temperature above 700°C.

9. A method of preparing a catalyst material according to claim 5 to 7, comprising the steps of: a. Impregnating the support with a Co containing solution, e.g. Co (NO3) 2*6H20 b. Drying c. Impregnating the support with a NI containing solution, e.g. Ni (NO3) 2*6H20 d. Drying e. Calcining. f. Reducing.

10. Use of the method according to any of the claims 1 to 6 for producing 1¾ .