METHOD FOR PRODUCING CATALYSTS USING 3D PRINTING TECHNOLOGY

Abstract

The invention relates to a method for producing iron-containing shaped catalyst bodies by means of 3D printing technology and to iron-containing shaped catalyst bodies that are obtainable by this method and to their use as catalysts in the ammonia synthesis or the Fischer-Tropsch reaction.

Claims

1. A method for producing iron-containing shaped catalyst bodies, comprising the steps of: a) applying a pulverulent starting material or starting material mixture comprising at least one iron compound in a thin layer to a base, b) subsequently irradiating this layer at selected sites so that the powder at these sites becomes connected, thereby connecting the powder particles to one another, c) removing the unconnected powder, so that the connected powder remains in the form of the shaped catalyst body.

2. The method as claimed in claim 1, wherein between step b) and step c) steps a) and b) are repeated until the shape of the shaped catalyst body has formed.

3. The method as claimed in claim 1, wherein step a) a mixture of Fe in oxidation state 0 and FeO, Fe.sub.2O.sub.3 or Fe.sub.3O.sub.4, preferably a mixture of Fe and Fe.sub.3O.sub.4, is applied.

4. The method as claimed in claim 3, wherein the iron compounds contained in the mixture are transformed at least partially into other iron compounds.

5. The method as claimed in claim 3, wherein the starting material mixture applied is pulverulent Fe(0) and Fe.sub.3O.sub.4 in the form of magnetite and these are transformed at least partially into wuestite.

6. The method as claimed in claim 1, wherein the fraction of wuestite in the iron compounds of the shaped catalyst body obtained is at least 50 wt %, preferably at least 80 wt %, more preferably at least 85 wt %, with greater preference at least 90 wt %, and very preferably 100%.

7. A shaped catalyst body produced by a method as claimed in claim 1.

8. The shaped catalyst body as claimed in claim 7, wherein the fraction of wuestite in the iron compounds of the shaped catalyst body is at least 50 wt %, preferably at least 80 wt %, more preferably at least 85 wt %, with greater preference at least 90 wt %, and very particularly 100 wt %.

9. The shaped catalyst body as claimed in claim 7, wherein it has a pore volume in the range from 10 to 100 mm.sup.3/g.

10. A method for ammonia synthesis from hydrogen and nitrogen with a shaped catalyst body produced by a method as claimed in claim 1 6.

11. A method for synthesizing a hydrocarbon mixture from hydrogen and carbon monoxide with a shaped catalyst body produced by a method as claimed in claim 1 6.

12. The method as claimed in claim 11, wherein it comprises a Fischer-Tropsch reaction.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0049] FIG. 1 shows a photo of a shaped body structure in the form of a bead having three cylindrical channels which intersect one another orthogonally, an all-round indentation between the channels, and also semicircular indentations on the bead surface.

[0050] FIG. 2 shows a photo of a shaped body structure in the form of a three-dimensional letter C.

[0051] FIG. 3 shows a photo of a shaped body structure in the form of a cylinder having three cylindrical channels which intersect one another orthogonally.

[0052] FIG. 4 shows the x-ray powder diffractogram of comparative catalyst 1.

[0053] FIG. 5 shows the x-ray powder diffractogram of the inventive catalyst 3.

EXPERIMENTAL SECTION

Measurement Methods

Pore Volume

[0054] The pore volume was determined using the PASCAL 440 mercury porosimeter from Thermo Electron Corporation. Measurement took place according to ASTM-D4284-12.

[0055] For the conduct of the measurements, the sample was first dried at 60° C. for 16 h. The sample was thereafter evacuated in a dilatometer at room temperature for 30 min (p<0.01 mbar) and filled with mercury. Following insertion into the autoclave of the PASCAL 440, the pressure was slowly increased to up to 4000 barg. The evaluation took place on the assumption of cylindrical pores, a contact angle of 140°, and a mercury surface tension of 480 dyn/cm.

Side Crush Strength

[0056] The side crush strength (SCS) was measured using the Zwick 0.5 instrument from Zwick with a 500N load cell. Evaluation took place using the test Xpert II software. At least 50 individual samples were measured and the average side crush strength was calculated by adding up the individual values and dividing them by the number of samples measured. The side crush strength/diameter (SCSD) was ascertained by first dividing the value of the side crush strength for the respective sample by its diameter. The individual values obtained in this way were added up and divided by the number of samples measured.

X-Ray Powder Diffractometry

[0057] The crystal structures and also their weight fraction in the shaped catalyst body were determined by means of x-ray diffractometry and Rietveld refinement. The sample was measured in a D4 Endeavor from BRUKER over a range from 5 to 90°2Θ (step sequence 0.020°2Θ, 1.5 seconds measuring time per step). The radiation used was CuKα1 radiation (wavelength 1.54060 Å, 40 kV, 35 mA). During the measurement the sample plate was rotated about its axis at a velocity of 30 revolutions per min. The diffractogram of the reflection intensities obtained was subjected to quantitative calculation by means of Rietveld refinement and the fraction of the respective crystal structure in the sample was determined. The fraction of the respective crystal structure was determined using the TOPAS software, Version 6, from BRUKER.

Elemental Analysis

[0058] Chemical elements were determined by means of ICP (inductively coupled plasma) measurement according to DIN EN ISO 11885. Potassium was determined by means of AAS (atomic absorption spectrometry) measurement according to “E13/E14 Deutsche Einheitsverfahren zur Wasser Abwasser and Schlammuntersuchung Band 1, 1985” [E13/E14 unified German methods for water, wastewater and sludge analysis, volume 1, 1985].

Example 1: Comparative Catalyst 1

[0059] Comparative catalyst 1 was produced by mixing and homogenizing a mixture of magnetite and iron powder in a stoichiometric ratio of 1:1 and then melting it in an arc furnace. When the mixture was fully melted, the melt was cooled in a melting form and the cooled mass was converted to particles by breaking up the material in a jaw crusher. The pore volume was 7.5 ml/g. The x-ray powder diffractogram is shown in FIG. 4.

Example 2: Comparative Catalyst 2

[0060] Comparative catalyst 2 was produced by melting a commercially available magnetite ore in an arc furnace. When the ore was completely melted, the melt was cooled in a melting form and the cooled mass was converted to particles by breaking up the material in the jaw crusher.

Example 3: Inventive Catalyst 3

[0061] The inventive catalyst 3 was produced by mixing and homogenizing a mixture of magnetite and iron powder in a stoichiometric ratio of 1:1 and subjecting the mixture to a three-dimensional printing operation in an M2 printer from ConceptLaser. In this case a layer of the mixture with a layer thickness of 1.5 mm was introduced and was treated with a laser beam at 400 W power so as to give shaped bodies of granular form. After the printing process, the unconnected particles were removed from the printed shaped bodies.

[0062] As a result of the production method, the particles were predominantly in the form of wuestite. The pore volume was 16.2 mL/g. The x-ray powder diffractogram is shown in FIG. 5.

Example 4: Inventive Catalyst 4

[0063] The inventive catalyst 4 was produced by mixing and homogenizing a mixture of magnetite and iron powder in a stoichiometric ratio of 1:1 and of Al, K and Ca compounds as promoters and subjecting the mixture to a three-dimensional printing operation in an M2 printer from ConceptLaser. In this case a layer of the mixture with a layer thickness of 1.5 mm was introduced and was treated with a laser beam at 400 W power so as to give shaped bodies of granular form. After the printing process, the unconnected particles were removed from the printed shaped bodies.

[0064] As a result of the production method, the particles were predominantly in the form of wuestite.

Application Example 1

[0065] The inventive catalysts 3 and 4 and also the comparative catalysts 1 and 2 were employed in a reaction for ammonia synthesis.

[0066] For this reaction, 5 g of catalyst sample in the form of the fraction having a particle diameter of 450 to 550 micrometers were introduced into a reactor and, at a reactor pressure of 90 bar, a gas stream consisting of nitrogen (22.5 volume %), hydrogen (67.5 volume %) and argon (10 volume %) was passed through. The temperature in the reactor interior was raised continuously to 520° C. and maintained at this temperature until the reduction of the catalyst was at an end. The pressure was subsequently increased to 100 bar, cooling took place to a temperature of 400° C., and these conditions were retained for 22 hours. After the 22 hours, the concentration of ammonia formed was detected and the temperature was subsequently raised to 520° C. and retained for 14 hours in order to produce accelerated deactivation of the catalyst. Thereafter the procedure described above (holding of the temperature at 400° C. for 22 h, followed by a temperature increase to 520° C. for 14 h) was repeated twice more (once more for catalyst 4). The results of the ammonia concentrations are summarized in table 2.

TABLE-US-00001 Ammonia yield per cycle [kg.sub.NH3/ (kg.sub.catalyst * h)] Catalyst Cycle 1 Cycle 2 Cycle 3 Comparative catalyst 1 0.150 0.137 0.129 Comparative catalyst 2 0.063 0.037 0.00 Catalyst 3 0.165 0.151 0.145 Catalyst 4 0.455 0.444 —