HYDROTALCITE-PRECURSOR BASED CATALYST WITH IMPROVED PERFORMANCE FOR LTS REACTION

Abstract

The present invention relates to a novel catalyst for LTS processes, the method of its preparation and LTS process by use of this catalyst.

Claims

1. Catalyst for an LTS reaction, comprising an amorphous Cu—Zn—Al mixed oxide.

2. Catalyst according to claim 1, whereby it comprises domains of CuO, ZnO and a Zn spinel, preferably a Zn spinel of gahnite structure, as determined by Pair Distribution Function (PDF) analysis.

3. Catalyst according to claim 1, wherein the catalyst is present as a shaped catalyst body, preferably as a tableted shaped body.

4. Catalyst according to claim 3, wherein the catalyst is present as a tableted shaped body with a side crush strength of from 40 to 250 N, preferably of from 80 to 220 N, more preferably of from 100 to 220 N, most preferably of from 150 N to 210 N.

5. Catalyst according to claim 1, wherein the amount of Cu is in the range of from 30 to 50 mol-%, preferably of from 30 to 45 mol-%, the amount of Zn is in the range of from 15 to 45 mol-%, preferably of from 20 to 40 mol-%, and the amount of Al is is in the range of from 15 to 50 mol-%, preferably in the range of from 20 to 40 mol-%, in relation to the overall amount of Cu, Zn and Al in the catalyst.

6. Catalyst according to claim 1, wherein the phase content in weight percent, as determined by PDF analysis, of CuO is in the range of from 10 to 20, preferably in the range of from 15 to 20, of ZnO is in the range of from 1 to 10, preferably of from 2 to 7, and of the Zn spinel of gahnite structure is in the range of from 70 to 89, preferably in the range of from 75 to 85.

7. Process for the preparation of the catalyst according to claim 1, comprising the following steps: a) Providing an aqueous solution comprising solved Cu, Zn and Al compounds b) Providing an aqueous solution comprising a carbonate c) mixing the solution obtained in step a) and the carbonate solution obtained in step b) to obtain a mixture comprising a precipitate of mixed Cu—Zn—Al hydroxide-carbonate d) Ageing the mixture obtained after step c) e) Separating the precipitate from the solution and optionally washing and/or drying the precipitate f) Calcining the precipitate at a temperature in the range of from 200° C. to 600° C., preferably in the range of from 200 to 500° C., more preferably in the range of from 300° C. to 500° C., most preferably in the range of from 350° C. to 500° C., for a duration in the range of from 15 minutes to 8 hours, preferably in the range of from 0.5 to 6 h, more preferably in the range of from 1 hour to 6 hours.

8. Process according to claim 7, wherein the precipitate after step f) is formed to obtain a shaped catalyst body in a step g).

9. Process according to claim 7, wherein the pH value after step c) is 8 or higher, preferably lies within a range of from 8 to 9, more preferably within 8.5 to 9.

10. LTS reaction by use of a catalyst according to any of claims 1 to 6.

11. LTS reaction according to claim 10, whereby the catalyst is reduced before usage.

12. LTS reaction according to claim 10 or 11, wherein a synthesis gas comprising CO, CO.sub.2 and H.sub.2 is used and wherein the CO content is 60% or less, preferably 20% or less, more preferably in the range of from 0.1 to 20%.

Description

[0070] The examples below demonstrate in more detail specific embodiments of the invention.

[0071] FIG. 1 shows the CO conversion of the catalysts according Examples 1 to 3 and Comparison Examples 1 and 2 at varying temperatures.

[0072] FIG. 2 shows the CO conversion of the catalysts according Examples 4 to 6 and Comparison Examples 1 and 2 at varying temperatures.

METHODS

[0073] Bulk Density

[0074] The determination of the bulk density of the shaped catalyst body was carried out in that a 100 mL measuring cylinder was completely filled with the catalyst samples. The bulk density was calculated by dividing the weight of catalyst samples filled into the measuring cylinder by the volume of 100 mL.

[0075] Loss on Ignition

[0076] The determination of the loss on ignition for the purposes of the present invention was carried out in that about 1-2 g of a sample of the material to be analyzed were weighted and this sample subsequently being heated under from room atmosphere to 900° C. and maintained at this temperature for 3 hours. The sample was subsequently cooled under a protective atmosphere and the remaining weight was measured. The difference between weight before and after the thermal treatment corresponds to the loss on ignition.

[0077] Side Crush Strength

[0078] The determination of the side crush strength of the shaped catalyst body was carried out in accordance with ASTM D4179-11, whereby no preheating of the samples was performed. Here, a statistically sufficient number of pellets (at least 20 pellets) were measured and the arithmetic mean of the individual measurements was calculated. This arithmetic mean corresponds to the side crush strength of a particular sample. For the reduced shaped catalyst body the same method was applied, whereby the samples, prior to measurement, were reduced in a mixture of hydrogen and nitrogen and kept under nitrogen during measurement.

[0079] Elemental Analysis

[0080] The determination of chemical elements was carried out by means of ICP (Inductively Coupled Plasma) measurement in accordance with DIN EN ISO 11885.

[0081] BET Surface Area

[0082] The specific BET surface area was determined by means of nitrogen adsorption in accordance with DIN 66131. The catalyst obtainable by the process of the invention preferably has a BET surface area in the range from 20 to 100 m2/g, in particular from 30 to 80 m2/g and particularly preferably from 40 to 60 m2/g.

[0083] Pore Volume

[0084] The pore volume of the shaped catalyst body was measured by the mercury porosimetry method in accordance with DIN 66133.

[0085] Structural Determination by PDF Analysis

[0086] The determination of local structures by PDF analysis was conducted, in that first XRD data of calcined materials and an empty capillary for reference were measured in transmission mode (1 mm diameter capillaries) by an Empyrean diffractometer using Molybdenum radiation (Q.sub.max17.5 Å.sup.−1) using variable counting time (VCT) method. PDF data from recorded XRD data were generated by Malvern Panalytical HighScore Plus software. Analysis of the experimental PDF data was performed using PDFgui program by fitting the observed PDF data against the calculated data which were generated by model structures (.cif files) in PDFgui. Contribution of the empty capillary was subtracted from the background of the observed data before fitting. Instrument related parameters such as peak broadening (Qbroad) and peak dampening (Qdamp) factors were determined by analyzing the PDF of a standard crystalline powder (measured in the same way as for the samples) and those were fixed throughout the data fitting process. Unit cell parameters and atomic displacement parameters of individual phases were refined stepwise.

[0087] Loss on Attrition

[0088] The loss on attrition was determined in that for a sample of approx. 110 g any fines were first separated by use of a 1 mm sieve, afterwards the samples was thermally treated at 120° C. for 3 hours and weighted.

[0089] Then 100 g of the sample were placed into a closed steel drum and rotated 1800 times at 60 rpm. Afterwards the sample was placed into a 1 mm sieve and separated from any fines. Finally, the sample was again thermally treated at 120° C. for 3 hours and weighted. The loss on attrition was calculated as difference between initial weight and final weight, divided by the initial weight.

EXAMPLES

[0090] Precursor A

[0091] In a solution of 9.031 kg concentrated nitric acid in 4.5 L deionized water 1.725 kg sodium aluminate and 0.565 kg zinc oxide were solved. The so obtained solution was added to a solution of 2.727 kg Cu(NO.sub.3).Math.2.5H.sub.2O dissolved in 4 L deionized water.

[0092] Afterwards the resulting solution was mixed with additional deionized water to result in an overall volume of 20 L.

[0093] The precipitating solution was provided by dissolving 1.136 kg NaCO.sub.3 in 20 L deionized water followed by the addition of 3.000 kg of saturated sodium hydroxide solution and filling up to 30 L with deionized water.

[0094] The metal containing solution and the precipitating solution were then added dropwise into a batch containing 15 L deionized water, whereas the pH value rapidly increased to pH 9 and was kept at this pH during this addition and whereas the formation of a bluish suspension started. Once the addition of the metal-containing was finished, the addition of precipitating solution was stopped and the resulting bluish suspension was stirred for an additional hour at room temperature. The precipitate was removed from the suspension by filtration on a chamber filter press. The filter cake was washed with deionized water until the filtrate had an electrical conductivity of <250 μS/cm. This filter cake was used for preparation of the catalyst samples of Example 1 to 3. It revealed a Cu content of 31.6 mol %, a Zn content of 18.7 mol % and an Al content of 49.8 mol %.

[0095] Precursor B

[0096] In a solution of 7.007 kg concentrated nitric acid in 4.5 L deionized water 1.337 kg sodium aluminate and 0.576 kg zinc oxide were solved. The so obtained solution was added to a solution of 3.422 kg Cu(NO.sub.3).Math.2.5H.sub.2O dissolved in 4 L deionized water.

[0097] Afterwards the resulting solution was mixed with additional deionized water to result in an overall volume of 20 L.

[0098] The precipitating solution was provided by dissolving 1.136 kg NaCO.sub.3 in 20 L deionized water followed by the addition of 3.500 kg of saturated sodium hydroxide solution and filling up to 30 L with deionized water.

[0099] The metal containing solution and the precipitating solution were then added dropwise into a batch containing 15 L deionized water, whereas the pH value rapidly increased to pH 9 and was kept at this pH during this addition and whereas the formation of a bluish suspension started. Once the addition of the metal-containing solution was finished, the addition of precipitating solution was stopped and the resulting bluish suspension was stirred for an additional hour at room temperature. The precipitate was removed from the suspension by filtration on a chamber filter press. The filter cake was washed with deionized water until the filtrate had an electrical conductivity of <250 μS/cm. This filter cake was used for preparation of the catalyst samples of Example 4 to 6. It revealed a Cu content of 40.8 mol %, a Zn content of 19.6 mol % and an Al content of 39.6 mol %.

Example 1

[0100] The filter cake of Precursor A was dried at 120° C. for 12 h, granulated and sieved by a 1 mm sieve and calcined at 450° C. for 2 h in a batch rotary calciner, whereby the filter cake was heated within the calciner with a heating ramp of 300° C./h. The calcined material was mixed with 2 wt. % graphite, compacted and tableted to result in tablets of 4.8 mm width and 3.2 mm height.

Example 2

[0101] The filter cake of Precursor A was suspended in deionized water to achieve a solid content of 18 wt. %. The suspension was processed by spray drier having an entrance temperature of 280° C. and outlet temperature of 110° C. The spray-dried precursor was calcined in a continuous rotary calciner at 500° C. for 15 minutes and with a mass flow rate of 300 g/h. The calcined material was mixed with 2 wt. % graphite, compacted and tableted to result in tablets of 4.8 mm width and 3.2 mm height.

Example 3

[0102] The same procedure as for Example 2 was applied with the exception that Cs.sub.2CO.sub.3 was added to the suspension before the spray-drying step resulting in a Cs content of the catalyst of 0.8 wt %.

Example 4

[0103] The filter cake of Precursor B was dried at 120° C. for 12 h, granulated and sieved by a 1 mm sieve and calcined at 450° C. for 2 h in a batch rotary calciner, whereby the filter cake was heated within the calciner with a heating ramp of 300° C./h. The calcined material was mixed with 2 wt. % graphite, compacted and tableted to result in tablets of 4.8 mm width and 3.2 mm height.

Example 5

[0104] The filter cake of Precursor B was suspended in deionized water to achieve a solid content of 18 wt. %. The suspension was processed by spray drier having an entrance temperature of 280° C. and outlet temperature of 110° C. The spray-dried precursor was calcined in a continuous rotary calciner at 500° C. for 15 minutes and with a mass flow rate of 300 g/h. The calcined material was mixed with 2 wt. % graphite, compacted and tableted to result in tablets of 4.8 mm width and 3.2 mm height.

Example 6

[0105] The same procedure as for Example 5 was applied with the exception that Cs.sub.2CO.sub.3 was added to the suspension before the spray-drying step resulting in a Cs content of the catalyst of 0.8 wt %.

Comparison Example 1

[0106] A solution was provided by dissolving 14.16 mol Cu(NO.sub.3).sub.2.Math.2.5H.sub.2O, 2.93 mol ZnO and 7.04 mol sodium aluminate in a nitric acid solution resulting in a volume of 20 L.

[0107] The metal containing solution and a 3.3M NaOH solution were then added dropwise into a batch vessel containing 15 L deionized water, whereas the pH value rapidly raised and kept within a range of 9.5-10. Once the addition of the metal-containing solution was finished, the addition of precipitating solution was stopped and the resulting bluish suspension was stirred for additional 3 hours at room temperature. The precipitate was removed from the suspension by filtration on a chamber filter press. The filter cake was washed with deionized water until the filtrate had an electrical conductivity of <250 μS/cm. This filter cake was dried at 120° C. for 6 hours, followed by calcination at 400° C. for 15 minutes and with a mass flow rate of 300 g/h. It revealed a Cu content of 60.5 mol %, a Zn content of 12.5 mol % and an Al content of 27.0 mol %.

[0108] The resulting material was afterwards mixed with 2 wt. % graphite, compacted and tableted to result in tablets of 0.48 mm width and 3.2 mm height.

Comparison Example 2

[0109] A solution was provided by dissolving 6.81 mol Cu(NO.sub.3).sub.2.Math.2.5H.sub.2O, 8.88 mol ZnO and 4.81 mol sodium aluminate in a nitric acid solution resulting in a volume of 20 L. The metal containing solution was heated to 90° C. and added dropwise into a batch vessel containing a precipitating solution obtained by dissolution of 1.350 kg Na.sub.2CO.sub.3 in 26 L deionized water, whereas this solution is intensively stirred during the addition of the metal containing solution.

[0110] During addition of the metal containing solution, the pH value of the precipitating solution decreases from initially 10 to 5 after complete addition of the metal containing solution.

[0111] Once the addition of the metal-containing solution was finished, the resulting bluish suspension was stirred for additional 30 minutes at 90° C. The precipitate was removed from the suspension by filtration on a chamber filter press. The filter cake was washed with deionized water until the filtrate had an electrical conductivity of <250 μS/cm. This filter cake was calcined at 450° C. for 24 h in a muffle furnace. It revealed a Cu content of 33.6 mol %, a Zn content of 44.1 mol % and an Al content of 22.3 mol %.

[0112] The resulting material was afterwards mixed with 2 wt. % graphite, compacted and tableted to result in tablets of 4.8 mm width and 3.2 mm height.

[0113] Table 1 summarizes some characteristic data of the prepared catalysts.

TABLE-US-00001 TABLE 1 Properties of Examples 1 to 6 and Comparative Examples 1 and 2 BET Loss Hg Average Bulk surface CO.sub.2 on pore pore density area content attrition volume Porosity radius SCS SCS-RS 100 mL Example [m.sup.2/g] [wt %] [%] [mm.sup.3/g] [%] [nm] [N] [N] [kg/L] Example 1 123 4.1 n.d. 282 43.25 10.52 196 n.d. n.d. Example 2 174 2.6 1.79 406 52.08 7.88 173 n.d. n.d. Example 3 173 2.6 1.86 389 52.08 7.35 170 100 0.69 Example 4 79 5.6 n.d. 289 48.25 12.64 206 n.d. n.d. Example 5 111 4.4 1.61 412 55.48 14.00 168 n.d. n.d. Example 6 103 4.6 1.51 419 57.47 14.80 164 154 0.73 Comparison 107 — 5.00 114 29.41 4.59 175 81 1.47 Example 1 Comparison 86 3.5 3.00 393 60.84 14.64 191 173 0.84 Example 2

Application Example 1

[0114] The catalysts of Example 1 to 6 as well as of Comparison Example 1 and 2 were tested in the CO conversion reaction.

[0115] A reactor with 2 mm inner diameter was loaded with 220 mg of the corresponding sample, which was provided by grinding the corresponding tablets and separating a sieve fraction from 200-300 μm.

[0116] The reaction took place at a pressure of 25 barg with a synthesis gas feed comprising 3 vol % CO, 17 vol % CO.sub.2, 60 vol % H.sub.2 and 20 vol % N.sub.2, a steam/gas ratio of 0.35 at different temperatures. One can see in FIG. 1 and FIG. 2 that the samples according to the invention show improved CO conversion and reduced deactivation rates as compared to the comparison examples.