Method for preparing solids from a mixture of at least two malachite powders

Abstract

The invention relates to a method for preparing a solid comprising a step of mixing a set of compounds comprising at least two Cu.sub.2(OH).sub.2CO.sub.3 powders of different particle sizes and at least one binder and the use of the solid prepared by means of this method.

Claims

1. Method for preparing a solid comprising the steps of: a)_mixing a set of compounds comprising at least two Cu.sub.2(OH).sub.2CO.sub.3 powders with different particle sizes and at least one binder; b)_contacting the mixture of step a) with an aqueous solution and kneading the paste thus obtained; c)_extruding the paste kneaded in step b) at a pressure of between 3 and 25 MPa; d)_calcinating the extrudates at a temperature of between 140 C. and 500 C. and for a duration of between 10 minutes and 6 hours under a gaseous flow comprising oxygen.

2. Method according to claim 1, wherein the said set of compounds comprises 0.1 to 99.9 wt. % of a first malachite powder, the D.sub.50 of which is between 1 and 15 m and 99.9 to 0.1 wt. % of a second malachite powder, the D.sub.50 of which is between 25 and 100 m, the weight percentage being expressed relatively to the total weight of the malachite powders.

3. Method according to claim 1, wherein the said set of compounds is dry-mixed in step a), i.e. without adding liquid.

4. Method according to claim 1, wherein the said binder is selected from clays, or selected from the group consisting of alumina, a precursor of alumina, silica and mixtures thereof.

5. Method according to claim 1, wherein the amount of binder used in the preparation method is such that the said binder represents less than 50 wt. % of the prepared solid.

6. Method according to claim 1, wherein the said aqueous solution of the said step b) contains an acidic or basic peptizing agent.

7. Method according to claim 6, wherein the said aqueous solution of the said step b) contains nitric acid, the ratio of HNO.sub.3 mass/metal oxides mass being between 0.5 and 10 wt. %.

8. Method according to claim 6, wherein the said basic peptising agent is selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonia, tetraethylammonium hydroxide (TEAOH), ammonium carbonate and mixtures thereof, the ratio of the basic peptizing agent mass/metal oxides mass being between 1 and 10 wt. %.

9. Method according to claim 1, wherein the aqueous solution of the said step b) is an aqueous solution with no added acid or base.

10. Method according to claim 1, wherein the extrudates obtained from step c) are dried at a temperature of between 70 and 160 C. for a duration of between 1 and 24 hours before being calcined in step d).

11. Method according to claim 1, wherein step d) of calcination is carried out at a temperature of between 200 C. and 500 C.

Description

DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a schematic representation of a breakthrough curve which can be obtained according to the protocol for measuring the impurity capture capacity by the solids, described below. In FIG. 1, t.sub.p is the breakthrough time and t.sub.f is the end of the breakthrough time.

(2) Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

(3) In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.

(4) The entire disclosures of all applications, patents and publications, cited herein and of corresponding French application No. 17/55.303, filed Jun. 13, 2017 are incorporated by reference herein.

EXAMPLES

(5) Protocol for Measuring the Impurity Capture Capacity By the Solids Prepared

(6) The impurity capture capacity of solids prepared by means of the method according to the invention is measured using a breakthrough test.

(7) For the test to determine the H.sub.2S capture capacity, the test is carried out at a temperature of 50 C., at a pressure of 0.3 MPa, and with an hourly volume velocity (HVV) of 1530 h.sup.1. Hourly volume velocity can be understood as the ratio of the volumetric flow rate of gas measured at 0 C. and 1 atm to the volume of the solid tested. The gas used for the test contains 0.9 vol. % of H.sub.2S in nitrogen. The H.sub.2S content present in the gas leaving the reactor containing the solid is determined by gas chromatography.

(8) The species i capture capacity by the solid prepared by means of the method according to the invention is determined by carrying out a material balance. The species i capture capacity, as defined within the present invention, corresponds to the amount of the species i accumulated by the solid before breakthrough (i.e. at the time t.sub.p indicated in FIG. 1, which schematically represents a breakthrough curve), this being calculated by means of the following equation:

(9) $q_i=M_i{D}_i^E{}_0^{t_p}\left(1-\frac{C_i^S}{C_i^E}\right)\mathrm{dt}$

(10) Where:

(11) q.sub.i: is the mass of the species i captured by the solid (in g),

(12) D.sub.i.sup.E: is the inflow of the species i (in mol.Math.min.sup.1),

(13) M.sub.i: is the molar mass of the species i (in g.Math.mol.sup.1),

(14) C.sub.i.sup.E: is the species i content of the inflow gas,

(15) C.sub.i.sup.S: is the species i content at the reactor outlet,

(16) t.sub.p: is the time needed for the breakthrough of the species i (in minutes) as shown in FIG. 1.

(17) In FIG. 1, t.sub.p is the breakthrough time and t.sub.f is the end of the breakthrough time.

(18) The species i capture capacity of the solid tested is provided by the equation:

(19) $C_i=\frac{q_i}{m}$

(20) where m is the mass of adsorbent used during the test.

Example 1

According to the Prior Art

(21) In example 1, the reference solids A1, A2, A3, A4 and A5 are prepared according to the following procedure: a) mixing a set of compounds comprising a Cu.sub.2(OH).sub.2CO.sub.3 powder and a binder; b) contacting the mixture of step a) with an aqueous solution (peptisation) and kneading the paste thus obtained in a Z-arm mixer for 30 minutes with an arm rotation speed of 25 rotations.Math.minutes.sup.1; c) extruding the paste kneaded in step b) by means of a piston extruder, with a diameter of 3 mm and a length of 5 to 10 mm at a variable pressure depending on the solids; d) calcinating the extrudates at a variable temperature depending on the solids, carried out for 1 hour, under an air flow.

(22) In step a) a malachite powder P1 is used, the D.sub.50 of which is 48 m.

(23) A bentonite clay was used as a binder.

(24) The CuO contents or mass percentage of oxides (CuO from the decomposition of the malachite) after loss on ignition (550 C. for 2 hours) are 80 wt. % for solids A1, A2, A3 and A4, and 60 wt. % for solid A5 (with the bentonite binder as the complement). These contents are determined according to the following equation:

(25) $\%\mathrm{weight}\mathrm{CuO}\mathrm{after}\mathrm{LOI}=\frac{\frac{2.Math.M_{\mathrm{CuO}}}{M_{{{\mathrm{Cu}}_2\left(\mathrm{OH}\right)}_2{\mathrm{CO}}_3}}.Math.m_{{{\mathrm{Cu}}_2\left(\mathrm{OH}\right)}_2{\mathrm{CO}}_3}}{m_{\mathrm{binder}}+\frac{2.Math.M_{\mathrm{CuO}}}{M_{{{\mathrm{Cu}}_2\left(\mathrm{OH}\right)}_2{\mathrm{CO}}_3}}.Math.m_{{{\mathrm{Cu}}_2\left(\mathrm{OH}\right)}_2{\mathrm{CO}}_3}}$

(26) Where m.sub.binder is the mass of the binder introduced in step a), m.sub.Cu2(OH)2CO3 is the mass of the Cu.sub.2(OH).sub.2CO.sub.3 malachite introduced in step a), M.sub.CuO is the molar mass of CuO (=80 g/mol), M.sub.Cu2(OH)2CO3 is the molar mass of Cu.sub.2(OH).sub.2CO.sub.3 malachite (=222 g/mol).

(27) For solids A1, A2 and A3, the amount of NaOH base is 4% by weight relatively to the total amount of Cu.sub.2(OH).sub.2CO.sub.3 introduced.

(28) For solids A4 and A5, deionised water is used as the aqueous solution for step b) of kneading.

(29) During the extrusion, the pressure varies between 50 and 150 bar depending on the formulation used.

(30) The formulations of solids A1, A2, A3, A4 and A5 are given in Table 1.

(31) TABLE-US-00001 TABLE 1 Test for capturing Calcination H.sub.2S: Sulphur temperature captured at % oxides ( C.)/duration tp (g S/g EGG Designation after LOI Binder Peptisation (h) solid) (daN .Math. mm.sup.1) Solid A1 80% Bentonite 4% NaOH 140 C./1 h 0.22 0.5 Solid A2 80% Bentonite 4% NaOH 250 C./1 h 0.25 0.5 Solid A3 80% Bentonite 4% NaOH 350 C./1 h 0.24 0.5 Solid A4 80% Bentonite water 250 C./1 h 0.26 0.3 Solid A5 60% Bentonite water 250 C./1 h 0.16 0.6

(32) The mechanical strength of the extrudates is determined by a grain by grain crushing test (EGG) as previously described.

(33) The mechanical strength of solids A1 to A5 is too low taking into consideration the constraints associated with an industrial use. The EGG values measured are indeed lower than 0.7 daN.Math.mm.sup.1, whatever the calcination temperature and the presence or lack of sodium hydroxide during peptisation when a single powder having a single particle size distribution is used.

(34) The increase in binder content and the decrease in malachite content in solid A5 results in a slight increase in mechanical strength which is nevertheless insufficient, to the detriment of the sulphur capture capacity thereof. In this latter case, the sulphur capacity becomes weak compared to that of the solids according to the invention.

Example 2

According to the Invention

(35) In example 2, the solids referenced as B1 to B4 according to the invention are prepared by kneading and extruding according to the following procedure: a) mixing a set of compounds comprising two Cu.sub.2(OH).sub.2CO.sub.3 powders and a binder; b) contacting the mixture of step a) with an aqueous solution (peptisation) and kneading the paste thus obtained in a Z-arm mixer for 30 minutes with an arm rotation speed of 25 rotations.Math.minutes.sup.1; c) extruding the paste kneaded in step b) by means of a piston extruder, with a diameter of 3 mm and a length of 5 to 10 mm at a variable pressure depending on the solids; d) calcinating the extrudates at a variable temperature depending on the examples, carried out for 1 hour, under air flow.

(36) In step a) two malachite powders P1 and P2, having different particle sizes, are used. The D.sub.50 of powder P1 is 48 m, and the D.sub.50 of powder P2 is 5 m.

(37) The relative amounts of the introduced malachite P1 and P2 are expressed using the ratios % P1 and % P2 defined by:

(38) $\%\mathrm{malachite}P1=\frac{m_{P1}}{m_{P1}+m_{P2}}$$\%\mathrm{malachite}P2=\frac{m_{P2}}{m_{P1}+m_{P2}}$

(39) Where m.sub.P1 is the mass of malachite P1 introduced in step a), and m.sub.P2 is the mass of malachite P2 introduced in step a),

(40) A bentonite clay was used as a binder.

(41) The content of CuO from the decomposition of malachite after loss on ignition (550 C. for 2 hours) is 80 wt. % for solids B1 to B4. This content is determined according to the following equation:

(42) $\%\mathrm{weight}\mathrm{CuO}\mathrm{after}\mathrm{LOI}=\frac{\frac{2.Math.M_{\mathrm{CuO}}}{M_{{{\mathrm{Cu}}_2\left(\mathrm{OH}\right)}_2{\mathrm{CO}}_3}}.Math.m_{{{\mathrm{Cu}}_2\left(\mathrm{OH}\right)}_2{\mathrm{CO}}_3}}{m_{\mathrm{binder}}+\frac{2.Math.M_{\mathrm{CuO}}}{M_{{{\mathrm{Cu}}_2\left(\mathrm{OH}\right)}_2{\mathrm{CO}}_3}}.Math.m_{{{\mathrm{Cu}}_2\left(\mathrm{OH}\right)}_2{\mathrm{CO}}_3}}$

(43) Where m.sub.binder is the mass of the binder introduced in step a), m.sub.Cu2(OH)2CO3 is the mass of the Cu.sub.2(OH).sub.2CO.sub.3 malachite powders introduced in step a) m.sub.Cu2(OH)2CO3=m.sub.P1+m.sub.p2), M.sub.CuO is the molar mass of CuO (=80 g/mol), M.sub.Cu2(OH)2CO3 is the molar mass of Cu.sub.2(OH).sub.2CO.sub.3 malachite (=222 g/mol).

(44) For solids B1, B2, B3, B4, B5 and B6, deionised water is used as the aqueous solution for step b) of kneading.

(45) For solid B7, the amount of NaOH base is 4% by weight relatively to the total amount of introduced Cu.sub.2(OH).sub.2CO.sub.3.

(46) During the extrusion, the pressure varies between 50 and 200 bar depending on the used formulation.

(47) The formulations of the solids are given in Table 2.

(48) TABLE-US-00002 TABLE 2 Test for capturing H.sub.2S: Calcination Sulphur % P1 of % P2 of % oxides temperature captured at total total Dm after ( C.)/duration tp (g S/g EGG Designation malachite malachite (m) LOI Binder Peptisation (h) solid) (daN .Math. mm.sup.1) Solid B1 87.5% 12.5% 42.6 80% Bentonite water 250 C./1 h 0.25 0.8 Solid B2 75% 25% 37.3 80% Bentonite water 250 C./1 h 0.24 1.2 Solid B3 50% 50% 26.5 80% Bentonite water 250 C./1 h 0.26 1.2 Solid B4 25% 75% 15.8 80% Bentonite water 250 C./1 h 0.25 1.2 Solid B5 87.5% 12.5% 42.6 80% Bentonite water 140 C./1 h 0.23 0.7 Solid B6 87.5% 12.5% 42.6 80% Bentonite water 350 C./1 h 0.22 0.7 Solid B7 87.5% 12.5% 42.6 80% Bentonite 4% NaOH 250 C./1 h 0.20 0.9

(49) The use of two Cu.sub.2(OH).sub.2CO.sub.3 powders of different particle sizes in the preparation method according to the invention, with Dm for starting powders blend between 15 and 45 m, makes it possible to obtain solids having satisfactory mechanical properties (EGG greater than 0.7 daN.Math.mm.sup.1).

(50) Furthermore, the solids have satisfactory sulphurisation capacities, greater than 0.15 grams of sulphur/gram of solid in the test conditions described in the document.

Example 3

Comparative Example

(51) In example 3, the solids C1 and C2 are prepared by kneading and extruding according to the operating method of Example 2.

(52) The two malachite powders P1 and P2 used to prepare the solid C have the following particle sizes: D.sub.50 for powder P1 is 50 m and D.sub.50 for powder P1 is 50 m.

(53) Solid C is tested with the same conditions as those used for Example 2 tests.

(54) Table 3 presents the formulation of solids C and the obtained results.

(55) TABLE-US-00003 TABLE 3 Test for capturing H.sub.2S: Calcination Sulphur % P1 of % P2 of % oxides temperature captured at total total Dm after ( C.)/duration tp (g S/g EGG Designation malachite malachite (m) LOI Binder Peptisation (h) solid) (daN .Math. mm.sup.1) Solid C1 93.75% 6.25% 47.5 80% Bentonite water 250 C./1 h 0.25 0.6 Solid C2 96.87 3.13 48.7 80% Bentonite water 250 C./1 h 0.25 0.6

(56) The EGG values measured for the solids C1 and C2 are lower than 0.7 daN.Math.mm.sup.1. The mechanical strength of solids C1 and C2 is too low taking into consideration the constraints associated with an industrial use.

(57) The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

(58) From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.