METHOD FOR PREPARING A CATALYST FOR ONE-STEP PRODUCTION OF BUTADIENE FROM ETHANOL, CATALYST AND USE THEREOF

Abstract

The present invention relates to a process for the production of butadiene by condensation of ethanol using a catalyst containing sillica-supported elements from group 3A and group 4B of the periodic table. The catalyst of the present invention has high activity and selectivity to butadiene in the synthesis reaction of said olefin from ethanol.

Claims

1. A METHOD FOR PREPARING A CATALYST FOR ONE-STEP PRODUCTION OF BUTADIENE FROM ETHANOL, characterized by comprising the following steps: (a) adding an element from group 4B of the periodic table to SiO.sub.2, through dry impregnation, using an aqueous solution of the chloride of this metal; (b) drying the solid obtained in a) at 120° C. for 10 h and calcining at 500° C. for 4 h at a rate of 10° C.min.sup.−1 under synthetic air flow (60 mL.min.sup.−1); (c) impregnating the solid obtained in b) with an aqueous solution of a metal ion nitrate of the element from group 3A of the periodic table; (d) drying the solid obtained in a) at 120° C. for 10 h and calcining at 500° C. for 4 h at a rate of 10° C.min.sup.−1 under synthetic air flow (60 mL.min.sup.−1);

2. The METHOD, according to claim 1, characterized in that the element from group 3A of the periodic table is preferably gallium and the element from group 4B of the periodic table is preferably hafnium.

3. A CATALYST, obtained according to the method defined in claim 1, characterized by comprising in its composition: a) a SiO.sub.2 based support; b) elements from group 3A and group 4B of the periodic table.

4. The CATALYST, according to claim 3, characterized in that the element from group 3A is preferably gallium.

5. The CATALYST, according to claim 4, characterized by having a gallium content between 0.1% and 5% by weight in relation to the support.

6. The CATALYST, according to claim 3, characterized in that the element from group 4B is preferably hafnium.

7. The CATALYST, according to claim 6, characterized by having a hafnium content between 0.5% and 15% by weight in relation to the support.

8. USE OF THE CATALYST, as defined in claim 3, characterized by being in the process of production of butadiene from ethanol carried out in a continuous-flow tubular reactor at a temperature between 250 and 450° C., pressure between 1 and 5 atm and space velocity (WHSV) between 1 and 15 g.sub.ethanolg.sub.cath.sup.−1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention is described in detail below, with reference to the enclosed drawing, which represents an embodiment of the same in a schematic manner, not limiting the inventive scope. The drawing describes:

[0019] FIG. 1 illustrates a graph of the behavior of Ga/Hf/SiO.sub.2 catalyst in time-on-stream, according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The method of preparing the catalyst for use in the production of butadiene, according to the present invention, comprises the following steps: [0021] a) Adding to SiO.sub.2, through dry impregnation, an element from group 4B of the periodic table, preferably Hf, using an aqueous solution of the chloride of this metal; [0022] b) drying the solid obtained in a) at 120° C. for 10 hours and calcining at 500° C. for 4 hours at a rate of 10° C.min.sup.−1 under synthetic air flow (60 mL.min.sup.−1); [0023] c) impregnating the solid obtained in b) with an aqueous solution of a metal ion nitrate of the element from group 3A of the periodic table, preferably element Ga; [0024] d) drying the catalyst obtained in c) at 120° C. for 10 hours and calcining at 500° C. for 4 hours at a rate of 10° C.min.sup.−1, under synthetic air flow (60 mL.min.sup.−1).

[0025] The catalyst thus prepared has in its composition 0.1% to 5% by weight of gallium with respect to the support and 0.5% to 15% by weight of hafnium with respect to the support.

[0026] The butadiene synthesis reaction via ethanol condensation using catalysts containing silica-supported elements from group 3A (Ga) and group 4B (Hf) of the periodic table was carried out in a Plug Flow Reactor (PFR) at a pressure from 1 to 5 atm, temperatures from 250 to 450° C. and space velocity (WHSV) between 1 to 15 g.sub.ethanol g.sub.cath.sup.−1.

EXAMPLES

[0027] The examples below illustrate a few embodiments of the invention, and prove its feasibility, not constituting any form of limitation of the invention.

[0028] Example 1: Preparation of catalysts doped with elements from group 3A and group 4B of the periodic table.

[0029] The preparation of the catalysts took place via successive dry impregnation using SiO.sub.2. Initially, the support was impregnated with an aqueous solution of the element from group 4B, followed by drying at 120° C. for 10 hours and calcination at 500° C. for 4 hours (10° C.min.sup.−1) under synthetic air flow (60 mL.min.sup.−1). Then, the materials were impregnated with an aqueous solution of a metal ion nitrate of elements from group 3A of the periodic table. These catalysts were also dried and calcined under the same conditions already described in the addition of the element from group 4B.

[0030] Example 2: The catalytic tests were carried out in a PFR micro reactor.

[0031] The data presented in Table 1 was obtained after approximately 3 hours of reaction. The analyzes of the gas mixture composition at the reactor outlet and inlet were carried out by gas chromatography.

[0032] The catalysts used were X/MO.sub.2/SiO.sub.2, wherein M=Zr or Hf=4% at. and X=Ga, In or Cd=0.6% at., wherein Si=95.4% at.

[0033] The tests in Table 1 were performed under experimental conditions of temperature, pressure, flow rate and ethanol: N.sub.2 ratios of 385° C., 1 atm, 25 mL.min.sup.−1, 3:97 or 20:80 v/v, respectively.

[0034] The results in Table 1 show that, comparing the Cd, In and Ga promoters (tests 1, 2 and 3), when Hf/SiO.sub.2 is used, the latter presents greater activity and selectivity to butadiene.

[0035] Comparing tests 3 and 4 (low ethanol concentration) that differ in terms of the use of Zr and Hf, it is found that the presence of the latter results in greater selectivity to butadiene, while the conversion of both has very similar values.

[0036] Comparing the same catalysts employing a 6.5 times greater content of ethanol in the reaction mixture, tests 6 and 7, it is noted again that, for Hf, selectivity to butadiene is greater than for Zr, while the conversion is virtually equal. These results also show that, in the presence of Hf, the C balance approaches 100%.

[0037] Test 5 shows that without Ga the activity and selectivity to butadiene of the Hf/SiO.sub.2 system is very low.

[0038] Test 8 shows that using 400 mg of Ga/Hf/SiO.sub.2 and a concentration of 20% ethanol in N.sub.2 it is possible to achieve high values of conversion and selectivity to butadiene.

TABLE-US-00001 TABLE 1 Behavior of catalysts in the synthesis of butadiene from ethanol. C.sub.ethanol, m, X, S.sub.BD, S.sub.ethene, S.sub.act, C, Y.sub.BD correspond to ethanol:N2 v/v ratio, catalyst mass, ethanol conversion, selectivities to 1,3-butadiene, ethylene, acetaldehyde, balance of carbon and yield in 1,3-butadiene, respectively. catalyst C.sub.ethanol/% m/g X/% S.sub.BD/% S.sub.ethene/% S.sub.act/% C/% Y.sub.BD/% 1 Cd/Hf/SiO.sub.2 3 0.1 94.2 43.4 24.8 5.0 85.2 40.9 2 In/Hf SiO.sub.2 3 0.1 97.2 57.0 5.1 16.6 78.2 36.0 3 Ga/Hf/SiO.sub.2 3 0.1 99.5 62.4 11.2 6.5 92.2 62.1 4 Ga/Zr/SiO.sub.2 3 0.1 97.1 58.3 13.3 8.6 93.7 56.6 5 Hf/SiO.sub.2 20 0.4 53.8 11.3 33.8 2.1 52.4 6.1 6 Ga/Zr/SiO.sub.2 20 0.3 92.4 54.4 15.6 7.4 87.7 50.3 7 Ga/Hf/SiO.sub.2 20 0.3 91.5 67.7 9.8 6.6 94.2 61.9 8 Ga/Hf/SiO.sub.2 20 0.4 97.7 71.0 9.9 4.0 95.9 69.4

[0039] Example 3: Isoconversion test results.

[0040] Table 2 shows the results obtained from Isoconversion tests for catalyst Ga/Zr/SiO.sub.2 and Ga/Hf/SiO.sub.2. The testes of Table 2 were performed under experimental conditions of temperature, pressure, flow rate, ethanol: N.sub.2 ratio of 385° C., 1 atm, 25 mL.min.sup.−1, 3:97 v/v, respectively.

[0041] Comparing tests 9 and 10, it can be seen that to achieve 55% conversion (isoconversion) in the case of the Hf-based catalyst, a space velocity (WHSV) 50% greater than that of the Zr-containing system is used. This results shows that the Hf catalyst is more active than that of Zr. It has been further observed that selectivity to butadiene is slightly lower than that of Zr.

TABLE-US-00002 TABLE 2 Isoconversion tests (50%), with WHSV being the space velocity used. The other symbols are the same as in Table 1. catalysts WHSV/g.sub.etanolg.sub.cath.sup.−1 S.sub.BD/% S.sub.ethene/% S.sub.act/% 9 Ga/Zr/SiO.sub.2 6.2 27.6 11.7 30.2 10 Ga/Hf/SiO.sub.2 9.6 24.7 9.8 32.8

[0042] Example 4: Behavior of catalyst Ga/Hf/SiO.sub.2, according to the present invention.

[0043] FIG. 1 shows the result of the stability test of approximately 25 hours for catalyst Ga/Hf/SiO.sub.2. The variables mass, temperature, pressure, flow rate, ethanol: N.sub.2 ratio were 100 mg, 385° C., 1 atm, 25 mL.min.sup.−1, 3:97 v/v, respectively.

[0044] As can be seen in FIG. 1, after 25 hours of reaction, the ethanol conversion decreases from 99.6% to 92.1%, while the selectivity to butadiene reaches a maximum of around 62%, ending the run at around 56%. Furthermore, FIG. 1 shows a reasonably stable behavior considering the catalyst mass used.

[0045] Finally, the results show that the catalysts containing Hf and Ga are very active, selective to butadiene and reasonably stable.

[0046] It should be noted that, although the present Invention has been described in relation to the examples above, it may undergo changes and adaptations by skilled artisans, depending on the specific situation, but provided that it is within the Inventive scope defined herein.