CATALYST FOR PRODUCING OLEFIN HAVING ENHANCED STABILITY, CONVERSION RATE AND SELECTIVITY, AND PREPARATION METHOD THEREOF

Abstract

Disclosed are a catalyst for producing olefin and a preparation method thereof. The catalyst for producing olefin includes: a support including an alumina and a sub-support component; and a catalytic component comprising a metal component and an alkali metal impregnated on the support. The preparation method includes: providing a support comprising a sub-support component and an alumina; preparing pre-catalyst by dipping a metal component oxide in the support and calcining it; and dipping a metal component oxide and an alkali metal oxide in the pre-catalyst and calcining it.

Claims

1. A catalyst for producing olefin comprising: a support including an alumina and a sub-support component; and a catalytic component comprising a metal component and an alkali metal impregnated on the support.

2. The catalyst of claim 1, wherein the sub-support component is selected from zirconium, zinc and platinum.

3. The catalyst of claim 2, wherein the sub-support component is zirconium, which exists in the mole fraction of 0.01 to 0.1 relative to aluminum of the alumina (Zr:Al).

4. The catalyst of claim 1, wherein the metal component comprises anyone selected from an oxide of chromium, vanadium, manganese, iron, cobalt, molybdenum, copper, zinc, cerium and nickel.

5. The catalyst of claim 4, wherein the metal component is chromium, which is 10 to 20 wt % of the catalyst.

6. The catalyst of claim 1, wherein the alkali metal is potassium, which is 0.5 to 2.0 wt % of the catalyst.

7. The catalyst of claim 1, wherein the surface area of the catalyst is 80300 m.sup.2/g, and the acidity of the alumina is not more than 0.5 mol NH.sub.3/m.sup.2.

8. The preparation method of the catalyst for producing olefin comprises: providing a support comprising a sub-support component and an alumina; preparing pre-catalyst by dipping a metal component oxide in the support and calcining it; and dipping a metal component oxide and an alkali metal oxide in the pre-catalyst and calcining it.

9. The method of claim 8, wherein the sub-support component is selected from zirconium, zinc and platinum.

10. The method of claim 9, wherein the sub-support component is zirconium, which exists in the mole fraction of 0.01 to 0.1 relative to aluminum of the alumina (Zr:Al).

11. The method of claim 8, wherein the metal component comprises anyone selected from an oxide of chromium, vanadium, manganese, iron, cobalt, molybdenum, copper, zinc, cerium and nickel.

12. The method of claim 11, wherein the metal component is chromium, which is 10 to 20 wt % of the catalyst.

13. The method of claim 8, wherein the alkali metal is potassium, which is 0.5 to 2.0 wt % of the catalyst.

14. The method of claim 8, wherein the surface area of the catalyst is 80300 m.sup.2/g, and the acidity of the alumina is not more than 0.5 mol NH.sub.3/m.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a graph describing the propane conversion rate of the catalyst according to Comparative example and the present invention.

[0020] FIG. 2 is a graph describing the propylene selectivity of the catalyst according to Comparative example and the present invention.

[0021] FIG. 3 is a graph describing Carbon Balance of the catalyst according to Comparative example and the present invention.

[0022] FIG. 4 is a graph describing the conversion rate after the hydrothermal treatment according to Comparative example and the case of the support impregnated with zirconium simultaneously.

[0023] FIG. 5 is a graph describing the selectivity after the hydrothermal treatment according to Comparative example and the case of the support impregnated with zirconium simultaneously.

DETAILED DESCRIPTION

[0024] The present invention is to provide the catalyst for producing olefin, which comprises a support including an alumina and a sub-support component; and a catalytic component comprising a metal component and an alkali metal impregnated on the support.

[0025] Hereinafter, preferable examples of the present invention will be described referring to the attached figures. It is to be understood, however, that these examples can be modified to various other type and are not to be construed to limit the scope of the present invention.

[0026] The catalyst according to the present invention comprises a support and a catalytic component.

[0027] The support comprises an alumina and a sub-support component, and the catalytic component impregnated on the support is a metal component and an alkali metal.

[0028] The sub-support component comprises anyone or combination selected from zirconium, zinc and platinum. The sub-support component is preferably zirconium, which exists in the mole fraction of 0.01 to 0.1 relative to aluminum of the alumina (Zr:Al).

[0029] The durability of the catalyst according to the present invention is enhanced by the sub-support component. The function to excite CH bond of paraffin feedstock is more excellent than using only the alumina as a support. In result, hydrocarbon conversion rate and olefin yield are excellent, and olefin selectivity is enhanced. Especially, zirconium plays roles in enhancing the durability of the alumina support.

[0030] When the amount of the sub-support component, especially zirconium, is less than 0.01 of mole ratio relative to aluminium, the characteristic effect of the durability enhancement is not accomplished. When more than 0.1, the impregnated metal component and alkali metal cannot be polydispersed because of the rapid decrease of the surface area of the alumina support.

[0031] The metal component comprises anyone selected from an oxide of chromium, vanadium, manganese, iron, cobalt, molybdenum, copper, zinc, cerium and nickel. The metal component is preferably chromium, which is 10 to 20 wt % of the catalyst.

[0032] When the amount of the metal component, especially chromium, is less than 10 wt %, the rapid inactivation is incurred because the active site of the main catalyst is too small in chromium phase. When more than 20 wt %, main active phase in chromium can be reduced due to metal-support interaction and excessive metallic binding force. Therefore the optimal loading amount within the above range is required.

[0033] The alkali metal is preferably potassium, which is preferably comprised at 0.5 to 2.0 wt % of the catalyst so that the acidity of the alumina is controlled to be not more than 0.5 mol NH.sub.3/m.sup.2.

[0034] When the amount of the alkali metal, especially potassium, is less than 0.5 wt %, because the acid site of the alumina support cannot be controlled, the side reaction of the acid decomposition reaction is incurred so that excessive coke is generated, and the active phase of chromium cannot be controlled so that the yield becomes to be decreased. And when more than 2 wt %, the subcomponent potassium reduces the porosity of the alumina so that the mass transfer for the catalytic activation during the contact with the reactant is hindered.

[0035] The alumina support preferably has phase at the preparation temperature of 550850 C. higher than the dehydrogenation temperature, and has the surface area of 80300 m.sup.2/g within this range.

[0036] When the support is prepared at the temperature less than the reaction temperature of the dehydrogenation, the thermal deformation of the catalyst can be incurred during the dehydrogenation reaction. When it is prepared at the temperature over 850 C., the surface area of the catalyst is small due to the crystallization of the support so that the mass transfer for the catalytic activation during the contact with the reactant is hindered.

[0037] An another embodiment of the present invention is to provide the preparation method of the catalyst for producing olefin, which comprises providing a support comprising a sub-support component and an alumina; preparing the pre-catalyst by impregnating a metal component oxide on the support and calcining it; and dipping a metal component oxide and an alkali metal oxide in the pre-catalyst and calcining it.

[0038] Despite of the above preparation method, it is obvious to a skilled person that various modifications and changes can be made within the scope of the present invention.

[0039] Hereinafter, the present invention will be described in more detail using Examples and Preparation examples.

[0040] <Preparation Example>

[0041] 1. Support (Zr-Al2O3) Preparation

[0042] Catapal B (alumina sold by Sasol) 13.89 kg added with water 25 kg is agitated for 30 minutes, and 1.83 kg of ZrO(NO.sub.3).sub.2 and 25 kg of water is mixed and further agitated for 2.5 hours. Then, it is spray dried (feed velocity 0.56 g/min, atomizer 6000 rpm, inlet temperature 208 C., outlet temperature 125 C.), sieving separated (sieving: 75200 m), and calcined at 650 C. for 6 hours.

[0043] 2. Catalyst [(5% Cr+0.5% K)/5%Cr/ZrAl.sub.2O.sub.3] Preparation

[0044] 0.482 g of CrO.sub.3 and 2.5 g of water is mixed and impregnated with 5 g of the support as prepared above, dried at 120 C., and calcined at 700 C. for 3 hours (pre-catalyst).

[0045] 0.482 g of CrO.sub.3, 0.068 g of KNO.sub.3 and 2.5 g of water is mixed and impregnated with 5.25 g of 5% Cr/ZrAl.sub.2O.sub.3 as prepared above, dried at 120 C., and calcined at 700 C. for 3 hours so that the catalyst of the present invention is prepared.

[0046] <Experiment for Conversion Rate and Selectivity>

[0047] In order to confirm the conversion rate and the selectivity of the catalyst prepared according to the present invention, GC (FID, TCD) analysis is conducted at a fixed bed Quarts downflow reactor charged with the catalyst and maintained at the space velocity of 8400 ml/g.sub.cat.hr under 600 C. and atmospheric pressure. The experimental result is described in FIG. 1 to FIG. 3.

[0048] As shown in FIG. 1 and FIG. 2, when the catalyst of the present invention is impregnated with the metal component and the alkali metal (potassium:K) at the same time, the conversion rate and the selectivity are verified to be excellent. Furthermore, as shown in FIG. 3, the coke generation caused by the side reaction is small in the catalyst of the present invention (Carbon Balance).

[0049] <Stability Experiment>

[0050] In order to verify the hydrothermal stability of the catalyst prepared according to the present invention, in the case that the sub-support component (zirconium:Zr) is added to the alumina support of the catalyst according to the present invention and the other case that the sub-support component is not added to the catalyst (Comparative example), the conversion rate and the selectivity are measured in the same manner as the above after the catalyst is forced to be treated with 800 C. and 100% steam for 24 hours (FIG. 4 and FIG. 5).

[0051] As shown in FIG. 4 and FIG. 5, in the case that sub-support component (zirconium:Zr) is added to the alumina support of the catalyst according to the present invention, the hydrothermal stability is verified to be excellent. In the above, preferable examples of the present invention is described in detail. However, it is obvious to a skilled person that the claimed scope of the present invention is not limited to these examples, and various modifications and changes can be made within the scope of the present invention.

[0052] The present invention relates to the catalyst having enhanced stability, conversion rate and selectivity for producing olefin, and a preparation method thereof.