WO2008038855A1

WO2008038855A1 - A method for regenerating catalysts

Info

Publication number: WO2008038855A1
Application number: PCT/KR2006/005107
Authority: WO
Inventors: Hyun-Sik Han; Jin-Won Kim; Jae-Woo Kim
Original assignee: Heesung Engelhard Corporation
Priority date: 2006-09-25
Filing date: 2006-11-29
Publication date: 2008-04-03
Also published as: KR100824763B1; KR20080027614A

Abstract

The present invention provides a method of regenerating a catalyst using the oxidizability of NO2, a method of regenerating a catalyst, including the step of injecting NO or air into an oxidation catalyst to generate NO2, and a method of regenerating a catalyst, including the step of directly injecting NO or air into a regeneration catalyst, rather than an oxidation catalyst. Further, the present invention provides a useful method of regenerating a catalyst, in which the sintering of the catalyst can be prevented because the regeneration temperature is decreased, in which coke is burned, thus increasing the regeneration efficiency of the catalyst, thereby maintaining the activity of the catalyst, and in which the cost of maintaining the catalyst is low.

Description

A METHOD FOR REGENERATING CATALYSTS

Technical Field

[1] The present invention relates to a method of regenerating a catalyst, and, more particularly, to a useful method of regenerating a chemical catalyst that must be regenerated, the active sites of which are closed by coke and the surface area of which are decreased. Background Art

[2] In a procedure of processing petrochemical raw materials and synthetic raw materials, the raw materials, present in a feed stream, are introduced into a reactor, and the raw materials are then converted into products, or the impurities included in the raw materials are removed using a catalyst in the reactor. Since the economical operation of reactors and plants is influenced by the state of the catalyst, the state of the catalyst is an important factor. The conversion ratio of raw materials into products, the amount of products, the operation temperature of reactors, and the like vary depending on the activity of the catalyst.

[3] Catalyst activity decreases as time passes, because factors, such as impurities, the concentration of impurities in a feed stream, the kinds of side reaction products, the operation time of reactor, and the like, have an influence on the catalyst. For example, since coke, generated by the polymerization of raw materials, adheres to the surface of a Pt/ Al O catalyst, used for a dehydrogenation reaction, a Cu/ Al O catalyst, used for a selective hydrogenation reaction, and the like, the catalyst surface area, which can be used for the reactions, is decreased. Further, in a solid acid catalyst, such as zeolite, the deposition of coke also becomes a typical factor that deteriorates the activity of the catalyst. For this reason, the yield of products decreases correspondingly. Accordingly, after a reactor has been operated for a predetermined time, the used catalyst must be regenerated or must be replaced with a new catalyst. Disclosure of Invention

Technical Problem

[4] Various methods of regenerating a catalyst are used in the field of processing petrochemical raw materials. Methods of regenerating a catalyst by removing coke from the surface thereof using vapor or through a combustion reaction using air, or methods of regenerating a catalyst using specific solvents are commonly known.

[5] However, methods of regenerating a catalyst using vapor or air have many problems. In the methods, since the regeneration of the catalyst is conducted at high temperatures, there is a problem in that the activity of the catalyst is decreased due to the sintering of the catalyst. Therefore, the combustion temperature of coke is slowly increased in order to prevent the sintering of the catalyst, thus increasing the regeneration time of the catalyst. In addition to this, the methods are problematic in that CO is generated due to imperfect combustion, and the catalyst is damaged due to the rapid generation of heat. Moreover, the methods have problems in that the costs for maintaining a high temperature for a long time or additional costs caused by the interruption of production are incurred.

[6] Meanwhile, methods of regenerating a catalyst by extracting catalytic poison materials from the catalyst using solvents are problematic in that another regeneration process for removing a solvent from the catalyst must be conducted, and in that there are environmental restrictions on treating the solvent.

[7] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a method of regenerating a catalyst, which can be conducted regardless of the kind of reactor or catalyst.

[8] Another object of the present invention is to provide a method of regenerating a catalyst, which can be accomplished using a catalyst regeneration apparatus which is simply designed and economically manufactured.

[9] A further object of the present invention is to provide an environment-friendly catalyst regeneration method, which can minimize the discharge of harmful materials. Technical Solution

[10] In order to accomplish the above objects, the present invention provides a method of regenerating a catalyst using the oxidizability of NO .

[11] The present invention provides a method of regenerating a catalyst, including the step of injecting NO or air into an oxidation catalyst to generate NO .

[12] The present invention provides a method of regenerating a catalyst, including the step of directly injecting NO or air into a regeneration catalyst, rather than an oxidation catalyst.

[13] The present invention provides a method of regenerating a catalyst, further including the step of removing NO and noxious gases remaining after the regeneration of the catalyst

[14] Hereinafter, the above and other objects, features and advantages of the present invention will be more clearly described with reference to the attached drawings. A better understanding of the present invention may be obtained through the following embodiments which are set forth to illustrate, but are not to be construed as the limit of the present invention. The basic idea of the present invention provides a method of generating a catalyst while maintaining the physical properties of the catalyst, by burning coke etc., which is a material damaging a catalyst, adhered on the surface of a catalyst at low temperature using the oxidizability of NO .

Advantageous Effects

[15] The present invention provides a method of regenerating a catalyst using the oxidizability of NO , a method of regenerating a catalyst, including the step of injecting NO or air into an oxidation catalyst to generate NO , and a method of regenerating a catalyst, including the step of directly injecting NO or air into a regeneration catalyst, rather than an oxidation catalyst. Further, the present invention provides a useful method of regenerating a catalyst, in which the sintering of the catalyst can be prevented due to the decrease in regeneration temperature, in which coke is burned, and thus the regeneration efficiency of the catalyst is increased, thereby maintaining the activity of the catalyst, and in which the manufacture of the catalyst is easy, and the cost of maintaining the catalyst is low. Further, the present invention provides an environment-friendly method of regenerating a catalyst which can minimize the discharge of noxious gases by refluxing NO, generated after the combustion of coke, using NO to an oxidation catalyst housing and removing the NO and noxious gases remaining after the regeneration of catalyst using a selective catalytic reduction (SCR) apparatus. Brief Description of the Drawings

[16] FIG. 1 is a schematic view showing a conventional method of generating a catalyst using air;

[17] FIG. 2 is a schematic view showing a method of generating a catalyst according to the present invention;

[18] FIG. 3 is a graph showing a concentration profile of CO and CO, obtained when a

Cu/ Al O catalyst is regenerated according to the conventional method shown in FIG. 1;

[19] FIG. 4 is a graph showing a concentration profile of CO and CO to temperature, obtained when a Cu/Al O catalyst is regenerated using the oxidizability of NO according to the present invention;

[20] FIG. 5 is a graph showing a profile of a precious metal catalyst, that is, Pt/A12O3, through a method of generating a catalyst using air;

[21] FIG. 6 is a graph showing a profile of a precious metal catalyst, that is, Pt/ Al O , through a method of generating a catalyst using NO ;

[22] FIG. 7 is a graph showing a profile of a Pt/ Al O catalyst when the temperature thereof is maintained at 35O⁰C and is then increased to 600⁰C; and

[23] FIG. 8 is a graph showing a profile of temperature and CO in a zeolite catalyst through a method of generating a catalyst using air and NO . Best Mode for Carrying Out the Invention

[24] FIG. 1 is a schematic view showing a conventional method of generating a catalyst using air, and FIG. 2 is a schematic view showing a method of generating a catalyst according to the present invention. Specifically, FIGS. 1 and 2 shows methods of generating a catalyst, which were designed and tested using a Cu/ Al O catalyst used for a selective hydrogenation reaction.

[25] According to a conventional method of generating a catalyst using air, since the regeneration of a Cu/ Al O catalyst is conducted at a temperature of at least 35O⁰C or higher, there is a problem in that the activity of the catalyst is deteriorated due to the sintering of the catalyst. However, according to the method of regenerating the catalyst of the present invention, the oxidizability of NO is used to burn coke. Specifically, NO and air are introduced into an oxidation catalyst unit, and NO , generated therefrom, is introduced into the Cu/ Al O catalyst that is to be regenerated, thereby decreasing the regeneration temperature of the Cu/Al O catalyst to 25O⁰C ~ 300⁰C. More preferably, NO, which is a side product obtained through a reaction of a regeneration catalyst and NO , may be circulated to achieve the object of the present invention.

[26] Various oxidation catalysts may be used in the present invention, and particularly, a

Pt/ Al O catalyst, which is commonly known, may be used as the oxidation catalyst of the present invention.

[27] FIG. 3 shows a concentration profile of CO and CO, obtained when a Cu/Al O

2 2 3 catalyst is regenerated according to the conventional method shown in FIG. 1. As seen in the CO concentration profile, coke starts to burn at 300⁰C, with CO concentrations peaking at about 35O⁰C and about 45O⁰C. It can be predicted that the Cu/Al O catalyst is difficult to regenerate at 35O⁰C because the coke is burned incompletely as is apparent from the peak at 45O⁰C. The conventional method, shown in FIG. 3, was conducted at an air flow rate of 100 ml/min while the temperature was increased at a rate of 4°C/min. [28] In order to realize the method of regenerating a catalyst according to the present invention, an oxidation catalyst (Pt/ Al O ) unit is located at the front end of a Cu/Al O catalyst unit, which is the catalyst unit to be regenerated. When NO and air are injected into an inlet of the oxidation catalyst unit, chemical reactions, represented by Equation below, occur.

[29] Oxidation catalyst unit

[30] 2NO + 02 → 2NO

[31] Catalyst regeneration unit

[32] NO + C → NO + CO [33] NO 2 + CO → NO + CO 2

[34] Total reaction

[35] 2NO 2 + C → 2NO + CO 2 ,

[36] In this case, since 2NO can be circulated to the oxidation catalyst unit, the same results can be obtained regardless of whether the oxidation catalyst unit is located at the front or rear end of the catalyst regeneration unit.

[37] Based on the above Equation, FIG. 4 shows a profile of temperature and CO and

CO when a Cu/ Al O catalyst is regenerated using the oxidizability of NO according to the present invention. From FIG. 4, it can be seen that the change of concentration in CO , that is, the combustion of coke, starts at a minimum temperature of 200⁰C. Further, it can be seen that the second peak, at a temperature of about 45O⁰C, shown in FIG. 3, disappears. Moreover, the concentration profile of CO supports a reaction mechanism for forming CO in the above Equation. The method of regenerating a catalyst, shown in FIG. 4, is conducted at a flow rate of 4.66% of NO/N 2 balance of 20 ml/min and a flow rate of air of 80 ml/min while the temperature is increased at a rate of 4°C/min.

[38] According to the above idea and embodiment realizing the same, a method of regenerating a catalyst using the oxidizability of NO , specifically, a method of regenerating a catalyst by injecting NO and air into an oxidation catalyst and thus burning coke using the oxidizability of NO , generated therefrom, is advantageous in that the regeneration temperature of the catalyst is decreased, in that the regeneration efficiency of the catalyst is increased due to the combustion of coke, thus maintaining the activity of catalyst constant, in that productivity is increased due to the decrease in regeneration time, and in that damage to the catalyst, attributable to the rapid generation of heat, can be prevented because the temperature in a reactor can be controlled by controlling the concentration of the injected NO.

[39] The above embodiment relates to a method of regenerating a Cu/ Al O catalyst, which is a nonprecious metal catalyst. In addition to this method, the present inventors have tested a method of regenerating a Pt/ Al O catalyst, which is a precious metal catalyst, under the same conditions as those of the method of regenerating a Cu/ Al O catalyst, with the aim of determining whether or not an oxidation catalyst unit requires an oxidation catalyst unit to be located at the front end thereof, because the precious metal catalyst itself can serve as an oxidation catalyst for oxidizing NO.

[40] A Pt/ Al O catalyst, which is used for a selective hydrogenation reaction, was employed in order to achieve this purpose, and the profile of the Pt/ Al O catalyst was created under the same conditions as those for the Cu/ Al 2 O 3 cataly ^J st. FIG. 5 shows a profile of the Pt/ Al O catalyst through a method of generating a catalyst using air, and FIG. 6 shows a profile of the Pt/ Al O catalyst through a method of generating a catalyst using NO . As shown in FIGS. 5 and 6, in the method of generating the Pt/ Al

2 O catalyst using only air, it was found that CO was detected at a temperature of 500⁰C or lower, but, in the method of generating the Pt/ Al O catalyst using NO , it was found that CO was not detected even at a temperature of about 400⁰C. Therefore, it can be seen that the method of generating the Pt/ Al O catalyst using NO has a better regeneration effect than the method of generating the Pt/ Al O catalyst using only air. Meanwhile, in order to verify the regeneration effect at a low temperature using the oxidizability of NO , FIG. 7 shows a profile of a Pt/ Al O catalyst when the temperature thereof is maintained at 35O⁰C and is then increased to 600⁰C. As shown in FIG. 7, it can be seen that coke, adhered on the surface of the test catalyst, is mostly burned and regenerated at a temperature of 35O⁰C.

[41] The catalyst, which is used in the method of generating a catalyst using the oxidizability of NO , is not limited to the Cu/ Al O catalyst and the Pt/Al O catalyst. For this purpose, the present inventors created a profile of a zeolite catalyst under the same conditions as those for the Cu/ Al O catalyst and the Pt/Al O catalyst. FIG. 8 shows a profile of temperature and CO in the zeolite catalyst through a method of generating a catalyst using air and NO . In the method of regenerating the zeolite catalyst using air, it can be seen that carbon starts to burn at a temperature of about 32O⁰C, and that the concentration of CO is greatest at a temperature of about 37O⁰C. In contrast, in the method of regenerating the zeolite catalyst using NO , it can be seen that carbon is burned at a temperature ranging from 15O⁰C to 32O⁰C, and that the concentration of CO is greatly lowered even at a temperature of about 37O⁰C, at which the concentration thereof is greatest. Accordingly, it can be verified that the regeneration temperature is decreased, and that damage to the catalyst, attributable to the generation of heat occurring when carbon is rapidly burned, can be prevented.

[42] Table 1 shows the results of an analysis of carbon contents when a Cu/ Al O catalyst is regenerated using the oxidizability of NO , and Table 2 shows the results of an analysis of carbon contents when a Pt/Al O catalyst is regenerated using the oxidizability of NO . As shown in Table 1 and Table 2, it can be seen that the regeneration performance in the catalyst regeneration method of the present invention is far higher than that in the conventional catalyst regeneration method at the same temperatures, and that the regeneration performance therein is increased as time passes, even at low temperatures.

[43] Table 1

[44] Table 2

[45] Accordingly, in a precious metal catalyst, rather than a nonprecious metal catalyst, serving as an oxidation catalyst, no oxidation catalyst unit for generating NO is additionally required. However, in order to control the regeneration temperature of the catalyst and increase the regeneration efficiency of the catalyst, the oxidation catalyst unit may be mounted. Industrial Applicability

[46] As described above, although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Accordingly, the idea of the present invention provides a method of regenerating a catalyst, in which coke, which is a material adhered on the surface of a catalyst, is burned using the oxidizability of NO , in which an oxidation catalyst unit may be located at the front or rear end of a catalyst regeneration unit to introduce NO , and in which NO, which is generated from the catalyst regeneration unit, can be recirculated, unlike conventional catalyst regeneration technologies using air.

Claims

[1] A method of regenerating a catalyst, in which a nonprecious metal catalyst, a precious metal catalyst or a solid acid catalyst is regenerated, comprising the step of burning coke using the oxidizability of NO . [2] The method of regenerating a catalyst according to claim 1, further comprising the step of injecting NO and air into an oxidation catalyst unit located at a front or rear end of a catalyst regeneration unit to generate NO . [3] The method of regenerating a catalyst according to claim 2, wherein the oxidation catalyst unit comprises a platinum group metal-containing catalyst. [4] The method of regenerating a catalyst according to claim 2 or 3, further comprising the step of refluxing NO generated from the catalyst regeneration unit.