JP2007319859A - Adsorbent of nitrogen oxides, production and regeneration method thereof, and removing method of nitrogen oxides - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adsorbent suited to adsorb and remove nitrogen oxides of low concentration, production and regeneration methods thereof, and a method efficiently cleaning gas containing nitrogen oxides of low concentration. <P>SOLUTION: This adsorbent is for treating exhaust gas with concentrations of nitrogen oxides and/or sulfur oxides of 5 ppm or less. The adsorbent for nitrogen oxides and/or sulfur oxides contains at least one kind of element selected from (A) tin, antimony and bismuth, and at least one kind of element selected from (E) alkaline earth metal elements, titanium, silicon and zirconium, excluding one having ilmenite structure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a nitrogen oxide and / or sulfur oxide adsorbent, a method for producing and regenerating the adsorbent, and a method for removing nitrogen oxide and / or sulfur oxide using the adsorbent. Hereinafter, nitrogen oxides and / or sulfur oxides may be referred to as “nitrogen oxides”.

  With regard to the method of removing nitrogen oxides from fixed nitrogen oxide sources such as boilers, conventionally, contact that selectively reduces nitrogen oxides using ammonia as a reducing agent and converts them into harmless nitrogen and water. The reduction method is widely used as the most economical method.

  On the other hand, nitrogen oxides contained in ventilation gas or air at road tunnels, sheltered roads, deep underground spaces, road intersections, underground parking lots, etc., and gases emitted from combustion equipment used at home The concentration of is about 5 ppm, which is significantly lower than the nitrogen oxide concentration in the boiler exhaust gas, the gas temperature is normal, and the amount of gas is enormous. In order to efficiently remove nitrogen oxides by applying the above catalytic reduction method to a conventional ammonia reduction method, for example, the ventilation gas of a road tunnel, the temperature of the ventilation gas needs to be 300 ° C. or higher. As a result, a great deal of energy is required, so there is an economical problem in applying the catalytic reduction method as it is.

  For these reasons, the above ammonia reduction method cannot be used directly, and it is desirable to efficiently remove nitrogen oxides from exhaust gas having a low nitrogen oxide concentration, for example, 5 ppm or less, such as road tunnel ventilation gas. It is rare. Therefore, a method for removing low-concentration nitrogen oxides by adsorbing them on an adsorbent and an adsorbent suitable for this method have been proposed.

  The present applicant has proposed various adsorbents suitable for adsorbing and removing nitrogen oxides from such low-concentration nitrogen oxide-containing gases (Patent Documents 1 to 10).

  In addition, as a method for efficiently removing nitrogen oxides from a gas containing sulfur oxides in addition to nitrogen oxides, the present applicant removed sulfur oxides in advance and then brought them into contact with an adsorbent for nitrogen oxides. A method of adsorbing and removing nitrogen oxides is proposed (Patent Document 11).

  Furthermore, the present applicant has also proposed a method of regenerating by heating an adsorbent whose performance has been reduced by use in the presence of a reducing agent (Patent Document 12).

JP-A-10-128105 JP-A-10-192698 JP-A-10-309435 JP-A-11-28351 JP-A-11-28352 JP 2000-51655 A JP 2000-225318 A JP 2000-325780 A JP 2001-38200 A JP 2002-248348 A JP-A-10-76136 JP 2000-225317 A

  The object of the present invention is (1) an adsorbent suitable for adsorbing and removing nitrogen oxides, etc., particularly suitable for adsorbing and removing low concentrations of nitrogen oxides of about 5 ppm or less, and (2) It is to provide a production method, (3) a method for regenerating the adsorbent, and (4) a method for removing nitrogen oxides or the like using the adsorbent.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following invention.
(1) An adsorbent for treating exhaust gas having a nitrogen oxide and / or sulfur oxide concentration of 5 ppm or less, and (A) at least one element selected from tin, antimony, and bismuth; ) Adsorbent of nitrogen oxide and / or sulfur oxide, characterized by containing at least one element selected from alkaline earth metal elements, titanium, silicon and zirconium (however, those having an ilmenite structure) except).
(2) The nitrogen oxide and / or sulfur oxide adsorbent according to (1) above, wherein the adsorbent precursor containing the component elements (A) and (E) is heated in a reducing atmosphere. Manufacturing method.
(3) A method for regenerating the adsorbent of (1) above, wherein the adsorbent is heated in the presence of a reducing agent, and the method for regenerating an adsorbent of nitrogen oxide and / or sulfur oxide .
(4) Nitrogen oxide and / or sulfur oxide adsorbed and removed by contacting a gas containing nitrogen oxide and / or sulfur oxide with the adsorbent of (1) above; Or a method for removing sulfur oxides.
(5) Nitrogen oxide or a gas containing nitrogen oxide and sulfur oxide is brought into contact with the adsorbent of claim 1 to adsorb and remove nitrogen oxide or nitrogen oxide and sulfur oxide, and this nitrogen oxidation Or adsorbent that adsorbs nitrogen oxides and sulfur oxides in the presence of a reducing agent to desorb nitrogen oxides, regenerate the adsorbents, and denitrate the desorbed nitrogen oxides A method for purifying nitrogen oxides or a gas containing nitrogen oxides and sulfur oxides, comprising:

  Further, a gas containing nitrogen oxides and sulfur oxides is first contacted with an adsorbent for sulfur oxides to adsorb and remove sulfur oxides, and then the remaining gas containing nitrogen oxides is treated according to the above (5). May be.

  The adsorbent of the present invention has high adsorption performance for nitrogen oxides and the like, in particular, low concentrations of nitrogen oxides and exhibits excellent durability.

  By using the adsorbent of the present invention, a gas containing nitrogen oxides can be efficiently purified.

The adsorbent of the present invention is for adsorbing nitrogen oxides having a low concentration of 5 ppm or less, that is, nitrogen oxides and / or sulfur oxides. This nitrogen oxide is shown as NOx, and specifically, NO and NO ₂ can be mentioned. Further, the sulfur oxide is represented by SOx, and specifically includes SO ₂ . The adsorbent of the present invention can treat nitrogen oxides and sulfur oxides simultaneously or individually, and is particularly excellent in NO ₂ adsorption removal.

  The adsorbent of the present invention comprises at least one selected from tin, antimony and bismuth (component A), an alkaline earth metal element (at least one element selected from Be, Mg, Ca, Sr and Ba), titanium , At least one element selected from silicon and zirconium (component E), preferably an alkaline earth metal element. Specific examples include adsorbents containing antimony and calcium or tin and calcium.

  The proportion of component A is appropriately selected in the range of 1 to 99.5% by mass, preferably 5 to 99% by mass (the remainder is component B, total 100% by mass) in consideration of adsorption performance of nitrogen oxides and the like. do it.

  The form of component A in the adsorbent may be in any form as long as adsorption performance such as nitrogen oxide is obtained. For example, a metal (a simple substance), an oxide, a complex oxide, a hydroxide, a carbonate, a sulfate, a halide, and the like can be given. Similarly, a suitable form of the component E can be selected as appropriate.

  Starting materials for component A and component E include metals (elemental), oxides, hydroxides, carbonates, nitrates, sulfates, halides, organic metal salts, organic salts such as acetates and oxalates of each element. Acid salts and the like can be used.

Said adsorbent can be manufactured by the following method, for example.
(1) Powders of starting materials of component A and component E, or powder and an aqueous solution are mixed and stirred together with commonly used molding aids, molded by an extruder, and then dried at 50 to 120 ° C. If necessary, it is further calcined at 200 to 600 ° C., preferably 250 to 500 ° C. for 1 to 10 hours, preferably 2 to 6 hours, in air or in an inert gas such as nitrogen.

  Among the adsorbents, those obtained by further heat-treating the molded product obtained by the method (1) in a reducing atmosphere to reduce or alloy at least a part of the component elements are preferably used. In the present invention, a molded body that is heat-treated in a reducing atmosphere for the purpose of reduction or alloying, for example, a molded body obtained by the method (1) is referred to as an “adsorbent precursor”.

  The above “reducing atmosphere” means an atmosphere containing at least one reducing agent selected from hydrogen and combustible organic compounds. Examples of the combustible organic compound include hydrocarbons, preferably saturated or unsaturated hydrocarbons having 1 to 4 carbon atoms. In the present invention, hydrogen or hydrocarbons, particularly hydrogen, is preferably used as the reducing agent. Representative examples of the hydrocarbons include saturated or unsaturated hydrocarbons such as propane, butane, ethylene, propylene, and butadiene.

The reducing agent is usually diluted with another gas and used as a mixed gas with an inert gas such as nitrogen, for example. Specifically, when hydrogen is used as the reducing agent, it is used as a mixed gas of hydrogen and an inert gas such as nitrogen. The concentration of hydrogen in the mixed gas is usually 0.1 to 20% by volume, preferably 0.5 to 10% by volume. The air, water vapor (H 2 _O), may also be a mixed gas of carbon dioxide gas, in general, it is preferable to use a mixed gas of an inert gas such as described above. In the case of a combustible organic compound, the concentration in the mixed gas is usually 0.001 to 1% by volume, preferably 0.01 to 0.5% by volume.

  The heating temperature is usually 200 to 600 ° C, preferably 300 to 500 ° C, more preferably 300 to 450 ° C.

  The heat treatment of the present invention is preferably performed under ventilation of a reducing agent. In the case where the heat treatment is performed under ventilation of the reducing agent, the degree of ventilation is not particularly limited, and may be performed under such a condition that a new reducing agent is supplied.

  The adsorbent of the present invention is selected from at least one element selected from copper and cobalt (component B), alkali metal element (component C), and iron element (component D) in addition to the components A and E described above. It may contain at least one component. Hereinafter, adsorbent 1 and adsorbent 2 as specific examples will be described.

(Adsorbent 1)
It is an adsorbent containing component A, component B, component C and component E. As component C, potassium is usually used, and as component E, calcium is usually used. Specifically, tin, copper, potassium and calcium, tin, cobalt, potassium and calcium, antimony, copper, potassium and calcium, antimony, cobalt, potassium and calcium, bismuth, copper, potassium and calcium, and bismuth, cobalt, Mention may be made of adsorbents containing potassium and calcium.

  There are no particular restrictions on the form of each element in the adsorbent, and any metal (single), oxide, complex oxide, hydroxide, carbonate, hydrogen carbonate, etc., as long as it has adsorption performance such as nitrogen oxides. It may be in any form such as a salt, sulfate, halide, or organometallic salt.

  About the ratio of each component in adsorption agent, component A is 1-89.5 mass%, Preferably it is 5-85 mass%, and component B is 0.5-89 mass%, Preferably it is 1-81 mass%. Component C is 1 to 30% by mass, preferably 1 to 20% by mass, and Component E is 9 to 97.5% by mass, preferably 13 to 93% by mass.

  As the raw materials for Component A and Component E, the compounds described above can be used. Component B materials include metals (elemental), oxides, hydroxides, carbonates, nitrates, sulfates, halides, organic metal salts, and organic acid salts such as acetates and oxalates of each element. Can be used. In addition to component C hydroxides, carbonates, bicarbonates, nitrates, nitrites, organic acid salts such as acetates, oxalates, citrates, sorbates, etc. Can be used.

  The adsorbent containing component A, component B, component C and component E is, for example, a molding aid generally used as a starting material powder of component A, component B or component E, or a powder and an aqueous solution. And after stirring and molding with an extrusion molding machine, drying at 50 to 120 ° C., then 200 to 600 ° C., preferably 250 to 500 ° C. for 1 to 10 hours, preferably 2 to 6 hours, in air or It is obtained by firing in an inert gas such as nitrogen to produce a molded body, and then impregnating the molded body with an aqueous solution of the starting material of component C and drying.

(Adsorbent 2)
An adsorbent containing component A, component B, component C, component D and component E. As component C, potassium is usually used, and as component E, calcium is usually used. Specifically, tin, copper, potassium, iron and calcium, tin, cobalt, potassium, iron and calcium, antimony, copper, potassium, iron and calcium, antimony, cobalt, potassium, iron and calcium, bismuth, copper, potassium And adsorbents containing iron and calcium, and bismuth, cobalt, potassium, iron and calcium.

  There are no particular restrictions on the form of each element in the adsorbent, and any metal (single), oxide, complex oxide, hydroxide, carbonate, hydrogen carbonate, etc., as long as it has adsorption performance such as nitrogen oxides. It may be in any form such as a salt, sulfate, halide, or organometallic salt.

  About the ratio of each component in adsorption agent, component A is 1-89.5 mass%, Preferably it is 5-85 mass%, and component B is 0.5-89 mass%, Preferably it is 1-81 mass%. Component C is 1-30% by mass, preferably 1-20% by mass, Component D is 1-89.5% by mass, preferably 1-81% by mass, and Component E is 8-96. 5 mass%, preferably 12-92 mass%.

  As raw materials for Component A, Component B, Component C, and Component E, the compounds described above can be used. As the raw material of component D, iron metal (simple substance), oxide, hydroxide, nitrate, sulfate, halide, organic metal salt, organic acid salt such as acetate and oxalate can be used. .

  The adsorbent containing component A, component B, component C, component D and component E can be produced according to the same method as described above.

The ratio of each component in the adsorbent is as follows: component A, component B, component C, component D and component E are converted to oxides. Specifically, tin is SnO ₂ , antimony is Sb ₂ O ₃ , Bismuth is Bi ₂ O ₃ , copper is CuO, cobalt is Co ₃ O ₄ , alkali metal is X ₂ O (X is alkali metal), iron is Fe ₂ O ₃ , alkaline earth metal is YO (Y is alkaline earth) Metal), titanium is converted to TiO ₂ , silicon is converted to SiO ₂ , and zirconium is converted to ZrO ₂ .

  In the adsorbent of the present invention, at least one element selected from platinum, gold, ruthenium, rhodium, palladium, manganese, nickel, lead, zinc, vanadium, niobium, chromium, molybdenum and tungsten (component (F)) Preferably, it may contain at least one element selected from platinum, gold, ruthenium, rhodium, palladium, manganese, nickel and lead.

  Specific examples include adsorbents containing component A, component B, component C, component E and component F, and component A, component B, component C, component D, component E and component F.

About content of the component F, 0.01-10 mass% as metal conversion in the case of platinum, gold | metal | money, ruthenium, rhodium and palladium with respect to the total amount of each component of an adsorbent, Preferably it is 0.05-5 mass %. In the case of manganese, nickel, lead, zinc, vanadium, niobium, chromium, molybdenum and tungsten, oxide conversion (MnO ₂ , NiO, Pb ₃ O ₄ , ZnO, V ₂ O ₅ , Nb ₂ O ₅ , CrO ₃ , MoO ₃ and WO ₃ ) are 0.5 to 30% by mass, preferably 1 to 20% by mass.

  These elements are contained in the form of, for example, a metal (a simple substance), an oxide, a complex oxide, or the like. Among these elements, platinum, gold, ruthenium, rhodium, palladium, manganese, nickel and lead are preferable, and ruthenium is particularly preferably used.

  Starting materials for these elements include metals (elemental), oxides, hydroxides, carbonates, nitrates, sulfates, halides, organic metal salts, organic acid salts such as acetates and oxalates, Ammine complexes and the like can be used.

Among the adsorbents described above, the adsorbent containing component A and component B is preferably such that at least a part of component A and at least a part of component B form an alloy. The remaining component A and component B may be in any form such as metal (simple substance), oxide, composite oxide, sulfate, halide, organometallic salt.
In general, an alloy is obtained by adding another metal element or a non-metal element to a certain metal, and forms thereof include solid solutions, eutectics, intermetallic compounds, or those in which they coexist. An alloy means any of a solid solution, an intermetallic compound, or an alloy in which a solid solution and an intermetallic compound coexist. Here, a solid solution is a phase in which atoms existing at a lattice point of one crystal phase are completely irregularly replaced with another type of atom, or another type of atom is distributed statistically in the lattice gap. And the two or three components each occupy a specific lattice point of the crystal lattice, it is regarded as another new crystal phase (intermetallic compound) and is not a solid solution (for example, Chemistry Dictionary 3, 706, 1960, Kyoritsu Publishing Co., Ltd.). In addition, an intermetallic compound is a compound in which two or more metal elements are combined at a simple integer ratio and have new properties different from those of the constituent metal elements. In addition to these, non-metallic elements such as boron, carbon, silicon, germanium, arsenic, antimony, selenium, tellurium and the like may be included (for example, Chemical Dictionary 2, page 915, 1960, Kyoritsu Shuppan Co., Ltd.).

The adsorbent containing the component [AB] alloy can be produced by the same method as described in the production of the adsorbent containing the component A and the component B. That is, when tin is used as component A and copper is used as component B, the above-mentioned tin and copper starting material powder, or powder and an aqueous solution are mixed with a commonly used molding aid, stirred, and extruded. After molding with a machine, after drying at 50 to 120 ° C., 200 to 600 ° C., preferably 250 to 500 ° C. for 1 to 10 hours, preferably 2 to 6 hours, in air or an inert gas such as nitrogen, etc. To form a molded body made of tin oxide (SnO ₂ ) and copper oxide (CuO). The molded body as the adsorbent precursor thus obtained is heated in a reducing atmosphere to convert at least part of tin and at least part of copper into a tin-copper alloy.

  The above “reducing atmosphere” means an atmosphere containing at least one reducing agent selected from hydrogen and combustible organic compounds. Examples of the combustible organic compound include hydrocarbons, preferably saturated or unsaturated hydrocarbons having 1 to 4 carbon atoms. In the present invention, hydrogen or hydrocarbons, particularly hydrogen, is preferably used as the reducing agent. Representative examples of the hydrocarbons include saturated or unsaturated hydrocarbons such as methane, ethane, propane, butane, ethylene, propylene, and butadiene.

The reducing agent is usually diluted with another gas and used as a mixed gas with an inert gas such as nitrogen, for example. Specifically, when hydrogen is used as the reducing agent, it is used as a mixed gas of hydrogen and an inert gas such as nitrogen. The concentration of hydrogen in the mixed gas is usually 0.1 to 20% by volume, preferably 0.5 to 10% by volume. The air, water vapor (H 2 _O), may also be a mixed gas of carbon dioxide gas, in general, it is preferable to use a mixed gas of an inert gas such as described above. In the case of a combustible organic compound, the concentration in the mixed gas is usually 0.001 to 1% by volume, preferably 0.01 to 0.5% by volume.

  The heating temperature is usually 200 to 600 ° C, preferably 300 to 500 ° C, more preferably 300 to 450 ° C.

  The heat treatment of the present invention is preferably performed under ventilation of a reducing agent. In the case where the heat treatment is performed under ventilation of the reducing agent, the degree of ventilation is not particularly limited, and may be performed under such a condition that a new reducing agent is supplied.

The tin-copper alloy can be confirmed by measuring the lattice spacing (d value) by X-ray diffraction. That is, since the d value of Cu ₃ Sn is 2.16 ± 0.01, 2.08 ± 0.01, and 1.24 ± 0.01, the above d value is shown in the X-ray diffraction diagram of the adsorbent. If there is a corresponding peak, it can be said that an amount of tin-copper alloy effective for adsorbing nitrogen oxide or the like is contained.

  The adsorbent containing tin and cobalt, the adsorbent containing antimony and copper, and the adsorbent containing antimony and cobalt are also tin-cobalt alloy, respectively, similar to the adsorbent containing tin and copper, respectively. Adsorbents including antimony-copper alloys and antimony-cobalt alloys are preferably used. The adsorbent containing these alloys can be produced in the same manner as the adsorbent containing tin and copper.

The tin-cobalt alloy has Co ₃ Sn ₂ d values of 2.93 ± 0.01, 2.09 ± 0.01, and 2.06 ± 0.01, so in the X-ray diffraction diagram of the adsorbent The peak corresponding to the d value can be confirmed.

The antimony-copper alloy is adsorbed because the d value of Cu ₂ Sb is 2.82 ± 0.01, 2.56 ± 0.01, 2.07 ± 0.01, and 1.99 ± 0.01. It can be confirmed by a peak corresponding to the d value in the X-ray diffraction pattern of the agent.

  Since the antimony-cobalt alloy has SbCo d values of 2.16 ± 0.01, 2.08 ± 0.01, and 1.24 ± 0.01, the above d in the X-ray diffraction diagram of the adsorbent is used. It can be confirmed by the peak corresponding to the value.

Note that the lattice spacing (d value) measuring apparatus and measuring conditions are as follows.
(apparatus)
Rigaku RU-300 series (measurement conditions)
X-ray: CuKα1 / 50kV / 300mA
Goniometer: Wide-angle goniometer attachment: ACS-43 (horizontal type)
Filter: Not used Counter monochromator: Curved crystal monochromator Divergence slit: 1 deg
Scattering slit: 1 deg
Receiving slit: 0.3mm
Counter: Scintillation counter Scan mode: Continuous scan speed: 4 ° / min
Scan step: 0.01 °
Scanning axis: 2θ / θ
Scanning range: 30-60 °
θ offset: 0 °
Fixed angle: 0 °
Integration count: 3
(Data processing conditions)
Smoothing method: Weighted average smoothing score: 25
Backland removal method: Sonnevelt-Visser method intensity ratio (Kα2 / Kα1): 0.500
There is no restriction | limiting in particular about the shape of the adsorbent of this invention, It can select suitably from column shape, cylindrical shape, spherical shape, plate shape, honeycomb shape, and the other shape | molded integrally. For this molding, a general molding method such as tableting molding or extrusion molding can be used. In the case of a spherical shape, the average particle diameter is usually 1 to 10 mm. In the case of a honeycomb-like adsorbent, it is the same as a so-called monolithic carrier, and can be manufactured by an extrusion molding method or a method of winding up a sheet-like element. The shape of the gas passage port (cell shape) may be any of a hexagon, a tetragon, a triangle, or a corrugation. The cell density (number of cells / unit cross-sectional area) is usually 25 to 800 cells / in 2 (× 2.54 cm), preferably 25 to 500 cells / in 2 (× 2.54 cm).

  According to the method of the present invention, a gas containing nitrogen oxides or the like is brought into contact with the adsorbent to adsorb nitrogen oxides or the like to purify the gas. A typical example of the gas is a ventilation gas or an atmospheric gas from the road tunnel or the like, and the method of the present invention uses a nitrogen oxide from a gas having a low concentration of nitrogen oxide and sulfur oxide of 5 ppm or less. It is preferably used for adsorption removal of sulfur oxides.

There is no restriction | limiting in particular about the contact method of the said gas and adsorption agent, Usually, gas is introduce | transduced in the layer which consists of this adsorption agent. About this process condition, since it changes with properties of the gas etc. which should be processed, it cannot be specified unconditionally, For example, the temperature of the gas supplied to an adsorbent layer is usually 0-100 ° C, and especially 0-50 ° C. It is preferable to do this. Also, the space velocity of the gas supplied to the adsorbent layer (SV) is usually a 1,000~100,000hr ^-1 (STP), in the range of 4,000~60,000hr ^-1 (STP) preferred .

  The adsorbent of the present invention, which adsorbs nitrogen oxides or the like and has a reduced adsorbing power, can be efficiently regenerated by heat treatment in the presence of a reducing agent. For example, nitrogen oxides and sulfur oxides are usually contained in ventilation gas or the air in road tunnels, etc. Therefore, the adsorbent used in such places contains nitrogen oxides and sulfur oxides. Although adsorbing power is reduced by adsorption, the nitrogen oxide adsorbed in this manner can be efficiently desorbed by heat treatment in the presence of a reducing agent.

  The reducing agent used in the regeneration treatment of the present invention means hydrogen and a combustible organic compound. Representative examples of combustible organic compounds include hydrocarbons, preferably saturated or unsaturated hydrocarbons having 1 to 4 carbon atoms, or oxygen-containing organic compounds, specifically fatty acids, alcohols and aldehydes, Preferable examples include lower fatty acids having 1 to 4 carbon atoms, lower alcohols having 1 to 4 carbon atoms, and lower aldehydes having 1 to 4 carbon atoms. Among these, C1-C4 saturated or unsaturated hydrocarbons and lower fatty acids are preferably used. The flammable organic compounds can be used alone or in combination of two or more. In the present invention, hydrogen, saturated or unsaturated hydrocarbons having 1 to 4 carbon atoms or lower fatty acids, particularly hydrogen, are preferably used as the reducing agent.

  Representative examples of the hydrocarbons include saturated or unsaturated hydrocarbons such as methane, ethane, propane, butane, ethylene, propylene, and butadiene. Representative examples of the lower fatty acids include mono- or di- or saturated such as formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, malonic acid, succinic acid, tartaric acid, malic acid, acrylic acid, methacrylic acid, maleic acid, etc. Or unsaturated carboxylic acid can be mentioned.

  The reducing agent is usually diluted with another gas and used as a mixed gas with an inert gas such as nitrogen, for example. Specifically, when hydrogen is used as the reducing agent, it is used as a mixed gas of hydrogen and an inert gas such as nitrogen or helium. The concentration of hydrogen in the mixed gas is usually 0.1 to 20% by volume, preferably 0.5 to 10% by volume. In addition, although it can also be set as a mixed gas with air, generally it is good to use as a mixed gas with the above inert gas. Also in the case of a combustible organic compound, it is used as a mixed gas with an inert gas such as nitrogen. The concentration of the combustible organic compound in the mixed gas is usually 0.001 to 1% by volume, preferably 0.01 to 0.5% by volume. In the case where the combustible organic compound is solid, it may be supplied by dissolving it in water and spraying it as an aqueous solution.

Examples of the gas that can be used for diluting the reducing agent include water vapor (H ₂ O) and carbon dioxide gas in addition to the inert gas such as nitrogen and helium and air. Thus, representative examples of the mixed gas include a combination of hydrogen and an inert gas, and a combustible organic compound and an inert gas.

  Regarding the heating temperature in the regeneration process, according to the present invention, regeneration is possible at 600 ° C. or less. The heating temperature is usually 200 to 600 ° C, preferably 300 to 500 ° C, more preferably 300 to 450. The adsorbent to be regenerated is usually at room temperature, but the rate of temperature rise up to the heating temperature is not particularly limited and can be determined as appropriate.

  The heating time varies depending on the degree of adsorption of nitrogen oxides, the heating temperature, and the like, and thus cannot be specified unconditionally, but can be appropriately selected in the range of usually 30 minutes to 10 hours, preferably 30 to 5 hours.

  The regeneration treatment of the present invention is preferably performed under ventilation of a reducing agent. When the regeneration process is performed under ventilation of the reducing agent, there is no particular limitation on the degree of ventilation, and the conditions may be such that a new reducing agent is supplied. In general, a reducing agent may be introduced from an inlet side into an apparatus (adsorbent layer) filled with an adsorbent and then distributed to the outlet side.

  The adsorbent regenerated by the regeneration treatment of the present invention can be reused for adsorption removal of nitrogen oxides and the like.

  When the adsorbent is regenerated, a gas (exhaust gas) containing the desorbed nitrogen oxides is generated. After removing the nitrogen oxides in the exhaust gas to make them harmless, they are released into the atmosphere. preferable. The method for removing nitrogen oxides in the exhaust gas, that is, the denitration method is not particularly limited, and can be performed by a conventionally known denitration method. Specifically, for example, ammonia may be added to the exhaust gas as a reducing agent and brought into contact with a denitration catalyst to reduce nitrogen oxides to nitrogen and water.

  When purifying the gas by efficiently removing nitrogen oxide from the gas containing sulfur oxide in addition to nitrogen oxide, remove the sulfur oxide in advance, and then contact the adsorbent of the present invention to oxidize nitrogen. Adsorbing and removing an object improves the durability of the adsorbent and can effectively remove nitrogen oxides over a long period of time.

  The method for removing sulfur oxide is not particularly limited, and a method of removing gas by washing with water, a method of removing gas by contacting with an adsorbent for adsorption of sulfur oxide, and the like can be used. Among these, a method using an adsorbent for sulfur oxide is suitably used from the viewpoint that the apparatus becomes compact and consumes less energy.

  Any adsorbent for sulfur oxide may be used as long as it can adsorb SOx, and an adsorbent containing at least one selected from activated carbon, transition metal, alkali metal and alkaline earth metal is particularly preferable. Used for. Typical examples of the transition metal include Ni, Co, Fe, Mn, Cr, Mo, W, V, Nb, Zn, and Cu. Representative examples of alkali metals and alkaline earth metals include Li, Na, K and Mg, Ca, Ba. The form of these elements in the adsorbent is not particularly limited, and any form may be used as long as it can adsorb SOx. Specific examples include oxides, carbonates, sulfates, chlorides, and hydroxides.

  The adsorbent for sulfur oxide contains at least one of alkaline earth metal, alumina, silica, titania, zirconia, silica-alumina, alumina-zirconia, silica-titania, silica-zirconia and titania-zirconia as a carrier. You may go out.

  One of the preferred embodiments of the present invention is that a gas containing nitrogen oxides and sulfur oxides is first contacted with an adsorbent for sulfur oxide to adsorb and remove sulfur oxides, and then contacted with the adsorbent of the present invention. And removing the nitrogen oxides to purify the gas. Thereby, the durability of the adsorbent of the present invention is improved.

The invention is further illustrated by the following examples, which illustrate advantageous embodiments of the invention. X-ray diffraction was performed under the following conditions using the following apparatus.
(apparatus)
Rigaku RU-300 series (measurement conditions)
X-ray: CuKα1 / 50kV / 300mA
Goniometer: Wide-angle goniometer attachment: ACS-43 (horizontal type)
Filter: Not used Counter monochromator: Curved crystal monochromator Divergence slit: 1 deg
Scattering slit: 1 deg
Receiving slit: 0.3mm
Counter: Scintillation counter Scan mode: Continuous scan speed: 4 ° / min
Scan step: 0.01 °
Scanning axis: 2θ / θ
Scanning range: 30-60 °
θ offset: 0 °
Fixed angle: 0 °
Integration count: 3
(Data processing conditions)
Smoothing method: Weighted average smoothing score: 25
Backland removal method: Sonnevelt-Visser method intensity ratio (Kα2 / Kα1): 0.500
Example 1
After adding a suitable amount of water to 161.5 g of tin oxide (SnO ₂ ) and 288.5 g of calcium carbonate, the mixture was mixed well with a kneader, and then molded into a pellet having a diameter of 5 mm and a length of 5 mm by an extruder. The pellet was dried at 100 ° C. for 10 hours and then calcined at 450 ° C. for 5 hours in an air atmosphere to obtain a pellet-shaped adsorbent precursor. The composition of this adsorbent precursor was Sn: Ca (as SnO ₂ : CaO) = 49.9: 50.1 (mass%). Next, this adsorbent precursor was heat-treated at 450 ° C. for 2 hours under a flow of hydrogen / nitrogen (5/95 vol%) to obtain an adsorbent (1).

(Example 2)
In Example 1, except that antimony oxide (Sb ₂ O ₃ ) was used instead of tin oxide (SnO ₂ ), Sb: Ca (as Sb ₂ O ₃ : CaO) = 50. An adsorbent (2) having a composition of 0: 50.0 (% by mass) was obtained.

(Example 3)
In a kneader while adding an appropriate amount of water to antimony oxide (Sb ₂ O ₃ ) 45.0 g, copper oxide (CuO) 45.0 g, iron oxide (α-Fe ₂ O ₃ ) 90.0 g, and calcium carbonate 270.0 g After mixing well, it was molded into a pellet having a diameter of 5 mm and a length of 5 mm with an extrusion molding machine. The pellet was dried at 100 ° C. for 10 hours and then calcined at 450 ° C. for 5 hours in an air atmosphere. Furthermore, after impregnating this pellet in 6N-potassium acetate aqueous solution for 2 minutes, it dried at 120 degreeC for 5 hours, and obtained the pellet-shaped adsorbent precursor. The composition of this adsorbent precursor is Sb: Cu: K: Fe: Ca (as Sb ₂ O ₃ : CuO: K ₂ O: Fe ₂ O ₃ : CaO) = 12.3: 12.2: 9.8 : 24.5: 41.2 (mass%).

Next, the adsorbent precursor was heat-treated at 400 ° C. for 2 hours under a nitrogen atmosphere to obtain an adsorbent (3). X-ray diffraction analysis of the adsorbent (3) was performed, and it was confirmed that the adsorbent (3) contained Cu ₂ Sb.

Example 4
In Example 3, an adsorbent (4) having the composition shown in Table 1 was obtained in the same manner as in Example 3 except that cobalt oxide (Co ₃ O ₄ ) was used instead of copper oxide (CuO). X-ray diffraction analysis of the adsorbent (4) was performed, and it was confirmed that the adsorbent (4) contained SbCo.

(Example 5)
The nitrogen oxide adsorption ability and sulfur oxide adsorption ability of the adsorbent (1) and the adsorbent (2) were evaluated by the following methods.
(Evaluation method (1))
17.3 ml of the adsorbent was filled in a glass reaction tube having an inner diameter of 30 mm. A synthesis gas (A) having the following composition was introduced into the adsorbent layer under the following conditions.
<Composition of synthesis gas (A)>
Nitric oxide (NO): 0.9 ppm, Nitrogen dioxide (NO ₂ ): 0.1 ppm, Sulfur dioxide (SO ₂ ): 0.05 ppm, H ₂ O: 1.9% by volume, remaining: air <treatment conditions>
Gas amount: 17.3 NL / min, treatment temperature: 25 ° C., space velocity (SV): 60,000 hr ⁻¹ (STP), gas humidity: 60% RH
One hour after the introduction of the synthesis gas (A), the concentration of nitrogen oxide (NO ₂ ) in the synthesis gas at the inlet and outlet of the adsorbent layer was measured by a chemiluminescent NOx meter and sulfur oxide (SO ₂ ). ₂ ) The concentration was measured with an ultraviolet absorption SO ₂ meter, and the NO ₂ and SO ₂ removal rates were calculated according to the following formula.
NO ₂ removal rate (%) = {(inlet NO ₂ concentration−outlet NO ₂ concentration) / (inlet NO ₂ concentration)} × 100
SO ₂ removal rate (%) = {(inlet SO ₂ concentration−outlet SO ₂ concentration) / (inlet SO ₂ concentration)} × 100
The results are shown in Table 2.

(Example 6)
The nitrogen oxide adsorption ability and sulfur oxide adsorption ability of the adsorbents (3) to (4) were evaluated by the following methods.
(Evaluation method (2))
After measuring the nitrogen oxide adsorption ability and sulfur oxide adsorption ability of each adsorbent in the same manner as in the evaluation method (1), the gas composition was changed and the following accelerated durability test was conducted.
<Accelerated durability test>
Synthesis gas (B) having the following composition was introduced into the adsorbent layer under the following conditions.
<Composition of synthesis gas (B)>
Nitric oxide (NO): 2.7 ppm, Nitrogen dioxide (NO ₂ ): 0.3 ppm, Sulfur dioxide (SO ₂ ): 0.15 ppm, H ₂ O: 1.9% by volume, remaining: air <treatment conditions>
Gas amount: 17.3 NL / min, treatment temperature: 25 ° C., space velocity (SV): 60,000 hr ⁻¹ (STP), gas humidity: 60% RH
After performing the accelerated durability test for 200 hours, one hour after the introduction of the synthesis gas (A), the nitrogen oxide (NO ₂ ) concentration and sulfur oxide in the synthesis gas at the inlet and outlet of the adsorbent layer The (SO ₂ ) concentration was measured in the same manner as in the evaluation method (1), and the NO ₂ and SO ₂ removal rates were calculated. The results of the evaluation test are shown in Table 3.

(Example 7)
In Example 6, a regeneration test was performed using the adsorbent (3) after the accelerated durability test, and the nitrogen oxide removal ability and sulfur oxide removal ability after regeneration were evaluated by the following methods.
<Regeneration test>
A regeneration gas having the following composition was introduced into each adsorbent after the accelerated durability test under the following conditions.
<Regenerative gas composition>
Hydrogen: 5% by volume, remaining nitrogen <treatment conditions>
Gas amount: 1.7 NL / min, temperature rising rate: 250 ° C./hr, processing temperature: 400 ° C., processing time: 1 hour After the above regeneration, cooling to room temperature and the same method as the evaluation method (1) The adsorption performance of the adsorbent after regeneration was evaluated by measuring the nitrogen oxide adsorption capacity and sulfur oxide adsorption capacity of the adsorbent. The results are shown in Table 4.

(Example 8)
(Preparation of adsorbent for sulfur oxide)
286 liters of aqueous ammonia (NH ₃ , 25%) was added to 400 liters of water, and 24 kg of Snowtex NCS-30 (Nissan Chemical Co., Ltd. silica sol, containing about 30% by mass of SiO ₂ ) was added thereto. In the resulting solution, titanyl sulfate aqueous solution (containing 250 g / liter as TiO ₂ , total sulfuric acid concentration 1,100 g / liter) 153 liters added to 300 liters of water and diluted titanium-containing sulfuric acid aqueous solution gradually with stirring. To obtain a coprecipitated gel. The gel was filtered, washed with water, and dried at 200 ° C. for 10 hours. Subsequently, it was fired in an air atmosphere at 600 ° C. for 6 hours, further pulverized using a hammer mill, and classified by a classifier to obtain a powder having an average particle diameter of 10 μm. The composition of the obtained powder (hereinafter referred to as TS-1) was Ti: Si = 4: 1 (atomic ratio).

After adding an appropriate amount of water to 500 g of TS-1 powder and kneading well with a kneader, it was molded into a pellet having a diameter of 5 mm and a length of 5 mm with an extruder. The pellet was dried at 100 ° C. for 10 hours and then calcined at 350 ° C. for 3 hours in an air atmosphere. Further, the pellet was impregnated with 6N-sodium carbonate aqueous solution for 2 minutes and then dried at 120 ° C. for 5 hours. The composition of the adsorbent for sulfur oxide thus obtained was TS-1: Na (as TS-1: Na ₂ O) = 76.1: 23.9 (mass%).

(Evaluation methods)
In the evaluation method (1) and the evaluation method (2) of Example 6, 19 ml of the above-mentioned adsorbent for sulfur oxide was used in the preceding stage with respect to the gas flow, and 17% of the adsorbent (3) obtained in Example 3 was used in the subsequent stage. The nitrogen oxide adsorption ability and sulfur oxide adsorption ability were evaluated in the same manner as in Evaluation Method (1) and Evaluation Method (2) of Example 5 except that 3 ml was filled. The results are shown in Table 5.

  From the results of Table 3 and Table 5, it is understood that the durability performance of the adsorbent (3) is improved by installing the sulfur oxide adsorbent in the previous stage.

Example 9
In Example 8, the nitrogen oxide adsorbing ability and the sulfur oxide adsorbing ability were evaluated in the same manner as in Example 8 except that the adsorbent (4) obtained in Example 4 was used as the latter adsorbent. The results are shown in Table 5.

  From the results of Table 3 and Table 5, it is understood that the durability performance of the adsorbent (4) is improved by installing the sulfur oxide adsorbent in the previous stage.

Claims (5)

  An adsorbent for treating exhaust gas having a concentration of nitrogen oxide and / or sulfur oxide of 5 ppm or less, comprising (A) at least one element selected from tin, antimony and bismuth, and (E) alkaline earth A nitrogen oxide and / or sulfur oxide adsorbent (except for those having an ilmenite structure), characterized by containing at least one element selected from a metal group element, titanium, silicon and zirconium.   2. The production of an adsorbent for nitrogen oxide and / or sulfur oxide according to claim 1, wherein the adsorbent precursor containing the component elements (A) and (E) is heated in a reducing atmosphere. Method.   A method for regenerating an adsorbent according to claim 1, wherein the adsorbent is heated in the presence of a reducing agent.   A nitrogen oxide and / or sulfur oxide is characterized by contacting a gas containing nitrogen oxide and / or sulfur oxide with the adsorbent of claim 1 to adsorb and remove nitrogen oxide and / or sulfur oxide. Removal method.   Nitrogen oxide or a gas containing nitrogen oxide and sulfur oxide is brought into contact with the adsorbent of claim 1 to adsorb and remove nitrogen oxide, or nitrogen oxide and sulfur oxide, and the nitrogen oxide, or The adsorbent that adsorbs nitrogen oxides and sulfur oxides is heated in the presence of a reducing agent to desorb the nitrogen oxides, regenerate the adsorbents, and denitrate the desorbed nitrogen oxides. A method for purifying a nitrogen oxide or a gas containing nitrogen oxide and sulfur oxide.