SG186571A1 - Method for regenerating catalyst for production of methacrylic acid and process for preparing methacrylic acid - Google Patents

Abstract

METHOD FOR REGENERATING CATALYST FOR PRODUCTION OF METHACRYLIC ACID AND5 PROCESS FOR PREPARING METHACRYLIC ACIDProvided are a method for regenerating a catalyst for the production of methacrylic acid, which enables to satisfactorily restore catalytic activity and catalyst life of a used catalyst used for the production of methacrylic acid,10 and a process for preparing methacrylic acid by using the regenerated catalyst obtained by the method. The method for regenerating a catalyst for the production of methacrylic acid comprising a heteropolyacid compound containing phosphorus, molybdenum and copper comprises step (1) mixing a used catalyst, a nitrate ion, an ammonium ion and water to form an aqueous15 slurry A wherein the atomic ratio of copper to molybdenum has beenadjusted to a predetermined ratio, step (2) forming an aqueous slurry B wherein the atomic ratio of copper to molybdenum has been adjusted to a predetermined ratio, and step (3) drying and calcining an aqueous slurry C obtained by mixing the aqueous slurry A obtained in step (1) with the20 aqueous slurry B obtained in step (2), wherein the atomic ratio of copper to molybdenum in the heteropolyacid compound is from 0.05 :12 to 0.25 : 12.

Description

i

DESCRIPTION

METHOD POR REGENERATING CATALYST VOR PRODUCTION OF

METHACRYLIC ACID AND

PROCESS FOR PREPARING METHACRYLIC ACID

Background of the Invention Technical Field

[0001]

The present application claims the Paris Convention priority based on Japanese Patent Application No. 2011-138216 filed on June 22, 2011, the sutive content of which 1s incorporated herein by reference.

The present invention relates to a method for regenerating a catalyst for the production of methacrylic acid by performung a regeneration 18 treatment on a used catalyst {spent catalyst) comprising a heteropolvacid compound containing phosphorus, molybdenum and copper and to a process for preparing wethacrylic acid using the regenerated catalyst obtained hy the regeneration method.

Background Art

[0002]

It 1s known that catalytic activity of a catalyst for the production of mathacrylic acid comprising a heteropolyacid compound containing phosphorus, molybdenum and copper is reduced due to heat load or the Uke when i018 used for a long trae In a gas phase catalytic oxidation reaction using methaerclein or the like as a raw material. [000s]

As a regeneration method of such a used catalyst, there have been proposed methods (see Patent Documents 1-8) for obtaining a regenerated

AY catalyst which comprises a heteropolyacid compound in which the atomis ratio of copper to molybdenum {Cu * Me) 18 0.30 12, wherein the methods comprise the steps of mining the used catalyst, a nitrate ion and an ammonium on to shiain an aqueous slurry, drying the shary to obtain a dried catalyst, and then caleining the dried catalyst. a5

Prior Art Document

Patent Document

[0004]

Patent Document 10 JP-A-2008-80232 8 Patent Document £1 JP-A-2008-86028

Patent Document 30 JP-A-2008-83588

Patent Document 47 JP-A-2008-248084

Patent Document 50 JP-A-2006-2480G35

Patent Document 6 JP-A-2010-207684 1G

Summary of the Invention

Problems to be Solved by the Invention fonos]

However, regenerated catalysts obtained by the conventional 186 methods ave not always satisfactory in the catalytic activity and catalyst hfe. 0008]

An obijeet of the present Invention is to provide a method for regenerating a catalyst for the production of methacrylic acid, which satisfactorily restores catalytic activity and catalyet life of & used catalyst used for the production of methacrylic acid as well as to provide a process for preparing methacrylic acid at a high yield for a long time by using the regenerated catalyst obtained by the method.

[0007]

The inventors had conducted an intensive research to solve the 2% above-described problem and accomplished the present invention,

[0008]

More specifically, the present invention has the following configuration.

[1] A method for regenerating a catalyst for the production of methacrylic acid comprising a heteropolyacid compound containing phosphorus, molybdenum and copper, wherein the method comprises the following steps (1) to (3), and wherein the atomic ratio of copper fo molybdenum (Cu ® Me) in the heteropolyacid compound constituting a regenerated catalyst is from 0.05 112 +0 025 1 18, step (1): mixing a used catalyst used for the production of methacrylic acid, a nitrate lon, an ammonium ion and water to form an agueous slurry A in which the atomic ratio of copper to molybdenum {Cut

Mo) has been adjusted to from 0.10112 to 0.50 18, step (2) mixing at least 2 compound containing molybdenmm among § compounds containing constituent elements of the heteropolyacid compound with water to form an agueous slurry B in which the atomic ratio of copper to molybdenum (Cu Mo) has been adjusted to from 00 12 60 L280 12, and stop {3 mixing the agueous slurry A obtained in step {1) with the agueous slurry B obtained in step (2) fo form an agueous slurry C, and then drying and calcining the aqueous slurry C [21 The method according $o [1], whersin the heteropolyacid compound further contains at least one clement X selected from the group consisting of potassium, rubidium, cesium and thallium, the atomic ratio of the element X to molybdenum (X Mo) in the heteropolyacid compound constituting the regenerated catalyst is from (4.5 7 12 to 2112, the atomie ratio of the element X to molybdenum (X Mo) contained in the agusous slurry A instep (1) is from 2° 12 to 41 12, and the atomic ratio of the element

X to molybdennm (X : Mo) contained in the agueous slurry B in step (8) is from 00 1850 0.5 1 18

[3] The method according to [1 or [2], wherein the agusous shurey © obtained in step (3) is a slurry obtained by mixing the aqueous slurry 4 obtained in step (1), the agueous slurry B obtained in step (2) and a compound containing copper. fa] The method aceording to [3], wherein the agueous slurry 4, the agueous shury B and the compound containing copper are mixed so that the atomic ratio of copper to molybdenum (Cu Mo) contained in the aqueous shurry © ig within the range of from (4.058 1 12 to 0.25 1 18. {81 The method according to any one of [1 to [4], wherein at least one of the aqueous slurry A obtained in step {1} and the agueous slurry C obtained in step (8) is a slurry subjected fo a wet pulverization treatment. {6] The method according to any one of [1] to 15], wherein the aqueous shirry O obtained in step (3) is a slurry subjected to a heat treatment at 100°C or more. [71 The method according to any ons of [1] to 18], wherein the aqueous slurry A obtained in step (1) contains 0.1 to 5.0 moles of the ammonium jon per one mole of the nitrate ion.

I8] The method according $0 any one of [1] to [7], wherein the pH of a

Hauid phase of the agueous slurry A obtained in step (1) is 8 or less, 19] The method according to any one of [1 to [8], wherein the heteropolyvacid compound further contains vanadium and af least one © element selected from the group consisting of arsenic, antimony, boron, silver, bismuth, tron, cobalt, lanthanum and cerium. : F101 A process for preparing methacrylic acid, the process comprising the stops off regenerating a catalyst for the production of methacrylic acid hy the regeneration method according to any one of {1} to [8], and subjecting a compound selected from the group consisting of methacrolein, ischutylaldehyde, ischutane and isobutyric acid to a gas phase catalytic oxidation reaction in the presence of the regenerated catalyst. ib

Effects of the Invention

[6008]

According to the present invention, catalytic activity and catalyst life of a used catalyst used for the production of methacrylic acid are satisfactorily restored. Also, methacrylic acid is produced at a high yield for a long time with the use of the regenerated catalyst chimined by the method.

Detailed Description of the Invention [e010]

Herelnafter, the present invention will be described in detail. A method for regenerating a catalyst for the production of methacrylic acid of the present invention comprises subjecting a used catalyst for the production of methacrylic acid used for the production of reethacrylic acid to a regeneration ireatment, whereby a speoific regenerated catalyst is obtamed. [oo1d

The catalyst for the production of methacrylic acid which can be regenerated by the regeneration method of the present invention (hereinafter sometimes referred to as an "object catalyst”) may be a catalyst comprising a heteropolyacid compound containing phosphorus, molybdenum 35% and copper. The catalyst may comprise a free heteropolyacid or a salt of a heteropolyacid, Among these, a catalyst comprising an acidic salt (a partially neutralized salt) of a hetevopolyacid is preferable, and a catalyst comprising an acidic salt of a Kegein type heteropolyacid is more preferable. 0012] i Further, the heteropolyacid compound preferably contains at least one slement X selected from the group consisting of potassium, rubidinm, cesium and thallium, and more preferably contains the element X| vanadium and ai least one element thereinafier referred to as "element YY) selected . frora the group consisting of copper, arsenic, antimony, boron, silver, bismuth, ron, cobalt, lanthanum and cerium.

[0013]

The heteropolyacid compound which constitutes the catalyst for the production of methacrylic acid {object catalyst) preferably has, in the state of a fresh catalyst hefors use for the production of methacrylic acid, the 18 following composition formula (1

FalMon Cu VaXo Yes {i} wherein F, Mo, Cu and V represent phosphorus, molybdenum, copper and vanadium, respectively: X represents at least one element X selected from the group consisting of potassium, rubidium, cestum and thalliomd Y vepresents at least one element {element V) selected from the group consisting of arsenic, antimony, boron, silver, bismuth, iron, cobalt, ; lanthanum and certum’ O represents oxygens a, b, ©, d, & and { are numbers satisfying O<asd, Gel, 08d, 0gesd and 088, when bis 12) x is a value determined depending on the oxidation states of other elements and, in the case where each of X and Y represents two or move elements, a ratio of the total of two or wore eleraents 18 required to satisfy O<e<d and §«<ik3, when b

[0014]

In particular, from the viewpomt of a yield of methacrylic acid and catalyst Hfe, the atomic ratio of copper to molybdenum (Cu: Mo) is preferably from 0.07 112 £0 0.80 1 12 in the composition of the heteropolyacid compound which constitutes the fresh catalyst, Also, fron the viewpoint of a yield of methacrylic acid and catalyst life, the element X is preferably contained in the heteropolyacid compound which constitutes the fresh

Ih catalyst, and, in such a case, the atomic ratio of the element X to

& molvbdentm (Mo! is preferably from 0.50 12 to 2012, fon15]

The frash catalyst may be those which ave produced by any conventional method, for example, a method comprising the steps of mixing § compounds each contatming the respective element among the elements described above which constitute the heteropolyacid compound {for exaraple, an oxo acid, an oxo acd sall, an oxide, a nitrate, a carbonate, a bicarbonate, a hydroxide, a halide or an ammine complex of each element), molding the mixture into a desired shape, and calcining the molded mixture. 1g Among compounds containing the respective element, examples of a compound containing phosphorus include phosphoric acid, phosphates and the lke examples of a corppound containing molybdenum include molybdie acd, molyhdates such as ammoninm molybdate, molybdenum oxide, molybdenum chlovide and the like! examples of a compound containing copper include copper oxide, copper nitrate, tetraamminecoppeyr dinitrate, copper carbonate, copper hydroxide, copper chloride and the like! examples of a compound containing vanadinm include vanadic acid, vanadates {metavanadates) such as ammonium vanadate Gmmontum metavanadats), vanadium oxide, vanadium chloride and the hke! and examples of a compound containing the element X include oxides such as potassium oxade, rubidium oxide and costum oxide, nitrates such as potassium nitrate, rubidium nitrate, cesium nitrate and thallium nitrate, carbonates such as potassium carbonate, rubidium carbonate and cesium carbonate, hicarbonates such as potassimm hydrogen carbonate and cesium hydrogen 2% carbonate, hydroxides such as potassium hydroxide, rubndium hydroxide and cesium hydroxide, halides such as potassium chloride, rubidium chloride, cesium fluoride, cesium chloride, cesiuwn bromide and cesium iodide; and the hike. Examples of a compound containing the element Y include an oxo acid, an oxo acid salt, an oxide, a nitrate, a carbonate, a hydroxide and a halide. a [001s]

In general, when the fresh catalyst having the above-described preferable catalyst composition 1s used for producing methacrylic acid, the catalytic activity may sometimes decrease due to heat load and the hike.

According to the regeneration method of the present invention, such a used 35% catalyst with decreased catalytic activity is subjected to the regeneration

; treatment in which the atomic ratio of copper to molybdenum {Cut Mo) is adjusted to frora 0.0580 18 to 0.25 1 12 by mixing two kinds of aqueous shuries, and then drying and caleining the mixture, When the Cu Mo ratio in the regenerated catalyst is from 0.05 712 £0 0.25 1 18, it 18 possible to produce the

S methacrylic acid with satisfactory conversion and selsctivity for a long time,

Further, in the regeneration method of the present invention, the atomic ratio of the element X to molybdenum (X ' Mo) in the regenerated catalyst is preferably from 0.5 112 to 27 12 from the viewpoints of catalytic activity and catalyst Life. [ooLT

According to the regeneration method of the present invention, the regenerated catalyst is obtained through steps (1) to {3M

In step {1}, an agueous slurry A is obtained by mixing the used catalyst, a nitrate lon, an ammoniom ion and water, and adjusting the atomic ratio of copper to molybdenum (Cut Mo! in the obtained slurry to from 0.100 18 to 0.501 12, proferably from 0.20 112 40 0.40 1 12. Further, from the viewpoint of effectively restoring the catalytic activity in the regenerated catalyst to be obtained, the atomic ratic of the element X fo molybdenum (X ° Mo} in the aqueous ghurry Als preferably adjusted to from 200 201804118, more preferably from 2.5112 0 3.5012. The conversion and selectivity in the production of methacrylic acid using the resulling regenerated catalyst are improved by mixing the nitrate ion and the

SYMON 100.

[0018] 28 For supplying the nitrate ion, for example, nitric acid and nitrates such as ammonium nitrate may be used as a nifrate ion sources, besides nitrates containing the elements which constitute the object catalyst. For supplying the ammonium ion, for example, ammonia and ammonium salts such as ammonium nitrate, ammonium carbonate, ammonivm hydrogen carbonate and ammonium acetate may be used as an ammonium On Sours, besides ammonium salts containing the elements which constitute the object catalyst. Preferably, nitrates and ammonium salts containing the elements which constitute the obisct catalyst are used as the nitrate ion source and the ammoninm ion source, More preferably, nitric acid, ammeonda and ammonium nitrate are used so as to adjust the ratio of the anymoninm on fo the nitrate ion within the ranges described below. {0019}

In the aqueous slurry A prepared in step (1), as to the ratio of the ammonium ion to the nitrate lon, the amount of the ammonium ion per mole of the nitrate fon is preferably 0.1 to 3.0 moles, more preferably 0.5 to 2.5 moles in view of effectively restoring the catalytic activity in the regenerated catalyst to be obtained. 10020]

When preparing the aqueous sharry A, the atomic ratio of copper to molybdenum (Cu Mo) contained in the aqueous slurry A should be adjusted within the abovespecified range {Cu Mo in aqueous shurry A). Specifically, the atomic ratio may be adjusted by adding at least one of a compound containing capper {(copper-containing compound) and a corapound containing molybdenum (molybdenum containing compound). An amount of such a compound may be determined so as to keep the atomic ratio of copper to molybdenum (Cu: Mo) in the agueous slurey A after the addition of the coppercontaining corapound and/or molybdenum containing compound within the above-specified range, based on a catalyst composition {kinds and amounts of constituent elements) of the used catalyst, The catalyst

SU compositions of the fresh catalyst and the used catalyst may sometimes be different from each other since molybdenum in the catalyst for the production of methacrylic acid scatters or dissipates due to heat load and the

Like caused hy long period of use of the catalyst in the production of methacrylic acid. Therefore, a catalyst composition (kinds and amounts of constituent elersents) of the used catalyst before regeneratinn is preferably analyzed by flunrescend X-ray analysis, inductively coupled plasma (CP) pmission spectrometry or the like. When the Cu @ Mo ratio in the used catalyst before regeneration is within the above-specified range of Cu * Mo ratio in the aqueous slurry A, neither the copper-containing compound nor

A the molybdenumr-containing compound may he added, or the coppercontaining compound andfor the molybdenum containing compound may be added insofar as the Cu! Mo ratio in the agueous slurry Ais kept within the above specified range. 0021]

Ha When preparing the aqueous slurry 4, the atomue ratio of the

E: element X to molybdenum {X © Mo} contained in the aqueous slurry A is proferably adjusted within the sbove-specified range (XX Mo ratio in the agusous slurry A). Specifically, the atomic ratio may he adjusted by adding at least one of a compound containing the element X {element X-containing compound) and a molybdenum containing compound. An amount of such a compound may be determined so as to keep the atomic ratio of the element X to molybdenum X 1 Mo} in the composition after the addition of the element : Xrcontaining compound and/or the molvbdenum-containing compound within the above specified range, based on a catalyst composition of the used 13 catalyst before regeneration, which is detected by the above-described analysis, When the ¥ : Mo ratio in the used catalyst before regeneration is within the abovespecified range of X { Mo ratio in the aqueous slurry A, neither the element X-containing compound nor the molybdenum containing compound may be added, or the element X-containing compound and/or the molybdenum-containing compound may be added insofar as the Cu Me ratio and the X Mo ratio in the aqueous slurry A are kept within the aboverspectied range, fon2z]

As the molybdenunmeoontaining compound and the copper-containing 8% compound to be mixed In the preparation of the agueous slurry A, one or mors compounds may be suitably selected from the compounds containing molybdenum and the compounds containing copper which are usable for the production of fresh catalyst as described above. {0023}

Also, when preparing the aguecus slurry A, a compound containing an element constituting the catalyst other than molybdenum and copper may be added if necessary, based on the composition of the used catalyst.

As the compound containing an element constituting the catalyst other than molybdenum and copper, ons or more compounds may he suitably selected from the compounds containing each element, which are used in the production of fresh catalyst. {oo24l

Detonized water may be usually used as water to be supplied for the preparation of the aqueous slurry A. The amount of water supplied is usually from 1 to 20 parts by weight based on one part by weight of molybdenum in the resulting agusous slurry A, that 1s, the total weight of molvhdenum contained in the used catalyst and molybdenum contained in the molybdenum containing compound supplied. 0025] & When preparing the aqueous slurry A, the mixing order of sach component described above is not particularly mated and may be arbitrarily set. 10026]

When preparing the agueous slurry A, the used catalyst may be 10 mixed as such or may be thermally pretreated.

[0027]

A temperature of the thermal pretreatment of the used catalyst is not particulaely limited and is preferably Hom 380°C $0 800°C. Treatment time for the thermal treatment is not particularly imited and is usually from 0.1 to 24 hours, preferably from 0.5 $0 10 hours, The thermal pretreatment may be carried out in an atmosphere of oxidizing gas such as oxygen-contaluing gas or in an atmosphere of non-oxidizing gas such as nitrogen, [002s] “6 When the used catalyst used in the preparation of the agueous slurry

As a molded catalyst, the nwlded catalyst may be wsed as such or may be previcusly pulverized by a conventional method, if necessary. When the used catalyst used in the preparation of the aqueous slurry A is subjected to both of the pulverization treatment and the thermal pretreatment, the order of these treatments is not particularly Bmited, while the pulverization treatment 1s usually carried out prior to the thermal pretreatment. (0029)

The liquid phase of the aqueous slurry A obtained in step (1) preferably has pH of 8 or less. When pH of the hguid phase of the agueous

Hy slurry A exceeds 8, the catalytic activity may not be satisfactorily restored.

[0030]

In step (2), the aqueous slurry B is obdained by mixing at least the compound containing molybdenum among the compounds containing the constituent elements of the heteropolyaaid compound consisting the objective 33 catalyst with water so that the atomic ratio of copper to molybdenum (Cu

Ma} in the resulting slurry is from 001240 0.25 1 12. feos]

In the preparation of the aqueous slurry B, at least the molyhdenum-containing compound is used as starting compounds of the § heteropolyacid compound, and the coppercontaining compound is used so as to keep the atomic ratio of copper to molybdenum in the compound containing molybdenum (Cn Mo) within the above-specified range {Cut Mo ratio in the aqueous slurry BY. Accordingly, when the atomic ratio of copper to molybdenum (Cn © Mo) is adjusted to 0° 12, there 1s no need to mix the 13 coppercontalning compound,

[0032]

As the molybdenum-containing compound and the copper-containing compound supplied in the preparation of the agquecus slurry B, one or more compounds may be suitably selected from the above-described molybdenum containing compounds and the coppercontaining compounds which can be used in the production of the object catalyst, f00a3]

When preparing the agueocus slurry B, a compound containing an clement constituting the catalyst other than molybdenum and copper may be added, if necessary. As the compound containing an element constituting the catalyst other than molybdenum and copper, one ar more compounds may be suitably selected from the compounds containing each element, which are used in the production of the object catalyst. Among the compounds, a compound containing the element X is preferably added. The atomic ratio of the element X to molybdenum (X Mo) in the aqueous slurry

Bis preferably adjusted fo from 0 18 to 0.5 © 12, more preferably from 0112 to 0.87 1E.

[0034]

Delonized water may be usually used as water to be supplied in the

AG preparation of the aguecus slurry B. The amount of water mixed is gsually from 1 to 20 parts by weight based on one part by weight of molybdenum present in the resulting aqueous sharry B.

[0035]

When preparing the aqueous shurry B, the mixing crder of each 88 component described above is not particularly Bmited and may be arbitrardy i2

[0036]

Inn step (8), the aqueous slurry A obtained in step (1) and the agusous slurry B obtained in step (2) are mixed fo obtain an agusous slurry CA & mixing ratio between the agueous slurry A and the aqueous slurry B is not particularly Hmited and may be adjusted so that the atomic ratio of copper to molybdenum {Cu Mo) in the heteropolyacid compound constituting the finally-obtained regenerated catalyst is from 0.05 0 12 to 0.25 112 by taking wmbo account the amounts of molybdenum and copper contained in the aguecus slurry C0 Specifically, it is possible to attain the Cu Mo ratio of from 0.05 1 12 to 0.25 1 12 in the heteropolyaad compound constituting the finally-obtained regenerated catalyst by, for example, adjusting the mixing ratic of the agueous slurry A and the agueous slurry B fo attain the atomic ratio of copper to molybdenum contained in the aqueous slurey C of from 16 0.05 112 40 0.85 112 and then dyying and caloining the obiained agusous slurry ©. 0037]

The mixing order, the temperature and the stirring conditions are not particularly mited and may be arbitrarily set, when the aqueous slurry (is prepared. 0038]

In the preparation of the aqueous shurry C, when mixing the aqueous slurry A with the aqueous slurry B, or when or after the heat treatment described later in this specification is carried gut, a compound containing an clement constituting the object catalyst and water may be added, if necessary, and the copper-containing compound is preferably added. It is possible to affectively restore the catalytic activity hy mixing the compound containing copper in the preparation of the aqueous sharry €. Ino such a case, the compound containing an element constituting the catalyst in the form of an

HM agueous suspension is preferably added. The miming ratio thereof may be suitably selected so that the heteropolyacid compound constituting the finally ohtained regenerated catalyst has a coraposition which satisfies the ahove described formula (U, and that the atomic ratio of copper to molvhdenum (Cn Mod is from 0.150 12 0 0.25 1 12. Specifically, when the agueous slurry 1s obtained by mixing the aqueous sharry A, the aqueous

1d slurry Band the compound containing copper, for example, it 18 posable to attain the Cu Mo ratio of from 0.05 7 12 to 0.25 1 12 in the heteropolyacid compound constituting the finally-ohtained regenerated catalyst by adjusting the mixing ratio of the aqueous slurry A, the aqueous slurry B and the compound containing copper within the range by which the atomic ratio of copper to molybdenum (Cu ! Mo) contained in the agueous slurry © is kept to from 0.05 112 to 0.25 1 12, and then drving and calcining the obtained aqueous slurry

[0030]

In the preparation of the aguecus slurry ©, the atomic ratio of the glement X to molybdenum (X 1 Mo) is preferably adjusted so that the atomic ratio in the hetervopolyvacid compound constituting the fnallyobtained regenerated catalyst 1s from 0.5 7 18 to 2 1 12 by taking into account the amounts of molvhbdenum and the element X contained in the agueous slurry 16 C0 Specifically, it is possible to attain the Cu! Mo ratio of from 0.05 12 0 (3.25 7 12 and the X Mo ratio of from 0.51 12 to 2 1 12 10 the heteropolyanid compound constituting the fnally-oblained regenerated catalyst by, for example, adjusting the mixing ratio of the aqueous slurry A and the aqueous shrry B se that the atomie ratio (XD Mo) of the element X to molybdenum contained in the aqueous slurry © is within the range of from 0.580 1840 21 12 when the atomic ratio of copper to molybdenum (Cu: Mo) contained in the agusous slurry © 1s kept to from 0.05 112 t0 (0.25 1 12, and then drying and calcining the obiained aqueous slurry C. Here, for the purpose that the Cu:

Mo ratio and the X ' Mo ratio satisfy the above specified ranges, at least one of the compound containing the element X {element X containing compound) and the molybdenum containing compound may be added to the agueous slurry C as required.

[0040]

When newly adding water in the preparation of the aqueous slurry C, deionized water may be usually used as the water to be added.

[0041]

In step (3), the aqueous slurry © is then dried. The dyving method 1s not particularly Bmited, and a method usually employed in this art field, such as evaporation-to-deyness, spray drying, dew drying and flash deving 3% may be employed. The drying conditions are not particularly Bmited and i4 may be suitably selected so as to satisfactorily decrease a water condent in the mixed slurry. For exanaple, the drying teraperature is usually below 300°C. {60421 8 The aqueous slurry Cis preferably subjected to a heat freatment at 100°C or more prior to the drying described above since the heat treatment erniables to stably obtain methacrylic acid at a high yield for a long time, As the heat treatment, for example, the aqueous slurry C is aged by heating at a temperature of 100°C or more in a closed vessel. When such a heat 13 treatment is performed on the agueous slurry C, the catalytic activity is effectively restoved. An upper mit of the heating teraperature in the heat treatment is preferably 200°C or less, move preferably 150°C or less.

Heating time in the heat treatment is usually (1 hour or mors, preferably 2 hours or move, in order to attain a satisfactory effect of restoring the catalytic activity, while it is preferably 20 hours or less from the viewpoint of productivity. When chaining the aqueous slurry € by mixing the agusous slurey A, the agnecus slurry B and the compound containing copper, the heat treatment of the aqueous sharry CO at 100°C or more may be performed, for example, by emploving (A) a method of performing the heat freatoent at 100°C or more on the mixed slurry of the agueous slurry A, the aqueous slurry B and the compound containing copper, (B) a method of performing the heat treatment at 100°C or more on the mixed slurry of the aqueous slurry A and the aqueous slurry B, and then adding the compound containing copper, followed by performing heat treatment at 100°C or more on the resulting mixed slarry, or the hike.

[0043]

The dried product obtained after the drving may be molded into a desived shape such as a ring, a pellet, a sphere or a cylinder before caleination or pre-caleination described later, if necessary. The molding may be carvied out by a method ovdinanly eraploved in this art field, such as tableting or extrusion molding. For molding, water, 2 molding aid or a pore-forming agent may be added to the dried product, if necessary.

Examples of the molding aid include ammonium nitrate as well as ceramic fiber and glass fiber. In particular, ammonium nitrate functions ag a 38 pore-forming agent besides a molding aid iB

[0044]

Preferably, the molded catalyst (hereinafter sometimes referred to as a "dried product” obtained by the above-described molding process is subsequently subjected to terpperature-humidity conditioning. When the § molded catalyst ia subjected to the temperature-humidity conditioning before calemation or pre-caleination, a uniform and more stable catalyst 1s obtained. in particular, the temperature-humidity conditioning is carried out by exposing the molded catalyst to an atmospheres having a temperature of 40°0 to 100°C and a relative humidity of 10% to 80% for about O05 to 10 hours,

The conditioning may be carried cut, for example, in a container having controlled temperature and humidity or by blowing a gas having controlled temperature and humidity to the molded catalyst, An air is usually used as an atmosphere gas when carrying out the conditioning, while an inert gas such as rabrogen may be used.

[0045]

The dried product obtained after drying is preferably treated {prevcaleined) ln an atmosphere of oxidizing gas or nonoxidizing gas at a temperature of about 180°C to 300°C prior to the calcination described below.

[0046]

In step (8), the dried product obtained after drying is subsequently calcined. The calcination can be carried out by a method usually used in this art field and the method is not particularly hmited., For example, i may be carried out in an atmospheres of oxidizing gas such as oxygen or in an atmosphere of non-oxidizing gas such as nitrogen. A caloination temperature is usually 300°C or more. In order to satisfactorily restores the catalyst Hie, the caleination is carried out preferably by a wuulti-step process 1 an atmosphere of oxidizing gas or non-exidizing gas, move preferably by a tworstep process comprising the Brst caloination step which is earned oud in an atmosphere of oxidizing gas and the second calcination step which is 80 carried out in an atmosphere of nonroxidizing gas.

[0047]

The oxidizing gas used nn the calcination process contains an oxidizing material, and examples of such a gas include oxygen-containing gas, When the oxygenrcontaining gas is used, the conceniration of oxygen in the oxygen-containing gas 1s usually from about 1 to 30% by volume. As a source of oxygen, an aly or pure oxygen may be usually used, and it may be diluted with an inert gas, if necessary. The oxidizing gas may optionally contain water. Howsver, the concentration of water in the oxidizing gas is usually 10% by volume or less. The oxidizing gas is preferably an air § Usually, the caleination in the atmosphere of oxidizing gas is carried out in the stream of the above-described oxidizing gas. A temperature in the calcination carried out in the atmosphere of the oxidizing gas is usually from 360°C to 410°C, preferably from 880°C to 400°C, {00481

The nowoxidizing gas used in the caloination contains substantially no oxidizing material such as oxygen. Specific examples of the nonroxidizing gas include an inert gas such as nitrogen, carbon dioxide, heliven and argon. The noncoxidizing gas may optionally contain water,

However, the concentration of water in the non-oxidizing gas is usually 10% 18 by volume or less. In particular, nitrogen gas is preferably used as the nonoxidizing gas, Usually, the caleination in the atmosphere of nonoxidizing gas is carvied out in the stream of the above-described nowoxidizing gas, A temperature in the calcination carried out in the atmosphere of the nonoxidizing gas is usually from 420°C to 500°C, preferably from 420°C to 450°C.

[0049]

In the method for regenerating a catalyst for the production of methacrylic acid of the present invention, at least ons of the aqueous shury A and the agueous slurry © is preferably subjected to & wet pulverization treatment from the viewpoint of effectively restoring catalytic activity and catalyst Life. fo0s0]

The wet pulverization treatment is a treatment which is performed for pulverizing a solid content in the slurry and is usually performed by

SU using a wet pulverization treatment apparatus. Examples of the wet pulverization treatment apparatus include a ball mill, an oscillating ball mil, a rod mill, a medium stirring type mill, an oscillation rod mill and a jet mill

In the wet pulverization treatment, the pulverization is preferably performed so as to attain a particle diameter of 5.0 pu or less, mors 3% preferably 2.0 um or less. The particle diameter in the present invention

Means an average pariicle diameter of a solid content in an aguecus slurry, and can be obtained, for example, by measuring a volume basis median diameter with a laser diffvaction/scatiering type particle size distribution measurement apparatus, :

A solid content concentration in the aqueous slurry before the wet pulverization treatment is preferably 20 to 80 wi.% fom the viewpoint of attaining high pulverizing efficiency. In order to satisfy the concentration range, the slurry may be concentrated or diluted, while concentrating conditions and diluting conditions are not particularly Hmited. 10052]

The wet pulverization treatment is performed during preparation of at least one of the agueous slurry & and the aqueous sharry ©. From the viewpoint of a degree of restoration of catalyst life among others, only the agueous shurey A or both of the aqueous slurry A and the aqueous slurry € ave preferably subjected to the wet pulverization treatment. In order to subject only the aqueous slurry A to the wet pulverization treatment, br example, in steps (1) to (3), the aqueous shurry A after the wet pulverization treatment and the aqueous slurry B are mixed to obiain the aqueous slurry 2 Cand then the aqueous starry © 1s dried and calcined. In order to subject the agueous slurry A and the aqueous slurry to the wet pulverization treatment, for example, in steps (1 to (3), the aqueous slurry A after the wet pulverization treatment and the agueous slurry B are mixed to obtain a mixed slurry: the wet pulverization treatment is performed on the mixed “8 slurry to obtain the aqueous shurry (0 and the obtained agueocus slurry is subjected fo drying and calcination.

[0055]

When performing the heat treatment at 100°C or more on the aqueous slurry ©, the wet pulverization treatment may be performed before the heat treatment or may be performed after the heat treatment. The wet pulverization freatment is preferably performed after the heat treatment.

[0084]

It is possible to obtain the regenerated catalyst having satisfactory catalytic activity and catalyst life as described above. The regenerated 38 catalyst comprises a heteropolyacid compound, like the object catalyst, and nay comprise a free hetevopolvacid or the salt of a heteropolyaoid., Among these, a catalys! comprising an acidic salt of a heteropolyacid is preferable, ard a catalyst comprising an acidic salt of a Kegan type hetevopolyacid is more preferable. In the heteropolyacid compound constituting the regenerated catalyst, the atomic ratio of copper to molybdenum {Cu Mo) is from $0.08 1 12 to 0.256 1 12, and the Cu { Mo ratio is preferably from 0.1512 to 0.25 112, Also, the heteropolyacid compound constituting the regenerated catalyst preferably has the composition which satisfies the formula (1, and the atomic ratio of the element X to molvhdenum X Mal is preferably from 0.5 118 to 2 0 18,

[0055]

In general, the method for regenerating a catalyst for the production of methacrylic acid of the present invention applies fo a used catalyst which has been used in the production of methacryvhic acid. Further, the regeneration method of the present invention may be applied to, for example, a catalyst which has not been used in the production of methacrylic acid, such as loss powder produced during the production of a fresh catalyst, or a catalyst which does not have desired properties. Excellent effects which are attained in the regeneration of used catalyst are also attained in these cases, [oon]

The process for preparing methacyhe acld according to the presend invention comprises subjecting a compound selected from the group consisting of methacrolein, isobutyl aldehyde, isobutane and sobutyric acid (hereinafter sometimes referred to as a "raw material for methacrylic acid” to a gas phase catalytic oxadation reaction in the presence of a catalyst for the production of methacrylic acid which is regenerated by the regeneration method of the present invention. With the use of the regenerated catalyst of the present vention as described above, it is possible to produce methacrylic acid while maintaining high conversion and high selectivity fora 3G long time, fnoaT]

Methacrylic acid 1s usually prepared by charging the catalyst for the production of methacrylic acid in a fxed-bed multitubular reactor, and supplying a starting gas mixture containing oxygen and the raw material for 88 methacrylic acid to the reactor, although a reaction system such as a

Huidized bed or a moving bed may also be used. As an oxygen source, an air or pure oxygen is usually used. Besides oxygen and the raw material for methacrylic acid, the starting gas mixture may contain nitrogen, carbon dioxide, carbon monoxide, water vapor and the like. fooas]

The raw material for methacrylic acid, which is contained in the starting gas mixture, does not necessarily have to be a purified material of high purity. For example, as methacrolein, a methacrolein-containing reaction product gas obtained by a gas phase catalytic oxidization reaction of isobutylene or tert-butyl alcohol may be used without purifying the reaction product gas to high purity methacrolein, The starting gas mixture may contain one raw material for methacrylic seid or two or mors raw materials for methacrylic acid. [oosg]

The reaction conditions of the method for preparing methacrvie acid may arbitrarily selected depending on the kind of the raw material for methacrylic acid contained in the starting gas mixture, ete. For example, when methacrolein 1s used as the raw material for methacrylic and, the reaction is carried out usually under conditions such that a concentration of £0 methacrelsin in the starting gas mixture 18 1 to 10% by volume, the concentration of water vapor is 1 to 308% by volume, a molar ratio of oxygen to methacrolein is 1 to B, a space velocity is B00 to 8000 hb (based on the normal state), a reaction temperature is 250°C to 850°C, and a reaction pressure 1s 8.1 to 0.8 MPa. When ischutane is used as a raw material for methacrylic acid, the reaction is carried out usually under conditions such that a concentration of ischutane in the starting gas mixture 18 1 to 85% by volume, a water vapor concentration ig 3 to 30% by volume, a molar ratio of oxygen to isobutane 1s 0.08 to 4, a space velocity ig 400 to 5000 h1 {based on the normal stage), a reaction temperature is 280°C to 400°C, and a reaction 3 pressure is 0.1 to 1 MPa. When wsobutyl aldehyde or tsobutyrie acid is used as a raw material for methacrvhic acid, substantially the same reaction conditions as those employed when methacrolein is used as the raw material are adopted, The space velocity may he determined by dividing an amount of the starting gas mixture passing through the reactor per one hour (7A) by 45 a catalyst volume (1) in the reactor.

Hixamples 10060]

Hereinafter, the present invention is explained in move detail in comjunction with examples, which do not limit the scope of the present invention in any way.

An air used in the examples contains 3.5% by volume of water {corresponding to water content of atmosphere}, and nitrogen used in the sxamples is substantially free of water. 0 10081

The catalyst composition analysis and catalyst property evaluation of the catalysts obtained in the following examples were performed as follows.

HER

Catalyst Composition {ratio of elements constituting catalyst)

A catalyst composition was determined by analyzing a catalyst by fuorsscent X-ray analysis using a fluorescent Xray analyzer, Z8X Primus II manufactured by Rigaku Corporation.

[0063]

Particle Diameter

An average particle diameter {a volume basis median diameter! of a solid content in a slurry was measured by using a laser diffraction/scattering type particle size distribution measurement apparatus, LA-820 manufactured by Horiba, Led, Water was used as a dispersion medium, and the measurement was performed at a relative refractive index of 1.80 (value relative to water)

[0064]

Activity Test of Catalyst

Nine grams (9 g} of a catalyst was charged into a glass micro-veactor having an mney diameter of 18 mw, and a furnace temperature {temperature of furnace for heating micro-resctor) was raised to 385°C,

Subsequently, a starting gas mixture composed of 4% by volume of methacrolein, 12% by volume of molecular oxygen, 17% by volume of water vapor and 87% by volume of nitrogen, prepared by mixing methacrolein, air, steam and nitrogen, was fod to the reactor at a space velocity of 870 bh, and 28 a reaction was carried out for one hour to artificially deteriorate the catalyst,

Then, after lowering the furnace temperature to 280°C, the starting gas mixture having the same composition as above was fed to the microreactor at the same space velocity as above, and the reaction was started. After carrying out the reaction for one hour from the start of the reaction at the

H furnace temperature of 280°C, an exit gas {gas after reaction) was sampled and analyzed by gas chromatography, and conversion of methacrolein (36), selectivity of methacrylic acid 86) and a yield of methacrylic acid (3%) were calenlated by the following equations.

Conversion (36) = [moles of methacrolein reacted (noles of methacrolein fed] x 100

Selectivity (36) = [{moles of methacrylic acid generatedifimoles of methacrolein reacted x 100

Yield (8) = conversion (36) x selectivity (363/100 10068] 1% Reference Example i

Preparation of Fresh Catalyst

In 824 kg of ion-exchange water heated to 40°C, 38.2 kg of cosium nitrate {CsNOgl, 27.4 kg of 78 wi% orthovhosphorie acid and 25.2 ke of 70 wi. 9% nitric acd were dissolved to prepare Liquid a. Separately, 287 ke of ammonium molybdate tetrahydeate INH eMorOo04H20] was dissolved in 330 kg of tovrexchangs water heated to 40°C, followed by suspending 8.18 kg of ammonium metavanadate INFO! therein to prepare Liquid §.

[0088]

After Liguid o was dropwise added to Liquid § while stirring and maintaining the temperature of Liguids « and § to 40°C, the mixture was further stirred at 120°C for 5.8 hours in a closed vessel, and then a suspension of 10.2 kg of antimony trioxide [Bhs and 10.2 kg of copper nitrate trihydrate [CulNOge HO in 28 ke of ion-exchange water was added thereto, Thereafter the mixture was stirred at 120°C for 5 hours in the closed vessel. Of the resulting slurry, a particle dlametey of a solid content was 1.0 om. The resulting slurry was dried with a spray dever. To 100 parts by weight of the resulting dried powder, 4 parts by weight of ceramic fibers, 18 parts by weight of aramonium nitrate and 9.7 parts by weight of ion-exchange water were added, and the resulting maxture was 3& kneaded and extrusion molded into cylinders each having a diameter of 5

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Preparation of Aqueous Slurry A2

Agueous slurry Al was diluted by adding ion exchange water to the whole quantity thereof to obtain 850 g of a slurry {solid content 18 concentration! 28 wi.%). The obtained slurry was poured into an alumina container together with 1870 g of alumina balls each having a diameter of 158 mi, a pulverization was carried out by continuously rotating the container with the use of a rotational ball mill at a speed of 58 rpm for 16 hours, and

Aqueous Sharey AZ was obtained. Of Aqueous Slurry A2, a particle diameter of a solid content was 1.8 pm, a molar ratio of the ammonium ion to the nitrate ion was 1.9, and a Hguwid phase had pH of 6.4. The atomic ratios of the metal elements, Le, phosphorus, molybdenum, vanadium, antimony, copper and cesium, contained in Aguecus Slurry AZ were 1.5, 18, 0.50, (1.5, 0.29 and 3.2, respectively, the atomic ratio of copper to molybdenum was 0.2818, and the atomic ratio of cesium fo melybdenum was 3.20 12.

[0071]

Step (2)! Preparation of Aqueous Shurey Bi

In 105 g of tonexchange water heated to 40°C, 1898 g of 75 wi.% orthophosphorie acid and 12.3 g of 67.5 wt.% nitric acid were dissolved to 3 prepare Laguid a. Separately, in 1688 g of ion-exchange water heated to 40°C, 13% g of ammonium molybdate tetrahydrate was dissolved, and then 3.85 g of arnmonium metavanadate was suspended therein to prepare Liquid b. To

Tdguid a, Liquid b was dropwise added while stirring to obtain Aqueous

Slarry Bl containing a heteropolyvacid compound, The atomic ratios of the metal elements, Le. phosphorus, molybdenum and vanadium, contained in

Aguecus slurry Bl were 1.5, 12 and 0.50, respectively, while the ratios of antimony, copper and cesium were all zero (0), and thus the atomic ratio of copper to molybdenum and the atomic ratio of cesium to molybdenum were both 0112, {oo7al

Step (3) Preparation of Aqueous Slurry C3 478 ¢ of Aqueous Slurry AZ was taken out and mixed with the whole guantily of Aguecus Slurry Bl, and then the mixture was stirred in a closed vessel at 120°C for 8 hours. Then, a suspension of 4.80 g of antimony trioxide and 1.539 g of copper nitrate trihydrate in 3.67 g of ton-exchange water was added to the mixture, and the mixture was further stirred in the closed vessel at 120°C for 5 hours fo obtain Agueous Slurry C1. Of Aguecus

Shurey C1, a particle diameter of a solid content was 1.4 um. The atomic ratios of the metal slements, Le. phosphorus, molybdenum, vanadium, 1& antimony, copper and cesimm, contained in Aqueous Slurry C1 were 1.5, 18, 0.50, 0.5, 0.19 and 1.4, respectively, the atomic ratio of copper to molybdenum was (4.18 7 18, and the atomic ratio of cesium to molybdenum was 1.4 012.

[0073]

Drying and Calcination of Aqueous Slurry C1

The thus-obtained Aqueous Slurry OF was dried at 135°C. Tu 100 paris by weight of the dried product obtained, 2 parts by weight of ceramic fiber, 13 parts hy wolght of aramonium nitrate and 7 parts by weight of winrexchange water wore added, and the mixture was kneaded and extruded 88 indo cylinders each having a diameter of 5 um and a height of 6 mem. The resuliing molded catalyst was dried at a temperature of 30°C and a relative humidity of 30% for 3 hours. After the deying, the catalyst was calcined by maintaining i in an air stream at 20°C for 28 hours, then at 250°C for one hour, then mn an air stream at 390°C for 4 hours and further in a nitrogen aly sfream at 435°C for 4 hours, and finally the molded catalyst was recovered to obtain Regenevated Catalyst {R1). The atomic ratios of metal elements, i.e. phosphorus, molybdenum, vanadium, antimony, copper and cesium, contained in Regenerated Catalyst (RI) were 1.5, 12, 0.50, 0.5, 0.19 and 1.4, respectively, the atonde ratio of copper to molybdenum was 0.18 112, and the 3& atomic ratio of cesium to molybdenum was 1.4112. The results of activity test of Regenerated Catalyst (R1) are shown in Table L

[0074]

Steps (1) and (2): Preparation of Aqueous Slurries AZ and B1

Agueous Slurries AZ and Bl were obfained in the same manner as in

Example 1

[0078]

Step (3) Preparation of Aqueous Shurry O32 475 g of Aqueous Slurry AZ was taken ont and mixed with the whole quantity of Aqueous Slurry Bl, and then the mixture was stirred in a closed vessel at 120°C for 8 howrs, Then, a suspension of 4.80 ¢ of antimony trioxide and 3.18 g of copper nitrate tnthydrate in 7.84 g of ion-exchange water was added to the mixture, and the mixtures was further stivred in the closed vessel at 120°C for b hours to obtain Aqueous Slurry OF. Of Aqueous

Slurry CF, a particle diameter of a solid content was 1.4 ym. The atomic ratios of the metal elements, Lo, phosphorus, molybdenum, vanadinm, antimony, copper and cesium, contained in Aqueous Shury C2 were 1.5, 12, (L8G, 0.5, 0.24 and 1.4, respectively, the atomic ratio of copper to molybdenum was 0.24 1 12, and the atomic ratio of cesivm to molybdenum was 1.4012 {novel

Dyying and Caleination of Aqueous Slurry OF

Aqueous Slurry C2 was dried and caloined in the same manner as in

Drying and Caloination of Aquesus Slurry C1 of Example 1 to obtain 28 Hegenerated Catalyst (RZ). The atomic ratios of metal elements, Le, phosphorus, molybdenum, vanadium, antimony, copper and cesium, contained in Regonerated Catalyst (R2) were 1.5, 18, 0.50, 0.5, 0.24 and 1.4, respectively, the atomic ratio of copper to molybdenum was $.24 112, and the atomic ratio of cesium to molybdenum was 1.4 1 12. The rasulls of activity

ME test of Regenerated Catalyst (RZ) are shown in Table 1.

[0077]

Example 8

Steps {1} and (2): Preparation of Aguecus Slurries A2 and Bl

Aqueous Slurries A2 and Bl were obtained in the same manner as in a Example 1.

[0078]

Steps (3): Preparation of Aqueous Sharry (8 475 g of Agusous Slurry AZ was taken out and mixed with the whole quantity of Aguecus Slurry Bl, and then the mixture was stirred in a closed & vessel at 120°C for & hows. Then, a suspension of 4.80 g¢ of antimony trioxide and 0.80 g of copper nitrate trihydrate in 1.83 g of lon-exchange water was added to the mixture, and the mixture was firther stirred in the closed vessel at 120°C for 5 hours to obtain Aqueons Slurry C8. Of Aqueous

Shurry (3, a particle diameter of a solid content was 1.4 um. The atomic ratios of the metal slements, Le, phosphorus, molybdenum, vanadium, antimony, copper and cesium, contained in Agueous Slurry U8 were 1.5, 12, (L840, 0.8, 0.18 and 1.4, respectively, the atomic ratio of copper to molybdenum was 0.18 112, and the atomic ratio of cesium to molybdenum was 1.4 18, {0079

Drying and Calcination of Agueous Slurry C3

Agueous Slurry C8 was dried and calcined in the same manner asin

Drying and Caleination of Aguecus Slurry C1 of Example 1 to oblain

Regenerated Catalyst (R3). The atomic ratios of metal elements, Le. phosphorus, molybdenum, vanadium, antimony, copper and cesium, contained in Regenerated Catalyst (R38) were 1.5, 12, 0.50, 0.5, 0.18 and 1.4, respectively, the atomic ratio of copper to molybdenum was 0.16 1 12, and the atomic ratio of cesium to molybdenum was 1.41 12. The resulis of activity test of Regenerated Catalyst (R3) are shown in Table 1. a5 0080]

Example 4

Steps (1) and (2) Preparation of Aqueous Slurries Al and B1

Agusous Slurries A1 and BI were obtained in the same manner as in

Fxample 1 {o081]

Step (3) Preparation of Aqueous Slurry C4

Aguecus Slurry Al was diluted by adding ion-exchange water fo the whole quantity thereof to obtain 850 g of a slurry (solid content concentration: 28 wi). 475 g of the obtained slurry was taken out and mixed with the whole guantity of Aqueous Slurry BL, and then the mixture was stirred in a closed vessel at 120°C for § hours. Then, a suspension of 4.80 g of antimony trioxide and 1.68 g of copper nitrate trihydrate in 3.87 g of ioncexchange water was added to the mixture, and the mixture was further stirred in the closed vessel at 120°C for 8 hours to obtain Aqueous Slurey C4. 8 Of Aqueous Slurry C4, a particle diameter of a solid content was 11.4 pm.

The atomic ratios of the metal elements, Le. phosphorus, molybdenum, vanadium, antimony, copper and cesium, contained in Aqueous Slurry C4 were 1.5, 14, (80, 0.8, 0.19 and 1.4, respectively, the atomic ratio of copper to molybdenum was 0.181 12, and the atomic ratio of cesium to molybdenum was 1.4312 fonss]

Drying and Caleination of Aqueous Slurey C4

Aguesous Slurry (4 was dried and calcined in the same manner asin

Drying and Calcination of Aqueous Shurry C1 of Example 1 to obtain Regenerated Catalyst (R€). The atomic ratios of metal elements, Le. phosphorus, molvbdenum, vanadium, antimony, copper and cesium, contained in Regenerated Catalyst (Bd) were 1.5, 12, 0.50, 0.5, 0.19 and 1.4, respectively, the atomic ratio of copper to molybdenum was 0.19 112, and the atomic ratio of cesium to molybdenum was 1.4 1 12. The resulis of activity test of Regenerated Catalyst (R4) are shown in Table L {0088}

Example &

Steps (1) and (2) Preparation of Aqueous Shurries AS and Bl

Aqueous Slurries AZ and Bl were obtained in the same manner as in

Example L foosd]

Step (3) Preparation of Aqueous Slurry OF 478 g of Aqueous Slurry AZ was taken out and mixed with the whale quantity of Aqueons Slurry Bl, and then, a suspension of 4.80 ¢ of antimony

AG tooxide and 1.5% g of copper nitrate trihydrate in 3.67 g of lon-exchange water was added to the mixture, Then, the mixture was stirred in a closed vessel at 120°C for 5 hours to obtain Aqueous Slurry CB. Of Aqueous Slurry (0B, a particle diameter of a solid content was 1.23 um. The atomic ratios of the metal elements, Lo. phosphorus, molybdenum, vanadivm, antimony, 35% copper and cesium, contained in Agueous Shuey C3 were 1.5, 12, 0.50, 0.5,

(0.189 and 1.4, regpectively, the atomic ratio of copper to molybdenum was (L181 18, and the atomic vatio of cesium to molybdenum was 1.4 112, fossa]

Drying and Calcination of Aqueous Slurry C8

B Aqueous Slurry OF was dried and calaned in the same manner as in

Drying and Calctnation of Agueous Slurry C1 of Example 1 to obtain

Regenerated Catalyst (B58). The atomic ratios of metal elements, Le. phosphorus, molybdenum, vanadium, antimony, copper and cesium, contained in Regenerated Catalyst (RE) were 1.5, 12, (50, 0.5, (1.19 and 1.4, respectively, the atomic ratio of copper to molybdenum was 0.18 1 12, and the atomic ratio of cesium to molybdenum was 1.47 12. The results of activity test of Regenerated Catalyst (RS) ave shown in Table 1. [60s]

Comparative Example 1 18 Steps {1 and (2) Preparation of Aqueous Shurries AZ and Bl

Aqueous Slurries AZ and B1 were obtained in the same manner as in

Example 1.

[0087]

Step (3) Preparation of Aqueous Slurry 08 475 g of Aqueous Slurry AZ was taken out and mixed with the whole guantity of Aqueous Slurry Bl, and then the mixture was stirred at 120°C for § hours in a closed vessel. Then, a suspension of 4.80 g of autirwony trioxide and 4.97 g of copper nitvate trihydrate in 11.0 ¢ of ion-exchange water was added to the mixture, and the mixture was stirred in the closed 28 vessel at 120°C for 5 hours to obtain Aguecus Slurry 08, Of Agusous Slurry

C8, a particle diameter of a solid content was 1.8 um. The atomic ratios of the metal elements, Le. phosphorus, molybdenum, vanadium, antivsony, copper and cesitom, contained in Aqueous Slurry ©8 were 1.5, 12, 0.50, Q.5, (1.289 and 1.4, respectively, the atomic ratio of copper to molybdenum was

S00 0.48 112) and the atomic ratio of cesium to molybdenum was 1.41 12,

[6088]

Drying and Caleination of Aqueous Shary O68

Aqueous Slurry CF was dried and calcined in the same manner as in

Drying and Calcination of Aqueous Sharry C1 of Example 1 io obtain 3% Regenerated Catalyst {(R6). The atomic ratios of metal elements, 1a.

phosphorus, molybdenum, vanadium, antimony, copper and cesium, contained in Regenerated Catalyst (B68) were LE, 12, 0.50, 0.5, 0.99 and 1.4, raspectively, the atomic ratio of copper to molybdenum was 0.28 © 19, and the atomic ratio of cesium to molybdenum was 1.4 1 12. The results of activity test of Regenerated Catalyst (B6) are shown in Table 1. {0n80]

TABLE 1

EE rn aqueous slurry {Cu : Mo ratio Activity test result {atomic ratio) | imeatalyst

AausousAqueous {atomic ratio} Conversion Selectivity, Yield slurry Alsharry Bi {9%} {(%6) 1 (%)

Ref Bx 1 | ~~ [= 08003 80 8x 4

[0680]

Ag shown in Table 1, it is found that cach of the catalysts obtained in

Examples 1 to 5 enables to obtain methacrviic acid at a high vield after the artificial deterioration and to produce methacrylic acid at a satisfactory vield for & long time as compared to the catalyst obtained in Comparative

Example 1.

Claims (7)

1. A method for regenerating a catalyst for the production of methacrylic acid comprising a heteropolyvacid compound containing 4 phosphorus, molybdenum and copper, wherein the method comprises the following steps (1) to (3), and wherein the atomic ratio of copper to molybdenum (Cu! Mo) in the heteropolyacid compound constituting a regenerated catalyst is from 0.08 1 12 to 0.850 12, step (1) mixing a used catalyst used for the production of methacrylic acid, a nitrate ion, an ammonium ion and water to form an aqueous slurry A in which the atomic ratio of copper to molybdenum (Cu: Ro! has been adjusted to from 0.101 12 to 0.50 © 13, step (2) mixing at least a compound containing molybdenum among corapounds containing constituent elements of the heteropolyacid compound with water to form an aqueous shyry B in which the atomie ratio of copper to molybdenum (Cu Mo) has been adjusted to from 00 12 t0 0.250 18, and step (3) mixing the agueous slurry A obtained in step {1) with the aqueous shurey B obtained in step (2) to form an agueous slurry ©, and then drying and calcining the aqueous slurry C.

2. The method according fo claim 1, wherein the heteropolyacid compound further contains at least one element X selected from the group consisting of potassium, rubidium, cesium and thallium, Bi the atomic ratio of the element X io molybdenum (X : Mo} in the heteropolyacid compound constituting the regenerated catalyst is from 0.5 12602112, the atomic ratio of the element X fo molybdenum (X : Mo) contained in the agueous shirry A in step {1 is from 2: 1% to 4: 12, and S40 the atomic ratio of the element X to molybdenum (X : Mo) contained in the agueous slurry B in step (3) is from 0:12 60 0.5 © 19

3. The method according to claim 1, wherein the agusous slurry C obtained in step (3) is a slurry obtained by mixing the agueouns slurry A obtained in step (1), the aqueous slurry B

’ n . fg . _ a =e. . ohtained in step (2) and a compound containing copper. 4, The method according to claim 3, wherein the agueous slurry 4, the aqueous shury B and the compound containing copper ars mixed so that the atomic ratio of copper to molybdenum (Cu Meo) contained in the agusous slurry © is within the range 2m im > 5 * § of from 0.05 12 t0 0.25 1 12.

5. The method according to any one of claims 1 io 4, wherein at least one of the aqueous slurry A obtained in step (1) and the auecus slurry © obtained in step (3) is a shurry subjected fo a wet pulvertzation treatment.

6. The method according to any one of claims 1 40 4, wherein the agueous slurry © ohtained in step (3) is a slavery subjected to a i . . - SEY haat treatment at 100°C or more. ~~ FEY " : z on CEN

7. The method according to any one of claims 1 to 4, wherein . . - , - - v a Eg a the aqueous slurry A obtained in step (1) contains €.1 fo 5.0 moles of CTR * - - 8 . 3 . 5 the ammonium ion per ons mole of the nitrate ion. pe oF SS - ets } oN ry on ye oy ~ oo ~¥ A bn on trond Tan eno PEE so aR ed $ EY, CO HI enn edo RA. - SND ar ea Yen or YE A ex? en a Fhe Retaramo emer corm mmTr ire, Sree @erm dad HO Vara oi any and at tan ob LAE DETOTGHGGACIA COmMPpHiid INTHE CONUALAN Vail ang av least ANG AloMant eo leotar Fert FRG oro crime ete ab Tea tTivey mae enter ewe UNE SEN SERCTaQ TIN TRE groUn CONSISTING OF asm, auiiinomy, noaron, CT NraT tania tb Tran oven Frey TE Tei and ren FRAN AY SY 30 OY even ar T STIVEY, DINIMULHD, Iron, SONAL, aniaanum ana garum, HEY ¥ Ey A & 3 +3 or Ve Sel PIE TITIES CET a Oo i : oe ro oeTera fing on ent lua fhe Fhe teed siete of wet mere iie acid he the TEHTLETAWNHE of CAA SL AY $8 DIGEUNLETIGNR OG MI LAQUIYAN ald BY LA BY CETTE © errr a Ted ao Fama ed Sear FR arrear 1 mT Seat Qt adie od 3 SAHNTCWNE @ CLINETOURG SRISGLEN INNIN wie gYOUE GOASIsNgE oF a2 methacrolein, isobutylaldehyds, isobutane and iscbutyric acid to a gas phase catalytic oxidation reaction in the presence of the regenerated catalyst.