Abstract: In the reaction of catalytic gas phase oxidation by means of a shell-and-tube type reactor adapted to circulate a heating medium to the shell of the reactor through the medium of a circulation device connecting an annular conduit connected thereto, a method for the catalytic gas phase oxidation characterized by subjecting a part of the heating medium extracted from the shell of the reactor to heat exchange, introducing the heating medium resulting from the heat exchange into the proximity of a heating medium circulation inlet on the inlet side of the circulation device or the annular conduit on the outlet side of the reactor. The flow rate of the heating medium after the heat exchange is preferred to be in the range of 2-40 vol. % based on the flow rate of the heating medium within the shell of the reactor and the temperature difference of the heating medium at the inlet and the outlet to be in the range of 15-150° C.

Abstract: This invention is related to a shell-and-tube type reactor provided with reaction tubes packed with a catalyst and adapted to circulate a heat medium to the fluid outside the tubes and is characterized by a method introducing a gas into the catalyst beds so as to retain the relative humidity of the catalyst in the range of more than 40% while elevating the temperature of the reactor thereby starting up the reactor. This method prevents the catalyst from degradation of activity due to absorption of moisture, exalts the service life of the catalyst, and permits stable production of methacrylic acid.

Abstract: A catalyst which is a complex oxide catalyst represented by the following general formula (1):

Abstract: The present invention provides a process for producing acrylic acid, by which process the problem, such that the catalyst placed on the gas inlet side deteriorates faster than that placed on the gas outlet side, is solved, so that the catalyst can be used stably for a long time.

Abstract: A catalyst useful for the gas phase oxidation of alkanes to unsaturated aldehydes or carboxylic acids is disclosed. Processes for preparing the catalyst and using the catalyst to convert alkanes to unsaturated aldehydes or carboxylic acids are also disclosed.

Abstract: A mixed metal oxide catalytic system comprises a catalyst having the formula

Abstract: The application of an electric current to catalysts useful for the vapor phase oxidation of hydrocarbons allows for processes for obtaining enhanced catalytic processing of a given feed material with a given catalyst, processes allowing the ready change-over from one product of a given feed stream to another product of that feed stream without the need to change catalyst, and processes allowing the ready change over from one feed stream to another feed stream with the concomitant change over from one product to another product without the need to change catalyst.

Abstract: A process for producing acrylic acid through vapor-phase catalytic oxidation of acrolein or acrolein-containing gas with molecular oxygen or a molecular oxygen-containing gas using a catalyst-filled fixed bed shell-and-tube reactor is provided, which is characterized in that plural catalysts of different activity levels which are prepared by changing the kind and/or amount of alkaline metal(s) therein are filled in the reaction tubes in such an arrangement that the activity levels rise from the gas-inlet side toward the gas-outlet side of said tubes. According to this process, not only yield and productivity of acrylic acid are improved but also excessive heat, accumulation in the catalyst layer can be inhibited and catalysts degradation under heat is prevented, resulting in prolongation of catalyst life.

Abstract: The invention relates to a method for the synthesis of aliphatic carboxylic acids by the catalytic oxidation of aldehydes with oxygen, or oxygen-containing gas mixtures. Metals of groups 5 11 of the periodic table of elements, or the compounds thereof are used as catalyst, in amounts of up to 5 ppm, based upon the amount of aldehyde used.

Abstract: In the production of acrolein and acrylic acid by the catalytic gas phase oxidation of propylene with a molecular oxygen-containing gas, a method is provided which enables acrolein and acrylic acid to be stably produced with a high yield for a long time from propylene by effectively repressing such secondary reactions as are responsible for the formation of organic acids, high boiling compounds, and tarry compounds, the deposition of carbonized materials, and the deterioration of the quality of products. The content of unsaturated hydrocarbons (excluding propylene) of 2-5 carbon atoms in the raw material for propylene is kept below 500 ppm (by weight). Particularly, it is proper to use a raw material for propylene which has a content of unsaturated hydrocarbons (excluding propylene) of 2-5 carbon atoms of not more than 200 ppm (by weight) and a total content of diene and acetylenic compounds of 2-5 carbon atoms of not more than 200 ppm (by weight).

Abstract: A catalyst which is a complex oxide catalyst represented by the following general formula (1): MoaVbWcCudAeBfCgDhEiOx  (1) (in which Mo is molybdenum; V is vanadium, W is tungsten, Cu is copper, A is at least an element selected from antimony, niobium and tin; B is at least an element selected from alkaline earth metals; C is at least an element selected from silicon, aluminum, titanium and zirconium; D is at least an element selected from phosphorus, tellurium, cerium, lead, arsenic and zinc; E is at least an element selected from Group IA and Group IIIb elements of the periodic table, boron, iron, bismuth, cobalt, nickel and manganese; and O is oxygen; a, b, c, d, e, f, g, h, i and x denote the atomic ratios of Mo, V, W, Cu, A, B, C, D, E and O, respectively; and where a=12, 2≦b≦15, 0≦c≦10, 0<d≦6, 0≦e≦6, 0<f≦10, 0<g≦10, 0≦h≦5, 0≦i≦5, and x is a numerical value determined by the extents of oxidation of the other elements) which is character

Abstract: In a method for synthesizing methacrylic acid by using a fixed bed tube type reactor provided with a catalyst bed into which a solid oxidation catalyst is filled and with a heat medium bath and by flowing a raw material gas containing methacrolein and oxygen through the catalyst bed, the catalyst bed does not have any sections in which a temperature difference between the heat medium bath and the catalyst bed (&Dgr;T) exceeds 35° C., and two or more high temperature zones in which each &Dgr;T is 15 to 35° C. are provided. According to this method, mathacrylic acid can be manufactured in higher yields.

Abstract: The present invention provides a process for preparing a catalyst and the same for use in production of methacrylic acid, which is characterized by molding a raw material including a powder containing phosphorus and molybdenum at the specific pressure. The invention also provides a process for preparing methacrylic acid by gas phase oxidation and/or oxidative dehydrogenation of at least one compound selected from the group consisting of methacrolein, isobutyraldehyde and isobutyric acid in the presence of the catalyst.

Abstract: Improved catalyst for use in production of methacrylic acid by vapor phase oxidation reaction and/or vapor phase oxidative dehydrogenation reaction of at least one compound selected from methacrolein, isobutylaldehyde and isobutyric acid is provided. This improved catalyst is a composition composed of (A) complex oxide containing as essential components molybdenum and phosphorus, which is per se known as a catalyst for the above reaction(s), and (B) complex oxide containing as essential components cerium and zirconium. When this improved catalyst is used, the operation for producing methacrylic acid can be stably continued over prolonged period.

Abstract: The present invention provides a catalyst composition for the production of carboxylic acids by the oxidation of the corresponding unsaturated aldehydes, and methods for making and using the catalyst compositions. The catalysts include compositions of the formula: MoaVbAlcXdYeOz wherein X is at least one element selected from W and Mn; Y is at least one element selected from Pd, Sb, Ca, P, Ga, Ge, Si, Mg, Nb, and K; a is 1; b is 0.01-0.9; c is 0<0.2; d is 0<0.5; e is 0<0.5; and z is an integer representing the number of oxygen atoms required to satisfy the valency of the remaining elements in the composition. Using the catalyst composition of the present invention, one may effectively oxidize the desired starting materials at relatively high levels of conversion, selectivity, and productivity, and with minimal side products.

Abstract: A catalyst for the production of acrylic acid by the vapor-phase catalytic oxidation of acrolein or acrolein-containing gas and a method for the production of acrylic acid by the use of this catalyst are provided. The catalyst of this invention comprises (A) a catalyst having Mo and V as essential components and used for the production of acrylic acid by vapor-phase catalytic oxidation of acrolein and (B) a solid acid having acid strength (Ho) of not more than −11.93. Since this catalyst excels in catalytic activity and service life, it allows acrylic acid to be produced stably at a high yield for a long time.

Abstract: In a process for the preparation of acrolein and/or acrylic acid from propane, the propane is subjected, in a first reaction stage, to an oxydehydrogenation with molecular oxygen under homogeneous and/or heterogeneous catalysis to give propene and the product gas mixture formed in the first reaction stage is then used for the preparation of acrolein and/or acrylic acid by gas-phase catalytic propene oxidation.

Abstract: The present invention provides a method for stabilizing waste oil which is taken of each chemical apparatus of the manufacturing line of (meth)acryl acid and/or ester thereof, and treating the waste oil such as draining it out of the production apparatus, for example, a distillation tower from its bottom, sending and transporting it by a pump through a pipeline, and storing it in a storage tank in a simple manner while keeping the waste oil in a stable state. The waste oil can be stabilized by coexisting with solvent. The solvent used in the present invention is typically at least one selected from the group consisting of water, alcohol, ether, carboxylic acid, ketone, aromatic hydrocarbons, and aliphatic hydrocarbons.

Abstract: A process for vapor phase catalytic oxidation of methacrolein to produce methacrylic acid at high yield and with stability over a prolonged period is provided. The process is characterized, in the occasion of producing methacrylic acid by vapor phase catalytic oxidation of methacrolein using a fixed bed shell-and-tube reactor, in that (1) the catalyst layer in each reaction tube is divided into at least two layers in the axial direction of the tube to provide plural reaction zones, and (2) each of the reaction zones is filled with the catalyst in such a manner that the amount of the catalytically active component per unit volume of the reaction tube decreases from the gas inlet portion toward the gas outlet portion.

Abstract: In a process for the preparation of acrolein by gas-phase partial oxidation under heterogeneous catalysis, a reaction gas starting mixture which contains propene and molecular oxygen in a molar C3H6:O2 ratio of >1 is reacted in reaction zones connected in series, at elevated temperatures, over solid-state catalysts, further molecular oxygen being added to the reaction gas mixture in the course of the partial oxidation.

Abstract: A method of producing acrylic acid using a catalyst for acrolein oxidation reaction. Metallic salt components of the catalyst including molybdate, vanadate and tungstate are dissolved in water. An additional metallic salt component of the catalyst is added to the aqueous solution of the salts to form a suspension of the catalyst. In the suspension, the total weight of water is about 0.8 to about 5 times of the total weight of the metallic salts in the catalyst. This method of preparing suspension minimizes the amount of water required to dissolve the metallic salts, which reduces the amount of time and energy to be used in evaporating water from the suspension in the following step of obtaining catalyst. Additionally, in obtaining catalyst from the suspension prepared by this method, it is possible to avoid the deterioration of the catalytic performance since less heat is required to evaporate the water. Disclosed also is a method of producing a carrier-retained catalyst.

Abstract: Improved catalyst for use in production of methacrylic acid by vapor phase oxidation reaction and/or vapor phase oxidative dehydrogenation reaction of at least one compound selected from methacrolein, isobutylaldehyde and isobutyric acid is provided. This improved catalyst is a composition composed of (A) complex oxide containing as essential components molybdenum and phosphorus, which is per se known as a catalyst for the above reaction(s), and (B) complex oxide containing as essential components cerium and zirconium. When this improved catalyst is used, the operation for producing methacrylic acid can be stably continued over prolonged period.

Abstract: An improved method for the selective vapor phase oxidation of acrolein to acrylic acid in a recirculating solids reactor system using a particulate molybdenum vanadate multimetal oxide as oxidant involving specific reactant concentrations (preferably 5 mol % to 30 mol % propylene, 0 to 20 mol % oxygen, 0 to 70 mol % water, and the remainder inert gas), solids particle size (20 to 300 micrometers), temperature (250 to 450° C.) and gas (1 to 15 seconds) and solids (2 to 60 seconds) residence times. Such a process leads to improved selectivity, conversion and solids conversion ratio.

Abstract: A process is provided which can effectively inhibit occurrence o f hot spots in reaction zones or heat accumulation at the hot spots, in the occasion of producing acrolein and acrylic acid through vapor phase oxidation of propylene in the presence of a catalyst using a fixed bed shell-and-tube reactor, said catalyst having a composition represented by a general formula (1):

Abstract: An improved method for manufacturing acrylic acid by vapor phase oxidation of propylene in a single step or reaction stage using as solid phase oxidant a mixture of two particulate solids comprising a bismuth molybdate multimetal oxide (e.g., Mo12Co3.5Bi1.1Fe0.8W0.5Si1.4K0.05Ox) and a molybdenum vanadate multimetal oxide (e.g., Mo12V4.8Sr0.5W2.4Cu2.2Ox). Such a process is advantageously carried out in a recirculating solids reactor system wherein the particulate mixture of solids in an oxidized state reacts with a feed gas containing propylene in a vertical riser reactor and after separation from the acrylic acid gaseous product the particulate mixture of solids in a reduced state is regenerated by contact with an oxygen containing gas in a separate regeneration reactor before recirculation to the riser for further reaction.

Abstract: In an industrial process for the heterogeneously catalyzed gas-phase oxidation of propane with molecular oxygen to give acrolein, the feed gas mixture having an initial undiluted molar ratio of the reactants propane:O2 of 7:3 is diluted with the reactant propane and, if desired, inert gases in such a way that the feed gas mixture comprises more than 70% by volume of propane and at least 5% by volume of O2.

Abstract: Biodegradable resin products consisting essentially of a polymeric resin of starch, polyesters of polylactic acid and polycaprolactone. In admixture with the resin is a particulate vapor phase corrosion inhibitor selected from amine salts, ammonium benzoate, triazole derivatives, tall oil imidazolines, alkali metal molybdates, alkali dibasic acid salts, and mixtures thereof, and is present in an amount ranging from between about 1% and 3% by weight of the polymeric resin.

Abstract: A mixed metal oxide catalytic system consisting of molybdenum, vanadium, palladium, lanthanum, niobium and X, wherein X is copper and/or chromium, providing higher yields of acrylic acid and acrolein in the low temperature oxidation of propylene with a molecular oxygen-containing gas without the production of side products such as CO.

Abstract: Multimetal oxide materials containing molybdenum, vanadium, copper and one or more of the elements tungsten, niobium, tantalum, chromium and cerium and having a multiphase structure, and their use for the preparation of acrylic acid from acrolein by gas-phase catalytic oxidation, and oxometallates of the HT Cu molybdate structure type which contain Cu, Mo and at least one of the elements W, V, Nb and Ta.

Abstract: In a process for the continuous heterogeneously catalyzed gas-phase partial oxidation of an organic compound in an oxidation reactor, whose feed gas mixture comprises, apart from the organic compound to be partially oxidized and molecular oxygen as oxidant, at least one diluent gas which is essentially inert under the conditions of the heterogeneously catalyzed gas-phase partial oxidation, where the essentially inert diluent gas consists partly of combustible gases, after passage through the oxidation reactor, the combustible constituents of the inert diluent gas present in the product gas stream leaving the oxidation reactor are not recirculated to the heterogeneously catalyzed gas-phase partial oxidation, but are put to further use for the purposes of another chemical reaction.

Abstract: A method for gas-phase oxidation of an organic compound such as acrolein is provided, which includes oxidizing the organic compound with an oxidizing agent in the presence of a catalyst, to produce a product such as acrylic acid, wherein the catalyst includes a multimetal oxide material having at least two phases and of the formula III{A}.sub.p {B}.sub.q (III),wherein ##EQU1## M.sup.1, M.sup.2, a, b, c, x, M.sup.3, d, e, y, p and q are defined in the claims,which contains the moiety {A}.sub.p in the form of three-dimensional regions A which are delimited from their local environment owing to their chemical composition differing from their local environment and are of the chemical compositionA Mo.sub.12-a-b-c V.sub.a M.sub.b.sup.1 M.sub.c.sup.2 O.sub.xand the moiety {B}.sub.q in the form of three dimensional regions B which are delimited from their local environment owing to their chemical composition differing from their local environment and are of the chemical compositionB M.sub.12.sup.3 Cu.sub.d H.sub.e O.

Abstract: Solid mixed oxides composition of formula (I):Mo.sub.12 V.sub.a Sr.sub.b W.sub.c Cu.sub.d Si.sub.e O.sub.x(I)2.ltoreq.a.ltoreq.14, 0.1.ltoreq.B.ltoreq.6, 0.ltoreq.c.ltoreq.12, 0.ltoreq.d.ltoreq.6, 0.ltoreq.e.ltoreq.15; x is the quantity of oxygen bonded to the other elements and depends on their oxidation states, are used in the manufacture of acrylic acid by oxidation of acrolein, the said solid composition reacting with acrolein according to the redox reaction (1):SOLID.sub.oxidized +ACROLEIN.fwdarw.SOLID.sub.reduced +ACRYLIC ACID(1).To manufacture acrylic acid, a gaseous mixture of acrolein and of water vapor and, if appropriate, of an inert gas is passed over a solid composition of formula (I), to conduct the redox reaction (1) by operating at a temperature of 200 to 500.degree. C., at a pressure of 1.01.times.10.sup.4 to 1.01.times.10.sup.6 Pa (0.1 to 10 atmospheres), and with a residence time of 0.01 second to 90 seconds, in the absence of molecular oxygen.

Abstract: A catalyst having a high activity and mechanical strength and a process for preparing it are provided. The catalyst comprises molybdenum, vanadium, copper and antimony as essential components. The peak in X-ray diffractometry of the catalytically active component with Cu--K.alpha. line is largest at 22.2.+-.0.30.degree. (2.theta.).

Abstract: A coated catalyst which consists of a hollow cylindrical carrier and a catalytically active oxide material applied to the outer surface of the carrier, the applied catalytically active oxide material being applied in a coat thickness of from 10 to 1000 .mu.m, and having a specific catalytic surface area of from 20 to 30 m.sup.2 /g and an abrasion of <10, preferably <5, particularly preferably <0,5, % by weight in the turntable abrasion test. The catalyst is useful in the preparation of acrylic acid by the gas phase oxidation of acroleins.

Abstract: An oxide catalyst comprising the elements Mo, V and Nb with small amounts of phosphorus, boron, hafnium, Te and/or As. The modified catalyst provides both higher selectivity and yield of acetic acid in the low temperature oxidation of ethane with molecular oxygen-containing gas. A process for the higher selective production of acetic acid by the catalytic oxidation of ethane with oxygen, in the presence of the improved catalyst.

Abstract: A method for packing of catalyst, which comprises mixing, into a shaped catalyst containing at least molybdenum and iron, used in the gas-phase catalytic oxidation of propylene, isobutylene, tert-butyl alcohol or methyl tert-butyl ether with molecular oxygen to synthesize an unsaturated aldehyde and an unsaturated carboxylic acid both corresponding to the raw material used, metal-made Raschig rings as auxiliary packing material having a bulk volume of 0.3-3.5 times that of the shaped catalyst and a packing density of 0.5-1.5 kg/l, and packing the resulting mixture into a fixed bed type reactor; and a process for producing an unsaturated aldehyde and an unsaturated carboxylic acid, which comprises subjecting propylene, isobutylene, tert-butyl alcohol or methyl tert-butyl ether to gas-phase catalytic oxidation using molecular oxygen, in a fixed bed type reactor wherein a catalyst is packed by the above method.

Abstract: Acrylic acid can be produced efficiently by subjecting acrolein to catalytic gas-phase oxidation in the presence of a molybdenum/vanadium-based oxide catalyst prepared by using particular substances as the raw materials of the individual metal elements constituting the catalyst. A preferable example of such a catalyst is prepared by using, as the raw materials of vanadium, ammonium metavanadate and at least one vanadium oxide in which the valency of vanadium is larger than 0 but smaller than 5; as the raw material of copper, copper nitrate; and, as at least part of the raw material(s) of antimony, at least one antimony oxide in which the valency of antimony is larger than 0 but smaller than 5.

Abstract: A process for the catalytic gas-phase oxidation of acrolein to acrylic acid in a multiple contact tube fixed-bed reactor through whose space surrounding the contact tubes only one heat-exchange medium circuit is passed, at elevated temperature on catalytically active multimetal oxides with an acrolein conversion for a single pass of .gtoreq.95 mol % and an acrylic acid formation selectivity of .gtoreq.

Abstract: As an improvement for the process for production of acrylic acid by subjecting acrolein or an acrolein-containing gas to gas-phase oxidation with molecular oxygen in a fixed bed multitubular reactor, there is provided a novel process capable of producing acrylic acid at a high yield by suppressing the generation of heat spots in catalyst or the build-up of heat in hot spots of catalyst. The process comprises filling, in each of reactor tubes, two or more kinds of catalyst particles of different volumes so as to form a plurality of catalyst layers in the axial direction of the tube in such a manner that the particle volume of catalyst layer becomes smaller as the position of catalyst layer changes from the raw material gas inlet side of the tube to the raw material gas outlet side, each catalyst particle comprising, as the active component, a compound oxide containing at least Mo and V.

Abstract: A catalyst for the production of methacrylic acid by the vapor-phase catalyst oxidation and/or oxidative dehydrogenation of at least one compound selected rom the group consisting of methacrolein, isobutyl aldehyde, and isobutyric acid and a method for the production of methacrylic acid by the use of this catalyst are provided. The catalyst of this invention comprises (A) a composite oxide having Mo and P as essential components and used for the production of methacrylic acid by vapor-phase catalytic oxidation and/or oxidative dehydrogenation of methacrolein, isobutyl aldehyde, and/or isobutyric acid and (B) a solid acid having acid strength (Ho) of not more than -11.93. Since this catalyst excels in catalytic activity and service life, it allows methacrylic acid to be produced stably at a high yield for a long time.

Abstract: There is provided a process for efficient production of a solid catalyst usable for synthesis of methacrylic acid from methacrolein which comprises adding a lower alcohol or acetone to a dried product obtained from a mixed solution or aqueous slurry containing at least Mo, P and V as catalyst components and shaping the mixture by extrusion molding.

Abstract: Multimetal oxide compositions having a two-phase structure and comprising molybdenum, hydrogen, one or more of the elements phosphorus, arsenic, boron, germanium and silicon, one or more of the elements niobium, tantalum and antimony and one or more of the elements copper, iron, cobalt, nickel, zinc, cadmium, manganese, magnesium, calcium, strontium and barium, and their use for the preparation of methacrylic acid by gas-phase catalytic oxidation.

Abstract: Multimetal oxide compositions which comprise, as basic constituents, the elements Mo, V, W, Cu and Ni in oxidic form in certain molar ratios, and the preparation of these multimetal oxide compositions, and their use as catalysts for the gas-phase catalytical oxidation of acrolein to acrylic acid.

Abstract: A process for removal of solid organic matters formed and deposited in the reaction system when an unsaturated aldehyde or an unsaturated aidehyde-containing gas is subjected to catalytic gaseous oxidation in the presence of an oxidizing catalyst to prepare an unsaturated carboxylic acid corresponding thereto, which process comprises contacting the solid organic matters with a mixed gas containing at least 3 volume % of molecular oxygen and at least 0.1 volume % of steam at a temperature of 260.degree. to 450.degree. C.

Abstract: A catalytic system based on oxygen, vanadium, phosphorus, and molybdenum corresponding to the formula H.sub.m X.sub.n Me.sub.p PMo.sub.12-x V.sub.x O.sub.40, wherein X represents the VO.sup.2+ cation with 0<n.ltoreq.2, H represents protons with 0.ltoreq.m<4, 0.ltoreq.x.ltoreq.3, Me is a metal ion, especially an ion of a transition metal, with 0.ltoreq.p.ltoreq.t, t depending on the charge of the corresponding ion, is useful for the oxydehydrogenation of saturated carboxylic acids to .alpha.,.beta.-unsaturated acids and for oxidizing aldehydes to acids.

Abstract: A method of preparing methacrolein and/or methacrylic acid by catalytic gas phase oxidation of isobutane in the presence of a catalyst, wherein said catalyst is a catalyst containing divanadyl pyrophosphate and represented by general formula (1)P.sub.a V.sub.b X.sub.c Y.sub.d Z.sub.e O.sub.x (1)wherein P, V, and O represent phosphorus, vanadium and oxygen, respectively; X represents at least one element selected from the group consisting of cobalt and nickel; Y represents at least one element selected from the group consisting of niobium, tantalum, manganese, iron, copper, zinc, lanthanum, neodymium, samarium, cerium, zirconium, chromium, magnesium, tungsten, tin, hafnium, uranium, indium, cadmium, molybdenum, antimony, bismuth, rhodium, silver and sulfur; Z represents at least one element selected from the group consisting of potassium, rubidium, cesium and thallium; a, b, c, d, e, and x represent atomic ratios, respectively, provided that when a is 1, b is 0.2 to 2, c is 0.

Abstract: A process for the catalytic gas-phase oxidation of acrolein to acrylic acid in a fixed-bed reactor with contacting tubes, at elevated temperature on catalytically active oxides with a conversion of acrolein for a single pass of .gtoreq.95%, wherein the reaction temperature in the flow direction along the contacting tubes in a first reaction zone before the starting reaction gases containing the reactants enter the contacting tubes is from 260.degree. to 300.degree. C. until an acrolein conversion of from 20 to 40% is reached, and the reaction temperature is subsequently reduced by a total of from 5.degree. to 40.degree. C., abruptly or successively in steps or continuously along the contacting tubes until a methacrolein conversion of .gtoreq.95% has been reached, with the proviso that the reaction temperature in this secondary reaction zone is not lower than 240.degree. C.

Abstract: This invention provides a method for producing methacrylic acid by the use of a catalyst having activity for methacrolein oxidation and superior thermal resistance and capable of preparation with good reproducibility.Methacrylic acid is produced by allowing methacrolein and an oxygen-containing gas to undergo a catalytic gas phase oxidative reaction in the presence of a catalyst containing divanadyl pyrophosphate as an active ingredient. It is allowed that some of the vanadium atoms in the above catalyst are pentavalent or all of the vanadium atoms have been oxidized into pentavalent vanadium ions.In addition, the above catalyst can be produced from an oxide of vanadium and an oxyacid of phosphorus and has higher catalytic activity when it contains 0.001 to 40 mole % excess phosphorus as calculated in phosphoric acid equivalent. The compound VO(H.sub.2 PO.sub.4).sub.2 is preferable for an excess of phosphorus.

Abstract: A process for the catalytic gas-phase oxidation of methacrolein to methacrylic acid in a fixed-bed reactor with contacting tubes, at elevated temperature on catalytically active oxides with a conversion of methacrolein for a single pass of from 40 to 95 mol%, wherein the reaction temperature in the flow direction along the contacting tubes in a first reaction zone from entry of the starting reaction gases containing the reactants into the contacting tubes is from 280 to 340.degree. C. until a methacrolein conversion of from 20 to 40% is reached, and the reaction temperature is subsequently reduced by a total of from 5.degree. to 40.degree. C., abruptly or successively in steps or continuously along the contacting tubes until a methacrolein conversion of from 45 to 95% has been reached, with the proviso that the reaction temperature in this second reaction zone is not lower than 260.degree. C.

Abstract: A process for the production of acrylic acid by the two-stage catalytic vapor-phase oxidation of propylene with molecular oxygen, the first stage for oxidizing propylene to produce mainly acrolein and the second stage for oxidizing acrolein to produce mainly acrylic acid, which process comprises supplying to the first-stage reaction a raw gas containing a saturated aliphatic hydrocarbon having 1 to 5 carbon atoms in an amount in the range of 5 to 70% by volume, carbon dioxide in an amount in the range of 3 to 50% by volume, and the aliphatic hydrocarbon and the carbon dioxide in a total amount in the range of 20 to 80% by volume and further containing steam in an amount in the range of 0.5 to 8 mol per mol of propylene.