Abstract: The present invention provides an apparatus for producing (meth)acrylic acid and a process for producing (meth)acrylic acid with this apparatus wherein the apparatus enables to produce (meth)acrylic acid stably for a long period of time by effectively inhibiting the polymerization of (meth)acrylic acid in its production process (for example, in a reboiler). At least a part of the apparatus is made of a nickel-chromium-iron alloy with a molybdenum content of 3 to 20 mass %, but not including 3 mass %, or with a molybdenum content of 1 to 4 mass % and a copper content of 0.5 to 7 mass %.

Abstract: This invention provides a method of determining the proteolytic activity of the in vivo secretases, particularly the &bgr;-secretase and &ggr;-secretase that produce the A&bgr; peptides found in the plaques of Alzheimer Dementia (AD) patients. The invention also provides methods of isolating such secretases and methods of selecting agents that affect the activity of such secretases for developing drugs to treat or prevent dementia.

Abstract: The invention provides process for oxidative dehydrogenation of lower alkanes, by vapor phase oxidative dehydrogenation of C2-C5 lower alkanes in the presence of a catalyst and molecular oxygen to produce the corresponding olefins, in which the catalyst has a composition expressed by a general formula (1) below: A&agr;Sb&bgr;W&ggr;D&dgr;Ox   (1) in which A is at least one metal selected from the group consisting of molybdenum and chromium; Sb is antimony; W is tungsten; O is oxygen; and D is at least one metal selected from the group consisting of V, Nb, Ta, Fe, Co, Ni, Cu, Ag, Zn, B, Tl, Sn, Pb, Te, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce and Sm; &agr;, &bgr;, &ggr;, &dgr; and x denote atomic numbers of A, Sb, W, D and O, respectively, where when &agr;=1, &bgr;=0.5-10, &ggr;=0.1-10 and &dgr;=0-3; and x is a numerical value determined by the state of oxidation of those elements other than oxygen.

Abstract: Process for the production of vinyl acetate in which ethylene, acid and oxygen-containing gas are combined at elevated temperature in the presence of a catalyst material to produce (i) a product mixture comprising vinyl acetate, (ii) a liquid by-product comprising acetic acid and (iii) a gaseous by-product comprising carbon dioxide. The liquid by-product is separated from the product mixture and treated to reduce the water content therein before being recycled to the reactor such that the water entering the reactor comprises less than 6 wt %, (preferably less than 4 wt %, more preferably less than 3 wt %) of the total of acetic acid and water entering the reactor.

Abstract: A process for isolating acrylic acid forward during catalytic gas phase oxidation of propene, which entails separating acrylic acid from the gas phase oxidation reaction using an absorbent containing biphenyl, diphenyl ether or dimethyl phthalate; and extracting acrylic acid from acid water of the gas phase reaction with a solvent containing biphenyl, diphenyl ether or dimethyl phthalate.

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: An improved method which enables stable and effective recovery of acrylic acid over a prolonged period is provided, said method comprising contacting an acrylic acid-containing gas obtained upon gas-phase catalytic oxidation of propylene and/or acrolein, with water, whereby collecting the acrylic acid in form of an aqueous solution, introducing said aqueous solution into an azeotropic separation column and distilling it in the presence of an azeotropic solvent to isolate and recover the acrylic acid, in which polymerization of the acrylic acid in the azeotropic separation column is prevented. Said method is characterized by using as the azeotropic solvent either a mixed solvent composed of solvent A (eg., ethyl acrylate, methyl methacrylate, etc.) and solvent B (eg., toluene, heptane, etc.) (first embodiment) or the solvent A alone (second embodiment).

Abstract: The present invention is a method to produce an unsaturated carboxylic acid which includes the steps of: providing an epoxy compound; contacting the epoxy compound with carbon monoxide in the presence of a catalytically effective amount of a catalyst system comprising tin and cobalt under conditions effective for carbonylation of the epoxy; and recovering a .alpha.-.beta. unsaturated carboxylic acid product. The preferred epoxy is ethylene oxide which is reacted to acrylic acid by the method of the present invention.

Abstract: A method for producing acrylic acid from propylene at high efficiency by two-stage catalytic oxidation using a single fixed bed shell-and-tube heat exchanger type reactor is provided. The method comprises dividing the shell space of said reactor into an upper space and lower space with a partition plate, allowing a heating medium to circulate in each of the spaces substantially independently of each other, and carrying out the vapor phase oxidation under specific conditions. Said specific conditions including providing a first stage catalyst layer at lower portion of each of the reaction tubes, a second stage catalyst layer at upper portion thereof and an inert substance layer therebetween, and making void ratio of the inert substance layer 40-99.5%.

Abstract: The present invention concerns a method for producing acrolein and acrylic acid by carrying out vapor phase catalytic oxidation of propylene with molecular oxygen or a gas containing molecular oxygen using a oxidation catalysts comprising Mo, Bi and Fe as an essentially element and a fixed bed multitubular reactor, which comprisesa) using a plurality of supported catalysts having different activities, which was obtained, for example, by different calcination method in the production process of the supported catalysts,b) setting a catalyst layer in a reaction tube, which is formed by dividing it into plural portions in the tube axial direction, andc) arranging the aforementioned plural supported catalysts in such order that the activity becomes high toward the outlet from the inlet of the material gas in the reaction tube axial direction.

Abstract: A process for producing refined methacrylic acid comprising the steps of oxidizing methacrolein and the like catalytically in a vapor phase to form a methacrylic acid-containing gas, cooling and condensing the gas to an aqueous methacrylic acid solution, adding to the solution an organic solvent that forms two liquid phases with water to carry out an extraction operation and thereby to obtain an extract, bringing the extract into contact with water to mix them together, separating the mixture into an organic phase and a water phase, and distilling the organic phase. According to this process, highly refined methacrylic acid containing little dibasic acids such as maleic acid and citraconic acid can be obtained economically and without increasing wastes that are unrecoverable to the process.

Abstract: A catalyst for the production of unsaturated aldehyde and unsaturated acid, obtained by loading a catalytically active component on a carrier and calcining the loaded catalyst, characterized by an average particle diameter of the catalyst of 4 to 16 mm, an average particle diameter of the carrier of 3 to 12 mm, a calcining temperature of 520 to 600.degree. C. and an amount of the catalytically active component loaded on the carrier of 5 to 80% by weight ?weight of the catalytically active component)/(weight of the catalytically active component+weight of the carrier+weight of a strength improver)!, and a process for producing unsaturated aldehyde and unsaturated acid with the catalyst.

Abstract: In a process for producing acrylic acid, wherein propylene and/or acrolein is catalytically oxidized with molecular oxygen in a vapor phase and the gas resulting from the oxidation is cooled and/or absorbed in water to form a crude aqueous acrylic acid, followed by azeotropic distillation to remove the water with an entrainer of a boiling point of no higher than 130.degree. C. on the crude aqueous acrylic acid which may have, upon necessity, undergone removal of aldehydes contained therein to produce acrylic acid purified in that the crude aqueous acrylic acid is substantially dehydrated, the improvement which comprises conducting the azeotropic distillation under such conditions that concentrations of the entrainer and water in the bottom product of the azeotropic distillation are from 5% to 30% by weight and no higher than 0.

Abstract: Methods of use of compounds and compounds for the treatment of disorders characterized by the cerebral deposition of amyloid are provided. Among the compounds are those of formulae (I), (II) and (III): ##STR1## in which R.sub.1 is preferably 2-methyl propene, 2-butene, norleucine; R.sub.2, R.sub.4, and R.sub.8 are each independently methyl or ethyl; R.sub.3 is preferably iso-butyl or phenyl; R.sub.5 is preferably iso-butyl; R.sub.6 is H or methyl; R.sub.7 -(Q).sub.n is preferably benzyloxycarbonyl or acetyl; Q is preferably --C(O)--; RB is preferbly iso-butyl; R.sub.A =--(T).sub.m --(D).sub.m --R.sub.1, is which T is preferably oxygen or carbon, and D is preferably a mono-unsaturated C.sub.3-4 alkenyl being more preferred; and X is an alcohol, particularly a secondary alcohol.

Abstract: Peptidomimetics of the formula C.beta.X where C is cysteine, X is any naturally occuring amino acid, and .beta. is a hydrophobic spacer, most notably 2-phenyl-4-aminobenzoic acid. These compounds are effective inhibitors of p2lras farnesyltrasferase, block Ras-dependent oncogenic signalling and inhibit human tumor growth in vivo in animal models. Pro-drugs made by functionalizing terminal amino and carboxylic acid groups of peptides and peptidomimetics are also disclosed. Such functionalized derivatives demonstrate increased cell uptake. Other structural modifications are also disclosed.

Abstract: In a process for preparing acrolein, acrylic acid or a mixture thereof from propane, propane is partially dehydrogenated to propylene in a first stage, the product gas mixture resulting therefrom is, after separating off hydrogen and water vapor, used as feed to an oxidation reactor, the propylene formed in the dehydrogenation is partially oxidized in the oxidation reactor using molecular oxygen in the presence of non-dehydrogenated propane as inert diluent gas to give acrolein, acrylic acid or a mixture thereof and the propane present in the product gas mixture of the partial oxidation is subsequently recirculated to the dehydrogenation stage A.

Abstract: An ethylene stream which contains ethane as an impurity or a propylene stream which contains propane as an impurity is subjected to adsorption at a temperature of 50.degree. to 200.degree. C. in a bed of adsorbent which selectively adsorbs ethylene or propylene, thereby adsorbing substantially all of the ethylene or propylene. The purified ethylene or propylene stream is then subjected to partial oxidation in the presence of oxygen and, optionally ammonia to produce various partial oxidation products. The process is operated on a low per pass conversion with recycle of unreacted ethylene or propylene. In the system of the invention the adsorption unit may be upstream or downstream of the partial oxidation reactor.

Abstract: A process for producing acrylic acid is described, which process comprising providing a mixed gas of acrylic acid and by-products produced by catalytic gas phase oxidation of propylene and/or acrolein, contacting the mixed gas with water to obtain an aqueous solution, and adding an azeotrope solvent to the aqueous solution for distillation to obtain a mixture of the by-products, water and the azeotrope solvent from a tower top and acrylic acid from a tower bottom. Highly pure acrylic acid is obtained by using, as the azeotrope solvent, a mixed solvent of solvent A selected from diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl-tert-butyl ketone, n-propyl acetate and mixtures thereof and solvent B selected from toluene, heptane, methyl cyclohexane and mixtures thereof.

Abstract: Petrochemicals are produced by the vapor phase reaction of a hydrocarbon with substantially pure oxygen in the presence of a suitable catalyst. In the improved process, the principal product is removed, carbon monoxide, present in the reactor effluent as a byproduct, is oxidized to carbon dioxide and part of the gaseous effluent, comprised mainly of carbon dioxide and unreacted hydrocarbon, is recycled to the reactor. Removal of carbon monoxide from the recycle stream reduces the hazard of a fire or explosion in the reactor or associated equipment. The use of carbon dioxide as the principal diluent increases heat removal from the reactor, thereby increasing the production capacity of the reactor.

Abstract: In the production of methacrylic acid by the vapor phase catalytic oxidation of isobutylene, t-butanol, methacrolein isobutyl aldehyde or isobutyric acid, or mixture thereof, the reaction product gas is condensed by contact with an aqueous phase containing methacrylic acid and acetic acid thereby forming an aqueous solution of methacrylic acid and a gas phase containing methacrolein and methacrylic acid. The aqueous solution of methacrylic acid is extracted with a saturated hydrocarbon solvent containing from 6-9 carbon atoms. The methacrylic acid is extracted into the solvent phase and an aqueous phase containing acetic acid is also formed. Methacrolein is recovered from the gas containing methacrolein and methacrylic acid by contacting the gas with an aqueous phase containing methacrylic acid and acetic acid. An aqueous phase containing methacrylic acid, acetic acid and methacrolein is formed in the methacrolein recovery step.

Abstract: A process and intermediates for the manufacture of S-3-methylheptanoic acid from S-citronellol; a novel crystalline form of immunoregulatory N-(S-3-methylheptanoyl)-D-gamma-glutamyl-glycyl-D-alanine, an immunoregulatory agent; and an improved process and intermediates therefor.

Abstract: A process for reacting a fluid phase (gaseous and/or liquid phase) in contact with a solid phase in a reaction zone, wherein the improvement in said process comprises reacting the fluid phase in contact with the solid phase in a horizontally-oriented fluidized bed vessel. The vessel includes at least two compartments or stages, and includes means for vibrating the vessel. The process of the present invention enables one to effect fluidization of the solid phase independently of the flow rate or velocity of the fluid phase, thus enabling proper contact time of the fluid phase with the solid phase and minimizing the amount of fluid phase reactant to be recycled.

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 is provided for the purification of methacrylic acid. The process can easily remove dibasic acids and aldehydes containing in trace amounts as impurities. According to the process, crude methacrylic acid obtained as an aqueous solution by vapor-phase catalytic oxidation of isobutylene, tertiary butanol, methacrolein or isobutyl aldehyde is treated with at least one compound selected from the group consisting of m-aminophenol, m-phenylenediamine, 2,4-diaminotoluene and 2,4-diamino-diphenylamine, followed by distillation, optionally, in the presence of a p-phenylene diamine.

Abstract: A process and intermediates for the manufacture of S-3-methylheptanoic acid from S-citronellol; a novel crystallline form of immunoregulatory N-(S-3-methylheptanoyl)-D-gamma-glutamyl-glycyl-D-alanine, an immunoregulatory agent; and an improved process and intermediates therefor.

Abstract: The process for oxidation of propylene to acrolein and the oxidation of propylene to acrylic acid in two stages with acrolein as an intermediate are improved by use of essentially inert essentially anhydrous diluent gases to replace steam in the reaction streams. In particular, the use of essentially inert essentially anhydrous diluents which raise the composite heat capacity of the diluent gas mixture to at least about 6.5 calories/(gram-mole) (.degree.C.) will improve selectively to desired products and will reduce both the waste water load on the system and by-product formation. Reduction in second-stage catalyst efficiency is compensated for by introducing steam to the feed to the second-stage, and/or by increasing the operating temperature of the second-stage, and/or by increasing the active surface area of the second-stage catalyst.

Abstract: An improved process is provided for the production of a petrochemical by the vapor phase reaction of a hydrocarbon with an oxygen-containing gas in the presence of a suitable catalyst to produce a flammable gaseous product stream comprising the desired petrochemical, unreacted hydrocarbon, oxygen, carbon monoxide and carbon dioxide. In the improved process, a cooled or liquefied inert gas is injected as a quench fluid into the gaseous product stream exiting the hydrocarbon oxidation reactor, thereby cooling the stream to a temperature below the autoignition temperature of the flammable components of the stream, the petrochemical is recovered from the gaseous product and unreacted hydrocarbon is removed from the gaseous product and recycled to the reactor.

Abstract: In order to recover methacrolein and/or methacrylic acid by quenching a reaction product gas obtained by catalytic oxidation of isobutylene or the like, the reaction product gas is charged into a quench column through a double-wall pipe and is then brought into contact with a condensate as a cooling medium. Deposition of terephthalic acid and the like inside the column is prevented by controlling the temperature of a bottom in the quench column and that of an overhead gas of a quench column unit. An aromatic carboxylic acid, aromatic aldehyde, metal powder is added to an aqueous solution of methacrylic acid, which contains terephthalic acid and the like, so that the terephthalic acid and the like are caused to precipitate for their removal.

Abstract: Certain novel multiply promoted Mn-Sb oxides are superior catalysts for the ammoxidation of olefins to the corresponding unsaturated nitriles, the selective oxidation of olefins to unsaturated aldehydes and acids, and the oxydehydrogenation of olefins to diolefins.

Abstract: A method for oxidizing organic compounds by contacting organic compounds with molecular oxygen in the presence of a noble metal pyrochlore having the formula:A.sub.2+x B.sub.2-x O.sub.7-ywherein A is a pyrochlore structure metal cation, and B is one or more of Ru, Rh, Ir, Os, and Pt; x and y are greater than or equal to 0 and less than or equal to 1.0, at a temperature up to about 200.degree. C.

Abstract: A method of isolating and recovering methacrylic acid from a methacrylic acid-containing reaction product gas resulting from the vapor-phase catalytic oxidation of isobutylene, tertiary butanol or isobutyraldehyde, which comprises introducing the reaction product gas comprising methacrylic acid and various by-products including high boiling substances at a high temperature of 250.degree. to 300.degree. C. into a cooling zone, rapidly cooling the gas therein to a temperature of not more than 100.degree. C. to condense methacrylic acid and thus isolate methacrylic acid, while also converting the high boiling substances to fumes, thereafter introducing the cooled gas containing said fumes into a venturi scrubber, contacting it therein with an aqueous medium to remove said fumes, finally introducing the treated gas into a methacrylic acid-absorbing zone and absorbing methacrylic acid by absorption into an aqueous medium.

Abstract: A process for improving the activity of tellurium containing metal oxide catalysts useful as catalysts for oxidation, ammoxidation or oxidative dehydrogenation of organic compounds by heating the catalysts together with an activity-improving agent to a temperature up to about 900.degree. C. in a gaseous atmosphere. The process can be effectively applied to deteriorated or spent catalysts, the activity of which has been deteriorated due to use for a long period of time.

Abstract: A 1,2-unsaturated carboxylic acid or its ester such as acrylic or methacrylic acid or its alkyl ester is purified to remove aldehyde impurities contained therein by treating the acid or its ester with a mercapto containing compound in the presence of an acid catalyst.

Abstract: A process for conducting a combination of fixed and fluid-bed catalytic reactions is achieved by employing fixed-bed catalysts on supports within the fluid bed. The fluid-bed catalysts may move in both directions through the fixed bed, thereby giving advantages of both types of beds in one reactor.

Abstract: A process for separation of methacrylic acid from a methacrylic acid-containing, gaseous reaction mixture obtained by subjecting methacrolein or a compound which can afford methacrolein under reaction conditions and molecular oxygen to gas phase reaction in the presence of a catalyst for oxidation under the coexistence of an inert gas for dilution which comprises (a) cooling the gaseous reaction mixture from a reactor wherein the gas phase reaction has been effected to separate into condensable components including methacrylic acid, acetic acid and water vapor as a condensed liquor and non-condensable components including methacrolein as a non-condensed gaseous mixture, (b) eliminating contaminating methacrolein from the condensed liquor and (c) contacting the resulting condensed liquor with an organic solvent to extract methacrylic acid, followed by separation into an organic solvent solution including methacrylic acid and an aqueous solution as waste water, characterized in that (1) the inert gas for diluti

Abstract: Provided is a perfume composition containing a straight-chain trans-6-alkenoic acid represented by the general formula ##STR1## wherein n is an integer of 1 to 4.

Abstract: A catalyst for production of methacrylic acid, said catalyst being molded in a ring-like shape having an outside diameter of 3.0 to 10.0 mm, an inside diameter 0.1 to 0.7 times the outside diameter and a length 0.5 to 2.0 times the outside diameter, said catalyst comprising a catalytically active material having the composition represented by the following general formulaMo.sub.a P.sub.b A.sub.c B.sub.d C.sub.e D.sub.f O.sub.

Abstract: Iron-bismuth-molybdate catalysts further containing specific promoter elements have been found to exhibit excellent redox stability even under high stress conditions in the catalytic oxidation of olefins to unsaturated aldehydes and acids.

Abstract: A process for isolating methacrylic acid by solvent extraction from an aqueous methacrylic acid solution obtained from a gas phase catalytic oxidation reaction, characterized in that the aqueous methacrylic acid solution is previously first contacted with an extraction solvent, polymers precipitated out from the aqueous methacrylic acid solution are removed and the remainder is fed into an extraction column.

Abstract: In a process for producing chemical substances comprising steps of cooling, condensing and solvent-absorbing the reaction product gas having a high temperature formed in a reactor, an absorption type refrigerator or an absorption type heat pump is driven by using, as the driving source, a heat source having such a temperature as not to be advantageous for the heat exchange in the process, which heat source has been taken out of the steps of cooling the reaction product gas, condensing it or solvent-absorbing it to obtain a refrigerant or a hot water having a temperature higher than the temperature of the heat source, and the refrigerant or the hot water is used as a cooling source or a heating source in the steps comprised in said process for producing chemical substances.

Abstract: Vapor phase process for the preparation of unsaturated aldehydes, carboxylic acids and mixtures thereof which comprises contacting a gaseous mixture of an open-chain olefin of from 3 to 8 carbon atoms, water and oxygen at an elevated temperature up to about 250.degree. with a solid catalyst comprising a catalytically effective amount of noble metal promoted by a solid acid consisting of mixed metal oxides.

Abstract: A process for conducting a combination of fixed and fluid-bed catalytic reactions is achieved by employing fixed-bed catalysts on supports within the fluid bed. The fluid-bed catalysts may move in both directions through the fixed bed, thereby giving advantages of both types of beds in one reactor.

Abstract: A method for preparing attrition resistant, high percentage active component catalysts comprises using two types of silica, one of which is fumed silica, in a two stage catalyst preparation.

Abstract: An improved process for the catalytic oxidation of propylene to acrylic acid the improvement comprising conducting the process in the presence of an effective amount of hydroquinone. The improved process is particularly applicable to the aqueous liquid phase reaction of propylene with molecular oxygen using a supported palladium catalyst.

Abstract: Bismuth molybdate catalysts formed from a precatalyst slurry which uses an organic liquid or mixture of an organic liquid and water as the liquid medium of the slurry exhibit superior catalytic properties.

Abstract: A process for separating and recovering organic compounds from an oxygen-taining recycle gas deriving from an ozonization process is disclosed. The process comprises the separation of products in form of fumes from the gas, the countercurrent scrubbing of the gas with a polyoxyalkyleneglycol containing 2-4 carbon atoms, pre-treated with a monocarboxylic acid anhydride and/or the countercurrent scrubbing of the gas with the polyoxyalkyleneglycol or with an excess of a base. The organic compounds are recovered either by stripping (at atmospheric pressure or under vacuum) or by hydrolysis followed by distillation (at atmospheric pressure or under vacuum).

Abstract: The present invention is a reactor that consists of a single shell that contains a reaction zone and a regeneration zone. The reaction zone and regeneration zone are arranged in such a manner that (a) a particulate solid may be transferred by flow of gases from the regeneration zone to the reaction zone by a first route and then back to the regeneration zone by a second route; and (b) the gases passing through the regeneration zone are not transferred to the reaction zone and the gases passing through the reaction zone are not transferred to the regeneration zone.

Abstract: In the recovery of acrylonitrile from the gross reaction product produced during the commercial ammoxidation of propylene to produce acrylonitrile, an ammoxidation waste gas containing at least 65% nitrogen, carbon dioxide, carbon monoxide and a small amount of unreacted propylene is produced. In accordance with the invention, this ammoxidation waste gas is passed through a catalytic converter containing an oxidation or ammoxidation catalyst to convert the unreacted propylene into valuable product.

Abstract: In a process for producing acrylic acid which comprises contacting with water an acrylic acid-containing reaction product gas which has been obtained by the catalytic vapor phase oxidation of an olefinic compound of a general formula, CH.sub.2 .dbd.CHX, wherein X represents at least one group selected from the group consisting of CH.sub.

Abstract: An oxidizable hydrocarbon is oxidized in a reaction zone at elevated temperature in the presence of a liquid reaction medium by introducing the hydrocarbon and a feed stream containing molecular oxygen to the reaction zone under conditions sufficient to oxidize at least a portion of the hydrocarbon; withdrawing at least a portion of the liquid reaction medium from the reaction zone; passing at least a portion of the withdrawn liquid reaction medium to an oxygen injection zone located external to the reaction zone; contacting the liquid in said oxygen-injection zone with a gas stream containing molecular oxygen under conditions sufficient to form a two-phase gas/liquid mixture; and passing said two-phase gas/liquid mixture to the reaction zone as the feed of molecular oxygen thereto.