Abstract: This invention relates to a process for preparing an ethylene oxide catalyst by depositing silver and one or more alkali metal promoters on an alpha alumina carrier in which a fired carrier body is impregnated with a source of titania in a liquid medium that upon heating yields titania and is then calcined to generate titania uniformly dispersed in the carrier in an amount of up to about 10 percent by weight, basis the total weight of the carrier, and subsequently drying the carrier having said silver and alkali metal supported thereon.

Abstract: Process for regenerating a silver catalyst deactivated by coking during the gas phase epoxidation of 1,3-butadiene by reacting the coked catalyst with a gas mixture containing at least 5% by volume of water vapor and up to 95% by volume of oxygen at temperatures of from 100 to 500 .degree. C.

Abstract: Heterogeneous vapor phase oxidation and other reactions are carried out at the surface of a solid catalyst, with both gaseous reactants and the solid catalyst being dispersed in a recirculating liquid solvent. Reaction and product absorption are combined into a single processing step, with enhanced catalyst performance, and product selectivity and product yields, enhanced mass and heat transfer characteristics and reduced risk of forming explosive mixtures in the course of a particular reaction.

Abstract: The catalytic performance of a supported silver catalyst in a propylene epoxidation process is improved by first contacting the catalyst at an elevated temperature with a treatment stream comprised of carbon dioxide. The carbon dioxide-treated catalyst is thereafter contacted with a feedstream containing propylene, molecular oxygen, but essentially no carbon dioxide under conditions effective to form propylene oxide.

Abstract: Direct oxidation of propylene to propylene oxide is accomplished using alkaline earth metal compound-supported silver catalysts containing an inorganic chloride promoter and a potassium promoter derived from a potassium salt containing a nitrogen oxyanion or precursor thereof.

Abstract: A silver catalyst for ethylene oxidation to ethylene oxide is provided containing a promoter combination consisting of an alkali metal component, a sulfur component, and a fluorine component, the catalyst being essentially free of rhenium and transition metal components.

Abstract: A propylene epoxidation process wherein a supported silver catalyst is utilized may be operated at high efficiency even in the absence of any organic chloride in the feedstream, provided the catalyst is first contacted at an elevated temperature with a treatment stream comprised of an organic chloride and molecular oxygen.

Abstract: Propylene is oxidized to propylene oxide in the vapor phase using an oxygen-containing gas and a supported silver catalyst comprising silver and a support comprised in whole or in substantial part of certain alkaline earth metal compounds. The alkaline earth metal compound may, for example, be a calcium compound such as calcium titanate, tribasic calcium phosphate, calcium molybdate, or calcium fluoride, a magnesium compound such as magnesium aluminate, or a strontium compound such as strontium titanate. Such supports provide significantly higher selectivity to the desired epoxide than would be expected from the performance of related materials. Propylene oxide selectivity may be further enhanced through the introduction of nitrogen oxide species such as NO, alkyl halides such as ethyl chloride, and carbon dioxide into the oxygen-containing gas.

Abstract: Disclosed are improved processes for the recovery of 3,4-epoxy-1-butene (epoxybutene) from an epoxidation effluent comprising epoxybutane, butadiene, oxygen and an inert diluent obtained by the selective epoxidation of butadiene with an oxygen-containing gas in the presence of a catalyst and an inert gas. Epoxybutene is separated from the effluent by means of an absorption process using an extractant comprising liquid butadiene and, optionally, a hydrocarbon diluent. The formation of butenediols, by the reaction of epoxybutene and water, in the recovery process is inhibited by the addition of a base, preferably an alkali metal base, to the recovery system.

Abstract: The invention relates to a silver catalyst for the partial oxidation of ethylene with molecular oxygen in the gas phase to form ethylene oxide and a process for preparing ethylene oxide using this catalyst. The catalyst is superior to comparable catalysts of the prior art through an increased selectivity (at high activity) and/or a more favorable ageing behavior. The process for preparing ethylene oxide is distinguished by improved economics.

Abstract: A process for the catalytic vapor-phase oxidation of ethylene with a molecular oxygen-containing gas, in a reactor comprising a multitude of reaction tubes containing a supported silver catalyst and surrounded by a heat-exchange fluid which enters the reactor in liquid form and leaves the reactor in vapor form, characterized in that between 5 and 100 wt % of the liquid heat-exchange fluid is introduced to the reactor at its downstream end, at a temperature which is at least 20.degree. C. below the temperature of the heat-exchange fluid on leaving the reactor.

Abstract: Oxirane compounds are formed by vapor phase catalytic molecular oxygen oxidation of a C.sub.3 -C.sub.10 olefin using a silver catalyst, and the selectivity to the oxirane product is enhanced by preconditioning the catalyst by contact with the olefin at elevated temperature in the absence of oxygen; oxygen is periodically pulsed to the reaction.

Abstract: An improved silver catalyst for the oxidation of ethylene with molecular oxygen is made by impregnating a porous support with a silver salt of a neo acid; subjecting the impregnated support to a low temperature activation by heating at a temperature in the range of 250.degree. C. to 300.degree. C. on a moving belt in an atmosphere containing less oxygen than air, and post impregnating the support with an alkali metal, preferably cesium.

Abstract: This invention relates to an ethylene oxide catalyst having improved initial selectivity which catalyst comprises silver, a promoting amount of alkali metal, a promoting amount of rhenium and a promoting amount of rhenium-co-promoter selected from phosphorus, boron and mixtures thereof, supported on a porous refractory support.

Abstract: 3,4-Epoxy-1-butene is prepared by the gas phase epoxidation of 1,3-butadiene by means of oxygen or oxygen-containing gases over silver-containing catalysts and isolation of the 3,4-epoxy-1-butene from the reaction exit mixture by performing the gas phase epoxidation in the presence of from 6 to 80 mol % of water vapor, based on the gas mixture supplied to the reactor.

Abstract: An improved silver catalyst for the oxidation of ethylene with molecular oxygen is made by impregnating a porous support with a silver salt of an acid; subjecting the impregnated support to a multi-stage activation by heating and post impregnating the support with an cesium carbonate or bicarbonate from an anhydrous alcohol solution followed by washing with alcohol solvent and rapid drying to produce a finished catalyst having from 1-6.times.10.sup.-3 gew of the alkali metal per kg of catalyst.

Abstract: A method of controlling the build-up of organic and/or inorganic contaminants (e.g., carbonates, nitrates, nitrites, and the like) in an aqueous process stream, comprising directing at least some of the contaminated stream to a heating means wherein at least some of the contaminants are decomposed. Thereafter, the decomposition products are removed and the purified stream is returned to the process. In a preferred embodiment, the process is an alkylene oxide manufacturing process, and the contaminated aqueous stream is the effluent from a catalyzed scrubbing system for removal of carbon dioxide. Organic contaminants are decomposed to carbon dioxide, which is flashed off; inorganic salts which are decomposed to gases are flashed off; inorganic salts which are not converted to gases are scrubbed out.

Abstract: An improved silver catalyst for the oxidation of ethylene with molecular oxygen is made by impregnating a porous support with a silver salt of a neo acid; subjecting the impregnated support to a low temperature activation by heating at a temperature in the range of 250.degree. C. to 300.degree. C. on a moving belt in an atmosphere containing less oxygen than air, and post impregnating the support with an alkali metal, preferably cesium.

Abstract: A process of manufacturing ethylene oxide is presented in ethylene and free oxygen are reacted in the presence of methane, carbon dioxide, and argon in a reactor to form an effluent comprising ethylene oxide; the effluent is then withdrawn and ethylene oxide is removed from the effluent to obtain a recycle stream; carbon dioxide and argon are removed from the recycle stream to obtain a treated recycle stream which is supplied to the reactor along with additional reactants and methane, wherein removing argon comprises separating a side stream from the recycle stream, passing the side stream to the feed inlet of a membrane unit, removing an argon-containing stream from the permeate outlet of the membrane unit, removing a retentate stream from the retentate outlet of the membrane unit, adding the retentate stream to the recycle stream, and purging the permeate side of the membrane unit with inert gas.

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 catalyst for the production of ethylene oxide is disclosed which comprises an .alpha.-alumina carrier having the outer surface thereof and the surface of pores therein coated with an amorphous silica-alumina mixture having a total Si and Al content in the range of from 3.times.10.sup.-4 to 2.times.10.sup.-1 g/g of carrier and an Si/Al ratio in the range of from 0.05 to 50.0 g/g, 5 to 25% by weight based on perfected catalyst of minute metallic silver particles, and 0.0001 to 0.05 gram equivalent weight per kg of perfected catalyst of cesium. The catalyst, when used for the production of ethylene oxide by the catalytic vapor-phase oxidation of ethylene with molecular oxygen, possesses high selectivity, high activity, and high durability to ensure a long service life.

Abstract: Olefine oxides are produced by contacting an olefine with oxygen in the presence of a silver containing catalyst and a chlorine-containing reaction modifier; the performance of the catalyst is improved by contacting it with a nitrate or nitrite forming substance for example nitric oxide.

Abstract: This invention relates to an ethylene oxide catalyst which contains silver and one or more alkali metal promoters supported an a carrier having a crush strength of at least about 5 pounds and a settled packing density of at least about 30 pounds/cubic foot which comprises first and second alpha alumina components with a first alpha alumina component in the form of particles having a median crystallite size of from about 0.4 to about 4 microns providing from about 95% to about 40% of the total weight of alpha alumina in the carrier and a second alpha alumina component generated in situ by a sol-gel process and providing the balance of the alpha alumina in the carrier. Titania is optionally added to the carrier.

Abstract: An improved silver catalyst for the oxidation of ethylene with molecular oxygen is made by impregnating a porous support with a silver salt of an acid; subjecting the impregnated support to a multi-stage activation in an atmosphere containing less oxygen than air by heating at a first temperature in the range of 150.degree. to 200.degree. C. for less than an hour, heating at a second temperature in the range of from greater than 200.degree. C. to 300.degree. C. for less than one hour, heating at a third temperature in the range of from greater than 300.degree. C. to 400.degree. C. for less than one hour and finally heating at a fourth temperature in the range of from greater than 400.degree. C. to 500.degree. C.; and post impregnating the support with an alkali metal, preferably cesium, from an anhydrous alcohol solution followed by washing with alcohol solvent and rapid drying to produce a finished catalyst having from 1-6.times.10.sup.-3 gew of the alkali metal per kg of catalyst.

Abstract: Disclosed herein is an improved gas phase process for the selective epoxidation of non-allylic olefins wherein the epoxidation is carried out in the presence of certain inert, paraffin hydrocarbons. Such hydrocarbons possess higher heat capacities as compared to other materials, e.g., nitrogen, argon, methane and helium, typically used as inert diluents in olefin epoxidations. The disclosed process is particularly useful for the continuous manufacture of 3,4-epoxy-1-butene from 1,3-butadiene.

Abstract: A silver salt solution suitable for depositing silver on a support in the preparation of silver catalysts is made by reacting a silver compound with a neo-acid, in a hydrocarbon solvent. The reaction is completed under reflux conditions, thereby removing water formed by the reaction and reacting at least 90% of the unreacted acid. Therefore, the solution may be used without further processing to impregnate a porous support, thereby providing a catalyst useful for oxidation of ethylene oxide.

Abstract: A gas stream from a reaction in which ethylene oxide is produced by reacting ethylene with oxygen which gas stream comprises oxides of nitrogen and steam the gas stream is contacted with an aqueous alkaline quench solution and ethylene oxide is then recovered from the gas stream. A substantial amount of oxides of nitrogen is removed from the gas stream during the treatment with the quench solution.

Abstract: Disclosed are improved processes for the recovery of 3,4-epoxy-1-butene (EpB) from an epoxidation effluent comprising EpB, butadiene, oxygen and butane obtained by the selective epoxidation of butadiene with an oxygen-containing gas in the presence of a catalyst and an inert gas. EpB is separated from the effluent by means of an absorption process using liquid mixture of butadiene and butane as the absorbent material. The inclusion of butane in the epoxidation and recovery processes permits the use of lower pressures in the absorption of the EpB product.

Abstract: The production of ethylene oxide by the catalytic vapor phase oxidation of ethylene with a molecular oxygen-containing gas is effected in a reactor provided with a preheating zone, a reaction zone, a cooling zone, a partition plate separating the first two portions from the third portion, and a multiplicity of reaction tubes piercing the two separated sections by a method which comprises supplying hot water to the cooling zone of the reactor, forwarding zone of the hot water discharged from the cooling zone to a gas-liquid separation tank, circulating the remainer of the hot water in conjunction with the cooling hot water to the cooling zone, supplying the hot water separated in the gas-liquid separation tank to the reaction zone to remove the heat of the oxidation reaction, and circulating the hot water extracted in the form of a gas-liquid mixed phase to the gas-liquid separation tank.

Abstract: A silver catalyst suitable for the oxidation of ethylene is provided in which the silver within a support particle, e.g., alumina, is non-uniformly distributed so that the silver concentration is clearly greater on the geometric surface and in the surface layer just beneath less than 0.5 mm thick than in the interior of the particles. The concentration of silver in the layer is two to a thousand times the concentration in the interior of the catalyst.

Abstract: Disclosed is an improved process for the epoxidation of ethylene, wherein ethylene is reacted with oxygen in a mol ratio of about one, in the presence of a silver metal catalyst and a halide gas phase inhibitor, at a pressure of about 200 to 300 psig, said improvements comprising: introducing into the reaction zone a feed gas mixture comprising:30 to 90 mol % ethylene,0 to 55 mol % methane,0 to 15 mol % one or more inert, non-hydrocarbon gases or mixtures thereof,0 to 10 mol % carbon dioxide,2 to 10 mol % oxygen,1 to 50 ppm organic halide gas phase inhibitor, and maintaining the temperature in the reaction zone between 180.degree. and 350.degree. C.

Abstract: In a direct-oxidation ethylene oxide process of the type comprising a) reacting a feed gas stream including ethylene and a commercially-pure oxygen in one or more reactors and b) absorbing out ethylene oxide from the product stream from the one or more reactors in a first absorption zone, the improvement comprising recovering unreacted ethylene from an ethylene-rich argon purge gas stream via an absorber and a stripper in combination, recycling the recovered ethylene to the feed gas stream, and purging an ethylene-lean argon purge gas stream.

Abstract: A herbicidal hydroxyethyl-cyclopropyl-azolyl derivative of the formula ##STR1## in which R.sup.1 represents halogen, phenyl or the grouping --Z-R.sup.3, whereinZ represents oxygen, sulphur, SO or SO.sub.2 andR.sup.3 represents alkyl, phenyl or benzyl,R.sup.2 represents alkenyl, optionally substituted furyl, optionally substituted thienyl or the radical of the formula ##STR2## wherein R.sup.4 represents difluoromethoxy, 1,1,2,2-tetrafluoroethoxy, 1,1,2-trifluoro-2-chloro-ethoxy, cyano, formyl, alkoximinoalkyl, carbalkoxy, dialkoxyalkyl, phenoxyalkyl which is optionally substituted in the phenyl moiety by halogen, or benzyloxy which is optionally substituted in the phenyl moiety by halogen andR.sup.5 represents hydrogen or halogen, orR.sup.4 and R.sup.5 are linked in the ortho-position and together represent --O--CH.sub.2 --O--, orR.sup.2 represents the radical of the formula ##STR3## in which R.sup.6 represents difluoromethoxy, 1,1,2,2-tetrafluoroethoxy or 1,1,2-trifluoro-2-chloro-ethoxy, orR.sup.

Abstract: Catalysts for the epoxidation of alkene, especially ethylene, to the corresponding alkylene oxide, e.g., ethylene oxide, which catalysts contain a high silver content on carriers having a high surface area and a high pore volume are disclosed. Methods for making and using such catalysts are also disclosed.

Abstract: Disclosed is a process for the production of an alkylene oxide in which an alkene, and an oxygen containing gas are reacted in the presence of a flame suppressor under conditions of low alkene conversion and high alkylene oxide selectivity in which unreacted alkene is recycled to the reactor and there is efficient removal of nitrogen and carbon dioxide.

Abstract: A silver catalyst suitable for the oxidation of ethylene is provided in which the silver within a support particle, e.g., alumina, is non-uniformly distributed so that the silver concentration is clearly greater on the geometric surface and in the surface layer just beneath less than 0.5 mm thick than in the interior of the particles. The concentration of silver in the layer is two to a thousand times the concentration in the interior of the catalyst.

Abstract: This invention relates to a process for starting up a fixed bed ethylene oxide reactor containing a supported silver catalyst promoted with one or more alkali metal promoter(s) which involves heating the reactor to slightly below normal operating conditions, passing an ethylene containing gas over the catalyst, adding a chlorohydrocarbon moderator to the gas passing over the catalyst and after approximately 0.1-5 milliliters of moderator (basis liquid) per cubic foot of catalyst has been added, then adding oxygen to the gas passing over the catalyst to initiate the ethylene oxidation reaction and subsequently raising the reactor temperature and gas flow rates to operating conditions.

Abstract: Process is disclosed for the slective monoepoxidation of styrene, styrene analogs, and styrene derivatives. Such compounds are contacted with an oxygen-containing gas in the presence of a promoted, optionally supported silver catalyst under defined reaction conditions, thereby selectively producing opoxides in good yield.

Abstract: Disclosed are processes for the manunfacture of 3,4-epoxy-1-butene (EpB) and, particularly, for the recovery of EpB from an epoxidation effluent comprising EpB, butadiene, oxygen and an inert gas obtained by the selective epoxidation of butadiene with an oxygen-containing gas in the presence of a catalyst and an inert gas. EpB is separated from the effluent by means of an absorption process using liquid butadiene as the absorbent material.

Abstract: A process for preparing silver-containing catalysts and their carriers for the production of ethylene oxide via ethylene oxidation and also to the applications of said catalysts in producing ethylene oxide.Commercial trihydrated .alpha.-alumina, boehmite, carbonaceous materials, a fluxing agent, fluoride and a binder are mixed with water, kneaded and extruded to form strips which are cut and shaped. The shaped bodies are dried, calcined and converted to a .alpha.-alumina bodies i.e., carriers. This process is characterized by using trihydrated .alpha.-alumina, boehmite alumina and carbonaceous materials which have a good matching of particle sizes and proportions in preparing alumina carriers with the following pore structure:______________________________________ specific surface area 0.2-2 m.sup.2 /g pore volume >0.5 ml/g pore radius >30.mu., 25-10% of total volume <30.mu., 75-90% of total volume.

Abstract: An improved process for the production of oxides from hydrocarbons by reaction with oxygen, air or a gas enriched in oxygen relative to air, preferably the latter, in the presence of a suitable catalyst. An alkane, e.g. propane, is converted to an alkene in a catalytic dehydrogenator. The product stream is introduced into an oxidation reactor. Product formed therein is recovered in a conventional quench tower. The pressure of the gaseous effluent from the quench tower is raised and it is introduced into an absorber/stripper unit to form a recycle stream containing unreacted alkane and alkene as well as a minor amount of oxygen, typically 1-2 percent by volume, and a waste stream comprising the remainder of the quench tower gaseous phase. The recycle stream enters a selective oxidation unit wherein oxygen is removed, and the product recycled to the dehydrogenator.

Abstract: An improved process is provided for the production of oxides from alkanes by reaction with oxygen, air or a gas enriched in oxygen relative to an air in the presence of an oxidation catalyst. An alkane, e.g. propane, is converted to an alkene in a multistage dehydrogenator. The product stream is withdrawn from an intermediate reactor in the dehydrogenator, other than the first and the last reactor, and introduced into an oxidation reactor. The product formed in the oxidation reactor is recovered in a conventional quench tower. The gaseous effluent from the quench tower is treated in a pressure swing adsorption (PSA) unit to form a gaseous stream containing the unreacted alkane and alkene as well as a minor amount, i.e. less than about 2 percent by volume, of oxygen and nitrogen, if present in the feed to the oxidation reactor.

Abstract: An improved process is provided for the production of oxides from hydrocarbons by reaction with oxygen, air or a gas enriched in oxygen relative to air, preferably the latter in the presence of an oxidation catalyst. An alkane, e.g. propane, is converted to an alkene in a catalytic dehydrogenator. The product stream is introduced into an oxidation reactor. The product formed therein is recovered in a conventional quench tower. The gaseous effluent from the quench tower is treated in a separator to produce an adsorbed stream, an oxygen-enriched stream, a waste stream and, if desired, a hydrogen-enriched stream. The oxygen-enriched stream may be recycled to the oxidation reactor depending on the nitrogen content thereof. The adsorbed stream plus at least a portion of the hydrogen-enriched stream is introduced into a selective oxidation unit to remove the remaining oxygen and then recycled to the dehydrogenator. The remainder of the hydrogen-enriched stream, if any, may be taken as product or vented.

Abstract: An improved silver catalyst for the oxidation of ethylene with molecular oxygen is made by impregnating a support with a silver salt prepared by reacting a silver compound with a neo-acid, in a hydrocarbon solvent with the reaction completed under reflux conditions; drying and activating the resultant precatalyst by heating in air; thereafter impregnating the activated catalyst with an amount, 800 to 5000 wppm of alkali metal, preferably Cs, to deactivate the catalyst to form a catalyst precursor and heating the catalyst precursor at 450.degree.-700.degree. C. for 0.1 to 4.5 hours at a steady state in a substantially inert atmosphere to reactivate it.

Abstract: A process is provided for epoxidation of an alkene in the presence of an oxygen-containing gas which comprises contacting the alkene and the oxygen-containing gas under epoxidation conditions in the presence of at least one gaseous efficiency-enhancing member of a redox-half reaction pair and a supported silver catalyst, the catalyst comprising a catalytically effective amount of silver on a solid porous support having a stability-enhancing morphology and an efficiency-enhancing amount of at least one efficiency-enhancing salt of a member of a redox-half reaction pair, the support having a surface area of at least about 0.7 m.sup.2 /g and a particulate matrix which contains particles having at least one substantially flat major surface.

Abstract: A process is provided for the epoxidation of an alkene in the presence of an oxygen-containing gas which comprises contacting the alkene and the oxygen-containing gas under epoxidation conditions in the presence of at least one efficiency-enhancing gaseous member of a redox-half reaction pair and a solid catalyst, the catalyst comprising a catalytically-effective amount of silver on a solid support and an efficiency-enhancing amount of at least one efficiency-enhancing salt of a member of a redox-half reaction pair, the support having less than about 50 ppm, by weight, of leachable sodium.

Abstract: A process is provided for epoxidation of an alkene in the presence of an oxygen-containing gas which comprises contacting the alkene and the oxygen-containing gas under epoxidation conditions in the presence of at least one gaseous efficiency-enhancing member of a redox-half reaction pair, a performance-enhancing amount of a fluorine-containing substance and a supported silver catalyst comprising a catalytically-effective amount of silver on a solid porous support and at least one efficiency-enhancing salt of a member of a redox-half reaction pair.

Abstract: An improved process is provided for the production of oxides from hydrocarbons by reaction with oxygen, air or a gas enriched in oxygen relative to air, preferably the latter, in the presence of an oxidation catalyst. An alkane, e.g. propane, is converted to an alkene in a dehydrogenator. The product stream is introduced into an oxidation reactor. The product formed therein is recovered in a quench tower. The gas phase from the quench tower is treated in a PSA unit to form a gaseous stream containing the unreacted alkane, alkene, a minor amount of oxygen, i.e. less than about 2 percent by volume, and nitrogen if present in the feed to the oxidation reactor. The gaseous stream, which may or may not contain hydrogen depending on the adsorbent on the PSA unit, is introduced into a selective oxidation unit to remove the remaining oxygen and then recycled to the dehydrogenator.

Abstract: Process is disclosed for the selective epoxidation of olefins having no allylic hydrogens. Such olefins are contacted with an oxygen-containing gas in the presence of a silver catalyst and an organic halide under defined reaction conditions, thereby selectively producing epoxides in good yield.

Abstract: Improved performance is obtained in a multi-tube reactor for oxidation of ethylene to ethylene oxide by providing a distribution zone for the coolant located downstream of the catalyst and a contiguous cooling zone. The effluent gases from the oxidation are cooled in the cooling zone by a fluid, which has been only slightly preheated and distributed uniformly in the distribution zone by contact with tubes in which the effluent gases are in low-turbulence flow. Uniform distribution of the coolant provides substantially equal cooling of the effluent gases in each tube, thus minimizing the variation in effluent gas temperature among the tubes. Preferably, the tubes in the cooling section are packed with inert particles to facilitate heat transfer, while the tubes are empty in the distribution section to reduce heat transfer.