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: The present invention has for its object to provide a production method of a pyromellitic anhydride which is not only conducive to an increased catalyst life and, hence, an enhanced operating rate of a plant (reduced downtime) and a reduction in catalyst cost but also conducive to reductions in byproducts and, hence, savings in the cost of after-treatments such as collection and purification. A production method of a pyromellitic anhydride comprising a step for catalytic gas-phase oxidation of a starting mixture gas consisting of a tetraalkylbenzene and/or a trialkylbenzaldehyde and a molecular oxygen-containing gas in a fixed-bed type reactor having a catalyst bed wherein the production method of a pyromellitic anhydride is carried out under the condition that the moisture content of said starting mixture gas to be introduced into the catalyst bed is not more than 2 volume %.

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: The present invention has for its object to provide a production method of a pyromellitic anhydride which is not only conducive to an increased catalyst life and, hence, an enhanced operating rate of a plant (reduced downtime) and a reduction in catalyst cost but also conducive to reductions in byproducts and, hence, savings in the cost of after-treatments such as collection and purification.

Abstract: A method for the production of methacrylic acid comprising the steps of simultaneously introducing at least one compound selected from the group consisting of methacrolein and isobutyl aldehyde and a molecular oxygen-containing gas into a heat exchanger type shell-and-tube reaction vessel packed with an oxide catalyst containing molybdenum and phosphorus thereby effecting catalytic vapor-phase oxidation reaction and/or catalytic vapor-phase oxidative dehydrogenation reaction and consequently forming methacrylic acid, which method is characterized by having the empty space in the gas outlet part of said reaction vessel with a solid filler.

Abstract: This invention relates to a improved method for the production of methacrylic acid by the steps of subjecting isobutylene and/or tertiory hutanol to catalytic vapor-phase oxidation with molecular oxygen in a first reactor, then supplying the resultant gax mixture to a second reactor, a rodlike or plate like insert set being placed in the empty space of gas inlet part of the tube of said second reactor.

Abstract: A catalytic vapor phase oxidation reactor which comprises a fixed-bed shell and tube heat exchange apparatus in which a bundle of a multiplicity of tubes filled with at least one type of oxidizing catalyst are disposed in a shell and these tubes are passed through the apertures formed in at least one perforated shield plate to partition the inside of the shell into at least two heat transfer medium feed zones and in such a manner that each of the tubes passing through the perforated shield plate is not in direct contaction with the shield plate but the outer surface of the tube and the inner surface of the aperture are spaced apart by a distance of between 0.2-5 mm, supplying feed gas to the tubes of the reactor, and conducting exothermic catalytic vapor phase oxidation while controlling the temperatures for the heat transfer medium in each of the zones so that the temperature difference between each of the zones can be maintained between 0.degree.-100.degree. C.

Abstract: A process for catalytic vapor phase oxidation which comprises using a fixed-bed shell and tube heat exchange type reactor in which a bundle of a multiplicity of tubes filled with at least one type of oxidizing catalyst are disposed in a shell and these tubes are passed through the apertures formed in at least one perforated shield plate to partition the inside of the shell into at least two heat transfer medium feed zones and in such a manner that each of the tubes passing through the perforated shield plate is not in direct contaction with the shield plate but the outer surface of the tube and the inner surface of the aperture are spaced apart by a distance of between 0.2-5 mm, supplying feed gas to the tubes of the reactor, and conducting exothermic catalytic vapor phase oxidation while controlling the temperatures for the heat transfer medium in each of the zones so that the temperature difference between each of the zones can be maintained between 0.degree.-100.degree. C.