Abstract: A process for regenerating a solid catalyst which has been used for producing propylene oxide through an epoxidation reaction of propylene with an organic peroxide in a reactor packed with the solid catalyst, which comprises allowing a liquid to flow through the catalyst packed in the reactor at a temperature not lower than the maximum reaction temperature of the epoxidation reaction. According to the present invention, a catalyst can be regenerated with extremely high efficiency without taking the catalyst to be regenerated out of the reactor.

Abstract: A process for regenerating a solid catalyst which has been used for producing propylene oxide through an epoxidation reaction of propylene with an organic peroxide in a reactor packed with the solid catalyst, which comprises allowing a liquid to flow through the catalyst packed in the reactor at a temperature not lower than the maximum reaction temperature of the epoxidation reaction.

Abstract: A process for producing 1,3-di-(2-hydroperoxy-2-propyl)benzene comprising an oxidizing step, an extracting step with an aqueous solution and a recycling step wherein the accumulated equilibrium concentration of 1,3-di-(2-hydroxy-2-propyl)benzene in the circulating oil obtained by an extracting step with an aqueous solution is 4.2% by weight or less. The process enables to avoid inconveniences like occlusion of inside space of an apparatus and failure of detection of measuring machines and allows continuous safe operation.

Abstract: A process for extraction of hydroperoxides wherein 1,3-di-(2-hydroperoxy-2-propyl)benzene and 3-(2-hydroxy-2-propyl)-1-(2-hydroperoxy-2-propyl)benzene are extracted from a raw solution comprising 1,3-di-(2-hydroperoxy-2-propyl)benzene, 3-(2-hydroxy-2-propyl)-1-(2-hydroperoxy-2-propyl)benzene and an aqueous sodium hydroxide solution, said process using methyl isobutyl ketone containing not more than 10 ppm by weight of a phenol or phenols as a solvent for extraction.