Abstract: A method for producing N-vinyl-2-pyrrolidone by crystallization including: controlling a water content in a feed N-vinyl-2-pyrrolidone solution at an inlet of a crystallizer so as to be not lower than 0.7% by weight and not higher than 10% by weight based on the total weight of the N-vinyl-2-pyrrolidone solution; and supplying the feed N-vinyl-2-pyrrolidone solution to a crystallization process.

Abstract: A method for producing N-vinyl-2-pyrrolidone by crystallization including: controlling a water content in a feed N-vinyl-2-pyrrolidone solution at an inlet of a crystallizer so as to be not lower than 0.7% by weight and not higher than 10% by weight based on the total weight of the N-vinyl-2-pyrrolidone solution; and supplying the feed N-vinyl-2-pyrrolidone solution to a crystallization process.

Abstract: High-purity NVP can be produced by comprising at least two crystallization processes and supplying the mother liquor from the first crystallization process to the second crystallization process. Further, high-purity NVP can be obtained continuously and stably without plugging caused by depositing of crystals on the heat transfer surface of a crystallizer by controlling the water content in a feed NVP solution at the inlet of the crystallizer so as to be not lower than 0.7% by weight and not higher than 10% by weight.

Abstract: In the production of aziridines or N-vinyl amides respectively from an alkanolamine or an alkanolamide by the known method comprising a reaction step, a collecting step and/or a condensation step, a purifying step, and a recovering step, this invention is directed toward preventing formation of a solid substance in the vacuum pumps and the vacuum lines. The object of this invention is accomplished by performing the decompression at the purifying step and the decompression at the recovering step in mutually different decompression systems.

Abstract: In the production of aziridines or N-vinyl amides respectively from an alkanolamine or an alkanolamide by the known method comprising a reaction step, a collecting step and/or a condensation step, a purifying step, and a recovering step, this invention is directed toward preventing formation of a solid substance in the vacuum pumps and the vacuum lines. The object of this invention is accomplished by performing the decompression at the purifying step and the decompression at the recovering step in mutually different decompression systems.

Abstract: In order to carry out various vapor-phase reactions (e.g., the preparation of aziridine compounds by a vapor-phase intramolecular dehydration reaction) with industrial advantages, there is provided a process which can effectively prevent the adhesion of tarry matter to piping and the like. This process is applicable, for example, to the preparation of aziridine compounds by using a reactor for carrying out the vapor-phase intramolecular dehydration reaction of an alkanolamine, a collection column for collecting an aziridine compound present in the reaction gas, and a distillation column for distilling the collector liquid to obtain a purified aziridine compound, and is characterized in that at least the piping section extending from the outlet of the reactor to the inlet of the collection column is maintained at a temperature which is not lower than 200° C., or in that the reaction gas is brought into contact with a collector prior to its introduction into the collection column.

Abstract: There is provided a method of efficiently removing polymer stuck to the inside and/or on the surface of packings of a distillation tower, when nitrogen-containing polymerizable monomers (for example, ethyleneimine) are distilled. Said method consists of washing the inside and/or packings of a distillation tower with an acidic liquid (for example, aqueous solution of acetic acid).

Abstract: In the case where a carbon steel shell and tube type reactor is used and, for example, ethylene is subjected to catalytic gaseous oxidation to manufacture ethylene oxide, if rust is formed on the internal surface of the tubes, impurities such as aldehydes are formed. The cause of formation of the rust is that when the catalyst in the reactor is exchanged, dew is formed on the internal surface of the tubes. The present invention provides, as a method for preventing the rust formation, a method which comprises, in conducting the catalyst exchange work, maintaining the temperature of the internal surface of the tubes higher than the dew point at the work atmosphere (for example, filling the shell side with water and maintaining the temperature of the water higher than the temperature of the atmosphere).

Abstract: A method for the production of monoethylene glycol of high purity is disclosed which comprises subjecting ethylene to catalytic vapor phase oxidation with a molecular oxygen-containing gas thereby obtaining an ethylene oxide-containing gas, exposing the ethylene oxide-containing gas to an absorbing solution and stripping the resultant ethylene oxide-containing solution in a stripper, condensing the vapor emanating from the top of the stripper thereby obtaining crude ethylene oxide, subjecting at least part of the crude ethylene oxide to a hydration reaction, adding an alkaline substance to the hydration reaction solution in an amount of not less than 0.5 atomic equivalent weight relative to the chlorine atom contained in the hydration reaction solution or dehydrating the hydration reaction solution and introducing the side cut technique to the monoethylene glycol rectification column, and acquiring the monoethylene glycol from the side cut part.

Abstract: In a composite process for subjecting ethylene to catalytic gas phase oxidation thereby obtaining ethylene oxide and causing this ethylene oxide to react with water thereby obtaining ethylene glycol, a method for producing the ethylene glycol is provided which permits effective utilization of the energy at the step for dehydrating and concentrating the resultant aqueous ethylene glycol solution. In the production of ethylene glycol by the supply of the aqueous ethylene glycol solution to a concentrating treatment at the multi-effect evaporator, the method contemplated by this invention for the production of ethylene glycol comprises utilizing as the source of heating at least one specific step the steam generated in the multi-effect evaporator.

Abstract: In order to carry out various vapor-phase reactions (e.g., the preparation of aziridine compounds by a vapor-phase intramolecular dehydration reaction) with industrial advantages, there is provided a process which can effectively prevent the adhesion of tarry matter to piping and the like. This process is applicable, for example, to the preparation of aziridine compounds by using a reactor for carrying out the vapor-phase intramolecular dehydration reaction of an alkanolamine, a collection column for collecting an aziridine compound present in the reaction gas, and a distillation column for distilling the collector liquid to obtain a purified aziridine compound, and is characterized in that at least the piping section extending from the outlet of the reactor to the inlet of the collection column is maintained at a temperature which is not lower than 200° C., or in that the reaction gas is brought into contact with a collector prior to its introduction into the collection column.

Abstract: There is provided a method of efficiently removing polymer stuck to the inside and/or on the surface of packings of a distillation tower, when nitrogen-containing polymerizable monomers (for example, ethyleneimine) are distilled. Said method consists of washing the inside and/or packings of a distillation tower with an acidic liquid (for example, aqueous solution of acetic acid).

Abstract: In a composite process for subjecting ethylene to catalytic gas phase oxidation thereby obtaining ethylene oxide and causing this ethylene oxide to react with water thereby obtaining ethylene glycol, a method for producing the ethylene glycol is provided which permits effective utilization of the energy at the step for dehydrating and concentrating the resultant aqueous ethylene glycol solution. In the production of ethylene glycol by the supply of the aqueous ethylene glycol solution to a concentrating treatment at the multi-effect evaporator, the method contemplated by this invention for the production of ethylene glycol comprises utilizing as the source of heating at least one specific step the steam generated in the multi-effect evaporator.

Abstract: In manufacturing ethylene oxide by catalytic vapor phase oxidation of ethylene, a process comprising adding, as liquid, an organic halide as a reaction inhibitor into the ethylene raw material gas flow is provided. According to this process, ethylene oxide can be manufactured stably and in high selectivity.

Abstract: In manufacturing ethylene oxide by catalytic vapor phase oxidation of ethylene, a process comprising adding, as liquid, an organic halide as a reaction inhibitor into the ethylene raw material gas flow is provided. According to this process, ethylene oxide can be manufactured stably and in high selectivity.