A process for recovering by-products of a substituted aromatic hydrocarbon oxidation reaction, comprising cooling one or more of a vapor stream directed to a high-pressure absorber (380), a solvent-rich scrubbing stream (381) directed to a high-pressure absorber (380), and a water-rich liquid stream (383) directed to a solvent recovery zone, by heat exchange with a cooled spent scrubbing liquid withdrawn from a low-pressure scrubber (430).

A process for recovering by-products of a substituted aromatic hydrocarbon oxidation reaction, comprising cooling one or more of a vapor stream directed to a high-pressure absorber (380), a solvent-rich scrubbing stream (381) directed to a high-pressure absorber (380), and a water-rich liquid stream (383) directed to a solvent recovery zone, by heat exchange with a cooled spent scrubbing liquid withdrawn from a low-pressure scrubber (430).

A novel process can be used for purifying methyl methacrylate (MMA) contaminated with low-boiling components by distillation, where the process involves producing MMA by oxidative esterification, and a crude product containing methyl propionate (MP), methyl isobutyrate (MIB), and methacrolein (MAL) as low-boiling components. The process is compatible with MMA produced from C.sub.2-based methacrolein containing the low-boiling components specified.

A novel process can be used for purifying methyl methacrylate (MMA) contaminated with low-boiling components by distillation, where the process involves producing MMA by oxidative esterification, and a crude product containing methyl propionate (MP), methyl isobutyrate (MIB), and methacrolein (MAL) as low-boiling components. The process is compatible with MMA produced from C.sub.2-based methacrolein containing the low-boiling components specified.

The invention provides a method for separating and preparing triterpenoid acids in seabuckthorn pomace, which mainly comprises extracting and purifying triterpenoid acids, and purifying and separating using a chromatographic method under specific conditions. The present invention effectively separates two groups of isomers of triterpene acid from seabuckthorn pomace simultaneously at the first time through specific methods and conditions, and provides possibility for further research and utilization of seabuckthorn pomace.

The invention provides a method for separating and preparing triterpenoid acids in seabuckthorn pomace, which mainly comprises extracting and purifying triterpenoid acids, and purifying and separating using a chromatographic method under specific conditions. The present invention effectively separates two groups of isomers of triterpene acid from seabuckthorn pomace simultaneously at the first time through specific methods and conditions, and provides possibility for further research and utilization of seabuckthorn pomace.

A diester-based material can be prepared continuously including a reaction part in which a total of n reaction units from a first reaction unit to an nth reaction unit are connected in series, the reaction unit including a reactor which esterifies dicarboxylic acid and alcohol, includes: esterifying dicarboxylic acid and alcohol in a reactor of the first reaction unit to produce a reaction product, and supplying a lower discharge stream including the reaction product to a reaction unit at a rear end, wherein an operating pressure of the reactor of the first reaction unit is 0.4 kg/cm.sup.2G to 5.5 kg/cm.sup.2G, an operating pressure is reduced from a reactor of any one reaction unit of reaction units from a second reaction unit to the nth reaction unit, and an operating temperature is increased from the reactor of the first reaction unit to the reactor of the nth reaction unit.

A diester-based material can be prepared continuously including a reaction part in which a total of n reaction units from a first reaction unit to an nth reaction unit are connected in series, the reaction unit including a reactor which esterifies dicarboxylic acid and alcohol, includes: esterifying dicarboxylic acid and alcohol in a reactor of the first reaction unit to produce a reaction product, and supplying a lower discharge stream including the reaction product to a reaction unit at a rear end, wherein an operating pressure of the reactor of the first reaction unit is 0.4 kg/cm.sup.2G to 5.5 kg/cm.sup.2G, an operating pressure is reduced from a reactor of any one reaction unit of reaction units from a second reaction unit to the nth reaction unit, and an operating temperature is increased from the reactor of the first reaction unit to the reactor of the nth reaction unit.

A process can be used for preparing methyl methacrylate by direct oxidative esterification of methacrolein. Methyl methacrylate is used in large amounts for preparing polymers and copolymers with other polymerizable compounds. In addition, methyl methacrylate is an important synthesis unit for a variety of specialty esters based on methacrylic acid (MAA) which can be prepared by transesterification with the appropriate alcohol. There is consequently a great interest in very simple, economic and environmentally friendly processes for preparing this starting material. A corresponding optimized workup of the reactor output from the oxidative esterification of methacrolein, through which unconverted methacrolein (MAL) can be recycled very efficiently, is useful. In addition, the process can be carried out in a manner which compared to known variants is markedly more energy- and water-saving.

A process can be used for preparing methyl methacrylate by direct oxidative esterification of methacrolein. Methyl methacrylate is used in large amounts for preparing polymers and copolymers with other polymerizable compounds. In addition, methyl methacrylate is an important synthesis unit for a variety of specialty esters based on methacrylic acid (MAA) which can be prepared by transesterification with the appropriate alcohol. There is consequently a great interest in very simple, economic and environmentally friendly processes for preparing this starting material. A corresponding optimized workup of the reactor output from the oxidative esterification of methacrolein, through which unconverted methacrolein (MAL) can be recycled very efficiently, is useful. In addition, the process can be carried out in a manner which compared to known variants is markedly more energy- and water-saving.