The present invention relates to a reaction control method in which a conversion rate of a reaction may be predicted from a flow rate of a feed introduced into a reactor and a flow rate of product water generated in the reactor, and through which the conversion rate of the reactor may be easily controlled.

The invention relates to a method of separating a first contaminant from a feed stream further comprising a condensation polymer. The invention further relates to a reactor system for carrying out the method, comprising at least one depolymerization vessel, configured for depolymerizing a condensation polymer into monomer, dimer, trimer and/or oligomer, which depolymerizing occurs in an alcoholic solvent, wherein said condensation polymer is provided as a feed stream further comprising a first contaminant, the reactor system comprising a separation stage, said separation stage comprising a separation vessel, downstream of the depolymerization vessel, configured for collecting a first contaminant, wherein said first contaminant is separated from the alcoholic solvent on the basis of a density separation so that the first contaminant is arranged on top of the alcoholic solvent.

The invention relates to a method of separating a first contaminant from a feed stream further comprising a condensation polymer. The invention further relates to a reactor system for carrying out the method, comprising at least one depolymerization vessel, configured for depolymerizing a condensation polymer into monomer, dimer, trimer and/or oligomer, which depolymerizing occurs in an alcoholic solvent, wherein said condensation polymer is provided as a feed stream further comprising a first contaminant, the reactor system comprising a separation stage, said separation stage comprising a separation vessel, downstream of the depolymerization vessel, configured for collecting a first contaminant, wherein said first contaminant is separated from the alcoholic solvent on the basis of a density separation so that the first contaminant is arranged on top of the alcoholic solvent.

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 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 for preparing dialkyl terephalate comprising the following steps:—i) providing furan-2,5-dicarboxylate; ii) esterifying the furan-2,5-dicarboxylate with alcohol to form furan-2,5-carboxylic acid dialkyl ester; iii) reacting the furan-2,5-carboxylic acid dialkyl ester with ethylene under Diels Alder conditions, elevated temperature and pressure and in the presence of a catalyst such that dialkyl terephthalate is produced; wherein the Diels-Alder reaction is free from solvent; wherein the catalyst comprises a clay comprising metal ions and having Lewis acidity.

A process for preparing dialkyl terephalate comprising the following steps:—i) providing furan-2,5-dicarboxylate; ii) esterifying the furan-2,5-dicarboxylate with alcohol to form furan-2,5-carboxylic acid dialkyl ester; iii) reacting the furan-2,5-carboxylic acid dialkyl ester with ethylene under Diels Alder conditions, elevated temperature and pressure and in the presence of a catalyst such that dialkyl terephthalate is produced; wherein the Diels-Alder reaction is free from solvent; wherein the catalyst comprises a clay comprising metal ions and having Lewis acidity.

This invention relates to a process for making a polycondensation pre-polyester, a polyester or both, comprising the following steps: A. Acylation of at least one diacid chloride with at least one alcohol to form at least one diester; B. Partial hydrolysis of the diester product of Step A to form at least one monoacid; C. Esterifying the monoacid of Step B with at least one diol to form a diester; D. Reacting the diester of Step C under acidic conditions to form a diacid; and subsequently, performing either Step E or Step F as follows: E. Bisalkylation of the diacid of Step D with at least one haloalcohol to form a pentamer, or F. Esterifiying the diacid of Step D under esterification conditions with at least one diol to form a pentamer, provided that the diol is not the same as the diol used in Step C.

The present disclosure relates to a system which increases the efficiency of an entire process by integrating a reflux unit in a system for producing a diester-based composition in which a plurality of reactors are connected in series.