A polyester polyol is synthesized through an esterification reaction with a sebacic acid by-product fatty acid as a raw material; wherein the sebacic acid by-product fatty acid is refined from a by-product produced during preparing a sebacic acid from a castor oil; the sebacic acid by-product fatty acid includes, in weight percentage: a palmitic acid 15-25%, a stearic acid 10-16%, an oleic acid 45-57%, and a linoleic acid 12-28%. A method for preparing the polyester polyol is provided, as well as a polyurethane controlled-release fertilizer envelope and a polyurethane controlled-release fertilizer. The sebacic acid by-product fatty acid is used as a raw material to synthesize the polyester polyol because of a low price. The prepared fertilizer has excellent envelope and controlled-release performance, product structure performance is stable, cost performance is high, and degradation performance is sufficient after being applied to soil.

A polyester polyol is synthesized through an esterification reaction with a sebacic acid by-product fatty acid as a raw material; wherein the sebacic acid by-product fatty acid is refined from a by-product produced during preparing a sebacic acid from a castor oil; the sebacic acid by-product fatty acid includes, in weight percentage: a palmitic acid 15-25%, a stearic acid 10-16%, an oleic acid 45-57%, and a linoleic acid 12-28%. A method for preparing the polyester polyol is provided, as well as a polyurethane controlled-release fertilizer envelope and a polyurethane controlled-release fertilizer. The sebacic acid by-product fatty acid is used as a raw material to synthesize the polyester polyol because of a low price. The prepared fertilizer has excellent envelope and controlled-release performance, product structure performance is stable, cost performance is high, and degradation performance is sufficient after being applied to soil.

A polyester polyol is synthesized through an esterification reaction with a sebacic acid by-product fatty acid as a raw material; wherein the sebacic acid by-product fatty acid is refined from a by-product produced during preparing a sebacic acid from a castor oil; the sebacic acid by-product fatty acid includes, in weight percentage: a palmitic acid 15-25%, a stearic acid 10-16%, an oleic acid 45-57%, and a linoleic acid 12-28%. A method for preparing the polyester polyol is provided, as well as a polyurethane controlled-release fertilizer envelope and a polyurethane controlled-release fertilizer. The sebacic acid by-product fatty acid is used as a raw material to synthesize the polyester polyol because of a low price. The prepared fertilizer has excellent envelope and controlled-release performance, product structure performance is stable, cost performance is high, and degradation performance is sufficient after being applied to soil.

A polyester polyol is synthesized through an esterification reaction with a sebacic acid by-product fatty acid as a raw material; wherein the sebacic acid by-product fatty acid is refined from a by-product produced during preparing a sebacic acid from a castor oil; the sebacic acid by-product fatty acid includes, in weight percentage: a palmitic acid 15-25%, a stearic acid 10-16%, an oleic acid 45-57%, and a linoleic acid 12-28%. A method for preparing the polyester polyol is provided, as well as a polyurethane controlled-release fertilizer envelope and a polyurethane controlled-release fertilizer. The sebacic acid by-product fatty acid is used as a raw material to synthesize the polyester polyol because of a low price. The prepared fertilizer has excellent envelope and controlled-release performance, product structure performance is stable, cost performance is high, and degradation performance is sufficient after being applied to soil.

A method for producing a methanol precursor, methyl trifluoroacetate, having high-purity includes the steps of (a) preparing methyl bisulfate by mixing a catalyst with an acid solution comprising a sulfur-containing acid to provide a first mixture and supplying methane gas to the first mixture to prepare the methyl bisulfate; and (b) preparing methyl trifluoroacetate (CF.sub.3CO.sub.2CH.sub.3) by adding trifluoroacetic acid (CF.sub.3CO.sub.2H) to the first mixture including the methyl bisulfate to provide a second mixture and distilling the second mixture under heating to prepare, separate and purify the methyl trifluoroacetate (CF.sub.3CO.sub.2CH.sub.3). Methanol may be produced by adding water to the methyl trifluoroacetate (CF.sub.3CO.sub.2CH.sub.3). A methyl ester represented by Formula 2 below may be produced by adding a carboxylic acid represented by Formula 1 below to the methyl trifluoroacetate (CF.sub.3CO.sub.2CH.sub.3):
R.sub.1CO.sub.2H  (1), where R.sub.1 is selected from C.sub.1-C.sub.10 alkyl groups,
R.sub.1CO.sub.2CH.sub.3  (2), where R.sub.1 is as defined in Formula 1.

A method for producing a methanol precursor, methyl trifluoroacetate, having high-purity includes the steps of (a) preparing methyl bisulfate by mixing a catalyst with an acid solution comprising a sulfur-containing acid to provide a first mixture and supplying methane gas to the first mixture to prepare the methyl bisulfate; and (b) preparing methyl trifluoroacetate (CF.sub.3CO.sub.2CH.sub.3) by adding trifluoroacetic acid (CF.sub.3CO.sub.2H) to the first mixture including the methyl bisulfate to provide a second mixture and distilling the second mixture under heating to prepare, separate and purify the methyl trifluoroacetate (CF.sub.3CO.sub.2CH.sub.3). Methanol may be produced by adding water to the methyl trifluoroacetate (CF.sub.3CO.sub.2CH.sub.3). A methyl ester represented by Formula 2 below may be produced by adding a carboxylic acid represented by Formula 1 below to the methyl trifluoroacetate (CF.sub.3CO.sub.2CH.sub.3):
R.sub.1CO.sub.2H  (1), where R.sub.1 is selected from C.sub.1-C.sub.10 alkyl groups,
R.sub.1CO.sub.2CH.sub.3  (2), where R.sub.1 is as defined in Formula 1.

Processes are described for purifying a biphenyldicarboxylic acid product containing one or more impurities, particularly at least formylbiphenylcarboxylic acid. In the processes, at least a portion of the biphenyldicarboxylic acid product is contacted with an alcohol under conditions effective to esterify at least part of the biphenyldicarboxylic acid and at least part of the formylbiphenylcarboxylic acid and produce an esterification effluent containing biphenyldicarboxylic acid diester and formylbiphenylcarboxylic acid ester. At least part of the biphenyldicarboxylic acid diester is then separated from the esterification effluent by crystallization. Advantageously, a polyester product may be produced from the separated biphenyldicarboxylic acid diester.

Processes are described for purifying a biphenyldicarboxylic acid product containing one or more impurities, particularly at least formylbiphenylcarboxylic acid. In the processes, at least a portion of the biphenyldicarboxylic acid product is contacted with an alcohol under conditions effective to esterify at least part of the biphenyldicarboxylic acid and at least part of the formylbiphenylcarboxylic acid and produce an esterification effluent containing biphenyldicarboxylic acid diester and formylbiphenylcarboxylic acid ester. At least part of the biphenyldicarboxylic acid diester is then separated from the esterification effluent by crystallization. Advantageously, a polyester product may be produced from the separated biphenyldicarboxylic acid diester.

Processes are described for purifying a biphenyldicarboxylic acid product containing one or more impurities, particularly at least formylbiphenylcarboxylic acid. In the processes, at least a portion of the biphenyldicarboxylic acid product is contacted with an alcohol under conditions effective to esterify at least part of the biphenyldicarboxylic acid and at least part of the formylbiphenylcarboxylic acid and produce an esterification effluent containing biphenyldicarboxylic acid diester and formylbiphenylcarboxylic acid ester. At least part of the biphenyldicarboxylic acid diester is then separated from the esterification effluent by crystallization. Advantageously, a polyester product may be produced from the separated biphenyldicarboxylic acid diester.

The disclosed methods for preparing and isolating carboxylic esters ensure a high product purity and minimize technical complexity. These methods are based on the reaction of a carboxylic acid with an alcohol in an aqueous medium. In some examples, the alcohol is used both for the esterification and for the precipitation of the salts, preferably ammonium salts, formed in the synthesis.