The invention provides a process for refining bio-based propylene glycol, wherein impurities having boiling points close to that of propylene glycol are separated. In this process, C.sub.5-C.sub.20 oleophilic alcohol compounds, C.sub.5-C.sub.20 alkanes and/or C.sub.4-C.sub.20 oleophilic ketone compounds are subjected to azeotropism as an azeotropic solvent together with the bio-based propylene glycol to obtain an azeotrope containing propylene glycol. Then the azeotropic solvent in the azeotrope is separated to obtain a crude propylene glycol which is further purified to obtain propylene glycol.

The invention provides a process for refining bio-based propylene glycol, wherein impurities having boiling points close to that of propylene glycol are separated. In this process, C.sub.5-C.sub.20 oleophilic alcohol compounds, C.sub.5-C.sub.20 alkanes and/or C.sub.4-C.sub.20 oleophilic ketone compounds are subjected to azeotropism as an azeotropic solvent together with the bio-based propylene glycol to obtain an azeotrope containing propylene glycol. Then the azeotropic solvent in the azeotrope is separated to obtain a crude propylene glycol which is further purified to obtain propylene glycol.

The invention provides a process for refining bio-based propylene glycol, wherein impurities having boiling points close to that of propylene glycol are separated. In this process, C.sub.5-C.sub.20 oleophilic alcohol compounds, C.sub.5-C.sub.20 alkanes and/or C.sub.4-C.sub.20 oleophilic ketone compounds are subjected to azeotropism as an azeotropic solvent together with the bio-based propylene glycol to obtain an azeotrope containing propylene glycol. Then the azeotropic solvent in the azeotrope is separated to obtain a crude propylene glycol which is further purified to obtain propylene glycol.

A product 1,3-butylene glycol, in which 2,4-dinitrophenylhydrazine derivatives of 2-(hydroxyethyl)-2,6-dimethyl-1,3-dioxane have a weight proportion of 90 ppm or less, as calculated from a sum of absorbance of peaks thereof in an HPLC analysis under specific conditions after specific sample preparation.

A product 1,3-butylene glycol, in which 2,4-dinitrophenylhydrazine derivatives of 2-(hydroxyethyl)-2,6-dimethyl-1,3-dioxane have a weight proportion of 90 ppm or less, as calculated from a sum of absorbance of peaks thereof in an HPLC analysis under specific conditions after specific sample preparation.

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).

The invention relates to a process and a plant for producing pure methanol, wherein the crude methanol stream discharged from a methanol synthesis unit is decompressed in a decompression vessel, is subsequently at least partially freed of low-boiling by-products in a prerun column and is then supplied to a single- or multi-stage methanol purification apparatus from which a pure methanol product stream is finally discharged. According to the invention the tops product stream from the prerun column is subjected to a scrubbing step with a methanol-selective scrubbing medium, thus at least partially recovering methanol present and sending a methanol-depleted tops product stream to the offgas disposal apparatus.

The invention relates to a process and a plant for producing pure methanol, wherein the crude methanol stream discharged from a methanol synthesis unit is decompressed in a decompression vessel, is subsequently at least partially freed of low-boiling by-products in a prerun column and is then supplied to a single- or multi-stage methanol purification apparatus from which a pure methanol product stream is finally discharged. According to the invention the tops product stream from the prerun column is subjected to a scrubbing step with a methanol-selective scrubbing medium, thus at least partially recovering methanol present and sending a methanol-depleted tops product stream to the offgas disposal apparatus.

The present invention provides a process for purifying a monoterpene or sesquiterpene having a purity greater than about 98.5% (w/w). The process comprises the steps of derivatizing the monoterpene (or sesquiterpene) to produce a monoterpene (or sesquiterpene) derivative, separating the monoterpene (or sesquiterpene) derivative, and releasing the monoterpene (or sesquiterpene) from the derivative. Also encompassed by the scope of the present invention is a pharmaceutical composition comprising a monoterpene (or sesquiterpene) having a purity greater than about 98.5% (w/w). The purified monoterpene can be used to treat a disease such as cancer. The present monoterpene (or sesquiterpene) may be administered alone, or may be co-administered with radiation or other therapeutic agents, such as chemotherapeutic agents.