Process for purifying methanol by distillation

Claim 2

A process for purifying methanol from a starting mixture of synthetic crude methanol consisting essentially of methanol, 8 to 30% by weight water and up to 0.5% by weight ethanol comprising: a. feeding said starting mixture to a distillation column at a level which when said column is in equilibrium operation, the water content within said column at said level is lower than in said mixture producing over a region of the column below the feed level a substantially constant methanol to water weight ratio, b. withdrawing water as bottoms, c. withdrawing product methanol from the upper part of the column, and d. withdrawing a side stream enriched in ethanol from a level below the end of the region remote from the feed level.

Claim 3

A process according to claim 1 in which the ethanol enriched stream is withdrawn at the point at which the methanol mole fraction is 0.4.

Claim 4

A process according to claim 1 wherein said region occupies 10 to 20% of the length of the column.

Claim 5

A process for purifying methanol from a starting mixture of synthetic crude methanol comprising: a. subjecting a crude methanol mixture to water extractive distillation and removing a methanol-containing stream as bottoms: b. subjecting said methanol containing stream as bottoms to a coarse distillation separation of methanol wherein the methanol containing stream is collected overhead to produce a starting mixture consisting essentially of methanol, 8 to 30% by weight water and up to 0.5% by weight ethanol; c. feeding said starting mixture to a distillation column at a level which when said column is in equilibrium operation, the water content is lower within said column at said level than in said mixture producing over a region of the column below the feed level a substantially constant methanol to water weight ratio; d. withdrawing water as bottoms, e. withdrawing product methanol from the upper part of the column, and f. withdrawing a side stream enriched in ethanol from a level below the end of the region remote from the feed level.

Claim 6

A process for purifying methanol from a starting mixture of synthetic crude methanol comprising: a. subjecting a crude methanol mixture to water extractive distillation and removing a methanol-containing stream as bottoms: b. subjecting said methanol containing stream as bottoms to a coarse distillation separation of methanol wherein the methanol containing stream is collected overhead to produce a starting mixture consisting essentially of methanol, 8 to 30% by weight water and up to 0.5% by weight ethanol; c. feeding said starting mixture to a distillation column at a level which when said column is in equilibrium operation, the water content is lower within said column at said level than in said mixture producing over a region of the column below the feed level a substantially constant methanol to water weight ratio; d. withdrawing water as bottoms, e. withdrawing product methanol from the upper part of the column, and f. withdrawing a side stream enriched in ethanol from a level below the end of the region remote from the feed level.

Claim 7

A process for producing purified methanol comprising: a. subjecting a crude methanol mixture containing as impurities water, ethanol and low boiling impurities to a distillation in which said mixture is freed of components boiling at a the boiling point of methanol to produce a starting mixture of methanol, 8 to 30% by weight water and up to 0.5% ethanol; b. feeding said starting mixture to a distillation column at a level which when said column is in equilibrium operation, the water content is lower within said column at said level than in said mixture producing over a region of the column below the feed level a substantially constant methanol to water weight ratio; c. withdrawing water as bottoms, d. withdrawing product methanol from the upper part of the column, and e. withdrawing a side stream enriched in ethanol from a level below the end of the region remote from the feed level.

Claim 8

A process for producing purified methanol comprising: a. subjecting a crude methanol mixture containing as impurities water, ethanol and low boiling impurities to a distillation in which said mixture is freed of components boiling at a the boiling point of methanol to produce a starting mixture of methanol, 8 to 30% by weight water and up to 0.5% ethanol; b. feeding said starting mixture to a distillation column at a level which when said column is in equilibrium operation, the water content is lower within said column at said level than in said mixture producing over a region of the column below the feed level a substantially constant methanol to water weight ratio; c. withdrawing water as bottoms, d. withdrawing product methanol from the upper part of the column, and e. withdrawing a side stream enriched in ethanol from a level below the end of the region remote from the feed level.