IES60958B2 - Solvent purification (Methanol) - Google Patents

Description

Solvent Purification The invention relates to solvent purification, in particular to a process for purifying Methanol containing impurities such as Acetone, Methyl Ethyl Ketone, Water, Formic Acid, Formaldehyde, Acetic Acid and Methyl Esters, catalytic amounts of acid and the like.

Methanol is widely used in selective recrystallisation and extractive distillation. Because of its favourable dielectric, solvent and optical properties it is also widely used in analytical chemistry, particularly in high performance liquid chromatography (hplc), organic synthesis, pesticide residue analysis, UV and IR spectroscopy, purge and trap analysis, and DNA and peptide synthesis .

As analytical chemistry techniques and analytical machines become ever more sophisticated there is a need to develop processes for producing Methanol to a very high level of purity for use as a standard in such equipment.

This invention is therefore directed towards providing a process for producing Methanol having a very high level of purity in a cost efficient manner.

According to the invention there is provided a purification process for the purification of Methanol containing impurities such as Acetone, Methyl Ethyl Ketone, Water, Formic Acid, Formaldehyde, Acetic Acid and Methyl Esters to produce highly purified Methanol, the process comprising of the steps of :adding a reducing agent to Methanol containing said impurities; - 2 adding a strong base to the mixture; distilling the mixture in a distillation column; and recovering purified Methanol from the distillation column.

In one particularly preferred embodiment of the invention the Methanol is further purified by adding an additional base to the mixture prior to distillation. Preferably, the additional base is a weak base such as sodium carbonate.

Preferably the mixture is heated after addition of the reducing agent. Advantageously the mixture is heated to a temperature of at least 65°C for a period of one hour.

In a preferred embodiment of the invention, after addition of the base, the mixture is heated to reflux and the mixture is sampled over time to monitor the levels of impurities present.

In one embodiment of the invention the mixture is cooled prior to addition of the base.

Preferably, the reducing agent is lithium aluminium 20 hydride.

The invention also provides purified Methanol whenever purified by the process of the invention.

The invention will be more clearly understood from the following description thereof given by way of example only with reference to the accompanying drawing which is a schematic diagram of a custom designed distillation apparatus used in the process of the invention.

Referring to the drawing, there is illustrated a custom designed distillation apparatus used in the process of the invention comprising a distillation column 1 of packed raschig rings having from 30 to 40 theoretical plates. Feed material is added into a boiling vessel 2 through an inlet valve 3. The feed material is heated by passing through a reboiler 5 having a steam heated coil 6. Vapour from the distillation column 1 is condensed by passing cooling water through a coil 7 in the condenser 8. Reflux material is returned to the column 1 through a reflux line 9. When the desired purity level has been reached the material is fed through an outlet line 10 to a collection vessel 12. The material may be passed through molecular sieves 11 prior to delivery to the collection vessel 12.

EXAMPLE Feedstock Methanol containing impurities such as Acetone, Methyl Ethyl Ketone, Water, Formic Acid, Formaldehyde, Acetic Acid and Methyl Esters was purified by the following process . 100L of feedstock Methanol is added to the reflux vessel described above and approximately 50g of a reducing agent such as lithium aluminium hydride is added. A small quantity of a strong base such as potassium hydroxide is also added. The strong base acts as an hydrolysing agent.

The mixture is then heated for at least one hour at a temperature of at least 65°C. A weak base such as sodium carbonate is then added to the mixture in an amount of at least lOOg (up to 500g) and the mixture is heated to reflux. The levels of impurity present are monitored. When the levels of impurities have reached desired values the mixture is allowed to cool.

The Methanol purified by this process has a purity of at least 99.9% with a water content of less than 0.1%, an acidity level of less than .001% and a residue level of less than .0001%.

The high grade purified Methanol is used in HPLC analysis and has a wide range of application including applications in organic synthesis and in residue analyses, purge and trap analysis and UV-IR Spectroscopy.

The invention is not limited to the embodiment 10 hereinbefore described which may be varied in detail.

Claims (5)

1. A purification process for the purification of Methanol containing impurities such as Acetone, Methyl Ethyl Ketane, Water, Formic Acid, Formaldehyde, Acetic Acid and Methyl Esters to produce Methanol, the process comprising the steps of :adding a reducing agent to Methanol containing impurities; adding a strong base to the mixture; distilling the mixture in a distillation column; and recovering purified Methanol from the distillation column.

2. A process as claimed in claim 1 wherein the strong base is potassium hydroxide.

3. A process as claimed in claim 1 or 2 wherein the Methanol is further purified by adding an additional base, preferably a weak base such as sodium carbonate to the mixture prior to distillation, preferably the mixture is heated to a temperature of at least 65°C for a period of at least one hour, after addition of the reducing agent, preferably, after addition of the base, the mixture is heated to reflux and the mixture is sampled over time to monitor the levels of impurities present, preferably the reducing agent is lithium aluminium hydride.

4. A process substantially as hereinbefore described with reference to the Examples.

5. Purified Methanol whenever purified by a process as claimed in any preceding claim.