TH81467B - The process for preparing propylene oxide. - Google Patents

Abstract

DC60 (09/08/44) A procedure for the preparation of propylene oxide in the presence of methanol, where propylene oxide is separated from a mixture containing propylene oxide and methanol, and the resulting mixture containing methanol is processed, which involves separating methanol from a mixture containing methanol and methyl formate during the processing.

Claims (9)

OCR 08PV 1. The process for the preparation of propylene oxide in the presence of methanol in which (i) in at least one reaction step propylene oxide is prepared from propylene and hydrogen peroxide in the presence of methanol, giving a mixture (Gi) consisting of methanol, propylene oxide and water, (ii) propylene oxide is separated from the mixture (Gi) giving a mixture (Gii) consisting of methanol and water, (iii) water is separated from the mixture (Gii) giving a mixture (Giii) consisting of methanol and methylformate, (iv) methanol is separated from the mixture (Giii), and (v) the methanol separated in (iv) is fed back into (i). 2. The process under Claim 1, in which the separation of methanol from a mixture (Giii) comprising methanol and methylformate is carried out in a distillation column with at least 5 theoretical plates at a pressure ranging from 0.2 to 50 bar. 3. The process under claim 1 or 2 where the methanol separated in (iv) at the time of workup contains less than 500 ppm of methylformate. 4. Any of the processes under Requisitions 1 through 3 in which the separation of water in (i) from the mixture (Gii) is carried out by distillation using a distillation column with at least 5 theoretical plates 20, where the distillation is carried out at a pressure ranging from 0.5 to 40 bar. 5. Any of the processes under claims 1 through 3 in which water is removed by distillation in (iii), where (W) of a mixture (Gw) primarily composed of methanol and methylformate is separated from mixture (Gii) at the top of the first distillation column, (x) the mixture obtained at the bottom of the first distillation column is used as feed for the second distillation column, (y) of a mixture (Gy) primarily composed of methanol and methylformate is obtained from the top of the second distillation column, and (z) mixtures (Gw) and (Gy) are combined to obtain mixture (Giii). 6. Any of the processes under claims 1 through 5 in which propylene oxide prepared in (i) is separated by distillation from the mixture (Gi). 7. Any of the processes under Requisitions 1 through 5 in which the separation of propylene oxide in (ii) is carried out in at least two steps of (a) and (b), in which (a) propylene is separated from mixture (G) which, apart from methanol, propylene oxide and water, contains propylene that has not been previously reacted in (1) to yield mixture (Ga) containing methanol, propylene oxide and water, and (b) propylene oxide is separated from mixture (Ga) to yield mixture (Gii). 8. The process pursuant to claim 7, where the separation in (a) and (b) is carried out by distillation (a) at a pressure range from 0.2 to 25 bar in a column with at least 5 theoretical plates and (b) at a pressure range from 0.3 to 10 bar in a column with at least 20 theoretical plates. 9. Any of the processes under Requisitions 1 through 8 in which propylene oxide is prepared using a zeolite catalyst, preferably a titanium silicalite catalyst, and specifically a titanium silicalite catalyst with the TS-1 structure.