A method for purifying 1,3-propanediol, said method comprising the steps of:
(1) The 1,3-propanediol aqueous solution obtained by hydrogenating 1925.24g of 3-hydroxypropionaldehyde was adjusted to pH 5.5 with triethanolamine, heated to 80°C for reflux for 2 hours, and cooled to room temperature to obtain the reaction product;
(2) The reaction product in step (1) is subjected to the first rectification, and the temperature at the bottom of the tower is controlled at 151° C. for dehydration. The moisture content in the obtained 1,3-propanediol-containing product is ≤0.05wt% (still residue), and the product containing 1,3-propanediol The 1,3-propanediol product was subjected to the second vacuum rectification at 0.4kPa and 151°C to remove the heavy components to obtain 194.3g of crude 1,3-propanediol;
(3) The crude 1,3-propanediol in step (2) is heated to 70°C for resin adsorption. Resin adsorption column of styrene and divinylbenzene cross-linked resin, and 70°C circulating water jacket insulation resin;
The product after the resin adsorption is subjected to the third rectification, the pressure of the third rectification is 0.2kPa, the temperature at the bottom of the tower is 103-110°C, the light component impurities are removed, and the fraction at the top of the tower at 76-82°C is collected. 190.5 g of 1,3-propanediol are obtained.
Step 1: In a 100ml reactor, add 20ml of vinyl acetate as raw material for vinyl carboxylate, 20ml of toluene as solvent, 0.2g of Co2(CO)8 as olefin hydroformylation catalyst, and seal the reactor. Replaced 3 times with nitrogen, 3 times with CO+H2 (according to mol ratio, CO:H2=1:1), and pressurized to 2.0 MPa with CO+H2, and heated to 115°C reaction temperature. The CO+H2 pressure in the reactor was adjusted and stabilized at 7.0MPa reaction pressure through the pressure stabilizing valve, the stirring speed was adjusted to 800rmp, and the hydroformylation reaction was started. The CO+H2 consumed by the reaction is indicated by the pressure change of the gas storage tank until the gas is no longer consumed as the end of the reaction. The reaction kettle is lowered to room temperature, discharges unreacted gas, analyzes the reaction product composition with gas chromatography, quantifies by internal standard method, calculates the conversion rate of vinyl acetate, the selectivity to 2-acetoxypropanal and the selectivity to 3-acetoxypropanal Aldehyde selectivity. In this embodiment, the conversion rate of vinyl acetate is 99.0%, the selectivity of 2-acetoxypropionaldehyde is 45.2%, and the selectivity of 3-acetoxypropionaldehyde is 53.4%. The product obtained by the reaction was washed with water 3 times, 50ml/time, the catalyst therein was separated into the water phase, and the remaining organic phase was separated by rectification to separate the solvent toluene and unreacted vinyl acetate to obtain the crude product of the first step reaction. After analysis, the crude product contains 45.0% of 2-acetoxypropionaldehyde, 52.8% of 3-acetoxypropionaldehyde, and a small amount of other components, which are used as raw materials for the second step reaction. The crude product of the first step reaction is further separated by rectification to obtain 2-acetoxypropionaldehyde with a content of 99.5% and 3-acetoxypropanal with a content of 99.5%, which are also used as raw materials for the second step reaction.
The second step: in a 100ml reactor, add 20ml of the crude product obtained in the first step reaction as a reaction raw material, 30ml of toluene as a solvent, and 0.5g of Raney nickel as an aldehyde hydrogenation catalyst, and replace it with nitrogen for 3 times , replaced by hydrogen 3 times, and then pressurized to 0.5MPa with hydrogen. Warming up to 60C reaction temperature. The pressure of the reactor H2 was adjusted and stabilized at 2.0MPa reaction pressure through the pressure stabilizing valve, the stirring speed was adjusted to 800rmp, and the reaction was started. The H2 consumed by the reaction is indicated by the change in the gas storage tank pressure until no more hydrogen is consumed. The reaction kettle is lowered to room temperature, unreacted gas is discharged, the reaction product is formed by gas chromatography analysis, and the internal standard method is used for quantification, and the conversion rate of 2-acetoxypropionaldehyde and 3-acetoxypropionaldehyde is calculated, and the conversion rate of 2-acetoxypropionaldehyde is calculated. The selectivity of propanol and 3-acetoxypropanol. In this embodiment, the conversion rates of 2-acetoxypropanal and 3-acetoxypropanal are respectively 98.2% and 98.5%, the selectivity of 2-acetoxypropanol and the selectivity of 3-acetoxypropanol The selectivities were 98.9% and 99.2%, respectively. Collect the reaction product, remove the catalyst by filtration, and then remove the solvent toluene and unreacted 2-acetoxypropionaldehyde and 3-acetoxypropionaldehyde by rectification to obtain the crude product of the second step reaction as the third step reaction raw material. The crude product contained 44.5% of 2-acetoxypropanol and 53.7% of 3-acetoxypropanol and a small amount of other components. The crude product of the second step reaction is further separated by rectification to obtain 2-acetoxypropanol with a content of 99.5% and 3-acetoxypropanol with a content of 99.5%, which are also used as raw materials for the third step reaction.
The third step: in a 100ml reactor, add 20ml of the crude product obtained in the second step reaction as a reaction raw material, 30ml of water, and 0.2g of concentrated sulfuric acid as an ester hydrolysis catalyst, seal the reactor, replace with nitrogen for 3 times, and keep The nitrogen pressure is 0.2 MPa, the reaction pressure is raised to 80° C., and the reaction is carried out at a constant temperature for 8 hours while stirring. The reaction kettle was lowered to room temperature, and the nitrogen was vented, and the reaction liquid was analyzed by gas chromatography, and the internal standard method was used to quantify, and the conversion rate of 2-acetoxypropanol and 3-acetoxypropanol, and 1,2-propanediol, 1, 3-Propanediol selectivity. In this example, the conversion rates of 2-acetoxypropanol and 3-acetoxypropanol were 98% and 98.5%, respectively, and the selectivities of 1,2-propanediol and 1,3-propanediol were 99.5% and 99.8% respectively. %. Product can obtain 1,2-propanediol, 1,3-propanediol and acetic acid through rectifying separation, wherein 1,2-propanediol, 1,3-propanediol are as product, and acetic acid can be returned to used raw material vinyl carboxylate of the present invention as co-product in the preparation of esters.