Hydroxypropionaldehyde oxidation

Propanediol is a colorless liquid that boils at 210-211°C. It is soluble in water, alcohol, and ether. It is an intermediate for polyester production. It could be produced via the hydroformylation of ethylene oxide which yields 3-hydroxypropionaldehyde. Flydrogenation of the product produces 1,3-propanediol. 

In ambient air, the primary removal mechanism for acrolein is predicted to be reaction with photochemically generated hydroxyl radicals (half-life 15-20 hours). Products of this reaction include carbon monoxide, formaldehyde, and glycolaldehyde. In the presence of nitrogen oxides, peroxynitrate and nitric acid are also formed. Small amounts of acrolein may also be removed from the atmosphere in precipitation. Insufficient data are available to predict the fate of acrolein in indoor air. In water, small amounts of acrolein may be removed by volatilization (half-life 23 hours from a model river 1 m deep), aerobic biodegradation, or reversible hydration to 0-hydroxypropionaldehyde, which subsequently biodegrades. Half-lives less than 1-3 days for small amounts of acrolein in surface water have been observed. When highly concentrated amounts of acrolein are released or spilled into water, this compound may polymerize by oxidation or hydration processes. In soil, acrolein is expected to be subject to the same removal processes as in water. 

Oxidation of aqueous solutions (10% wlw ) of 3-hydroxypropionaldehyde (HPA) in the presence of 3 % Pd/C catalysts at pH 8 produces malonic acid. Complete conversion, with 96.7 % yield, was achieved with large amounts of catalyst (33% wlw Pd relative to HPA) [91]. Starting from 3-hydroxypropionic acid the malonic acid selectivity was 95.4 % at 97 % conversion. In the presence of 5 % Pt/C catalysts (28 % wlw Pt with respect to HPA), aqueous solutions (10% wlw) of 3-hydroxypropionaldehyde were oxidized into 3-hydroxypropionic acid, an intermediate used to prepare pharmaceutical and agricultural products. The best yield, obtained without pH regulation, was 92.9% at 97.2% conversion [92]. 

PROBABLE FATE photolysis photooxidation m atmosphere, photooxidation half-life in air 3.4-33.7 hrs, reacts with photochemically produced hydroxyl radicals with a half-life of 0.001 hr oxidation occurs slowly hydrolysis not an important process volatilization principle transport mechanism, expected to volatilize quickly from dry soil, volatilization half-life from a model river 10 days sorption not an important process biological processes biotrans-formation occurs, biodegradation is slow at low concentrations reversible hydration to beta-hydroxypropionaldehyde, half-life 21 days... 

This process consists of a three-step reaction propylene is oxidized to acrolein, aaolein is hydrated to 3-hydroxypropionaldehyde, which then is reduced to PDO (Amtz 1991). 

This route consists of a two-step reaction. Firstly, ethylene oxide is carbonylated with carbon monoxide and hydrogen to form 3-hydroxypropionaldehyde. 3-Hydroxypropionaldehyde is purified and then reduced to PDO by hydrogen. The chemical catalysts used in the route are important for the selectivity and yield of the products, especially in the first reaction. The availability on a large scale with low cost and stability of ethylene oxide merits the use of this route, but the high cost of equipment and difficulty in preparing the catalysts hamper its industrial applications (Slaugh et al. 1995, 2(X)1). 

Most of the commercial synthesis of 1,3-PD is from acrolein by Degussa (now owned by DuPont) and from ethylene oxide by Shell [13]. The Degussa Company starts from acrolein and the process consists of the following three steps (Scheme 4.1). The first step is the oxidation of propylene to acrolein, the second is the addition of water to produce 3-hydroxypropionaldehyde, and the third is the catalytic hydrogenation of 3-hydroxypropionaldehyde to 1,3-PD. The selectivity of water addition to acrolein is only around 70-80% when zeolites or ion exchange resins are used. Recently, Tsunoda and Nomura [14] reported that a siUcoaluminophosphate-based molecular sieve afforded a selectivity of 96% when the reaction was conducted in aqueous solution at 60 C. 

Previously, PTT was produced based on 1,3-PD by chemical synthesis. The traditional chemical routes of commercial synthesis for 1,3-PD production are from acrolein by DuPont and from ethylene oxide by Shell. The route of DuPont is that acrolein is converted to 3-hydroxypropionaldehyde (3-HPA) by hydration, followed to produce 1,3-PD by hydrogenation (Lawrence and Sullivan, 1972). Shell followed the method of hydroformylation of ethylene oxide to 3-hydroxypropanal. This is subsequently extracted and hydrogenated for the production of 1,3-PD (Sullivan, 1993). 

In the reductive pathway, 3-hydroxypropionaldehyde is formed by the action of a vitamin B 12-dependent glycerol dehydratase. The 3-hydroxypropionaldehyde is then reduced by the enzyme 1,3-PD dehydrogenase. The oxidative and reductive pathways of glycerol dissimilation form a balance, as the role of the PDO pathway is to regenerate reducing equivalents in the form of reduced nicotinamide dinucleotide (NADH2) produced from the dihydroxyacetone pathway (Deckwer 1995 Zeng et al. 1997 Cameron et al. 1998). 

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