Sebacic acid process, catalysts

A number of process improvements have been described, and iaclude the use of white mineral oil having a boiling range of 300—400°C (60) or the use of a mixture of cresols (61). These materials act to reduce the reaction mixture s viscosity, thus improving mixing. Higher sebacic acid yields are claimed by the use of catalysts such as barium salts (62), cadmium salts (63), lead oxide, and salts (64). 

Another alternative method to produce sebacic acid iavolves a four-step process. First, butadiene [106-99-0] is oxycarbonylated to methyl pentadienoate which is then dimerized, usiag a palladium catalyst, to give a triply unsaturated dimethyl sebacate iatermediate. This unsaturated iatermediate is hydrogenated to dimethyl sebacate which can be hydrolyzed to sebacic acid. Small amounts of branched chain isomers are removed through solvent crystallizations giving sebacic acid purities of greater than 98% (66). 

To understand how to control process conditions to give methyl, 4-pentadienoate, the reaction mechanism must be examined. (See Equation 2.). -palladium hydride elimination from 4 gives rise to trans and cis-methyl penta-, 4-dienoate which is the desired monocarbonylation intermediate for sebacic acid. The desired mono-carbonylation reaction is promoted by low carbon monoxide pressure ( 1000 psig) while high pressure (1800 psig) gives excellent 1,4-dicarbonylation product yield. The mono-carbonylation reaction is also facilitated by using a Lewis Acid as a co-catalyst and iodide as the preferred palladium counter-ion (Table III.). Chloride is the preferred palladium counter-ion for 1,4-dicarbonylation. 

There are several processing steps involved to form DMDA from sebacic acid [10]. Firstly, sebacic acid is exposed and reacts with a nitrogen source such as gaseous ammonia to form diammonium sebacate. Upon continuous dehydration at elevated temperatures (200-220 °C) the dinitrile octamethylene dicyanide (C10H16N2) is formed which, after purification, is hydrogenated (80-100 °C, 2.5 MPa) in the presence of KOH and a nickel catalyst. Pure DMDA is subsequently obtained through vacuum distillation. 

The synthesis of terpoly(ester-6-ether-6-amide)s is a four-step process (Scheme 2) [12,17-20]. The second, third and fourth step take place in the presence of a magnesium titanate organometallic complex as a catalyst (10 wt% solution in n-butanol). The first step involves a hydroljdic condensation polymerization (the pressure decreases from 0.8-1.5 MPa to 0.1 MPa, at 280-320°C for 6-10 h) in the presence of sebacic acid as a stabilizer of the molecular weight. 

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