Effect of process variables, degree of ethoxylation and alcohol structure on relative ethoxylation rate constants

Abstract

Supercritical fluid chromatographic determinations of ethylene oxide distributions in ethoxylated alcohols with subsequent computer calculations of relative propagation to initiation ethoxylation rate constants for each ethoxylated oligomer have been carried out for normal octanol under varying reaction conditions. A number of other alcohols were also ethoxylated under essentially constant conditions. In the normal octanol studies, within an approximately fifteen-fold change in absolute ethoxylation rates due to v~iations in temperature, pressure, and potassium hydroxide catalyst concentration, the data indicate that such changes do not affect ethylene oxide distributions. Suggestions by ear-Her workers of changes in relative ethoxylation rate constants with the average degree of ethoxylation were verified. Chain length for normal alcohol feeds does not affect distributions in the C-8 to C-13 range, but branching at the carbon a to the hydroxyl carbon increases the relative propagation to initiation rate constants, and a secondary alcohol exhibits an even higher ratio.KEY WORDS: Ethoxylated alcohols, ethoxylation process variables, ethylene oxide oligomer distributions, non-ionic surfactants, relative rate constants, and supercritical fluid chromatography.

Biodegradable hyperbranched polyether-lipids with in-chain pH-sensitive linkages

“…Fast proton exchange results in the protonated form of cholesterol and deprotonated adducts of initiator and the first monomer unit. [47][48][49] This leads to different kinetics in the initiation step and the propagation step, since the ethoxylated cholesterol exhibits higher reactivity than the cholesterol alkoxide. Hence, significant amounts of free initiator are found in the reaction mixture when oligomers are targeted.…”

Surfactants

“…This is true for all alkaline catalysts, although the deviations in the case of alkaline-earth compounds are less strongly pronounced than in the case of sodium hydroxide or sodium methoxide [97]. The distribution pattern of the homologous polyethylene glycol ethers in an ethoxylate obtained by alkaline catalysis is independent of the temperature, pressure, and catalyst concentration [98], [99]. The occasionally observed dependence of the homologue distribution on the stirring rate can be attributed to an insufficiently complete mixing of the reactor contents.…”