Fatty methyl ester hydrogenation to fatty alcohol: Reaction inhibition by glycerine and monoglyceride

Abstract

The present work demonstrates the rate-limiting effect of varying levels of both glycerine and monoglyceride through a series of batch hydrogenations of fatty dodecyl methyl ester, using copper chromite as the catalyst. Reactions were carried out at 3000 psig H 2 , 280°C with catalyst levels varying between 1.25 and 1.80%. With increasing contaminant levels of glycerine (0.0, 0.1, 0.5, 5 wt%), conversion of fatty methyl ester to alcohol is correspondingly reduced (95, 89, 80, 2 wt%). On a molar basis of contaminant, monoglyceride equally reduces the conversion of methyl ester to alcohol. In both cases the latent appearance of fatty-fatty ester results from the slower hydrogenation rate. Chemistry is proposed outlining the thermal decomposition of glycerine or glyceride to intermediate components (acetol and acrolein), leading to the generation of propanediols. Experimental studies indicate that diols effectively deactivate the copper chromite catalyst, limiting the rate of fatty methyl ester hydrogenation. Catalyst deactivation is not permanent, suggesting catalyst site blockage by physical adsorption of the polyhydroxyl components. The complete understanding of this interaction holds promise for the development of glycerine/monoglyceride-insensitive catalysts. In addition, a brief overview of methyl ester hydrogenation inhibition effects of some heteroelements, water, and soap is presented. FIG. 3. Dodecyl methyl ester hydrogenation (depletion) vs. time as a function of glycerine (Gly) contamination. FIG. 4. Dodecanol generation vs. time as a function of glycerine (Gly) contamination. FIG. 5. Dodecyl dodecanoate generation and depletion vs. time as a function of glycerine (Gly) contamination. JAOCS, Vol. 76, no. 8 (1999) SCHEME 2 FIG. 7. Hydrogenation of dodecyl methyl ester with time in the presence or absence of 1,2-propanediol.

Deactivation Mechanism of Cu/Zn Catalyst Poisoned by Organic Chlorides in Hydrogenation of Fatty Methyl Ester to Fatty Alcohol

“…2, the selectivity of lauryl alcohol decreased slightly at first, from 97% to about 85%, and then sharply, from about 85% to about 20%, with the chlorine concentrations increasing from 0 to 0.5 mmol/ g catalyst . According to reference [27], as the lauryl alcohol generation decreases with increasing contaminant level, so follows the generation of the fatty-fatty ester, the appearance of its maximal level increasingly delayed. Behavior of this system is similar to hydrogenations under unfavorable thermodynamic conditions, i.e., low H 2 pressure or low temperature.…”

Deactivation study of Ru‐Sn‐B/Al2O3 catalysts during selective hydrogenation of methyl oleate to fatty alcohol

“…The catalyst with 1000 ppm of S becomes nearly inactive. More experimental data on copper chromite deactivation were reported by Thakur et al…”

Effect of water on Cu/Zn catalyst for hydrogenation of fatty methyl ester to fatty alcohol

“…Fully pre-reduced catalyst appears to be relatively immune to low levels of water contamination, e.g., 0.1 wt% of water in methyl laurate. Thakur [23] investi- …”

“…Works [21][22][23] have been carried out for nature of the reaction inhibition caused by those compounds. Controversies still remain concerning the effect of water on the activity of the catalyst.…”

“…Controversies still remain concerning the effect of water on the activity of the catalyst. In some references [23,24], the catalyst was put in the reactor, and reduced in the reactor. The authors suggested that the presence of water inhibited the reduction of catalyst to its active form and blocked active sites by occlusion which resulted in lower activity of the catalyst, while others [21] showed that water had no influence on the catalyst activity.…”