Multifunctional Amine Modifiers for Selective Dehydration of Methyl Lactate to Acrylates

Dehydration of methyl lactate to acrylic acid and methyl acrylate was experimentally evaluated over a Na-FAU zeolite catalyst impregnated with multifunc-tional diamines. 1,2-Bis(4-pyridyl)ethane (12BPE) and 4,4 '-trimethylenedipyridine (44TMDP), at a nominal loading of 40 wt % or two molecules per Na-FAU supercage, afforded a dehydration selectivity of 96 +/- 3% over 2000 min time on stream. Although 12BPE and 44TMDP have van der Waals diameters approximately 90% of the Na-FAU window opening diameter, both flexible diamines interact with internal active sites of Na-FAU as characterized by infrared spectroscopy. During continuous reaction at 300 degrees C, the amine loadings in Na-FAU remained constant for 12BPE but decreased as much as 83% for 44TMDP. Tuning the weighted hourly space velocity (WHSV) from 0.9 to 0.2 h-1 afforded a yield as high as 92% at a selectivity of 96% with 44TMDP impregnated Na-FAU, resulting in the highest yield reported to date.

Automated summary

Dehydration of methyl lactate to acrylic acid and methyl acrylate was efficiently achieved over a Na-FAU zeolite catalyst impregnated with multifunctional diamines. 12BPE and 44TMDP with a loading of 40 wt% or two molecules per Na-FAU supercage showed a dehydration selectivity of 96%, with 44TMDP achieving the highest reported yield of 92% at a selectivity of 96% by tuning the weighted hourly space velocity.