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 Na-FAU zeolite catalyst impregnated with multifunctional 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, exceeding the selectivity target of 90% for commercial viability. During continuous reaction at 300 °C, the amine loadings in Na-FAU remained constant for 12BPE but decreased as much as 83% for 44TMDP. 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. 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.