Acrylic acid and the four primary acrylate derivatives are the cornerstone of a $10B market with broad application across super-absorbent polymers, paints, coatings, and adhesives industries. Producing these chemicals necessary for modern life from sustainable pathways is of key interest. We focus on the use of feeds derived from lactic acid, a product sustainably fermented from a range of bio-derived sugar sources.<br/><br/>Co-feeding an inert and site-selective chemical titrant to form an inorganic / organic composite can provide desirable selectivity tuning. Here, a selectivity enhancement from 60 to upwards of 80 C % was demonstrated for methyl lactate dehydration to methyl acrylate and acrylic acid over a composite Na-FAU based zeolite catalyst using amines as titrants to suppress side reactions on in situ-generated Brønsted acid sites (BASs). We evaluate the effectiveness of BAS titration by considering both the basicity and steric properties of the titrant molecule with the goal to maximize the selectivity enhancement and present here the results of several different amine titrants which outperform the previously studied pyridine. While higher basicity of titrant amines favors stronger adsorption on BASs, steric limitations hinder site binding through contributions from internal diffusion limitations and local steric repulsion between the titrant and the zeolite wall around the BAS. Titrant bases with proton affinities above ∼1040 kJ/mol and sizes below 85% of the NaY supercage window or pore diameter are predicted to afford dehydration selectivities above 90 C % to acrylate products.

On increasing dehydration selectivity of methyl lactate to acrylates with inorganic-organic composite catalysts

ACS Spring 2022

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