Selective Dehydration of Lactic Acid to Acrylic Acid in the Gas Phase

Background• In order to reduce global reliance on fossil fuels

(especially petroleum), research has been conducted on the conversion of biorenewable feedstocks into products typically produced through petroleum cracking [1].

• Lactic acid, the most prevalent product of the fermentation process, has been dehydrated to acrylic acid – a precursor for plastics – over a variety of salts and catalysts. Because of acrylic acid’s current industrial source as a product of petroleum cracking, the conversion of renewable lactic acid into acrylic acid is of particular interest to green chemists [2].

• The highest selectivity to acrylic acid ever achieved [S(AA)=72.3%] was accomplished through modification of zeolite Na-Y [3]. Therefore, investigations into the modification of zeolite Na-Y and the effects of these modifications are currently being undergone

Purpose• To investigate the effects of different forms of Na-Y

zeolite [impregnations with different cations] on the catalyst’s ability to selectively dehydrate lactic to acrylic acid in the gas phase. It is hoped that this investigation will allow tailoring of catalyst properties, such as basic and acidic characteristics, and will lead to a better understanding of these characteristics on the selectivity of the catalyst.

Methods• Zeolite catalysts were prepared through wet-

impregnation of a standardized Na-Y zeolite.

• The evaporation of aqueous lactic acid is carried out using a glass reactor. The liquid feed is pumped into an evaporation zone located above the catalyst and the vapor is driven through the catalyst bed by nitrogen. Zeolite catalyst is utilized in a fixed-bed flow reactor with integrated evaporator. Products are collected in a cooling trap utilizing a dry ice-acetone bath.

Ph.D candidate Gregor Nafe with reactor used for selective dehydration of lactic acid in the gas phase

On a trip around Lake Geneva at the picturesque town of Meersburg.

Jonathan Hunt, Centre College

Acrylic acid A can be produced by dehydration of lactic acid, with propionic acid B, acetaldehyde C, 2,3-pentanedione D and polylactic acid (PLA) E being the main side products.

Flow apparatus for evaporation inside the vapour-phase reactor.

Application of Results• Data collected from these experiments contribute to a

better understanding of the zeolite catalysts, their acidic and basic properties, and how to manipulate them

• Such understanding could lead to the synthesis of catalysts which may be used in industry, allowing lactic acid to serve as a feasible precursor for acrylic acid on a large scale

References[1] J. Zhang, Y. Zhao, M. Pan, X. Feng, W. Ji, C.-T. Au, ACS Catal. 1 (2011) 32-41. [2] C. T. Lira, P. J. McCrackin, Ind. Eng. Chem. Res. 32 (1993) 2608-2613. [3] G. C. Gunter, D. J. Miller, J. E. Jackson, J. Catal. 148 (1994) 252-260.