An advanced process for producing structurally selective dimer acids to meet new industrial uses

Authors: ZHANG, JIANWEI - South China University Of Technology; Nunez, Alberto; Strahan, Gary; Ashby, Richard - Rick; Huang, Kun; MOREAU, ROBERT - Former ARS Employee; YAN, ZONGCHENG - South China University Of Technology; CHEN, LI - South China University Of Technology; Ngo, Helen

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2020
Publication Date: 2/1/2020
Citation: Zhang, J., Nunez, A., Strahan, G.D., Ashby, R.D., Huang, K., Moreau, R.A., Yan, Z., Chen, L., Lew, H.N. 2020. An advanced process for producing structurally selective dimer acids to meet new industrial uses. Industrial Crops and Products. https://doi.org/10.1016/j.indcrop.2020.112132.
DOI: https://doi.org/10.1016/j.indcrop.2020.112132

Interpretive Summary: Dimer acids are a class of important industrial biobased materials that are usually produced from the plant oil fatty acids with clay as catalyst to activate the reaction. However, clay is a non-reusable catalyst, which leads to tons of catalyst waste to heavily burden the environment. Thus, a new solid catalyst is needed in order to create a more sustainable catalytic system. ARS researchers found that zeolites are great alternatives for clay catalysts for producing dimer acids. Four different kinds of solid zeolites were selected to investigate the factors that affect the dimer acid yields from soybean oil fatty acids. The research revealed several important findings: 1) the reaction temperature and time had the most dramatic effects; 2) the unsaturated components in the feedstock and the acid sites of the zeolites significantly influenced the composition of the dimer acids; 3) the textual properties of zeolites caused a significant difference to the structures of the dimer acids; 4) the zeolites possessed considerable activities even after being reused more than 10 times. The discovery of this new zeolite process can serve as a new and more environmentally friendly approach to produce dimer acids.

Technical Abstract: As a class of very important industrial intermediates, dimer acids are commercially produced through the polymerization of fatty acids using clay as catalyst. However, clay cannot be reused and leads to significant quantities of hazardous waste. Moreover, the applications of dimer acids are hindered by their disputed structures due to the limited selectivity of clay. This study proposed four different types of zeolites to replace clay for producing dimer acids from soybean oil fatty acids. The textural properties and acid sites of zeolites significantly affect the alicyclic/aliphatic ratios and the dimer/trimer ratios of dimer acids, which confirms the structural selectivity of zeolites. In addition, the reusability of zeolite catalysts is demonstrated by their continued high activity, even after having been used more than 10 times. This study may provide valuable information for improving the production of dimer acids and their downstream industrial uses.