Chemo-catalytic Esterification and Transesterification over Organic Polymer-Based Catalysts for Biodiesel Synthesis

The major sources of fuels in today's world predominantly come from traditional fossil resources such as coal, petroleum and natural gas, which are limited and nonrenewable. Meanwhile, their consumption releases large undesirable greenhouse gas and noxious gases. Therefore, the development of renewable and sustainable feedstocks to replace traditional fossil resources has attracted great interest. Biodiesel, mainly produced through esterification and transesterification reaction from renewable oil resources using acids and bases as catalysts, is deemed as a green and renewable biofuel that shows enormous potential to replace fossil diesel. Compared to homogeneous catalytic systems, the development of efficient and stable heterogeneous catalysts is vital to synthesizing biodiesel in an efficient and green manner. Among the developed solid catalysts, organic polymer- based catalytic materials are an extremely important topic, wherein distinct advantages of higher concentration of active sites and better stability of active groups are associated with each other. In this review, effective catalytic valorization of sustainable feedstocks into biodiesel via transesterification and esterification reactions mediated by functionalized organic polymer-based catalysts is discussed. Special emphasis has been given to the synthetic routes to the versatile organic polymers-based catalytic materials, and some other interesting catalytic roles derived from physicochemical property, like adjustable hydrophilicity and hydrophobicity along with swelling property in transesterification and esterification, are also illustrated.