Hierarchical Zeolite from Coal Fly Ash Using the Biosurfactant Manosyleritritol Lipids-B as a Novel Green Mesoporogen Agent

Abstract

The hierarchical zeolite 13X (SiAl = 1.50) was synthesized from coal fly ash using an alternative template for the first time. The manosyleritritol lipids-B (MEL-B) > 95% purity, a biosurfactant from Pseudozyma tsukubaensis, was used as a pore directing agent in a two-step process. The hierarchical zeolite was pre-treated with oxalic acid and subsequently subjected to desilication with ammonium hydroxide aided by MEL-B using a hydrothermal reactor at 150 ºC for 5 h. The acid pretreatment was effective with 12.10% structural aluminium removal, since it increased the Si/Al ratio from 1.50 to 1.71 and also preserved the crystalline structure for the dealuminated zeolite with 20 mM oxalic acid. The zeolite, treated with 0.55 g of MEL-B, showed remarkable textural properties, with a pore diameter of 3.72 nm, a mesopore volume of 0.520 cm3/g, a high surface area of 418 m2/g and a total volume of 0.787 cm3/g. Thermal analysis showed that the biosurfactant degrades at 172 ºC, lower temperature than the synthetic surfactants. Regarding the experiments with 0.25 g of MEL-B, it was possible to increase the pore diameter by 40.8% due to the high molecular weight of the biosurfactant (893.9 g/mol), which provided a notable increase in the textural and morphological properties of the zeolites. The high performance in the generation of secondary porosity, low environmental impact, lower calcination temperature, low biosurfactant mass required to generate hierarchical pores are promising technical implementation on inorganic-bio-nanomaterials technology.