Natural and Modified Montmorillonite Clays as Catalysts for Synthesis of Biolubricants.

Francisco Luna,Enrique Rodríguez-Castellón,Karim Sapag,Juan Cecilia,Rosana Saboya,Célio Cavalcante,Deicy Barrera

doi:10.3390/ma11091764

Abstract

In this study, natural and modified clays were evaluated as catalysts in an esterification reaction to obtain bio-based lubricants. The biolubricants are environmentally preferred to petroleum-based lubricants because they are biodegradable and non-toxic. Other advantages include very low volatility due to the high molecular weight and excellent viscosity properties with temperature variations. Modifications in natural clay were performed intending to obtain materials with different textural properties that could improve the reaction under study. The modified clays were obtained in two ways: by pillarization using Al13 Keggin polyoxocations or by acid treatments with H2SO4, HCl and HNO3. All samples were evaluated for the esterification reaction of fatty acids from castor oil (FACO) using 2-ethyl-hexanol. During the reaction step, a zeolite-based adsorbent was used for water removal to increase the reaction equilibrium conversion. Gas chromatography and nuclear magnetic resonance were performed to ensure the formation of the products. The highest conversion of fatty acids to esters was obtained using pillared clays. Adding adsorbent in the reaction medium (10 g of 3A zeolite to 100 g of FACO), the conversion improved from 74–88 wt % after 6 h at 50 °C.

Highlights

The depletion of fossil fuels has led to the research and development of more environmentally-benign alternative energy sources since petroleum-based lubricants may pollute the air due to their volatility, as well as contaminate the soil, which can seriously affect health [1,2]
All samples were evaluated in the esterification reaction of the formation of pillars of castor oil (FACO) with EH for the synthesis potential biolubricants
When using pillared clays, the FACO to esters conversion notably increased to values around 74 wt %

Summary

Introduction

The depletion of fossil fuels has led to the research and development of more environmentally-benign alternative energy sources since petroleum-based lubricants may pollute the air due to their volatility, as well as contaminate the soil, which can seriously affect health [1,2]. Biolubricants are compounds that are more readily biodegradable and non-toxic, so these products lack danger to the environment [2,4,5]. Biolubricants display several performance benefits such as a higher viscosity index, lower volatility, higher flash point, better lubricity, higher char stability, higher resistance to humidity, lower compressibility or higher dispersancy [2,4,6,7,8,9] in comparison to traditional petroleum-based lubricants.

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Conclusion