Synthesis and Characterization of Functionalized Poly(glycidyl methacrylate)-Based Particles for the Selective Removal of Nitrogen Compounds from Light Gas Oil: Effect of Linker Length

In this work, four poly­(glycidyl methacrylate-<i>co</i>-ethylene glycol methacrylate) [PGMA-<i>co</i>-EDGMA] functionalized particles were synthesized and characterized, and tested in gas oil adsorption. Particles consisted of identical polymer support (PGMA-<i>co</i>-EDGMA, henceforth referred to as PGMA) and π-acceptor moiety (2,4,5,7-tetranitroflorenone, TENF), while the linkers (linear diamines) were varied from a two- (diaminoethane, DAE (<b>2</b>)), a three- (diaminopropane, DAP­(<b>3</b>)) to a four-carbon (diaminobutane, DAB­(<b>4</b>)) containing compounds. The particles notation takes the form: PGMA-DAE­(<b>2</b>)-TENF, PGMA-DAP­(<b>3</b>)-TENF, PGMA-DAB­(<b>4</b>)-TENF and PGMA-DAB­(<b>4</b>)­5-TENF, where 5 denotes the synthesis in 5% (vol./vol.) linker and 95% (vol./vol.) toluene solution, while for other three, 100% (vol./vol.) linker was used. Particles were characterized by, among others, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), elemental carbon, hydrogen, nitrogen and sulfur analysis (CHNS) and scanning electron microscopy (SEM). The change in linker length did not result in a significant effect on loading as similar amounts of TENF were immobilized on the polymeric particles regardless of the linker length. From the adsorption studies of light gas oil (LGO), results showed that diaminopropane (PGMA-DAP­(<b>3</b>)-TENF) substituted particles gave the highest % adsorption of nitrogen compounds, followed by the diaminobutane (PGMA-DAB­(<b>4</b>)-TENF)-based particles, while no significant differences between the particles with diaminoethane (PGMA-DAE­(<b>2</b>)-TENF) and PGMA-DAB­(<b>4</b>)­5-TENF were observed. The results further showed that all the four types of particles selectively adsorbed nitrogen compounds, while the sulfur concentration in LGO remained unchanged under the following adsorption process conditions: ambient temperature (24 °C), time (24 h), particles to oil loading ratio (1:4 wt./wt.) and stirring speed (400 rpm). Generally, steric hindrance around the TENF molecules, on the surface of the particles, had a major role to play in the adsorption process than the length of the linker