Acylated carboxymethyl chitosan grafted with MPEG-1900 as a high-efficiency demulsifier for O/W crude oil emulsions

In this work, due to its excellent adsorption performance, biodegradability, and low toxicity, chitosan was used as the raw material to synthesize a series of new oil-in-water (O/W) type crude oil demulsifiers. First, an acyl group was introduced onto the chitosan molecule. Then, sodium chloroacetate was used as a carboxymethylation reagent to introduce a carboxymethyl group into the acylated chitosan. Furthermore, polyethylene glycol monomethyl ether with an average molecular weight of 1900 (MPEG-1900) was used to react with acylated carboxymethyl chitosan to synthesize chitosan-based O/W type demulsifiers. The molecular structures of the synthetic chitosan derivatives were characterized using Fourier-transform infrared spectroscopy (FTIR) and 1 H nuclear magnetic resonance techniques. The results showed that the surface tension decreased with an increase in the concentration of polysaccharide demulsifiers, which included MPEG-1900-A 4 CMC, MPEG-1900-A 6 CMC, and MPEG-1900-A 8 CMC. The demulsification efficiency of these synthetic demulsifiers reached a maximum over 100 min at a concentration of 200 ppm at 50 °C. The as-synthesized chitosan derivatives showed good demulsification performance.