Novos hidrogéis à base de glicerina de Biodiesel derivado do óleo de mamona

Abstract

During the biodiesel production, around 70% of the produced total residue corresponds to glycerine (1,2,3-propanetriol). Taking into consideration the large quantity produced and the residue control, it becomes evident the necessity to produce new products from this co-product. In this way glycerine esters P.A and biodiesel originated from castor oil (“glicerina loira” and bidistilled) with acrylic acid, reaction catalyzed with sulphuric acid, were synthesized to obtain hydrogels. An investigation of the esterification reaction was carried out through infrared spectroscopy, nuclear magnetic resonance of 13C and rheology. The yield was calculated by back titration using the sodium periodate method. The best reaction was verified for the glycerine esters and acrylic acid p.a, catalyzed with 10% at 60 ºC with three hours of reaction. Hydrogels were synthesized utilizing obtained esters, potassium persulfate as a initiator, N,N'– methylenebis crylamide as a reticulating agent and TEMED (N,N,N,N -tetramethyl-ethylenediamine as a accelerator of the reaction. The water absorption capacity by the hydrogels was investigated through the swelling kinetics data. The hydrogels had maximum absorption between 20 to 25 g of H2O/g of dry gel and reached the equilibrium in 5 minutes. The hydrogels which presented the best swelling results were analyzed by the methods BET (Brunauer, Emmet, Teller and BJH (Barret, Joyner, Halenda) with the means of determining the surface area and pore distribution. Most of the hydrogel pores are found in the mesoporous regions (10 to 500 Å). The pores of the hydrogel ester of glycerine P.A are 5 times bigger than the “glicerina loira” hydrogel ester of glycerine. The hydrogels were also used as biodiesel dehumidifier. The humidity content in the biodiesel samples were determined by Karl-Fischer’s volumetric method. The hydrogels reduced the humidity content of the biodiesel from 0.23% to 0.07-0.09%. The “glicerina loira” hydrogel ester of glycerine (derived from the biodiesel) had a better performance in the withdrawal of the biodiesel humidity, attributed to the small size of the pores which prevents the passage of the long ester chain and enables the absorption of water in the hydrogel