Study of new alternatives for removal of sulfur from diesel

Abstract

This work aims to develop new methods of removing sulfur from commercial diesel using surfactants and microemulsion systems. Its main purpose is to propose new technologies and add economic viability to the process. First, for the choice of the surfactant, a preliminary study was made using an extraction formulation based on a Winsor-I microemulsion system formed with either dodecyl ammonium chloride (DDAC) or ethoxylated nonylphenol (RNX95) as surfactant. It was verified that RNX95 was the best surfactant to be used in microemulsion systems to modify adsorbent surfaces, and as extracting agents in liquid-liquid extraction operations. Vermiculite treated with a microemulsion system was used as adsorbent. The microemulsion system used in the modification of the vermiculite surface was composed of RNX95 (surfactant), butan-1-ol (cosurfactant), n-hexane (oil phase), and distilled water (aqueous phase). Batch adsorption tests were carried out to assess the ability of vermiculite to adsorb sulfur from diesel. The experiments were performed according to a factorial design (23 ) evaluating the effects of temperature, concentration of CaCl2 in the aqueous phase, and vermiculite granule size. The best result was obtained at 60°C, 1500-ppm CaCl2 aqueous solution, and -48+65 mesh vermiculite particle size. Under such conditions, the vermiculite adsorbed 4.24 mg of sulfur/g of adsorbent, corresponding to 68.7% sulfur removal. Two and six-stage liquid-liquid extraction experiments were performed using the same surfactant-to-diesel ratio. The process yielded 46.8% sulfur removal in the two-stage experiment, and 73.15% in the six-stage one. An alternative study, for comparison purposes, was made using bentonite and diatomite as adsorbents. The batch experiments were done using microemulsion systems with the same aqueous phases used in the vermiculite study, with 20-ppm and 1500-ppm BaCl2 solutions. With bentonite, the best adsorption capacity was 7. 53 mg sulfur/g adsorbent with distilled water as aqueous phase of the microemulsion system, and with diatomite the best result was 17.04 mg sulfur/g adsorbent using a 20- ppm CaCl2 solution