PRODUCTION OF SILVER DOPED RICE HUSK ASH FOR DESULPHURIZATION OF RAW CRUDE FEED STOCK

The presence of sulphur compounds in petroleum is a cause of concern as it affects the products, unit operations, processes and environmental. Because of the importance of sulphur removal, various methods were used in time past for sulphur removal from petroleum products, recording there limiting factors, ranging from high cost to lower yield of sulphur removal. In this study, the removal of sulphur from Nigerian Escravos crude oil using silver doped rice husk ash was carried out. Methods of preparation of the adsorbent includes the collection of the rice husk, wet beneficiation of the sample, ashing and subsequently dosing of the silver nitrate solution. The resulting adsorbent vis-à-vis the raw material were characterized using proximate, ultimate analyses as well as XRD, XRF, SEM and BET for elemental, structural, morphological and surface area determination respectively. Other characterization properties includes pH, bulk density, particle size, pore volume, porosity, volatile matter content, moisture and ash content. The characteristic peaks from the XRD points to partial coverage of the rice husk ash with silver, while the XRF and SEM continued to change in the composition and morphology. The BET result gave an improved increment in the surface area and pore dimensions, capable of handling the molecular dimension of Sulphur and its compounds. Sulphur removal was done using design of Design of Experiment and subsequently applied for the removal of sulphur in a batch reactor connected to reflux condenser. The amount of adsorbent dosage of 2g, temperature at 99.990C and contact time of 78.72mins gave sulphur removal of 94.4885% from the Escravos crude oil, having a desirability value of 0.969. The adsorption process was modeled using Freundlich, Lagmuir, Dubinin-Radushkevich and Floxy-Huggins isotherms. Langmuir isotherm gave a regression of 0.9856 and with KL value of 5.68L/g of adsorbent, indicating a very good adsorption capacity of the adsorbent with qm value of 23.81L/mg which is favourable for both low and high initial concentration of Sulphur. The adsorption kinetics was favourably described by the pseudo second order model with rate constant of 0.005g mg-1sec-1having R2 0f 0.9983. Based on the adsorption isotherms and kinetics considered adsorption mechanism proposed followed a physio-chemisorption process. Accordingly, Ag/RHA was found to be a competitive adsorbent for Sulphur removal from crude oil.