Biological removal of nitrogen compounds in heavy oil

Abstract

The occurrence of organic nitrogen compounds in crude petroleum and shale oils poses a problem of considerable importance to the petroleum industry. The deleterious effect of nitrogen compounds on cracking catalysts and the indication that they contribute to gum formation in gasolines are aspects of this problem. Pyridine - a representative nitrogen compound in heavy oil - was degraded by Rhodococcus sp. KCTC 3218 in a water-heavy oil two phase system. The pyridine degradation rate was affected by the presence of hydrocarbons such as n-hexadecane. This microorganism formed flocs which could be a barrier to mass transfer between the cells in flocs and pyridine dissolved in water. This problem could be overcome by the addition of a surfactant such as Triton X-100. The ratio of water to heavy oil was important to separate the heavy oil phase from water. The culture medium was emulsified by a sort of biosurfactant secreted by this microorganism. The emulsified oil phase returned to its natural state when the ratio of water to heavy oil was 1.5. Above this ratio, the emulsified oil phase remained an emulsion after decantation. Pyridine in heavy oil was completely degraded in 15 hr at this water to heavy oil ratio when the concentration of pyridine in heavy oil is 700 ppm and the cell concentration was 0.32 g/L DCW. N-methyl pyrrolidone have a good selectivity for pyridine and almost constant distribution coefficients regardless of the concentration of pyridine in the heavy oil.