Polymeric Sugar Based Surfactants for Different Petroleum Applications

Abstract

The present work treats some problems that encounter petroleum industry. These problems involve: sludge formation inside tanks, stabilizing emulsions formed during enhanced oil recovery and crude oil transportation. There are several methods for treating petroleum sludge among these methods, the chemical treatment of sludge has attracted great attention because access to valuable and useful materials from the sludge via this method. Most of the chemicals used in this purpose and not environmentally safe so that a great need was emerged for environmentally safe and friendly materials. Beside, exploitation of natural materials such as cellulose, chitosane, chitin…etc affords a wide range of environmentally safe chemical formulations. In this respect, glucose was obtained from cellulose by liquefaction process and used to prepare several glucose fatty ester ethoxylates having different HLB values. The cellulose, Glucose, Glucose esters and ethoxylated glucose esters were all characterized by the common spectroscopic tools. Some properties such as HLB, cloud points and partition coefficient were calculated and determined. The data reveal that HLB values increase by increasing the length of polyethylene glycol chain and decreases by elongating the alkyl chain for the same length PEG. It is clear that the cloud point is HLB dependent since the solvation of nonionics is mainly due to hydrogen bonding formation between PEG chain and the water. The longer PEG chain, the greater the bonds formed. These bonds will require higher energy to break them down. Moreover, their surface properties were calculated and related to their chemical composition. From the ethoxylated glucose ester surfactants, GA's were the most efficient in lowering the surface tension of aqueous solutions. The increase in the hydrocarbon chain length from adipic to palmitic to stearic caused an increase of the CMC. Whereas the increase in the poly (ethylene glycol) chain length within the same group leads to decrease in CMC. These trends can be correlated to the HLB values of these surfactants. It has been mentioned that the more soluble the nonionic surfactant, the greater its tendency to lower the surface tension of water It was found that the critical micelle concentration decreases by increasing the molecular weight of the prepared surfactants but it increases by temperature. Amin (the minimum area occupied by molecule) increases by both the increase in temperature and molecular weight. Thermodynamic parameters of micellization and adsorption were calculated in order to imagine the mechanism by which these surfactants reduce the surface tension of aqueous solution. The prepared surfactants were tested as demulsifiers for petroleum sludge. It was observed that there is an optimum concentration for each group of surfactants at which a maximum percentage of water is separated from the sludge. It was found that the optimum surfactant concentrations are 300, 400 and 500ppm for groups GA, GP and GS respectively. This may be related to the water solubility of these surfactants. The smaller the CMC values, the more effective will be the surfactant at low concentration. The data showed that the surfactant with longest PEG chain (of highest HLB value) achieved maximum water separation in its group. So that GA4000was the best demulsifier and achieved about 90% water separation from the sludge after six hours of application. The oil phase recovered from the treated sludge was analyzed for its hydrocarbon composition. It was found that the oil phase separated from the sludge using GA4000 is very rich in the lower molecular weight hydrocarbons. Furthermore, several factors affecting the demulsification efficiency such as temperature, demulsifier concentration and contact time were studied. For most of the emulsions, it is observed that the emulsion stability decreases with increasing temperature, because at high temperatures the viscosity of the continuous phase decreases with the increase in the rate of collision of dispersed phase droplets. It was observed that the amount of water separated increases by raising temperature at any concentration. Upon investigating the effect of contact time on demulsification efficiency, it was found that after 6 hrs, the percentage of water separation exceeded 50% for most of the investigated samples. The oil phase separated from the sludge after treatment with the prepared surfactants is rich in the low molecular weight hydrocarbons which may be an indication of their efficiency as emulsifiers for petroleum sludge. The oil recovered from the treated sludge was mixed with fresh crude oil in order to modify its API. The data reveal that the change in the composition of the recovered oil phase is related to the demulsifier HLB. The higher HLB value shifts the composition for the range of C6-C12.