Correlation of polymerization conditions with drag reduction efficiency of poly(1-hexene) in oil pipelines

摘要

High molecular weight with long linear side branches are frequently used in oil pipelines as one of the main classes of drag reducer agents ( DRAs). We studied the effects of polymerization conditions, including reaction temperature, monomer concentration and cocatalyst concentration ratio ( Al/Ti), on the polymerization yield and molecular weight of the resultant poly( 1-hexene) made by Ziegler-Natta catalyst and their consequent effects on the drag reduction efficiency in a loop test. The experimental results verified that the catalyst activity increased from 115 to 220 kgPH/molTi.atm, while the molecular weight of poly( 1-hexene) dropped from 2100 to 1030 kDa, as the reaction temperature was increased from 0 to 50 degrees C. The loop test results also revealed that the highest pressure drop was achieved using the polymer synthesized at 0 degrees C and by subsequent increase in reaction temperature the pressure drop decreased. Furthermore, the catalyst activity increased from 143 to 262 kgPH/molTi.atm by increasing Al/Ti ratio, while the molecular weight increased up to a maximum level of 1500 kDa at Al/Ti = 143 and decreased at higher cocatalyst contents. Similarly, the results showed the maximum pressure drop of 20 % at Al/Ti = 143. Finally, by increasing monomer concentration, the catalyst activity and polymer molecular weight increased from 75 to 262 kgPH/molTi. atm for the former, and from 700 to 1800 kDa for the latter which resulted in maximum pressure drop by 25 %. Moreover, the pressure drop for each utilized poly( 1-hexene) was increased proportionately with DRA's concentration, and interestingly enough, DRAs were further effective at more turbulent flows with higher Reynolds numbers.