Small associative molecule thickeners for ethane, propane and butane

•Tributyltin fluoride (TBTF) is an effective natural gas liquids (NGL) thickener.•TBTF dissolves in NGL without the need for a heating and cooling cycle.•Hydroxyaluminum di-2-ethylhexanoate (HAD2EH) thickens propane and butane.•A heating/cooling cycle is required to dissolved HAD2EH in propane or butane.•Crosslinked phosphate esters are modest NGL thickeners that form translucent fluids.

The abilities of three classes of low molecular weight, metal-based, associative compounds to thicken high pressure ethane, propane or butane have been assessed with a close clearance falling ball viscometer. Tributyltin fluoride (TBTF) does not require a heating/cooling cycle to attain dissolution, and at a concentration of 1 wt% in ethane, propane or butane yields 70–100-fold viscosity increases at 25 °C. Increasing temperature substantially reduces TBTF’s thickening ability. Although hydroxyaluminum di-2-ethylhexanoate (HAD2EH) is insoluble in ethane, it does dissolve in liquid propane or butane after mixing at ∼100 °C and cooling to temperatures as low as 40 °C. HAD2EH induces small viscosity increases in propane, but is a very effective butane thickener. Increasing temperature causes a relatively small decrease in HAD2EH’s thickening performance. Combining a phosphate ester and a crosslinker in ethane, propane or butane yields a translucent liquid with viscosity increases that are significantly less than those attained with TBTF or HAD2EH.

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