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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