Combined Effect of Depressor Additive and Heat Treatment on the Rheological Properties of Highly Paraffinic Oils

Abstract

The transportation of paraffinic oils, particularly from Kazakhstan, is hindered by the formation of asphalt–resin–paraffin deposits (ARPDs), which complicate production and transport processes. While chemical treatments using inhibitors and depressants are commonly used, they are often less effective for oils with high paraffin contents and unique compositions, such as those found in Kazakhstan. This study presents a novel approach to synthesizing a depressor additive (PTE) tailored specifically for paraffinic oils, addressing the limitations of existing commercial additives. The PTE additive, derived from pyromellitic acid dianhydride (PMDA), polyoxyethylene sorbitan trioleate (Tween-85), and arachidyl alcohol (1-eicosanol), was tested on paraffinic oil blends from West Kazakhstan (WKOM) and Kumkol-Akshabulak (KAOM) under combined thermal treatment conditions at 60 and 90 °C. Rheological analyses indicated that heat treatment alone improved cold-flow properties, but these effects were transient. However, the introduction of PTE at concentrations of 500–1000 ppm produced a significant, sustained reduction in yield loss temperature (from 18 to 3 °C in WKOM and from 12 to 0 °C in KAOM) and decreased effective viscosity to 0.167 Pa s for WKOM and 0.245 Pa s for KAOM at 0 °C. Microscopic analysis confirmed that PTE alters paraffin crystallization, forming large lamellar structures that prevent network formation and maintain oil fluidity. The PTE additive demonstrated consistent effectiveness over 10 days, surpassing the stability and impact of commercial additives. These findings highlight PTE as a tailored, effective solution for enhancing cold-flow properties in high-paraffin oils.