Self-Assembling Behavior in Decane Solution of Potential Wax Crystal Nucleators Based on Poly(co-olefins)

Abstract

The control of the precipitation and gelation of long chain paraffins from oil remains an enduring technological challenge regarding the processing and recovery of refined fuels and waxy crudes. Wax crystal modifiers based on polyethylene-poly(ethylene-propylene) (PE-PEP) diblock copolymers function as efficient nucleators for wax crystals in middle distillate fuels. These diblock polymers selfassemble in oil to form expansive platelike aggregates consisting of a PE core cloaked behind the amorphous PEP brush layer. The PE core thus promotes nucleation of solubilized long chain alkanes. Additional candidate structures for wax crystal nucleators include linear and star copolyolefins where the composition variation signals the alteration between crystalline and amorphous segments. This study focuses upon the self-assembling behavior in solution of these materials. The characteristics of the single chains and the aggregates formed at lower temperatures were determined via small-angle neutron scattering. Both plates and needlelike structures were found. The placement of the amorphous and crystalline blocks in the arms of the star shaped polymers was found to influence the architecture of the self-assembled micelles. As a point of comparison a commercial copolymer of ethylene-vinyl acetate (EVA) was also investigated. The EVA material was found to be relatively "undisciplined" in comparison to the structurally more uniform anionically prepared counterparts.

Recent advances on mitigating wax problem using polymeric wax crystal modifier

“…5. This characteristic makes PE-PEP copolymers promising flow improvers for waxy crude oils (Ashbaugh et al 2002;Schwahn et al 2002b). However, researches addressing the application and mechanism of PE-PEP in flow improvement and/or wax inhibition are rarely reported in recent years.…”

Interaction of Paraffin Wax Gels with Random Crystalline/Amorphous Hydrocarbon Copolymers

“…It is known that a fraction (∼50%) of the EVA nucleator material undergoes precipitation prior to any wax formation. 23 Thus, activity is diminished via the premature formation and precipitation of self-assembled aggregates.…”

Tailored Polymer Additives for Wax (Paraffin) Crystal Control

“…For PEB-n materials with lesser crystallinity an attenuated or "no peak" feature was noticed in the SANS patterns. That indicates a more homogeneous polymer density inside rods (Schwahn et al, 2002a).…”

“…In this case, the objects have diffuse rather than fractally rough interfaces. An observed structural level and its associated powerlaw for simple well defined shape objects can be analyzed using the graphical presentation of data in terms of Guinier approximation, ln(Q p d/d) vs. Q 2 , which delivers in a direct way the "forward scattering" and the size of the objects (Schwahn et al, 2002a).…”

“…Small-angle neutron scattering (SANS) technique exploiting on one side the strength of contrast matching and, on other side, the wide length scale explored, from 1nm up to 1m, is a dedicated technique to investigate and elucidate complex morphologies such as those occurring in a wax-polymer-oil system (Richter et al, 1997;Leube et al, 2000;Monkenbusch et al, 2000;Schwahn et al, 2002aSchwahn et al, , 2002bAshbaugh et al, 2002;Radulescu et al, 2003Radulescu et al, , 2004Radulescu et al, , 2006Radulescu et al, , 2008Radulescu et al, , 2011. An eloquent example is that of diblock polymers (Fig.…”