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Exploiting Synergistic Effects of Intermolecular Interactions To Synthesize Hybrid Rejuvenators To Revitalize Aged Asphalt
journal contribution
posted on 2019-08-23, 22:15 authored by Farideh Pahlavan, Alireza Samieadel, Shuguang Deng, Elham FiniThis paper examines the merits of
using a hybrid bio-oil derived
from algae and swine manure to rejuvenate aged bitumen by restoring
the bitumen properties which are degraded during oxidative aging.
Nitrogen-containing compounds have been found to be effective for
decreasing the size of molecular agglomerates which are intensified
during aging provided they adequately penetrate into the oxidized
asphaltene agglomerations. The enhancement effect is mainly attributed
to their electronic structures, including the polar head and hydrocarbon
tail which can interact with asphaltene with CH−π interactions.
In this study, we hypothesize that combining bio-oils extracted from
high-protein algae and swine manure can help balance the heteromolecule
content, which in turn leads to synthesizing an effective hybrid biorejuvenator
to revitalize aged bitumen. Computational analysis was used to determine
the specific rejuvenation mechanisms between the hybrid biorejuvenator
and an oxidized asphaltene dimer found in the aged bitumen. Our analysis
via density functional theory showed that the biorejuvenation process
involves a two-step mechanism: First, the biorejuvenators interact
with polar sites of the asphaltene nanoaggregates in aged bitumen
to increase intersheet spacing referred to as the lock-and-key mechanism.
Second, the biorejuvenators intercalate into the intersheet spacing
within the stacks of asphaltene to induce deagglomeration. Accordingly,
the hybrid biorejuvenator was designed to have molecules targeting
either of the two mechanisms. Therefore, blending molecules of the
algae-based bio-oil, which are mainly effective in the first step
with those of swine-manure-based bio-oil, which are effective in the
second step led to a biorejuvenator with significantly higher efficiency
than either of them individually. This was attributed to heteroaromatic
motifs and nitrogen-carrying compounds with a hydrocarbon tail, which
contribute to opening (lock-and-key) and intercalation mechanisms,
respectively. The enhanced efficiency of the hybrid biorejuvenator
was further verified via a series of laboratory experiments as well
as molecular dynamics simulations; it was found that the hybrid biorejuvenator
is more effective to increase crossover modulus and decrease size
of asphaltene nanoaggregates of aged bitumen than the swine-manure-based
bio-oil and the algae-based bio-oil alone. Regardless of the bitumen
origin, the hybrid biorejuvenator was able to promote deagglomeration
of oxidized asphaltene and revitalize aged bitumen.