TY - JOUR
T1 - Effect of reaction media on hydrogenolysis of polyethylene plastic waste
T2 - Polymer-surface interactions in small alkane/polymer blends
AU - Zare, Mehdi
AU - Kots, Pavel A.
AU - Hinton, Zachary R.
AU - Epps, Thomas H.
AU - Korley, La Shanda T.J.
AU - Caratzoulas, Stavros
AU - Vlachos, Dionisios G.
N1 - Publisher Copyright:
© 2024 Elsevier B.V.
PY - 2024/8/15
Y1 - 2024/8/15
N2 - The polymer reaction media and its properties can be altered by recycling a fraction of liquid products or adding alkane solvents. Less clear is whether this strategy affects hydrogenolysis. Herein, we investigated the effect of short-chain alkanes Cn consisting of n carbons (n=8, 16, and 32) on the upcycling of high-density polyethylene (HDPE) plastic waste to lubricant-range products over Ru/TiO2 catalysts by multiscale simulations and experiments. First, we trained a force field for polymer/surface interactions on a Ru22 nanoparticle (NP) supported on TiO2. Using replica exchange molecular dynamics simulations, we studied the effect of small hydrocarbons on the adsorption of a surrogate polymer, C142, on the catalyst. We found segregation of long chains (C142) at the catalyst surface due to the enthalpy gained by adsorbing more C-C bonds of the long chains, compensating for entropic losses upon adsorption. Short-chain molecules decrease the adsorbed carbons of long chains on the Ru NP due to blocking Ru active sites. Compared to the bulk chains, competitive adsorption results in a broader, heavy-tailed distribution of end-to-end distance of adsorbed chains. Our experiments demonstrated that catalyst activity declines significantly beyond simple dilution due to changes in polymer adsorption, and tuning the reaction media by creating suitable blends impacts hydrogenolysis. Density distributions for a 50:50%wt mixture of PP and PE show that PE chains are segregated at the surface, so they are prone to C-C bond breaking much faster than PP chains. H/D exchange experiments show preferential deuteration of PE, while CH3 groups of PP remain undeuterated. This may be explained by the preferential sorption of PE over PP, leading to specific distribution in the polymer blend.
AB - The polymer reaction media and its properties can be altered by recycling a fraction of liquid products or adding alkane solvents. Less clear is whether this strategy affects hydrogenolysis. Herein, we investigated the effect of short-chain alkanes Cn consisting of n carbons (n=8, 16, and 32) on the upcycling of high-density polyethylene (HDPE) plastic waste to lubricant-range products over Ru/TiO2 catalysts by multiscale simulations and experiments. First, we trained a force field for polymer/surface interactions on a Ru22 nanoparticle (NP) supported on TiO2. Using replica exchange molecular dynamics simulations, we studied the effect of small hydrocarbons on the adsorption of a surrogate polymer, C142, on the catalyst. We found segregation of long chains (C142) at the catalyst surface due to the enthalpy gained by adsorbing more C-C bonds of the long chains, compensating for entropic losses upon adsorption. Short-chain molecules decrease the adsorbed carbons of long chains on the Ru NP due to blocking Ru active sites. Compared to the bulk chains, competitive adsorption results in a broader, heavy-tailed distribution of end-to-end distance of adsorbed chains. Our experiments demonstrated that catalyst activity declines significantly beyond simple dilution due to changes in polymer adsorption, and tuning the reaction media by creating suitable blends impacts hydrogenolysis. Density distributions for a 50:50%wt mixture of PP and PE show that PE chains are segregated at the surface, so they are prone to C-C bond breaking much faster than PP chains. H/D exchange experiments show preferential deuteration of PE, while CH3 groups of PP remain undeuterated. This may be explained by the preferential sorption of PE over PP, leading to specific distribution in the polymer blend.
KW - Multiscale simulation
KW - Plastic waste
KW - Polyethylene
KW - Solvent effects, Ru/C
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U2 - 10.1016/j.apcatb.2024.123969
DO - 10.1016/j.apcatb.2024.123969
M3 - Article
AN - SCOPUS:85188997723
SN - 0926-3373
VL - 351
JO - Applied Catalysis B: Environmental
JF - Applied Catalysis B: Environmental
M1 - 123969
ER -