Conversion of Polyolefin Waste to Liquid Alkanes with Ru-Based Catalysts under Mild Conditions

<p>Chemical upcycling of waste polyolefins via hydrogenolysis offers unique opportunities for selective depolymerization compared to high temperature thermal deconstruction. Here, we demonstrate the hydrogenolysis of polyethylene into liquid alkanes under mild conditions using ruthenium nanoparticles sup-ported on carbon (Ru/C). Reactivity studies on a model <i>n</i>-octadecane substrate showed that Ru/C catalysts are highly active and se-lective for the hydrogenolysis of C(sp³)-C(sp³) bonds at temperatures ranging from 200-250°C. Under optimal conditions of 200°C in 20 bar H2, polyethylene (average Mw ~4,000) was converted into liquid <i>n</i>-alkanes with yields of up to 45% by mass after 16 h using a 5 wt% Ru/C catalyst, with the remaining products comprising light alkane gases (C1-C6). At 250°C, nearly stoichiometric yields of CH4 were obtained from polyethylene over the catalyst. The hy-drogenolysis of long chain, low-density polyethylene (LDPE) and a post-consumer LDPE plastic bottle to produce C7-C45 alkanes was also achieved over Ru/C, demonstrating the feasibility of this reac-tion for the valorization of realistic post-consumer plastic waste. By identifying Ru-based catalysts as a class of active materials for the hydrogenolysis of polyethene, this study opens new avenues for the valorization of plastic waste under mild conditions.<br></p>

Conversion of Polyolefin Waste to Liquid Alkanes with Ru-Based Catalysts under Mild Conditions

<p>Chemical upcycling of waste polyolefins via hydrogenolysis offers unique opportunities for selective depolymerization compared to high temperature thermal deconstruction. Here, we demonstrate the hydrogenolysis of polyethylene into liquid alkanes under mild conditions using ruthenium nanoparticles sup-ported on carbon (Ru/C). Reactivity studies on a model <i>n</i>-octadecane substrate showed that Ru/C catalysts are highly active and se-lective for the hydrogenolysis of C(sp³)-C(sp³) bonds at temperatures ranging from 200-250°C. Under optimal conditions of 200°C in 20 bar H2, polyethylene (average Mw ~4,000) was converted into liquid <i>n</i>-alkanes with yields of up to 45% by mass after 16 h using a 5 wt% Ru/C catalyst, with the remaining products comprising light alkane gases (C1-C6). At 250°C, nearly stoichiometric yields of CH4 were obtained from polyethylene over the catalyst. The hy-drogenolysis of long chain, low-density polyethylene (LDPE) and a post-consumer LDPE plastic bottle to produce C7-C45 alkanes was also achieved over Ru/C, demonstrating the feasibility of this reac-tion for the valorization of realistic post-consumer plastic waste. By identifying Ru-based catalysts as a class of active materials for the hydrogenolysis of polyethene, this study opens new avenues for the valorization of plastic waste under mild conditions.<br></p>

Low temperature isomerizational transformation of gas gasoline on modified zeolite catalysts

New multicomponent catalytic systems synthesized by modifying zeolites (НМOR17 and HZSM-5) and γ-Al2O3 with metals (Co, Ni), zirconium dioxide and subsequent sulfation and tungestation of the obtained samples. It was shown that the introduction of zirconia into the M/MOR (where M = Co, Ni) system allows one to lower the isomerization temperature by 140-160°С, turning the medium-temperature skeletal-isomerisation catalyst M/MOR into a low-temperature M/MOR/ZrO2. It was found that sulfated Co/MOR/ZrO2/SO42- and Co/HZSM-5/ZrO2/SO42- have a higher isomerization activity, which makes it possible to increase the content of isomeric C5-C6 components with high octane numbers in gas gasoline from 43 to 66%. It was found that upon contacting the gas gasoline with the Co/MOR/ZrO2/SO42- or Co/HZSM-5/ZrO2/SO42- catalytic systems, efficient processing of higher molecular weight C7+ alkanes occurs not only into iso-C5 and C6, but also into n-pentane whose content in contact products rises from 19 to 40%. For the first time it was found that at temperatures of 160-200 °C, impurity gaseous C4- alkanes in the gas gasoline are consumed of when contacted with synthesized catalysts, turning into liquid alkanes. It was established that sulfated catalysts have more isomerizing activity in the low-temperature isomerization conversion of gas gasoline than volframated ones. The effect of the concentration of SO42- ions on the activity of the catalysts was studied and it was found that 2 wt.% is satisfactory for the studied catalysts. The temperature dependence of the activity of the most active of the synthesized catalysts in this process – Co/HZSM-5/ZrO2/SO42-, was studied. The results showed that the optimum temperature for the isomerization functioning of the selected catalyst is 180 oC. The change in the activity of the optimal catalyst (Co/HZSM-5/ZrO2/SO42-) depending on the reaction period was also studied. It was established that with the course of the process, the activity of the catalyst increases and reaches a maximum of 30 minutes work. After this, the activity of the catalyst gradually decreases. In this case, the total concentration of iso-C5 and iso-C6 increases by 22.9% and reaches 66.1%, and the conversion of C7+ components of gas gasoline is 69.2%.

Highly efficient alloyed NiCu/Nb2O5 catalyst for the hydrodeoxygenation of biofuel precursors into liquid alkanes

Hydrodeoxygenation (HDO) is a crucial process for the synthesis of biofuels from renewable biomass.