@article {49291, title = {Depolymerization of waste polyethylene to linear alkenes via sequential dehydrogenation and metathesis}, journal = {Green Chemistry}, volume = {26}, year = {2024}, month = {OCT}, pages = {10558-10566}, type = {Article}, abstract = {

Polyethylene (PE) is the most abundantly sourced plastic and significant efforts are needed for its end-of-life management. The deconstruction of PE is an uphill task and requires the breaking of highly stable C-C bonds. Here we demonstrate that PE can be deconstructed to value-added dodecene, along with other long-chain alkenes. The PCP-iridium complex catalyzes the dehydrogenation of commercial and post-consumer polyethylene waste to produce dehydrogenated polyethylene (DHP) with 0.5-1.0\% unsaturation. The DHP was subjected to an ethylene cross-metathesis reaction in the presence of suitable catalysts. Through meticulous optimization of reaction parameters, 63\% selectivity toward dodecene, with 26\% overall yield, was achieved. The practical significance of our method has been demonstrated by subjecting post-consumer plastic waste to dehydrogenation followed by ethylene metathesis to produce dodecene as a major product, together with long-chain alkenes. The PE deconstruction has been confirmed by recording molar mass before and after depolymerization using high-temperature gel permeation chromatography. The existence of dodecene has been unambiguously ascertained using GC, GC-MS, NMR, and IR spectroscopy. Thus, these results demonstrate the conversion of waste PE to value-added dodecene and long-chain alkenes under mild reaction conditions.

}, issn = {1463-9262}, doi = {10.1039/d4gc03646h}, author = {Khopade, Kishor V. and Rajput, Nikhita S. and Rangappa, Raghavendrakumar and Barsu, Nagaraju and Chikkali, Samir H.} } @article {49528, title = {Electrochemical deconstruction of waste polyvinylidene chloride (PVDC) to value-added products in batch and flow}, journal = {Chemistry-A European Journal}, volume = {31}, year = {2025}, month = {FEB}, type = {Article}, abstract = {

Chlorinated polymers have made enormous contributions to materials science and are commercially produced on a large scale. These chlorinated polymers could be recycled as chlorine sources to efficiently produce valuable chlorinated compounds owing to their facile release of HCl. Although the thermal stability of PVDC is low compared to PVC, this can be advantageous in terms of easy and fast dehydrochlorination. Herein, we report an efficient electrochemical chlorination using poly(vinylidene chloride) (PVDC) as a chlorine source that works in an undivided cell and applies to a good number of examples. This method works on commodity polymers such as waste PVDC-PVC pharma blister film, PVDC-PO multilayer food packaging, and compression molded sheets of Ixan PVDC (with heat stabilizer) with similar efficiency. Furthermore, this method also provides the dechlorination of PVDC up to 98 \%, leading to unsaturated dechlorinated material. Converting PVDC into more stable unsaturated compounds, the release of harmful chlorine-containing gases during incineration can be minimized. Additionally, this method is not only restricted to batch processes but an electroflow process for PVDC dechlorination and electrosynthesis has also been demonstrated.

}, keywords = {chlorination, Electrochemical recycling, Electroflow-synthesis, Graphitic material, Polyvinylidene chloride}, issn = {0947-6539}, doi = {10.1002/chem.202403980}, author = {Mishra, Subhadip and Kar, Sourav and Rangappa, Raghavendrakumar and Patil, Prashant and Kadam, Vijay and Chikkali, Samir H. and Samanta, Ramesh C.} } @article {49522, title = {Ruthenium-catalyzed deconstruction of polyolefins: a strategy to up-cycle waste polyethylene to value-added alkene}, journal = {Angewandte Chemie-International Edition}, volume = {64}, year = {2025}, month = {APR}, type = {Article}, abstract = {

Synthesis of value-added products from post-consumer waste polyolefins is fascinating as well as challenging. Here we report ruthenium-catalyzed up-cycling of the polyethylene to long-chain alkene derivatives. The developed methodology mainly involves two steps i.e., dehydrogenation of polyethylene through hydrogen atom transfer and its metathesis using the HG-II catalyst. The dehydrogenation of polyethylene using ruthenium catalysis derived up to 3.38 \%, of double bonds; with 90 \% of the recovered polyolefin material. The obtained unsaturated polyethylene was subjected to cross-metathesis with ethylene using HG-II catalytic system. This resulted in the synthesis of predominantly dodecene (C12) derivatives, with 58 \% selectivity, along with other derivatives of varying chain lengths. The overall reaction produced terminal and internal olefins in the ratio 1:0.8 respectively. The dehydrogenation of polyethylene and its deconstruction was confirmed by NMR spectroscopy, Gel Permeation Chromatography (GPC) and Differential Scanning Calorimetry (DSC). The origin of C12 selectivity has been demonstrated by control experiments. The scope of the methodology was extended to post-consumer waste polyethylene which gave high conversion to value-added dodecene derivatives as a major product.

}, keywords = {Deconstruction, Homogeneous catalysis, ruthenium, Upcycling, Waste plastic}, doi = {10.1002/anie.202422609}, author = {Padhi, Ganeshdev and Khopade, Kishor V. and Moyilla, Nageswararao and Rangappa, Raghavendrakumar and Chikkali, Samir H. and Barsu, Nagaraju} }