ABSTRACT
In this work, we looked at the most recent advances in the field of plastics hydrocracking from a technology standpoint. A patent search was supplemented by a literature review to evaluate the development of the hydrocracking technology for plastics recycling. We observed that the patent and academic literature output rapidly increased over the past decade, highlighting the recent emergence of this technology to tackle the plastic waste problem. A majority of patents arise from academia, where plastics recycling is a growing research topic. Although innovations for plastics hydrocracking have been reported, most of them disclose the use of catalysts in batch reactors, whereas very few patents describe the process. Continuous operation at pilot scale will be essential to gather process data towards industrialisation and further assess the commercial viability of theplastics hydrocracking technology.
ABSTRACT
Catalytic hydrogenolysis is a promising approach to transform waste plastic into valuable chemicals. However, the transformation of N-containing polymers, such as polyamides (i.e. nylon), remains under-investigated, particularly by heterogeneous catalysis. Here, we demonstrate the hydrogenolysis of various polyamides catalysed by platinum-group metal nanoparticles supported on CeO2. Ru/CeO2 and Pt/CeO2 are both highly active but display different selectivity; Ru/CeO2 is selective for the conversion of all polyamides into water, ammonia, and methane, whereas Pt/CeO2 yields hydrocarbons retaining the carbon backbone of the parent polyamide. Density functional theory computations illustrate that Pt nanoparticles require higher activation energy for carbon-carbon bond cleavage than Ru nanoparticles, rationalising the observed selectivity. The high activity and product selectivity of both catalysts was maintained when converting real-world polyamide products, such as fishing net. This study provides a mechanistic basis for heterogeneously catalysed polyamide hydrogenolysis, and a new approach to the valorisation of polyamide containing waste.
ABSTRACT
Carbon-carbon bond cleavage mechanisms play a key role in the selective deconstruction of alkanes and polyolefins. Here, we show that the product distribution, which encompasses carbon range and formation of unsaturated and isomerization products, serves as a distinctive feature that allows the reaction pathways of different catalysts to be classified. Co, Ni, or Ru nanoparticles immobilized on amorphous silica-alumina, Zeo-Y and ZSM-5, were evaluated as catalysts in the deconstruction of n-hexadecane model substrate with hydrogen to delineate between different mechanisms, i.e., monofunctional- (acid site dominated) or bifunctional-hydrocracking (acid site & metal site) versus hydrogenolysis (metal site dominated), established from the product distributions. The ZSM-5-based catalysts were further studied in the depolymerization of polyethylene. Based on these studies, the catalysts are plotted on an activity-mechanism map that functions as an expandable basis to benchmark catalytic activity and to identify optimal catalysts that afford specific product distributions. The systematic approach reported here should facilitate the acceleration of catalyst discovery for polyolefin depolymerization.
ABSTRACT
This Personal Account reviews the sequence of scientific discoveries that led to a catalytic plastic conversion technology that resulted in the creation of a spin-off company called Plastogaz from the Ecole Polytechnique Fédérale de Lausanne (Switzerland). The story begins with research on the catalytic valorization of CO2 , carried out by two PhD students and a master student, and the connections and steps subsequently made, ultimately leading to a plastic transformation technology. The Personal Account highlights the value of diverse research topics within a research group, the benefits of connections between chemistry and chemical engineering, that can lead to interesting synergies and atypical breakthroughs.
Subject(s)
Polymers , Catalysis , Humans , SwitzerlandABSTRACT
We report a ruthenium-modified zeolite which efficiently transforms propylene carbonate to propylene glycol and methane, under solvent-free conditions. The catalyst achieved high product selectivity and no significant ageing effect was observed after multiple cycles. The resulting liquid product (water-containing glycol) can be directly used as anti-freeze solution and the gas phase can directly be used as an energy carrier in the form of H2 -enriched methane. This process efficiently bridges energy storage and an important chemical synthesis under sustainable (CO2 consuming) conditions.
ABSTRACT
A nickel-catalyzed highly regioselective 1,4-addition reaction of boronic acids to dienones to form products with an all-carbon quaternary center is described. The 3-alkenyl group of dienones is the key for the reaction to proceed smoothly. A mechanism involving the coordination of the dienyl group to the nickel center is proposed.
