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PET non-catalyzed, non-isothermal hydrolysis can produce 94% terephthalic acid (TPA) yield in 75 seconds. 

We screen various acid catalysts (mineral, carboxylic, carbonic acids, zeolites, ionic liquids, and metal salts) for PET hydrolysis. 

Many corporations and nations have pledged to reach net-zero emissions within a few decades. Meeting such targets for greenhouse gases, plastics, etc. requires systematic methods to guide investment in technologies and value-chain alternatives, and develop roadmaps. The proposed framework is a multi-period planning model to guide optimal reforms in cradle-to-cradle life-cycle networks across the time horizon. It aims to meet environmental targets while minimizing the total annualized marginal cost of natural resources and the investment cost associated with adoption of novel technologies. This considers the evolution of technology readiness levels as S-curves or continuous time Markov-chains. Integrated Assessment models account for climate change, decarbonization due to energy mix changes, and carbon taxes. Multiple climate change scenarios and shared socioeconomic pathways are used to model the future. In addition to providing roadmaps, the outputs can also be used to identify technologies that will be robust to future scenarios. 

As the demand for PET plastic products continues to grow, developing effective processes to reduce their pollution is of critical importance. Pyrolysis, a promising technology to produce lighter and recyclable components from wasted plastic products, has therefore received considerable attention. In this work, the rapid pyrolysis of PET was studied by using reactive molecular dynamics (MD) simulations. Mechanisms for yielding gas species were unraveled, which involve the generation of ethylene and TPA radicals from ester oxygen−alkyl carbon bond dissociation and condensation reactions to consume TPA radicals with the products of long chains containing a phenyl benzoate structure and CO2. As atomistic simulations are typically conducted at the time scale of a few nanoseconds, a high temperature (i.e. >1000 K) is adopted for accelerated reaction events. To apply the results from MD simulations to practical pyrolysis processes, a kinetic model based on a set of ordinary differential equations was established, which is capable of describing the key products of PET pyrolysis as a function of time and temperature. It was further exploited to determine the optimal reaction conditions for low environmental impact. Overall, this study conducted a detailed mechanism study of PET pyrolysis and established an effective kinetic model for the main species. The approach presented herein to extract kinetic information such as detailed kinetic constants and activation energies from atomistic MD simulations can also be applied to related systems such as the pyrolysis of other polymers. 

For chemical recycling of plastic wastes to be viable, chemical products generated in recycling need to find markets. A network model of the U.S. chemical manufacturing industry was used to assess at what cost points, and the extent to which, chemical products from thermal pyrolysis of polyethylene might find markets in the current U.S. chemical manufacturing industry. Network modeling determined the cost points at which the simulated industry network utilized the thermal pyrolysis products and which processes were displaced by the supply of recycled materials. The characteristic feature of the simulations is the large number of processes in the chemical manufacturing network that are impacted by the availability of a relatively small number of products from polyethylene recycling. In the case of polyethylene recycling, the capital cost requirements for expanding capacity to effectively utilize the recycled materials is greater than the capital required for the pyrolysis process. This suggests that identifying scenarios where recycled materials can be utilized in processes that have excess capacity will be a critical consideration in techno-economic analyses of recycling plastics. 

Post-consumer polyethylene terephthalate (PET) was hydrolyzed in pure water over a wide range of temperatures (190−400 °C) and pressures (1−35 MPa) to produce terephthalic acid (TPA). Solid or molten PET was subjected to water as a saturated vapor, superheated vapor, saturated liquid, compressed liquid, and supercritical fluid. The highest TPA yields were observed for the hydrolysis of molten PET in saturated liquid water. Isothermal and non-isothermal hydrolysis of PET was also explored. Rapidly heating the reactor contents at about 5−10 °C/s (“fast” hydrolysis) led to high TPA yields, as did isothermal PET hydrolysis, but within 1 min instead of 30 min. Notably, these conditions resulted in the lowest environmental energy impact metric observed to date for uncatalyzed hydrolysis. 

The urgency of action toward mitigating climate change and reducing material leakage into the environment is inspiring a plethora of innovative technologies, supply chains, and policy actions. These are targeted toward reducing greenhouse gas emissions, natural resource uptake, and decoupling technological systems from fossil-based linear economies using circularity strategies. Industrial and governmental stakeholders are keen to rank these proposed eco-innovations and emerging alternatives based on their scope of contributing to a sustainable and circular economy to meet global warming curtailment and pollution mitigation targets. We describe a novel methodological framework that relies on a multiobjective optimization of cradle-to-cradle life-cycle pathways to screen from a large database of conceptual eco-innovations and rank them based on their potential for establishing a Sustainable Circular Economy (SCE). This methodology is implemented for a motivating case study to evaluate numerous packaging eco-innovations based on their improvement potential and readiness for adoption within the grocery bags value-chain network. It is demonstrated that a preliminary screening step identifies the 10 most promising eco-innovations from a large superset of alternatives, which if developed and adopted can help transition the value chain to a future scenario with net-zero emissions and adherence to the recycled and renewable-content targets set by the United States Plastics pact but at a higher cost.