Production of hydrogen and carbon nanotubes via catalytic thermo‐chemical conversion of plastic waste: review

Abstract

BACKGROUND: Plastic waste has been growing at an alarming rate with dissatisfactory recycling rates. It has a potential to be used for the recovery of hydrogen and carbon nanotubes due to its intrinsic properties. RESULTS: Thermo-chemical processes may be used to tap into the recovery of these resources from the wastes. Catalysts can be employed to increase the gaseous yield and to optimize the process parameters. Hydrogen production is greatly influenced by the catalyst properties, temperature, steam and feedstock. Similarly, the carbon deposits formed are influenced by many factors such as type of metal catalyst used and metal-support interaction. This review focuses on studies employing catalytic thermo-chemical processes for extracting hydrogen and carbon nano structures from plastic wastes while evaluating the role of parameters such as temperature, catalyst type, catalyst composition, steam/feed ratio, feed rate, feedstock and their effect on the product yields. CONCLUSION: In view of increasing concerns regarding waste management, climate change and energy security the possibility of employing waste products for producing clean energy in a sustainable manner is appealing and needs additional fundamental research.C 5+ and cracking products. There is a decrease in catalyst deactivation rate due to increased gasification of deposited coke, faster J Chem Technol Biotechnol 2020; 95: [11][12][13][14][15][16][17][18][19]

Marine Environmental Plastic Pollution: Mitigation by Microorganism Degradation and Recycling Valorization

“…Yet, these are not efficient enough to deal with the plastic pollution problem; alternatively, chemical decomposition can be applied to depolymerize and repolymerize plastic material in a sustainable number of cycles (Jehanno et al, 2019). Several recent reviews on this topic have been published, and they focus on characteristic plastic transformation routes, such as thermochemical routes (Lopez et al, 2017;Uzoejinwa et al, 2018), carbonization route , petrochemical routes and hydrocracking (Thybaut and Marin, 2016;Hassan et al, 2019), production of hydrogen and nanotubes (Sharma and Batra, 2020), bioconversion by immobilized enzymes (Bilal and Iqbal, 2019), plastic gasification (Lopez et al, 2018), and catalytic pyrolysis (Qiu et al, 2018). In addition to these reviews, the aim of this section is to evaluate recent literature focusing on chemical methods complementary to biodegradation and applied (or applicable) to some of the major plastic pollutants.…”

Hydrogen and Carbon Nanotubes from Pyrolysis-Catalysis of Waste Plastics: A Review

“…33,40]. While fixed bed reactors have a simple design, are easy to operate and are of low cost, they have disadvantages of poor heat transfer rates and low gas-solid contact [46], which is particularly problematic at larger scale. They are also difficult to scale-up because of the higher manpower required for operation in relation to the tonnages of plastic waste throughput of the plant, resulting in higher operational costs and lower cost effectiveness [24].…”

The Use of Heterogeneous Catalysis in the Chemical Valorization of Plastic Waste

“…[54] There are many reviews that cover the pyrolysis, hydrocracking, and gasification of plastic waste with emphasis on the technique (i. e., operating conditions) and specific end product. [5,11,23,[27][28][29][30][31][32][33][34][35][36][37][38][39][41][42][43][44][45][46][47][48][49][50][51][52][54][55][56][57][58][59][60][61][62][63] Here, we present a comprehensive review of the various catalysts that have investigated for PSW conversion, focusing on the effects of catalyst properties on the outcome of the plastic conversion. This review aims to draw a connection between the impact of the textural properties of the catalyst and its performance for plastic conversion with hopes that this can be a useful resource for the development and design of future improved plastic waste conversion catalysts.…”

“…Thermal cracking is attractive because it can be carried out locally at waste collection and plastic segregation points with technologies that are environmentally friendly while yielding desirable materials [27] . The product outcome is largely dependent on the process conditions (i. e., temperature) and composition of the plastic waste and because of this, the production of low molecular weight materials requires high operation temperatures ( T >500 °C) [2,6,11,12,14–16,23–52] . Along with the dependence on pyrolysis temperature, thermal cracking yields a broad range of hydrocarbons with respect to the carbon number, making the large‐scale production of renewable materials (the main goal of the circular economy), transportation‐quality fuels (secondary products), and valuable chemicals difficult.…”

“…There are many reviews that cover the pyrolysis, hydrocracking, and gasification of plastic waste with emphasis on the technique (i. e., operating conditions) and specific end product [5,11,23,27–39,41–52,54–63] . Here, we present a comprehensive review of the various catalysts that have investigated for PSW conversion, focusing on the effects of catalyst properties on the outcome of the plastic conversion.…”