P.T.Williams

Integrated carbon capture and utilisation (ICCU) is an emerging technology for simultaneous CO2 adsorption and conversion into value-added products. This provides a more sustainable approach compared to carbon capture and storage. Dual-functional materials (DFMs) that couple CO2 sorbents (e.g. CaO) and catalysts (e.g. Ni) enable direct utilisation of sorbed CO2 for reactions like dry reforming of methane (DRM). However, the potential interactions between sorbent and catalyst components within DFMs may induce distinct mechanisms compared to individual materials. Elucidating these synergies and interfacial phenomena is vital for guiding the rational design of DFMs. This article investigates the respective roles of Ni/SiO2 catalyst and sol–gel synthesised CaO sorbent in integrated CO2 capture and utilisation via dry reforming of methane (ICCU-DRM) using a decoupling approach. Through decoupled …

Conventional catalytic pyrolysis of waste plastics for H2 production faces challenges due to excessively high reaction temperatures. This study introduced a NiCeOx/β catalyst for low-temperature H2 production from polyethylene (PE), aiming to enhance H2 yield through nonthermal plasma (NTP) and catalytic active sites. Experimental results confirmed the efficacy of NTP in promoting collision between high-potential-energies active species and plasma-catalyst interactions, identifying acidic sites as primary catalytic active sites. Both experiments and density functional theory (DFT) calculations confirmed NiO and CeO2 particles as metallic active sites, exhibiting thermodynamic and kinetic benefits for primary products from PE pyrolysis. Under optimal conditions, the highest H2 yield and selectivity respectively reached 32.71 mmol/g and 82.10 % at a PE/(NiCeOx/β) ratio of 1:4, reaction temperature of 400 °C, and …

Five common single plastics and nine different household, commercial and industrial waste plastics were processed using a three-stage (i) pyrolysis, (ii) catalytic steam reforming and (iii) water gas shift reaction system to produce hydrogen. Pyrolysis of plastics produces a range of different hydrocarbon species which are subsequently catalytically steam reformed to produce H2 and CO and then undergo water gas shift reaction to produce further H2. The process mimics the commercial process for hydrogen production from natural gas. Processing of the single polyalkene plastics (high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP)) produced similar H2 yields between 115 mmol and 120 mmol per gram plastic. Even though PS produced an aromatic product slate from the pyrolysis stage, further stages of reforming and water gas shift reaction produced a gas yield and …

Ash derived from the oxidation of waste tire and processed municipal solid waste in the form of refuse-derived fuel have been investigated for their potential as catalysts in the pyrolysis catalytic steam reforming of high-density polyethylene to produce hydrogen-rich syngas. The surface morphology, element distribution, pore structure and metal composition of the ashes were characterized to explore the effects of these ash properties on the catalytic process. Further work using tire ash investigated the influence of the process parameters, catalytic temperature and catalyst plastic ratio in relation to the production of hydrogen and syngas. The results showed that tire ash had a higher specific surface area and pore volume than refuse-derived fuel ash, resulting in a slightly higher hydrogen yield compared to refuse derived fuel ash. An increase in the temperature of the catalytic steam reforming process with the tire ash …

Pyrolysis-catalytic steam reforming of waste plastics to produce hydrogen-rich syngas has been investigated using tire char as a sacrificial catalyst in a two-stage pyrolysis-catalytic steam reforming reactor system. The simultaneous steam reforming of the pyrolysis volatiles and ‘sacrificial’ steam gasification of tire char increased the overall yield of syngas and hydrogen in the gas products. Manipulating the catalyst temperature, steam input, char catalyst:plastic ratio influenced hydrogen yield. The presence of metals such as Zn, Fe, Ca and Mg in tire char, play a catalytic role in steam reforming reactions. The syngas production achieved when the catalyst temperature was 1000 °C and steam weight hourly space velocity was 8 g h−1 g−1 catalyst was 135 mmol H2 g-1plastic and 92 mmol CO g-1plastic. However, increasing the amount of char catalyst (4:1 char catalyst:plastic ratio) enabled hydrogen yields of 211 …

Hydrothermal co-liquefaction of biomass and polyolefin plastic feedstocks offers the advantage of potential synergistic reaction environments for producing liquid products of high fuel quality. In this present study, hydrothermal liquefaction and co-liquefaction of sawdust, low-density polyethylene and high-density polyethylene were investigated in a batch reactor from 350 °C to 450 °C and autogenic pressures below 30 bar. The novel low-pressure hydrothermal processing method was carried out with and without low-cost Ni–Cu/Al2O3 bimetallic catalyst. Thermal degradation of the sawdust started at 350 °C, whereas the plastics could only completely degrade at 450 °C, which was then chosen as the optimum reaction temperature. The catalysed process led to an increase in oil yield from the sawdust, with carbon enrichment by 16.3% and 22% deoxygenation. Furthermore, the catalyst promoted the formation of …

Correction to: Decomposition of biomass gasification tar model compounds over waste tire pyrolysis char Page 1 Vol.:(0123456789) 1 3 Waste Disposal & Sustainable Energy https://doi.org/10.1007/s42768-023-00150-6 CORRECTION Correction to: Decomposition of biomass gasification tar model compounds over waste tire pyrolysis char Amal S. Al‑Rahbi1,2 · Paul T. Williams1 © The Author(s) 2023 Correction to: Waste Disposal & Sustainable Energy (2022) 4:75–89 https://doi.org/10.1007/s42768-022-00103-5 The section ‘Conflict of Interest’ has been amended; ‘Paul T. Williams is the Editorial Board member of Waste Disposal & Sustainable Energy.’ The revised ‘Conflict of Interest’ is as follows: Paul T. Williams is the Editorial Board mem- ber of Waste Disposal & Sustainable Energy. On behalf of all authors, the corresponding author states that there is no conflict of interest. The original article has been corrected. …

Global warming and climate change require urgent reduction of CO2 emissions. Integrated carbon capture and utilisation combined with dry reforming of methane (ICCU-DRM) has the potential to mitigate greenhouse gas emissions by capturing and converting CO2 and CH4 into valuable syngas. However, the performance and stability of dual-functional materials (DFMs) are unclear under real-world flue gas conditions, particularly in the presence of steam and O2. In this study, we elucidated the mechanisms of the performance of a Ni0.05/CaO0.95 DFM under various flue gas conditions and investigated the combined effects of steam and O2 on CO2 uptake, CO and H2 yields and cyclic stability. Our approach includes the synthesis and evaluation of the DFM using advanced characterisation techniques, such as XRD, in-situ infrared spectroscopy, CH4-TPR, SEM, EXD, FIB-SEM, BET, and XPS, to gain insights into …

Single plastics and mixed waste plastics from different industrial and commercial sectors have been investigated in relation to the production of hydrogen and syngas using a pyrolysis–catalytic steam reforming process. The catalyst used was a carbonaceous char catalyst produced from the pyrolysis of waste tires. Total gas yields from the processing of single plastics were between 36.84 and 39.08 wt % (based on the input of plastic, reacted steam, and char gasification) but those in terms of the gas yield based only on the mass of plastic used were very high. For example, for low-density polyethylene (LDPE) processing at a catalyst temperature of 1000 °C, the gas yield was 445.07 wt % since both the reforming of the plastic and also the steam gasification of the char contributed to the gas yield. The product gas was largely composed of H2 and CO, i.e., syngas (∼80 vol %), and the yield was significantly increased …

Dechlorination is essential for the chemical recycling of waste polyvinyl chloride (PVC) plastics. This study investigated the use of non-thermal plasma (NTP) for chlorine removal, with a focus on the effects of treatment time and discharge power on dechlorination efficiency. The results showed that longer treatment times and higher discharge powers led to better dechlorination performance. The maximum efficiency (98.25%) and HCl recovery yield (55.72%) were achieved at 180 W power after 40 min of treatment where 96.44% of Cl existed in the form of HCl gas, 1.44% in the liquid product, and 2.12% in the solid residue product. NTP at a discharge power of 150 W showed better dechlorination performance compared to traditional thermal pyrolysis treatment in temperatures ranging from 200 to 400 °C. The activation energy analysis of the chlorine removal showed that compared to pyrolysis-based dechlorination …

The three-stage (i) pyrolysis, (ii) catalytic steam reforming, and (iii) water gas shift processing of waste plastic for the production of hydrogen have been investigated. The (i) pyrolysis and (ii) catalytic steam reforming process conditions were maintained throughout, and the experimental program investigated the influence of process conditions in the (iii) water gas shift reactor in terms of catalyst type (metal–alumina), catalyst temperature, steam/carbon ratio, and catalyst support material. The metal–alumina catalysts investigated in the (iii) water gas shift stage showed distinct maximization of hydrogen yield, which was dependent on the catalyst type at either higher temperature (550 °C) (Fe/Al2O3, Zn/Al2O3, Mn/Al2O3) or lower temperature (350 °C) (Cu/Al2O3, Co/Al2O3). The highest hydrogen yield was found with the Fe/Al2O3 catalyst; also, increased catalyst Fe metal loading resulted in improved catalytic …

High-density polyethylene (HDPE) was pyrolyzed in a fixed-bed reactor and the derived pyrolysis volatiles passed directly to a second-stage fixed-bed reactor for catalytic steam reforming with the aim to produce hydrogen-rich syngas. The catalysts used were biochar produced from the pyrolysis of waste biomass and solid waste char produced from the pyrolysis of processed municipal solid waste in the form of refuse-derived fuel (RDF). The influence of char catalyst temperature and steam input were used to optimize the production of H2 syngas. Other types of waste plastics (low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), and poly(ethylene terephthalate) (PET)) were also investigated to compare with the production from HDPE. The highest yields of syngas (H2, CO) were produced at 3.83 g gplastic–1 for biochar as the catalyst and 2.73 g gplastic–1 for RDF char as the catalyst, when the …

Different types of single waste plastics and a range of real-world mixed waste plastics from several different industrial and commercial sources have been processed in a pyrolysis-plasma/catalytic experimental reactor system for the production of hydrogen. The hydrocarbons produced from the pyrolysis stage were catalytically (Ni/MCM-41) steam reformed in a low temperature, non-thermal plasma/catalytic reactor. The polyolefin plastics, high density polyethylene, low density polyethylene and polypropylene produced the highest yield of hydrogen at 18.0, 17.3 and 16.3 mmol g−1plastics respectively. The aromatic structured polystyrene produced a lower hydrogen yield of 11.9 mmol g−1plastics and polyethylene terephthalate with an aromatic and oxygenated structure produced only 10.2 mmol g−1plastics and a high yield of carbon oxide gases. The real-world mixed plastic waste produced yields of hydrogen in …

Bio-oil produced from the pyrolysis of biomass is chemically complex, viscous, highly acidic, and highly oxygenated. Copyrolysis of biomass and plastics can enhance oil quality by raising the H/C ratio, leading to improved biofuel properties. In this work, copyrolysis of polystyrene and biomass was passed to a second-stage dielectric barrier discharge nonthermal plasma reactor with the aim to further improve the product bio-oil. Pyrolysis of the polystyrene and biomass produces volatiles that pass to the second stage to undergo cracking and autohydrogenation reactions under nonthermal plasma conditions. There was a synergistic interaction between biomass and polystyrene in terms of overall oil and gas yield and composition even in the absence of the nonthermal plasma. However, the introduction of the nonthermal plasma produced a marked increase in monocyclic aromatic hydrocarbons (e.g., ethylbenzene …

A two-stage pyrolysis–nonthermal plasma/catalytic steam reforming reactor system was used to produce hydrogen from waste high-density polyethylene in relation to different catalyst support materials. The catalyst support materials investigated were MCM-41, Y-zeolite, ZSM-5, Al2O3, TiO2, dolomite, BaTiO3, CaTiO3, and Mo2C. Some of the materials suppressed the generation of plasma, while others enhanced it by improving the generation of microdischarges and surface discharges. Among the tested materials, MCM-41 gave the highest gas yield of 29.2 wt % and a hydrogen yield of 11 mmol g–1plastic. The coupling of the catalyst with the plasma environment resulted in synergy in terms of enhanced total gas yield and hydrogen production, which were higher than those in the absence of plasma (catalyst alone) or plasma alone (no catalyst). Other parameters investigated using the MCM-41 support material …

Waste tires are solid wastes with large annual output and with the potential for great harm to the environment. The pyrolysis of waste tires can recycle energy and produce reusable products. Although there are many reviews in the literature in regard to the pyrolysis characteristics of waste tires, no one paper focuses on reviewing and summarizing the tire char. This paper critically appraises the achievements of earlier reports and literature and assesses the current state-of-the-art for the production and application of tire char from waste tires. Initially, the thermal decomposition behavior of different tire rubbers is discussed and compared where it is shown that the different components of waste tire rubber have different thermal degradation characteristics. The influencing factors on the yield and quality of tire char are discussed and assessed in terms of different pyrolysis reactors and technologies, tire type and …

Biomass and waste polystyrene plastic (ratio 1:1) were co-pyrolysed followed by catalysis in a two-stage fixed bed reactor system to produce upgraded bio-oils for production of liquid fuel and aromatic chemicals. The catalysts investigated were ZSM-5 impregnated with different metals, Ga, Co, Cu, Fe and Ni to determine their influence on bio-oil upgrading. The results showed that the different added metals had a different impact on the yield and composition of the product oils and gases. Deoxygenation of the bio-oils was mainly via formation of CO2 and CO via decarboxylation and decarbonylation with the Ni–ZSM-5 and Co–ZSM-5 catalysts whereas higher water yield and lower CO2 and CO was obtained with the ZSM-5, Ga–ZSM-5, Cu–ZSM-5 and Fe–ZSM-5 catalysts suggesting hydrodeoxygenation was dominant. Compared to the unmodified ZSM-5, the yield of single-ring aromatic compounds in the …

Integrated CO2 capture and utilisation (ICCU) is a promising strategy for restricting carbon emissions and achieving carbon neutrality. Bifunctional combined materials (BCMs), containing adsorbents and active catalysts, are widely applied in this process. Producing syngas via reverse water–gas shift reaction (RWGS) and integrating with Fischer-Tropsch (F-T) synthesis is an attractive and valuable CO2 utilisation route. This work investigated a series of Ni/support-CaO BCMs (supports = ZrO2, TiO2, CeO2 and Al2O3) for the integrated CO2 capture and RWGS (ICCU-RWGS) process. The Ni/support-CaO BCMs were prepared by physically mixing various metal oxide supports loaded Ni with sol–gel derived CaO. The ICCU-RWGS performance (CO2 conversion, CO yield and CO generation rate) of these BCMs followed the order during tested conditions (550–750 °C): Ni/CeO2-CaO > Ni/TiO2-CaO > Ni/ZrO2 …

The production of hydrogen (H2) from the pyrolysis–catalytic steam reforming of polyethylene, polystyrene (PS) and polyethylene terephthalate waste plastics was investigated using a two-stage reactor. The highest yield of hydrogen (125 mmol/gplastic) was obtained with PS at a catalyst temperature of 900°C and steam input weight hourly space velocity of 7.59 g/(h/gcatalyst) with a 10 wt% nickel/aluminium oxide (Ni/Al2O3) catalyst. Further investigation using PS showed that the process parameters of high catalyst temperature (900°C) and optimised steam input rate significantly increased the yield of hydrogen. Examination of several different catalysts (nickel/aluminium oxide, iron/aluminium oxide, copper/aluminium oxide, cobalt/aluminium oxide) showed that nickel/aluminium oxide had by far the highest catalytic activity and selectivity towards the yield of hydrogen.

Pyrolysis of fibrous biomass followed by alkali (KOH and K2CO3) chemical activation of the pyrolysis char for the production of activated carbon fibre matting material has been investigated. For KOH, activation initially involved the melting of the KOH and reaction with the disorganised/volatile material of the char, producing hydrogen gas and K2CO3 and further developing the existing pore structure of the char. At higher temperatures (>700 °C), pore widening occurs due to physical activation with less reaction of the alkali molten phase with the char. Metallic potassium or other potassium species may also contribute to the pore widening process. Chemical activation with K2CO3 occurs at higher temperatures (>600 °C) and is controlled by the decomposition of K2CO3 to K2O and CO2. The development of surface area and porosity occurs through reaction of the pyrolysis char with K2O and CO2. The production of CO …