The synergistic mechanism between coke depositions and gas for H2 production from co-pyrolysis of biomass and plastic wastes via char supported catalyst

High activity in the dry reforming of methane using a thermally switchable double perovskite and in situ generated molecular level nanocomposite

This work emphasizes the dry reforming of methane (DRM) reaction on citrate sol-gel-synthesized double perovskite oxides. Phase pure La2NiMnO6 shows very impressive DRM activity with H2/CO = 0.9, hence revealing a high prospect of next-generation catalysts. Although the starting double perovskite phase gets degraded into mostly binary oxide phases after a few hours of DRM activity, the activity continues up to 100 h. The regeneration of the original double perovskite out of decomposed phases by annealing at near synthesis temperature, followed by the spectacular retention of activity, is rather interesting and hitherto unreported. This result unravels unique reversible thermal switching between the original double perovskite phase and decomposed phases during DRM without compromising the activity and raises challenge to understand the role of decomposed phases evolved during DRM. We have addressed this unique feature of the catalyst via structure-property relationship using the in situ generated molecular level nanocomposite.

Multifunctional catalyst-assisted sustainable reformation of lignocellulosic biomass into environmentally friendly biofuel and value-added chemicals

Rapid urbanization is increasing the world's energy demand, making it necessary to develop alternative energy sources. These growing energy needs can be met by the efficient energy conversion of biomass, which can be done by various means. The use of effective catalysts to transform different types of biomasses will be a paradigm change on the road to the worldwide goal of economic sustainability and environmental protection. The development of alternative energy from biomass is not easy, due to the uneven and complex components present in lignocellulose; accordingly, the majority of biomass is currently processed as waste. The problems may be overcome by the design of multifunctional catalysts, offering adequate control over product selectivity and substrate activation. Hence, this review describes recent developments involving various catalysts such as metallic oxides, supported metal or composite metal oxides, char-based and carbon-based substances, metal carbides and zeolites, with reference to the catalytic conversion of biomass including cellulose, hemicellulose, biomass tar, lignin and their derivative compounds into useful products, including bio-oil, gases, hydrocarbons, and fuels. The main aim is to provide an overview of the latest work on the use of catalysts for successful conversion of biomass. The review ends with conclusions and suggestions for future research, which will assist researchers in utilizing these catalysts for the safe conversion of biomass into valuable chemicals and other products.

A review on co-pyrolysis of agriculture biomass and disposable medical face mask waste for green fuel production: recent advances and thermo-kinetic models

The Association of Southeast Asian Nations is blessed with agricultural resources, and with the growing population, it will continue to prosper, which follows the abundance of agricultural biomass. Lignocellulosic biomass attracted researchers' interest in extracting bio-oil from these wastes. However, the resulting bio-oil has low heating values and undesirable physical properties. Hence, co-pyrolysis with plastic or polymer wastes is adopted to improve the yield and quality of the bio-oil. Furthermore, with the spread of the novel coronavirus, the surge of single-use plastic waste such as disposable medical face mask, can potentially set back the previous plastic waste reduction measures. Therefore, studies of existing technologies and techniques are referred in exploring the potential of disposable medical face mask waste as a candidate for co-pyrolysis with biomass. Process parameters, utilisation of catalysts and technologies are key factors in improving and optimising the process to achieve commercial standard of liquid fuel. Catalytic co-pyrolysis involves a series of complex mechanisms, which cannot be explained using simple iso-conversional models. Hence, advanced conversional models are introduced, followed by the evolutionary models and predictive models, which can solve the non-linear catalytic co-pyrolysis reaction kinetics. The outlook and challenges for the topic are discussed in detail.

Structure-oriented conversions of plastics to carbon nanomaterials

The accumulation of waste plastics has caused serious environmental issues due to their unbiodegradable nature and hazardous additives. Converting waste plastics to different carbon nanomaterials (CNMs) is a promising approach to minimize plastic pollution and realize advanced manufacturing of CNMs. The reported plastic-derived carbons include carbon filaments (i.e. carbon nanotubes and carbon nanofibers), graphene, carbon nanosheets, carbon sphere, and porous carbon. In this review, we present the influences of different intrinsic structures of plastics on the pyrolysis intermediates. We also reveal that non-charring plastics are prone to being pyrolyzed into light hydrocarbons while charring plastics are prone to being pyrolyzed into aromatics. Subsequently, light hydrocarbons favor to form graphite while aromatics are inclined to form amorphous carbon during the carbon formation process. In addition, the conversion tendency of different plastics into various morphologies of carbon is concluded. We also discuss other impact factors during the transformation process, including catalysts, temperature, processing duration and templates, and reveal how to obtain different morphological CNMs from plastics. Finally, current technology limitations and perspectives are presented to provide future research directions in effective plastic conversion and advanced CNM synthesis.

The impact factors in transforming plastics into carbon nanomaterials are reviewed.

The carbon morphology tendency from different plastics is revealed.

Directions for future research on plastic carbonization are presented.

Value-Added Products from Catalytic Pyrolysis of Lignocellulosic Biomass and Waste Plastics over Biochar-Based Catalyst: A State-of-the-Art Review

As the only renewable carbon resource on Earth, lignocellulosic biomass is abundant in reserves and has the advantages of environmental friendliness, low price, and easy availability. The pyrolysis of lignocellulosic biomass can generate solid biochar with a large specific surface area, well-developed pores, and plentiful surface functional groups. Therefore, it can be considered as a catalyst for upgrading the other two products, syngas and liquid bio-oil, from lignocellulosic biomass pyrolysis, which has the potential to be an alternative to some non-renewable and expensive conventional catalysts. In addition, as another carbon resource, waste plastics can also use biochar-based catalysts for catalytic pyrolysis to solve the problem of accumulation and produce fuels simultaneously. This review systematically introduces the formation mechanism of biochar from lignocellulosic biomass pyrolysis. Subsequently, the activation and modification methods of biochar catalysts, including physical activation, chemical activation, metal modification, and nonmetallic modification, are summarized. Finally, the application of biochar-based catalysts for lignocellulosic biomass and waste plastics pyrolysis is discussed in detail and the catalytic mechanism of biochar-based catalysts is also investigated.

Hydrogen-Rich Gas Production with the Ni-La/Al2O3-CaO-C Catalyst from Co-Pyrolysis of Straw and Polyethylene

Ni-based catalysts have been extensively investigated because of their superior catalytic performance. In this study, the Ni-La/Al2O3-CaO-C catalyst was prepared by homogeneous precipitation, employed in the co-pyrolysis of soybean straw with polyethylene to produce hydrogen. The optimal experimental conditions were identified by discussing the carrier synthesis ratio, feedstock ratio, and addition of La. Additionally, the stability of the catalyst was evaluated. It was established that the carrier was produced using a molar ratio, the raw ingredients ratio of 5:5, and that the optimum catalytic action was obtained when La was added. Co-pyrolysis of soybean straw with polyethylene (PE) that was catalyzed by Ni-La/Al2O3-CaO-C generated 55.45 vol% of H2 under ideal experimental circumstances. After six applications, the H2 yield was 33.89 vol%, compared to 27.5 vol% for the Ni/Al2O3-CaO-C catalyst. The experimental results indicate that Ni-La/Al2O3-CaO-C exhibits superior catalytic activity and stability than Ni/Al2O3-CaO-C.

Synergistic effect of the cotton stalk and high-ash coal on gas production during co-pyrolysis/gasification

The synergistic effect of the cotton stalk (CS) and the high-ash coal (HAC) on the gas production in the co-pyrolysis/gasification processes was studied using the newly designed quartz boat in this work. The gas yield and the concentrations of main gas components were quantitatively compared between the co-pyrolysis/gasification and the individual pyrolysis/gasification. The results showed that the gas yield during the co-pyrolysis was promoted at 950℃. There was almost no interaction between CS and HAC, since the co-pyrolytic gas yield exhibited a linear relationship with CS mixing ratio of 20% to 60%. The catalytic effect of alkali metals and alkaline earth metals that existed in CS, was enhanced by the addition of steam, and the synergistic effect was reduced while gas yield was enhanced with CS blending ratio increasing during co-gasification. The results provided a method to enhance synergistic effect between biomass and coal during co-pyrolysis/gasification in this study.