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Plastic waste management is an area of concern globally, given the accumulation of plastics in landfills and the natural environment. Gasification can convert mixed plastic waste (MPW) to synthesis gas (syngas), a mixture of carbon monoxide (CO) and hydrogen (H2), which can be further converted to commodity chemicals. In this work, we present techno-economic analysis (TEA) and life cycle assessment (LCA) for two gasification pathways that produce methanol and hydrogen from MPW feedstock. In particular, we modeled the gasifier as a dual fluidized bed reactor for MPW gasification in a greenfield, standalone facility. Our analysis indicates that the minimum selling price (MSP) of methanol and hydrogen produced by MPW gasification is $0.70 kg−1 and $3.41 kg−1, respectively. For comparison, we also evaluate the production of methanol and hydrogen from municipal solid waste. For MPW gasification processes, the syngas yield (kg syngas per kg plastic) and waste plastic feedstock price have the largest impact on MSP. Waste plastic feedstock prices of <$0.02 kg−1 can enable MPW-based processes to achieve cost parity with existing fossil-fuel-derived pathways. Additionally, LCA indicates that methanol and hydrogen produced from MPW gasification can reduce the total supply chain energy use by 52% and 56% respectively when compared with fossil-fuel-derived pathways. However, the greenhouse gas emissions (GHG) from MPW-gasification pathways are estimated to increase by 166% and 36% for methanol and hydrogen, respectively, compared to their current production pathways. Due to the co-product credit of steam and electricity export, MPW gasification pathways have lower levels of smog formation, acidification, non-carcinogenics, ozone depletion, eutrophication and particulates than the respective incumbent processes. Since waste streams are the feedstocks in this study, no energy burden was assigned to the upstream processes. Overall, this work identifies syngas yield and waste plastic feedstock price as the two critical variables with the largest impact on the MSP of products produced by MPW gasification. The outcomes of this work can help guide future research in MPW gasification. [ABSTRACT FROM AUTHOR]

Partial deoxygenation of bio-oil by catalytic fast pyrolysis with subsequent coupling and hydrotreating can lead to improved economics and will aid commercial deployment of pyrolytic conversion of biomass technologies. Biomass pyrolysis efficiently depolymerizes and deconstructs solid plant matter into carbonaceous molecules that, upon catalytic upgrading, can be used for fuels and chemicals. Upgrading strategies include catalytic deoxygenation of the vapors before they are condensed (in situ and ex situ catalytic fast pyrolysis), or hydrotreating following condensation of the bio-oil. In general, deoxygenation carbon efficiencies, one of the most important cost drivers, are typically higher for hydrotreating when compared to catalytic fast pyrolysis alone. However, using catalytic fast pyrolysis as the primary conversion step can benefit the entire process chain by: (1) reducing the reactivity of the bio-oil, thereby mitigating issues with aging and transport and eliminating need for multi-stage hydroprocessing configurations; (2) producing a bio-oil that can be fractionated through distillation, which could lead to more efficient use of hydrogen during hydrotreating and facilitate integration in existing petroleum refineries; and (3) allowing for the separation of the aqueous phase. In this perspective, we investigate in detail a combination of these approaches, where some oxygen is removed during catalytic fast pyrolysis and the remainder removed by downstream hydrotreating, accompanied by carbon–carbon coupling reactions in either the vapor or liquid phase to maximize carbon efficiency toward value-driven products (e.g. fuels or chemicals). The economic impact of partial deoxygenation by catalytic fast pyrolysis will be explored in the context of an integrated two-stage process. Finally, improving the overall pyrolysis-based biorefinery economics by inclusion of production of high-value co-products will be examined. [ABSTRACT FROM AUTHOR]

During catalytic upgrading over HZSM-5 of vapors from fast pyrolysis of biomass (ex situ CFP), water reacts with aromatic intermediates to form phenols that are then desorbed from the catalyst micropores and produced as products. We observe this reaction using real time measurement of products from neat CFP and with added steam. The reaction is confirmed when 18O-labeled water is used as the steam source and the labeled oxygen is identified in the phenol products. Furthermore, phenols are observed when cellulose pyrolysis vapors are reacted over the HZSM-5 catalyst in steam. This suggests that the phenols do not only arise from phenolic products formed during the pyrolysis of the lignin component of biomass; phenols are also formed by reaction of water molecules with aromatic intermediates formed during the transformation of all of the pyrolysis products. Water formation during biomass pyrolysis is involved in this reaction and leads to the common observation of phenols in products from neat CFP. Steam also reduces the formation of non-reactive carbon in the zeolite catalysts and decreases the rate of deactivation and the amount of measured “coke” on the catalyst. These CFP results were obtained in a flow microreactor coupled to a molecular beam mass spectrometer (MBMS), which allowed for real-time measurement of products and facilitated determination of the impact of steam during catalytic upgrading, complemented by a tandem micropyrolyzer connected to a GCMS for identification of the products. [ABSTRACT FROM AUTHOR]

The conversion of biomass primary pyrolysis vapors over several β-zeolites with silica-to-alumina ratios (SAR) varying from 21 to 250 was carried out in a flow microreactor to investigate the effect of number of acid sites on product speciation and deactivation of the catalyst. Experiments were conducted using a horizontal fixed bed semi-batch reactor in which up to 40 discrete 50 mg boats of biomass were pyrolyzed and the vapors upgraded over 0.5 g of the catalyst. Products were measured with a molecular beam mass spectrometer (MBMS). These studies were complemented using a tandem micropyrolyzer connected to a GCMS (py-GCMS) for speciation and quantifying the products. In the py-GCMS experiments, several 0.5 mg loads of pine were pyrolyzed sequentially and the vapors upgraded over 4 mg of catalyst. In all of these experiments, real-time measurements of the products formed were conducted as the catalyst aged and deactivated during upgrading. The results from these experiments showed that: (1) fresh catalyst for β-zeolites with lower SAR (more acid sites) produced primarily aromatic hydrocarbons and olefins with no detectable oxygen-containing species; (2) a suite of oxygenated products was observed from fresh catalysts with high SAR (few acid sites), indicating that 0.5 g of these catalyst materials did not have sufficient acid sites to deoxygenate vapors produced from pyrolysis of 50 mg of pine. This suite of oxygen containing products consisted of furans, phenol and cresols. The amount of coke deposited on each catalyst and the yield of aromatic hydrocarbons increased with the number of acid sites. However, while the catalysts were active, the biomass selectivity towards coke and hydrocarbons remained essentially constant on the catalysts of varying SAR. [ABSTRACT FROM AUTHOR]

Pyrolysis offers a rapid and efficient means to depolymerize lignocellulosic biomass, resulting in gas, liquid, and solid products with varying yields and compositions depending on the process conditions. With respect to manufacture of "drop-in" liquid transportation fuels from biomass, a potential benefit from pyrolysis arises from the production of a liquid or vapor that could possibly be integrated into existing refinery infrastructure, thus offsetting the capital-intensive investment needed for a smaller scale, standalone biofuels production facility. However, pyrolysis typically yields a significant amount of reactive, oxygenated species including organic acids, aldehydes, ketones, and oxygenated aromatics. These oxygenated species present significant challenges that will undoubtedly require pre-processing of a pyrolysisderived stream before the pyrolysis oil can be integrated into the existing refinery infrastructure. Here we present a perspective of how the overall chemistry of pyrolysis products must be modified to ensure optimal integration in standard petroleum refineries, and we explore the various points of integration in the refinery infrastructure. In addition, we identify several research and development needs that will answer critical questions regarding the technical and economic feasibility of refinery integration of pyrolysis- derived products. [ABSTRACT FROM AUTHOR]

Lignin depolymerisation is traditionally facilitated with homogeneous acid or alkaline catalysts. Given the effectiveness of homogeneous basic catalysts for lignin depolymerisation, here, heterogeneous solid-base catalysts are screened for C-O bond cleavage using a model compound that exhibits a common aryl-ether linkage in lignin. Hydrotalcite (HTC), a layered double hydroxide (LDH), is used as a support material as it readily harbours hydroxide anions in the brucite-like layers, which are hypothesised to participate in catalysis. A 5 wt% Ni/HTC catalyst is particularly effective at C-O bond cleavage of a model dimer at 270 °C without nickel reduction, yielding products from C-O bond cleavage identical to those derived from a base-catalysed mechanism. The 5% Ni-HTC catalyst is shown to depolymerise two types of biomass-derived lignin, namely Organosolv and ball-milled lignin, which produces alkyl-aromatic products. X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy show that the nickel is well dispersed and converts to a mixed valence nickel oxide upon loading onto the HTC support. The structure of the catalyst was characterised by scanning and transmission electron microscopy and X-ray diffraction, which demonstrates partial dehydration upon reaction, concomitant with a base-catalysed mechanism employing hydroxide for C-O bond cleavage. However, the reaction does not alter the overall catalyst microstructure, and nickel does not appreciably leach from the catalyst. This study demonstrates that nickel oxide on a solid-basic support can function as an effective lignin depolymerisation catalyst without the need for external hydrogen and reduced metal, and suggests that LDHs offer a novel, active support in multifunctional catalyst applications. [ABSTRACT FROM AUTHOR]