This study presents the results of a preliminary assessment on the technology, economics, and sustainability of using waste plastics as a feedstock to produce low molecular weight olefins via pyrolysis and gasification pathways. We also studied the formation of formaldehyde – an important polymer precursor – via the gasification of waste plastics. Process pathways for recovery of ethylene and propylene and production of formaldehyde from a simulated mixed plastic waste were constructed based on literature data. They included direct and indirect pathways based on either gasification or pyrolysis as the primary conversion step. Results of these studies have shown that significant economic challenges exist of producing olefins via pyrolysis and gasification, with the latter pathway especially difficult. Base costs of pyrolysis naphtha from waste plastics are higher when compared to the same material produced from fossil feedstocks. Base olefin costs for one direct route are two times higher than comparable costs from steam cracking of fossil naphtha. These costs are driven primarily by feedstock costs; some pyrolysis scenarios become more economically feasible when very low feedstock costs are used. Similarly, for gasification, the cost of methanol – the central intermediate – was found to be noticeable higher when produced by gasification of waste plastics compared to current selling prices, which negatively impacts all pathways that go through methanol as the central intermediate. Life-cycle assessment indicates that the production of pyrolysis naphtha from plastics is a carbon intensive operation; no major advantages were found in terms of greenhouse gas emissions for any of the pathways producing C2 and C3 olefins. The results of this study can serve as the baseline for future comparison to other plastic waste valorization processes.

This study analyzes catalytic fast pyrolysis as a conversion technology for mixed plastic waste, highlighting key economic and environmental drivers and potential opportunities for process improvements.

This work examines the feasibility of a greenfield mixed plastics waste gasification facility with process modeling, TEA, and LCA.

The Propane Education and Research Council (PERC) has engaged with the National Renewable Energy Laboratory (NREL) to develop information that is critical to understanding the current and future landscape for renewable propane (RP) and the value proposition for recovery of RP from existing and planned HEFA biorefineries. In summary the following outcomes are identified from this study: (1) production of incremental RP by increasing the severity of the hydroisomerization step is insignificant to the overall propane yield from a HEFA biorefinery, however production of renewable butane (or LPG2) is quite significant thus suggesting alternate strategies for valorizing these fractions; (2) the value proposition for recovering RP and renewable LPG is quite strong, with capital recovery payback periods of 14 months for a small biorefinery producing 3.5 million gallons per year RP to as short as 2 months for a large biorefinery producing 87 million gallons per year RP. Paybacks for renewable LPG are as much as 50% shorter; and (3) current and projected expansions of renewable diesel will greatly expand the potential availability of RP as a by-product. Several promising new pathways are under development but will not significantly increase production of RP for the next decade.

Co-processing bio-oils with petroleum-derived feeds in the existing multitrillion dollar refining and distribution infrastructure is an attractive option for introducing renewable energy into the fuels marketplace. Considerable research on co-processing bio-oils and vacuum gas oil (VGO) in fluid catalytic cracking units (FCC) using equilibrium catalysts (E-Cats) demonstrated that biomass-derived molecules decreased activity of and increased carbon laydown on E-Cat. In this work, C-13-labeled biomass was co-processed with VGO using either an E-Cat or a proprietary zeolite Johnson Matthey catalyst (CP758), which is optimzed for upgrading biomass vapors in a riser reactor, to evaluate the fate of biogenic carbon in FCC products. The results from both catalysts indicate that biogenic carbon was incorporated into alkenes and aromatic hydrocarbons. While no biogenic carbon was found in linear alkanes, it was observed in cycloalkanes during experiments with E-Cat but not with CP758. All produced CO2 was biogenic as was most of the carbon laydown on the catalysts. Several partially deoxygenated biomass compounds, such as alkylphenols and benzofurans, unexpectedly contained small amounts of carbon from VGO. Although this study was conducted with labeled biomass and not bio-oil, it provides insights to reaction mechanisms for co-processing bio-oil and VGO in an FCC, which is required to develop catalysts that efficiently convert bio-oil components during FCC co-processing. This work also demonstrates that comprehensive catalyst development utilizing both biomass- and fossil-derived feeds is required to maximize the incorporation of biogenic carbon into transportation fuels.

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.

Fast pyrolysis is heating on the order of 1000 °C/s in the absence of oxygen to 40–600 °C, which causes decomposition of the biomass. Liquid product yield from biomass can be as much as 80% of starting dry weight and contains up to 75% of the biomass energy content. Other products are gases, primarily carbon monoxide, carbon dioxide, and methane, as well as solid char and ash. Residence time in the reactor is only 0.5–2 s so that relatively small, low-capital-cost reactors can be used. The low capital cost combined with greenhouse gas emission reductions relative to petroleum fuels of 50–95% makes pyrolysis an attractive process. The pyrolysis liquids have been investigated as a refinery feedstock and as stand-alone fuels. Utilization of raw pyrolysis oil has proven challenging. The organic fraction is highly corrosive because of its high organic acid content. High water content lowers the net heating value and can increase corrosivity. It can be poorly soluble in petroleum or petroleum products and can readily absorb water. Distillation residues can be as high as 50%, viscosity can be high, oils can exhibit poor stability in storage, and they can contain suspended solids. The ignition quality of raw pyrolysis oils is poor, with cetane number estimates ranging from 0 to 35, but more likely to be in the lower end of that range. While the use of raw pyrolysis oils in certain specific applications with specialized combustion equipment may be possible, raw oils must be significantly upgraded for use in on-highway spark-ignition (SI) and compression-ignition (CI) engines. Upgrading approaches most often involve catalytic hydrodeoxygenation, one of a class of reactions known as hydrotreating or hydroprocessing. This chapter discusses the properties of raw and upgraded pyrolysis oils, as well as the potential for integrating biomass pyrolysis with a petroleum refinery to significantly reduce the hydroprocessing cost.

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.

This study investigates the role of β-zeolite acid site density on hydrocarbon and coke yields.

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 arylether 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 degrees 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.

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 pyrolysis-derived 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.

The objective of this research project was to test the hypothesis that separation of char with its associated mineral matter from pyrolysis vapors before condensation will lead to improved bio-oil quality and stability with respect to storage and transportation. The metric prescribed by the U.S. Department of Energy (DOE) to evaluate stability in this case was a 10-fold reduction in the rate of increase of viscosity as determined by an accelerated aging test. The primary unit operation that was investigated for this purpose was hot gas filtration. A custom-built heated candle filter system was fabricated by the Pall Corporation and furnished to the National Renewable Energy Laboratory (NREL) for this test campaign. This system consisted of a candle filter element in a containment vessel surrounded by heating elements on the external surface of the vessel. The filter element and housing were interfaced to NREL's existing 0.5 MTD pyrolysis process development unit (PDU). For these tests, the pyrolysis reactor of the PDU was operated in the entrained-flow mode. The hot gas filter (HGF) test stand was installed on a slipstream from the PDU, so that both hot gas filtered oil and bio-oil that was not hot gas filtered could be collected for purposes of comparison. Two filter elements from Pall Corporation were tested: (1) porous sintered stainless-steel (PSS) metal powder and (2) sintered ceramic powder. A sophisticated bio-oil condensation and collection system was designed and fabricated at NREL and interfaced to the slipstream filter unit. The test campaign on vapor-phase filtration of biomass-derived pyrolysis oil demonstrated that a bio-oil with substantially improved properties can be obtained by application of hot gas filtration. The ceramic filter element and test stand supplied by Pall Corporation and the vapor condensation and collection system designed and fabricated by NREL both demonstrated very good operability. Application of periodic blowback was shown to be effective in maintaining the filter element pressure drop within acceptable limits, and filter plugging was never experienced. A bio-oil with greatly reduced alkali and alkaline earth metals and very low solids content was produced. Bio-oil obtained by hot gas filtration with a PSS element had elevated iron content, suggesting that the material of construction is not suitable for this application. The PSS-filtered bio-oil also did not pass the viscosity metric of a 10-fold reduction in the rate of viscosity increase as determined by the accelerated aging test at 80 degrees C. Bio-oil obtained by hot gas filtration with a ceramic (Dia-Schumalith sintered ceramic powder) filter element was also low in alkali and alkaline earth metals and total solids and did not exhibit high iron content. The ceramic-filtered oil passed the viscosity metric, indicating that this oil should be much improved with respect to storage and transport stability. Total mass loss because of hot gas filtration was estimated to be in the range of 10-30% by weight.

Salicornia bigelovii straw was characterized and evaluated as a potential lignocellulosic bioethanol feedstock. S. bigelovii used in the study was grown in the United Arab Emirates using saltwater (40ppt) for irrigation. Salt removal was performed prior to pretreatment to protect the processing equipment and avoid inhibition of enzymes and yeast. Composition of the washed biomass was comparable to traditional lignocellulosic biomasses with relatively high glucan and xylan content (26 and 22g/100gDM, respectively) but with lower lignin content (7g/100gDM). The washed feedstock was subjected to hydrothermal pretreatment, producing highly digestible (up to 92% glucan-to-glucose conversion) and fermentable (up to 100% glucose-to-ethanol conversion) fiber fractions. Liquid fractions obtained in the pretreatment did not show inhibition towards Saccharomyces cerevisiae. No significant differences among the enzymatic convertibility and microbial fermentability of the fibers as well as low xylose recoveries suggest that lower severity pretreatment conditions could be exploited for S. bigelovii.

The hypothesis that was tested in this task was that separation of char, with its associated mineral matter from pyrolysis vapors before condensation, will lead to improved oil quality and stability with respect to storage and transportation. The metric used to evaluate stability in this case was a 10-fold reduction in the rate of increase of viscosity as determined by ASTM D445 (the accelerated aging test). The primary unit operation that was investigated for this purpose was hot-gas filtration. A custom-built heated candle filter system was fabricated by the Pall Corporation and furnished to NREL for this test campaign. This system consisted of a candle filter element in a containment vessel surrounded by heating elements on the external surface of the vessel. The filter element and housing were interfaced to NREL?s existing 0.5 MTD pyrolysis Process Development Unit (PDU). For these tests the pyrolysis reactor of the PDU was operated in the entrained-flow mode. The HGF test stand was installed on a slipstream from the PDU so that both hot-gas filtered oil and bio-oil that was not hot-gas filtered could be collected for purposes of comparison. Two filter elements from Pall were tested: (1) porous stainless steel (PSS) sintered metalmore » powder; (2) sintered ceramic powder. An extremely sophisticated bio-oil condensation and collection system was designed and fabricated at NREL and interfaced to the filter unit.« less

The thermochemical research platform at the National Bioenergy Center, National Renewable Energy Laboratory (NREL) is primarily focused on conversion of biomass to transportation fuels using non-biological techniques. Research is conducted in three general areas relating to fuels synthesis via thermochemical conversion by gasification:(1) Biomass gasification fundamentals: chemistry and mechanisms of tar formation(2) Catalytic tar reforming and syngas cleaning(3) Syngas conversion to mixed alcoholsIn addition, the platform supports activities in both technoeconomic analysis (TEA) and life cycle assessment (LCA) of thermochemical conversion processes. Results from the TEA and LCA are used to inform and guide laboratory research for alternative biomass-to-fuels strategies. Detailed process models are developed using the best available material and energy balance information and unit operations models created at NREL and elsewhere. These models are used to identify cost drivers which then form the basis for research programs aimed at reducing costs and improving process efficiency while maintaining sustainability and an overall net reduction in greenhouse gases. (C) 2011 Elsevier B.V. All rights reserved.

Rising world demands for oil and a finite petroleum reserve have renewed interest in alternate liquid fuel sources that are diverse, secure, and affordable. Biomass is a renewable source of carbon that is abundant in many regions of the world. A focal point in alternative fuel research is the production of biofuels derived from lignocellulosic material and especially biofuels made with waste biomass or feedstocks grown on marginal land. Several different routes of thermochemical biomass conversion, including production of bio-oil through pyrolysis with subsequent bio-oil upgrading and production of syngas through gasification with subsequent gas to liquid fuel synthesis will be discussed. The material development needs in each stage will be identified.