The High Lords of Pyrolysis travel under the unlikely cover identities of “George Huber” and “Robert Brown” — but we know them in their true superhero identities of “The Catalyst” and “The Godfatha”.
Of late, they have assembled what might be best described as the Justice League of Pyromaniax — although the various superheroes prefer to stick to their alter egos as everyday academics at a series of prestigious institutions around the world. But we know better.
They’ve chosen not to assemble in live-action form at Lysis (the fabled, rumored, unseen High Temple of Pyro) — which seems to have quantum properties, because it is found simultaneously in Madison, Wisconsin and Ames, Iowa. Instead, the Justice League has assembled online in a journal format.
The Journal they are appearing in — Energy Technology, helmed by the irrepressible John Uhlrich, is slightly less visually striking than we’re used to in the DC or Marvel Extended Universe, but the latest storylines are far more compelling. It’s being marketed by the mortals at Wiley under the unassuming identity of “Special Issue on Pyrolysis for Energy Technologies”, but why not think of it, more simply, as Burn! Convert! Unleash! As usual, they’re fighting villains from the swamp planet Petro and protecting the peace-loving citizens of Terra from the amoral digital trading evildoers of the Nymex star cluster.
The Pyrolysis Backstory
As the Catayst and the Godfatha explain in more detail here, in fast pyrolysis, biomass is subjected to White House conditions of heat and pressure, and thereby converted primarily into a liquid state known as pyrolysis oil, which is cheap and useful for generating process heat and power. You can burn the witches, but you can’t power the broomsticks — pyro oil is too unstable with too much oxygen.
Accordingly, a host of technologies have been developed in the Caverns of Invention, under a variety of names. Among them: fractional pyrolysis, hydrotreating of pyrolysis oils, autothermal pyrolysis, hydropyrolysis, in situ catalytic pyrolysis, and ex situ catalytic pyrolysis.
So, where are the gallons? According to the High Lords, “Most commercial development of pyrolysis technology is empirical in nature, still dependent on an Edisonian approach to innovation,” and what is needed is a “wide ranging exploration of the science and engineering challenges of pyrolysis energy technologies”. Hence the assembly of the Justice League in this digital conclave.
The Supreme Equilibrium: Zero-Cost Fuel
No one in the field has quite yet broken through to something as compelling as Stark Enterprises Arc Reactor technology. But two themes are emerging. First, the opportunities radical improvement of catalytic performance in targeting hydrocarbons out of a fast pyrolysis process. Second, a broadening range of feedstocks to increasingly embrace zero-cost and negative-cost waste. The breakthrough remains to be made to advance sufficiently on these fronts and then join them together into something that even the Starks haven’t yet achieved: zero-cost fuels. It’s there to be done, it’s a valid target, were the feedstocks to be sufficiently odious and expensive to deal with any other way, and the catalysts sufficiently robust, inexpensive and selective.
It really ought to be an XPRIZE: the development of a cost-free fuel where there is perfect equilibrium between the negative cost of feedstock and the actual cost of conversion. If ever there was a technology that could deliver on this target, pyrolysis would be our first choice and the Knights of the 5 Temples, which we have digested and summarized below, are the X-Men who might just get us to that point. Not to mention a host of sustainable, affordable, reliable and scalable set of molecules for chemistry and propulsion, both, along the way.
The High Lords assembled the contributions, broadly speaking, into five Temples of Knowledge.
Chemistry and feedstock
The High Lords write: ”Fonts et al. demonstrate that sewage sludge can be pyrolyzed to a variety of important products including α-olefins and ammonia. Several papers note that pyrolysis chemistry, and Zhou et al. review the chemistry of hemicellulose pyrolysis while Xu et al. review catalytic upgrading of the phenolic compounds.”
“Proano-Aviles et al. used a computational fluid-dynamic model to…find that nominal heating rates are more than five times slower than often assumed. A dimensional analysis of an auger-type fast pyrolysis reactor by Funke et al. provides insight into transport phenomena in pyrolysis. Meanwhile, Di Blasi et al. review the literature on the exothermicity of biomass pyrolysis.”
“Routray et al. study the hydrotreating of condensed pyrolysis oil, while Nolte et al. consider deoxygenation of pyrolysis vapors. Schultz et al. demonstrate increasing the aromatic yields by over 50 %. Paasikallio et al. explore how the catalyst-to-biomass feed ratio. Shao et al. show that the product selectivity…is a strong function of the amount of coke on the catalyst. Gamliel et al. add hydrogen to the reactor in a process known as hydropyrolysis. Westerhof et al. look at fractional condensed pyrolysis oil and alcohol to biofuels and methyl levulinate.”
Scaling of Pyrolysis
“Some studies in this issue were performed in larger pilot or process development units. Conti et al. used a 2.0 kg hr−1 thermocatalytic reforming reactor to demonstrate the co-pyrolysis of biomass and various organic wastes. Wang et al. conducted CFP studies in a 0.7–1.4 kg per day fluidized bed reactor using a variety of non-zeolitic catalysts. Paasikallio used a 0.5 kg hr−1 circulating fluidized bed reactor to study CFP.”
“Herron et al. demonstrate that the design of a fractional pyrolysis system must be performed in conjunction with the design of the system used to upgrade the fractionated products.”
The Knights of Lysis and their Transformative Powers
Advances in Upgrading Lignin Pyrolysis Vapors by Ex Situ Catalytic Fast Pyrolysis
Lujiang Xu, Prof. Dr. Ying Zhang and Prof. Dr. Yao Fu
It burns, it burns! The Review starts with the understanding of the ex situ catalytic fast pyrolysis (CFP) process and the pathways and reactions of lignin vapors in the ex situ CFP process and then focuses on recent progress in the deoxygenation and upgrading of lignin-derived model phenols, real lignin, and real bio-oil to hydrocarbons by the ex situ CFP process over different catalysts (zeolites, metallic catalysts, and supported transition metals).
Aromatic Hydrocarbon Production from Eucalyptus urophylla Pyrolysis over Several Metal-Modified ZSM-5 Catalysts
Dr. Emerson L. Schultz, Dr. Charles A. Mullen and Dr. Akwasi A. Boateng
Eucalyptic aromatics: The conversion of eucalyptus wood to aromatic hydrocarbons by catalytic fast pyrolysis over several metal-modified ZSM-5 zeolites is studied by pyrolysis-GC–MS. Ga modification of the zeolite leads to higher yields of aromatic hydrocarbons. The use of other metals can adjust the selectivity for individual compounds. These products can be used as renewable fuel additives or petrochemicals for use in a variety of current petroleum-derived products.
Assessment of the Production of Value-Added Chemical Compounds from Sewage Sludge Pyrolysis Liquids
Dr. Isabel Fonts, Andrea Navarro-Puyuelo, Nadia Ruiz-Gómez, Dr. María Atienza-Martínez, Dr. Alberto Wisniewsky and Dr. Gloria Gea
From sludge to useful chemicals: An analytical procedure is developed and used to separate, identify, and quantify value-added chemical compounds present in sewage sludge pyrolysis liquids. Chemicals of greatest interest are selected in terms of current level of production, renewable or nonrenewable origin source, and price. The building blocks of the raw material that result in these chemicals and the most favorable pyrolysis operational conditions for their production are discussed.
Bifunctional Ni-ZSM-5 Catalysts for the Pyrolysis and Hydropyrolysis of Biomass
David P. Gamliel, Dr. George M. Bollas and Dr. Julia A. Valla
Under pressure: In this work, we explore pyrolysis options, namely, high pressure, hydrogen, and metal-loaded ZSM-5 catalysts, to improve catalyst deoxygenation capacity and reduce excessive production of solids in biomass catalytic fast pyrolysis. We present a reaction scheme that describes the impacts of pressure, H2, and Ni on the biomass pyrolysis product distribution.
Biofuel and Methyl Levulinate from Biomass-Derived Fractional Condensed Pyrolysis Oil and Alcohol
Dr. Roel. J. M. Westerhof, Dr. Stijn R G. Oudenhoven, Dr. Xun Hu, Prof. Dr. Hero J. Heeres, Prof. Dr. Chun-Zhu Li, Prof. Dr. Manuel Garcia-Perez and Prof. Dr. Sascha R. A. Kersten
Replacing hydrogen for stabilization: Biomass-derived pyrolysis oil is stabilized by alcohol or hydrogen and a catalyst followed by deep hydrotreatment. The energy efficiency from biomass to fuel is in both cases around 46+/−2 %. Preliminary results with acid-leached biomass show that 43 % of the levoglucosan in the pyrolysis oil is converted to methyl levulinate, after the pyrolysis oil was purified.
Catalytic Conversion of Furan to Hydrocarbons using HZSM-5: Coking Behavior and Kinetic Modeling including Coke Deposition
Shanshan Shao, Huiyan Zhang, Rui Xiao and Dekui Shen
Coke deposition matters: A catalytic fast pyrolysis pathway is proposed with benzofuran as a primary product, all olefins and aromatic hydrocarbons as secondary products, and polycyclic aromatic hydrocarbons as a tertiary product. The product selectivity changes with temperature and coke deposition, whereas no effect is observed if the weight hourly space velocity and partial pressure are varied. A kinetic model considering coke deposition is built to correlate the product distribution with coke content.
Catalytic Fast Pyrolysis: Influencing Bio-Oil Quality with the Catalyst-to-Biomass Ratio
Ville Paasikallio, Dr. Konstantinos Kalogiannis, Dr. Angelos Lappas, Dr. Jani Lehto and Prof. Juha Lehtonen
Bio-oil or wastewater? Catalytic fast pyrolysis with acidic zeolites produces bio-oil and an aqueous byproduct, which has to be further processed. We examine the effect of an excess of catalyst on the process as a method to influence the balance between the bio-oil and the aqueous phase. The use of more catalyst influences the characteristics of both product fractions but does not effectively eliminate the presence of aqueous-phase organics.
A Critical Review on Hemicellulose Pyrolysis
Dr. Xiaowei Zhou, Dr. Wenjun Li, Dr. Ross Mabon and Prof. Dr. Linda J. Broadbelt
Go green, biomass to biofuels: Fast pyrolysis is a promising thermochemical technology that breaks down renewable and abundant lignocellulosic biomass into a primary liquid product in seconds, which can be catalytically upgraded into transportation fuels and multiple commodity chemicals. Here we review the status of pyrolysis of hemicellulose, which is one of the three major components of lignocellulosic biomass. Recent results and challenges as well as future prospects are addressed.
Dimensional Analysis of Auger-Type Fast Pyrolysis Reactors
Dr. Axel Funke, Prof. Dr. Edmund Henrich, Prof. Dr. Nicolaus Dahmen and Prof. Dr. Jörg Sauer
Easy rules: Modeling of fast pyrolysis reactors is difficult, even with state of the art computational tools, because of the complex interactions that take place and multiple challenges of quantifying them. Dimensionless numbers derived from a dimensional analysis can be used to derive a simple set of design rules for the scale-up of well-running reactors; these are demonstrated by using auger-type reactors as an example.
Heat and Mass Transfer Effects in a Furnace-Based Micropyrolyzer
Juan Proano-Aviles, Jake K. Lindstrom, Patrick A. Johnston and Prof. Robert C. Brown
If you can’t stand the heat… Heat and mass transfer in a micropyrolysis system are studied both experimentally and computationally. These studies indicate that heating rates in micropyrolyzers are more modest than is sometimes assumed and that diffusion from the interior of sample cups limits mass transfer rates if intact deep cups are used. The use of a perforated shallow cup increases levoglucosan yields from the pyrolysis of cellulose by 10 %.
Hydrodeoxygenation of Pyrolysis Oils
Dr. Kamalakanta Routray, Kevin J. Barnett and Prof. George W. Huber
High and low, what a glow: A two-stage low temperature hydrogenation–high temperature hydrodeoxygenation (HDO) reactor setup is used to produce fungible liquid fuels from pyrolysis oil. Well-characterized bio-oil and HDO products provide insight into the detailed reaction pathways occurring during HDO. Fuel yields are compared to state-of-the-art in the field and potential improvements in bio-oil HDO are outlined.
Influence of the Feedstock on Catalytic Fast Pyrolysis with a Solid Acid Catalyst
Dr. Kaige Wang, Dr. Ofei D. Mante, Jonathan E. Peters and Dr. David C. Dayton
The type of feedstock does matter: It is not clear how the feedstock variety affects the catalytic biomass pyrolysis process under development at RTI. In this study, product yields and distributions from seven types of biomass with distinct compositions are investigated. Both the inorganic and organic compositions of the feedstocks are correlated with the product distribution and biocrude quality for the catalytic pyrolysis process.
On the Experimental Evidence of Exothermicity in Wood and Biomass Pyrolysis
Prof. Colomba Di Blasi, Dr. Carmen Branca and Dr. Antonio Galgano
Turn up the heat: Biomass pyrolysis is characterized by remarkable reaction-induced overheating, the effects of which become especially evident for packed-bed reactors. Overheating mainly originates from the activity of secondary vapor-phase reactions, which are favored by scarcely porous solid microstructures such as in the case of some agroindustrial residues.
A Perspective on Catalytic Strategies for Deoxygenation in Biomass Pyrolysis
Michael W. Nolte and Dr. Brent H. Shanks
Strategic oxygen removal: Fast pyrolysis represents a technology for converting solid, lower density biomass into a denser liquid intermediate. However, bio-oil requires upgrading before its widespread utilization. In this work, we review the different catalytic strategies used in deoxygenating biomass to produce a compatible liquid for refinery integration.
A Systems-Level Roadmap for Biomass Thermal Fractionation and Catalytic Upgrading Strategies
Dr. Jeffrey A. Herron, Tyler Vann, Nhung Duong, Prof. Daniel E. Resasco, Prof. Steven Crossley, Prof. Lance L. Lobban and Prof. Christos T. Maravelias
Mapping it out: We use conceptual process modeling to propose a general roadmap for the design of a biorefinery by employing a multistage thermal decomposition system of biomass. The choice of the number of thermal decomposition stages and upgrading strategies requires careful consideration of the chemistries available to upgrade the different species in the thermal fractions.
Thermocatalytic Reforming of Biomass Waste Streams
Dr. Roberto Conti, Nils Jäger, Johannes Neumann, Dr. Andreas Apfelbacher, Dr. Robert Daschner and Prof. Andreas Hornung
TCR: The thermocatalytic reforming (TCR®) of organic wastes offers a significantly higher product quality compared to the state of the art. With the use of TCR® technology, high-quality bio-oil and syngas from low-grade biomass are produced because of reformer heating. The TCR® process is a promising technology to utilize biomass residues for the production of biofuels and sustainable energy from combined heat and power engines.
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