Catalysis Center for Energy Innovation for Biomass Processing:Research Strategies and Goals
Dionisios G.Vlachos •Jingguang G.Chen •
Raymond J.Gorte •George W.Huber •Michael Tsapatsis
Received:30August 2010/Accepted:21September 2010/Published online:5October 2010ÓSpringer Science+Business Media,LLC 2010
Abstract Production of energy and chemicals from bio-mass is of critical importance in meeting some of the challenges associated with decreasing availability of fossil fuels and addressing global climate change.In the current article,we outline a perspective on key challenges of biomass processing.We also introduce the Catalysis Center for Energy Innovation (CCEI),one of the 46Energy Frontier Research Centers established by the Department of Energy in the spring of 2009,and CCEI’s overall
research strategies and goals along with its cross-cutting research thrusts that can enable potential technological breakthroughs in the utilization of biomass and its deriva-tives.The center focuses on developing innovative heter-ogeneous catalysts and processing schemes that can lead to viable biorefineries for the conversion of biomass to chemicals,fuels,and electricity.In order to achieve this go
al,a group of over twenty faculty members from nine institutions has been assembled to bring together comple-mentary expertise covering novel materials synthesis,advanced characterization,multiscale modeling,surface science,catalytic kinetics,and microreactors.
Keywords Biomass ÁCatalysis ÁFuels ÁChemicals ÁFuel cells ÁMaterial synthesis ÁModeling ÁKinetics
1Introduction
The decreasing availability of fossil fuels in conjunction with global climate change,the projected increases in energy demand,and the increasing concerns for national security and energy independence require a paradigm shift in energy production and utilization [1].Production of energy and chemicals from biomass appears as one of the most promising,viable,long-term solutions to our future energy portfolio [2].Biomass is a renewable resource with nearly a neutral carbon balance.It has been projected that *1/3of the US transportation fuels and 25%of all organic chemicals can be replaced from non-food interfering (lig-nocellulosic)biomass [3]by processing *1.3billion tons per year of biomass [4].However,to begin utilization of lignocellulosic biomass as a feedstock,processes need to be developed that can economically convert biomass into fuels and chemicals.Catalysis and reaction engineering
D.G.Vlachos (&)ÁJ.G.Chen
Department of Chemical Engineering,University of Delaware,150Academy St,Newark,DE 19716,USA e-mail:vlachos@udel.edu J.G.Chen
e-mail:jchen@udel.edu
R.J.Gorte
Department of Chemical and Biomolecular Engineering,
University of Pennsylvania,220South 33rd Street,311A Towne Building,Philadelphia,PA 19104,USA e-mail:gorte@seas.upenn.edu
G.W.Huber
Department of Chemical Engineering,University of
Massachusetts-Amherst,159Goessmann Lab,Amherst,MA 01003,USA
e-mail:huber@ecs.umass.edu
M.Tsapatsis
Department of Chemical Engineering and Materials Science,University of Minnesota,151Amundson Hall,421Washington Avenue SE,Minneapolis,MN 55455,USA e-mail:tsapatsis@umn.edu
D.G.Vlachos ÁJ.G.Chen ÁR.J.Gorte ÁG.W.Huber ÁM.Tsapatsis
Catalysis Center for Energy Innovation (CCEI),Newark,DE,USA
Catal Lett (2010)140:77–84DOI 10.1007/s10562-010-0455-4
will be two key disciplines that will play a critical role in developing these economical processes[5].
Lignocellulosic biomass is a solid.Hence,thefirst step in any biomass conversion process is the decomposition of the solid biomass into its building blocks or intermediates (see Fig.1).There are three major routes for biomass decomposition:gasification,pyrolysis,and hydrolysis. Hydrolysis can be achieved using enzymes or mineral acids.Gasification and pyrolysis are typically classified as thermochemical conversion of biomass.Challenges with current enzymatic routes for biomass utilization are that they are slow and costly.Traditional thermochemical ,pyrolysis and gasification)result in substantial char and tar formation that limit heat transfer and thus process scale-u
p[6–8].
Several exciting new catalytic routes have recently demonstrated that it is entirely feasible to convert biomass to fuels and chemicals using heterogeneous catalysts.Exam-ples of these technologies include vapor and aqueous phase reforming(resulting in green hydrogen)[9–12],catalytic fast pyrolysis[13],and other selective catalytic transfor-mation of various biomass derivatives[14].While the recently introduced processes are exciting,they exhibit moderate efficiency and/or rely on extensions of catalysts and materials from the petrochemical industry discovered by-and-large via an Edisonian trial-and-error approach.The economic conversion of biomass to chemicals,fuels,and electricity demands developments of the underpinning sci-ence to optimize recently introduced processes or to develop new technologies that are economically competitive with the existing petroleum infrastructure[4].The tremendous opportunity for transforming these exciting discovery-based advances into effective science-based technologies could have an unprecedented impact on the US economy and enhance our energy independence,as well as on the envi-ronment and the daily life of this and of future generations.
In the spring of2009,the Department of Energy(DOE) announced the creation of46Energy Frontier Research Centers to deal with various renewable energy topics.The Catalysis Center for Energy Innov
ation(CCEI)is one of the few DOE funded centers whose focus is on heteroge-neous catalysis.Our center builds upon the long tradition of the Center for Catalytic Science and Technology (CCST)at the University of Delaware and extends its expertise within a virtual center among eight partnering institutions and national labs(University of Pennsylvania, Caltech,University of Minnesota,University of Massa-chusetts-Amherst,Lehigh University,University of North Carolina,University of Southern California,and Brook-haven National Labs).As a center,we provide an inte-grated approach to solving scientific and engineering problems that span across scales and disciplines,ranging from synthesis and characterization of novel catalysts to development and application of a multiscale modeling toolbox to reaction and reactor evaluation to technology transfer.The challenging problems being tackled in this center could only be solved with multidisciplinary efforts.
The remainder of this article describes overarching challenges in biomass processing,the mission and goals of CCEI in overcoming these challenges,and an outline of its technological platforms.
2Scientific Challenges in Biomass Processing Biomass processing exhibits multiple challenges.First, biomass is a complex feedstock whose selective conversion requires multiphase catalysis in complex environments. Products from the hydrolysis of biomass(including sugars, small polyols,etc.)are over-functionalized molecules, compared to crude oil.Lignocellulosic-derived molecules contain a large fract
ion of oxygen with an atomic carbon to oxygen ratio usually close to1:1.This high oxygen content causes these molecules to have a low energy density. Selective deoxygenation,without breaking any C–C bond, produces chemicals with up to six carbon atoms.Fuel production may even require condensation reactions to increase the number of carbon atoms of building blocks. This results in a liquid fuel that couldfit in the jet or diesel fuel range.In contrast,production of syngas and hydrogen require mainly C–C bond breaking without C–O bond cleavage.Overall,the transformation of biomass deriva-tives into valuable chemicals and fuels requires a funda-mental understanding of the chemistry and how the catalyst can be tuned to adjust the product selectivity.
Second,substantial departures from the catalytic routes and catalysts currently employed in refineries
and 78  D.G.Vlachos et al.
petrochemical plants are needed.Some of these processes currently rely on environmentally harsh ,use of acids(homogeneous catalysis),such as the dehydration chemistry in HCl.Due to the low volatility and thermal stability of biomass derivatives,selective transformation of these molecules,without destruction of the carbon back-bone,will happen in solution rather than via vapor/solid heterogeneous catalysis.Solvents can play a profound role not only in economics but also in catalytic , they can affect the detailed molecular structure and par-ticipate in the reaction,such as through proton transfer. Typical supports and ,noble metals on alu-mina and silica)are not hydrothermally stable in water at relatively high temperatures,and thus,simple extension from gas/solid reactions to biomass conversion may not work in cases where solvents are involved.While micro-porous materials can deliver unprecedented selectivity, their pore size may be too small for efficient processing of most of the larger molecules.In addition,conversion of biomass to chemicals currently relies in multistep reaction schemes.For example,the conversion of cellulosic bio-mass to hydroxymethylfurfural(HMF)requires at least three steps,namely acid hydrolysis to glucose,isomeriza-tion of glucose to fructose,and dehydration of fructose to HMF.Obviously,single pot chemistry can offer major process intensification,but this requires making suitable multifunctional mater
ials and selecting the reaction media (e.g.,solvent,additives)carefully.Overall,novel materials with nanoscale resolution suitable for processing biomass derivatives,which allow for fast internal diffusion,shape selectivity,and multifunctional catalytic action in adjacent sites,are needed in carefully chosen solvents to ensure efficient,highly selective,and benign processes.This in turn requires major advances in catalytic materials(solid supports,active sites,solvents)engineering.
Third,the phenomenal advances in mechanistic under-standing and rational catalyst design,  e.g.,which have resulted in recent years from advanced characterization and quantum modeling[15,16],cannot be extended easily to the multiphase reaction media of biomass.Novel theoret-ical and simulation platforms and cutting-edge character-ization tools are,therefore,necessary to provide the microscopic understanding needed for catalyst design and technology advancement.
Forth,the lignocellulosic biomass feedstock is inher-ently complex and its chemical makeup varies with loca-tion,type,and season.This situation is reminiscent of refineries.Biomass ,via pyrolysis) typically leads to coke(char and tar)formation that requires continuous regeneration.Furthermore,the process is inherently slow and thus typically unsuitable for small scale processing of biomass(processing in a radius of 50miles has been suggested based on economics)[17].Furthermore,the high temperature decomposition product consists of a large number of compound
s,rendering fun-damental,first-principles modeling intractable.Overall, some lumping type of approach is necessary that can treat both the complexity of the feedstock and of the product distribution.
The aforementioned challenges underscore the need to understand the reaction mechanisms in order to provide feedback on how to design the complex,multiphase reac-tion environments required to achieve desirable selectivi-ties and yields.We plan to achieve substantial progress in one of the most challenging scientific problems in renew-able energy through integration of cross-cutting thrusts with technological platforms within the CCEI.
3Mission,Goals,and Scientific Approach of the CCEI The mission of CCEI is3-fold,namely to:
1.develop the enabling science leading to improved or
radically new heterogeneous catalytic technologies for viable and economic operation of biorefineries from various lignocellulosic biomass feedstocks;
3.educate the workforce needed to develop and imple-
ment these new technologies
To realize cost-efficient biorefineries,CCEI’s research has three major goals,namely to:
chemicals,fuels and electricity through a fundamental understanding of the chemistry and catalyst perfor-mance;
2.design novel multiscale hierarchical materials with
nanoscale resolution suitable for processing biomass-derivatives in the complex,multiphase media of bio-mass to ensure efficient,highly selective,and benign processes;and
3.promote catalyst design and technology advancement
through novel theoretical and multiscale simulation platforms and cutting-edge characterization tools
Since biomass feedstocks vary considerably with source and the number of candidate reactions is huge,it is simply impractical to cover the entire spectrum of possible reac-tions,intermediates and processes.Instead,CCEI’s scien-tific approach is to develop a fundamental science-base for controlling the scission and formation of C–H,O–H,C–C and C–O bonds in prototype chemical reactions and pro-
cesses that are expected to form the backbone of biore-fineries.Such fundamental knowledge would provide guidance for catalyst and process design and lead to tech-nological innovations needed for biorefineries.With this as
Catalysis Center for Energy Innovation for Biomass Processing79
our overall scientific philosophy,we have organized our research efforts in three overall technological platforms,depicted in Fig.2as white boxes,leading to chemicals,fuels,and electricity.Three cross-cutting thrusts (blue boxes in Fig.2)encompass development of novel hierar-chical multiscale materials,multiscale modeling,and characterization and will enable scientific breakthroughs of technological platforms.
4Outline of Research Approaches 4.1Chemicals
The objective of this thrust is to develop technologies for production of chemicals and hydrogen or syngas from biomass derivatives (e.g.,sugars,glycerol,ethylene glycol,etc.).The key innovation in this thrust is to develop active,selective,stable,and inexpensive catalysts that will enable effective transformation of oxygenates to desirable prod-ucts.In the furans sub-thrust (Fig.2),we focus on selective transformation of sugars to value-added chemicals,while retaining or increasing the number o
f carbon atoms.Examples include the isomerization of glucose to fructose and the conversion of sugars to more valuable chemicals,such as HMF,ethylmethylfurfural (EMF),etc.by selective deoxygenation (mainly C–O bond scission;  e.g.,via dehydration).The furans sub-thrust explores mainly acid and base catalytic functional groups and may involve metal ,for hydrogenation.In a second sub-thrust (Fig.2),we study reforming of oxygenates for hydrogen and/or syngas production via selective C–C bond scission.Aside from its potential use in fuel cells,syngas could be used to make synfuels via Fischer Tropsch (FT)and
provides a means to upgrade fuels and chemicals in both (chemicals and fuels)thrusts by selective deoxygenation and hydrogenation.Metal catalysis is essential for hydro-genation and reforming.4.1.1Reforming Technology
Our goal is to understand and control the bond scission of O–H,C–H,C–O and C–C bonds of alcohols and polyols through catalysis.Our experimental efforts include several parallel research approaches:surface science measurements on well-defined single crystal surfaces,synthesis and characterization of supported catalysts,and catalytic eval-uation in vapor phase and liquid phase using batch and flow reactors.Fundamental surface science studies of smaller oxygenates,such as ethanol,ethylene glycol,and glycerol,provide insights into the bond scission mechanisms in biomass-de
rived molecules.For example,Fig.3shows the recent surface science and theoretical studies of ethanol,ethylene glycol and glycerol on Pt(111),Ni(111)and two bimetallic surfaces structures,surface Ni–Pt–Pt(111)and subsurface Pt–Ni–Pt(111)[18].Surface science results reveal that glycerol reacts on Pt(111)and Ni/Pt(111)sur-faces to form H 2and CO as gaseous products.Increased reforming yield is observed on Ni–Pt–Pt(111),compared to Pt(111)and Pt–Ni–Pt(111).More importantly,the reactiv-ity trend of glycerol is similar to ethylene glycol and eth-anol,with increasing reforming yield as the d -band center shifts closer to the Fermi level [19,20].These smaller,experimentally tractable oxygenates can serve as good models for reforming of larger oxygenates.Furthermore,the trend of reforming activity with d -band center should provide guidance in identifying other bimetallic catalysts for reforming [21].Similar theoretical and
experimental
Fig.2Scientific structure of the CCEI
80
D.G.Vlachos et al.
surface science studies are currently performed on more complicated molecules,including glycoaldehyde and glu-cose.Relevant supported monometallic and bimetallic catalysts,predicted from surface science experiments and theoretical calculations,have been synthesized and char-acterized using a wide range of characterization techniques,including Extended X-ray Absorption Fine Structure (EXAFS)[22].These catalysts are in the process of being evaluated for the conversion of representative C2(ethylene glycol)and C3(glycerol)oxygenates using batch and flow reactors.A main objective is to determine how the activity and pathways are affected by the presence of liquid.EXAFS measurements will also be performed under in situ condi-tions to determine how the composition and structures of the monometallic and bimetallic catalysts are affected during reforming reactions.It is anticipated that these combined theoretical and experimental efforts,on both model surfaces and supported catalysts,should reveal design principles to identify desirable catalysts for the selective bond scission in the conversion of biomass-derived molecules.reactor technology
4.1.2Selective Transformation for Production of Furans Among our objectives is the development of ne
w hetero-geneous catalysts for the isomerization reaction of glucose to fructose,and for the conversion of fructose to HMF and the production of value added derivatives of HMF (e.g.,EMF).For example,it was discovered that a large pore zeolite that contains tin (Sn-Beta synthesized in the
presence of hydrofluoric acid)is able to isomerize glucose to fructose in aqueous media with high activity and selectivity (Fig.4)[1].
Progress was also made in the preparation of hierar-chical micro/mesoporous and multifunctional catalysts.Materials that were synthesized using novel colloidal templating approaches [23]include carbons,titania and zeolites with precisely controlled ordered mesoporosity.They will be further modified for catalytic activity and tested for catalytic performance.
We also aim at understanding of the reaction mecha-nisms,the magnitude of diffusion resistances and the nat-ure of adsorption and liquid/liquid equilibrium and,ultimately,to tailor their interplay for highest yield of desirable products.For example,we combine experiments with molecular simulations in order to understand the sorption of organic molecules in microporous materials,such as zeolites.The goal of this effort is to contribute toward the selection or design of materials with superior adsorption selectivity for sugars,HMF,and related mole-cules.To that end,we have devised a novel,hybrid Molecular Dynamic
s/Grand Canonical Monte Carlo (MD/GCMC)methodology which can handle adsorption while allowing for dynamically fluctuating pores.We have applied this method to calculate isotherms for HMF and furfural adsorption in silicalite,in zeolite Beta and in Faujasite,and found them to be in very good agreement with the experimental data reported previously by us [24].We have also initiated efforts to explore multifunctional catalysts and/or combinations of catalysts (e.g.,Lewis acid or base catalyzed isomerizations with Brønsted acid cata-lyzed dehydrations and etherifications)to efficiently accomplish desirable reaction sequences (e.g.,glucose to fructose to HMF,glucose to fructose to HMF to EMF).For example,the Sn-Beta catalyst is able to perform the isomerization reaction in highly acidic,aqueous environ-ments with equivalent activity and product distribution as in media without added acid.This enables Sn-Beta
to
Fig.3Correlation of experimentally measured reforming yield and theoretically predicted d -band center on Pt–Ni monometallic and bimetallic surfaces (from [18])
Catalysis Center for Energy Innovation for Biomass Processing 81

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