microwave-assisted pyrolysis of biomass catalysts to improve product selectivity

Microwave-assisted pyrolysis of biomass:Catalysts to improve product selectivity

Yiqin Wan a ,b ,Paul Chen b ,*,Bo Zhang b ,Changyang Yang b ,Yuhuan Liu a ,b ,Xiangyang Lin a ,b ,Roger Ruan a ,b

a Biomass Energy Center and State Key Laboratory of Food Science,Nanchang University,Nanchang,China

b

Center for Biore?ning and Department of Bioproducts and Biosystems Engineering,University of Minnesota,1390Eckles Ave.,St.Paul,MN 55108,United States

1.Introduction

Declining supplies of fossil energy resources and adverse impacts of fossil energy uses on the global environment have prompted strong interests in renewable energy.A wide array of renewable energy technologies is being researched.Among them are biomass-based energy technologies such as processes con-verting corn to ethanol,soybean to biodiesel,lignocellulosics to bioethanol or bio-oils.Rising food prices have caused serious concerns over corn to bioethanol and soybean to biodiesel approaches.Increasing attention is drawn to conversion of lignocellulosics to biofuels such as ethanol,bio-oils,and gas.Pyrolysis,a thermochemical conversion process,is an attractive way to produce liquid fuels from solid biomass feedstock.Pyrolysis is one of the thermochemical conversion processes widely studied.Pyrolysis is normally carried out in the absence of oxygen at temperature above 400–5008C.During pyrolysis,large molecules in biomass decompose or depolymerize at high temperature to gaseous phase leaving some solid charcoal behind [1].The gaseous phase consists of condensable and incondensable compounds.The condensable compounds can be cooled down to yield bio-oils and

chemicals.Like all other renewable technologies,biomass pyr-olysis is facing many technical challenges.For example,the liquid fuels produced from pyrolysis of biomass are complex in chemical composition and highly unstable in terms of physical consistency,chemical properties,and combustion characteristics,and often highly acidic,seriously limiting the practical use of these liquid fuels.Researchers have been seeking solutions to these problems.Post-pyrolysis upgrading is a common approach to stabilizing bio-oils.Upgrading processes may involve physical or chemical methods.Solvent blending and ?ltration are physical upgrading methods [2–6],but they are not very effective.We recently developed a two-step fractionation procedure to separate bio-oil to light oil,heavy oil,and chemicals [7].The light oil fraction,with no combustion residue and a much lower boiling point,is a good alternative fuel for engines.However,this procedure produces only about 25%light oil fraction.Chemical upgrading employs catalytic cracking and reforming such as hydrotreatment and thermal cracking to de-oxygenate the bio-oil.Recent research in this area has made incremental advances in improving the bio-oil quality.Nevertheless,use of pyrolytic oils remains unpractical due to the aforementioned problems.

Pyrolysis of biomass occurs at high temperature and is not well understood.Some suggest a ?ve-step process [8]:(1)biomass is heated,(2)volatiles evolve from the organics,and carbonization occurs,(3)out?ow of hot volatiles and cooler unpyrolyed fuel

J.Anal.Appl.Pyrolysis 86(2009)161–167

A R T I C L E I N F O Article history:

Received 17November 2008Accepted 13May 2009

Available online 29May 2009Keywords:Pyrolysis Microwave Bio-oils Catalysis Catalysts Corn stover Aspen Biofuels

A B S T R A C T

This study was intended to evaluate the effects of catalysts on product selectivity of microwave-assisted pyrolysis of corn stover and aspen wood.Metal oxides,salts,and acids including K 2Cr 2O 7,Al 2O 3,KAc,H 3BO 3,Na 2HPO 4,MgCl 2,AlCl 3,CoCl 2,and ZnCl 2were pre-mixed with corn stover or aspen wood pellets prior to pyrolysis using microwave heating.The thermal process produced three product fractions,namely bio-oil,gas,and charcoal.The effects of the catalysts on the fractional yields were studied.KAc,Al 2O 3,MgCl 2,H 3BO 3,and Na 2HPO 4were found to increase the bio-oil yield by either suppressing charcoal yield or gas yield or both.These catalysts may function as a microwave absorbent to speed up heating or participate in so-called ‘‘in situ upgrading’’of pyrolytic vapors during the microwave-assisted pyrolysis of biomass.GC–MS analysis of the bio-oils found that chloride salts promoted a few reactions while suppressing most of the other reactions observed for the control samples.At 8g MgCl 2/100biomass level,the GC–MS total ion chromatograms of the bio-oils from the treated corn stover or aspen show only one major furfural peak accounting for about 80%of the area under the spectrum.We conclude that some catalysts improve bio-oil yields,and chloride salts in particular simplify the chemical compositions of the resultant bio-oils and therefore improve the product selectivity of the pyrolysis process.

?2009Elsevier B.V.All rights reserved.

*Corresponding author.Tel.:+16126257721;fax:+16126243005.E-mail address:chenx088@https://www.360docs.net/doc/6f2732547.html, (P.Chen).Contents lists available at ScienceDirect

Journal of Analytical and Applied Pyrolysis

j ou r n al h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /j a a p

0165-2370/$–see front matter ?2009Elsevier B.V.All rights reserved.doi:10.1016/j.jaap.2009.05.006

volatiles,(4)volatiles condense to liquid(tar)with incondensable gas,and(5)autocatalytic secondary reactions(decomposition or repolymerization)take place[9].Some interventions in step2may induce and/or alter certain chemical reactions,resulting in different chemical pro?les of the volatiles.Recently,researchers became interested in in situ upgrading of the biomass pyrolysis vapors,i.e.,evolved volatiles from thermal decomposition of organics react directly and immediately on catalysts pre-mixed with the biomass feedstock[10–13].Such in situ catalytic upgrading of the biomass pyrolysis vapors is also known as catalytic pyrolysis.This approach could eventually eliminate the costly condensation and re-evaporation procedures used in upgrading traditional pyrolytic oil.

Studies on a range of catalysts have been reported in the literature.Some catalysts produced more hydrocarbons than others and some not at all.Catalytic pyrolysis usually produces additional water and coke-solid residue and thus reduces the yield of the organic phase of the bio-oil.We found that chlorides favor production of light oil and especially water solubles and metal-

oxides favor heavy oil,and thus total oil yield,while nitrates favor gas production[14].Bio-oils from current catalytic pyrolysis processes are still not up to the industry standards,primarily due to the still complex chemical composition.However,a positive effect on the quality of the organic phase was noticed,and research has been directed towards the design of selective catalysts for either increasing the production of speci?c compounds(e.g.phenols)or minimizing the formation of undesirable compounds(e.g.acids, carbonyls).Zinc chloride was found to catalyze decomposition of cellulose in solution at high temperature,and chloride salts were found to promote conversion of sugars to furfural[15–17].Some studies employed alkali and alkaline earth metal in pyrolysis and gasi?cation of different biomass[18–21].They found that metal salts,especially alkaline earth metal chlorides such as MgCl2and ZnCl2,increased the yield of char at low temperature but decreased the yield of char at high temperature.Our earlier studies show that chloride salts favor liquid production in microwave-assisted pyrolysis of corn stover and aspen[14].Therefore,it is necessary to study how catalysts change the chemical pro?les of bio-oils under microwave-assisted pyrolysis conditions.

Microwave-assisted pyrolysis(MAP)is a relatively new pyrolysis technique which provides many advantages over conventional processes[22].The objective of the present study was to evaluate the product selectivity of microwave-assisted pyrolysis(MAP)of cellulosic materials as affected by using metal oxides and chloride salts as catalysts.The selected catalysts were mixed with the biomass materials at different ratios prior to the microwave pyrolysis.The condensable volatiles collected from the biomass pyrolysis runs were analyzed using GC–MS.

2.Experimental process

2.1.Materials

Dry corn stover and aspen pellets were provided by Lone Tree Manufacturing(Bagley,MN).The major physical and chemical properties of corn stover and aspen are given in Table1.Analytical grade chemicals MgCl2á6H2O,AlCl3á2H2O,LiCl,and CuSO4á6H2O were purchased from Mallinckrodt Baker Inc.,ZnCl2from Fisher Scienti?c Inc.,MgSO4and MgO from J.T.Baker Inc.,Al2O3from Matheson Coleman&Bell,and Ni(NO3)2,Mg(NO3)2from Alfa Acsar.

2.2.Preparation of mixture of biomass and catalysts

To determine the in?uence of different chemicals on the microwave-assisted pyrolysis,100g dry biomass was mixed with 8g powders/crystals of oxides of sodium,potassium,magnesium,calcium,zinc,and copper,and some acids prior to the pyrolysis.After early analysis,we found that MgCl2had strong impact on the MAP products.Therefore different dosages of MgCl2were further tested.

2.3.Microwave-assisted pyrolysis(MAP)

The pyrolysis of biomass was carried out in a Panasonic NN-SD787S microwave cavity oven by placing100g prepared samples in a quartz?ask,which in turn was placed inside the microwave cavity.The time for microwave treatment was around20min.A constant power input of875W at the microwave frequency of 2450MHz was used for each batch.Since monitoring temperature during microwave heating was dif?cult,the temperatures of the biomass mixtures were measured immediately after heating was terminated.The observed temperatures ranged from450to5508C. The volatile pyrolyzates were condensed with?ve condensers.The temperature of the cooling water was about0–58C.The fraction collected from the bottles connected on the bottom of the condensers is a pyrolytic liquid(bio-oil).The solid char residue was allowed to cool to room temperature before it was weighed. The condensates adhering to the interior wall of the quartz?ask were washed with ethanol into the pyrolytic liquid collection bottle.All liquids collected were concentrated at408C using a vacuum rotovap(Buchi R-141,Flawil,Switzerland)to a near constant weight,and the weight was recorded.The weight of gas product was calculated using following equation:

weight of gas?initial biomassàpyrolytic liquid mass

àchar residue mass

2.4.GC–MS analysis of bio-oils

Chemical compositions of the liquid products were analyzed using an Agilent7890-5975C gas chromatography/mass spectro-meter(Santa Clara,CA)with a DB-5-MS capillary column.The GC was programmed at458C for0.5min and then increased at158C/ min to2908C,and?nally held with an isothermal for5min.The injector temperature was2508C,and the injection size was1m l. The?ow rate of the carrier gas(helium)was1.2ml/min.The ion source temperature was2308C for the mass selective detector.The compounds were identi?ed by comparison with the NIST Mass Spectral Database.

2.5.Data analysis

All experiments were performed in quintuplicate.The data presented in this paper are averaged values.Statistical analysis of Table1

Properties of corn stover and aspen pellets.

Properties Corn stover Aspen wood Diameter(mm) 6.2 4.8 Length10–204–8

Bulk density at208C(kg/m3)340240 Moisture 6.4 5.9 Elemental composition(wt.%)

Carbon40.445.4 Hydrogen 5.3 4.8 Nitrogen 1.10.5

Sulfur0.10.0 Oxygen(by difference)53.149.3

Gross heating value(MJ/kg)24.517.9 Chemical composition(wt.%)

Lignin1819 Cellulose3753 Hemicellulose2727

Others181

Y.Wan et al./J.Anal.Appl.Pyrolysis86(2009)161–167 162

the data was conducted using MS Excel?.The standard deviations are presented along with the fractional yield data.

3.Results and discussion

3.1.Product fractional yields

The microwave-assisted pyrolysis of corn stover and aspen wastes produced three fractions of products,i.e.,bio-oil,gas,and solid charcoal.The fractional yields are shown in Fig.1.The result shows that the catalysts used in our study affected the fractional yields to different degrees.In general,KAc,Al2O3,MgCl2,H3BO3, and Na2HPO4increased the bio-oil yield.For KAc,the increase in bio-oil fraction is accompanied by a reduction in charcoal without a change in gas production.The situation for Al2O3is just opposite of that for KAc,i.e.,the increase in bio-oil fraction is associated mainly with a decrease in gas.For MgCl2,H3BO3,and Na2HPO4,the increase in bio-oil fraction is accompanied by reduction in both charcoal and gas but by different degrees.For MgCl2and H3BO3,the increase in bio-oil is associated mainly with gas reduction while for Na2HPO4,the high yield of bio-oil is coincident more signi?cantly with charcoal reduction than with gas reduction.These observed differences indicate that catalysts affected bio-oil production differently.Al2O3did not improve the thermal decomposition of

biomass ef?ciency(no signi?cant change in charcoal fraction)but promoted the generation of condensable volatiles(more gaseous compounds can be condensed to liquid).KAc helped convert more solid biomass to volatiles among which the amount of non-condensable(gas)was similar to that in the control experiment with a net gain in the condensables.MgCl2,H3BO3,and NaHPO4are the mixed cases of Al2O3and KAc where solid biomass conversion and the ratio of condensables to non-condensables increased to different degrees.

How the catalysts affected the fractional yields are unknown. We believe that both physical and chemical mechanisms are involved.The added chemical compounds may have acted

as Fig.1.Product fractional yields of microwave-assisted pyrolysis of corn

stover. Fig.2.Total ion chromatograms from GC–MS analysis of pyrolytic oils from corn stover when different catalysts were used(8g/100g biomass).FF:furfural.

Y.Wan et al./J.Anal.Appl.Pyrolysis86(2009)161–167163

microwave absorbers and/or chemical catalysts.Earlier studies involving mixing salts or oxides with feedstock were unable to separate the microwave absorbent effect from chemical catalysis effect.For example,Monsef-Mirzai et al.[23]used CuO and Fe 3O 4as microwave receptors for microwave-assisted pyrolysis of coal.They attributed the observed differences in the fractional yields and gas and tar compositions between CuO and Fe 3O 4treated samples to heating rate.However,the chemical catalysis induced

by CuO and Fe 3O 4should not be ruled out.Dom?

′nguez et al.[24]found that the use of graphite and char as microwave absorbers did change the heating rate and fractional yields however the chemical pro?les of the liquid products remained the same regardless of the type of microwave absorber used.Our previous studies showed that varying microwave input power resulted in noticeable difference in fractional yields and gas composition but not liquid composition.In the present study,the increased bio-oil yields are probably related to the so-called ‘‘in situ upgrading’’of the pyrolytic vapors emitted from thermal decomposition of biomass.Different catalysts may affect the upgrading reactions differently.The reduced charcoal fraction yield may be related to two factors.The ?rst factor is that some catalyst may actually promote thermal decomposition of biomass.The second factor is that some catalysts may act as a microwave absorption promoter,which may increase the heating rate that is often responsible for increased conversion ef?ciency as well as liquid yield.The ?rst factor may also be responsible for the signi?cant variations in chemical composition of the bio-oils as described later on.

We conducted more experiments on MgCl 2.Table 2shows the bio-oil and charcoal yields as a function of MgCl 2percentage when MgCl 2was used as catalyst in microwave-assisted pyrolysis of corn stover and aspen.For corn stover,the charcoal yield did not change much with MgCl 2addition,but the bio-oil yield increased with increasing MgCl 2addition.For aspen,MgCl 2tends to increase the charcoal yield as well as the bio-oil yield.The results shown in Table 2suggest that MgCl 2is effective in ‘‘in situ upgrading’’which changes the ratio of condensables to non-condensables.This is consistent with the MgCl 2results shown in Fig.1.The results in Table 2also indicate that corn stover and aspen differ in fractional yields.It is unclear how this difference is related to the chemical compositions of the two materials (Table 1

).

Fig.3.Total ion chromatograms from GC–MS analysis of pyrolytic oils from corn stover when MgCl 2was used at different levels.X:unidenti?ed compound;FF:furfural;MFE:beta-methoxy-(S)-2-furanethanol.

Table 2

Bio-oil and charcoal fractional yields of microwave-assisted pyrolysis of corn stover and aspen pellets.Biomass MgCl 2á6H 2O (g/100g sample)Bio-oil (%)Charcoal (%)Corn Stover

037.03?1.9628.63?0.58239.44?2.2528.33?0.63442.70?1.1129.26?0.36842.61?1.8928.01?0.97Aspen

035.87?0.0625.24?0.16235.46?2.5830.69?2.07438.97?0.3628.75?0.258

41.12?1.41

28.04?0.71

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164

3.2.GC–MS analysis of the bio-oils

The pyrolytic bio-oils were characterized using GC–MS,and the results are shown in Figs.2–4and Tables 3and 4.Fig.2shows the total ion chromatograms (TIC)of GC–MS analysis of bio-oil samples from microwave-assisted pyrolysis of corn stover when different chloride salts were used as catalysts.There were about 53compounds detected by GC–MS in the bio-oil from

non-catalyst

Fig.4.Total ion chromatograms from GC–MS analysis of pyrolytic oils from aspen when MgCl 2was used at different levels.X:unidenti?ed compound;FF:furfural;MFE:beta-methoxy-(S)-2-furanethanol.

Table 3

Compounds detected with GC–MS in the bio-oils from microwave-assisted pyrolysis of corn stover.Retention time

Peak name

Area%

Without catalyst

MgCl 2(g/100biomass)2

482.6541-Hydroxy-2-butanone 2.63 1.92– 2.002.912Unidenti?ed compound X –– 6.65–3.226Furfural

4.31 6.8013.4079.583.360– 4.17––3.4262-Furanmethanol

4.24 1.78––3.679Furan,tetrahydro-2,5-dimethoxy-–0.71 1.36 4.333.840Furan,tetrahydro-2,5-dimethoxy-–0.69 1.24 2.953.9672-Cyclopenten-1-one,2-methyl-–0.910.63 1.824.063Butyrolactone

2.68 2.21––4.1632-Cyclopenten-1-one,2-hydroxy- 1.96

3.43 1.68–

4.4752-Furanethanol,beta-methoxy-(S)–9.76 1.72–4.713Phenol

6.74 6.28 3.56 5.685.1592-Cyclopenten-1-one,2-hydroxy-3-methyl- 3.93 3.08 2.27–5.625Phenol,4-methyl- 3.51 2.84 1.36–5.906Phenol,2-methoxy- 4.33 3.49 2.58 3.655.9661,3-Propanediamine,N-methyl- 5.56–––6.560Phenol,4-ethyl- 3.51 2.11––6.8921,2-Benzenediol

2.16–6.968Butanoic acid,pentyl ester –10.31

3.78–7.068Benzofuran,2,3-dihydro-9.63 3.13–8.0302-Methoxy-4-vinylphenol 3.33 1.87 2.44–8.356Phenol,2,6-dimethoxy- 5.08 3.98 2.66–9.583Levoglucosan

– 4.187.70–12.951n -Hexadecanoic acid 2.34–––14.114

Oleic Acid

2.88

–

–

–

Note :About 36kinds of components of bio-oil from corn stover without any catalyst whose area %less than 1.82%were not displayed.

Y.Wan et al./J.Anal.Appl.Pyrolysis 86(2009)161–167165

treated samples (control).We found that all chloride salts promoted furfural production,but ZnCl 2and MgCl 2also effectively suppressed the production of other chemicals.MgCl 2gave a very clean spectrum with only one major peak which is furfural.This is evidenced by data shown in Table 3.The area for furfural increased from 4.31%in the control sample to 79.58%in the sample treated with 8g MgCl 2.Most of other chemicals decreased or simply disappeared when MgCl 2was used.The rest of the area (around 20%)is made up of 1-hydroxy-2-butanone,tetrahydro-2,5-dimethoxy-furan,2-methyl-2-cyclopenten-1-one,phenol,and 2-methoxy-phenol.

We conducted more experiments on corn stover and aspen using MgCl 2at different levels (Figs.3and 4).We noticed a gradual increase in furfural and a decrease in other chemicals with increasing MgCl 2.At lower levels of MgCl 2,we also noticed a sudden increase and/or appearance of furfural (FF),beta-methoxy-(S)-2-furanethanol (MFE)peaks and an unidenti?ed peak X.Fig.5shows the electron ionization (EI)spectrum for this unidenti?ed compound X.The MFE and X peaks disappear when 8g of MgCl 2was used.Our results show that 8g MgCl 2per 100g of dry biomass is necessary to produce spectra with a single major furfural peak with minimal appearance of other chemicals.However,these results also indicate that the chemical pro?les can be altered through adjusting the dosage of catalysts,suggesting that it is possible to target certain desirable products by controlling the dosage.Further study is necessary to explore other catalysts which

Table 4

Compounds detected with GC–MS in the bio-oils from microwave-assisted pyrolysis of aspen.Retention time

Peak name

Area %

Without catalyst

MgCl 2(g/100biomass)2

482.6581-Propanol,2-methyl- 2.22–––2.912Unidenti?ed compound X –10.5214.09–3.226Furfural

3.58 3.349.9483.003.4262-Furanmethanol

3.17–

–

–3.679Furan,tetrahydro-2,5-dimethoxy-–7.343.840Furan,tetrahydro-2,5-dimethoxy-– 4.944.1632-Cyclopenten-1-one,2-hydroxy- 2.13 1.360.36–4.4982-Furanethanol,beta-methoxy-(S)–8.3711.26–4.713Phenol

4.47 3.24 3.09–

5.1592-Cyclopenten-1-one,2-hydroxy-3-methyl- 2.58 1.45 1.83–5.625Phenol,4-methyl- 2.69 1.430.85–5.906Phenol,2-methoxy- 3.20 2.43 1.75 4.72

6.401 6.92 3.976.588Phenol,3,5-dimethyl- 2.60–6.867Phenol,2-methoxy-4-methyl- 2.78 2.65 2.04–6.8921,2-Benzenediol

2.72 2.52 2.57–8.0302-Methoxy-4-vinylphenol 2.12–8.356Phenol,2,6-dimethoxy- 4.51

3.08 1.97–9.1963-Hydroxy-4-methoxybenzoic acid 2.63 1.980.96–9.237Phenol,2-methoxy-4-(1-propenyl)- 2.10 1.04––9.7061,6-Anhydro-beta-D -glucopyranose

4.45 1.62 4.73–10.179(E)-Stilbene

1.92–––11.229

Phenol,2,6-dimethoxy-4-(2-propenyl)- 2.41

1.09

–

–

Note :About 81kinds of components of bio-oil from aspen without any catalyst whose area %less than 1.82%were not

displayed.

Fig.5.Electron ionization spectrum of unidenti?ed compound X.

Y.Wan et al./J.Anal.Appl.Pyrolysis 86(2009)161–167

166

could suppress most undesirable chemical reactions while maximizing reactions leading to production of desirable products (other than furfural).

Table4shows the chemical composition of bio-oils from microwave-assisted pyrolysis of aspen.There were about99 chemicals in the bio-oil from the control sample but only3major chemicals in the bio-oil from aspen samples treated with MgCl2. Furfural accounts for approximately83%,and tetrahydro-2,5-dimethoxy-furan and,2-methoxy-phenol for17%.The difference in furfural yield between corn stover and aspen may be attributed to their large difference in cellulose content instead of hemicellulose since they have the same hemicellulose https://www.360docs.net/doc/6f2732547.html,mercial production of furfural is achieved through converting the hemicellulosic fraction of the lignocellulosic to monosaccharides (pentoses)by acid hydrolysis,which are further dehydrated to produce furfural.Additional chemical pathways for conversion of cellulose to furanic compounds in different reaction systems including pyrolysis have been proposed by researchers[25–27].

We tested other catalysts(results not shown).Among them, Mg(ClO4)2behaved similarly with MgCl2,while most of other catalysts had little effect on the composition of the bio-oils.In addition,we tested MAP of aspen and corn stover using a mixture of MgCl2and some metal oxides including MgO,MgSO4,H3BO3. These oxides did not affect or improve the function of MgCl2 (results not shown).

4.Conclusions

Medal oxides,salts,and acids including K2Cr2O7,Al2O3,KAc, H3BO3,Na2HPO4,MgCl2,AlCl3,CoCl2,and ZnCl2when pre-mixed with corn stover or aspen wood pellets prior to pyrolysis were found to affect the fractional yields of bio-oil,gas and char and the chemical pro?les of the bio-oils.KAc,Al2O3,MgCl2,H3BO3,and Na2HPO4were found to increase the bio-oil yield.The increase in bio-oil yield was accompanied by change in charcoal or gas yields or both,suggesting that the catalysts used may affect the fractional yields through different mechanisms.The catalysts may function as a microwave absorbent to speed up heating or they may participate in the so-called‘‘in situ upgrading’’of pyrolytic vapors during the microwave-assisted pyrolysis of biomass.Catalysts may play an important role in solid-to-vapor conversion and reforming of vapors during the microwave-assisted pyrolysis process.The GC–MS analysis indicated that use of the catalysts signi?cantly reduce the number of compounds in the bio-oils.At lower levels of MgCl2,we observed two to three major peaks on the spectra.At8g MgCl2per100biomass level, furfural peak accounting for about80%of the area under the spectrum.These results indicate that MgCl2is effective in improving the product selectivity of the microwave-assisted pyrolysis and that it is possible to control the product pro?les by varying the catalysts and the dosages used.We are conducting similar experiments using a much larger continuous pilot scale microwave-assisted pyrolysis system.Further study is needed to study additional catalysts and investigate the feasibility of controlling microwave-assisted pyrolysis for production of target chemicals.

Acknowledgements

This work was supported by the Open Foundation of the State Key Laboratory of Food Science,Nanchang University,China Ministry of Education PCSIRT Program(IRT0540),and by US Department of Energy and US Department of Agriculture and University of Minnesota Initiative for Renewable Energy and the Environment grants.

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