Reactions of Model Compounds of Biomass-Pyrolysis Oils over ZSM

Jul 23, 2009 - Increasing the (H/C)eff ratio of the feed with methanol increased significantly the hydrocarbon yield of furfural but not that of carbo...
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Chapter 27

of

Reactions of Model Compounds Biomass-Pyrolysis Oils over ZSM—5 Zeolite Catalysts

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Le H . Dao, Mohammed Haniff, André Houle, and Denis Lamothe Laboratoire de Recherche Sur les Matériaux Avancés, INRS-Energie, Institut National de la Recherche Scientifique, 1650, Montée Sainte—Julie, Varennes, Quebec J 0 L 2P0, Canada

The catalytic conversion of model compounds (e.g. cyclopentanone, cyclopentenone, furfural, glycerol, glucose, fructose and their derivatives usually found in the pyrolysis oils of biomass materials) to hydrocarbon products over H-ZSM-5, Zn-ZSM-5 and Mn-ZSM-5 zeolite catalysts have been studied in a fixed bed microreactor at temperatures ranging from 350°C to 500°C. Although the deoxygenation of cyclopentanone was completed at 400°C, low yields of hydrocarbons were obtained for furfural, glycerol and carbohydrate derivatives. This is due possibly to thermal polymerization at reaction temperatures of 400°C and higher. Increasing the (H/C) ratio of the feed with methanol increased significantly the hydrocarbon yield of furfural but not that of carbohydrates. Reaction mechanisms for deoxygenation and tar formation are proposed. eff

I t has been shown t h a t s y n t h e t i c z e o l i t e s such as ZSM-5 c a n be used t o c o n v e r t oxygenated compounds d e r i v e d from biomass m a t e r i a l s i n t o h y d r o c a r b o n s which c a n be used as f u e l s o r c h e m i c a l s f e e d s t o c k s (1,2,3,4). However, t h e p y r o l y s i s o i l s o b t a i n e d from biomass mater i a l s by d i f f e r e n t t h e r m a l and t h e r m o c h e m i c a l p r o c e s s e s (5,6) showed poor h y d r o c a r b o n y i e l d s and h i g h t a r c o n t e n t when c o n t a c t e d o v e r ZSM-5 z e o l i t e c a t a l y s t s a t h i g h temperatures ( 7 , 8 ) . S i n c e the p y r o l y s i s o i l s a r e composed o f a wide v a r i e t y of oxygenated compounds s u c h as c y c l o p e n t a n o n e , c y c l o p e n t e n o n e , f u r f u r a l , p h e n o l , c a r b o h y d r a t e and c a r b o x y l i c a c i d d e r i v a t i v e s (9,10); i t i s d i f f i c u l t to p o i n t out e x a c t l y which f a m i l y o f compounds i s c o n t r i b u t i n g more t o the o b s e r v e d t a r and t o t h e r a p i d d e a c t i v a t i o n o f the c a t a l y s t s . C a t a l y t i c s t u d i e s on model compounds which a r e u s u a l l y found i n t h e biomass p y r o l y s i s o i l s a r e t h e r e f o r e p r i m o r d i a l i n o r d e r t o d e t e r m i ne t h e b e s t c a t a l y t i c system f o r the u p - g r a d i n g o f p y r o l y s i s o i l s t o u s e f u l h y d r o c a r b o n p r o d u c t s . The r e a c t i o n s of some p h e n o l i c , c a r b o n y l and c a r b o x y l i c a c i d d e r i v a t i v e s over ZSM-5 c a t a l y s t s a r e a l r e a d y

0097-6156/88/0376-0328$06.00/0 © 1988 American Chemical Society

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

27. DAO ET AL.

Model Compounds of Biomass-Pyrolysis Oils

329

reported (7,11). The p r e s e n t paper thus r e p o r t s t h e r e s u l t s f o r t h e conversion of cyclopentanone, cyclopentenone, furfural, glycerol, g l u c o s e and f r u c t o s e , and t h e i r i s o p r o p y l e n e d e r i v a t i v e s over H-ZSM5 and Zn and Mn-exchanged ZSM-5 z e o l i t e c a t a l y s t s a t temperatures r a n g i n g from 350°C t o 500°C. Some r e a c t i o n s a r e supplemented w i t h methanol i n t h e i r f e e d s , so as t o determine t h e e f f e c t of i n c r e a s e d (H/C) r a t i o ( s e e T a b l e 1 f o r d e f i n i t i o n ) on t h e d e o x y g e n a t i o n yields. e f f

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Experimental P r e p a r a t i o n and c h a r a c t e r i z a t i o n o f t h e c a t a l y s t s . The s y n t h e s i s of t h e sodium form o f ZSM-5 was done a c c o r d i n g t o p r o c e d u r e #2 g i v e n i n t h e p a t e n t of Derouane and V a l y o c s i k ( 1 2 ) . The o n l y d i f f e r e n c e was t h e use of s i l i c a f i b e r (Strem C h e m i c a l s ) i n s t e a d o f s i l i c a g e l powder. The Na-ZSM-5 z e o l i t e was exchanged s e v e r a l times w i t h 10% aqueous s o l u t i o n o f Ν Η ^ Ν 0 (10 ml p e r g of z e o l i t e ) a t 80°C. The z e o l i t e was then d r i e d a t 100°C and c a l c i n a t e d a t 500°C so as t o o b t a i n t h e H-ZSM-5 c a t a l y s t . Mn-ZSM-5 c a t a l y s t was p r e p a r e d by h e a t i n g t h e ammonium exchanged z e o l i t e w i t h a 10% s o l u t i o n of manga­ nese n i t r a t e a t 80°C f o r 3 hours (10 ml p e r g z e o l i t e ) . A f t e r wash­ ing and d r y i n g , t h e c a t a l y s t was c a l c i n a t e d a t 500°C. Zn-ZSM-5 c a t a l y s t was p r e p a r e d i n a s i m i l a r f a s h i o n t o t h a t of t h e manganese f o r m u s i n g a 10% s o l u t i o n of z i n c n i t r a t e . The X-ray d i f f r a c t i o n p a t t e r n o f the z e o l i t e i s s i m i l a r t o those r e p o r t e d i n t h e l i t e r a t u ­ re. The c h e m i c a l c o m p o s i t i o n i s shown i n T a b l e 1. 3

P r e p a r a t i o n o f t h e c a r b o h y d r a t e i s o p r o p y l e n e d e r i v a t i v e s ( 1 3 ) . 20 g of the c a r b o h y d r a t e was mixed w i t h 250 ml of acetone and 10 ml o f cone. I1 S0^. The m i x t u r e was s t i r r e d a t room temperature f o r about 24 hours and then f i l t e r e d t o remove any u n r e a c t e d s o l i d . The f i l ­ t r a t e was n e u t r a l i z e d w i t h s o l i d NaHC0 d r i e d o v e r MgSO^, f i l t e r e d and t h e excess acetone was removed on a r o t a r y e v a p o r a t o r t o y i e l d the y e l l o w s o l i d d e r i v a t i v e s . 2

3

Apparatus. The c a t a l y t i c c o n v e r s i o n was s t u d i e d i n a c o n t i n u o u s f l o w q u a r t z m i c r o r e a c t o r w i t h a f i x e d - b e d o f d i l u t e d c a t a l y s t s . The r e a c t i o n c o n d i t i o n s a r e r e p o r t e d i n T a b l e 1. A f t e r an e x p e r i m e n t a l r u n (about 3 t o 4 h o u r s ) , t h e t a r on t h e c a t a l y t i c bed was d e t e r m i ­ ned by t a k i n g the d i f f e r e n c e i n weight of t h e r e a c t o r b e f o r e and a f t e r p l a c i n g i t i n a f u r n a c e s e t a t 500°C i n t h e p r e s e n c e o f a i r . The r e a c t i o n p r o d u c t s were a n a l y z e d by GC and GC/MS ( T a b l e 1 ) . Results F i g u r e 1 shows the y i e l d s o f c o n v e r s i o n and the p r o d u c t s d i s t r i b u ­ tion (Cj'Cg h y d r o c a r b o n s , a r o m a t i c , p o l y a r o m a t i c s and t a r ) as a f u n c t i o n of r e a c t o r temperature f o r pure c y c l o p e n t a n o n e over H-ZSM5 / b e n t o n i t e (80/20 Wt.%) c a t a l y s t . The c o n v e r s i o n i s completed a t 350°C. The main r e a c t i o n i s a t h e r m a l d e c a r b o n y l a t i o n of c y c l o p e n ­ tanone, g i v i n g h y d r o c a r b o n fragment t h a t r e a c t s f u r t h e r on t h e c a t a l y t i c bed t o produce a l i p h a t i c , a r o m a t i c and p o l y a r o m a t i c h y d r o ­ carbons. C y c l o p e n t e n o n e which i s p a r t i a l l y deoxygenated (32%) over H-ZSM-5/bentonite (80/20 Wt.%) a t 450°C, c a n be c o m p l e t e l y c o n v e r t e d

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

330

PYROLYSIS OILS FROM BIOMASS TABLE 1 C h e m i c a l c o m p o s i t i o n o f ZSM-5 samples Component (WT%) Na 0 Al 0~ 2

o

sio

2

3

MnO ZnO Ti0 L.O.I.*

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2

Zn-ZSM-5

H-ZSM-5

Mn-ZSM-5

0.55 2.25 86.86

0.69 2.33 91.05 0.78

0.59 7.02

0.64 3.26

0.26 0.38 6.68

65.47 0.40

66.32 0.49

70.80 0.38

0.49 2.10 87.62

Molar Ratio

sio M i o 2

Na 0/Al 0 2

2

3 3

* L.0.1. means l o s s on i g n i t i o n o f sample w e i g h t . REACTION CONDITIONS C a t a l y s t weight Temperature Pressure I n e r t gas WHSV ** R e a c t i o n time **

The weight h o u r l y

10 g ( 8 0 % ZSM-5 + 20% b e n t o n i t e ) 350-560°C atmospheric pressure h e l i u m (~ 3 mfc/min) variable 3 hours

space v e l o c i t y (WHSV) i s d e f i n e d a s : WHSV

β

g o f i n j e c t e d feed per hour g of c a t a l y s t

ANALYTICAL CONDITIONS •

Gas chromatography: HP 5890 GC w i t h DB-5 (SE-54) column (30m χ 0.25mm, 1.0 μ ) For l i q u i d : 70°C (4 m i n ) , t h e n 4°C/min t o 160°C t h e n 20 m i n a t 160°C Gas : 33°C ( i s o t h e r m a l ) • GC/MS : HP 5890 GC and MS d e t e c t o r Pona column and DB-5 column HYDROGEN/CARBON EFFECTIVE RATIO ( l i a ) The e f f e c t i v e hydrogen i n d e x (EHI) i s d e f i n e d a s : EHI

(H/C) e f f

H

20 - 3N

2S

where H, C, 0, Ν and S a r e atoms p e r u n i t weight o f sample of* hydro­ gen, carbon, oxygen, n i t r o g e n and s u l f u r , r e s p e c t i v e l y .

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

27. DAO ET AL. to hydrocarbons

Model Compounds of Biomass-Pyrolysis Oils

331

by the a d d i t i o n of methanol t o the f e e d ( c y c l o p e n t e -

none /methanol 70/30 Wt.%). T a b l e 2 shows the r e a c t i o n of pure f u r f u r a l ( ( H / C ) =* 0) o v e r v a r i o u s c a t i o n exchanged ZSM-5 c a t a l y s t s a t 400°C. The h y d r o c a r b o n y i e l d s range from 6.6 t o 9.4% and the oxygenated compounds y i e l d s v a r y from 25.6 t o 50%. These v a l u e s r e f l e c t the poor performance of a l l the t h r e e c a t a l y s t s i n d e o x y g e n a t i n g f u r f u r a l . The l a r g e quant i t i e s of f u r a n and CO o b s e r v e d a r e m a i n l y due t o the t h e r m a l d e c a r b o n y l a t i o n of f u r f u r a l . H i g h e r t a r c o n t e n t s were o b t a i n e d f o r the m e t a l exchanged c a t a l y s t s (21.2 and 25.9%) than the H-ZSM-5 form (14.2%). The low water c o n t e n t s ( r a n g i n g from 2.7 t o 7.0%) produced f r o m t h e s e d i f f e r e n t r e a c t i o n s i n d i c a t e poor c a t a l y t i c d e o x y g e n a t i o n of f u r f u r a l . C0 which i s produced from p y r o l y t i c r e a c t i o n i s obt a i n e d i n low y i e l d s . The y i e l d s f o r the a l i p h a t i c (9.0%) and o l e fin (8.5%) a r e r e l a t i v e l y s m a l l e r than those f o r the a r o m a t i c (47.7%) and p o l y a r o m a t i c . e f f

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2

F i g u r e 2 shows the p r o d u c t d i s t r i b u t i o n s f o r the r e a c t i o n of various f u r f u r a l / m e t h a n o l mixtures o v e r H-ZSM-5/bentonite (80/20 Wt.%) a t 450°C.; o n l y the major components i n the p r o d u c t s a r e shown. The a b s c i s s a i n F i g u r e 2 i s g i v e n i n both i n c r e a s i n g p e r c e n t a g e of methanol and i n c r e a s i n g ( H / C ) f £ r a t i o f o r the f e e d . As the c o n t e n t of methanol i n c r e a s e s , the y i e l d s f o r h y d r o c a r b o n s and water i n c r e a s e w h i l e t h o s e f o r t a r , f u r a n and CO d e c r e a s e . The d r a s t i c augmentation of h y d r o c a r b o n s and water y i e l d s c o n j u g a t e d w i t h the d i m i n u t i o n of f u r a n w i t h i n c r e a s i n g methanol c o n c e n t r a t i o n i n d i c a t e that s i g n i f i c a n t c a t a l y t i c deoxygenation i s t a k i n g p l a c e . For a m i x t u r e o f 55/45 Wt.% m e t h a n o l / f u r f u r a l ( ( H / C ) - 0.85), f u r a n i s c o m p l e t e l y removed from the r e a c t i o n p r o d u c t s ana o n l y s m a l l q u a n t i t i e s of o t h e r oxygenated compounds were p r e s e n t (< 0.3%). The y i e l d s f o r the o t h e r p r o d u c t s were s i m i l a r t o t h o s e o b s e r v e d p r e viously for furfural. Only a t 70/30 Wt.% m e t h a n o l / f u r f u r a l m i x t u r e t h e r e was a s i g n i f i c a n t r e d u c t i o n i n the t a r c o n t e n t (6.7 o r 14.1% on carbon b a s i s ) . The average C 0 p r e s e n t was 0.3%. e

e i f

2

T a b l e 3 shows the p r o d u c t d i s t r i b u t i o n f o r r e a c t i o n s of f u r f u - , r a l / m e t h a n o l (30/70 Wt.%) o v e r v a r i o u s c o n c e n t r a t i o n of H-ZSM-5/supp o r t a t 450°C. By d i l u t i n g the c a t a l y s t w i t h b e n t o n i t e from 80 t o 18 Wt.%, the h y d r o c a r b o n s y i e l d s r a i s e d from 30.6 t o 41.4%. Changi n g the s u p p o r t m a t e r i a l from b e n t o n i t e to S i 0 - A l 0 caused a s m a l l r e d u c t i o n i n the h y d r o c a r b o n y i e l d ( 3 6 . 3 % ) ; however, t h e r e was l e s s t a r formed when compared t o the o t h e r c a s e s . The p r o d u c t s s e l e c t i v i t i e s were s i m i l a r t o those of p r e v i o u s c a s e s . T a b l e 4 shows the p r o d u c t s from the r e a c t i o n of glycerol [ ( H / C ) £ £ o f 0.67] o v e r v a r i o u s c a t i o n exchanged ZSM-5 z e o l i t e s a t 400°C. The r e a c t i o n w i t h Zn-ZSM-5 gave the b e s t y i e l d of h y d r o c a r bons (14.4%) and the lowest y i e l d of oxygenated compounds ( 1 1 . 5 % ) . The t a r and CO c o n t e n t s f o r the t h r e e c a t a l y t i c systems were h i g h ( t h e t a r ranged from 14.0 t o 19.3% and the carbon monoxide from 5.1 t o 7.8%). I t s h o u l d be noted t h a t the major component i n the oxygenated p r o d u c t s i s 2 - p r o p e n a l . T a b l e 5 shows the p r o d u c t s d i s t r i b u t i o n f o r the r e a c t i o n of a m i x t u r e g l y c e r o l / m e t h a n o l f e e d ( 5 5 / 4 4 Wt.%) w i t h ( H / C ) - 1.25 o v e r H-ZSM-5 at 400°C. Compared t o the r e s u l t s i n T a b l e 4, an i n c r e a s e i n h y d r o c a r b o n s y i e l d s and a d e c r e a s e i n t a r and oxygenated compounds y i e l d s were o b s e r v e d . By d i l u t i n g H-ZSM-5 w i t h b e n t o n i t e 2

2

3

e

e f f

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

PYROLYSIS OILS FROM BIOMASS

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332

00

400

500

TEMPERATURE (°C)

Figure 1. Reaction of cyclopentanone over H-ZSM-5/bentonite (80/20) at a d i f f e r e n t reactor temperature.

Figure 2. Reaction of furfural/methanol mixtures over H-ZSM-5/bentonite (80/20g) at a reactor temperature of 400 °C and a WHSV of 0.238 ± 0.018 h r - . 1

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

333

Model Compounds of Biomass-Pyrolysis Oils

27. DAO ET AL.

TABLE 2 R e a c t i o n o f f u r f u r a l o v e r c a t i o n exchanged ZSM-5 a t 400°C and WHSV o f 0.281 hr~* Experimental conditions: Catalyst

composition:

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T o t a l product

80% H-ZSM-5, 80% Zn-ZSM-5, 80% Mn-ZSM-5 20% b e n t o n i t e , 20% b e n t o n i t e , 20% b e n t o n i t e

distribution

(Wt.%)

Furan J Oxygenated hydrocarbons Tar CO C0 H 0 Hydrocarbons 2

2

Product

selectivity

Aliphatics, 0 - C Olefins, C - C Aromatics Polyaromatics χ

2

47.0 50.0 14.2 22.8 0.6 4.4 8.00

23.8 25.6 21.2 36.3 4.8 2.7 9.42

27.8 40.7 25.9 17.9 1.9 7.0 6.6

8.8 8.5 50.6 32.1

7.6 10.6 48.8 32.9

10.5 6.5 43.9 39.1

(Wt.%)

8

g

TABLE 3 R e a c t i o n o f f u r f u r a l / m e t h a n o l (30/70) f e e d { ( H / C ) over H-ZSM-5 a t 450°C

e f f

- 1.17}

Experimental c o n d i t i o n s : Catalyst WHSV

c o m p o s i t i o n : 80% H-ZSM-5, 18% 20% b e n t o n i t e , 82% (hr~l) 0.029

T o t a l product Oxygenated Tar CO

co

hydrocarbons* 6.7 9.4 0.5 52.7 h y d r o c a r b o n s 30.6

Deoxygenated

selectivity

Aliphatics, C - C Olefins, C - C Aromatics Polyaromatics 1

2

Mainly

H-ZSM-5 SiO - A l 0 o

i.zi

d i s t r i b u t i o n. (Wt.%)

2

Product

18% H-ZSM-5, b e n t o n i t e , 82% 1.26

g

Q

1.4 7.6 7.8 0.6 41.6 41.1

0.8 4.9 7.2 0.3 50.4 36.3

11.6 3.0 72.8 12.6

20.7 3.6 60.8 14.8

(Wt.%) 1.8 2.9 83.5 11.9

f u r a n and b e n z o f u r a n ,

d e r i v a t i v e s and d i m e t h y l e t h e r .

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

2

3

a

334

PYROLYSIS OILS FROM BIOMASS TABLE 4 R e a c t i o n of g l y c e r o l ( ( H / C ) ^ ^ = 0.67) over v a r i o u s c a t i o n exchanged ZSM-5 a t 400°C and a WHSV o f 0.228 h r " e

1

Experimental c o n d i t i o n s : Catalyst

c o m p o s i t i o n : 80% H-ZSM-5, 80% Zn-ZSM-5, 80% Mn-ZSM-5 20% b e n t o n i t e , 20% b e n t o n i t e , 20% B e n t o n i t e

T o t a l product

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Oxygenated Tar CO

d i s t r i b u t i o n (Wt.%)

hydrocarbons*

co

2

Hydrocarbons Product

selectivity

A l i p h a t i c s , Cj - C Olefins, C - C Aromatics Polyaromatics 2

32.7 14.0 7.8 0.3 40.2 5.0

11,5 15.8 6.1 3.7 48.2 14.4

16,7 19.3 5.1 1.4 49.6 7.8

15.8 5.9 60.1 18.5

5.5 9.6 63.5 21.4

9.4 8.4 44.1 38.1

(Wt.%)

Q

6

Mainly 2-propenal

and t r a c e s o f a c e t o n e

TABLE 5 R e a c t i o n o f g l y c e r o l / m e t h a n o l (55/45) f e e d {(H/C) ~ - 1.25} o v e r H-ZSM-5 a t 400°C and WHSV o f 1.44 h r ^ Experimental c o n d i t i o n s : Catalyst

composition:

T o t a l product Oxygenated Tar CO

80% H-ZSM-5 20% b e n t o n i t e

d i s t r i b u t i o n (Wt.%)

hydrocarbons*

co t^o 2

Hydrocarbons Product

selectivity

Aliphatics, 0 - C > Olefins, C - C Aromatics Polyaromatic Q

χ

2

18% H-ZSM-5 82% b e n t o n i t e

g

Mainly 2-propenal,

18.0 11.8 4.9 0.9 45.4 19.1

25.6 5.9 1.1 0.6 50.6 16.2

15.2 8.9 56.8 19.0

16.0 11.7 59.2 13.0

(Wt.%)

and t r a c e s o f methanol and d i m e t h y l e t h e r

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

27. DAO ET AL. from

335

Model Compounds of Biomass-Pyrolysis Oils

80 t o 18%, l e s s

t a r was formed

(5.9%) but t h e y i e l d

of hydro­

carbons a l s o d i m i n i s h e d . T a b l e 6 shows r e s u l t s f o r r e a c t i o n s o f g l u c o s e and g l u c o s e d e r i v a t i v e done over H-ZSM-5 a t 450°C. W i t h t h e a d d i t i o n o f metha­ n o l , t h u s a n i n c r e a s e o f ( H / C ) f £ , t h e r e was a n i n c r e a s e i n t h e hydrocarbon y i e l d s f o r the g l u c o s e / w a t e r / m e t h a n o l (20/50/30) and g l u c o s e d e r i v a t i v e / w a t e r / m e t h a n o l (27.6/12.2/60.2) c a s e s compared t o t h a t o f t h e g l u c o s e / w a t e r (20.3/79.7) c a s e . A l s o , t h e r e was a s i ­ m u l t a n e o u s d e c r e a s e i n t a r c o n t e n t w i t h an i n c r e a s e i n ( H / C ) of the feed. However i n a l l cases t h e h y d r o c a r b o n y i e l d s a r e low and the t a r c o n t e n t s too h i g h f o r a v i a b l e c a t a l y t i c p r o c e s s . The h i g h w a t e r c o n t e n t o b s e r v e d i n a l l experiments (29.2 t o 66.1%) i s not o n l y due t o c a t a l y t i c d e o x y g e n a t i o n through l o s s o f water but a l s o due t o p o l y c o n d e n s a t i o n r e a c t i o n s o f g l u c o s e and i t s d e r i v a t i v e . These c o n d e n s a t i o n r e a c t i o n s produce p o l y m e r i c oxygenated compounds which are r e s p o n s i b l e f o r the h i g h t a r content observed. Oxygenated compounds, CO and C 0 a r e minor p r o d u c t s which a r e n o r m a l l y o b t a i n e d from t h e r m a l d e c o m p o s i t i o n o f biomass m a t e r i a l s ( 1 4 ) . The p r o d u c t s e l e c t i v i t y i n d i c a t e s a h i g h p e r c e n t a g e o f a l i p h a t i c (23.6 t o 50.5%) and a r o m a t i c (34.2 t o 53.2%). E x c e p t f o r the r e a c t i o n w i t h g l u c o ­ se/water, t h e o l e f i n c o n t e n t s a r e low f o r t h e o t h e r two r e a c t i o n s . The p r o d u c t i o n o f p o l y a r o m a t i c s ( m a i n l y indene and naphthalene d e r i ­ vatives) i s rather high. e

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e f f

2

To t e s t t h e e f f e c t o f s u p p o r t and t h e c a t a l y s t efficiency, e x p e r i m e n t s were done w i t h 18% H-ZSM-5 ( i n s t e a d o f 80%) d i s p e r s e d i n 82% b e n t o n i t e . The c a t a l y t i c bed would have l e s s a c i d i c s i t e s which a r e known t o promote p o l y m e r i z a t i o n o f t h e c a r b o h y d r a t e s and hence t o reduce t h e h y d r o c a r b o n y i e l d s . T a b l e 7 shows t h e r e s u l t s f o r e x p e r i m e n t s done on t h e d i l u t e d c a t a l y t i c bed. Only i n t h e methanol added f e e d s t h e r e was a s i g n i f i c a n t i n c r e a s e i n t h e h y d r o c a r b o n y i e l d s and a d e c r e a s e i n t h e t a r c o n t e n t . Thus, r e d u c i n g t h e number o f a c i d i c s i t e s does not seem t o reduce t h e e x t e n t o f t h e p o l y m e r i ­ z a t i o n of carbohydrates. When t h e c a t a l y t i c s u p p o r t m a t e r i a l was changed from b e n t o n i t e t o S i O - A 1 0 , t h e y i e l d s o f hydrocarbons i n c r e a s e d f o r both cases as shown i n T a b l e 8. Deoxygenation of g l u c o s e / w a t e r f e e d (20.3/79.7 Wt.%) w i t h Mn and Zn exchanged ZSM-5 a r e r e p o r t e d i n T a b l e 9. T h e r e was a r e d u c t i o n i n t h e h y d r o c a r b o n s y i e l d s when compared t o s i m i l a r r e a c t i o n s w i t h H-ZSM-5. The t a r c o n t e n t s were as h i g h as those r e a c t i o n s r e p o r t e d b e f o r e . 2

3

The d e o x y g e n a t i o n o f f r u c t o s e and i t s d e r i v a t i v e over ZSM-5 c a t a l y s t s a r e shown i n T a b l e 10. The r e s u l t s o b t a i n e d a r e s i m i l a r t o those r e p o r t e d b e f o r e f o r g l u c o s e and i t s d e r i v a t i v e . As t h e (H/C) r a t i o i n c r e a s e d , t h e h y d r o c a r b o n s y i e l d s i n c r e a s e d and the tar contents decreased. e f f

Discussion Cyclopentanone c a n be deoxygenated i n h i g h y i e l d t o h y d r o c a r b o n s o v e r H-ZSM-5 above 350°C. The main r e a c t i o n i s a t h e r m a l d e c a r b o n y l a t i o n o f c y c l o p e n t a n o n e t o g i v e CO and C^Hg fragment t h a t c a n r e a c t f u r t h e r on t h e c a t a l y t i c bed t o produce a l i p h a t i c , a r o m a t i c and polyaromatic hydrocarbons. Cyclopentenone with ( H / C ) f f 0.8 i s more d i f f i c u l t t o deoxygenated. The a d d i t i o n o f methanol r a i s e s t h e (H/C) r a t i o and p e r m i t s t h e complete d e o x y g e n a t i o n o v e r H-ZSM-5. β

e

f

f

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

336

PYROLYSIS OILS FROM BIOMASS TABLE 6 R e a c t i o n o f g l u c o s e and g l u c o s e d e r i v a t i v e o v e r 80% H-ZSM-5 and 20% b e n t o n i t e a t 450 °C

Experimental conditions: R e a c t a n t c o m p o s i t i o n : 20 .3% 79 .7% WHSV

(hr"l)

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0i/O

g l u c o s e , 20.0% water, 0.062 0.0

e f f

27.6% g l u c o s e derivative 30.0% methanol, 60.2% methanol 12.2% water 50.0% water 0.313 0.195 1.59 1.36 glucose

T o t a l p r o d u c t d i s t r i b u t i o n (Wt.%) Oxygenated hydrocarbons Tar 65.1 CO 2.1 co 1.5 29.1 H6 Hydrocarbons 2.2

0.7 * 33.3 0.5 1.4 59.7 4.4

3.9 ** 14.1 0.2 0.9 66.1 14.8

P r o d u c t s e l e c t i v i t y (Wt.%) Aliphatics, - C 23.6 Olefins, C - C 41.6 Aromatics 34.8 Polyaromatics***

35.7 3.8 53.3 7.2

50.5 2.7 43.2 3.6

2

2

8

2

6

R e a c t i o n o f g l u c o s e and and 82% Experimental conditions: R e a c t a n t c o m p o s i t i o n : 20 .3%

TABLE 7 glucose d e r i v a t i v e over b e n t o n i t e a t 450°C

18% h-ZSM-5

glucose

27.6%

79 .7% water 1

WHSV (hr"" ) (H/C)

0.862 0.0

e f f

20.0%

glucose

glucose derivative 30.0% methanol 60.2% methanol 12.2% water 50.0% water 1.12 1.195 1.59 1.46

T o t a l p r o d u c t d i s t r i b u t i o n (Wt.%) Oxygenated hydrocarbons 0.6 * Tar 51.3 CO 3.8 co 2.8 39.4 H6 Hydrocarbons 2.1

1.0 * 21.0 1.8 0.3 57.9 18.1

4.2 ** 11.1 0.8 0.8 64.3 18.8

P r o d u c t s e l e c t i v i t y (Wt.%) Aliphatics, C - C 29.0 Olefins, C - C 7.3 Aromatics 45.2 Polyaromatics*** 18.3

43.6 1.2 45.3 10.0

17.5 14.0 55.8 12.7

2

2

Q

x

2

6

M a i n l y f u r a n and b e n z o f u r a n d e r i v a t i v e s ; ** M a i n l y acetone and furan derivatives; * * * M a i n l y indene and naphthalene derivatives

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

337

Model Compounds of Biomass-Pyrolysis Oils

27. DAO ET AL.

TABLE 8 R e a c t i o n o f g l u c o s e and g l u c o s e d e r i v a t i v e and 82% S i O ^ A L , 0

over

18% H-ZSM-5

?

Experimental conditions: Reactant composition:

WHSV

(hr"l)

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(H/C)

eff

T o t a l product d i s t r i b u t i o n Oxygenated hydrocarbons Tar CO

co

2

H 0 Hydrocarbons 2

Product s e l e c t i v i t y Aliphatics, 0 - C Olefins, C - C Aromatics Polyaromatics χ

2

20.0% g l u c o s e 30.0% methanol 50.0% water 1.18 1.59

27.6% g l u c o s e d e r i v a t i v e 60.2% methanol 12.2% water 1.11 1.46

(Wt.%) 0.1 14.3 1.6 0.4 62.4 21.2

0.2 6.9 1.8 0.5 53.5 37.2

19.0 12.0 65.6 3.4

21.0 8.3 62.0 8.7

(Wt.%)

Q

6

TABLE 9 R e a c t i o n o f 20.3% g l u c o s e and 79.7% water o v e r and z i n c exchanged ZSM-5 Experimental conditions: Catalyst composition WHSV

0i/O

(hr~l) e f f

80% Mn-ZSM-5 20% b e n t o n i t e 0.046 0.0

T o t a l p r o d u c t d i s t r i b u t i o n (Wt.%) Oxygenated hydrocarbons Tar 72.3 CO 2.6 co 1.9 H 0 22.3 0.9 Hydrocarbons 2

2

Product s e l e c t i v i t y Aliphatics, C - C Olefins, C - C Aromatics Polyaromatics L

2

Q

g

manganes

80% Zn-ZSM-5 20% b e n t o n i t e 0.055 0.0

53.1 2.2 4.2 39.8 0.7

(Wt.%) 26.0 42.8 31.0

35.4 2.6 62.0

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

338

PYROLYSIS OILS FROM BIOMASS

TABLE 10 R e a c t i o n o f f r u c t o s e and f r u c t o s e d e r i v a t i v e o v e r v a r i o u s ZSM-5 a t 450°C Experimental

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Reactant

conditions:

composition:

Catalyst composition:

80% H-ZSM-5 20% bentonite

WHSV ( h r ~ l ) (H/C)

0.06 0.0

e f f

T o t a l product

0.0 37.3 2.6 2.2 60.6 0.7

2

H6 2

Hydrocarbons Product

selectivity

Aliphatics C -C Olefins, C - C Aromatics Polyaromatic*** x

2

19.8% fructose 29.8% methanol 50.4% water

80% H-ZSM-5 20% bentonite 0.14 1.17

27.6% fructose derivative 60.2% methanol 12.2% water

80% H-ZSM-5 20% bentonite

80% Zn-ZSM-5 20% bentonite

80% Mn-ZSM-5 20% bentonite

0.22 1.49

0.19 1.49

0.157 1.49

0. 1* 28. 9 2. 8 2. 1 58. 5 7. 7

3.6** 14.91 0.8 1.2 46.2 33.4

0.6** 10.7 1.2 1.6 61.4 24.9

0.3** 13.2 1.3 1.0 58.7 25.5

21.5 14.1 52.1 12.3

33.2 5.6 54.8 6.3

9.8 8.1 70.7 11.4

8.6 9.7 71.4 10.2

d i s t r i b u t i o n (Wt.%)

Oxygenated hydrocarbons Tar CO

co

19.8% fructose 80.2% water

Q

6

(Wt.%)

17.4 18.8 48.5 15.3

M a i n l y f u r a n and b e n z o f u r a n d e r i v a t i v e s and d i m e t h y l e t h e r M a i n l y a c e t o n e and f u r a n d e r i v a t i v e s and benzofurane d e r i v a t i v e s and d i m e t h y l e t h e r M a i n l y indene and naphthalene d e r i v a t i v e s

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

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27. DAO ET AL.

339

Model Compounds of Biomass-Pyrolysis Oils

Both f u r f u r a l and g l y c e r o l c a n undergo p y r o l y t i c r e a c t i o n s a t t h e temperature s t u d i e d . Both t h e p y r o l y t i c p r o d u c t s and t h e f e e d s c a n take p a r t i n the c a t a l y t i c d e o x y g e n a t i o n o v e r ZSM-5 t o produce h y ­ drocarbons. The h i g h t a r c o n t e n t o b s e r v e d i n many of t h e r e a c t i o n s r e p o r t e d c a n be e x p l a i n e d by t h e p y r o l y t i c r e a c t i o n s . A t h i g h tem­ p e r a t u r e s , f u r f u r a l c a n undergo many t h e r m a l r e a c t i o n s . I t has been shown (15) t h a t f u r f u r a l , under a c i d i c c o n d i t i o n s , c a n p o l y m e r i z e d by an a l d o l - t y p e r e a c t i o n t o produce h i g h m o l e c u l a r r e s i n r e f e r r e d as f u r f u r a l b l a c k . The major p y r o l y t i c r e a c t i o n of f u r f u r a l i s d e c a r b o n y l a t i o n t o produce f u r a n and CO as r e p o r t e d i n t h e l i t e r a t u ­ r e (16) and a l s o o b s e r v e d i n most of t h e r e a c t i o n s o f f u r f u r a l ( T a ­ b l e s 2 and 3 ) . Under h i g h temperature and a c i d i c c o n d i t i o n s , f u r a n c a n p o l y m e r i z e d t o humin ( 1 6 ) . G l y c e r o l c a n undergo d e h y d r a t i o n a t h i g h temperature t o produce a c r o l e i n ( 2 - p r o p e n a l ) (17) w h i c h c a n r e a c t f u r t h e r t o form polymers ( p o l y a c r o l e i n ) (18) ( T a b l e s 4 and 5 ) . Once a l l t h e s e polymers a r e formed, they remain on t h e c a t a l y t i c bed c o n t r i b u t i n g t h e n t o t h e t a r c o n t e n t s and t h e d e a c t i v a t i o n o f t h e catalysts. T a b l e s 6 t o 10 show t h a t t h e y i e l d s o f h y d r o c a r b o n s obtained f o r most of t h e r e a c t i o n o f c a r b o h y d r a t e s over ZSM-5 c a t a l y s t s were low when compared t o t h e y i e l d s o f t a r formed on t h e r e a c t o r bed. The r e s u l t s a l s o i n d i c a t e t h a t t h e z e o l i t e c a t a l y s t s a r e not r e s p o n ­ s i b l e f o r t h e h i g h t a r c o n t e n t s o b s e r v e d , s i n c e most of the t a r s were formed on t h e top o f t h e c a t a l y t i c bed. Two p o s s i b l e reasons f o r t h e h i g h t a r c o n t e n t a r e t h e low ( H / C ) f r a t i o i n t h e f e e d as a l s o r e p o r t e d by o t h e r a u t h o r s (11) and t h e p o l y m e r i z a t i o n of t h e c a r b o h y d r a t e s and t h e i r d e r i v a t i v e s a t temperatures above 150°C. F i r s t l y , i f the ( H / C ) i s lower than 1, t h e c o n v e r s i o n t o h y d r o ­ c a r b o n w i l l be s m a l l because t h e main d e o x y g e n a t i o n r e a c t i o n i s the e l i m i n a t i o n o f water which i s dependant o f t h e a v a i l a b i l i t y o f t h e h y d r o g e n i n t h e o r g a n i c components of t h e f e e d (2,4,11). Glucose a n d f r u c t o s e a n d t h e i r d e r i v a t i v e s w i t h ( H / C ) ^ * r a t i o < 0.7 a r e t h e r e f o r e e x p e c t e d t o g i v e poor h y d r o c a r b o n s y i e l d s ( T a b l e s 6-10). However, s u p p l e m e n t i n g t h e s e c a r b o h y d r a t e s w i t h compounds w i t h h i g h (H/C) (e.g. methanol with ( H / C ) 2 . 0 ) , i t i s p o s s i b l e to i n c r e a s e the ( H / C ) of the feed. T a b l e s 6, 7 and 10 show t h e e f f e c t o f a d d i n g methanol t o t h e c a r b o h y d r a t e s f e e d s ; t h e r e was a simultaneous i n c r e a s e i n hydrocarbons y i e l d s with i n c r e a s e (H/C) ff· N e v e r t h e l e s s , as t h e i n c r e a s e i s s m a l l and t h e t a r c o n t e n t s t i l l t o o h i g h , t h e c a t a l y t i c u p g r a d i n g would be d i f f i c u l t i n a f i x e d - b e d reactor. T h e r e f o r e more c o s t l y p r o c e s s e s such as a f l u i d i z e d bed s y s t e m (11a) a r e n e c e s s a r y . The h i g h t a r c o n t e n t c a n be produced by t h e d e c o m p o s i t i o n and p o l y m e r i z a t i o n o f c a r b o h y d r a t e s . I t I s known t h a t g l u c o s e can undergo t h e r m a l p o l y m e r i z a t i o n and d e c o m p o s i t i o n a t temperatures h i g h e r than 150°C ( 1 9 ) . P o l y c o n d e n s a t i o n o f g l u c o s e c a t a l y z e d by a c i d produced polymers ( p o l y g l u c o s e ) w i t h a wide range of molecular weights. Other n o n - v o l a t i l e decomposition products which c o n t r i b u t e t o the t a r c o n t e n t a r e l e v o g l u c o s a n and 1,6-anhyd r o g l u c o f u r a n o s e ( 2 0 ) . One consequence o f t h e n o n - v o l a t i l e p r o d u c t s on t h e c a t a l y t i c bed i s t h a t they c a n b l o c k t h e pores of ZSM-5 and, hence, p r e v e n t i n g d e o x y g e n a t i o n of the v o l a t i l e compounds. Thermal d e c o m p o s i t i o n o f g l u c o s e c a n a l s o produce v o l a t i l e p r o d u c t s (5-hydroxymethyl f u r f u r a l , f u r f u r a l , f u r y l hydroxymethyl ketone) which c a n undergo d e o x y g e n a t i o n over ZSM-5 c a t a l y s t s t o y i e l d t h e s m a l l e

f

e f f

β

e f f

e f f

e f f

e

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

340

PYROLYSIS OILS FROM BIOMASS

amount of h y d r o c a r b o n s o b s e r v e d . The e x p e r i m e n t a l r e s u l t s s u g g e s t t h a t the r a t e of p r o d u c t i o n o f v o l a t i l e p r o d u c t s i s much s l o w e r than the r a t e of p r o d u c t i o n o f n o n - v o l a t i l e p r o d u c t s i n a f i x e d - b e d c a t a ­ l y t i c system. Hence, t h e poor h y d r o c a r b o n y i e l d and the h i g h t a r content. The d e r i v a t i v e s o f g l u c o s e and f r u c t o s e g i v e b e t t e r h y d r o ­ c a r b o n y i e l d s , p r o b a b l y b e c a u s e o f t h e i r h i g h e r R/C ff r a t i o and a l s o because most of the hydroxy groups r e s p o n s i b l e f o r the forma­ t i o n of p o l y g l u c o s e a r e blocked. However, t h e t a r c o n t e n t s f o r t h e s e d e r i v a t i v e s r e a c t i o n s a r e s t i l l too h i g h . e

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Conclusion C y c l o p e n t a n o n e c a n be deoxygenated w i t h h i g h y i e l d t o h y d r o c a r b o n s o v e r ZSM-5 a t 400°C. The a d d i t i o n o f methanol t o c y c l o p e n t e n o n e p e r m i t s t o r a i s e t h e ( H / C ) f £ r a t i o o f t h e f e e d and, hence, i t s complete d e o x y g e n a t i o n . The r e a c t i o n o f f u r f u r a l and g l y c e r o l o v e r ZSM-5 c a t a l y s t s a t temperatures between 400°C and 500°C produces p y r o l y t i c p r o d u c t s o f d i f f e r e n t degree o f v o l a t i l i t y . The v o l a t i l e f r a c t i o n i s deoxygenated by t h e c a t a l y s t s t o produce h y d r o c a r b o n s w h i l e the n o n - v o l a t i l e f r a c t i o n remained on the c a t a l y t i c bed c a u s ­ i n g the d e a c t i v a t i o n o f the z e o l i t e and the enhancement o f the t a r content. G l u c o s e and f r u c t o s e undergo t h e r m a l r e a c t i o n s which p r o ­ duce a s i g n i f i c a n t amount o f t a r and a s m a l l amount o f v o l a t i l e products. The v o l a t i l e f r a c t i o n i s deoxygenatd by ZSM-5 c a t a l y s t s to produce h y d r o c a r b o n s . e

Acknowledgments T h i s work was s u p p o r t e d by g r a n t s from t h e N a t u r a l S c i e n c e s and E n g i n e e r i n g R e s e a r c h C o u n c i l o f Canada and from the Quebec M i n i s t r y of S c i e n c e s and T e c h n o l o g y . Literature

cited

1. Weiz, P.B., Hagg, W.O., Rodewald, P.G., Science, 1979, 206, 57. 2. Frankiewicz, T.C., U.S. Patent 4 308 411, 1981. 3. Dao, L.H., Haniff, Μ., Preprint tenth Canadian Symposium on Catalysis, 1986, p. 278. 4. Chen, N.Y., Koenig, L.R., U.S. Patent 4 503 273, 1985. 5. Hasnain, S., Editor Fifth Canadian Bioenergy R&D Seminar; Elsevier: London, 1984. 6. Chornet, E., Overend, R., Editor Compte-rendu de l'atelier de travail sur la liquefaction de la biomasse, 1983. 7. Chantal, P.D., Kaliaguine, S., Grandmaison, J.L., Applied Catalysis, 1985, 8, 133. 8. Dao, L.H., Canadian Patent 1.201.080, 1985. 9. Schirmer, R.E., Pahl, T.R., Eliot Fuel, 1984, 368. 10. Dao, L.H., Hebert, P., Houle, Α., Haniff, M., Proceeding of the Ninth Biennal Congress of the International solar Energy Society, 1986, Vol. 3, 1812. 11. a. Chen, N.Y., Walsh, D.E., Koenig, L.R., Preprint Amer. Chem. Soc. Div. Fuel Chem, 1987, 32(2), p. 264.; b. Chang, C.D., Silvestri, A.J., J. Catalysis, 1977, 47, 249; c. Chang, C.D., Silvestri, A.J., U.S. Patent 3,998,898, 1976.

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.

27. DAO ET AL.

Model Compounds of Biomass-Pyrolysis Oils

341

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12. Derouane, E.G., Valyacsik, E.W., European Patent 157521, 1985. 13. Shafizadek, F., Fu, Y.J., Carbohydr. Res., 1973, 29, 113. 14. Neuth, F.H., Adv. Carbohydr. Chem, 1951, 6, 83. 15. Kraushaar, B., Kompa, H., Schrolliens, H., Schulz-Eskloff, G., Acta Phys. et Chim. (Szeged), 1985, 31, 581. 16. Acheson, R.M., An Introduction to the Chemistry of Heterocyclic Compounds, Johns Wiley and Sons, NY, 1976, p. 126. 17. Segur, J.B., In Glycerol, Miner C.S., Dalton N.M., Editor Reinhold: NY, 1953, p. 335. 18. Derouane, E.G., J. Catalysis, 1981, 70, 123. 19. Smith, P.C., Guehtlein, H.E., Converse, A.O., Solar Energy, 1982, 28, 41. 20. Houminer, Y., Patai, S., Israel J. Chem, 1969, 7, 513. RECEIVED March 31, 1988

In Pyrolysis Oils from Biomass; Soltes, Ed J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.