Pyrolysis Oils from Biomass - American Chemical Society

Chapter 27

of

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

Downloaded by EMORY UNIV on January 27, 2016 | http://pubs.acs.org Publication Date: September 30, 1988 | doi: 10.1021/bk-1988-0376.ch027

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


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


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.*


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 .


27. DAO ET AL. to hydrocarbons


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


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


PYROLYSIS OILS FROM BIOMASS


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


333


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:


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 .


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


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


hydrocarbons*

co t^o 2


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


27. DAO ET AL. from

335


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


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


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)


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


337


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)


(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


338


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


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


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


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



27. DAO ET AL.

339


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


340


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


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

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27. DAO ET AL.


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Pyrolysis Oils from Biomass - American Chemical Society

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