Biohydrogen Generation and Other Methods - Hydrogen Generation, Storage, and Utilization - page 56

30

Walnut shell
Corncob
Olive husk
Wheat straw
Sunflower shell

25

20

15

10

750 800 850 900 950 1000

Temperture, K

1050 1100 1150

FIGURE 4.2 Plots for yields of hydrogen-rich gas from pyrolysis of agricultural residues versus tem-
perature in the presence of 30% Na 2 CO 3 . Source : Reproduced with permission from Demirbas [27].

for the utilization of bio-oil. Hydrogen production from renewable bio-oil is
an attractive idea for fuel, energy, and agricultural applications. In recent
years, hydrogen production via steam reforming of bio-oil has attracted more
and more attention. But because of the complicated composition of bio-oil
and carbon deposition on catalyst surface in the reaction process, currently,
studies have mainly focused on steam reforming of model compounds in
bio-oil and reforming catalysts [31]. The bio-oil can be stored and shipped
to a centralized facility where it is converted to hydrogen via catalytic steam
reforming and shift conversion [32]. Catalytic steam reforming of bio-oil at
1025-1125 K over a Ni-based catalyst is a two-step process that includes the
shift reaction [33]:

Bio-oil H O CO H + → +

2

(4.4)

2

CO H O CO + → + H

2 .

(4.5)

2 2

The overall stoichiometry gives a maximum yield of 0.172 g H 2 ·g -1 bio-oil
(11.2% based on wood) [33].

CH O + 1 26 . H O CO → + 2 21 . H .

(4.6)

1 9 . 0 7 . 2 2 2

In reality, this yield will always be lower because both the steam reforming
and water-gas shift reactions are reversible, resulting in the presence of some