*3.1.1 Effect of temperature on pyrolysis yield with dp (0.3* ≤ *dp* ≤ *0.6 mm)*

**Figure 5** represents the pyrolysis yields of cistus seeds with a heating rate of 21°C. min�<sup>1</sup> starting from a temperature of 300°C. The yields of charcoal, pyrolysis oil and gas are quite close. When the temperature increases from 300 to 400°C we observe, on the one hand, an increase of liquid from 34.7 to 51.76%, and on the other hand a slight decrease of coal yield and gas yield down to 18.2%. In the range of 400 to 425°C, the liquid continues to increase along with a decrease in gas yield. At temperatures between 425 and 475°C a plateau of yield for the three (Bio-Oil, solid and gas) was noticed with a maximum yield of liquid at 450°C which is equal to 52.24%. From 475 to 500°C we observe a drop in the yield of solid and liquid in parallel and an increase in the yield of gas.

For the sizes that vary between 0.3; 0.4 and 0.5 mm at the same temperature we notice a small variation in the yield of pyrolysates which is equal to 0.2%. For this reason we have taken the particle size between 0.3 and 0.6 mm to complete the study.

#### *3.1.2 Effect of heating rate on pyrolysis yields*

**Figure 6** shows the effect of heating rate on pyrolysate yields. The liquid and gas yields increase from 43.2 to 52.24% and from 27.60 to 17.51%, respectively when the *Valorization of Forest Waste for the Production of Bio-oils for Biofuel and Biodiesel DOI: http://dx.doi.org/10.5772/intechopen.105366*

**Figure 5.** *Yield of pyrolysis products at various pyrolysis temperatures of seeds.*

heating rate is increased from 7 to 21°C.min�<sup>1</sup> . The increase in liquid yield with increasing heating rate may be due to higher heating rates breaking thermal barriers and mass transfer in the particles. The gas yield also increases with increasing heating rates due to the cracking of pyrolysis vapors at higher heating rates. The solid yield was increased slightly from 29.2 to 30.24 wt% when the heating rate was increased from 7 to 21°C.min�<sup>1</sup> .

#### *3.1.3 Effect of particle size on pyrolysis yields*

The effect of particle size on the yields of pyrolysis products is shown in **Figure 7**, under the temperature of 450°C and the heating rate equal to 21°C.min�<sup>1</sup> . Oil yield increased from 38 to 43.07% followed by a slight decrease in solid yield from 33.4 to

**Figure 6.** *Effect of heating rate on pyrolysis yields of seeds.*

**Figure 7.** *Yield of pyrolysis products with different particle size seeds.*

32.11 wt% and gas yield decreased from 28.6 to 24.82 wt% when the particle size increased from less than 0.075 to 0.15 mm and from 0.15 to 0.3 mm. And for particle sizes from 0.3 to 0.6 mm, the bio-oil yield follows a progressive increase until the maximum yield of 52.24%.

On the other hand the yield of gas and solid decreases from 24.82 to 17.51% and from 32.11 to 30.24% respectively. For particle sizes from 0.6 to 0.9 mm, the solid yield increases to 35.1%, and the gas and bio-oil yields decrease from 17.51 to 17.3% and from 52.24 to 47.6% respectively. For smaller particle sizes, the yield favors cracking hydrocarbons. The increases in solid yield with increasing particle size for the biomass sample could be due to a greater temperature gradient, within the particles. Thus at some point, the core temperature is lower than the surface temperature, this eventually gives rise to an increase in solid yield.

#### **3.2 Cistus shells**

#### *3.2.1 Effect of temperature on the pyrolysis yield*

**Figure 8** shows the slow yields of pyrolysis products of cistus shells with the particle size of 2–3 mm at different temperatures from 300 to 500°C. The liquid yields and gas increased 38.53 to 44.6% by weight and 23.64 to 26.49%, respectively, while the solid yield decreased from 47.82 to 28.91% when the pyrolysis temperature is increased from 300 to 400°C.

In the temperature range of 400 to 450°C, it is observed a small decrease in solid and gas pass yield of 28.91 to 25.18% and from 26.49 to 21.51%, respectively, and the yield of bio-oil follow the increase maximum yield which was 53.31%. The low yield of liquid and low temperature gas is due to the incomplete decomposition of the shell. The decrease in the bio-oil yield and the increase in the gas yield of 47.11 and 28.6% respectively were observed at 500°C could be due to secondary cracking pyrolysis vapor and solid char. Similar results were observed in the study slow pyrolysis fixed bed of *Carpinus Betulus* residues *(U. Morali et al),* the same trend was predicted by other researchers *(Kar Yakup and Ilknur Demiral)* different Pyrolysis of the liquid could be due to different biomass components.

*Valorization of Forest Waste for the Production of Bio-oils for Biofuel and Biodiesel DOI: http://dx.doi.org/10.5772/intechopen.105366*

**Figure 8.** *Yield of pyrolysis products at various pyrolysis temperatures of shells.*

#### *3.2.2 Effect of particle size on pyrolysis yields*

The effect of particle size on products yields was assessed by running pyrolysis experiments with a final temperature of 450°C and heating rate equal to 40°C.min�<sup>1</sup> . Results are summarized in **Figure 9**. The lowest oil yield (35%) was obtained using the feedstock of tiniest particles (0.3–0.6 mm), which conversely afforded the maximal amount of gas products (38%) and a charcoal yield equal to 27%. When the particle size was increased to 1–2 mm, the oil yield was incremented to 48%, while both gas (27%) and char (25%) yields decreased.

The peak of oil production (yield = 53.31%), in conjunction with a further decline of gas (20%) and char (26.69%) yields, was achieved using 2–3 mm particles. Interestingly, the formation of charcoal (yield = 32.1%) reached a maximum when biggest

**Figure 9.** *Yield of pyrolysis products with different particle size shells.*

#### **Figure 10.**

*Effect of heating rate on pyrolysis yields of shells.*

particles (3–3.5 mm) were used, showing a significant effect of particle size on the performance of carbonization processes. On one hand, the use of smaller particles could promote the cracking of hydrocarbons, and the longer residence time of volatiles in the reactor would lead to the decrease of liquid yield. On the other hand, the increase of biomass particles size could produce a larger temperature gradient within the particles, so that at some point, the core temperature is lower than the surface, which might possibly lead to an increase in solid products yield.

#### *3.2.3 Effect of heating rate on pyrolysis yields*

Pyrolysis of cistus shells with particle size from 2 to 3 mm was next performed with a final temperature of 450°C and different heating rates. As shown in **Figure 10**, both oil and gas yields evenly grew upon increasing the heating rate from 10 to 40°C. min�<sup>1</sup> , passing from 48.33 and 19.20%, respectively, at 10°C.min�<sup>1</sup> to 53.31 and 21.5%, respectively, at 40°C.min�<sup>1</sup> . The char yield dropped from 32.47 to 25.19%. This change can be ascribed to the shorter residence time and reduced incidence of cracking for pyrolysis vapors, which also account for the increased yield of tar. At 40°C. min�<sup>1</sup> , the optimal heating rate for the production of oil (yield = 53.31%), the yields of charcoal and gas underwent a further slight reduction. Finally, for heating rates greater than 40°C.min�<sup>1</sup> , decreased oil yield against increased solid and gas yields due to the fast pyrolysis of cistus seeds were observed.

#### **3.3 Bio-oil**

The obtained bio-oil is characterized by FTIR spectroscopy to determine the different functional groups existing. **Figures 11** and **12** shows the infrared spectrum of the bio-oil of cistus seeds and shells. **Tables 4** and **5** represents the results of elemental analysis of the bio-oil and the calorific values.

The analysis of the bio-oil of cistus seeds by Fourier Transform Infrared (FTIR) (**Figure 11**) shows the C-H bonds of cyclobutane in symmetrical and antisymmetrical vibration between (2800–2900 cm�<sup>1</sup> ), the aliphatic ketones (1705–1725 cm�<sup>1</sup> ), the C=C bonds of aromatics and phenols between (1550–1600 cm�<sup>1</sup> ), the C-O bonds of

*Valorization of Forest Waste for the Production of Bio-oils for Biofuel and Biodiesel DOI: http://dx.doi.org/10.5772/intechopen.105366*

**Figure 11.** *FTIR spectrum of bio-oil (Cistus seeds).*

**Figure 12.** *FTIR spectrum of bio-oil (Cistus shells).*

esters between (1210–1260 cm<sup>1</sup> ), C-OH bonds of primary and secondary alcohols between (1050–1080 cm<sup>1</sup> ), and between (1110–1220 cm<sup>1</sup> ), C-N bonds of aromatic amines between (1020–1220 cm<sup>1</sup> ), C-H bonds of mono and disubstituted aromatics between (650–900 cm<sup>1</sup> ) and finally the presence of (Z) and (E) isomers of alkenes between (650–750 cm<sup>1</sup> ) and (950–1010 cm<sup>1</sup> ).

Bio-oil analysis of cistus shells by oven transformation (FTIR) (**Figure 12**), shows -OH groups of phenols and acids between at 3352.67 cm<sup>1</sup> and 2622.47 cm<sup>1</sup> respectively, the C=O of acids at 2173.98 cm<sup>1</sup> and aromatic ketones at 1697.75 cm<sup>1</sup> , the C C of alkynes at 2118.51 cm<sup>1</sup> , the C=C of alkenes at 1642, 10 cm<sup>1</sup> and, the C-N of amines at 1516.63 cm<sup>1</sup> , the C-H of aldehydes at 1370.73 cm<sup>1</sup> , the C-N of aromatic amides at 1275.43 cm<sup>1</sup> , the C-O of esters and ethers at 1082.50 cm<sup>1</sup> , the nitrile groups -NO2 at 930.64 cm<sup>1</sup> and finally the C-H bonds of polycyclic and substituted aromatic groups between 679 and 757.04 cm<sup>1</sup> .


#### **Table 4.**

*Elemental analysis of bio-oil from seeds.*


#### **Table 5.**

*Elemental analysis of bio-oil from shells.*

The results of **Table 5** shows that our bio-oil extracted by fixed bed pyrolysis contains more carbon compared to Apricol, hornbeam and walnut shells, but the percentage of oxygen in the bio-oil is smaller than Apricol, hornbeam and walnut bio-oils. In addition, we observe a total absence of sulfur in our bio-oil. We do not forget that the energetic value of the bio-oil is the highest compared to the bio-oils quoted in the literature and close to that of the oil which varies from 40 to 44 MJ.kg�<sup>1</sup> (**Table 6**).

The second method for the measurement of the kinematic viscosity is obtained by measuring the time of flow of a given volume of liquid under the effect of gravity (the dynamic viscosity (η) in (g.cm�<sup>1</sup> .s�<sup>1</sup> or mPa.s) of a fluid is obtained by multiplying its kinematic viscosity (γ) in (cm<sup>2</sup> .s�<sup>1</sup> or stokes (cSt)) by its density (ρ)). Experimentally

*Valorization of Forest Waste for the Production of Bio-oils for Biofuel and Biodiesel DOI: http://dx.doi.org/10.5772/intechopen.105366*


#### **Table 6.**

*Properties physicochemical experimental obtained by the mechanic study.*


#### **Table 7.**

*Properties physicochemical experimental obtained by the volume study.*

not having a viscometer the measurement of the time of flow of a volume V = 10 cm3 of liquid in a graduated burette of length 20 cm, the temperature of 20 °C the results are grouped in **Table 7** gave: η = γ/ρ with ρ in g.cm�<sup>3</sup> [26].

We can deduce from the unit of kinematic viscosity the relationship that links the volume of liquid, the time of decantation and the length of the burette γ = V/L.t These results allow to highlight the small difference in viscosity between the bio-oil of seeds and shells of cistus and biodiesel. So we can improve the density of our bio-oil by


#### **Table 8.**

*Fuel properties of cistus seeds and shells pyrolysis oil.*

adding a percentage of ethanol to increase the calorific value and thus bringing its density closer to the density of commercial fuels. To improve the bio-oil we can refine it by the reactions of trans-esterification to mimic the acids and the methyl esters of the vegetable oils as well as the ethyl ethers.

To confirm the experimental results found in this study concerning viscosity and density, measurements results are obtained at 20°C, were made using an apparatus (Anton paar DMATM4500M) with a (Software Version 2.93.9364.129) (**Table 8**).

## **4. Conclusion**

A parametric study focused mainly on the impact of temperature, size and heating rate on the yield of pyrolysates. The ex-beech liquids show high solid residue and gas contents, good homogeneity and yields up to 52.24% for seeds and 53.34% for shells at 450°C. Chemical analyses were also carried out to characterize the pyrolysis products obtained in order to determine the oxygen, carbon and hydrogen contents in the solid residues and in the liquids.

So far, the percentage of C, O, N and H of the pyrolysis oils as a whole is high compared to other biomasses located in the literature and also present important and very high calorific powers in comparison with wood and with other biomass as castor, black cumin, karanja, apricol, walnut and hornbeam The main innovative character of this study lies in the adopted approach which consists in valorizing the bio-oils of pyrolysis, in particular in the production of biofuels in a first time and in a second time the synthesis of chemical products with the aim of use in cosmetic, pharmaceutical and food. The valorization of the solid (charcoal) as a bioadsorbent which will be detailed in another chapter.

## **Acknowledgements**

This work is the result of research on the valorization of bioresources, it is a chapter of my doctoral thesis.

## **Conflict of interest**

The author declares no conflict of interest.

## **Institutional Review Board Statement**

Not applicable.
