**6. Experimental methodology**

### **6.1. Chemicals and reagents**

Most of the chemical reagents used in this study, such as toluene for separation of bio-oil from the solvent, were purchased from Wako Chemicals (Japan).

### **6.2. Experimental methods**

The apparatus for hydrothermal experiments (AKICO Co. Japan) shown in Fig. 4 consists of a batch-type Inconel reactor (about 8.8 cm3 inner volume) and a heating electric furnace. Mechanical stirring of reactor is provided with a cyclic horizontal swing span of 2 cm fixed at a frequency of 60 cycles per minute. The amount of solvent used in each experiment depends on the desired reaction pressure. Only water was used as solvents for liquefaction experiments. Critical temperatures (Tc) and pressures (Pc) for water are Tc = 375°C, Pc = 22.1 MPa, respec‐ tively. It took about 15 min to reach the set reaction temperature of 210 to 300°C. The reaction time was varied from 0.5 to 8 h. After the reaction time elapsed, batch reactor was quenched

in a water bath for rapid cooling. The degradation products were then separated for analyses. The degradation rate (DR) was then calculated from the amount of resin removed from the sample on the basis of the amount of resin originally present, and reported in %. resin removed from the sample on the basis of the amount of resin originally present, and reported in %.

10 Book Title

depends on the desired reaction pressure. Only water was used as solvents for liquefaction

experiments. Critical temperatures (Tc) and pressures (Pc) for water are Tc = 375°C, Pc =

22.1 MPa, respectively. It took about 15 min to reach the set reaction temperature of 210 to

300°C. The reaction time was varied from 0.5 to 8 h. After the reaction time elapsed, batch

reactor was quenched in a water bath for rapid cooling. The degradation products were then

at a frequency of 60 cycles per minute. The amount of solvent used in each experiment

**4.2. Algal biomass (microalgae or macroalgae)**

products.

464 Biofuels - Status and Perspective

**5. Objectives of the study**

**6. Experimental methodology**

a batch-type Inconel reactor (about 8.8 cm3

the solvent, were purchased from Wako Chemicals (Japan).

**6.1. Chemicals and reagents**

**6.2. Experimental methods**

Algae are considered to be primitive plants lacking in roots, stems and leaves [17]. This inherent structure of these type of plants makes it very suitable for energy production [18]. Thus, its use as feedstocks for bio-oil production is gaining popularity in recent years due also to the presence of some functional components including oils, proteins and carbohydrates [8]. Among the various types of algae, microalgae are the most potential energy source because cultivation and production of these biofeedstocks do not match those for food production [5]. The concept of bio-oil conversion using these materials has been introduced in 1970s, but mainly focused on direct thermochemical method. Recently, liquefaction under hydrothermal condition has also received increasing attention because of the advantages the method can offer for rapid reaction, no pre-drying of samples and no restrictions due to lipid contents [8]. Hydrothermal liquefaction (HTL) converts biomass feedstocks into four phases including the biocrude oil (or simply referred to as bio-oil), aqueous products, solid residue and gaseous

This work focused on the conversion of biomass (mainly oil palm biomass) to bio-oil by liquefaction under hydrothermal conditions using sub- and supercritical water. The effects of operating parameters such as temperature and pressure on the liquefaction were studied. The obtained bio-oil was then characterized using various analytical methods such as TG-DTA and GC-MS analyses. Other approaches like the use of catalysts to enhance liquefaction rates and selectivity of the products, and coupling of microwave irradiation will also be introduced.

Most of the chemical reagents used in this study, such as toluene for separation of bio-oil from

The apparatus for hydrothermal experiments (AKICO Co. Japan) shown in Fig. 4 consists of

Mechanical stirring of reactor is provided with a cyclic horizontal swing span of 2 cm fixed at a frequency of 60 cycles per minute. The amount of solvent used in each experiment depends on the desired reaction pressure. Only water was used as solvents for liquefaction experiments. Critical temperatures (Tc) and pressures (Pc) for water are Tc = 375°C, Pc = 22.1 MPa, respec‐ tively. It took about 15 min to reach the set reaction temperature of 210 to 300°C. The reaction time was varied from 0.5 to 8 h. After the reaction time elapsed, batch reactor was quenched

inner volume) and a heating electric furnace.

Schematic diagram of a batch reactor inside the electric furnace (arrows indicate cyclic horizontal movement for mixing of samples inside the reactor)

**Figure 4.** Schematic diagram of the reactor and actual apparatus for solvothermal experiments (Tmax=500o C, Pmax=50MPa).

Biomass samples were loaded into the reactor (8.8 mL) with distilled water at a sample to water ratio of 1:10. The reactor was inserted into the heating chamber preheated at the desired temperature, and then was allowed to react for 1 h. After 1 h had elapsed, the heater was turned off and the reactor was quenched in water at room temperature. After sufficiently cooling the reactor, its content was washed and rinsed with water and toluene. The toluene solution was subjected under vacuum in a rotary evaporator set at T=60°C to remove toluene and obtained the bio-oil for further analyses.

### **6.3. Gas Chromatography-Mass Spectrometry (GC-MS) analysis**

The obtained bio-oil was analyzed by gas chromatography-mass spectrometry (GC-MS, Hewlett Packard-6890 series, Palo Alto, CA), coupled with a mass selective detector (Hewlett Packard-5973). The GC conditions were as follows:

**Fig. 4**. Schematic diagram of the reactor and actual apparatus for solvothermal experiments

Oven Temperature: 40°C (3 min) → 230°C → 300°C (3 min), rate = 5°C /min

Injector/Detector Temperature: 250°C, Injection Volume: 0.5 µL

Carrier Gas: Helium (split ratio of 12: 1, flow rate of 24 mL min-1)

Ionizing energy: 70 eV

(Tmax=500oC, Pmax=50MPa).

The compounds corresponding to the peaks appearing in the chromatograms resulting from the GC-MS analyses were identified by comparing the mass spectra of each peak with those stored in the database (the NIST library).

### **6.4. Thermogravimetry-Differential Thermal Analysis (TG-DTA) analysis**

To determine the temperature-dependent mass behavior of biomass, thermogravimetrydifferential thermal analysis (TG-DTA) was performed using EXSTAR 6000 TG/DTA6300 apparatus (Seiko Instruments. Inc., Japan). The temperature range investigated was from 35 to 500°C at a heating rate of 20°C /min under N2 gas flow.
