Bio-Oil

To study
the different types of biochars obtained, and based on previous experience,^{8 (link),9 (link),17 (link),39 (link)} rice husk was used because of its physicochemical properties. The
moisture contents of the four biochars were measured (according to
the ISO 589 standard and by means of a halogen moisture analyzer HR83,
Mettler Toledo), and the following analyses were done: proximate analysis
(in a TA Instruments Discovery 5500 TGA according to the ASTM D5142
standard), ultimate analysis (Vario–Macro of Elementar, according
to the ASTM D5373 and ISO 19579 standards), and HHV (Parr 6200 isoperibolic
bomb calorimeter following the ASTM D5865 standard). The contents
of the three natural polymers that make up the biomass were determined
according to the methodology proposed by different authors,^{6 (link),7 (link),39 (link)} by means of a deconvolution of
the DTG curves obtained in the same equipment used for proximate analysis
(TGA Discovery 5500 TA Instruments). For the determination of the
three components, an algorithm was developed in Scilab 6.0.1 that
solves the ordinary differential equations of a kinetic model that
considers the three independent parallel reactions corresponding to
the degradation of each component.^{6 (link),7 (link),11 (link),39 (link)} Similarly, the algorithm
uses a direct search optimization established by Nelder–Mead
to find the values of the best fit for the kinetic model (frequency
factors and activation energies) and for the contents of two of the
three polymers. The objective function to be minimized is the sum
of the squared differences between the experimental TGA values and
those calculated by the model. All of the physicochemical characteristics
of the biochar used in this study are shown in Table 4, where wt % d.b. represents the weight percent on a dry basis
and wt % w.b. represents the weight percent on a wet basis.
It is observed that the moisture content of the four
biochars is
quite low. The fixed carbon in all biochars ranged between 48.65%
and 54.59%. High volatile matter content and low ash content indicate
significant conversion to pyrogenic vapor during heat treatment and
low biochar yield.^{63 (link),64 (link)} Higher volatile biomass is undesirable
for bio-oil production together with biochar.^{63 (link)}Table 1 shows the
carbon, hydrogen, sulfur, hydrogen and nitrogen composition of both
the raw material and all the biochars obtained, noting that the carbon
content increases considerably with respect to the raw material. The
contents of C, H, N, S, and O of the biochar were studied, and it
was possible to observe that the C content was high and the contents
of N and S were quite low. Similarly, it can be seen that at a temperature
of 450 °C there is a small amount of cellulose on the polymer
content and a large amount of lignin, but all of the hemicellulose
had already been consumed. For temperatures of 500, 550, and 600 °C,
only lignin was observed in its content, and this is in accordance
with research in which it is argued that after 500 °C hemicellulose
and cellulose completely degraded.^{6 (link),7 (link),11 (link),39 (link)}Likewise, the
surface area of each of the biochars obtained was
evaluated with methylene blue dye, which is widely used for mineral
clay. In recent years, it has been used for biochar because its amorphous
and asymmetric compositions do not show good results, as seen from
BET isotherms.^{65 (link)} Therefore, methylene blue
adsorption measurements are used for a more accurate determination
of the surface area for liquid adsorption applications.^{38 (link),65 (link)} In the same way, and to evaluate the pore size, a BET area analysis
was carried out on an AutoChem II 2920 equipment (Micromeritics).
To determine functional groups, FTIR analysis was performed using
an infrared spectrometer (PerkinElmer, model spectrum Two V10.4.2)
equipped with an attenuated total reflection (ATR) accessory (PerkinElmer),
operating in the spectral range of 4000–400 cm^–1 with a resolution of 4 cm^–1.

Toluene, cyclopentanone, acetic acid, furfural and guaiacol were mixed with a volume ratio of 1 : 1 : 1 : 1 : 1 to represent simulated bio-oil. All these reagents were analytically pure. The catalytic tests were conducted on a fixed bed reactor, as shown in Fig. S1.† For each run, 5 g of catalyst was placed on the insulating spacers of the catalyst reaction bed, and the reaction temperature was 400 °C. Model bio-oil (10 mL) was gasified and introduced into the 400 °C preheated reactor using a peristaltic pump at a flow rate of 20 ml h⁻¹ for 30 min with N₂ as the carrier. N₂ flushing was maintained for another 20 min after the experiment was complete to ensure that all condensable gas was cooled and collected. The liquid was dissolved in chloroform, and the mass of the liquid after removing chloroform was reported as M_L. The yield of liquid after upgrading was defined as follows: where M_L is the mass of the upgraded liquid and M₀ is the mass of the total simulant component before the reaction.
The conversion of each model component was calculated as follows: where W_a and W_b are the mass of each model component after and before the reaction, respectively. For the regeneration study, the spent catalysts were regenerated using a muffle furnace by heating for 3 h at 550 °C, and then the catalytic activity was tested. The parameters of the regeneration catalytic activity experiments were the same as those of the catalytic tests mentioned above.