## 3 Results and Discussion
### Thermal Degradation and Kinetic Analysis of Sargassum spp.
[PERSON] and [PERSON] proposed a method for determining the \(E_{a}\) and \(n\) of the degradation of biomass [29] that allows to obtain \(E_{a}\) by calculating the slope that results from the T\(-\)Ts graph (\(x\)-axis) vs. ln[ln[1/(1 - \(\alpha\))]] (\(y\)-axis), as shown in Figure 3.  
As Figure 3 shows, there is a good linear adjustment and a slope with a value of 0.07397. Based on Figure 3 and the point of maximum velocity (DTG), we obtained a temperature value of approximately 550 K. Consideration of the constant of ideal gases (R = 8.314 J K\({}^{-1}\) mol\({}^{-1}\)) allows the calculation of the activation energy. Our result was an approximate value of 186.03 kJ/mol, which is similar to the figures reported by other researchers who have studied _Sargassum_ spp. [45; 52; 53]. The fact that the correlation coefficient (R\({}^{2}\)) presents a value of 0.9810-1 indicates that the Horowitz-Metzger method is acceptable  
Figure 3: Activation energy (\(E_{a}\)) of _Sargassum_ ssp. obtained using the Horowitz and Metzger method. for predicting both \(E_{a}\) and \(n\). It is important to recall that \(E_{a}\) is the minimum amount of energy required to achieve a reaction, and that as it increases, the reaction velocity decreases. Upon comparing the \(E_{a}\) of _Sargassum_ spp. (186.03 kJ/mol) to recent kinetic studies of terrestrial biomass from western Mexico (like _Pinus pseudostrobus_, _Pinus leiophyllla_, and _Pinus montezumae_, which have average values of 120.84, 140.71 and 147.05 kJ/mol respectively) [52], the \(E_{a}\) of the _Sargassum_ spp. studied herein (also from Mexico) was slightly higher. Added to an exploitable energy in the order of 1.24 gigajoules (GJ)/m\({}^{3}\) (see below), this result is acceptable for generating biofuels in a pyrolysis reactor. Figure 4 presents the graph of the degree of advance (\(\alpha\)) vs. \(d\omega\)/\(dT\). According to [PERSON]'s method, it is possible to calculate the reaction order by placing the value of \(\alpha_{m}\) at the point of maximum degradation velocity (\(d\omega\)/\(dT\)). This procedure generated a value of \(\alpha_{m}\approx 0.3637\). Based on the approach in Equation (8) for \(n\), we obtained an \(n\) value that approached 1. Another important kinetic parameter is the frequency factor (\(Z\)). Using Equation (9), we calculated \(Z\) by considering a heating velocity of \(\beta\) = 10 \({}^{\circ}\)C/min, the activation energy of 186.03 kJ/mol, an \(R\) value equal to 0.008314 kJ K\({}^{-1}\) mol\({}^{-1}\), and a temperature (\(T\alpha\)), of 1173 K. This produced an approximate value for \(Z\) of \(5.76\times 10^{5}\) min\({}^{-1}\). Considering the surface of the study material, reports indicate that the factor \(Z\) can vary on the order of magnitude values above six. In the case of a value for the reaction order (\(n\)) that is very close to 1, there are reports that the factor \(Z\) can vary in a range of \(10^{5}\) to \(10^{18}\) s\({}^{-1}\). For the _Sargassum_ spp. analyzed in our study we obtained a relatively low frequency factor, perhaps due to a reaction that occurred on the surface of the biomass. However, if the surface is not involved, then this magnitude of \(Z\) (\(<\)10\({}^{9}\) s\({}^{-1}\)) could result from the formation of some -unidentified and more densified structure or compound [54; 55].