**2. Results and Discussion**

### *2.1. Effect of Heating Rate on Conversion and Reaction Rate*

Heating rates were varied for date palm biomass at 5 K/min, 10 K/min and 15 K/min to observe their effects on peak temperatures and also to obtain isoconversional data points for kinetic analysis. The mass loss curve for the two biomasses and co-pyrolysis are shown in Figure 1. Each mass loss curve (*α*) in Figure 1 is the resulting average of triplicates. The mass loss (*α*) is explained in Section 3.

**Figure 1.** Comparison of the mass loss (*α*) curves of *S. bigelovii*, *P. dactylifera*, and mixtures of them, at different heating rates (K/min).

The mass loss curves for both biomasses show pyrolysis took place through an identical pathway. Co-pyrolysis biomass followed a pathway between the two pure biomasses as might be predicted; theoretical and kinetic parameters lie between those of the two pure biomasses. The pathway can be categorized into three main phases: Evaporation of water, passive pyrolysis and active pyrolysis which corresponds to the first two phases having characteristic peaks associated with them on the DTG diagram in Figure 2. The evaporation of water occurs around 373 K, corresponding to the first peak on the curve. Active pyrolysis was observed to take place between 473 K and 633 K as seen with the two peaks in this region. Passive pyrolysis began after active pyrolysis and continued till the end of mass loss.

**Figure 2.** Decomposition rates (*dα*/*dt*) of *S. bigelovii*, *P. dactylifera*, and mixtures of them, at different heating rates (K/min) showing peak temperatures.

Gasparovic et al. [15] studied the decomposition of hemicellulose, cellulose and lignin and concluded that the decomposition of these three components typically occurred at temperature ranges between 473 K to 653 K, 523 K to 653 K and 453 K up to 1075 K, respectively. This observation reveals that the decomposition of all hemicellulose and cellulose took place during active pyrolysis but decomposition of lignin took place in both active and passive pyrolysis phases.

Increasing heating rate increases the rate of reaction but does not significantly affect the conversion yields at the end of the experiment. Lower heating rates for *S. bigelovii* actually increased the total conversion at the end of the process although the rate of reaction was slower. The reaction rate for all heating rates peaked between 588 K and 602 K during the active pyrolysis phase. These peak temperatures were employed in the kinetic parameter determination using the Kissinger method.

From Figure 2, it is clear that the rate of reaction at all phases of pyrolysis increased with increasing heating rates. However, increased heating rates also led to a more non-uniform reaction decomposition process during the active pyrolysis phase. From the diagram, it can be seen that though the rate of decomposition generally increases with the heating rate and during the active pyrolysis phase, there are no distinct peaks.
