Thermocatalytic Decomposition of Sesame Waste Biomass over Ni-Co-Doped MCM-41: Kinetics and Physicochemical Properties of the Bio-Oil

Abstract

The increase in industrialization and development has tremendously diminished fossil fuel resources. Moreover, the excessive use of fossil fuels has resulted in the release of various toxic gases and an increase in global warming. Hence, necessitating the need to search for a renewable energy source. In this study, sesame waste biomass (SWB), which is abundantly available in Pakistan, has been used as feedstock for obtaining bio-oil using the pyrolysis technique. Pyrolysis was carried out using thermogravimetry and a pyrolysis chamber. Firstly, thermogravimetric analysis was performed on biomass with/without a laboratory synthesized catalyst Ni/Co/MCM-41 in nitrogen at different temperature programmed rates of 5, 10, 15, and 20 °C/min. A four-stage weight loss was observed that pointed toward the vaporization of water, and degradation of hemicelluloses, cellulose, and lignin. The kinetics parameters were determined using the Kissinger equation. The activation energy for the decomposition reaction of hemicelluloses, cellulose, and lignin, without catalyst, was observed as 133.02, 141.33, and 191.22 kJ/mol, respectively, however, with catalyst it was found as 91.45, 99.76, and 149.65 kJ/mol, respectively. In the catalyzed reaction the results showed the lowest activation energy, which is an indication of the fact that the catalyst is successful in reducing the activation energy to a sufficient level. As the TG/DTG showed active degradation between 200 and 400 °C, therefore, the waste sesame biomass over Ni-Co/MCM-41 was pyrolyzed within the same temperature range in the pyrolysis chamber. Temperature and time were optimized for maximum oil yield. A maximum oil yield of 38% was achieved at 330 °C and 20 min. The oil obtained was studied using GCMS. The physicochemical characteristics of the oil were assessed, and it was found that if the oil was upgraded properly, it could serve as a fuel for commercial use.

1. Introduction

Energy is a critical economic factor in the development of a country [1]. Fossil fuels have been the major sources of energy for many of the past decades; however, with a sudden rise in industries, the fossil fuel reserves are continuously depleting [2]. Moreover, the use of fossil fuels results in the emission of different toxic gases into the environment, which also contributes to the greenhouse effect. Hence, it necessitates the need to search for renewable energy [3]. Therefore, scientists across the world are looking for renewable energy sources that are not exhaustible and environmentally friendly [4]. Thus, more attention is being paid to biomass due to its low cost and eco-friendly nature [5,6,7].

Energy is obtained from biomass using different techniques, i.e., combustion, biochemical, and pyrolysis. In combustion, the biomass is fully oxidized at elevated temperatures and the heat produced is used instantaneously for heating or generating power. This process is not preferred due to the drawbacks associated with it, i.e., low efficiency, unwanted ash, and increased carbon dioxide [3]. The two commonly used biochemical processes for biomass conversion into energy are anaerobic digestion and fermentation; however, these processes are more time-consuming and less efficient. Therefore, pyrolysis is one of the best options as it produces liquid fuel, non-condensable gases, and solid fuel at modest temperatures [8,9].

Although many pyrolysis techniques are being in-vogue, the pyrolysis of biomass is usually carried out by slow pyrolysis, which is quite favorable for the production of olefins and aromatics [10]. The quality and quantity of products that are obtained are greatly dependent on the composition of the biomass, reaction time, temperature, and type of catalyst [11,12]. As oxygenated compounds are found in abundance in bio-oil, they cause it to decrease in stability, heating value, volatility, and pH, while increasing its viscosity. Hence, to improve the value of fuel, a catalyst needs to be used in the pyrolysis chamber. The catalyst initiates a series of reactions resulting in the conversion of big molecules to light hydrocarbons [13,14].

The most widely used catalysts for the pyrolysis of biomass are zeolites and metal oxides [15,16,17]. Natural materials have also been used as catalysts for such purposes [18]. Any porous material, whether natural or manmade, can be used for this purpose due to the pore volume and an accessible high surface area. In this connection, MCM-41 has a framework of cylindrical mesospores arranged in one dimension, with a large surface area, and a pore volume that has been widely utilized by many researchers.

Adam et al. [19] investigated the degradation of spruce wood over Al-MCM-41. The products obtained were analyzed by GCMS, while the acetic acid, furfural, and furans were detected as the major hydrocarbons in the oil. Nilsen et al. [20] incorporated Zn, Cu, and Fe into Al-MCM-41 and the modified catalysts improved the quality of oil; however, Zn–Al-MCM-41 was observed to more effectively reduce the coke production. Antonakou et al. [21] concluded that a low ratio of Si/Al in Al/MCM-41 had a positive effect on the bio-oil yield. Fontes et al. [22] studied the pyrolysis of biomass using Ti-MCM-41 with Si/Ti in different ratios. The Ti-MCM-41 with a Si/Ti ratio of 50 was found to be more efficient in yielding a high quantity of hydrocarbons. Li et al. [23] used loaded MCM-41 with 1, 5, and 10% of La in rape straw pyrolysis. The 5% La-loaded catalyst showed good efficiency with a hydrocarbon content of 35% and was also successful in lowering the coke content on the catalyst surface, resulting in an increase in the selectivity for aromatic hydrocarbons.

Mesoporous Al/MCM-41 has also been used in combination with microporous ZSM-5 for biomass pyrolysis and MCM-41 was observed to obstruct coke development on ZSM-5, while both helped each other in improving the yield [24,25]. Ratnasari et al. [26] studied the kinetics of biomass pyrolysis over a mixture of H-ZSM-5 and Al/MCM-41 and noted a decrease in the activation energy of the reaction in the presence of a catalyst. Ni/P/MCM-41 was also tried by Li et al. [27] for levoglucosenone production from biomass and revealed its best selectivity and activity in the production of levoglucosenone.

From the aforementioned literature, we concluded that the doping of another material over MCM-41 could further improve the catalytic behavior. For this purpose, different metals, such as Zn, Al, Cu, and Fe were used to increase the catalytic efficiency of MCM-41, yet an extensive gap still exists in the discovery of the influence of more metals on the efficiency, selectivity, and activity of MCM-41. Therefore, a 9% Ni/8% Co/MCM-41 composition, which has not been explored previously, was attempted for the pyrolysis of biomass waste. Among the biomass, sesame (botanical name: Sesamum indicum L. and a local name of Til) is the most significant plant grown abundantly in Pakistan. The utilization of sesame timber in Pakistan is restricted only to cooking food and baking bricks, whereas most of the timber is dumped and wasted. Therefore, the present work focused on the use of Ni/Co/MCM-41 as a catalyst for bio-oil yield from sesame biomass and to improve the quality of the oil being produced. Moreover, the effects of the catalyst on the reduction of the maximum degradation temperature and activation energy were also evaluated.

2. Experimental

2.1. Materials and Method

Sesame plant waste was gathered from a harvested crop in the district Multan, south of Punjab, Pakistan. These were crushed into minute pieces and sieved through mesh no. 35 to provide suitable particles for pyrolysis. Then, it was washed, dried, and mixed with the required amount of catalyst for further studies. Chemicals, i.e., ammonia solution 32%, phosphoric acid, tetraethyl orthosilicate, cetyltrimethylammonium bromide, cobalt nitrate, nickel nitrate, and citric acid were procured from Sigma-Aldrich and Sharlu. N₂ (99.99% pure) was purchased from New Khyber Oxygen Limited Peshawar.

2.2. Synthesis and Characterization of Catalyst

Ni/Co/MCM-41 was synthesized by templating the mechanism by using the support materials of MCM-41 and pure cetyltrimethylammonium bromide, tetraethyl orthosilicate, ammonia, and water. Firstly, MCM-41 was prepared by dissolving 1 g of cetyltrimethylammonium bromide in 102.5 mL of ammonium hydroxide and 135 mL water, before the solution was stirred for 35 min to produce a rod-style homogeneous micelle. Then, 5 mL of tetraethyl orthosilicate was poured into it, and it was stirred for 2 h until a snowy slurry was attained. This slurry was repeatedly washed with water, dried, and calcined at 550 °C for 6 h.

Secondly, 9% Ni/8% Co/MCM-41 was synthesized using the sol-gel method, utilizing the prepared MCM-41 as support. To synthesize the 9% Ni/8% Co/MCM-41, 1.1 g of citric acid was dissolved in 35 mL of water before 0.535 g nickel nitrate hexahydrate and 0.476 g cobalt nitrate hexahydrate were added into it. Finally, 1 g of MCM-41 was dissolved into the solution, and it was stirred at 60 °C unless a gel appeared. The formed gel was aged for 3 days, without stirring, at ambient temperature, and then, calcined at 550 °C for 6 h and stored in a container for further study.

The morphology of the prepared Ni/Co/MCM-41 was assessed using a scanning electron microscope JSM5910 JEOL, Akishima-shi, Japan. The crystalline/amorphous feature was observed through XRD (JDX-3532, JEOL Japan). The elemental analysis was conducted using EDX (INCA100, Oxford instruments, Oxford, UK). The surface features were determined through NOVA 2200e Quantachrome US, surface area, and a pore size analyzer.

2.3. Preparation of Biomass for Analysis

Three separate samples raw, acid-washed, and mixed with a catalyst were prepared for pyrolysis. The demineralized biomass was prepared by treating it with a 2 N solution of phosphoric acid, filtering it through a vacuum pump, and washing and drying it at 105 °C for 20 h. The catalyst-loaded biomass was prepared by impregnating it with 5% of 9% Ni/8% Co/MCM-41.

2.4. Thermogravimetry

Sesame waste biomass, in the absence/presence of the catalyst, was pyrolyzed in a thermobalance (Q500 TG coupled with DSC 8000) at various temperature programmed rates and the resulting information was applied to determine the kinetic parameters, using the Kissinger equation (Equation (1)):

$$\ln \left(\frac{\beta }{T_m^2}\right)=\ln \left[\frac{A.R}{E_a}\right]-\frac{E_a}{R{T}_m}$$

(1)

where β and T_m stand for heating rate and peak degradation temperature, other well-known terms have their respective meanings. E_a and A-factor were determined from the plots of ln($\beta$/$T_m^2$) versus 1/T_m [28].

2.5. Pyrolysis of Biomass

The degradation of the biomass was performed in a salt bath from 300 to 400 °C in nitrogen. The temperature of the pyrolysis chamber was monitored by a temperature controller (Shimaden, E234017, Tokyo, Japan), via thermocouple. Experiments were performed in a glass vessel attached to a condenser and the oil obtained was studied through GCMS (DSQ II, Thermo Scientific, Waltham, MA, USA). The data obtained were matched with an NIST MS library and the peaks were identified accordingly.

2.6. Physicochemical Properties

The physicochemical properties, such as density, viscosity, fluidity, and the specific gravity of the oil obtained were determined. For density, the Pycnometer, with a capacity of 25 mL, was used, while the viscosity was determined using the Ostwald viscometer, whereby water was used as the standard liquid. Fluidity was calculated by taking the reciprocal of the determined bio-oil viscosity and for specific gravity determination, the ratio of the density of the bio-oil to the density of the water was noted.

3. Results and Discussion

3.1. Characterization of Catalyst

Figure 1a,b show the SEM pictures of the MCM-41 and 9% Ni/8% Co/MCM-41, respectively. The micrographs show spongy features outlining the spherical and the ordered morphology with less agglomeration, which shows that the surface features of the MCM-41 have not been changed following the addition of Ni and Co because they are less than 10%, which was also confirmed by using XRD and with the appearance of an intense peak. These results are in accordance with the findings by Grün et al. [29], who noted that the as-prepared MCM-41 particles were spherical in shape and less agglomerated. Likewise, Nejat et al. [30] assessed the morphologies of MCM-41, Ni/MCM-41, and Co/MCM-41 using a field emission scanning electron microscopy and observed that the particles were spherical in shape and uniform in size with a diameter of 50 nm and that there was no change in their morphology following the incorporation of Co and Ni. Wu et al. [31] observed no change in the surface morphology of Ni-MCM-41 with Ni loadings of 5, 10, and 20%, however, at 40%, a prominent change in the surface features was observed, with an increase in the bulky NiO outside the pores.

The chemical composition of the catalyst was determined through EDX. Figure 1c shows no traces of nickel or cobalt in the pure MCM-41, whereas, in Figure 1d, the prominent peaks for Ni and Co can be seen to show a successful incorporation of Ni and Co onto MCM-41. Moreover, the presence of Si and O, in both figures, points toward the silicate nature of MCM-41, which has also been previously confirmed by Parangi et al. [32]. Parangi and co-authors, while performing EDX analysis of 12TPA-MCM-41, observed that Si and O had an atomic percentage of 30.44 and 67.40, respectively. Abrokwah et al. [33] observed from the EDX of a different metal-impregnated MCM-41 that Cu, Pd, Zn, and Sn were highly distributed in MCM-41, whereas Ni and Co showed little dispersion with only a slight agglomeration.

Figure 1e shows the XRD of MCM-41. The broad peak at 2θ = 22.7 is due to siliceous MCM-41 [33]. These observations are consistent with some earlier studies. Salam et al. [34] performed XRD on sulfated Zr-MCM-41 and observed a strong peak at 2θ = 21°. However, in the case of 9% Ni/8% Co/MCM-41, some broad lines were noted that point toward the amorphous nature of the catalyst. Moreover, in addition to the broad peak at 2θ = 23.2°, some weak signs were also observed at 2θ = 36.3°, 43.1°, and 60.6° due to the Ni and Co incorporation onto MCM-41, as shown by Figure 1f [35,36]. The crystallite size determined from the XRD data was noted to be 32 nm. The investigated data are in consonant with the findings reported by Nejat et al. [30]. The absence of an intense peak may be due to a decrease in the amount of the doped materials over the support, i.e., 9% Ni and 8% Co, respectively. The outcomes are in agreement with the reported observation by Wu et al. [31]. The authors impregnated MCM-41 with 5,10, 20, and 40% Ni and analyzed the samples using XRD. In all the samples, a broad peak was noted at 23°, yet, no peak was observed for the 5% and 10% loaded samples. For the 20% loaded sample, the obtained peaks were also not prominent, while, three sharp peaks were observed at 37°, 43°, and 64° in the 40% loaded sample. Liu et al. [37] attributed the broadness of the XRD peak of Ni/Zr/MCM-41 to the impregnation of a second metal ion, resulting in the substitution of Si⁺⁴ and a change in the T–O–T bond angle and a decrease in the order of mesostructures. The specific surface area of MCM-41 and 9% Ni/8% Co/MCM-41 was assessed using the Brunauer–Emmett–Teller method and the pore size was assessed using the Barrett–Joyner–Halenda method. MCM-41 was observed to possess a surface area of 511.91 m²/g, a pore volume of 0.017 cm³/g, and a pore radius of 15.16 A°, whereas the same properties for 9% Ni/8% Co/MCM-41 were 343.78 m²/g, 0.026 cm³/g, and 16.442 Å, respectively. A decrease in the values of these parameters points toward the incorporation of nickel and cobalt, which results in the obstruction of the pore channel from the deposition of these species into the pores. A similar pattern was also observed by Gucbilmez et al. [38], who noted a reduction in the specific surface area and pore volume in V/MCM-41, with a rise in the ratio of vanadium to silicon. In another study by Ma et al. [39], they also observed a decrease in the surface area of Cu/MCM-41, with an increase in the percentage loading of copper over MCM-41.

3.2. Surface Morphology and Chemical Composition of Waste Sesame Biomass

SEM-EDX of sesame biomass in raw, demineralized, and catalyst incorporation was performed. The SEM pictures are presented in Figure 2a–c. Figure 2b contains tiny pores, which have been produced as a result of the treatment with the acid solution due to the removal of the minerals. Figure 2c indicates that the catalyst has effectively been distributed onto the surface of the demineralized sample [40].

Figure 2d–f shows the EDX of the raw, acid-treated, and catalyst-impregnated samples. The untreated sample shown in Figure 2a contains Zn, Cu, Fe, Ca, K, S, Si, P, Al, C, Mg, and Na. These minerals, especially the alkali metals, greatly affect the pyrolysis of the biomass, which act as a catalyst [41,42]; thus, it is essential to remove these minerals and study the influence of 9% Ni/8% Co/MCM-41 alone on the pyrolysis of sesame waste biomass. Figure 2e shows the EDX of the demineralized sample indicating complete removal of all the minerals after an acid wash. Figure 2f presents the loading of the acid-washed sample with 9% Ni/8% Co/MCM-41.

3.3. Thermogravimetric Analysis and Kinetic Study

In order to make a kinetic interpretation of the pyrolysis reaction, the experiments were performed with/without catalyst at various temperature programmed rates and the obtained results were used to calculate the kinetics parameters using the Kissinger method (Equation (1)). The subsequently constructed plots are presented in Figure 3a and b. The Ea and frequency factors were evaluated from the slope and intercept of the plots, and these are presented in

Table 1. Kinetic parameters were calculated using the Kissinger model with/without a catalyst.

Components	Catalytic		Non-Catalytic
	Ea (kJ/mol)	A (min−1)	Ea (kJ/mol)	A (min−1)
Hemicellulose	133.02	2.3 × 108	91.45	8.0 × 105
Cellulose	141.33	8.0 × 109	99.76	3.8 × 106
Lignin	191.22	1.1 × 1011	149.65	1.6 × 109

. The results exhibit that pyrolysis of sesame biomass is a complex reaction, with many steps that mainly consist of the degradation of hemicellulose, cellulose, and lignin, while each step follows a typical behavior independent of each other [43]. These results are in harmony with previous reports. Ahmad, et al. [44] evaluated the pyrolysis kinetics of para grass using KAS and OFW equations and observed an Ea value from 103 to 233 kJ mol⁻¹. Chen et al. [45] attributed the increase in Ea with %conversion to the decomposition of hemicellulose, cellulose, and lignin. Nisar et al. [46] carried out a thermogravimetric analysis of almond shells with/without zinc oxide and the decomposition was found to be a multistep reaction. Torres-García et al. [47] observed the decomposition of peanut shells as a multistep reaction involving the degradation of hemicellulose with an Ea of 172 kJ/mol, cellulose with an Ea of 203.4 kJ/mol, and lignin with an Ea of 218 kJ/mol using the Kissinger equation.

3.4. Pyrolysis of Biomass and Characterization of Bio-Oil

The influence of temperature on the product yields was checked by pyrolysis of biomass from 310 to 400 °C with catalyst for 40 min. The products formed are shown in Figure 4a. The figure shows the maximum bio-oil at 320 °C. An increase in gas and a decrease in biochar were noted with a rise in the temperature, which is because of the secondary degradation of the bio-oil [48,49]. Moreover, the effect of the time on the oil yield was also assessed at an optimized temperature, and an optimum time of 20 min was observed for the maximum oil yield, as shown in Figure 4b. The observations match well with previously reported studies [50]. Nizamuddin et al. [51] investigated the pyrolysis of biomass and an improvement in the percentage yield of the liquid fraction was noted with the elevation in temperature and the increase in time, up to a certain level, and then a reduction was noted. The trend has a similarity with our observation. GCMS was used for the analysis of bio-oil recovered from catalytic reactions at optimized conditions, as depicted by the chromatogram in Figure 5, whereas the detected compounds are provided in

Table 2. Compounds traced in GCMS of bio-oil recovered from the catalyzed decomposition of sesame waste.

Peak No.	R/Time (min)	Compound Name	Mol. Formula	Mol. wt.	Percent Area
1	1.85	Furfural	C5H4O2	96	19.35
2	2.73	Cyclopropane,2-(1,1-dimethyl-2-pentenyl)-1,1-dimethyl	C12H22	166	5.78
3	3.30	2-Furancarboxaldehyde, 5-methyl	C6H6O2	110	9.94
4	4.22	1,2-Cyclopentanedione, 3-methyl	C6H8O2	112	10.70
5	5.01	Phenol, 2-methoxy-	C7H8O2	124	7.91
6	5.40	Maltol	C6H6O3	126	3.72
7	5.87	2-Myristynoic acid	C14H24O2	224	0.48
8	6.44	Phenol, 2-methoxy-4-methyl-	C8H10O2	138	2.89
9	6.78	1,4:3,6-Dianhydro-à-d-glucopyranose	C6H8O4	144	3.06
10	7.13	2-Furancarboxaldehyde, 5-(hydroxymethyl)	C6H6O3	126	4.92
11	7.60	Phenol, 4-ethyl-2-methoxy-	C9H12O2	152	2.28
12	8.05	2-Oxabicyclo[3.3.0]oct-7-en-3-one, 7-(1-hydroxypentyl)-	C12H18O3	210	1.19
14	8.60	Phenol, 2,6-dimethoxy-	C8H10O3	154	6.94
14	9.21	Vanillin	C8H8O3	152	3.22
15	9.78	1,2,4-Trimethoxybenzene	C9H12O3	168	2.28
16	10.29	Ethanone, 1-(4-hydroxy-3-methoxyphenyl)-	C9H10O3	166	1.29
17	10.80	Silane, dimethoxymethylphenyl	C9H14O2Si	182	3.37
18	11.63	Phenol,2,6-dimethoxy-4-(2propenyl)-	C11H14O3	194	1.69
19	12.28	Benzaldehyde,4-hydroxy-3,5-dimethoxy-	C9H10O4	182	3.75
20	13.08	Ethanone,1-(4-hydroxy-3,5-dimethoxyphenyl)-	C10H12O4	196	2.33
21	13.47	3,5-Dimethoxy-4 hydroxyphenylaceticAcid	C10H12O5	212	1.34
22	14.02	Ethanone,1-(4-hydroxy-3,5-dimethoxyphenyl)-	C10H12O4	196	0.58
23	14.55	3,9;7,8-Diepoxybicyclo[4.3.0]nonane-6á-ol-2-one,9à-acetoxy-4-isopropenyl-5-methoxycarbonyl-1-methyl-	C18H22O8	366	0.15
24	14.89	7,9-Di-tert-butyl-1-oxaspiro(4,5)deca-6, 9-diene-2,8-dione	C17H24O3	276	0.32
25	15.28	Estra-1,3,5(10)-trien-17á-ol	C18H24O	256	0.32
26	15.56	3,5-Dimethoxy-4-hydroxycinnamaldehy	C11H12O4	208	0.88
27	16.09	Curan-19,20-diol, 16,17-didehydro-, (19S)-	C19H24N2O2	312	0.07
28	16.52	8-Octadecenoic acid, methyl ester	C19H36O2	296	0.07
29	17.17	Octadecanoic acid	C18H36O2	284	0.38
30	18.58	2-Nonadecanone 2,4-dinitrophenylhydrazine	C25H42N4O4	462	0.02
31	18.93	9,12,15-Octadecatrienoic acid, 2,3-bis[(trimethylsilyl)oxy]propyl ester,(Z,Z,Z)-	C27H52O4Si2	496	0.05
32	20.21	1,2-Benzenedicarboxylicacid,diisooctyl ester	C24H38O4	390	0.32
33	21.78	2,5-Dimethoxy-4-ethylamphetamine	C13H21NO2	223	0.12
34	26.35	Sertindole	C24H26ClFN4O	440	0.43

. The existence of phenols is ascribed to the degradation of lignin. Furfural production points towards the decomposition of hemicellulose, whereas the occurrence of different acids in the oil is because of the incomplete decomposition of hemicelluloses, cellulose, and lignin [52]. It can be illustrated from the table that the oil possesses mostly small molecules of furan, aldehydes, ketones, acids, and phenols [53]. It can also be observed from the GCMS analysis that the presence of valuable products, such as furfural, phenols, and maltol has increased the quality of the oil. Aromatics were also found in abundance, which is in conformity with the results of Zhang et al. [54]. Ateş et al. [55] studied the pyrolysis of sesame biomass from 400 to 700 °C. A maximum yield of 37.20 wt.% of bio-oil was obtained at 550 °C with alkenes, alkanes, and branched hydrocarbons in abundance. Jeon et al. [56] performed the catalytic decomposition of biomass and recovered a good quality of oil, compared to the uncatalyzed reaction.

3.5. Physicochemical Characteristics of Bio-Oil

The bio-oil from the catalytic decomposition of the waste sesame biomass had a dark brown color and pungent order. Its physicochemical properties, such as the viscosity, fluidity, density, and specific gravity and API gravity were determined and compared to other bio-oils to determine its characteristics (as shown in

Table 3. Comparison of physicochemical characteristics of bio-oil obtained from different sources.

Biomass	Viscosity (cP)	Density gm−3	Fluidity (cP)−1	Specific Gravity	API Gravity	Reference
Rice husk	82.43	1.190	-	-	-	[58]
Rice husk/Al-MCM-41	1.65	-	-	-	-	[59]
Mango seed	149	-	-	-	-	[60]
Almond shell	<100	-	-	-	-	[61]
Cobalt-impregnated sesame stalk	176	1.047				[40]
Sesame waste biomass/Ni/Co/MCM-41	1.13	1.01	0.975	1.231	−1.687	This work

). From these properties, it was observed that the bio-oil is dependent on the nature and type of catalyst used. These observations agree with earlier reports. He et al. [57] investigated the physicochemical characteristics of bio-oil produced from switch grass and observed variations in the viscosity and density of the bio-oil with a change in the experimental conditions. The authors noted that there are no ideal conditions for bio-oil production with all the wanted characteristics and these must be adjusted according to the specific use of the bio-oil. Furthermore, a comparison of the different properties of the oil obtained in this work with previously reported studies (Table 3) indicates that the values of the viscosity and density of the bio-oil produced from the degradation of the sesame waste biomass in the presence of Ni/Co/MCM-41 are reduced compared to the oils obtained from the various sources of biomass in the presence/absence of different catalysts. Bio-oil with a higher viscosity and density results in inefficient atomization during the spraying of the oil, which leads to the accuracy of the fuel injectors becoming limited. Therefore, the oil produced from the decomposition of the sesame waste biomass in the presence of Ni/Co/MCM-41 has bright prospects in the replacement of commercial fuels.

4. Conclusions

MCM-41 was successfully prepared by employing a templating mechanism followed by 9% Ni/8% Co/MCM-41 using the sol-gel process. Characterization of the catalyst using SEM-EDX, XRD, and the surface area analyzer confirmed the successful incorporation of cobalt and nickel onto MCM-41, in the desired percentage. The prepared catalyst was used for the decomposition of sesame waste biomass in a pyrolysis chamber. The products obtained were studied through GC-MS. Thermogravimetry was used to determine the kinetics parameters. It has been concluded that 9% Ni/8% Co/MCM-41 reduced the maximum degradation temperature from 340 to 320 °C along with a reduction in the average activation energy, using the Kissinger model. The physicochemical characteristics of the oil were evaluated, and it was concluded that the bio-oil if upgraded properly, can be made equivalent to commercial fuel.