Corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 557 ARID ZONE JOURNAL OF ENGINEERING, TECHNOLOGY & ENVIRONMENT ORIGINAL RESEARCH ARTICLE SYNCHRONIZED ANALYSIS OF BIODIESEL FROM KHAYA SENEGALENSIS OILS USING FTIR, GC-MS AND NMR AT TOP PARAMETRIC CONDITIONS. Z. D. Ishaya1*, J. Samuel2, G. E. Ede3, D. S. Yawas1, J. Y. Bwede1 1* Department of Mechanical Engineering, Ahmadu Bello University, Zaria, Nigeria. 2 Department of Mechanical Engineering, Baze University Abuja, Nigeria. 3 Department of Mechanical Engineering, University of Jos, Nigeria. *Corresponding author’s email: zdishaya@abu.edu.ng, waidungiz@gmail.com ARTICLE INFORMATION ABSTRACT Alternatives to costly fossil fuel have witnessed rekindled interest because of the depletion of fossil reserves and environmental concerns. In this study, non-edible vegetable oil from Khaya Senegalensis (KS), which grows well in semi-arid zones was converted to biodiesel via transesterification under the reaction condition of 1.25 % π‘π‘Žπ‘‚π» catalyst and 1: 6 Oil-methanol molar ratio. FTIR, GC-MS and NMR techniques were concurrently used to monitor common or similar peaks in the conversion process in an extensive cross comparison to validate other techniques' results. Furthermore, the composition of conventional diesel with the vegetable biodiesel produced were simultaneously analyzed. The results showed that conversion peaks were aligned, and successful delivered 82.02 % yield. The results from FTIR, GC-MS and NMR investigations all agreed, on the conversion of triglyceride molecules in the crude KS oil to fatty methyl esters in the biodiesel. Both produced biodiesel and conventional diesel were observed to contain alkanes and alkenes functional groups, that impart good fuel properties. Received: 24th April 2025 Revised: 19th May 2025 Accepted: 20th May 2025 Keywords: Khaya senegalensis Fatty methyl esters FTIR GC-MS NMR Functional groups Β© 2025 Faculty of Engineering, University of Maiduguri, Nigeria. All rights reserved. 1.0 Introduction Fossil liquid fuel in the form of expensive gasoline and diesel, is mostly utilized in the transport and electrical power sectors to power internal combustion engines. The exhaust products from these engines are not problem-free. The exhaust emissions comes along with environmental pollutants that contaminate the air, also the emissions are responsible for climate change and coronary disease (Ishaya et al., 2020a). Carbon (IV) oxide (𝐢𝑂2) concentration in the atmosphere has reached alarming levels due to the production and consumption of fossil fuels. According to Banik et al., (2018), 86 % of the world energy consumption, 20 % of CO2 emissions and almost all fuel needed in the transport sector are from fossil sources. With the increasing trends of human population and global demand for motorized mobility, there shall be increased fossil fuel consumption, pollutants emission and environmental sustainability challenges. Biodiesel is a fuel obtained from plant oil, and it is characteristically similar to petrol-diesel, but it is nontoxic, renewable, sustainable, and environmentally harmless (Olagbende et al., 2021). When biodiesel is used in diesel engines, it presents excellent combustion properties due to its low sulfur, low aromatic content and high cetane number (Chaudhary et al., 2018). Non- edible oil from cheap tropical feedstock such as Khaya senegalensis (KS) that are easily cultivated in arid or semi-arid conditions, are used as alternatives and in the sustainable production of biodiesel (Sukkasi et al., 2010 and Dai et al., 2014). Some studies in the area of biodiesel production include: Alahmar et al., (2025) that investigated the efficient way of producing biodiesel from waste cooking oil by the use of a bifunctional catalyst. Similarly, Rao et al., (2025) studied the synthesis and optimization of biodiesel production from Trichosanthes cucumerina seed using Prosopis juliflora catalyst and reported the optimized conditions as 60 mg of biomass at 70 o C for a reaction time of 60 min to yield 46.31% catalyst, that was used in transesterification reaction to yield 97.42% biodiesel. Additionally, Farouk et al., (2024) worked on the optimized production of biodiesel from waste cooking oil using nano-catalyst and reported an optimized conditions of 7:1 methanol to oil ratio, 50 o C reaction temperature and 60 minutes reaction time using response surface methodology. Weldeslase et al., AZOJETE June 2025. Vol.21(2):557-568 Published by the Faculty of Engineering, University of Maiduguri, Maiduguri, Nigeria. Print ISSN: 1596-2490, Electronic ISSN: 2545-5818 https://doi.org/10.63958/AZOJETE/2025/21/02/020 www.azojete.com.ng mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com http://www.azojete.com.ng/ Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 557-568. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 558 (2023) investigated the optimized production of biodiesel from waste cooking oil using a πΆπ‘Žπ‘‚ catalyst and reported 96.5% biodiesel conversion at 14:1 methanol to oil molar ratio, 57.5 o C reaction temperature, 5% wt catalyst loading and 2 hours reaction time. Zubairu et al., (2021) produced synthesized biodiesels and hybrid oil blends from Jatropha curcas and Thevetia peruviana seeds oil, and reported high biodiesel yield of 90.0%, 86.1%, 90.7%, 92.2% and 88.2% for five hybrid blends at 60 o C reaction temperature and 1 hour reaction time with 1% (w/w) KOH catalyst. Kaisan et al., (2018) Carried out a comparison of Jatropha and Neem seed biodiesel and reported that Jatropha biodiesel contained 91.9 % methyl ester while Neem biodiesel contained 70.2 %. Nahadi & Atadashi, (2018) Studied the effects of variation of catalyst concentration on the production of biodiesel from coconut oil. The results showed that 96 % biodiesel was obtained at 1 % w/w catalyst concentration, 1: 6 oil to methanol ratio, 55 ℃ reaction temperature and 60 minutes reaction time. Furthermore, Ofoegbu & Kelle, (2013) determined the edibility of Thevetia peruviana seed oil using GC-MS, FTIR and UV-VIS techniques. The results showed that the oil has nutritional benefits provided the traces of cyanide are removed. The study of the biodiesel production process using solid acid catalyst was investigated by Gebremariam & Marchetti, (2021), the results showed that variation in oil cost and the price of biodiesel strongly affects the viability of the production process. Similarly, Alhassan et al., (2017) characterized Khaya senegalensis stem bark, the 1H NMR results indicated a carbon-carbon double bond, aromatic protons, and protons are attached directly to electronegative atoms. Additionally, Bolale et al., (2019) carried out FTIR and GC-MS analyses on Canna indica, the FTIR results showed the presence of aromatic 𝑂 βˆ’ 𝐻 stretch (3300 π‘π‘šβˆ’1) and aromatic 𝐢 = 𝐢 stretch (1451 and 1640 π‘π‘šβˆ’1), and the GC-MS result showed the presence of di-alpha-tocopherol. Also, the chemical modification of Camelina oil was investigated by Sharma et al., (2020), its 1H NMR spectra showed CH- protons and secondary alcohols at 2.9 βˆ’ 3.2 and 4.25 βˆ’ 3.35 π‘π‘π‘š, respectively. A research was conducted by Odo et al., (2017) using FTIR and GC-MS analyses on the Brenania brieyi root extract, and reported the presence of pentadecanoic acid (17.04 %), 9, 12-hexadecanoic acid (10.18 %), 9-Octadecanoic acid (60.53 %) in the methanol extract, and hexadecanoic acid (11.29 %), 9-Octadecanoic acid (54.85 %), 9, 12-Octadecanoic (3.90 %) in the chloroform extracts. Similar studies by Hossain et al., (2021) investigated triglyceride conversion of waste frying oil, and reported that the 1H NMR showed glycerine peaks, 𝛼 βˆ’ 𝐢𝐻2 protons and a 98.48 % biodiesel conversion. For this study, the aim is to convert Khaya senegalensis crude oil to biodiesel at 1.25 𝑀𝑑. % π‘π‘Žπ‘‚π» catalyst loading and 1: 6 alcohol to methanol molar ratio. Other researchers have considered the alcohol-to-methanol ratio between 1: 6 to 1: 12 for different feedstock and catalyst loading between 0.5 to 1.0 𝑀𝑑%.The Khaya senegalensis feedstock was investigated in the present study because it is non-edible, it is commonly available within the semi-arid region of northern Nigeria, and no previous studies were conducted on the feedstock under this defined conditions. The FTIR, GC-MS, and 1H NMR techniques used in the present study is to indicate the justifications for the conversion of triglyceride molecules to fatty acid methyl esters (biodiesel). 2. Materials and Methods The Khaya senegalensis winged seed kernels were collected from the trees in Samaru-Zaria in Nigeria and the oil was extracted using mechanical expeller press. The reagents used for the conversion of crude oil to biodiesel were of analytical grade (Assay 99.5%). The reagents details are outlined as follows: Sodium Hydroxide (NaOH) pellets, Propan-2-ol (CH3H7OH), Sulphuric acid (H2SO4), 0.1M Potassium Hydroxide (KOH) and Methanol (CH3OH). The first stage was to pretreat the crude oil using propan-2-ol, then followed by the determination of free fatty acid and acid value. The crude oil was titrated with 0.1M of KOH until the acid value reduces to ≀ 0.5%. The second stage transesterification reaction to convert the crude oil to biodiesel was carried out at an oil-to-alcohol molar ratio of 1:6 using NAOH catalyst for 1 hour at 60 o C. The details of the procedure are contained in an earlier study by Ishaya et al., (2020a). 2.1 Fourier Transform Infrared (FTIR) Spectroscopy Agilent technologies FTIR Spectrophotometer (54VA Agilent technologies Cary 630 FTIR Spectrophotometer Part G8043-64002, Serial No. MY14470031, made in Malaysia) was used to take the infrared spectrum of samples. The potassium bromide disc method was used to obtain the IR spectra of samples. 650 to 4000 π‘π‘šβˆ’1 scanning range was used in this study, functional groups were identified in the crude oil, biodiesel and diesel samples using the FTIR spectra. http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 557-568. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 559 2.2 Gas Chromatography-Mass Spectrometry (GC-MS) GC-MS-QO2010 Shimadzu Japan was used in the analysis. A fused silica column was filled with Elite-5MS (95 % dimethylpolysiloxane 5 % biphenyl, 30 π‘š Γ— 0.25 π‘šπ‘š 𝐼𝐷 Γ— 250 πœ‡π‘š 𝑑𝑓). Helium as carrier gas, flow constantly at 1 π‘šπ‘™/π‘šπ‘–π‘›, was used to separate the components. The temperature of the injector was set at 250 ℃ for the chromatographic run. The extract (1 πœ‡π‘™) was injected into the instrument, and the temperature was at 70 ℃ (0 π‘šπ‘–π‘›), followed by an increase to 280 ℃ at the rate of 10 ℃ π‘šπ‘–π‘›βˆ’1, subsequently the temperature was kept at 280`℃ for 5 π‘šπ‘–π‘›. The mass detector conditions were set: the transfer line was at 250 ℃; ion source temperature was at 200 ℃; and ionization mode electron impact was at 70 𝑒𝑉. Also, the mass detector scan time of 0.5 𝑠𝑒𝑐 was set, at scan interval of 0.1 𝑠𝑒𝑐. In this study, chemical compounds were detected in the crude oil, biodiesel and their respective quantities as reported by the GC-MS spectrometer. The National Institute Standard and Technology (NIST) library was used as a reference to compare and interpret the GC-MS results. Compounds were identified according to molecular mass, structure and fragments calculated. The unknown components spectrum was compared with that of the NIST library, and the closest match was taken. 2.3 NMR Spectroscopy All the 1H-NMR spectra were recorded with an Agilent Technologies 400/𝑆4/𝑃𝐢 + spectrometer (850 Watts Agilent technologies UK Ltd, 400MHz Nuclear Magnetic Resonance VNMRJ Premium Compact+ AR, Part G8504-64002, Serial No. MRY0023179, made in England) operating at 2.38 π‘π‘Žπ‘Ÿ Helium vessel and 2.5 bar Nitrogen vessel. The reference standard was tetramethyl-silane (TMS), and chemical shifts were reported relative to it. All experiments were conducted at room temperature. 3. Results and Discussion 3.1 Crude Khaya Senegalesis oil FTIR From Figure 1 and Table 1, the = 𝐢 βˆ’ 𝐻 bond was observed at 3004 π‘π‘šβˆ’1, 𝐢 βˆ’ 𝐻 alkyl symmetric and asymmetric strong stretches at 2855 βˆ’ 2922 π‘π‘šβˆ’1, 𝐢 = 𝑂 very strong stretch at 1744 π‘π‘šβˆ’1, 𝐢 βˆ’ 𝐻 terminal alkane bond at 1461 π‘π‘šβˆ’1 and 𝐢 βˆ’ 𝑂 βˆ’ 𝐢. Figure 1 indicated that the alkanes, alkenes, carboxylic and esters functional groups were present in Khaya Senegalensis crude oil. As reported by Hellier et al., (2018) and Karmakar et al., (2021), the fatty acids attached to the glycerol backbone are usually long chains containing 14 βˆ’ 22 carbon atoms. Some of the attached carbon atoms are either methyl, methylene, carbonyl, carboxylic or esters in structure. This however, is consistent with the findings by Hellier et al., (2018) and Karmakar et al., (2021) because it shows the presence of a triglyceride molecule with alkane carbon atoms, alkene carbon atoms, carboxylic carbon atoms and esters carbon atoms. Figure 1: FTIR spectra of crude Khaya senegalesis oil. http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 557-568. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 560 Table 1: Functional groups in crude Khaya senegalensis oil. S/N Wavelength (π’„π’Žβˆ’πŸ) Functional group 1 3004 = 𝐢 βˆ’ 𝐻 weak stretch (alkene) 2 2922, 2855 𝐢 βˆ’ 𝐻 strong stretch (alkanes) 3 1744 𝐢 = 𝑂 strong stretch (alkanoic & ester) 4 1461 𝐢 βˆ’ 𝐻 medium stretch (terminal alkane bend) 5 1375 𝐢 βˆ’ 𝑂 weak stretch (alkanoic) 6 1162 𝐢 βˆ’ 𝑂 medium stretch, (esters) 7 1028 𝐢 βˆ’ 𝑂 βˆ’ 𝐢 weak stretch (alkanoate) 8 723 𝐢 = 𝐢 βˆ’ 𝐻 medium stretch (alkene bending) This study results from Table 1 conforms with Cheah et al., (2020), which observed 𝐢 βˆ’ 𝑂 stretching at 1059 π‘π‘šβˆ’1, alkane 𝐢 βˆ’ 𝐻 stretching at 2900 π‘π‘šβˆ’1, ester 𝐢 = 𝑂 stretching at 1700 π‘π‘šβˆ’1, and alkene 𝐢 = 𝐢 stretching at 1650 π‘π‘šβˆ’1. Also, the study is consistent with (Tulashie et al., 2018), who observed – 𝐢𝐻2 stretching vibrations at 2853.09 and 2922.27 π‘π‘šβˆ’1 and – 𝐢 = 𝑂 bond stretching at 1741.91 π‘π‘šβˆ’1. 3.2 Crude Khaya Senegalesis oil GC-MS Figure 2: GC-MS spectra of crude Khaya senegalesis oil. Table 2: Compounds present in crude Khaya senegalesis. PK RT Area % Library/ID Formula 1 15.713 1.41 Methyl 6-methyl heptanoate 𝐢9𝐻18𝑂2 2 16.357 1.98 Hexadecanoic acid, ethyl ester 𝐢18𝐻36𝑂2 3 16.440 9.05 Hexadecanoic acid 𝐢16𝐻32𝑂2 4 17.427 6.45 11-Octadecenoic acid, methyl ester 𝐢19𝐻36𝑂2 5 17.628 1.23 Methyl 8-hydroxyoctanoate 𝐢9𝐻18𝑂3 6 18.013 14.79 9-Octadecenoic acid, ethyl ester 𝐢20𝐻38𝑂2 7 18.170 43.81 Oleic acid 𝐢18𝐻34𝑂2 8 18.304 11.54 Nonadecanoic acid 𝐢19𝐻38𝑂2 9 19.665 6.60 cis-Oleic acid 𝐢18𝐻34𝑂2 10 19.665 3.15 10-Undecenal 𝐢11𝐻20𝑂 From Figure and Table 2; the GC-MS analysis of crude Khaya Senegalensis oil showed the presence of 10 compounds. Major compounds include: Oleic acid 𝐢18𝐻34𝑂2 at retention time of 18.170 π‘šπ‘–π‘› occupying the largest mass spectra area of 43.81 %, 9-Octadecenoic acid, ethyl ester (𝐢20𝐻38𝑂2) at retention time 18.013 π‘šπ‘–π‘› with a mass spectra area of 14.79 %, Nonadecanoic acid (𝐢19𝐻38𝑂2) at retention time 18.304 π‘šπ‘–π‘› with a mass spectra area 11.54 %, Hexadecanoic acid (𝐢16𝐻32𝑂2) at retention time 16.440 π‘šπ‘–π‘› occupying 9.05 % mass spectra area, 11-Octadecenoic acid, methyl ester 𝐢19𝐻36𝑂2 at retention time 17.427 π‘šπ‘–π‘› with a mass spectra area of 6.45 %, cis-Oleic acid (𝐢18𝐻34𝑂2) at retention time 19.665 π‘šπ‘–π‘› with a mass spectra area 6.60 %, 10-Undecenal (𝐢11𝐻20𝑂) at retention time 20.727 π‘šπ‘–π‘› occupying 3.15 % mass spectra area. The GC-MS result showed that triglycerides with oleic fatty acid represent a larger portion of the KS vegetable oil. Oleic acid is a monounsaturated fatty acid with 18-carbon atoms. This GC-MS result conforms with the FTIR result in Figure 1, indicating similar compounds as discussed. The 18-carbon atoms in the KS triglyceride http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 557-568. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 561 molecule connotes a good parameter for biodiesel production because it will contribute to a higher heating value of the fuel and also a short ignition delay. Similarly, the un-saturation in the KS triglyceride molecule will enhance the fluidity of the fuel when the biodiesel is finally produced. 3.3 KS Crude oil NMR Figure 3 show the chemical shift of the signals shown in Table 3. Figure 3: 1H-NMR spectrum of crude KS oil Table 3: Chemical shift of main resonances in KS. S/N Chemical Shift (π’‘π’‘π’Ž) Multiplicity Nature of carbon 1 5.31 βˆ’ 5.28 𝐻𝐢 = 𝐢𝐻 2 4.11 βˆ’ 4.27 – 𝐢𝐻2 𝑂𝐢𝑂𝑅 3 2.26 𝛼 βˆ’ 𝐢𝐻2 4 1.22 βˆ’ 1.97 (𝐢𝐻2)𝑛 5 0.83 𝐢𝐻3 The result shows that the duplets with peaks at 5.31 and 5.28 π‘π‘π‘š correspond to protons attached to carbon-carbon double bonds in the KS triglyceride molecule. This is in agreement with the GC-MS result in Figure 2 and FTIR result in Figure 1 of KS crude oil. All results agree on the presence of an alkene functional group, and this is consistent with Fu et al., (2021). Furthermore, the result indicates a triplet and a duplet centered at 4.25 and 4.12 π‘π‘π‘š. This is mostly assigned to protons attached to the triglyceride backbone (𝐢𝐻2 βˆ’ 𝐢𝑂𝑂𝑅) in the sn 1’ 3’ position. This finding conforms with (Khosa, 2021), which shows a triglyceride as one molecule of glycerol attached to three molecules of fatty acid. This NMR observation is consistent with Truzzi et al., (2021), and it also agrees with the GC-MS and FTIR result on the presence of carboxylic and ester functional groups. Figure 3 also shows a triplet at 2.26 π‘π‘π‘š that corresponds to protons attached to Ξ±- carbon and (𝐢𝐻2)𝑛 Protons in the region of 1.22 – 1.97 π‘π‘π‘š. This shows the existence of alkanes in the triglyceride molecule and is consistent with (Sharma et al., 2020). Protons of 𝐢𝐻3 are also observed at 0.83 π‘π‘π‘š, which is in tandem with Fu et al., (2021). Based on the 1H-NMR result in Figure 3, the study observed that: alkanes, alkenes, carbonyl and esters chemical environments are present in Khaya senegalensis crude oil. This result, together with the GC-MS and FTIR results, further confirms the triglyceride molecule with oleic acid as the major fatty acid in the KS vegetable oil. 3.4 FTIR of KS Biodiesel at 1.25 % Catalyst From Figure 4 as interpreted in Table 4, the = 𝐢 βˆ’ 𝐻 bond was observed at 3004 π‘π‘šβˆ’1, 𝐢 βˆ’ 𝐻 alkyl symmetric and asymmetric strong stretches at 2922 βˆ’ 2855 π‘π‘šβˆ’1, 𝐢 = 𝑂 very strong stretch at 1740 π‘π‘šβˆ’1, 𝐢 βˆ’ 𝐻 terminal alkane bond at 1461, 1435 π‘π‘šβˆ’1 and 𝐢 βˆ’ 𝑂 βˆ’ 𝐢 at 1095 π‘π‘šβˆ’1. The study also identified the 𝐢 βˆ’ 𝑂 ester group at 1190, 1170 π‘π‘šβˆ’1, the 𝐢 βˆ’ 𝑂 carboxylic group at 1380 π‘π‘šβˆ’1, and the 𝐢 βˆ’ 𝐻 bend at 723 π‘π‘šβˆ’1. http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 557-568. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 562 Figure 4: FTIR spectra of Khaya senegalesis biodiesel Table 4: Functional groups in Khaya senegalensis biodiesel. S/N Wavelength (π’„π’Žβˆ’πŸ) Functional group 1 3004 = 𝐢 βˆ’ 𝐻 weak stretch (alkene) 2 2922, 2855 𝐢 βˆ’ 𝐻 strong stretch (alkanes) 3 1740 𝐢 = 𝑂 strong stretch (alkanoic & ester) 4 1461, 1435 𝐢 βˆ’ 𝐻 medium stretch (terminal alkane bend) 5 1380 𝐢 βˆ’ 𝑂 weak stretch (alkanoic) 6 1190, 1170 𝐢 βˆ’ 𝑂 medium stretch, (esters) 7 1095 𝐢 βˆ’ 𝑂 βˆ’ 𝐢 weak stretch (alkanoate) 8 723 𝐢 = 𝐢 βˆ’ 𝐻 medium stretch (alkene bending) Comparing Figure 4 with Figure 1 and Table 4 with Table 1, the following observations were made: the alkanes and alkenes were unaltered during the conversion since peaks at 3004 π‘π‘šβˆ’1 and 2922 βˆ’ 2855 π‘π‘šβˆ’1, 1461 π‘π‘šβˆ’1 and 723 π‘π‘šβˆ’1 were observed in both crude oil and biodiesel of KS. However, the position of the 𝐢 = 𝑂 shifted from 1744 π‘π‘šβˆ’1 in the crude oil to 1740 π‘π‘šβˆ’1 in the biodiesel, indicating some sort of transformation. From this, it can be said that the carboxylic functional group in the crude oil has been converted to the ester group during the transesterification reaction. Similarly, the occurrence of 1190, 1170 π‘π‘šβˆ’1 peaks in the biodiesel due to the 𝐢 βˆ’ 𝑂 bond indicates a formation of esters, since natural esters occurred at 1062 π‘π‘šβˆ’1 in the crude KS oil. Based on this result, it is deduced that triglyceride molecules have been converted to fatty acid methyl esters (biodiesel). This study is consistent with Dass et al., (2018), who observed 𝐢 = 𝑂, 𝐢 = 𝐢, 𝐢 βˆ’ 𝑂, 𝐢 βˆ’ 𝐢 stretch and 𝐢 βˆ’ 𝐻 bending at 1744.4, 1461.1, 1237.6, 1162.9 and 723.1 π‘π‘šβˆ’1, respectively, in biodiesel produced from a Mahogany fruit shell. In the same way Alhassan et al., (2017) attributed 1709, 1248 and 1611 π‘π‘šβˆ’1 to 𝐢 = 𝑂, 𝐢 βˆ’ 𝑂 and 𝐢 = 𝐢 groups, respectively, that the present study is in agreement with. 3.5 GC-MS of KS Biodiesel at 𝟏. πŸπŸ“ % Catalyst Figure 5: GC-MS spectra of Khaya senegalesis biodiesel at 1.25 % cat. Conc. http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 557-568. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 563 Table 5: Compounds present in Khaya senegalesis biodiesel at 1.25 % cat. Conc. PK RT Area % Library/ID Formula 1 13.630 0.34 Tridecanoic acid, methyl ester 𝐢14𝐻28𝑂2 2 15.779 10.20 Palmitic acid, methyl ester 𝐢17𝐻34𝑂2 3 17.494 12.22 11-Octadecenoic acid, methyl ester 𝐢19𝐻36𝑂2 4 17.815 38.13 9-Octadecenoic acid, methyl ester 𝐢19𝐻36𝑂2 5 17.856 14.09 5-Octadecenoic acid, methyl ester 𝐢19𝐻36𝑂2 6 18.230 5.81 Oleic acid 𝐢18𝐻34𝑂2 7 19.288 2.79 Octadecyl vinyl ether 𝐢20𝐻40𝑂 8 19.442 3.96 Eicosanoic acid, methyl ester 𝐢21𝐻42𝑂2 9 19.583 1.98 Tetradecanoic acid methyl ester 𝐢16𝐻32𝑂2 10 20.796 7.51 9-Octadecenal 𝐢18𝐻32𝑂 11 20.933 1.85 2-Butyloctanol 𝐢12𝐻26𝑂 12 21.030 1.10 Eicosanoic acid, methyl ester 𝐢21𝐻42𝑂2 The GC-MS analysis of the Khaya senegalensis biodiesel showed the presence of 12 compounds. Major compounds include: 9-Octadecenoic acid, methyl ester at retention time of 17.815 π‘šπ‘–π‘› occupying the largest area of 38.13 %, 5-Octadecenoic acid, methyl ester at retention time 17.856 π‘šπ‘–π‘› with area of 14.09 %, 11- Octadecenoic acid, methyl ester at retention time 17.494 π‘šπ‘–π‘› with area 12.22 %, Palmitic acid, methyl ester at retention time 15.779 π‘šπ‘–π‘› occupying 10.20 % area, (-Octadecenal at retention time 20.796 π‘šπ‘–π‘› with area of 7.51 %, Oleic acid at retention time 18.230 π‘šπ‘–π‘› with area 5.81 %, Eicosanoic acid, methyl ester at retention time 19.442 π‘šπ‘–π‘› occupying 3.96 % area. The percentage area shows the amount of each compound present in the biodiesel as a percentage. The higher the area it occupies the larger the compound percentage in the mixture. For a biodiesel it is expected that methyl ester occupies a larger area. From the result the total methyl esters accounted for 82.02%. The effect of methyl esters on biodiesel includes imparting high heating value and short ignition delay in the biodiesel. Comparing Figure 2 with Figure 5 and Table 2 with Table 5, it was observed that 25.86 % ester in the crude oil has increased to 82.02 % in the biodiesel. This result is in agreement with Figure 4, which shows the conversion of triglyceride molecules to fatty acid methyl esters. The outcome of the present study conforms with Dass et al., (2018), who reported 9-octadecenoic acid (Z), methyl ester, Hexadecanoic acid (Z) methyl ester, 12-octadecenoic acid (Z), methyl ester in biodiesel produced from Mahogany fruit shell. 3.6 NMR of KS Biodiesel From Figure 6, the chemical shift of the signals is shown in Table 6 of KS biodiesel. As shown from the results, there are no peaks in the range 4.00 βˆ’ 4.20 ppm, indicating that conversion of triglyceride molecules has taken place. This is further confirmed by the presence of peaks at 3.6 ppm, implying the formation of fatty acid methyl esters. This result further validates the FTIR result of biodiesel in Figure 4 and GCMS result of biodiesel in Figure 5. The NMR result of the present study is consistent with a study as reported elsewhere (Hossain et al., 2021). Similarly, from Figure 6, a peak was observed at 5.3 ppm, corresponding to carbon- carbon double in the biodiesel. Other carbon-carbon single bonds were also identified in the range 2.3 βˆ’ 0.9 ppm. These results are consistent with that of Fu et al., (2021). Figure 6: 1H-NMR spectrum of KS biodiesel http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 557-568. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 564 Table 6: Chemical shift of main resonances in KS biodiesel. S/N Chemical Shift (π’‘π’‘π’Ž) Multiplicity Nature of carbon 1 5.3 𝐻𝐢 = 𝐢𝐻 2 3.6 𝐻3𝐢 βˆ’ 𝑂 3 2.3 𝛼 βˆ’ 𝐢𝐻2 4 1.9 𝐻2𝐢 βˆ’ 𝐢 = 𝐢 5 1.3 βˆ’ 1.6 (𝐢𝐻2)𝑛 6 0.9 𝐢𝐻3 From Figure 6, the chemical shift of the signals is shown in Table 6 of KS biodiesel. As shown from the results, there are no peaks in the range 4.00 βˆ’ 4.20 π‘π‘π‘š, indicating that conversion of triglyceride molecules has taken place. This is further confirmed by the presence of peaks at 3.6 π‘π‘π‘š, implying the formation of fatty acid methyl esters. This result further validates the FTIR result of biodiesel in Figure 4 and GCMS result of biodiesel in Figure 5. The NMR result of the present study is consistent with a study as reported elsewhere (Hossain et al., 2021). Similarly, from Figure 6, a peak was observed at 5.3 π‘π‘π‘š, corresponding to carbon- carbon double in the biodiesel. Other carbon-carbon single bonds were also identified in the range 2.3 βˆ’ 0.9 π‘π‘π‘š. These results are consistent with that of Fu et al., (2021). Based on the 1H-NMR result in Figure 6, the present study further observed: alkanes, alkenes, carbonyl and esters chemical environments present in Khaya senegalensis biodiesel. The 1H-NMR results in Figure 6 are consistent with the FTIR result of biodiesel in Figure 4 and GC-MS result of biodiesel in Figure 5. 3.7 Conventional Diesel FTIR From Figure 7 and Table 7 of FTIR of the conventional or reference diesel, 𝐢 βˆ’ 𝐻2 and 𝐢 βˆ’ 𝐻3 asymmetric and symmetric bonds were observed at 2952 π‘π‘šβˆ’1 and 2955, 2855 π‘π‘šβˆ’1, respectively, 𝐢 = 𝐢 at 1602 π‘π‘šβˆ’1, 𝐢 βˆ’ 𝐻2/𝐢 βˆ’ 𝐻3 alkane bend at 1379 βˆ’ 1457 π‘π‘šβˆ’1, and = 𝐢 βˆ’ 𝐻 bending at 723 βˆ’ 850 π‘π‘šβˆ’1. The 𝐢 βˆ’ 𝐻2 and 𝐢 βˆ’ 𝐻3 asymmetric and symmetric bond observed in this study is consistent with observations by Qasim et al., (2017), likewise the 𝐢 = 𝐢 bond observed in this study is in concords with report by Ismail et al., (2009), and lastly the 𝐢 βˆ’ 𝐻2/𝐢 βˆ’ 𝐻3 alkane bend and = 𝐢 βˆ’ 𝐻 observed in the conventional diesel agrees with studies by Attia et al., (2020). Figure 7: FTIR spectra of conventional diesel. Table 7: Functional groups in conventional diesel. S/N Wavelength (π’„π’Žβˆ’πŸ) Functional group 1 2952 𝐢 βˆ’ 𝐻2 medium stretch (alkene) 2 2922, 2855 𝐢 βˆ’ 𝐻3 asym./sym. strongh stretch (alkanes) 3 1602 𝐢 = 𝐢 weak stretch (conjugated alkene) 4 1457, 1379 𝐢 βˆ’ 𝐻2/𝐢 βˆ’ 𝐻3 medium stretch (alkane bending) 5 812, 740 𝐢 = 𝐢 βˆ’ 𝐻 weak stretch (alkene bending) Based on the FTIR result in Figure 7, it was observed that basic hydrocarbons (alkanes and alkenes functional groups) are present in conventional biodiesel. This finding is consistent with a similar report by Mueller et al., (2012) on the structure of hydrocarbon fuel. http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 557-568. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 565 3.8 Conventional Diesel NMR From Figure 8 – the NMR graph of the conventional diesel, of which the correspondent chemical shift of the signals is represented in Table 8. The result has shown; protons in terminal methyl (𝐢𝐻3) groups were observed between the range 0.71 βˆ’ 0.9 π‘π‘π‘š. Methylene (𝐢𝐻2)𝑛 groups in the range 1.09 βˆ’ 2.0 π‘π‘π‘š and 𝛼 βˆ’ 𝐢𝐻2 protons in the range 2.0 βˆ’ 2.8 π‘π‘π‘š. The chemical shift of the terminal methyl group is consistent with the report by Vukovi et al., (2018), and that of methylene and 𝛼 βˆ’ 𝐢𝐻2 groups are in accordance with findings by Sharma et al., (2020). Figure 8: 1H-NMR spectrum of conventional diesel. Table 8: Chemical shift of main resonances in conventional diesel. S/N Chemical Shift (π’‘π’‘π’Ž) Multiplicity Nature of carbon 1 0.71 βˆ’ 0.9 𝐢𝐻3 2 1.09 βˆ’ 2.0 (𝐢𝐻2)𝑛 3 2.0 βˆ’ 2.8 𝛼 βˆ’ 𝐢𝐻2 Based on the 1H-NMR result in Figure 8, the study observed that alkanes and alkenes chemical environments are present in the conventional diesel. The chemical environments identified by the 1H-NMR in Figure 8 are in agreement with the FTIR result of conventional diesel in Figure 7 that identifies alkane and alkenes functional groups. Comparing the produced biodiesel and conventional diesel, the FTIRs in Figures 1 and 4 both agree that both fuels contain alkanes and alkenes functional groups. The presence of alkanes contributes to the combustion efficiency and high cetane number of the fuels. Alkenes, on the other hand, contribute improved flow properties to the fuels, and this is in conformity to Ishaya et al.,, (2022). However, the 1H-NMR spectrum of KS biodiesel differs from that of conventional diesel in that it contains fatty acid methyl esters. These esters are long-chain hydrocarbons (between 12 βˆ’ 22 carbon atoms). The existence of these long chains will impart high heating value and short ignition delay in the biodiesel. Comparing earlier studies under the same experimental conditions by Ishaya et al., (2020a) at 0.50 % catalyst concentration, and Ishaya et al., (2020b) at 1.00 % catalyst concentration on the same feedstock, with the present study at 1.25 % catalyst concentration; the biodiesel yield are 55.99 %, 71.73 % and 82.02 %. The result shows that as the concentration of catalyst is increased, there is a corresponding increase in biodiesel yield (Zubairu et al., 2021). This trend is attributed to increased catalytic activity that results in lowering of the activation energy, thereby favoring biodiesel yield. This observation is consistent with studies by Ishaya et al., (2020a), Ishaya et al., (2020b). 4. Conclusion In this study, triglyceride conversion in KS crude vegetable oil to fatty acid methyl esters at 1.25 % π‘π‘Žπ‘‚π» catalyst concentration and 1: 6 oil-methanol molar ratio. It was observed through the GCMS technique that 25.86 % ester in the crude oil was converted to 82.02 % in the biodiesel via transesterification reaction. The FTIR and 1H-NMR technique used in this study further supports and confirms the conversion of triglyceride molecules in the crude oil to fatty acid methyl esters in the biodiesel. The comparison between the biodiesel http://www.azojete.com.ng/ mailto:zdishaya@abu.edu.ng mailto:waidungiz@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 557-568. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: zdishaya@abu.edu.ng, waidungiz@gmail.com 566 produced and the conventional diesel by FTIR and 1H-NMR technique shows that both fuels contain alkanes and alkenes functional groups. The present study is consistent with earlier previous studies in that 9- Octadecenoic acid, methyl ester was the major ester formed in the biodiesel. The present study also conforms with earlier studies such that, as catalyst concentration increases, the biodiesel yield increases also: 0.50 % catalyst concentration – 55.99 % biodiesel yield, 1.00 % catalyst concentration – 71.73 % biodiesel yield, and 1.25 % catalyst concentration – 82.02 % biodiesel yield. 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