A system for producing biodiesel from Jatropha curcas oil using a superhydrophobic spherical activated carbon catalyst

Abstract

A system for biodiesel production from Jatropha curcas oil using a superhydrophobic spherical activated carbon catalyst, comprising: a) a catalyst manufacturing unit configured to produce a superhydrophobic spherical activated carbon catalyst (SSAC@PhSO3H) with a water contact angle of at least 163°, the catalyst manufacturing unit comprising: a carbonization subsystem configured for the hydrothermal treatment of cellulose at 190 °C, an activation subsystem configured to activate hydrothermal carbon with ZnCl2 by pyrolysis at 500 °C, a sulfonation subsystem configured for the sulfonation of activated carbon with 4-benzenediazonium sulfonate (4-BDS), and a hydrophobization subsystem configured to esterify hydroxyl groups with caprylic acid using phosphotungstic acid; b) a transesterification reaction unit configured to enable the transesterification of Jatropha curcas oil with methanol in the presence of the superhydrophobic catalyst; and c) a separation unit configured to separate the biodiesel product from the glycerol by-product and to recover the catalyst.

Description

AREA OF INVENTION

[0001] The present disclosure relates to a system for the production of biodiesel from Jatropha curcas oil using a superhydrophobic spherical activated carbon catalyst. More precisely, the present invention provides a system for the synthesis of an acid-functionalized superhydrophobic spherical activated carbon catalyst (SSAC@PhSO3H) and for the subsequent transesterification of non-edible starting materials such as Jatropha curcas oil using the synthesized catalyst. BACKGROUND OF THE INVENTION

[0002] Conventional biodiesel production systems using solid acid catalysts are subject to significant technical limitations due to water poisoning of the active sites. Existing sulfonic acid-functionalized solid catalysts exhibit insufficient catalytic efficacy because byproduct water readily adsorbs onto hydrophilic SO3H groups, eliminating or reducing their acidity. This in-situ water formation leads to unintended hydrolytic side reactions through the co-adsorption of reactants and products onto SO3H centers.

[0003] Current catalyst production systems typically employ direct sulfonation methods using H₂SO₄ or ClSO₃H alkylation, which leads to loose bonding and significant deactivation (30–40% of the original activity) due to acid leaching. Furthermore, conventional hydrothermal carbonization systems produce spherical hydrocarbons with low surface area and porosity, limiting their broader application.

[0004] Existing superhydrophobic catalyst systems are based on petroleum-derived raw materials, which are characterized by high costs, sustainability concerns, and inherently low thermal stability, limiting their industrial application.

[0005] There is a need for an improved catalyst system that addresses the following fundamental challenges: (i) water poisoning of acidic active sites in transesterification reactions, (ii) catalyst deactivation by leaching of sulfonic acid groups, (iii) limitations of the small surface area of ​​spherical carbon-containing materials, and (iv) sustainability concerns related to petroleum-derived catalyst precursors.

[0006] In light of the preceding discussion, it is clear that there is a need for a system for biodiesel production from Jatropha curcas oil using a superhydrophobic spherical activated carbon catalyst. Summary of the invention

[0007] The present disclosure relates to a system for biodiesel production from Jatropha curcas oil using a superhydrophobic spherical activated carbon catalyst (SSAC@PhSO3H). The system comprises a catalyst preparation unit for the synthesis of a superhydrophobic catalyst by sequential carbonization, activation, sulfonation, and hydrophobization; a transesterification reaction unit for oil conversion by microwave irradiation; and a separation unit for the recovery of biodiesel and catalyst. The system achieves superior biodiesel yields with consistent catalyst stability over multiple reaction cycles.

[0008] The present disclosure aims to provide a system for the production of biodiesel from Jatropha curcas oil using a superhydrophobic spherical activated carbon catalyst (SSAC@PhSO3H), wherein the system comprises: a catalyst manufacturing unit configured to produce a superhydrophobic spherical activated carbon catalyst (SSAC@PhSO3H) with a water contact angle of at least 163°, the catalyst manufacturing unit comprising: a carbonization subsystem configured to hydrothermally treat cellulose at 190 °C, an activation subsystem configured to activate hydrothermal carbon with ZnCl2 by pyrolysis at 500 °C, a sulfonation subsystem configured to sulfonate activated carbon using 4-benzenediazonium sulfonate (4-BDS), and a hydrophobization subsystem configured toThe system esterifies hydroxyl groups in the sulfonated carbon skeleton with caprylic acid using phosphotungstic acid as a catalyst. It also includes a transesterification reaction unit that enables the transesterification of Jatropha curcas oil with methanol in the presence of the superhydrophobic catalyst. Furthermore, the system includes a separation unit that separates the biodiesel product from the glycerol byproduct and recovers the catalyst.

[0009] One objective of the present disclosure is to provide a system for the production of biodiesel from Jatropha curcas oil using a superhydrophobic spherical activated carbon catalyst.

[0010] Another objective of the present disclosure is to overcome the water poisoning of acidic active sites in biodiesel production by developing superhydrophobic properties in solid acid catalysts while maintaining high catalytic activity and surface area.

[0011] Another objective of the present disclosure is to achieve improved catalyst stability and reusability by covalent bonding of sulfonic acid groups via reductive arylation, thereby minimizing catalyst deactivation and leaching during transesterification reactions.

[0012] Another objective of the present disclosure is to provide a cost-effective and sustainable system configured to utilize non-edible feedstocks for biodiesel production while meeting international fuel quality standards and achieving commercial viability.

[0013] To further clarify the advantages and features of the present disclosure, the invention is explained in more detail with reference to specific embodiments illustrated in the accompanying drawing. This drawing merely shows typical embodiments of the invention and is therefore not to be understood as limiting its scope. The invention is described and explained more precisely and in greater detail with reference to the accompanying drawing. BRIEF DESCRIPTION OF THE FIGURE

[0014] These and other features, aspects, and advantages of the present disclosure will be better understood if the following detailed description is read with reference to the accompanying drawing, in which the same symbols consistently represent the same parts. The following applies: Fig. Figure 1 shows a block diagram of a system for biodiesel production from Jatropha curcas oil using a superhydrophobic spherical activated carbon catalyst according to an embodiment of the present disclosure.

[0015] Experts will also recognize that the elements in the drawing are shown for the sake of simplicity and are not necessarily to scale. For example, the flowcharts illustrate the process by highlighting the main steps to enhance understanding of the aspects of this disclosure. Furthermore, with regard to the design of the device, one or more components of the device may be represented in the drawing by conventional symbols, and the drawing may show only the specific details relevant to understanding the embodiments of this disclosure, so as not to clutter the drawing with details that are readily apparent to those skilled in the art after reading this description. DETAILED DESCRIPTION:

[0016] For a better understanding of the inventive principles, reference is made below to the embodiment shown in the drawing, which is described in specific terminology. However, this does not limit the scope of the invention. Changes and further modifications of the illustrated system, as well as further applications of the inventive principles, are possible, as would normally occur to a person skilled in the art in the field of invention.

[0017] It is clear to the person skilled in the art that the preceding general description and the following detailed description are exemplary and explanatory of the invention and are not intended as a limitation of it.

[0018] References in this specification to “an aspect”, “another aspect”, or similar expressions mean that a particular feature, structure, or property described in connection with the embodiment is included in at least one embodiment of the present disclosure. Therefore, occurrences of the expressions “in one embodiment”, “in another embodiment”, and similar expressions in this specification may all refer to the same embodiment, but need not.

[0019] The terms "includes," "include," or other variations thereof are intended to cover non-exclusive inclusion, so that a process or method that includes a list of steps may not only contain those steps but may also include other steps not expressly listed or inherent in such process or method. Likewise, the statement "includes..." in the case of one or more devices, subsystems, elements, structures, or components does not, without further limitations, preclude the existence of other devices, subsystems, elements, structures, components, or additional devices, subsystems, elements, structures, or components.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as understood by a person skilled in the art in the field of the invention. The system, methods, and examples provided here serve only for illustration and are not to be construed as a limitation.

[0021] Embodiments of the present disclosure are described in detail below with reference to the attached drawing.

[0022] Fig. Figure 1 shows a block diagram of a system (100) for biodiesel production from Jatropha curcas oil using a superhydrophobic spherical activated carbon catalyst according to an embodiment of the present disclosure.

[0023] Referring to Fig.1 The system (100) comprises: a catalyst manufacturing unit (102) for the production of a superhydrophobic spherical activated carbon catalyst (SSAC@PhSO3H) with a water contact angle of at least 163°, wherein the catalyst manufacturing unit (102) comprises: a carbonization subsystem (102a) for the hydrothermal treatment of cellulose at 190 °C, an activation subsystem (102b) for the activation of hydrothermal carbon with ZnCl2 by pyrolysis at 500 °C, a sulfonation subsystem (102c) for the sulfonation of activated carbon using 4-benzenediazonium sulfonate (4-BDS), and a hydrophobization subsystem (102d) for the esterification of hydroxyl groups with caprylic acid using phosphotungstic acid.The system (100) further comprises: a transesterification reaction unit (104) to facilitate the transesterification of Jatropha curcas oil with methanol in the presence of the superhydrophobic catalyst; and a separation unit (106) configured to separate the biodiesel product from the glycerol by-product and recover the catalyst.

[0024] In one embodiment, the catalyst production unit (102) is configured to produce a superhydrophobic spherical activated carbon catalyst with a surface area of ​​at least 1461 m². 2 G - 1 and an acid density of at least 6.26 mmol g -1 herstellt .

[0025] In one embodiment, the transesterification reaction unit (104) comprises microwave irradiation equipment configured to maintain the reaction conditions at 80 °C temperature, 100 psi pressure and 50 W power for a period of 40 minutes.

[0026] In one embodiment, the transesterification reaction unit (104) is also configured to be operated with a methanol-oil molar ratio in the range of 5:1 to 20:1 and a catalyst loading in the range of 1 to 7 wt.%.

[0027] In one embodiment, the separation unit (106) comprises a filter system for recovering the catalyst and a gravity separation system for separating biodiesel and glycerin.

[0028] In one embodiment, the system (100) further comprises a characterization unit (108) configured to analyze the properties of the superhydrophobic catalyst, wherein the characterization unit (108) includes equipment for determining functional groups, crystalline nature, composition, thermal stability, morphology, surface area, pore size, acidity and wettability.

[0029] In one embodiment, the system (100) also includes a biodiesel analysis unit (110) configured to determine the formation and purity of biodiesel using 1 H-NMR-, 13 Checked using C-NMR, GCMS and FTIR analyzers.

[0030] The present invention relates to a comprehensive biodiesel production system that addresses the fundamental challenges associated with water poisoning of solid acid catalysts by developing superhydrophobic properties. The system comprises a sophisticated catalyst manufacturing unit that converts cellulose precursors into a superhydrophobic spherical activated carbon catalyst in a multi-stage process. This involves hydrothermal carbonization at 190 °C, followed by ZnCl₂-mediated pyrolytic activation at 500 °C to achieve a large surface area of ​​over 1461 m². 2 G -1 zu erreichen.The catalyst production unit also includes a sulfonation subsystem that covalently binds sulfonic acid groups via reductive arylation with 4-benzenediazonium sulfonate, thus ensuring greater stability compared to conventional direct sulfonation methods. The hydrophobization subsystem is configured to esterify the inherent hydroxyl groups of the biochar with caprylic acid using phosphotungstic acid as a catalyst, thereby generating superhydrophobic properties with water contact angles exceeding 163°. The transesterification reaction unit is equipped with a microwave irradiation system capable of maintaining precise reaction conditions at 80°C, 40-minute reaction time, 100 psi pressure, and 50 W power. This enables the efficient conversion of Jatropha curcas oil to biodiesel with methanol-to-oil molar ratios of 5:1 to 20:1 and catalyst loadings of 1 to 7 wt%.The separation unit consists of filtration and gravity separation systems configured to recover the superhydrophobic catalyst and separate biodiesel from the glycerol byproduct. The system demonstrates exceptional performance, achieving biodiesel yields of 98.8% under optimized conditions while maintaining catalyst stability for at least 10 consecutive reaction cycles with yields exceeding 86.8%. The biodiesel produced meets European standards EN 14212 and ASTM D6757 at production costs of approximately USD 0.37 per kg (USD 0.32 per liter), making it commercially viable. The system also includes characterization and analysis units configured to verify catalyst properties and biodiesel quality through comprehensive analytical techniques, including spectroscopic, thermal, and morphological analyses.

[0031] In one embodiment, the system for biodiesel production from Jatropha curcas oil comprises a catalyst preparation unit for the production of a superhydrophobic spherical activated carbon catalyst (SSAC@PhSO3H) using high-purity, analytical-grade materials from commercial suppliers. Materials used in the catalyst synthesis process include cellulose, sulfanilic acid, hypophosphoric acid, acetone, sodium nitrite, zinc chloride, hydrochloric acid, sulfuric acid, caprylic acid, phosphotungstic acid, and ethanol. These reagents were used without further purification to ensure experimental efficiency and reproducibility. Additionally, Jatropha curcas oil (JCO) with a molecular weight of approximately 900 g / mol was obtained and used as the starting oil in the transesterification process.

[0032] In one embodiment, the system comprises a catalyst manufacturing unit that also includes several integrated subsystems to enable sequential and controlled synthesis of the catalyst. The carbonization subsystem is configured to perform the hydrothermal carbonization of cellulose in demineralized water in a 100 mL Teflon-coated stainless steel autoclave, which is maintained at 190 °C for 20 hours. Following hydrothermal treatment, the carbonized product is dried at 80 °C to obtain spherical hydrocarbon (SHC). After carbonization, the activation subsystem is configured to impregnate the hydrothermally treated carbon with zinc chloride (ZnCl₂), followed by pyrolysis for 2 hours at 500 °C. This process produces spherical activated carbon (SAC) with a large surface area and porous structure.The sulfonation subsystem is then configured to chemically graft sulfonic acid groups onto the activated carbon via arylation with 4-benzenediazonium sulfonate (4-BDS), resulting in sulfonated activated carbon, SAC@PhSO3Hn (where n = 2, 4, 6 indicates the weight ratio of 4-BDS ​​to SAC). To impart superhydrophobic properties and minimize catalyst leaching, the hydrophobization subsystem is configured to esterify the hydroxyl groups present on the sulfonated carbon backbone with caprylic acid, which contains a long hydrophobic octyl chain. This reaction is catalyzed by phosphotungstic acid and leads to the formation of the final superhydrophobic spherical activated carbon catalyst, designated SSAC@PhSO3H, which is characterized by its high water contact angle and improved resistance to aqueous degradation.

[0033] In one embodiment, the system for producing biodiesel from Jatropha curcas oil comprises a transesterification reaction unit configured to evaluate the catalytic performance of the superhydrophobic spherical activated carbon catalyst (SSAC@PhSO3H) in the conversion of Jatropha curcas oil (JCO) to biodiesel. Within the transesterification reaction unit (104), a controlled reaction environment is created in which 1 mmol (900 mg) of JCO, 15 mmol (480 mg) of methanol, and 5 wt% (45 mg) of the SSAC@PhSO3H catalyst, relative to the mass of JCO, are added to a 10 ml microwaveable reaction vessel. The unit is equipped with a microwave irradiation system capable of maintaining precise reaction parameters, including a temperature of 80 °C, a pressure of 100 psi, and a power input of 50 W. The reaction mixture is stirred at 700 rpm to ensure uniform heat and mass transfer.Under these optimized conditions, the transesterification reaction is complete within 40 minutes, as confirmed by analytical techniques such as thin-layer chromatography. To determine the optimal operating parameters, the transesterification reaction unit is configured to allow systematic trials under varying key synthesis and reaction conditions. These include methanol-to-oil molar ratios of 5:1 to 20:1, catalyst loadings of 1 to 7 wt%, reaction temperatures of 60 °C to 90 °C, and reaction times of 20 to 50 minutes. Each trial is repeated twice to ensure reproducibility and consistency, with a tolerance of error within 5%. Upon completion of the reaction, the separation unit is activated to facilitate the isolation and recovery of the products. The catalyst is separated from the reaction mixture by filtration using Grade 1 Whatman filter paper.A sequential rinse with methanol and acetone (2 × 10 ml) is then performed to completely remove all remaining reactants and byproducts. The excess methanol in the reaction mixture is then evaporated under reduced pressure, and a gravity-based phase separation is used to separate the biodiesel from the glycerol byproduct, thus completing the transesterification process.

[0034] In one embodiment, the system for biodiesel production from Jatropha curcas oil includes a characterization unit configured for the comprehensive analysis of the physical, structural, and chemical properties of the synthesized catalyst SSAC@PhSO3H. This unit is equipped with several analytical instruments designed for the evaluation of functional groups by Fourier-transform infrared spectroscopy (FTIR), the crystalline nature by X-ray diffraction (XRD), the elemental composition by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS), the thermal stability by thermogravimetric analysis (TGA), and the morphology by scanning electron microscopy (SEM) together with elemental mapping.Furthermore, the characterization unit includes surface characterization tools for measuring the specific surface area and pore size distribution using Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) adsorption isotherms, respectively. The unit is also configured to determine the total acidity of the catalyst by temperature-programmed ammonia desorption (NH3-TPD) and to assess the catalyst's wettability by measuring the water contact angle, thus confirming superhydrophobicity. The system also includes a biodiesel analysis unit that confirms biodiesel formation, assesses purity, and determines the fatty acid methyl ester (FAME) content using proton nuclear magnetic resonance (PNR). 1 H-NMR), carbon-13 nuclear magnetic resonance ( 13The biodiesel yield is quantified using C-NMR), gas chromatography-mass spectrometry (GC-MS), and FTIR spectroscopy. To assess biodiesel performance, the biodiesel analysis unit calculates the biodiesel yield and the JCO conversion efficiency using the following formula: Biodiesel yield or JCO conversion (%) = (Amount of biodiesel produced / Amount of oil used) × 100 the 1 The methoxy and α-carbonylmethylene protons observed by H-NMR were quantified according to the following equation: FAME content in biodiesel (%) = 100 × (2 × AOMe / 3 × AA − CH2) where A OMe the integral of methoxy protons in methyl esters and A a-CH2 the integral of the α-carbonylmethylene protons.

[0035] The characterization unit is also configured to determine the sulfonic acid group density of the catalyst using an acid-base titration method adapted to the Ning and Niu procedure. The acid density is calculated using the following formula: CSO3H = (C NaOH × V NaOH) / m c

[0036] Here, C SO3H is the sulfone group density in mmol / g, C NaOH is the concentration of the sodium hydroxide solution in mol / l, and V NaOH is the volume of sodium hydroxide used in ml and m³. c the mass of the catalyst in grams.

[0037] This integrated configuration ensures thorough validation of both catalyst performance and biodiesel product quality.

[0038] In one embodiment, the system for biodiesel production from Jatropha curcas oil is also equipped with an integrated experimental modeling framework designed to optimize the parameters of the transesterification reaction using statistical tools. The experimental modeling is performed via a computational unit to improve the transesterification reaction with a design of experiments (DOE) module based on the Response Surface Methodology (RSM) using a Central Composite Design (CCD) approach. This DOE module is configured to evaluate the influence of four independent transesterification parameters—reaction temperature (A, °C), methanol-oil molar ratio (B, mol / mol), catalyst concentration (C, wt.%), and reaction time (D, minutes)—on the dependent variable, biodiesel yield (Y, %). The design framework includes five coded levels for each parameter: central (0), factorial (-1 and +1), and axial (-α and +α) points.A total of 30 test runs will be carried out, using the CCD formula (2. n + 2n + 6), where n represents the number of independent variables. Six replicate runs are performed at the central point to estimate the pure experimental error. To ensure statistical robustness and evaluate the effects and interactions between the variables, the DOE module is configured to perform an analysis of variance (ANOVA) and calculate the coefficient of determination (R²). 2The statistical significance of the model is determined, quantifying the agreement between predicted and actual responses. The model's statistical significance is validated by analyzing p-values ​​(significance threshold < 0.05) and F-values, all within a 95% confidence interval. The selected ranges for each independent variable are based on previous studies of biodiesel production from Jatropha curcas oil. The DOE module is also configured to perform response surface analyses and solve regression equations to determine the optimal values ​​of the process variables. Three-dimensional response surface plots are generated to visually interpret the individual and interactive effects of the independent variables on biodiesel yield. Regression modeling and statistical calculations are performed using Design-Expert software.To validate the reliability of the model and the predictions, a quadratic regression equation is derived and used to estimate the maximum biodiesel yield. The contribution factor of each process parameter is calculated as the sum of the squares of the respective parameter, thus quantitatively assessing its influence on the final yield. The contribution factor is determined using the following formula: Contribution factor (%) = (SS f / SS T ) × 100, where SS is the sum of the squares for a given factor and SS T The total sum of squares for the model. This modeling function within the transesterification reaction unit improves system accuracy, efficiency, and process optimization for biodiesel production.

[0039] In one embodiment, the system for biodiesel production from Jatropha curcas oil is also configured to perform a reaction kinetic and thermodynamic analysis of the transesterification reaction enabled by the superhydrophobic spherical activated carbon catalyst (SSAC@PhSO3H). This analysis is performed using a computing unit that models the reaction kinetics under the assumption of pseudo-first-order behavior. This assumption is valid due to the use of excess methanol, which exceeds the stoichiometric requirement for transesterification and thus renders the reverse reaction negligible.

[0040] Under these conditions the reaction rate (-r JCO ) expressed as follows: -r JCO = -d[JCO] / dt = k[JCO], where [JCO] is the concentration of Jatropha curcas oil, k is the rate constant and t is the reaction time.

[0041] To determine the rate constant k, the system calculates the fraction of JCO that is converted to methyl ester over different time intervals (t) (x t) , using the integrated first-order velocity expression: −1n(1−xt)=kt

[0042] The rate constants obtained at different reaction temperatures (in the range of 50 °C to 80 °C) are then used to determine the activation energy (E a ) to estimate using the Arrhenius equation: k = A·exp(-E a / RT), which can be linearized as follows: In k = In A - (E a / RT).

[0043] Here, T represents the absolute reaction temperature in Kelvin, A is the pre-exponential factor, and R is the universal gas constant (8.314 × 10⁻⁶). -3 kJ · K -1 ·mol -1 ). A plot of In k against 1 / T yields a straight line, from whose slope (-E a / R) and y-intercept (In A) the activation energy or the pre-exponential factor can be calculated.

[0044] In addition to kinetic modeling, the computing unit is also configured to evaluate thermodynamic parameters of the reaction. The system applies the Eyring-Polanyi equation to calculate the change in enthalpy (ΔH). ) , entropy (ΔS ) and Gibbs free energy (ΔG ) to determine during the reaction process. The Eyring-Polanyi equation is: ln(k / T)=(ΔS‡ / R)−(ΔH‡ / RT)+ln(kb / h) where k b is the Boltzmann constant (1.38 × 10 -23 J·K -1 ), h is the Planck constant (6.626 × 10 -31 J·s) and T is the absolute temperature. The Gibbs free activation energy (ΔG) ) is then calculated as follows: ΔG‡=ΔH‡−TΔS‡

[0045] Through this integrated kinetic and thermodynamic modeling function, the system ensures a comprehensive understanding of the catalytic efficiency and energy dynamics in the biodiesel production process.

[0046] With a large surface area (1461 m²) 2 G -1 ), a high acid density (6.26 mmol g -1With a water contact angle of 163.4°, the catalyst exhibits superior performance and remarkable water repellency, reinforcing its superhydrophobic properties. Response Surface Methodology based on the Central Composite Design (RSM-CCD) approach predicted a maximum biodiesel yield of 98.8% (80°C, 5 wt%, 15:1 methanol-to-oil molar ratio (MOMR), 40 min). Life cycle cost analysis (LCCA) estimates biodiesel production costs at USD 0.37 per kg, highlighting its high commercial viability. Compared to H₂SO₄ sulfonated biochar, SSAC@PhS03H retains its inherent activity (86.8 ± 0.4% yield in the 10th minute).Despite the lack of spherical morphology even after nine consecutive reaction cycles, the fuel properties of JCO biodiesel still met the European standard EN 14 212 and the standards of the American Society for Testing and Materials (ASTM D6757), highlighting its potential for industrial biodiesel production.

[0047] The system for biodiesel production from Jatropha curcas oil introduces a novel, shaped solid acid catalyst with enhanced hydrophobic properties, specifically designed for catalytic applications in biodiesel synthesis. The system is structured to address key industrial challenges associated with the widespread use of porous solid acid catalysts in heterogeneous catalysis and offers a scalable solution for commercial implementation. The catalyst fabrication unit is configured to synthesize a spherical superhydrophobic solid acid catalyst (SSAC@PhSO3H) characterized by a large BET surface area, increased sulfonic acid density, and a water contact angle of up to 163.4°.This catalyst is synthesized in a sequential process involving the activation of hydrothermally carbonated cellulose with ZnCl₂, arylsulfonation with benzenediazonium sulfonate, and esterification of hydroxyl groups with caprylic acid to produce cellulose caprylate. These features improve the accessibility of the acid sites to organic reactants while minimizing the negative effects of water generated during the reaction. The transesterification reaction unit demonstrates the catalyst's operational robustness, achieving consistently high biodiesel yields (>85%) over nine consecutive reaction cycles under mild, optimal conditions. Catalyst stability is maintained, with leaching of active sites being negligible due to the integration of stable caprylate units, which contribute to both thermal and hydrothermal durability.The system utilizes controlled surface wettability to enable rapid reactant adsorption and efficient product desorption, thereby improving both catalytic activity and catalyst lifetime. This also contributes to reducing the overall synthesis costs for both the catalyst and the biodiesel product. Furthermore, the enhanced hydrophobicity of the catalyst supports oleophilic substrate interaction, suppresses ester hydrolysis, and maintains elevated acid concentrations without compromising hydrophobic performance. Beyond its role in biodiesel production, the system demonstrates a high-value application for biochar through the use of a green synthesis pathway that employs diazonium-based grafting and esterification to produce functional cellulose esters. This approach enables the efficient catalysis of various organic reactions with immiscible liquid phases under mild conditions.This invention contributes to sustainable biomass waste management and offers a practical method for synthesizing functional carbon materials. Furthermore, it expands the application potential of biochar and positions it as a viable alternative to modern carbon-based materials such as graphene and carbon nanotubes.

[0048] The drawing and the preceding description show examples of embodiments. Those skilled in the art will recognize that one or more of the described elements can be combined to form a single functional element. Alternatively, certain elements can be divided into several functional elements. Elements of one embodiment can be added to another embodiment. For example, the sequence of the processes described here can be changed and is not limited to the manner described here. Furthermore, the actions of a flowchart need not be implemented in the sequence shown; nor does it necessarily have to be performed by all actions. Actions that are not dependent on other actions can also be performed in parallel with the other actions. The scope of the embodiments is in no way limited by these specific examples.Numerous variations are possible, whether explicitly stated in the specification or not, such as differences in structure, dimensions, and material use. The range of embodiments is at least as broad as specified in the following claims.

[0049] Advantages, further benefits, and problem solutions have been described above with reference to specific embodiments. However, the advantages, benefits, problem solutions, and all components that can lead to an advantage, benefit, or solution occurring or becoming more apparent are not to be construed as critical, necessary, or essential features or components of individual or all claims. REFERENCES 100 A system for the production of biodiesel from Jatropha Curcas oil using a superhydrophobic spherical activated carbon catalyst. 102 Catalyst preparation unit 102a Carbonization subsystem 102b Activation Subsystem 102c Sulfonation subsystem 102d Hydrophobing Subsystem 104 transesterification reaction unit 106 Separation unit 108 Characterization Unit 110 Biodiesel analyzer

Claims

[1] A system for biodiesel production from Jatropha curcas oil using a superhydrophobic spherical activated carbon catalyst, comprising: a) a catalyst manufacturing unit configured to produce a superhydrophobic spherical activated carbon catalyst (SSAC@PhSO3H) with a water contact angle of at least 163°, the catalyst manufacturing unit comprising: a carbonization subsystem configured for the hydrothermal treatment of cellulose at 190 °C, an activation subsystem configured to activate hydrothermal carbon with ZnCl2 by pyrolysis at 500 °C, a sulfonation subsystem configured for the sulfonation of activated carbon with 4-benzenediazonium sulfonate (4-BDS), and a hydrophobization subsystem configured to esterify hydroxyl groups with caprylic acid using phosphotungstic acid; b) a transesterification reaction unit configured to enable the transesterification of Jatropha curcas oil with methanol in the presence of the superhydrophobic catalyst; and c) a separation unit configured to separate the biodiesel product from the glycerol by-product and to recover the catalyst. [2] System according to claim 1, wherein the catalyst manufacturing unit is configured to produce a superhydrophobic spherical activated carbon catalyst with a surface area of ​​at least 1461 m² 2 G -1 and an acid density of at least 6.26 mmol g -1 manufactures. [3] System according to claim 1, wherein the transesterification reaction unit comprises microwave irradiation equipment configured to maintain the reaction conditions at 80 °C temperature, 100 psi pressure, 40 minutes time and 50 W power. [4] System according to claim 1, wherein the transesterification reaction unit is further configured to operate with a methanol-oil molar ratio in the range of 5:1 to 20:1 and a catalyst loading in the range of 1 to 7 wt.%. [5] System according to claim 1, wherein the separation unit comprises a filter system for recovering the catalyst and a gravity separation system for separating biodiesel and glycerin. [6] System according to claim 1, further comprising a characterization unit configured to analyze the properties of the superhydrophobic catalyst, wherein the characterization unit comprises equipment for determining functional groups, crystalline nature, composition, thermal stability, morphology, surface area, pore size, acidity and wettability. [7] System according to claim 1, further comprising a biodiesel analysis unit configured to determine the formation and purity of biodiesel using 1 H-NMR-, 13 Checked using C-NMR, GCMS and FTIR analyzers.

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