Preparation and Performance Analysis of a New Methanol-Mixed Gel Fuel Applied in Chemical Energy Storage.

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Learn more: PMC Disclaimer | PMC Copyright Notice ACS Omega . 2026 May 20;11(21):30655–30662. doi: 10.1021/acsomega.5c12308 Preparation and Performance Analysis of a New Methanol-Mixed Gel Fuel Applied in Chemical Energy Storage Hui Jin 1 , Ao Zhou 2, * , Hui Zhu 3 , Yangyang Li 4, * , Yujia Wang 5 , Xin Liu 5 , Songfeng Li 6 Author information Article notes Copyright and License information 1 School of Automotive Engineering, Lanzhou Institute of Technology, Lanzhou 730050, China 2 School of Mechanical Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China 3 Shaanxi Automobile Group Holdings Ltd., Xi’an 710200, China 4 Key Laboratory of Shaanxi Province for Development and Application of New Transportation Energy, Chang’an University, Xi’an 710064, China 5 State Grid Shaanxi Electric Power Research Institute, Xi’an 710100, China 6 School of Energy and Power, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu 212100, China * Email: cn_zhouao@163.com . Tel.: +86-931-4955702. * Email: thunderrock@126.com . Tel.: +86-029-82335517. Received 2025 Nov 23; Accepted 2026 May 15; Revised 2026 Apr 26; Collection date 2026 Jun 2. © 2026 The Authors. Published by American Chemical Society This article is licensed under CC-BY-NC-ND 4.0 PMC Copyright notice PMCID: PMC13234811  PMID: 42255552 Abstract The development of green and low-carbon new energy is one of the effective ways to deal with environmental pollution and climate change. Methanol, as an electrocatalytic product, is an excellent energy source and fuel. However, liquid methanol poses issues such as volatility, flammability, and explosiveness during use and long-term storage. This study presented a new methanol–sodium stearate–water-mixed gel. The performance of this mixed gel as a methanol energy storage carrier was evaluated. The results indicated that the gel points of the mixed gel increased with the increased contents of water and gelling agent. The maximum gel point reach approximately 35 °C, which is beneficial for reducing the requirements for the storage temperature. However, an excessive content of the gelling agent would lead to a decrease in the calorific value. The calorific value of the mixed gel containing 10% water is comparable to that of the mixed gel containing 5% gelling agent. Therefore, the scheme of adding water to increase the gel point has a better effect. Additionally, as the content of the gelling agent increased, the three-dimensional network structure formed by the interwoven fibers within the mixed gel became more compact. Meanwhile, the precipitation phenomenon of the gelling agent occurred during the gelation process, resulting in the lower structure of the mixed gel being denser than the upper structure. Therefore, in the large-scale production process of the mixed gel, the gel preparation container should be selected to be flat in shape to improve the uniformity. 1. Introduction Energy and the environment have become the two most challenging and crucial issues worldwide. Over the past few decades, research has been striving to innovate and develop new technologies to alleviate environmental problems and solve the issue of energy shortage. Energy storage is one of the effective ways to achieve this goal. , Chemical energy storage has attracted much attention as one form of energy storage. Chemical energy storage usually uses chemical substances such as hydrogen, ammonia, and methanol as carriers. Taking into account the cost and the safety of long-term storage as the premise, methanol has more advantages compared with the other two chemical substances. Methanol, the simplest saturated monohydric alcohol, generates fewer byproducts after combustion. , At the same time, methanol is produced in a wide range of ways; it can be produced by biological fermentation technology or synthesized using hydrogen from water electrolysis combined with carbon dioxide. − With the rapid development of new green and low-carbon energy in the future, methanol, as a product of carbon dioxide electrocatalytic reduction, will be a promising clean fuel. However, at room temperature, methanol is a liquid with volatile, low-flash-point, flammable, and explosive properties. Liquid methanol still has significant safety hazards and high fire risks during storage, transportation, and use. , Therefore, the problem of storage, transportation, and use of liquid methanol could be solved by adding a gelling agent to prepare methanol gel fuel. Meanwhile, methanol gel, as a new way of energy storage, is one of the effective ways to solve the randomness, volatility, and intermittent defects of new energy technology. Methanol gel is a type of alcohol-based gel. Alcohol gel is mainly composed of alcohol and is prepared through a certain process after adding a gelling agent, a curing agent, and an appropriate amount of colorants or performance improvers. At present, the commonly used gelling agents for alcohol gel fuels are mostly organic gels, such as cellulose derivatives and sodium stearate. Some research has shown that in organic gel-based fuels, polymer chains are interconnected through hydrogen bonds and hydrophobic associations to form a three-dimensional network. On the one hand, this three-dimensional network structure effectively captures alcohol molecules to inhibit evaporation. On the contrary, this network structure maintains the mechanical strength of the gel fuel. These make it possible for the long-term, safe storage of methanol. Notably, the addition of the gelling agent results in distinct evaporation, atomization, and combustion processes for the alcohol-based gels, which are different from those of pure alcohol fuels. − Through the investigation of the evaporation process of n -butanol-hydroxypropyl methyl cellulose (HPMC) gel droplets under high-temperature and high-pressure conditions, it was found that the evaporation process is divided into three distinct phases: droplet heating, vaporization, and crust formation. When the ambient temperature rose from 600 to 700 °C, the evaporation rate of the gel fuel significantly increased, while the increased environmental pressure and mass concentration of the gelling agent had minimal impact on the evaporation rate. De Cataldo and Gentile evaluated the thermal stability of methanol–methyl cellulose gel fuel via thermogravimetric analysis. The evaporation of methanol in the gel system occurred when the temperature was 33 °C, and when the temperature reached 60 °C, the weight loss of the system was 76% due to the complete evaporation of methanol. They also observed that adding calcium chloride could reduce the methanol mass loss to less than 40% with the temperature of 60 °C. As for the combustion characteristics, Sharma et al. conducted a systematic study on the combustion process of ethanol-based gel fuels containing organic gellants HPMC and methyl cellulose (MC). The results demonstrated that the combustion processes of the two fuels could be divided into three different stages: transient heating stage, disruptive burning stage, and carbonization stage. During the transient heating stage, phase separation occurred, and viscoelastic shells were formed. In the disruptive burning stage, oscillatory-transient bursting was observed in the HPMC system, whereas only transient bursting was observed in the MC system. However, the jetting of ethanol vapor was observed during the combustion of both fuels. However, studies have shown that the presence of the gellant layer hinders mass transfer, thus prolonging the ignition delay period of the gel droplets. Meanwhile, as the ethanol gel droplets evaporated, the expansion and vapor jetting phenomena occurred, which increased the average combustion rate of the gel droplets compared to pure ethanol fuel. Similarly, when investigating the autoignition characteristics of ethanol–hydroxypropyl cellulose gels, Naseem et al. found that the cage-like structure formed in the gel network could encapsulate high-temperature gases and flames within the network, thus extending the ignition delay period. Miglani et al. also discovered that jetting enabled the advective transport of unreacted fuel vapor from the droplet to the flame. As a result, the fuel efflux increased and the F/O mixing time scales shortened, which in turn promoted combustion. The bursting frequency of the droplet could be regulated by adjusting the initial concentration of the gelling agent. These findings strongly demonstrate that the gel shell controls the rupture and jetting behaviors of the gel droplets. Additionally, the effect of the alcohol carbon chain length on the calorific value of alcohol gel fuel was also studied. The results revealed that the calorific value of ethanol gel fuel was significantly higher than that of pure liquid ethanol fuel. In contrast, for other alcohol fuels from propanol to heptanol, the calorific values of gel fuels were lower than those of their respective pure liquid fuels. Furthermore, with the increase in the concentration of the gelling agent, the calorific value of each alcohol-based gel fuel exhibited an obvious decrease. Through the review of the above literature, it is obvious that current research primarily focuses on multicarbon alcohol gel fuels, while there are few relevant studies on methanol gel fuel. In this study, a new method for preparing methanol gel was proposed in this paper. The sodium stearate was used as the gelling agent, and methanol and water were used as solvents to synthesize a methanol-mixed gel. As is known, the higher the gel point of a gel, the higher the critical temperature for the gel to transform into a sol. The three-dimensional structure inside the gel is less likely to be disrupted, which can inhibit the escape of the methanol fuel. This is conducive to reducing the cost and risk of long-term storage of methanol gel. Meanwhile, the methanol-mixed gel with sodium stearate as the gelling agent can maintain its solid-state characteristics during the combustion process and avoid the problem of liquid flow. It can be widely applied in catering, outdoor activities, emergency support, and emerging energy fields. In the catering industry, it can be utilized in buffet warmers in hotels and restaurants to provide a continuous and stable heat source for food heating. For outdoor scenarios, methanol gel fuel serves as a portable fuel for cooking and heating during camping, picnics, hiking, and other outdoor activities, and it is compatible with small stoves and outdoor barbecues. In emergency situations, it can act as a temporary heating fuel in remote areas and power off disasters. Moreover, methanol gel fuel can function as a chemical energy storage carrier for new-energy power systems. Therefore, the methanol-mixed gel requires a relatively high calorific value. Furthermore, during the large-scale production of methanol-mixed gels, the volume of the gel preparation container is relatively large. It is necessary to clarify whether the vertical height has an impact on the upper- and lower-layer structures of the gel to facilitate the selection of the structural shape of the gel production container. For these reasons, this study investigates the effects of the proportion of each component of the methanol-mixed gel fuel on the calorific value, gel point, and gel microstructure. So far, there is no research literature on these aspects of the methanol–sodium stearate–water-mixed gel. 2. Materials and Methods 2.1. Materials Methanol and sodium stearate (C 17 H 35 COONa) with a purity of around 99.5%, used as base fuel and gelling agent, respectively, were purchased from Sinopharm Group Chemical Reagent Co., LTD (Shanghai, China). 2.2. Preparation of Methanol Gel Fuels In this study, the controlled single-variable method was employed to prepare methanol-mixed gels. For the preparation of a sodium stearate–water–methanol-mixed gel with mass fractions of 3, 10, and 87%, respectively, 3 g of sodium stearate and 10 g of water were weighed into a reaction flask. Then, 87 g of anhydrous methanol was added. Subsequently, the reaction flask was placed in a water-bath heating tank, in which the water temperature was controlled at approximately 65 °C, and a glass rod was used to stir the mixture at a constant speed until the sodium stearate was completely dissolved. Finally, after cooling the homogeneous solution at room temperature for 2 h, the methanol-mixed gel with a specific mass ratio could be prepared. It should be noted that preliminary experiments revealed that for the samples investigated in this study, a gelling agent (sodium stearate) content of 3–5% was suitable for gel formation under anhydrous conditions. When the gelling agent content was below 3%, gel formation became difficult and time-consuming, and additional cooling was required to prepare the gel. When the gelling agent content exceeded 5%, the resulting gels were inhomogeneous, the gelling agent could not be completely dissolved, and flocculent structures were observed in the gel. Water typically acts as the gel solvent in most gels. To enhance gel performance while ensuring gel formation at the optimal 3% gelling agent content at room temperature, water was added during gel preparation. It was found that a water content of 10% moderately improved the gel’s effectiveness. However, excessive water addition diminished the efficacy of methanol fuel storage. Consequently, the water content was controlled within 10%. Methanol-mixed gels with other mass ratios were prepared using the same method, and the compositions of test gel samples are detailed in Table . 1. Compositions of Test Mixed Gel Samples. sample name methanol (wt %) water (wt %) sodium stearate (wt %) 3% 97% 0% 3% 4% 96% 0% 4% 5% 95% 0% 5% 3% + 5% 92% 5% 3% 3% + 10% 87% 10% 3% Open in a new tab 2.3. Measurement of the Gel Point The electroconductivity method was used to measure the gel point of the test gel in this paper. Because when the solution reaches the gel point, the solution is transformed into a gel, and a network structure is formed inside it, which limits the movement of ions, leading to a sudden drop in conductivity. The gel point testing system is shown in Figure . A digital conductivity sensor was employed to measure the conductivity of the methanol-mixed gel in the test system. First, the digital conductivity sensor was connected to an RS485 serial port adapter and a 10 V power transformer, with the RS485 port connected to the computer. Then, the sensor was fixed at the mouth of the test bottle, with its probe submerged halfway into the gel. The test bottle was placed in a constant temperature water bath at 65 °C, and data collection began after powering on. When the collected temperature reached 60 °C, the sol process ended. Then, the test bottle was taken out and placed on a rack in a pre-prepared bucket of ice–water mixture (0 °C), ensuring that the contact area of the test bottle with the ice–water mixture remained the same. Subsequently, the data collection for the gelation process was carried out. Finally, the collected data were analyzed to determine the gel point of the methanol-mixed gel. 1. Open in a new tab Schematic diagram of the conductivity testing system. 2.4. Measurement of the Calorific Value A microcomputer oxygen bomb calorimeter was used to measure the calorific value of mixed gels in this study. First, the empty capsule was weighed by an electronic balance, and then the total mass of the methanol-mixed gel and capsule was weighed. Subsequently, the total calorific value of the fuel and capsule was measured by a microcomputer oxygen bomb calorimeter, and the calorific value of the fuel was calculated based on the premeasured calorific value of the capsule. 2.5. Spectral Measurement The gel sample spectrum was acquired by a Fourier infrared spectrometer (Beijing Beifen-Ruili Analytical Instrument (Group) Co., Ltd., China). During the test, the spectral range of the spectrometer was 4000–400 cm –1 , the number of scans was 16, and the resolution was set to 4 cm –1 . Then, the methanol-mixed gel was completely melted in a constant temperature water tank, and 1–2 mL of the solution was dropped on the potassium bromide window of the detachable liquid pool with the glue head dropper. The infrared spectrum of the sample could be collected after covering another window and tightening the screw of the liquid pool. It was worth noting that before the test, the empty liquid pool needed to be loaded into the Fourier infrared spectrometer to collect the background so that the infrared spectrum of the tested sample would subtract the background infrared spectrum by default. 2.6. Microstructure Characterization The microstructure of methanol gel was characterized by a Quanta 250 FEG (FEI, United States of America) instrument. During sample preparation, a certain mass of the mixed gel was placed on a glass slide and then inserted into a vacuum drying oven. The oven was evacuated to 0.1 MPa, and the internal temperature was set to 100 °C. After drying the sample for 4 h, the dried mass was measured and stored in a sealed container. Additionally, to enhance the conductivity of the sample and optimize the scanning electron microscopy (SEM) imaging results, all samples underwent gold sputtering treatment before scanning. 3. Results and Discussion 3.1. Gel Point Study Figure shows the influence of different water contents on the tendency of electrical conductivity changes of the mixed gels during the sol–gel process. As observed from Figure , in the sol region, the electrical conductivity decreases initially with increasing temperature, then sharply rises to a peak value, and subsequently decreases to a certain value before stabilizing. The peak value of the conductivity with the increase in temperature indicates that there is a most suitable temperature range for ion migration during the process of temperature rise. It can also be seen from the data that when the temperature rises to the maximum of 60 °C, the mixed gel has completely melted into a transparent liquid, but the migration of ions is inhibited. According to these phenomena, it can be considered that the migration ability of ions is related to the gel point of the mixed gel. In addition, the stable conductivity values of the mixed gels containing 3% (sodium stearate), 3% + 5% (sodium stearate + water), and 3% + 10% (sodium stearate + water) are between 2400 and 2600, 2600 and 3000, and 2900 and 3300 uS/cm, respectively. It can be seen that with the increase in water content, the stable conductivity value in the sol process increases, which indicates that water can promote the migration of ions and also indicates that the mixed solution with water has better ionization effect. 2. Open in a new tab Conductivity under different water contents: (a) 3% + 0% (sodium stearate + water), (b) 3% + 5% (sodium stearate + water), and (c) 3% + 10% (sodium stearate + water). As for the gel region, the electrical conductivity also exhibits a peak value with the decrease in temperature, the time required for mixed gels to reach the peak electrical conductivity decreases with increased water content, and the corresponding temperatures of the peak values are 17.1, 24.1, and 34.6 °C, respectively. The data show that with the increase in water content, the optimal migration temperature range of ions in the solution narrows. At the same time, with the increase in water content, the temperature sensitivity of the electrical conductivity increases, the inflection point temperature rises, and the stable conductivity value at the highest temperature is gradually increased. Figure shows the influence of different gel contents on the electrical conductivity changes of mixed gels in the sol–gel process. As seen from Figure , under the influence of different gel contents, the electrical conductivity changes trend of the mixed gel in the whole sol–gel process is consistent with that of the study on the influence of water content. In the sol region, compared with the mixed gels containing 3 and 4% sodium stearate, the electrical conductivity of the mixed gel containing 5% sodium stearate does not show an obvious extremum as the temperature rises to 60 °C. This phenomenon shows that the mixed gel containing 5% sodium stearate does not inhibit ion migration after complete melting because the increase in gel content promotes the increase in Na + concentration, enhancing the ability of ion migration. 3. Open in a new tab Conductivity under different sodium stearate contents: (a) 3%, (b) 4%, and (c) 5%. However, in the gel region, the mixed gel containing 3% sodium stearate does not show a significant decrease in electrical conductivity when the temperature drops to 20 °C during the gelation process, suggesting that the mixed gel with a 3% proportion has a relatively broad temperature control range. The mixed gel containing 5% sodium stearate showed an earlier extremum point in electrical conductivity during the gelation process. The main reason for the decrease in electrical conductivity is that the mixed gel system changes from a uniform sol to gel during the process of temperature reduction, and the migration of Na + in the gel pore is hindered. It can also be seen from Figure that with the increase in gel content, the temperature corresponding to the extreme electrical conductivity point (gel point) gradually increases, and the corresponding temperatures of the extreme electrical conductivity point of the three mixed gels are 17.1, 21.3, and 37.6 °C, respectively. Through the conductivity study, it was found that to obtain a higher gel point to reduce storage costs and long-term storage risks, the mixed gel containing 5% sodium stearate or the mixed gel containing 3% sodium stearate and 10% water met the requirements. 3.2. Calorific Value Study Figure shows the change trend of the calorific value of mixed gel with different proportions. As can be seen from Figure , the calorific value of mixed gel decreases with the increase in water content. With the increase in the gelling agent content, the calorific value of the mixed gel first increases and then decreases. When the gelling agent content is 4%, the calorific value of the mixed gel is the highest. However, the calorific value is significantly reduced when the proportion of the gelling agent is 5% and the water content is 10%. When the water content of the mixed gel is too high, the proportion of methanol fuel in the mixed gel decreases obviously, resulting in a decrease in the calorific value. In addition, when the gel content is higher, more residue is generated by the combustion of mixed gel, and the gel fuel is not fully burned, which also causes a decrease in the gel calorific value. 4. Open in a new tab Low calorific values for different mixed gel samples. 3.3. Infrared Spectroscopic Study Figure shows the infrared spectra of the different methanol–gelling-mixed gels, methanol, and sodium stearate. Among them, the infrared spectral data of pure methanol and pure sodium stearate are from the OMNIC spectral library. It can be seen from Figure that the infrared spectrum of the methanol-mixed gel is the superposition of the spectra of pure sodium stearate and pure methanol in a certain proportion. Apart from the difference in the intensity of the wave peaks, no new wave peaks appeared. Therefore, no chemical reaction occurs inside the gel, which proves that the methanol gel is a physically cross-linked gel. The data in the figure indicate that with the increase in the gelling agent content, the stretching vibration intensity of the carboxylate radical (COO) of sodium stearate at 1450 and 1560 cm –1 increases. Meanwhile, the hydroxyl group (OH) of methanol becomes flatter at the stretching vibration peak of 3400 cm –1 and migrates to the lower waveband, raising the vibration peak of the lower waveband. Because sodium stearate contains a carboxylate radical, it can provide two acceptors for hydrogen bond formation. The OH of methanol can provide one donor and one acceptor for hydrogen bond formation. As a result, the intermolecular hydrogen bonds are formed between sodium stearate and methanol. The force of the hydrogen bond is less than that of the chemical bond; therefore, the vibration frequency is lower than that of the chemical bond. This causes the vibration frequency of the OH stretching of methanol to shift toward a lower wavenumber and raise the vibration wave band. Furthermore, since the total mass of the mixed gel is fixed, as the content of sodium stearate increases, the content of methanol decreases accordingly and the number of hydrogen bonds formed between molecules of different components increases. The effect of hydrogen bonds is stronger, which will lead to an increase in the vibration intensity of the carboxylate radical. 5. Open in a new tab Infrared spectra of the different methanol gels, methanol, and sodium stearate. Figure shows the infrared spectra of pure water and water-containing methanol-mixed gels. It can be seen that due to the addition of water, the peak of the water-containing methanol-mixed gel becomes wider at 3400 cm –1 and a new peak appears at 1645 cm –1 . The former might be the superposition of the stretching vibration peak of water molecules and the OH stretching vibration peak of methanol, or it could be because water molecules are more likely to form hydrogen bonds, thus making the wave peak wider. The appearance of the new peak is due to the bending vibration of water molecules. With the increase in water content, the peak at 3400 cm –1 becomes flatter, and the intensity of the vibration peak of sodium stearate increases. This is because water is a good solvent, and water molecules can easily form hydrogen bonds with each other. Furthermore, since water can provide two donors and acceptors for the formation of hydrogen bonds, it is prone to form new hydrogen bonds with carboxylate and hydroxyl groups. The presence of water molecules can form a greater variety of hydrogen bonds, which can link methanol molecules and sodium stearate molecules in multiple ways, build longer molecular chains, and enhance the effect of hydrogen bonding. Therefore, the vibration intensity of the carboxylate of sodium stearate increases with an increase in the water content, promoting the formation of a three-dimensional network structure in the solution. 6. Open in a new tab Influence of water content on the infrared spectrum of the methanol-mixed gel. 3.4. Microstructure Study Figure shows the SEM images of the lower and upper layers of the samples of 3% + 10% (sodium stearate + water), 3% (sodium stearate), and 5% (sodium stearate) methanol-mixed gel. Among them, the upper layer is the upper surface of the sample, while the lower layer is the part of the bottom of the sample close to the wall. The study of micromorphology aims to analyze whether the gelling agent undergoes precipitation and whether differences exist in the structures formed at the upper and lower layers by observing the structures of the upper and lower layers of the sample. From Figure a,b, it can be observed that the SEM images of the mixed gel exhibit directional textures. Figure a shows that the gel structure is fractured. This is because during the vacuum drying process of the methanol gel sample, the evaporation of the liquid causes the network structure to contract, resulting in the fracture of part of the network structure. Figure c indicates that there are many fiber structures in the gel sample that connect the shrunk network together and the network structure has obvious holes. In Figure d, fibrous structures are also observed to interweave within the stacked plate-like structure. Relevant studies have shown that sodium stearate powder is a layered crystal, and there are plate-like structures and fibrous structures in the gel with it as the gelling agent. It can be clearly found through the comparison between Figure b,d that the addition of water will induce the crystal structure to transform from plate-like to fibrous. Crystal morphologies are governed by the anisotropy of the growth rates along different crystallographic directions. Fast-growing crystallographic planes tend to vanish and exert a negligible effect on the final crystal form. In contrast, slow-growing planes dominate and ultimately determine the crystal morphology. In the system with sodium stearate as the gelling agent, the inner side packing energy of the sodium stearate molecular layer is lower than the interlayer end-group packing energy. The growth rate along the hydrocarbon chain axis is relatively slow, while the growth rate within the basal plane is faster. This leads to the formation of plate-like crystals. When the system is added with water, the water acts as a polar solvent, which will affect the relative growth rates of different crystal faces, promoting the growth of the fibrous crystals. 7. Open in a new tab SEM images of the upper and lower layers of different mixed gel samples: (a) 3% + 10% lower layer, (b) 3% + 10% upper layer, (c) 3% lower layer, (d) 3% upper layer, (e) 5% lower layer, and (f) 5% upper layer. It can also be observed that the addition of water promotes a more orderly spatial arrangement of gel fibers and higher compactness. In Figure e,f, the fibrous structure is almost invisible in the mixed gel sample, and the gel system forms a network structure. The pores in this network structure are smaller than those in Figure c, and the compactness of the network structure is also higher. According to this, it can be found that when the content of the gelling agent is relatively small, the three-dimensional structure shows an uneven phenomenon, and there are also some complex shapes. Meanwhile, with the increase in the gelling agent content, the three-dimensional structure becomes uniform and the formed crystals tend to be shorter, with smaller and more regular pore sizes formed. In addition, by comparing the SEM images of the upper and lower layers of each sample, it is observed that the three-dimensional structures of the upper layers are less dense than those of the lower layers. This phenomenon also indicates that the gelling agent precipitates during the gelation process. A previous study has shown that, at the same water content, an increase in sodium stearate content enhances the yield stress and structural strength of the gel. However, the precipitation of the gelling agent during the gelation process can result in an uneven structural strength within the prepared gel samples. This heterogeneity may cause the upper layer of the gel block to undergo structural damage during subsequent stacking and storage, resulting in methanol exudation and posing risks to the storage safety of the gel fuel. Therefore, the gel preparation container should be as flat as possible to reduce its vertical height. By correlating SEM images with low calorific value data, it can be observed that the gel containing 5% water shows no obvious reduction in the low calorific value at a gelling agent content of 3%. This indicates that the fibrous structure induced by water addition is more conducive to the complete combustion of the gel fuel than the lamellar structure. In addition, the low calorific value of the gel fuel first increases and then decreases significantly with an increasing gelling agent content. The initial increase is related to the rising gelling agent content, while the subsequent decrease is mainly caused by the densified gel network and reduced porosity at higher gelling agent contents, which hinder the full combustion of the gel. 4. Conclusions In this study, the sodium stearate was used as the gelling agent to synthesize methanol–sodium stearate–water-mixed gel through the sol–gel method. The electrical conductivity study showed that the gel points of the mixed gels with different gelling agent contents were 17.1 °C (3%), 21.3 °C (4%), and 37.6 °C (5%), respectively. When the gelling agent content is fixed at 3%, the increase in water content could also raise the gel point of the mixed gel. The gel points of the mixed gels with different water contents were 17.1 °C (3% + 0%), 24.1 °C (3% + 5%), and 34.6 °C (3% + 10%), respectively. However, the calorific value of the mixed gel decreases with the increase in water content, while it first increases and then decreases with the increase in the gelling agent content. It was found that an excessive content of gelling agent leads to incomplete combustion of the mixed gel, generating more residue, which is not conducive to improving the combustion efficiency. The calorific value of the mixed gel with 10% water and 3% sodium stearate is comparable to that of the mixed gel containing 5% sodium stearate. Therefore, the scheme of adding water to increase the gel point of the mixed gel is better. The test results of the Fourier transform infrared spectrometer show that the mixed gel prepared in this study is a physical gel, and the three-dimensional structure is constructed among the gelling agent, methanol, and water through hydrogen bond interactions. With the increase in the sodium stearate content, the number of hydrogen bonds increases. Additionally, the increase in the water content will also enhance the effect of hydrogen bonds. The SEM images show that the three-dimensional structures formed inside the gel are plate-like and fibrous. With the increase in the sodium stearate content, the three-dimensional network structure formed by the interweaving of the fiber structure becomes tighter. Water can induce the transformation of structures from plate-like to fibrous. Furthermore, by comparing the SEM images of the upper and lower layers, it was found that the structure of the lower layer of the mixed gel was denser than that of the upper layer, indicating that the gelling agent precipitation phenomenon occurred in all mixed gels during the gelation process. According to this, the gel preparation container should be as flat as possible to reduce the vertical height in the industrial production process of methanol-mixed gel. Acknowledgments This study was supported by the Gansu Science and Technology Project in China (25JRRA950), the Innovation Fund Project for University Teachers in Gansu Province (2025B-248), the Shaanxi Innovation Capability Support Plan (2024ZC-KJXX-107), and the China Postdoctoral Science Foundation (2023M741841). The authors declare no competing financial interest. References Mahlia T. M. I., Saktisahdan T. J., Jannifar A., Hasan M. H., Matseelar H. S. C.. 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