Applied of Synthesis Furfural Based on Cassava Stems ( Manihot utilissima ) As Fuel Additive to Gasoline

Furfural is a potential compound derived from biomass, which can be further converted to biofuels as renewable and alternative energy. In this study, synthetic crude furfural from cassava stem was blended as fuel additive to gasoline (pertalite) and then induced by electromagnetic field. Analysis was carried out on engine performance and exhaust gas emissions produced by Kohler engines. Variations formed by samples crude furfural and commercial furfural (C 5 H 4 O 2 ), and time variations of electromagnetic induction for 0 and 30 minutes. The blending composition of gasoline and furfural in a mixture of 1,500 ml fuel is 96% : 4%. The best results from increasing torque, cranking power and saving fuel consumption were obtained from variations in the use of crude furfural additives induced by electromagnetic fields (CFE). Exhaust emissions produced by pure Pertalite are still lower than fuels with furfural additives. The content of water and impurities in crude furfural causes the additive unmixed with Pertalite which is non-polar and hydrophobic.


Introduction
Climate change and ecological issues are a common concern on our planet.The use of fossil fuels in vehicles releases emission of harmful gases like CO2, CO, HC, SO2, and NOx.These gases can cause stratospheric ozone depletion and threat to human health as well as to the Earth's ecosystem (Balan et al., 2017).The necessity of reducing the environmental impact, the development of non-fossil fuel based on renewables sources, including biofuels, is an option to reduce gas emissions released by vehicles.
Furfural and its derivatives offer a promising as a potential biofuel (Natsir et al., 2020).The use of furans as oxygenated fuels is promising as various furanic compounds have high heating value, prominent detonation resistance, low water solubility, and excellent volatility (Ahmad, et al., 2022).Furfural derivatives as fuel additives is received special attention because their properties: high octane number and high heating value that have a positive effect on vehicle fuel consumption (Tarazanov et al., 2020).Several studies reported the furfural derivatives (furan compounds, furfural ethers, furfuryl amines, and others) as octane boosters.Based on the analysis of physicochemical and operating properties, 2-methylfuran and furfuryl amine were produced better high-octane number than other derivatives.In addition, the effect of high-octane number was produced cleaner exhaust emissions (Ershov et al., 2017).Furfural derivatives, ethyl furfuryl ether (EFE), was blended with gasoline up to a level of 30 wt%.EFE additives have resulted in higher stability and high-octane number (Mariscal et al., 2016).
In contrast, a literature found that two factors hinder furfural (C5H4O2) use as a fuel additive.First, furfural is unstable.For instance, when purified via distillation at atmospheric pressure (boiling point is 161.7°C), it develops a faint brown color.Second, furfural has a low energy content because of its high oxygen to carbon ratio.Moreover, chemical upgrade of furfural can yield 2-methyltetrahydrofuran (MTHF) and ethyl levulinate (EL), two chemicals of furfural derivatives that can be used as fuel additives in gasoline and diesel, respectively (Silva et al., 2018).
Furfural is produced by hydrolysis and dehydration of xylene contained in lignocellulose (Lange et al., 2012).Cassava stem is lignocellulose consists of 39.29% cellulose, 24.34% hemicellulose and 13.42% lignin (Lismeri et al., 2016).Several studies reported the use of sulfuric acid (H2SO4) as acid catalyst to hydrolyze furfural from biomass (Andaka, 2011;Mardina et al., 2014;Amborowati et al., 2016;Anggraini, 2018).In another study, furfural was synthesized with different acid catalysts (H2SO4, and HCl), various concentrations, and reaction times.The optimum yield of furfural as a distillate product was produced by 2% H2SO4 catalyst at temperature of 100 o C for 2 hours hydrolysis process (Hambali, 2016).The use of H2SO4 catalyst is more effective because H2SO4 has a higher number of H + ions than HCl so that the breaking of chemical bonds takes place better.Siregar (2007) has succeeded to produce fuel saver which is based on electromagnetic for saving the automotive fuel consumption.The produced fuel saver which is installed in the fuel line of internal combustion engine rig can reduce energy consumption and the opacity of the emission gas.The research resulted that the fuel saver which is produced could save fuel consumption about 30.79% especially for number of winding 4000 coils and diameter of wire 0.35 mm.Another study was installed solenoid electromagnetic element to a petroleum residue vacuum batch reactor and it affected in lower residual vacuum density and viscosity (Pramito et al., 2019).In this case, the treatment of electromagnetic field induction had a resonant effect when applied to fuel.The resonance will make the chain in the hydrocarbon bonds more reactive so that the C and H bonds will breaking and able to bind O2 better.This will make the combustion reaction between fuel and O2 becomes ideal .
In this study, to synthesize furfural from cassava stem, H2SO4 catalyst with concentration of 2% was used in the hydrolysis process because of its effectiveness.Furthermore, electromagnetic field was applied to the fuel by induction before being injected into the fuel tank to increase combustion efficiency and reduce fuel consumption.This work aims to find out the influence of various furfural additives (commercial furfural, and crude furfural based on cassava stem) and inducting electromagnetic field on engine performance and exhaust gas emissions.The parameters of engine performance are torque, cranking power, and specific fuel consumption.

Materials
Cassava stem was collected from Terbanggi Besar, Central Lampung, Indonesia.Distilled water and sulfuric acid (H2SO4) ≥98% (Sigma-Aldrich) were used for acid catalyst in hydrolysis process.Furfural (C5H4O2) ≥98% was purchased from Sigma-Aldrich, Germany.This commercial furfural as fuel additive is compared to the performance of additive crude furfural synthesized based on cassava stem.The gasoline (Pertalite) was purchased from Pertamina gas station.

Hydrolysis Process
Cassava stems were crushed and sieved with range between 60 and 80 mesh then to dehydrate the moisture contents.The cassava stem was dried in oven at 105 o C until a constant mass is obtained.25 grams of cassava stems and 250 ml of 2% H2SO4 solution were heated.The hydrolysis process (Figure 1) was carried out at temperature of 95 o C for 2 hours.The furfural as a product distillate from the hydrolysis process is cooled and then filtered to be separated from the residue.(Andaka, 2011)

Purification Process
The hydrolyze solution was purified through an evaporation process for 1 hour.Vacuum rotary evaporator in Figure 2 (Buchi Rotavapor R-100, Switzerland) was used at pressure conditions of 23 mbar and water bath temperature of 40 o C to separate the solvent contained therein and obtain furfural with higher purity.This tool was set at 40 o C to get the optimum distillation conditions, in this tool it is recommended to provide a temperature difference of 20 o C respectively between the heating bath and the evaporation flask, then between the evaporation flask and the condenser.

Electromagnetic Induction
The electromagnet used in this study had number of winding 800 coils, diameter of wire 0.75 cm, socket height 7 cm, electric currents of induction 10 Amperes, and magnetic induction 0.0178 Tesla.Figure 3   Commercial furfural and crude furfural as fuel additives were blended with gasoline.The fuel mixture was put into a 2 liters beaker glass with a composition ratio of furfural : gasoline, which is 1,440 ml : 60 ml or 96% : 4%.The fuel mixture of furfural additives and gasoline were stirred manually by spatula until the mixture blended well, then covered the beaker glass with aluminum foil and preserved for 24 hours in order to ensure the fuel mixture is homogeneous or completely mixed.The process of electromagnetic field induction was carried out with time variations of 0 minute and 30 minutes.Table 1 shows fuel additives variations.

Engine Performance and Exhaust Gas Emission Tests
The tools for testing engine performance (Figure 4) are the Kohler 4-stroke gasoline engine (TecQuipment TD201), instrument unit of VDAS (Versatile Data Acquisition System) and Exhaust Gas Analyzer Stargas 898.In the TecQuipment VDAS application, fill data density and the calorific value of the mixed fuel as shown in Table 2. Data collection was repeated with variations of KFNE, CFNE, KFE and CFE fuels.The calorific value of the mixed fuel can be calculated using Equation 1.
The opening valve of load water flow rate is 1 cycle and data retrieval of engine performance was carried out on 2,000 rpm when the engine speed has stabilized.The data had been recorded for 5 data with 1 second intervals and it done for 3 repetitions.The engine performance parameters are obtained, those are torque, cranking power (bP) and specific fuel consumption (BSFC).
Emission measurements were operated by inserting the sensor probe into the exhaust gas engine, then waiting until the numbers on the Stargas 898 Analyzer's screen are constants.From the results of exhaust emission testing, obtained gas levels of CO, CO2, HC and O2 for the variations of the fuel mixture.

Furfural Yield Analysis
The yield of furfural in crude furfural product was examined on UV-Vis Spectrophotometry (Shimadzu UV-1800, Japan).Each sample with various concentrations were placed on the sample holder to measure how much a chemical substance absorbs light.The absorption of radiation by a sample is measured at a wavelength of 276 nm.
Theoretically the calculation of the maximum furfural wavelength of 276 nm can be calculated using Woodward Fieser rules.α,βunsaturated aldehydes is 207 nm, double bond extended conjugation is 30 nm, and homodiene compound is 39 nm.

Functional Group Analysis
The presence of furfural in the crude furfural product can be confirmed by using FTIR Spectroscopy based on functional group similarities with pure furfural standard and furfural IR spectra.Functional group analysis was carried out using FTIR spectroscopy (Agilent Cary 630 FTIR spectrometer, US) in the scanning ranges of 500-4000 cm -1 at room temperature.

Yield of Furfural in Product
The absorbance of commercial furfural solution at maximum wavelength of 276 nm was analyzed as a standard reference in order to analyzing the product.Figure 5 is furfural standard curve, a graph of correlation between absorbance of the standard solution and its concentration in solution.The yield of furfural in crude furfural product was calculated using equation y = 0.2047x+ 0.06 and it obtained concentration of furfural 2,129.946ppm (0.213%).

Functional Group of Crude Furfural and Commercial Furfural
The spectrum from crude furfural obtained from reaction using sulfuric acid catalyst at 95 o C were compared to spectrum using commercial furfural as standard.Furfural structure is mainly characterized by the presence of aldehyde group with C=O stretch, C─H stretch off C=O, as well as aromatic ring furan consisting of C=C─H asymmetric stretch (Ahmad et al. 2020).
Figure 7 shows the FTIR analysis for crude furfural product.The presence of peak at wavelength 1750-1625 cm -1 indicated the presence of O-H stretch (Mohamad, 2020).The peak at 1148 cm -1 could be attributed to the cyclic ethers C-O stretch (Nandiyanto, 2019).The absorbance of 1021,3 cm -1 located in spectral could be attributed to the stretching vibration of C-O (Zhuang, 2020).Spectral range of 872,2-842,4 cm -1 could be attributed to the C-H out of plane bending vibration from aromatic ring and their derivatives (Zhuang, 2020).In addition, there are various peaks in the liquid product which were not exhibited in the pure furfural standard.For example, the strong and broad absorption peaks observed at a range of 3450-3200 cm -1 indicated the presence of alcohol and phenolic groups in the crude furfural (Mohamad, 2020).The detail of the furfural spectrum and its characteristic wavelength is shown in Table 3.

Organoleptic Analysis
The organoleptic test in this study was based on vision to analyze the physical characteristics of fuel variations.Crude furfural based on cassava stem was mixed with uniform stirring into pertalite, but the blending was experienced problem.When crude furfural was mixed into a beaker glass containing pertalite, the crude furfural immediately settles at the bottom while pertalite is at the top.It caused by the density of crude furfural larger than pertalite and due to the impurity substances weren't purified during the purification process of synthetic furfural based on cassava stems.Figure 6 shows the discrepancy between commercial furfural and crude furfural based on cassava stem.
Pertalite and crude furfural didn't mix homogeneously, it formed two-phase mixture (heterogeneous mixture).So that, only a few particles of crude furfural which floated in pertalite that injected in the fuel tank to prevent the emerge of deposits and destruction on the engine.In testing fuel with crude furfural additives variation, the engine tends to be difficult to start and makes knocking sounds from the engine.While good additive properties in fuel have parameters quality that improve combustion quality, antiknocking and anti-denotation properties.The solubility of commercial furfural and crude furfural are different.Commercial furfural is less soluble in water but soluble in alcohol, ether, benzene and hydrocarbons compound.However, crude furfural tends to be completely soluble in water and alcohol.This is because the solvent and catalyst used in the hydrolysis process is H2SO4 2% with distilled water as the solvent.According to the law of solubility, polar compounds will in polar solvents and non-polar compounds will dissolve in non-polar solvents.
Based on the results of this experiment, it can be stated that crude furfural is a polar compound so it can be dissolved in polar solvents such as water.Crude furfural which has polar bonds and pertalite which has nonpolar bonds cannot bond because of the mismatch between the charges on the molecules (Wardiyah, 2016).Therefore, pertalite is hydrophobic or can't bind to water.Unlike pertalite, which is hydrophobic, commercial furfural is amphiphilic.Amphiphilic is a chemical compound that can bind water (hydrophilic) and fat (lipophilic).In addition, commercial furfural has a polar molecular bond, so it can mix and bind with water.However, the polar molecular bonds in commercial furfural are weak so that when commercial furfural mixed with pertalite fuel that has non-polar bonds, it can form a homogenous mixture for a long time.

Effect of Furfural Additives on Engine Performance
The effect of mixing furfural additives into pertalite was tested on engine performance, namely torque, cranking power (bP) and specific fuel consumption (BSFC).

Torque
Torque is a measuring value of a motor's ability to produce work.The effects of furfural additives in torque presented in Figure 8.The torque produced by commercial furfural additives with and without electromagnetic field induction (KFNE, and KFE) were lower than pure pertalite, the result decreased from 7.83 Nm to 6.745 Nm and 7.43 Nm respectively.The effect of crude furfural additives without electromagnetic field induction (CFNE) reduces the torque value into 7.055 Nm.However, the fuel with crude furfural additives and was treated by electromagnetic field (CFE), produces higher torque value from 7.83 Nm to 8.175 Nm.The addition of a magnetic field gives a stronger de-clustering effect on fuel (Siregar, 2007).

Cranking Power (bP)
Cranking power (bP) is a measure of the motor's ability to perform work resulting from engine rotation (torque).Figure 9 shows cranking power parameters produced by Kohler engine with commercial furfural additives (KFNE, and KFE) implies reduction in powers compared to pure pertalite.The result tends to reduce from 1636.87 W to 1423.165W (KFNE) and 1569.965W (KFE).In addition, the power generated by the engine is also decreased into 1479.2W by using crude furfural additives without electromagnetic field induction (CFNE).The crude furfural additives fuel treated by electromagnetic field (CFE) produced higher power, its resulted 1731.035W. Treatment of magnetic field to the fuel can increase the thermal efficiency of the engine (Hamdani et al., 2016).

Specific Fuel Consumption (BSFC)
Specific fuel consumption (BSFC) states the amount of fuel used for the electric power generated, or can be defined as a comparison of the mass flow consumption rate of the fuel used with the power generated by the engine.From Figure 10 it can be seen the Kohler engine consumed 0.375 kg/kWh fuel when used pertalite and fuel with crude furfural additive inducted by electromagnetic field (CFE).

Effect of Furfural Additives on Exhaust Emissions
The exhaust gas emissions in the form of CO, CO2, and HC are the reference for the exhaust gas quality on this experiment as presented in Figure 11.The CO gases released by engine from pure pertalite is still better than the variation of furfural additive fuel, with CO levels of 0.416 vol%.

Conclusion
This study aimed to applied furfural as fuel additives and treated electromagnetic field induction into fuel.Crude furfural yield of 0.213% was obtained from the synthesis of cassava stems.From the experiment, crude furfural additive and pertalite was formed twophase mixture (heterogeneous mixture), it might be due to the difference in polarity properties.The analysis based on torque and crank power performance, commercial furfural additives without electromagnetic field induction (KFNE) produced the lowest torque and crank power, while crude furfural additives fuel treated by electromagnetic field (CFE) produced the highest torque and crank power.Moreover, pertalite and fuel with crude furfural additive inducted by electromagnetic field (CFE) had the same amount of fuel consumptions and more efficient than other fuel variations.Pertalite released the lowest CO emission on exhaust gas emission testing.CFNE and KFE fuels released the same CO2 emission levels which the amount is better than other various fuel.The lowest HC emission was emitted by CFNE fuel.Besides that, the highest CO, CO2, and HC emissions was released by CFE fuel.

Figure 4 .
Figure 4. Engine performance test tool

Figure 7 .
Figure 7. FTIR analysis of commercial furfural and crude furfural product based on cassava stem at temperature reaction 95 o C.

Figure 8 .
Figure 8.Effect of furfural additives and induction of electromagnetic fields on torque performance.

Figure 9 .
Figure 9.Effect of furfural additives and induction of electromagnetic fields on cranking power performance.

Figure 10 .
Figure 10.Effect of furfural additives and induction of electromagnetic fields on specific fuel consumption.

Table 2 .
Density and calorific value of mixed fuel