High Performance Alternative Diesel Engine Fuel using Modified Rice Straw Catalyst

Background: The world depends almost on fossil fuels. This leads to depletion of oil and an increase in environmental pollution. Therefore, the researchers search to find alternative fuels. Waste cooking oil (WCO) was selected as feedstock for biodiesel production to eliminates the pollution problems. The agricultural waste is very big and without cost, this leads to the use of the rice straw in preparing a catalyst for biodiesel production. Results: The reusability of the acidic catalyst confirmed that the conversion efficiency was high until after 8 cycles of the production. The highest conversion efficiency of the converting WCO extended to 90.38% with 92.5% maximum mass yield and methyl ester content 97.7% wt. at the optimized conditions. The result was indicating that B15 is the best blend for thermal efficiency and specific fuel consumption. All emission concentrations decrease with increasing the engine load, especially for B15 fuels compared to the diesel oil. Conclusion: The novelty of this paper is assessing the methyl esters from the local WCO as an alternative fuel for diesel engines using a heterogeneous catalyst based on the agricultural waste. The performance of the diesel engines and its exhaust emissions have been experimentally investigated with the produced biodiesel of WCO as a blend (B10, B15, and B20) compared to the diesel.


Background
The world needs energy sources that are environmentally friendly and alternative as biofuels to significantly depleted energy sources due to their great importance in our daily life and to reduce environmental pollution resulting from fossil fuels. Biodiesel is an unconventional fuel with environmental values. Biodiesel has several properties that make it attractive as a substitute for diesel fuels. It is characterized as an oxygenated, low emission, free sulfur, nontoxic and biodegradable compare to fuels (petroleum) [1]. It is a liquid transportation fuel which performed from renewable material like WCO. The use of WCO reduced the biodiesel production price, where its cost is less than virgin oils three times since it is renewable in nature and low value [2][3]. Gas emissions are a serious problem with pollution. Besides the biodiesel saves about 90th tons of the energy used compared to the energy consumed by the traditional fuel [3][4][5]. Biodiesel mixed with the diesel fuel in various proportions to be suitable for the compression ignition engine and no required for any modifications to be done to the engine. Various catalyst types are utilized in the transesterification method of the edible oils into the fatty acid methyl Esters (FAMEs). These catalysts are experimentally established and are well documented within the open literature. Despite the effectiveness of the uniform acid catalyst, it will cause absolute contamination issues that will need good separation and product purification processes. This might result in a higher cost. Free fatty acid (FFA) contents are not affected by the heterogeneous acid catalyst that considers the benefits of using this catalyst, especially for equivalent time conduct of esterification and transesterification process, no need for the more washing step of biodiesel and less complicated separation methods of the catalyst [6] [7]. The disposal of agricultural waste needs more financial or environmental costs. That means it is important to convert agricultural waste into useful materials to reduce its effect on the environment. One of these useful materials is the production of a useful catalyst [8][9][10]. our work is interesting in the protection of the environment from the pollution caused by agricultural waste and diesel engine emissions. Also, to reduce the rate of petroleum resources. It is done by the biodiesel production from the harmful environmental waste and assesses the likelihood of applying this biodiesel as an alternative fuel to the diesel engine. It is performed by the comparison between the efficiency of the performance parameters and the exhaust gas emissions on diesel fuel.

Catalyst characterization
The polycyclic aromatic sulfonate catalyst structure (RS-SO 3 H) was confirmed through the

Biodiesel production
From the equations (1) and (2) and the Gas Chromatograph technique in Table (1), the highest conversion efficiency% of converting WCO into biodiesel extended to 90.38 % with 92.5% maximum mass yield % and 97.7% wt. methyl ester content at the optimized conditions (50 g oil used at 70 °C and methanol: oil molar ratio (20: 1) at 10 %wt. catalyst at for 6 h). The aspen plus program was used in the description of the biodiesel production process starting from catalyst synthesis and depended on the lab scale as shown in (figures 3,4). Figure (3) described the heterogeneous catalyst synthesis process, while figure (4) shows the process scheme commencing with the biodiesel synthesis and followed by the downstream processing steps to obtain the pure biodiesel and glycerol products. Table (2) shows the feed and product material flow details for the process. The reusability of the acidic catalyst was studied at the optimized condition where the conversion efficiency% decreased from 90.37 to 88.56% after 8 cycles as discussed in detail in our work [10].

Fuel sample characterization
The properties of the pure biodiesel prepared (B100), the commercial diesel fuel (D100), and the ASTM standards biodiesel D6751 are given in the table (3). Pour point ºC Acid value (mg KOH/gm biodiesel) It is explained that the diesel oil viscosity is lower than the biodiesel fuel. The biodiesel density is around 6.09% greater than the diesel oil. The heating value is nearly 14% lower than the diesel oil. Therefore, it is essential to extend the injected fuel quantity into the combustion chamber to supply the same quantity of power. Fuels having flash point exceeding 63°C are considered nonviolent. Thus, biodiesel with a high flash point (90 o C) is a very secure fuel to handle and storage. The flashpoint biodiesel blends (B10, B15, B20) is much above than the diesel oil which makes the biodiesel a desirable choice as concerns safety. The WCO methyl ester can be utilized as elegant diesel fuel in the cold weather because of its high pour point according to the diesel oil [11].

Performance of the diesel engine fueled by the biodiesel blends
Performing the diesel engine has been experimentally examined with the produced methyl esters of WCO as biodiesel blend (B10, B15, and B20) compared to the diesel oil. Engine performance parameters such as the thermal efficiency, specific fuel consumption, air-fuel ratio, and the exhaust gas temperature were assessed for several engine loading conditions and at 1500 rpm steady rotation speed.

 Specific fuel consumption
The brake specific fuel consumption is expressed as the proportion of mass fuel consumption to brake power. Figure (5) pointed out the Variant of specific fuel consumption at several loads for the WCO biodiesel blends (B10, B15, and B20) and diesel oil. the specific fuel consumption decreases with a rise in load because of an increase in fuel consumption [4][5] [12]. B15 is that the best blend comparing with the other proportions due to most investigators agree that a small increase in the biodiesel fuel is required by the engine to achieve the identical output power as a compensation for the lower calorific value of the biodiesel.   The exhaust gas temperature at several engine loads for the biodiesel blended (B10, B15, B20, and D100) is given in Figure (7). Decreasing the exhaust gas temperature refers to high thermal efficiency. The exhaust gas temperature increases by the rise of the load. This increase could also be because of the higher temperature interior of the engine chamber which makes more fuel burning to satisfy the higher load needs. Relating to fossil diesel, the exhaust gas higher temperatures are recorded for the biodiesel blends for all engine loads.
B20 is that the best blend comparing with the other proportions at the different loads [14][15] [16].  the load for tested fuels and increases for the biodiesel blend proportions. B20 is the best one which has high efficiency comparing with the other blends. Since the diesel oil has a lower exhaust temperature, so, the volumetric efficiency is high [17] 18] [19].

Figure (8) Effect of engine brake power on volumetric efficiency for different engine loads
for biodiesel blended (B10, B15, B20 and D100).

 Air-Fuel ratio
The Impacts of air-fuel ratio for different engine loads for the biodiesel blended (B10, B15, B20, and D100) are noted in Figure (9). Comparing with the diesel fuel (D100), the Air-fuel ratio for B10 is approximately the best blends otherwise the other blends as a result of the complete combustion [20][21] [22].

Figure (9)
Effect of engine brake power on air-fuel ratio for different engine loads for biodiesel blended (B10, B15, B20 and D100).

Exhaust emissions and oxygen concentration
The exhaust emissions of the diesel engine been experimentally investigated with the produced WCO methyl esters as biodiesel blends (B10, B15, and B20) compared to the diesel oil. The engine emissions like CO 2 , CO, HC, and the oxygen concentration were measured at the engine various loading conditions and a constant rotation speed of 1500 rpm.

 CO 2 emissions
The variance of CO 2 emissions with the engine load for the biodiesel blended proportions (B10, B15, B20, and D100) is shown in Figure (10). The increases in engine load increase CO 2 emissions due to the greater fuel entry during the load increasing. CO 2 emissions from B15 are lower than B10, B20, and the diesel fuel [23] [24].

 Oxygen concentration
The effect of the oxygen concentration with the engine load for the biodiesel blended (B10, B15, B20, and D100) is indicated in a figure (13). The O 2 content decrease in the exhaust gas with the increase in load because of the fuller mixture being burnt interior the engine chamber. The higher exhaust temperature leads to the largest portion of the oxygen available in the cylinder to be additionally reacting with the carbon to form CO and CO 2 at the higher loads. Therefore, a lesser amount of O 2 is liberated into the atmosphere. B20 is the best blend, in this case, comparing to the other blends and the diesel fuel [28][29] [30].

Figure (13) Effect of engine brake power on O 2 Emission for biodiesel blended proportions
(B10, B15, B20 and D100).  2) The specific fuel consumption decreases as well as the engine load increases. B15 is the best blend comparing with the other proportions due to the slight increase in the biodiesel fuel needed by the engine to accomplish the same output power as recompense.

Comparison between (diesel-biodiesel) blends (b10, b15, b20) for diesel engine exhaust emissions
3) Increasing the engine loads causes increasing in thermal efficiency. Thermal efficiency increased for B15 compared to the other blend proportion because of its calorific value is closer than the diesel fuel.
4) The volumetric efficiency reduces with the rise of loads for tested fuels and increases for the biodiesel blend proportions. B20 is the best one which has high efficiency comparing with the other blends.
5) The increase in the exhaust gas temperature is due to the increase in the loads. Elevated exhaust gas temperatures are noted for the biodiesel blends related to the fossil diesel for the engine loads. B20 is the best blend comparing with the other proportions at the different loads.

Catalyst Synthesis
As point out in our previous literature study [10], the novel catalyst of the polycyclic aromatic sulfonates RS-SO3H was created from the agricultural waste (rice straw). The chemical process was described in the chemical reaction equation in figure (14). First, it was prepared from the fast pyrolysis for the Egyptian rice straw at the conditions of temperature at 510 ± 5 ºC for 8 ± 2 sec. The resulting brown, black matter was ground to a powder. A 10 gm was sulfonated with 100 ml 95% sulfuric acid for 15 h at 150 ºC. After cooling, the prepared catalyst was washed by using the hot distilled water to remove the excess of the sulfonate ions. Finally, the prepared catalyst was dried at the temperature of 80 ºC for 24 h in an electrical oven [31].

Figure (14)
The chemical process equation of the prepared catalyst.

Biodiesel production
As point out, the organic residue of WCO was removed by the settling and filtration process through the fiber filter. The filtrate was dried at 90°C in the electrical oven. As discussed in detail in our previous literature report [10], the transesterification process was carried under the different conditions of the temperature, time, the catalyst concentrations, and the molar ratio between solvent (methanol) and WCO to get the highest conversion efficiency % of changing raw material with the maximum mass yield (%) of the acidic methyl ester (biodiesel).
The maximum mass yield% of the biodiesel produced was calculated at the optimized conditions as discussed in our previous work from the equation (4)

Biodiesel fuel for diesel engine
The present investigation measures the performance and the exhaust emissions of the diesel engine using biodiesel prepared. The tests were conducted by using diesel fuel as an origin line data. The biodiesel prepared was burned in a diesel engine at different load conditions in steps of 25%. The results achieved from the experimental investigations are used to study the performance parameters and the exhaust emissions [11].  Check out all the measuring instruments and make sure of zero reading adjustments.

Experimental test procedure
 Run the engine.
 Warm up the engine for 15 minutes under no load condition using diesel fuel.
 Wait a period for the engine to reach steady state operation conditions.