Feasibility study of synthesized carbon as catalyst in biodiesel production

Abstract

Keywords: Carbon; Wood Biomass; Heterogeneous Catalyst; Biodiesel; Transesterification

Introduction

The requirement for sustainable catalyst during biodiesel production is at large. This drives many researchers in pursuing locally available materials for use as feed stock [1-3] and catalyst materials [4-7]. This is due to increased cost in biodiesel production due to usage of chemicals as catalyst materials. A study on biodiesel prepared by the process of transesterification for Rapeseed (RA) and Mahua (MU) biodiesel through equivalent volume of 1:1 is performed for 100% of RA, MU and dissimilar blends of rapeseed-mahua (RM) along with diesel. The results portrayed optimal performance for BL20 blends, and the results are closer to diesel. Similar emission characteristics are also observed for BL20 blend, such as reduction in carbon monoxide, hydrocarbons and smoke during full loading situations at 20.66%, 8.56% and 6.9% respectively, compared to diesel. The oxides of nitrogen are obtained to be slightly greater by 3.77% than diesel [8]. An investigation on transesterification of waste vegetable oil using eggshell as heterogeneous catalyst where the calcination of eggshells took place at 800°C in a furnace shows that the catalyst has large pore diameters of 92.1A and higher surface area of 30.7 m2/g. Optimization of various parameters was performed by central composite RSM (95% confidence level) and an optimum yield of 91% was obtained at operating factors of 65°C, 22.5:1, 5h 30min and

Materials And Methods

Sample Collection and Preparation Woodchips which are easily available in the market were collected from the locality of Imphal, India. Fig 1 shows the process of catalyst preparation from raw materials. The

Figure 1. Procedure of preparation of catalyst (C) derived from wood chips.

steps involve includes- drying of the woodchips in a microwave oven for about 1 hour ensuring no moisture is left within the sample. This is followed by pre-crushing of the chips into smaller size before carbonization for ease in fitting the samples inside the crucible in a muffle furnace. The samples are subjected to an elevated temperature of 400°C. The samples being kept at microwave oven, weighing and finally being kept at the crucible are shown in Fig 2. The samples after carbonization are then crushed using a mortar and pestle, shown in Fig 3. The samples are then kept tightly inside an airtight container. The transesterification was conducted using the synthesized catalyst using optimal conditions from Singh and Verma (2019) [2].

Figure 2. Wood chips placed inside microwave oven for drying, weighing and crucible inside a muffle furnace.

Sample Analysis and Characterization The diffracted patterns from the C samples are recorded using X-Ray Diffraction (XRD) instrument. Then from these data, Scherrer equation have been applied for calculation fo the grain size, the equation being shown in Eq. (1). The sizes of the grain for the different samples obtained after exposure at variations of temperature and exposure time are thereby tabulated in Table 1.

Scherrer constant, k = 0.9; Wavelength of X-ray, λ = 1.5406 Å for Cu-Kα = 0.15406 nm; β = Full width half maxima (radians); θ = Angle of diffraction (degree) The infrared spectroscopy was measured using PerkinElmer (Spectrum 2) FTIR spectrometer coupled

Figure 5. IR spectra for charcoal of wood chips after carbonization.

with LiTaO3 detector and Spectrum 10TM software. The SEM and EDX analysis were conducted using Nova Nano SEM attached with EDX analyzer.

Results And Discussion

Figure 4 shows the pattern results of X-ray diffraction for the charcoal of wood chips catalyst samples where TR13, TR14, TR16 and TR17 represents the samples Uningthou (400°C, 90 minutes), Yenthou (400°C, 90 minutes), Uningthou (400°C, 120 minutes) and Yenthou (400°C, 120 minutes). From the figure, it is observed that the pattern of XRD for the numerous samples demonstrates the diffraction peak at 28.61°, 28.54° and 30.02° corresponding to

Table 2. Elemental composition of Yenthou (400°C for 120 minutes) Sl. No.

(0 0 2), (1 0 0) and (1 0 1) of the face centered cubic phase respectively, which indicates the formation of carbon. This is coherent to findings of others research [17-19]. The crystal size, which have been calculated using above equation (1), is tabulated in Table 1. These findings will be corelated with the findings of FT-IR. The IR spectra of the samples are shown in Fig 5. Vibration of C = C bonds of carboxyl acids and the variations of the ketones of lignin & hemicellulose are observed at 1568 cm-1. The charcoal spectra at around 1600 cm-1 can be endorsed to the vibration of C = C groups of aromatic rings generally interrelated to the existence of lignin and also to the development of aromatic compounds instigated by the removal of hydrogen and oxygen of aliphatic compounds. This shown formation of good bonds during the process. The presence of a band at 1500 cm-1 (C=C) created due to uneven temperature distribution between 240°C & 380°C indicated the presence of an aromatic rings in the wood and charcoal obtained. This can also be attributed to the loss of oxygenated collections and thermal deprivation of this group in hemicellulose. It can be noted that the findings of FT-IR are well correlated with the findings specified in the x-ray diffraction spectrometer. The findings reported by other researchers in the similar area also concur with the present findings. The scanning electron microscopy image has been tested for Yenthou exposed at 400°C for 120 minutes since it displays the best possible formation of the catalyst amongst the samples tested. The morphology is shown in Fig 6. The

EDX analysis for the sample is also tested and is reported in Fig. 7 From the EDX analysis, the formation of carbon particles in the samples at high quality can be observed. The percentage composition of the sample, as detected by the EDX is shown in Table 2. A confirmation test using the synthesis catalyst for possible extraction of methyl esters from waste cooking oil has been conducted. The catalyst Yenthou exposed at 400°C for 120 minutes displays the best possible formation of the catalyst amongst the samples tested. An optimal parameter of 5% (wt.%) catalyst loading, 10:1, alcohol to oil ratio, 75°C reaction temperature and 60 minutes reaction time as reported by Singh and Verma (2019) [19] when employed for performing transesterification reaction. An inverted conical flask was employed for collecting the oil after the transesterification reaction. The transesterified oil was kept cooling in the flask for 3 hrs. Then the glycerol and esters were separated in the flask. The heavier glycerol was then removed using a stop cork. The experiments were conducted for five times to check for fluctuation in the results. A conversion rate of 87.4 ±1.3% has been observed. The catalyst showed good reusability up to 3 times.

Conclusion

The present study has been conducted in using carbon synthesized from wood biomass for possible use as catalyst during biofuel production. The following are important aspects of the present study: • The patters observed from XRD shows FCC phase corresponding to (0 0 2), (1 0 0) and (1 0 1) at 28.61°, 28.54° and 30.02° respectively. The average grain size of the samples was obtained to be 29.737 nm for the sample by using the Scherrer equation. • The FTIR analysis of the samples depicts formation of C=C bonds, which is attributed to presence of carboxyl acids, observed at 1568 cm-1, while peaks around 1600 cm-1 and 1500 cm-1 indicate presene of C=C due to aromatic rings. • The SEM & EDX analysis of the sample shows good formation of carbon in the catalyst and the weight % of the components are obtained to be 89.18% and 10.82% for C and O respectively. • Transesterification was conducted using the catalyst (yenthou, 400°C and 120 min) at waste cooking oil at 5% (wt%), 10:1, 75°C and 60 min for catalyst loading rate, alcohol-to-oil ratio, reaction temperature and reaction time respectively. • The methyl ester conversion rate was observed to be 87.4±1.3% with reusability of 3 times. The synthesized catalyst proved to be a potential source for use as catalyst during biodiesel production. Therefore, it can be a source of cheap and economically viable candidate for use as heterogeneous catalyst.

Nomenclature

Calcium oxide Energy dispersive x-ray spectroscopy Fatty acid methyl ester Free fatty acids Fourier transforms infra-red spectroscopy Full wave half maxima Potassium hydroxide Response surface methodology Scanning electron microscopy X-ray powder diffraction

Data Availability Statement

The authors confirm that the data that supports the findings of this study are available within the article. Raw data that support the finding of this study are available from the corresponding author, upon reasonable request.

Conflict Of Interest

The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethics

There are no ethical issues with the publication of this manuscript.

References

1. The article references can be accessed from the .pdf file.

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