Slow Catalytic Pyrolysis of Saccharum munja using Bio-genically Synthesized Nickel Ferrite Nanoparticles for the Production of high yield Biofuel

Slow Catalytic of Saccharum using Bio-genically Synthesized Nickel Ferrite Nanoparticles for the Production high In this study, the slow pyrolysis has been performed in a fixed bed reactor using Saccharum munja as raw biomass material and bio-genically synthesized nickel ferrite nanoparticles (NF-NPs) as a catalyst at an optimum temperature of 450 o C. In the absence of any catalyst, the obtained yield of bio-oil was 43.3 %. The maximum yield of bio-oil (72 %) was obtained with 0.4 g of NF-NPs. With 0.2g of ZSM-5, the obtained bio-oil yield was 44.5 %. The characterization of NF-NPs was studied by using UV-VIS analysis and Fourier Transform Infrared (FT-IR) spectroscopy. The characterization of Bio-char was done by using FT-IR a considerable increase in yield of bio-oil and bio-char in presence of [Ni-Fe 2 O 4 nanoparticles. that ferrite nanoparticles were an efficient catalyst for the pyrolysis of a comparison of NF-NPs ZSM-5 in the process of pyrolysis of Saccharum munja . It is the NF-NPs as catalyst high yield of bio-oil (55%) obtained while ZSM-5 (44.5%) bio-oil was obtained. Comparison of yields of bio-oil, bio-char and bio-gas by using 0.2g, 0.3g, 0.4g Ni-Fe 2 O 4 NPs (catalyst) Figure . It in the amount of the catalyst, the yield of bio-oil was increased. The bio-oil yield was increased from 55% to 65% and then to 72%. The increase in yield confirms that NF-NPs act as a highly efficient catalyst in the pyrolysis of Saccharum munja . The catalyst mainly increases the speed of reaction. Hence, in pyrolysis of Sacchrum munja without catalyst, the yield is low so ZSM-5 a catalyst was to increase the yield of bio-oil but the yield was only increased by 1-2%. Then another catalyst Nickel-Ferrite NPs was used in different amount which increased the yield of bio-oil very effectively. This concludes that nickel ferrite NPs acted as a more efficient catalyst than ZSM-5 for enhancing the yield of bio-oil. bio-oil, (72%)


INTRODUCTION
Nanoparticles are synthesized by various chemical means like co-precipitation or by green method etc. Kandpal et al., 2014). Nanoparticles have a vast variety of applications in different areas of medical science (Pasban Ziyarat et al., 2014), agriculture (Nair et al., 2010), water treatment (Farooqi et al., 2019), energy and transportation (Abedi et al. 2011). Green chemistry refers to the scheming of chemical products and their processes to eradicate or limit the usage and generation of harmful substances (Anastas & Eghbali 2010;. Green synthesis of metal nanoparticles mainly includes plants that possess alkaloids, phenols, terpenoids, and tannins. The plant also acts as a reducing and capping agent to convert the metal ions into the zero-valent state by reduction process to form stable metal nanoparticles (Din et al., 2019. Nanoparticles are an effective catalyst for the pyrolysis of biomass. Mostly metallic nanoparticles used are; nickel ferrite nanoparticles (NF-NPs). Nickel ferrite is used in sensors (Ahmed, 2017), microwave absorber (Che et al., 2006), nanowires and electrochromic coatings (Verma et al., 2006). The thermal breakdown of biomass in an inert environment (where oxygen is not present) in the presence of a catalyst, is known as catalytic pyrolysis. Its beginning temperature is 350-550 ºC and goes towards the high temperature of about 700-800 ºC (Fisher et al. ,2002). It also refers to the chemical bond's breakdown with the help of heat in a non-oxygen atmosphere. In the reaction of pyrolysis, large chains of hydrocarbons split into smaller pieces through de-polymerization, decarboxylation and aromatization reactions (Ferreira et al., 2020). The main benefit of the pyrolysis process is that it recycled waste material and gives valuable products (Scheirs & Kaminsky 2006). Pyrolysis is classified into slow (350-550 ºC), flash (650-1250 ºC) and fast (1050-1650 ºC) pyrolysis. In a slow pyrolysis process, the time of residence of vapors are large enough (5-30 min) that the components at this state quickly combine to produce solid as well as liquid materials. High residence time also affects the quality and amount of biofuel obtained (Tippayawong et al., 2008). In slow pyrolysis, the major by-product obtained is biochar (Tomczyk et al., 2020). The slow pyrolysis process takes more time (up to an hour) for completion as compared to flash and fast pyrolysis. The heating rate for slow, flash and fast pyrolysis is 0.2-1.1, 10-200, and greater than 1000 K/s. Furthermore, in flash pyrolysis maximum quantity of bio-oil (75%) attained. But flash pyrolysis has one major drawback of oil rusting due to poor temperature stability. In fast pyrolysis, the biomass size should be less than 2 mm and a high heating rate along with a short period for vapor stay (Jeong et al., 2020). Various important factors affect the process of pyrolysis such as alkali metal (Oasmaa et al., 2015), the temperature of biomass used in pyrolysis, amount of, size of the particle (Zhou et al., 2014), time of residence of vapors , pressure, and rate of heating (Montoya et al., 2017). With diverse biomasses, various types of catalysts are investigated (Nokkosmäki et al., 2000). ZSM-5, when used in pyrolysis reaction, helps in the refining of aromatic content but on the other hand, it reduces the yield of liquid (Zhang et al., 2013). But in the case of silica-alumina, the yield of char and gaseous products increases (Zabeti et al., 2012).
The most important catalyst used in pyrolysis includes Metal oxides or Zeolites. Metal oxides include Cu/Al2O3 (Chattopadhyay et al., 2009), ZnO , MgO (Pütün, 2010), MnO, CaO, CuO (Chen, 2003) were used in pyrolysis reaction. In Zeolites, ZSM-5 is very common, but HZSM-5 is also used (Foster et al., 2012). Among various biomasses, Saccharum munja usually termed as munj belongs to the grass family and mostly found in dry areas in Pakistan. Its extract has many benefits in the area of nanotechnology, medical science, and ecology. It helps in reduction of dyspraxia and heat burns (Rahar et al., 2010). It can be used as biomass for the production of bio-products (bio-fuel and bio-char).
In line with the biogenic synthesis of NPs, to the best of our knowledge, this is a novel study on the fabrication of NF-NPs using plant extract of Syzygium aromaticum (clove). The plant extract contains alkaloids, flavonoids, phenols and terpenoids which have a high ability to act as reducing and capping agents. Furthermore, the catalytic efficiency of bio-genically synthesized NF-NPs is studied by the slow pyrolysis of Saccharum munja. A catalyst increases the efficiency and yield of pyrolysis products as well as decrease the time of reaction. Saccharum munja is easily available, cost-effective, and has low moisture content so it can be used as a biomass in the pyrolysis process and gives energy which is of low cost. Characterization of plant assisted synthesis of NF-NPs has been studied with UV-VIS analysis and FT-IR technique. Characterization of obtained by-products bio-oil or biochar has been done by FT-IR.

EXPERIMENTAL Materials
Nickel nitrate hexahydrate (Ni(NO3)2.6H2O) (~97%) and Iron nitrate nonahydrate (Fe(NO3)3.9H2O) (≥98%) were bought from Sigma-Aldrich. These chemicals were of analytical grade hence they need no additional purification. Syzygium aromaticum (clove) was taken from the local market, Lahore, Pakistan. The Saccharum munja was collected as biomass feedstock from the city of Lahore in Punjab Province Pakistan. Prior to all the procedures the biomass was air-dried, grounded in a rotary cutting mil with a 2-6 mm particle size and then dried at 60 O C until constant weight attained.

Preparation of Plant Extract
Syzygium aromaticum (clove) was washed with distilled water for removal of impurities as shown in Figure 1a. Then it was dried in an oven for 2 hr for the removal of moisture and ground into a fine powder (Figure 1b). For the preparation of 5% extract, 5 g of clove powder was dissolved in 100 mL of de-ionized water. Then, it was placed on a hot plate at 70-80 O C for 15-20 min with constant magnetic stirring. The solution was then filtered by using Whatman's filter paper. The filtrate was stored at 40 O C in the refrigerator for further use (Figure 1c). Phytochemical analysis of clove extract was performed which shows that it can act as strong reducing as well as capping agent.

Synthesis of Ni-Fe2O4 Nanoparticles
Nanoparticles were prepared by microwave combustion method (MCM). For this purpose, 10 mL of 2% [Ni(NO3)2.6H2O] and 10 ml of 8% [Fe(NO3)3.9H2O] were added in 100 ml beaker. Then, they were stirred together for 1 hr. Then, 20 ml of Syzygium aromaticum (clove) extract was added in it and again stirred together for 30 min. The obtained solution was then poured in an autoclave and subjected to a microwave oven for 10 min. After that, the autoclave was placed in an oven at 200 O C for 24 hr. At last, the solution from autoclave was poured into a petri dish. 1 mL was taken for the UV-VIS analysis. The remaining solution was dried in an oven at 65 O C for 1-2 days. NF-NPs were prepared and stored in airtight sample bottles as shown in Figure 1d.

Pyrolysis Procedure
The process of pyrolysis was performed in a reactor which was made up of stainless steel and the type of reactor is a fixed-bed reactor as shown in Figure 2. In this process, 10 g of biomass (Saccharum munja) was taken in a pyrolysis reactor tube. After that, the inert gas nitrogen supply with a flow rate of 150 mL/min was provided in order to ensure oxygen-free environment. All the apparatus was tightly sealed by using Plaster of Paris or by a special type of tape. The output pipes had a connection with the sample gathering bottles as well as with the pyrolysis tube. The bottles were placed in chromatographic tanks having a certain amount of ice in them. Ice was used to lower the temperature and condense the vapors into liquid. In the first chromatographic tank, NaCl is added which allows the gathering of all the bio-oil in 1 st sample bottle. The heat supply was provided by setting the temperature of the pyrolysis reactor at 450 O C. Temperature raised at the rate of 10 o C/min. Hence, optimum conditions were provided to achieve maximum yield of pyrolysis by-products. The reaction was completed within 45-50 min. Bio-oil was collected from bottles and stored in sample bottles while bio-char was collected from the pyrolysis tube and kept in airtight packets. The same method was repeated with 0.2, 0.3, and 0.4 g of NF-NPs were added as a catalyst along with 10 g of Saccharum munja. Another experiment with 0.2 g of ZSM-5 catalyst was added along with 10 g of Saccharum munja (munj) in the reactor tube. Additionally, the percentage yield of products obtained can be calculated by applying formula; Yield of Bio − oil (%) = Weight of Bio oil Initial weight of Bio mass × 100 Yield of Biochar (%) = Weight of Bio char Initial weight of Bio mass × 100 Yield of Bio − gas (%) = 100 − (Yield of Bio − oil + Yield of BioChar)

Characterization
The Nickel ferrite (Ni-Fe2O4) nanoparticles prepared by the green method were characterized for their optical properties by using UV-VIS spectrophotometer (UVD-3500, Labomed Inc. USA Double beam and resolution of 0.1 nm). Ultraviolet-visible spectroscopy is a useful technique for the analysis of nanoparticle. It is the first step for the conformation of nanoparticles formation by analyzing the maximum peak of absorption and estimating conduction band oscillations in response to the electromagnetic radiations. UV-VIS analysis gives the results in the range of 200-800 nm. The Perkin Elmer, RX 1 FT-IR spectrophotometer was employed to scan the FT-IR pattern of nanoparticles as well as of bio-char. For this purpose prepared nanoparticles and biochar were separately taken in a sample bottle and then the spectrum was attained from 4000 to 650 cm -1 (near infra-red region) for defining structural moieties of biochar and nanoparticles (Maensiri et al., 2007).

UV-VIS Analysis of Nickel-Ferrite Nanoparticles
The production of NF-NPs by reducing metallic ions in the MCM method was verified by the UV-VIS spectroscopy. All the metallic nanoparticles have a specific color change which is depending upon their respective shape and size. The appearance of NF-NPs changed from black to reddish-brown. It has been observed that the characteristic band for NF-NPs developed in the range 300-420 nm due to the dispersion and absorption phenomenon of magnetic NF-NPs and it is in complete agreement with previous studies (Rodrigues et al., 2015). Here, NF-NPs provide a maximum absorption peak at 310 nm displayed in Figure 3. Stability, large yield and well-dispersity of nanoparticles are confirmed by the sharpness as well the intensity of the peak. No additional peak represents the purity of NF-NPs.

FT-IR Characterization of Nickel Ferrite NPs
For the identification of different functional groups in NF-NPs, FT-IR analysis was done as shown in Figure 4. Usually, metal oxides form absorption peaks in the fingerprint region normally less than 1000 cm -1 . These absorption bands are due to vibrations among different atomic levels. The peak formed at 3352.94 cm -1 is due to the symmetric vibration of a hydroxyl group. Meanwhile, the absorption band at 1038 cm -1 shows the bending vibrations of -OH group. A peak at 1573.97 cm -1 corresponds to the presence of C=C symmetric stretching. The peaks at 2889 and 1357 cm -1 are for stretching vibration of CH2. The absorption peaks at 597 cm -1 and 508.13 cm -1 represent the M-O in the nickel ferrite (Mohammed et al., 2020). Additionally, these two peaks represent the tetrahedral and octahedral structure of the positive ion of nickel ferrite (Kamnev & Ristić, 1997). Stretching of the CH3 group is shown by peak at 2851 cm -1 . The absorption bands of NF-NPs are correlated with the values given in the literature reported by Sivakumar et al. (2011). Figures 5 and 6 showed the FT-IR analysis of bio-char of Saccharum munja in the absence and presence of a catalyst. The visible band at 746, 1037, 1118, 1446, 1556, 2163 and 3146 cm -1 indicates the present content of organic residues i.e. C-C aromatic bending in fatty acid, lignin and polysaccharides, hydroxyl group and polymeric CH3 group, respectively. A band at 747 cm -1 indicates C-H aromatic bending which indicates the presence of aromatic in synthesized biochar. Absorption bands at 1038 and 1446 cm -1 represent the C-O stretching vibrations which correspond to the presence of ketones, alcohol, phenols, and esters. The absorbance peak at 1556 cm -1 shows the possibility of stretching vibration of the C=C group due to the presence of lignin. Similar results have been reported by Kumar et al. (2017). C=C bending vibration is indicated by 2165 cm -1 .   Figure 7 displayed the slow Pyrolysis of Saccharum munja without a catalyst. In the absence catalyst, the by-products obtained at 450 O C are bio-oil (43.3%), bio-char (27.5%) and bio-gas (29.2%). While by-products obtained in the presence of 0.2g NF-NPs are bio-oil (55%), bio-char (28.2%) and bio-gas (16.8%) as shown in Figure 8a. Slow catalytic pyrolysis of Saccharum munja with 0.3g NF-NPs gave bio-oil (65%), bio-char (24.90%) and bio-gas (10.10%) at 450 O C (Figure 8b). By pyrolysis of Saccharum munja, the byproducts obtained which is bio-oil (72%), bio-char (22.70%) and bio-gas (5.30%) at 450 O C by using 0.4g of NF-NPs (Figure 8c). Additionally, in the presence of 0.2g of ZSM-5 the by-products were obtained are bio-oil (44.5%), bio-char (26.3%) and bio-gas (29.2%) at 450 O C (Figure 8d).  A comparison of yields in the presence of various catalysts provides feasibility to find a better catalyst. Figure 9a showed that there was a considerable increase in yield of bio-oil and bio-char in presence of  nanoparticles. This proved that nickel ferrite nanoparticles were an efficient catalyst for the pyrolysis of biomass. Meanwhile, Figure 9b shows a comparison of NF-NPs and ZSM-5 in the process of pyrolysis of Saccharum munja. It is confirmed from the figure that by using NF-NPs as catalyst high yield of bio-oil (55%) was obtained while with ZSM-5 (44.5%) bio-oil was obtained. Comparison of yields of bio-oil, bio-char and bio-gas by using 0.2g, 0.3g, 0.4g Ni-Fe2O4 NPs (catalyst) has been displayed in Figure 9c. It had been shown from the graph that, by an increase in the amount of the catalyst, the yield of bio-oil was increased. The bio-oil yield was increased from 55% to 65% and then to 72%. The increase in yield confirms that NF-NPs act as a highly efficient catalyst in the pyrolysis of Saccharum munja. The catalyst mainly increases the speed of reaction. Hence, in pyrolysis of Sacchrum munja without catalyst, the yield is low so ZSM-5 as a catalyst was used to increase the yield of bio-oil but the yield was only increased by 1-2%. Then another catalyst Nickel-Ferrite NPs was used in different amount which increased the yield of bio-oil very effectively. This concludes that nickel ferrite NPs acted as a more efficient catalyst than ZSM-5 for enhancing the yield of bio-oil.
According to the experimental reports and pervious literature, the chemical reaction pyrolysis action of nanoparticles was suggested.

Lignin → Phenols → Coke
Equation 1-4 showed that during catalytic pyrolysis the biomass component cellulose depolymerized into anhydrosugars (Zheng et al., 2019). The anhydrosugars after dehydration, decarboxylation, and decarbonylation converted into furans which diffuse into channels of NF-NPs catalyst undergo oligomerization to form hydrocarbon pool and coke product obtained. Lignin and hemicellulose after thermal breakdown depolymerized into phenol, pyrans, and furans respectively. The phenol, pyrans or furans diffuse into pores of NF-NPs catalyst which after dehydration or condensation converted into coke.

CONCLUSION
Biogenically synthesized highly efficient NF-NPs were used for the efficient conversion of biomass thermo-chemically. Saccharum munja (munj) possesses excellent characteristics to be used as biomass in slow catalytic pyrolysis for the production of bioenergy. As a waste, munj is highly cost-effective for the production of bio-oil, bio-char, and bio-gas, as well as it comprises less dangerous effects on the environment. Pyrolysis of Saccharum munja was carried out without any catalyst which gives a yield of by-products as bio-oil (43.3%), bio-char (27.50%) and bio-gas (29.20%). The same reaction was performed with 0.2g of NF-NPs as a catalyst, which gives bio-oil (55%), bio-char (28.20%) and bio-gas (16.80%). With 0.3g catalyst (65%) bio-oil, (24.90%) bio-char and (10.10%) bio-gas was obtained. With 0.4g catalyst (72%) bio-oil was obtained. The amount of catalyst has a considerable effect on bio-oil yield. It increases from 43.3% to 55% then 65% and finally to 72%. All the reactions were carried out at 450 O C . An additional reaction was carried out with 0.2g ZSM-5 which gives (44.5%) bio-oil yield. It shows that NF-NPs are more efficient catalyst than ZSM-5 for pyrolysis of Saccharum munja. The maximum yield of bio-oil (72%) was obtained with a 0.4g catalyst. FT-IR characterization of bio-char was performed for the analysis of the functional group.