Mohammad Saleem Khan

Conversion of Mixed Low-Density Polyethylene Wastes into Liquid Fuel by Novel CaO/SiO2 Catalyst Mohammad Saleem Khan, Inamullah, Mohammad Sohail & Noor Saeed Khattak Journal of Polymers and the Environment formerly: `Journal of Environmental Polymer Degradation' ISSN- J Polym Environ DOI 10.1007/s- 1 23 Your article is protected by copyright and all rights are held exclusively by Springer Science +Business Media New York. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com”. 1 23 Author's personal copy J Polym Environ DOI 10.1007/s- ORIGINAL PAPER Conversion of Mixed Low-Density Polyethylene Wastes into Liquid Fuel by Novel CaO/SiO2 Catalyst Mohammad Saleem Khan1 • Inamullah1 • Mohammad Sohail1 • Noor Saeed Khattak1 Ó Springer Science+Business Media New York 2016 Abstract Plastic wastes disposal can be done by various methods such as landfill, incineration, mechanical and chemical recycling but these are restricted due to some environmental, economic and political problems. Conversion of these plastic wastes into valuable products by degradation is the best option. In the present work waste low density polyethylene was degraded by catalytic process using CaO/SiO2 as mixed catalyst. The conditions for catalytic degradation were optimized for the production of maximum liquid fuel. It was found that the yield of liquid product was up to 69.10 wt% at optimum condition of temperature (350 °C), time (90 min) and catalyst feed ratio (1:0.4). Liquid fuels obtained from the catalytic degradation were further separated into various fractions by fractional distillation. Composition of liquid fuels was analyzed by FTIR spectroscopy, which showed that the liquid fuels mostly consist of paraffinic and naphthenic hydrocarbons. Different fuel properties such as density, specific gravity, American petroleum institute gravity (API gravity), viscosity, kinematic viscosity, refractive index, refractive intercept and flash point of both the parents and various fractional fuels were determined. All the properties of the obtained fuels are in close agreement with the fuel properties of gasoline, kerosene and diesel. It was found that our catalyst is very much efficient in terms of time, degradation temperature and amount of catalyst. Keywords LDPE Fractional distillation FTIR Paraffinic Naphthenic hydrocarbons & Mohammad Saleem Khan-1 National Centre of Excellence in Physical Chemistry, University of Peshawar, Peshawar, KPK 25120, Pakistan Introduction In the modern era, plastics play a vital role in our daily life activities due to the fact that plastic is lightweight, nonbiodegradable and of low cost. Worldwide plastic production has been growing as these materials are replacing glass and metal. Today, an average person living in Western Europe or North America consumes 100 kilograms of plastic each year, mostly in the form of packaging. Asia uses just 20 kilograms per capita, but this figure is expected to grow rapidly as economies in the region expand. The total global production of plastics has increased from around 1.3 million metric tons (MT) in 1950 to 299 million MT in 2013, which show a very high rise in its production [1]. During 2013, Europe produced about 20 % plastic out of the total production (299MT) of the world while China is among the top with 24.8 % of the total production [2]. Statistical data for Western Europe to the consumption of plastic products 98 kg per capita for 2003 and 64 kg per capita for 1993 [3]. In USA the % age of municipal plastic wastes (MPW) has been increased from 8 wt% in 2000 to 13 wt% in 2013 [4]. These materials are mainly composed of thermoplastic materials i.e., polyolefin, low density polyethylene (LDPE17 %), high density polyethylene (HDPE-11 %), polypropylene (PP 16 %) and the remaining are thermosets [3]. The disposal of these product to the environment is getting reduced due to strict legislations, it is hoped that it will be reduced up to 35 % in 2020 [5, 6]. Severe environmental problems are associated with the extensive use of these plastic materials due to their nonbiodegradable nature [7–9]. Killing rate of aquatic organisms in the ocean concerned with the mistake of plastic for food is about one million per year. During the years 1988 and 1998, Bangladesh was devastated due to severe 123 Author's personal copy J Polym Environ flooding caused by the plastic bags which blocked sewers and drains, and thus they were banned completely in 2002 [10]. Several methods are used for the disposal of plastic wastes i.e., land filling, incineration, mechanical and chemical recycling [6, 11–13]. However, some serious problems are associated with most of these techniques for example land filling is quite expensive, causes environmental pollution and also require huge space, while incineration is not acceptable because it releases gases and soot particles to the environment [14, 15]. Mechanical recycling has also been tested on a variety of plastic wastes but the recycled materials are generally of low quality and having less marketed value [16]. In addition to the above mentioned problems associated with the forgoing discussed methods of recycling; most countries of the world are facing the crisis of energy and fossil fuels. Production rate of petroleum in the whole world is 26 billion barrels per year which is small as compared to the consumption rate of petroleum which is close to 30 billion barrel per year. Due to the economic situation or limited resources, most countries of the world cannot produce their own fuels. They import most of their fuels from other countries, which create major oscillation in their economy. Furthermore, from the combustion of these fuels, various hazardous and greenhouse gases are released into the atmosphere [11]. To address the above mentioned problems, some efforts were made by different researchers to convert the waste plastics by chemical recycling into fuels. Miskolczi et al. [17] carried out the thermal degradation of different mixtures of the waste polymers in a horizontal tube reactor. It was found that the operating parameters like temperature and residence time had a considerable effect on the yield of the product, whereas the chemical structure of waste polymer also had a considerable effect on the properties of the products. Catalytic degradation of waste plastics (LDPE) was carried out by Shah et al. [18] in a laboratory scale batch reactor using different catalysts such as silica, alumina, calcium carbide, magnesium oxide, zinc oxide and homogeneous mixture of silica and alumina. They found that CaC2 and SiO2 are the best catalysts for the degradation of LDPE in terms of reaction time and liquid volume respectively. Sivakumar and Anbarasu [19] used a stainless steel reactor for the cracking of LDPE applying NiMo/Al2O3 catalyst and investigated the effect of catalyst on the liquid yield, gaseous fraction and residue. Shah et al. [20] carried out the degradation of LDPE using lead sulfide as a catalyst and investigated the effects of different reaction conditions like temperature, time and amount of catalyst on the amount and composition of the derived gas, oil and wax. Osueke and Ofondu [21] used silica-alumina 123 for the catalytic pyrolysis of LDPE, thus yielded intense liquid hydrocarbons for the catalyst to waste ratio of 1:4 at a temperature of about 550 °C. Jan et al. [22] catalytically degraded high density polyethylene (HDPE) using MgCO3 as a catalyst and investigated the effects of different parameters like temperature, time and catalyst ratio on the yield of liquid product. Mabood et al. [11] carried out the catalytic degradation of LDPE using CaC2 as a catalyst while investigating the effect of temperature, time and amount of catalyst on the yield of the degradation products. Biodegradation by microorganism is another option but, different parameters like 3-dimensional structure, high molecular weight, hydrophobicity and absence of functional groups in the LDPE obstruct microbial attack. Biochemical process involved in the degradation or conversion of LDPE to liquid fuel is expensive method as compared to other processes (thermal or catalytic), because biochemical process required bio-extraction from plants or microorganism which requires much more time and cost. The present work has been done on pyrolysis of LDPE using novel mixed catalyst i.e., CaO/SiO2 prepared in our lab. Products obtained from the degradation processes were analyzed and compared with standard values for Petrol, Kerosene and Diesel. Up to the best of our knowledge, mixed catalyst CaO/SiO2 has not been reported for such studies so it will open a new opportunity for such studies and waste management of LDPE. Experimental Materials Waste plastics (LDPE) were collected from the Peshawar University campus and town areas of Peshawar city (Pakistan). The waste plastics were washed with liquid soap and then dried at room temperature and atmosphere. For achieving large surface area, waste plastics were cut into small pieces with the help of scissor. Equal molar mixture of analytical grade reagents Calcium oxide (Merck) and Silicon dioxide (Scharlau) was used as a catalyst. Methods Thermogravimetric Study Thermogravimetric analysis of the waste plastics (LDPE) was carried out by using Perkin Elmer Diamond TG/DTA (USA). During analysis temperature was increased from 40 up to 1000 °C at the rate of 20 °C/min. The sample temperature was measured with a thermocouple directly at the crucible very close to the sample. Author's personal copy J Polym Environ Procedure of Catalytic Degradation 10 grams of the waste plastic LDPE along with a fixed amount of catalyst CaO/SiO2 (1:1 molar ratio) was fed into the 50 mL round bottom (RB) flask heated by a heating mantle. A temperature sensor was immersed inside the RB flask in order to maintain a constant temperature inside the reactor. The RB flask was connected with the water condenser through the distillation head. The condenser was in turn connected with the adapter which allowed the condensed liquid oil to pass into a pre weighed receiving flask. The whole reaction assembly was supported by an iron stand and was made air tight to avoid any gas or vapor loss. The weight of liquid product was measured from the weight difference between flask with liquid oil and empty flask. Similarly the weight of solid residue was determined from the weight difference between RB flask with residue and empty RB flask. The weight of gaseous products was calculated from the mass balance between the waste plastic (LDPE) and liquid oil and residue. The mass percentage of product composition was then determined by using the following formula given below. % Conversion ¼ðmass of LDPE mass of residue Þ =ðmass of LDPEÞ 100 ð1Þ % Oil ¼ ðmass of oilÞ=ðmass of LDPEÞ 100 ð2Þ % of residue ¼ ðmass of residueÞ=ðmass of LDPEÞ 100 ð3Þ % of Gas = % Conversion % Oil ð4Þ Optimization Study of Different Parameters for Catalytic Degradation of Waste Plastic (LDPE) 120 Weight (%) - Separation of Derived Oils into Various Fractions by Fractional Distillation Process Oil obtained during catalytic degradation of waste plastic LDPE was separated into five fractions by fractional distillation process at various temperature ranging from 20 to 300 °C. Characterization of the Liquid Products FT-IR Analysis FT-IR analysis of liquid samples was carried out by using Shimadzu IR Prestige-21 instrument, which showed the different functional groups present in the liquid oils samples. Fuel Properties Different fuel properties such as density, specific gravity, API gravity, refractive index, refractive intercept, refractive index parameter, viscosity, kinematic viscosity and flash point were investigated. 120 L. wt% S. wt% G. wt% T. conv. wt% - 40 0 20 0 Catalyst Weight Optimization The effect of catalyst weight on the degradation of waste plastic LDPE was studied in the range of 0–5 grams of catalyst (CaO/SiO2) for 10 grams of LDPE sample at optimum temperature and one hour reaction time. % Conversion Temperature Optimization Ten grams of the waste plastic LDPE sample along with 2 grams catalyst was pyrolysed for 60 min at different temperatures i.e., 250, 300, 350 and 400 °C. Based on the maximum conversion into liquid oil, the temperature for catalytic degradation was optimized. Heating Time Optimization The effect of heating time on the catalytic degradation of waste plastic LDPE sample was investigated in the range of 30–120 min time at the optimum conditions of temperature and catalyst weight. 0 200 400 600 Temperature 800 1000 (oC) Fig. 1 TGA curve of waste low density polyethylene 1200 230 280 330 Temperature [oC] 380 430 Fig. 2 Temperature optimization for catalytic degradation of waste plastic LDPE. Conditions: Weight of LDPE sample = 10 g, Temp Temperature, Heating time = 60 min, L liquid, S solid, G gas, T. Conv. Total conversion into liquid and gas, Wt% weight percent 123 Author's personal copy J Polym Environ 25 mL specific gravity bottle was used to investigate density and specific gravity of liquid oil. The pre-weighed bottle was filled from the sample oil up to the mark and then its final weight was taken. The difference between the final and initial weights gave the weight of liquid oil. Then density of the sample was measured using the following formula, G. wt% ð5Þ API gravity of liquid oil was calculated by the formula given below. API gravity ¼ 141:5=ðspecific gravityÞ 131:5 I¼ n2 1 n2 þ 2 ð7Þ Refractive intercept of liquid oil was calculated by the formula given below. RI ¼ n d 2 ð8Þ d = density. Formula used for the calculation of specific refraction (Rs) is. Rs ¼ n2 1 1 n2 þ 2 d ð9Þ Ostwald capillary tube viscometer was used to find out the viscosity of liquid oil. Kinematic viscosity of liquid oil was calculated by using the following formula. m ¼ g=d ð10Þ 120 L. wt% S. wt% G. wt% % Conversion 100 80 T. conv. wt% - ð6Þ Refractive index (n) of liquid oil was determined by using refractometer (ATAGO no 11274, Japan). Refractive index parameter (I) of liquid oil was determined by using the following formula. S. wt% 80 % Conversion Density ðd Þ ¼ mass=volume L. wt% 100 0 0.1 0.2 0.3 0.4 Catalyst feed ratio 0.5 0.6 Fig. 4 Catalyst weight optimization for catalytic degradation of waste plastic LDPE Flash point of liquid oil was determined by using closed cup Pensky-Martens flash point (MKIV Series, made in England) apparatus. Results and Discussion Thermogravimetric Study of Waste LDPE TGA was carried out to determine the variation of weight with respect to temperature as shown in Fig. 1. It is clear from the curve that the weight change begins at about 180 °C and ends at about 525 °C. At 525 °C 96 % of the weight change occurs after which no change in the weight was observed up to 1000 °C. It shows the presence of about 4 % of the residue, which consist of carbonized substances formed during the degradation of waste LDPE. KyongHwan Leea et al. [23] also reported similar results for waste LDPE. The maximum weight loss at around 430 °C is due to the volatization process. Many side reactions such as isomerization, polycondensation and cracking of side chain from aromatic rings also take place [18, 24–28]. 60 Table 1 Fractional distillation study of oil obtained by catalytic degradation of LDPE 40 S. No Sample Temperature °C Wt% of each fraction 20 1 B1 20–100 13.00 2 B2 100–150 10.82 3 B3 150–200 13.87 4 B4 200–250 19.52 5 B5 250–280 22.60 6 B6 C280 19.30 0 20 50 80 Time [min] 110 140 Fig. 3 Heating time optimization for catalytic degradation of waste plastic LDPE 123 Author's personal copy J Polym Environ Degradation Mechanism of Polyethylene temperature for the catalytic degradation of LDPE has also been reported [18]. Degradation mechanism of Polyethylene depends upon method which is used. Thermal degradation is cost and time effective but here in the project approach was made to covert LDPE to liquid fuel by low temperature using catalyst. So this is a kind of catalytic thermal degradation. The use of catalyst further reduces time and so much more economical. In fact our catalyst has shown efficient results when compared to other catalyst. Nisar et al. has shown catalytic degradation temperature of LDPE using Alumina acidic catalyst and the degradation temperature reduction they obtained was 460 °C with 20 wt% of acidic Alumina catalyst [29] while our catalyst has the max. degradation temperature at 430 °C. It shows our catalyst is more efficient. The radical chain mechanism scheme given by Bockhorn et al. [30] for thermal degradation of LDPE seems to be valid here in our case because the FTIR studies of ours prove the formation of paraffin and olefins from our samples (see Tables 5, 6). Optimization Study of Different Parameters for Catalytic Degradation of Waste Plastic (LDPE) Temperature Optimization LDPE sample was catalytically decomposed at different temperatures by using a fixed amount of CaO/SiO2 as mixed catalyst. The results are summarized in Fig. 2. It can be seen from these results that the highest quantity i.e., 33.8 wt% of liquid product was obtained at 350 °C. A decrease in the yield of liquid products was observed beyond this temperature, which may be due to further conversion of liquid fraction into gaseous products leading to higher fraction of gases and decrease in liquid oil fraction. The purpose of temperature optimization was to investigate the appropriate temperature at which highest yield of liquid fraction is achieved. Similar effect of decrease in liquid fraction with increase in temperature beyond the optimum Heating Time Optimization In order to investigate the effect of residence time on the catalytic degradation of waste LDPE, the waste LDPE sample was catalytically degraded at optimum condition of temperature and catalyst weight for different periods of time. Results are summarized in Fig. 3. From these results, it was found that maximum amount (69.10 wt%) of liquid oil was obtained at the reaction time of 90 min. Beyond this time no increase in the yield of liquid oil fraction was observed. Catalyst Weight Optimization In order to determine the optimum weight of catalyst for the degradation of waste LDPE into liquid oil products, waste LDPE was pyrolysis with varied weights of catalyst at optimum condition of temperature. From the results in Fig. 4 it was observed that in the absence of catalyst only 12 wt% of liquid oil was obtained, while in the presence of catalyst the conversion into liquid oil increased up to 44.2 wt% at the catalyst feed ratio of 0.4. This means that 4 g of catalyst is the optimum weight for 10 g of waste LDPE. Below the optimum weight of catalyst minimum yield of liquid oil is obtained, while above the optimum weight of catalyst a decrease in the yield of liquid oil was observed which leads to increased amount of gaseous products. This is due to the fact that the rate of reaction i.e., process of cracking increased by the higher amount (weight) of catalyst hence leading to the higher yield of gaseous product. Similar trend is given in literature [11].This result also shows that both liquid and gaseous products are possible depending on the amount of catalyst. Higher amount of catalyst enhances gaseous production. The efficiency of catalyst is also clear from these results. Table 2 Physical properties of parent oil and its fractions obtained by catalytic pyrolysis of waste plastic (LDPE) S. No Sample Density (g/cm3) Specific gravity API gravity Visco (CP) Kinematic visco (mm2/s) Flash point (oC) Refr. index (n) Refr. intercept (RI) Refr. index parameter (I) Specific refr. (cD) 1 B 0.760 0.761 54.44 1.44 1.890 35 1.441 1.061 0.264 0.3473 2 B1 0.694 0.695 72.10 0.63 0.911 25 1.401 1.058 0.245 0.3532 3 B2 0.755 0.756 55.67 1.00 1.324 44 1.422 1.044 0.254 0.3366 4 B3 0.774 0.775 51.08 1.89 2.440 67 1.430 1.045 0.258 0.3338 5 B4 0.787 0.788 48.07 2.46 3.121 87 1.438 1.0476 0.262 0.3336 6 B5 0.802 0.803 44.71 3.34 4.161 102 1.445 1.047 0.266 0.3332 123 Author's personal copy J Polym Environ Table 3 Standard parameters of gasoline, diesel and kerosene oil S. No Parameters Gasoline Diesel Kerosene 1 Density (g/mL) 0.736/0.725 0.834 - 2 Specific gravity 0.70 0.85 0.78 3 API gravity 65 23–30 - 4 Viscosity (centipoises) - 2.0–4.5 0.9–1.5 5 Kinematic viscosity (mm2/s) 5.0 3.77–5.0 2.2 37.8–38 55–60 50–55 o 6 Flash point ( C) Fractional Distillation Study Liquid oil collected from catalytic degradation of waste LDPE was further separated into various fractions at different temperatures using fractionating column. The results are also shown in Table 1. This data show that 13 wt% of the oil was collected in the temperature range of 20–100 °C, 10.82 wt% was collected in the temperature range of 100–150 °C, 13.87 wt% was collected in the temperature range of 150–200 °C, 19.52 wt% was collected in the temperature range of 200–250 °C, 22.60 wt% was collected in the temperature range of 250–280 °C while 19.30 wt% was collected at C280 °C. So a total of 79.81 wt% of the oil was collected up to 280 °C which lies in the range of petrol, kerosene and diesel oil [16]. Characterization of Liquid Products Fuel Properties Fuel Properties of Parent Oil and its Fraction Obtained by Catalytic Degradation of Waste Plastic (LDPE) and its Comparison with Standard Gasoline, Kerosene and Diesel Different physical parameters like density, viscosity, refractive index etc. were measured for the parent 105 % Transmittance - - 307955 85 - 1457.49 80 75 70 - 2849.05 3000 2500 2000 1500 1000 500 Wave number cm -1 Fig. 5 FTIR spectra of the oil (B) obtained by the catalytic degradation of waste LDPE using CaO/SiO2 as catalyst 123 and its different fractions. The results are shown in Table 2. Density of the parent oil (B) was 0.760 g/cm3 which lie in between the value of gasoline to kerosene - g/cm3). Density of the fraction B1 was 0.694 g/cm3 which is lower than the density of gasoline (0.736/0.725 g/cm3). Densities of the fractions B2 (0.758 g/ cm3) and B3 (0.774 g/cm3) lie in between the gasoline and kerosene - g/cm3). Densities of the fractions B4 and B5 are 0.787 g/cm3 and 0.802 g/cm3 which come in the category of kerosene - g/cm3). Specific gravity value for the parent oil was 0.761, which show an intermediate value between gasoline to kerosene (0–0.78). Specific gravity of the fraction B1 (0.695) is lower than the specific gravity value for gasoline (0.736/0.725). Specific gravities of the fractions B2 and B3 were 0.756 and 0.775 respectively which fall in between the value of gasoline and kerosene (0.70–0.78). Specific gravity values for the fractions B4 (0.788) and B5 (0.803) are comparable with the specific gravity value for kerosene (0.78). The value of API gravity for the parent oil was 54.44, which is an intermediate value between gasoline and kerosene (41.7–65). API gravity value for fraction B1 (72.10) was slightly higher than the API gravity value for gasoline (65). The values of API gravities for the fractions B2, B3, B4 and B5 range from 55.67 to 44.71 and can be classified between gasoline and kerosene (41.7–65). Viscosity value for the parent oil was 1.44 centipoise, which comes in the category of kerosene (0.9–1.5). Fraction B1 has a viscosity value of 0.63 centipoise, which is lower than the viscosity value for gasoline - centipoise). The viscosity value for fraction B2 (1.00 centipoise) comes in the category of kerosene (0.9–1.5 centipoise).The fraction B3 has a viscosity value of 1.89 centipoise, which comes in between the value for kerosene and diesel (1.5–2.0 centipoise). Viscosity values for fractions B4 (2.46 centipoise) and B5 (3.34 centipoise) are in agreement with the viscosity value for diesel (2.0–4.5 centipoise). Kinematic viscosity values of parent oil B (1.890 mm2/ s), fraction B1 (0.911 mm2/s) and B2 (1.324 mm2/s) are lower than the standard value for kerosene (2.2 mm2/s). Kinematic viscosity values for fractions B3, B4 and B5 Author's personal copy J Polym Environ Table 4 Assignment of bands in FTIR spectra of sample B S. No Wave number (cm-1) Energy (J) Assignment Functional group 1 3079.55 -J t N–H H bonded NH [14, 16] 2 2923.47 -J t C–H C–CH3 [14, 18] 3 2849.05 -J t C–H C–CH3 [16] 4 2733.03 - t C–H C–CH3 [14, 15] 5 2672.29 -J t C–H C–CH3 [16, 17] -20 Reference 6 1821.93 3.62 9 10 t C–H Non conj. [14, 16] 7 1645.94 -J tC=C Conjugated [14, 16] 8 1457.49 -J c C–H CH3 [14, 18] 9 1372.61 -J d CH3 CH3 [14] 10 990.26 -J t C–C –CH = CH2 [14, 16] J -20 11 904.60 1.80 9 10 J c C–H –CH = CH2 [14, 17] 12 723.16 -J q C–C –CH = CH– (cis) [13, 16] t stretching vibration d bending vibration q rocking vibration c deformation vibration Transmittance (%) 110 B2 B4 B3 B1 range from 2.440 to 4.161 mm2/s, which comes in the category of diesel (3.77–5.0 mm2/s). Flash point value for parent oil (35 °C) and fraction B1 (25 °C) are below the standard value for gasoline (37.8–38 °C). Fraction B2 has a flash point value of 44 °C, which lie in between the value for gasoline and kerosene (38–50 °C). Fractions B3, B4 and B5 have flash point values of 67, 87 and 102 °C respectively, which are higher than the flash point value for diesel (55–60 °C). Refractive index value for the parent oil was 1.441, while the refractive indices values for the fractions B1 to B5 increased from 1.401 to 1.445. This increase in the refractive index values from fraction B1 to B5 indicate that with the increase in temperature the molecular mass of hydrocarbons also increases. Paraffin have lower values of refractive indices, nephthane have intermediate values B5 - B1 B2 B3 B4 B5 3500 3000 2500 2000 1500 1000 500 Wave number (cm-1) Fig. 6 FTIR spectra of fraction B1–B5 Table 5 Assignment of bands in FTIR spectra of samples (B1–B5) S. No. Wave number (cm-1) Assign Fun.group Ref. B1 B2 B3 B4 B5 1 3079.55 3079.55 3079.55 3079.55 3079.55 t N–H H–NH [14] 2 3 - - - - - t C–H t C–H C–CH3 C–CH3 [14] [16] 4 - 2733.03 2733.03 2733.03 2733.03 t C–H C–CH3 [16] 5 - - 2666.83 2666.83 2666.83 t C–H C–CH3 [14] 6 1821.93 1821.93 1821.93 1821.93 1821.93 t C–H Non conj. [16] 7 1639.21 1639.21 1639.21 1639.21 1639.21 tC=C Conj. [15] 8 1457.49 1457.49 1457.49 1457.49 1457.49 c C–H CH3 [14] 9 1373.39 1373.39 1373.39 1373.39 1373.39 d CH3 CH3 [14] 10 1008.95 989.26 989.26 989.26 989.26 t C–C –CH = CH2 [16] 11 904.60 904.60 904.60 904.60 904.60 c C–H –CH = CH2 [14] 12 723.16 723.16 723.16 723.16 721.20 q C–C –CH = CH– (cis) [16] 123 Author's personal copy J Polym Environ Transmittance (%) 120 Kerosene Gasoline Diesel - Gasoline Kerosene Diesel - 3500 3000 2500 2000 1500 1000 500 -1 Wave number (cm ) Fig. 7 FTIR spectra of standard gasoline, kerosene and diesel while aromatics are associated with higher values of refractive indices [11]. Refractivity intercept (RI) was calculated for further identification of the hydrocarbon groups present in the parent and various fractional fuels, as it gives a specific value for each hydrocarbon group. RI values for paraffin, nephthane and aromatic hydrocarbons are in the range of-,- and- respectively [19]. RI value for the parent and different fractional fuels of our samples lies in the range of- which shows the presence of paraffin and naphthenic hydrocarbons in the derived oil. Standard parameters of gasoline, diesel and kerosene oil are also shown in Table 3 for comparison. FT-IR Analysis FT-IR Analysis of the Parent Oil Obtained from the Catalytic Degradation of Waste LDPE Using CaO/SiO2 as Catalyst FT-IR spectra of the parent oil given in Fig. 5 shows that the following types of functional groups are Table 6 Assignment of bands in FTIR spectra of gasoline, kerosene and diesel 123 S. No. present. Band at wave number 3077.32 cm-1 indicates the H bonded NH functional group. The Peaks at 2923.64 cm-1, 2727.57 cm-1 and 2666.83 cm-1 show C– CH3 functional group. Peaks at 1821.02 cm-1 and 1641.35 cm-1 are due to non-conjugated functional group. Peaks at 1454.65 cm-1 and 1377.28 cm-1are for CH3, peaks at 989.83 cm-1 and 904.17 cm-1 represent –CH = CH2 functional group and the peak at 722.47 cm-1is due to –CH = CH– (cis). Calculated energy values for the band at wave number 3077.32 cm-1 is- J, band at 2923.64 cm-1 is- J, band at 2727.57 cm-1 is- J, band at 2666.83 cm-1 is- J, band at 1821.02 cm-1 is- J, band at 1641.35 cm-1 is- J, band at 1454.65 cm-1 is- J, band at 1377.28 cm-1 is- J, band at 989.83 cm-1 is- J, band at 904.17 cm-1 is- J and band at 722.47 cm-1 is- J. The FTIR is in agreement with literature reports [22, 31, 32]. Each wave number along with their assignment is presented in Table 4. FT-IR Analysis of the Fractional Fuels Obtained from the Fractional Distillation of the Parent Oil (B) FT-IR spectra of the different fractional fuels from B1 to B5 are given in Fig. 6. The peaks for the following groups such as hydrogen bonded NH, C–CH3, non-conjugated, CH3, –CH2 = CH2, –CH = CH2 and –CH = CH– (cis) were identified which are common to all five fractions. The whole result is presented in Table 5. Comparison of the FT-IR Spectra of Liquid Products Obtained from the Catalytic Degradation Process of Waste LDPE with the FT-IR Spectra of Standard Gasoline, Kerosene and Diesel Oil FT-IR spectra of the standard gasoline, kerosene and diesel oil obtained from Shell oil was also carried out as shown in Fig. 7. FT-IR spectra of Wave number (cm-1) Gasoline Kerosene Assignment Fun. Group Reference Diesel 1 3025.04 - - t C–H C–CH3 [14] 2 2958.61 - - t C–H C–CH3 [14] 3 2927.70 2922.25 2922.25 t C–H C–CH3 [14] 4 2873.19 2849.83 2855.28 t C–H C–CH3 [14] 5 2727.03 728.35 2728.35 t C–H C–CH3 [14] 6 1609.35 1603.39 1610 tC=C Conjugated [14] 7 1463.72 1452.04 1464.50 c C–H CH3 [14] 8 1378.84 1373.16 1373.39 d CH3 CH3 [14] 9 734.84 717.71 735.62 q C–C –CH = CH–(cis) [14] Author's personal copy J Polym Environ liquid oil Figs. 5 and 6 show similar peaks position to that of the FT-IR spectra gasoline, kerosene and diesel oil whose results are summarized in Table 6. This means that liquid oil obtained has these kinds of fuel materials. Conclusion It is concluded from experimental results that rapid liquefaction of LDPE (waste plastic) can be obtained by catalytic conversion using CaO/SiO2 catalyst. It was found that catalytic conversion process is more efficient in terms of temperature, heating time and liquid fuel yield. 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