2498
Energy & Fuels 2006, 20, 2498-2503
Characterization of Liquid Products Obtained from Cocracking of Petroleum Vacuum Residue with Plastics M. Ahmaruzzaman* and D. K. Sharma Centre for Energy Studies, Indian Institute of Technology, Delhi, New Delhi-110016, India ReceiVed February 17, 2006. ReVised Manuscript ReceiVed May 30, 2006
Coprocessing of the petroleum vacuum residue (XVR) with polystyrene, polypropylene, and Bakelite has been undertaken in a batch reactor under isothermal conditions at atmospheric pressure. The liquids obtained by coprocessing have been characterized by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance (NMR), 13C NMR, gel permeation chromatography (GPC), inductively coupled argon plasma, and gas chromatography analyses. The main aim of the characterization of the liquid products was to find out the molecular weight distributions as well as the determination of average structural parameters. The GPC analysis showed that the liquids derived from XVR are quite complex, containing a complex range of products. The liquid products obtained from coprocessing showed that there is an interaction of reacting species when they are cracked together. It is also interesting that the liquid products obtained from coprocessing with plastics contained less than 1 ppm of Ni and V. The detailed results obtained are reported.
Introduction The coprocessing of petroleum vacuum residue with plastics was studied for exploring the possibility of its utilization to obtain lighter products, which may have an interesting product pattern. To understand the chemical reactions and chemical transformations, which could have taken place, during the coprocessing of petroleum residue with plastics, it was necessary to characterize the products obtained from coprocessing. In addition, characterization of the products would help in deciding the end use of the product. For example, cokes may have several applications which come out in the end of cracking. These cokes as such or after activation can be used for the removal of toxic substances from wastewater. The removal of toxic substances from wastewater using residue carbon (carbon slurry, activated carbon, bottom ash, etc.) has been reported in the literature.1-7 The cracking of petroleum residue (heavy ends of petroleum) mainly yields liquid products of hydrocarbon, although coke and gas are also formed. Analyses of the average structural parameters of these hydrocarbon constitutes of liquid products obtained from the cracking of petroleum residue helps toward understanding their physicochemical characteristics. Of such parameters, the type and distribution of isoparaffins determine the low-temperature and rheological properties of liquid feedstocks. 1H and 13C nuclear magnetic resonance (NMR) techniques have been utilized for the estimation of structural * Author to whom correspondence should be addressed. E-mail:
[email protected]. (1) Gupta, V. K.; Srivastava, S. K.; Mohan, D. Ind. Eng. Chem. Res. 1997, 36, 2207. (2) Mohan, D.; Gupta, V. K.; Srivastava, S. K.; Chander, S. Colloids Surf., A 2001, 177, 169. (3) Gupta, V. K.; Ali, I. J. Colloid Interface Sci. 2004, 271, 321. (4) Gupta, V. K.; Sharma, S. Ind. Eng. Chem. Res. 2003, 42 (25), 6619. (5) Gupta, V. K.; Mittal, A.; Gajbe, V. J. Colloid Interface Sci. 2005, 284 (1), 89. (6) Gupta, V. K.; Ali, I.; Saini, V. K.; Van Gerven, T.; Van der Bruggen, B.; Vandecasteele, C. Ind. Eng. Chem. Res. 2005, 44 (10), 3655. (7) Jain, A. K.; Gupta, V. K.; Bhatnagar, A.; Suhas. J. Hazard. Mater. 2003, 101 (1), 31.
parameters of low- and higher-boiling petroleum cuts.8-11 Sarpal et al.12 also reported the identification of hydrocarbon types in fuels by using the NMR technique. The products of the thermal cracking of waste plastics are mainly liquid mixtures of hydrocarbons boiling in the range 35-360 °C, gaseous hydrocarbons as well as solid residues, similar to wax or coke. Thus, the conversion of plastics into fuels, chemicals, or monomers represents an interesting alternative because it could be merged into standard petrochemical or petroleum refinery industrial operation. The coprocessing of petroleum vacuum residue with plastics may synergize the cracking process to produce stabilized products as a result of several electrophilic reactions. Williams and Williams13 analyzed the products derived from the fast pyrolysis of plastic waste. The oils were analyzed for their functional groups using Fourier transform infrared (FT-IR) spectroscopy. The molecular weight distribution was also determined using size exclusion chromatography. It was found that, as the temperature was increased, the amount of aromatic compounds in the oil increased. The molecular weight range was also affected. Basic physicochemical properties of gasoline and diesel fuels obtained from waste plastics by thermal treatment were characterized by Walendziewski.14 Gersten et al. 15 characterized the liquid products obtained from the combined pyrolysis of a waste polymers and oil shale mixture. The analyses of the liquid product obtained from polyethylene pyrolysis have been reported by Horvat and Ng.16 They analyzed the liquid products by using gas chromatography (GC) and 1H NMR spectral studies. (8) Hasan, M. U.; Bukhari, A.; Ali, M. F. Fuel 1985, 64, 839. (9) Gillet, S.; Rubini, P.; Delpuech, J. J.; Escalier, J. C.; Valentin, P. Fuel 1981, 60, 221. (10) Cookson, D. J.; Rolls, C. L.; Smith, B. E. Fuel 1989, 68, 788. (11) Snape, C. E. Fuel 1983, 62, 621. (12) Sarpal, A. S.; Mukherjee, S.; Bansal, V.; Kapur, G. S. Fuel Int. 2000, 1, 3. (13) Williams, E. A.; Williams, P. T. J. Anal. Appl. Pyrolysis 1997, 40, 347. (14) Walendziewski, J. Fuel 2002, 81, 473. (15) Gersten, J.; Fainberg, V.; Garbar, A.; Hetsroni, G.; Shindler, Y. Fuel 1999, 78, 987. (16) Horvat, N.; Ng, F. T. T. Fuel 1999, 78, 459.
10.1021/ef060070c CCC: $33.50 © 2006 American Chemical Society Published on Web 09/14/2006
Characterization of Liquid Products
Thus, to understand the chemical reactions and chemical transformations, which could have taken place, during the cocracking of petroleum vacuum residue (XVR) with plastics, such as polystyrene (PS), polypropylene (PP), and Bakelite (BL), the characterization of the liquid products obtained has been carried out presently. The main aim of the characterization of the liquid products was to find out the molecular weight distributions as well as the determination of average structural parameters. The techniques used for characterization were mainly FT-IR, 1H NMR, 13C NMR, high-performance liquid chromatography, gel permeation chromatography (GPC), inductively coupled argon plasma (ICAP), and GC analyses. Experimental Section Materials and Method. A stainless steel reactor was fabricated. The material used for the construction of the steel reactor was selected as SS304. The length and diameter of the reactor were 10 and 2.5 cm, respectively. The cracking experiments were conducted in batch mode using the stainless steel microreactor under ambient pressure conditions. In a typical experiment, the reactor was flushed with nitrogen and heated to the desired temperature. The feedstock (XVR as well as PS, PP, and BL along with their mixture, 1:1 wt/wt) was taken in a small crucible-type container. The feedstock (4 g) was introduced into the reactor as soon as the reactor reached the desired temperature and was kept at this temperature for 2 h. After reaction, the microreactor was flushed with nitrogen and the crucible was taken out from the reactor and then quickly cooled to room temperature by immersing it in cold water. The residue left inside the reactor was treated with tetrahydrofuran (THF) and then filtered through Whatman 42 filter paper to separate THF-soluble material from coke/char. The liquid product was collected in a small vessel maintained at room temperature. The volume of gas produced was measured through the displacement of water. Each experiment was performed three times at each experimental condition, and the reproducibility of the experimental data was calculated to be within (2%. Liquid Product Analyses. FT-IR. The IR spectra were recorded as thin films between KBr windows. A total of 40 scans were provided to get a better signal-to-noise ratio. The spectra were recorded at 4 cm-1 resolutions on a Nicolet Magna 750 FTIR system equipped with deuterated triglycene sulfate. NMR. 1H and 13C NMR spectra were recorded on 300 MHz Bruker spectrospin instruments. The liquid samples were diluted with CDCl3 containing 0.1 M chromium acetyl acetonate as the relaxation agent and tetra methylsilane (TMS) as the internal reference. ICAP. The liquid samples were diluted 10 times with aviation turbine fuel and were subjected to ICAP analyses. A multielement standard (S-21) was used for calibration. The ICAP operating parameters were as follows: RF (power) kw, 1.3 (organic); coolant gas, 18LPM; nebulizing type, V-groove; nebulizing pressure, 36 PSI; auxiliary gas (PSI), 1.2 (organic); sample uptake, 1.0 mL/ min; and integration time, 5 s. GPC. GPC analyses were carried using tetrahydrofuran as the solvent. The GPC parameters were as follows: UV detectors, model M-2487 dual wavelength; RI detectors, model M-2410; flow, 1 mL/ min; column, PL GEL -100 Å, 60 cm column, 5µ; and the standard used was paraffins having a molecular weight of 618, 492, 310, and 170. GC. The analyses were performed using a Perkin-Elmer 8500 gas chromatograph equipped with a split/splitless injector and flame ionization detector. Details of the column and other conditions are given as follows: column condition, capillary column; stationary phase, nonpolar bonded methyl silicone; length, 100 mm; initial temperature, 80 °C/min; initial holdup time, 2 min; programming rate, 6 °C/min; final temperature, 310 °C; injector temperature, 300 °C; detector temperature, 300 °C; carrier gas, helium; and gas flow rate, 30 mL/ min.
Energy & Fuels, Vol. 20, No. 6, 2006 2499 Table 1. Molecular Weight Distribution of the Liquid Products Obtained by Coprocessing of Petroleum Vacuum Residue with Plastics sample XVR (380 °C) XVR (460 °C) PS
PP BL XVR + PS XVR + PP XVR + BL
molecular weight (%)
Mn
Mw
MP
polydispersity
100 100 18.8 26.1 37.7 17.4 100 53.1 46.9 36.7 41.6 21.8 100 85.4 14.6
106 105 1514 177 101 44 263
