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Characterization of liquid products from the co-cracking of ternary and quaternary mixture of petroleum vacuum residue, polypropylene, Samla coal and Calotropis Procera
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Characterization of liquid products from the co-cracking of ternary and quaternary mixture of petroleum vacuum residue, polypropylene, Samla coal and Calotropis Procera M. Ahmaruzzaman *, D.K. Sharma Centre for Energy Studies, Indian Institute of Technology Delhi, New Delhi 110016, India Received 27 June 2007; received in revised form 12 January 2008; accepted 15 January 2008 Available online 7 February 2008
Abstract The co-cracking of the petroleum vacuum residue (XVR) with polypropylene (PP), Samla coal (SC) and Calotropis procera (CL) has been carried out in a batch reactor under isothermal conditions at atmospheric pressure. The liquids obtained by co-cracking have been characterized by Fourier transform infrared spectroscopy, high performance liquid chromatography, 1H nuclear magnetic resonance (NMR), 13C NMR, gel permeation chromatography (GPC), and inductively coupled argon plasma analyses. It was found that the liquid products obtained from the co-cracking of ternary and quaternary mixtures of the petroleum vacuum residue with polypropylene, coal and C. procera contained less than 1 ppm of Ni and V. The HPLC analyses indicates that the liquids obtained from the cracking of ternary mixture of XVR+PP+CL were mainly aliphatic in nature (saturates content 87.4%). NMR analyses showed that the aromatic carbon contents decreased (15.0%) in the liquid products derived from the co-cracking of quaternary mixtures of XVR+PP+SC+CL compared to their theoretical averages (taking the averages of aromatic carbon contents of the liquids from XVR, PP, SC and CL individually). The overall results indicated that there exists a definite interaction of reactive species when XVR, PP, SC and CL were co-cracked together. Ó 2008 Elsevier Ltd. All rights reserved. Keywords: Co-cracking; Petroleum vacuum residue; Polypropylene; Samla coal
1. Introduction The rapid consumption of conventional light petroleum crude reserves has prompted the increasing need to refine lower quality heavier crude oils. The heavier crude yields more high boiling residues such as vacuum residue (VR), which may have to be refined to yield lighter and value added products. Processing of this heavier feedstock needs the development of down processing technologies such as hydro-cracking with attendant risk of catalytic poisoning and need for high hydrogen pressure and thick walled reactors and rugged valves. This leads to serious consideration of the development of technologies for the co-processing of *
Corresponding author. Tel.: +91 3842 242915. E-mail address: md_a2002@rediffmail.com (M. Ahmaruzzaman).
0016-2361/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2008.01.007
vacuum residues with other organic polymers such as coal, plastics and petrocrops [1]. The co-processing of petroleum vacuum residue, plastics, coal and biomass may also be employed as a way of eliminating waste materials and producing at the same time valuable products for industry. Pyrolysis of coal is a good method for producing chemicals such as BTX and light olefins, but the yields of these products are limited because of the low hydrogen to carbon ratio in coal [2]. For this reason, it is necessary to supply hydrogen from other sources. Petroleum residues, which are hydrogen-rich compounds, can act as hydrogen donors in co-processing reactions. Thus, co-processing of petroleum vacuum residue with coal may synergize the production of lighter and value added products. Lazaro et al. [3] reported that the tar obtained from the coal/oil mixture is more similar to the tar from oil than to the tar from coal,
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M. Ahmaruzzaman, D.K. Sharma / Fuel 87 (2008) 1967–1973
Nomenclature XVR PP
petroleum vacuum residue polypropylene
reflecting synergy in the co-pyrolysis reactions. Suelves et al. [4] have studied the co-cracking of coal and petroleum residue. They reported that there exists significant synergistic interaction when coal and petroleum residue are copyrolysed. Joo and Curtis [5] have shown that heavy petroleum resid acts as an effective bridging solvent that when added to coal and waste plastics provide a medium for their mutual dissolution. Pyrolysis of waste plastics is also currently being investigated as a feasible processing method for waste plastics with the goal of producing fuels or chemical feedstocks. Waste plastics are also being fed as refinery and coker feeds [6]. Co-processing of waste plastics with coal provides another alternative to the production of fuels and chemical feedstocks from waste plastics. Inclusion of the abundant hydrocarbon resource coal in the pyrolysis of waste plastics not only provides additional hydrocarbon feedstock but also increases the capacity for producing quantities of fuels and chemical feedstocks. The feasibility of co-processing coal with waste plastics is dependent on the type of plastic and catalyst used. Researchers have investigated the direct liquefaction of coal with waste plastics and have evaluated a number of different processing parameters and catalysts [7–9]. The problems which they have encountered include the incompatibility of the starting reactants and the need for specific catalysts and reaction parameters to promote the desired reactions for each reactant. Thermal and catalytic co-processing of waste tires and coal was performed using waste tires from two sources and coals of three different ranks [10]. Bituminous coals yielded higher conversions than either subbituminous coal or lignite when co-processed with waste tire. The efficiency of the conversion of co-processed coal and waste plastics to THF soluble material depends upon the composition of the plastics, and the type of solvent used, if any. Co-processing of waste plastics with vacuum residue can achieve the purpose of waste recycling into commercially viable chemicals and fuels. Co-processing of waste lubricating oil with coal or plastics has also been studied as waste lubricating oil can provide good solvency for the straight chain common thermoplastics and coal [11,12]. Gersten et al. [13] characterized the liquid products obtained from combined pyrolysis of waste polymer/oil shale mixture. UzumKesici et al. [14] studied the co-pyrolysis of single plastic waste stream in low temperature carbonization with coal and characterized the tars obtained from coal/polystyrene co-processing. Co-cracking of coal with waste plastics in two separate stages was investigated in order to tailor the reaction conditions and catalysts used in each stage for the materials present [15].
SC CL
Samla coal Calotropis procera
The co-processing of petroleum vacuum residue with polypropylene, Samla coal and Calotropis procera was studied for exploring the possibility of their utilization to obtain liquid products. The characterization of the liquid products obtained from the co-cracking of ternary (XVR+PP+SC and XVR+PP+CL, 1:1:1, wt/wt) and quaternary mixtures (XVR+PP+SC+CL, 1:1:1:1, wt/wt) have been carried out presently, in order to state the occurrence of interaction among petroleum vacuum residue, coal, polypropylene and petrocrops. The techniques used for characterization were mainly FT-IR, 1H NMR, 13C NMR, high-performance liquid chromatography, gel permeation chromatography (GPC), and inductively coupled argon plasma (ICAP) analyses. To the best of our knowledge, no one has yet characterized the liquid products obtained from the co-cracking of ternary and quaternary mixtures of XVR, PP, SC and CL. 2. Experimental 2.1. Materials and method The analyses of the materials (XVR, PP, SC and CL) used for co-cracking were reported in the previous paper [16]. In a typical experiment, the reactor was flushed with nitrogen and heated to the desired temperature. The feedstocks (XVR as well as PP, SC, and CL along with their ternary, 1:1:1, wt/wt and quaternary mixture, 1:1:1:1 wt/ wt) were taken in a small crucible-type container and introduced into the reactor as soon as the reactor reached the desired temperature (460 °C); it was kept at this temperature for 2 h. The liquid product was collected in a small vessel maintained at room temperature and as such used for analysis. The reproducibility of the cracking experiments was ±2–3%. The details of the reactor and experimental set up have been reported elsewhere [17]. 2.2. Liquid product analyses 2.2.1. FT-IR The IR spectra were recorded as thin films between KBr windows. A total of forty 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 FT-IR system equipped with deuterated triglycene sulphate). 2.2.2. NMR 1 H 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
M. Ahmaruzzaman, D.K. Sharma / Fuel 87 (2008) 1967–1973
acetonate as the relaxation agent and tetra methyl silane (TMS) as the internal reference. 2.2.3. ICAP The liquid samples were diluted 10 times with aviation turbine fuel and were subjected to ICAP analyses. A multi element standard (S-21) was used for calibration. The ICAP operating parameters were as follows: RF (Power) kw, 1.3 (organic); Coolant gas, 18 LPM; 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. 2.2.4. HPLC HPLC analyses were carried out using n-hexane as the solvent. The column used was the amino propyl silica–dual column (25 cm 4.6 mm). The instrument used was the Waters 515 with UV and RI detectors. 2.2.5. GPC GPC analyses were carried using tetra hydro furan 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 ˚ , 60 cm column, 5 l; and the standard used GEL-100 A was paraffins a having molecular weight of 618, 492, 310, and 170. 3. Results and discussion 3.1. GPC analyses Table 1 shows the molecular weight distribution of the liquid products obtained from the co-processing of petroleum vacuum residue with polypropylene, coal and petrocrops at 460 °C. The liquids obtained from the cracking of petroleum vacuum residue were analyzed using the gel permeation chromatography method and detailed discussion has been reported in the previous paper [18]. The liquid products obtained from the cracking of PP at 460 °C were found to have a Mn and Mw of 263 and Table 1 Molecular weight distribution of the liquid products obtained by cocracking of petroleum vacuum residue with polypropylene, coal and petrocrop Sample
Molecular weight (%)
Mn
Mw
Mp
Poly dispersity
XVR
100 22.6 62.0 15.4 100 63.2 36.8 100 100 100
105 1228 365 138 263 <100 225 187 180 239
168 1253 450 144 305
209 1379 316 184 275
1.60 1.02 1.23 1.04 1.16
273
1.10 1.40 1.40 1.15
SC PP CL XVR+PP+SC XVR+PP+CL XVR+PP+SC+CL
204 260 273 276
1969
305, respectively. Williams and Williams [19] also reported the similar molecular weight distribution of the PP pyrolysed liquids (Mn and Mw of 280 and 439, respectively). The polydispersity index was found to be 1.16. The liquid products obtained from the cracking of coal at 460 °C also showed a range of molecular weight. A total of 22.6% of the liquid products possess a number average and molecular weight average of 1228 and 1253, respectively. Most of the liquid products (62.0%) had a number average and weight average molecular weight of 365 and 450, respectively. Herod et al. [20] showed that more than 50% of the coal derived liquids are likely to be composed of material with molecular masses in the 1000–5000 U ranges. However, Kershaw and Black [21] reported that the THF soluble fraction of coal-tar pitch (average MW = 835) contains more highly condensed aromatic ring systems and significantly different alkyl substituents than the lower molecular weight fractions. About 60% of the aliphatic carbon in this higher molecular weight fraction is in the – CH2CH3 or >CHCH3 groups, while in the lower molecular weight fractions –CH2– and –CH3 groups predominate. The liquid products derived from the cracking of C. procera at 460 °C showed that 63.2% of the liquids possess molecular weight less than 100, indicating the oil to be a low-viscosity-oil. A total of 36.8% of the liquid products have a number average (Mn) and weight average molecular weight (Mw) of 225 and 204, respectively. The polydispersity index was found to be 1.1. However, Herod et al. [22] reported that much of the work that indicates upper mass limits of 1000–1500 U for coal tars, pitches, and petroleum asphaltenes can be explained in terms of limitations of the particular analytical techniques. The liquid products obtained from the co-cracking of the ternary mixture of XVR+PP+SC (1:1:1, wt/wt) showed a number average of 187 and weight average molecular weight of 260. While the number and weight average data for the liquid products was reduced for co-cracking liquids derived from the ternary mixture of XVR+PP+SC, the molecular weight distribution was also reduced. However, the polydispersity index suggest that the liquids are quite complex containing a complex range of compounds. The peak average molecular weight of the liquid products from the ternary mixture of XVR+PP+SC was found to be 260. The molecular weight distribution of the liquid products derived from the co-cracking of XVR+PP+CL (1:1:1, wt/ wt) has been shown in the Table 1.The liquid products were found to have a Mn and Mw of 180 and 273, respectively. It was found that there was an overall reduction of the molecular weight distribution of the liquid products when they were co-cracked together. This suggests that there is a definite interaction of reactive species (free radicals generated from XVR, PP, and CL) during co-cracking of the ternary mixture of XVR+PP+CL, which produces a range of molecular weight chemical species. Lazaro et al. [23] observed relative similarity between GPC profiles of the tars from the coal/waste lubricating oil mixture and that of the waste lubricating oil (alone). In addition, the
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at 888 cm 1 may be assigned to the characteristic vibrational mode of the out-of-plane C–H bending in alkenes. The FT-IR spectrum indicated that the liquid products from the cracking of coal contained phenols (broad band at nearly 3300 cm 1) whereas the liquid products from the cracking of XVR and PP did not contain phenols. Interestingly, the liquid products from the co-cracking of XVR+PP+SC showed no peak for phenols, indicating that the higher hydrogen contents of XVR and PP acted as a hydrogenation medium for the coal product in the cocracking of the mixture. The liquid products derived from the co-cracking of XVR+PP+CL gave very similar FT-IR spectra, which consist essentially of the mixed spectra from each component. The spectra contain dominantly paraffinic (alkane) peaks (and also alkene) derived from the petroleum residue and polypropylene. For example, the alkane and alkene peaks are illustrated by the presence of CH3, –CH2 and C–H functional groups between 2800 and 3000 cm 1 and 1350–1500 cm 1 and alkene structures is indicated by the peaks between 980 and 890 cm 1. The presence of broad peak at nearly 3437 cm 1 due to the phenolic –OH groups arises from the C. procera. The FT-IR spectra of the liquid products obtained from the co-cracking of XVR+PP+SC+CL was found to be closely resembled to that obtained from petroleum residue and polypropylene rather than that from the coal and C. procera. Although, a small broad peak appears at 3427 cm 1 due to the presence of –OH groups. Like the liquid products from XVR and PP, the presence of peaks between 3000 and 2800 cm 1 and the peak in the region from 1350 to 1500 cm 1 due to the C–H bonds indicate the presence of aliphatic group. The peak at 1657 cm 1 indicates the presence of olefinic compounds. The presence of ketonic functional group is made evident by the 1722 cm 1 C@O stretching band.
excluded GPC peak corresponding to the largest molecules of the coal tar almost disappeared in the mixture tar and was smaller than that for the waste lubricating oil (alone). They also showed that the coal/oil mixture tar did not show an intermediate behaviour between the waste lubricating oil and the coal samples; therefore, there appears to be a degree of synergistic interaction between the two samples during co-pyrolysis. The liquid products derived from the quaternary mixtures of XVR+PP+SC+CL (1:1:1:1, wt/wt) showed a number and weight average molecular weight of 239 and 276, respectively. Thus, it was found that there was an overall reduction of molecular weight distributions when XVR+PP+SC+CL were co-cracked together. This may be due to the fact that the presence of XVR, PP, SC and CL together in a reactor generates a plethora of reactive moieties as radicals or radical ions, which synergises and co-synergises the cracking of different fuels/ materials. The peak average molecular weight of the liquid products obtained from XVR+PP+SC+CL was found to be 273, which was almost the same as that of the liquid from PP cracking. In addition, the polydispersity index was reduced compared to the liquids derived from the individual XVR, PP, SC and CL cracking. The liquid products from the cracking of quaternary mixture of XVR+PP+SC+CL were found to be more viscous compared to the liquid derived from the ternary mixture of XVR+PP+SC and XVR+PP+CL. 3.2. FT-IR analyses The overall spectrum of the liquid products from the cracking of XVR is dominated by the presence of alkane compounds and that of the PP cracking liquid products is dominated by the presence of alkane and alkene compounds, as reported in the previous paper [18]. The FTIR analysis showed that the liquid products from the cracking of CL are dominated by the presence of mostly aliphatic components. The FT-IR spectrum of the liquid products obtained from the co-cracking of XVR+PP+SC closely resembled to that obtained from petroleum residue and polypropylene rather than that from the coal. Like the liquids from XVR and PP, the presence of peaks between 3000 and 2800 cm 1 and the peak in the region from 1350 to 1500 cm 1 due to the C–H bonds indicate the presence of aliphatic groups. The peak at 1649 cm 1 indicates the presence of olefinic compounds. The intense absorption band
3.3. Metal analyses Results from metal analyses of the original petroleum vacuum residue and the liquid products obtained from the cracking of XVR as well as co-cracking with polypropylene, coal and petrocrops are shown in Table 2. It is interesting that the liquid products obtained from the coprocessing of petroleum residue with coal, polypropylene and petrocrops contained less than 1 ppm of Ni and V. These liquid products, can, therefore be utilized in secondary conversion processes (such as Fluid catalytic cracking,
Table 2 Metal analyses of the liquid products obtained from co-cracking of petroleum vacuum residue with polypropylene, coal and Calotropis procera Liquid (from)
Zn, ppm
Ca, ppm
Fe, ppm
Mg, ppm
Na, ppm
XVR (original) XVR PP XVR+PP+SC XVR+PP+CL
12 5 2 6 10
3 <1 <1 1 4
5 <1 <1 <1 <1
5 <1 <1
4 <1 <1
Al, ppm
Ni, ppm
V, ppm
<1 <1 1 1
51 <1 <1 <1 <1
94 <1 <1 <1 <1
M. Ahmaruzzaman, D.K. Sharma / Fuel 87 (2008) 1967–1973
Hydrocracking, etc.) in petroleum refinery operations. The demetalation reactions are thought to proceed by way of thermal breakdown of asphaltenic and metal-containing compounds of the residue and of the coal to reactive radicals. These fragments which are generated as a result of thermal treatment react with each other and form very small amounts of metal-containing insolubles which then deposit on the solid fraction of the co-cracked mixture. The above results also indicate that the metals under study are trapped in the char during cracking as well as co-cracking processes; however, the retention depends on each metal. In particular, Ni, V, and Fe show the biggest retention, so that the contents of these metals in the liquid products are significantly lower than in the parent petroleum residue. It was reported [24] that removal of metallic impurities from the liquid products during co-processing of coal with heavy oil was probably due to their deposition on the coal residue or pitch. Audeh and Yan [25] also showed that the petroleum residue is substantially demetalated when coprocessed with coal. Visbreaking with coal followed by deasphalting gives 81% and 89% demetalation of nickel and vanadium from the Joliet vacuum residue [26]. Orr et al. [11] reported that the oils derived from co-cracking coals of different rank with the automotive crankcase oil indicated that these oils were lower in overall trace metals compared with the trace metal content of untreated automobile crankcase oil. Metal-free distillates/liquids was generated by co-processing coal and residual oil whereby the metals contained in the resid are deposited on the solid portion of the coal which remains after the volatilized/solubilized portion of the coal is generated and removed [27]. 3.4. 1H and
13
C NMR spectral analyses
Definitions of 1H and 13C NMR chemical shifts for hydrocarbons are shown in the Table 3. The detailed analyses of the liquid products derived from the cracking of XVR have been reported in the previous paper [18]. The Table 3 Definitions of 1H and
13
1971
1
H NMR spectrum showed that the liquid products from the cracking of polypropylene were highly aliphatic in nature. The liquid products derived from the cracking of coal showed that aliphatic hydrogen distributions were mainly Ha (18.4%) and Hb+c (52.0%) and some HCH3 (15.1%). The 13C NMR spectrum showed that approximately 45.1% of the total carbon present in the liquid products obtained from the cracking of coal arises from the aromatic species. The overall 13C NMR spectrum of the liquids from the cracking of C. procera was found to be quite complex probably due to the large number of components as well as the complex structure of each individual component present in the liquid products. The 1H NMR spectrum of the liquid products obtained from the co-cracking of XVR+PP+SC indicates that aliphatic components constitute the principal molecular species present (94.7%). It was also found that the aliphatic hydrogen contents in the liquid products increased when XVR, PP and SC were co-cracked together compared to their theoretical values. This may be due to the fact that XVR and PP may be acted as a H-donor medium for the coal cracking products. Approximately, 1.3% of the total hydrogens present in the liquids arise from aromatic species. The 13C NMR spectrum of the liquid products from the co-cracking of XVR+PP+SC showed the presence of two sharp peaks at 111.5 (terminal methyl carbon, @CH2) and 144.2 ppm (methyl carbon in the vinyl group, –CH@), respectively. A small peak at 167.4 ppm indicates the presence of carbonyl type compounds and constitutes 0.1% of the total carbons. Approximately, 13.3% of the total carbons present in the liquid products arise from aromatic species. The spectral pattern in the aliphatic region is quite complex. The 13C NMR spectrum of the liquids obtained from the co-cracking of XVR+PP+CL clearly demonstrates that aliphatic compounds constituted the principal molecular species present. The integrated data provide an estimate of 83.1% aliphatic hydrocarbons. Approximately, 12.2%
C NMR chemical shifts for hydrocarbons
Parameters
Chemical Shift (d)
Definition
HA HS Ha Hb+c HCH3 CS CPa CPb CPn CPc CA CAH
9.0 6.0 4.0 0.5 4.0 2.0 2.0 1.0 1.0 0.5 10.0 50.0 14.1 22.7 29.6 30.1 32 100 150 100–130
% % % % % % % % % % % %
Aromatic protons Aliphatic protons CH3, CH2 and CH protons a to aromatic ring CH2 and CH protons of alkyl chains b or further to ring and CH3 protons b to the ring CH3 protons of alkyl chains c or further from aromatic ring or CH3 of saturated compounds Saturated aliphatic carbons Carbon of terminal methyl group of alkyl chain a CH3–(CH2)n– (n P 4) Carbon of CH2 group b to terminal methyl of alkyl chain with n P 4 Carbon of c or higher of alkyl chain CH3 CH2 CH2 (CH2)n CH2 CH2 Carbon of c CH2 in CH3 (CH2)c CH2 (CH2)n Aromatic carbon Protonated carbon
Formulae for NMR parameters of hydrocarbons. C/H = Carbon to hydrogen ratio = [CS + CA]/[2CS + CA]. FS = C/H ratio of saturated part of sample. FA = C/H ratio of aromatic part of sample. ACL = average chain length = 2CP/CPa.
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Table 4 Average structural parameters (derived from 1H and 13C NMR data) of the liquid products obtained from co-cracking of petroleum vacuum residue with polypropylene, coal and Calotropis procera Liquid from
XVR
PP
CL
SC
XVR+PP+SC
XVR+PP+CL
XVR+PP+SC+CL
CA CS CPa CPb CPn CPc CP HA Ha Hb+c HCH3 HS H/C CAL CN + CI CAH ACL
14.3 85.7 7.4 7.1 29.4 5.7 49.5 4.0 10.1 62.8 22.5 95.4 1.9 2.7 36.2 7.4 13.5
– 90.3 5.0 6.8 5.8 0.7 18.3 – 3.1 45.3 45.9 94.4 1.9 – 72.0 – 7.3
17.2 79.6 1.5 3.2 11.8 2.2 18.7 2.9 10.6 53.3 23.0 86.8 1.8 21.7 60.8 11.9 24.3
45.1 52.9 3.9 3.8 23.2 3.5 34.3 13.8 18.4 52.0 15.1 85.5 1.5 – 18.6 – 17.6
13.3 81.0 6.0 3.7 12.9 3.4 26.0 1.3 6.0 44.4 44.3 94.7 1.9 5.7 55.1 7.6 8.72
12.2 83.1 4.5 2.3 12.6 1.8 21.2 – – – – – 1.9 – 62.0 – 9.4
4.1 90.5 3.6 2.5 10.4 1.8 18.3 2.2 4.9 51.2 38.4 94.5 2.0 – 72.3 – 10.4
of the total carbons present in the liquid products arise from aromatic species. Comparing the theoretical value of the individual cracking products from XVR, PP and CL, it was found that naphthenic and iso-paraffinic carbons were increased (5.7%) in the liquids from the co-cracking of XVR+PP+CL. Table 4 showed the detailed results. From an analysis of the integrals of the aliphatic regions, it was estimated that approximately 21.2% of the aliphatic/saturated carbons are straight-chain alkanes with an average of about 10 carbons in the alkyl group. The spectral pattern for the methyl hydrogens (0.5– 1.1 ppm) in the 1H NMR spectrum of the liquid products obtained from the co-cracking of XVR+PP+SC+CL showed an overlapping complex multiplet splitting of the hydrogen. However, the integrated spectral region suggests that approximately 94.5% of the total hydrogens are present in aliphatic moieties. It was found that aliphatic hydrogen contents in the liquid products derived from the co-cracking of XVR+PP+SC+CL increased compared to their theoretical average values. The 13C NMR spectrum of the liquid products obtained from the co-cracking of XVR+PP+SC+CL showed the presence of two intense sharp peaks at 111.5 and 144.4 ppm and relative intensities were found to be 2.5% and 2.9%, respectively. Approximately, 4.2% of the total carbons arise from the aromatic species and 90.5% from the aliphatic species. The aromatic carbon contents in the liquid products decreased (15.0%) compared to theoretical averages. The spectral pattern in the aliphatic region is quite complex. Although, the aliphatic spectral region is quite complex, one can estimate a number average chain length of about 10 carbons. Naphthenic and iso-paraffinic carbon contents were found to be 72.3%. It was observed that naphthenic and iso-paraffinic carbon contents in the liquid products were increased (25.4%) when XVR, PP, SC and CL were co-cracked together, compared to their theoretical average values.
3.5. HPLC analyses The determination of the aliphatics (mainly saturates) and aromatic groups (mono, di and polyaromatics) in the liquid products obtained from the cracking of petroleum vacuum residue along its co-cracking with coal, plastics and biomass, is of great importance for their utilization. These compositional data are needed for the optimization of refining process and their product performance evaluation. In the present study, no attempts were made to analyze the individual components present in the liquid products obtained from the co-cracking of petroleum vacuum residue with coal, polypropylene and petrocrop. There may be more than thousands of compounds present in each of the liquid or oil fractions. Considering the fact that oil and other fractions are used as mixtures only, attempts were made to analyze the mixture of these compounds present in different fractions. However, in this situation mostly the group functional class analyses of the liquid products obtained from the co-cracking of petroleum vacuum residue were carried out by HPLC. Petroleum vacuum residue (XVR) was found to contain 72.1% saturates, 11.8% monoaromatics and 14.4% polyaromatics. The liquid products derived from the co-cracking of the ternary mixtures of XVR+PP+SC showed the presence of maximum amount of saturates (80.8%). However, the monoaromatics and polyaromatics contents in the liquid products were found to be 9.5% and 5.9%, respectively. The liquids obtained from the ternary mixture of XVR+PP+CL were mainly aliphatic in nature (saturates content 87.4%). The liquid products also contained diaromatics and polyaromatics compound. However, the presence of these species in the liquid products was found to be very low (Table 5).
M. Ahmaruzzaman, D.K. Sharma / Fuel 87 (2008) 1967–1973 Table 5 Analyses of the liquid products obtained from co-cracking of petroleum vacuum residue by HPLC Sample
Saturates
Mono aromatics
Di aromatics
Polyaromatics
XVR (original) XVR XVR+PP+CL XVR+PP+SC
72.1 71.7 87.4 80.8
11.8 15.8 6.8 9.5
1.7 7.2 2.6 3.8
14.4 5.3 3.2 5.9
4. Conclusions Average structural parameters of the liquid products obtained from the co-cracking of ternary and quaternary mixture of XVR, PP, SC and CL were obtained from NMR analyses. From ICAP analyses it was found that the liquid products obtained from co-cracking were found to contain less than 1 ppm Ni and V, although XVR contained 51 and 94 ppm, Ni and V respectively. This shows that the metals, under study are trapped in the char during cracking as well as co-cracking of XVR with PP, SC and CL. However, the retention depends on each metal. These liquid products obtained from the co-cracking may be utilized in secondary conversion processes (such as Fluid catalytic cracking, Hydrocracking, etc.) in petroleum refinery operations. Number average and Weight average molecular weight were found to be 239 and 276, respectively in the co-cracking liquid products obtained from quaternary mixture of XVR+PP+SC+CL. The detailed analyses of the liquid confirmed that there was clear evidence that mixing of the petroleum residue with coal, polypropylene and C. procera influenced the concentrations of individual chemical compounds in the derived liquids. From FT-IR analyses it was found that the oil obtained from cracking of petroleum vacuum residue (XVR) was aliphatic in nature. The Samla coal (SC) derived liquids were found to contain phenolic compounds. The liquid products from co-cracking of XVR+PP+SC showed no peak for phenols, indicating that the higher hydrogen contents of XVR and PP acted as a hydrogenation medium for the coal product in the co-cracking of the mixture. References [1] Pant R, Chaturvedi K. Chemical analysis of Calotropis procera latex. Current Sci 1989;58:740–2. [2] Miura K, Mae K, Asaoka S, Hashimoto K. A new coal flash pyrolysis method utilizing effective radical transfer from solvent to coal. Energy Fuel 1991;5:340–6. [3] Lazaro MJ, Moliner R, Suelves I, Domeno C, Nerin C. Co-pyrolysis of a mineral waste oil/coal slurry in a continuous-mode fluidized bed reactor. J Anal Appl Pyrol 2002;65:239–52.
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[4] Suelves I, Moliner R, Lazaro MJ. Synergetic effects in the copyrolysis of coal and petroleum residues: influences of coal mineral matter and petroleum residue mass ratio. J Anal Appl Pyrol 2000;55:29–41. [5] Joo HK, Curtis CW. Catalytic coprocessing of plastics with coal and petroleum resid using NiMo/Al2O3. Energy Fuel 1996;10:603–11. [6] Joo HK, Curtis CW. Coprocessing of waste plastics with coal and petroleum residue. ACS Fuel Chem Div Prepr 1995;40:643–7. [7] Luo M, Curtis CW. Effect of reaction parameters and catalyst type on waste plastics liquefaction and coprocessing with coal. Fuel Process Technol 1996;49:177–96. [8] Luo M, Curtis CW. Thermal and catalytic coprocessing of Illinois no. 6 coal with model and commingled waste plastic. Fuel Process Technol 1996;49:91–117. [9] Luo M, Curtis CW. Catalytic two stage coprocessing of waste plastics with coal. ACS Fuel Chem Div Prepr 1996;41:1032. [10] Tang Y, Curtis CW. Thermal and catalytic coprocessing of waste tires with coal. Fuel Process Technol 1996;46:195–215. [11] Orr EC, Shi Y, Shao L, Liang J, Ding W, Anderson LL, et al. Waste oils used as solvents for different ranks of coal. Fuel Process Technol 1996;49:233–46. [12] Cakici AI, Yanik J, Ucar S, Karayildirim T, Anil H. J Mat Cycles Waste Manage 2004;6:20. [13] Gersten J, Fainberg V, Garbar A, Hetsroni G, Shindler Y. Utilization of waste polymers through one-stage low-temperature pyrolysis with oil shale. Fuel 1999;78:987–90. [14] UzumKesici ES, Casal-Banciella MD, McRae C, Snape CE, Taylor D. Co-processing of single plastic waste streams in low temperature carbonization. Fuel 1999;78:1697–702. [15] Luo M, Curtis CW. Two stage coprocessing of coal with model and commingled waste plastics mixtures. Fuel Process Technol 1999;59:163–87. [16] Ahmaruzzaman M, Sharma DK. Characterization of liquid products obtained from co-cracking of petroleum vacuum residue with coal and biomass. J Anal Appl Pyrol 2008;81:37–44. [17] Ahmaruzzaman M, Sharma DK. Co-processing of petroleum vacuum residue with coal, plastics and biomass and its synergistic effects. Energy Fuel 2007;21:891–7. [18] Ahmaruzzaman M, Sharma DK. Characterization of liquid products obtained from co-cracking of petroleum vacuum residue with plastics. Energy Fuel 2006;20:2498–503. [19] Williams PT, Williams EA. Interaction of plastics in mixed-plastics pyrolysis. Energy Fuel 1999;13:188–96. [20] Herod AA, Lazaro M-J, Domin M, Islas CA, Kandiyoti R. Molecular mass distributions and structural characterization of coal derived liquids. Fuel 2000;79:323–37. [21] John RK, Black KJT. Structural characterization of coal-tar and petroleum pitches. Energy Fuel 1993;7:420–5. [22] Herod AA, Bartle KD, Kandiyoti R. Characterization of heavy hydrocarbons by chromatographic and mass spectrometric methods: an overview. Energy Fuel 2007;21(4):2176–203. [23] Lazaro M-J, Moliner R, Suelves I, Herod AA, Kandiyoti R. Characterization of tars from the co-pyrolysis of waste lubricating oils with coal. Fuel 2001;80:179–94. [24] Miller TJ, Panvelker SV, Wender Y, Shah YT, Huffman GP. Thermal non-catalytic coprocessing of Illinois no. 6 coal with Maya resid and Boscan crude. Fuel Process Technol 1989;23:23–8. [25] Audeh CA, Yan TY. Coprocessing of petroleum residue and coal. Ind Eng Chem Res 1987;26:2419–23. [26] US Patent No. 4544479, Recovery of metal values from petroleum residua and other fractions; 1982. [27] US Patent No. 4390409, Co-processing of residual oil and coal; 1983.
Fuel 87 (2008) 1967–1973 www.fuelfirst.com
Characterization of liquid products from the co-cracking of ternary and quaternary mixture of petroleum vacuum residue, polypropylene, Samla coal and Calotropis Procera M. Ahmaruzzaman *, D.K. Sharma Centre for Energy Studies, Indian Institute of Technology Delhi, New Delhi 110016, India Received 27 June 2007; received in revised form 12 January 2008; accepted 15 January 2008 Available online 7 February 2008
Abstract The co-cracking of the petroleum vacuum residue (XVR) with polypropylene (PP), Samla coal (SC) and Calotropis procera (CL) has been carried out in a batch reactor under isothermal conditions at atmospheric pressure. The liquids obtained by co-cracking have been characterized by Fourier transform infrared spectroscopy, high performance liquid chromatography, 1H nuclear magnetic resonance (NMR), 13C NMR, gel permeation chromatography (GPC), and inductively coupled argon plasma analyses. It was found that the liquid products obtained from the co-cracking of ternary and quaternary mixtures of the petroleum vacuum residue with polypropylene, coal and C. procera contained less than 1 ppm of Ni and V. The HPLC analyses indicates that the liquids obtained from the cracking of ternary mixture of XVR+PP+CL were mainly aliphatic in nature (saturates content 87.4%). NMR analyses showed that the aromatic carbon contents decreased (15.0%) in the liquid products derived from the co-cracking of quaternary mixtures of XVR+PP+SC+CL compared to their theoretical averages (taking the averages of aromatic carbon contents of the liquids from XVR, PP, SC and CL individually). The overall results indicated that there exists a definite interaction of reactive species when XVR, PP, SC and CL were co-cracked together. Ó 2008 Elsevier Ltd. All rights reserved. Keywords: Co-cracking; Petroleum vacuum residue; Polypropylene; Samla coal
1. Introduction The rapid consumption of conventional light petroleum crude reserves has prompted the increasing need to refine lower quality heavier crude oils. The heavier crude yields more high boiling residues such as vacuum residue (VR), which may have to be refined to yield lighter and value added products. Processing of this heavier feedstock needs the development of down processing technologies such as hydro-cracking with attendant risk of catalytic poisoning and need for high hydrogen pressure and thick walled reactors and rugged valves. This leads to serious consideration of the development of technologies for the co-processing of *
Corresponding author. Tel.: +91 3842 242915. E-mail address: md_a2002@rediffmail.com (M. Ahmaruzzaman).
0016-2361/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2008.01.007
vacuum residues with other organic polymers such as coal, plastics and petrocrops [1]. The co-processing of petroleum vacuum residue, plastics, coal and biomass may also be employed as a way of eliminating waste materials and producing at the same time valuable products for industry. Pyrolysis of coal is a good method for producing chemicals such as BTX and light olefins, but the yields of these products are limited because of the low hydrogen to carbon ratio in coal [2]. For this reason, it is necessary to supply hydrogen from other sources. Petroleum residues, which are hydrogen-rich compounds, can act as hydrogen donors in co-processing reactions. Thus, co-processing of petroleum vacuum residue with coal may synergize the production of lighter and value added products. Lazaro et al. [3] reported that the tar obtained from the coal/oil mixture is more similar to the tar from oil than to the tar from coal,
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M. Ahmaruzzaman, D.K. Sharma / Fuel 87 (2008) 1967–1973
Nomenclature XVR PP
petroleum vacuum residue polypropylene
reflecting synergy in the co-pyrolysis reactions. Suelves et al. [4] have studied the co-cracking of coal and petroleum residue. They reported that there exists significant synergistic interaction when coal and petroleum residue are copyrolysed. Joo and Curtis [5] have shown that heavy petroleum resid acts as an effective bridging solvent that when added to coal and waste plastics provide a medium for their mutual dissolution. Pyrolysis of waste plastics is also currently being investigated as a feasible processing method for waste plastics with the goal of producing fuels or chemical feedstocks. Waste plastics are also being fed as refinery and coker feeds [6]. Co-processing of waste plastics with coal provides another alternative to the production of fuels and chemical feedstocks from waste plastics. Inclusion of the abundant hydrocarbon resource coal in the pyrolysis of waste plastics not only provides additional hydrocarbon feedstock but also increases the capacity for producing quantities of fuels and chemical feedstocks. The feasibility of co-processing coal with waste plastics is dependent on the type of plastic and catalyst used. Researchers have investigated the direct liquefaction of coal with waste plastics and have evaluated a number of different processing parameters and catalysts [7–9]. The problems which they have encountered include the incompatibility of the starting reactants and the need for specific catalysts and reaction parameters to promote the desired reactions for each reactant. Thermal and catalytic co-processing of waste tires and coal was performed using waste tires from two sources and coals of three different ranks [10]. Bituminous coals yielded higher conversions than either subbituminous coal or lignite when co-processed with waste tire. The efficiency of the conversion of co-processed coal and waste plastics to THF soluble material depends upon the composition of the plastics, and the type of solvent used, if any. Co-processing of waste plastics with vacuum residue can achieve the purpose of waste recycling into commercially viable chemicals and fuels. Co-processing of waste lubricating oil with coal or plastics has also been studied as waste lubricating oil can provide good solvency for the straight chain common thermoplastics and coal [11,12]. Gersten et al. [13] characterized the liquid products obtained from combined pyrolysis of waste polymer/oil shale mixture. UzumKesici et al. [14] studied the co-pyrolysis of single plastic waste stream in low temperature carbonization with coal and characterized the tars obtained from coal/polystyrene co-processing. Co-cracking of coal with waste plastics in two separate stages was investigated in order to tailor the reaction conditions and catalysts used in each stage for the materials present [15].
SC CL
Samla coal Calotropis procera
The co-processing of petroleum vacuum residue with polypropylene, Samla coal and Calotropis procera was studied for exploring the possibility of their utilization to obtain liquid products. The characterization of the liquid products obtained from the co-cracking of ternary (XVR+PP+SC and XVR+PP+CL, 1:1:1, wt/wt) and quaternary mixtures (XVR+PP+SC+CL, 1:1:1:1, wt/wt) have been carried out presently, in order to state the occurrence of interaction among petroleum vacuum residue, coal, polypropylene and petrocrops. The techniques used for characterization were mainly FT-IR, 1H NMR, 13C NMR, high-performance liquid chromatography, gel permeation chromatography (GPC), and inductively coupled argon plasma (ICAP) analyses. To the best of our knowledge, no one has yet characterized the liquid products obtained from the co-cracking of ternary and quaternary mixtures of XVR, PP, SC and CL. 2. Experimental 2.1. Materials and method The analyses of the materials (XVR, PP, SC and CL) used for co-cracking were reported in the previous paper [16]. In a typical experiment, the reactor was flushed with nitrogen and heated to the desired temperature. The feedstocks (XVR as well as PP, SC, and CL along with their ternary, 1:1:1, wt/wt and quaternary mixture, 1:1:1:1 wt/ wt) were taken in a small crucible-type container and introduced into the reactor as soon as the reactor reached the desired temperature (460 °C); it was kept at this temperature for 2 h. The liquid product was collected in a small vessel maintained at room temperature and as such used for analysis. The reproducibility of the cracking experiments was ±2–3%. The details of the reactor and experimental set up have been reported elsewhere [17]. 2.2. Liquid product analyses 2.2.1. FT-IR The IR spectra were recorded as thin films between KBr windows. A total of forty 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 FT-IR system equipped with deuterated triglycene sulphate). 2.2.2. NMR 1 H 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
M. Ahmaruzzaman, D.K. Sharma / Fuel 87 (2008) 1967–1973
acetonate as the relaxation agent and tetra methyl silane (TMS) as the internal reference. 2.2.3. ICAP The liquid samples were diluted 10 times with aviation turbine fuel and were subjected to ICAP analyses. A multi element standard (S-21) was used for calibration. The ICAP operating parameters were as follows: RF (Power) kw, 1.3 (organic); Coolant gas, 18 LPM; 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. 2.2.4. HPLC HPLC analyses were carried out using n-hexane as the solvent. The column used was the amino propyl silica–dual column (25 cm 4.6 mm). The instrument used was the Waters 515 with UV and RI detectors. 2.2.5. GPC GPC analyses were carried using tetra hydro furan 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 ˚ , 60 cm column, 5 l; and the standard used GEL-100 A was paraffins a having molecular weight of 618, 492, 310, and 170. 3. Results and discussion 3.1. GPC analyses Table 1 shows the molecular weight distribution of the liquid products obtained from the co-processing of petroleum vacuum residue with polypropylene, coal and petrocrops at 460 °C. The liquids obtained from the cracking of petroleum vacuum residue were analyzed using the gel permeation chromatography method and detailed discussion has been reported in the previous paper [18]. The liquid products obtained from the cracking of PP at 460 °C were found to have a Mn and Mw of 263 and Table 1 Molecular weight distribution of the liquid products obtained by cocracking of petroleum vacuum residue with polypropylene, coal and petrocrop Sample
Molecular weight (%)
Mn
Mw
Mp
Poly dispersity
XVR
100 22.6 62.0 15.4 100 63.2 36.8 100 100 100
105 1228 365 138 263 <100 225 187 180 239
168 1253 450 144 305
209 1379 316 184 275
1.60 1.02 1.23 1.04 1.16
273
1.10 1.40 1.40 1.15
SC PP CL XVR+PP+SC XVR+PP+CL XVR+PP+SC+CL
204 260 273 276
1969
305, respectively. Williams and Williams [19] also reported the similar molecular weight distribution of the PP pyrolysed liquids (Mn and Mw of 280 and 439, respectively). The polydispersity index was found to be 1.16. The liquid products obtained from the cracking of coal at 460 °C also showed a range of molecular weight. A total of 22.6% of the liquid products possess a number average and molecular weight average of 1228 and 1253, respectively. Most of the liquid products (62.0%) had a number average and weight average molecular weight of 365 and 450, respectively. Herod et al. [20] showed that more than 50% of the coal derived liquids are likely to be composed of material with molecular masses in the 1000–5000 U ranges. However, Kershaw and Black [21] reported that the THF soluble fraction of coal-tar pitch (average MW = 835) contains more highly condensed aromatic ring systems and significantly different alkyl substituents than the lower molecular weight fractions. About 60% of the aliphatic carbon in this higher molecular weight fraction is in the – CH2CH3 or >CHCH3 groups, while in the lower molecular weight fractions –CH2– and –CH3 groups predominate. The liquid products derived from the cracking of C. procera at 460 °C showed that 63.2% of the liquids possess molecular weight less than 100, indicating the oil to be a low-viscosity-oil. A total of 36.8% of the liquid products have a number average (Mn) and weight average molecular weight (Mw) of 225 and 204, respectively. The polydispersity index was found to be 1.1. However, Herod et al. [22] reported that much of the work that indicates upper mass limits of 1000–1500 U for coal tars, pitches, and petroleum asphaltenes can be explained in terms of limitations of the particular analytical techniques. The liquid products obtained from the co-cracking of the ternary mixture of XVR+PP+SC (1:1:1, wt/wt) showed a number average of 187 and weight average molecular weight of 260. While the number and weight average data for the liquid products was reduced for co-cracking liquids derived from the ternary mixture of XVR+PP+SC, the molecular weight distribution was also reduced. However, the polydispersity index suggest that the liquids are quite complex containing a complex range of compounds. The peak average molecular weight of the liquid products from the ternary mixture of XVR+PP+SC was found to be 260. The molecular weight distribution of the liquid products derived from the co-cracking of XVR+PP+CL (1:1:1, wt/ wt) has been shown in the Table 1.The liquid products were found to have a Mn and Mw of 180 and 273, respectively. It was found that there was an overall reduction of the molecular weight distribution of the liquid products when they were co-cracked together. This suggests that there is a definite interaction of reactive species (free radicals generated from XVR, PP, and CL) during co-cracking of the ternary mixture of XVR+PP+CL, which produces a range of molecular weight chemical species. Lazaro et al. [23] observed relative similarity between GPC profiles of the tars from the coal/waste lubricating oil mixture and that of the waste lubricating oil (alone). In addition, the
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at 888 cm 1 may be assigned to the characteristic vibrational mode of the out-of-plane C–H bending in alkenes. The FT-IR spectrum indicated that the liquid products from the cracking of coal contained phenols (broad band at nearly 3300 cm 1) whereas the liquid products from the cracking of XVR and PP did not contain phenols. Interestingly, the liquid products from the co-cracking of XVR+PP+SC showed no peak for phenols, indicating that the higher hydrogen contents of XVR and PP acted as a hydrogenation medium for the coal product in the cocracking of the mixture. The liquid products derived from the co-cracking of XVR+PP+CL gave very similar FT-IR spectra, which consist essentially of the mixed spectra from each component. The spectra contain dominantly paraffinic (alkane) peaks (and also alkene) derived from the petroleum residue and polypropylene. For example, the alkane and alkene peaks are illustrated by the presence of CH3, –CH2 and C–H functional groups between 2800 and 3000 cm 1 and 1350–1500 cm 1 and alkene structures is indicated by the peaks between 980 and 890 cm 1. The presence of broad peak at nearly 3437 cm 1 due to the phenolic –OH groups arises from the C. procera. The FT-IR spectra of the liquid products obtained from the co-cracking of XVR+PP+SC+CL was found to be closely resembled to that obtained from petroleum residue and polypropylene rather than that from the coal and C. procera. Although, a small broad peak appears at 3427 cm 1 due to the presence of –OH groups. Like the liquid products from XVR and PP, the presence of peaks between 3000 and 2800 cm 1 and the peak in the region from 1350 to 1500 cm 1 due to the C–H bonds indicate the presence of aliphatic group. The peak at 1657 cm 1 indicates the presence of olefinic compounds. The presence of ketonic functional group is made evident by the 1722 cm 1 C@O stretching band.
excluded GPC peak corresponding to the largest molecules of the coal tar almost disappeared in the mixture tar and was smaller than that for the waste lubricating oil (alone). They also showed that the coal/oil mixture tar did not show an intermediate behaviour between the waste lubricating oil and the coal samples; therefore, there appears to be a degree of synergistic interaction between the two samples during co-pyrolysis. The liquid products derived from the quaternary mixtures of XVR+PP+SC+CL (1:1:1:1, wt/wt) showed a number and weight average molecular weight of 239 and 276, respectively. Thus, it was found that there was an overall reduction of molecular weight distributions when XVR+PP+SC+CL were co-cracked together. This may be due to the fact that the presence of XVR, PP, SC and CL together in a reactor generates a plethora of reactive moieties as radicals or radical ions, which synergises and co-synergises the cracking of different fuels/ materials. The peak average molecular weight of the liquid products obtained from XVR+PP+SC+CL was found to be 273, which was almost the same as that of the liquid from PP cracking. In addition, the polydispersity index was reduced compared to the liquids derived from the individual XVR, PP, SC and CL cracking. The liquid products from the cracking of quaternary mixture of XVR+PP+SC+CL were found to be more viscous compared to the liquid derived from the ternary mixture of XVR+PP+SC and XVR+PP+CL. 3.2. FT-IR analyses The overall spectrum of the liquid products from the cracking of XVR is dominated by the presence of alkane compounds and that of the PP cracking liquid products is dominated by the presence of alkane and alkene compounds, as reported in the previous paper [18]. The FTIR analysis showed that the liquid products from the cracking of CL are dominated by the presence of mostly aliphatic components. The FT-IR spectrum of the liquid products obtained from the co-cracking of XVR+PP+SC closely resembled to that obtained from petroleum residue and polypropylene rather than that from the coal. Like the liquids from XVR and PP, the presence of peaks between 3000 and 2800 cm 1 and the peak in the region from 1350 to 1500 cm 1 due to the C–H bonds indicate the presence of aliphatic groups. The peak at 1649 cm 1 indicates the presence of olefinic compounds. The intense absorption band
3.3. Metal analyses Results from metal analyses of the original petroleum vacuum residue and the liquid products obtained from the cracking of XVR as well as co-cracking with polypropylene, coal and petrocrops are shown in Table 2. It is interesting that the liquid products obtained from the coprocessing of petroleum residue with coal, polypropylene and petrocrops contained less than 1 ppm of Ni and V. These liquid products, can, therefore be utilized in secondary conversion processes (such as Fluid catalytic cracking,
Table 2 Metal analyses of the liquid products obtained from co-cracking of petroleum vacuum residue with polypropylene, coal and Calotropis procera Liquid (from)
Zn, ppm
Ca, ppm
Fe, ppm
Mg, ppm
Na, ppm
XVR (original) XVR PP XVR+PP+SC XVR+PP+CL
12 5 2 6 10
3 <1 <1 1 4
5 <1 <1 <1 <1
5 <1 <1
4 <1 <1
Al, ppm
Ni, ppm
V, ppm
<1 <1 1 1
51 <1 <1 <1 <1
94 <1 <1 <1 <1
M. Ahmaruzzaman, D.K. Sharma / Fuel 87 (2008) 1967–1973
Hydrocracking, etc.) in petroleum refinery operations. The demetalation reactions are thought to proceed by way of thermal breakdown of asphaltenic and metal-containing compounds of the residue and of the coal to reactive radicals. These fragments which are generated as a result of thermal treatment react with each other and form very small amounts of metal-containing insolubles which then deposit on the solid fraction of the co-cracked mixture. The above results also indicate that the metals under study are trapped in the char during cracking as well as co-cracking processes; however, the retention depends on each metal. In particular, Ni, V, and Fe show the biggest retention, so that the contents of these metals in the liquid products are significantly lower than in the parent petroleum residue. It was reported [24] that removal of metallic impurities from the liquid products during co-processing of coal with heavy oil was probably due to their deposition on the coal residue or pitch. Audeh and Yan [25] also showed that the petroleum residue is substantially demetalated when coprocessed with coal. Visbreaking with coal followed by deasphalting gives 81% and 89% demetalation of nickel and vanadium from the Joliet vacuum residue [26]. Orr et al. [11] reported that the oils derived from co-cracking coals of different rank with the automotive crankcase oil indicated that these oils were lower in overall trace metals compared with the trace metal content of untreated automobile crankcase oil. Metal-free distillates/liquids was generated by co-processing coal and residual oil whereby the metals contained in the resid are deposited on the solid portion of the coal which remains after the volatilized/solubilized portion of the coal is generated and removed [27]. 3.4. 1H and
13
C NMR spectral analyses
Definitions of 1H and 13C NMR chemical shifts for hydrocarbons are shown in the Table 3. The detailed analyses of the liquid products derived from the cracking of XVR have been reported in the previous paper [18]. The Table 3 Definitions of 1H and
13
1971
1
H NMR spectrum showed that the liquid products from the cracking of polypropylene were highly aliphatic in nature. The liquid products derived from the cracking of coal showed that aliphatic hydrogen distributions were mainly Ha (18.4%) and Hb+c (52.0%) and some HCH3 (15.1%). The 13C NMR spectrum showed that approximately 45.1% of the total carbon present in the liquid products obtained from the cracking of coal arises from the aromatic species. The overall 13C NMR spectrum of the liquids from the cracking of C. procera was found to be quite complex probably due to the large number of components as well as the complex structure of each individual component present in the liquid products. The 1H NMR spectrum of the liquid products obtained from the co-cracking of XVR+PP+SC indicates that aliphatic components constitute the principal molecular species present (94.7%). It was also found that the aliphatic hydrogen contents in the liquid products increased when XVR, PP and SC were co-cracked together compared to their theoretical values. This may be due to the fact that XVR and PP may be acted as a H-donor medium for the coal cracking products. Approximately, 1.3% of the total hydrogens present in the liquids arise from aromatic species. The 13C NMR spectrum of the liquid products from the co-cracking of XVR+PP+SC showed the presence of two sharp peaks at 111.5 (terminal methyl carbon, @CH2) and 144.2 ppm (methyl carbon in the vinyl group, –CH@), respectively. A small peak at 167.4 ppm indicates the presence of carbonyl type compounds and constitutes 0.1% of the total carbons. Approximately, 13.3% of the total carbons present in the liquid products arise from aromatic species. The spectral pattern in the aliphatic region is quite complex. The 13C NMR spectrum of the liquids obtained from the co-cracking of XVR+PP+CL clearly demonstrates that aliphatic compounds constituted the principal molecular species present. The integrated data provide an estimate of 83.1% aliphatic hydrocarbons. Approximately, 12.2%
C NMR chemical shifts for hydrocarbons
Parameters
Chemical Shift (d)
Definition
HA HS Ha Hb+c HCH3 CS CPa CPb CPn CPc CA CAH
9.0 6.0 4.0 0.5 4.0 2.0 2.0 1.0 1.0 0.5 10.0 50.0 14.1 22.7 29.6 30.1 32 100 150 100–130
% % % % % % % % % % % %
Aromatic protons Aliphatic protons CH3, CH2 and CH protons a to aromatic ring CH2 and CH protons of alkyl chains b or further to ring and CH3 protons b to the ring CH3 protons of alkyl chains c or further from aromatic ring or CH3 of saturated compounds Saturated aliphatic carbons Carbon of terminal methyl group of alkyl chain a CH3–(CH2)n– (n P 4) Carbon of CH2 group b to terminal methyl of alkyl chain with n P 4 Carbon of c or higher of alkyl chain CH3 CH2 CH2 (CH2)n CH2 CH2 Carbon of c CH2 in CH3 (CH2)c CH2 (CH2)n Aromatic carbon Protonated carbon
Formulae for NMR parameters of hydrocarbons. C/H = Carbon to hydrogen ratio = [CS + CA]/[2CS + CA]. FS = C/H ratio of saturated part of sample. FA = C/H ratio of aromatic part of sample. ACL = average chain length = 2CP/CPa.
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M. Ahmaruzzaman, D.K. Sharma / Fuel 87 (2008) 1967–1973
Table 4 Average structural parameters (derived from 1H and 13C NMR data) of the liquid products obtained from co-cracking of petroleum vacuum residue with polypropylene, coal and Calotropis procera Liquid from
XVR
PP
CL
SC
XVR+PP+SC
XVR+PP+CL
XVR+PP+SC+CL
CA CS CPa CPb CPn CPc CP HA Ha Hb+c HCH3 HS H/C CAL CN + CI CAH ACL
14.3 85.7 7.4 7.1 29.4 5.7 49.5 4.0 10.1 62.8 22.5 95.4 1.9 2.7 36.2 7.4 13.5
– 90.3 5.0 6.8 5.8 0.7 18.3 – 3.1 45.3 45.9 94.4 1.9 – 72.0 – 7.3
17.2 79.6 1.5 3.2 11.8 2.2 18.7 2.9 10.6 53.3 23.0 86.8 1.8 21.7 60.8 11.9 24.3
45.1 52.9 3.9 3.8 23.2 3.5 34.3 13.8 18.4 52.0 15.1 85.5 1.5 – 18.6 – 17.6
13.3 81.0 6.0 3.7 12.9 3.4 26.0 1.3 6.0 44.4 44.3 94.7 1.9 5.7 55.1 7.6 8.72
12.2 83.1 4.5 2.3 12.6 1.8 21.2 – – – – – 1.9 – 62.0 – 9.4
4.1 90.5 3.6 2.5 10.4 1.8 18.3 2.2 4.9 51.2 38.4 94.5 2.0 – 72.3 – 10.4
of the total carbons present in the liquid products arise from aromatic species. Comparing the theoretical value of the individual cracking products from XVR, PP and CL, it was found that naphthenic and iso-paraffinic carbons were increased (5.7%) in the liquids from the co-cracking of XVR+PP+CL. Table 4 showed the detailed results. From an analysis of the integrals of the aliphatic regions, it was estimated that approximately 21.2% of the aliphatic/saturated carbons are straight-chain alkanes with an average of about 10 carbons in the alkyl group. The spectral pattern for the methyl hydrogens (0.5– 1.1 ppm) in the 1H NMR spectrum of the liquid products obtained from the co-cracking of XVR+PP+SC+CL showed an overlapping complex multiplet splitting of the hydrogen. However, the integrated spectral region suggests that approximately 94.5% of the total hydrogens are present in aliphatic moieties. It was found that aliphatic hydrogen contents in the liquid products derived from the co-cracking of XVR+PP+SC+CL increased compared to their theoretical average values. The 13C NMR spectrum of the liquid products obtained from the co-cracking of XVR+PP+SC+CL showed the presence of two intense sharp peaks at 111.5 and 144.4 ppm and relative intensities were found to be 2.5% and 2.9%, respectively. Approximately, 4.2% of the total carbons arise from the aromatic species and 90.5% from the aliphatic species. The aromatic carbon contents in the liquid products decreased (15.0%) compared to theoretical averages. The spectral pattern in the aliphatic region is quite complex. Although, the aliphatic spectral region is quite complex, one can estimate a number average chain length of about 10 carbons. Naphthenic and iso-paraffinic carbon contents were found to be 72.3%. It was observed that naphthenic and iso-paraffinic carbon contents in the liquid products were increased (25.4%) when XVR, PP, SC and CL were co-cracked together, compared to their theoretical average values.
3.5. HPLC analyses The determination of the aliphatics (mainly saturates) and aromatic groups (mono, di and polyaromatics) in the liquid products obtained from the cracking of petroleum vacuum residue along its co-cracking with coal, plastics and biomass, is of great importance for their utilization. These compositional data are needed for the optimization of refining process and their product performance evaluation. In the present study, no attempts were made to analyze the individual components present in the liquid products obtained from the co-cracking of petroleum vacuum residue with coal, polypropylene and petrocrop. There may be more than thousands of compounds present in each of the liquid or oil fractions. Considering the fact that oil and other fractions are used as mixtures only, attempts were made to analyze the mixture of these compounds present in different fractions. However, in this situation mostly the group functional class analyses of the liquid products obtained from the co-cracking of petroleum vacuum residue were carried out by HPLC. Petroleum vacuum residue (XVR) was found to contain 72.1% saturates, 11.8% monoaromatics and 14.4% polyaromatics. The liquid products derived from the co-cracking of the ternary mixtures of XVR+PP+SC showed the presence of maximum amount of saturates (80.8%). However, the monoaromatics and polyaromatics contents in the liquid products were found to be 9.5% and 5.9%, respectively. The liquids obtained from the ternary mixture of XVR+PP+CL were mainly aliphatic in nature (saturates content 87.4%). The liquid products also contained diaromatics and polyaromatics compound. However, the presence of these species in the liquid products was found to be very low (Table 5).
M. Ahmaruzzaman, D.K. Sharma / Fuel 87 (2008) 1967–1973 Table 5 Analyses of the liquid products obtained from co-cracking of petroleum vacuum residue by HPLC Sample
Saturates
Mono aromatics
Di aromatics
Polyaromatics
XVR (original) XVR XVR+PP+CL XVR+PP+SC
72.1 71.7 87.4 80.8
11.8 15.8 6.8 9.5
1.7 7.2 2.6 3.8
14.4 5.3 3.2 5.9
4. Conclusions Average structural parameters of the liquid products obtained from the co-cracking of ternary and quaternary mixture of XVR, PP, SC and CL were obtained from NMR analyses. From ICAP analyses it was found that the liquid products obtained from co-cracking were found to contain less than 1 ppm Ni and V, although XVR contained 51 and 94 ppm, Ni and V respectively. This shows that the metals, under study are trapped in the char during cracking as well as co-cracking of XVR with PP, SC and CL. However, the retention depends on each metal. These liquid products obtained from the co-cracking may be utilized in secondary conversion processes (such as Fluid catalytic cracking, Hydrocracking, etc.) in petroleum refinery operations. Number average and Weight average molecular weight were found to be 239 and 276, respectively in the co-cracking liquid products obtained from quaternary mixture of XVR+PP+SC+CL. The detailed analyses of the liquid confirmed that there was clear evidence that mixing of the petroleum residue with coal, polypropylene and C. procera influenced the concentrations of individual chemical compounds in the derived liquids. From FT-IR analyses it was found that the oil obtained from cracking of petroleum vacuum residue (XVR) was aliphatic in nature. The Samla coal (SC) derived liquids were found to contain phenolic compounds. The liquid products from co-cracking of XVR+PP+SC showed no peak for phenols, indicating that the higher hydrogen contents of XVR and PP acted as a hydrogenation medium for the coal product in the co-cracking of the mixture. References [1] Pant R, Chaturvedi K. Chemical analysis of Calotropis procera latex. Current Sci 1989;58:740–2. [2] Miura K, Mae K, Asaoka S, Hashimoto K. A new coal flash pyrolysis method utilizing effective radical transfer from solvent to coal. Energy Fuel 1991;5:340–6. [3] Lazaro MJ, Moliner R, Suelves I, Domeno C, Nerin C. Co-pyrolysis of a mineral waste oil/coal slurry in a continuous-mode fluidized bed reactor. J Anal Appl Pyrol 2002;65:239–52.
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