Characterization of Liquids Derived From Laboratory Coking of Decant

Energy & Fuels 2009, 23, 2637–2645

2637

Characterization of Liquids Derived From Laboratory Coking of Decant Oil and Co-Coking of Pittsburgh Seam Bituminous Coal with Decant Oil ¨ mer Gu¨l,† Caroline Clifford,*,† Leslie R. Rudnick,‡ and Harold H. Schobert† O EMS Energy Institute, The PennsylVania State UniVersity, UniVersity Park, PennsylVania 16802 and Ultrachem Incorporated, New Castle, Delaware 19720 ReceiVed January 8, 2009. ReVised Manuscript ReceiVed February 27, 2009

In this study, decant oil and a blend of Pittsburgh seam bituminous coal with decant oil were subjected to coking and co-coking in a laboratory-scale delayed coker. Higher yields of coke and gas were obtained from co-coking than from coking. Coal addition into the feedstock resulted in lighter overhead liquid. GC/MS analyses of gasoline, jet fuel, and diesel show that co-coking of coal/decant oil gave higher quantity aromatic components than that of coking of decant oil alone. Simulated distillation gas chromatography analyses of overhead liquids and GC/MS analyses of vacuum fractions show that when coal was reacted with a decant oil, the coal constituents contributed to the distillable liquids. To address the reproducibility of the liquid products, overhead liquid samples collected at the first, third, and fifth hours of experiments of 6 h duration were evaluated using simulated distillation gas chromatography and 1H and 13C NMR. NMR analyses of the liquid products showed that, even though there were slight changes in the 1H and 13C spectra, the standard deviation was low for the time-dependent samples. Simulated distillation gas chromatography showed that the yields of refinery boiling range materials (i.e., gasoline, jet fuel, diesel, and fuel oil cuts) were reproducible between runs. Fractionation of the overhead liquids into refinery boiling range materials (gasoline, jet fuel, diesel, fuel oil fractions) showed that the boiling range materials and chemical compositions of fractions were found to be reproducible.

For some time we and our colleagues have been investigating processes for introducing coal, or coal-derived materials, into oil refinery operations. The original aim of this work was the development of a coal-based jet fuel that would have high stability in the pyrolytic degradation regime, allowing it to be used as an on-board heat sink in addition to being the source of propulsion energy. The most important factor controlling the high-temperature thermal stability of jet fuels is chemical composition.1-3 Hydroaromatics and cycloalkanes, e.g., tetralin and decalin, stabilize free radical processes and improve various thermal properties.1,4-9 Coal-derived liquids that are rich in aromatics, such as naphthalene and methylnaphthalenes, can be

converted into hydroaromatic and cycloparaffin compounds by downstream hydrotreatment and saturation. These liquids are thus ideal candidates to be upgraded into thermally stable jet fuel.1,2 One approach to production of coal-based liquid fuels has involved blending refined chemical oil from coal tar with light cycle oil, hydrotreating, and fractionating.1,2 Liquids from this process have been successfully tested in a turboshaft engine and a solid-oxide fuel cell.10 A second approach is to add pulverized coal along with a petroleum-derived liquid as the feed to a delayed coker; this is the topic of the present paper. Delayed coking converts “bottom of the barrel” materials to more valuable, lower boiling products with a coke byproduct.11-26 Residua, thermal cracking tars, decant oil from catalytic

* To whom correspondence should be addressed. † The Pennsylvania State University. ‡ Ultrachem Incorporated. ¨ .; Rudnick, L. R.; Schobert, H. H. Energy Fuels 2006, 20, (1) Gu¨l, O 2478–2485. ¨ .; Rudnick, L. R.; Schobert, H. H. Energy Fuels 2008, 22, (2) Gu¨l, O 433–439. (3) Altin, O.; Rudnick, L. R. Prepr. Pap.sAm. Chem. Soc., DiV. Fuel Chem. 2004, 49 (1), 30–33. (4) Rudnick, L. R.; Whitehurst, D. D. The Effect of SolVent Composition of the Liquefaction BehaVior of Western Sub-Bituminous Coal; Presented at the EPRI Contractor’s Meeting, Palo Alto, CA,May 7-8, 1980. (5) Derbyshire, F. J.; Odoerfer, G. A.; Rudnick, L. R.; Varghese, P.; Whitehurst, D. D. Fundamental studies in the conVersion of coals to fuels of increased hydrogen content; EPRI Report AP- 2117 under Research Project 1655-1; EPRI: Pleasant Hill, CA, Nov 1981; Vols. 1 and 2. (6) Whitehurst, D. D.; Buttrill, S. E., Jr.; Derbyshire, F. J.; Farcasiu, M.; Odoerfer, G. A.; Rudnick, L. R. Fuel 1982, 61, 994–1005. (7) Rudnick, L. R.; Whitehurst, D. D. In New Approaches in Coal Chemistry; Blaustein, B. D., Bockrath, B. C., Friedman, S., Eds.; ACS Symposium Series 169; American Chemical Society: Washington, D.C., 1981; pp 153-171.

(8) Rudnick, L. R.; Whitehurst D. D.; Derbyshire, F. J. SolVent Compositional Changes During SCT Coal ConVersion; Presented at the AIChE Meeting, Orlando, FL,Feb 28-Mar 3, 1982. (9) Coleman, M. M.; Sobkowiak, M.; Fearnley, S. P.; Song, C. Prepr. Pap.sAmer. Chem. Soc., DiV. Petrol. Chem. 1998, 43 (3), 353–356. (10) Balster, L. M.; Corporan, E.; DeWitt, M. J.; Edwards, J. T.; Ervin, J. S.; Graham, J. L.; Lee, S. Y.; Pal, S.; Phelps, D. K.; Rudnick, L. R.; Santoro, R. J.; Schobert, H. H.; Shafer, L. M.; Striebich, R. C.; West, Z. J.; Wilson, G. R.; Woodward, R.; Zabarnick, S. Fuel Process. Technol. 2008, 89, 364–378. ¨ .; Rudnick, L. R.; Schobert, H. H. Energy Fuels 2006, 20, (11) Gu¨l, O 1647–1655. (12) White, J. L. In Petroleum DeriVed Carbons; Marvin, M. L., O’Grady, T. M., Eds.; ACS Symposium Series 21; American Chemical Society: Washington, D.C., 1976; p 440. (13) Romero Palazon, E.; Marsh, H.; Rodriguez-Reinoso, F.; Menendez, R. Extended Abstracts, 18th Biennial Conference on Carbon; American Carbon Society: Newcastle upon Tyne, U.K., Sep 1988; p 237. (14) Mochida, I.; Korai, Y.; Fujitsu, H.; Oyama, T.; Nesumu, Y. Carbon 1987, 25, 259–264. (15) Marsh, H.; Calvert, C.; Bacha, J. J. Mater. Sci. 1985, 20, 289– 302.

1. Introduction

10.1021/ef900022f CCC: $40.75  2009 American Chemical Society Published on Web 04/21/2009

2638

Energy & Fuels, Vol. 23, 2009

cracking, or tars from ethylene manufacture have been used as feedstocks. Coke quality varies with the chemical composition of the feedstock, a fact that creates a significant incentive to examine the coking process and how it relates to the composition of the feedstock.11,27,28 A wide spectrum of processes and processing conditions has been reported.11,29-39 We use the term co-coking to describe a process in which pulverized coal is added to the feed to the coker. Coal is fed as a slurry with a coker feed, which in the work reported here was a decant oil. Volatile components of the coal and decant oil would be vaporized and subsequently condensed. The resulting coal-based liquid and coke would then be refined to produce a thermally stable jet fuel, other transportation fuels, and value-added carbon byproduct. This study addresses the coking of decant oil and co-coking of bituminous coal/decant oil blends. In this study, the focus is on the liquid products obtained from the process of coking and co-coking and the contribution of coal to the overhead liquids. 2. Experimental Section 2.1. Materials. The petroleum-based decant oil used in this study represents a typical decant oil with a sulfur content of 3.0 wt %. The decant oil was obtained from United Refining Co., Warren, PA, and is labeled EI-107. The coal used in this study was a Pittsburgh seam bituminous coal and is labeled EI-186. The coal was obtained from Mine No. 84, CONSOL Energy Inc. in (16) Mochida, I.; Oyama, T.; Korai, Y.; Qiug Fei, Y. Fuel 1988, 67, 1171–1181. (17) Brooks, J. D.; Taylor, G. H. In Chemistry and Physics of Carbon; Walker, P. L., Jr., Ed.; Marcel Dekker Inc.: New York, 1968; Vol. 4, p 243. (18) Marsh, H.; Walker, P. L., Jr. In Chemistry and Physics of Carbon; Walker, P. L., Jr., Ed.; Marcel Dekker Inc.: New York, 1979; Vol. 15, p 228. (19) Marsh, H.; Menendez, R. In Introduction to Carbon Science; Marsh, H., Ed.; Butterworths: London, 1989; p 59. (20) Buechler, M.; White, J. L. 15th Biennial Conference on Carbon; American Carbon Society: Philadelphia, PA, 1981; p 182. (21) Mochida, I.; Korai, Y.; Oyama, T.; Nesumi, Y.; Todo, Y. Carbon 1989, 27, 359–365. (22) Mochida, I.; Matsuoka, H.; Fujitsu, H.; Korai, Y.; Takeshita, K. Carbon 1981, 19, 213–216. (23) Diefendorf, R. J. 16th Biennial Conference on Carbon; American Carbon Society: San Diego, CA, 1983; p 26. (24) Mochida, I.; Korai, Y.; Oyama, T. Carbon 1987, 25, 273–278. (25) White, J. L.; Buechler, M.; Ng, C. B. Carbon 1982, 20, 536–538. (26) Lewis, R. T.; Lewis, I. C.; Greinke, R. D.; Strong, L. S. Carbon 1987, 25, 289. (27) Rudnick, L. R.; Galya, L. G. Energy Fuels 1991, 5, 733–738. (28) Rudnick L. R.; Galya, L. G. A Study of Structural and Chemical Changes of Liquid Products During Coking of Petroleum Residua; Presented at the 21st Biennial Conference on Carbon, Buffalo, NY, Jun 13-18, 1993; pp 338-339. (29) Nirell, K. G. Delayed coking process and method of formulating delayed coking feed charge. U.S. Patent 6,048,448, 2000. (30) Goyal, S. K.; Faagau, G. S. Coking process with decant oil addition to reduce coke yield. U.S. Patent 4,832,823, 1989. (31) Varghese, P. Coking of coal with petroleum residua. U.S. Patent 4,427,532, 1984. (32) Wynne F. E., Jr.; Lopez, J.; Zaborowsky, E. J. Coke from coal and petroleum. U.S. Patent 4,259,178, 1981. (33) Li, K. W. Manufacture of petroleum coke with fines recycling. U.S. Patent 4,082,650, 1978. (34) Chen, N. Y.; Walsh, D. E. Delayed coking process. U.S. Patent 4,302,324, 1981. (35) York E. D.; Rustam, K. F.; Hall, R. D. Delayed coking and dedusting process. U.S. Patent 4,421,629, 1983. (36) Allan, D. E. Delayed coking process with split fresh feed. U.S. Patent 4,492,625, 1985. (37) Calderon, J. L.; Betancourt, H. Process and facility for making coke suitable for metallurgical purposes. U.S. Patent 4,551,232, 1985. (38) Becraft, L. G. Method for producing isotropic coke. U.S. Patent 5,174,891, 1992. (39) Rudnick, L. R. Process for upgrading heavy petroleum feed stock. U.S. Patent 4,642,175, 1987.

Gu¨l et al. Table 1. Proximate and Ultimate Analysis of the Feeds Used in this Study proximate

analysisa

coal

decant oil

Pittsburgh Seam EI-186

EI-107

0.99 35.6 63.4

0.22

ash (wt %)c volatile matter (wt %) fixed carbon (wt %) carbon (wt %) hydrogen (wt %) nitrogen (wt %) sulfur (wt %) oxygen (by diff.) (wt %)

ultimate analysisa 84.6 5.3 1.6 1.1 6.4

89.6 7.2 0.2 3.0 -

fluidity datab fluid temperature range (°C) maximum fluidity (ddpm) softening temperature (°C)

93 29 527 385

organic petrography (vol. % mineral matter free) total vitrinte (vol. %) 96.2 total liptinite (vol. %) 1.5 total inertinite (vol. %) 2.3 ash mineral composition (%) silicon dioxide 41.8 aluminum oxide 27.3 ferric oxide 13.6 phosphorus pentoxide 0.61 calcium oxide 5.65 magnesium oxide 0.74 sodium oxide 0.72 potassium oxide 1.64 a Values reported on a dry basis. plastometer. c wt % ) weight percent.

b

Determined using a Geisler

Table 2. Conditions and Product Distributions for Coking and Co-Coking Experiments DO coking

DO/coal co-coking 1-4

conditions

DO/coal (100/0)

DO/coal (80/20)

feed time (h) hold at 500 °C (h) feed rate (g/min) preheater inlet (°C) preheater outlet (°C) coke drum inlet (°C) coke drum lower/middle (°C) coke drum top (°C) material fed to reactor (g)

6 24 16.7 148 446 471 474 476 5960

6 24 16.7 121 436 500 494 477 5912

product coke + liquid product (g) liquid/coke coke (wt %) liquid product (wt %) gas (wt %)

mean of 4 replicates 5876 3.2 22.2 70.5 5.8

5360 2.3 27.8 62.9 7.7

Washington Co., PA. Proximate and ultimate analyses for these feedstocks are shown in Table 1. The fluidity data, petrographic analyses, and ash mineral composition of coal (only major elements) are also given in Table 1. 2.2. Apparatus. The large laboratory-scale delayed coker (LSDC) consisted of a 7.5 cm i.d. × 102.5 cm cylindrical reactor unit having an internal volume of approximately 4.5 L. The preheater was a 2.5 cm o.d. × 51 cm stainless steel tube fitted directly to the bottom of the reactor. This was fed by a 0.95 cm (3/8 in.) o.d. feed line that was outside the furnace and was heated to 120 °C using heating tape. This design configuration allows for essentially trouble-free pumping of the coal-decant oil slurry over a wide temperature range. The temperature gradient through this 51 cm preheater is on the order of 200 °C, with an outlet temperature of 432-441 °C. This was connected to a 0.64 cm (1/4 in.) o.d. line that carried feedstocks from the feed pump. Further details of the design and construction of this unit and initial results can be found elsewhere.11

Coking of Pittsburgh Seam Bituminous Coal

Energy & Fuels, Vol. 23, 2009 2639

Table 3. Distribution of 1H NMR Signals of Original Decant Oil and Overhead Liquids Obtained from Delayed Coking and Co-Coking band, ppm

DO (original)

DO coking

DO/coal co-coking 1-4, mean

0.5-1.0 1.0-1.7 1.7-1.9 1.9-2.1 2.1-2.4 2.4-3.5 3.5-4.5 4.5-6.0 aliphatic (total) 6.0-7.2 7.2-8.3 8.3-8.9 8.9-9.3 aromatic (total)

4.8 10.7 0.9 2.2 17.9 19.2 1.3 0.0 57.0 10.3 29.7 2.9 0.1 43.0

5.7 12.5 1.1 3.8 20.9 10.8 0.5 0.1 55.5 13.4 29.8 1.3 0.01 44.5

5.6 12.7 1.3 4.3 20.4 12.4 0.5 0.08 57.2 13.3 28.0 1.4 0.04 42.8

Table 4. Distribution of 13C NMR Signals of Original Decant Oil and Overhead Liquids Obtained from Delayed Coking and Co-Coking band, ppm

DO (original)

DO coking

DO/coal co-coking 1-4, mean

11.0-12.5 12.5-15.0 15.0-18.0 18.0-20.5 20.5-22.5 22.5-24.0 24.0-27.5 27.5-37.0 37.0-60.0 aliphatic (total) 108.0-118.0 118.0-129.5 129.5-133.0 133.0-135.0 135.0-138.0 138.0-160.0 aromatic (total)

0.2 1.3 1.6 4.6 4.5 1.0 1.5 6.5 3.9 25.0 1.2 49.7 10.2 3.6 5.1 5.1 75.0

0.2 1.4 1.4 4.3 4.6 1.0 1.1 6.8 2.6 23.4 1.6 52.3 9.4 3.2 4.9 5.1 76.6

0.2 1.5 1.5 4.5 4.4 0.9 1.1 6.4 2.6 23.1 1.5 49.5 10.6 3.8 5.4 6.1 76.9

2.3. Reaction Procedures. The following operating conditions were used: coke drum inlet temperature 500 °C, coke drum pressure 25 psig, coal/decant oil slurry feed rate 16.7 g/min, and feed introduction to the coker 6 h. At the conclusion of each experiment, the coke drum was maintained at that temperature for an additional 24 h to ensure carbonization of nonvolatile components. The detailed conditions and product distributions for co-coking experiments are given in Table 2. Coal was fed in slurry form with the decant oil (coal/decant oil ratio was 1:4) into the coker. The slurry feed in these experiments was continuous and measured gravimetrically with time. The feed was initially charged to a heated feedstock vessel that was continuously mixed throughout the co-coking experiment to achieve and maintain homogeneity. The feedstock vessel was placed on a balance for monitoring the feeding rate. The temperature of this vessel was kept at 66 °C. Feed was heated in the lines prior to the preheater to about 120 °C and then to about 440 °C in the preheater. Heated feedstock from the preheater was fed to the coker drum. Light hydrocarbons that exit from the top of coker drum pass through a series of condensers. The liquid products were passed through a series of condensers and valves to facilitate the isolation of liquid as a function of reaction time. At the conclusion of the experiment the mass of the liquid condensate was determined. In addition, the carbonaceous solid was removed from the coke drum and weighed. Gas yield was calculated by difference. The work reported here is based on 12 runs. During each run approximately 20-25 mL liquid samples were taken at predetermined time intervals. To assess the liquid process repeatability, 4 of the 12 runs (the third, fifth, seventh, and ninth) were selected as representatives. From each selected run, the first, third, and fifth hourly samples and combined oils were

characterized to probe process repeatability as well as reproducibility between runs. While this paper mainly deals with liquid products isolated during coking and co-coking, the solid products are mentioned here to completely describe the reaction system and the reproducibility of the system. The solids from these runs were characterized in detail, and results will be reported in a subsequent publication. 2.4. Analytical Procedures. The collected overhead liquids from coking and from each co-coking experiment were vacuum distilled into cuts corresponding to gasoline, jet fuel, diesel, and fuel oil. Original decant oil was also vacuum fractionated. These distillations were performed on the bulk overhead liquid samples to obtain the actual yields of each boiling-range material. The use of vacuum minimizes sample decomposition. The distillations were conducted in a 2 L flask mounted in a heating mantle. A 1200 g sample was weighed into the flask, and a magnetic stirrer was used to ensure a homogeneous temperature in the liquid inside the flask. Approximately 5-10 mmHg vacuum was used for distillation, and the temperature/pressure readings were corrected to boiling point so that the corresponding cut, gasoline (initial boiling point (IBP)–180 °C), jet fuel (180-270 °C), diesel (270-332 °C), fuel oil (332 °C–final boiling point (FBP)), could be made. 1H and 13C NMR analyses, using a Bruker AMX 360 NMR spectrometer operating at 9.4 T, were performed on liquid samples. Samples were dissolved in a 1/1 volume ratio in CDCl3 containing 1 vol % of tetramethylsilane (TMS) as standard. A pulse width was 5 µs with a pulse delay of 5 s for 1H with a 90° tip angle and a 5 µs pulse width and a pulse delay of 45 s for 13C with a 70° tip angle were used to ensure quantitative results. In 13C analyses, Cr(AcAc)3 (20 mg) was used per 2 mL of overhead liquid/CDCl3 mixture. Peaks were assigned based on chemical shift values from the literature.2,11,40 Simulated distillation gas chromatography (SimDist-GC) was performed according to ASTM D 2887 using an HP 5890 GC-FID fitted with a MXT-500 simulated distillation column (10 m, 0.53 mm i.d., and 2.65 µm) (Restek). Carrier gas flow rate was adjusted to 13 mL/min for SimDist GC analysis, and SimDis Expert 6.3 software was used to calculate the percentage of fractions. GC/MS analysis, using a Shimadzu QP5000 spectrometer, was performed on vacuum-fractionated liquid samples. The temperature program for gasoline was 35 °C (10 min), programmed from 35 to 175 °C at 4 °C/min, and then held at 175 °C for an additional 5 min (total run time was 50 min). The temperature program for jet fuel was 40 °C (4 min), from 40 to 220 °C at 4 °C/min, and then held at 220 °C for an additional 10 min (total run time was 59 min). The program for diesel was set as 40 °C (0 min), programmed from 40 to 120 °C at 15 °C/min, from 120 to 250 °C at 4 °C/min, and then held at 250 °C for an additional 8 min (total run time was 46 min). A XTI-5 ((Restek) 30 m × 0.25 mm × 0.25 µm) column was used for the GC/MS analyses.

3. Results and Discussion In this paper, the discussion focuses on the effect of coal on yield distribution, the overhead liquid distribution, and the composition of liquid fractions. It should be noted here that when coking and co-coking results are compared and discussed, co-coking results represent the mean of four replicates. The process reproducibility will also be discussed. It should also be noted here that gasoline, jet fuel, diesel, and fuel oil are mentioned throughout the manuscript; these titles actually refer to the gasoline fraction, jet fuel fraction, diesel fraction, and fuel oil fraction, as they were not further processed to be actual commercial fuels and are defined by boiling cut points in the experimental section for the analytical procedure for vacuum distillation and SimDist-GC. (40) Rodriguez, J.; Tierney, J. W.; Wender, I. Fuel 1994, 73 (12), 1870– 1875. (41) Fickinger, A. E.; Badger, M. W.; Mitchell, G. D.; Schobert, H. H. Prepr. Pap.sAmer. Chem. Soc., DiV. Fuel Chem. 2000, 45 (2), 299–303.

2640


Gu¨l et al.

Table 5. Product Distributions of Overhead Liquid by Weight from Vacuum Distillation run no.

IBP-180°C, IBP-356 °F Gasoline

180-270 °C, 356-518 °F jet fuel

270-332 °C, 518-630 °F diesel

332-FBP °C, 630-FBP °F fuel oil

DO (original) DO coking mean of DO/coal co-coking 1-4

0.2 0.8 2.4

0.6 3.5 4.0

4.0 3.5 5.0

94.6 91.7 87.7

Table 6. Product Distributions of Overhead Liquid by Weight from Simulated Distillation Gas Chromatography run no.

IBP-180°C, IBP-356 °F Gasoline

180-270 °C, 356-518 °F jet fuel

270-332 °C, 518-630 °F diesel


DO (original) DO coking mean of DO/coal co-coking 1-4

0.9 1.4 2.1

0.8 3.4 3.6

3.2 5.9 4.6

94.1 88.4 88.8

3.1. Effect of Coal on Yield Distribution. Delayed coking of decant oil and co-coking of decant oil/coal blends were conducted in the large laboratory-scale delayed coker described in section 2.2. The conditions used in each of the experiments and yield data are shown in Table 2. Coking of decant oil alone produced 22.2% coke, 70.5% liquid, and 5.8% gas (gas yield was calculated by difference). It is also noteworthy to mention here that the contents of the preheater after reaction (which is ∼1.5%) were included in the calculation of gas yields. The overall coking yields measured in the work reported here are comparable to those reported from an industrial delayed coking process (70% liquids, 20% coke, and 10% gas).41-43 Co-coking of decant oil/coal blend produced higher coke and gas yields but less liquid product than those of coking. The average percent values for coke, liquid, and gas yields from the co-coking of decant oil/coal blend are 27.8%, 62.9%, and 7.7%, respectively. The liquid/coke ratio is another indicator to show an increase in coke and a decrease in liquid yield: 3.2 for coking against 2.3 for co-coking (Table 2). We reported in a previous publication a similar finding, that coal addition into the coker feedstock resulted in a higher coke yield and less liquid yield.11 3.2. Composition of Liquid Product and Comparison of Fractionation Yields: Effect of Coal on Liquid Stream. Collected overhead liquids from coking and co-coking and original decant oil were analyzed using 1H and 13C NMR. Cocoking NMR analyses results, given in Tables 3 and 4, show the distribution of 1H and 13C NMR results, respectively. On the basis of the 1H NMR spectra of coking and co-coking overhead liquids, aliphatic hydrogens mostly consisted of (1) CH3 hydrogens R to aromatic carbons (2.1-2.4 ppm), (2) CH2 hydrogens β and further from aromatic rings and some β CH3 hydrogens (1.0-1.7 ppm), and (3) CH and CH2 hydrogens R to aromatic carbons (2.4-3.5 ppm). Aromatic hydrogens mostly consisted of two- to four-ring fused-ring hydrogens and singlering aromatic hydrogens. No essential differences were observed between bands and total aliphatic and aromatic hydrogen for the coking and co-coking overhead liquids (Table 3). As determined by 1H NMR, the average values were 57.2% versus 55.5% for total aliphatics and 42.8% versus 44.5% for total aromatic hydrogens as calculated for coking and co-coking overhead liquids, respectively. These overall values are almost the same as the original decant oil feedstock values that are 57.0% and 43.0%. However, there were some slight structural differences between the original decant oil and overhead liquids when examining the individual contributions; the overhead liquids from coking and co-coking showed an increase in methyl groups on aromatics (2.1-2.4 ppm) and a decrease in CH and (42) Speight, J. G. The Chemistry and Technology of Coal; Dekker: New York, 1994; Chapter 16, part I. (43) DeBiase, R.; Elliott, J. D.; Hartnett, T. E. Petroleum DeriVed Carbons; ACS Symposium Series 303; American Chemical Society: Washington, D.C., 1986; p 155.

CH2 groups (2.4-3.5 ppm), suggesting cracking of the alkyl groups on the aromatics. These data suggest that the light fraction of decant oil and coal-derived light hydrocarbons was codistilled during the course of the delayed co-coking of decant oil and coal. 13C NMR results indicated the overhead liquid content consisted of mainly aromatic carbons. From integration of the 13C NMR signals, average total aliphatic and total aromatic carbons were 23.1% versus 23.4% and 76.9% versus 76.6% for coking and co-coking overhead liquids, respectively. From the 13C NMR spectra, the aliphatic carbons mostly consisted of (1) CH2 carbons that are in alkyl substituents, in rings joined by ethylene groups, in some CH2 naphthenic, or in some rings joined by methylene (27.5-37.0 ppm), (2) CH3 carbons that are substituted to a hydroaromatic and to a naphthenic CH2 (18.0-20.5 ppm), and (3) CH3 carbons that are connected directly to a hydroaromatic and naphthenic CH2 (20.5-22.5 ppm). On the other hand, aromatic carbons were comprised of (1) protonated aromatic and internal (quaternary) aromatic carbons (118.0-129.5 ppm) and (2) internal aromatic carbons (129.5-133.0 ppm) (Table 4). Total aliphatic carbons in the original decant oil were very slightly higher than overhead liquids of coking and co-coking (∼23% against 25%), with the reverse being true for the total aromatic carbons (∼77% against 75%), although these reported values are within the experimental error range. Original decant oil and bulk overhead liquids from coking and co-coking were vacuum fractionated. Approximately 1200 g of liquid sample was processed in a 2 L flask as described in section 2.4. Results are shown in Table 5. The boiling ranges were gasoline (IBP-180 °C), jet fuel (180-270 °C), diesel (270-332 °C), and fuel oil (332 °C-FBP). The vacuum distillation of original decant oil produced: 0.2% gasoline, 0.6% jet fuel, 4.0% diesel, and 94.6% fuel oil. Vacuum fractionation yields of overhead liquid obtained from decant oil coking were 0.8% gasoline, 3.5% jet fuel, 3.5% diesel, and 91.7% fuel oil. Average values for the bulk overhead liquid from co-coking were gasoline 2.4%, jet fuel 4.0%, diesel 5.0%, and fuel oil 87.7%. Coal addition into the coker increased the amount of lighter products, e.g., gasoline, jet fuel, diesel. It would be expected that the primary liquid from co-coking would be fed into other refinery operationsshydrotreating, hydrogenation, and/or hydrocrackingsto produce marketable liquid products. Unless there was interest in running co-coking specifically as a source of fuel oil, the fuel oil fraction would likely be hydrocracked to enhance the yields of the lighter liquids. Simulated distillation gas chromatography (SimDist-GC, ASTM D 2887) was also used to determine the boiling range materials of the original decant oil, bulk overhead liquids from delayed coking and co-coking. Table 6 summarizes the amount of refinery fractions from the materials examined in this study.



Table 7. Simulated Distillation Boiling Point Distributions of Coker Distillates % dista

DO (original)

DO coking

DO/coal co-coking 1-4

IBP 10 20 30 40 50 60 70 80 90 FBP

76.0 345.2 360.1 370.3 379.9 391.6 404.4 419.5 436.0 460.7 498.5

76.0 326.8 346.6 358.9 364.9 374.7 384.3 396.0 410.2 428.7 466.5

40.7 308.6 345.3 388.0 397.5 406.0 414.8 426.4 440.4 459.1 509.6

a

Percent distilled.

Original decant oil contained 0.9% gasoline, 0.8% jet fuel, 3.2% diesel, and 94.1% fuel oil range material. When decant oil was coked in the laboratory-scale delayed coker, boiling range materials for the overhead liquid obtained were 1.4% gasoline, 3.4% jet fuel, 5.9% diesel, and 88.4% fuel oil. When the same decant oil was blended with the Pittsburgh Seam coal and then delayed co-coked, the overhead liquid contained 2.1% gasoline, 3.6% jet fuel, 4.6% diesel, and 88.8% fuel oil on average. The SimDist-GC results obtained are similar to the actual yields of the fractions isolated from the vacuum distillation (Tables 5 and 6). Delayed coking or co-coking increased the lighter boiling range materials in the overhead liquid, but co-coking liquid product was even lighter than that of decant oil coking. One can conclude thermal cracking of small coal constituents and subsequently distilling out of coal-derived material contributed to the overhead liquid; it is also possible that inherent mineral matter in the coal might have acted as a catalyst and helped to produce a lighter material via catalytic cracking of larger molecules. Boiling point distributions of the original decant oil and overhead liquids from coking and from co-coking are given in Table 7. As expected, boiling point distributions showed that the coking process converted heavy material into lower boiling lighter compounds (Table 6, compare original decant oil and DO coking overhead liquid). On the other hand, cocoking of the decant oil/coal blend resulted in a wider boiling point distribution than that of coking. One can conclude that coal-derived materials may have contributed to both lighter and heavier components of the overhead liquid. It is also possible that catalytic cracking reactions may occur via the coal mineral matter (e.g., clays, which are abundant minerals in coals, can serve as cracking catalysts) (Table 1).44-47 Some of the reactive intermediates produced from catalytic or thermal cracking may have contributed to lighter liquid products formation by abstracting hydrogen from any other molecule; some of them may have coupled and increased the higher molecular weight components by retrogressive reactions.41,44,48,49 3.3. Effect of Coal on Compositions of Liquid Fractions. Vacuum distillation fractions of overhead liquids from coking and co-coking were analyzed by GC/MS. The components were grouped as paraffins, cycloparaffins, benzenes, ¨ .; Gafarova, P.; Hesenov, A.; Schobert, H. H.; Erbatur, O. (44) Gu¨l, O Energy Fuels 2007, 21, 2216–2225. ¨ ner, M.; Bolat, E.; Dincer, S. Energy Sources 1992, 14, 81–94. (45) O ¨ ner, M.; O ¨ ner, G.; Bolat, E.; Yalin, G.; Kavlak, C.; Dincer, S. (46) O Fuel 1994, 73, 1658–1666. ¨ ner, M. In Coal; Kural, O., Ed.; Istanbul Technical (47) Olcay, A.; O University: Istanbul, Turkey, 1994; Chapter 28. (48) Dutta, R. P.; Schobert, H. H. Catal. Today 1996, 31, 65–77. (49) Peng, Y. Ph.D. Dissertation, The Pennsylvania State University: University Park, PA, 1995.

indanes, naphthalenes, and polycyclic aromatic hydrocarbons (PAH). The results are shown in Table 8. The gasoline fraction of coking overhead liquid only consisted of paraffins (58.0%), cycloparaffins (11.8%), and benzenes (30.2%). Co-coking resulted in higher percentages of cycloparaffins (18.6%), benzenes (36.1%), and lower paraffins (43.2%) than those of gasoline from coking. In addition, the gasoline fraction from co-coking had a very small quantity of indanes and naphthalenes (Table 8). This suggests that co-coking gasoline could be a highoctane blend stock for the gasoline pool in a refinery. Jet fuel from coking or co-coking had a higher percentage of paraffins and naphthalenes but lower benzenes and cycloparaffins than those of gasoline. When the jet fuels obtained from coking and co-coking are compared, jet fuel from co-coking had higher aromatic (sum of benzenes + indanes + naphthalenes) (43.8% vs 19.76%) and cycloparaffins (3.4% vs 1.3%) but less paraffin (52.7% vs 78.8%) than those of jet fuel from coking. On the basis of much previous work from our Institute,1,2,10,51,52 this indicates that downstream hydrotreating and ring saturation of the striaght-run jet fuel cut from co-coking would produce a fuel having excellent pyrolytic stability, high volumetric energy density, and good low-temperature behavior. The diesel fraction had the least paraffins and cycloparaffins but the most naphthalenes and polycyclic aromatics. Diesel obtained from cocoking had higher polycyclic aromatics than that from coking (36.3% vs 19.6%). On this basis, the straight-run diesel cut from the primary co-coking liquid would likely be of low cetane number and not a good diesel engine fuel as is. However, downstream refining could potentially provide a useful addition to the diesel pool. GC/MS results are consistent with the NMR data discussed below, that coal addition into the feedstock resulted in an increase in aromaticity of the liquid. Collected vacuum-distillation fractions of co-coking were also characterized using 1H and 13C NMR. Table 9 shows 1H NMR integration results for the various distillation fractions from cocoking and decant oil as well as the data for the whole overhead liquid. The aliphatic proton contents as measured by 1H NMR showed a decrease from 89.3% to 52.9% from gasoline to fuel oil. Detailed breakdowns of NMR intensities of the four fractions are summarized in Table 9. Diaromatic and most of tri- and tetraromatic hydrogens became dominant in diesel and, especially, fuel oil fractions (Table 9). Since the aliphatic or alkylaromatic structures reported to the lighter fractions, the fuel oil fraction necessarily had less aliphatic and more aromatic hydrogen. The aliphatic hydrogen in the fuel oil was lower than that in the bulk overhead liquid, and the aromatic hydrogen was higher (Table 9). 13C NMR results are given in detail in Table 10, with a trend of decreasing aliphatic carbon percentage and increasing the aromatic carbon percentage from gasoline to fuel oil. Gasoline had the highest aliphatic carbon (66.4%), while the fuel oil fraction had the lowest (21.1%). The dominant aliphatic carbon type in 13C NMR integration region is 27.5-37.0 ppm, which corresponds to CH2 carbon of a substitution or ring joining ethylene or methylene group. On the other hand, protonated aromatic carbons and some internal (quaternary) aromatic carbons constitute the highest portion of the aromatic carbons (118.0-129.5 ppm) (Table 10). The primary goal of our present refinery integration project is to produce coal-based jet fuel. Hydroaromatics and cyclo(50) Roan, M. A.; Boehman, A. L. Energy Fuels 2004, 18, 835–843. (51) Altin, O.; Rudnick, L. R. Prepr. Pap.sAm. Chem. Soc., DiV. Fuel Chem. 2004, 49, 30–33. (52) Artok, L.; Davis, A.; Mitchell, G. D.; Schobert, H. H. Energy Fuels 1993, 7, 67–77.

2642


Gu¨l et al.

Table 8. Composition of Vacuum Fractions Based on GC/MSa Results gasoline

jet fuel

classification

DO coking

DO/coal co-coking 1-4 (mean)

paraffins cycloparaffins benzenes indanes naphthalenes PAH

58.0 11.8 30.2 0.0 0.0 0.0

43.2 18.6 36.1 1.6 0.5 0.0

a

diesel

DO coking


DO coking


78.8 1.3 7.3 1.7 10.76 0.0

52.7 3.4 17.5 4.7 21.6 0.0

17.6 1.8 20.4 1.8 38.9 19.6

5.9 1.2 20.2 3.2 33.1 36.3

Percent distributions belong to the ratio of GC-MS peak areas.

Table 9. Distribution of 1H NMR Average Values for Vacuum Fractions from Four Replicate Co-Coking Runs (DO/Coal 1-4) NMR band

decant oil/ coal co-coking

gasoline

jet fuel

diesel

fuel oil


5.6 12.7 1.3 4.3 20.4 12.4 0.5 0.08 57.2 13.3 28.0 1.4 0.04 42.8

22.5 37.7 3.5 5.0 13.1 3.0 0.0 4.5 89.3 9.6 1.0 0.0 0.0 10.7

15.1 48.0 1.0 2.3 8.9 8.4 0.1 2.0 85.7 7.7 6.6 0.0 0.0 14.3

8.9 20.0 1.5 2.6 15.9 17.5 0.8 0.3 67.5 9.8 21.3 1.5 0.0 32.5

3.9 8.8 0.9 3.2 21.0 14.3 0.8 0.0 52.9 12.7 32.3 2.1 0.0 47.1

Table 10. Distribution of 13C NMR Average Values for Vacuum Fractions from Four Replicate Co-Coking Runs (DO/Coal 1-4) NMR band

decant oil/ coal co-coking

gasoline

jet fuel

diesel

fuel oil

11.0-12.5 12.5-15.0 15.0-18.0 18.0-20.5 20.5-22.5 22.5-24.0 24.0-27.5 27.5-37.0 37.0-60.0 aliphatic (total) 108.0-118.0 118.0-129.5 129.5-133.0 133.0-135.0 135.0-138.0 138.0-160.0 aromatic (total)

0.2 1.5 1.5 4.5 4.4 0.9 1.1 6.4 2.6 23.1 1.5 49.5 10.6 3.8 5.4 6.1 76.9

1.2 7.2 2.5 4.6 6.6 6.8 4.9 24.5 8.3 66.4 2.5 16.2 4.8 1.5 4.1 4.5 33.6

0.8 6.8 2.1 4.1 4.3 5.6 2.5 31.2 2.1 58.6 2.6 20.5 5.1 3.4 2.4 6.7 40.6

0.4 2.3 2.0 4.7 4.5 1.7 2.3 11.7 5.7 35.2 1.0 39.1 8.0 4.4 3.9 8.5 64.8

0.1 1.0 1.4 4.4 4.5 0.7 1.1 5.0 2.9 21.1 1.2 52.1 10.7 3.6 5.5 5.8 78.9

paraffins have been reported as having higher thermal stability.1,2,4-8 Coal-derived liquids that are rich in aromatic compounds can be converted into hydroaromatic and cycloparaffins by hydrotreatment and saturation processes.11 The hydrotreatment could also result in increasing the yield of the lighter fractions. It has been reported that saturation of two-ring or higher condensed aromatics may be achieved during the production of coal-based liquid under hydrogen atmosphere.44,52,53 Coal-derived liquids are thus ideal candidates to be upgraded into thermally stable jet fuel.1,2 As shown in Tables 8, 9, and 10, co-coking of a decant oil/coal blend produced a jet fuel which is richer in aromatic compounds than that of coking of decant oil alone. 3.4. Reproducibility. 3.4.1. Process Reproducibility and Yield Distribution. Delayed co-coking of decant oil/coal blends was conducted in the large laboratory-scale delayed coker (53) Storch, H. H. J. Ind. Eng. Chem. 1945, 37, 340–351.

described in section 2.2. Four runs were performed primarily to obtain data for assessing coker operating reproducibility. The conditions used in each of the experiments are described in Table 11. Feed rate, the amount of fed material, and the coker temperatures were reproducible experiment to experiment. Average values (including the standard deviation) of coke, liquid, and gas yields were 27.8 ( 0.8%, 62.9 ( 1.0%, and 7.7 ( 0.3%, respectively. Liquid/coke ratios of these four replicate experiments were also very close to each other (2.3 ( 0.1%). In terms of coke, liquid, and gas products, reproducibility was shown to be excellent (Table 11, compare DO/coal 1-4). 3.4.2. Composition of Liquid Product As a Function of Reaction Time. Small samples were taken at the first, third, and fifth hours during the 6 h reaction. Tables 12 and 13 show the distribution of 1H and 13C NMR results, respectively, as a function of time. Pooled standard deviation was calculated according to the book Fundamentals of Analytical Chemistry.54 Mean and pooled standard deviations are given in the last two columns of Tables 12 and 13, respectively. All 12 samples are within pooled standard deviation range of 0.06-1.7% for 1H NMR (Table 12) and 0.03-1.1% for 13C NMR (Table 13). Even though there was no significant difference between integrated 1H NMR peaks (all 12 samples are within pooled standard deviation range of 0.06-1.7%, Table 12), when each individual run is evaluated separately, the first hour sample always had higher total aliphatic hydrogens than the third and fifth hour samples (the reverse was true for the total aromatic hydrogen). This is consistent with our previous work, which showed that at the initial stage of reaction mostly long-carbon-chain aliphatics or aliphatic side-chain-containing aromatics were thermally cleaved and distilled.11 It has been reported that aliphatic side chains on aromatic systems are cleaved at g450 °C.42 Upon further thermal cracking, distillable aromatics may come from trapped aromatic structures originally trapped in the coal or from thermally cracked molecules arising from the coke artifact as it is forming.11 Either or both of these effects could account for the increased aromatic hydrogen signals with increasing reaction time. As determined by 1H NMR, the average values were 57.2 ( 1.7% for total aliphatics and 42.8 ( 1.7% for total aromatics as calculated for 12 samples of four similar runs (Table 12). 13C NMR results indicated that the total aliphatic carbons decrease with time for each individual experiment (Table 13), and the initial samples always had higher total aliphatic carbon. The overhead liquid content consisted of mainly aromatic carbons; this is consistent with 1H NMR data. From integration of the 13C NMR signals, average total aliphatic and total aromatic carbons were 23.1 ( 1.1% and 76.9 ( 1.1%, respectively. (54) Skoog, D. A.; West, D. M. Fundamentals of Analytical Chemistry, 4th ed.; Saunders College Publishing: Philadelphia, 1982; p 58.



Table 11. Conditions and Product Distributions for Co-Coking Experiments DO/coal co-coking 1

DO/coal co-coking 2

DO/coal co-coking 3

DO/coal co-coking 4

DO/coal (80/20)

DO/coal (80/20)

DO/coal (80/20)

DO/coal (80/20)

6 24 16.7 120 440 495 489

6 24 16.7 123 432 500 497

6 24 16.8 122 432 500 495

6 24 16.8 120 441 505 496

conditions feed time (h) hold at 500 °C (h) feed rate (g/min) preheater inlet (°C) preheater outlet (°C) coke drum inlet (°C) coke drum lower/ middle (°C) coke drum top (°C) material fed to reactor (g)

472 5898

481 5984

479 5746

476 6022

5364 2.2 28.2 62.8 7.4

5405 2.2 28.6 61.7 8.1

5195 2.3 27.6 62.8 7.7

5474 2.4 26.8 64.1 7.5

product

mean and std. dev.

coke +liquid product (g) liquid/coke coke (wt %) liquid product (wt %) gas (wt %)

2.3 ( 0.1 27.8 ( 0.8 62.9 ( 1.0 7.7 ( 0.3

Table 12. Distribution of 1H NMR Signals As a Function of Time of Delayed Co-Coking of Pittsburg Seam Coal with Decant Oil (4:1 Ratio) DO/coal co-coking 1

DO/coal co-coking 2

DO/coal co-coking 3

DO/coal co-coking 4

band, ppm

1st h

3rd h

5th h

1st h

3rd h

5th h

1st h

3rd h

5th h

1st h

3rd h

5th h

mean of 12 samples

spool


6.2 15.5 1.0 3.3 19.3 13.8 0.4 0.1 59.6 12.1 26.7 1.5 0.1 40.4

6.0 13.6 1.4 5.0 20.6 10.0 0.2 0.1 56.8 14.6 27.6 1.0 0.0 43.2

5.7 13.4 1.2 4.1 20.4 11.7 0.5 0.1 57.1 13.4 28.2 1.3 0.0 42.9

6.0 14.0 1.2 3.8 20.2 13.3 0.6 0.2 59.2 12.8 26.6 1.4 0.0 40.8

5.3 11.7 1.3 4.5 21.1 11.2 0.4 0.1 55.5 14.1 29.2 1.2 0.0 44.5

5.1 11.5 1.1 3.8 20.3 13.1 0.7 0.1 55.7 12.8 29.7 1.8 0.1 44.3

5.9 13.3 1.3 4.5 20.9 12.0 0.4 0.0 58.4 13.3 27.1 1.2 0.0 41.6

5.9 12.7 1.6 5.8 21.1 9.2 0.3 0.1 56.6 14.9 27.5 1.0 0.0 43.4

5.3 12.1 1.0 3.4 19.7 14.2 0.8 0.0 56.6 12.0 29.3 2.1 0.0 43.5

5.9 12.8 1.6 5.7 21.5 10.3 0.3 0.1 58.1 14.9 26.2 0.8 0.1 41.9

5.0 11.3 1.2 4.0 20.5 12.6 0.6 0.1 55.3 13.3 29.8 1.6 0.0 44.7

5.9 12.8 1.6 5.7 21.5 10.3 0.3 0.1 58.1 14.9 26.2 0.8 0.1 41.9

5.6 12.7 1.3 4.3 20.4 12.4 0.5 0.08 57.2 13.3 28.0 1.4 0.04 42.8

0.5 1.4 0.3 1.1 0.8 2.0 0.2 0.06 1.7 1.3 1.6 0.5 0.06 1.7

Table 13. Distribution of 13C NMR Signals As a Function of Time of Delayed Co-Coking of Pittsburg Seam Coal DO/coal co-coking 1

DO/coal co-coking 2

DO/coal co-coking 3

DO/coal co-coking 4

band, ppm

1st h

3rd h

5th h

1st h

3rd h

5th h

1st h

3rd h

5th h

1st h

3rd h

5th h

mean of 12 samples

spool

12.5-11.0 15.0-12.5 18.0-15.0 20.5-18.0 22.5-20.5 24.0-22.5 27.5-24.0 37.0-27.5 60.0-37.0 aliphatic (total) 118.0-108 129.5-118.0 133.0-129.5 135.0-133.0 138.0-135.0 160.0-138.0 aromatic (total)

0.2 1.7 1.5 4.7 4.5 1.1 1.1 7.4 2.3 24.4 1.1 47.7 10.9 3.9 5.7 6.4 75.6

0.1 1.5 1.5 4.4 4.3 0.8 1.0 6.6 2.1 22.3 1.0 48.9 11.1 3.9 5.7 7.1 77.7

0.2 1.4 1.5 4.4 4.5 1.0 1.2 6.9 3.0 23.9 1.7 49.4 10.5 3.7 5.3 5.6 76.1

0.2 1.7 1.7 4.8 4.4 0.8 1.0 6.5 2.0 23.0 1.2 47.9 10.9 4.1 5.7 7.2 77.0

0.2 1.4 1.5 4.4 4.4 0.8 1.0 5.9 2.5 22.1 1.4 50.6 10.8 3.8 5.4 6.0 77.9

0.2 1.4 1.5 4.6 4.3 0.6 0.9 5.4 2.1 20.9 1.4 50.4 11.0 3.9 5.6 6.7 79.1

0.2 1.6 1.6 4.7 4.5 0.9 1.2 6.8 2.9 24.3 1.5 48.9 10.4 3.8 5.3 5.8 75.7

0.2 1.4 1.5 4.4 4.4 0.9 1.1 6.5 2.9 23.3 1.5 49.7 10.5 3.9 5.2 6.0 76.7

0.2 1.4 1.5 4.4 4.4 0.9 1.2 6.2 2.8 22.9 2.0 50.4 10.5 3.7 5.2 5.4 77.1

0.2 1.5 1.6 4.6 4.5 1.0 1.3 6.8 3.2 24.5 1.5 49.0 10.3 3.9 5.1 5.7 75.5

0.2 1.3 1.5 4.3 4.4 0.8 1.1 5.9 2.8 22.3 1.9 50.9 10.5 3.7 5.3 5.5 77.8

0.2 1.4 1.5 4.5 4.4 0.9 1.2 6.4 2.8 23.3 2.0 50.3 10.3 3.8 5.0 5.3 76.7

0.2 1.5 1.5 4.5 4.4 0.9 1.1 6.4 2.6 23.1 1.5 49.5 10.6 3.8 5.4 6.1 76.9

0.03 0.1 0.1 0.2 0.1 0.1 0.1 0.5 0.4 1.1 0.3 1.1 0.3 0.1 0.3 0.7 1.1

Simulated distillation gas chromatography (SimDist-GC, ASTM D 2887) was used to examine whether there were changes in the amounts of materials in different boiling ranges during the 6 h feeding. Table 14 summarizes the amount of refinery fractions from the materials examined in this study for four replicate runs. These data show very good agreement among samples. When the first, third, and fifth hour samples are compared in terms of boiling range material, the first hour sample always had slightly lighter boiling range materials in the overhead liquid than those of third and fifth hour samples

(Table 14). The reproducibility of cut point ranges between replicate experiments was also found to be very good. Pooled standard deviations were calculated between 0.4% and 1.7%. The averages and standard deviations for gasoline, jet fuel, diesel, and fuel oil were 2.6 ( 0.5%, 4.6 ( 0.6%, 6.1 ( 0.4%, and 86.1 ( 1.7%, respectively. Boiling point distributions of the time-dependent samples from co-coking are given in Table 15. Samples collected at the first hour always had lower boiling point distributions than samples from the third and fifth hours. After the first

2644


Gu¨l et al.

Table 14. Boiling Point Distributions by Simulated Distillation Gas Chromatography of Time-Dependent Samples IBP-180 °C, IBP-356 °F Gasoline

180-270 °C, 356-518 °F jet fuel

270-332 °C, 518-630 °F diesel


1st h 3rd h 5th h mean and std dev.

2.9 2.5 2.6 2.7 ( 0.2

DO/coal co-coking 1 5.7 4.9 4.8 5.1 ( 0.5

6.6 5.9 5.9 6.1 ( 0.4

83.9 87.0 87.0 86.0 ( 1.8


3.5 2.1 2.2 2.6 ( 0.8

DO/coal co-coking 2 5.3 3.7 3.7 4.2 ( 0.9

6.9 5.9 5.8 6.2 ( 0.6

83.4 87.4 87.3 86.0 ( 2.3


2.6 2.7 2.1 2.5 ( 0.3

DO/coal co-coking 3 5.0 5.0 3.9 4.6 ( 0.6

6.5 6.2 5.6 6.1 ( 0.5

85.0 85.2 87.5 85.9 ( 1.4

1st h 3rd h 5th h mean and std dev. mean and spoolvalues for 12 samples

2.8 2.3 2.5 2.5 ( 0.3 2.6 ( 0.5

DO/coal co-coking 4 4.7 4.0 4.4 4.4 ( 0.4 4.6 ( 0.6

6.0 5.5 5.8 5.8 ( 0.3 6.1 ( 0.4

85.5 87.3 86.5 86.4 ( 0.9 86.1 ( 1.7

Table 15. Simulated Distillation Boiling Point Distributions of Coker Distillates DO/coal co-coking 1

DO/coal co-coking 2

DO/coal co-coking 3

DO/coal co-coking 4

% dista

1st h

3rd h

5th h

1st h

3rd h

5th h

1st h

3rd h

5th h

1st h

3rd h

5th h

IBP 10 20 30 40 50 60 70 80 90 FBP

43.9 294.9 339.9 378.2 392.8 401.9 409.4 419.6 432.1 448.7 495.9

48.5 318.5 346.5 391.4 399.0 407.1 416.3 429.1 442.4 461.1 510.2

45.1 319.0 343.5 387.7 398.1 406.2 415.5 427.6 443.1 462.3 515.2

39.5 273.6 341.6 380.3 394.1 402.6 410.1 420.0 432.8 450.8 499.2

40.7 320.8 350.8 392.4 400.1 408.2 417.3 429.2 443.7 462.2 511.2

40.2 319.8 350.6 392.6 400.7 408.9 418.4 431.1 446.5 467.1 524.6

38.3 299.1 341.9 385.0 394.6 403.6 411.2 421.4 433.8 450.3 497.4

38.5 299.6 342.3 387.5 396.5 405.7 414.7 426.7 440.5 459.7 510.3

38.5 322.1 349.4 391.9 399.9 408.0 417.3 429.8 445.5 466.0 523.5

37.9 302.6 342.3 385.6 394.7 403.8 411.1 420.9 432.7 448.8 491.9

38.0 319.6 349.6 391.9 400.3 408.7 419.2 431.9 446.6 468.4 524.4

39.1 313.7 345.6 391.4 399.4 407.6 417.0 429.3 444.9 464.1 511.8

a

Percent distilled.

Table 16. Product Distributions of Overhead Liquid by Weight from Simulated Distillation Gas Chromatography run no. DO/coal co-coking 1 DO/coal co-coking 2 DO/coal co-coking 3 DO/coal co-coking 4 average and standard deviation of DO/coal 1-4

IBP-180 °C, IBP-356 °F gasoline

180-270 °C, 356-518 °F jet fuel

2.1 2.0 2.2 2.1 2.1 ( 0.1

3.4 3.4 3.7 3.8 3.6 ( 0.2

sample, an increase was observed for each percentage distilled, but then the percentage distilled values became almost stable with time. These data are in agreement with proton and carbon NMR data, which show that more PAH structures come from the coker with increasing reaction time, because the total aromatic hydrogens and carbons increased with time and the PAH contribution to the overhead liquid increased the boiling ranges with time (Tables 12, 13 and 15). One can expect that aliphatic components contributed to the lower boiling distillates of the first hour sample, while more PAH contributed to the latter ones. Because the coke drum temperatures were kept up at the desired temperature during the coking experiment, thermal cracking of molecules from the carbonaceous solid artifact may have increased the PAH structure quantity in the overhead liquid for the latter samples. As the reaction time increases, the more coal-incorporated coke builds up in the coker drum and the fresh feed material is forced to go through the coke artifact. As the fresh

270-332 °C, 518-630 °F diesel 4.4 4.4 4.4 5.0 4.6 (0.3

332-FBP °C, 630-FBP °F fuel oil 89.1 89.2 88.7 88.2 88.8 ( 0.5

feedstock enters the coke drum, lighter liquid may remove physically trapped hydrocarbons in the carbonaceous material;11 moreover, thermally cracked coal-derived materials may also be removed and distilled out concurrently. On the other hand, during the travel of feedstock along the coke formed from coal and decant oil, some reactions may have been catalyzed by the inherent coal mineral matter45-48 toward the formation of distillable liquid. 3.4.3. Comparison of Fractionation Yields of Bulk OVerhead Liquid Products in Terms of Reproducibility. In addition to the small quantities of liquid samples taken at time intervals, the remaining coker liquid was collected in a single container for further characterization. This liquid we refer to as bulk overhead liquid. Bulk overhead liquids were analyzed using SimDist-GC as described previously. Product distributions by weight are given in Table 16. The values were all within experimental error. Standard deviations were



Table 17. Product Distributions of Overhead Liquid by Weight from Vacuum Distillation run no. DO/coal co-coking 1 DO/coal co-coking 2 DO/coal co-coking 3 DO/coal co-coking 4 average and standard deviation of DO/Coal 1-4

IBP-180 °C, IBP-356 °F gasoline

180-270 °C, 356-518 °F jet fuel

2.6 2.0 2.4 2.4 2.4 ( 0.3

5.0 3.8 3.6 3.5 4.0 ( 0.7

very low. Yields were calculated as 2.1 ( 0.1% gasoline, 3.6 ( 0.2% jet fuel, 4.6 ( 0.3% diesel, and 88.8 ( 0.5% fuel oil. The bulk overhead liquids were also vacuum fractionated. Results are given in Table 17. Reproducibility was very good. Average values were gasoline 2.4 ( 0.3%, jet fuel 4.0 ( 0.7%, diesel 5.0 ( 0.3%, and fuel oil 87.7 ( 0.5%. There is very good agreement between the results obtained by SimDist-GC and the actual yields of the fractions isolated from the vacuum distillation (Tables 16 and 17). 4. Summary and Conclusions Delayed coking of decant oil and co-coking of decant oil/ coal blends were studied using a large laboratory-scale coker. Co-coking produced higher coke and gas yields but less liquid product. No essential differences were observed between bands in 1H and 13C NMR of the bulk overhead liquids of coking and co-coking. Original decant oil and bulk overhead liquids from coking and co-coking were vacuum fractionated. Delayed coking or co-coking increased the lighter boiling range materials in the overhead liquid, but co-coking liquid product was even lighter than that of coking. Introduction of coal into the system via co-coking increased the amount of lower boiling materials. Boiling point distributions of original decant oil and the bulk overhead liquids by SimDist-GC showed that the coking process converted heavy material into a lower boiling liquid and cocoking gave a wider boiling point distribution than that of coking. The wider boiling point distribution from co-coking suggests that the coal-derived materials may have contributed to the overhead liquid due to thermal and possibly catalytic cracking reactions via the coal mineral matter. GC/MS results showed that the gasoline fraction mostly consisted of paraffins, cycloparaffins, and benzenes. The jet fuel mostly consisted of paraffins, benzenes, and naphthalenes, but diesel was mostly comprised of PAH, naphthalenes, benzenes, and paraffins. GC/ MS results of vacuum distillation fractions of bulk overhead

270-332 °C, 518-630 °F diesel 5.0 5.5 4.8 4.8 5.0 (0.3

332-FBP °C, 630-FBP °F fuel oil 87.3 87.4 87.9 88.3 87.7 ( 0.5

liquids showed that gasoline, jet fuel, and diesel fractions from co-coking had more cycloparaffins, benzenes, and naphthalenes and less paraffins than those of coking. Coal addition into the feedstock resulted in an increase in aromaticity of the liquid. Co-coking of coal/decant oil produced a jet fuel that is richer in one- and two-ring aromatic compounds than that of coking of decant oil alone. Fractions from co-coking overhead liquid analyzed using 1H and 13C NMR showed that aliphatic hydrogen decreased in the vacuum distillation fractions from 89% to 53% in progressing from gasoline to fuel oil and aliphatic carbon decreased from 66% to 21%. Aromatic compounds can be converted to hydroaromatics and cycloalkanes that are shown to be ideal candidates for thermally stable jet fuel.1,2,4-9 Hydrotreatment could also result in increasing the percentage of the jet fuel fraction. Reproducibility of co-coking of coal with a decant oil in four separate experiments was shown to be excellent. Standard deviations for coke, liquid, and gas yields were found to be 0.8%, 1.0%, and 0.3%, respectively. Time-dependent samples showed a slight decrease in aliphatic hydrogen/carbon and corresponding increase in total aromatic hydrogen/carbon in 1H and 13C NMR. Samples from the first hour of operation always had a higher amount of lower boiling range materials (gasoline, jet fuel, diesel) and lower boiling point distributions than those from the third and fifth hour. The boiling point distributions from co-coking experiments were found to be relatively repeatable. Very good agreement was observed between yields measured using simulated distillation GC and vacuum distillation yields of the coker liquids. Acknowledgment. This work was funded by the United States Department of Energy (DOE), Grant # DE-FC26-03NT41828. We thank Glenn Decker for his efforts in equipment design changes and in performing the reactions. EF900022F

Characterization of Liquids Derived From Laboratory Coking of Decant

Recommend Documents