76
Energy & Fuels 1992,6 , 76-82
Conclusions We have demonstrated that a concept of atmospheric equivalent boiling point (AEBP) can be extended from a volatility separation (distillation) to a solubility separation (SEF, sequential elution fractionation). The extended AEBP scale encompasses the entire “boiling range” of petroleum, including hypothetical AEBP ranges of nondistillable residue fractions. The AEBP distribution curves, extending up to approximately 1650 OC (3000 OF), allow the comparison of entire heavy petroleums and their fractions on a common, rational basis. We have further demonstrated the continuity of changing petroleum composition as a function of AEBP. Such continuity of change is important when interpolating or extrapolating physical and chemical properties of petroleum fractions. It also provides decisive clues for the choice and the interpretation of analytical measurements performed on “heavy ends” fractions. We think the principle of AEBP is sound, but some of
the underlying separation and measuring techniques can stand improvement. For example, one aspect needing attention is that of measuring a correct number-average molecular weight for solvent-derived (SEF) fractions. So far, VPO measurements of such fractions in the polar solvent pyridine a t 90 “C give results 2-3-fold lower than those obtained by measurements in toluene.2 However, even these may still be too high and may thus inflate the calculated mid-AEBPs. The rapid progress in supercritical fluid extraction (SFE) offers a new way for the solubility fractionation of nondistillable residua, and supercritical fluid chromatography (SFC) as a SIMDIS method may provide the means for a direct measurement of AEBP’s for solubility fractions.
Acknowledgment. We express our appreciation to R. J. Clay for his assistance in plotting the data. We are also grateful to Chevron Research and Technology Co. for supporting this work and allowing publication of this paper.
Characterization of Synthetic Gasoline from the Chloromethane-Zeolite Reaction Curt M. White,* Louise J. Douglas, Joseph P. Hackett, and Richard R. Anderson Indirect Liquefaction Division, Pittsburgh Energy Technology Center, P.O. Box 10940, Pittsburgh, Pennsylvania 15236 Received August 15, 1991. Revised Manuscript Received September 24, 1991 Products from the reaction of chloromethane with a zeolite have been characterized using highresolution gas chromatography combined with either mass spectrometry or Fourier transform infrared spectroscopy. Hydrocarbon gases having four carbons and less were about 53 wt 9% of the total product. A condensed liquid product constituted about 47 wt 9% of the product. Over 240 compounds were analytically separated from the condensed liquid product by gas chromatography, allowing the identification of 106 products that constituted about 89 wt 9% of the condensed liquid product. Acyclic and cyclic alkanes and olefins, as well as aromatics, make up the majority of the condensed liquid product, which contained compounds having carbon numbers up to 13. Chloroalkanes, also found in the product, are thought to arise from addition of hydrogen chloride to olefins. Hydrocarbon products from the reaction of chloromethane and zeolite are qualitatively similar to those from the reaction of methanol and zeolite, although the isomer distribution was quantitatively different among the polymethylbenzenes. 1,2,4-Trimethylbenzene was the major organic product, constituting 45 wt 9% of the condensed liquid product. Hydrocarbon products containing four carbons and less were analyzed using a porous layer open tubular column coated with Al,O,/KCl. The alumina stationary phase reacted with 2-chloropropane to form propene. Reaction of the stationary phase with the analytes limits the use of alumina columns for characterization of products from this reaction. The chloromethane, produced in the first step of the Introduction process by oxyhydrochlorination of is subseThe conversion of both methane and methanol to gasoline-range hydrocarbons is of great commercial and eco(I) Fox,M. J.; Chen, T.-P.; Degen, B. D. Direct Methane Conoersion nomic importance. Conversion of methane to methanol Process Evaluations. Bechtel National, Inc., July, 1988. Prepared for on a commercial scale is accomplished by first the US. Department of Energy under contract No. DEAC22-87PC79814. it to carbon monoxide and hydrogen, followed by reduction (2) Noceti, R. P.; Taylor, C. E. United States Patent 4,769,504, Sept. of the carbon monoxide to methanol. Since methane can 6,1988. (3) Taylor, C. E.; Noceti, R. P.; Schehl, R. R. In Methane Conuersion; be converted to in One this may be Bibby, D. M., Chang, C. D., Howe, R. F., Yurchak, S., Eds.; Elsevier: a viable alternative to the methanol-to-gasoline process.’ Amsterdam, 1988; pp 483-489. (4) Taylor, C. E.; Noceti, R. P. Catalysis Theory and Practice, ProIn the Pittsburgh Energy Technology Center’s methaneceedings 9th Congress On Catalysis; Phillips, M. J., Ternan, M., Eds.; to-gasoline &loromethane is the intermediate in The Chemical Institute of Canada: Ottawa, Canada, 1388; Vol. 2. the conversion of methane to a high-octane liquid f ~ e l . ~ - ~ (5) Pieters, W. J. M.; Conner, W. C.; Carlson, E. J. Appl. Catal. 1984, 1I, 35-48.
* Author to whom correspondence should be addressed.
(6) Conner, W. C.; Pieters, W. J. M.; Gates, W.; Wilkalis, J. E. Appl. Catal. 1984, 11, 49-58.
This article not subject to U.S. Copyright. Published 1992 by the American Chemical Society
Synthetic Gasoline from the Chloromethane-Zeolite Reaction quently passed over a ZSM-5catalyst in the second step to produce gasoline. The purpose of this investigation was to develop and apply reliable analytical techniques to characterize synthetic gasoline derived from the reaction of chloromethane with a zeolite. This information can be used to attempt to develop an understanding of the reaction pathways and mechanisms. Before the effects of process operating conditions on product distribution can be determined, reliable analytical tools must be developed to characterize the product. A few compounds had been tentatively identified in an earlier paper: and Lersch and Bandermann recently published a paper where some characterization of a product from the reaction of chloromethane with a zeolite was presented.* Others have investigated the reaction of chloromethane over zeo1ites.%l2 However, no detailed information on the composition of the products from this reaction is available in the literature. Detailed qualitative and quantitative information concerning the products is important for many reasons. Product end uses are largely determined by the compounds present in the fuel. Determination of the exact nature of any organochlorine compounds in the fuel is important for environmental and health reasons and to design means for their removal. Total chlorine content must be within established limits for fuels to curtail corrosion in automotive applications. Detailed analytical information on the nature of the products, especially the exact isomer distribution, is useful for process development and quality control programs. This information allows development of relationships between the abundance of individual hydrocarbons and both octane rating and engine performance. Further, knowledge concerning the nature and distribution of products from a reaction is necessary to develop insight into the reaction mechanisms and pathways. At present, the analytical technique that provides the greatest potential for resolution and detection of individual isomeric hydrocarbons and chlorinated hydrocarbons in the gasoline boiling range is capillary gas chromatography (GC). This is particularly true when long, highly efficient, chemically inert columns are used in combination with both infrared and mass spectrometric detection. This paper reports the results of analyzing liquid and gaseous products formed during the reaction of chloromethane with a zeolite by high-resolution open-tubular gas chromatography. Liquid products trapped in a refrigerated bath held at 20 "C were separated using a single 100-m column coated with 100% dimethylpolysiloxane and identified by either mass spectrometric or Fourier transform infrared (FTIR)spectroscopic detection. These identifications were corroborated by comparing the retention indices measured for sample components with those of over 400 gasolinerange compounds recently measured under identical cond i t i o ~ ~ .Gaseous '~ products were separated using a porous layer open tubular column (PLOT) coated with A1203/KC1. Gaseous products were identified by combined gas chroand by matching matography-mass spectrometry (GC-MS) retention times with authentic standards.
Energy & Fuels, Vol. 6, No. 1, 1992 77
Experimental Section Crystalline ZSM-5 was obtained from Mobil Oil Corp. in the ammonium form with a silica-to-aluminaratio of 701. The ammonium form was converted to the acid form by calcining in air at 538 "C for 16 h. Reactions were conducted in a 1.25 cm i.d. X 18 cm Vycor reactor contained in a split-tube furnace heated to 360 "C. The reactor was fitted with a thermocouple well to monitor reactor temperature,which ranged between 350 and 370 "C. The pressure inside the reactor was slightly greater than 1 atm. Approximately 1 g of catalyst was packed into a 2-cm vertical bed with quartz wool above and below the bed. The amount of coke formed on quartz wool was substantially less than that formed on glass wool. Reactor feeds were supplied from compressed gas cylinders and controlled by Brooks ratio mass flow controllers. The liquid condensate was collected in a refrigerated bath (20 "C) during a 185-h experiment. The reactor was operated at approximately360 "C employing chloromethane and nitrogen flows of 8.2 and 5.0 ml/min, respectively, at a weight hourly space velocity of 1.04 g of CH&I per gram of catalyst per hour. Separation of the liquid products was accomplished utilizing an HP 5890A capillary gas chromatograph equipped with a high-pressure pneumatics system capable of reaching 60 psi column head presaure, a split injector held at 250 "C, and a flame ionization detector (FID) at 250 "C. An HP Model 18593A autosampler was used to introduce samples to the chromatograph and an HP Model 5895A Chem Station was used to measure peak areas and retention times to the nearest 0.01 of a minute. The chromatographwas equipped with a 100 m X 0.25 mm i.d. fused silica column coated with a 0.5-wm film of 100% dimethylpolysiloxane (Petrocol DH obtained from Supelco)and placed in the approximate center of the oven. The column was temperature programmed from 30 to 220 "C at 1 "Cfmin. A helium carrier gas having an average linear velocity of 31 c m / s at 30 O C was used. Retention indices were determined by adding a mixture of nalkane bracketing standards to the product and calculating the retention indices using the van den Do01 and Kratz eq~ati0n.l~ Retention indexes so calculated were compared to the retention indices of hundreds of gasoline-range hydrocarbons determined using identical chromatographicconditions. The identifications made in this manner were confirmed by combined GC-MS and/or GC-FTIR usingthe same chromatographic column and conditions as described above. GC-MS was performed using an HP 5988A system equipped with an HP 5890A GC. The spectrometer employed an ion source temperature of 200 "C, an electron multiplier voltage of 2600 V, and 70 eV ionization potential and was scanned from 20 to 250 amu every 1.7 s. Further confirmation of these identifications was obtained by combined GC-FTIR using a Digilab FTS 65 GC/C 32 system equipped with an HP 5880 GC. The GC-FTIR experiments were performed by one of the authors (CMW) at Digilab in Cambridge, MA. A separate reaction of chloromethane with zeolite was conducted where the product vapors exiting the reactor were directly sampled and analyzed. The reaction conditions were similar to those described above except that the diluent gas was helium spiked with 3% nitrogen instead of pure nitrogen. The low-boii, low molecular weight proucts were determined by directly sampling the reactor effluent product vapor and analyzing it by gas chromatography using a 50 m X 0.32 mm porous layer open tubular (PLOT) column containing AI2O3/KC1. The PLOT column, obtained from Chrompack, was operated isothermally at 70 O C for 8 min, then programmed to 220 "C at 8 "C/min using a helium carrier gas.
Results and Discussion (7) Comer, W. C.; Pieters, W. J. M.; Signorelli,A. J. Appl. Catal. 1984, 11, 59-71. (8) Lersch, P.; Bandermann, F. Katalyse 1989,118,183-201. (9)Ione, K. G.; Stepanov, V. G.; Romannikov, V. N.; Shepelev, S. E. Khim. Tverd. Topl. 1982,16,29-43. (IO) Romannikov, V. N.; Ione, K. G. Kinet. Catal. 1984,25, 75-80. (11)Brophy, J. H.; Font Freide, J. J. H. M.; Tomkinson, J. D. International Patent WO 8502608, June 20, 1985. C A 103(16) 126291j. (12)Brophy, J. H.; Font Freide, J. J. H. M.; Tomkineon, J. D. International Patent WO 8404863,Nov. 7, 1985. C A 104(14)112626f. (13)White, C. M.;Douglas,L. J.; Hackett, J.; Kail, S.; Spock, P. S.; Anderson, R. R. High Resolut. Chromatogr., in press.
A heavily instrumented bench-scale microreactor is being used to study the nature of the reaction of chloromethane and a zeolite. This bench-scale reactor is useful for the study of reaction kinetics, pathways, and mechanisms, but does not necessarily form products representative of those formed by a larger reactor. It should also be noted that a commercial-scale process would be ex(14)van den Dool, H.; Kratz, P. D. J. Chromatogr. 1963,1I,463-471.
White et al.
78 Energy & Fuels, Vol. 6, No. 1, 1992
CHLOROMETHANE/ZEOLITE LIQUID CONDENSATE
I
I
50
I
I
90
I
I
I
I
70
60
I
I
I
I
100
110
I
00
I
12@
lM
101
y$J
A
I I
130
I
*'T
A
-I I 150
140
160
TIME (MIN)
Figure 1. High-resolution gas chromatogram of the liquid condensate from the chloromethane/zeolitereaction. The chromatogram was obtained using a 100 m X 0.25 mm i.d. fused silica column coated with a 0.5-rm film of dimethylpolysiloxane (Petrocol DH from Supelco),and a helium average linear velocity of 31 cm/s. The column was linear temperature programmed from 30 to 220 "C at 1 "C/min. Numbered chromatographic peaks are identified in Table I.
pected to employ an alumina-supported zeolite, while the unsupported crystalline form was used here. Hydrocarbon gases having four carbons and less were about 53 wt % of the total product. A condensed liquid product constituted about 47 w t % of the total product. Compounds having carbon numbers up to 13 were found in the condensed liquid product. Over 240 compounds were analytically separated from the condensed liquid product using a 100 m X 0.25 mm wall-coated open tubular column coated with a 0.5-pm film of 100% dimethylpolysiloxane, allowing the identification of 106 products that constituted about 89 wt % of the condensed liquid product. The high-resolution gas chromatographic profile of the liquid condensate is shown in Figure 1. The first portion of the chromatogram is expanded to allow a more detailed view of the early eluting compounds. Numbered chromatographic peaks are identified in Table I along with the methods of identification and the gas chromatographic retention indices determined for the peaks in the sample and the authentic compounds.13 The average deviation between retention indexes measured on peaks from the sample and known retention indexes measured using authentic standards was 0.31 index units. This gas chromatographic procedure allows separation and identification of hydrocarbons to 12 carbons in less than 2 h. Pentamethylbenzene elutes in 111 min. The identifications in Figure 1and Table I are positive; that is, each compound is identified by a t least two different analytical techniques. The estimated weight percent of each product reported in Table I is simply the area percent data taken from a chromatogram generated using
a flame ionization detector. Unfortunately, the direct relationship between peak area percent and weight percent is not always correct because, in some cases, two or more compounds coelute and only one could be identified. Additionally, the flame ionization detector response for hydrocarbons is different than that for chlorinated hydrocarbons. However, on balance, the relationship between area percent and weight percent is approximately correct. The wall-coated open tubular column coated with a 0.5-pm film of dimethylpolysiloxane provided excellent separation of most analytes. This column has been used regularly for months without significant degradation of performance even though it is exposed to substantial amounts of hydrogen chloride each time a sample is introduced. Improved separation would be possible by decreasing column diameter, increasing its length and/or using an initial temperature lower than 30 "C. The liquid condensate did not contain significant amounts of low boiling, low molecular weight products. These compounds were determined during another experiment by sampling the reactor effluent a t the reactor exit and analyzing it using on-line gas chromatography employing an alumina PLOT column. Compounds in the product vapor having four carbons and less are listed in Table 11. These identifications were made by matching the retention times of sample peaks with those of authentic standard hydrocarbons, and by combined GC-MS. The weight percent values in Table I1 are weight percent of each compound in the total product. Compounds having four carbons or less account for about 53 wt 7% of the total product. Total conversion of chloromethane to products
Synthetic Gasoline from the Chloromethane-Zeolite Reaction was about 99% under the reaction conditions used. Although the alumina PLOT column provides excellent separation of hydrocarbon gases, its use for analysis of products from the reaction of chloromethane over zeolite is severely limited because the alumina stationary phase reacts with chloroalkanes. When a PLOT column was installed in the GC-MS and a dilute solution of 2-chloropropane, a known product of the reaction (see Table I), was injected, no 2-chloropropane peak eluted. Instead, a broad hump eluted that was identified as propene based upon its mass spectrum. I t must be concluded that 2chloropropane dehydrohalogenates on alumina. Others have reported the reaction of chlorinated hydrocarbons on alumina PLOT c ~ l u m n s . ' ~ J ~ The compounds identified in the product from the reaction of chloromethane over zeolite are qualitatively similar to those reported in the product from the reaction of methanol over zeolite, except for the presence of organochlorine compounds. With few exceptions, the hydrocarbon products identified by others from the methanol r e a c t i ~ n ' ~ have - ~ ' been identified herein as products from the chloromethane reaction. Detailed chemical analysis of the products formed during the chloromethane-zeolite reaction can provide considerable insight into the nature of intermediates, reaction mechanisms, and reaction pathways that occur in the zeolite's intracrystalline space, in turn suggesting ways to improve the process. For example, although only a few weight percent of the products contain chlorine, a large portion of them are 2-chloroalkanes. The reaction also produces hydrogen chloride and terminal olefins. Using this evidence, it is postulated that the 2-chloroalkanes are formed by Markovnikov addition of hydrogen chloride to the terminal olefins. The addition reaction may occur after the olefins exit the zeolite bed but while still in the reactor's heated zone or post reactor. The detection of organochlorine compounds in the product from the reaction of chloromethane and zeolite is not in agreement with the results of Lersch and Bandermanna who reported that chlorinated hydrocarbons could not be observed under the conditions they used. Possibly, the addition of hydrogen chloride to olefins can be controlled by reactor design and configuration. This may be why Lersch and Bandermann did not observe chlorinated products. The small scale of the reactor used here limits configuration changes to repress chlorocarbon formation. The liquid condensate contained organochlorine compounds that were not positively identified and thus are not listed in Table I. The approximate amount of all chlorocarbons, including those that were not positively identified but thought to contain chlorine (based on interpretation of mass spectra), was approximately 4 wt %. Chlorinated aromatics were not present in readily detectable amounts; chlorinated aromatic concentrations of approximately 0.20 mg/mL of gasoline are expected to produce recognizable mass spectra. 2-Chloro-2-methylpentane, peak number 56 in Figure 1, was identified on the basis of its mass and infrared spectra. The retention index of a pure sample of this compound was not determined; however, the measured (15)Noij, Th.; Rijks, J. A.; Cramers, C. A. Chromatographia 1988,26, 139-141. (16)Noij, Th.; Fabian, P.; Borchers, R.; Cramers, C.; Rijks, J. Chromatographia 1988,26,149-156. (17)Chang, C. D.;Silvestri, A. J. J. Catal. 1977,47, 249-259. (18)Chang, C. D.Catal. Rev. Sci. Eng. 1983,25,1-118. (19)Anderson, M.W.;Klinowski, J. Nature 1989,339,200-203. (20)Bloch, M.G.;Callen, R. B.; Stockinger, J. H. J. Chromatogr. Sci. 1977,15, 504-512. (21)Stockinger, J. H.J. Chromatogr. Sci. 1977,15, 198-202.
Energy &Fuels, Vol. 6, No. 1, 1992 79 retention index of this peak (766.54) agrees well with the predicted retention index for this compound. The retention index of 2-chloro-Zmethylpentane was estimated by extrapolating the graph of the retention indexes versus carbon number of 2-chloro-2-methylpropane(530.04) and 2-chloro-2-methylbutane (647.88). The estimated retention index of 2-chloro-2-methylpentane is 765.72. Using the measured retention index of 2-chloro-2-methylpentane (766.54) from the sample, along with the values measured on authentic standards of the lower carbon number homologues, the retention indexes of 2-chloro-2-methylhexane and 2-chloro-2-methylheptanewere estimated to be 884.65 f 0.51 and 1002.90 f 0.74, respectively. The reaction mixture did not contain recognizable amounts of 3-chloro-1-propene (allyl chloride) or chloromethylbenzenes, as would be expected if free-radical chlorination were occurring. The absence of these compounds in readily detectable amounts implies the absence of C1', and, thus, Clz. The reaction mixture was searched for these compounds by searching for their known mass spectra within a few minutes of their known retention times. No evidence for them was found. The reaction products contain all possible methyl-substituted benzene isomers to pentamethylbenzene. The normalized isomer distribution of polymethylated benzenes found in the product formed from the reaction of chloromethane over zeolite a t 360 "C, their distribution in the product from the reaction of methanol over zeolite a t 371 OC, and their thermodynamic equilibrium distribution a t 360 "C are shown in Table III.17J8 The normalized distributions in Tables 111and IV were computed from the FID area percents of Table I. Integration of cross-correlated extracted ion mass chromatograms, using 15 characteristic mass spectral peaks, confirmed the FID derived normalized distribution results. Although the products formed in the chloromethane/ zeolite reaction are qualitatively similar, except for the presence of organochlorine compounds, to those formed in the methanol/zeolite reaction, quantitative differences exist in the distribution of isomeric polymethylated benzenes. The quantitative differences in the distribution of products may be due to the use of different zeolite catalysts and different operating conditions. The distribution of dimethylbenzenes in the product from the reaction of chloromethane over zeolite is very close to that found in the product from the reaction of methanol over zeolite and the equilibrium distribution a t 360 "C. The 1,3-isomer predominates and the dimethylbenzenes appear to be in thermodynamic equilibrium. The normalized isomer distribution of the ethylmethylbenzenes, shown in Table 111, differs significantly from that of the dimethylbenzene isomers. The l,&isomer still predominates over the other isomers, but there is a much lower amount of 1-ethyl-2-methylbenzene than 1,2-dimethylbenzene. The distribution among trimethylbenzene and tetramethylbenzene isomers in the product is significantly different from that in the thermodynamic equilibrium mixture. At 360 OC, 1,2,4-trimethylbenzene is the major organic product formed in the reaction and constitutes about 45 wt % of the condensed liquid product. Polymethylation is favored because the ring is activated following addition of the first methyl group and because of the excess chloromethane present. The other trimethylbenzene isomers, 1,2,3- and 1,3,5-,are present in the condensed liquid product a t only 0.8 and 1.5 wt %, respectively. The 1,2,4-isomer has a kinetic diameter of 6.1 A while the 1,2,3- and 1,3,5-isomers have kinetic diameters
80 Energy & Fuels, Vol. 6,No. 1, 1992
White et al.
Table I. Compounds Identified in the Liquid Condensate and Their Approximate Concentration in the Liquid Condensate' peak 1 2 3 4
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61
62 63 64 65 66 67 68 69 70 71 72 73 74 75
compound chloromethane 2-methylpropane butane (E)-2-butene (Z)-2-butene chloroethane 3-methyl-1-butene 2-methylbutane 1-pentene 2-chloropropane 2-methyl-1-butene pentane (E)-e-pentene (Z)-2-pentene 2-methyl-2-butene 1-chloropropane 2-chloro-2-methylpropane cyclopen tane 2-methylpentane 3-methylpentane 2-methyl-1-pentene 1-hexene 2-chlorobutane hexane (E)-3-hexene (Z)-3-hexene (E)-2-hexene (Z)-2-hexene (E)-3-methyl-2-pentene methylcyclopentane 2,3-dimethyl-2-butene 1-methylcyclopentene and benzene 2-chloro-2-methylbutane cyclohexane 2-methylhexane (E)-5-methyl-2-hexene 1,l-dimethylcyclopentane cyclohexene 3-methylhexane cis-1,3-dimethylcyclopentane trans-l,3-dimethylcyclopentane trans-1,2-dimethylcyclopentane (E)-3-heptene heptane (Z)-3-heptene (E1-2-heptene (Z)-2-heptene methylcyclohexane 1,1,3-trimethylcyclopentane ethylcyclopentane 3-methylcyclohexene 4-methylcyclohexene ln,2(3,4n-trimethylcyclopentane methylbenzene 2-methylheptane 4-methylheptane 2-chloro-2-methylpentane Itu,2n,4(3-trimethylcyclopentane 3-methylheptane cis-1,3-dimethylcyclohexane trans-3-ethyl-1-methylcyclopentane cis-3-ethyl-1-methylcyclopentane ethylbenzene 1,3-dimethylbenzene 1,4-dimethylbenzene 2-methyloctane 1,2-dimethylbenzene (1-methylethy1)benzene propylbenzene 1-ethyl-3-methylbenzene 1-ethyl-4-methylbenzene 1,3,5-trimethylbenzene 1-ethyl-2-methylbenzene 1,2,4-trimethylbenzene (2-methylpropy1)benzene
GC-MS X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X
X X X X X X X
X X X X X X X X X X X X X X X X X X
X
X X X
X X
X X X X X X X X
method of identification GC-FTIR measd RI 332.92 353.53 400.00 406.42 X 418.18 423.96 445.14 X 465.18 483.67 X 490.72 493.79 X 500.00 X 505.09 X 510.30 514.38 528.79 530.66 554.24 560.52 577.32 583.43 584.79 598.87 600.0 601.03 602.28 603.43 610.48 615.42 X 620.67 624.32 641.72 647.89 651.09 661.02 661.50 665.48 667.76 670.56 677.50 680.73 683.95 697.72 X 700.00 701.00 703.99 710.92 X 716.41 X 719.35 X 727.03 729.10 729.80 735.35 748.65 763.50 764.38 766.54 768.44 X 770.68 771.77 783.61 785.94 844.50 853.85 854.85 864.77 X 875.88 909.43 938.65 X 946.60 948.48 X 954.28 963.29 X 980.80 994.39
known RI 332.92 353.53 400.00 408.40 416.44 424.09 445.18 465.11 483.39 491.40 493.58 500.00 504.91 510.35 513.84 528.77 530.04 554.13 560.46 577.22 583.35 584.67 598.38 600.0 601.42 602.19 603.38 610.48 615.32 620.81 624.38 642.00 647.88 651.14 661.15 661.57 665.63 667.80 670.60 677.64 680.98 684.01 697.50 700.00 700.88 703.99 710.93 716.54 719.32 727.17 729.06 729.83 735.37 749.00 763.03 764.57 768.82 770.98 771.54 844.74 853.38 854.75 864.60 875.89 909.62 938.20 946.91 948.90 954.69 963.66 978.78 994.48
estimated wt % 0.002 0.005 0.004 0.003 0.003 0.003 0.003 0.060 0.004 0.012 0.009 0.043 0.027 0.014 0.028 0.006 0.146 0.022 0.209 0.093 0.008 0.005 0.030 0.109 0.014 0.037 0.013 0.017 0.080 0.296 0.016 0.136 0.911 0.016 0.165 0.017 0.064 0.021 0.162 0.151 0.144 0.086 0.073 0.074 0.072 0.017 0.015 0.090 0.071 0.163 0.015 0.027 0.071 2.452 0.078 0.044 0.254 0.020 0.070 0.031 0.154 0.130 1.473 8.789 4.847 0.051 4.041 0.008 0.195 2.419 1.427 0.701 0.154 45.343 0.090
Synthetic Gasoline from the Chloromethane-Zeolite Reaction
Energy & Fuels, Vol. 6, No. 1, 1992 81
Table I (Continued) method of identification compound GC-MS GC-FTIR measd RI (1-methvlDroDvl)benzene X 996.50 1,2,3-trimkth;ibenzene X X 1004.87 X 1-methyl-3-(1-methylethy1)benzene 1007.40 1010.45 X l-methyl-4-(1-methylethy1)benzene X 2,3-dihydro-lH-indene 1015.41 X X 1,3-diethylbenzene 1034.43 1-methyl-3-propylbenzene X 1037.02 1,4-diethylbenzene X X 1040.66 butylbenzene X 1041.77 X l-ethyl-3,5-dimethylbenzene 1044.03 1-methyl-2-propylbenzene X 1052.22 2-ethyl-1,4-dimethylbenzene X X 1062.32 X 4-ethyl-1,3-dimethylbenzene 1063.94 4-ethyl-1,2-dimethylbenzene X 1069.99 1,2,4,5-tetramethylbenzene X X 1102.07 X X 1104.97 1,2,3,5-tetramethylbenzene X 2,3-dihydro-5-methyl-lH-indene 1120.99 1,2,3,4-tetramethylbenzene X X 1135.84 X X 1140.47 1,2,3,4-tetrahydronaphthalene X naphthalene 1160.26 X 1,2,3,4-tetrahydr0-6-methylnaphthalene 1246.28 X pentamethylbenzene X 1265.42 X X 2-methylnaphthalene 1270.79 I-methylnaphthalene X 1285.68 X 1,2,3,4-tetrahydr0-2,6-dimethylnaphthalene 1301.61 X 1,2,3,4-tetrahydr0-2,7-dimethylnaphthalene 1302.75 X 1,2,3,4-tetrahydr0-6-ethylnaphthalene 1339.38 2,6-dimethylnaphthalene X X 1381.93 X X 1,6-dimethylnaphthalene 1383.86 X 1,5-dimethylnaphthalene X 1398.40 X 2,3,6-trimethylnaphthalene X 1509.73
peak 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106
known RI 996.78 1005.04 1007.84 1010.90 1015.61 1034.64 1037.76 1040.69 1042.19 1044.15 1052.67 1063.12 1064.79 1070.74 1101.84 1104.26 1122.37 1140.85 1158.51 1246.78 1265.49 1271.01 1286.53 1301.47 1302.11 1340.02 1381.69
estimated wt %
0.070 0.382 0.076 0.072 0.086 0.268 0.325 0.393 0.070 0.047 0.002 0.122 0.221 1.094 5.381 0.717 0.537 0.301 0.120 0.150 0.226 0.092 0.472 0.038 0.146 0.018 0.020 0.343 0.487 0.130 0.051
"The liquid condensate is approximately 47 wt % of the total product. Table 11. Compounds Identified in t h e Gas S t r e a m a n d Their ADDrOXimate Weight P e r c e n t i n t h e Total ProductD
Table IV. Normalized Weight P e r c e n t Distribution of Monoalkylbenzenes compound normalized % methylbenzene 56 ethylbenzene 34 propylbenzene 4.5 (1-methy1ethyl)benzene 0.2 (1-methylpropyl)benzene 1.6 (2-methylpropyl)benzene 2.1 butylbenzene 1.6 ~
Deak 1 2 3 4 5 6 7 8 9 10 11 ~~~~
comDound methane ethane ethene propane propene 2-methylpropane butane (E)-2-butene 1-butene 2-methylpropene (n-2-butene
estimated wt % of total product 0.17 0.11 2.14 12.30 3.95 17.50 8.36 2.23 0.58 4.92 1.29
"The gas stream is 53 wt % of the total product. Table 111. Normalized Polyalkylbenzene Isomer Distributions chloromethane/ methanol/ equilibrizeolite zeolite" um (360 compound (360 'C) (371 "C) "C) 22.9 21.5 24.4 1,2-dimethylbenzene 54.6 53.2 49.7 1,3-dimethylbenzene 23.9 22.4 27.4 1,Cdimethylbenzene 6.4 0.8 8.9 1,2,3-trimethylbenzene 78.7 97.7 63.7 1,2,4-trimethylbenzene 14.9 1.5 27.4 1,3,5-trimethylbenzene 9.3 4.7 15.9 1,2,3,4-tetramethylbenzene 44.2 11.2 50.6 1,2,3,5-tetramethylbenzene 46.6 1,2,4,5-tetramethylbenzene 84.1 33.5 24.4 3.9 1-ethyl-2-methylbenzene 60.5 I-ethyl-3-methylbenzene 53.2 35.6 22.4 1-ethyl-4-methylbenzene a
From ref 17.
of 6.4 and 6.7 A, respe~tive1y.l~According to Anderson and Klinowski, the smaller 1,2,4-isomer may diffuse from the zeolite pores more readily than the larger isomers.lg The larger trimethylbenzene isomers may be formed in the
pores of the zeolite, but must isomerize to the 1,2,4-isomer before diffusing out of the catalyst. Tetra- and pentamethylbenzenes are also found in the product but in substantially lower amounts. These larger molecules have difficulty diffusing out of the intracrystalline pores of the ZSM-5 network. The tetramethylbenzene isomers are not present in the condensed liquid product as an equilibrium distribution. Among the tetramethylbenzenes formed, the 1,2,4,5-isomer (durene), which has a kinetic diameter of 6.1 A, predominates over the larger but more thermodynamically favored tetramethylbenzene isomer^.'^ Because the 1,2,4,5-isomer has a slightly smaller kinetic diameter, it diffuses out of the pores faster than the other tetramethylbenzenes. The 1,2,4,5-isomer is also the tetramethylbenzene isomer made in largest amount by the methanol/zeolite reaction at 371
"C. The preponderance of benzene alkylation is by methyl substitution, although other larger alkyl groups are present. Examination of the normalized distribution of monoalkylbenzenes (methylbenzene, ethylbenzene, propylbenzene, (1-methylethyl)benzene, (1-methylpropy1)benzene, (2-methylpropyl)benzene, and butylbenzene, shown in Table IV) reveals that, as the number of alkyl carbons increases, the amount of product at each carbon number generally decreases. Propylbenzene (0.195wt 9'0)
82 Energy & Fuels, Vol. 6,No, 1, 1992
is present in larger amount than (1-methylethy1)benzene (0.008 wt % ). Simple Friedel-Crafts alkylation of benzene is expected to form (1-methy1ethyl)benzene (isopropylbenzene) preferentially over propylbenzene irrespective of the propylating agent. The reaction mixture contains alkanes, both normal and branched, as well as cyclic alkanes. Alkanes may be produced in a variety of ways including reduction of the corresponding olefins by hydrogen generated by either cyclization and/or aromatization reactions. Alternately, alkanes could be formed by direct hydrogen transfer from aromatizing compounds to olefins or by cracking of alkyl groups from alkylated aromatics. Among the acyclic normal and branched alkanes, the isoalkanes predominate over the corresponding n-alkanes. Similarly, isoolefins are present in the product in higher amounts than the corresponding linear alpha olefins. Isoalkanes and isoolefins are desirable constituents of chemical feedstocks and of gasoline blending additives.l' It is interesting to note the qualitative similarities between the hydrocarbons present in the product from the reaction of chloromethane over zeolite and those from low boiling petroleum distillates. Both contain normal and isoalkanes (Bmethylalkanes) as well as anteisoalkanes (3-methylalkanes), although the quantitative distribution among isomers is different in the two materials. Both contain cyclic alkanes. Petroleum contains mono- and dimethylcyclopentanes and cyclohexanes, as does the product from the reaction of chloromethane and zeolite. Qualitatively, the distribution of hydrocarbons in the two materials is surprisingly similar, particularly when one considers that petroleum is formed from biogenic precursors and the chloromethane/zeolite product is completely synthetic. The similarities extend to the aromatic hydrocarbons.
Summary Under the conditions used during the reaction of chloromethane with zeolite described herein, 99 wt % of the chloromethane was consumed. Approximately 53 wt ?& of the totalproduct contained four carbons and less, while approximately 47 wt % of the total product was a condensed liquid. Over 240 compounds were separated from the condensed liquid, and 106 of them were positively identified using gas chromatographic retention indexes, combined GC-MS and GC-FTIR. Almost half, 45 wt ?& , of the condensed liquid product was 1,2,4-trimethylbenzene. Compounds having carbon numbers up to 13 were found in the condensed liquid product. Acyclic and cyclic alkanes and olefins as well as aromatics make up the majority of the condensed liquid product. Chloroalkanes, also found in the product, are thought to arise from addition of hydrogen chloride to olefins. Hydrocarbon products from the chloromethane/zeolite reaction are qualitatively similar to those from the reaction of methanol and zeolite, although the isomer distribution is quantitatively different among the polymethylbenzenes. In the case of monoalkylbenzenes, as the number of alkyl carbons increases, the amount of that compound in the condensed liquid product generally decreases. The 100 m X 0.25 mm 100% dimethylpolysiloxane open-tubular column is very useful for separation and analysis of gasoline-range hydrocarbon samples. The linear temperature-programmed retention indexes previously measured on hundreds of gasoline-range hydrocarbons and chlorocarbons are particularly useful for tentative identification of unknown components. The average deviation between retention indexes measured on peaks from the
White et al. sample and known indices measured using authentic standards was 0.31 index units. The alumina PLOT columns were found to have limited use for analysis of products from the reaction because chloroalkanes dehydrohalogenated on the alumina. Acknowledgment. We thank Mobil Research and Development Corp. in Paulsboro, NJ, for providing the ZSM-5 catalyst. Conversations with the following individuals materially aided the development of the work: Charles Taylor, Richard Noceti, and Richard Schehl. Reference in this work to any specific commercial product, process, or service is to facilitate understanding and does not necessarily imply endorsement or favoring by the United States Department of Energy. Registry No. Chloromethane, 74-87-3; 2-methylpropane, 75-28-5; butane, 106-97-8;(E)-2-butane,624-64-6; (2)-2-butene, 590-18-1; chloroethane, 75-00-3; 3-methyl-l-butene, 563-45-1; 2-methylbutane,78-78-4; 1-pentene,109-67-1;2-chloropropane, 75-29-6; 2-methyl-l-butene, 563-46-2;pentane, 109-66-0;(E)-2pentene, 646-04-8;(2)-2-pentene, 627-20-3;2-methyl-2-butene, 513-35-9; 1-chloropropane,540-54-5;2-chloro-2-methylpropane, 507-20-0; cyclopentane, 287-92-3; 2-methylpentane, 107-83-5; 3-methylpentane, 96-14-0;2-methyl-l-pentene,763-29-1;1-hexene, 592-41-6;2-chlorobutane,78-86-4; hexane, 110-54-3;(E)-3-hexene, 13269-52-8; (Z)-3-hexene,7642-09-3; (E)-2-hexene,4050-45-7; (Z)-2-hexene,7688-21-3; (E)-3-methyl-2-pentene,616-12-6; methylcyclopentane, 96-37-7; 2,3-dimethyl-2-butene,563-79-1;1methylcyclopentene, 693-89-0;2-chloro-2-methylbutane,594-36-5; cyclohexane, 110-82-7;2-methylhexane,591-76-4;(E)&methyl2-hexene, 7385-82-2; 1,l-dimethylcyclopentane,1638-26-2; cyclohexene, 110-83-8; 3-methylhexane, 589-34-4; cis-1,3-dimethylcyclopentane, 2532-58-3; benzene, 71-43-2;trans-1,3-dimethylcyclopentane, 1759-58-6;trans-1,2-dimethylcyclopentane, 822-50-4; (E)-3-heptene, 14686-14-7;heptane, 142-82-5;(27-3heptene, 7642-10-6; (E)-2-heptene, 14686-13-6; (Z)-2-heptene, 6443-92-1; methylcyclohexane, 108-87-2; 1,1,3-trimethylcyclopentane, 4516-69-2; ethylcyclopentane, 1640-89-7; 3-methylcyclohexene, 591-480;4-methylcyclohexene, 591-47-9;la,2/3,4atrimethylcyclopentane, 16883-48-0; methylbenzene, 108-88-3; 2-methylheptane, 592-27-8; 4-methylheptane, 589-53-7; 2chloro-2-methylpentane, 4325-48-8; la,2a,4&trimethylcyclopentane, 4850-28-6; 3-methylheptane, 589-81-1; cis-1,3-dimethylcyclohexane,63804-0; trans-3-ethyl-l-methylcyclopentane, 2613-65-2; cis-3-ethyl-l-methylcyclopentane, 2613-66-3; ethylbenzene, 100-41-4; 1,3-dimethylbenzene, 108-38-3; 1,4-dimethylbenzene, 106-42-3; 2-methyloctane, 3221-61-2; 1,2-dimethylbenzene, 95-47-6;(1-methylethyl)benzene,98-82-8;propylbenzene, 103-65-1; l-ethyl-3-methylbenzene,620-14-4; 1ethyl-4methylbenzene, 622-96-8; 1,3,5-trimethylbenzene,10867-8; l-ethyl-2-methylbenzene, 611-14-3; 1,2,4-trimethylbenzene,9563-6, (2-methylpropyl)benzene,53893-2; (1-methylpropyl)benzene, 135-98-8; 1,2,3-trimethylbenzene, 526-73-8; l-methyl-3-(1methylethyl)benzene, 535-77-3; l-methyl-4-(l-methylethyl)benzene, 99-87-6; 2,3-dihydro-lH-indene,496-11-7; 1,3-diethylbenzene, 141-93-5;l-methyl-3-propylbenzene, 1074-43-7;1,4-diethylbenzene, 105-05-5; butylbenzene, 104-51-8;l-ethyl-3,5-dimethylbenzene,934-74-7; l-methyl-2-propylbenzene,1074-17-5; 2-ethyl-1,4-dimethylbenzene, 1758-88-9; 4-ethyl-1,3-dimethylbenzene, 874-41-9; 4-ethyl-1,2-dimethylbenzene,934-80-5; 1,2,4,5-tetramethylbenzene, 95-93-2; 1,2,3,5-tetramethylbenzene,
527-53-7; 2,3-dihydro-5-methyl-lH-indene, 874-35-1; 1,2,3,4tetramethylbenzene, 488-23-3; 1,2,3,4-tetrahydronaphthalene, 119-64-2; naphthalene, 91-20-3; 1,2,3,4-tetrahydro-6-methylnaphthalene, 1680-51-9; pentamethylbenzene, 700-12-9; 2methylnaphthalene, 91-57-6; 1-methylnaphthalene, 90-12-0; 1,2,3,4-tetrahydro-2,6-dimethylnaphthalene, 7524-63-2; 1,2,3,4tetrahydro-2,7-dimethylnaphthalene, 13065-07-1; 1,2,3,4-tetrahydre6-ethylnaphthalene, 22531-20-0;2,6-dimethylnaphthalene, 581-42-0; 1,6-dimethylnaphthalene, 575-43-9; 1,5-dimethylnaphthalene, 571-61-9; 2,3,6-trimethylnaphthalene,829-26-5; methane, 74-82-8; ethane, 74-84-0; ethene, 74-85-1;propane, 7498-6; propene, 115-07-1;1-butene, 106-98-9; 2-methylpropene, 115-11-7.
