Shabtai, J
1994
Studies of Thermal and Catalytic Hydroliquefaction of Model Compounds, Waste Polymers, and Coal by High-Pressure TG/GC/MS
Liu, K.; Jakab, E.; Zmierczak, W.; Shabtai, J.S. and Meuzelaar, H.L.C.
ACS Preprints, Division of Fuel Chemistry, 39(2):576-580, 1994. (Proceedings of the ACS National Meeting, and the 17th Annual Symposium of the Rocky Mountain Fuels, Golden, CO, March 1994 and the ACS Meeting, Division of Fuel Chemistry, San Diego, CA, March 1994.) Funded by ACERC and the Consortium for Fossil Fuels Liquefaction Science.
A recently developed on-line high-pressure themogravimetry (TG)/gas chromatography (GC)/mass spectrometry (MS) system provides certain advantages over other on-line analysis techniques for high-pressure reactors reported previously. The high pressure TG/GC/MS system enables the simulation of solvent-free thermal and catalytic reactions for polymers and coal. During the reactions the total weight change is monitored and the volatile intermediate products are identified. It requires only very small amounts (10-100 mg) of sample and can be operated at high pressure under different atmospheres (N2, He, H2, etc.). Current efforts to recycle lower grade post consumer polymers such as colored polyethylene and polystyrene or used rubber tires, are concentrated on co-processing with coal. Purely thermal degradation processes involve both decomposition and condensation (recombination) reactions and the resulting product is highly olefinic and often aromatic. In order to improve the yield and selectivity of the process, a great deal of effort has been spent on finding the proper catalysts. Catalysts selected for the present studies include ZrO2/SO4, (NH4)2MoS4 and carbon black. Carbon black present in waste rubber tires has been reported to be very selective for the cleavage of specific alkylaryl bonds. (NH4)2MoS4 has been shown to improve the liquid yields in coal liquefaction. The superacid catalyst Zr2O2/SO4 possesses markedly higher hydrogenolytic activity compared to that of conventional SiO2-supported soluble Fe salts.
1992
Spectroscopic Studies of Coal Maceral Depolymerization Effected by an Iron-Based Catalyst
Wang, H.P.; Lo, R.; Sommerfeld, D.A.; Huai, H.; Pugmire, R.J.; Shabtai, J.S. and Eyring, E.M.
Fuel, 71(7):723-729, 1992. Funded by US Department of Energy.
Demineralized Hiawatha (Utah) coal was divided into narrow density fractions of resinite and vitrinite macerals using a density gradient centrifugation technique. The distribution of an iron-based catalyst in the coal maceral matrix was studied using an electron probe microanalyser. The data indicate that the iron catalyst is evenly dispersed inside the vitrinite. This uniform dispersion is preserved upon mild (275ºC) hydrotreatment and attendant partial depolymerization of the vitrinite maceral. However, the iron catalyst does not completely penetrate into the resinite maceral matrix due to a lack of microporosity. The small amount of dispersed iron catalyst in the resinite causes some depolymerization of maceral components, e.g. dimers, trimers, or higher polymers, into monomers. Due to the insufficient dispersion of the iron catalyst in the resinite a competing thermal breakdown of the maceral occurs. This apparently involved a partial dehydrogenation reaction that may be favored during the hydrotreatment of resinite.
High-Resolution Chromatographic Characterization of Depolymerized Coals of Different Rank: Aliphatic and Aromatic Hydrocarbons
Carlson, R.E.; Critchfield, S.; Vorkink, W.P.; Dong, J.-Z.; Pugmire, R.J.; Bartle, K.D.; Lee, M.L.; Zhang, Y. and Shabtai, J.S.
Fuel, 71(1):1-29, 1992. Funded by US Department of Energy, Gas Research Institute and ACERC.
A selective, low temperature depolymerization procedure has been applied to four Argonne coals of different rank to produce products that are representative of the original coal macromolecular structure, and that are amenable to chromatographic analysis. The products of this depolymerization procedure retained most of the original aromatic and functional group structures of the original coals. A comparison of liquid C-13 NMR spectra of the products and solid-state C-13 NMR spectra of the original coals showed only minor changes in the aromaticities of two of the coals, and some loss of the carbonyl carbons in all of the coals.
Tetrahydrofuran pre-extracts of the four coals and their depolymerized products were separated into chemical classes by adsorption chromatography. Two of these fractions, which contained aliphatic hydrocarbons and polycyclic aromatic hydrocarbons were analyzed using gas chromatography/mass spectrometry. Structural identifications were based on a combination of chromatographic retention and mass spectral fragmentation data. For the lower rank coals, the compositions of the pre-extracts were quite different from the corresponding depolymerized products, and they contained an abundance of molecular biological markers. The compositions of the pre-extracts became more similar to the depolymerized products as rank increased.
On-Line GC/MS Analysis of High Pressure Conversion Reactions of Model Compounds for Coal-Derived Liquids
Huai, H.; Tsai, C.H.; Shabtai, J.S. and Meuzelaar, H.L.C.
ACS Division of Fuel Chemistry Preprints, 37(2):925-932, 1992 (203rd ACS National Meeting, San Francisco, CA, April 1992). Funded by Consortium for Fossil Fuel Liquefaction.
Direct coal liquefaction involves complex and insufficiently defined chemical reactions. In order to improve direct coal liquefaction processes, it is necessary to improve our understanding of key chemical reactions. Unfortunately, due to the high pressure and high temperature requirements of most coal liquefaction processes, real-time on-line reaction monitoring by advanced spectroscopic and/or chromatographic techniques has generally been impossible until now. Thus, relatively little is known about the precise reaction pathways as well as the intermediate reaction products involved. This is particularly true for conversion reactions carried out in batch reactors such as autoclaves. Due to the relatively long residence times primary reaction products formed in batch type autoclaves are quite susceptible to secondary, or even tertiary reactions. Consequently, real-time on-line monitoring experiments are needed to elucidate reaction pathways in autoclaves.
Although several on-line systems have been developed for coal conversion at near-ambient pressure or high vacuum conditions, there are no repots of on-line chromatography/spectroscopy based systems built for monitoring high-pressure conversion reactions. Therefore, the development of a direct GC/MS interface for near-real time analysis of high-pressure reaction products, while minimally disturbing the reaction process, has been undertaken in our laboratory.
It is well established that coal contains fused aromatic and hydroaromatic ring clusters, composed of an average of two to tour condensed ring units, connected by various alkylene, ether, sulfide and direct (Ar)C-C(Ar) bridges. Liquefaction reactions are primarily thought to involve these connecting bridges, especially ether linkages and alkylene linkages. In recent years, a number of workers have subjected coal-model compounds to various coal conversion conditions in order to confirm that certain coal structures are reactive during coal conversion and to infer the conversion mechanisms of real coals from mechanisms determined for such compounds.
The present paper reports the design and testing of a newly developed on-line GC/MS monitoring system for high pressure reactions and its application to the investigation of hydrogenation and hydrodeoxygenation (HDO) of model compounds, such as diphenyl methane and dibenzyl ether, under both catalytic and thermal conditions.
1991
Analysis of Depolymerization Products of Various Rank Coals Using High Resolution Chromatographic Techniques
Carlson, R.E.; Vorkink, W.P.; Lee, M.L.; Zhang, Y. and Shabtai, J.S.
1991 Pittsburgh Coal Conference and Exposition on Analytical Chemistry and Applied Spectroscopy, Chicago, IL, March 1991. Funded by ACERC.
Elucidation of the organic structure of coal is vital to designing and optimizing processes for direct coal usage (e.g., combustion or coal conversion), and the efficient utilization of this abundant natural resource. Due to the extremely complex macromolecular structure of coal, present structural information is sparse. The analysis of coal and coal derived materials has been approached by numerous analytical and chemical techniques. However, many of those methods fail to yield specific information concerning the macromolecular network, or they significantly alter the network. Solvent extracts have provided valuable information concerning the "easily" extractable portion of the coal matrix, again leaving the macromolecular skeleton virtually unexplored. Structural investigations of coal carried out at high temperatures (>300ºC) lead to free radical rearrangement, crosslinking and thermal cracking of the sample.
A mild depolymerization method has been developed which yields a tetrahydrofuran (THF) soluble product that represents 50 to >70% of the original material, depending on coal rank. Detailed analysis of these products was performed using high-resolution gas chromatography and gas chromatography/mass spectrometry. The qualitative and quantitative results of four depolymerized Argonne coals (Beulah Zap, Illinois No. 6, Utah Blind Canyon, Pocahontas No.3) will be discussed and compared to room temperature solvent extracts (THF) of the same coals.
Shabtai, J
1994
Studies of Thermal and Catalytic Hydroliquefaction of Model Compounds, Waste Polymers, and Coal by High-Pressure TG/GC/MS
Liu, K.; Jakab, E.; Zmierczak, W.; Shabtai, J.S. and Meuzelaar, H.L.C.
ACS Preprints, Division of Fuel Chemistry, 39(2):576-580, 1994. (Proceedings of the ACS National Meeting, and the 17th Annual Symposium of the Rocky Mountain Fuels, Golden, CO, March 1994 and the ACS Meeting, Division of Fuel Chemistry, San Diego, CA, March 1994.) Funded by ACERC and the Consortium for Fossil Fuels Liquefaction Science.
A recently developed on-line high-pressure themogravimetry (TG)/gas chromatography (GC)/mass spectrometry (MS) system provides certain advantages over other on-line analysis techniques for high-pressure reactors reported previously. The high pressure TG/GC/MS system enables the simulation of solvent-free thermal and catalytic reactions for polymers and coal. During the reactions the total weight change is monitored and the volatile intermediate products are identified. It requires only very small amounts (10-100 mg) of sample and can be operated at high pressure under different atmospheres (N2, He, H2, etc.). Current efforts to recycle lower grade post consumer polymers such as colored polyethylene and polystyrene or used rubber tires, are concentrated on co-processing with coal. Purely thermal degradation processes involve both decomposition and condensation (recombination) reactions and the resulting product is highly olefinic and often aromatic. In order to improve the yield and selectivity of the process, a great deal of effort has been spent on finding the proper catalysts. Catalysts selected for the present studies include ZrO2/SO4, (NH4)2MoS4 and carbon black. Carbon black present in waste rubber tires has been reported to be very selective for the cleavage of specific alkylaryl bonds. (NH4)2MoS4 has been shown to improve the liquid yields in coal liquefaction. The superacid catalyst Zr2O2/SO4 possesses markedly higher hydrogenolytic activity compared to that of conventional SiO2-supported soluble Fe salts.
1992
Spectroscopic Studies of Coal Maceral Depolymerization Effected by an Iron-Based Catalyst
Wang, H.P.; Lo, R.; Sommerfeld, D.A.; Huai, H.; Pugmire, R.J.; Shabtai, J.S. and Eyring, E.M.
Fuel, 71(7):723-729, 1992. Funded by US Department of Energy.
Demineralized Hiawatha (Utah) coal was divided into narrow density fractions of resinite and vitrinite macerals using a density gradient centrifugation technique. The distribution of an iron-based catalyst in the coal maceral matrix was studied using an electron probe microanalyser. The data indicate that the iron catalyst is evenly dispersed inside the vitrinite. This uniform dispersion is preserved upon mild (275ºC) hydrotreatment and attendant partial depolymerization of the vitrinite maceral. However, the iron catalyst does not completely penetrate into the resinite maceral matrix due to a lack of microporosity. The small amount of dispersed iron catalyst in the resinite causes some depolymerization of maceral components, e.g. dimers, trimers, or higher polymers, into monomers. Due to the insufficient dispersion of the iron catalyst in the resinite a competing thermal breakdown of the maceral occurs. This apparently involved a partial dehydrogenation reaction that may be favored during the hydrotreatment of resinite.
High-Resolution Chromatographic Characterization of Depolymerized Coals of Different Rank: Aliphatic and Aromatic Hydrocarbons
Carlson, R.E.; Critchfield, S.; Vorkink, W.P.; Dong, J.-Z.; Pugmire, R.J.; Bartle, K.D.; Lee, M.L.; Zhang, Y. and Shabtai, J.S.
Fuel, 71(1):1-29, 1992. Funded by US Department of Energy, Gas Research Institute and ACERC.
A selective, low temperature depolymerization procedure has been applied to four Argonne coals of different rank to produce products that are representative of the original coal macromolecular structure, and that are amenable to chromatographic analysis. The products of this depolymerization procedure retained most of the original aromatic and functional group structures of the original coals. A comparison of liquid C-13 NMR spectra of the products and solid-state C-13 NMR spectra of the original coals showed only minor changes in the aromaticities of two of the coals, and some loss of the carbonyl carbons in all of the coals.
Tetrahydrofuran pre-extracts of the four coals and their depolymerized products were separated into chemical classes by adsorption chromatography. Two of these fractions, which contained aliphatic hydrocarbons and polycyclic aromatic hydrocarbons were analyzed using gas chromatography/mass spectrometry. Structural identifications were based on a combination of chromatographic retention and mass spectral fragmentation data. For the lower rank coals, the compositions of the pre-extracts were quite different from the corresponding depolymerized products, and they contained an abundance of molecular biological markers. The compositions of the pre-extracts became more similar to the depolymerized products as rank increased.
On-Line GC/MS Analysis of High Pressure Conversion Reactions of Model Compounds for Coal-Derived Liquids
Huai, H.; Tsai, C.H.; Shabtai, J.S. and Meuzelaar, H.L.C.
ACS Division of Fuel Chemistry Preprints, 37(2):925-932, 1992 (203rd ACS National Meeting, San Francisco, CA, April 1992). Funded by Consortium for Fossil Fuel Liquefaction.
Direct coal liquefaction involves complex and insufficiently defined chemical reactions. In order to improve direct coal liquefaction processes, it is necessary to improve our understanding of key chemical reactions. Unfortunately, due to the high pressure and high temperature requirements of most coal liquefaction processes, real-time on-line reaction monitoring by advanced spectroscopic and/or chromatographic techniques has generally been impossible until now. Thus, relatively little is known about the precise reaction pathways as well as the intermediate reaction products involved. This is particularly true for conversion reactions carried out in batch reactors such as autoclaves. Due to the relatively long residence times primary reaction products formed in batch type autoclaves are quite susceptible to secondary, or even tertiary reactions. Consequently, real-time on-line monitoring experiments are needed to elucidate reaction pathways in autoclaves.
Although several on-line systems have been developed for coal conversion at near-ambient pressure or high vacuum conditions, there are no repots of on-line chromatography/spectroscopy based systems built for monitoring high-pressure conversion reactions. Therefore, the development of a direct GC/MS interface for near-real time analysis of high-pressure reaction products, while minimally disturbing the reaction process, has been undertaken in our laboratory.
It is well established that coal contains fused aromatic and hydroaromatic ring clusters, composed of an average of two to tour condensed ring units, connected by various alkylene, ether, sulfide and direct (Ar)C-C(Ar) bridges. Liquefaction reactions are primarily thought to involve these connecting bridges, especially ether linkages and alkylene linkages. In recent years, a number of workers have subjected coal-model compounds to various coal conversion conditions in order to confirm that certain coal structures are reactive during coal conversion and to infer the conversion mechanisms of real coals from mechanisms determined for such compounds.
The present paper reports the design and testing of a newly developed on-line GC/MS monitoring system for high pressure reactions and its application to the investigation of hydrogenation and hydrodeoxygenation (HDO) of model compounds, such as diphenyl methane and dibenzyl ether, under both catalytic and thermal conditions.
1991
Analysis of Depolymerization Products of Various Rank Coals Using High Resolution Chromatographic Techniques
Carlson, R.E.; Vorkink, W.P.; Lee, M.L.; Zhang, Y. and Shabtai, J.S.
1991 Pittsburgh Coal Conference and Exposition on Analytical Chemistry and Applied Spectroscopy, Chicago, IL, March 1991. Funded by ACERC.
Elucidation of the organic structure of coal is vital to designing and optimizing processes for direct coal usage (e.g., combustion or coal conversion), and the efficient utilization of this abundant natural resource. Due to the extremely complex macromolecular structure of coal, present structural information is sparse. The analysis of coal and coal derived materials has been approached by numerous analytical and chemical techniques. However, many of those methods fail to yield specific information concerning the macromolecular network, or they significantly alter the network. Solvent extracts have provided valuable information concerning the "easily" extractable portion of the coal matrix, again leaving the macromolecular skeleton virtually unexplored. Structural investigations of coal carried out at high temperatures (>300ºC) lead to free radical rearrangement, crosslinking and thermal cracking of the sample.
A mild depolymerization method has been developed which yields a tetrahydrofuran (THF) soluble product that represents 50 to >70% of the original material, depending on coal rank. Detailed analysis of these products was performed using high-resolution gas chromatography and gas chromatography/mass spectrometry. The qualitative and quantitative results of four depolymerized Argonne coals (Beulah Zap, Illinois No. 6, Utah Blind Canyon, Pocahontas No.3) will be discussed and compared to room temperature solvent extracts (THF) of the same coals.