Liu, K
1996
Catalytic Reactions in Waste Plastics, HDPE and Coal Studies by High-Pressure Thermogravimetry with On-Line GC/MS
Liu, K. and Meuzelaar, H.L.C.
Fuels Processing, 49:55-67, 1996. Funded by Consortium for Fossil Fuel Liquefaction Science.
High pressure thermogravimetry (TG) with rapid on-line gas chromatography/mass spectrometry (GC/MS) has been used to investigate the effects of different catalysts on decomposition reactions of commingled wasted plastics (predominately PE), high density polyethylene (HDPE) and mixtures of DECS-6 with waste plastics in H2 at 900 psig. This permits direct evaluation of relative decomposition and residual char amounts as well as yield and include solid super acids such as Fe2O3/SO42-, Al2O3/SO, Al2O3/SO42- promoted by 0.5% Pt, and ZrO2/SO42- (all added at 10 wt%), as well as a conventional cracking catalyst of SiO2/Al2O3 in a 4:1 ratio, a hydrocracking catalyst of NiMo/Al2O3, HZSM-5>NiMoAl2O3 mixed with SiO2 Al2O3> (both added at 50%), and a HZSM-5 zeolite catalyst (added at 10%). Under these conditions cracking activity for waste plastics reveals the following order: SiO2/Al2O3, HZSM-5>NiMo/Al mixed with Si2O3O2Al2O3 solid super acids. Of the solid super acids studied the ZrO2/SO42- catalyst possesses the highest cracking activity, and the approximate order of cracking activity is ZrO2/SO42- > Al2O3/SO42- > Pt/Al2O3/SO42- > Fe2O3/SO42->no catalyst. The stronger the cracking catalyst, the lighter the aliphatic products and the more abundant the isometric constituents. Similar results are found for HDPD with these catalysts. For co-processing of coal with commingled waste plastic the HZSM-5 zeolite catalyst shows the most promising results by increasing the rate of the decomposition reactions at 420ºC nearly tenfold. Hydrocracking catalysts, such as NiMo/Al2O3 mixed with SiO2/Al2O3, show potential promise for processing of coal with commingled waste plastic due to their combined hydrogenation and cracking ability. By contrast, a superacid such as ZrO2/SO42- or cracking catalyst such as SiO2/Al2O3 appears to have little effect on the decomposition rate of the mixture. To what extent these findings are influenced by transport limitations (e.g., due to incomplete mixing or degree of crystallinity) and/or catalyst pretreatment is being studied further.
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.
Investigation of Physical Control Mechanisms in the Thermal Decomposition of Coal by Means of On-Line Mass Spectrometric Techniques
Nie, X.; Liu, K.; Maswadeh, W.; Tripathi, A. and Meuzelaar, H.L.C.
ACS Preprints, Division of Fuel Chemistry, 39(2):558-563, 1994. (Also presented at the 17th Annual Symposium of the Rocky Mountain Fuels Society, Golden, CO, March 1994, and at the ACS Meeting, San Diego, CA, March 1994.) Funded by ACERC and the Consortium for Fossil Fuel Liquefaction Science.
During the past decade marked progress has been made with regard to our understanding of the chemical processes occurring during the thermal degradation ("devolatilization," "desorption + pyrolysis") of coal and several advanced mechanistic models offering a qualitative and quantitative description of these processes, e.g., FG-DVC and CPD models, are now available. By contrast, there appears to be a comparative lack of progress in the description and understanding of the physical processes involved. It is becoming increasingly clear that the frequent lack of interlaboratory reproducibility almost invariably originates within the physical parameters of the experiment. Although heating rate, particle size and reactor pressure have long been recognized as the dominant physical parameters influencing the rates and product yields of coal devolatilization processes, current models pay little or no attention to heat and mass transport limitations. In fact, particle size is not an input parameter in these models. Furthermore, although most industrial scale coal devolatilization processes occur at near ambient pressures, current renewed interest in high pressure coal conversion processes would seem to dictate a more detailed look at the effects of pressure.
The objective of the research reported here is to exploit the capabilities of two novel experimental techniques, based on the on-line coupling of microscale, TG-type reactors to mass spectrometry and combined gas chromatography/mass spectrometry systems. The TG/GC/MS technique has high-pressure TG capabilities and will be described separately at this meeting. The direct TG/MS instrument is characterized by a heated, all quartz interface and will be discussed here. The complementary nature of both systems enables us to investigate the nature and extent of physical control mechanisms over a broad range of experimental conditions.
1993
Microscale Simulation of High Pressure Thermal and Catalytic Conversion Processes in Coal and Waste Polymers with On-Line GC/MS
Liu, K.; Jakab, E.; McClennen, W.H. and Meuzelaar, H.L.C.
Proceedings of the 206th American Chemical Society National Meeting, ACS Preprints, Fuel Chem. Div., 38 (3): 823-830, Chicago, IL, August 1993. Funded by US Department of Energy.
Over 279 million automotive tires are discarded in the United States each year. These used tires cause serious environmental problems since they are non-biodegradable, occupy considerable landfill space, and emit noxious fumes when burned. One of the promising approaches to deal with used rubber is the co-processing of it with coal to produce hydrocarbon liquids for use as fuels and specialty chemicals. Recently there have been numerous studies on co-processing of tire rubber and coal since depolymerized rubber has good solvent properties and the carbon black which constitutes of about 20-30% of the rubber is a good catalyst for depolymerization and possibly enhanced coal liquefaction. Monitoring sample weight loss as a function of temperature with on-line analysis of the evolved products during the co-processing reactions is necessary to elucidate mechanisms and kinetics of the key conversion reactions. Due to the high pressure and high temperature required by some of the most interesting processes, it is difficult to continuously monitor the weight loss and reaction intermediates without interrupting the reactions.
On-line analysis techniques for high-pressure conversion reactions have been reported previously, but these systems did not monitor total weight loss vs reaction temperature. They also were not applied directly to coal conversion studies because of the strong potential for plugging of sample orifices with pulverized coal. Microscale simulation of coal conversion reactions has been performed by high-pressure thermogravimetry with on-line combined gas chromatography and mass spectrometry (TG/GC/MS). It requires only a small sample size and can be operated at high temperature and pressure. The weight loss and low molecular weight products can be monitored vs reaction temperature. Analysis of pyrolysis and hydropyrolysis of coal, rubber and coal with tire rubber, with our without catalyst, by high pressure TG/GC/MS are reported here.
Development of On-Line GC/MS Monitoring Techniques for High-Pressure Fuel Conversion Processes
Nie, X.; McClennen, W.H.; Liu, K. and Meuzelaar, H.L.C.
Proceedings of the 206th American Chemical Society National Meeting, ACS Preprints, Fuel Chem. Div., 38 (4), Chicago, IL, August 1993. Funded by US Department of Energy.
It is well known that on-line analytical methods offer considerable advantages over conventional off-line procedures for fuel conversion processes. Although many on-line spectroscopic detection systems for thermal process reactors have been reported, they have had only very little application to high-pressure reactors. Therefore, relatively little is known about the precise pathways and intermediate products involved in high-pressure reactions. The application of real time, on-line chromatographic and/or spectroscopic techniques capable of throwing light on these processes is hampered by the high temperatures and pressures inside the reactor which complicate direct interfacing to standard analytical instruments.
Thermogravimetry (TG) can provide detailed information on thermally driven conversion reactions, especially when combined with on-line detection and identification techniques such as Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS). However, high pressure TG systems have only recently become available for studying the basic pyrolysis and especially hydropyrolysis reactions involved in coal liquefaction, thus, the combined chromatographic/spectroscopic interfaces for such high pressure systems are only now producing results. Other high-pressure reactors of interest include those used to study the thermal processes in liquid fuels or in solvent-based coal conversion. Thus there have been recent reports of on-line GC/MS monitoring of a high pressure recirculating autoclave used to study coal derived liquid model compounds. Other work in our laboratory has examined the supercritical pyrolytic degradation of jet fuels with on-line GC/IR/MS. Several of these systems have involved the use of a patented automated vapor sampling (AVS) inlet with short column or so-called "transfer line" gas chromatography (TLGC) with MS or FTIR.
This paper presents the experimental descriptions and results from three high-pressure systems using a variety of components. The first is a high pressure TG/GC/MS system used to study coal hydropyrolysis. The other two use quartz-tubing reactors to examine the liquid and gaseous products from the thermal decomposition of jet fuels.
Liu, K
1996
Catalytic Reactions in Waste Plastics, HDPE and Coal Studies by High-Pressure Thermogravimetry with On-Line GC/MS
Liu, K. and Meuzelaar, H.L.C.
Fuels Processing, 49:55-67, 1996. Funded by Consortium for Fossil Fuel Liquefaction Science.
High pressure thermogravimetry (TG) with rapid on-line gas chromatography/mass spectrometry (GC/MS) has been used to investigate the effects of different catalysts on decomposition reactions of commingled wasted plastics (predominately PE), high density polyethylene (HDPE) and mixtures of DECS-6 with waste plastics in H2 at 900 psig. This permits direct evaluation of relative decomposition and residual char amounts as well as yield and include solid super acids such as Fe2O3/SO42-, Al2O3/SO, Al2O3/SO42- promoted by 0.5% Pt, and ZrO2/SO42- (all added at 10 wt%), as well as a conventional cracking catalyst of SiO2/Al2O3 in a 4:1 ratio, a hydrocracking catalyst of NiMo/Al2O3, HZSM-5>NiMoAl2O3 mixed with SiO2 Al2O3> (both added at 50%), and a HZSM-5 zeolite catalyst (added at 10%). Under these conditions cracking activity for waste plastics reveals the following order: SiO2/Al2O3, HZSM-5>NiMo/Al mixed with Si2O3O2Al2O3 solid super acids. Of the solid super acids studied the ZrO2/SO42- catalyst possesses the highest cracking activity, and the approximate order of cracking activity is ZrO2/SO42- > Al2O3/SO42- > Pt/Al2O3/SO42- > Fe2O3/SO42->no catalyst. The stronger the cracking catalyst, the lighter the aliphatic products and the more abundant the isometric constituents. Similar results are found for HDPD with these catalysts. For co-processing of coal with commingled waste plastic the HZSM-5 zeolite catalyst shows the most promising results by increasing the rate of the decomposition reactions at 420ºC nearly tenfold. Hydrocracking catalysts, such as NiMo/Al2O3 mixed with SiO2/Al2O3, show potential promise for processing of coal with commingled waste plastic due to their combined hydrogenation and cracking ability. By contrast, a superacid such as ZrO2/SO42- or cracking catalyst such as SiO2/Al2O3 appears to have little effect on the decomposition rate of the mixture. To what extent these findings are influenced by transport limitations (e.g., due to incomplete mixing or degree of crystallinity) and/or catalyst pretreatment is being studied further.
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.
Investigation of Physical Control Mechanisms in the Thermal Decomposition of Coal by Means of On-Line Mass Spectrometric Techniques
Nie, X.; Liu, K.; Maswadeh, W.; Tripathi, A. and Meuzelaar, H.L.C.
ACS Preprints, Division of Fuel Chemistry, 39(2):558-563, 1994. (Also presented at the 17th Annual Symposium of the Rocky Mountain Fuels Society, Golden, CO, March 1994, and at the ACS Meeting, San Diego, CA, March 1994.) Funded by ACERC and the Consortium for Fossil Fuel Liquefaction Science.
During the past decade marked progress has been made with regard to our understanding of the chemical processes occurring during the thermal degradation ("devolatilization," "desorption + pyrolysis") of coal and several advanced mechanistic models offering a qualitative and quantitative description of these processes, e.g., FG-DVC and CPD models, are now available. By contrast, there appears to be a comparative lack of progress in the description and understanding of the physical processes involved. It is becoming increasingly clear that the frequent lack of interlaboratory reproducibility almost invariably originates within the physical parameters of the experiment. Although heating rate, particle size and reactor pressure have long been recognized as the dominant physical parameters influencing the rates and product yields of coal devolatilization processes, current models pay little or no attention to heat and mass transport limitations. In fact, particle size is not an input parameter in these models. Furthermore, although most industrial scale coal devolatilization processes occur at near ambient pressures, current renewed interest in high pressure coal conversion processes would seem to dictate a more detailed look at the effects of pressure.
The objective of the research reported here is to exploit the capabilities of two novel experimental techniques, based on the on-line coupling of microscale, TG-type reactors to mass spectrometry and combined gas chromatography/mass spectrometry systems. The TG/GC/MS technique has high-pressure TG capabilities and will be described separately at this meeting. The direct TG/MS instrument is characterized by a heated, all quartz interface and will be discussed here. The complementary nature of both systems enables us to investigate the nature and extent of physical control mechanisms over a broad range of experimental conditions.
1993
Microscale Simulation of High Pressure Thermal and Catalytic Conversion Processes in Coal and Waste Polymers with On-Line GC/MS
Liu, K.; Jakab, E.; McClennen, W.H. and Meuzelaar, H.L.C.
Proceedings of the 206th American Chemical Society National Meeting, ACS Preprints, Fuel Chem. Div., 38 (3): 823-830, Chicago, IL, August 1993. Funded by US Department of Energy.
Over 279 million automotive tires are discarded in the United States each year. These used tires cause serious environmental problems since they are non-biodegradable, occupy considerable landfill space, and emit noxious fumes when burned. One of the promising approaches to deal with used rubber is the co-processing of it with coal to produce hydrocarbon liquids for use as fuels and specialty chemicals. Recently there have been numerous studies on co-processing of tire rubber and coal since depolymerized rubber has good solvent properties and the carbon black which constitutes of about 20-30% of the rubber is a good catalyst for depolymerization and possibly enhanced coal liquefaction. Monitoring sample weight loss as a function of temperature with on-line analysis of the evolved products during the co-processing reactions is necessary to elucidate mechanisms and kinetics of the key conversion reactions. Due to the high pressure and high temperature required by some of the most interesting processes, it is difficult to continuously monitor the weight loss and reaction intermediates without interrupting the reactions.
On-line analysis techniques for high-pressure conversion reactions have been reported previously, but these systems did not monitor total weight loss vs reaction temperature. They also were not applied directly to coal conversion studies because of the strong potential for plugging of sample orifices with pulverized coal. Microscale simulation of coal conversion reactions has been performed by high-pressure thermogravimetry with on-line combined gas chromatography and mass spectrometry (TG/GC/MS). It requires only a small sample size and can be operated at high temperature and pressure. The weight loss and low molecular weight products can be monitored vs reaction temperature. Analysis of pyrolysis and hydropyrolysis of coal, rubber and coal with tire rubber, with our without catalyst, by high pressure TG/GC/MS are reported here.
Development of On-Line GC/MS Monitoring Techniques for High-Pressure Fuel Conversion Processes
Nie, X.; McClennen, W.H.; Liu, K. and Meuzelaar, H.L.C.
Proceedings of the 206th American Chemical Society National Meeting, ACS Preprints, Fuel Chem. Div., 38 (4), Chicago, IL, August 1993. Funded by US Department of Energy.
It is well known that on-line analytical methods offer considerable advantages over conventional off-line procedures for fuel conversion processes. Although many on-line spectroscopic detection systems for thermal process reactors have been reported, they have had only very little application to high-pressure reactors. Therefore, relatively little is known about the precise pathways and intermediate products involved in high-pressure reactions. The application of real time, on-line chromatographic and/or spectroscopic techniques capable of throwing light on these processes is hampered by the high temperatures and pressures inside the reactor which complicate direct interfacing to standard analytical instruments.
Thermogravimetry (TG) can provide detailed information on thermally driven conversion reactions, especially when combined with on-line detection and identification techniques such as Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS). However, high pressure TG systems have only recently become available for studying the basic pyrolysis and especially hydropyrolysis reactions involved in coal liquefaction, thus, the combined chromatographic/spectroscopic interfaces for such high pressure systems are only now producing results. Other high-pressure reactors of interest include those used to study the thermal processes in liquid fuels or in solvent-based coal conversion. Thus there have been recent reports of on-line GC/MS monitoring of a high pressure recirculating autoclave used to study coal derived liquid model compounds. Other work in our laboratory has examined the supercritical pyrolytic degradation of jet fuels with on-line GC/IR/MS. Several of these systems have involved the use of a patented automated vapor sampling (AVS) inlet with short column or so-called "transfer line" gas chromatography (TLGC) with MS or FTIR.
This paper presents the experimental descriptions and results from three high-pressure systems using a variety of components. The first is a high pressure TG/GC/MS system used to study coal hydropyrolysis. The other two use quartz-tubing reactors to examine the liquid and gaseous products from the thermal decomposition of jet fuels.