Calvin Mukarakate - Academia.edu (original) (raw)

Uploads

Papers by Calvin Mukarakate

Applied Spectroscopy Reviews

Journal of Hazardous Materials

Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents... more Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents are available free via www.OSTI.gov.

Green Chemistry

An integrated experimental and computational study to understand the catalytic upgrading of bioma... more An integrated experimental and computational study to understand the catalytic upgrading of biomass vapors into high yield of alkenes.

Frontiers in Chemistry

Hierarchically structured porous materials often exhibit advantageous functionality for many appl... more Hierarchically structured porous materials often exhibit advantageous functionality for many applications including catalysts, adsorbents, and filtration systems. In this study, we report a facile approach to achieve hierarchically structured, porous cerium oxide (CeO 2) catalyst particles using a templating method based on nanocellulose, a class of renewable, plant-derived nanomaterials. We demonstrate the catalyst performance benefits provided by this templating method in the context of Catalytic Fast Pyrolysis (CFP) which is a promising conversion technology to produce renewable fuel and chemical products from biomass and other types of organic waste. We show that variations in the porous structures imparted by this templating method may be achieved by modifying the content of cellulose nanofibrils, cellulose nanocrystals, and alginate in the templating suspensions. Nitrogen physisorption reveals that nearly 10-fold increases in surface area can be achieved using this method with respect to commercially available cerium oxide powder. Multiscale electron microscopy further verifies that bio-derived templating can alter the morphology of the catalyst nanostructure and tune the distribution of meso-and macro-porosity within the catalyst particles while maintaining CeO 2 crystal structure. CFP experiments demonstrate that the templated catalysts display substantially higher activity on a gravimetric basis than their non-templated counterpart, and that variations in the catalyst architecture can impact the distribution of upgraded pyrolysis products. Finally, we demonstrate that the templating method described here may be extended to other materials derived from metal chlorides to achieve 3-dimensional networks of hierarchical porosity.

Green Chemistry

We demonstrate production and separation of coproducts through catalytic fast pyrolysis using wel... more We demonstrate production and separation of coproducts through catalytic fast pyrolysis using well-described and scalable operations achieving 97 wt% purity.

Wiley Interdisciplinary Reviews: Energy and Environment

Applied Catalysis B: Environmental

ABSTRACT The main objective of the present work was the study of different ZSM-5 catalytic formul... more ABSTRACT The main objective of the present work was the study of different ZSM-5 catalytic formulations for the in situ upgrading of biomass pyrolysis vapors. An equilibrium, commercial diluted ZSM-5 catalyst was used as the base case, in comparison with a series of nickel (Ni) and cobalt (Co) modified variants at varying metal loading (1–10 wt.%). The product yields and the composition of the produced bio-oil were significantly affected by the use of all ZSM-5 catalytic materials, compared to the non-catalytic flash pyrolysis, producing less bio-oil but of better quality. Incorporation of transition metals (Ni or Co) in the commercial equilibrium/diluted ZSM-5 catalyst had an additional effect on the performance of the parent ZSM-5 catalyst, with respect to product yields and bio-oil composition, with the NiO modified catalysts being more reactive towards decreasing the organic phase and increasing the gaseous products, compared to the Co3O4 supported catalysts. However, all the metal-modified catalysts exhibited limited reactivity towards water production, while simultaneously enhancing the production of aromatics and phenols. An interesting observation was the in situ reduction of the supported metal oxides during the pyrolysis reaction that eventually led to the formation of metallic Ni and Co species on the catalysts after reaction, which was verified by detailed XRD and HRTEM analysis of the used catalysts. The Co3O4 supported ZSM-5 catalysts exhibited also a promising performance in lowering the oxygen content of the organic phase of bio-oil.

Mixed-metal oxides possess a wide range of tunability and show promise for catalytic stabilizatio... more Mixed-metal oxides possess a wide range of tunability and show promise for catalytic stabilization of biomass pyrolysis products. For materials derived from layered double hydroxides, understanding the effect of divalent cation species and divalent/trivalent cation stoichiometric ratio on catalytic behavior is critical to their successful implementation. In this study, four mixed-metal 2 oxide catalysts consisting of Al, Zn, and Mg in different stoichiometric ratios were synthesized and tested for ex-situ catalytic fast pyrolysis (CFP) using pine wood as feedstock. The catalytic activity and deactivation behavior of these catalysts were monitored in real-time using a lab-scale pyrolysis reactor and fixed catalyst bed coupled with a molecular beam mass spectrometer (MBMS), and data were analyzed by multivariate statistical approaches. In comparing Mg-and Zn-Al catalyst materials, we demonstrate that the Mg-Al materials possessed greater quantities of basic sites, which we attribute to their higher surface areas, and they produced upgraded pyrolysis vapors which contained less acids and more deoxygenated aromatic hydrocarbons such as toluene and xylene. However, detrimental impacts on carbon yields were realized via decarbonylation and decarboxylation reactions and coke formation. Given that the primary goals of catalytic upgrading of bio-oil are deoxygenation, reduction of acidity, and high carbon yield, these results highlight both promising catalytic effects of mixed-metal oxide materials and opportunities for improvement.

ACS Sustainable Chemistry & Engineering

Green Chemistry

Partial deoxygenation of bio-oil by catalytic fast pyrolysis with subsequent coupling and hydrotr... more Partial deoxygenation of bio-oil by catalytic fast pyrolysis with subsequent coupling and hydrotreating can lead to improved economics and will aid commercial deployment of pyrolytic conversion of biomass technologies.

ACS Sustainable Chemistry & Engineering

Catalyst synthesis Experimental Systems Characterizations of as-synthesized MFI nanosheet (Figure... more Catalyst synthesis Experimental Systems Characterizations of as-synthesized MFI nanosheet (Figure S1-S5) Catalytic fast pyrolysis (Table S1-S4, Figure S6-S8) S2 Synthesis of the surfactant. In a typical synthesis of the surfactant, 3.9 g 1-bromodocosane and 17.2 g N,N,N',N'-tetramethyl-1,6-diaminohexane were dissolved in 50 mL dry toluene and 50 mL dry acetonitrile and heated at 60°C while stirring for 10 h under inert N 2 atmosphere. 1, 2 The intermediates were filtered and washed with cold diethyl ether, and dried under vacuum overnight. The intermediates were then mixed with 1-bromohexane (in a molar ratio of 0.01:0.02) with an injection of 30 mL dry acetonitrile and refluxed for 10 h. The products were filtered and then washed with cold diethyl ether and dried under vacuum overnight. Synthesis of MFI nanosheet. An aqueous acidic solution was prepared by dissolving Al 2 SO 4 •18H 2 O (0.2 M) and H 2 SO 4 (0.4 M) in distilled H 2 O. The surfactant was dissolved in 4.5 M NaOH solution, followed by an addition of the acidic solution drop-wise under vigorous stirring. The mixtures were agitated at 60 °C for 1 h. After cooling to room temperature, TEOS and the balance of distilled H 2 O (the total amount of H 2 O according to the gel composition subtract the amounts used in the acidic solution and basic solution) were quickly added and stirring continued at 60 °C for 1 h. The resultant gel was transferred to a 300 mL Teflon-lined autoclave, heated at 150 °C for 5 days under tumbling at 60 rpm. The zeolite products were filtered and washed with copious methanol. Pre-characterization, ammonium ion exchange of the products was repeated three times. In each treatment the zeolite products were soaked in 1 M NH 4 NO 3 at 80 °C for 2 h, filtered and dried at 120 °C. Protonated catalyst was achieved through calcination at 550 °C for 4 h in air. Nitrogen sorption analysis. Physisorption analysis was performed at 77 K using a Micromeritics Tristar-II instrument. Samples were degassed under N 2 flow at 90 °C for 60 min and then at 350 °C for 480 min to remove physisorbed impurities on the surface of samples. Full isotherms, specific surface area, pore volume, and pore size distribution

ACS Sustainable Chemistry & Engineering, 2016

The Journal of Chemical Physics, Sep 14, 2011

Pccp Physical Chemistry Chemical Physics, 2006

The Journal of Chemical Physics, Sep 14, 2011

Applied Spectroscopy Reviews

Journal of Hazardous Materials

Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents... more Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents are available free via www.OSTI.gov.

Green Chemistry

An integrated experimental and computational study to understand the catalytic upgrading of bioma... more An integrated experimental and computational study to understand the catalytic upgrading of biomass vapors into high yield of alkenes.

Frontiers in Chemistry

Hierarchically structured porous materials often exhibit advantageous functionality for many appl... more Hierarchically structured porous materials often exhibit advantageous functionality for many applications including catalysts, adsorbents, and filtration systems. In this study, we report a facile approach to achieve hierarchically structured, porous cerium oxide (CeO 2) catalyst particles using a templating method based on nanocellulose, a class of renewable, plant-derived nanomaterials. We demonstrate the catalyst performance benefits provided by this templating method in the context of Catalytic Fast Pyrolysis (CFP) which is a promising conversion technology to produce renewable fuel and chemical products from biomass and other types of organic waste. We show that variations in the porous structures imparted by this templating method may be achieved by modifying the content of cellulose nanofibrils, cellulose nanocrystals, and alginate in the templating suspensions. Nitrogen physisorption reveals that nearly 10-fold increases in surface area can be achieved using this method with respect to commercially available cerium oxide powder. Multiscale electron microscopy further verifies that bio-derived templating can alter the morphology of the catalyst nanostructure and tune the distribution of meso-and macro-porosity within the catalyst particles while maintaining CeO 2 crystal structure. CFP experiments demonstrate that the templated catalysts display substantially higher activity on a gravimetric basis than their non-templated counterpart, and that variations in the catalyst architecture can impact the distribution of upgraded pyrolysis products. Finally, we demonstrate that the templating method described here may be extended to other materials derived from metal chlorides to achieve 3-dimensional networks of hierarchical porosity.

Green Chemistry

We demonstrate production and separation of coproducts through catalytic fast pyrolysis using wel... more We demonstrate production and separation of coproducts through catalytic fast pyrolysis using well-described and scalable operations achieving 97 wt% purity.

Wiley Interdisciplinary Reviews: Energy and Environment

Applied Catalysis B: Environmental

ABSTRACT The main objective of the present work was the study of different ZSM-5 catalytic formul... more ABSTRACT The main objective of the present work was the study of different ZSM-5 catalytic formulations for the in situ upgrading of biomass pyrolysis vapors. An equilibrium, commercial diluted ZSM-5 catalyst was used as the base case, in comparison with a series of nickel (Ni) and cobalt (Co) modified variants at varying metal loading (1–10 wt.%). The product yields and the composition of the produced bio-oil were significantly affected by the use of all ZSM-5 catalytic materials, compared to the non-catalytic flash pyrolysis, producing less bio-oil but of better quality. Incorporation of transition metals (Ni or Co) in the commercial equilibrium/diluted ZSM-5 catalyst had an additional effect on the performance of the parent ZSM-5 catalyst, with respect to product yields and bio-oil composition, with the NiO modified catalysts being more reactive towards decreasing the organic phase and increasing the gaseous products, compared to the Co3O4 supported catalysts. However, all the metal-modified catalysts exhibited limited reactivity towards water production, while simultaneously enhancing the production of aromatics and phenols. An interesting observation was the in situ reduction of the supported metal oxides during the pyrolysis reaction that eventually led to the formation of metallic Ni and Co species on the catalysts after reaction, which was verified by detailed XRD and HRTEM analysis of the used catalysts. The Co3O4 supported ZSM-5 catalysts exhibited also a promising performance in lowering the oxygen content of the organic phase of bio-oil.

Mixed-metal oxides possess a wide range of tunability and show promise for catalytic stabilizatio... more Mixed-metal oxides possess a wide range of tunability and show promise for catalytic stabilization of biomass pyrolysis products. For materials derived from layered double hydroxides, understanding the effect of divalent cation species and divalent/trivalent cation stoichiometric ratio on catalytic behavior is critical to their successful implementation. In this study, four mixed-metal 2 oxide catalysts consisting of Al, Zn, and Mg in different stoichiometric ratios were synthesized and tested for ex-situ catalytic fast pyrolysis (CFP) using pine wood as feedstock. The catalytic activity and deactivation behavior of these catalysts were monitored in real-time using a lab-scale pyrolysis reactor and fixed catalyst bed coupled with a molecular beam mass spectrometer (MBMS), and data were analyzed by multivariate statistical approaches. In comparing Mg-and Zn-Al catalyst materials, we demonstrate that the Mg-Al materials possessed greater quantities of basic sites, which we attribute to their higher surface areas, and they produced upgraded pyrolysis vapors which contained less acids and more deoxygenated aromatic hydrocarbons such as toluene and xylene. However, detrimental impacts on carbon yields were realized via decarbonylation and decarboxylation reactions and coke formation. Given that the primary goals of catalytic upgrading of bio-oil are deoxygenation, reduction of acidity, and high carbon yield, these results highlight both promising catalytic effects of mixed-metal oxide materials and opportunities for improvement.

ACS Sustainable Chemistry & Engineering

Green Chemistry

Partial deoxygenation of bio-oil by catalytic fast pyrolysis with subsequent coupling and hydrotr... more Partial deoxygenation of bio-oil by catalytic fast pyrolysis with subsequent coupling and hydrotreating can lead to improved economics and will aid commercial deployment of pyrolytic conversion of biomass technologies.

ACS Sustainable Chemistry & Engineering

Catalyst synthesis Experimental Systems Characterizations of as-synthesized MFI nanosheet (Figure... more Catalyst synthesis Experimental Systems Characterizations of as-synthesized MFI nanosheet (Figure S1-S5) Catalytic fast pyrolysis (Table S1-S4, Figure S6-S8) S2 Synthesis of the surfactant. In a typical synthesis of the surfactant, 3.9 g 1-bromodocosane and 17.2 g N,N,N',N'-tetramethyl-1,6-diaminohexane were dissolved in 50 mL dry toluene and 50 mL dry acetonitrile and heated at 60°C while stirring for 10 h under inert N 2 atmosphere. 1, 2 The intermediates were filtered and washed with cold diethyl ether, and dried under vacuum overnight. The intermediates were then mixed with 1-bromohexane (in a molar ratio of 0.01:0.02) with an injection of 30 mL dry acetonitrile and refluxed for 10 h. The products were filtered and then washed with cold diethyl ether and dried under vacuum overnight. Synthesis of MFI nanosheet. An aqueous acidic solution was prepared by dissolving Al 2 SO 4 •18H 2 O (0.2 M) and H 2 SO 4 (0.4 M) in distilled H 2 O. The surfactant was dissolved in 4.5 M NaOH solution, followed by an addition of the acidic solution drop-wise under vigorous stirring. The mixtures were agitated at 60 °C for 1 h. After cooling to room temperature, TEOS and the balance of distilled H 2 O (the total amount of H 2 O according to the gel composition subtract the amounts used in the acidic solution and basic solution) were quickly added and stirring continued at 60 °C for 1 h. The resultant gel was transferred to a 300 mL Teflon-lined autoclave, heated at 150 °C for 5 days under tumbling at 60 rpm. The zeolite products were filtered and washed with copious methanol. Pre-characterization, ammonium ion exchange of the products was repeated three times. In each treatment the zeolite products were soaked in 1 M NH 4 NO 3 at 80 °C for 2 h, filtered and dried at 120 °C. Protonated catalyst was achieved through calcination at 550 °C for 4 h in air. Nitrogen sorption analysis. Physisorption analysis was performed at 77 K using a Micromeritics Tristar-II instrument. Samples were degassed under N 2 flow at 90 °C for 60 min and then at 350 °C for 480 min to remove physisorbed impurities on the surface of samples. Full isotherms, specific surface area, pore volume, and pore size distribution

ACS Sustainable Chemistry & Engineering, 2016

The Journal of Chemical Physics, Sep 14, 2011

Pccp Physical Chemistry Chemical Physics, 2006

The Journal of Chemical Physics, Sep 14, 2011