Oktay Erbatur - Academia.edu (original) (raw)

Papers by Oktay Erbatur

Research paper thumbnail of Preparation of Polyethylene-Reduced Graphene Oxide and Polyethylene-Reduced Graphene Oxide-Aramid Composites

Journal of the Institute of Science and Technology

Research paper thumbnail of Improving activity of Pt supported metal catalysts by changing reduction method of Pt precursor for hydrogen production from biomass

International Journal of Hydrogen Energy, 2015

Research paper thumbnail of Does reduced or non-reduced biomass feed produce more gas in aqueous-phase reforming process?

Fuel, 2015

ABSTRACT There has been increasing interest in the production of gaseous and liquid biofuels from... more ABSTRACT There has been increasing interest in the production of gaseous and liquid biofuels from biomass. Biomass feed type and its content to be used in the conversion process are very important parameters to produce high yield biofuel. In this study, reduced and non-reduced forms of biomass-derived compound (glucose) and actual biomass hydrolysate feeds were evaluated to produce hydrogen-rich gas mixture by aqueous-phase reforming (APR) in presence of supported Ru catalyst. Various hydrogenation conditions were tested for effective conversion. The results showed that reduced solutions always produced significantly higher gas yield with high hydrogen selectivity. Although biomass hydrolysate was composed of variety of complex compounds, it exhibited significantly better performance compared to glucose, simple biomass model compound.

Research paper thumbnail of Developing Pt based bimetallic and trimetallic carbon supported catalysts for aqueous-phase reforming of biomass-derived compounds

International Journal of Hydrogen Energy, 2015

ABSTRACT In the present work, a series of Pt-based bimetallic and trimetallic activated carbon (A... more ABSTRACT In the present work, a series of Pt-based bimetallic and trimetallic activated carbon (AC) and multiwalled carbon nanotube (MWCNT) supported catalysts at a 10 wt% total metal loading were prepared by wetness impregnation method to evaluate gasification performance of lignocellulosic biomass hydrolyzate and glucose solution for hydrogen-rich gas production by aqueous-phase reforming (APR) process. The Ru, Ni and Sn were added as promoter to platinum based supported catalysts with a 1:1 atomic ratio for bimetalic catalysts and 1:1:1 for trimetallic catalysts. The interactions between metals and the effect of alloy formation on gasification activity of the catalysts were investigated. The catalytic activity of Pt-MWCNT catalyst increased 21.2% by the addition of Ru metal. Bimetallic PtRu-MWCNT catalyst had a significantly higher catalytic activity and hydrogen selectivity compared to monometallic Pt-MWCNT for APR of biomass compounds. Since Ni and Ru metals promoted the activity of platinum catalysts, those catalysts could be used for displacement of platinum catalysts due to their low cost and relatively good catalytic activity in gasification of biomass-derived compounds.

Research paper thumbnail of Evaluation of various carbon materials supported Pt catalyts for aqueous-phase reforming of lignocellulosic biomass hydrolysate

International Journal of Hydrogen Energy, 2014

ABSTRACT Currently, under huge pressure from energy demands and environmental problems, much atte... more ABSTRACT Currently, under huge pressure from energy demands and environmental problems, much attention is being paid to produce fuel and chemicals from lignocellulosic biomass. In this matter, development of active and also recyclable catalysts are essential. In the present study, various types of carbon supported Pt reforming catalysts were prepared for use in gasification of wheat straw biomass hydrolysate by aqueous-phase reforming. The supports tested were various carbon materials having different surface and structures that were activated carbon (AC), single- and multi-walled carbon nanotubes (SWCNT and MWCNT), superdarco carbon (SDC) and graphene oxide (GO). The catalysts prepared using these supports were evaluated based on gasification yield, carbon amount consumed in the process, sugar alcohols formation and breaking down of organic compounds in the hydrolysate. Compared to other carbon-based supports tested, Pt on activated carbon showed best performance for gasification of biomass hydrolysate. This catalyst was also active on carbon consumption, sugar alcohols production and breaking down soluble organic compounds in the hydrolysate. The second active catalyst, Pt on single-walled carbon nanotube, showed significantly higher activity compared to multi-walled carbon nanotube since large polysaccharides molecules were not able to enter into narrow graphene sheets in multi-walled carbon nanotube to react with Pt deposited inside graphene layers.

Research paper thumbnail of Influence of particle size of support on reforming activity and selectivity of activated carbon supported platinum catalyst in APR

Research paper thumbnail of NMR Characterization of Solid Fossil Fuels. Coal and Oil Shale

Nuclear Magnetic Resonance in Modern Technology, 1994

NMR CHARACTERIZATION OF SOLID FOSSIL FUELS. COAL AND OIL SHALE GARY E. MACIEL Department of Chemi... more NMR CHARACTERIZATION OF SOLID FOSSIL FUELS. COAL AND OIL SHALE GARY E. MACIEL Department of Chemistry Colorado State University Fort Collins, Colorado 80523 USA and OKTAY ERBATUR Chemistry Department Cukurova University Adana PKI, Turkey ABSTRACT.] H ...

Research paper thumbnail of 13C NMR Investigation of the Chemical Structures of Coking and Non-Coking Coals in the Original and Reductively Alkylated Solid States

Research paper thumbnail of Chemical structures of pyridine extracts and residues of coals as indicated by solid state 13C NMR

Journal of Molecular Structure, 1984

ABSTRACT The pyridine extracts and the residues of four Turkish coals were investigated in the so... more ABSTRACT The pyridine extracts and the residues of four Turkish coals were investigated in the solid state by CP/MAS C-13 NMR. No systematic correlation was observed between the ranks of the coals and the aromaticities of the pyridine extracts. There were pronounced structural differences between the pyridine extracts and the corresponding parent fuels and these differences were most prominent in the lower rank coals. In general, the C-13 NMR spectra of the residues were quite similar to those of the corresponding parent fuels.

Research paper thumbnail of Degradation of aldrin in adsorbed system using advanced oxidation processes: comparison of the treatment methods

Journal of Hazardous Materials, 2004

In this study, Fenton, UV/Fenton, UV/H 2 O 2 , UV/Fe 2+ advanced oxidation processes have been ap... more In this study, Fenton, UV/Fenton, UV/H 2 O 2 , UV/Fe 2+ advanced oxidation processes have been applied for degradation of aldrin adsorbed on Na-montmorillonitte and activated carbon. Aldrin adsorbed on Na-montmorillonitte was degraded more efficiently than that of on activated carbon. For example, in UV/Fenton technique 95% of aldrin was removed from Na-montmorillonitte while 50% degradation was observed on activated carbon. Degradation of aldrin adsorbed on Na-montmorillonitte has also been achieved effectively using UV/Fe 2+ technique despite the absence of H 2 O 2. All AOPs but Fenton have been observed nearly equally effective for degradation of aldrin on Na-montmorillonitte sorbent. Fenton reaction exhibited least activity in degradation aldrin adsorbed on Na-montmorillonitte. The experiments with activated carbon sorbent indicated that phenyl groups in activated carbon structure and aldrin molecules exhibited competitive behavior on reaction with OH • radicals. The results of infrared spectroscopy support this assumption. The degradation efficiency of aldrin using activated carbon sorbent was determined in the following order: UV/Fenton > UV/H 2 O 2 > Fenton > UV/Fe 2+ .

Research paper thumbnail of Study on the stability of supercritical fluid extracted rosemary (Rosmarinus offcinalis L.) essential oil

Journal of Analytical Chemistry, 2010

The aim of this study was to examine the influence of storage conditions and duration on composit... more The aim of this study was to examine the influence of storage conditions and duration on composition and antioxidant activity of supercritical fluid (SCF) extracted essential oil of rosemary (Rosmarinus officinalis L.). Supercritical extraction was carried out sequentially by using SCF carbondioxide in the first two steps and with 5% ethanol as entrainer in the third step. The compositions of the extracts were determined by gas chro matography/mass spectrometry. The total phenolics were analyzed using Folin Ciocalteau assay. Antioxidant activities of the extracts were tested by β carotene linoleic acid bleaching method. The extracts stored at 4°C in the dark for 14 weeks were associated with slight changes in their composition. However, storage under indirect day light at room temperature caused considerable changes in the composi tions of the oils due to the chemical transformations in some of their components. Both the total phenolic contents and the antioxidant activities were significantly decreased after storage.

Research paper thumbnail of Preparation of activated carbon supported Pt catalysts and optimization of their catalytic activities for hydrogen gas production from the hydrothermal treatment of biomass-derived compounds

International Journal of Hydrogen Energy, 2012

ABSTRACT In the fields of energy science, it is a challenging issue to develop a highly active ca... more ABSTRACT In the fields of energy science, it is a challenging issue to develop a highly active catalyst for hydrogen-rich gas production from biomass-derived compounds. In the present study, active reforming catalysts for use of gasification of glucose, biomass-derived compound, in aqueous medium were developed by deposition of platinum on active carbon (AC) support using nanotechnological approaches in supercritical carbon dioxide (ScCO2) media and impregnation (IMP) in aqueous media. Effects of reduction methods for platinum metal and chemical treatment for AC support were evaluated for hydrogen production activity.It was observed that reduction of platinum precursor first by NaBH4 and then heat treatment resulted in more active catalysts compared to one single reduction method applied. The metal particles deposited on AC in ScCO2 had smaller sizes than those prepared by IMP in aqueous media. In case of IMP catalysts, NaBH4 and heat treatment double reduction methods applied catalysts showed greater activity for hydrogen production than those prepared by ScCO2 deposition technique. Activity of CH3COOH and HCl treated supports exhibited higher catalytic performance compared to H3PO4 and KOH treated supports however, untreated AC had still better activity in hydrogen production.

Research paper thumbnail of Electrolysis of coal slurries to produce hydrogen gas: Relationship between CO2 and H2 formation

International Journal of Hydrogen Energy, 2011

The purpose of this study was to produce hydrogen gas by electrolysis of coal slurries and to inv... more The purpose of this study was to produce hydrogen gas by electrolysis of coal slurries and to investigate the relation between hydrogen (H 2) and carbon dioxide (CO 2) formation. Electrolysis of coal slurries was evaluated at 40 C and 1.0 V cell potential to examine H 2 and CO 2 relationship. When electrolysis was performed after the coal slurry was mixed with Fe(II)/Fe(III) ions and stirred overnight (>12 h), no CO 2 gas was observed at the anode compartment. The results of total organic carbon (TOC) indicated that after electrolysis, few organic compounds were transformed into the solution and these organic compounds did not convert into CO 2. GC analysis, on the other hand, revealed that the H 2 collected at the cathode was pure and did not require any further purification process. Hydrogen generation or electrolysis efficiency of coal slurries cannot be calculated or estimated by examining CO 2 generation as reported in the literature. Low temperature and low cell potential were not sufficient to oxidize coal quantitatively.

Research paper thumbnail of Aqueous-phase reforming of biomass using various types of supported precious metal and raney-nickel catalysts for hydrogen production

International Journal of Hydrogen Energy, 2010

Aqueous-phase reforming (APR) of real biomass was studied for production of hydrogen gas. Wheat s... more Aqueous-phase reforming (APR) of real biomass was studied for production of hydrogen gas. Wheat straw, an abundant by-product from wheat production was used as representative lignocellulosic biomass. Wheat straw was hydrolyzed in an environmentally benign-sub critical water condition. APR experiments of wheat straw hydrolysates were performed using commercial catalysts which were made of Pt, Pd and Ru doped on carbon, activated carbon and alumina supports for production of hydrogen rich gas mixture. The activity and selectivity of two commercial raney-nickel catalysts were also monitored in terms of hydrogen production. Among the precious metal catalysts tested, activity of the metals for hydrogen production was in the following descending order: Pt > Ru > Pd. Results indicated that alumina support significantly lowered the catalytic performance of the catalysts. Based on whole catalyst material, raney-nickel catalysts were more active than supported precious metal catalysts tested.

Research paper thumbnail of Comparison of batch aqueous-phase reforming of glycerol and lignocellulosic biomass hydrolysate

Fuel, 2012

The present study was designed to evaluate gasification performance of glycerol, overproduced fro... more The present study was designed to evaluate gasification performance of glycerol, overproduced from biodiesel fuel production, and lignocellulosic biomass hydrolysate for hydrogen gas production by aqueousphase reforming (APR) process. Lignocellulosic biomass hydrolysate was prepared by solubilization of wheat straw under subcritical water condition. APR experiments were performed in a batch type reactor at 250 and 300°C in the presence of various commercial reforming catalysts such as raney nickel and Pt doped on carbon and alumina supports. Although the gas composition was similar, lower amount of gas was produced when APR of glycerol performed at higher temperature in the presence of a Pt catalyst. Hydrogen production activity of Pt on alumina catalyst was same as Pt on carbon support at 250°C, however, the activity significantly reduced at 300°C. The gasification performance of biomass hydrolysate was quite low compared to glycerol solution. The Pt on carbon was the most effective catalyst for total organic carbon (TOC) removal from glycerol while raney nickel was the most active one for TOC removal from wheat straw biomass hydrolysate.

Research paper thumbnail of Reductive ethylation in ethereal solvents

Fuel, 1984

Organic compounds, in pa~icular anthracene and naphthalene, and two coals have been reductively e... more Organic compounds, in pa~icular anthracene and naphthalene, and two coals have been reductively ethylated in tetrahydrofuran (THF) and diglyme using alkali metals to form anions and ethyl iodide to produce ethylates. Product distributions were sensitive to experimental conditions. The rate of anion formation was controlled by their rate of desorption, probably as contact ion pairs, from the alkali metal surface. The enthalpy of formation of a solvated contact ion pair was 2500 kJ mole-' mainly due to dipole-solvent interaction. 18-crown-6 ether was used to diagnose that, when treated with potassium in THF, anthracene gave solvated contact ion pairs and probably di-anions whose reactions were characterized by the formation of ethyldihydroanthracene. Naphthalene under identical conditionsgave loosely solvated mono-anions which reacted by electron transfer to give diethyldihydronaphthalene. With other alkali metals anthracene and naphthalene gave similar product distributions. The behaviour of other polynuclear aromatic hydrocarbons and of two coals was classified in the same way. It is suggested that when coals are readily solubilized by reductive alkylation mono-alkyldihydro products will predominate.

Research paper thumbnail of Upgrading lignites via thermal reduction with coke-oven gas

Fuel, 1991

Three Turkish lignites of varying rank were processed by using coke-oven gas under various proces... more Three Turkish lignites of varying rank were processed by using coke-oven gas under various processing conditions. Proximate and ultimate analyses and microscopic investigations with a polarized-reflected light microscope were carried out for all of these samples. Gaseous ...

Research paper thumbnail of Investigation of the chemical structures of coking and non-coking coals in original and reductively alkylated solid states via 13C n.m.r. and i.r. spectroscopies

Fuel, 1986

Chemical structures of four Turkish coals in original and reductively alkylated forms were invest... more Chemical structures of four Turkish coals in original and reductively alkylated forms were investigated in the solid state by CP/MAS 13 C nmr and ir spectroscopies. Dilatation properties of these samples were also determined. It was observed that, while the aliphatic parts of the coking coals ...

Research paper thumbnail of Investigation of pyridine extracts and residues of coals by solid-state 13C n.m.r. spectroscopy

Fuel, 1986

The 13 C nmr technique of cross polarization with magic angle spinning was applied to seven coals... more The 13 C nmr technique of cross polarization with magic angle spinning was applied to seven coals in their original states and the components obtained after pyridine extraction. It was observed that for the higher rank coals, short and straight alkyl groups are preferentially transferred ...

Research paper thumbnail of The effect of additives on hydrodesulfurization of dibenzothiophene over bulk molybdenum sulfide: Increased catalytic activity in the presence of phenol

Fuel Processing Technology, 2008

The effect of various additive organic reagents on the activation of MoS 3 as molybdenum sulfide ... more The effect of various additive organic reagents on the activation of MoS 3 as molybdenum sulfide catalyst precursor during hydrodesulfurization reaction of dibenzothiophene was studied. It was found that the presence of phenol or 1-naphthol greatly promoted the activity of the catalyst, while tetralin, 9,10-dihydrophenanthrene, ethylbenzene, and pyridine reagents were found to be detrimental for the activity of the catalyst.

Research paper thumbnail of Preparation of Polyethylene-Reduced Graphene Oxide and Polyethylene-Reduced Graphene Oxide-Aramid Composites

Journal of the Institute of Science and Technology

Research paper thumbnail of Improving activity of Pt supported metal catalysts by changing reduction method of Pt precursor for hydrogen production from biomass

International Journal of Hydrogen Energy, 2015

Research paper thumbnail of Does reduced or non-reduced biomass feed produce more gas in aqueous-phase reforming process?

Fuel, 2015

ABSTRACT There has been increasing interest in the production of gaseous and liquid biofuels from... more ABSTRACT There has been increasing interest in the production of gaseous and liquid biofuels from biomass. Biomass feed type and its content to be used in the conversion process are very important parameters to produce high yield biofuel. In this study, reduced and non-reduced forms of biomass-derived compound (glucose) and actual biomass hydrolysate feeds were evaluated to produce hydrogen-rich gas mixture by aqueous-phase reforming (APR) in presence of supported Ru catalyst. Various hydrogenation conditions were tested for effective conversion. The results showed that reduced solutions always produced significantly higher gas yield with high hydrogen selectivity. Although biomass hydrolysate was composed of variety of complex compounds, it exhibited significantly better performance compared to glucose, simple biomass model compound.

Research paper thumbnail of Developing Pt based bimetallic and trimetallic carbon supported catalysts for aqueous-phase reforming of biomass-derived compounds

International Journal of Hydrogen Energy, 2015

ABSTRACT In the present work, a series of Pt-based bimetallic and trimetallic activated carbon (A... more ABSTRACT In the present work, a series of Pt-based bimetallic and trimetallic activated carbon (AC) and multiwalled carbon nanotube (MWCNT) supported catalysts at a 10 wt% total metal loading were prepared by wetness impregnation method to evaluate gasification performance of lignocellulosic biomass hydrolyzate and glucose solution for hydrogen-rich gas production by aqueous-phase reforming (APR) process. The Ru, Ni and Sn were added as promoter to platinum based supported catalysts with a 1:1 atomic ratio for bimetalic catalysts and 1:1:1 for trimetallic catalysts. The interactions between metals and the effect of alloy formation on gasification activity of the catalysts were investigated. The catalytic activity of Pt-MWCNT catalyst increased 21.2% by the addition of Ru metal. Bimetallic PtRu-MWCNT catalyst had a significantly higher catalytic activity and hydrogen selectivity compared to monometallic Pt-MWCNT for APR of biomass compounds. Since Ni and Ru metals promoted the activity of platinum catalysts, those catalysts could be used for displacement of platinum catalysts due to their low cost and relatively good catalytic activity in gasification of biomass-derived compounds.

Research paper thumbnail of Evaluation of various carbon materials supported Pt catalyts for aqueous-phase reforming of lignocellulosic biomass hydrolysate

International Journal of Hydrogen Energy, 2014

ABSTRACT Currently, under huge pressure from energy demands and environmental problems, much atte... more ABSTRACT Currently, under huge pressure from energy demands and environmental problems, much attention is being paid to produce fuel and chemicals from lignocellulosic biomass. In this matter, development of active and also recyclable catalysts are essential. In the present study, various types of carbon supported Pt reforming catalysts were prepared for use in gasification of wheat straw biomass hydrolysate by aqueous-phase reforming. The supports tested were various carbon materials having different surface and structures that were activated carbon (AC), single- and multi-walled carbon nanotubes (SWCNT and MWCNT), superdarco carbon (SDC) and graphene oxide (GO). The catalysts prepared using these supports were evaluated based on gasification yield, carbon amount consumed in the process, sugar alcohols formation and breaking down of organic compounds in the hydrolysate. Compared to other carbon-based supports tested, Pt on activated carbon showed best performance for gasification of biomass hydrolysate. This catalyst was also active on carbon consumption, sugar alcohols production and breaking down soluble organic compounds in the hydrolysate. The second active catalyst, Pt on single-walled carbon nanotube, showed significantly higher activity compared to multi-walled carbon nanotube since large polysaccharides molecules were not able to enter into narrow graphene sheets in multi-walled carbon nanotube to react with Pt deposited inside graphene layers.

Research paper thumbnail of Influence of particle size of support on reforming activity and selectivity of activated carbon supported platinum catalyst in APR

Research paper thumbnail of NMR Characterization of Solid Fossil Fuels. Coal and Oil Shale

Nuclear Magnetic Resonance in Modern Technology, 1994

NMR CHARACTERIZATION OF SOLID FOSSIL FUELS. COAL AND OIL SHALE GARY E. MACIEL Department of Chemi... more NMR CHARACTERIZATION OF SOLID FOSSIL FUELS. COAL AND OIL SHALE GARY E. MACIEL Department of Chemistry Colorado State University Fort Collins, Colorado 80523 USA and OKTAY ERBATUR Chemistry Department Cukurova University Adana PKI, Turkey ABSTRACT.] H ...

Research paper thumbnail of 13C NMR Investigation of the Chemical Structures of Coking and Non-Coking Coals in the Original and Reductively Alkylated Solid States

Research paper thumbnail of Chemical structures of pyridine extracts and residues of coals as indicated by solid state 13C NMR

Journal of Molecular Structure, 1984

ABSTRACT The pyridine extracts and the residues of four Turkish coals were investigated in the so... more ABSTRACT The pyridine extracts and the residues of four Turkish coals were investigated in the solid state by CP/MAS C-13 NMR. No systematic correlation was observed between the ranks of the coals and the aromaticities of the pyridine extracts. There were pronounced structural differences between the pyridine extracts and the corresponding parent fuels and these differences were most prominent in the lower rank coals. In general, the C-13 NMR spectra of the residues were quite similar to those of the corresponding parent fuels.

Research paper thumbnail of Degradation of aldrin in adsorbed system using advanced oxidation processes: comparison of the treatment methods

Journal of Hazardous Materials, 2004

In this study, Fenton, UV/Fenton, UV/H 2 O 2 , UV/Fe 2+ advanced oxidation processes have been ap... more In this study, Fenton, UV/Fenton, UV/H 2 O 2 , UV/Fe 2+ advanced oxidation processes have been applied for degradation of aldrin adsorbed on Na-montmorillonitte and activated carbon. Aldrin adsorbed on Na-montmorillonitte was degraded more efficiently than that of on activated carbon. For example, in UV/Fenton technique 95% of aldrin was removed from Na-montmorillonitte while 50% degradation was observed on activated carbon. Degradation of aldrin adsorbed on Na-montmorillonitte has also been achieved effectively using UV/Fe 2+ technique despite the absence of H 2 O 2. All AOPs but Fenton have been observed nearly equally effective for degradation of aldrin on Na-montmorillonitte sorbent. Fenton reaction exhibited least activity in degradation aldrin adsorbed on Na-montmorillonitte. The experiments with activated carbon sorbent indicated that phenyl groups in activated carbon structure and aldrin molecules exhibited competitive behavior on reaction with OH • radicals. The results of infrared spectroscopy support this assumption. The degradation efficiency of aldrin using activated carbon sorbent was determined in the following order: UV/Fenton > UV/H 2 O 2 > Fenton > UV/Fe 2+ .

Research paper thumbnail of Study on the stability of supercritical fluid extracted rosemary (Rosmarinus offcinalis L.) essential oil

Journal of Analytical Chemistry, 2010

The aim of this study was to examine the influence of storage conditions and duration on composit... more The aim of this study was to examine the influence of storage conditions and duration on composition and antioxidant activity of supercritical fluid (SCF) extracted essential oil of rosemary (Rosmarinus officinalis L.). Supercritical extraction was carried out sequentially by using SCF carbondioxide in the first two steps and with 5% ethanol as entrainer in the third step. The compositions of the extracts were determined by gas chro matography/mass spectrometry. The total phenolics were analyzed using Folin Ciocalteau assay. Antioxidant activities of the extracts were tested by β carotene linoleic acid bleaching method. The extracts stored at 4°C in the dark for 14 weeks were associated with slight changes in their composition. However, storage under indirect day light at room temperature caused considerable changes in the composi tions of the oils due to the chemical transformations in some of their components. Both the total phenolic contents and the antioxidant activities were significantly decreased after storage.

Research paper thumbnail of Preparation of activated carbon supported Pt catalysts and optimization of their catalytic activities for hydrogen gas production from the hydrothermal treatment of biomass-derived compounds

International Journal of Hydrogen Energy, 2012

ABSTRACT In the fields of energy science, it is a challenging issue to develop a highly active ca... more ABSTRACT In the fields of energy science, it is a challenging issue to develop a highly active catalyst for hydrogen-rich gas production from biomass-derived compounds. In the present study, active reforming catalysts for use of gasification of glucose, biomass-derived compound, in aqueous medium were developed by deposition of platinum on active carbon (AC) support using nanotechnological approaches in supercritical carbon dioxide (ScCO2) media and impregnation (IMP) in aqueous media. Effects of reduction methods for platinum metal and chemical treatment for AC support were evaluated for hydrogen production activity.It was observed that reduction of platinum precursor first by NaBH4 and then heat treatment resulted in more active catalysts compared to one single reduction method applied. The metal particles deposited on AC in ScCO2 had smaller sizes than those prepared by IMP in aqueous media. In case of IMP catalysts, NaBH4 and heat treatment double reduction methods applied catalysts showed greater activity for hydrogen production than those prepared by ScCO2 deposition technique. Activity of CH3COOH and HCl treated supports exhibited higher catalytic performance compared to H3PO4 and KOH treated supports however, untreated AC had still better activity in hydrogen production.

Research paper thumbnail of Electrolysis of coal slurries to produce hydrogen gas: Relationship between CO2 and H2 formation

International Journal of Hydrogen Energy, 2011

The purpose of this study was to produce hydrogen gas by electrolysis of coal slurries and to inv... more The purpose of this study was to produce hydrogen gas by electrolysis of coal slurries and to investigate the relation between hydrogen (H 2) and carbon dioxide (CO 2) formation. Electrolysis of coal slurries was evaluated at 40 C and 1.0 V cell potential to examine H 2 and CO 2 relationship. When electrolysis was performed after the coal slurry was mixed with Fe(II)/Fe(III) ions and stirred overnight (>12 h), no CO 2 gas was observed at the anode compartment. The results of total organic carbon (TOC) indicated that after electrolysis, few organic compounds were transformed into the solution and these organic compounds did not convert into CO 2. GC analysis, on the other hand, revealed that the H 2 collected at the cathode was pure and did not require any further purification process. Hydrogen generation or electrolysis efficiency of coal slurries cannot be calculated or estimated by examining CO 2 generation as reported in the literature. Low temperature and low cell potential were not sufficient to oxidize coal quantitatively.

Research paper thumbnail of Aqueous-phase reforming of biomass using various types of supported precious metal and raney-nickel catalysts for hydrogen production

International Journal of Hydrogen Energy, 2010

Aqueous-phase reforming (APR) of real biomass was studied for production of hydrogen gas. Wheat s... more Aqueous-phase reforming (APR) of real biomass was studied for production of hydrogen gas. Wheat straw, an abundant by-product from wheat production was used as representative lignocellulosic biomass. Wheat straw was hydrolyzed in an environmentally benign-sub critical water condition. APR experiments of wheat straw hydrolysates were performed using commercial catalysts which were made of Pt, Pd and Ru doped on carbon, activated carbon and alumina supports for production of hydrogen rich gas mixture. The activity and selectivity of two commercial raney-nickel catalysts were also monitored in terms of hydrogen production. Among the precious metal catalysts tested, activity of the metals for hydrogen production was in the following descending order: Pt > Ru > Pd. Results indicated that alumina support significantly lowered the catalytic performance of the catalysts. Based on whole catalyst material, raney-nickel catalysts were more active than supported precious metal catalysts tested.

Research paper thumbnail of Comparison of batch aqueous-phase reforming of glycerol and lignocellulosic biomass hydrolysate

Fuel, 2012

The present study was designed to evaluate gasification performance of glycerol, overproduced fro... more The present study was designed to evaluate gasification performance of glycerol, overproduced from biodiesel fuel production, and lignocellulosic biomass hydrolysate for hydrogen gas production by aqueousphase reforming (APR) process. Lignocellulosic biomass hydrolysate was prepared by solubilization of wheat straw under subcritical water condition. APR experiments were performed in a batch type reactor at 250 and 300°C in the presence of various commercial reforming catalysts such as raney nickel and Pt doped on carbon and alumina supports. Although the gas composition was similar, lower amount of gas was produced when APR of glycerol performed at higher temperature in the presence of a Pt catalyst. Hydrogen production activity of Pt on alumina catalyst was same as Pt on carbon support at 250°C, however, the activity significantly reduced at 300°C. The gasification performance of biomass hydrolysate was quite low compared to glycerol solution. The Pt on carbon was the most effective catalyst for total organic carbon (TOC) removal from glycerol while raney nickel was the most active one for TOC removal from wheat straw biomass hydrolysate.

Research paper thumbnail of Reductive ethylation in ethereal solvents

Fuel, 1984

Organic compounds, in pa~icular anthracene and naphthalene, and two coals have been reductively e... more Organic compounds, in pa~icular anthracene and naphthalene, and two coals have been reductively ethylated in tetrahydrofuran (THF) and diglyme using alkali metals to form anions and ethyl iodide to produce ethylates. Product distributions were sensitive to experimental conditions. The rate of anion formation was controlled by their rate of desorption, probably as contact ion pairs, from the alkali metal surface. The enthalpy of formation of a solvated contact ion pair was 2500 kJ mole-' mainly due to dipole-solvent interaction. 18-crown-6 ether was used to diagnose that, when treated with potassium in THF, anthracene gave solvated contact ion pairs and probably di-anions whose reactions were characterized by the formation of ethyldihydroanthracene. Naphthalene under identical conditionsgave loosely solvated mono-anions which reacted by electron transfer to give diethyldihydronaphthalene. With other alkali metals anthracene and naphthalene gave similar product distributions. The behaviour of other polynuclear aromatic hydrocarbons and of two coals was classified in the same way. It is suggested that when coals are readily solubilized by reductive alkylation mono-alkyldihydro products will predominate.

Research paper thumbnail of Upgrading lignites via thermal reduction with coke-oven gas

Fuel, 1991

Three Turkish lignites of varying rank were processed by using coke-oven gas under various proces... more Three Turkish lignites of varying rank were processed by using coke-oven gas under various processing conditions. Proximate and ultimate analyses and microscopic investigations with a polarized-reflected light microscope were carried out for all of these samples. Gaseous ...

Research paper thumbnail of Investigation of the chemical structures of coking and non-coking coals in original and reductively alkylated solid states via 13C n.m.r. and i.r. spectroscopies

Fuel, 1986

Chemical structures of four Turkish coals in original and reductively alkylated forms were invest... more Chemical structures of four Turkish coals in original and reductively alkylated forms were investigated in the solid state by CP/MAS 13 C nmr and ir spectroscopies. Dilatation properties of these samples were also determined. It was observed that, while the aliphatic parts of the coking coals ...

Research paper thumbnail of Investigation of pyridine extracts and residues of coals by solid-state 13C n.m.r. spectroscopy

Fuel, 1986

The 13 C nmr technique of cross polarization with magic angle spinning was applied to seven coals... more The 13 C nmr technique of cross polarization with magic angle spinning was applied to seven coals in their original states and the components obtained after pyridine extraction. It was observed that for the higher rank coals, short and straight alkyl groups are preferentially transferred ...

Research paper thumbnail of The effect of additives on hydrodesulfurization of dibenzothiophene over bulk molybdenum sulfide: Increased catalytic activity in the presence of phenol

Fuel Processing Technology, 2008

The effect of various additive organic reagents on the activation of MoS 3 as molybdenum sulfide ... more The effect of various additive organic reagents on the activation of MoS 3 as molybdenum sulfide catalyst precursor during hydrodesulfurization reaction of dibenzothiophene was studied. It was found that the presence of phenol or 1-naphthol greatly promoted the activity of the catalyst, while tetralin, 9,10-dihydrophenanthrene, ethylbenzene, and pyridine reagents were found to be detrimental for the activity of the catalyst.