Gas Chromatography-thermal Conductivity Detector Research Articles

Forensic utility of carboxyhemoglobin levels in postmortem spleen specimens in South Korea

In order to determine whether CO poisoning was the definitive cause of death, the concentration of carboxyhemoglobin (COHb) in spleen specimens was analyzed using a gas chromatography-thermal conductivity detector. 125 cases of forensic autopsy reports containing COHb analysis requests were analyzed and subdivided into two groups, improbable and highly probable of CO intoxication. In the first group which consists of 100 cases, the results of COHb analysis were negative, and the circumstances of death, as well as the postmortem findings could not validate the exposure to CO. In the second group which consists of 25 cases, the results of COHb were positive, and both postmortem findings and circumstances of death confirmed the exposure to CO. In the cases of indoors and vehicle fires or those including the use of briquettes, COHb levels reached 43.1–97.5 %, whereas in individuals without any feature of CO poisoning had COHb level high as 29.8 %. However, certain cases without any connection to fire nor CO exposure also contained significant amount of CO based on post-mortem analysis. This study focuses on cases without any relationship to fire or CO and proves that COHb levels below 30 % may be considered as a contributing factor to but not exclusively as the cause of death.

Performance of NiO doped on alkaline sludge from waste photovoltaic industries for catalytic dry reforming of methane.

Alkali sludge (AS) is waste abundantly generated from solar photovoltaic (PV) solar cell industries. Since this potential basic material is still underutilized, a combination with NiO catalyst might greatly influence coke resentence, especially in high-temperature thermochemical reactions (Arora and Prasad, RSC Adv. 6:108,668-108688, 2016). This paper investigated alkaline sludge containing 3CaO-2SiO2 doped with well-known NiO to enhance the dry reforming of methane (DRM) reaction. The wet-impregnation method was used to prepare the xNiO/AS (x = 5-15%) catalysts. Subsequently, all catalysts were tested by using X-ray diffraction (XRD), nitrogen adsorption/desorption (BET), temperature-programmed reduction of hydrogen (H2-TPR), temperature-programmed desorption of carbon dioxide (TPD-CO2), field emission scanning electron microscopy (FESEM-EDX), and X-ray photoelectron spectroscopy (XPS). The spent catalysts were analyzed by thermogravimetric analysis (TGA/DTG), transmission electron microscopy (TEM), and temperature-programmed oxidation (TPO). The catalytic performance of xNiO/AS catalysts was investigated in a fixed bed reactor connected with gas chromatography thermal conductivity detector (GC-TCD) at a CH4:CO2 flow rate of 30 mL-1 during a 10-h reaction by following (Shamsuddin et al., Int. J. Energy Res. 45:15,463-15,480, 2021d). For optimization parameters, the effects of NiO concentration (5, 10, and 15%), reaction temperature (700, 750, 800, 850, and 900 °C), catalyst loading (0.1, 0.2, 0.3, 0.4, and 0.5 g), and gas hourly space velocity (GHSV) range from 3000, 6000, 9000, 12,000, and 15,000 h-1 were evaluated. The results showed that physical characteristics such as BET surface area and porosity do not significantly impact NiO percentages of dispersion, whereas chemical characteristics like reducibility are crucial for the catalysts' efficient catalytic activity. Due to the active sites on the catalyst surface being more accessible, increased NiO dispersion resulted in higher reactant conversion. The catalytic performance on various parameters that showed 15%NiO/AS exhibited high reactant conversion up to 98% and 40-60% product selectivity in 700 °C, 0.2 g catalyst loading, and 12,000 h-1 GHSV. According to spent catalyst analyses, the catalyst was stable even after the DRM reaction. Meanwhile, increased reducibility resulted in more and better active site formation on the catalyst. Synergetic effect of efficient NiO as active metal and medium basic sites from AS enhanced DRM catalytic activity and stability with low coke formation.

Catalytic upgrading of bio-oil from halophyte seeds into transportation fuels

Because of socioeconomic considerations, wide-scale production of biofuel necessitates the utilization of nonedible biomass feedstock that does not compete for land and fresh water resources. In this regard, Salicornia bigelovii (SB) is the most investigated halophyte species. The high oil content in SB seeds has sparked mounting research that aims to utilize SB as an industrial crop in the production of bio-oil, particularly in coastal areas where these plants thrive. However, the oil extracted from the pyrolysis of raw SB seeds is largely dominated by oxygenated fatty acids, most notably 9,12-octadecadienoic acid and 9,17-octadecadienal, typical to that of other crops. The pyrolysate bio-oil of the raw SB seeds exhibited a relative yield of oxygenated compounds that decreased from 57.05 % at 200 °C to 9.81 % at 500 °C, and the relative yield of nitrogenated compounds increased from 4.86 % at 200 °C to 21.97 % at 500 °C. To improve the quality of the produced bio-oil, herein we investigated the catalytic hydrodeoxygenation (HDO) of the fragments that were produced from the thermal degradation of SB seeds. A 5 %Ni–CeO2 catalyst was prepared and characterized by a wide array of methods X-ray diffraction, X-ray photoelectron spectroscopy, temperature programmed reduction, scanning electron microscope, Brunauer-Emmett-Teller analysis, and thermogravimetric analyzer. The catalytic run was executed between 200 and 500 °C in a flow reactor. The deployed catalytic methodology displayed a profound HDO capacity. At 400 °C, for instance, the gas chromatography mass spectroscopy (GC–MS) detected loads of paraffin and aromatic compounds exists at appreciable values of 48.0 % and 28.5 %, respectively. With a total relative yield of 43.2 % (at 400 °C), C8–C15 species (i.e., jet fuel fractions) were the most abundant species in the upgraded SB bio-oil. The release of H2, CO, CO2, and CH4 was analyzed qualitatively and quantitatively using gas chromatography thermal conductivity detector and Fourier infrared spectroscopic analysis. When the Ni–CeO2 catalyst was utilized, a complete deoxygenated bio-oil was obtained from SB seeds using the surface-assisted HDO reaction. On the basis of the elemental analysis, the biochar's hydrogen and oxygen contents were found to decrease significantly. Density functional theory computations showed mechanisms for reactions that underpinned the experimentally observed hydrodeoxygenation process. Outcomes presented herein shall be instrumental toward the effective utilization of halophyte in the production of commercial transportation fuels.

Does grain size influence hydrocarbons generation and mesoporosity during artificial thermal maturation of an organic-rich mudstone?

To assess how the grain size/rock fabric of laboratory-matured shale samples impact oil, gas production, and the formation of pores during laboratory thermal maturation, cores (4.5 mm*1 cm) of bulk rock, millimetric equidimensional rock fragments (3*3 mm), and fine grind powder (<200 μm) were obtained from an organic-rich mudstone (Kimmeridge Clay Fm. “KCF”, Yorkshire, UK) and artificially matured under anhydrous conditions. The composition of the organic matter (OM), porosity, and thermal maturity were characterized using nitrogen adsorption, Rock-Eval® VI pyrolysis, GC/TCD (Gas-Chromatography/Thermal Conductivity Detector), and GC/MS (Gas Chromatography/Mass Spectrometry). While only a few differences in geochemical composition and porosity exist between rock fragments and powders, a greater gap is observed with the cores. Probably due to lower surface contact between the organic components themselves and clay mineral surfaces (which can act as a catalyst of oil and gas generation) less intense OM thermal degradation processes were observed for the cores. The use of cores rather than powder and fragments results in: (i) the production of lower extractible OM concentrations; (ii) lower amounts of gas (C1–C5 and CO2); (iii) lower pore volumes and smaller pore sizes during maturation. This preliminary work highlights the importance of considering the fabric of the rock being artificially matured and shows that the use of cores with an intact rock fabric (e.g. cores), closer to natural conditions, could be more suitable when studying OM thermal degradation and porosity. In comparison with previous works, this also demonstrated that depending on the maturation system used (e.g. semi-confined, confined) the differences in the amount of hydrocarbons generated and porosity observed between powder and cores during maturation could differ significantly and find their origin in different processes.

Effect of Fe/Cu catalysts supported on zeolite/active carbon hybrid on bio-oil quality derived from catalytic pyrolysis of granular bacteria biomass

Catalytic conversion of granular bacteria biomass to biofuel through pyrolysis was thoroughly studied. The hybrid of beta zeolite and active carbon (ZAC) resulted a support of catalyst with the BET surface area of 302 cm2/g. The highly active bimetallic Fe/Cu catalysts were prepared using wetness incipient impregnation on ZAC hybrid support (Fe5CuXZAC, X = 0.5, 1 and 2). To compare the activity of catalysts, catalytic pyrolysis tests of granular bacteria was performed. The pyrolysis tests in presence of Fe5Cu2ZAC remarkably decreased nitrogen compounds and total oxygenates of the bio-oil from 41.6 and 24.7 to 30.0 and 15.6 area%, respectively. Also, good selectivity of bimetallic Fe/Cu catalysts supported on ZAC toward aromatization reactions with the maximum yield for Fe5Cu2ZAC has made it a novel catalyst for pyrolytic conversion of granular bacteria biomass to aromatic hydrocarbons.The synthesized samples were characterized by Fourier transform infrared (FTIR) spectrometer, field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP), BET (Brunauer–Emmett–Teller) and temperature-programmed desorption (TPD) techniques. The products were analyzed by a gas chromatography-thermal conductivity detector (GC-TCD), a gas chromatography-mass spectrometry (GC–MS) and CHNS. Temperature-programmed oxidation (TPO) analysis was performed to study probable deposited carbon on the used catalysts.

The evolution of species concentrations in turbulent premixed flames crossing the soot inception limit

The current study quantifies the impact of equivalence ratio and rate of strain on the spatial distribution of major species and soot precursors in premixed turbulent ethylene flames crossing the soot inception limit. A back-to-burnt (BTB) opposed jet configuration is used to provide accurate control of the turbulent and chemical timescales. The upper nozzle features fractal grid generated turbulence and premixed ethylene/air mixtures with flames stabilised against well-defined hot combustion products emerging from the lower nozzle. The study combines simultaneous PAH/CH2OPLIF and elastic light scattering (ELS) with probe sampling. Gas chromatography-mass spectrometry (GCMS) and gas chromatography-thermal conductivity detector (GC–TCD) were used to quantify concentrations of major species and poly-aromatic hydrocarbons (PAHs). The laser based diagnostics show that the rate of strain exerts a dominant impact on the growth of soot particles with low turbulent Reynolds numbers (50≤Ret≤94) used to promote soot formation. The probe measurements indicate that acetylene, 1-methylnaphthalene (1–MN), m/z = 154, m/z = 276 and benzo(a)pyrene correlate with soot formation and that the equivalence ratio is the controlling PAH growth parameter. It is further shown that the spatial extent of the PAH containing reaction zone exceeds three integral length scales.

Effect of acid treatment and Na2CO3 as a catalyst on the quality and quantity of bio-products derived from the pyrolysis of granular bacteria biomass

The intense growth rate of granular bacteria biomass (GB) in anaerobic wastewater treatment units has made environmental problems with its disposal. In this research the potential of pyrolysis method to convert granular bacteria biomass to biofuels was completely investigated. The non-catalytic experiments were performed in a temperature range of 400 to 700 °C and the maximum liquid product yield on dry ash-free basis (55.0 %wt.) was obtained at optimum temperature of 550 °C. Pyrolysis of pretreated granular bacteria with 5 wt% HCl (PGB) and then impregnation with Na2CO3 (IPGB) was studied to improve the bio-oil quality as well as higher amount of synthesis gas. Feedstock pretreatment with acid decreased the gas yield in 550 °C while Na2CO3 pretreatment had reverse effect, with H2 yield (mmol/g feed) of 2.9, 2.4 and 1.8 for IPGB, GB and PGB respectively. It means Na2CO3 exhibited excellent catalytic activity toward producing hydrogen-rich hydrocarbons. Acid treatment increased bio-oil weight percent with little effect on the quality, while the IPGB pyrolysis resulted 8.3% and 8.6% decrease in the oxygenates and nitrogenates respectively and 19.5% increase in the hydrocarbons which improved the higher heating value (HHV) from 32.6 MJ/kg to 33.7 MJ/kg in comparison with GB. The raw and treated biomass was characterized by using thermogravimetric analysis (TGA-DTG), X-ray fluorescence (XRF), elemental analyses (CHNS), field emission scanning electron microscope (FESEM) and scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS). The bio-products were analyzed by a gas chromatography-thermal conductivity detector (GC-TCD), a gas chromatography-mass spectrometry (GC–MS) and CHNS.

Electroless Production of Fertilizer (Struvite) and Hydrogen from Synthetic Agricultural Wastewaters.

The drive toward sustainable phosphorus (P) recovery from agricultural and municipal wastewater streams has intensified. However, combining P recovery with energy conservation is perhaps one of the greatest challenges of this century. In this study, we report for the first time the simultaneous electroless production of struvite and dihydrogen from aqueous ammonium dihydrogen phosphate (NH4H2PO4) solutions in contact with either a pure magnesium (Mg) or a Mg alloy as the anode and 316 stainless steel (SS) as the cathode placed in a bench-scale electrochemical reactor. During the electroless process (i.e., in the absence of external electrical power), the open circuit potential (OCP), the formation of struvite on the anode, and the generation of dihydrogen at the cathode were monitored. We found that struvite is formed, and that struvite crystal structure/morphology and precipitate film thickness are affected by the concentration of the HnPO4n-3/NH4+ in solution and the composition of the anode. The pure Mg anode produced a porous 0.6-4.1 μm thick film, while the AZ31 Mg alloy produced a more compact 1.7-9.9 μm thick struvite film. Kinetic analyses revealed that Mg dissolution to Mg2+ followed mostly a zero-order kinetic rate law for both Mg anode materials, and the rate constants (k) depended upon the struvite layer morphology. Fourier-transform infrared spectrometry, X-ray diffraction, and scanning electron microscopy indicated that the synthesized struvite was of high quality. The dihydrogen and Mg2+ in solution were detected by a gas chromatography-thermal conductivity detector and ion chromatography, respectively. Furthermore, we fully demonstrate that the reactor was able to remove ∼73% of the HnPO4n-3 present in a natural poultry wastewater as mainly struvite. This study highlights the feasibility of simultaneously producing struvite and dihydrogen from wastewater effluents with no energy input in a green and sustainable approach.

Commercial TiO 2 loaded with NiO for improving photocatalytic hydrоgen prоduction in the presence оf simulated solar radiation

Five NiO/TiO2 materials with a different mass ratiо оf NiO tо TiO2 (3.3, 6.7, 16.3, 23.7, and 36.8%) were synthesized by wet impregnation process and characterized by DR UV-vis, scanning electrоn micrоscоpe, transmissiоn electrоn micrоscоpy, X-ray diffractiоn methоd, N2 physisorption, and temperature-programmed reduction. The characterizatiоn confirmed the existence of nano-sized cubic NiO on the commercial TiО2. The оbserved interactiоn between TiO2 and NiО phases confirmed that the оbtained material dоes nоt constitute a physical mixture оf twо species. The photocatalytic hydrоgen generatiоn efficiency [mоnitored by gas chromatography–thermal conductivity detector (GC-TCD)] of these materials from methanol-water mixtures under simulated solar radiation and artificial UV radiation was investigated. For some synthesized NiO/TiO2 materials, higher photocatalytic efficiency was found compared with the commercial TiO2 Degussa P25 catalyst. Also, the obtained results showed that 0.125 g L−1 of 6.7%NiO/TiO2 and 5% (v/v) of methanol were the optimal operating parameters. Furthermоre, fоr the mоst efficient phоtоcatalytic system under the influence оf simulated solar radiation, a 1.8 times higher hydrоgen prоduction rate was achieved cоmpared tо that under the influence оf artificial UV radiatiоn.

Electrochemical Reduction of Carbon Dioxide on Lanthanum Based Transition Metal Oxide Electrocatalysts

Among the various methods available for reduction of CO2, the electrochemical reduction method stands out due to it being capable of producing industrially important fuels, organic chemicals and pure oxygen. Such process takes place in an electrochemical cell, where carbon dioxide is reduced to at room temperature and atmospheric pressure, using only water, carbon dioxide and electricity at specific electrochemical potentials. Here, electrocatalysts have an important role to play, for enhancing the kinetics of the process and also for rendering the formation of desired products feasible at some selected potentials. In the present research, we are exploring the usage of La-based transition metal (TM) oxides, crystallizing in perovskite structure, as electrocatalysts. The synthesis of these metal oxides is cost effective and tuning the performance via doping is facile. Furthermore, these perovskites are stable in stoichiometric, as well as non-stoichiometric, forms and due to the basicity of La exhibits affinity for CO2. Accordingly, here we have investigated the efficiency and effectiveness of different La-based TM oxides, as electrocatalysts, towards the formation of industrially relevant products upon reduction of CO2. It may be mentioned here that, in order to enhance the efficiency of the electrocatalysts, as well as the mass transport of CO2 to the surface of the electrocatalysts, we have designed a new electrolysis cell where gas diffusion electrode (GDE) containing the electrocatalysts is used as working electrode. All the La-based TM oxides (i.e., LaCoO3, LaCrO3, LaFeO3, LaMnO3, LaNiO3) were synthesized via citrate solution-combustion route and calcined in air atmosphere at 850 oC for 6 h, with the heating rate being 10 oC/minute. Phase evolution of the TM oxides before and after usage, as electrocatalysts, were checked using X-ray diffraction (XRD; EMPYREAN PANalytical diffractometer) having Cu Kα radiation and scanning at a rate of 1 o/min between 10 to 90o. Inorganic Crystal Structure Database was used for the phase analysis of the powder catalysts. The composition of the perovskite catalysts (in terms of the ratios of the metals) were quantitatively analyzed by energy dispersive spectroscopy (EDS; QUANTA 200). Morphologies of the oxide particles were observed using scanning electron microscopy (SEM) JEOL JSM-7600F. The specific surface area of the perovskite catalysts were measured via BET using Micromeritics 3 FLEX Surface Characterization. The electrochemical CO2 reduction reaction was performed in an electrolysis cell via chronoamperometry using Biologic potentiostat (Model VSP 300). The reduction reactions were carried out on gas diffusion electrode (GDE) using basic aqueous electrolyte. The applied potentials were -1.1 V, -1.3 V, -1.5 V, -1.7 V, -1.9 V and -2.1 V vs. Hg/HgO, as reference electrode. The chronoamperometry experiments were performed for 3 h at each potential. The current densities obtained during the electrochemical CO2 reduction experiments were obtained for all the La-based TM oxide electrocatalysts used, viz., LaCoO3, LaCrO3, LaFeO3, LaMnO3, LaNiO3. The liquid products present in the electrolyte after the experiments were analyzed by high performance liquid chromatography (HPLC) using Agilent 1260 infinity series model with Aminex HPX-87H column. The gaseous products were analyzed by gas chromatography - thermal conductivity detector (GC-TCD) using Nucon 5700 gas chromatography. XRD scans recorded with the as-synthesized and calcined La-based TM oxides indicate that the oxides were phase pure (as shown in Fig. 1). The crystal structure was established as perovskite. The composition of the as-synthesized and calcined perovskite electrocatalysts, as determined using EDS, were in good agreement with the target compositions. The current densities were fairly stable during the 3 h long experiments for all the potentials studied; with an example being shown in Fig. 2. All the electrocatalysts produced formate (HCOO-), acetate (CH3COO-) and hydrogen as the products of electrochemical CO2 reduction. Furthermore, ethanol (C2H5OH) and 1-propanol (C3H7OH) were also formed on LaCoO3, with LaMnO3 being able to produce 1-propanol (C3H7OH) as one of the products. Hence, as per the present set of results in the context of the formation of desired products, LaCoO3 and LaMnO3 seem to be more promising among the La-TM-oxide electrocatalysts studied here. Keywords: CO2 reduction, transition metal oxide, electrocatalyst, chronoamperometry, reaction product. Figure 1

Photo-electrochemical hydrogen evolution over FTO/Ni0.98Si0.02O2-Ni electrode induced by visible and UV light irradiation

Photo-electrochemical properties of fluorine-doped tin oxide (FTO)/nickel oxide-nickel (Ni0.98Si0.02O2-Ni) with isolated Si sites are discussed. The Ni0.98Si0.02O2-Ni photo-electrocatalyst without any noble metal was prepared using a one-step chemical reduction precipitation method. Photo-electrochemical properties were investigated by cyclic voltammetry and chronoamperometry techniques in aqueous alkaline solution at pH 8.0. The photo-electrochemical response of the catalyst showed sensitivity to visible and UV light. The catalyst produced hydrogen from water at a rate of 0.5 mmol g−1 h−1 with the reduction of CO2 into CO under visible light in the absence of any light sensitizer or a noble metal. The metallic Ni amount in the catalyst system was optimized to obtain the best photo-electrocatalyst. The first principle DFT study showed that the incorporation of Si sites allowed absorbance of visible light. The catalyst was characterized by powder x-ray diffraction (PXRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma- atomic emission spectroscopy (ICP-AES), Brunauer–Emmett–Teller (BET), cyclic voltammetry, and chronoamperometry. The products were analyzed by gas chromatography- thermal conductivity detector (GC-TCD).

The combined process of pyrolysis and catalytic conversion from rice straw toward light olefin hydrocarbon with supported metal catalyst

Light olefins are one of the most common petrochemical raw materials produced using non-renewable natural resources. Nowadays, lignocellulosic biomass is a promising source of feedstock ingredients for the production of olefins by pyrolysis. This study, the process is developed by a combination of pyrolysis and catalytic cracking processes with operating temperature around 500°C and N2 flow rate around 150 ml/min. The supported metal catalyst namely La/Al2O3 and Zn/Al2O3 made with the impregnation method are used as catalysts. The catalytic pyrolysis process was carried out in a fixed bed turbular reactor with electric furnace as the heat source. To comprehend the catalytic cracking with catalyst, the experiment was also performed in condition without catalyst so that it could be compared to pyrolysis process itself. The The output of pyrolysis is condensed by using cold absorption trap with aceton. FT-IR (Fourier Transform - Infrared) and GC-TCD (Gas Chromatography-Thermal Conductivity Detector) serve as analytical instrument in order to identify the presence and the quantity of light olefins group in bio-oil and bio-gas. In this method, there are several variations to be determine, there are type of catalyst and catalyst composition (1%, 5%, and 10%).

Production of bio-oil via hydrothermal liquefaction of birch sawdust

The effect of weight ratio of plywood manufacturing by-product birch sawdust (BS) to water (1/2–1/8), reaction temperature (200–340°C), initial H2 pressure (0–10MPa), residence time (5–90min), catalysts amount (0.25–7.0wt.%) and type (FeSO4, ZnSO4, NiSO4, Raney-nickel, Ni65%/SiO2Al2O3, Na2CO3 and NaOH) on hydrothermal liquefaction of BS was investigated. High yield of bio-oil (54.1%) with calorific value (CV) 24.9MJ/kg under developed optimal experimental conditions in the presence of NaOH (5wt.%) utilizing weight ratio of BS to water 1/4, residence time 5min, mixing speed 250rpm at 300°C without pressurized particular inert gas or H2 atmosphere was achieved. Compounds in bio-oil analyzed by gas chromatography-mass spectrometry (GC-MS) have suitable chemical structures for conversion into renewable hydrocarbons. Marketable solid residue (SR) with yield 7.1%, high CV (29.8MJ/kg) and perspective characteristics for industrial application was obtained. Produced gas in process analyzed by gas chromatography-thermal conductivity detector (GC–TCD) contains 60.1vol.% of CO2.

VALIDATION OF ANALYTICAL METHOD FOR DETERMINATION OF HIGH LEVEL CARBON DIOXIDE (CO2) IN NITROGEN GAS (N2) MATRIX USING GAS CHROMATOGRAPHY THERMAL CONDUCTIVITY DETECTOR

High accurate result of carbon dioxide (CO2) measurement is of great importance since the result (data) is used as the foundation for decision making related to regulated monitoring program and law enforcement. In this study, therefore, method for measurement of high level of carbon dioxide (CO2) in nitrogen (N2) matrix using gas chromatography thermal conductivity detector (GC-TCD) was validated to achieve the optimum performance of the method. For this purposes, identity confirmation, selectivity, limit of detection (LoD), limit of quantitation (LoQ), repeatability, reproducibility, accuracy, and linearity of the method were evaluated. The result shows that the GC-TCD method has good precision in term of repeatability and reproducibility having values of 0.07 and 0.37%, respectively. No bias of the method can be found and an excellent linearity of the method was obtained in the range of 2 - 13.97% mol/mol. Thus, based on the result evaluation under given criteria of this study, it can be concluded that the GC-TCD method is reliable and suitable for determination of high level of CO2 in N2 matrix.

Comparison between GC-TCD and GC-FID for the determination of propane in gas mixture

A method comparison between gas chromatography-thermal conductivity detector (GC-TCD) and chromatography-flame ionization detector (GC-FID) for the analysis of propane (C3H8) are reported in this study. To achieve the study purpose for producing valid and reliable result, the method comparison process was conducted by investigating several keys of analytical parameter of both GC-TCD and GC-FID method including method sensitivity, precision, accuracy, and method linearity. Investigation of the GC's parameter were conducted by analyzing the C3H8 (% mol/mol) in nitrogen (N2) balance (known as C3H8 certified reference material). The results show that the GC-FID method was found to display more sensitive, precise, and accurate than GC-TCD method for the analysis of C3H8. The sensitivity of the GC-FID are 66 times higher than GC-TCD method. In addition, the GC-FID exhibits a wider linear range (0.161 -2.18%mol/mol) than the GC-TCD method (0.242 – 2.18%mol/mol).

Modeling and optimizing of steam pyrolysis of dimethyl formamide by using response surface methodology coupled with Box-Behnken design

A non-catalytic steam pyrolysis of N,N-dimethyl formamide (DMF) was studied in a SS 316 plug flow reactor at atmospheric pressure as a waste solvent minimization method. The reaction products were analyzed by using gas chromatography-thermal conductivity detector and high performance liquid chromatography-refractive index detector. The optimization of process variables namely, temperature, flow rate and water to DMF ratio (v/v) for the maximum conversion of DMF have been studied by response surface methodology (RSM) coupled with a Box-Behnken design. The analysis of variance (ANOVA) data shows the conversion of DMF significantly enhances with temperature. Higher flow rate has adverse effect on DMF conversion, whereas water to DMF ratio (v/v) shows negligible effect on conversion of DMF. With the help of a developed RSM model, the highest conversion of DMF (89.82wt%) was predicted at 1100°C, 0.48ml/min and water:DMF ratio of 1.35 (v/v). Based on the experimental design, eight empirical models were developed those depict the interacting effect of different sets of operating variables on conversion of DMF and yield of seven products. Effect of process variables on yield of CO2 and N2 were studied, individually. Oxidative pyrolysis of DMF was also investigated, which shows significant reduction in the coke formation with increasing H2O2 to DMF mol ratio.

Observation of atmospheric oxygen/nitrogen ratio aboard a cargo ship using gas chromatography/thermal conductivity detector

Measurements of atmospheric O2/N2 ratio and CO2 concentration have been used to analyze the −ΔO2/ΔCO2 ratio to obtain information on CO2 sources, e.g., anthropogenic or terrestrial biogenic sources (respiration or wildfire). In this study we report on the development of a shipboard system for measuring atmospheric O2/N2 ratio by using the gas chromatography/thermal conductivity detector (GC/TCD) technique. The standard error for a one hour average (N = 6) is found to be ± 5 per meg (±1 ppm). The shipboard measurements have been conducted since the end of September 2007 on the Voluntary Observing Ship TRANS FUTURE 5, a cargo ship sailing between Japan, Australia, and New Zealand every six weeks. Spatially, the observation covers latitudes between 41°S and 33°N over the western Pacific. Air masses with high CO2 concentration are observed along the coastline of Australia and New Zealand. In more than two thirds of the cases (17 of 23 events) detected between September 2007 and July 2009, values of the −ΔO2/ΔCO2 ratio are less than 1.15, indicating dominance of biogenic sources (e.g., respiration or wildfire) of CO2.

Characterization of bio-oil from induction-heating pyrolysis of food-processing sewage sludges using chromatographic analysis

In this study, gas chromatography–mass spectrometry (GC–MS) was used to analyze the pyrolytic bio-oils and gas fractions derived from the pyrolysis of industrial sewage sludges using induction-heating technique. The liquid products were obtained from the cryogenic condensation of the devolatilization fraction in a nitrogen atmosphere using a heating rate of 300 °C/min ranging from 25 to 500 °C. The analytical results showed that the pyrolysis bio-oils were very complex mixtures of organic compounds and contained a lot of nitrogenated and/or oxygenated compounds such as aliphatic hydrocarbons, phenols, pyridines, pyrroles, amines, ketones, and so on. These organic hydrocarbons containing nitrogen and/or oxygen should originate from the protein and nucleic acid textures of the microbial organisms present in the sewage sludge. The non-condensable devolatilization fractions were also composed of nitrogenated and oxygenated compounds, but contained small fractions of phenols, 1H-indoles, and fatty carboxylic acids. On the other hand, the compositions in the non-condensable gas products were principally carbon dioxide, carbon monoxide and methane analyzed by gas chromatography–thermal conductivity detector (GC–TCD).

Co-pyrolysis of Polypropylene and Biomass

Polypropylene (PP) with biomass such as saw dust, rice husk, and corn cob were copyrolyzed in a fixed bed reactor at the temperatures of 450°C, 500°C, 550°C, and 600°C under nitrogen atmosphere. The effect of activated carbon as catalyst on pyrolysis liquid was also studied. The thermogravimetric behavior for two kinds of material was observed by thermogravimetric analysis. The gaseous products were analyzed by Gas Chromatography-Thermal Conductivity Detector (GC-TCD), Gas Chromatography-Flame Ionization Detector (GC-FID) for the blend of 50% PP, and 50% biomass. The copyrolysis liquids were investigated by Infrared Absorption Spectroscopy (IR), GC-MS, and liquid chromatography. The result showed that a suitable pyrolysis temperature was between 500°C and 550°C, and a fast heating rate for the reactor should be required. Fast carrier gas was beneficial to the formation of the aliphatic compounds. When the pyrolysis temperature reached 600°C, C3H6 and H2 were the main valuable gases, which were 20% and 10% (v/v), respectively. The occurrence of the activated carbon may improve the capability for the removal of the oxygen of pyrolysis liquid.

Detection of regional scale sea-to-air oxygen emission related to spring bloom near Japan by using in-situ measurements of the atmospheric oxygen/nitrogen ratio

Abstract. We have been carrying out in-situ monitoring of atmospheric O2/N2 ratio at Cape Ochi-ishi (COI; 43°10' N, 145°30' E) in the northern part of Japan since March 2005 by using a modified gas chromatography/thermal conductivity detector (GC/TCD). The standard deviation of the O2/N2 ratio is estimated to be about ±14 per meg (≈3 ppm) with intervals of 10 minutes. Thus, the in-situ measurement system has a 1σ precision of ± 6 per meg (≈1.2 ppm) for one-hour mean O2/N2 ratio. Atmospheric potential oxygen (APO≈O2+1.1 CO2), which is conserved with respect to terrestrial photosynthesis and respiration but reflects changes in air-sea O2 and CO2 fluxes, shows large variabilities from April to early July 2005. Distribution of satellite-derived marine primary production indicates occurrences of strong bloom in the Japan Sea and the latitudinal band between 30° and 40° N in the western North Pacific in April and in the Okhotsk Sea and northeastern region near Hokkaido Island in the North Pacific in June. Back trajectory analysis of air masses indicates that high values of APO, which last for several hours or several days, can be attributed to the oxygen emission associated with the spring bloom of active primary production.