Thermal Conductivity Detector Research Articles

PH-Optimized Biomethane Production: Evaluating Carrier Materials for Ex-situ Biomethanation

Choosing the appropriate carrier material for ex-situ biomethanation is a critical factor to consider when developing biogas upgrading technologies. The chosen material for biomethanation in a biotrickling filter reactor functions as a substrate that immobilises microorganisms, which act as catalysts in the reaction for producing biomethane. This study conducted experiments on waste-derived materials, including glass foam and vulcanised wood ash material, in addition to polyurethane foam and expanded clay pellets. Pretreratment of wood ash was done to lower the pH of material. The manometric test measured the rate of CH4 generation by quantifying pressure fluctuations. The validity of these results was confirmed by analysing product gas samples using a Shimadzu Nexis GC-2030 gas chromatograph, which was equipped with two parallel lines, a flame ionisation detector (FID) and a thermal conductivity detector (TCD). In order to enhance the biomethane concentration in the end product, two strains of Methanobacterium alcaliphilum were evaluated alongside biogas sludge as the inoculum. These strains of microorganisms are methanogens that utilise hydrogen and can thrive in a high pH environment. Thus, they have the potential to demonstrate improved biomethane production outcomes when a vulcanised wood ash filter is used as the carrier material.

Post‐combustion carbon dioxide adsorption of concurrent activated and surface modified palm kernel shell‐derived activated carbon

AbstractThis research applied a concurrent activation and surface modification (CAM) process to synthesize palm kernel shell‐derived activated carbon (PKSdAC) to obtain CO2 affinity surface functionalization. The CAM process is a simplified activated carbon activation process that is cost‐effective. The CAM process used in this study integrates sulphuric acid activation and barium chloride functionalization. The formation of barium sulphate is targeted to incorporate barium through a reduction process with carbon‐containing material at elevated temperatures into PKSdAC to obtain basic metal surfaces functional group for chemical adsorption. The optimal temperature for CAM‐PKSdAC CO2 adsorption performance was at 40–60 °C, established through temperature‐programmed desorption of CO2 (TPD‐CO2) analysis. The CAM‐PKSdAC adsorption performance was tested using a lab‐scale adsorption system. The bed CO2 content was determined using gas chromatography coupled with a thermal conductivity detector (GC‐TCD) by manual syringe injection. CAM‐PKSdAC exhibited a high CO2 adsorption capacity of 0.89 mmol g−1 from TPD‐CO2, and 1.91 mmol g−1 from GC‐TCD at 40 °C and 1 bar. It showed comparable CO2 adsorption capacity to conventional surface modified‐activated PKSdAC (1.96 mmol g−1) while higher than commercial and modified ACs (1.14–1.60 mmol g−1), but lower than potassium hydroxide modified ACs (1.81–2.10 mmol g−1) at 40 °C and 1 bar. Barium promoted chemisorption of CO2 as supplementary reaction, which increases adsorption capacity. The non‐linear Dubinin Radushkevich model strongly correlates with the experimental adsorption data for CAM‐PKSdAC adsorption, indicating the physisorption process via micropore filling on CAM‐PKSdAC. CAM‐PKSdAC showed moderate reusability with negligible variation in adsorption capacity after 10 adsorption–desorption cycles. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

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.

Experimental investigation on hydrogen transfer in coupled metal hydride reactors for multistage hydrogen purification application

Three stage metal hydride hydrogen separation system was tested, wherein each stage was configured with 1.2 kg of LaNi4.7Al0.3, LaNi5 and La0.9Ce0.1Ni5, placed in descending order of their equilibrium bed pressure respectively as R1 (La0.9Ce0.1Ni5) > R2 (LaNi5) > R3 (LaNi4.7Al0.3). Hydrogen absorption capacity obtained for R1, R2 and R3 were 15.91 g, 15.93 g and 16.02 g respectively for 3rd activation cycle, performed at 30 bar and 25 °C. For coupled reactor operation, optimum hydrogen transfer was for desorbing reactor at 90 °C and absorbing reactor at 20 °C, which was 12.31 g for R1 to R2 in 350 s, 13.33 g for R2 to R3 in 300 s and 13.38 g for R1 to R2 in 280 s, constituting to 1.03, 1.11 and 1.12 wt% of hydrogen storage respectively. Further, the system was tested for hydrogen purification, wherein inlet sample with 80% impurity (18% Ar, 20% CO2, 20% N2, 20% CH4 and 2% CO) and 20% H2 was used for purification study. According to Thermal Conductivity Detector (TCD) results, the system delivered 91.54%, 99.996% and 99.9999% pure hydrogen respectively for stage 1, stage 2 and stage 3 purification. The system works within low temperature range of 20–90 °C.

A high-precision experimental measurement system and method for the parahydrogen concentration and the Ortho-Para hydrogen catalyst's catalytic performance

An experimental system that combines the measurement of parahydrogen concentration with the assessment of ortho-para hydrogen catalyst's catalytic performance was created for this investigation. The concentration of parahydrogen was detected by a thermal conductivity detector integrated into the gas chromatograph. The catalyst sample and the generator of standard gas were integrated into one experimental setup for easier operation. Meanwhile, a new method for catalytic performance evaluation of ortho-para hydrogen catalyst was developed based on this system. This method can decrease test time and yield more valuable test results than the conventional way. Throughout the experiments, the system's dependability was increased by optimizing the utilization of the carrier gas. The deviation analysis and repeatability verification of the relevant test data showed that the relative standard deviation was less than 0.35% and the mean value of the variation coefficient was less than 0.20%, which demonstrated the method had high accuracy, stability, and reliability. Further studies have shown that the catalysts should be densely packed inside the converter and kept out of the air to maximize their catalytic activity. These pertinent findings regarding the application of ortho-parahydrogen catalysts in this study can guide the design of the ortho-parahydrogen converter in actual hydrogen liquefiers. Moreover, the method and the procedure proposed in this study may contribute to the optimization of the ortho-parahydrogen catalyst production process as well as the calibration of the parahydrogen concentration in liquid hydrogen products.

Suppression of Carbon Dioxide Emissions from Soil Amended with Autoclaved Lightweight Aerated Concrete Under Different Compaction and Moisture Conditions

Carbon dioxide (CO2) emissions has been highlighted worldwide as a contributor to the greenhouse effect. Soil physical characteristics such as bulk density and moisture content can influence the emissions of greenhouse gasses (GHGs) from soil. Soil conditioners applied to soil can also affect the terrestrial CO2 emissions. Autoclaved lightweight aerated concrete (ALC) is in use at present as a soil conditioner or calcium silicate fertilizer, it is a type of porous material made from industrial waste. In this study, we determined the effect of ALC (Inenica, Clion Co., Ltd, Japan) on CO2 emissions from paddy soil with considering soil compaction and moisture content. Laboratory experiments were conducted using soils with and without ALC (0 and 5%), under two levels of compaction (compacted and non-compacted), and two soil moisture contents (60% and 100% water holding capacity: WHC) in 200 mL glass vials. All treatments with triplicates were incubated at 25° C for 21 days under aerobic conditions. Emissions of CO2 were determined at 0, 1, 3, 7, 14, and 21 days using gas chromatography with the thermal conductivity detector. The addition of ALC significantly decreased CO2 emissions from soil at the early stages of incubation. Emissions of CO2 were significantly lower at 100% WHC than at 60% WHC. Non-compacted treatments showed significantly higher emissions of CO2 than compacted treatments during the incubation time period. This is possibly due to improved soil aeration and porosity, which enhanced the activity of soil microorganisms responsible for the decomposition of organic matter. The interactions between moisture content with ALC addition and compaction on cumulative CO2 emissions were statistically significant (p<0.05). The effect of ALC addition on CO2 suppression was more effective at compacted and 100% WHC (51% reduction compared with control). Our study suggested that precise dosage of ALC application (5%) can effectively reduce CO2 emissions from soil, under 100% WHC and compaction conditions than 60% WHC and non-compaction conditions.
 
 Keywords: Aerobic, Autoclaved lightweight aerated concrete, Carbon dioxide, Compaction, Moisture content

Characteristic Evaluation of Gas Chromatography with Different Detectors for Accurate Determination of Sulfur Hexafluoride.

Sulfur hexafluoride (SF6), which survives in the atmosphere for an extremely long period of time, is the most potent greenhouse gas regulated under the Kyoto Protocol. So, the accurate monitoring of atmospheric SF6 plays an important role in the study of the control policies for reducing greenhouse gas emissions. The instruments for SF6 measurement are typically calibrated using certified reference materials. The concentrations of the commercially available SF6 reference materials usually have a broad range, from 1 μmol/mol to 6000 μmol/mol. Some characteristics including sensitivity, linear range, relative standard deviation, and accuracy are crucial for the determination of SF6 in such a broad concentration range. Therefore, the selection of a proper detector for the accurate determination of SF6 with such a broad range is extremely important to establish a gas chromatography (GC) method for developing SF6 reference materials. In this paper, several typical GC methods with different detectors, including a thermal conductivity detector (TCD), a pulsed discharge helium ionization detector (PDHID), and a flame photometric detector (FPD), were carefully established for the accurate determination of SF6 with different concentrations. The results show that an FPD detector has a relatively narrow linearity range, thus a quadratic equation should be established for building a calibration curve. The PDHID and TCD have good linearity with coefficients of 1.0000 in the concentration range of 10-100 μmol/mol (using a PDHID), and 100-1000 μmol/mol (using a TCD), respectively. Further considering the measurement errors of indication results, the PDHID is suitable for SF6 measurement when the concentrations are below 100 μmol/mol, whereas the TCD is suitable for SF6 measurement when the concentrations are over 100 μmol/mol. These results provide useful guidance in choosing an appropriate GC detector for the accurate determination of SF6, which are especially very helpful for developing SF6 reference materials.

Evaluating hydrogen production from glucose using graphite felt beads as a solid matrix in immobilized mixed cell reactor at thermophilic fermentation

This study has successfully evaluated graphite felt (GF) beads as a solid matrix to immobilize or trap the mixed cultures in an immobilized mixed-cell reactor (IMcR). The anaerobic sludge of palm oil mill effluent was used as an inoculum source in the IMcR with mixed culture. Here, glucose, sucrose, and starch were used as the model substrates to evaluate the performance of IMcR with GF beads for producing bio-hydrogen (BioH2). BioH2, effluent, and surface morphology of GF beads were analyzed by using gas chromatography equipped with a thermal conductivity detector, high-performance liquid chromatography, and scanning electron microscopy, respectively. The highest H2 yield (YH2) and production rates were obtained at 304.0 ± 13.2 mL g?1COD (corresponding to 2.26 mol mol?1glucose) and 1403 ± 61 mL L?1 day?1, respectively. IMcR with GF beads is a new approach for generating high YH2, which can be used for more than two months in an experimental run.

Comprehensive analysis of refrigerant R134a: Implications for estimating and managing greenhouse gas emissions

This study introduces a comprehensive analytical method for assessing refrigerant purity, offering various insights into accurate and precise estimations of greenhouse gas (GHG) emissions and the reclamation of refrigerants. Samples of three different states of CH2FCF3 (R134a), namely recovered R134a, reclaimed R134a, and new R134a, were prepared and analyzed for all impurities. Non-condensable gases (O2, N2, CH4, CO, and H2) were analyzed using gas chromatography (GC) with a thermal conductivity detector (TCD) and a pulsed discharge detector (PDD), and unidentified complex compound impurities containing C, H, Cl, and F were investigated using GC with mass spectrometry (MS) and an atomic emission detector (AED). The purities of the three samples were determined by calculating the total quantity of impurities and their uncertainties. The calculated values for the purities of recovered R134a, reclaimed R134a, and new R134a were 953,125.38 µmol/mol (1,272.45 µmol/mol, k = 2), 998,529.67 µmol/mol (31.58 µmol/mol, k = 2), and 998,803.56 µmol/mol (32.50 µmol/mol, k = 2), respectively. The majority of impurities detected were GHGs with high global warming potentials (GWPs) up to 11,200. Certain impurities were found at concentrations exceeding 1,000 µmol/mol. The annual GHG emissions resulting only from R134a impurities in South Korea were approximately 0.01 MtCO2eq. Because of the large number of GHGs in refrigerants, a comprehensive examination of refrigerant impurities is necessary for refrigerant monitoring and GHG inventory management.

Green synthesis of Ag2S nanoparticle from sweet cherry on ultrasound-assisted prepared NiMoO4/g-C3N4 nanocomposite for photocatalytic H2 production

Photocatalytic hydrogen production from water is important in terms of producing various photocatalysts because it is an environmentally friendly, clean, and renewable energy source. In this work, we reported that NiMoO4/g-C3N4/Ag2S were obtained through the green synthesis method using sweet cherry. The structural, morphological, and optical features of synthesized photocatalysts were evaluated by XRD, FTIR, UV–visible DRS, SEM, TEM, and XPS. In addition, the electrochemical measurements were investigated. The hydrogen production yields of all photocatalysts were determined by gas chromatography with a thermal conductive detector for a total reaction time of 4 h. The resulting NiMoO4/g-C3N4/Ag2S has the highest hydrogen production rate with 2040.2 μmol g−1 h−1 compared to NiMoO4, g-C3N4, Ag2S and NiMoO4/g-C3N4. In this catalyst design system, in the entity of an electric field created by the S-scheme heterostructure of NiMoO4/g-C3N4/Ag2S, influential directional migration of photocarriers is acquired, and recombination of useful charge carriers is avoided. This work highlights the utilization of green synthesis of ternary nanocomposite from sweet cherry for photocatalytic hydrogen production.

Thermogravimetric and thermovolumetric study of municipal solid waste (MSW) and wood biomass for hydrogen-rich gas production: a case study of Tashkent region.

Application of municipal solid and wood waste, as dominant sources of biomass, could be a promising alternative for producing energy from renewables via thermochemical gasification technology. In this paper, a study of thermogravimetric analysis (TGA) and excurrent gas composition produced by the municipal solid waste (MSW) and wood biomass gasification is presented. Thermogravimetric and heat flow curves for waste samples were performed at the temperature interval of 20-890 °C with a heating rate of 10 °C min-1 under a nitrogen atmosphere. According to thermal analysis data, differential scanning calorimetry (DSC) curves, the degradation stages of waste samples was determined, which correspond to the mono- or bimodal evolution of volatile compounds and the degradation of the resulting carbon residue. The gasification experiments were conducted in a high-pressure quartz reactor at temperatures of 850, 900, and 950 °C, using steam (0.3 g/min) and argon (2 dm3/min) as the gasifying agents. To ascertain the syngas composition, gas chromatography was employed in conjunction with a thermal conductivity detector. Both types of biomass showed remarkably similar syngas compositions. The highest concentration of hydrogen-rich gases was recorded at 950 °C for wood biomass, with 42.9 vol% and 25.2 vol% for hydrogen (H2) and carbon monoxide (CO), and for MSW, with an average 44.2 vol% and 18 vol% for H2 and CO. Higher temperatures improved the syngas composition by promoting endothermic gasification reactions, increasing hydrogen yield while decreasing tar and solid yields. This research helped to comprehend the evolution of the gasification process and the relationship between increased H2 and CO production as the gasification temperature increased.

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.

Development of gas chromatography for dissolved gas in oil based on nitrogen plasma discharge detection principle

The gas chromatography detection technology of dissolved gas in oil based on the nitrogen plasma discharge detection principle was studied. This technology detected the characteristic emission light emitted by the excited molecule after the ionization of the detected molecule motivated by the plasma generated by the nitrogen molecule under the action of a high-energy electromagnetic field and realized the quantitative detection of different molecules. Compared with the previous national standard commonly used hydrogen flame ionization detector (FID) and thermal conductivity detector (TCD) gas chromatography, it has a lower detection limit. The advanced chromatographic system with the original process realizes the detection of dissolved gas in transformer oil, which has good linearity and repeatability and can ensure the accuracy of measurement data. The analysis only used nitrogen and did not use hydrogen to prevent explosion hazards. Nitrogen is at least ten times cheaper than helium and is more economical than helium ion chromatography in consumables. The device can detect the small content of the characteristic gas in the transformer oil and the slight change of the content to prevent the occurrence of dangerous accidents.

Etching-Free Wafer-Level Fabrication of Suspended Mesh-Type Nanoheaters

Recently, various strategies have been demonstrated to reduce the operating power of electrothermal devices by implementing a miniaturized Joule-heating-based heater. To operate the heaters with low power, the miniaturized heating element must be well-insulated by spacing it apart from the substrate. The conventional microfabrication methods for implementing small-size (e.g., sub-micrometer to micrometer scales) and suspended heater architecture have relied on the etching process [1], which requires accurate and delicate process control. Moreover, the etching process becomes more complicated to prevent damage to the delicate heater structures, hindering yield and reliability. Therefore, a trade-off has occurred between the reduction in power consumption (i.e., heater size reduction) and production cost (e.g., cost, time, and high-tech development).Prior to this research, we demonstrated the fabrication of suspended 1D nanoheaters by depositing a thin Au layer selectively on top of a suspended carbon nanowire and their applications as ultralow-power gas sensors [2, 3]. Although the suspended nano-sized carbon heater body was patterned without an etching process, the Si substrate had to be etched in an isotropic manner to form a built-in shadow mask to facilitate batch nanofabrication.Here, we present a novel wafer-level fabrication method of a suspended sub-micrometer-sized mesh-type heater without using any conventional etching process. The mesh structure is separated from the substrate by 7–8 μm through two-step UV exposure on a negative photoresist layer: the first exposure is executed with large energy for post-forming, and the second exposure forms a suspended structure at the surface of the photoresist with small UV energy. This monolithic polymer structure is then pyrolyzed and converted to a suspended glassy carbon mesh. The suspended mesh consists of sub-micrometer-sized grid-shaped lines (width 200~500 nm, grid size ~ 10 μm). A thin (~ 50 nm) metal film is deposited on the top of the mesh for use as a heater layer by a directional evaporation method. During the directional deposition, the metal deposited on the substrate in the shape of the suspended mesh. Therefore, as long as the photomask size of the metal coating is smaller than the entire mesh size, the metal layer on the substrate is disconnected. Consequently, suspended mesh-type heaters can be facilitated without the etching process. Furthermore, various heater shapes can be engraved according to the photomask patterns of the mesh structure and metal layer, enabling customized mass production. At this conference, the fabrication of the various types of mesh-type nanoheaters and their applications as gas sensors will be presented. Reference [1] Choi, K. W.; Lee, J. S.; Seo, M. H.; Jo, M. S.; Yoo, J. Y.; Sim, G. S.; Yoon, J. B. Batch-fabricated CO gas sensor in large-area (8-inch) with sub-10 mW power operation. Sens. Actuators, B Chem. 2019, 289, 153–159.[2] Kim, T.; Cho, W.; Kim, B.; Yeom, J.; Kwon, Y. M.; Baik, J. M.; Kim, J. J.; Shin, H. Batch Nanofabrication of Suspended Single 1D Nanoheaters for Ultralow‐Power Metal Oxide Semiconductor‐Based Gas Sensors. Small 2022, 2204078.[3] Cho, W.; Kim, T.; Shin, H. Thermal conductivity detector (TCD)-type gas sensor based on a batch-fabricated 1D nanoheater for ultra-low power consumption. Sens. Actuators, B Chem. 2022, 371, 132541.

BENEFITS OF USING A FID TO MEASURE THE MULTICOMPONENT GAS MIXTURES

The development of the oil and gas complex is one of the priority areas of the Azerbaijan economy. Oil and gas are among the most competitive Azerbaijan goods and are in high and stable demand from global consumers. Therefore, increased attention is paid to product quality. One of the methods for quality control of petroleum products is gas chromatography. Today it is a widely used physical and chemical research method. The capabilities of a gas chromatography are mainly determined by the enormous separating power of the chromatographic columns and the characteristics of the detectors. If the chromatographic column is sometimes called the heart of the chromatograph, then the detector can be called the brain of the chromatograph [1,2]. Effective development of an analysis technique, its successful implementation, troubleshooting of a chromatograph, and metrological certification are impossible without the ability to make the right choice of a detector, operate it competently, and correctly interpret the detector signal. About 50 detectors have been proposed for gas chromatography, but only a few of them are used in practice. The most used are the flame ionization detector and the thermal conductivity detector. The article shows the advantage of using a flame ionization detector to measure important physical and chemical properties, such as density, caloric content, the ratio of the number of carbon atoms to the number of hydrogen atoms C/H. Keywords: Chromatography, gas-mixture, density, hydrocarbon, heat of combustion, calorific value, flame ionization detector, number of carbon atoms, sensitivity, quality.

Enhanced hydrogen gas detectability of sweep heating thin-wire thermal conductivity detector

Enhanced hydrogen gas detectability was demonstrated with the sweep heating thin-wire thermal conductivity detector. The employment of the thinner wire contributes to expanding the detectability. Also, the method for compensating room temperature is proposed based on the resistance measured at the minimum current, which represents room temperature. Therefore, the temperature compensation can be performed without an additional thermometer. Nevertheless, the effect of the compensation is significant, and the fluctuations due to room temperature were removed almost completely. Accordingly, the sensor can detect down to 0.3%H2 (3000 ppm) concentration with 0.1%H2 resolution (0.00007 W/(m∙K) resolution in thermal conductivity), even though the sensing element is only the bulk thin-wire and the operation temperature is near room temperature. This detectability is comparable to the MEMS-based sensor. Therefore, the sweep heating is very powerful, practical, and cost-effective driving method. This is because the sweep heating can acquire much more information as compared with the typical heating methods.

Normal butane oxidation: Measurements of autoxidation products in a jet-stirred reactor

The autoxidation of n-butane was studied experimentally in a jet-stirred reactor at 1 atm (560–720 K) and 10 atm (530–1030 K) for an equivalence ratio of 1. Samples of reacting mixtures were analysed in the gas phase by gas chromatography (GC) using several detectors (Flame ionization detector, thermal conductivity detector, quadrupole mass spectrometer), hydrogen peroxide analyser, and Fourier transform infrared spectroscopy. In addition to the fuel and oxygen, 37 products were quantified. Liquid phase samples were obtained by trapping the reacting mixtures in cooled acetonitrile (273 K). The liquid samples were analysed by high resolution mass spectrometry (HRMS Orbitrap Q-Exactive), either after flow injection or separation by high pressure liquid chromatography (HPLC). Besides stable species, several other low-temperature oxidation products, such as hydroperoxides and ketohydroperoxides, were detected. Products of third O2 addition on fuel’s radicals were also detected by high resolution mass spectrometry. To assess the presence of hydroxyl or hydroperoxyl groups in the products of oxidation we performed H/D exchange with D2O. Qualitative and quantitative results showed the same trends in terms of variation of mole fractions and signal intensities versus reacting temperature. Kinetic modelling was performed using a literature detailed kinetic reaction mechanism already used to simulate previous n-butane oxidation experiments in the cool-flame regime, showing that improvements are needed to better describe the oxidation of n-butane under the present conditions.

Co-anaerobic digestion of sawdust and chicken manure with plant herbs: Biogas generation and kinetic study

Plant herbs specifically serai wangi (SW) and peppermint (PPM) are selected for its insect repellent properties as the use of chicken manure (CM) in anaerobic digestion (AD) potentially attract flies due to the digestate produced. Hence, the addition of SW and PPM in the AD system of CM could deter flies' infestation while producing biogas. Previous work has shown that AD of sawdust (SD) and CM with these plant herbs were able to produce biogas and reduce the flies attraction towards the digestate. However, the combination of SW and PPM for AD of CM has yet to be investigated. This work describes the effect of mixing SW and PPM on the co-AD of SDCM with respect to biogas production, methane yield and kinetic analysis. The mixture of SW and PPM was varied at different concentrations. The composition of methane in biogas was characterized every 10 days by using gas chromatography (GC) equipped with a thermal conductivity detector (TCD). The results suggest that co-AD of 10SW10PPM exhibited the highest biogas production (52.28 mL/gvs) and methane yield (30.89 mL/gvs), which the purity of methane increased by 18.52% as compared to SDCM. However, increasing the concentration of SW and PPM does not significantly improve the overall process. High R2 (0.927–0.999), low RMSE (0.08–0.61) and low prediction error (<10.00%) were displayed by the modified Gompertz, logistic and Cone models. In contrast, Monod and Fitzhugh model is not preferred for the co-AD of SDCM with a mixture of SW and PM, as a high prediction error is obtained throughout the study. Increasing the dosage of PPM decreases the maximum cumulative methane yield, ranging from 31.76 to 7.01 mL/gvs for modified Gompertz and 89.56 to 19.31 mL/gvs for logistic model. The Modified Gompertz obtained a lag phase of 10.01–28.28 days while the logistic model obtained a lag phase of 37.29–52.48 days.

Rapid method for determination of biogas composition by gas chromatography coupled to a thermal conductivity detector (GC-TCD)

ABSTRACT The search for alternative fuel sources to replace non-renewable energy is a highly relevant topic in current research studies. Both biomethane and biohydrogen can be obtained from several anaerobic biological processes, which have some advantages over traditional energy supply chains, especially due to the ability to use various wastes and/or wastewaters as feedstock for the biogas production, which is considered a renewable fuel. These features combined with low energy inputs support the potential of these processes to play a key role in replacing fossil energy sources in the coming decades, as well as helping to avoid climate changes. Thus, it is essential to accurately determine the composition of the biogas generated in different biological processes, regardless of the application: from lab-scale studies to industrial plants. In this work, a gas chromatography set consisting of a Shimadzu/TCD GC-2030 equipped with a Supelco Carboxen 1010PLOT column was used to determine hydrogen (H2), nitrogen (N2), methane (CH4) and dioxide carbon (CO2) by a low-cost manual injection procedure”. Two analytical curves (low and high ranges) were obtained for each target, which enables analysing biogas containing low and high concentrations of the targets. The validation parameters evaluated, namely, [i] linearity, working range, linear working range and sensitivity; [ii] limit of detection (LOD); [iii] limit of quantification (LOQ); and [iv] precision, expressed through repeatability and intermediate precision attested the reliability of the method for numerous applications.

Thermal decomposition of polypropylene plastics through vacuum pyrolysis

The technique of thermal pyrolysis has a great contribution to waste-to-energy platform and circular economic mission. This study used an internal heating process for the vacuum pyrolysis of plastic waste. Eight heating tubes were placed inside a reactor to accelerate heat transfer to the feedstock. Uniform temperature distribution was achieved in <1 h. After 90 min, three phases of pressure profiles were identified: decomposing samples, maximum feedstock cracking, and stability occurrences. Internal pressure decreased with the reduction of condensable gas. Pyrolytic oil was similar to conventional fuels (gasoline and diesel), with the percentage of lower hydrocarbons C5–C10 at 73%, C11–C22 at 18%, and >C22 at 9%. Gas chromatography–thermal conductivity detector analysis of noncondensable gases revealed that the main product of PP with 75% area was C2H6. Furthermore, the Taguchi method was used to optimize the vacuum pyrolysis of waste to energy. Optimal operating conditions for maximum pyrolytic yields were as follows: temperature 425 °C, heating rate 15 °C/min, residence time 6 h, and output flow rate 0.1 L/min. Moreover, the physical properties, cetane number, soot propensities, and auto-ignition temperature of pyrolytic oil were comparable to petroleum diesel. The heating value of the oil product was 55.96 MJ/kg, which was higher compared with petroleum fuels. Vacuum pyrolysis mass, carbon, and energy balances were also determined. This study demonstrated the novel use of internal heating in vacuum pyrolysis. Ultimately, this study provided a new technique of internal heating method in vacuum pyrolysis.