Temperature-programmed Process Research Articles

Study of the Effect of Drying on the Pore Structure and Rate of Oxygen Consumption and Heat Release of Immersed Lignite

To reveal the influence mechanism of the drying process of immersed coal on the spontaneous combustion characteristics, we measured the pore structure of coal with low-field nuclear magnetic resonance and conducted the temperature-programmed spontaneous combustion experiment. The results showed that the pore volume content of the pores with pore sizes of less than 100 nm was significantly reduced. The diameter range of 100–1000 nm was gradually generated after 8 h of coal drying, and the proportion of large pores and cracks larger than 1000 nm increased significantly during the drying process of the immersed coal. The oxygen consumption rate and the heat release rate were significantly affected by the degree of dryness and the temperature of coal samples in the temperature-programmed process. The turning point temperature was 140°C; below the turning point temperature, the raw coal had the fastest oxygen consumption and maximum heat release. When the coal temperature was higher than 140°C, the oxygen consumption rate and the heat release rate of the coal sample that was dried for 24 h were higher than those for the raw coal, followed by the samples that were dried for 8 h and dried for 48 h. The main reason is that the water content of the coal sample decreases to 11.4% and the porosity increases to 16.5% after drying for 24 h, while the proportion of pores or cracks larger than 1000 nm increases significantly to 87.17%, the largest increase range and the pore connectivity will reach the maximum.

Synthesis of Pyridine Heterocyclic Low-Melting-Point Phthalonitrile Monomer and the Effects of Different Curing Agents on Resin Properties.

A phthalonitrile monomer (DPTP) containing pyridine with sulfide bonds was prepared and cured into polymers using different curing agents under the same temperature-programmed process. We characterized and comprehensively evaluated the effects of different curing agents on the thermal and thermomechanical properties of phthalonitrile resin, showing that the DPTP monomer cured with naphthalene-containing curing agent exhibited the best performance among the three polymers. Differential scanning calorimetric (DSC) investigation manifested that the melting point of the DPTP monomer was 61 °C, with a processing window of about 170 °C, suggesting the presence of a wide processing range. Thermogravimetric analysis (TGA) demonstrated the outstanding heat resistance, T5%, of 460 °C in nitrogen, at the same time demonstrating superior long-term stability compared with other commonly used polymer materials, which proves the long-term usage under high temperatures of 300 °C. Dynamic mechanical analysis (DMA) revealed that the storage modulus at 50 °C was 3315 MPa, and the glass transition temperature (Tg) of the polymer was more than 350 °C. Therefore, DPTP resins have favorable thermal stability as well as prominent thermomechanical properties.

Carbon monoxide production using a steel mill gas in a combined chemical looping process

Up to 9% of the global CO2 emissions come from the iron and steel industry. Here, a combined chemical looping process to produce CO, a building block for the chemical industry, from the CO2-rich blast furnace gas of a steel mill is proposed. This cyclic process can make use of abundant Fe3O4 and CaO as solid oxygen and CO2 carriers at atmospheric pressure. A proof of concept was obtained in a laboratory-scale fixed bed reactor with synthetic blast furnace gas and Fe3O4/CaO = 0.6 kg/kg. CO production from the proposed process was investigated at both isothermal conditions (1023 K) and upon imposing a temperature program from 1023 to 1148 K. The experimental results were compared using performance indicators such as CO yield, CO space time yield, carbon recovery of the process, fuel utilisation, and solids’ utilisation. The temperature-programmed CO production resulted in a CO yield of 0.056 ± 0.002 mol per mol of synthetic blast furnace gas at an average CO space time yield of 7.6 mmol kgFe−1 s−1 over 10 cycles, carbon recovery of 48% ± 1%, fuel utilisation of 23% ± 2%, and an average calcium oxide and iron oxide utilisation of 22% ± 1% and 11% ± 1%. These experimental performance indicators for the temperature-programmed CO production were consistently better than those of the isothermal implementation mode by 20% to 35%. Over 10 consecutive process cycles, no significant losses in CO yield were observed in either implementation mode. Process simulation was carried out for 1 million metric tonnes per year of equivalent CO2 emissions from the blast furnace gas of a steel mill to analyse the exergy losses in both modes of operation. Comparison of the exergy efficiency of the temperature-programmed process to the isothermal process showed that the former is more efficient because of the higher CO concentration achievable, despite 20% higher exergy losses caused by heat transfer required to change temperature.

Monodisperse pillar[5]arene-based polymeric sub-microsphere for on-line extraction coupling with high-performance liquid chromatography to determine antioxidants in the migration of food contact materials

The monodisperse pillar[5]arene-based polymeric sub-microsphere was prepared by polycondensation of hydroxylated pillar[5]arene and cyanuric chloride through a one-pot reaction in mild condition. The preparation was realized by a simple two-step temperature-programmed process without heating operation. The obtained polymeric sub-microsphere exhibited monodisperse and regular spherical structure with uniform particle size distribution of 220–320 nm accounting for 94%. The prominent adsorption capacity of the polymeric sub-microsphere for antioxidants was demonstrated and attributed to the synergistic effect of the cladding interaction with the π-electron rich cavity and hydrophilic interaction with terminal hydroxyl on pillar[5]arene. Then the pillar[5]arene sub-microsphere was packed into a micro-column to realize effective on-line enrichment of antioxidants coupling with high-performance liquid chromatography (HPLC). The flow rate of extraction and desorption solvent, clean-up and desorption volume were assessed to optimize the method. The method showed wide linear ranges with R2 greater than 0.9926, low limits of detection (0.030–0.20 μg/L) and limits of quantification (0.10–0.67 μg/L). The developed method was successfully applied to determine trace antioxidants in the migration of food contact materials with simulated solution, which demonstrated the promising potential of this method for practical analysis. Furthermore, the migration behavior of antioxidants from food packaging materials into different food matrix was also investigated.

Sulfur Transformation Behavior of Inorganic Sulfur-Containing Compounds in Chemical Looping Combustion

Chemical looping combustion (CLC) is a promising technology for fuel conversion with inherent carbon capture. Because sulfur is an integral part of coal, the existence of sulfur contaminants in coal may degrade the purity of CO₂ and deteriorate the performance of the oxygen carrier in the CLC process. To uncouple the complex behavior of inorganic sulfur in coal, sulfur release of three inorganic sulfur-containing compounds (FeS₂, FeSO₄, and CaSO₄) mixed with activated carbon during the temperature-programmed process and the CLC process using iron ore as an oxygen carrier were investigated in a batch fluidized bed reactor at 950 °C. The results showed that, in the temperature-programmed process, the initial decomposition temperatures of FeS₂, FeSO₄, and CaSO₄ were about 400, 500, and 650 °C, respectively. During the reduction and oxidation stages of CLC, SO₂ was the main sulfur-containing gaseous compound. The sulfur stability of CaSO₄ was higher than those of FeS₂ and FeSO₄. The fractions of sulfur converted to gaseous species in the reduction stage (XS,g,ᵣₑd) of FeS₂ and FeSO₄ reached 90.38 and 87.42%, respectively, within 20.5 min, while the corresponding value was 53.97% for CaSO₄. During 5 cyclic redox experiments at 950 °C, the fraction of sulfur converted to gas species was almost maintained stable, while the energy-dispersive X-ray spectroscopy analysis showed the accumulation of sulfur after the cyclic reaction.

Temperature-Program Assisted Synthesis of Novel Z-Scheme CuBi₂O₄/β-Bi₂O₃ Composite with Enhanced Visible Light Photocatalytic Performance.

Novel Z-Scheme CuBi2O4/β-Bi2O3 composite photocatalysts with different mass ratios and calcination temperatures were firstly synthesized by the hydrothermal method following a temperature-programmed process. The morphology, crystal structure, and light absorption properties of the as-prepared samples were systematically characterized, and the composites exhibited enhanced photocatalytic activity toward diclofenac sodium (DS) degradation compared with CuBi2O4 and β-Bi2O3 under visible light irradiation. The optimal photocatalytic efficiency of the composite, achieved at the mass ratio of CuBi2O4 and β-Bi2O3 of 1:2.25 and the calcination temperature of 600 °C is 92.17%. After the seventh recycling of the composite, the degradation of DS can still reach 82.95%. The enhanced photocatalytic activity of CuBi2O4/β-Bi2O3 is closely related to OH•, h+ and O2•−, and the photocatalytic mechanism of CuBi2O4/β-Bi2O3 can be explained by the Z-Scheme theory.

Modulation of Active Sites in Supported Au38(SC2H4Ph)24 Cluster Catalysts: Effect of Atmosphere and Support Material

We investigate the distinctly different interaction of thiolate-protected cluster Au38(SC2H4Ph)24 with two diverse support materials Al2O3 and CeO2. The catalytic surfaces have been heated in different atmospheres, and the removal of the thiolate ligands has been studied. Thermogravimetry (TG), temperature-programmed process coupled with mass spectrometer (TPRDO-MS), and X-ray absorption spectroscopy (XAFS) studies were performed to understand the desorption of thiol ligands depending on conditions and support material. Depending on the atmosphere and the support material the fate of the thiol ligands is different upon heating, leading to metallic Au in the case of Al2O3 and to cationic Au with CeO2. The thiolate removal seems to be a two-step procedure. The catalytic activity of these Au38-supported clusters was studied for the aerobic oxidation of cyclohexane. Conversion was higher for the gold clusters supported on CeO2. Surprisingly, a significant amount of cyclohexanethiol was found, revealing the ac...

Effects of drying process of Yuanzhi (Radix Palygalae) on its bioactive ingredients

ObjectiveTo study the effects of the drying processing in terms operational parameters on the bioactive constituents of six Yuanzhi (Radix Palygalae) samples across China. MethodsSix Yuanzhi (Radix Palygalae) samples were investigated using thermogravimetry analysis. The heating courses were set in two ways: the temperature-programmed process from room temperature to 150°C, and the constant-temperature course at 50°C, 70°C and 90°C. ResultsThe peak temperature of six Yuanzhi (Radix Palygalae) samples ranged from 78°C to 88°C. The mass loss rate of Yuanzhi (Radix Palygalae) alcohol-soluble extract was significantly increased when heated at 90°C. Four types of bioactive ingredients were detected in volatile oils of Yuanzhi (Radix Palygalae) sample from Shanxi province by Gas Chromatography-mass spectrometry analysis. Fourier Transform Infrared Spectroscopy results showed that the drying temperature exerted a great influence on types and amount of ingredients of Yuanzhi (Radix Palygalae). The kinetic study showed that the constant-temperature drying process of Yuanzhi Radix Palygalae) samples could be well described by the Page Model, especially for the drying process at 50°C, in which R2 and SD values were more than 0.98 and less than 0.04, respectively. The drying constant k of three Yuanzhi (Radix Palygalae) samples from Shanxi, Gansu and Shaanxi provinces in China was corresponding to the Arrhenius equation, and their activation energies were 28.07, 25.38 and 21.48 kJ/mol, respectively. ConclusionThe drying process of Yuanzhi (Radix Palygalae) was very important for bioactive ingredients improvement in Yuanzhi (Radix Palygalae). Temperature was a thermodynamic property significantly affecting the process.

In Situ to Operando Spectroscopy: From Proof of Concept to Industrial Application

The strong influence of the reaction environment on the actual catalyst structure is the driving force to combine in situ studies under actual catalytic operation with simultaneous catalytic activity/selectivity measurement. Such combination of experiments is the basic concept of Operando Methodology. Nowadays, Catalysis Science cannot be understood without spectroscopy; in particular advanced spectroscopy under controlled conditions. The term ‘‘in situ’’ spectroscopy is well established, while operando spectroscopic methodology has been introduced into the catalysis literature in 2002 [1–3]. The details of this Latin term are described elsewhere [4]. ‘‘Operando is Latin for ‘‘working’’ since the spectrum is of an ‘‘operating’’ catalyst. ‘‘In situ’’ is Latin for ‘‘on site’’; it means no temporal discrimination. Advanced in situ studies are run during treatment, and may be variable-programmed; i.e., in situ studies versus a variables (pressure, temperature, reactant concentration, etc.); e.g., during a temperature-programmed processes: TPR-in situ, TPO-in situ, or TPSR-in situ. ‘‘Reaction in situ’’ analyses provide information on catalysts under transient or steady state conditions. However, many in situ reactor cell designs may not be appropriate for true catalytic reaction kinetic studies. The term ‘‘operando’’ provides a single word that underlines the simultaneous evaluation of both catalyst active site structure and catalytic activity/selectivity. It is critical that an operando reactor cell satisfies the requirements of both an in situ cell and those of a catalytic reactor used for the targeted reaction. Understanding a catalyst, is understanding three stories: a story of birth, a story of life, and a story of death. This special issue provides important analyses using in situ and operando techniques to analyze these stories. Catalyst activity is determined by its structure, phase, and also particle shape and size; the role of synthesis conditions on these parameters during synthesis, drying, calcination is reported in the contributions by Martin and Bruckner. A general perspective of spatially resolved and spectroscopic studies are provided by the contributions of Molenbroek, Urakawa and Ferri. Specific research on spatially resolved analysis of working catalysts are provided by the papers of Grunwaldt and Koptyug. Specific research using single or combined spectroscopic techniques are reported by Weckhuysen, Newton, MartinezArias, Tanabe, Mims, Chuang and Khatib. Increasing the quantity of information on performance and structure on a fundamental basis provides a rational approach to highthroughput methodologies. Thus, there is a major opportunity on the development of high-throughput operando systems, contributions Zhang and Lauterbach show spectroscopic high-throughput applications. All spectroscopic analyses depend on spectra, the contribution by Garland underlines the use of advanced software to handle spectra. In summary, understanding catalytic structure-activity relationships stands on two pillars, structure and activity. The Operando methodologies blend these pillars into a single approach. This issue reflects important progress of in situ to operando methodologies, provide a proof of concept and illustrate fundamental and applied research. M. A. Banares (&) Catalytic Spectroscopy Laboratory, Institute for Catalysis and Petroleum Chemistry, CSIC, Marie Curie, 2, 28049 Madrid, Spain e-mail: banares@icp.csic.es

Sensors Based on SNO2 As a Detector for CO Oxidation in Air

This work describes properties of sensors based on SnO2 , which were used as detectors in the temperature-programmed surface reaction (TPSR) of CO oxidation. Usually, the detection in temperature-programmed processes is realized by using TCD (katharometer) or a mass spectrograph. In our work we present preliminary results which show that the sensors manufactured from SnO2 can also be used to this aim.

Temperature-Programmed Decomposition, Oxidation, and Reduction Studies of Co2(CO)8 Supported on Alumina

Co2(CO)8 supported on alumina pretreated at different temperatures was studied by temperature-programmed processes (temperature-programmed decomposition, TPDE; temperature-programmed oxidation, TPO; and temperature-programmed reduction, TPR). The gaseous decomposition and reaction products were analyzed by mass spectrometry and gas-phase IR spectroscopy. Oxygen and hydrogen consumptions by the surface species were followed with a TCD. The pretreatment of the support was found to affect the TPDE profile of cobalt carbonyls. CO ligands were removed more straightforwardly in the presence of OH groups producing a narrow TPDE profile. A broader TCD profile was found for the support with predominantly Lewis acid/base sites. The presence of OH groups also favored decomposition of surface cobalt carbonyl species, giving the lowest Tmax. Oxidation and reduction of samples were observed to depend on the preceding treatment. Decarbonylation of the sample under inert gas intensified the interactions between cobalt an...

Recovery of acetone vapor by a thermal swing adsorber with activated carbon.

An experimental and theoretical study was made of the adsorption and desorption of acetone vapor from a nitrogen stream using a fixed bed of activated carbon. A linear driving force mass transfer model was found to provide a good fit to the experimental data. The system was found to be an intraparticle mass transfer-controlled process. The regeneration of activated carbon loaded with acetone was investigated by employing a temperature-programmed process for minimum energy consumption and volume of hot purge gas requirement. The energy requirement could be economically met by regenerating an adsorber at the characteristic temperature for optimal holding time followed by an appropriate rate of decreasing the temperature of purge gas. It was found that an adsorbed bed initially heated at a higher temperature can lead to a smaller purge gas requirement.

Dynamic and thermodynamic consequences of adsorbate lateral interactions in surface reaction kinetics

The effects of lateral interactions on the two-dimensional distribution of adspecies on solid surfaces and their consequences for reaction kinetics are demonstrated for the bimolecular reactive systemA+B→AB. The discussion concentrates on systems where one reactant,A, is stationary while the other,B, is freely diffusing and instantaneously relaxing. A modified Bethe-Peierls-type lattice gas approximation is formulated in order to account for the rapidly-equilibrating distribution ofB atoms. The approximation takes into account all nearest and next nearest neighbor interactions between the adspecies and the nonuniformity of the lattice available toB implied by the presence of immobileA's on the surface. This model is combined with a Monte Carlo simulation of the reactive events in order to calculate reaction rates, e.g., in temperature-programmed processes. The rates are compared with full Monte Carlo simulations (for all kinetic processes), showing good agreement between the two schemes, except at very high coverages, where very long range correlations in the system which are ignored in the lattice gas approximation must be taken into account.