Search

Here, we reported a ceria–copper binary oxide synthesized using the sol–gel approach, which exhibited much improved catalytic activity and stability for abating N,N-dimethylformamide (DMF) at low temperature.

The pyrolysis of three-component surrogate fuel for jet fuel has been studied experimentally in flow reactor using synchrotron photoionization and molecular beam mass spectrometry techniques with temperature range of 850–1150 K. Alkenes are the most abundant products in the decomposition process. Other important intermediates such as alkanes, alkynes, polycyclic aromatic hydrocarbons were also identified and quantified. Detailed kinetic reaction model involving 462 species and 3170 reactions have been developed by validating against the measured results as well as oxidation data reported previously with reasonable predictions. Detailed rate of production and sensitivity analysis indicated T135MCH mainly decay through demethylation and H-abstraction reactions. Moreover, n-propylbenzene consumption is more sensitive to CH 3 than H, while n-dodecane and T135MCH prefer H radical. The reactions between fuel and fuel-derived radicals show limited effect on surrogate fuel consumption. Reactivity changes of NPB and NC12H26 were investigated through the comparison of fuel conversion ratio. The coupling effect was displayed via the common and important sensitive reactions which are related to the H and CH3 radicals. Present experimental data and reaction model will contribute to a better understanding of combustion behavior of 3C surrogate fuel. Thus, the results of present work could contribute to comprehensive investigation of jet fuel combustion properties.

Hydrogen cyanide (HCN) is an important intermediate during the conversion of fuel nitrogen to NOx. The mechanism of HCN oxidation to NO, N2, and N2O on the CaO (100) surface model was investigated using density functional theory calculations to elucidate the effect of in-furnace SOx removal on HCN oxidation in circulating fluidized bed boilers. HCN adsorption on the CaO (100) surface releases as high as 1.396 eV and the H C bond is strongly activated. The CaO (100) surface could catalyze the oxidation of CN radical to NCO with the energy barrier decreasing from 1.560 eV for the homogeneous case to 0.766 eV on the CaO (100) surface. The succeeding oxidation of NCO by O2 forming NO is catalyzed by the CaO (100) surface with the energy barrier decreasing from 0.349 eV (homogeneous process) to 0.026 eV on the CaO (100) surface, while the reaction between NCO and NO forming either NO or N2 is prohibited in comparison with corresponding homogeneous routes. The rate constants of these reactions under fluidized bed combustion temperature range are provided, and the calculation results lead to the conclusion that CaO (100) surface catalyzes the HCN conversion and improves the NO selectivity during HCN oxidation in the HCN/O2/NO atmosphere, which could well explain previous experimental observations. Kinetic parameters of HCN oxidation on the CaO (100) surface are provided in the Arrhenius form for future kinetic model development.

Cu-based oxides oxygen carriers and catalysts are found to exhibit attractive activity for CO oxidation, but the dispute with respect to the reaction mechanism of CO and O2 on the CuO surface still remains. This work reports the kinetic study of CO oxidation on the CuO (111) surface by considering the adsorption, reaction and desorption processes based on density functional theory calculations with dispersion correction (DFT-D). The Eley–Rideal (ER) CO oxidation mechanism was found to be more feasible than the Mars-van-Krevelen (MvK) and Langmuir–Hinshelwood (LH) mechanisms, which is quite different from previous knowledge. The energy barrier of ER, LH, and MvK mechanisms are 0.557, 0.965, and 0.999 eV respectively at 0 K. The energy barrier of CO reaction with the adsorbed O species on the surface is as low as 0.106 eV, which is much more active in reacting with CO molecules than the lattice O of CuO (111) surface (0.999 eV). A comparison with the catalytic activity of the perfect Cu2O (111) surface shows that the ER mechanism dictates both the perfect Cu2O (111) and the CuO (111) surface activity for CO oxidation. The activity of the perfect Cu2O (111) surface is higher than that of the perfect CuO (111) surface at elevated temperatures. A micro-kinetic model of CO oxidation on the perfect CuO (111) surface is established by providing the rate constants of elementary reaction steps in the Arrhenius form, which could be helpful for the modeling work of CO catalytic oxidation.

The oxidation of benzaldehyde (A1CHO) at atmospheric pressure in a jet-stirred reactor at equivalence ratios of 0.4 and 2.0 within 475–900 K was studied. The intermediates and products were identified by synchrotron radiation photoionization and molecular beam mass spectrometry. Compared with previous studies, 29 species such as HCHO, CH3O, H2O2, ketene, furan, 2,4-cyclopentadiene-1-one (C5H4O), furfural, o-benzoquinone, 1,4-benzenediol and 1,4-cyclohex-2-enedione were newly detected. A kinetic model, involving 376 species and 2163 reactions was proposed, which reasonably predicted the experimental value. Rate-of-production analysis shows that H-abstractions reactions involving H atoms, OH, CH3, HO2 and phenoxy radicals dominate the consumption of A1CHO. The decarbonylation reactions and ring opening reactions have a certain contribution to the promotion of oxidation process. Phenoxy radicals, phenol and C5H4O are one of the most significant intermediates for A1CHO oxidation. Sensitivity analysis shows that A1CHO+OH=A1CO+H2O and H2O2(+M) =OH+OH(+M) are among the most sensitive reactions to promote the consumption of A1CHO at both conditions while the reaction A1OH+O2=A1O+HO2 has strong inhibiting effect. A1CHO is more difficult to produce benzene compared with benzyl alcohol oxidation while is easier to generate phenol at the same condition. These results will enrich the understanding the oxidation mechanism and soot formation of A1CHO as a potential aromatic fuel.

Pyrolysis of 1,2,4-trimethylcyclohexane (T124MCH) at 30 and 760 Torr has been investigated by using VUV-synchrotron photoionization molecular-beam mass spectrometry. In general, the ambient pressure leads to peak-shaped profiles of light hydrocarbons, while the monotonically increasing curves are observed for light hydrocarbons and aromatics in pyrolysis of T124MCH at low pressure. A detailed mechanism involving 530 species and 3160 reactions developed by the authors previously was used for the simulation of T124MCH with reasonable predictions. The consumption of T124MCH followed similar patterns at both pressures, namely the H-abstractions on the first, secondary, and tertiary carbon atoms are the main consumption reactions of T124MCH. The isomerization reactions transform the C9H17 radicals to branch-chain hydrocarbons, which are the precursors of light hydrocarbons such as ethane and propene. Sensitivity analysis indicates that the CH3 consumption reactions are the most significant promoting reactions at both pressures. Isomerization reactions of T124MCH tend to play significant inhibiting effect on T124MCH pyrolysis. Compared to T124MCH oxidation, T124MCH pyrolysis tends to produce large quantities of benzene and toluene. These results will improve the understanding of the combustion and soot formation of T124MCH as a potential aviation surrogate fuel.

The effective valuation of catalyst supports in the catalytic oxidation makes the contribution to understand the support effect of great interest. Here, the role of active substrate in the performance and stability of Cu-Fe-Co ternary oxides was studied towards the complete catalytic oxidation of CO. The Cu-Fe-Co oxide thin films were deposited on copper grid mesh (CUGM) using one-step pulsed-spray evaporation chemical vapor deposition method. Crystalline structure and morphology analyses revealed nano-crystallite sizes and dome-top-like morphology. Synergistic effects between Cu, Fe and Co, which affect the surface Cu2+, Fe3+, Co3+ and chemisorbed oxygen species (O2− and OH−) of thin films over the active support and thus result in better reducibility. The thin film catalysts supported on CUGM exhibited attractive catalytic activity compared to the ternary oxides supported on inert grid mesh at a high gas hourly space velocity. Moreover, the stability in time-on-stream of the ternary oxides on CUGM was evaluated in the CO oxidation for 30 h. The adopted deposition strategy of ternary oxides on CUGM presents an excessive amount of adsorbed active oxygen species that play an important role in the complete CO oxidation. The catalysts supported on CUGM showed better catalytic conversion than that on inert grid mesh and some literature-reported noble metal oxides as well as transition metal oxides counterparts, revealing the beneficial effect of the CUGM support in the improvement of the catalytic performance.

This study aims to investigate the co-combustion mechanism of coal and corn residue on a fixed-bed reactor at low temperature, the decomposition characteristics were studied by advanced vacuum ultraviolet photoionization mass spectrometry (PI−TOFMS). The mass spectra and evolution profiles of combustion products (from 300 to 800 °C) were measured. As reaction temperature increased, the relative ion intensities of typical combustion products were investigated, and the difference with previous pyrolysis study was also discussed. The results reveal that cellulose and lignin in corn residue is faster to react than hemicellulose. Coal has an influence on the lignin rather than cellulose and hemicellulose of corn residue in blend. Coal has no effect on the production of furfuryl alcohol obtained from coal-corn residue blend. The current study on the co-combustion mechanism is beneficial to optimize the product distribution and improve combustion efficiency.

Cerium oxide nanopowder (CeOx) was prepared using the sol–gel method for the catalytic oxidation of N, N-dimethylformamide (DMF). The phase, specific surface area, morphology, ionic states, and redox properties of the obtained nanocatalyst were systematically characterized using XRD, BET, TEM, EDS, XPS, H2-TPR, and O2-TPO techniques. The results showed that the catalyst had a good crystal structure and spherelike morphology with the aggregation of uniform small grain size. The catalyst showed the presence of more adsorbed oxygen on the catalyst surface. XPS and H2-TPR have confirmed the reduction of Ce4+ species to Ce3+ species. O2-TPR proved the reoxidability of CeOx, playing a key role during DMF oxidation. The catalyst had a reaction rate of 1.44 mol g−1cat s−1 and apparent activation energy of 33.30 ± 3 kJ mol−1. The catalytic performance showed ~82 ± 2% DMF oxidation at 400 °C. This work’s overall results demonstrated that reducing Ce4+ to Ce3+ and increasing the amount of adsorbed oxygen provided more suitable active sites for DMF oxidation. Additionally, the catalyst was thermally stable (~86%) after 100 h time-on-stream DMF conversion, which could be a potential catalyst for industrial applications.

Pyrolysis study of iso-propylbenzene (IPB) at 30 and 760 torr was carried out by using synchrotron photoionization and molecular beam mass spectrometry techniques. 0.5%IPB was diluted by helium and heated to 798–1148 K in a flow tube. Styrene was the most abundant aromatic intermediate at both pressures. Several polycyclic aromatics were only observed at 760 torr, such as 2-ethenyl-1, 4-dimethyl-benzene, fluorene, anthracene, phenanthrene, 2-methyl-anthracene and pyrene, while fulvene, 1, 3-cyclohexadiene, and 5-ethenylidene-1, 3-cyclopentadiene were only detected at 30 torr. A detail mechanism involving 306 species and 1990 reactions was developed by updating ipso-addition and unimolecular dissociation reactions of IPB as well as reactions related to styrene, indene and naphthalene. The mechanism could predict the pyrolysis of IPB and production of other intermediates well. Rate-of-production analysis shows that the formations of 2-phenethyl, 1-iso-phenylpropyl and 2-iso-phenylpropyl radicals are the main consumption reactions of IPB independent of pressure. Sensitivity analysis indicates that the unimolecular dissociation of IPB forming 2-phenethyl radical is the most significant promoting reaction at both pressures. H-abstraction reaction forming 1-iso-phenylpropyl radical tends to play a significant inhibiting effect on IPB consumption at 30 torr, while the most inhibiting reaction is self-combination of methyl radicals at 760 torr. Compared to n-propylbenzene experiments reported by Liu et al. (Combustion and Flame, 191 (2018) 53–65) and Yuan et al. (Combustion and Flame,186 (2017) 178–192.), IPB tends to produce larger quantities of benzene, styrene and indene under pyrolysis and oxidation conditions. These results will improve the understanding of the combustion and soot formation of IPB as a potential aviation surrogate fuel.

The atmospheric oxidation of benzyl alcohol (A1CH2OH) has been investigated in a jet-stirred reactor (JSR) at equivalence ratios of 0.4 and 2.0 within 700–1100 K. Mole fraction profiles of 19 species were analyzed by online GC and GC/MS techniques. Rate constants of the unimolecular decomposition of A1CH2OH to benzyl and OH, bimolecular reaction with O2, H-abstractions by OH, H and HO2 as well as ipso-addition reactions with CH3 and OH radicals were calculated. H-abstraction reactions of benzaldehyde (A1CHO) were also calculated. Based on the experimental observations and theoretical calculations, a detailed kinetic model involving 304 species and 1903 reactions was developed with reasonable prediction against the measured data. In general, the peak concentrations of hydrocarbons and aromatic species in the rich condition is relatively higher than those in the lean condition, while the oxygenated species exhibit the contrary tendencies. The temperatures of peak values of intermediates at lean condition are relatively lower than those at rich condition. Benzene is mainly produced via the ipso-addition of A1CH2OH. The rate-of-production analysis indicates that the consumption of A1CH2OH is dominated by H-abstraction reactions giving rise to A1CHOH, followed by the reaction sequence of A1CHOH→ A1CHO→ A1CO→ A1-→ A1OO→ A1O→ A1OH. The sensitivity analysis demonstrates that the decomposition of H2O2 to two OH radicals exhibits a strong promoting effect for the lean condition, while the H-abstraction of benzyl alcohol by OH radical producing A1CHOH and H2O exhibits a strong promoting effect for the rich condition. Reaction of A1OH and O2 producing A1O and HO2 presents a strong inhibiting effect at both conditions. Moreover, the benzene formation is at the same level in the oxidation of both A1CH2OH and anisole, suggesting that A1CH2OH could be potentially used as alternative fuels for engine applications.

A comparison study of the oxidation of n-propylbenzene (NPB), iso-propylbenzene (IPB), 1,3,5-trimethylbenzene (T135MB), 1,2,4-trimethylbenzene (T124MB) in a same jet-stirred reactor was performed to find a most suitable transport fuel as a surrogate component. The experimental results show that IPB with the weakest C H bond tends to be the most active fuel among the four C9H12 fuels, while T135MB is the slowest. Ten common intermediates detected in all experiments and eight characteristic intermediates were comprehensively compared, including hydrocarbons, aromatics and oxygenated species. NPB and IPB tend to produce more hydrocarbons and benzene, while T124MB and T135MB generate more toluene and acrolein. Based on the previous studies, an universal mechanism was presented by involving the four sub-mechanisms with good prediction on the measured results. The rate-of-production analysis shows that H-abstraction on the methyl or propyl is the dominant consumption pathway of C9H12 fuels, while C9H11 radicals maintains bigger differences than the initial reactions. Sensitivity analysis shows that CH3 is the key intermediate in the consumption of propylbenzenes, and OH plays similar role in the oxidation of trimethylbenzenes. Moreover, the production pathways of the aldehydes and PAHs in the oxidation were also discussed to understand the pollutant formations. Benzyl and styrene are believed to be the main precursors of aldehydes and PAHs, respectively. In general, these results provide better understanding of the oxidation and combustion of C9H12 fuels as potential surrogate fuel constituents for kerosene and diesel. Furthermore, the comprehensive experimental and modeling studies of C9H12 fuels could also offer the guidance function for the surrogate component selection.

The pyrolysis and oxidation of nitromethane (NM) were studied in a plug flow reactor over the temperature range of 735–1476 K at 5 Torr and in a jet-stirred reactor over the temperature range of 600–875 K at atmospheric pressure, respectively. Mole fraction profiles of major products and intermediates were identified with tunable synchrotron vacuum ultraviolet photoionization and molecular-beam mass spectrometry. The current study represents the first comprehensive characterization of NM conversion under these conditions. The experimental results were compared to predictions with a detailed chemical kinetic model involving 364 species and 2389 reactions. The rate constants for significant dissociation reactions CH3NO2 = CH3 + NO2 and CH3NO2 = HCNO + H2O were calculated by the RRKM/Master Equation method using Variflex program in this work. The model provided an overall reasonable agreement with the measured data, but for pyrolysis conditions future work is required to improve predictions of some intermediates. Rate-of-production analysis indicates that the primary decomposition pathways of NM are different for pyrolysis and oxidation due to the effects of C N bond fission and roaming mediated isomerization. From the sensitivity analysis, the two pathways mentioned above have promoting effects on NM consumption for all the studied conditions, while the reaction of CH3+NO2 CH3O+NO with inhibiting effect at Φ=2.0 shows promoting effects for Φ=0.4 and pyrolysis. This work extends the experimental database and helps to improve the understanding of low temperature chemistry of NM.

The low-temperature oxidation (LTO) of pyridine was studied in a jet-stirred reactor over the temperature range of 700–1000 K at atmospheric pressure and equivalence ratio of 2.0. Mole fraction profiles of the reaction products were obtained based on molecular beam mass spectrometry and tunable vacuum ultraviolet synchrotron photoionization techniques. Hydrogen peroxide, methanamine, acetylenamine, ethenamine, acetaldimine, ethylamine, allyamine, and methylformamide were newly identified compared with previous studies of pyridine flame and pyrolysis. HCN was found to be the dominant N-containing species of pyridine LTO. Pyrrole, acrylonitrile, acetonitrile, and ammonia were also found at the same level of N2O and NO. Based on the new measurements and updated rate constants of several reactions including the H-abstractions of pyridine as well as the oxidation of ortho-pyridyl using density functional theory calculations, a new pyridine LTO kinetic model consisting of 588 species and 3516 reactions was developed with a reasonable agreement with the experimental results. In general, the predictions of the predominant species have been improved compared with the existing model. Rate-of-production analysis indicates that pyridine mainly consumes via C5H5N→C5H4N→C5H4NO2→HCN+CO+ C H 2 CH C ˙ O , and C5H5N→C5H5NO→C2H2+HCN+CH2CO. Sensitivity analysis shows that C5H4N+O2=>C5H4NO2, and C5H5N+OH C5H4N+H2O have significant promoting effect on pyridine consumption, while the reverse of C5H4N+HO2 C5H4NO+OH has strong inhibiting effect. The results will enrich the understanding of pyridine low-temperature oxidation mechanism, which can be applied to the fields of coal pre-treatment, staged combustion and mild combustion.

Thin film catalysts have been recently reported as promising catalysts owing to their good catalytic activity and reduced material amount, leading to low-cost efficient catalysts for gaseous emissions control. Here, we report the slight loading of Cu in cobalt spinel using a one-step pulsed-spray evaporation chemical vapor deposition (PSE-CVD) synthesis technique for efficient short-chain volatile organic compounds (VOCs) emissions treatment. Crystalline structure and morphology analyses revealed nano-crystallite sizes and open-like morphology. The catalytic performance was evaluated through the complete oxidation of C3H6, as a short-chain representative model of VOCs, at a high gas hourly space velocity (GHSV). Very good activity was obtained towards the complete abatement of C3H6 at low temperature and no carbon monoxide (CO) was formed during the oxidation process. Slightly-promoted Co3O4 catalyst with Cu introduction resulted in high catalytic activity comparing to the performance of the catalysts in the literature, due to the high dispersion of Cu and high active surface oxygen amount. Moreover, to evaluate the capability of the used catalysts under near realistic reaction conditions, CO2 effect on the catalytic activity was performed and the catalyst exhibited very good results. Thus, the adopted slightly-doping strategy to tailor a high active catalyst at low temperature could establish a very promising route to strongly enhance the activity of such other catalysts towards gas emissions abatement at low temperature.

Active amorphous lanthanum-based thin films were synthesized through one-step pulsed spray evaporation chemical vapor deposition (PSE-CVD) technique at 320 °C for CO oxidation. The obtained films were characterized in terms of phase, composition and morphological properties. X-ray diffraction (XRD) analysis revealed an amorphous nature of the deposited catalysts; and scanning electron microscope (SEM) showed a transition of morphology due to Co doping from sharp to round shaped edges. Chemical composition analysed by EDS and XPS disclose similar trends in amount of cobalt increment and lanthanum decrement. XPS deconvolution revealed pure lanthanum sample (La100) constitutes mainly of lanthanum oxide and lanthanum hydroxide; while, doping with 10% of cobalt (La90Co10) introduces formation of cobalt ions (Co3+ and Co2+) together with La3+ions and low formation of oxygen lattice. Increment of Co to 20% (La80Co20) resulted increasing of Co2+/Co3+, CO32−/OH−formation ratios and oxygen lattice (Olat) content, which may play a key role in the catalytic activity. Complete oxidation of CO was evaluated by online-FTIR. Based on light-off curves, La80Co20 catalyst exhibited the most efficient catalytic activity with T90 of 203 °C, due to increment of lattice oxygen (Olat), Co2+/Co3+ and CO32−/OH−; while, La90Co10 catalyst exhibited lowest catalytic activity which is linked to low Olat and inhibited catalytic effect of water formed at the surface. Thus, the doping strategy of La by Co at low temperature is a good approach for CO abatement. Moreover, DFT calculations demonstrated that amorphous lanthanum oxide is very feasible for CO adsorption.

High penetration of photovoltaic (PV) power into the energy system could be challenged by its limited dispatchability related to fluctuations and intermittency of solar illumination. We demonstrate an integrated PV-thermochemical (PVTC) device that backs up PV output with dispatchable power generated by solar-thermal enriched fuel. The H2-rich fuel as derived from PV-thermal-driven endothermic chemical reaction enables an overall experimental solar-to-power efficiency of 43.7%, among which more than 40% is contributed by solar thermal energy. This represents a 9.2 percentage points advance over all prior solar PV-thermal power efficiencies reported to date. A modular PVTC prototype based on a triple-junction PV cell and methanol reforming reaction was demonstrated with 24 h continuous operation at a sustained power output of 27.4 W. Cost analysis indicates levelized cost of electricity (LCOE) ranges of 0.173 – 0.273 $ kWh-1 and 0.097 – 0.197 $ kWh-1 for 5 kW and 100 kW PVTC systems, respectively, which are considerably lower than that of PV-battery combination (0.578 – 0.802 $ kWh-1).

The oxidation of furfural has been studied experimentally in a jet-stirred reactor (JSR) under fuel-lean (Φ = 0.4) and fuel-rich conditions (Φ = 2.0) in the temperature range of 650–950 K; in addition, laminar burning velocity data have been measured at T = 473 K and p = 1 bar within a wide fuel-air range. From the JSR experiments, 13 species profiles have been identified and quantified by GC–MS and GC. A detailed kinetic reaction model involving 382 species and 2262 reactions was developed by exploiting the experimental data base provided within the present work as well as experimental data reported in literature. The rate coefficients of reactions of H abstraction, H addition as well as of decomposition of furfural were calculated by quantum chemical methods at CBS-QB3 level. A general agreement was achieved when simulating the experimental data. Rate of production analysis as well as sensitivity analysis were performed to get a deeper insight into the combustion of furfural, e.g. for the jet-stirred reactor data at around 50% fuel conversion, as well as sensitivity analysis of laminar flame speeds conducted for a fuel-air ratio Φ = 0.9, 1.2, and 1.6. According to the analysis, the main consumption pathways of furfural oxidation were identified as H abstraction reactions of the R-CHO (aldehyde) group by H, OH, O, and HO2 to produce a furfural radical (furfural-6). At pyrolysis condition, the dominant pathways within the furfural decay were found to occur via ring opening by splitting the C O bond followed by isomerization to form α-pyrone (C5H4O2). Even more, the measured laminar flame speed data are well reproduced by the reaction model developed within the present work. The experimental data base as well as the developed reaction model will assist and contribute to a more detailed understanding of the combustion behavior of furfural and of furan derivatives as well.

The low-temperature oxidation of 1,2,4-trimethylcyclohexane (T124MCH) as a representative of cyclohexanes was studied in a jet-stirred reactor at temperatures ranging between 600 and 1100 K, φ = 0.4 and 2.0. Mole fraction profiles of 28 species were obtained with online GC and GC–MS techniques. Based on the experimental observations and new calculations of the rate constants for the H-abstractions from the methyl groups of T124MCH by H/OH, a new kinetic model involving 530 species and 3160 reactions was developed with a reasonable agreement with the measured species profiles. With φ increasing, T124MCH consumption shifts to higher temperatures, and the reaction zone becomes broader by 50 K. Rate-of-production analysis reveals that T124MCH consumption is generally governed by C H bond cleavage to form nine cyclic C9H17 radicals, which mostly isomerize to linear C9H17 radicals and then decompose by β-scission. Sensitivity analysis reveals that reactions related to C2H3 and C3H6 play important roles in the consumption of T124MCH. Compared to cyclohexane, n-propylcyclohexane and 1,2,4-trimethylbenzene, T124MCH is the most comprehensive fuel which could produce obvious concentrations of hydrocarbon, aromatic, and oxidized intermediates. These results could improve the understanding of the oxidation process of T124MCH as a surrogate compound for kerosene and diesel to release the active intermediates and soot precursors.

This paper proposes a hybrid adaptive ant colony algorithm (HAACA) to realize product family multi-objective optimization design through scale-based product platform theory model. The Pareto-optimal solution was obtained via HAACA, and then the fuzzy optimization method is presented to extract the optimal solution of multi-objective optimization problem. The multi-objective optimization method was carried out in two stages. In the first stage, each product is optimized independently via HAACA and the product platform constant parameter and its value is obtained according to the change ratio of design variables. In the second stage, the scaling variables of each product are solved via HAACA based on the optimization objectives improving the performance in constraint of restrictions and the best compromise solution is extracted based on fuzzy optimization method.

Pyrolysis of acetone was investigated in a jet-stirred reactor coupled with on-line GC and GC–MS in the temperature range 700–1136 K at atmospheric pressure. Six species, namely 1-C4H8, iC4H8, nC4H10, iC4H10, C5H6 and C6H6, were newly identified and quantified. A kinetic mechanism involving 296 species and 1836 reactions, including subsets of acetone and 2-butanone, was developed with reasonable predictions against the experimental data. C–C bond cleavage releasing CH3CO and CH3 radicals is the chain-initiation and the most intensively promoting reaction for the consumption of acetone. Its high-pressure limit rate constant was recalculated as k1 = 1.12 × 106·T3.84·exp(−78.6 kcal mol−1/RT) at the CBS-QB3 level. Besides this step, H- and CH3-abstractions of acetone by CH3 radical, with the calculated high-pressure limit rate constant as k4 = 1.38·T3.49·exp(−8.58 kcal mol−1/RT) and k7 = 5.70·T3.96·exp(−41.7 kcal mol−1/RT), respectively, govern the major consumption routes of acetone. CH3 radicals contribute as the key species to the production of the major hydrocarbons such as CH4, C2H4 and C2H6, and minor branches to benzene and C2H5COCH3. Moreover, the present kinetic mechanism could predict fairly the mole fractions of the gas species in the high-temperature pyrolysis of acetone and the ignition delay times of acetone at different temperature and pressure region, which indicates the applicability of this model in a wide-range condition.

This study reports the control of catalytic properties of Fe3O4 thin films through adjusting the particles size and optical properties. Structure analysis of the obtained materials by X-ray diffraction indicated the formation of pure magnetite structure of Fe3O4. X-ray photoelectron spectroscopy showed that the surfaces of the samples were mainly composed of Fe2+, Fe3+, O2−, CO32− and OH−. Scanning electronic microscopy displayed a smooth films surface with an agglomerated crystallite grains. Both XRD and SEM exhibits particles size increases (∼40 to ∼60 nm) with the substrate temperature (Ts), while micro-strain in the sample decreased. The correlation of the Ts with optical energy band gaps (EgOpt) determined from UV visible (UV–vis) measurements indicated the increase of indirect (2.17 ≤ Eg2Opt≤ 2.25 eV) and direct (2.78 ≤ Eg1Opt≤ 2.95 eV) band gap of Fe3O4. Fe3O4 samples have been successfully tested towards the total oxidation of CO. While the change in EgOpt of Fe3O4 has been explained on the basis of the variation in the grain size and likely adsorbed oxygen (OAds) with Ts, the catalytic performance was suggested to be strongly dependent on the films microstructure, catalysts surface composition and more importantly with the EgOpt and OAds variation. Moreover, theoretical calculations based on DFT method of CO oxidation over Fe3O4 film surface catalyst demonstrated that OAds was the most involved oxygen species during the catalytic process, revealing that the LH mechanism is the most appropriate route for the CO catalytic oxidation over MvK and ER mechanisms. This approach of highlighting the interplay among the particle size, optical and catalytic properties with DFT calculations can pave the way to better understand the catalytic behavior of other transition metal oxides.

Biogas produced from anaerobic digestion processes is considered as an important alternative to natural gas and plays a key role in the emerging market for renewable energy. Aiming at achieving a more sustainable and efficient biomethane production, this work proposed a novel energy system, which integrates concentrating photovoltaic/thermal (C-PV/T) hybrid modules into a biogas plant with chemical absorption for biogas upgrading. The investigated energy system was optimized based on the data from an existing biogas plant, and its techno-economic feasibility was evaluated. Results show that about 7% of the heat consumption and 12% of the electricity consumption of the biogas plant can be covered by solar energy, by using the produced heat in a cascade way according to the operating temperature of different processes. The production of biomethane can also be improved by 25,800 N m3/yr (or 1.7%). The net present value of the integrated system is about 2.78 MSEK and the payback period is around 10 years. In order to further improve the economic performance, it is of great importance to lower the capital cost of the C-PV/T module.

A series of Co-Cu binary oxides dispersed homogenously on an inert support were prepared by pulsed-spray evaporation chemical vapor deposition for kinetic study of catalytic combustion. The physicochemical properties of the as-prepared samples were comprehensively characterized in terms of structure, morphology and composition. The results disclosed the formation of cubic binary oxides with amorphous surface. With the progressive introduction of copper into the cobalt spinel, the crystallite size tended to increase due to the incorporation of large Cu2+ ionic radius. Co3+, Co2+, Cu2+, lattice and adsorbed oxygen species were confirmed to co-exist at the surfaces of the binary oxides. The obtained samples exhibited excellent performance for C3H6 oxidation with a high gas hourly space velocity of 150,000 mL·g−1·h−1. The light-off curves shifted towards lower temperature with more Cu incorporation, which was linked to the increase in Co3+/Co2+, and the rearrangement and synergetic effects of Co, Cu and lattice oxygen. The reaction rate increases linearly with the increase in C3H6 concentration by following r=1.12*[C3H6]0.27, without reaching kinetic limitation stage. Moreover, an attractive durability of the binary oxides was observed in the C3H6 oxidation during 50 h. This work provides an inspiration and attractive strategy to develop efficient Co-Cu binary oxides for catalytic applications.