Thermodynamic study and methanothermal temperature-programmed reaction synthesis of molybdenum carbide

Nanostructured molybdenum carbide （Mo2C） was successfully prepared from molybdenum trioxide （MoO3） using methanothermal temperature-programmed reaction. Thermodynamic analysis indicated that in presence of methane, the formation of Mo2C from MoO3 occurs through the path of MoO3 → MoO2→ Mo2C. The carburized MoO3 was characterized using X-ray diffraction （XRD）, CHNS/O analysis, Brunauer-Emmett-Teller （BET） analysis, and field-emission scanning electron microscopy （FESEM）. At final carburization temperatures of 700 and 800℃ and at methane contents ranging from 5vol% to 20vol%, Mo2C was the only solid product observed in the XRD patterns. The re- suits indicated that the effect of methane content on the formation of the carbide phase is substantial compared with the effect of carburization time. Elemental analysis showed that at a final temperature of 700℃, the carbon content of carburized MoO3 is very close to the theoretical carbon mass percentage in Mo2C. At higher carburization temperatures, excess carbon was deposited onto the surface of Mo2C. High-surface-area Mo2C was obtained at extremely low heating rates; this high-surface-area material is a potential electrocatalyst.

Characteristics of oxygen consumption of coal at programmed temperatures

Oxygen consumption is an important index of coal oxidation.In order to explore the coal-oxygen reaction,we developed an experimental system of coal spontaneous combustion and tested oxygen consumption of differently ranked coals at programmed temperatures.The size of coal samples ranged from 0.18~0.42 mm and the system heat-rate was 0.8℃/min.The results show that, for high ranked coals,oxygen consumption rises with coal temperature as a piecewise non-linear process.The critical coal temperature is about 50℃.Below this temperature,oxygen consumption decreases with rising coal temperatures and reached a minimum at 50℃,approximately.Subsequently,it begins to increase and the rate of growth clearly increased with temperature.For low ranked coals,this characteristic is inconspicuous or even non-existent.The difference in oxygen consumption at the same temperatures varies for differently ranked coals.The results show the difference in oxygen consumption of the coals tested in our study reached 78.6%at 100℃.Based on the theory of coal-oxygen reaction,these phenomena were analyzed from the point of view of physical and chemical characteristics,as well as the appearance of the coal-oxygen complex.From theoretical analyses and our experiments,we conclude that the oxygen consumption at programmed temperatures reflects the oxidation ability of coals perfectly.

NO adsorption and temperature programmed desorption on K_2CO_3 modified activated carbons

Fuel cell stacks as the automotive power source can be severely poisoned by a trace amount of NOx in atmosphere,which makes it necessary to provide clean air for fuel cell vehicles.In this work,activating commercial activated carbons with K2CO3 for the large enhancement of NO capture was studied.K2CO3 modified activated carbons(K2CO3 ACs)were prepared by impregnating activate carbons in K2CO3 solution under ultrasound treatment,followed by temperature programmed baking at 800 oC.The dynamic NO flow tests on K2CO3 ACs at room temperature indicated that NO adsorption capacity reached the maximum(96 mg/g)when K2CO3 loading was 19.5 wt%,which corresponded to a specific surface area of 1196.1 m2/g and total pore volume of 0.70 cm3/g.The ten-fold enhancement of NO adsorption on K2CO3 ACs compared to the unimpregnated activated carbon was mainly attributed to the formation of potassium nitrite,which was confirmed by FTIR and temperature programmed desorption measurements.Regeneration tests of NO adsorption on the optimum sample revealed that 76%of the NO adsorption capacity could be remained after the fourth cycle.

THE STUDY OF THE NON-STEADY KINETICS OF THE OXYDEHYDROGENATION OF ETHANE TO ETHYLENE OVER THE CATALYST OF Mo-V-Nb/Al_2O_3 BY THE TECHNIQUE OF TEMPERATURE PROGRAMMED TRANSIENT RESPONSE AND ELECTRIC CONDUCTIVITY

In this paper, instead of with the more expensive Fourier Transform Infrared Spectrometer(FTIR) a new technique of Temperature Programmed Transient Response(TP-TR) has been used with gas chromatography. Therefore, the TP-TR will be applied more widespreadly than ever before. With the technique of TP-TR and electric conductivity, the study is on the reaction mechanism and the adsorption behavior of the reactants and products to the present catalyst Mo-V-Nb/Al_2O_3 in the reaction from ethane through oxydehydrogenation to ethylene as the product. By Range-Kutta-Gill and Margarat methods, the kinetic parameters of the reaction elementary steps (i.e. rate constants, active energies and frequency factors) have been evaluated. The mathematical treatment coincides with the experimental results.

KINETICS OF IRON-BASED CATALYST IN TEMPERATURE-PROGRAMMED REDUCTION

In this work, Temperature-Programmed Reduction Processes of iron oxide and 12 other kinds of promoted iron oxides were investigated. It is suggested that the reduction activation energy can be expressed as a normal distribution. The distribution parameters were obtained by kinetic data fitting, which depends on the chemical and geometric characteristics of both the iron oxide and the promoter.

Study of the Temperature-Programmed Desorption of Carbon Dioxide (CO2) on Zeolites X Modified with Bivalent Cations

Study of physisorbed and chemisorbed carbon dioxide (CO2) species was carried out on the NaX zeolite modified by cationic exchanges with bivalent cations (Ca2+ and Ba2+) by temperature-programmed desorption of CO2 (CO2-TPD). Others results were obtained by infrared to complete the study. The results of this research showed, in the physisorption region (213 - 473 K), that the cationic exchanges on NaX zeolite with bivalent cations increase slightly the interactions of CO2 molecule with adsorbents and/or cationic site. Indeed, the desorption energies of physisorbed CO2 obtained on the reference zeolite NaX (13.5 kJ·mol-1) are lower than that of exchanged zeolites E-CaX and E-BaX (15.77 and 15.17 kJ·mol-1 respectively). In the chemisorbed CO2 region (573 - 873 K), the desorption energies related to desorbed species (bidentate carbonates: CO32-) on the exchanged zeolites E-CaX and E-BaX are about 81 kJ·mol-1, higher than the desorbed species (bicarbonates: HCO32-) on the reference R-NaX (62 kJ·mol-1). In addition, the exchanged E-BaX zeolite develops the secondary adsorption sites corresponding to bicarbonates species with desorption energies of 35 kJ·mol-1 lower to desorption energies of bicarbonates noted on the reference zeolite NaX.

High-temperature performance prediction of iron ore fines and the ore-blending programming problem in sintering

The high-temperature performance of iron ore fmes is an important factor in optimizing ore blending in sintering. However, the application of linear regression analysis and the linear combination method in most other studies always leads to a large deviation from the desired results. In this study, the fuzzy membership functions of the assimilation ability temperature and the liquid fluidity were proposed based on the fuzzy mathematics theory to construct a model for predicting the high-temperature performance of mixed iron ore. Comparisons of the prediction model and experimental results were presented. The results illustrate that the prediction model is more accurate and effective than previously developed models. In addition, fuzzy constraints for the high-temperature performance of iron ore in this research make the results of ore blending more comparable. A solution for the quantitative calculation as well as the programming of fuzzy constraints is also introduced.

Modeling viscosity of methane,nitrogen,and hydrocarbon gas mixtures at ultra-high pressures and temperatures using group method of data handling and gene expression programming techniques

Accurate gas viscosity determination is an important issue in the oil and gas industries.Experimental approaches for gas viscosity measurement are timeconsuming,expensive and hardly possible at high pressures and high temperatures(HPHT).In this study,a number of correlations were developed to estimate gas viscosity by the use of group method of data handling(GMDH)type neural network and gene expression programming(GEP)techniques using a large data set containing more than 3000 experimental data points for methane,nitrogen,and hydrocarbon gas mixtures.It is worth mentioning that unlike many of viscosity correlations,the proposed ones in this study could compute gas viscosity at pressures ranging between 34 and 172 MPa and temperatures between 310 and 1300 K.Also,a comparison was performed between the results of these established models and the results of ten wellknown models reported in the literature.Average absolute relative errors of GMDH models were obtained 4.23%,0.64%,and 0.61%for hydrocarbon gas mixtures,methane,and nitrogen,respectively.In addition,graphical analyses indicate that the GMDH can predict gas viscosity with higher accuracy than GEP at HPHT conditions.Also,using leverage technique,valid,suspected and outlier data points were determined.Finally,trends of gas viscosity models at different conditions were evaluated.

CALCULATION OF ADIABATIC TEMPERATURE THROUGH COMPUTER PROGRAM IN PROCESS OF COMBUSTION SYNTHESIS

The adiabatic temperature in the process of self-propagating high temperature synthesis iscalculated through FOXBASE language program on the base of establishing thermodynamic datapool concerned.The adiabatic temperature of some common self-propagating high temperaturesynthesis has been calculated,and the computed results are compared with the adiabatic tempera-ture reported.At the same time,the curve about the influence of preheating temperature andadding diluent on Tadis drawn as an example.

Program for the Recording Temperature Characteristic in the Furnace

This paper represents the program, which is used to record the temperature field homogeneity in the furnace, using measuring and acquisition system Agilent 34970. This program is made in Metrology Laboratories Orao a.d. in Bijeljina and was originally used to record the homogeneity of temperature field in vacuum furnaces. These fumaces installed in Orao a.d. Bijeljina are intended for heat treatment process of various spare parts for aircraft engines. It is very important to have good homogeneity of the temperature field in the furnace, in order to avoid spoilage in the production of spare parts and thus the great financial losses. Now, the program is used for recording temperature field homogeneity in many companies in the Republic of Srpska, Federation of Bosnia and Herzegovina, Serbia, Montenegro and Croatia. Beside of fumaces, this program is used to record homogeneity of temperature fields in sterilizers, refrigerators, freezers and other areas where temperature field homogeneity is important in manufacturing process technology. After finishing each test, we have received very useful information about the temperature distribution in working volume and discovered critical points, which was necessary to eliminate. Based on these data, some corrective measures are taken in order to ensure better homogeneity of temperature field of the furnace. In case that is not possible to make corrections on the furnace, then, based on temperature field homogeneity report, it is possible to determine optimal fumace working volume in which heat treatment of spare parts for aircraft engines is done. The aim of this is to minimize scrap material during heat treatment in the furnace.

Prediction of coal ash fusion temperatures using computational intelligence based models

In the coal-based combustion and gasification processes, the mineral matter contained in the coal (predominantly oxides), is left as an incombustible residue, termed ash. Commonly, ash deposits are formed on the heat absorbing surfaces of the exposed equipment of the combustion/gasification processes. These deposits lead to the occurrence of slagging or fouling and. consequently, reduced process efficiency. The ash fusion temperatures (AFTs) signify the temperature range over which the ash deposits are formed on the heat absorbing surfaces of the process equipment. Thus, for designing and operating the coal-based processes, it is important to have mathematical models predicting accurately the four types of AFTs namely initial deformation temperature, softening temperature, hemispherical temperature, and flow temperature. Several linear/nonlinear models with varying prediction accuracies and complexities are available for the AFT prediction. Their principal drawback is their applicability to the coals originating from a limited number of geographical regions. Accordingly, this study presents computational intelligenee (CI) based nonlinear models to predict the four AFTs using the oxide composition of the coal ash as the model input. The CI methods used in the modeling are genetic programming (GP), artificial neural networks, and support vector regression. The no table features of this study are that the models with a better AFT prediction and generalization performanee, a wider application potential, and reduced complexity, have been developed. Among the Ci-based models, GP and MLP based models have yielded overall improved performanee in predicting all four AFTs.

LabVIEW based temperature transmitter-a simple and realizable approachfor experimental cum application study in the laboratory

In this paper,we have presented a simple approach for experimental and application study on LabVIEW based temperature transmitter with NI myRIO device in the laboratory.In this work,to study the small range of temperature(40-100℃)although different temperature sensors can be used still,we have used here a K-type thermocouple as the measuring temperature sensor.The analog output voltage of thermocouple is amplified by instrumentation amplifier and the amplified signal is fed to the analog input of NI myRIO device which converts the analog input voltage signal as per the algorithm developed with virtual instrumentation based programming and provides the corresponding 4-20 mA output current signal in the analog output terminal of the device.Results show that input-output i.e.temperature-current relationship is linear.This low cost developed transmitter is very simple and it can be recommended for academic,scientific and industrial development of data acquisition systems,control and analysis of instruments.

Temperature stress analysis for bi-modulus beam placed on Winkler foundation

The materials with different moduli in tension and compression are called bi-modulus materials. Graphene is such a kind of materials with the highest strength and the thinnest thickness. In this paper, the mechanical response of the bi-modulus beam subjected to the temperature effect and placed on the Winkler foundation is studied. The differential equations about the neutral axis position and undetermined parameters of the normal strain of the bi-modulus foundation beam are established. Then, the analytical expressions of the normal stress, bending moment, and displacement of the foundation beam are derived. Simultaneously, a calculation procedure based on the finite element method （FEM） is developed to obtain the temperature stress of the bi-modulus struc- tures. It is shown that the obtained bi-modulus solutions can recover the classical modulus solution, and the results obtained by the analytical expressions, the present FEM proce- dure, and the traditional FEM software are consistent, which verifies the accuracy and reliability of the present analytical model and procedure. Finally, the difference between the bi-modulus results and the classical same modulus results is discussed, and several reasonable suggestions for calculating and optimizing the certain bi-modulus member in practical engineering are presented.

Diagnosis of Electron,Vibrational and Rotational Temperatures in an Ar/N2 Shock Plasma Jet Produced by a Low Pressure DC Cascade Arc Discharge

In this paper, a low pressure Ar/N2 shock plasma jet with clearly multicycle al- ternating zones produced by a DC cascade arc discharge has been investigated by an emission spectral method combined with Abel inversion analysis. Plasma emission intensity, electron, vi- brational and rotational temperatures of the shock plasma have been measured in the expansion and compression zones. The results indicate that the ranges of the measured electron temperature, vibrational temperature and rotational temperature are 1.1 eV to 1.6 eV, 0.2 eV to 0.7 eV and 0.19 eV to 0.22 eV, respectively, and it is found for the first time that the vibrational and rota- tional temperatures increase while the electron temperature decreases in the compression zones. The electron temperature departs from the vibrational and the rotational temperatures due to non-equilibrium plasma effects. Electrons and heavy particles could not completely exchange energy via collisions in the shock plasma jet under the low pressure of 620 Pa or so.

Improvement in cryosurvival of buffalo bull (Bubalus bubalis) sperm by altering freezing rate within critical temperature range

Objective:To optimize the cryopreservation of buffalo bull semen by altering freezing rates within critical temperature range (4℃ to -60℃). Methods: A total of 20 ejaculates each from 5 Murrah buffalo bulls were cryopreserved using programmable biofreezer in 2 phases. In the 1st phase, 9 freezing rates were applied at -2, -5, -10, -20, -30, -40, -50, -60 or -4℃/min (control) from 4℃ to -15℃;at -40℃/min from -15℃ to -60℃. In the 2nd phase, a fixed freezing rate was applied at -30℃/min from 4℃ to -15℃. Six freezing rates were applied at -10, -20, -30, -40 (control), -50 or -60℃/min from -15℃ to -60℃. The freezing from -60℃ to -140℃ were fixed at -50℃/min in both the phases. Post thaw semen quality was assessed in terms of motility, viability, membrane integrity (hypo-osmotic swelling test), sperm abnormalities, and active mitochondria. Data were arc sine transformed and analyzed through one-way analysis of variance using SPSS software. Results: In the 1st phase, percent individual motility, progressive motility and viability were similar among various protocols. Percent hypo-osmotic swelling reactive sperm was higher with freezing at -30℃/min. In the 2nd phase, percent individual motility, viability and hypo-osmotic swelling reactive sperm was higher with freezing at -50℃/min. Sperm head abnormalities were lower at -30℃/min in the 1st phase, but were similar among the protocols of the 2nd phase. Percent active mitochondria were higher at -30℃/min in the 1st phase and at -50℃/min in the 2nd phase.Conclusions:The optimum post thaw semen quality of buffalo bull could be obtained by applying freezing rate at -30℃/min (4℃ to -15℃) and at -50℃/min (-15℃ to -140℃), followed by plunging of straws in into liquid nitrogen for storage.

SIMPLE NONLINEAR OPTIMIZATION-BASED SELECTION OF INSULATION MATERIAL AND WINDOW TYPE IN TURKEY:EFFECT OF HEATING AND COOLING BASE TEMPERATURES

The energy-savings of four hypothetical households in different climatic regions of Turkey were calculated via a nonlinear mixed integer optimization model.The ideal insulation material,its optimum thickness,and the ideal window type were determined.The standard degree days method was used with five different base temperatures for heating and five different base temperatures for cooling.The climatic conditions of the region,the properties of the insulation options,the unit price of fuel and electricity and the base temperature are used as model inputs,whereas the combination of selected insulation material with its optimum thickness and window type are given as model outputs.Stone Wool was found to be the ideal wall insulation material in all scenarios.The optimum window type was found to depend on the heating or cooling requirements of the house,as well as the lifetime of insulation.The region where the energy saving actions are deemed most feasible has been identified as Erzurum(Region 4),followed by Antalya(Region 1).Finally,the effect of changing the base temperature on energy savings was investigated and the results showed that an approximate average increase of$15/°C in annual savings is possible.Our model can be used by any prospective home-owner who would like to maximize their energy savings.

Implicit characteristic parameter of a programmed temperature retention index database

In a programmed temperature retention index (PTRI) database, there exists a characteristic parameter rt0/β that can be calculated if the experimental parameters are clearly given. This characteristic parameter can be used to flexibly reproduce the original PTRI data under chromatographic conditions different from those originally given. As this characteristic parameter is not explicitly given, it is suggested to name this parameter as the implicit characteristic parameter (TCP) of a PTRI database. The ICP in White’s PTRI database was easily found and used satisfactorily to reproduce PTRI of some test compounds using either a Hewlett-Packard ultra-performance OV-1 column or a self-coated OV-1 column. The reproduction of PTRI could not be realized on columns of different materials. The fact that several PTRI databases measured on glass capillary columns could not satisfactorily be reproduced on fused silica column is explained.

A study on the reduction behayior of Fe_2(MoO_4)_3 with a combined in-situ temperature-programmed reduction- Mossbauer spectroscopic technique

In H2/N2 atmosphere, the reduction behavior of the stoichiometric compound, Fe2(MoO4)3, was studied by in-situ Mossbauer spectroscopy (in-situ MBS), temperature-programmed reduction (TPR) and X-ray diffraction (XRD). The results showed that the reduction products, β-FeMoO4, Mo4O11, MoO2, Fe3O4, Fe2Mo3O8, Fe and Mo, as well as iron-molybdenum alloys, were formed subsequently when the reduction temperature was raised. It was found that when Mo6+ were reduced to Mo4+, Fe2+ were oxidized to Fe3+. Due to the interactions among the metal ions and the electron transfers, the reduction processes of the metal ions in Fe2(MoO4)3 are very complex. According to the results of XRD and MBS obtained at various TPR stages, the reaction equations for the reduction stages were proposed. The Mossbauer spectrum of an intermediate species, Fe2Mo3O8, was found to exhibit two doublets, with I.S.=0.90mm/s and Q.S. =0.58 mm/s, and I.S. = 1.02mm/s and Q.S. = 1.04mm/s, respectively.

煤自燃程序升温实验及其在实验教学中的应用

该文利用程序升温实验系统,对三种氧气浓度(20.9%、10%和7%)所代表的采空区散热带、氧化带、窒息带进行了煤样自燃发火实验,采集了不同温度阶段的气体产物,分析了温度及氧气浓度对气体产物浓度的影响,并对指标气体进行了详细分类和评估。实验结果表明:交叉点温度CPT随着氧气浓度的升高而降低,干空气的交叉点温度为144.6℃,由经验关系计算得到的CPT值与实验数据相差仅6.08%;氧气浓度越高,临界温度越低,所产生的气体浓度越高;CO气体在不同的含氧环境下都是主要的氧化产物,可作为判断煤自燃发火的主要指标,C_(2)H_(4)和C_(3)H_(6)的产生表示煤体进入加速氧化状态,可作为判断煤自燃发火的辅助指标。

Al_(2)O_(3)基材作载体制备MoP加氢脱硫催化剂的研究

采用低温燃烧法和溶剂热法分别合成了富含五配位Al^(3+)物种的氧化铈改性Al_(2)O_(3)(Ce-Al_(2)O_(3))和介孔-大孔Al_(2)O_(3)(M-Al_(2)O_(3));通过程序升温还原浸渍法负载的Mo的磷酸盐前驱体制备了MoP催化剂。以二苯并噻吩(DBT)为模型含硫化合物评价了其加氢脱硫(HDS)性能。结果表明,M-Al_(2)O_(3)上制备纯相MoP所需磷酸盐前驱体的P/Mo摩尔比在1~1.2之间。DBT在MoP催化剂上转化率大小为MoP(1)/SiO_(2)>MoP(1)/Ce-Al_(2)O_(3)>MoP(1.2)/M-Al_(2)O_(3)。动力学研究表明,DBT在MoP(1)/Ce-Al_(2)O_(3)和MoP(1.2)/M-Al_(2)O_(3)上的HDS反应活化能几乎相同,显著小于MoP(1)/SiO_(2)上的活化能。在MoP催化剂上,直接脱硫(DDS)路径选择性随温度的增加而增加。在较低的温度下(如280℃),DBT主要通过加氢(HYD)反应路径脱硫;在较高的温度下(如360℃),DDS和HYD两条反应路径并重。