Catalytic decomposition of CH_4 over Ni-Al_2O_3-SiO_2 catalysts:Influence of pretreatment conditions for the production of H_2

This article reports the production of COx free hydrogen and carbon nanofibers by the catalytic decomposition of methane over Ni-Al2O3-SiO2 catalysts. The influence of reaction temperature, pretreatment temperature, and effect of reductive pretreatment on the decomposition of methane activity is investigated. The physico-chemical characteristics of fresh and deactivated samples were characterized using BET-SA, XRD, TPR, SEM/TEM, CHNS analyses and correlated with the methane decomposition results obtained. The Ni-Al-Si （4 ： 0.5 ： 1.5） catalyst reduced with hydrazine hydrate produced better H2 yields of ca. 1815 mol H2/mol Ni than the catalyst reduced with 5% H2/N2.

Production of hydrogen-rich gas and multi-walled carbon nanotubes from ethanol decomposition over molybdenum modified Ni/MgO catalysts

A series of molybdenum modified Ni/MgO catalysts （Ni-Mo/MgO） with different loading ratios of Ni ： Mo were prepared by impregnation method. Ethanol decomposition to co-produce multi-walled carbon nanotubes and hydrogen-rich gas at temperatures of 600-800 ℃ was inves- tigated over the synthesized Ni-Mo/MgO catalysts. The results showed that the catalytic activity depended strongly on the reaction temperature and loading ratio of Ni ： Mo. According to the gaseous and solid products obtained, the reaction pathways for ethanol decomposition were suggested.

Characteristics of La-modified Ni-Al_2O_3 and Ni-SiO_2 catalysts for CO_x-free hydrogen production by catalytic decomposition of methane

Hydrotalcite precursors of La modified Ni-Al2O3 and Ni-SiO2 catalysts prepared by co-precipitation method and the catalytic activities were examined for the production of COx-free H2 by CH4 decomposition. Physico-chemical characteristics of fresh, reduced and used catalysts were evaluated by XRD, TPR and O2 pulse chemisorptions, TEM and BET-SA techniques. XRD studies showed phases due to hydrotalcite-like precursors in oven dried form produced dispersed NiO species upon calcination in static air above 450 C. Raman spectra of deactivated samples revealed the presence of both ordered and disordered forms of carbon. Ni-La-Al2O3catalyst with a mole ratio of Ni : La : Al = 2 : 0.1 : 0.9 exhibited tremendously high longevity with a hydrogen production rate of 1300 molH2 mol 1 Ni. A direct relationship between Ni metal surface area and hydrogen yields was established.

Hydrogen production by catalytic decomposition of methane using a Fe-based catalyst in a fluidized bed reactor

Catalytic decomposition of methane using a Fe-based catalyst for hydrogen production has been studied in this work. A Fe/Al2O3 catalyst previously developed by our research group has been tested in a fluidized bed reactor （FBR）. A parametric study ot the effects of some process variables, including reaction temperature and space velocity, is undertaken. The operating conditions strongly affect the catalyst performance. Methane conversion was increased by increasing the temperature and lowering the space velocity. Using temperatures between 700 and 900℃ and space velocities between 3 and 6 LN/（gcat·h）, a methane conversion in the range of 25%-40% for the gas exiting the reactor could be obtained during a 6 h run. In addition, carbon was deposited in the form of nanofilaments （chain like nanofibers and multiwall nanotubes） with similar properties to those obtained in a fixed bed reactor.

Research on Anti-noise Processing Method of Production Signal Based on Ensemble Empirical Mode Decomposition(EEMD)

The grain production prediction is one of the most important links in precision agriculture. In the process of grain production prediction, mechanical noise caused by the factors of difference in field topography and mechanical vibration will be mixed in the original signal, which undoubtedly will affect the prediction accuracy. Therefore, in order to reduce the influence of vibration noise on the prediction accuracy, an adaptive Ensemble Empirical Mode Decomposition(EEMD) threshold filtering algorithm was applied to the original signal in this paper: the output signal was decomposed into a finite number of Intrinsic Mode Functions(IMF) from high frequency to low frequency by using the Empirical Mode Decomposition(EMD) algorithm which could effectively restrain the mode mixing phenomenon; then the demarcation point of high and low frequency IMF components were determined by Continuous Mean Square Error criterion(CMSE), the high frequency IMF components were denoised by wavelet threshold algorithm, and finally the signal was reconstructed. The algorithm was an improved algorithm based on the commonly used wavelet threshold. The two algorithms were used to denoise the original production signal respectively, the adaptive EEMD threshold filtering algorithm had significant advantages in three denoising performance indexes of signal denoising ratio, root mean square error and smoothness. The five field verification tests showed that the average error of field experiment was 1.994% and the maximum relative error was less than 3%. According to the test results, the relative error of the predicted yield per hectare was 2.97%, which was relative to the actual yield. The test results showed that the algorithm could effectively resist noise and improve the accuracy of prediction.

A novel two-stage Lagrangian decomposition approach for refinery production scheduling with operational transitions in mode switching

To address large scale industrial processes,a novel Lagrangian scheme is proposed to decompose a refinery scheduling problem with operational transitions in mode switching into a production subproblem and a blending and delivery subproblem.To accelerate the convergence of Lagrange multipliers,some auxiliary constraints are added in the blending and delivery subproblem.A speed-up scheme is presented to increase the efficiency for solving the production subproblem.An initialization scheme of Lagrange multipliers and a heuristic algorithm to find feasible solutions are designed.Computational results on three cases with different lengths of time horizons and different numbers of orders show that the proposed Lagrangian scheme is effective and efficient.

Litter production, decomposition and nutrient mineralization dynamics of Ochlandra setigera: A rare bamboo species of Nilgiri Biosphere Reserve, India

Litter production, decomposition and nutrient release dynam-ics of Ochlandra setigera, a rare endemic bamboo species of Nilgiri biosphere were studied during 2011-2012 using the standard litter bag technique. Annual litter production was 1.981 t？ha-1 and was continuous throughout the year with monthly variations. Litterfall followed a tri-phasic pattern with two major peaks in November, 2011 and January, 2012 and a minor peak in July, 2011. The rate of decomposition in O. setigera was a good fit to the exponential decay model of Olson （1963）. Litter quality and climatic conditions of the study site （maximum tem-perature, monthly rainfall and relative humidity） influenced the rate of decomposition. Nutrient release from the decomposing litter mass was in rank order N=Mg＆gt;K=Ca＆gt;P. Nutrient release from litter was con-tinuous and it was in synchrony with growth of new culms. Study of litter dynamics is needed before introduction of a bamboo species into degraded or marginal lands or Agroforestry systems.

Production of Hydrogen: Photocatalytic Decomposition of Dimethyl Ether over Metal-Promoted TiO₂Catalysts

The photo-induced vapor-phase decomposition of dimethyl ether was investigated on Pt metals deposited on pure and N-doped TiO2. Infrared spectroscopic measurements revealed that adsorption of dimethyl ether on TiO2 samples underwent partial dissociation to methoxy species. Illumination of the (CH3)2O-TiO2 and (CH3)2O-M/TiO2 systems led to the conversion of methoxy into adsorbed formate. In the case of metal-promoted TiO2 catalysts, CO bonded to the metals was also detected. Pure titania exhibited a very little photoactivity. Deposition of Pt metals on TiO2 markedly enhanced the extent of photocatalytic decomposition of dimethyl ether to give H2 and CO2 as the major products. A small amount of CO and methyl formate was also identified in the products. The most active metal was the Rh followed by Pd, Ir, Pt and Ru. When the bandgap of TiO2 was lowered by N-doping, the photocatalytic activity of metal/TiO2 catalysts appreciably increased. The effect of metals was explained by a better separation of charge carriers induced by illumination and by enhanced electronic interaction between metal nanoparticles and TiO2.

Paper-like Microfibrous Nickel Catalyst for Hydrogen Production via NH_3 Decomposition in Fuel Cell Applications

A sinter-locked three-dimensional network of microfibrous nickel catalyst has been fabricated based on wet layup papermaking and sintering processes and this novel approach permits the production of -11 W fuel cell power H2 via NH3 decomposition with a conversion of 97% at 750 ℃ in a bed of 0.6 cm^3.

Transition metal nanoparticles supported La-promoted MgO as catalysts for hydrogen production via catalytic decomposition of ammonia

The uniformly dispersed transition metal(Co, Ni and Fe) nanoparticles supported on the surface of La-promoted Mg O were prepared via a deposition-precipitation method for hydrogen production from catalytic decomposition of ammonia. X-ray diffraction, N2 adsorption-desorption, transmission electron microscopy, temperature-programmed reduction and temperature-programmed desorption were used to investigate the structure-activity relation of catalysts in NH3 decomposition. The results show that the strong interaction between active species and support can effectively prevent the active species from agglomerating during ammonia decomposition reaction. In addition, the introduction of La species not only facilitates the adsorption and decomposition of NH3 and desorption of N2, but also benefits the better dispersion of the active species. The prepared catalysts showed very high catalytic activity for ammonia decomposition compared with the same active composition samples that reported previously. Meanwhile, the catalysts showed excellent high-temperature stability and no any deactivation was observed, which are very promising candidates for the decomposition of ammonia to hydrogen.

Production of High Purity Multi-Walled Carbon Nanotubes from Catalytic Decomposition of Methane

Acid-based purification process of multi-walled carbon nanotubes （MWNTs） produced via catalytic decomposition of methane with NiO/TiO2 as a catalyst is described. By combining the oxidation in air and the acid refluxes, the impurities, such as amorphous carbon, carbon nanoparticles, and the NiO/TiO2 catalyst, are eliminated. Scanning electron microscopy （SEM） and transmission electron microscopy （TEM） images confirm the removal of the impurities. The percentage of the carbon nanotubes purity was analyzed using thermal gravimetric analysis （TGA）. Using this process, 99.9 wt% purity of MWNTs was obtained.

Mechanical Modeling and Analysis of Stability Deterioration of Production Well During Marine Hydrate Depressurization Production

Different from oil and gas production,hydrate reservoirs are shallow and unconsolidated,whose mechanical properties deteriorate with hydrate decomposition.Therefore,the formations will undergo significant subsidence during depressurization,which will destroy the original force state of the production well.However,existing research on the stability of oil and gas production wells assumes the formation to be stable,and lacks consideration of the force exerted on the hydrate production well by formation subsidence caused by hydrate decomposition during production.To fill this gap,this paper proposes an analytical method for the dynamic evolution of the stability of hydrate production well considering the effects of hydrate decomposition.Based on the mechanical model of the production well,the basis for stability analysis has been proposed.A multi-field coupling model of the force state of the production well considering the effect of hydrate decomposition and formation subsidence is established,and a solver is developed.The analytical approach is verified by its good agreement with the results from the numerical method.A case study found that the decomposition of hydrate will increase the pulling-down force and reduce the supporting force,which is the main reason for the stability deterioration.The higher the initial hydrate saturation,the larger the reservoir thickness,and the lower the production pressure,the worse the stability or even instability.This work can provide a theoretical reference for the stability maintaining of the production well.

Thermodynamic analysis of production of high purity titanium by thermal decomposition of titanium iodide

High purity titanium was prepared by thermal decomposition of titanium iodide.The feasible synthetic route and optimum decompositon temperaure were obtained by thermodynamic analysis in the process of thermal decomposition of titanium iodide and nucleation growth theory.The temperature for the formation of titanium iodide is in the range of 800-900 K,at which a large amount of titanium iodide vapour can be obtained.The decomposition temperature of titanium iodide is in the range of 1 300-1 500 K,at which a favourable decomposition rate can be achieved.The experiment results show that the purity of the produced titanium is more than 99.995%.

Evolving patterns of agricultural production space in China:A network-based approach

The agricultural production space,as where and how much each agricultural product grows,plays a vital role in meeting the increasing and diverse food demands.Previous studies on agricultural production patterns have predominantly centered on individual or specific crop types,using methods such as remote sensing or statistical metrological analysis.In this study,we characterize the agricultural production space(APS)by bipartite network connecting agricultural products and provinces,to reveal the relatedness between diverse agricultural products and the spatiotemporal characteristic of provincial production capabilities in China.The results show that core products are cereal,pork,melon,and pome fruit;meanwhile the milk,grape,and fiber crop show an upward trend in centrality,which is in line with diet structure changes in China over the past decades.The little changes in community components and structures of agricultural products and provinces reveal that agricultural production patterns in China are relatively stable.Additionally,identified provincial communities closely resemble China's agricultural natural zones.Furthermore,the observed growth in production capabilities in North and Northeast China implies their potential focus areas for future agricultural production.Despite the superior production capa-bilities of southern provinces,recent years have witnessed a notable decline,warranting special attentions.The findings provide a comprehensive perspective for understanding the complex relationship of agricultural prod-ucts'relatedness,production capabilities and production patterns,which serve as a reference for the agricultural spatial optimization and agricultural sustainable development.

Optimization of Gas Production from Hydrate-Bearing Sediments with Fluctuation Characteristics

As an important source of low-carbon,clean fossil energy,natural gas hydrate plays an important role in improving the global energy consumption structure.Developing the hydrate industry in the South China Sea is important to achieving‘carbon peak and carbon neutrality’goals as soon as possible.Deep-water areas subjected to the action of long-term stress and tectonic movement have developed complex and volatile terrains,and as such,the morphologies of hydrate-bearing sediments(HBSs)fluctuate correspondingly.The key to numerically simulating HBS morphologies is the establishment of the conceptual model,which represents the objective and real description of the actual geological body.However,current numerical simulation models have characterized HBSs into horizontal strata without considering the fluctuation characteristics.Simply representing the HBS as a horizontal element reduces simulation accuracy.Therefore,the commonly used horizontal HBS model and a model considering the HBS’s fluctuation characteristics with the data of the SH2 site in the Shenhu Sea area were first constructed in this paper.Then,their production behaviors were compared,and the huge impact of the fluctuation characteristics on HBS production was determined.On this basis,the key parameters affecting the depressurization production of the fluctuating HBSs were studied and optimized.The research results show that the fluctuation characteristics have an obvious influence on the hydrate production of HBSs by affecting their temperatures and pressure distributions,as well as the transmission of the pressure drop and methane gas discharge.Furthermore,the results show that the gas productivity of fluctuating HBSs was about 5%less than that of horizontal HBSs.By optimizing the depressurization amplitude,well length,and layout location of vertical wells,the productivity of fluctuating HBSs increased by about 56.6%.

Tea Production Response to Seasonal Rainfall Variability: Evidence from Rwanda

Tea is a very important cash crop in Rwanda, as it provides crucial income and employment for farmers in poor rural areas. From 2017 to 2020, this study was intended to determine the impact of seasonal rainfall on tea output in Rwanda while still considering temperature, plot size (land), and fertiliser for tea plantations in three of Rwanda’s western, southern, and northern provinces, western province with “Gisovu” and “Nyabihu”, southern with “Kitabi”, and northern with “Mulindi” tea company. The study tested the level of statistical significance of all considered variables in different formulation of panel data models to assess individual behaviour of independent variables that would affect tea production. According to this study, a positive change in rainfall of 1 mm will increase tea production by 0.215 percentage points of tons of fresh leaves. Rainfall is a statistically significant variable among all variables with a positive impact on tea output Qitin Rwanda’s Western, Southern, and Northern provinces. Rainfall availability favourably affects tea output and supports our claim. Therefore, there is a need for collaboration efforts towards developing sustainable adaptation and mitigation options against climate change, targeting tea farming and the government to ensure that tea policy reforms are targeted towards raising the competitiveness of Rwandan tea at local and global market.

Gas-Water Production of a Continental Tight-Sandstone Gas Reservoir under Different Fracturing Conditions

A numerical model of hydraulic fracture propagation is introduced for a representative reservoir(Yuanba continental tight sandstone gas reservoir in Northeast Sichuan).Different parameters are considered,i.e.,the interlayer stress difference,the fracturing discharge rate and the fracturing fluid viscosity.The results show that these factors affect the gas and water production by influencing the fracture size.The interlayer stress difference can effectively control the fracture height.The greater the stress difference,the smaller the dimensionless reconstruction volume of the reservoir,while the flowback rate and gas production are lower.A large displacement fracturing construction increases the fracture-forming efficiency and expands the fracture size.The larger the displacement of fracturing construction,the larger the dimensionless reconstruction volume of the reservoir,and the higher the fracture-forming efficiency of fracturing fluid,the flowback rate,and the gas production.Low viscosity fracturing fluid is suitable for long fractures,while high viscosity fracturing fluid is suitable for wide fractures.With an increase in the fracturing fluid viscosity,the dimensionless reconstruction volume and flowback rate of the reservoir display a non-monotonic behavior,however,their changes are relatively small.

A new production component method for natural gas development planning

Based on an analysis of the limitations of conventional production component methods for natural gas development planning,this study proposes a new one that uses life cycle models for the trend fitting and prediction of production.In this new method,the annual production of old and new wells is predicted by year first and then is summed up to yield the production for the planning period.It shows that the changes in the production of old wells in old blocks can be fitted and predicted using the vapor pressure model(VPM),with precision of 80%e95%,which is 6.6%e13.2%higher than that of other life cycle models.Furthermore,a new production prediction process and method for new wells have been established based on this life cycle model to predict the production of medium-to-shallow gas reservoirs in western Sichuan Basin,with predication error of production rate in 2021 and 2022 being 6%and 3%respectively.The new method can be used to guide the medium-and long-term planning or annual scheme preparation for gas development.It is also applicable to planning for large single gas blocks that require continuous infill drilling and adjustment to improve gas recovery.

Stochastic Production Frontiers and Decomposition of Output Growth： The Case of Citrus-Growing Farms in Tunisia

Abstract： The aim of this paper is to investigate the relative contribution of technical efficiency, technological change and increased input use to the output growth of the Tunisian citrus growing farms using a stochastic frontier production function approach applied to panel data for the period 2003-2005. Knowledge of the relative contribution of factors productivity and input use to output growth and improvements in technical efficiency is crucial to provide a comprehensive view of the state of the citrus producing sector in the country and help farm managers and policy makers draw appropriate policy measures. The proposed methodology is based on the use of a flexible translog functional form. Results indicate that technical efficiency of production in citrus producing farms investigated ranges from a minimum of 11.19% to a maximum of 96.82% with an average technical efficiency estimate of 49.97%. This suggests that citrus producers may increase their production by as much as 50.03% through more efficient use of production inputs. Furthermore, the production is characterized by increasing returns to scale, which on average was 1.057. Finally, investigation of the sources of production growth reveals that the contribution of total factor productivity is found to be the main source of that growth.

Sparse Modal Decomposition Method Addressing Underdetermined Vortex-Induced Vibration Reconstruction Problem for Marine Risers

When investigating the vortex-induced vibration(VIV)of marine risers,extrapolating the dynamic response on the entire length based on limited sensor measurements is a crucial step in both laboratory experiments and fatigue monitoring of real risers.The problem is conventionally solved using the modal decomposition method,based on the principle that the response can be approximated by a weighted sum of limited vibration modes.However,the method is not valid when the problem is underdetermined,i.e.,the number of unknown mode weights is more than the number of known measurements.This study proposed a sparse modal decomposition method based on the compressed sensing theory and the Compressive Sampling Matching Pursuit(Co Sa MP)algorithm,exploiting the sparsity of VIV in the modal space.In the validation study based on high-order VIV experiment data,the proposed method successfully reconstructed the response using only seven acceleration measurements when the conventional methods failed.A primary advantage of the proposed method is that it offers a completely data-driven approach for the underdetermined VIV reconstruction problem,which is more favorable than existing model-dependent solutions for many practical applications such as riser structural health monitoring.