Pre-reforming of liquefied petroleum gas over nickel catalysts supported on magnesium aluminum mixed oxides

A series of Ni/Mg_xAl catalysts with different Mg/Al molar ratios were prepared by impregnating Mg-Al mixed oxides with nickel nitrate aqueous solution and used for the pre-reforming of LPG in the temperature range of 400-500 °C. XRD and H₂-TPR results showed that the Ni/Mg_xAl catalysts calcined at 800 °C mainly consisted of γ-Al₂O₃, Mg(Ni)Al₂O₄ and Mg(Ni)O phases varying with Mg/Al molar ratio without free NiO species observed. The effects of Mg/Al molar ratio, S/C molar ratio and reaction temperature on the catalytic behavior of the Ni/Mg_xAl catalysts were investigated in detail. The results revealed that the catalyst with Mg/Al molar ratio of 1.25 had the highest catalytic activity and stability. The increase in S/C molar ratio promoted both the steam reforming of LPG and the methanation of carbon oxides and hydrogen. The stability tests of 15%Ni/Mg_1.25Al catalyst showed that the catalyst was stable for the pre-reforming of LPG, and the stability decreased with elevating the reaction temperature due to more coke deposition.     

液化石油气发动机的性能及故障特征

分析了液化石油气（LPG）作为发动机燃料时的特点，以及LPG－汽油双燃料发动机的性能特点和实用化技术，介绍LPG发动机的发展状况，对LPG－汽油双燃料发动机的故障特征作探讨，针对此类双燃料发动机的技术调整和改进方面提出了观点。     

Development of highly effective supported nickel catalysts for pre-reforming of liquefied petroleum gas under low steam to carbon molar ratios

The pre-reforming of commercial liquefied petroleum gas (LPG) was investigated over Ni–CeO₂ catalysts at low steam to carbon (S/C) molar ratios less than 1.0. It was found that the catalytic activity and selectivity depended strongly on the nature of the support and the interaction between Ni and CeO₂. The Ni–CeO₂/Al₂O₃ catalysts, which were prepared by impregnating boehmite (AlOOH) with an aqueous solution of cerium and nickel nitrates, exhibited the optimal catalytic activity and remarkable stability for the steam reforming of LPG in the temperature range of 275–375 °C. The effects of CeO₂ loading, reaction temperature and S/C ratio on the catalytic behavior of the Ni–CeO₂/Al₂O₃ catalysts were discussed in detail. The results showed that the catalysts with 10 wt.% CeO₂ had the highest catalytic activity, and higher S/C ratios contributed to LPG reforming and the methanation of carbon oxides and hydrogen. The XRD and H₂-TPR analyses revealed that the strong interaction between Ni and CeO₂ resulted in the formation of CeAlO₃ in the Ni–CeO₂/Al₂O₃ catalysts reduced. The stability tests of 15Ni–10CeO₂/Al₂O₃ catalyst at 350 °C indicated that the catalyst was stable, and the stability could be enhanced by increasing S/C ratio.     

Structured noble metal-based catalysts for the WGS process intensification

Pt/Re-based catalysts differently supported (Al₂O₃, ZrO₂, CeO₂, CeZrO₄) were prepared, characterized and tested for Water Gas Shift reaction, highlighting the excellent performance of the catalyst supported on the high reducible ceria-zirconia. With the intent to prepare a structured catalyst, based on the 1Pt/1Re/CeZrO₄ formulation, a highly heat conductive aluminum foam was washcoated with a primer of alumina, the resulting carrier was firstly impregnated with a solution of the salts precursors of ceria and zirconia, subsequently with the salts precursors of platinum and rhenium. The performance of the resulting structured catalyst was evaluated, for the Water Gas Shift reaction, in different conditions; moreover the performance, in adiabatic condition, was compared with a powder catalyst with the same chemical composition of the structured catalyst, highlighting the effect of the carrier. The back diffusion of the heat of the reaction throughout the carrier, allowed to reduce the ΔT on the catalytic bed and increase the CO conversion, with respect to the powder catalyst. The experimental results were validated with CFD simulations, by using the finite elements method software COMSOL Multiphysics^®.     

Comparison of thermochemical conversion processes of biomass to hydrogen-rich gas mixtures

Hydrogen can be produced from biomass materials via thermochemical conversion processes such as pyrolysis, gasification, steam gasification, steam-reforming, and supercritical water gasification (SCWG) of biomass. In general, the total hydrogen-rich gaseous products increased with increasing pyrolysis temperature for the biomass sample. The aim of gasification is to obtain a synthesis gas (bio-syngas) including mainly H₂ and CO. Steam reforming is a method of producing hydrogen-rich gas from biomass. Hydrothermal gasification in supercritical water medium has become a promising technique to produce hydrogen from biomass with high efficiency. Hydrogen production by biomass gasification in the supercritical water (SCW) is a promising technology for utilizing wet biomass. The effect of initial moisture content of biomass on the yields of hydrogen is good.     

Estimating the agricultural demand for natural gas and liquefied petroleum gas in the presence of measurement error in the data

The paper begins by discussing the importance of accurate estimates of the price elasticity of demand and some of the problems frequently encountered in obtaining these estimates. To these problems is added that associated with inaccuracy in the measurement of the dependent variable and one or more of the independent variables that affect the quantity demanded. Two diagnostics, i.e. the regression coefficient bounds and the bias correction factor, have been introduced to assess the effect that such measurement error has on the estimated coefficients of demand relationships. The use of these diagnostics will aid in assessing the integrity of the estimates obtained. In considering the demand for natural gas and the demand for liquefied petroleum gas by farmers in the USA, both the quantity demanded and the price data available for demand model estimation purposes contain measurement error. The regression coefficient bounds diagnostic was used to indicate a range over which the true price responsiveness of farmers to changes in energy prices lies. The results suggest that each 1% increase (decrease) in the price of energy will result in a decrease (increase) of between 0.41 and 0.17% in the quantity of natural gas demanded and a decrease (increase) of between 0.48 and 0.07% in the quantity of liquefied petroleum gas demanded. The bias correction factor was computed to evaluate the magnitude of the underestimation of the responsiveness of the quantity of natural gas and liquefied petroleum gas demanded to a change in the number of acres irrigated. For natural gas, the under-estimation was 26.5%, whereas, for liquefied petroleum gas, it was 9.5%.     

Synthesis gas conversion over Cu and Ca modified model Mo6S8 catalysts: A systematic theoretical investigation

We present a combined density functional theory (DFT) and microkinetic modeling study of synthesis gas conversion on Cu and Ca modified Mo₆S₈ catalysts to value-added products. Our results show that CO1 + H1 → HCO1 + (H) → H₂CO1 + (H) → H₃CO1 + (H) → CH₃OH1 → CH₃OH (g) is an optimal pathway on the Ca–Mo₆S₈ surface. With the combination of Energetic span model (ESM) and binding energy analysis, we conclude that Ca–Mo₆S₈ is a promising catalyst for formaldehyde and methanol from synthesis gas conversion. Meanwhile, the most energetically favorable outcome on the Cu–Mo₆S₈ surface is the production of ethanol. Microkinetics simulations are carried out on the basis of the first-principles data, which predict the synthesis gas conversion rate and the product distribution. This study demonstrates that introducing metal Cu or Ca into Mo₆S₈ will design high-performance catalysts with synergistic interactions for tuning selectivity.     

Ceria-coated replicated aluminium sponges as catalysts for the CO-water gas shift process

A study on the use of chemical conversion coating as a preparative technique for foam-based structured catalysts, in the water gas shift reaction, is presented. The results showed a significant correlation between the textural properties of the structure and the preparation technique, highlighting how chemical conversion coating is a suitable technique for highly porous structures. In the first part of the paper, the performance of two structured catalysts obtained by coating commercial aluminium foams, with different porosity, was compared. The activity tests suggested that diffusion phenomena occurred in the case of the uncompressed foams. These results were confirmed by evaluating the performance of a catalyst obtained by coating a compressed 5 PPI pore size commercial aluminium foam, which showed much higher activity, at the same contact time, with respect to the catalyst obtained with the corresponding non-compressed foam. Finally, the performance of a catalyst obtained by coating an aluminium sponge, synthesized by the replication technique, was compared to that of a catalyst obtained by coating a compressed 40 PPI pore size aluminium foam. The higher activity of the sponge-based catalysts confirmed the dependence of the activity on the textural properties of the structure: X-ray computed tomography images highlighted the narrow distribution of the pore sizes and the presence of “bottleneck type” connections in the sponge structure, which are beneficial for the activity of the catalyst.     

Morphological features of electrodeposited Pt nanoparticles and its application as anode catalysts in polymer electrolyte formic acid fuel cells

Electrodeposited Pt nanoparticles on carbon substrate show various morphologies depending on the applied potentials. Dendritic, pyramidal, cauliflower-like, and hemi-spherical morphologies of Pt are formed at potential ranges between −0.2 and 0.3 V (vs. Ag/AgCl) and its particle sizes are distributed from 8 to 26 nm. Dendritic bulky particles over 20 nm are formed at an applied potential of −0.2 V, while low deposition potential of 0.2 V causes dense hemi-spherical structure of Pt less than 10 nm. The influence of different Pt shapes on an electrocatalytic oxidation of formic acid is represented. Consequently, homogeneous distribution of Pt nanoparticles with average particle of ca. 14 nm on carbon paper results in a high surface to volume ratio and the better power performance in a fuel cell application.     

Combustion characteristics of mixture of anode off gas and LNG in reformer

Fuel processing system which converts hydrocarbon fuel into hydrogen rich gas (by stream reforming, partial oxidation, auto-thermal reforming) needs high temperature environment (600-1000 °C). Generally, anode off gas or mixture of anode off gas and LNG are used as input gas for a fuel reformer. In order to constitute efficient and low emission burner system for fuel reformer, it is necessary to elucidate the combustion and emission characteristics of fuel reformer burner. In this study, lean flat flame using the ceramic porous burner was analyzed numerically and experimentally. Burning velocity of anode off gas calculated by CHEMKIN simulation was 51.8 cm, which was faster than that of LNG having 40.63 cm/s at the stoichiometric ratio because of high composition of hydrogen in anode off gas. As composition of LNG in mixture of anode off gas + LNG is increased, the burning velocity decreases and in the other hand the adiabatic temperature increases. CO, NO_x were measured below 50 ppm in operating load range of the reformer. Blue flame pattern was found as stable flame region for design of fuel reformer and anode off gas flame was maintained in blue flame pattern at equivalence ratio 0.55-0.62 under 1-5 kW power range.     

Effects of Pt/C, Pd/C and PdPt/C anode catalysts on the performance and stability of air breathing direct formic acid fuel cells

Pt/C, Pd/C and PdPt/C catalysts are potential anodic candidates for electro-oxidation of formic acid. In this work we designed a miniature air breathing direct formic acid fuel cell, in which gold plated printed circuit boards are used as end plates and current collectors, and evaluated the effects of anode catalysts on open circuit voltage, power density and long-term discharging stability of the cell. It was found that the cell performance was strongly anode catalyst dependent. Pd/C demonstrated good catalytic activity but poor stability. A maximum power density of 25.1 mW cm⁻² was achieved when 5.0 M HCOOH was fed as electrolyte. Pt/C and PdPt/C showed poor activity but good stability, and the cell can discharge for about 10 h at 0.45 V (Pt/C anode) and 15 h at 0.3 V (PdPt/C) at 20 mA.     

Modelling and flow rate control methods for anode tail gas circulation intake system at SOFC

In the solid oxide fuel cell (SOFC) power generation system, the anode tail gas circulation intake system plays an important role in the entire system for efficient and stable operation. Currently, there are relatively few studies on the operating characteristics of claw pump, which works as the core component of the SOFC anode exhaust gas circulation intake system. Based on the prototype of 20 kW SOFC power generation system, this paper builds the emulation testbed for the anode exhaust gas circulation intake system and analyzes the working characteristics of the claw pump in the testbed firstly. The support vector regression (SVR) and Gauss process regression (GPR) methods are then used to establish the characteristics model of the claw pump based on the operation data. According to the verification results, GPR method owns higher prediction accuracy than SVR method in our case. Therefore, the GPR method is adopted to build the flow rate prediction model of the claw pump. Finally, the flow rate control method based on feedforward and model prediction (FMP) with GPR flow rate prediction model is proposed for the built anode tail gas circulation intake system. In experiments, the response time of the FMP method is within 22 s and the overshoot is less than 3.2%, whose performance is better than the traditional flow rate control method, such as PID or model predictive control.     

The influence of anode gas diffusion layer on the performance of low-temperature DMFC

The influence of the anode gas diffusion layers (GDLs) on the performances of low-temperature DMFCs, and the properties of mass transport and CO₂ removal on these anode GDLs were investigated. The membrane electrode assembly (MEA) based on the hydrophilic anode GDL, which consisted of the untreated carbon paper and hydrophilic anode micro-porous layer (comprised carbon black and 10 wt.% Nafion), showed the highest power density of 13.4 mW cm⁻² at 30 °C and ambient pressure. The performances of the MEAs tended to decline with the increase of the PTFE content in the anode GDLs due to the difficulty of methanol transport. The contact angle measurements revealed that the wettabilities of the anode GDLs decreased as the increase of PTFE content. The wettabilities of the GDLs were improved by addition of hydrophilic Nafion ionomer to the GDLs. From the visualizations of CO₂ gas bubbles dynamics on the anodes using a transparent cell, it was observed that uniform CO₂ gas bubbles with smaller size formed on hydrophilic anode GDLs. And bubbles with larger size were not uniform over the hydrophobic anode GDLs. It was believed that adding PTFE to the anode GDL was not helpful for improving the CO₂ gas transport in the anode GDL of the low-temperature DMFC.     

Hydrothermal gasification of microalgae over nickel catalysts for production of hydrogen-rich fuel gas: Effect of zeolite supports

A series of Ni catalysts with different zeolites were prepared by wet impregnation method and used to catalyze supercritical water gasification (SCWG) of microalgae for production of hydrogen-rich fuel gas under conditions of 430 °C, 60 min, ρ_H₂O = 0.162 g/cm³, 2 g/g Ni/zeolites. Compared with noncatalytic SCWG, the presence of Ni/zeolite could increase the hydrogen gasification efficiency and carbon gasification efficiency by promoting water–gas shift and steam reforming reactions which are mainly affected by the amount of strong acid sites and Ni, respectively. The highest carbon gasification efficiency (CGE) and hydrogen gasification efficiency (HGE) of 23.61% and 23.55% were achieved with Ni/HY (Na₂O, 0.8%). The gaseous produced mainly consisted of H₂ and CO₂. The H₂ content in the gaseous products varied from 27.15 to 40.51% depending on the Ni/zeolites and increased with increasing the SiO₂/Al₂O₃ molar ratio of HZSM-5, which is 2.3–3.6 times higher than that of produced without catalyst. The H₂ yield varied between 2.57 and 3.61 mmol/g depending on the Ni/zeolites and increased from 2.19 to 5.61 mmol/g with increasing the SiO₂/Al₂O₃ molar ratio from 50:1 to 170:1, which is 3.6–7.8 times higher than that of produced without catalyst. Coke formation, surface area loss, and sintering of Ni could decrease the activity of the Ni/zeolites.     

Mass spectroscopy for the anode gas layer in a semi-passive DMFC using porous carbon plate Part I: Relationship between the gas composition and the current density

In situ mass spectroscopy with a capillary probe was conducted for the anode gas layer of a semi-passive direct methanol fuel cell (DMFC) employing a porous carbon plate (PCP) in order to evaluate the gas composition in contact with the anode. Different types of PCPs were used for the DMFC, and then the relationship between the gas composition in the gas layer and the current density was investigated. The profiles of the CO₂ gas pressure, methanol and water vapor pressures were discussed on the basis of the current density and the resistance for the methanol and CO₂ transport through the PCP. The current density linearly and identically increased with the increase in the partial pressure of methanol, P_CH3OH, in the gas layer up to 7.5 kPa irrespective of the type of the PCP suggesting that the current was a function of P_CH3OH and it was rate limited by the methanol transport to the anode. The calculated liquid methanol concentration equivalent to the measured gas mixture in the gas layer was about 5–7 M in the optimum conditions. This confirmed that the actual methanol activity on the anode of the DMFC with the PCP was controlled by the PCP and was similar to that of the usual liquid feed DMFC even when a very high concentration of methanol was in the reservoir.     

Kinetic modeling and reaction pathways for thermo-catalytic conversion of carbon dioxide and methane to hydrogen-rich syngas over alpha-alumina supported cobalt catalyst

This study investigates the kinetic modeling and reaction pathway for the thermo-catalytic conversion of methane (CH₄) and Carbon dioxide (CO₂) over alpha-alumina supported cobalt catalyst. Rate data was obtained from the thermo-catalytic reaction at a temperature range of 923–1023 K and varying CH₄ and CO₂ partial pressure (5–50 kPa). The rate data was significantly influenced by the changes in the reaction temperature as well as the CH₄ and CO₂ partial pressure. To estimate the kinetic parameters, the rate data were fitted with five Langmuir-Hinshelwood kinetic models. The discrimination of the kinetic models using different parameters revealed that the Langmuir-Hinshelwood kinetic model with the assumption of CH₄ being associatively adsorbed on a single and CO₂ being dissociative adsorbed with bimolecular surface reaction best described the rate data. The analysis of the kinetic model using a non-linear regression solver results in activation energies of 15.88 kJ/mol, 36.78 kJ/mol, 65.51 kJ/mol, and 41.08 kJ/mol for CH₄ consumption, CO₂ consumption, H₂ production, and CO production, respectively. The thermo-catalytic reaction was influenced by carbon as indicated by the rate of carbon deposition which was mainly caused by methane cracking. The reaction pathway for the thermo-catalytic conversion of the CH₄ and CO₂ over the alpha-alumina supported cobalt catalyst can best be described as by CH₄ associative adsorption on the alpha-alumina supported cobalt catalyst single site and CO₂ dissociative adsorption with bimolecular surface reaction.     

Laminar burning velocities,Markstein lengths,and flame thickness of liquefied petroleum gas with hydrogen enrichment

In this paper, experimental data of laminar burning velocity, Markstein length, and flame thickness of LPG flames with various percentages of hydrogen (H₂) enrichments have been presented. The experiments were conducted under the conditions of 0.1 MPa, 300 K in a constant volume chamber. The tested equivalence ratios of air/fuel mixture range from 0.6 to 1.5, and the examined LPG contains 10%–90% of hydrogen in volume. Experimental results show that hydrogen addition significantly increase the laminar burning velocity of LPG, and the accelerating effectiveness is substantial when the percentage of hydrogen is larger than 60%. Effect of hydrogen addition on diffusion thermal instability, as indicated by Markstein length, was analyzed at various equivalence ratios. Hydrogen addition decreases the flame thickness. Equivalence ratio has more dominating effect on flame thickness than hydrogen does. For the fuel with 10% LPG and 90% hydrogen, the flame thickness values are close for all equivalence ratios.     

Influence on hydrogen production of the minor components of natural gas during its decomposition using carbonaceous catalysts

In this work, the catalytic decomposition of the minor hydrocarbons present in natural gas, such as ethane and propane, over a commercial carbon black (BP2000) is studied. The influence of the reaction temperature on the product gas distribution was investigated. Increasing reaction temperatures were found to increase both hydrocarbon conversion and hydrogen selectivity. Carbon produced by ethane and propane was predominantly deposited as long filaments formed by spherical aggregates with diameters on the order of nanometres. Furthermore, the influence of ethane and propane on methane decomposition over BP2000 was also investigated, showing enrichment in hydrogen concentration with the addition of small amounts of these hydrocarbons in the feed. Additionally, the positive catalytic effect of H₂S on methane decomposition over BP2000 is addressed.     

Behavior and mechanisms of Ni/ScSZ cermet anode deterioration by trace tar in wood gas in a solid oxide fuel cell

In order to determine both the criterion for diagnosing the deterioration of Ni/ScSZ cermet anodes in solid oxide fuel cells (SOFCs) by tar contaminants in wood gas and the tolerance limit of tar in wood gas for such anodes, the influence of tar concentration in wood gas on anode deterioration behavior was examined by means of scanning electron microscopy. We found that the anode degradation mechanism consisted of three phenomena: the disappearance of Ni particles, the destruction of sintered ScSZ, and carbon deposition. Furthermore, the Ni particle disappearance occurred at lower tar concentrations than did sintered ScSZ destruction and apparent carbon deposition. Therefore, we propose that the disappearance of Ni particles be set as the criterion for confirming deterioration of Ni/ScSZ cermet anodes in SOFCs by tar. On the basis of this criterion, the tolerance limit of toluene in fuel gas was determined to be 3 g/Nm³ when the operating temperature, steam to carbon molar ratio, and current density were 1073 K, 1, and 0.5 A/cm², respectively. The tolerance limit for tar for the fuel cell constructed herein was one to two orders of magnitude higher than that for internal combustion engines.     

Autothermal reforming of methane to synthesis gas: Modeling and simulation

Autothermal reforming (ATR), that is the combination of non-catalytic partial oxidation and adiabatic steam reforming, is an important process to produce synthesis gas (syngas) from natural gas. The main scope of this work is proposing a mathematical model considering an autothermal reformer consisting of two distinct sections; a combustion section and a catalytic bed section. In the combustion section, temperature and composition were predicted using 108 simultaneous elementary reactions considering 28 species. The results were considered as initial conditions for the catalytic bed section. A one-dimensional heterogeneous reactor model was used for kinetic simulation of the second section. Results of the model were compared by ATR process published data.