Syngas Research Articles

Coordination-Driven Self-Assembly of Complexes Constructed from Two Helical Ligands: Synthesis, Structures, and Selective Gas Adsorption Properties.

Two helical ligands (L1 and L2) were designed and synthesized by a Schiff base condensation reaction. Eight complexes, {[Zn(L1)I2]·H2O}n (1), [Cd2(L1)2I4(CH3OH)2] (2), [Hg2(L1)2I4] (3), [Ag(L1)NO3]n (4), [Ag2(L1)2(NO3)2DMSO]·H2O (5), {[Zn2(L2)2Cl4]·2CHCl3}n (6), {[Ag(L2)]·NO3}n (7), and {[Ag(L2)NO3]·CH3OH}n (8), were synthesized and characterized based on these two ligands. The crystal structures show that both Schiff base compounds exist as racemic ligands with equal amounts of P- and M-helicity, and the assembly of these racemic ligands with metal ions can lead to homochiral or heterochiral complexes via a chiral self-recognition or self-discrimination process. Complexes 2, 3, and 5 exist as heterochiral metallomacrocycles with a figure-eight conformation. Complexes 1, 6, and 8 exist as one-dimensional (1D) homochiral helical chain coordination polymers, while complexes 4 and 7 exist as 1D heterochiral helical chain coordination polymers. Furthermore, gas and vapor adsorption measurements show that all of the synthesized complexes exhibit good selective adsorption capacities toward methanol and ethanol vapor over N2, H2, and O2.

Bimetallic Ru–Pd supported on CeO2 for the catalytic partial oxidation of methane into syngas

A series of monometallic Ru, Pd, and bimetallic Ru–Pd catalysts loaded on CeO2 support have been prepared via mechanochemical and conventional incipient wetness impregnation methods and used in the partial oxidation of methane (POM) to obtain synthesis gas (H2 and CO). The influence of the preparation method, the order of addition of the metals, the Ru:Pd metal ratio, and the milling energy and time for samples prepared by the mechanochemical method, have been evaluated between 300 and 600 °C. The results revealed that bimetallic Ru–Pd/CeO2 catalysts outperform monometallic Ru–CeO2 and Pd–CeO2 for POM, both in terms of catalytic activity and stability. Additionally, the bimetallic Ru–Pd/CeO2 catalysts prepared by ball milling produced syngas at a much lower temperature compared to the conventional catalysts prepared by incipient wetness impregnation. Raman spectroscopy, temperature programmed reduction (H2–TPR), X–ray photoelectron spectroscopy (XPS) and high–resolution transmission electron microscopy (HRTEM) have been used to characterize the catalysts before and after reaction.

Study on the effect of hydrocarbon structure on the reactivity of the three-way catalytic converter

The effect of hydrocarbon structures on reduction of nitric oxide and oxidation of carbon monoxide and hydrocarbons on the palladium-rhodium catalyst supported on aluminum-cerium-zirconium oxide was examined with fixed-bed flow reactor using synthetic gas. As regards olefinic hydrocarbons, the lower the number of carbon atoms, the higher the rate of reduction of nitric oxide, the lower the number of carbon atoms, the greater the rate of oxidation of hydrocarbons and carbon monoxide. Olefinic hydrocarbons have a π bond and are highly adsorbed on catalytic sites. Consequently, it may be hypothesized that if the number of carbon atoms increases, the adsorption ability becomes too high and the reactivity of the hydrocarbons decreases. On the other hand, for paraffinic hydrocarbons, the greater the number of carbon atoms, the greater the rate of reduction of nitric oxide, and the more carbon atoms there are, the higher the oxidation rate of the hydrocarbon. In the case of paraffinic hydrocarbons, there are only σ bonds and less adsorption on the catalyst site, it is therefore assumed that the greater the number of carbon atoms, the greater the reactivity of the hydrocarbon. The results of the effects of these hydrocarbon structures on the overall three-way catalytic reaction activity provide an indicator of the development of new catalysts.

Dynamic Adsorption of H2S onto a Goethite-Based Material.

The use of adsorption technology to remove H2S from synthetic gas (H2S and N2) using a goethite-based adsorbent was investigated. The influence of the H2S feed concentration (150-600 mg), the adsorbent dosage (1-4 g), and the gas flow rate (210-540 cm3/min) on the breakthrough curves and H2S adsorption on the adsorbent at the breakthrough point was investigated. Dynamic column experiments were performed to provide data for the theoretical models and to verify the performance of the system in the adsorption process. The theoretical models used in the present work were found to predict the adsorption breakthrough performance reasonably well.

Potential Application of Canola Hull Fuel Pellets for the Production of Synthesis Gas and Hydrogen

The production of biopellets from agricultural residues is an effective method to overcome the expected shortage in the supply of fuel pellets in the future. This work focused on the new potential applications of fuel pellets to produce liquid and gas fuels through thermochemical and hydrothermal biomass-to-gas technologies. The outcomes also provide a basis to compare the effects of steam and hydrothermal gasification techniques on the properties of product and byproduct, as well as their potentials. For steam gasification, the syngas yield increased from 10.7 to 27.8 mmol/g (on a dry and ash-free basis) by a rise in the gasification temperature at a constant steam-to-biomass ratio. In the case of hydrothermal gasification, there was no carbon monoxide, and hydrogen was the main gas product, and with an increase in the temperature, the hydrogen yield rose from 0.4 mmol/g to 3.17 mmol/g with temperatures from 350 to 650 °C. CO had the largest share in the gas product from steam gasification, which was between 23.3 and 31.3 mol%. The range of the molar ratio of H2/CO for the steam gasification (1.13–1.40) showed the necessity of the further purification of gas products to utilize them as feed for liquid fuel production using the Fischer–Tropsch process. Examination of the mineral content of biochar that remained after the gasification techniques showed large essential elements in them compared with heavy metals, which shows potential for soil amendment. The results highlight the possibility of converting an agricultural residue into a value-added product with potential applications in the energy sector and agriculture.

Synthesis and characterization of molybdenum trioxide with an orthorhombic crystal structure for supercritical water gasification application

Supercritical water (SCW) catalytic gasification is promising for the production of synthetic gas from biomass. However, maintaining the activity of heterogeneous catalysts under high pressure and hydrothermal conditions is the most important. Therefore, this study investigates the activity and stability of molybdenum trioxide (MoO3) for the gasification of formaldehyde in SCW. MoO3 with an orthorhombic crystal structure was synthesized by the sol-gel method and tested in the gasification of formaldehyde in SCW. Structural and morphological changes of MoO3 with supercritical water gasification were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), a scanning electron microscope (SEM), N2 adsorption-desorption, thermogravimetric analysis (TGA), temperature-programmed desorption of oxygen (O2-TPD), temperature-programmed desorption with ammonia (TPD-NH3), and temperature-programmed reaction of hydrogen (H2-TPR). The XRD results show that MoO3 has an orthorhombic crystal structure. Its structure changed to a monoclinic structure upon gasification with supercritical water. SEM images showed that the rod-shaped catalyst particles transformed into thin planar plates at high pressure and temperature conditions in the presence of carbonaceous compounds. H2-TPR and XRD results showed that MoO3 was reduced to MoO2 during SCW gasification with hydrogen and carbonaceous compounds. Moreover, the oxygen stability of the catalyst changed during SCW gasification, and active oxygen species formed on the surface of the catalyst. Compared with homogeneous gasification, in the presence of the MoO3 catalyst, the fractions of CO2 and CH4 increased to 50% and 8.4%, respectively, and the fractions of H2 and CO decreased from 37.8% and 11.8% to 32.2% and 3.9%, respectively, due to the changed decomposition mechanism. Orthorhombic molybdenum oxide can be proposed as a promising catalyst for methane production.

Coupling Gasification with Liquid Organic Hydrogen Carrier Storage: Aspects of Dynamization of Biomass‐Based Power Production

AbstractGasification of biomass can yield synthesis gas for power generation. A problem is the poor adjustability to changes in load. To improve dynamics, integration of a hydrogen storage system based on liquid organic hydrogen carriers has been evaluated. Coupled with a gasification unit, it can remove hydrogen from the synthesis gas. If the power demand is high, dehydrogenation releases hydrogen to increase the energy content of the gas mixture. The proposed concept is discussed regarding three aspects: dynamics, energy demand, and reliability. Especially, if a load change is not a very short peak, the ability of the system to adjust is improved. To achieve this, energy input is needed, which lowers the overall efficiency. Furthermore, attention should be paid to protecting the catalysts from poisoning.

Energy-saving, environmentally friendly production of hydrogen from the hydrocarbon feed

A comparative analysis of technologies for hydrogen production from hydrocarbons is carried out. A diagram of a small-scale package unit for hydrogen production based on the partial oxidation of hydrocarbons is presented. The paper describes the developed design, physical model, and layout of a syngas generator. The technical characteristics of the gas generators make it possible to create transportable modules for the production of synthesis gas with unit capacity from 200 to 10,000 ncm3/hour. The following concentration of hydrogen was experimentally achieved at the output of the catalysis block of the installation in terms of dry hydrogen-containing gas: for diesel fuel-oxygen components – 60–62 vol%, for methane-oxygen components – 68–70 vol%. The correctness of the adopted technical solutions was confirmed by the creation of a full-scale sample of the operating mobile unit with a capacity of up to 300 ncm3/hour It also presents the results of studies on steady-state modes of partial oxidation in the combustion chamber of the gas generator for various fuel/oxidant combinations. The developed method of hydrogen production, used in the unit, makes it possible to significantly reduce capital investments and energy consumption in operation and almost eliminate harmful emissions into the environment.

Two stage co-pyrolysis improvement to produce synthetic oil and gas simultaneously from mixed municipal solid waste using natural dolomite-based catalyst

Among the two pyrolysis methods, the two-stage type gives better results than the single-stage in converting mixed municipal solid waste (MMSW) into synthetic oil (O-Synthec) and gaseous products (G-Synthec). However, the double energy supply for the heating process in the first and second reactors needs to be considered in terms of efficiency. Therefore to complete the research of two-stage pyrolysis, this study improvised a two-stage co-pyrolysis process supported by a Long Fixed-Bed Catalytic Insert (LFCi) attached to the inner wall of the reactor. In the test, 500 g of MMSW with 8 components was fed into a reactor with LFCi containing a dolomite natural catalyst. The co-pyrolysis process was carried out at a temperature variation of 400–550 °C, and the best results obtained were used as a reference for variations in reaction time from 120 to 210 min. Based on the physical and chemical properties, the co-pyrolysis O-synthec and G-synthec products were subjected to Gas Chromatography Mass Spectrometry (GCMS) analysis and American Society for Testing and Material (ASTM) standard to physical properties test. The results were compared with those of one-stage pyrolysis, direct catalytic and without catalyst. Based on the results, the presence of LFCi in the reactor had a significant effect in increasing the mass yield of O-Synthec at 550 °C with a residence time of 150 min. An increase of 20,14% and decrease 16.77% of O-Synthec and G-Synthec respectively were achieved compared to the uncatalyzed, although the presence of 15.5% peak area oxygenated fractions and 3.0% peak area acid needs to be considered as it impacts the calorific value. The dominant aromatic compound indicates that O-Synthec has similarities with conventional gasoline fuel. Meanwhile, the non-condensable gas (G-Synthec) produced contains a concentration of hydrocarbon compounds in the distribution of C1–C12, which is dominant with tripropylaluminum, formic acid and butenes. The high content of formic acid and tripropylaluminum compounds in G-Synthec must be considered because they are very corrosive and hazardous to the environment.

Forced Periodic Operation of Methanol Synthesis in an Isothermal Gradientless Reactor

AbstractMethanol synthesis from synthesis gas with heterogeneous Cu/ZnO/Al2O3 catalysts in an isothermal gradientless reactor is described. In a theoretical study, the potential of forced periodic operation (FPO) for improving reactor performance in terms of methanol production rate and methanol yield is explored. The approach is based on a detailed kinetic model and combines nonlinear frequency response (NFR) analysis with rigorous numerical multi‐objective optimization. Optimal steady‐state operation is compared with optimal forced periodic operation for a given benchmark problem with and without inert nitrogen in the feed. Further, the significant influence of the saturation capacity of the solid phase on the dynamic behavior in response to step changes and periodic input modulations is studied.

Synthesis and optical hydrogen gas sensing properties of ZnO/WO3 composite films with hierarchical structure

In this paper, the ZnO/WO3 composite films with hierarchical structure were successfully prepared by the colloidal template method and solvothermal method. The ZnO/WO3 composite films exhibit ordered porous ZnO and slender WO3 nanowires structure. The pore diameter of the porous ZnO layer is ∼1070 nm. The diameter and length of WO3 nanowires are 7–16 nm and 450–520 nm, respectively. After Pt catalyst was loaded by magnetron sputtering, the ZnO/WO3 composite films exhibit a shorter response time of 11.2 s to 4 % H2 at room temperature, which is half of that of WO3 nanowire films reported in the exist literatures. It’s attributed to the high aspect ratio of WO3 nanowires and open porous structure that lead to excellent synergistic effects for the diffusion of H2 gas and H atoms. The transmittance of ZnO/WO3 composite films can decrease by 61.8 % at 1500 nm wavelength. And the ZnO/WO3 composite films can detect different H2 concentrations at room temperature.

Internal association between combustion behavior and NOx emissions of pulverized coal MILD-oxy combustion affected by adding H2O

In practical pulverized coal Moderate or Intense Low-oxygen Dilution oxy-fuel combustion (MILD-oxy) process, the accumulation of steam results in the recycled flue gas consisting of highly concentrated H2O, particularly under wet flue gas recirculation. This work numerically studies the individual effect of H2O on the turbulence-chemistry interaction, aiming at revealing the internal association between combustion behavior and NOx emissions. Results show that H2O addition reduces the flame temperature by enhancing the radiative heat transfer. The extremum values of turbulent Damkӧhler number (Dat,max) and Karlovitz number (Kamin) are reduced and increased, respectively, denoting the slow-chemistry feature (Dat < 10 and Ka >> 1) in the reaction zone. With the promoted H2O level, the heterogeneous reactions on the char surface tend to be governed by kinetics due to the reduced reaction rate under low flame temperature. The gasification reaction is enhanced to produce more synthesis gas, and the burnout of char particle is prolonged. The in-furnace NO formation is inhibited under low Dat,max, while the NOx emissions are reduced directly due to the enhanced gasification reaction under low maximum surface Damkӧhler number (Das,max). The addition of H2O essentially establishes a moderate diffusion and reaction process under the kinetics-controlled regime to obtain the uniform thermal field and low-NOx emissions.

Bio-oil gasification for production of the raw gas as ammonia syngas

Biofuels can significantly reduce greenhouse gas emissions, create new jobs and reduce our dependence on fossil fuels. A bio-oil gasification-reforming system for production of the raw gas for ammonia synthesis was designed. The effects of gasification temperature, methane to bio-oil ratio, equivalence ratio (ER) and water to bio-oil ratio on the raw gas composition and its H2/N2 ratio were examined. The uniform design experiment were arranged to find some typical cases, in which the raw gas with H2/N2 ratio of 3.0 was generated from this gasification system, and the material balance of these typical cases were calculated. finally, the optimal case was selected among those typical cases The results showed that the raw gas with optimal H2/N2 ratio of 3.0 can be produced by adjusting the above-mentioned operating parameters in this gasification-reforming system, and the optimal case were performed under operational parameters including gasification temperature of 1005℃, methane to bio-oil ratio of 0.08, ER of 0.12, water to bio-oil ratio of 1.78. A small amount of methane was necessary for the preparation of the raw gas as ammonia syngas, therefore, the ammonia produced from the raw gas can be called bio-ammonia.

Investigation on carbon deposition deactivation of Fe-Ni-Ca/Al2O3 catalyst under volatiles reforming of biomass pyrolysis

The changes in the carbon deposition behavior of biomass pyrolysis volatile fraction reforming process with different catalysts (Fe, Fe-Ni, Fe-Ni-Ca) were investigated in a laboratory-scale fixed-bed reactor. The pyrolysis experiments were carried out on wheat straw (WS) at different temperature, observing changes in the experimental conditions after the addition of catalysts which were characterized by XRD, SEM-EDS and TEM analyses. The experimental results indicated that the temperature and catalyst had an effect on the product distribution, syngas composition, and the generation of carbon deposition. Both the increase of temperature and the addition of additives can reduce the formation of heavy oil and increase the yield of the synthesis gas. The addition of Ni to the A@ 5Fe catalyst as an additive increasing the transfer of Coke1 to Coke2, the addition of Ca to this catalyst resulted in an increase in the amount of Coke2 due to the formation of CaCO3, which also led to an increase in catalyst activity. The carbon deposition was divided into two parts to investigate the formation mechanism, providing some theoretical basis for extending the reactor life and catalyst activity.

Influence of Synthesis Gas Composition on Internal Combustion Engine Parameters

Abstract The presented article deals with the possibility of using synthesis gas produced from municipal waste in a spark-ignition combustion engine intended for a micro-cogeneration unit. The subject of investigation is the effect of fuel composition on the internal parameters of the internal combustion engine analysed from the course of pressure in the cylinder. The analysis shows that, in general, increasing the proportion of hydrogen increases the pressure rise rate as well as the rate of heat release in the cylinder. The presented results will serve to understand the processes taking place in the combustion engine as well as the importance of the composition of synthesis gas produced from renewable energy sources in order to achieve the highest possible energy and economic evaluation in the cogeneration unit.

Multicomponent vapor-liquid equilibrium measurements and modeling of triethylene glycol, water, and natural gas mixtures at 6.0, 9.0 and 12.5 MPa

Triethylene glycol (TEG) is commonly used for natural gas dehydration, and with subsea processing facilities on the rise, an increasing interest is being shown in complex phase equilibria involving petroleum fluids and polar compounds. In this study, examples of such phase equilibria have been studied. New measurements for multicomponent vapor-liquid equilibrium (VLE) of TEG/Water/Natural Gas systems have been performed at pressures ranging from 6.0 MPa to 12.5 MPa and temperatures in the range 15 °C to 40 °C. Two types of natural gas, a Synthetic Gas (xCH4=0.62) and a Real Gas (xCH4=0.92), were mixed with an aqueous TEG solution, with TEG weight percentages ranging from 95 wt.% to 99 wt.%. Glycol in gas (y1), water in gas (y2), and gas solubility in liquid (xNG) were measured with relative experimental uncertainties below 32%. Since the systems are highly associating, the Cubic-Plus-Association (CPA) equation of state (EoS) was selected to model their phase behavior . Different association schemes (4C, 4F, 5F, 6F and 5C) were tested for TEG, and the classical 4C scheme is shown to perform best. The CPA EoS performed in general terms well, considering the number of components in the systems, the associated complexities, and high measurement uncertainty for such low concentrations (<1 ppm) in the gas phase. Furthermore, the content of N2, CO2, CH4 and ethane were modelled in the liquid phase at various conditions.

Simulation of the operation of a gas turbine installation of a thermal power plant with a hydrogen fuel production system

The growth in demand for the production of heat and electricity requires an increase in fuel consumption by power equipment. At the moment, the most demanded thermal equipment for construction and modernization is gas turbine units. Gas turbines can burn a variety of fuels (natural gas, synthesis gas, methane), but the main fuel is natural gas of various compositions. The use of alternative fuels makes it possible to reduce CO2 and NOx emissions during the operation of a gas turbine. Under conditions of operation of thermal power plants at the wholesale power market, it becomes probable that combined cycle power units, designed to carry base load, will start to operate in variable modes. Variable operation modes lead to a decrease in the efficiency of power equipment. One way to minimize or eliminate equipment unloading is to install an electrolysis unit to produce hydrogen.In this article the technology of “Power to gas” production with the necessary pressure at the outlet of 30 kgf/cm2 (this pressure is necessary for stable operation of the fuel preparation system of the gas turbine) is considered. High cost of hydrogen fuel during production affects the final cost of heat and electric energy, therefore it is necessary to burn hydrogen in mixture with natural gas. Burning a mixture of 5% hydrogen fuel and 95% natural gas requires minimal changes in the design of the gas turbine, it is necessary to supplement the fuel preparation system (install a cleaning system, compression for hydrogen fuel). In addition, the produced hydrogen can be stored, transported to the consumer. For the possibility of combustion of a mixture of natural gas and hydrogen fuel in a gas turbine the methodology of calculation of thermodynamic properties of working bodies developed by a team of authors under the guidance of Academician RAS (the Russian Academy of Sciences) V.E. Alemasov has been adapted, resulting in a program that allows to obtain an adequate mathematical model of the gas turbine. The permissible range of the working body temperature is limited to 3000 K. This paper presents the developed all-mode mathematical model of a gas turbine.On the basis of mathematical modeling of a gas turbine, a change in the main energy and environmental characteristics is shown depending on the composition of the fuel gas. Adding 5% hydrogen to natural gas has little effect on the gas turbine air treatment system, the flow rate remains virtually unchanged. CO2 emissions decrease, but there is an increase in the amount of H2O in the turbine exhaust gases.

Agglomeration of Fe/SBA-15 with clays for Fischer–Tropsch synthesis

The huge contribution of the transportation sector to GHG emissions motivates the search for a sustainable and renewable alternative to fossil fuels. Fischer–Tropsch synthesis (FTS) is a catalytic process to convert synthesis gas into hydrocarbons for the production of fuels and chemicals. However, further development of FTS catalysts is still needed in order to make the process based on renewables economically viable. In this work mesoporous Fe/SBA-15 was synthesized. Two natural clays (hectorite and kaolin) were used as catalyst binders and promoters. The agglomeration with the clays did not disrupt the mesoporous structure of Fe/SBA-15. The effect of the clay and the effect of the catalyst form (i.e. powder or granules) on the FTS performance was investigated at 280 °C and 20 bar. Comparing catalysts agglomerated with kaolin and hectorite, better performance was observed for catalysts containing kaolin. Catalysts in the form of powder showed better performance in CO converted per gram of iron than the same catalysts in the form of granules. Granular catalysts promoted the formation of gaseous products.

Activity and Structure of Nano-Sized Cobalt-Containing Systems for the Conversion of Lignin and Fuel Oil to Synthesis Gas and Hydrocarbons in a Microwave-Assisted Plasma Catalytic Process

In this study, we present the results of lignin and fuel oil conversion to hydrogen, synthesis gas, and liquid hydrocarbons in the presence of nano-sized cobalt-containing systems in a microwave-assisted plasma catalytic process. The deposition of a small amount of cobalt on lignin increases its microwave absorption capacity and provides plasma generation in the reaction zone. The role of Co-containing particles in the above catalytic reactions is probably to activate the carbon bonds of lignin, which substantially increases the microwave absorption capacity of the system as a whole. The subsequent use of the cobalt-containing residue of lignin conversion as a catalytic system and MWI-absorbing material results in active fuel oil pyrolysis in a plasma catalytic process to afford gaseous and liquid hydrocarbons. In the plasma catalytic pyrolysis, fuel oil conversion is probably accompanied by the conversion of the organic matter of the residue and agglomeration of cobalt oxide particles.

A Systematic Approach to Study Complex Ternary Co-Promoter Interactions: Addition of Ir, Li, and Ti to RhMn/SiO2 for Syngas Conversion to Ethanol

The direct conversion of synthesis gas could open up economically viable routes for the efficient production of ethanol. RhMn/SiO2 represents one of the most active systems reported thus far. Potential improvements were reported by added dopants, i.e., Ir, Ti, and Li. Yet, combining these elements leads to contradicting results, owing to the complexity of the interactions in a multi-promoted system. This complexity is often encountered in heterogeneous catalysis. We report a systematic data-driven approach for the assessment of complex multi-promoter interactions based on a combination of design-of-experiment, high-throughput experimentation, statistical analysis, and mechanistic assessment. We illustrate this approach for the system RhMn/SiO2 promoted with Ir, Li, and Ti. Using this approach, we investigate the impact of promoters’ interactions on a mechanistic level. Our analysis depicts the means to learn hidden correlations in the performance data and, additionally, high performance for ethanol yield for the RhMnIr/SiO2 catalyst. The method presented outlines an efficient way to also elucidate co-promoter interactions in other complex environments.