Mol CH4 Research Articles

Techno-economic assessment of bio-hythane upgrading processes based on ionic liquids

Hythane, the blending of hydrogen (H2) and methane (CH4), is attracting attention as it could accelerate the H2 economy. H2 and CH4 can be extracted from organic material by fermentation and anaerobic digestion, respectively, but this alternative bio-hythane also contains carbon dioxide (CO2) that must be removed. This work addresses the use of Aprotic N‑Heterocyclic Anion-based ionic liquids (AHA-ILs) for bio-hythane upgrading. Three AHA-ILs ([P2228][2-CNPyr], [P2228][3-IPyra], and [P2228][4-BrIm]) were evaluated at process scale by conducting rate-based COSMO-based/Aspen Plus simulations of the upgrading processes. A wide range of operating conditions were screened by modifying key process variables such as the absorption pressure and the desorption temperature, and the bio-hythane composition. Energy and AHA-IL consumptions were analyzed together with variable operating cost (VOC). Energy demand and VOC were used to identify the Pareto optimal for each case study using a Python code. In addition, a detailed economic study was performed for the best three systems. The proposed processes are very versatile and are capable of handling bio-hythane of different compositions, being 10 %mol H2, 60 %mol CH4, and 30 %mol CO2 the most suitable for better process performance. For this case, the energy demand is about 0.51–0.56 kWh/Nm3 and VOC is about 1 cent. $/Nm3. The AHA-IL [P2228][3-IPyra] exhibited the best results for both variables. The energy requirement is in line with the minimum energy required for amine scrubbing technology, while VOC can be reduced by up to 17–48 % compared with electricity-intensive water scrubbing, pressure swing adsorption or membranes. Although higher investment is necessary, the assessed bio-hythane upgrading processes have the potential to operate around 0.1 $/Nm3, with VOC contributing about 8 % to the total cost.

Assessment of biogas and syngas production from sugarcane vinasse: A sustainable alternative for the production of renewable fuels

AbstractThe increasing demand for renewable energy sources as a substitute for fossil fuels has driven researchers to develop sustainable processes for biomass energy reuse in biofuel production. Based on this premise, the present study aimed to simulate the production process of synthesis gas (syngas) from vinasse, a by‐product of the sugar and alcohol industry, highlighting the applicability of this gas in transitioning toward a more renewable and sustainable energy future. The simulation was conducted in four distinct stages using the Aspen HYSYS® software. The first stage involved obtaining hydrated ethanol from sugarcane juice, followed by anaerobic digestion of vinasse to produce biogas. The third stage involved purifying the biogas to obtain biomethane. Finally, the simulation of steam methane reforming was performed to generate syngas. The modeling and simulation results demonstrated the feasibility of the process, as it generated 20.68 Nm3 of biogas (~55% vol CH4 and 45% vol CO2) per 1 Nm3 of vinasse, corresponding to 11.66 Nm3 of biomethane (~96.5% mol CH4), which aligns with national regulatory standards and the literature presented. Regarding syngas, both evaluated configurations yielded satisfactory results. The first configuration resulted in syngas with an H2/CO molar ratio of three, making it a viable source of pure hydrogen and a raw material for biofuel production, such as dimethyl ether and methanol. The second configuration, with an H2/CO molar ratio of two, holds great potential for its application in the synthesis of liquid fuels (Fischer‐Tropsch), serving as a direct substitute for gasoline, diesel, and jet fuel.

Energy use of biogas through chemical looping technologies with low-cost oxygen carriers

Biogas is a renewable fuel generated in the anaerobic digestion of organic material. The expansion of biogas as a bioenergy source in the next decades leads to find new ways for its energy exploitation such as the Chemical Looping technologies. In this work, a low-cost Fe-based residue was used as oxygen carrier in two processes with biogas, namely Chemical Looping Combustion (CLC) and Chemical Looping Reforming (CLR). CLC process is focused on the energy production with CO2 capture. CLC experiments showed higher methane combustion efficiency (∼86%) than those referred in literature with other low-cost Fe-based materials. CLR process is dedicated to the production of syngas or hydrogen without CO2 emissions. Ni- or Cu-based oxygen carrier had been successfully used in order to catalyse the methane reforming. Here, the Fe-based material was also used for CLR. The biogas composition facilitated dry reforming of biogas to obtain syngas. In the dry-CLR of biogas, it was possible to reach about 55% methane conversion with a yield to syngas of 1.3 mol (CO + H2)/mol CH4. A suitable management of the effluent gas is proposed to maximize CH4 conversion and syngas yield, which includes CO2 separation, H2 purification and CH4 recirculation. Both results confirm the potential of the energy use of biogas under these technologies and the promising results with the new oxygen carrier developed.

Enrichment of low-grade methane by dual reflux vacuum swing adsorption

Methane (CH4) has been recognized as a clean energy resource and crucial chemical feedstock. However, low-grade CH4 gases (<30%) such as coal mining gas are often released directly to the atmosphere due to limited economic values and technical challenges in enrichment, transportation and utilization, resulting in significant greenhouse gas (GHG) emissions and energy waste. In this work, a non-isothermal model of the dual reflux vacuum swing adsorption (DR-VSA) was developed on the Aspen Adsorption platform to numerically study the enrichment of low-grade CH4 from N2 gas by activated carbon (AC) and ionic liquidic zeolites (ILZ). Since the low-grade methane source was often at atmospheric pressure, feed gas was introduced to a high-pressure column (1 bar) and evacuation was operated in a low-pressure column (0.2 bar) by a vacuum pump, avoiding the utilization of compressors. Two cycle configurations with pressure reversal at the heavy end (type A) and light end (type B) were demonstrated and investigated. The parametric study of DR-VSA cycles was achieved by varying the operating variables such as the light reflux flow rate, theoretical heavy product purity and step duration. A new optimization approach was proposed and demonstrated using a dual convergence algorithm to iteratively vary operating conditions and a multiplicative score function to evaluate separation performances. Results indicated that the A-type cycle achieved better separation performance than the B-type cycle, and ILZ showed a significant superiority to the AC. In the case of 20% CH4 feed gas, the A-type process using ILZ adsorbents achieved a CH4 purity, recovery, and energy consumption of 80.2 mol.%, 95.5%, and 180.8 kJ/(mol CH4 captured), respectively. The enrichment of low-grade CH4 via the DR-VSA cycle is energy-sustainable and can generate high-quality fuel gas and GHG mitigation benefits.

Low‐Temperature and Highly Active Nickel Catalyst Based on Hydrotalcite Mg–Al for CO2 Methanation

Ni/hydrotalcite catalysts are synthesized by the coprecipitation method. Synthesis times are decreased and activation is performed with just a reductive calcination under mild conditions without the usual air‐calcination step. Compared with the other reported catalysts made of Ni/hydrotalcite, in terms of space–time yield (STY), the best synthesized catalyst is the most efficient one (STY = 137.19 mol CH4 h−1 L−1 at 300 °C) and this high efficiency is kept at low temperature (STY = 132.67 mol CH4 h−1 L−1 at 250 °C). Results show that the amount of reduced Ni, created upon the mild reduction, increases with the Ni loading and the Ni0 amount correlates with the catalytic activity. CO2 adsorption capacity remarkably increases with the Ni content but this trend does not correlate with the conversion. Surface areas, neither pore sizes, do not show a correlation with catalytic results. The most important result is the very high activity observed at temperatures below 300 °C. Characterization results indicate that the outstanding low‐temperature performance must be due to the presence of high amounts of small and reduced Ni crystallites with low interaction with the support. Developed catalysts are stable for 28 h at 300 °C.

Dissolved Methane in the World's Largest Semi‐Enclosed Estuarine System: The Estuary and Gulf of St. Lawrence (Canada)

AbstractWe report the first water‐column dissolved methane data set from the Estuary and Gulf of St. Lawrence (EGSL). Per surface‐water methane concentration and sea‐to‐air flux, the upper estuary behaved like a typical shallow macrotidal estuary, while the lower estuary and the gulf resembled outer shelf seas and ocean slopes, respectively. The EGSL emitted 166.3 (71.5–214.4) × 106 mol CH4 year−1 to the atmosphere, representing 0.3% (0.1%–0.4%) of the total emission from global estuarine environments. A net production of 11.7 × 107 mol CH4 year−1 was required to sustain this emission. Methane distributions in the upper estuary were dominated by physical mixing, while those in the lower estuary and the gulf bore characteristic subsurface maxima and deep minima shedding light on the methane consumption and production pathways. Elevated but highly variable near‐bottom methane concentrations (10.4–695.3 nmol L−1) transpired over pockmarks on the seabed of the lower estuary, inferring an upward diffusive flux of up to ∼700 mmol CH4 m2 d−1. Hypoxia in the lower estuary bottom water had little influence on methane concentrations. Lab incubations yielded methane cycling rates from a net production of 0.0068 nmol L−1 d−1 to net consumption with turnover times of 33.3–263 days. Methane in the EGSL was isotopically enriched with 13C (δ13CCH4: −40.9‰ to −27.4‰ relative to Peedee Belemnite). This study reveals that the EGSL is a smaller proportional contributor to methane emission from estuarine environments and that complex physical‐biogeochemical interactions control methane cycling and isotopic composition in this vast estuarine system.

Numerical and experimental investigation on air distributor design of fluidized bed reactor of sawdust pyrolysis

An improved biomass conversion in a lab-scale fluidized bed reactor (FBR) is achieved by optimizing the air distributor orifice size and number. Two approaches for introducing air were numerically and experimentally examined. These included perforated plate and downward orifice sparger. 3 mm and 5 mm orifice diameters, and 7, 9 and 13 holes were simulated at flow velocities of 2, 4, 6, and 8 times the minimum fluidization velocity, Umf. The simulation results revealed that increasing the orifice number has a positive effect on gas holdup, particularly for the perforated plate, which showed a uniform distribution of bubbles. The sparger configuration produced larger bubbles sizes, which could lead to better recirculation of solid flux, while stagnant particle zones were observed at the lower section of both distributors.A pyrolysis unit is also inserted at the top of freeboard of the FBR. For perforated plate with 6Umf, the pyrolysis process achieved thermal and cold gas efficiencies of 82.91% and 52.03%, respectively, while combustible gases with 41.6%mol CO, 8.7%mol CH 4 and 2.17%mol HC, were obtained. For sparger pipe and 6U mf _sp, 35.33 ppm NOx and 111 ppm SO 2 were measured in flue gas from combustion process at bed region.

Pilot scale assessment of methane capture from low concentration sources to town gas specification by pressure vacuum swing adsorption (PVSA)

Methane (CH4) is the second largest contributor to anthropogenic greenhouse gas (GHG) emissions. The separation of CH4 from nitrogen (N2) is crucial for the capture of CH4 from low concentration sources, such as coal seam gas, to reduce GHG emissions. Pressure vacuum swing adsorption (PVSA) provides a flexible and scalable method for CH4/N2 separation. In this work, a novel adsorbent (ILZ) was used in a 112 kg scale PVSA pilot facility to test the feasibility of separating CH4 from low concentration sources (4.7–44.5%). A product purity of 44.5% CH4 and a methane recovery of 81% were achieved from a feed gas containing just 4.7% CH4 via a 3-stage PVSA process. Such a product gas can then be transported using pipelines and used for either power generation or 4T town gases in China. The total energy consumption was 133 kJ per mol CH4 captured, which is 85% lower than its heating value (~880 kJ/mol). This study demonstrates that the capture of CH4 from large but low concentration sources incentivises GHG emissions reduction.

Optimization and analysis of syngas production from methane and CO2 via Taguchi approach, response surface methodology (RSM) and analysis of variance (ANOVA)

This study aims to figure out syngas production from methane and CO2 where the catalytic partial oxidation of methane over a rhodium-based catalyst bed in a Swiss-roll reactor is explored. The syngas yield from the best combination of gas hourly space velocity (GHSV), oxygen-to-methane molar ratio (O2/C ratio), and CO2-to- O2 molar ratio (CO2/O2 ratio) is acquired by a two-stage optimization, namely, the Taguchi approach followed by response surface methodology (RSM). In the first stage, the Taguchi approach suggests that the influences of the factors on the syngas yield are ranked by O2/C ratio > CO2/O2 ratio > GHSV, and the maximum syngas yield is 2.191 mol∙(mol-CH4)−1. Thereafter, the ranges of the three operating parameters are narrowed, and RSM and analysis of variance are used in the second stage to obtain a more precise optimization. In this stage, the significance of the regression coefficients indicating that GHSV and the combination of GHSV and O2/C ratio are pronounced. Based on the Box-Behnken experimental design, RSM analysis leads to the maximum syngas yield of 2.304 mol∙(mol CH4)−1, lifting the syngas yield by 5.15% in the second stage. These results reveal that the syngas yield from the two-stage optimization (Taguchi + RSM) is more efficient than from the single-stage.

Methanol-linked synergy between aerobic methanotrophs and denitrifiers enhanced nitrate removal efficiency in a membrane biofilm reactor under a low O2:CH4 ratio

Nitrate removal efficiency of aerobic methane oxidation coupled with denitrification (AME-D) process was elevated by enhancing the methanol-linked synergy in a membrane biofilm reactor (MBfR) under a low O2:CH4 ratio. After 140 days’ enrichment, the nitrate removal rate increased significantly from 3 to 4 mg-N L−1 d−1 to 22.09 ± 1.21 mg-N L−1 d−1 and the indicator, mol CH4 consumed/mol reduced NO3−-N (C/N ratio), decreased to 1.79 which was very close to the theoretical minimum value (1.27–1.39). The increased nitrate removal efficiency was largely related to the enhanced relationship between aerobic methanotrophs and methanol-utilizing denitrifiers. Type I methanotrophs and some denitrifiers, especially those potential methanol-utilizing denitrifiers from Methylobacillus, Methylotenera, Methylophilus and Methyloversatilis, were abundant in the MBfR sludge. Aerobic methanotrophs and potential methanol-utilizing denitrifiers were closely associated in many globular aggregates (5–10 μm diameter) in the MBfR sludge, which may have promoted the denitrifiers to capture methanol released by methanotrophs efficiently. If we assume methanol is the only cross-feeding intermediate in the MBfR, about 38–60% of the CH4 supplied would be converted to methanol and secreted rather than continuing to be oxidized. At least 63% of this secreted methanol should be utilized for denitrification instead of being oxidized by oxygen in the MBfR. These findings suggest that the nitrate removal efficiency of the AME-D process could be significantly improved.

Study of carbon dioxide and methane adsorption on carbon molecular sieves, raw and modified by waste engine oil

In this study, a carbon molecular sieve (CMS) was synthesized from walnut shells, followed by physical activation of the carbon content of the CMS. Adsorption of CO2 and CH4 onto raw and acid treated adsorbents were investigated using two sizes, 300?600 and 600?1180 ?m. The adsorbents were impregnated with two solvent mixtures of waste engine oil with kerosene and with thinner at a proportion of 1:1 at 25?C. The highest adsorption for CO2 and CH4 was obtained at the suitable size of a group of CMS(A) adsorbents, with acid treated adsorbents being more efficient than the raw adsorbents. The acid treated CMS(A-3) sample adsorbed 0.925 mol CO2 g-1 and 0.353 mol CH4 g-1. The results indicated that by decreasing the granulation size of group CMS(R) adsorbents, the adsorption capacities for CO2 and CH4 were reduced while increasing the granulation size of group CMS(A) adsorbents resulted in an enhancement in the adsorption capacity for CO2 and CH4. Moreover, acid treated adsorbents achieved enhanced adsorption capacity for CO2 and CH4. Further modifications reduced the adsorption capacity for CO2 and CH4 in impregnated adsorbents, due to a decrease in surface area, pore volume and pore size of the adsorbent.

Methanogenesis stimulation and inhibition for the production of different target electrobiofuels in microbial electrolysis cells through an on-demand control strategy using the coenzyme M and 2-bromoethanesulfonate

Electron allocation through the suppression or the stimulation of methanogenesis is critical for microbial electrolysis cells (MECs) to produce the desired target product (e.g., CH4 or H2). In this study, selective methanogenesis control using the coenzyme M (CoM) and 2-bromoethanesulfonate (2-BES) was investigated in a two-chambered MEC to evaluate the effect of CoM and 2-BES on the production of different electrobiofuels, net energy conversion efficiency and microbial community structure. Because the CoM is a crucial methyl-group carrier in the final process of methanogenesis, it was postulated that CoM would stimulate methanogenic activity at the anode, while a structural analog of the CoM (i.e., 2-BES) was expected to improve cathodic H2 yield using electrons conserved because of methanogen inhibition (electron equivalence: 8 mol e− = 1 mol CH4 = 4 mol H2). CoM injection in MECs significantly enhanced their CH4 production rate, purity, and yield by 4.5-fold, 14.5%, and 76.1%, respectively, compared to the control. Moreover, microbial community analysis indicated that Methanosaeta, the major acetoclastic methanogen, continued to dominate the microbial community but steadily decreased in relative abundance after the CoM injection. On the other hand, drastic increases in hydrogenotrophic methanogens, such as Methanoculleus and Methanolinea, were observed along with potential syntrophic acetate-oxidizing bacteria. In contrast, CH4 production in the 2-BES injected trials was significantly inhibited by 79.5%, resulting in a corresponding increase of H2 production by 145.5% compared to the control. Unlike the CoM, the microbial community did not noticeably change when 2-BES was injected, although the population size gradually decreased over time. Also, a single injection of CoM and 2-BES, even at low concentrations (500 μM), enabled the desired allocation of electrons as characterized by a high sensitivity, fast response, and negligible interference. In terms of energy conversion efficiency, methanogenesis stimulation approach resulted in higher net energy production than inhibition approach, whereas the remained electrons were not fully converted to hydrogen in case of the inhibition trial, thus producing less energy.

Petrophysical and geochemical characterization of potential unconventional gas shale reservoirs in the southern Karoo Basin, South Africa

Ten Permian black shale samples from the southern Karoo Basin (South Africa) were investigated regarding their shale gas generation potential, storage capacity and transport properties. Samples originate from a 671 m deep borehole (KZF-1), comprising the Collingham, Whitehill and Prince Albert Formations of the lower Ecca Group (Karoo Supergroup).Based on organic geochemical analyses (TOC, TS, Rock-Eval pyrolysis and vitrinite reflectance), the Whitehill Formation was deposited under anoxic marine depositional conditions and has reached high thermal maturity. The Collingham and Prince Albert Formation were deposited under suboxic to oxic conditions. The amount of total organic carbon (TOC) across all formations ranges between 0.5 and 6.1 wt.-%, and was highest for the Whitehill Formation samples. The organic matter in the different lithologies are highly overmature with vitrinite reflectance values around 4.0% VRr, and almost absent Rock-Eval S1 and S2 peaks. Peak gas generation probably occurred due to tectono-metamorphic overprinting during the Cape Orogeny (240–270 Ma).Permeability ranges from 10−22 to 10−19 m2 (1–100 nDarcy) and is lowest for the Whitehill and Prince Albert Formation. Porosity at ambient stress ranges from 4.1 to 6.3% and is highest within the Whitehill Formation. Neither permeability nor porosity show significant dependence upon induced stress. Excess sorption capacity is highest for the Whitehill Formation, nexcess10MPa ranging from 0.079 to 0.172 mmol/g. For the depth interval investigated here (671 m), the estimated total gas storage capacity (sum of free and adsorbed gas phase) of the Whitehill Formation is approximately 400 to 465 mol CH4 per m3 rock. Using a simple one-dimensional diffusion model, we calculated the potentially remaining stored amount of gas. In a modelled best-case scenario, it is assumed that dissipation of the gas only occurs through the side boundaries (fractured dykes system) whereas top and bottom are assumed to act as perfect seals. Assuming a fracture distance of 1000 m, the model predicts complete gas dissipation to take place within a period of 10−2 to 102 Ma. Regarding the peak gas generation at 240–270 Ma, the remaining shale gas potential is therefore considered extremely low.

Controls on volatile fatty acid concentrations in marine sediments (Baltic Sea)

Abstract Volatile fatty acids (VFA) are key intermediates in the degradation pathway of organic matter (OM) in marine sediments. They are products of fermentation and are utilized as substrates in the terminal steps of microbial OM mineralization, such as sulfate reduction and methanogenesis. We studied the distribution of formate, acetate, propionate and butyrate concentrations in the pore water throughout 100-m deep sedimentary sequences in the Baltic Sea. The sediments included both sulfate and methane zones and were retrieved during the Integrated Ocean Drilling Program Expedition 347. VFA concentrations were consistently low throughout the sulfate and methane zones, ranging from few hundred nanomolar to about hundred micromolar, thus pointing to efficient microbial utilization in the terminal OM mineralization steps in both zones. Concentrations of formate followed a different depth trend than the other three VFAs suggesting a different mechanistical control of the formate turnover. Calculations of the Gibbs energy reveal that acetoclastic methanogenesis is exergonic (up to −30 kJ (mol CH4)−1) throughout the sulfate zone and suggest that methanogens can potentially coexist with sulfate reducers in the sulfate zone while sharing acetate as a substrate. In the deeper methane-rich sediments, the energy yield of acetoclastic methanogenesis is generally very low (less negative than −10 kJ (mol CH4)−1). The uniformly low acetate concentrations in the methane zone suggest its active microbial turnover but the pathway from acetate to methane still remains unclear. Interestingly, acetoclastic sulfate reduction still yields at least −20 kJ (mol sulfate)−1 in the methane zone and, thus, sulfate reducers may utilize acetate as electron donor in the methane zone, which is in agreement with the earlier findings of sulfate reducers in methanogenic sediments.

Exergy Analysis on Pyrolysis Process of Oil Palm Empty Fruit Bunch

Exergy analysis is useful to evaluate the effectiveness of energy conversion process. This study is aimed to evaluate the effectiveness of oil palm empty fruit bunch conversion by pyrolysis process using the exergy analysis compared to the theoritical of the cellulose pyrolysis. The effect of pyrolysis temperature was evaluated based on the amount of selected syngas produced. The results show that Increasing the temperature of pyrolysis from 473 K until 723 K will increase the concentration of H2 and CH4, but it will reduce the concentration of CO. Based on exergy efficiency, the optimum composition of gases that can be produced in the pyrolysis process of 1 mol cellulose are 3 mol of H2, 5 mol of CO, and 1 mol of CH4 at a temperature of 723K. The maximum amount of exergy efficiency is 96.33% in the reaction 2. Based on Gibbs free energy, the maximum value of hydrogen will be produced start at temperature 628K.

Sandwiched SiO2@Ni@ZrO2 as a coke resistant nanocatalyst for dry reforming of methane

Design active and coke resistant Ni based catalysts is critical for implementation of dry reforming of methane technology. In this work, coke resistant SiO2@Ni@ZrO2 catalyst has been successfully prepared through precipitation of nickel nitrate with ammonia onto silica spheres, followed by coating with porous ZrO2 shell. Through thermal treatment in air and hydrogen, nickel nanoparticles with size of 6 nm were sandwiched between silica core and zirconia shell. The ZrO2 coated Ni catalyst exhibited a high activity of ˜13.0 mol CH4 per gram of Ni per hour for methane dry reforming at 700 °C, which is more than 6 times higher than that of SiO2@Ni catalyst under the same reaction condition. The SiO2@Ni@ZrO2 catalyst is also coke resistant as no carbon formation was observed for methane dry reforming at 700 °C for 20 h. As a comparison, carbon nanotubes formed over SiO2@Ni catalyst during dry reforming reaction with a coking rate of 0.019 g of carbon formed per gram of catalyst per hour. Operando XANES/EXAFS study of SiO2@Ni@ZrO2 catalyst confirmed metallic Ni phase during methane dry reforming from 400 to 800 °C. Theoretical calculations suggests that ZrO2 stabilized Ni clusters lowers the highest dissociation energy barrier of CH4 and CO2 by 1.37 and 2.56 eV comparing to bulk Ni, increasing dry reforming activity on SiO2@Ni@ZrO2 catalyst. Furthermore, the higher binding energy of CO2 over CH4 on SiO2@Ni@ZrO2 leads to enrichment of CO2 on catalyst surface, which mitigates coke formation.

Bimetallic Ni Pd/SBA-15 alloy as an effective catalyst for selective hydrogenation of CO2 to methane

Abstract It is very challenging but still promising to develop highly efficient heterogeneous catalysts for selective hydrogenation of CO2 to methane. Supported bimetallic Ni Pd/SBA-15 alloy catalysts with a varied ratio of Ni/Pd were prepared by one-pot wet chemical and impregnation method. A series of techniques were employed to characterize the elemental composition and alloy structure of as-synthesized Ni Pd/SBA-15 catalysts. The alloyed bimetallic Ni Pd/SBA-15 catalysts showed relatively higher catalytic activity compared with monometallic Pd or Ni-supported SBA-15 and several other published catalysts. The bimetallic catalyst with Ni:Pd atom ratio of 3:1 was most active in the formation of CH4 and yielded 0.93 mol CH4 per mol CO2 at 430 °C. This superior performance can be attributed to enhanced synergy between Ni and Pd with high dispersion of active sites.

The production of biogas from palm oil mill effluent as substrate with variation of agitation speed with fed-batch system

The purpose of this research is to determine the effect of variation of agitation speed on biogas production from palm oil mill effluent and cow dung as substrate by using modified digester fed-batch. The addition of agitation in the fermentation tank digester in this research to accelerate the contact between the microorganisms with the substrate so that the process runs more effectively. Thus biogas production with variations of agitation velocity have 90 and 102 rpm. The research is conducted by fed-batch that is the addition of substrate in fermentation tank as much as 1 liter for 2 days which aim to get optimum biogas production result. The results of this research indicate that the speed of agitation affects for biogas production. The optimum biogas production occurred at 102 rpm agitation speed after 30 days fermentation time was 26.5116% mol CH4.

Evaluation of Anaerobically Digested Biomass in Catalytic Supercritical Water Gasification for Biofuel Production

Digested water hyacinth with activated sludge as inoculum were obtained after anaerobic digestion at 35 and 45 ° C. High organic content of digested biomass were evaluated through gasification at supercritical conditions of water in the absence and presence of catalysts (KOH, NaOH, LiOH and K 2 CO 3 ) with 10 wt.% of volatile solid in feed. Supercritical water gasification of digested biomass was performed in batch reactor system at temperature and pressure ranges of 500 – 600 ° C and 350 –450 bar, respectively. The highest carbon gasification efficiency, hydrogen and methane yields were reached at 600 ° C (with samples digested at 45 ° C ) in the absence of catalyst as 84.6 ( g C in gaseous/g C in digestate) , 53.0 (mol H 2 %) and 12.5 (mol CH 4 %), respectively. High organic content of digested biomass was converted by supercritical water gasification to hydrogen and methane rich gas, and aqueous products (aliphatic hydrocarbons, phenol, substituted phenols, N-heterocyclic, substituted N-heterocyclics, and substituted benzene) that can be evaluated as platform chemicals.

CO2 activation by methane in a dual-bed configuration via methane cracking and iron oxide lattice oxygen transport – Concept and materials development

In this work we describe a novel process configuration for CO2 activation into CO via methane cracking. This is achieved in a two-reactor configuration by circulating supported iron oxide/iron particles with deposited carbon between the two reactors. Thermodynamic equilibrium calculations indicate that reactor configurations with counter-current gas-solids flow enable a high CO yield and concentration in the product gas. With both reactors in counter-current flow at 850 °C the potentially achievable production of CO is estimated at 3.7 mol CO per mol of CH4 with 84% purity in endothermal operation and 2.7 mol CO per mol of CH4 with 88% purity in autothermal operation. Fe/support composite materials are developed for this application to fulfill the function of oxygen transport between the two reactors and serve as a substrate for solid carbon formation. Fe/BaZr0.9Y0.1O3−δ (BZY) composites exhibit rapid reduction kinetics with H2 that we ascribe to mixed-ionic-electronic conduction imparted by in-situ iron doping of the BZY support. In addition, the high proton conductivity of this support results in high CH4 decomposition rates to form solid carbon and hydrogen, likely due to the acceleration of hydrogen abstraction from the methyl group on its surface. This mixed conductivity thus results in unique properties that can be exploited in such CH4 decomposition process configurations.