Would methanol formed from CO2 from the atmosphere give the advantage of hydrogen at lesser cost?

Our energy situation is called precarious because of the frequent changes in reports on the date of Hubert’s peak and the danger of oncoming global warming. Further, there is the several decades needed to build a new system of energy production and distribution. This paper describes various likely methods which we could use. It concludes that methanol synthesized from hydrogen and CO₂ removed from the atmosphere allows this substance to be used in our situation with zero net CO₂ results. It would then remove the problem of the cost of storage, transportation and reconversion to electricity which hangs on to the use of hydrogen itself. On the other hand its use would provide, in practice, a “liquid form” of hydrogen.     

Hydrogen production and CO2 fixation by flue-gas treatment using methane tri-reforming or coke/coal gasification combined with lime carbonation

The production of hydrogen and the fixation of CO₂ can be achieved by treatment of flue gases derived from fossil fuel fired power plants via catalytic methane tri-reforming or by coal gasification in the presence of CaO. A two-step process is designed to be carried out in two reactors: a) a catalytic gasifier or steam-reformer, operating exothermally at 900–1000 K, with inputs of the flue gas, a carbonaceous source, steam and air, as well as CaO from the calciner, and outputs of H₂, and of “spent” CaCO₃ to the calciner; b) a calciner, operating endothermally at 1100–1300 K, with inputs of spent CaCO₃ from the gasifier, make-up fresh CaCO₃, and outputs of CO₂, as well as of CaO, partly recycled to the gasifier and partly processed in a cement plant. Thermochemical equilibrium calculations along with mass/energy balances indicate that for flue-gas treatment by tri-reforming, CO₂ emission avoidance of up to ∼59% and fossil fuel savings of up to ∼75% may be attained when concentrated solar energy is supplied as high-temperature process heat for the calcination step, all relative to conventional H₂ production by coal gasification. If instead fossil fuel would be used to drive the calcination step, the CO₂ emission avoidance and the fuel savings would be only 20% and 67%, respectively. Estimated annual H₂ production from a coal-fired 500 MWe burner by the proposed flue-gas treatment using either CH₄-tri-reforming or coal gasification would amount to 0.7 × 10⁶ or 0.6 × 10⁶ metric tons H₂, respectively. Estimated fossil fuel consumption for H₂ production by tri-reforming or coke gasification would be 149 or 143 GJ fuel/ton H₂.     

Hydrogen production through sorption-enhanced steam methane reforming and membrane technology: A review

With the rapid development of industry, more and more waste gases are emitted into the atmosphere. In terms of total air emissions, CO₂ is emitted in the greatest amount, accounting for 99 wt% of the total air emissions, therefore contributing to global warming, the so-called “Greenhouse Effect”. The recovery and disposal of CO₂ from flue gas is currently the object of great international interest. Most of the CO₂ comes from the combustion of fossil fuels in power generation, industrial boilers, residential and commercial heating, and transportation sectors. Consequently, in the last years’ interest in hydrogen as an energy carrier has significantly increased both for vehicle fuelling and stationary energy production from fuel cells. The benefits of a hydrogen energy policy are the reduction of the greenhouse effect, principally due to the centralization of the emission sources. Moreover, an improvement to the environmental benefits can be achieved if hydrogen is produced from renewable sources, as biomass.     

Analysis of potential energy saving and CO2 emission reduction of home appliances and commercial equipments in China

China has implemented a series of minimum energy performance standards (MEPS) for over 30 appliances, voluntary energy efficiency label for 40 products, and a mandatory energy information label that covers 19 products to date. However, the impact of these programs and their savings potential has not been evaluated on a consistent basis. This paper uses modeling to estimate the energy saving and CO₂ emission reduction potential of the appliances standard and labeling program for products for which standards are currently in place, under development or those proposed for development in 2010 under three scenarios that differ in the pace and stringency of MEPS development. In addition to a baseline “frozen efficiency” scenario at 2009 MEPS level, the “Continued Improvement Scenario” (CIS) reflects the likely pace of post-2009 MEPS revisions, and the likely improvement at each revision step. The “Best Practice Scenario” (BPS) examined the potential of an achievement of international best-practice efficiency in broad commercial use today in 2014. This paper concludes that under “CIS”, cumulative electricity consumption could be reduced by 9503 TWh, and annual CO₂ emissions of energy used for all 37 products would be 16% lower than in the frozen efficiency scenario. Under a “BPS” scenario for a subset of products, cumulative electricity savings would be 5450 TWh and annual CO₂ emissions reduction of energy used for 11 appliances would be 35% lower.     

Gadolinia-doped ceria mixed with alkali carbonates for SOFC applications: II – An electrochemical insight

Composite materials based on gadolinia-doped ceria (GDC) and alkali carbonates (Li₂CO₃-K₂CO₃ or Li₂CO₃-Na₂CO₃) are potential electrolytes for low temperature solid oxide fuel cell applications (LTSOFC). This paper completes a first one dedicated to the thermal, structural and morphological study of such compounds; it is fully focussed on their electrical/electrochemical properties in different conditions, temperature, composition and gaseous atmosphere (oxidative or reductive). The influence of the gaseous composition on the Arrhenius conductivity plots is evidenced, in particular under hydrogen atmosphere. Finally, electrical conductivity determined by impedance spectroscopy is presented as a function of time to highlight the stability of such composites over 6000 h. First results on single cells showed performance at 600 °C of 60 mW cm⁻².     

Techno-economic assessment of a synthetic fuel production facility by hydrogenation of CO2 captured from biogas

In this study, a thermodynamic and economic analysis of a synthetic fuel production facility by utilizing the hydrogenation of CO₂ captured from biogas is carried out. It is aimed to produce methanol, a synthetic fuel by hydrogenation of carbon dioxide. A PEM electrolyzer driven by grid-tie solar PV modules is used to supply the hydrogen need of methanol. The CO₂ is captured from biogas produced in an actual wastewater treatment plant by a water washing unit which is a method of biogas purification. The required power which is generated by PV panels, in order to produce methanol, is found to be 2923 kW. Herein, the electricity consumption of 2875 kW, which is the main part of the total electricity generation, belongs to the PEM system. As a result of the study, the daily methanol production is found to be as 1674 kg. The electricity, hydrogen and methanol production costs are found to be $ 0.043 kWh^?1, $ 3.156 kg^?1, and $ 0.693 kg^?1, respectively. Solar availability, methanol yield from the reactor, and PEM overpotentials are significant factors effecting the product cost. The results of the study presents feasible methanol production costs with reasonable investment requirements. Moreover, the efficiency of the cogeneration plant could be increased via enriching the biogas while emissions are reduced.     

Challenges to a climate stabilizing energy future

The paper surveys the major challenges to stabilizing the atmospheric CO₂ concentration. Climate change, and policies to deal with it, is viewed as an energy problem. The energy problem stems from the fact that no combination of carbon-free energies is currently capable of displacing fossil fuels as the main sources of the world's base load energy requirements. The paper provides rough estimates of the amount of carbon-free energy required to stabilize climate, the potential contribution of “conventional” carbon-free energies, the contribution of renewable energies, and the size of an “advanced energy technology gap”. The findings indicate that stabilizing CO₂ concentration will require a long-term commitment to research, develop, and eventually deploy new energy sources and technologies including hydrogen. The paper suggests that the role of technology is what makes stabilizing CO₂ concentration economically feasible. In this respect energy technology and economics are complementary, with advances in the former requiring something more than a reliance on market-based instruments, such as carbon taxes and emission permits. The analysis has implications for the credibility of commitments to target climate change-related factors such as CO₂ emissions.     

Wind-hydrogen utilization for methanol production: An economy assessment in Iran

This study investigates the feasibility to synthesis methanol from its flue gas and wind hydrogen. The concept is to mitigate CO₂ emission through flue gas recovery. Synthesizing methanol, on the other hand requires hydrogen at the rate of 3 kmol/kmol of carbon dioxide. Electrolysis is one method by which hydrogen can be produced cleanly from renewable source. Here it is assumed that the electrolysis unit is fed with the electricity from neighbor wind farms. Oxygen will be produced as a byproduct in electrolysis unit. However, electrolytic oxygen could be utilized for partial oxidation of methane in autothermal reactor (ATR). Onboard water electrolysis facilitates the oxygen and hydrogen storage, delivery and marketing. This study focuses on an integrated system of methanol production which enables green methanol synthesis through a system with zero carbon emission. Green methanol synthesis is comprised of CO₂ capturing and recycling along with renewable hydrogen generation. The produced hydrogen and CO₂ will be directed to methanol synthesis unit. By employing the integrated system for methanol synthesis, we could reduce the cost of using renewable energy technology.     

Photoelectrocatalytic reduction of CO2 to methanol over CuFe2O4@PANI photocathode

The present study was aimed to convert CO₂ into methanol which not only addresses the potential solution for controlling the CO₂ concentration level in the atmosphere but also offers an alternative approach for the production of renewable energy source. In this perspective, a hybrid photocatalyst, PANI@CuFe₂O₄ was synthesized, characterized and used as a photocathode for photoelectrocatalytic (PEC) reduction of CO₂ to methanol in aqueous medium at an applied potential of ?0.4 V vs NHE under visible light irradiation. The combination of PANI with CuFe₂O₄ greatly increased the PEC CO₂ reduction to methanol owing to enhance the CO₂ chemisorption capacity by the photocathode surface and at the same time facilitated the separation of photogenerated electron-hole (e^?/h⁺) pairs. The incident photon to current efficiency (IPCE) and quantum efficiency (QE) for methanol formation in PEC CO₂ reduction could be achieved as 7.1 and 24.0% respectively. The rate of formation of methanol in PEC CO₂ reduction was found as 49.3 μmol g^?1h^?1 with 73% Faradaic efficiency. Compared to photocatalytic reaction, the PEC results demonstrated that the applied potential could effectively separate the photogenerated e^?/h⁺ pairs and therefore, enhanced the PEC CO₂ reduction activity of the hybrid photocatalyst.     

Comparison of the renewable transportation fuels,hydrogen and methanol formed from hydrogen,with gasoline – Engine efficiency study

The use of hydrogen derived methanol in spark-ignition engines forms a promising approach to decarbonizing transport and securing domestic energy supply. Methanol can be renewably produced from hydrogen in combination with biomass or CO₂ from the atmosphere and flue gases. From well to tank studies it appears that hydrogen derived methanol compares favourably with liquid or compressed hydrogen both in terms of production cost and energy efficiency. Since existing well to wheel studies are based on outdated technology, this paper tries to provide efficiency figures for state-of-the-art hydrogen and methanol engines using published data and measurements on our own flex-fuel engine.     

Bio-oil steam reforming,partial oxidation or oxidative steam reforming coupled with bio-oil dry reforming to eliminate CO2 emission

Biomass is carbon-neutral and utilization of biomass as hydrogen resource shows no impact on atmospheric CO₂ level. Nevertheless, a significant amount of CO₂ is always produced in biomass gasification processes. If the CO₂ produced can further react with biomass, then the biomass gasification coupled with CO₂ reforming of biomass will result in a net decrease of CO₂ level in atmosphere and produce the chemical raw material, syngas. To achieve this concept, a “Y” type reactor is developed and applied in bio-oil steam reforming, partial oxidation, or oxidative steam reforming coupled with CO₂ reforming of bio-oil to eliminate the emission of CO₂. The experimental results show that the reaction systems can efficiently suppress the emission of CO₂ from various reforming processes. The different coupled reaction systems generate the syngas with different molar ratio of CO/H₂. In addition, coke deposition is encountered in the different reforming processes. Both catalysts and experimental parameters significantly affect the coke deposition. Ni/La₂O₃ catalyst shows much higher resistivity toward coke deposition than Ni/Al₂O₃ catalyst, while employing high reaction temperature is vital for elimination of coke deposition. Although the different coupled reaction systems show different characteristic in terms of product distribution and coke deposition, which all can serve as methods for storage of the carbon from fossil fuels or air.     

Catalytic hydrogenation of CO2 from 600 MW supercritical coal power plant to produce methanol: A techno-economic analysis

Electricity and water from renewable hydropower plant are used as input for electrolysis unit to generate hydrogen, while CO₂ is captured from 600 MW supercritical coal power plant using post-combustion chemical solvent based technology. The captured CO₂ and H₂ generated through electrolysis are used to synthesize methanol through catalytic thermo-chemical reaction. The methanol synthesis plant is designed, modeled and simulated using commercial software Aspen Plus^®. The reactor is analyzed for two widely adopted kinetic models known as Graaf model and Vanden-Bossche (VB) model to predict the methanol yield and CO₂ conversion. The results show that the methanol reactor based on Graaf kinetic model produced 0.66 tonne of methanol per tonne of CO₂ utilized which is higher than that of the VB kinetic model where 0.6 tonne of methanol is produced per tonne of CO₂ utilized. The economic analysis reveals that 1.2 billion USD annually is required at the present cost of both H₂ production and CO₂ abatement to utilize continuous emission of 3.2 million tonne of CO₂ annually from 600 MW supercritical coal power unit to synthesize methanol. However, sensitivity analysis indicates that methanol production becomes feasible by adopting anyone of the route such as by increasing methanol production rate, by reducing levelised cost of hydrogen production, by reducing CO₂ mitigation cost or by increasing the current market selling price of methanol and oxygen.     

Methane decomposition over Co thin layer supported catalysts to produce hydrogen for fuel cell

Co/Al₂O₃/Silica Cloth Thin Layer Catalysts (CoAS) for Catalytic Decomposition of Natural Gas (CDNG) were investigated using a new Multilayer Catalytic Reactor (MCR). The influence of Co loading and reaction temperature was evaluated. Irrespective of Co loading, initial CH₄ conversion rises with T_R, while for lifetime and carbon capacity (C/Ni, number of CH₄ molecules decomposed for Ni atom until complete deactivation) it is not possible to find a direct relationship with other operating parameters or catalyst characteristics. However, Co loading significantly affects the catalytic activity: Co loading as high as 20 wt.% ensures both long lifetime and high H₂ productivity. On the contrary of what occurs using Ni-based catalysts and irrespective of reaction temperature investigated, filamentous coke forms with a “base” reaction mechanism and Co catalyst can be regenerated in oxygen without any problem, thus allowing to realize a dual-step process for the production of “CO_x-free” hydrogen stream.     

Ordered mesoporous MgO–Al2O3 composite oxides supported Ni based catalysts for CO2 reforming of CH4: Effects of basic modifier and mesopore structure

A series of ordered mesoporous MgO–Al₂O₃ composite oxides with various Mg containing were facilely synthesized via one-pot evaporation induced self-assembly strategy. These materials with advantageous structural properties and superior thermal stabilities were used as the supports of Ni based catalysts for CO₂ reforming of CH₄. These mesoporous catalysts behaved both high catalytic activities and long term stabilities toward this reaction. The effects of the mesopore structure and MgO basic modifier on catalytic performances were carefully studied. Specifically, their mesoporous frameworks could accommodate the gaseous reactants with more “accessible” Ni active centers; the “confinement effect” of the mesopores would effectively suppress the thermal sintering of the Ni nanoparticles; the modified MgO basic sites would enhance the chemisorption and activation of CO₂. Consequently, the catalytic activities and stabilities of these catalysts were greatly promoted. Therefore, the present materials were considered as promising catalyst supports for CO₂ reforming of CH₄.     

Simultaneous production of electricity and hydrogen from methanol solution with a new electrochemical technology

It is known that the reaction from methanol to hydrogen has a positive Gibbs free energy and therefore cannot occur spontaneously. In the present work, by utilizing the chemical energy of neutralization, a new electrochemical technology was developed to produce hydrogen and electricity from methanol solution simultaneously, without needing external energy input. In our designed electrochemical cell, hydrogen can be produced on cathode while methanol can be oxidized on anode with additional electricity production. The effect of anode surface area on hydrogen production rate and power output was also investigated. With anode apparent surface area of 6.15 cm², initial hydrogen production rate can reach up to 1.07 m³ H₂ m⁻³ d⁻¹ and the maximum power density output of 1.26 W m⁻² can be achieved, at the same time. Although it is only a preliminary work, our work is supposed to provide a new approach for the on-board hydrogen production for the application of various fuel cell technologies, which is urgently needed nowadays.     

Photoautotrophic hydrogen production by nitrogen-deprived Chlamydomonas reinhardtii cultures

In this study we have demonstrated the possibility of phototrophic hydrogen production in C. reinhardtii under N-deprived conditions. When tested under air + CO₂, and Ar + CO₂ N-deprived C. reinhardtii demonstrated decrease in PSII activity mainly due to over reduction of PQ, in addition no ascorbate accumulation was observed in cells. Under air + CO₂ atmosphere cells accumulated excessive amounts of starch. When incubated under Ar + CO₂ atmosphere cells accumulated starch as nitrogen replete cultures and no hydrogen production was observed. Hydrogen production (86 ml H₂ per one l of culture) occurred under Ar + CO₂ atmosphere when particular two-step illumination protocol was implicated. In oxygen producing and early oxygen consuming stage cells were illuminated under light intensity 169 μE m^?2 s^?1. When light was switched to 30 μE m^?2 s^?1, cultures quickly respired all oxygen and transient to anaerobic conditions with subsequent hydrogen production 2 h later. Actual quantum yield of C. reinhardtii cultures was measured in photobioreactor and maximal quantum efficiency of PSII of dark adapted cells together with JIP test were studied.     

Improved hydrogen storage capacity through hydrolysis of solid NaBH4 catalyzed with cobalt boride

In this article the feasibility of the reaction of liquid water with a solid NaBH₄/catalyst mixture for improved hydrogen storage capacity and on-demand H₂ generation is reported. The synthesized low-cost nanosized catalyst consists of a Co₂B core surrounded by an oxide layer, presenting a relatively large specific surface area (70 m² g⁻¹). Calorimetric experiments coupled to simultaneous measurements of the evolved hydrogen volume have shown the positive effect of the locally heat release during reduction of the superficial oxidized layer. The synergetic effects of the exothermicity of both the oxidized layer reduction and the hydrolysis reaction coupled to the high efficiency of the cobalt boride catalyst led to an “enhanced regime” observed at room temperature. The “enhanced regime” corresponds to a global reaction stoichiometry of 1 mol of NaBH₄ reacting with 3 mol of water, conducting to a hydrogen yield of 8.7 wt.%. Effects of temperature and catalyst content were studied.     

Chemical looping gasification of solid fuels using bimetallic oxygen carrier particles – Feasibility assessment and process simulations

The chemical looping gasification (CLG) process utilizes an iron-based oxygen carrier to convert carbonaceous fuels into hydrogen and electricity while capturing CO₂. Although the process has the potential to be efficient and environmentally friendly, the activity of the iron-based oxygen carrier is relatively low, especially for solid fuel conversion. In the present study, we propose to incorporate a secondary oxygen carrying metal oxide, i.e. CuO, to the iron-based oxygen carrier. Using the “oxygen-uncoupling” characteristics of CuO, gaseous oxygen is released at a high temperature to promote the conversion of both Fe₂O₃ and coal. Experiments carried out using a Thermal-Gravimetric Analyzer (TGA) indicate that a bimetallic oxygen carrier consisting of a small amount (5% by weight) of CuO is more effective for coal char conversion when compared to oxygen carrier without copper addition. ASPEN Plus^® simulations and mathematical modeling of the process indicate that the incorporation of a small amount of copper leads to increased hydrogen yield and process efficiency.     

Methanol production using hydrogen from concentrated solar energy

Concentrated solar thermal technology is considered a very promising renewable energy technology due to its capability of producing heat and electricity and of its straightforward coupling to thermal storage devices. Conventionally, this approach is mostly used for power generation. When coupled with the right conversion process, it can be also used to produce methanol. Indeed methanol is a good alternative fuel for high compression ratio engines. Its high burning velocity and the large expansion occurring during combustion leads to higher efficiency compared to operation with conventional fuels. This study is focused on the system level modeling of methanol production using hydrogen and carbon monoxide produced with cerium oxide solar thermochemical cycle which is expected to be CO₂ free. A techno-economic assessment of the overall process is done for the first time. The thermochemical redox cycle is operated in a solar receiver-reactor with concentrated solar heat to produce hydrogen and carbon monoxide as the main constituents of synthesis gas. Afterwards, the synthesis gas is turned into methanol whereas the methanol production process is CO₂ free. The production pathway was modeled and simulations were carried out using process simulation software for MW-scale methanol production plant. The methanol production from synthesis gas utilizes plug-flow reactor. Optimum parameters of reactors are calculated. The solar methanol production plant is designed for the location Almeria, Spain. To assess the plant, economic analysis has been carried out. The results of the simulation show that it is possible to produce 27.81 million liter methanol with a 350 MW_th solar tower plant. It is found out that to operate this plant at base case scenario, 880685 m² of mirror's facets are needed with a solar tower height of 220 m. In this scenario a production cost of 1.14 €/l Methanol is predicted.     

LaBa0.8Ca0.2Co2O5+δ cathode with superior CO2 resistance and high oxygen reduction activity for intermediate-temperature solid oxide fuel cells

The development of highly efficient cathode materials with durable performance and high resistance toward environmental impurity is crucial for realizing the practical applications of intermediate temperature - solid oxide fuel cells (SOFCs). Since CO₂ as the oxidation product of hydrocarbons is unavoidable in the surrounding air atmosphere for SOFCs operating on hydrocarbon fuels, CO₂ tolerance of the air electrode is a big concern. Herein, LaBa_0.8Ca_0.2Co₂O_5+δ (LBCC) double perovskite is proposed as a promising cathode with superior CO₂ tolerance and favourable oxygen reduction activity. It shows a relatively low area specific resistance of 0.128 Ω cm² at 600 °C in a CO₂-free synthetic air atmosphere, tested based on a symmetrical cell configuration (LBCC | Gd_0.2Ce_0.8O_1.9 | LBCC). In addition, under open-circuit voltage condition, it can run stably for more than 120 h in the air containing 1% CO₂ (1% CO₂, 21% O₂ and 78% N₂) at 650 °C. More attractively, the LBCC shows high reversibility in performance by removing CO₂ from air. An anode-supported single SOFC with thin film doped ceria electrolyte (～25 μm) and LBCC cathode shows a favourable peak power density of 1063 mW cm^?2 at 700 °C by using ambient air as the cathode atmosphere and hydrogen as the fuel.