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Nicotinamide adenine dinucleotide-dependent formate dehydrogenase from Candida boidinii was immobilized in a 1,2-dimyristoyl- sn -glycero-3-phosphocholine/cholesterol floating lipid bilayer on the gold surface as a biocatalyst for electrochemical CO 2 reduction. We report that, in contrast to common belief, the enzyme can catalyze the electrochemical reduction of CO 2 to formate without the cofactor protonated nicotinamide adenine dinucleotide. The electrochemical data indicate that the enzyme-catalyzed reduction of CO 2 is diffusion-controlled and is a reversible reaction. The orientation and conformation of the enzyme were investigated by surface-enhanced infrared reflection absorption spectroscopy. The α-helix of the enzyme adopts an orientation nearly parallel to the surface, bringing its active center close to the gold surface. This orientation allows direct electron transfer between CO 2 and the gold electrode. The results in this paper provide a new method for the development of enzymatic electrocatalysts for CO 2 reduction.

Carbon capture and storage (CCS) is an essential technology to mitigate global CO 2 emissions from power and industry sectors. Despite the increasing recognition of its importance to achieve the net-zero target, current CCS deployment is far behind targeted ambitions. A key reason is that CCS is often perceived as too expensive. The costs of CCS have however traditionally been looked at from the industrial plant perspective, which does not necessarily reflect the end user's one. This paper addresses the incomplete view by investigating the impact of implementing CCS in industrial facilities on the overall costs and CO 2 emissions of end-user products and services. As an example, we examine the extent to which an increase in costs of raw materials (cement and steel) due to CCS impacts the costs of building a bridge. Results show that although CCS significantly increases cement and steel costs, the subsequent increment in the overall bridge construction cost remains marginal (∼1%). This 1% cost increase, however, enables a deep reduction in CO 2 emissions (∼51%) associated with the bridge construction. Although more research is needed in this area, this work is the first step to a better understanding of the real cost and benefits of CCS.

The development of cost-effective catalysts for CO 2 reduction is highly desired but remains a significant challenge. The unsaturated coordination metal center in a catalyst is favorable for the process of catalytic CO 2 reduction. In this paper, two asymmetric salen ligands were used to synthesize two coordinatively unsaturated Co-salen complexes. The two Co-salen complexes exhibit an unsaturated coordination pattern and display high activity and CO selectivity for visible-light-driven CO 2 reduction in a water-containing system. The photocatalytic performance of 2 is higher than that of 1 because the reduction potential of the catalytic Co II center and the energy barrier of the catalytic transition states of 2 are lower than those of 1 , with turnover numbers (TON CO ), turnover frequencies (TOF), and CO selectivity values of 8640, 0.24 s -1 , and 97% for 2 , respectively. The photocatalytic reduction of CO 2 to CO for 2 is well supported by control experiments and density functional theory (DFT) calculations.

This paper describes an experimental system for simultaneous permeation of a pressurized test gas through different gas permeable membranes and provides a proof of concept for a novel approach for gas identification/fingerprinting for potential construction of electronic noses. The design, construction, and use of a six-channel system which allows simultaneous gas permeation from a single pressurized gas compartment through six different parallel membranes are presented. The permeated gas is accumulated in confined spaces behind the respective membranes. The rate of gas pressure accumulation behind each membrane is recorded and used as a measure of the gas permeation rate through the membrane. The utilized gas permeable membranes include Teflon AF, silicone rubber, track-etch hydrophilic polycarbonate, track-etch hydrophobic polycarbonate, track-etch polyimide, nanoporous anodic aluminum oxide, zeolite ZSM-5, and zeolite NaY. An analogy between the rate of pressure accumulation of the permeating gas behind the membrane and the charging of an electric capacitor in a single series RC circuit is proposed and thoroughly validated. The simultaneous permeation rates through different membranes demonstrated a very promising potential as characteristic fingerprints for 10 test gases, that is, helium, neon, argon, hydrogen, nitrogen, carbon dioxide, methane, ethane, propane, and ethylene, which are selected as representative examples of mono-, di-, tri-, and polyatomic gases and to include some homologous series as well as to allow testing the potential of the proposed system to discriminate between closely related gases such as ethane and ethylene or carbon dioxide and propane which have almost identical molecular masses. Finally, a preliminary investigation of the possibility of applying the developed gas permeation system for semiquantitative analysis of the CO 2 -N 2 binary mixture is also presented.

The removal of CO 2 from gases is an important industrial process in the transition to a low-carbon economy. The use of selective physical (co-)solvents is especially perspective in cases when the amount of CO 2 is large as it enables one to lower the energy requirements for solvent regeneration. However, only a few physical solvents have found industrial application and the design of new ones can pave the way to more efficient gas treatment techniques. Experimental screening of gas solubility is a labor-intensive process, and solubility modeling is a viable strategy to reduce the number of solvents subject to experimental measurements. In this paper, a chemoinformatics-based modeling workflow was applied to build a predictive model for the solubility of CO 2 and four other industrially important gases (CO, CH 4 , H 2 , and N 2 ). A dataset containing solubilities of gases in 280 solvents was collected from literature sources and supplemented with the new data for six solvents measured in the present study. A modeling workflow based on the usage of several state-of-the-art machine learning algorithms was applied to establish quantitative structure-solubility relationships. The best models were used to perform virtual screening of the industrially produced chemicals. It enabled the identification of compounds with high predicted CO 2 solubility and selectivity toward other gases. The prediction for one of the compounds, 4-methylmorpholine, was confirmed experimentally.

H 2 S and CO 2 are the main impurities in raw natural gas, which needs to be purified before use. However, the comprehensive utilization of H 2 S and CO 2 has been ignored. Herein, we proposed a fully resource-based method to convert toxic gas H 2 S and greenhouse gas CO 2 synchronously into CO and elemental S by using a novel electrochemical reactor. The special designs include that, in the anodic chamber, H 2 S was oxidized rapidly to S based on the I - /I 3 - cyclic redox system to avoid anode passivation. On the other hand, in the cathodic chamber, CO 2 was rapidly and selectively reduced to CO based on a porous carbon gas diffusion electrode (GDE) modified with polytetrafluoroethylene and cobalt phthalocyanine (CoPc). A high Faraday efficiency (>95%) toward CO was achieved due to the enhanced mass transfer of CO 2 on the GDE and the presence of the selective CoPc catalyst. The maximum energy efficiency of the system was more than 72.41% with a current density of over 50 mA/cm 2 , which was 12.5 times higher than what was previously reported on the H 2 S treatment system. The yields of S and CO were 24.94 mg·cm -2 ·h -1 and 19.93 mL·cm -2 ·h -1 , respectively. A model analysis determined that the operation cost of the synchronous utilization of H 2 S and CO 2 S in the existing natural gas purification technology. Overall, this paper provides efficient and simultaneous conversion of H 2 S in the existing natural gas purification technology. Overall, this paper provides efficient and simultaneous conversion of H 2 S and CO 2 into S and CO.

As more countries commit to a net-zero GHG emission target, we need a whole energy and industrial system approach to decarbonization rather than focus on individual emitters. This paper presents a techno-economic analysis of monoethanolamine-based post-combustion capture to explore opportunities over a diverse range of power and industrial applications. The following ranges were investigated: feed gas flow rate between 1-1000 kg ·s -1 , gas CO 2 concentrations of 2-42% mol , capture rates of 70-99%, and interest rates of 2-20%. The economies of scale are evident when the flue gas flow rate is <20 kg ·s -1 and gas concentration is below 20% mol CO 2 . In most cases, increasing the capture rate from 90 to 95% has a negligible impact on capture cost, thereby reducing CO 2 emissions at virtually no additional cost. The majority of the investigated space has an operating cost fraction above 50%. In these instances, reducing the cost of capital ( i.e. , interest rate) has a minor impact on the capture cost. Instead, it would be more beneficial to reduce steam requirements. We also provide a surrogate model which can evaluate capture cost from inputs of the gas flow rate, CO 2 composition, capture rate, interest rate, steam cost, and electricity cost.

Disputes around trade inequality have been growing over the last 2 decades, with different countries claiming inequality in different terms including monetary deficits, resource appropriation and degradation, and environmental emission transfer. Despite prior input-output-based studies analyzing multidimensional trade consequences at the sector level, there is a lack of bottom-up studies that uncover the complexity of trade imbalances at the product level. This paper quantifies four types of flows, monetary, resource, embodied energy use, and embodied greenhouse gas (GHG) emissions, resulting from aluminum trade for the four economies with the highest aluminum trade, that is, the United States, China, Japan, and Australia. Results show that the United States has a negative balance in monetary flows but a positive balance in resource flows, embodied energy use, and GHG emissions. China has a positive balance in monetary and resource flows but a negative balance in embodied energy use and GHG emissions. Japan has a positive balance in all flows, while Australia has a negative balance in all flows. These heterogeneous gains and losses along the global leaders of aluminum trade arise largely from their different trade structures and the heterogeneities of price, energy use, and GHG emission intensities of aluminum products; for example, Japan mainly imports unwrought aluminum, and its quantity is 3 times that of the exported semis and finished aluminum-containing products that have similar energy and GHG emission intensities but 20 times higher prices, while Australia mainly exports bauxite and alumina that have the lowest prices, the quantity of which is 25 times that of imported semis and finished products. This study suggests that resource-related trade inequalities are not uniform across economic and environmental impacts and that trade policies must be carefully considered from various dimensions.

Electrochemical conversion of carbon dioxide into valuable chemicals or fuels is an increasingly important strategy for achieving carbon neutral technologies. The lack of a sufficiently active and selective electrocatalyst, particularly for synthesizing highly reduced products, motivates accelerated screening to evaluate new catalyst spaces. Traditional techniques, which couple electrocatalyst operation with analytical techniques to measure product distributions, enable screening throughput at 1-10 catalysts per day. In this paper, a combinatorial screening instrument is designed for MS detection of hydrogen, methane, and ethylene in quasi-real-time during catalyst operation experiments in an electrochemical flow cell. Coupled with experiment modeling, product detection during cyclic voltammetry (CV) enables modeling of the voltage-dependent partial current density for each detected product. We demonstrate the technique by using the well-established thin film Cu catalysts and by screening a Pd-Zn composition library in carbonate-buffered aqueous electrolyte. The rapid product distribution characterization over a large range of overpotential makes the instrument uniquely suited for accelerating screening of electrocatalysts for the carbon dioxide reduction reaction.

Carbon dioxide (CO 2 ), an important gas molecule metabolite produced by the tricarboxylic acid cycle, is a direct signal for identifying cancers in cells and tissues. Herein, design and synthesis of a novel "breathable" block polymer supramolecular assembly probe consisting of a hydrophilic block, an amidine-containing CO 2 -responsive block, and an aggregation-induced emission (AIE) luminescence block to detect CO 2 metabolized by cancer cells is reported. The triblock copolymer poly-(4-undecoxy tetraphenyl ethylene methacrylate)- b -poly-(( N -amidino)-(2,3-dihydro-1 H -1, 4-methyl-1, 2,3-triazole)-(ethenylbenzene))- b -poly(ethylene oxide) (PTPE- b -PAD- b -PEO) was successfully synthesized and characterized. This triblock copolymer could be self-assembled into "breathable" aqueous solution vesicles. In the presence of CO 2 , the amidine-containing CO 2 -responsive block (PAD block) of the vesicle "inhales" an amount of CO 2 , which causes the volume of the vesicle to expand. The expansion of the vesicle induces the aggregation of the AIE luminescence block (PTPE block), which resulted in the fluorescence intensity enhancement. The supramolecular vesicles "exhale" CO 2 , and the volume and AIE phenomenon of the vesicles decrease when N 2 is passed into the solution. On the basis of this reversible change of fluorescence intensity, HeLa cervical cancer cells, CNE1 nasopharynx cancer cells, 5-8F nasopharynx cancer cells, 16HBE human bronchial epithelial cells, and GES-1 human gastric mucosa epithelial cells have all been successfully detected and identified.

Integrated Assessment Models based on Computable General Equilibrium (IAM/CGE) and dynamic Material Flow Analysis (dynamic MFA) are two most widely used prospective model families to assess large-scale and long-term socioeconomic metabolism (SEM) and inform sustainable SEM transition. The latter approach could complement the former by a more explicit understanding of service provision, in-use stocks, and material cycles in a mass balanced framework. In this paper, we demonstrated this by integrating the dynamic MFA and CGE model approaches for the Chinese building sector from 2012 to 2030. Our results revealed the impacts of building stock dynamics on sectoral and economy-wide CO 2 emissions: lower service saturation levels and later saturation time of building stock development could free up investment on buildings and accumulatively save up to 25.4 Gt in embodied CO 2 emissions of the building construction sector, representing a 2.7-fold of 2012 countrywide CO 2 emissions. However, the save-ups are partly compensated by an increase of embodied CO 2 emissions in the other sectors due to economy-wide rebound effect (ca. 18.8 Gt or about 74%). The integrated model we developed could help ensure both mass and monetary balances, explore rebound effects in prospective modeling, and thus better understand the economy-wide consequences of infrastructure development.

Amine-based absorption is the primary contender for postcombustion CO 2 capture from fossil fuel-fired power plants. However, significant concerns have arisen regarding the formation and emission of toxic nitrosamine and nitramine byproducts from amine-based systems. This paper reviews the current knowledge regarding these byproducts in CO 2 capture systems. In the absorber, flue gas NO x drives nitrosamine and nitramine formation after its dissolution into the amine solvent. The reaction mechanisms are reviewed based on CO 2 capture literature as well as biological and atmospheric chemistry studies. In the desorber, nitrosamines are formed under high temperatures by amines reacting with nitrite (a hydrolysis product of NO x ), but they can also thermally decompose following pseudo-first order kinetics. The effects of amine structure, primarily amine order, on nitrosamine formation and the corresponding mechanisms are discussed. Washwater units, although intended to control emissions from the absorber, can contribute to additional nitrosamine formation when accumulated amines react with residual NO x . Nitramines are much less studied than nitrosamines in CO 2 capture systems. Mitigation strategies based on the reaction mechanisms in each unit of the CO 2 capture systems are reviewed. Lastly, we highlight research needs in clarifying reaction mechanisms, developing analytical methods for both liquid and gas phases, and integrating different units to quantitatively predict the accumulation and emission of nitrosamines and nitramines.

Metabolic engineering of cyanobacteria has received attention as a sustainable strategy to convert carbon dioxide to fatty acid-derived chemicals that are widely used in the food and chemical industries. Herein, Synechococcus elongatus PCC 7942, a model cyanobacterium, was engineered for the first time to produce fatty acid ethyl esters (FAEEs) from CO 2 . Due to the lack of an endogenous ethanol production pathway and wax ester synthase (AftA) activity in the wild-type cyanobacterium, we metabolically engineered S. elongatus PCC 7942 by expressing heterologous AftA and introducing the ethanol pathway, resulting in detectable peaks of FAEEs. To enhance FAEE production, a heterologous phosphoketolase pathway was introduced in the FAEE-producing strain to supply acetyl-CoA. Subsequent optimization of the cyanobacterial culture with a hexadecane overlay resulted in engineered S. elongatus PCC 7942 that produced photosynthetic FAEEs (10.0 ± 0.7 mg/L/OD 730 ) from CO 2 . This paper is the first report of photosynthetic production of FAEEs from CO 2 in cyanobacteria.

Sorption-enhanced steam reforming (SESR) is an energy and cost efficient approach to produce hydrogen with high purity. SESR makes it economically feasible to use a wide range of feedstocks for hydrogen production such as methane, ethanol, and biomass. Selection of catalysts and sorbents plays a vital role in SESR. This article reviews the recent research aimed at process intensification by the integration of catalysis and chemisorption functions into a single material. Alkali metal ceramic powders, including Li 2 ZrO 3 , Li 4 SiO 4 and Na 2 ZrO 3 display characteristics suitable for capturing CO 2 at low concentrations (<15% CO 2 ) and high temperatures (>500 °C), and thus are applicable to precombustion technologies such as SESR, as well as postcombustion capture of CO 2 from flue gases. This paper reviews the progress made in improving the operational performance of alkali metal ceramics under conditions that simulate power plant and SESR operation, by adopting new methods of sorbent synthesis and doping with additional elements. The paper also discusses the role of carbonates formed after in situ CO 2 chemisorption during a steam reforming process in respect of catalysts for tar cracking.

Mineral reactions during CO 2 sequestration will change the pore-size distribution and pore surface characteristics, complicating permeability and storage security predictions. In this paper, we report a small/wide angle scattering study of wellbore cement that has been exposed to carbon dioxide for three decades. We have constructed detailed contour maps that describe local porosity distributions and the mineralogy of the sample and relate these quantities to the carbon dioxide reaction front on the cement. We find that the initial bimodal distribution of pores in the cement, 1-2 and 10-20 nm, is affected differently during the course of carbonation reactions. Initial dissolution of cement phases occurs in the 10-20 nm pores and leads to the development of new pore spaces that are eventually sealed by CaCO 3 precipitation, leading to a loss of gel and capillary nanopores, smoother pore surfaces, and reduced porosity. This suggests that during extensive carbonation of wellbore cement, the cement becomes less permeable because of carbonate mineral precipitation within the pore space. Additionally, the loss of gel and capillary nanoporosities will reduce the reactivity of cement with CO 2 due to reactive surface area loss. This work demonstrates the importance of understanding not only changes in total porosity but also how the distribution of porosity evolves with reaction that affects permeability.

Capture and utilization of CO2 as alternative carbon feedstock for fuels, chemicals, and materials aims at reducing greenhouse gas emissions and fossil resource use. For capture of CO2, a large variety of CO2 sources exists. Since they emit much more CO2 than the expected demand for CO2 utilization, the environmentally most favorable CO2 sources should be selected. For this purpose, we introduce the environmental-merit-order (EMO) curve to rank CO2 sources according to their environmental impacts over the available CO2 supply. To determine the environmental impacts of CO2 capture, compression and transport, we conducted a comprehensive literature study for the energy demands of CO2 supply, and constructed a database for CO2 sources in Europe. Mapping these CO2 sources reveals that CO2 transport distances are usually small. Thus, neglecting transport in a first step, we find that environmental impacts are minimized by capturing CO2 first from chemical plants and natural gas processing, then from paper mills, power plants, and iron and steel plants. In a second step, we computed regional EMO curves considering transport and country-specific impacts for energy supply. Building upon regional EMO curves, we identify favorable locations for CO2 utilization with lowest environmental impacts of CO2 supply, so-called CO2 oases.

In the context of the electrochemical and photochemical conversion of CO2 to liquid fuels, one of the most important issues of contemporary energy and environmental issues, the possibility of pushing the reduction beyond the CO and formate level and catalytically generate products such as methanol is particularly attractive. Biomimetic 2e(-) + 2H(+) is often viewed as a potential hydride donor. This has been the object of a recent interesting attempt (J. Am. Chem. Soc. 2014, 136, 14007) in which 6,7-dimethyl-4-hydroxy-2-mercaptopteridine was reported as a catalyst of the electrochemical conversion of CO2 to methanol and formate, based on cyclic voltammetric, (13)C NMR, IR, and GC analyses. After checking electrolysis at the reported potential and at a more negative potential to speed up the reaction, it appears, on (1)H NMR and gas chromatographic grounds, that there is neither catalysis nor methanol and nor formate production. (1)H NMR (with H2O presaturation) brings about an unambiguous answer to the eventual production of methanol and formate, much more so than (13)C NMR, which can even be misleading when no internal standard is used as in the above-mentioned paper. IR analysis is even less conclusive. Use of a GC technique with sufficient sensitivity confirmed the lack of methanol formation. The direct or indirect hydride transfer electrochemical reduction of CO2 to formate and to methanol remains an open question. Original ideas and efforts such as those discussed here are certainly worth tempting. However, in view of the importance of the stakes, it appears necessary to carefully check reports in this area.

Rising concentrations of atmospheric carbon dioxide ([CO2]) and subsequent changes in climate, including temperature and precipitation extremes, are very likely to alter pest pressures in both managed and unmanaged plant communities. Such changes in pest pressures can be positive (migration from a region) or negative (new introductions), but are likely to be accompanied by significant economic and environmental consequences. Recent studies indicate the range of invasive weeds such as kudzu and insects such as mountain pine beetle have already expanded to more northern regions as temperatures have risen. To reduce these consequences, a better understanding of the link between CO2/climate and pest biology is needed in the context of existing and new strategies for pest management. This paper provides an overview of the probable biological links and the vulnerabilities of existing pest management (especially chemical control) and provides a preliminary synthesis of research needs that could potentially improve the ability to monitor, mitigate, and manage pest impacts.

The capture of carbon dioxide with chemical solvents is one solution to mitigate greenhouse gas emissions from anthropogenic sources and thus tackle climate change. Recent research has been focused on optimizing new kinds of advanced absorbents including aqueous amine blends, but critical downsides such as the large energetic cost involved with the industrial process remain. To address this issue, a better understanding of the energetic interactions existing in solution is necessary. In this paper, we report direct experimental measurements of the energy cost involved in the solvation of CO2 in two aqueous amine blends at different temperatures. The chemical solvents were designed as aqueous mixtures of commonly used primary and tertiary amines to study the influence of the different chemical properties inferred by the amine class. We have also applied a thermodynamic model to represent the energetic effects that take place in solution during CO2 dissolution in these mixtures, where all parameters were taken from previous studies focused on single amine absorbents. The noteworthy agreement observed with the reported experimental heats of absorption and with literature vapor liquid equilibrium properties confirmed the relevance of the underlying molecular mechanisms considered in our model, and suggest that this model would prove useful to investigate CO2 dissolution in other amine blends.

This paper has changed the vague understanding that "the short-lived buildings have huge environmental footprints (EF)" into a concrete one. By estimating the annual floor space of buildings demolished and calibrating the average building lifetime in China, this paper compared the EF under various assumptive extended buildings' lifetime scenarios based on time-series environmental-extended input-output model. Results show that if the average buildings' lifetime in China can be extended from the current 23.2 years to their designed life expectancy, 50 years, in 2011, China can reduce 5.8 Gt of water withdrawal, 127.1 Mtce of energy consumption, and 426.0 Mt of carbon emissions, each of which is equivalent to the corresponding annual EF of Belgium, Mexico, and Italy. These findings will urge China to extend the lifetime of existing and new buildings, in order to reduce the EF from further urbanization. This paper also verifies that the lifetime of a product or the replacement rate of a sector is a very important factor that influences the cumulative EF. When making policies to reduce the EF, adjusting people's behaviors to extend the lifetime of products or reduce the replacement rate of sectors may be a very simple and cost-effective option.

As the largest magnesium producer in the world, China is facing a great challenge of greenhouse gas (GHG) emissions reduction. In this paper, the variation trend and driving factors of GHG emissions from Chinese magnesium production were evaluated and the measures of technology and policy for effectively mitigating GHG emissions were provided. First, the energy-related and process-oriented GHG inventory is compiled for magnesium production in China. Then, the driving forces for the changes of the energy-related emission were analyzed by the method of Logarithmic Mean Divisia Index (LMDI) decomposition. Results demonstrated that Chinese magnesium output from 2003 to 2013 increased by 125%, whereas GHG emissions only increased by 16%. The emissions caused by the fuels consumption decline most significantly (from 28.4 to 6.6 t CO2eq/t Mg) among all the emission sources. The energy intensity and the energy structure were the main offsetting factors for the increase of GHG emissions, while the scale of production and the international market demand were the main contributors for the total increase. Considering the improvement of technology application and more stringent policy measures, the annual GHG emissions from Chinese primary magnesium production will be controlled within 22 million tons by 2020.

This paper investigates the CO2 and N2O absorption behavior in the water-lean gamma amino propyl (GAP)-1/TEG solvent system using a wetted-wall contactor. Testing was performed on a blend of GAP-1 aminosilicone in triethylene glycol at varied water loadings in the solvent. Measurements were made with CO2 and N2O at representative lean (0.04 mol CO2/mol alkalinity), middle (0.13 mol CO2/mol alkalinity), and rich (0.46 mol CO2/mol alkalinity) solvent loadings at 0, 5, 10, and 15 wt % water loadings at 40, 60, and 80°C and N2O at (0.08-0.09 mol CO2/mol alkalinity) at 5 wt % water at 40, 60, and 80°C. CO2 flux was found to be nonlinear with respect to log mean pressure driving force (LMPD). Liquid-film mass transfer coefficients (k'g) were calculated by subtracting the gas film resistance (determined from a correlation from literature) from the overall mass transfer measurement. The resulting k'g values for CO2 and N2O in GAP-1/TEG mixtures were found to be higher than that of 5 M aqueous monoethanolamine under comparable driving force albeit at higher solvent viscosities. The k'g values for CO2 were also found to decrease with increasing solvent water content and increase with a decrease in temperature. These observations indicate that mass transfer of CO2 in GAP-1/TEG is linked to the physical solubility of CO2, which is higher in organic solvents compared to water. This paper expands on the understanding of the unique mass transfer behavior and kinetics of CO2 capture in water-lean solvents. [ABSTRACT FROM AUTHOR]

Sorption-enhanced steam reforming (SESR) is an energy and cost efficient approach to produce hydrogen with high purity. SESR makes it economically feasible to use a wide range of feedstocks for hydrogen production such as methane, ethanol, and biomass. Selection of catalysts and sorbents plays a vital role in SESR. This article reviews the recent research aimed at process intensification by the integration of catalysis and chemisorption functions into a single material. Alkali metal ceramic powders, including Li2ZrO3, Li4SiO4 and Na2ZrO3 display characteristics suitable for capturing CO2 at low concentrations (<15% CO2) and high temperatures (>500 °C), and thus are applicable to precombustion technologies such as SESR, as well as postcombustion capture of CO2 from flue gases. This paper reviews the progress made in improving the operational performance of alkali metal ceramics under conditions that simulate power plant and SESR operation, by adopting new methods of sorbent synthesis and doping with additional elements. The paper also discusses the role of carbonates formed after in situ CO2 chemisorption during a steam reforming process in respect of catalysts for tar cracking. [ABSTRACT FROM AUTHOR]

Radical changes to current national energy systems-including energy efficiency and the decarbonization of electricity-will be required in order to meet challenging carbon emission reduction commitments. Technology explicit energy system optimization models (ESOMs) are widely used to define and assess such low-carbon pathways, but these models only account for the emissions associated with energy combustion and either do not account for or do not correctly allocate emissions arising from infrastructure, manufacturing, construction and transport associated with energy technologies and fuels. This paper addresses this shortcoming, through a hybrid approach that estimates the upstream CO2 emissions across current and future energy technologies for the UK using a multiregional environmentally extended input-output model, and explicitly models the direct and indirect CO2 emissions of energy supply and infrastructure technologies within a national ESOM (the UK TIMES model). Results indicate the large significance of nondomestic indirect emissions, particularly coming from fossil fuel imports, and finds that the marginal abatement cost of mitigating all emissions associated with UK energy supply is roughly double that of mitigating only direct emissions in 2050.

The life-cycle greenhouse gas (GHG) emissions of alternative fuels that are capable of replacing conventional, petroleum-derived gasoline and diesel continue to be scrutinized for policy implementation. These alternative fuel technologies can also produce a number of value-adding nonfuel coproducts that require thorough and rigorous assessment in order to achieve an accurate life-cycle GHG emissions value. By using the gas to liquids (GTL) diesel pathway as a proxy for other alternative fuel pathways with coproducts, this paper examines how integration of coproduct analysis using the substitution method is possible within the existing framework and functionality of the GREET model. Using this approach, a GREET-compatible external tool was developed to calculate the life-cycle inventory of GTL coproducts to determine the life-cycle GHG emissions of GTL diesel using the substitution method. In addition to having built-in regional scenarios, this tool allows the user the flexibility to configure a given GTL product slate and to calculate the life-cycle GHG emissions of GTL diesel based on a given product composition. Using this protocol, the life-cycle GHG emissions of GTL diesel can range from 71.7 to 95.7 gCO2e/MJ on a well to wheel basis, with the range in carbon intensity being dependent on the mix of coproducts. These results highlight a weakly understood relationship between fuel and chemical products in LCA models. The coproduct integration approach described herein could potentially be incorporated into fuel LCA models, such as GREET, to allow users to further understand the potential environmental benefits of alternative fuel pathways, such as GTL.

In this paper, we demonstrated that ocean acidification (OA) had significant negative effects on the microscopic development of Saccharina japonica in a short-term exposure experiment under a range of light conditions. Under elevated CO2, the alga showed a significant reduction in meiospore germination, fecundity, and reproductive success. Larger female and male gametophytes were noted to occur under high CO2 conditions and high light magnified these positive effects. Under conditions of low light combined with high PCO2, the differentiation of gametophytes was delayed until the end of the experiment. In contrast, gametophytes were able to survive after having been subjected to a long-term acclimation period, of 105 days. Although the elevated PCO2 resulted in a significant increase in sporophyte length, the biomass abundance (expressed as individual density attached to the seed fiber) was reduced significantly. Further stress resistance experiments showed that, although the acidified samples had lower resistance to high light and high temperature conditions, they displayed higher acclimation to CO2-saturated seawater conditions compared with the control groups. These combined results indicate that OA has a severe negative effect on S. japonica, which may result in future shifts in species dominance and community structure.

Among various CO2 capture processes, the aqueous amine-based absorption process is considered the most promising for near-term deployment. However, the performance evaluation of newly developed solvents still requires complex and time-consuming procedures, such as pilot plant tests or the development of a rigorous simulator. Absence of accurate and simple calculation methods for the energy performance at an early stage of process development has lengthened and increased expense of the development of economically feasible CO2 capture processes. In this paper, a novel but simple method to reliably calculate the regeneration energy in a standard amine-based carbon capture process is proposed. Careful examination of stripper behaviors and exploitation of energy balance equations around the stripper allowed for calculation of the regeneration energy using only vapor-liquid equilibrium and caloric data. Reliability of the proposed method was confirmed by comparing to rigorous simulations for two well-known solvents, monoethanolamine (MEA) and piperazine (PZ). The proposed method can predict the regeneration energy at various operating conditions with greater simplicity, greater speed, and higher accuracy than those proposed in previous studies. This enables faster and more precise screening of various solvents and faster optimization of process variables and can eventually accelerate the development of economically deployable CO2 capture processes.

Understanding the exchange of carbon dioxide (CO2) and methane (CH4) between the geosphere and atmosphere is essential for the management of anthropogenic emissions. Human activities such as carbon capture and storage and hydraulic fracturing ("fracking") affect the natural system and pose risks to future global warming and to human health and safety if not engineered to a high standard. In this paper an innovative approach of expressing ground gas compositions is presented, using data derived from regulatory monitoring of boreholes in the unsaturated zone at infrequent intervals (typically 3 months) with data from a high frequency monitoring instrument deployed over periods of weeks. Similar highly variable trends are observed for time scales ranging from decades to hourly for boreholes located close to sanitary landfill sites. Additionally, high frequency monitoring data confirm the effect of meteorological controls on ground gas emissions; the maximum observed CH4 and CO2 concentrations in a borehole monitored over two weeks were 40.1% v/v and 8.5% v/v respectively, but for 70% of the monitoring period only air was present. There is a clear weakness in current point monitoring strategies that may miss emission events and this needs to be considered along with obtaining baseline data prior to starting any engineering activity.

The present paper describes the GasPro probe, a small, low-cost unit for in situ, continuous pCO2 monitoring. Laboratory tests defining its performance characteristics are reported, as are the results from a 60 h water-column deployment of 20 such units near a natural CO2 seep site off the coast of Panarea Island (Italy). The spatial-temporal evolution of dissolved CO2 movement is presented and possible origins and controlling mechanisms discussed. Results highlight the potential for this technology to be used for better understanding various dynamic physical and biochemical processes in marine environments, and for marine environmental monitoring of off-shore industrial sites. These experiments have allowed us to assess the advantages and disadvantages of the present GasPro prototype and to define areas for ongoing improvement.

Due to the complexity of power systems, tracking emissions attributable to a specific electrical load is a daunting challenge but essential for many environmental impact studies. Currently, no consensus exists on appropriate methods for quantifying emissions from particular electricity loads. This paper reviews a wide range of the existing methods, detailing their functionality, tractability, and appropriate use. We identified and reviewed 32 methods and models and classified them into two distinct categories: empirical data and relationship models and power system optimization models. To illustrate the impact of method selection, we calculate the CO2 combustion emissions factors associated with electric-vehicle charging using 10 methods at nine charging station locations around the United States. Across the methods, we found an up to 68% difference from the mean CO2 emissions factor for a given charging site among both marginal and average emissions factors and up to a 63% difference from the average across average emissions factors. Our results underscore the importance of method selection and the need for a consensus on approaches appropriate for particular loads and research questions being addressed in order to achieve results that are more consistent across studies and allow for soundly supported policy decisions. The paper addresses this issue by offering a set of recommendations for determining an appropriate model type on the basis of the load characteristics and study objectives. [ABSTRACT FROM AUTHOR]

This paper discusses the influence of the noncondensable impurities CO and CH4 on Carbon Capture and Storage (CCS) technology. We calculated and drew conclusions about the impact of both impurities in the CO2 on selected transport, injection, and storage parameters (pipeline pressure drop, storage capacity, etc.), whose analysis is necessary for the safe construction and operation of CO2 pipelines and for the secure long-term geological storage of anthropogenic CO2. To calculate these parameters, it is necessary to acquire data on the volumetric properties and the vapor-liquid equilibrium of the fluid being subjected to CCS. In addition to literature data, we used new experimental data, which are presented here and were obtained for five mixtures of CO2+CO with compositions characteristic of the typical emissions of the E.U. and the U.S.A. Temperatures and pressures are based on relevant CO2 pipeline and geological storage site values. From our experimental results, Peng-Robinson, PC-SAFT, and GERG Equations of State for were validated CO2+CO under the conditions of CCS. We conclude that the concentration of both impurities strongly affects the studied parameters, with CO being the most influential and problematic. The overall result of these negative effects is an increase in the difficulties, risks, and overall costs of CCS.

The concept of ethylene epoxidation over methyltrioxorhenium (MTO) catalyst could save the world from global warming since the epoxidation reaction never produces carbon dioxide as byproduct. Unlike the conventional gas epoxidation reaction with oxygen, this reaction takes place in the (ethylene) gas-expanded liquid solvent phase (methanol) while the reaction oxidant is hydrogen peroxide. The reaction takes place at temperatures and pressures close to the ethylene critical point (Pc = 50.42 bar; Tc = 48.56 °F) (Gas Encyclopedia by Air Liquide, https://encyclopedia.airliquide.com/ethylene). In this paper, an optimized design and operation for MTO based ethylene oxide (EO) production processes has been developed, which has less manufacturing costs compared with the one from the current literature ( Ind. Eng. Chem. Res. 2013, 52, 18−29). The developed EO system could produce 200,000 tons of ethylene oxide per year at a purity of 99.9%. It has two reactors for ethylene epoxidation and hydrogen peroxide decomposition, one flash drum, and three distillation columns for product and recycled material purification. The design has secured the safety of the operation by not presenting oxygen and flammable vapor mixtures in any of the process equipment. The EO manufacturing costs $0.52 per pound, and the fixed capital investment of the project is $66,240,000, which is estimated to be paid back after 7.3 years, while the net present value is $56,900,000. [ABSTRACT FROM AUTHOR]

This paper reports on Fe-Cu bimetallic catalysts supported on γ-alumina for selective CO2 hydrogenation to olefin-rich C2+ hydrocarbons. A strong synergetic promoting effect on C2+ hydrocarbon synthesis was observed over Fe-Cu bimetallic catalysts when the Cu/(Cu + Fe) atomic ratio was 0.17. Compared to monometallic Fe catalyst, the Fe-Cu bimetallic catalyst significantly enhances C2-C7 hydrocarbon formation and suppresses the formation of undesired CH4. The addition of K into Fe-Cu bimetallic catalysts inhibits the methanation and further enhances the formation of C2+ hydrocarbons in the meantime. The synthesis of olefin-rich C2-C4 hydrocarbons from CO2/H2 was achieved by using K-promoted Fe-Cu/Al2O3 catalysts with higher K/Fe atomic ratios (e.g., K/Fe = 0.5), where the selectivity of C2-C4 olefin contents was even higher than K-promoted Fe-Co catalysts under the same reaction conditions. [ABSTRACT FROM AUTHOR]

In this paper, we describe an experiment for the undergraduate physical chemistry laboratory in which students determine the speed of sound in the gases He, N2, CO2 , and CF3CH2F. The experimental apparatus consists of a closed acrylic tube containing the gas under study. White audio noise is injected into one end of the tube, and the sound amplitude is recorded as a function of time at the other end. The data are recorded and Fourier transformed in real time with a spectrum analyzer application on an Apple iPad. The resulting frequency spectrum of the cavity standing waves is used to determine the speed of sound in the gas by least-squares fitting, with experimental values that fall within about 0.2% or less of the accepted values. The speed of sound is related to the heat capacity ratio in the ideal gas limit, providing students with quantitative evidence of the nonideality of the gases at ambient pressure and temperature. The experiment demonstrates the power and accuracy of interferometry and Fourier analysis using a modern tablet computer. [ABSTRACT FROM AUTHOR]

3-Ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVL), a substituent d-lactone synthesized through telomerization of CO2 with 1,3-butadiene, is highly functionalized containing a six-membered ring and two vinyl groups. It can hardly be polymerized directly through common methods due to its poor polymerizability. In this paper, we report the controlled polymerization of a highly reactive trivinyl monomer derived from EVL, i.e. methyl-2-ethylidene-5-hydroxyhept-6-enoate methacrylate (MEDMA), which is synthesized through ring cleavage of EVL and subsequent esterification with methacryloyl chloride. Chemoselective RAFT polymerizations of MEDMA mediated by 2-cyanoprop-2-yl-dithiobenzoate (CPDB) are achieved and well-defined polymers with linear and hyperbranched topologies are obtained under optimized polymerization conditions. RAFT polymerizations show good control in producing linear PMEDMAs with predetermined molecular weights (4000 g/mol) and moderate polydispersity indices (below 1.22). The resultant hyperbranched PMEDMAs are fully characterized by ¹H NMR, 13C NMR, ¹H-13C HMQC, DEPT, DLS, and TEM. The incorporations of vinyl group in allylic ester into polymer chains lead to the hyperbranched topology. Both PMEDMAs are ready for the introduction of amino and carboxy groups through thiol-ene click chemistry, and the products self-assemble to the micelles with different morphologies. This protocol develops the utilization of EVL in synthetic polymers and is significant to the carbon dioxide transformation. [ABSTRACT FROM AUTHOR]

The water-in-oil emulsion-templating method is used in this work for fabrication of open cell aerogel foams from syndiotactic polystyrene (sPS). A surfactant-stabilized emulsion is prepared at 60-100 °C by dispersing water in a solution of sPS in toluene. sPS gel, formed upon cooling of the emulsion to room temperature, locks the water droplets inside the gel. The gel is solvent exchanged in ethanol and then dried under supercritical condition of carbon dioxide to yield the aerogel foams. The aerogel foams show a significant fraction of macropores with a diameter of a few tens of micrometers, defined as macrovoids that originated from the emulsified water droplets. In conjunction, customary macropores of diameter 50-200 nm are derived from sPS gels. The macrovoids add additional openness to the aerogel structures. This paper evaluates the structural characteristics of the macrovoids, such as diameter distribution, macrovoid interconnect density, and skin layer density, in conjunction with the final aerogel foam properties. [ABSTRACT FROM AUTHOR]

In CO2 geological storage, the interfacial tension (IFT) between supercritical CO2 and brine is critical for the storage capacitance design to prevent CO2 leakage. IFT relies not only on the interfacial molecule properties but also on the environmental conditions at different storage sites. In this paper, supercritical CO2-NaCl solution systems are modeled at 343-373 K and 6-35 MPa under the salinity of 1.89 mol/L using molecular dynamics simulations. After computing and comparing the molecular density profile across the interface, the atomic radial distribution function, the molecular orientation distribution, the molecular Gibbs surface excess (derived from the molecular density profile), and the CO2-hydrate number density under the above environmental conditions, we confirm that only the molecular Gibbs surface excess of CO2 molecules and the CO2-hydrate number density correlate strongly with the temperature- and pressure-dependent IFTs. We also compute the populations of two distinct CO2-hydrate structures (T-type and H-type) and attribute the observed dependence of IFTs to the dominance of the more stable, surfactant-like T-type CO2-hydrates at the interface. On the basis of these new molecular mechanisms behind IFT variations, this study could guide the rational design of suitable injecting environmental pressure and temperature conditions. We believe that the above two molecular-level metrics (Gibbs surface excess and hydrate number density) are of great fundamental importance for understanding the supercritical CO2-water interface and engineering applications in geological CO2 storage. [ABSTRACT FROM AUTHOR]

In this paper, the Li4SiO4 nanowires (NWs) were shown to be promising for CO2 capture with ultrafast kinetics. Specifically, the nanowire powders exhibited an uptake of 0.35 g g-1 of CO2 at an ultrafast adsorption rate of 0.22 g g-1 min-1 at 650-700 °C. Lithium silicate (Li4SiO4) nanowires and nanopowders were synthesized using a "solvo-plasma" technique involving plasma oxidation of silicon precursors mixed with lithium hydroxide. The kinetic parameter values (k) extracted from sorption kinetics obtained using NW powders are 1 order of magnitude higher than those previously reported for the Li4SiO4-CO2 reaction system. The time scales for CO2 sorption using nanowires are approximately 3 min and two orders magnitude faster compared to those obtained using lithium silicate powders with spherical morphologies and aggregates. Furthermore, Li4SiO4 nanowire powders showed reversibility through sorption-desorption cycles indicating their suitability for CO2 capture applications. All of the morphologies of Li4SiO4 powders exhibited a double exponential behavior in the adsorption kinetics indicating two distinct time constants for kinetic and the mass transfer limited regimes. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) levels are continuously growing, and CO2 is believed to be a significant contributor to global warming and climate change. Therefore, there is a great interest in the development of highly efficient technologies to curb CO2 emissions of current energy sources. In this context to combat such issues, poly(ionic liquid)s (PILs) offer an extremely versatile and tunable platform to fabricate a wide variety of sorbents for CO2 capture. To date, the majority of poly(ionic liquid)s studied for CO2 capture is related to carbochain polymers (acrylate and styrene polyelectrolytes), while it is generally accepted that polymers with more basic backbones such as amides, urethanes or amidoxines can considerably enhance the CO2 absorption capacity. Thus, a series of novel high molecular weight (Mn = (3.4-21.0) × 104) ionic polyurethanes (PUs) have been prepared using four different ionic diols based on ammonium, quinuclidinium, diquinuclidinium and imidazolium cations. Furthermore, a range of ionic PUs bearing 13 different counteranions including classical ((CF3SO2)2N, BF4, PF6, and N(CN)2) and less encountered anionic species such as acetate, lactate, tetracyanoborate, bis(pentafluoroethylsulfonyl)amide, CF3SO2-N-CN and MeHaln (Me = Fe(III), Cu(II), Zn(II), Hal = Cl, Br) was obtained through the ion exchange reactions using the same bromide PU precursor. This allowed to separately isolate the effect of diisocyanate, cations and anions nature on physical properties of ionic PUs. The obtained poly(ionic liquid)s demonstrate high thermal stability (up to 275 °C), have glass transition temperatures in the range of 30-78 °C and show remarkable CO2 capture. It was found that ionic PUs incorporating diquinuclidinium cation and CH3COO or BF4 anions exhibit the highest CO2 sorption (18.25 and 24.76 mg/g at 273 K and 1 bar), not only overcoming the CO2 capture reported to date for linear PILs, but even surpassing the highest value known for cross-linked meso-porous poly(ionic liquid)s (20.24 mg/g at 273 K and 1 bar). Altogether, this paper demonstrates the potential of poly(ionic liquid)s as efficient designing materials for CO2 capture. [ABSTRACT FROM AUTHOR]

This paper describes calibration strategies in laboratory conditions that can be applied to ensure accurate measurements of the isotopic composition of the CO2 in ultradry air, expressed as d13C and d18O on the VPDB scale, with either FT-IR (in this case a Vertex 70 V (Bruker)) or an isotope ratio infrared spectrometer (IRIS) (in this case a Delta Ray (Thermo Fisher Scientific)). In the case of FT-IR a novel methodology using only two standards of CO2 in air with different mole fractions but identical isotopic composition was demonstrated to be highly accurate for measurements of d13C and d18O with standard uncertainties of 0.09% and 1.03%, respectively, at a nominal CO2 mole fraction of 400 µmol mol-1 in air. In the case of the IRIS system, we demonstrate that the use of two standards of CO2 in air of known but differing d13C and d18O isotopic composition allows standard uncertainties of 0.18% and 0.48% to be achieved for d13C and d18O measurements, respectively. The calibration strategies were validated using a set of five traceable primary reference gas mixtures. These standards, produced with whole air or synthetic air covered the mole fraction range of (378-420) µmol mol-1 and were prepared and/or value assigned either by the National Institute of Standards and Technology (NIST) or the National Physical Laboratory (NPL). The standards were prepared using pure CO2 obtained from different sources, namely, combustion; Northern Continental and Southern Oceanic Air and a gas well source, with d13C values ranging between -35% and -1%. The isotopic composition of all standards was value assigned at the Max Planck Institute for Biogeochemistry Jena (MPI-Jena). [ABSTRACT FROM AUTHOR]

Mineral reactions during CO2 sequestration will change the pore-size distribution and pore surface characteristics, complicating permeability and storage security predictions. In this paper, we report a small/wide angle scattering study of wellbore cement that has been exposed to carbon dioxide for three decades. We have constructed detailed contour maps that describe local porosity distributions and the mineralogy of the sample and relate these quantities to the carbon dioxide reaction front on the cement. We find that the initial bimodal distribution of pores in the cement, 1-2 and 10-20 nm, is affected differently during the course of carbonation reactions. Initial dissolution of cement phases occurs in the 10-20 nm pores and leads to the development of new pore spaces that are eventually sealed by CaCO3 precipitation, leading to a loss of gel and capillary nanopores, smoother pore surfaces, and reduced porosity. This suggests that during extensive carbonation of wellbore cement, the cement becomes less permeable because of carbonate mineral precipitation within the pore space. Additionally, the loss of gel and capillary nanoporosities will reduce the reactivity of cement with CO2 due to reactive surface area loss. This work demonstrates the importance of understanding not only changes in total porosity but also how the distribution of porosity evolves with reaction that affects permeability. [ABSTRACT FROM AUTHOR]

With the arising of global climate change and resource shortage, in recent years, increased attention has been paid to environmentally friendly materials. Trees are sustainable and renewable materials, which give us shelter and oxygen and remove carbon dioxide from the atmosphere. Trees are a primary resource that human society depends upon every day, for example, homes, heating, furniture, and aircraft. Wood from trees gives us paper, cardboard, and medical supplies, thus impacting our homes, school, work, and play. All of the above-mentioned applications have been well developed over the past thousands of years. However, trees and wood have much more to offer us as advanced materials, impacting emerging high-tech fields, such as bioengineering, flexible electronics, and clean energy. Wood naturally has a hierarchical structure, composed of well-oriented microfibers and tracheids for water, ion, and oxygen transportation during metabolism. At higher magnification, the walls of fiber cells have an interesting morphology--a distinctly mesoporous structure. Moreover, the walls of fiber cells are composed of thousands of fibers (or macrofibrils) oriented in a similar angle. Nanofibrils and nanocrystals can be further liberated from macrofibrils by mechanical, chemical, and enzymatic methods. The obtained nanocellulose has unique optical, mechanical, and barrier properties and is an excellent candidate for chemical modification and reconfiguration. Wood is naturally a composite material, comprised of cellulose, hemicellulose, and lignin. Wood is sustainable, earth abundant, strong, biodegradable, biocompatible, and chemically accessible for modification; more importantly, multiscale natural fibers from wood have unique optical properties applicable to different kinds of optoelectronics and photonic devices. Today, the materials derived from wood are ready to be explored for applications in new technology areas, such as electronics, biomedical devices, and energy. The goal of this study is to review the fundamental structures and chemistries of wood and wood-derived materials, which are essential for a wide range of existing and new enabling technologies. The scope of the review covers multiscale materials and assemblies of cellulose, hemicellulose, and lignin as well as other biomaterials derived from wood, in regard to their major emerging applications. Structure--properties-- application relationships will be investigated in detail. Understanding the fundamental properties of these structures is crucial for designing and manufacturing products for emerging applications. Today, a more holistic understanding of the interplay between the structure, chemistiy, and performance of wood and wood-derived materials is advancing historical applications of these materials. This new level of understanding also enables a myriad of new and exciting applications, which motivate this review. There are excellent reviews already on the classical topic of woody materials, and some recent reviews also cover new understanding of these materials as well as potential applications. This review will focus on the uniqueness of woody materials for three critical applications: green electronics, biological devices, and energy storage and bioenergy. [ABSTRACT FROM AUTHOR]

This paper introduces an efficient scale-up design technology based on mathematical modeling and optimization approach. The target process is a vacuum pressure swing adsorption process which is preferred in purifying unconventional gas such as coalbed methane or landfill gas by sequestering carbon dioxide. The optimization results are validated very well from a pilot scale (10 N m³/h) to a large commercial scale (5000 N m³/h). The simulation and optimization model for the scale up design is established in gPROMS custom modeling tool. Judging from the reasonably very small differences between the optimization results and the vendor suggested data, it can be concluded that the scale-up design is very successful not by depending on the experimental and real plant experiences but by using a mathematical optimization modeling approach. [ABSTRACT FROM AUTHOR]

This paper presents experimental p-p-T measurements for nitrogen + methane mixtures containing approximately 0.25, 0.50, and 0.75 mole fraction methane at T = 300, 350, 400, and 470 K with p = 10-137 MPa. Methane, nitrogen, and argon are used as calibration fluids, and measurements on carbon dioxide and ethane verify the calibration methodology. An error contribution analysis indicates that the expanded uncertainty (95% confidence limit) is 0.1 kg⋅m-3 for densities lower than 200 kg⋅m-3 and 0.0005⋅p for higher densities. The GERG-2008 equation of state describes the measurements for all three mixtures to within ±0.0015⋅p with the largest deviations occurring at the highest pressures. [ABSTRACT FROM AUTHOR]

In order to improve the separation performance of CO2/CH4 on carbon molecular sieves (CMS), CMS was modified by metal in this study. The surface of CMS had −OH, which could provide a great support for the chemical modification. In this paper, different metal ions, precursors of potassium, loading concentration of potassium carbonate (K2CO3), and calcination temperature were investigated for CO2/CH4 separation. Results showed that CMS loaded with K2CO3 and calcined at 773-873 K was the best for CO2/CH4 separation. Compared with the untreated CMS, the adsorption capacity of CO2 for the best adsorbent increased from 1.15 to 1.72 mmol·g-1 and the value of separation factor increased from 1.9 to 2.75 mmol·g-1. The K2CO3 treatment was effective in generating metal oxide K2O and KO2, which could facilitate the adsorption of CO2 after K2CO3/CMS being calcined. However, the reaction between CH4 and metal was weak. In summary, K2CO3/CMS was proved to be one of the candidates for CO2/CH4 separation. [ABSTRACT FROM AUTHOR]

With tight regulations on the permissible sulfur content in transportation fuels, the oil and gas industry is mandated to adopt reliable and cost-effective desulfurization and acid gas (H2S and CO2) treatment techniques. At present, the Claus process is used to treat acid gas to recover sulfur, but the hydrogen content in H2S is wasted as low grade steam. A viable method of acid gas treatment is the simultaneous production of valuable syngas (H2 and CO) and sulfur through the thermal destruction of H2S and CO2. However, the optimum process conditions and blends of H2S and CO2 to increase syngas production are not known. In this paper, a detailed reaction mechanism is developed for the simultaneous decomposition of H2S and CO2 and is validated using different sets of experimental data. The effects of the relative composition of H2S and CO2 in the acid gas and the process conditions on the production of syngas and sulfur during thermolysis are reported. A synergistic effect is observed in the simultaneous decomposition of H2S and CO2, i.e., CO2 decomposition to CO is enhanced in the presence of H2S, and H2S conversion is improved in the presence of CO2. The temporal evolution of unwanted sulfurous compounds (SO2 and COS) are also studied at different residence times and temperatures. The major reactions leading to syngas formation during acid gas decomposition are identified. The developed kinetic model can facilitate the design and optimization of the syngas and sulfur recovery process from acid gas. [ABSTRACT FROM AUTHOR]

In this paper, we prepared binary Mn-Cu and M (M = Ce, Co, Cr, and Fe)-added ternary Mn-Cu-M oxide catalysts using the redox precipitation method, and their catalytic performances in low-temperature CO oxidation were investigated. The prepared catalysts were characterized using XRD, SEM, N2 adsorption/desorption isotherms, XPS, and H2-TPR techniques. It was observed that the CO oxidation performance at low temperature improved significantly when Cu and other dopants were added. The optimum molar ratio of Mn to Cu in a binary oxide catalyst was 1.0/0.1. The Mn-Cu-Co oxide catalyst had the highest activity, which was converted 90% of the CO at the relatively low temperature of 75 °C, among the prepared catalysts. It was concluded that the improvement of oxygen mobility and textural properties for Mn-Cu-Co catalyst are more favorably influenced on the enhanced catalytic activity. [ABSTRACT FROM AUTHOR]