Atmospheric Pressure Of Carbon Dioxide Research Articles

Electrosynthesis of cyclic carbonates from epoxides and atmospheric pressure carbon dioxide

The use of CO(2) for the preparation of value-added compounds has dramatically increased due to increased global warming concerns. We herein report an electrochemical cell containing a copper cathode and a magnesium anode that effectively converts epoxides and carbon dioxide to cyclic carbonates under mild electrochemical conditions at atmospheric pressure.

Rhodium(I)-Catalyzed Direct Carboxylation of Arenes with CO2 via Chelation-Assisted C−H Bond Activation

Rh-catalyzed direct carboxylation of unactivated aryl C-H bond under atmospheric pressure of carbon dioxide was realized via chelation-assisted C-H activation for the first time. Variously substituted and functionalized 2-arylpyridines and 1-arylpyrazoles underwent the carboxylation in the presence of the rhodium catalyst and a stoichiometric methylating reagent, AlMe(2)(OMe), to give carboxylated products in good yields. The catalysis is proposed to consist of methylrhodium(I) species as the key intermediate, which undergoes C-H activation to afford rhodium(III), followed by reductive elimination of methane to give nucleophilic arylrhodium(I). This approach demonstrates promising application of C-H bond activation strategy in the field of carbon dioxide fixation.

Net biological oxygen production in the ocean—II: Remote in situ measurements of O 2 and N 2 in subarctic pacific surface waters

Net community biological production in the euphotic zone of the ocean fuels organic matter and oxygen export from the upper ocean, which has a large influence on the atmospheric pressure of carbon dioxide and is the driving force for metabolite distributions in the sea. We determine the net annual biological oxygen production in the mixed layer of the northeast subarctic Pacific Ocean from in situ O 2 and N 2 measurements. Temperature, salinity, total gas pressure and O 2 were measured every 3 h for 9 months in 2007 at about 3 m depth on a surface mooring at Station P (50°N, 145°W). The concentration of nitrogen gas, N 2, determined from separate total gas pressure and pO 2 measurements, was used as an inert tracer of the physical processes that induce gas departure from thermodynamic equilibrium with the atmosphere. We use a simple model of the ocean’s mixed layer along with the nitrogen concentration to constrain the importance of bubbles, gas exchange and horizontal advection, which are then used in the oxygen mass balance to derive net biological oxygen production. The mixed-layer oxygen mass balance is dominated by exchange with the atmosphere, and we determine a mean summertime oxygen production of 24 mmol O 2 m −2 d −1. The annual pattern in the difference between the supersaturation of oxygen and nitrogen in the surface waters reveals very little net oxygen production during the winter at this location. The calculated annual net community production (NCP) of carbon from this new method, 2.5 mol m −2 yr −1, agrees to within its error of about×40% with previous determinations at this location from oxygen mass balance, NO 3 − draw down and 234Th measurements. This value is either indistinguishable from or lower than annual NCP measurements in the subtropical North Pacific, indicating that there is no experimental evidence for differences in annual NCP between the subarctic and subtropical North Pacific Ocean.

ChemInform Abstract: Silica‐Supported Aminopyridinium Halides for Catalytic Transformations of Epoxides to Cyclic Carbonates under Atmospheric Pressure of Carbon Dioxide.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Antarctic ice-sheet response to atmospheric CO<sub>2</sub> and insolation in the Middle Miocene

Abstract. Foraminiferal oxygen isotopes from deep-sea sediment cores suggest that a rapid expansion of the Antarctic ice sheet took place in the Middle Miocene around 13.9 million years ago. The origin for this transition is still not understood satisfactorily. One possible cause is a drop in the partial pressure of atmospheric carbon dioxide (pCO2) in combination with orbital forcing. A complication is the large uncertainty in the magnitude and timing of the reconstructed pCO2 variability and additionally the low temporal resolution of the available pCO2 records in the Middle Miocene. We used an ice sheet-climate model of reduced complexity to assess variations in Antarctic ice sheet volume induced by pCO2 and insolation forcing in the Middle Miocene. The ice-sheet sensitivity to atmospheric CO2 was tested for several scenarios with constant pCO2 forcing or a regular decrease in pCO2. This showed that small, ephemeral ice sheets existed under relatively high atmospheric CO2 conditions (between 640–900 ppm), whereas more stable, large ice sheets occurred when pCO2 was less than ~600 ppm. The main result of this study is that the pCO2-level must have declined just before or during the period of oxygen-isotope increase, thereby crossing a pCO2 glaciation threshold of around 615 ppm. After the decline, the exact timing of the Antarctic ice-sheet expansion depends also on the relative minimum in summer insolation at approximately 13.89 million years ago. Although the mechanisms described appear to be robust, the exact values of the pCO2 thresholds are likely to be model-dependent.

Silica-supported aminopyridinium halides for catalytic transformations of epoxides to cyclic carbonates under atmospheric pressure of carbon dioxide

Silica-supported 4-pyrrolidinopyridinium iodide was prepared by quaternization of 4-pyrrolidinopyridine with silica-supported alkyl iodide. The pyrrolidinopyridinium structure on the silica surface was confirmed by solid-state 13C CP MAS NMR. The silica-supported 4-pyrrolidinopyridinium iodide showed excellent catalytic performances for transformations of various epoxides to cyclic carbonates under atmospheric pressure of carbon dioxide (CO2). The reactions took place without any solvents or additives other than the catalyst. The catalyst was reusable with retention of activity and selectivity. 1-n-Hexyl-4-pyrrolidinopyridinium as a homogeneous catalyst showed a lower catalytic performance than the supported catalyst. Bifunctional catalysis involving acidic surface silanol and the basic 4-pyrrolidinopyridinium iodide was proposed.

Copper‐Catalyzed Four‐Component Coupling between Aldehydes, Amines, Alkynes, and Carbon Dioxide

AbstractA simple and efficient synthesis of oxazolidinones was developed through a copper‐catalyzed coupling of aldehydes, amines, and terminal alkynes under atmospheric pressure of carbon dioxide.

Coccolithophore cell size and the Paleogene decline in atmospheric CO 2

Alkenone-based Cenozoic records of the partial pressure of atmospheric carbon dioxide (pCO 2) are founded on the carbon isotope fractionation that occurred during marine photosynthesis (ε p37:2). However, the magnitude of ε p37:2 is also influenced by phytoplankton cell size — a consideration lacking in previous alkenone-based CO 2 estimates. In this study, we reconstruct cell size trends in ancient alkenone-producing coccolithophores (the reticulofenestrids) to test the influence that cell size variability played in determining ε p37:2 trends and pCO 2 estimates during the middle Eocene to early Miocene. At the investigated deep-sea sites, the reticulofenestrids experienced high diversity and largest mean cell sizes during the late Eocene, followed by a long-term decrease in maximum cell size since the earliest Oligocene. Decreasing haptophyte cell sizes do not account for the long-term increase in the stable carbon isotopic composition of alkenones and associated decrease in ε p37:2 values during the Paleogene, supporting the conclusion that the secular pattern of ε p37:2 values is primarily controlled by decreasing CO 2 concentration since the earliest Oligocene. Further, given the physiology of modern alkenone producers, and considering the timings of coccolithophorid cell size change, extinctions, and changes in reconstructed pCO 2 and temperature, we speculate that the selection of smaller reticulofenestrid cells during the Oligocene primarily reflects an adaptive response to increased [CO 2(aq)] limitation.

Synthesis of Cyclic Carbonates from Atmospheric Pressure Carbon Dioxide Using Exceptionally Active Aluminum(salen) Complexes as Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Synthesis of Cyclic Carbonates from Atmospheric Pressure Carbon Dioxide Using Exceptionally Active Aluminium(salen) Complexes as Catalysts

AbstractDimetallic aluminium(salen) complexes show exceptionally high catalytic activity for the synthesis of cyclic carbonates from terminal epoxides at ambient temperature and pressure. The process has the potential to contribute towards decreasing atmospheric carbon dioxide emissions from the burning of fossil fuels. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Efficient Fixation of Carbon Dioxide by Electrolysis — Facile Synthesis of Useful Carboxylic Acids —

Electrochemical fixation of atmospheric pressure of carbon dioxide to organic compounds is a useful and attractive method for synthesizing of various carboxylic acids. Electrochemical fixation of carbon dioxide, electrochemical carboxylation, organic halides, organic triflates, alkenes, aromatic compounds, and carbonyl compounds can readily occur in the presence of an atmospheric pressure of carbon dioxide to form the corresponding carboxylic acids with high yields, when a sacrificial anode such as magnesium or aluminum is used in the electrolysis. The electrochemical carboxylation of vinyl bromides was successfully applied for the synthesis of the precursor of nonsteroidal anti-inflammatory agents such as ibuprofen and naproxen. On the other hand, supercritical carbon dioxide (scCO 2) has significant potential as an environmentally benign solvent in organic synthesis and it could be used both as a solvent and as a reagent in these electrochemical carboxylations by using a small amount of cosolvent.

On the application and interpretation of Keeling plots in paleo climate research – deciphering δ<sup>13</sup>C of atmospheric CO<sub>2</sub> measured in ice cores

Abstract. The Keeling plot analysis is an interpretation method widely used in terrestrial carbon cycle research to quantify exchange processes of carbon between terrestrial reservoirs and the atmosphere. Here, we analyse measured data sets and artificial time series of the partial pressure of atmospheric carbon dioxide (pCO2) and of δ13C of CO2 over industrial and glacial/interglacial time scales and investigate to what extent the Keeling plot methodology can be applied to longer time scales. The artificial time series are simulation results of the global carbon cycle box model BICYCLE. The signals recorded in ice cores caused by abrupt terrestrial carbon uptake or release loose information due to air mixing in the firn before bubble enclosure and limited sampling frequency. Carbon uptake by the ocean cannot longer be neglected for less abrupt changes as occurring during glacial cycles. We introduce an equation for the calculation of long-term changes in the isotopic signature of atmospheric CO2 caused by an injection of terrestrial carbon to the atmosphere, in which the ocean is introduced as third reservoir. This is a paleo extension of the two reservoir mass balance equations of the Keeling plot approach. It gives an explanation for the bias between the isotopic signature of the terrestrial release and the signature deduced with the Keeling plot approach for long-term processes, in which the oceanic reservoir cannot be neglected. These deduced isotopic signatures are similar (−8.6‰) for steady state analyses of long-term changes in the terrestrial and marine biosphere which both perturb the atmospheric carbon reservoir. They are more positive than the δ13C signals of the sources, e.g. the terrestrial carbon pools themselves (−25‰). A distinction of specific processes acting on the global carbon cycle from the Keeling plot approach is not straightforward. In general, processes related to biogenic fixation or release of carbon have lower y-intercepts in the Keeling plot than changes in physical processes, however in many case they are indistinguishable (e.g. ocean circulation from biogenic carbon fixation).

Initial responses of carbonate-rich shelf sediments to rising atmospheric pCO 2 and “ocean acidification”: Role of high Mg-calcites

Carbonate-rich sediments at shoal to shelf depths (<200 m) represent a major CaCO 3 reservoir that can rapidly react to the decreasing saturation state of seawater with respect to carbonate minerals, produced by the increasing partial pressure of atmospheric carbon dioxide ( pCO 2) and “acidification” of ocean waters. Aragonite is usually the most abundant carbonate mineral in these sediments. However, the second most abundant (typically ∼24 wt%) carbonate mineral is high Mg-calcite (Mg-calcite) whose solubility can exceed that of aragonite making it the “first responder” to the decreasing saturation state of seawater. For the naturally occurring biogenic Mg-calcites, dissolution experiments have been used to predict their “stoichiometric solubilities” as a function of mol% MgCO 3. The only valid relationship that one can provisionally use for the metastable stabilities for Mg-calcite based on composition is that for the synthetically produced phases where metastable equilibrium has been achieved from both under- and over-saturation. Biogenic Mg-calcites exhibit a large offset in solubility from that of abiotic Mg-calcite and can also exhibit a wide range of solubilities for biogenic Mg-calcites of similar Mg content. This indicates that factors other than the Mg content can influence the solubility of these mineral phases. Thus, it is necessary to turn to observations of natural sediments where changes in the saturation state of surrounding waters occur in order to determine their likely responses to the changing saturation state in upper oceanic waters brought on by increasing pCO 2. In the present study, we investigate the responses of Mg-calcites to rising pCO 2 and “ocean acidification” by means of a simple numerical model based on the experimental range of biogenic Mg-calcite solubilities as a function of Mg content in order to bracket the behavior of the most abundant Mg-calcite phases in the natural environment. In addition, observational data from Bermuda and the Great Bahama Bank are also presented in order to project future responses of these minerals. The numerical simulations suggest that Mg-calcite minerals will respond to rising pCO 2 by sequential dissolution according to mineral stability, progressively leading to removal of the more soluble phases until the least soluble phases remain. These results are confirmed by laboratory experiments and observations from Bermuda. As a consequence of continuous increases in atmospheric CO 2 from burning of fossil fuels, the average composition of contemporary carbonate sediments could change, i.e., the average Mg content in the sediments may slowly decrease. Furthermore, evidence from the Great Bahama Bank indicates that the amount of abiotic carbonate production is likely to decline as pCO 2 continues to rise.

Carbonic anhydrase (Nce103p): an essential biosynthetic enzyme for growth of Saccharomyces cerevisiae at atmospheric carbon dioxide pressure

The NCE103 gene of the yeast Saccharomyces cerevisiae encodes a CA (carbonic anhydrase) that catalyses the interconversion of CO2 and bicarbonate. It has previously been reported that nce103 null mutants require elevated CO2 concentrations for growth in batch cultures. To discriminate between 'sparking' effects of CO2 and a CO2 requirement for steady-state fermentative growth, we switched glucose-limited anaerobic chemostat cultures of an nce103 null mutant from sparging with pure CO2 to sparging with nitrogen gas. This switch resulted in wash-out of the biomass, demonstrating that elevated CO2 concentrations are required even under conditions where CO2 is produced at high rates by fermentative sugar metabolism. Nutritional analysis of the nce103 null mutant demonstrated that growth on glucose under a non-CO2-enriched nitrogen atmosphere was possible when the culture medium was provided with L-aspartate, fatty acids, uracil and L-argininine. Thus the main physiological role of CA during growth of S. cerevisiae on glucose-ammonium salts media is the provision of inorganic carbon for the bicarbonate-dependent carboxylation reactions catalysed by pyruvate carboxylase, acetyl-CoA carboxylase and CPSase (carbamoyl-phosphate synthetase). To our knowledge, the present study represents the first full determination of the nutritional requirements of a CA-negative organism to date.

Stereospecific Electrochemical Carboxylation of β‐Bromostyrene by Use of Nickel(II) Catalyst.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Marked Decline in Atmospheric Carbon Dioxide Concentrations During the Paleogene

The relation between the partial pressure of atmospheric carbon dioxide (pCO2) and Paleogene climate is poorly resolved. We used stable carbon isotopic values of di-unsaturated alkenones extracted from deep sea cores to reconstruct pCO2 from the middle Eocene to the late Oligocene (approximately 45 to 25 million years ago). Our results demonstrate that pCO2 ranged between 1000 to 1500 parts per million by volume in the middle to late Eocene, then decreased in several steps during the Oligocene, and reached modern levels by the latest Oligocene. The fall in pCO2 likely allowed for a critical expansion of ice sheets on Antarctica and promoted conditions that forced the onset of terrestrial C4 photosynthesis.

Stereospecific Electrochemical Carboxylation of β-Bromostyrene by Use of Nickel(II) Catalyst

Abstract Electrochemical carboxylation of (E)- and (Z)-β-bromostyrenes (1) under an atmospheric pressure of carbon dioxide with a platinum cathode and a magnesium anode in the presence of 20 mol % of NiBr2·bpy proceeded with retention of stereochemistry to give the corresponding (E)- or (Z)-cinnamic acids (2). The stereochemical outcome of nickel(II)-catalyzed electrochemical carboxylations was discussed by comparison with predominant formation of a (Z)-isomer from either (E)- or (Z)-β-bromostyrenes.

Electrochemical Carboxylation of 2‐Iodoaromatic Compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Electrochemical Carboxylation of Bicyclo[n.1.0]alkylidene Derivatives.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Electrochemical Carboxylation of 2‐Iodoaromatic Compounds

The electrochemical reduction of a series of 2‐iodoaromatic substituted compounds in acetonitrile under an atmospheric pressure of carbon dioxide leads to ortho‐substitued aromatic carboxylic acid. The maximum yield of acid obtained by electrolysis performed in a diaphragm‐less cell at low temperature (5°C) with a sacrificial magnesium anode and by the use of a low current density was slightly higher than 70%.