CO2 Pressure Research Articles

Carbon dioxide hydrate formation in porous media under dynamic conditions

AbstractInjecting carbon dioxide (CO2) into subsea water zones where the in situ temperatures are below the hydrate‐forming temperature of CO2 has been recently proposed to lock CO2 inside the water zones in solid hydrate form. It is a common concern that CO2 may form hydrates during the injection period that will reduce well injectivity. CO2 injection into sandstone cores under simulated subsea temperatures of 2°C and 3°C was investigated in this study. Experimental result shows that, at 2°C temperature, flowing CO2 at Darcy velocity 0.033 cm/s begins to form hydrate in the sandstone core at about 3.06 MPa (450 psi), which is much higher than the minimum required pressure of 1.5 MPa (220 psi) for CO2 to form hydrate in static condition. The pressure ratio is 450/220 = 2.05. At 3°C temperature, flowing CO2 at Darcy velocity 0.045 cm/s begins to form hydrate in sandstone core at about 3.67 MPa (540 psi), which is much higher than the minimum required pressure of 1.87 MPa (275 psi) for CO2 to form hydrate in static conditions. The pressure ratio is 540/275 = 1.96. The reason why the required minimum pressure for CO2 to form hydrates in dynamic conditions is about double the required hydrate‐forming pressure in static conditions is not fully understood. It is speculated that the shear rate effect of flowing fluids should slow down the growth of hydrate crystals or break down hydrate films, resulting in delayed formation of bulk CO2 hydrates. More investigations in this area are needed in the future.

Comparison of low-pressure and standard-pressure pneumoperitoneum laparoscopic cholecystectomy in patients with cardiopulmonary comorbidities: a double blinded randomized clinical trial.

The benefits of low-pressure laparoscopic cholecystectomy (LPLC) in patients with cardiopulmonary comorbidities remain unclear. This study aimed to explore the feasibility and pulmonary effects of LPLC in patients with cardiopulmonary comorbidities. This was a multicenter, parallel, double-blind, randomized controlled trial. Eligible patients included patients with cardiac or pulmonary comorbidities, who were randomly assigned (1:1) to undergo LPLC (10 mmHg) or standard-pressure laparoscopic cholecystectomy (SPLC) (14 mmHg). The primary outcome was postoperative partial pressure of carbon dioxide (CO2). Surgical safety variables, patient recovery, pulmonary function parameters, and surgeon comfort were also compared between groups. This study enrolled 144 participants, with 124 participants extracted for the final analysis (62 in LPLC and 62 in SPLC group, respectively). The median postoperative PaCO2 was similar in the LPLC (43.3 mmHg) and SPLC (43.0 mmHg) groups (p = 0.988). Pulmonary parameters including postoperative pH, PaCO2, HCO3, and lactate levels were similar between the two groups. Postoperative base excess was significantly higher in the LPLC group (- 0.6 mmol/L [- 6.9 ~ 7.5] vs. -1.9 mmol/L [- 6.6 ~ 5.4]; p = 0.031). There was no between-group difference regarding intraabdominal operative time, rate of intraoperative bile spillage, blood loss, surgeon comfort during surgery, and conversion rate. Moreover, postoperative major complication rates, the median time to the first flatus, postoperative hospital stay, or mean postoperative visual analog scale score for pain were similar in both groups. This study found no reduction of partial pressure of CO2 with LPLC compared with SPLC for patients with cardiopulmonary comorbidities. LPLC with a pneumoperitoneum pressure of 10 mmHg may be safe and feasible for these patients when performed by experienced surgeons, although it does not improve pulmonary parameters. The trial is retrospectively registered at ClinicalTrials.gov (NCT04670952) on December 17, 2020.

Zinc bioinspired catalytic system for the valorisation of CO2 into cyclic carbonates

Cyclic organic carbonates are defined as key compounds for a sustainable chemical economy. Their synthesis from CO2 under mild conditions is a useful way to valorise this greenhouse gas as carbon source. Even if a wide range of catalysts were described to promote the carbon dioxide cycloaddition into epoxides, only few ones concern enzymatic systems. The zinc/L‐histidine active site of carbonic anhydrase inspired the present work, pointing out that the imidazole moiety of the amino acid ligand has a crucial role. An extensive study was undertaken to establish the structure‐activity relationship of imidazole derivatives, zinc salts and their respective catalytic activity in the CO2 cycloaddition reaction. The effect of aromatic, alkyl or iodine substituents and their position in N‐heterocycles were highlighted. A synergic effect was noted when combining imidazole compounds with zinc salts. The optimisation of reaction conditions emphasised the in‐situ ZnI2/1‐methylimidazole catalytic system is selective towards cyclic styrene carbonates and efficient under solvent‐free mild conditions (50°C, atmospheric CO2 pressure). Once reusing tests confirmed the catalytic system robustness, the reaction scope was enlarged to several epoxides resulting in 84‐99% yields of their corresponding cyclic carbonates.

Dependence of cyanobacterium growth and Mars-specific photobioreactor mass on total pressure, pN2 and pCO2

In situ resource utilization systems based on cyanobacteria could support the sustainability of crewed missions to Mars. However, their resource-efficiency will depend on the extent to which gases from the Martian atmosphere must be processed to support cyanobacterial growth. The main purpose of the present work is to help assess this extent. We therefore start with investigating the impact of changes in atmospheric conditions on the photoautotrophic, diazotrophic growth of the cyanobacterium Anabaena sp. PCC 7938. We show that lowering atmospheric pressure from 1 bar down to 80 hPa, without changing the partial pressures of metabolizable gases, does not reduce growth rates. We also provide equations, analogous to Monod’s, that describe the dependence of growth rates on the partial pressures of CO2 and N2. We then outline the relationships between atmospheric pressure and composition, the minimal mass of a photobioreactor’s outer walls (which is dependent on the inner-outer pressure difference), and growth rates. Relying on these relationships, we demonstrate that the structural mass of a photobioreactor can be decreased – without affecting cyanobacterial productivity – by reducing the inner gas pressure. We argue, however, that this reduction would be small next to the equivalent system mass of the cultivation system. A greater impact on resource-efficiency could come from the selection of atmospheric conditions which minimize gas processing requirements while adequately supporting cyanobacterial growth. The data and equations we provide can help identify these conditions.

A novel approach to accelerate the carbonation of γ-C2S under atmospheric pressure: Increasing CO2 dissolution and promoting calcium ion leaching via triethanolamine

An innovative approach to accelerate the carbonation of the γ-2CaO·SiO2 (γ-C2S) under atmospheric pressure was proposed by incorporating triethanolamine (TEA). The effect of TEA on the degree of carbonation (DOC) and the mechanical strength of γ-C2S were investigated, and the mechanism of carbonation accelerated by TEA under atmospheric pressure was analyzed. The results showed that as TEA concentration increased from 0.1 % to 5 %, the DOC initially increased and then decreased, with an optimal concentration of 1 %, where the DOC increased by 126.6 % compared to reference samples after 1 d of carbonation under atmospheric pressure, and this DOC was slightly higher than that of carbonated pastes without TEA under a CO2 pressure of 0.4 MPa. For γ-C2S mortar specimens, the flexural strength and compressive strength with 1 % TEA increased by 109.8 % and 99.3 %, respectively, and these values were slightly higher than those of specimens without TEA under CO2 carbonation pressure of 0.4 MPa. Additionally, at the optimal TEA concentration, CO2 solubility increased by 10.8 times and Ca2+ concentration increased by 94.7 %. This dual effect led to the carbonation rate under atmospheric pressure that could match or slightly exceed that under CO2 pressure of 0.4 MPa, which made this method a novel technique for accelerating carbonation.

Two Sustainable Pathways of MOF-Catalyzed Room Temperature Chemical Fixation of CO2 inside Alkynes under Atmospheric Pressure.

The rising atmospheric CO2 levels necessitate the development of effective materials for its mitigation. Utilization of adsorbent materials for the reversible physisorption of CO2 has a significantly less impact. Recognizing this need, herein, we present a nitrogen-rich, aqua-stable, Ag(0)-nanoparticle-doped metal-organic framework (MOF) designed for the irreversible chemical conversion of CO2 into valuable fine chemicals. We demonstrate two sustainable pathways for CO2 fixation, utilizing the catalyst, 1'@Ag NPs. The designed catalyst facilitates the cyclization of propargylic amines and alcohols under ambient temperature and pressure conditions. Remarkably, this is the first MOF-based catalyst that allows for quantitative conversion of propargylic amines into 2-oxazolidinones at room temperature with atmospheric CO2 pressure. The process successfully transforms various propargylic amines and alcohols into 2-oxazolidinones and α-alkylidene cyclic carbonates under the CO2 atmosphere. Additionally, the catalyst shows excellent recyclability, maintaining its activity and structural integrity across multiple reuse cycles. Control experiments revealed that the catalytic efficiency of 1'@Ag NPs is attributed to the highly exposed alkynophilic Ag(0) sites on its pore walls. Computational studies further elucidate the mechanistic pathway for CO2 fixation. This work highlights the potential of 1'@Ag NPs to enhance environmental sustainability by converting CO2 into valuable bioactive chemicals under mild conditions.

Distribution and air-sea fluxes of CO2 in coral reefs in the Greater Bay Area, China

From May to June 2021, the sea surface partial pressure of CO2 (pCO2) and air-sea CO2 fluxes around six coral reefs in the Great Bay Area (contain Pearl River Estuary (PRE) and Daya Bay) were investigated respectively. The distribution of seawater pCO2 around different coral reefs were quite different. The seawater pCO2 of the coral reef region of Daya Bay is relatively high, ranging from 268 to 496 µatm. In contrast, the pCO2 levels in the coral reef area of the PRE are significantly lower, with measurements ranging from 84 to 374 µatm. Further analysis showed that the distribution of seawater pCO2 around the coral reefs of the PRE were mainly affected by biological metabolism and seawater mixing, while those in Daya Bay were mainly controlled by temperature and seawater mixing. During the survey, the three coral reefs in the PRE were affected by algal blooms showing strong sinks of atmospheric CO2 ranging from −12.3 to −19.2 mmol CO2 m−2 d−1. However, the difference between the seawater pCO2 and atmospheric pCO2 in the three coral reefs of Daya Bay were all very small, and they were weak sources or sinks of atmospheric CO2, respectively.

Ligand-Free Iron-Catalyzed Carbonylation of Aryl Iodides with Alkenyl Boronic Acids: Access to α,β-Unsaturated Ketones.

The application of earth-abundant and low-toxicity iron catalysts as replacements for palladium in carbonylative coupling reactions remains challenging and largely unexplored. Reported here is a highly efficient iron-catalyzed carbonylation of aryl iodides with alkenyl boronic acids under ligand-free conditions, enabling the synthesis of α,β-unsaturated ketones even at atmospheric CO pressure. The broad applicability, including its effectiveness with α-branched enones and biologically active molecules, along with high yields and selectivity, underlines the general applicability of this catalytic system.

Effectiveness of ultra-/very-high-frequency oscillations combined with helium–oxygen gas mixture in a rabbit model

High-frequency oscillatory ventilation (HFOV) at frequencies of approximately 15 Hz is associated with optimal CO2 excretion. Higher frequencies using a nitrogen–oxygen gas mixture worsen CO2 excretion. An in vitro experiment using HFOV and a helium–oxygen gas mixture showed a significant increase in CO2 transport, which increased with increases in ventilation frequency. We hypothesised that in HFOV, the change in the arterial partial pressure of CO2 (PaCO2) would be greater at frequencies above 15 Hz when combined with helium–oxygen gas mixture administration. We tested this hypothesis in a hypoventilated healthy rabbit model by administering a helium–oxygen gas mixture at 15, 25, 35, and 45 Hz frequencies. One-way repeated measures ANOVA showed a significant decrease in PaCO2 among the four ventilation frequency groups. Post-hoc analysis showed significant differences between 15 and 35 Hz frequencies and between 15 and 45 Hz frequencies. The mean (standard error) decrease of PaCO2 was 10.8 (2.2), 14.1 (2.3), 21.3 (3.3), and 23.1 (2.5) mmHg at 15, 25, 35, and 45 Hz, respectively. Combination therapy of helium–oxygen gas mixture and high-frequency oscillation using ultra/very high frequencies (35–45 Hz) was associated with a greater PaCO2 decrease than that using the standard frequency (15 Hz).

Mixed venous to arterial pCO2-gap is poorly correlated to cardiac index in 1526 pulmonary artery catheter monitored critically ill patients

Abstract Background The CO2 gap is the difference between mixed venous and arterial CO2, and can be estimated by the difference in partial pressure in CO2 (Pv-aCO2 or ∆PCO2). ∆PCO2 is affected by cardiac output (CO), CO2 production and solubility. The central venous-to-arterial CO2 gap has been proposed as a less invasive surrogate for P(v-a)CO2 and has been investigated as a measure of adequacy of resuscitation, and to guide sepsis management. Nevertheless, the CO2-gap as determinant of CO has never been thoroughly investigated in large cohort of critically ill ICU-patients. This study aims to investigate the relationship between ∆PCO2 and cardiac index (CI) in a retrospective cohort of critically ill patients in a large quaternary cardiothoracic intensive care unit. Methods Over 62 months, pulmonary artery catheter monitored critically ill patients were identified and their case files reviewed in retrospect. Extracorporeal membrane oxygenation (ECMO) patients were excluded. P(v-a)CO2 measurements were defined as mixed venous and arterial pCO2 measurements drawn simultaneously or within maximum 30 minutes together with PA-measurements. Correlation coefficients were calculated between P(v-a)CO2 and CI, serum lactate, mixed venous saturations (SvO2), cardiac power index (CPI), inotropic score (IS), central venous pressure (CVP) and minute expiratory volume (MV)(Table 1). We used receiver operator characteristic (ROC) curves to assess the diagnostic performance of P(v-a)CO2 as a surrogate for CI lower than 2,2L/min/m2. Multivariate linear regression analysis was performed with P(v-a)CO2 as an dependent variable. Results 4414 P(v-a)CO2 measurements were identified from 1526 patients. Median P(v-a)CO2 was 0,86 kPa (0,66-1,1) or 6.45 mmHg (4.95-8.25), and mean CI was 2.7l/min/m2 (2.2-3.2). Correlation coefficients of P(v-a)CO2 with the other variables remained poor (> 0,35). The area under the ROC curve for P(v-a)CO2 as a predictor of CI<2.2l/min/m2 was 0.65, p<0.0001 (Fig. 1B). A value of P(v-a)CO2 > 6.9 mmHg was found to have the highest sensitivity and specificity, with a poor performance of 61.21% sensitivity and 62.73% specificity. Conclusion This large retrospective study in 1526 critically ill cardiac ICU-patients did not demonstrate a strong relationship between P(v-a)CO2 and CI, nor with any other hemodynamic variable found in the ICU patient cohort studied (Table 1). This raises scepticism regarding the efficacy of P(v-a)CO2 as a physiological goal in guiding resuscitation and management of this precarious patient group. Therefore, we argue that the PA-catheter remains the cornerstone in assessing critically ill (cardiothoracic) ICU patients.

Synthesis and catalytic application to form cyclic carbonates of novel Pd(II) Cu(II), and Fe(II) benzoate-based Schiff base metal complexes

This work describes the synthesis and characterisation of six novel Schiff base complexes, Cu(II), Pd(II), and Fe(II), which, under the right circumstances, function as very efficient catalysts for the production of cyclic carbonates from CO2 and epoxides. FT-IR spectroscopy, elemental analysis, UV–Vis spectroscopy, molar conductivity, melting point, and magnetic susceptibility measurements are among the spectroscopic methods used to characterize newly synthesized complexes. The molar conductivity values, ranging from 2.58 to 4.03 µS/cm, suggest that the complexes exhibit no molar conductivity. Co-catalysts, such as 4-(dimethylamino)pyridine, pyridine, triethylamine, and triphenyl phosphine, were used in these processes, both with and without one. 4-(Dimethylamino)pyridine was used as the co-catalyst in the catalytic studies. Additionally, a number of variables that affect the cycloaddition process were examined, including the temperature, CO2 pressure, reaction time, and co-catalyst. All novel catalysts exhibited exceptional catalytic activity and selectivity in the catalytic assays. Regarding the coupling of CO2 and epichlorohydrin as epoxides, the L2-Cu catalyst outperformed other catalysts in terms of catalytic activity (90.7%) and selectivity (98.9%).

Mineralization reaction between CO2 and coal ash produced from underground coal gasification: Implication for in situ carbon sequestration

Underground coal gasification (UCG) represents a promising clean and low-carbon energy technology, which could create a suitable cavity for in situ carbon sequestration by mineralization reaction between CO2 and coal ash produced from UCG. This may assist in achieving a net-zero carbon emission goal for UCG projects. To determine the carbonation efficiency and mineralization potential of CO2 mineral sequestration in abandoned UCG cavity, coal ash produced from the gasification of three different low-rank coal samples was used in this study. A comparative experiment was conducted using a group of high-calcium fly ash from a coal-fired power plant. All mineralization reaction experiments were performed in a high-temperature and high-pressure reactor, with CO2 pressures ranging from 2 to 8 MPa and temperatures ranging from 40 to 80°C. These conditions were selected to simulate the sequestration conditions in the UCG cavity. Real-time monitoring of CO2 pressure in the reactor was used to assess the impact of solid-to-water ratio, temperature, and pressure on the CO2 mineralization. X-ray diffraction and scanning electron microscopy were employed to identify the presence of newly formed carbonate minerals associated with mineralization reaction. The results indicated that the coal ash produced by gasification pretreatment at 900°C contains a substantial quantity of alkaline-earth oxides, such as calcium oxide (CaO), with a relative mass fraction reaching 25.9%. It provided an adequate supply of alkali metal ions for the mineralization reaction, which exhibited comparable efficacy in mineralizing CO2 to that observed in high-calcium fly ash. Without stirring, at lower solid-to-water ratio, the maximum amount of CO2 consumed through mineralization was increased by up to 74.12%. Carbonation efficiency decreased with rising temperatures below 70°C due to the limited dissolution of CO2 in water, it increased with elevated pressure but decreased in the supercritical state, potentially attributable to the dissolution of carbonate minerals in a supercritical CO2 environment. The process of mineralization reaction between CO2 and coal ash aligned well with the Surface Coverage Model (R2 values ranging from 0.92 to 0.99). A preliminary estimation based on Chinese coal reserves revealed that the potential of CO2 sequestration capacity in UCG cavities by mineralization ranging from 29 to 102 Gt, an additional 517 Gt CO2 may be stored when filled with fly ash. This paper provides theoretical bases for predicting the maximum carbonation efficiency under high-pressure and high-temperature conditions in UCG cavities, and research directions for achieving a net-zero carbon emission goal for UCG projects.

68 Feasibility of applying synchronized and proportional negative pressure ventilation in preterm infants with respiratory distress (NeoVest)

Abstract Background In preterm infants, application of negative pressure ventilation (NPV) may offer advantages to traditional methods of nasal continuous positive airway pressure (nCPAP). In a pre-clinical model, we recently described the “NeoVest”, a system consisting of a sealed abdominal interface and a ventilator that applies NPV in synchrony and in proportion to the diaphragm electrical activity (Edi) (Beck 2022). In animals with loaded breathing, the Neovest allowed a 50% reduction in Edi, and demonstrated specific diaphragm unloading, without hemodynamic effects. The NeoVest system, and its interface, have yet to be evaluated in human infants. Objectives The aim of the study was to evaluate the feasibility of applying synchronized and proportional NPV with an abdominal interface in infants with respiratory distress. Design/Methods This is a prospective feasibility trial. The inclusion criteria were admission to the Neonatal Intensive Care Unit with respiratory distress, birthweight>1.5kg, <6 weeks of age, FiO2 <0.35, clinically stable with no recent apneas and bradycardias, nCPAP <8 cm H2O and at least 48 hrs old, or post-extubation. After parental consent, the feeding tube was exchanged for a 6F “Edi catheter” (for feeding and measuring Edi), and sensors were placed (heart rate, oxygen saturation, transcutaneous CO2, and non-invasive blood pressure (BP)). Figure 1 shows the Neovest interface on a manikin. The five protocol steps were: nCPAP ON/NeoVest OFF (10 min), nCPAP ON/NeoVest ON (10 min), NO ASSIST (1 min), NeoVest only medium (10 min), NeoVest high (5 min), NeoVest low (5 min). Results Eight babies have been included to this point. The principal diagnoses were Respiratory Distress Syndrome and/or Transient Tachypnea of the Newborn. Mean weight was 2186±480g and age 10±8 days old. All babies tolerated the physical application of the vest. As shown in Figure 2, there was no significant difference in Edipk when the vest was placed (12.4±5.5 vs. 11.1±3.5 uV). During the period of no assist, Edipk was higher (18.8 ±7.3 uV) than nCPAP or NeoVest periods (p= 0.012), which were not significantly different from each other. Neural respiratory rate was the same for all periods tested. As per its design, the Neovest system delivered negative pressure in synchrony and in proportion to the Edi. Negative pressures applied (□PVEST) were -9±4, -11±4, and -7±5 cmH2O (Figure 2) for the three NeoVest periods. All infants were clinically stable with no disruptions to vital signs. Conclusion Applying synchronized and proportional negative pressure with the NeoVest system was feasible and showed promise with regards to diaphragm unloading. Future studies are required to evaluate the NeoVest utility for longer periods and compared to other methods of respiratory support.

The optimal dietary sodium and chloride level for broiler chicks fed a corn-soybean meal diet between 1 and 21 days of age.

The experiment was conducted to estimate the ideal dietary sodium (Na) and chloride (Cl) level for broilers during d 1 to 21 using a corn-soybean meal diet under a dietary Na:Cl ratio of 1:1. A total of 490 one-d-old Arbor Acres male broilers were randomly allotted by bodyweight to 1 of 7 treatments in a completely randomized design. Each treatment consisted of 7 replicate cages with 10 chicks per cage. Broilers were fed a Na and Cl-unsupplemented corn-soybean meal basal diet (control, containing 0.02% Na and 0.08% Cl) and the Na and Cl-supplemented basal diets containing 0.14%, 0.20%, 0.26%, 0.32%, 0.38% and 0.44% Na and Cl levels, respectively for 21 d. The results indicated that average daily gain, average daily feed intake, blood partial pressure of CO2 and concentrations of HCO3-, total CO2, Na+, Cl-, base excess and anion gap, tibial ash and ash Na contents of broilers were affected (P < 0.001) by dietary Na and Cl level, and increased linearly (P < 0.001) and quadratically (P < 0.001) with increasing Na and Cl levels. Feed/gain ratio, mortality, blood K+ concentration, serum osmotic pressure and K+, glucose and uric acid concentrations as well as heart, liver and kidney indices of broilers were affected (P < 0.01) by dietary Na and Cl level, and decreased linearly (P < 0.001) and quadratically (P < 0.001) with increasing Na and Cl levels. The estimates of dietary optimal Na and Cl levels were 0.07%-0.16% according to the best fitted broken-line or asymptotic models (P < 0.001) of the above sensitive indicators. Therefore, the optimal dietary Na and Cl level was suggested to be 0.16% to support all of the above Na and Cl metabolic requirements of broilers fed the corn-soybean meal diet during d 1 to 21, which is lower than the recommendation at 0.20% by the Chinese Feeding Standard of Chicken (2004).

Mixed-Linker Zr-Metal-Organic Framework with Improved Lewis Acidic Sites for CO2 Fixation Reaction Catalysis.

Applying the mixed-linker strategy in synthesizing metal-organic frameworks (MOFs) has drawn considerable attention as a heterogeneous catalyst owing to their easy synthesis and different functional ligands in their frameworks. Following this strategy, we have developed a mixed linker Zr(IV)-based MOF, [Zr6O4(OH)4(FUM)n(PZDC-NO2)6-n] (PZDC-NO2 = 4-nitro-3,5-pyrazoledicarboxylic acid, FUM = fumaric acid) denoted as MOF-801(PZDC-NO2) synthesized via this strategy which possess an electron-withdrawing group (-NO2) on secondary linkers. The MOF-801(PZDC-NO2) has been fully characterized via various analyses, such as Fourier transform infrared, powder X-ray diffraction, 13C/1H nuclear magnetic resonance, XPS, TGA, and N2 adsorption/desorption, SEM, EDX, etc. By considering the concurrent existence of acid-base active sites and the synergistic role of these sites, this mixed-linker MOF was used as a catalyst for the cycloaddition reaction of CO2 and epoxides under mild without-solvent conditions. MOF-801(PZDC-NO2) displays significant catalytic performance by producing the highest catalytic conversion of epoxide to cyclic carbonate (93%) with a turnover number of 130.7 in 8 h reaction time and 100 °C temperature under low-pressure CO2 pressure. The mixed-linker Zr-MOF exhibits exceptional stability and reusability, maintaining its structure and functionality after consecutive cycles of utilization. Finally, the reaction mechanism was further investigated by density functional theory calculations. The total energy of the reactants, intermediates, and products involved in the process.

Microscale heat and mass transfer characteristics of CO2 flooding in nanotubes of tight oil reservoirs

AbstractThe mechanism of heat and mass transfer in tight oil reservoirs after CO2 injection is complex. In this paper, first, a CO2 transfer model within microscale adjacent nanotubes in tight oil reservoirs is established. Then, the typical heat and mass transfer characteristics of microscale CO2 in tight oil reservoirs is analyzed, and the influence of grid density on the calculation results is discussed. Finally, the influence of thermal conductivity of tight oil reservoirs on CO2 physical properties parameters is revealed. Results show that: (a) From the inlet end of the thick nanotube to the outlet of the nanotube, the pressure of CO2 drops from 3.5 to 3.3697 MPa. (b) When the mesh length is equal to 5 nm, the CO2 pressure in the thin nanotube drops from 3.5 to 3.3329 MPa, and the CO2 pressure in the thick nanotube drops from 3.5 to 3.2018 MPa. (c) Organic amines react with CO2 to form salts, which can seal high permeability layers and cracks, but there is a risk of environmental pollution.

Photochemically Driven Palladium- Phosphinoacridine Catalysis: A Carboxylative Approach for Arylcarbamate Synthesis.

In this study, we demonstrate that phosphinoacridines are efficient bidentate ligands for palladium-catalyzed carboxylative C-N coupling reactions under blue LED irradiation. This method facilitates the direct synthesis of arylcarbamates using a range of non-activated aryl halides, such as iodides and bromides, with various amines under atmospheric pressure of CO2. The optimized conditions exhibit high tolerance to sensitive functional groups, resulting in very good to excellent yields of the desired products. This approach expands the scope of palladium-catalyzed carboxylation reactions and offers an environmentally friendly route to arylcarbamates.

Landfill-gas-to-biomethane via a new carbon capture and utilization technology: One-pot sodium chloride batch mineralization

A new landfill-gas-to-biomethane route adopts a new carbon capture and utilization process via sodium chloride (NaCl) mineralization. The new process exports chlorine (Cl2), dense carbon dioxide (CO2), hydrogen (H2) and sodium carbonate (Na2CO3). Process absorbs CO2 from landfill-gas with aqueous NaOH/Na2CO3 in batch multi-purpose columns that execute several processing steps in one-pot; namely: CO2 absorption; sodium bicarbonate (NaHCO3) precipitation; NaHCO3 filtration driven by pressurized CO2; NaHCO3 breakage to Na2CO3 via hot CO2 injection; Na2CO3 cooling via cold CO2 injection; and solid Na2CO3 disposal through column lateral doors. The one-pot columns avoid investment with several steady-state complex equipment like bubble-columns, centrifuges, filters, solid dryers, heaters, mud pumps and solid transporters. The depleted solvent from the one-pot columns is regenerated via steady-state, high current-density, brine electrolysis wherein solvent continually feeds cathodes, while brine continually feeds anodes as sodium source. Sodium reaches the cathode through selective Flemion F9010 ion-exchange membrane. CO2 is partially mineralized to Na2CO3 and partially exported as supercritical CO2. Process output-ratios per captured CO2 are: 1.159kgNa2CO3/kg, 0.7754kgCl2/kg, 0.4299kgCH4/kg, 0.0219kgGREEN−H2/kg and 0.51875kgCO2/kg, while the input-ratios are 1.2782kgNaCl/kg, 0.197kgH2O/kg and 1.7495kWh/kg. The new landfill-gas-to-biomethane (480,000Nm3/d landfill-gas) was evaluated environmentally and techno-economically reaching 48.6MMUSD investment, 112MMUSD/y revenues and 418.34MMUSD net value (30 years).

Operando XANES Reveals the Chemical State of Iron-Oxide Monolayers During Low-Temperature CO Oxidation.

We have used grazing incidence X-ray absorption near edge spectroscopy (XANES) to investigate the behavior of monolayer FeOxfilms on Pt(111) under near ambient pressure CO oxidation conditions with a total gas pressure of 1 bar. Spectra indicate reversible changes during oxidation and reduction by O2 and CO at 150ºC, attributed to a transformation between FeO bilayer and FeO2 trilayer phases. The trilayer phase is also reduced upon heating in CO+O2, consistent with a Mars-van-Krevelen type mechanism for CO oxidation. At higher temperatures, the monolayer film dewets the surface, resulting in a loss of the observed reducibility. A similar iron oxide film prepared on Au(111) shows little sign of reduction or oxidation under the same conditions. The results highlight the unique properties of monolayer FeO and the importance of the Pt support in this reaction. The study furthermore demonstrates the power of grazing-incidence XAFS for in situ studies of these model catalysts under realistic conditions.

Conversion of Carbon Dioxide into Molecular-based Porous Frameworks.

ConspectusThe conversion of carbon dioxide (CO2) to value-added functional materials is a major challenge in realizing a carbon-neutral society. Although CO2 is an attractive renewable carbon resource with high natural abundance, its chemical inertness has made the conversion of CO2 into materials with the desired structures and functionality difficult. Molecular-based porous materials, such as metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs), are designable porous solids constructed from molecular-based building units. While MOF/COFs attract wide attention as functional porous materials, the synthetic methods to convert CO2 into MOF/COFs have been unexplored due to the lack of synthetic guidelines for converting CO2 into molecular-based building units.In this Account, we describe state-of-the-art studies on the conversion of CO2 into MOF/COFs. First, we outline the key design principles of CO2-derived molecular building units for the construction of porous structures. The appropriate design of reactivity and the positioning of bridging sites in CO2-derived molecular building units is essential for constructing CO2-derived MOF/COFs with desired structures and properties. The synthesis of CO2-derived MOF/COFs involves both the transformation of CO2 into building units and the formation of extended structures of the MOF/COFs. We categorized the synthetic methods into three types as follows: a one-step synthesis (Type-I); a one-pot synthesis without workup (Type-II); and a multistep synthesis which needs workup (Type-III).We demonstrate that borohydride can convert CO2 into formate and formylhydroborate that serve as a bridging linker for MOFs in the Type-I and Type-II synthesis, representing the first examples of CO2-derived MOFs. The electronegativity of coexisting metal ions determines the selective conversion of CO2 into formate and formylhydroborate. Formylhydroborate-based MOFs exhibit flexible pore sizes controlled by the pressure of CO2 during synthesis. In pursuit of highly porous structures, we present the Type-I synthesis of MOFs from CO2 via the in situ transformation of CO2 into carbamate linkers by amines. The direct conversion of diluted CO2 (400 ppm) in air into carbamate-based MOFs is also feasible. Coordination interactions stabilize the intrinsically labile carbamate in the MOF lattice. A recent study demonstrates that the Type-III synthesis using alkynylsilane precursors enables the synthesis of highly porous and stable carboxylate-based MOFs from CO2, which exhibit catalytic activity in CO2 conversion. We also extended the synthesis of MOFs from CO2 to COFs. The Type-III synthesis using a formamide monomer affords stable CO2-derived COFs showing proton conduction properties. The precise design of CO2-derived building units enables expansion of the structures and functionalities of CO2-derived MOF/COFs. Finally, we propose future challenges in this field: (i) expanding structural diversity through synthesis using external fields and (ii) exploring unique functionalities of CO2-derived MOF/COFs, such as carriers for CO2 capture and precursors for CO2 transformation. We anticipate that this Account will lay the foundation for exploring new chemistry of the conversion of CO2 into porous materials.