Enhancement of reaction rates for catalytic benzaldehyde hydrogenation and sorbitol dehydration in water solvent by addition of carbon dioxide

Hydrogenation of 4-t-butylphenol over an activated carbon-supported rhodium catalyst in carbon dioxide solvent was analyzed based on phase observation with a view cell and calculations of the solubility of 4-t-butylphenol using the Peng-Robinson equation of state as a function of carbon dioxide pressure. The reaction experiments showed that the initial reaction rate of 4-t-butylphenol at 313 K under 2 MPa of hydrogen pressure was increased by the addition of carbon dioxide, especially above a total pressure of 11 MPa. Direct visual observation showed that the solubility of 4-t-butylphenol increased with higher carbon dioxide pressure. The calculations based on the Peng-Robinson equation of state also showed that the solubility of 4-t-butylphenol in the 4-t-butylphenol–carbon dioxide–hydrogen (2 MPa) system at 313 K significantly increased by addition of carbon dioxide above a total pressure of 11 MPa. We concluded that the increase in the hydrogenation rates was caused by the increased concentration of 4-t-butylphenol substrate in the carbon dioxide solvent.

We are trying to develop a methane-producing system using indigenous microbes in depleted oil fields as a new microbial enhanced oil recovery process. In particular, we aim to combine a microbial conversion of the residual oil into methane with the geological sequestration of carbon dioxide. The mechanism is as follows: Hydrocarbon-degrading bacteria are harnessed to produce hydrogen and/or acetate from residual oil in the depleted oil reservoir. Then, methane-producing microbes (methanogens) utilize the produced acetate or hydrogen and carbon dioxide, which is injected for geological sequestration, to generate methane. We successfully isolated hydrogen- and methane-producing microbes (hydrogen-producing bacteria and methanogens) from oil fields (Yabase and other oil fields) in Japan. Our analysis of microbial cultures incubated under high temperature and high pressure, the condition similar to in situ petroleum reservoir conditions, revealed that indigenous microbes in the reservoir brine are capable of generating methane by utilizing crude oil and carbon dioxide. Consumption/production rate of gases (methane and carbon dioxide) and acetic acid indicated that the methane production under reservoir conditions is likely mediated through two major pathways; the acetoclastic (acetic-acid utilizing) and the hydrogenotrophic (hydrogen and carbon-dioxide utilizing) pathways. Furthermore, by analyzing methane-producing ability of isolated microbes, we found that the syntrophic cooperation between hydrogen-producing bacteria and methanogens was critical for the methane producing under the reservoir condition. 0%.tures with carbon dioxideent Strikingly, addition of carbon dioxide accelerated methane production of the cultures. The methane production rate of the cultures, in which high concentration (10%) of carbon dioxide was supplied into the head spaces, was 0.30 mmol/L/Day. On the other hand, the cultures without the addition of carbon dioxide showed the methane production rate of 0.12 mmol/L/Day, significantly slower (ca. 40%) than the production rate of the cultures with carbon dioxide. These results suggested that addition (injection) of carbon dioxide into reservoirs might accelerate the microbial methane production. We further investigated the methanogenic communities and pathways in petroleum reservoirs by incubating the reservoir brine from the Yabase oil field, combined with radiotracer experiments and molecular biological analyses. The brine samples were incubated without exogenous-nutrient supplementation under the high-temperature and high-pressure condition (the in-reservoir condition). The radiotracer analysis (using 14C-biocarbonate and 14C-acetate) indicated that the methane production rate of hydrogenotrophic methanogenesis was 50-fold higher than that of acetoclastic methanogenesis, suggesting dominance of methane production by syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis in reservoir. In this study, we assessed the rate of oil biodegradation coupled with methanogenesis by using 14C-labeled toluene and hexadecane as tracers. The analysis revealed that the rate was very low, being only about one thousandth of that of the hydrogenotrophic methanogenesis. We are currently trying to enhance the crude-oil biodegradation for effective conversion of crude oil to methane. Our goal is to establish effective microbial conversion system from residual oil into methane in depleted oil fields as a new EOR technology.

Effects of simultaneous hydrogen enrichment and carbon dioxide dilution of fuel on soot formation in an axisymmetric coflow laminar ethylene/air diffusion flame

The process of carbonaceous materials gasification is especially relevant in Russia, where the volume of coal waste exceeds 120 million tons. A gasification installation for carbon-containing waste operating in the fixed-bed mode has been developed. Experiments on gasification of fine coal fraction samples (1–2 mm) were carried out using preheated air, a steam-air mixture, and air with added carbon dioxide as gasifying agents. The work used the methods of differential scanning calorimetry, thermogravimetric analysis, and chromatographic analysis. Additions of water vapor and carbon dioxide made it possible to increase the heat of combustion and increase the gasification efficiency to 54%. The operating mode of the gas generator was determined, ensuring the production of synthesis gas with a calorific value of 3.6 MJ/nm3. It is shown that the highest efficiency of gas generation is achieved in the steam-air gasification mode with the addition of water vapor in the amount of 0.1 kg per 1 kg of coal and with the use of air as a gasifying agent with the addition of carbon dioxide in a volume ratio of 100:5. It is established that an increase in the addition of water vapor and carbon dioxide above the optimal amounts leads to a decrease in the efficiency of the gasification process. The process can use waste from various industries, including oil sludge, which determines its significance for the effective management of carbon-containing waste and for achieving broader environmental and economic goals.

"The corrosion protection effect of the new S-1 reagent in media with the pH values of 2.0, 4.0, 6.0, as well as carbon dioxide and hydrogen sulfide added separately and combined to the mentioned media, was first tested under laboratory conditions. The protective effect of reagent S-1 was weak in the corrosion medium without hydrogen sulfide and carbon dioxide. However, as the acidity of the medium and the concentration of the reagent increases, the corrosion protection efficiency of the inhibitor also increases. The highest effect is observed at pH = 2.0 and reagent concentration of 30 mg/l. The corrosion protection effect of the reagent reaches 97% under these conditions. In the media with pH = 4.0 and pH = 6.0 without carbon dioxide and hydrogen sulfide, the protective effect of the inhibitor at the optimal concentration of 30 mg/l is 66% and 64%, respectively. In the medium with added carbon dioxide, the protective effect of inhibitor S-1 decreases at pH = 2.0 and, on the contrary, increases at the values of pH = 4.0 and pH = 6.0. Also, as the pressure of carbon dioxide in the medium increases, the protective effect of inhibitor S-1 increases. When hydrogen sulfide is added to the medium, it causes an increase in the corrosion rate and the protection efficiency of inhibitor S-1. However, in the medium without inhibitor, the increase of hydrogen sulfide concentration only up to CH2S = 400 mg/l is accompanied by an increase in the corrosion rate at all values of pH. The addition of 1000 mg/l of hydrogen sulfide to the corrosion medium leads to the decrease in the corrosion rate in the medium without inhibitors and a slight decrease in the protective effect at the concentration of the inhibitor Cinh = 10 mg/l. As the concentration of inhibitor S-1 increases in the medium with the addition of carbon dioxide and hydrogen, its corrosion protection effect also increases. In the range of Cinh = 10–30 mg/l, when PCO2 = 0.5 atm and CH2S = 200 mg/l, the protective effect is estimated at 38–99%, and when CH2S = 1000 mg/l, it is estimated at 17–79%. At PCO2 = 1.0 atm, the value of protective effect is 22–95% and 14–76%, and finally at PCO2 = 2.0 atm, the value of the corrosion protection effect of inhibitor S-1 is estimated at 44–92% and 15–75%, respectively. The coexistence of carbon dioxide and hydrogen sulfide in an aggressive medium leads to an increase in the protective effect of inhibitor S-1 compared to the medium containing only carbon dioxide, and reduces it in comparison to the medium with hydrogen sulfide. An increase in carbon dioxide pressure in the presence of hydrogen sulfide causes a decrease in the protective effect of inhibitor S-1. The protective effect of inhibitor S-1 is lower in the medium with hydrogen sulfide concentration of 1000 mg/l compared to a concentration of 200 mg/l. This case is also observed in the carbon dioxide free medium."

Effect of cross airflow on the flame geometrical characteristics and flame radiation fraction of ethylene jet fires with carbon dioxide addition

Dehydration of erythritol in high-temperature carbonated water

Electrocatalytic hydrogenation (ECH) is a promising route for low-temperature bio-oil treatment, wherein renewable electricity can be used to store hydrogen in hydrocarbon energy carriers used as transportation fuels.1 ECH of phenol and benzaldehyde (model compounds) shows rates and selectivity to hydrogenation that depend on the metal.2 As bio-oil is a mixture of compounds with different functionalities, development of a sustainable process towards bio-oil stabilization often requires the fundamental understanding of competitive hydrogenation pathways in presence of mixtures of model compounds. Thus, the present study aims to explore the hydrogenation kinetics and reaction pathways of simultaneous conversion of phenol and aromatic carbonyls on carbon supported metal catalysts. Under ECH, all catalysts tested (Rh/C, Pd/C, Ru/C, Cu/C) were active for benzaldehyde hydrogenation to benzyl alcohol, however, only Rh/C was active for the hydrogenation of phenol which yielded cyclohexanone and cyclohexanol. The hydrogenation activity of benzaldehyde increases in the following order Ru/C < Rh/C < Pd/C < Cu/C. H2 evolution reaction (HER) is the prevalent side reaction. Therefore, an important variable to study is the selectivity (Faradaic efficiency) defined as fraction of total electron used for hydrogenation. Hydrogenation selectivity was ~90% for both Ru/C and Pd/C, however, Rh/C and Cu/C showed ~50% selectivity. When phenol was co-fed alongside benzaldehyde, no phenol hydrogenation was noted on all catalysts tested. However, an enhancement in ECH rate of benzaldehyde (~2-4 fold depending on metal catalyst) was observed in case of Pd/C, Ru/C and Cu/C (Figure 1a). ECH of benzaldehyde was very similar on Rh/C in presence and absence of phenol. The presence of phenol in the feed increased Faradaic efficiency in case of Cu/C and decreased it on Rh/C and Ru/C. We hypothesize that phenol, co-adsorbed on the metal, affects the rates of HER hindering the reaction of hydronium ions with the metal. On the other hand, phenol interacts with benzaldehyde and thus, facilitates the hydrogenation and results in an enhancement in rate. Indeed, when the benzaldehyde hydrogenation was carried out on Pd/C with different phenolic compounds with varying pKa, increasing hydrogenation rates were noted with decreasing pKa of the phenolic compounds (Figure 1b). Although, an enhancement (x2) in benzaldehyde hydrogenation was noted with 20 mM of phenol, increasing phenol concentration further (until 200 mM) barely have an impact on the hydrogenation rate. However, no such enhancement was observed when the hydrogenation was studied with molecular H2 as the reduction equivalent instead of cathodic potential. This suggests that benzaldehyde hydrogenation might proceeds through an electrochemical step with direct involvement of the phenolic compounds. The results of the detail kinetic studies, and the corresponding reaction mechanisms will be addressed in this presentation. Figure 1

Comparative study on the effects of nitrogen and carbon dioxide on methane/air flames

Hydrogen production rates by Anabaena sp. strain TU37-1 obtained after an initial 1-day incubation period were approximately 70 to 80 and 3 to 9 micro mol (mg chl)(-1) h(-1) under argon and nitrogen atmospheres, respectively. Hydrogen production under argon was not enhanced by addition of carbon dioxide, but was enhanced to some extent under nitrogen by increasing the initial carbon dioxide concentration. Rates of hydrogen and oxygen production during the initial 7-hour period were 15 and 220 micro mol (mg chl)(-1) h(-1), respectively, in vessels with 18.5% initial carbon dioxide. Hydrogen production under nitrogen was enhanced by addition of carbon monoxide (1%). The rate obtained from the initial 1-day incubation period was about 40 micro mol (mg chl)(-1) h(-1), which corresponded to about 60% of that under argon. On the basis of these observations, a possible strategy for hydrogen production by nitrogen-fixing cyanobacteria under nitrogen in the presence of carbon monoxide is indicated.

It is predicted that the concentration of carbon dioxide in the ocean will continue to increase. This phenomenon certainly has an impact on the sustainability of the marine ecosystem, including the seagrass ecosystem. This study aims to determine the effect of carbon dioxide on the morphometrics and growth of E. acoroides seedling. This study was an experimental study where the seeds from the fruit were grown in a controlled environment for two months. There are two treatments, first treatment with the addition of carbon dioxide and second treatment without the addition of carbon dioxide. The results of this study indicate that there is significant result from the two treatments given. Seagrass seeds that grow on treatment with carbon dioxide gas generally have shorter morphological characteristics as well as their growth.

The controllable mass transfer and reaction rate for phase transfer hydrogenation of acetophenone across a well‐defined boundary were investigated. The effect of solvent was found important and 1‐butanol exhibited the best performance among the five investigated homologous alcohol solvents, consistent with its higher solubility in water and greater dielectric constant. Initial reaction rates increased with increasing electric potential, consistent with enhanced mass transfer across the aqueous/organic boundary. At longer reaction times, deactivation was apparent. It correlated with increasing voltage and is ascribed to lower equilibrium concentration of reactive species at the interface. External control over reaction rate was demonstrated by switching the applied electric potential over the course of the reaction. Effects of external electric field on enantioselectivity were also explored with reversal field direction. The changes correlate with catalyst decomposition.

High hydrostatic pressure (HHP) is used for microbial inactivation in foods. Addition of carbon dioxide (CO2) to HHP can improve microbial and enzyme inactivation. This study investigated microbial effects of combined HHP and CO2 on Escherichia coli, Bacillus subtilis, and Saccharomyces cerevisiae, and evaluated sensory attributes of treated feijoa fruit puree (pH 3.2). Microorganisms in their growth media and feijoa puree were treated with HHP alone (HHP), or saturated with CO2 at 1 atm (HHPcarb), or 0.4%w/w of CO2 was injected into the package (HHPcarb+CO2). Microbial samples were processed at 200 to 400 MPa, 25 °C, 2 to 6 min. Feijoa samples were processed at 600 MPa, 20 °C, 5 min, then served with and without added sucrose (10%w/w). Treated samples were analyzed for microbial viability and sensory evaluation. Addition of CO2 enhanced microbial inactivation of HHP from 1.7-log to 4.3-log reduction in E. coli at 400 MPa, 4 min, and reduction of >6.5 logs in B. subtilis (vegetative cells) starting at 200 MPa, 2 min. For yeast, HHPcarb+CO2 increased the inactivation of HHP from 4.7-log to 6.2-log reduction at 250 MPa, 4 min. The synergistic effect of CO2 with HHP increased with increasing time and pressure. HHPcarb+CO2 treatment did not alter the appearance and color, while affecting the texture and flavor of unsweetened feijoa samples. There were no differences in sensory attributes and preferences between HHPcarb+CO2 and fresh sweetened products. Addition of CO2 in HHP treatment can reduce process pressure and time, and better preserve product quality. A higher microbial inactivation of Escherichia coli, Bacillus subtilis and Saccharomyces cerevisiae by combining dense phase carbon dioxide and high hydrostatic pressure was observed. For sweetened products there were no significant differences in sensory attributes and preferences between samples treated by the combined method and the fresh samples. In conclusion, addition of CO2 in HHP treatment of juices could reduce process severity and improve product quality.

Options for recarbonation, remineralisation and disinfection for desalination plants

The ring-opening copolymerization of carbon dioxide and epoxides is a useful means to make aliphatic polycarbonates and to add-value to CO2. Recently, the first heterodinuclear Zn(ii)/Mg(ii) catalyst showed greater activity than either homodinuclear analogue (J. Am. Chem. Soc. 2015, 137, 15078-15081). Building from this preliminary finding, here, eight new Zn(ii)/Mg(ii) heterodinuclear catalysts featuring carboxylate co-ligands are prepared and characterized. The best catalysts show very high activities for copolymerization using cyclohexene oxide (TOF = 8880 h-1, 20 bar CO2, 120 °C, 0.01 mol% catalyst loading) or cyclopentene oxide. All the catalysts are highly active in the low pressure regime and specifically at 1 bar pressure CO2. The polymerization kinetics are analysed using in situ spectroscopy and aliquot techniques: the rate law is overall second order with a first order dependence in both catalyst and epoxide concentrations and a zero order in carbon dioxide pressure. The pseudo first order rate coefficient values are compared for the catalyst series and differences are primarily attributed to effects on initiation rates. The data are consistent with a chain shuttling mechanistic hypothesis with heterodinuclear complexes showing particular rate enhancements by optimizing distinct roles in the catalytic cycles. The mechanistic hypothesis should underpin future heterodinuclear catalyst design for use both in other (co)polymerization and carbon dioxide utilization reactions.