CO2 Production Research Articles

Novel Chemical Routes for Carbon Dioxide and Methane Production from Lignin Photodegradation: The Role of Environmental Free Radicals.

Sunlight irradiation significantly mediates plant litter's carbon dynamics and volatile carbon release in semi-arid and arid ecosystems. In this process, carbon loss is controlled by lignin, but the mechanisms of production of CO2 and CH4 during lignin photolysis are ambiguous. In this study, the photomineralization of plant litter and the lignocellulosic component collectively indicate that lignin is a major source of CO2 and CH4 emissions. Characterization and free radical analysis reveal that the production of CO2 is due to the oxidation and ring-opening reaction of the coniferyl alcohol unit, with the subsequent decarboxylation of carboxylic acid as an oxidation product. This reaction involves o-quinone formation by the reactions between O2, superoxide radical (O2·-), and persistent free radicals (PFRs)-bearing lignin. Of this, O2·- contributes to 43.2% of the photogenerated CO2, as a new pathway, derived from the electron transfer from PFRs to O2. Interestingly, photoinduced demethylation of the dimethoxybenzene-type compounds as the photolysis products of lignin results in a never-before-reported CH4 formation chemical route independent of that of O2. This mechanistic insight into the role of lignin in volatile carbon production from the irradiative plant litter will contribute to a deeper understanding of carbon balance in water-limited ecosystems.

Study on the Formation Mechanism of NOx Precursors During Density Functional Theory Pyrolysis of Leucine and Proline

ABSTRACT Incineration is an efficient method of resource utilization for kitchen waste. As an important stage of incineration, pyrolysis not only degrades kitchen waste but also generates pollutants such as nitrogen oxides. It is necessary to conduct in-depth research on the nitrogen conversion mechanism during its pyrolysis process. Most of the nitrogen in kitchen waste is concentrated in protein/amino acids. This article is based on the density functional theory calculation method, selecting typical compounds leucine and proline in kitchen waste as research objects, and studying their pyrolysis mechanism and the formation path of NOx precursors. A possible path for the cleavage of C-C/C-N bonds caused by hydrogen transfer to form NH3 and HCN has been proposed. Finally, it has been theoretically proven that the pyrolysis process of leucine tends to generate NH3 rather than HCN. And it was clarified that low energy barriers and high reaction rates are the reasons for the difference in production of these two NOx precursors. Meanwhile, the differences in the generation characteristics of NOx precursors for proline at different pyrolysis temperatures were theoretically explained. Finally, it was elucidated that leucine and proline preferentially undergo decarboxylation to complete the deoxygenation process, and the reason for the difference in CO production during the pyrolysis of the two amino acids was explained. In addition, this study found that the pyrolysis of leucine occurred preferentially than that of proline under the same conditions, and the yield of NOx precursor produced by leucine was higher than that of proline.

Wastewater treatment plant effluents increase the global warming potential in a subtropical urbanized river

Rivers play a pivotal role in global carbon (C) and nitrogen (N) biogeochemical cycles. Urbanized rivers are significant hotspots of greenhouse gases (GHGs, N2O, CO2 and CH4) emissions. This study examined the GHGs distributions in the Guanxun River, an effluents-receiving subtropical urbanized river, as well as the key environmental factors and processes affecting the pattern and emission characteristics of GHGs. Dissolved N2O, CO2, and CH4 concentrations reached 228.0 nmol L–1, 0.44 mmol L–1, and 5.2 μmol L–1 during the wet period, and 929.8 nmol L–1, 0.7 mmol L–1, and 4.6 μmol L–1 during the dry period, respectively. Effluents inputs increased C and N loadings, reduced C/N ratios, and promoted further methanogenesis and N2O production dominated by incomplete denitrification after the outfall. Increased urbanization in the far downstream, high hydraulic residence time, low DO and high organic C environment promoted methanogenesis. The strong CH4 oxidation and methanogenic reactions inhibited by the effluents combined to suppress CH4 emissions in downstream near the outfall, and the process also contributed to CO2 production. The carbon fixation downstream from the outfall were inhibited by effluents. Ultimately, it promoted CO2 emissions downstream from the outfall. The continuous C, N, and chlorine inputs maintained the high saturation and production potential of GHGs, and altered microbial community structure and functional genes abundance. Ultimately, the global warming potential downstream increased by 186 % and 84 % during wet and dry periods on the 20-year scale, and increased by 91 % and 49 % during wet and dry periods on the 100-year scale, respectively, compared with upstream from the outfall. In urbanized rivers with sufficient C and N source supply from WWTP effluents, the large effluent equivalently transformed the natural water within the channel into a subsequent "reactor". Furthermore, the IPCC recommended EF5r values appear to underestimate the N2O emission potential of urbanized rivers with high pollution loading that receiving WWTP effluents. The findings of this study might aid the development of effective strategies for mitigating global climate change.

Fabrication of double modified electrocatalyst by dual flame synthesis for enhancing electrochemical reduction of carbon dioxide

A rapid dual flame synthesis is developed for one-step preparation and modification of double modified ZnO catalysts with carbon doping and oxygen vacancies. The growth mechanism and nanostructure evolution are also investigated. The double modified ZnO with carbon doping and oxygen vacancies exhibies excellent performance in CO2 reduction to syngas, with a high current density of 14.02 mA/cm2 at −1.1 V vs. RHE and a maximum Faradaic efficiency of 71% for CO production. The maximum adjustable range of the CO/H2 ratio from 0.5 to 2.7. In a flow cell, the double modified ZnO exhibits a large current density of 126.8 mA/cm2 at −1.2 V vs. RHE. The maximum Faradaic efficiency for CO2 reduction to CO is 74.8% at 50 mA/cm2. Double modified ZnO maintains stable potential and Faradaic efficiency for over 5 h of electrolysis. Operando X-ray absorption spectroscopy and density functional theory calculations reveal that the active site is the Zn–Zn configuration, and that carbon dopant and oxygen vacancy promote CO2 activation and CO desorption, and reduce reaction overpotential of CO2RR.

Covalent Organic Framework Stabilized Single CoN4Cl2 Site Boosts Photocatalytic CO2 Reduction into Tunable Syngas.

Solar carbon dioxide (CO2) reduction provides an attractive alternative to producing sustainable chemicals and fuel. However, the construction of a highly active photocatalyst was challenging because of the rapid charge recombination and sluggish surface CO2 reduction. Herein, a unique Co-N4Cl2 single site was fabricated by loading Co species into the 2,2'-bipyridine and triazine-containing covalent organic framework (COF) for CO2 conversion into syngas under visible light irradiation. The resulting champion catalyst TPy-COF-Co enabled a record-high CO production rate of 426 mmol g-1 h-1, associated with the unprecedented turnover number (TON) and turnover frequency (TOF) of 2095 and 1607 h-1, respectively. The catalyst also exhibited favorable recycling performance and widely adjustable syngas production (CO/H2 ratio: 1.8:1-1:16). A systematical investigation includingoperandosynchrotron X-ray absorption fine structure (XAFS) spectroscopy, in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), and theoretical calculation indicated that the triazine-based COF framework promoted the charge transfer towards the single Co-N4Cl2 sites that greatly promoted the CO2 activation by lowering the energy barrier of *COOH generation, facilitating the CO2 transformation. This work highlights the great potential of the molecular regulation of COF-derived single-atom catalysts to boost CO2 photoreduction efficiency.

A comparative study on the slow pyrolysis of Miscanthus (Miscanthus×giganteus Greef et Deu.) cultivated on agricultural and contaminated soils: Assessment of distribution of final products

This study aims to investigate the slow pyrolysis behavior of uncontaminated (MSC-I - reference) and heavy metals contaminated (MSC-R) samples with heavy metals from the tailings of a Pb-Zn-Cu flotation mine, consisting of whole stems of Miscanthus. Physicochemical properties of raw materials were investigated through instrumental characterization techniques (Atomic Absorption Spectrometry (AAS), Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray diffraction (XRD)), while the pyrolysis process was monitored by simultaneous thermal analysis techniques (thermogravimetry (TG) – derivative thermogravimetry (DTG)), coupled with Mass spectrometry (MS), for evolved gas analysis. After determination of the lignocellulose content (cellulose, hemicellulose, and lignin) and extractive of the MSC-I and MSC-R samples, it was found that Pb, Zn, Fe, and Mn in MSC-R lead to very fast decomposition of extractive fraction, which facilitates their distribution in formed bio-char, together with lignin char-participation, acting catalytically. It was established that a much greater fraction of extractives decomposition products and non-volatile heavy metals are incorporated in MSC-R bio-char increasing its yield (23 %), compared to MSC-I bio-char yield (21.5 %). It was identified that MSC-R has increased production of H2, CO, and CO2, while decreased production of CH4, influenced by Fe (Fe has a significant positive effect on CO2 evaluation during MSC-R pyrolysis, enhancing decarboxylation process). It was established that CH4 reforming reactions catalyzed by iron additionally affect methane reduction, and increase production of H2, compared to the reference sample. Isoconversional kinetic analysis showed that pyrolysis reactions profile was strongly conditioned by the presence of heavy metals, such as Cd, Pb, and Zn, because they affect the modification of biomass lignocellulosic structure. Also, it was found that small amounts of Cd present in MSC-R can increase pyrolysis activation energy of three pseudo-components, and inhibit their deoxygenation, thus increasing yield of bio-char.

Predicting and understanding photocatalytic CO2 reduction reaction with IR spectroscopy-based interpretable machine learning framework.

The highly selective conversion of carbon dioxide into value-added products is extremely valuable. However, even with the aid of in situ characterization techniques, it remains challenging to directly correlate extensive spectral data carrying microscopic information with macroscopic performance. Herein, we adopted advanced machine learning (ML) approaches to establish an accurate and interpretable relationship between vibrational spectral signals and catalytic performances to uncover hidden physical insights. Focusing on photocatalytic CO2 reduction, our model is shown to effectively and accurately predict the CO production activity and selectivity based solely on the infrared (IR) spectral signals, the generalizability of which is additionally demonstrated with a new Bi5O7I photocatalytic system. More importantly, further model analysis has revealed a novel strategy to steer CO selectivity, the physical sanity of which is verified by a detailed reaction mechanism analysis. This work demonstrates the tremendous potential of machine-learned spectroscopy to efficiently identify reaction control factors, which can further lay the foundation for targeted optimization and reverse design.

Soil priming effect in the organic and mineral layers regulated by nitrogen mining mechanism in a temperate forest

AbstractSoil organic carbon (SOC) in temperate forests is a crucial part of the global C cycle. The C and nitrogen (N) inputs may greatly increase in forest ecosystems affected by atmospheric CO2 concentration, N deposition, and other climate change, which may further affect SOC dynamics in temperate forests. Nevertheless, how C and N inputs interact to influence the soil priming effect (PE) in the organic and mineral layers of temperate forests remains unclear. Here, we used easily available C and N sources, such as 13C‐glucose with 2% SOC contents and ammonium nitrate (input C:N ratio = 10), to examine the effects and mechanisms of exogenous C and N inputs on soil CO2 production and PE in both soil layers of a temperate forest. Our research revealed that exogenous C input caused a positive PE in both soil layers, with the mineral layer showing a larger PE per unit of SOC than the organic layer (OL). Although C input increased C loss from native SOC, soil net C accumulation still increased. The C and N inputs decreased the soil PE in both soil layers, suggesting that N input alleviates substrate N limitation and weakens microbial N mining in both soil layers. Meanwhile, the C and N inputs increased the exogenous C remaining in the organic layer, which was beneficial for soil C sequestration. Compared to the organic layer, the response of the mineral layer to C and N inputs was weaker. This study suggests that C and N interact to affect PE on SOC decomposition and this interaction should be considered in modeling and prediction of soil C cycling.

Intensified, Kilogram-Scaled, and Environment-Friendly: Chemoenzymatic Synthesis of Bio-Based Acylated Hydroxystyrenes.

Lignin-derived styrene derivatives are versatile building blocks for the manufacture of biobased polymers. As shown previously, phenol-protected hydroxystyrenes are accessible under industrially sound conditions (>100 g L-1, >95% yield) by subjecting biogenic phenolic acids to enzymatic decarboxylation and base-catalyzed acylation in nonaqueous media (wet cyclopentyl methyl ether, CPME). Herein, we demonstrate the production of 1 kg of 4-acetoxy-3-methoxy-styrene in a 10 L reactor and present practical adjustments to the up- and downstream processing that warrant a straightforward process and high isolated yields. Additionally, an environmental assessment is conducted, starting with a thorough E factor analysis to identify the sources that contribute most to the environmental burden (solvent and downstream processing). Also, the total CO2 production of the process is studied, including contributions from energy use and the treatment of generated wastes. The energy impact is evaluated through thermodynamic analysis, and the environmental footprint contributions by wastes-organic and aqueous fractions-are assessed based on CO2 emissions from solvent incineration and wastewater treatment, respectively. Overall, the holistic assessment of the process, its optimization, scale-up, product isolation, and environmental analysis indicate the feasibility of multistep chemoenzymatic reactions to deliver high-volume, low-value chemicals from biorefineries.

Recovery of ventilatory and metabolic responses to hypoxia in neonatal rats after chronic hypoxia

Chronic hypoxia (CH) during postnatal development attenuates the hypoxic ventilatory response (HVR) in mammals, but there are conflicting reports on whether this plasticity is permanent or reversible. This study tested the hypothesis that CH-induced respiratory plasticity is reversible in neonatal rats and investigated whether the initial plasticity or recovery differs between sexes. Rat pups were exposed to 3 d of normobaric CH (12 % O2) beginning shortly after birth. Ventilation and metabolic CO2 production were then measured in normoxia and during an acute hypoxic challenge (12 % O2) immediately following CH and after 1, 4–5, and 7 d in room air. CH pups hyperventilated when returned to normoxia immediately following CH, but normoxic ventilation was similar to age-matched control rats within 7 d after return to room air. The early phase of the HVR (minute 1) was only blunted immediately following the CH exposure, while the late phase of the HVR (minute 15) remained blunted after 1 and 4–5 d in room air; recovery appeared complete by 7 d. However, when normalized to CO2 production, the late phase of the hypoxic response recovered within only 1 d. The initial blunting of the HVR and subsequent recovery were similar in female and male rats. Carotid body responses to hypoxia (in vitro) were also normal in CH pups after approximately one week in room air. Collectively, these data indicate that ventilatory and metabolic responses to hypoxia recover rapidly in both female and male neonatal rats once normoxia is restored following CH.

A ligand-modulated photostable Mn(I)-carbonyl complex for preferential conversion of CO2 to CO in water.

A strategically designed redox-active ligand ensures proper electronic balance in an Mn(I)-carbonyl template to induce photostability and water solubility. This newly designed Mn-carbonyl complex showcased rapid CO2 reduction with preferential production of CO (faradaic efficiency ∼88%) as the only C1 product in pure water, even from a flue gas resource.

Heterogenization of a dinuclear cobalt molecular catalyst in porous polymers via covalent strategy for CO 2 photoreduction with record CO production efficiency

Heterogenization of a dinuclear cobalt molecular catalyst in porous polymers via covalent strategy for CO ₂ photoreduction with record CO production efficiency

Cyanobacteria decay alters CH4 and CO2 produced hotspots along vertical sediment profiles in eutrophic lakes

Cyanobacteria-derived organic carbon has been reported to intensify greenhouse gas emissions from lacustrine sediments. However, the specific processes of CH4 and CO2 production and release from sediments into the atmosphere remain unclear, especially in eutrophic lakes. To investigate the influence of severe cyanobacteria accumulation on the production and migration of sedimentary CH4 and CO2, this study examined the different trophic level lakes along the middle and lower reaches of the Yangtze River. The results demonstrated that eutrophication amplified CH4 and CO2 emissions, notably in Lake Taihu, where fluxes peaked at 929.9 and 7222.5 μmol/m2·h, mirroring dissolved gas levels in overlying waters. Increased sedimentary organic carbon raised dissolved CH4 and CO2 concentrations in pore-water, with isotopic tracking showing cyanobacteria-derived carbon specifically elevated CH4 and CO2 in surface sediment pore-water more than in deeper layers. Cyanobacteria-derived carbon deposition on surface sediment boosted organic carbon and moisture levels, fostering an anaerobic microenvironment conducive to enhanced biogenic CH4 and CO2 production in surface sediments. In the microcosm systems with the most severe cyanobacteria accumulation, average CH4 and CO2 concentrations in surface sediments reached 6.9 and 2.3 mol/L, respectively, surpassing the 4.7 and 1.4 mol/L observed in bottom sediments, indicating upward migration of CH4 and CO2 hotspots from deeper to surface layers. These findings enhance our understanding of the mechanisms underlying lake sediment carbon emissions induced by eutrophication and provide a more accurate assessment of lake carbon emissions.

Enhancing the safety and thermal stability of polyurethane filling materials in the mining industry through expanded graphite-based hydrated salts

The utilization of Polyurethane foaming materials (PUF) to seal coal fissures presents a significant challenge due to the substantial heat generated during the reaction process, potentially accelerating fires. In order to study this issue, we propose a novel low-heat polymerization mechanism by incorporating a hydrated salt phase change composite that efficiently absorbs polymerization heat while encapsulating liquid water using expanded graphite (EG). Our findings demonstrate that integrating 10 % EG-6 leak-free phase change material effectively reduces the reaction temperature to a safer 91.4 °C, ensuring minimal impact on the inherent properties of the material. Thorough analyses via TGA and in-situ IR experiments reveal a noteworthy 17 °C elevation in the modified PUF's thermodynamic characteristic temperature point. Additionally, we developed a mixed combustion model of PUF and coal to investigate the gas generation pattern of polyurethane in the mine-filled state where fire occurs. Specifically, the introduction of PUF reduced O2 consumption and CO production while increasing CO2 and C2H4 production, which is consistent with the reality of increased carbon hydrocarbon gases being monitored downhole. These findings suggest a synergistic, mutually beneficial relationship between the two during the low-temperature oxidation stage. This research offers perspectives for the development of polymer materials for coal mines and the safe application of actual filling.

GFP Chromophore Integrated Conjugated Microporous Polymers toward Bioinspired Photocatalytic CO2 Reduction to CO.

The development of highly active, durable, and low-cost metal-free catalysts for the photocatalytic CO2 reduction reaction (CO2RR) is an efficient and environmentally friendly solution to address significant problems like global warming and high energy demand. In the present study, we have demonstrated the design and synthesis of a donor-acceptor based conjugated microporous polymer (CMP), TPA-GFP, by integrating an electron donor, tris(4-ethynylphenyl)amine (TPA), with a green fluorescent protein chromophore analogue (Z)-4-(2-hydroxy-3,5-diiodobenzylidene)-1-(4-iodophenyl)-2-methyl-1H-imidazol-5(4H)-one (o-HBDI-I3) (GFP). In comparison to nondonor 1,3,5-triethynylbenzene (TEB) based TEB-GFP CMP, photocatalytic CO2 reduction using donor-acceptor based TPA-GFP CMP displays a 3-fold increment of CO production yield with a maximum CO yield of 1666 μmol g-1 at 12 h. Further, the CO selectivity increases significantly from a mere 54% in TEB-GFP to an impressive 95% in TPA-GFP. The impressive CO2 reduction efficiency and selectivity for TPA-GFP can be attributed to the efficient light-harvesting capability and facile charge separation and migration through donor-acceptor building units of the CMP. The mechanistic aspect of the photocatalytic CO2 reduction process is explored using in situ DRIFTS and DFT calculation, and a plausible photocatalytic mechanism is proposed.

Morphology effects of CeO2 on the performance of CaO-Cu/ CeO2 for integrated CO2 capture and conversion to CO

CeO2 support inhibits CaO sintering, and oxygen vacancy influences CO2 hydrogenation performance, making CeO2 widely applied in Integrated CO2 capture and in-situ conversion technology for reverse water–gas shift (ICCC-RWGS). Oxygen vacancy concentration was dependent on the morphology of CeO2, which would affect metal dispersion and CO2 hydrogenation conversion. However, Very little is known about the morphology effect of CeO2 on the carbon capture and in-situ hydrogenation performance of DFMs. Here, Cu/CeO2 with different CeO2 morphologies was synthesized, and high Cu dispersion was achieved on Cu/CeO2-R, exhibiting the best CO2 hydrogenation performance. Integrated Cu/CeO2 with CaO by physical mixing method, CaO-Cu/CeO2 was used to investigate the morphology effects of CeO2 on the performance of CaO-Cu/CeO2 for integrated CO2 capture and conversion to CO. CaO-Cu/CeO2-R exhibited the best capture-hydrogenation performance (CO2 conversion rate of 75 %, CO production rate of 9.72 mmol/g). The CeO2-R provided more surface oxygen vacancies, enhancing carbonate hydrogenation. The larger specific surface area and {110} crystal plane of CeO2-rod enhanced Cu dispersion, and the smaller particle size of CeO2-R enhanced its interaction with CaO, improving the cyclic stability of CaO-Cu/CeO2-R. The hydrogenation performance of CaO-Cu/CeO2 was dependent on the morphology of CeO2, providing insights into the design of high-activity metal catalytic components in ICCC-RWGS.

Environmental co-limitation on temperature responses of greenhouse gas production in floodplain sediments

Despite the rising interest in understanding how climate change could affect the emissions of greenhouse gases (GHGs) from river systems, including floodplains, we still lack a mechanistic understanding of how changing environmental conditions, such as moisture and nutrient availability, limit the temperature responses of GHG production in floodplain sediments. To examine the environmental co-limitations on the temperature responses of three major GHGs (CO2, CH4, and N2O) produced in floodplain sediments, sediments from a constructed wetland on the floodplain of the lower Han River were incubated for 24 d at four temperatures spanning 4–28 ℃, under three conditions (closed, open/wetting, and open/drying). The net production of all three GHGs exhibited nonlinear temperature responses with gas-specific patterns and magnitudes of response varying over the incubation period. During the later incubation phase, positive temperature responses were weakened for the net production of CO2 and CH4 in the dried treatments, whereas a similar weakening occurred for N2O production in the wet treatments. This, combined with incubation-induced changes in dissolved organic carbon and its fluorescence components, indicated the lack or excess of moisture and associated changes in O2 and organic carbon availability as critical co-limiting factors for the temperature responses of GHG production. Warming decreased δ13C in the CH4 emitted from wet and hypoxic sediments, implying a stronger warming effect on CH4 production over oxidation. Unlike many studies assuming a consistent relationship between temperature and GHG production in sediments irrespective of other environmental conditions, our results suggest that warming effects on the GHG emissions from floodplain sediments would depend on the balance between gas production and consumption under the prevailing constraints of moisture, O2, and labile carbon availability.

A novel ionic liquids phase change absorption system for carbon dioxide capture and utilization

In order to achieve low cost, and reduce energy consumption during regeneration, a novel ionic liquid phase change absorbent composed of tetraethylenepentamine [TEPA] imidazole [Im] and diethylene glycol dimethyl ether (DGME) and water was designed for CO2 capture applications. The absorbent [TEPAH][Im]+DM+H2O can achieves a CO2 absorption capacity of 2.08 mol CO2/mol ILs, the rich phase volume accounts for 15.6 vol%, and the mass fraction of CO2 is 99 %, this greatly reduces the regenerative volume of the absorption system, showing the potential of energy saving and emission reduction. After five absorption–desorption cycles, the regeneration efficiency of the system remained above 96 %. The CO2 capture mechanism was analyzed using both 13C NMR spectroscopy and density functional theory (DFT) calculations to elucidate its underlying processes. The cation [TEPAH]+ and the anion [Im]- each undergo a reaction with CO2 to produce carbamate, followed by hydrolysis of carbon dioxide to yield carbonate. The absorption system’s phase transition behavior primarily arises from variations in CO2 product solubility across solvents. Moreover, the ionic liquid facilitated the conversion of CO2 into quinazoline-2,4 (1H, 3H)-dione with a remarkable yield of 98 %. Even after five cycles, the ILs maintained substantial catalytic activity.

Photocatalytic performance of metal poly(heptazine imide) for carbon dioxide reduction

Poly(heptazine imide) (PHI), a carbon nitride polymer, is a highly efficient visible-light-driven photocatalytic material. We aimed to improve its photocatalytic performance for CO2 conversion. We prepared M-PHIs by encapsulating different metals (M = K, Li, Rb, and Na) and H-PHIs, in which the metal of each M-PHI was ion-exchanged with a proton. We evaluated their photocatalytic activities for CO2 conversion and found that Na-PHI and H-PHI, prepared from Na-PHI (H-PHI(NaCl)), showed more than twice the CO production efficiency of melon and other PHIs.The high CO production efficiency of Na-PHI and H-PHI(NaCl) was attributed to their extremely smaller particle size compared with those of the other PHIs. By closely examining the synthesis conditions of Na-PHI, we have identified a method to intentionally synthesize M-PHI with small particle size. These results provide a new strategy for highly efficient CO2 conversion using PHI.

Bench-Scale Gasification of Olive Cake in a Bubbling Fluidized Bed Reactor

The gasification of olive cake is a promising method for converting this material into valuable energy. This work offers interesting results about the effect of equivalence ratio and temperature on the composition and quality of the produced gas obtained during olive cake gasification in a fluidized bed plant with air as a gasification agent. Additionally, the efficiency of the gasification process was evaluated. The results show that, for a specific temperature, an equivalence ratio of 0.3 showed a higher cold gas efficiency. For example, at 850 °C and an equivalence ratio of 0.1, the cold gas efficiency was 22.7%; however, at the same temperature but at an equivalence ratio of 0.3, the cold gas efficiency was increased to 61.2%. In addition, for a constant equivalence ratio, by increasing the operating temperature, there was no significant increase in the lower heating value of the exit gas, and the gas flow was practically constant with temperature, but it varied substantially with the equivalence ratio, reaching values in the range of 3.44–14.89 NL/min (825.6–3573.6 NL/kg feed). Finally, the production of CO, H2, and CH4 is estimated to be higher for tests conducted with an equivalence ratio of 0.3.