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Water-gas shift reaction was applied to upcycle a waste-derived synthesis gas, which contains sulfur as an impurity. Pt/CeO2 was chosen as an appropriate catalyst through a metal and support screening study. The Pt/CeO2 catalyst showed stable catalytic activity without any deactivation for 100 h when the H2S was injected to 100 ppm, and still showed a sulfur tolerance even after 1,000 ppm of H2S was injected. In particular, the catalytic activity was fully regenerated when the H2S injection was stopped, regardless of the H2S concentration. The high sulfur tolerance and regeneration rate of Pt/CeO2 catalyst was due to the high oxygen storage capacity. This accelerates the redox mechanism of the water-gas shift reaction, and also helps the removal of the adsorbed sulfur on the Pt through the oxidation reaction with the mobile oxygen originated from the CeO2.

This study focuses on the applicability of single-atom Mo-doped graphitic carbon nitride (GCN) nanosheets which are specifically engineered with high surface area (exfoliated GCN), NH

The inherent recalcitrance of lignocellulosic biomass is a significant barrier to efficient lignocellulosic biorefinery owing to its complex structure and the presence of inhibitory components, primarily lignin. Efficient biomass pretreatment strategies are crucial for fragmentation of lignocellulosic biocomponents, increasing the surface area and solubility of cellulose fibers, and removing or extracting lignin. Conventional pretreatment methods have several disadvantages, such as high operational costs, equipment corrosion, and the generation of toxic byproducts and effluents. In recent years, many emerging single-step, multi-step, and/or combined physicochemical pretreatment regimes have been developed, which are simpler in operation, more economical, and environmentally friendly. Furthermore, many of these combined physicochemical methods improve biomass bioaccessibility and effectively fractionate ∼96 % of lignocellulosic biocomponents into cellulose, hemicellulose, and lignin, thereby allowing for highly efficient lignocellulose bioconversion. This review critically discusses the emerging physicochemical pretreatment methods for efficient lignocellulose bioconversion for biofuel production to address the global energy crisis.

The maximum production rate of dimethyl ether (DME) through direct CO2 (or CO) hydrogenations on the bifunctional Cu-ZnO-Al2O3 hybridized with highly crystalline ferrierite (FER) zeolite (CZA/FER) was observed at an optimal Si/Al molar ratio of ∼12 (CZA/FER(12)) due to its larger metallic surface area of Cu nanoparticles and relatively higher hydrophobic surface natures. The smaller size of metallic Cu nanoparticles in the larger Cu-ZnO-Al2O3 matrices decorated with smaller ZnO moiety effectively increased the hydrophobic surfaces of the CZA/FER(12), which further preserved the larger number of acidic sites on the FER surface. The phenomena also caused less aggregations of Cu nanoparticles by their stronger interactions in the Cu-ZnO-Al2O3 matrices. The higher CO2 (and CO) conversion and DME productivity of 4.53 mmol/(gcat h with lower CO formation rate of 0.90 mmol/(gcat h on the CZA/FER(12) were attributed to the stable preservations of the strongly interacted smaller Cu nanoparticles even under water excess environment by easily desorbing water molecules with its suppressed competitive adsorptions on the hydrophobic CZA/FER(12) surfaces.

Dry reforming of methane (DRM) is an attractive route to simultaneously consume both methane (CH4) and carbon dioxide (CO2) for the production of valuable syngas. Although nickel catalysts are cons...

Enhanced catalytic performance is required to increase the efficiency of hydrogen production from waste-derived synthesis gas via the high-temperature water-gas shift reaction (HT-WGSR). Herein, the effects of barium, zirconium, and neodymium doping on the physico-chemical properties of a Ce/Cu/Al2O3 catalyst as well as its catalytic performance for HT-WGSR are investigated. Ce/Cu/Al2O3 catalysts with various additives (barium, zirconium, and neodymium) prepared via a sequential impregnation method have been characterized by using N2 adsorption-desorption isotherms, X-ray powder diffraction (XRPD), N2O-titration, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and hydrogen temperature-programmed reduction (H2-TPR). Advantageously, barium and zirconium addition enhance the HT-WGSR activity and stability of the Ce/Cu/Al2O3 catalyst, whereas neodymium doping has a negative effect. Regarding the correlation of catalytic performance with the characterization results, it was found that catalytic activity and stability strongly depended on their oxygen vacancy concentration and strong-metal to support interaction.

To investigate the effect of Cu/CeO2 catalysts preparation methods for low temperature water−gas shift reaction, Cu/CeO2 catalysts were prepared with various impregnation sequences and applied to the water−gas shift reaction at a high gas hourly space velocity of 36,080 mL/g·h. The catalyst preparation method affected both the Cu−Ce synergistic effect and the physico−chemical properties of the Ce promoted Cu/CeO2 catalysts, such as specific surface area, Cu particle size, Cu dispersion, amount of active Cu species and oxygen vacancy concentration. Among the prepared catalysts, Cu–Ce/CeO2 showed the highest CO conversion because of the high contents of active Cu species and high concentration of oxygen vacancies.

Ni-MgO catalysts have been widely applied for carbon dioxide reforming (CDR) reaction due to their ability of anti-carbon formation. However, activation of Ni-MgO catalyst consumes considerable energy because of its very low reducibility. In this study, ZrO2, CeO2, and CeO2-ZrO2 promoted Ni-MgO catalysts were prepared via a facile coprecipitation method and applied to the CDR reaction. Among the prepared catalysts, the ZrO2-promoted Ni-MgO catalyst showed the highest methane conversion. The high catalytic performance of the ZrO2-promoted Ni-MgO catalyst is mainly due to easier reducibility, high Ni dispersion, and high specific surface area.

A comprehensive understanding of the cellular response of microbes to metal stress is necessary for the rational development of microbe-based biosorbents for metal removal. The present study investigated the copper (Cu) sorption and resistance mechanism of Bacillus cereus strain T6, a newly isolated Cu-resistant bacterium, by integrative analyses of physiochemistry, genomics, transcriptomics, and metabolomics. The growth inhibition assay and biosorption determination showed that this bacterium exhibited high tolerance to Cu, with a minimum inhibitory concentration of 4.0 mM, and accumulated Cu by both extracellular adsorption and intracellular binding. SEM microscopic images and FTIR spectra showed significant cellular surface changes at the high Cu level but not at low, and the involvement of surface functional groups in the biosorption of Cu, respectively. Transcriptomic and untargeted metabolomic analyses detected 362 differentially expressed genes and 60 significantly altered metabolites, respectively. Integrative omics analyses revealed that Cu exposure dramatically induced a broad spectrum of genes involved in Cu transport and iron homeostasis, and suppressed the denitrification pathway, leading to significant accumulation of metabolites for metal transporter synthesis, membrane remolding, and antioxidant activities. The results presented here provide a new perspective on the intricate regulatory network of Cu homeostasis in bacteria.

Hydrogen is mainly produced by steam reforming of fossil fuels. Thus, research has been continuously conducted to produce hydrogen by replacing fossil fuels. Among various alternative resources, waste is attracting attention as it can produce hydrogen while reducing the amount of landfill and incineration. In order to produce hydrogen from waste, the water–gas shift reaction is one of the essential processes. However, syngas obtained by gasifying waste has a higher CO concentration than syngas produced by steam reforming of fossil fuels, and therefore, it is essential to develop a suitable catalyst. Research on developing a catalyst for producing hydrogen from waste has been conducted for the past decade. This study introduces various catalysts developed and provides basic knowledge necessary for the rational design of catalysts for producing hydrogen from waste-derived syngas.

Deoxygenation by transition-metal-based catalysts is employed to produce a biofuel from fatty acids. In this study, the citric acid/CoMo ratio of an unsupported CoMo catalyst prepared by a sol–gel method was increased from 1 to 7 to investigate its effect on the physicochemical properties and performance of the catalyst. Deoxygenation was carried out at 300 °C under solvent- and hydrogen-free conditions. The CoMo-3 catalyst (e.g., citric acid/CoMo = 3) showed the highest oleic acid conversion rate, C9–C17 hydrocarbon selectivity, oxygen removal rate, and biofuel product quality. This catalyst exhibited the best catalytic performance because it had the highest amount of active species (CoMoO4). Catalyst acidity considerably effected on the catalytic performance. Additionally, the citric acid/CoMo ratio affected the formation of single/mixed Co and Mo oxides.

The loading amount of Ba promoter in the 15 wt% Co/CeO2 catalyst system was varied from 0 wt% to 3 wt%, and the resulting catalysts were used for the high-temperature water-gas shift (HTS) reaction. The catalysts were prepared by the incipient wetness co-impregnation method and studied through various characterization techniques such as X-ray diffraction, Brunauer–Emmet–Teller measurements, CO–chemisorption, H2–temperature programmed reduction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The doping of Ba as a promoter in the optimal amount (1–2 wt%) improves the reducibility of the catalyst and enhances its sintering resistance. However, the doping of an excessive amount (≥3 wt%) of the promoter lowers the reducibility of the catalyst, resulting in the instability of the active phase (Co0). Overall, the 1% BaCo/CeO2 catalyst exhibited the best performance even at a severe reaction condition (CO conc. = 38%, GHSV = 143,000 h−1) owing to the strong resistance to the sintering and high stability of the active phase.

In this study, the effects of the catalyst preparation method and CeO2 particle morphology of Pt/CeO2 catalysts for the water-gas shift reaction are compared. CeO2 supports having nanorod and nanocube morphologies were prepared. Over both types of supports, 1 wt% Pt was loaded via either the incipient wetness impregnation (IWI) method or the strong electrostatic adsorption (SEA) method. In total, four types of Pt/CeO2 catalysts were prepared, and these were characterized using various techniques and tested for the water-gas shift reaction. The cube-shaped-CeO2-based catalysts showed higher catalytic activities than the rod-shaped-CeO2-based catalysts due to the higher dispersion of Pt0 regardless of the catalyst preparation method. From the viewpoint of the catalyst preparation method, the IWI-prepared catalysts showed higher catalytic activity than the SEA-prepared catalysts regardless of the morphology of CeO2 because of the larger amount of oxygen vacancies induced by the strong interaction between PtOx and CeO2. These results highlight the fact that the catalyst preparation method and the morphology of the CeO2 support strongly affect the key factors (Pt0 dispersion and number of oxygen vacancies) separately, which are directly related to the catalytic activity in the water-gas shift reaction. It also confirms that both key factors should achieve high values to attain high catalytic activity.

To investigate the effect of precipitation on physico-chemical and catalytic properties of Cu-Zn-Al catalyst, the pH value and injection rate in the precipitation process were systematically changed, and the water-gas shift reaction was carried out. The Cu-Zn-Al catalyst showed the highest CO conversion when the optimized synthesis parameters (i.e., pH=10-10.5 and injection rate=30 ml/min) were employed. This is mainly due to the enhanced physicochemical properties such as a high Brunauer-Emmett-Teller surface area, small crystallite size, high Cu dispersion, and easier reducibility.

Herein, we have prepared a series of Cr-free Fe-Al-Cu catalysts by the homogeneous one-step co-precipitation method and examined their ability to promote the water gas shift (WGS) reaction and thus facilitate the production of hydrogen from waste-derived synthesis gas. The prepared catalysts are confirmed to possess γ-Fe2O3, which can be more easily transformed into Fe3O4 than α-Fe2O3. The surface area, Fe3O4 crystallite size, reducibility, and Cu dispersion of these catalysts significantly depend on the concentrations of metal precursor. The catalysts effectively promote the WGS reaction without facilitating undesirable side reactions, achieving efficient hydrogen production and high CO conversion. The characteristics of the best-performing sample are preserved when the production is scaled up by a factor of 40 and thus obtained large-scale Fe-Al-Cu catalyst exhibits excellent reducibility and high CO conversion. Both commercial Fe-Cr and large-scale Fe-Al-Cu catalysts achieve close-to-equilibrium CO conversions at a gas hourly space velocity (GHSV) of 3000 mL g−1 h−1, but the latter showed a higher conversion than the former at a GHSV of 40,057 mL g−1 h−1 owing to the promotional effect of Cu on the easier reducibility of Fe species and the formation of additional Cu active sites. Thus, we demonstrate the possibility of finding Cr-free alternatives and show that the reducibility, Fe3O4 crystallite size, and Cu dispersion of the best-performing catalyst could be maintained upon upscaling, which made this catalyst well suited for converting waste-derived synthesis gas into H2.

Plants serve as appropriate markers of worldwide pollution because they are present in almost every corner of the globe and bioaccumulate xenobiotic chemicals from their environment. The potential of a semi-aquatic plant, Ipomoea aquatica, to uptake and metabolize sulfamethoxazole (SMX) was investigated in this study. I. aquatica exhibited 100% removal of 0.05 mg L−1 SMX from synthetic media within 30 h. The I. aquatica achieved 93, 77 and 72% removal of SMX at 0.2, 0.5 and 1 mg L−1, respectively, after 48 h. This indicated that removal efficiency of I. aquatica was deteriorating at high concentrations of SMX. The chlorophyll and carotenoid content of I. aquatica was insignificantly influenced by SMX irrespective of its high concentration. Similarly, scanning electron microscopy (SEM) showed that exposure to SMX had an insignificant impact on morphology of the plant organelles. The mechanisms of removal by I. aquatica were explored by evaluating contributions of bioadsorption, bioaccumulation and biodegradation. There was negligible adsorption of SMX to plant roots. Accumulation of SMX within plant roots and stems was not observed; however, I. aquatica accumulated 17% of SMX in leaves. Thus, the major mechanism of elimination of SMX was biodegradation, which accounted for 82% removal of SMX. Gas chromatography-mass spectrometry (GC-MS) confirmed that I. aquatica biodegraded SMX into simpler compounds, and generated 4-aminophenol as its final product. A laboratory scale phytoreactor was used to investigate the application of I. aquatica in a simulated system, where it achieved 49% removal of SMX (0.2 mg L−1) in 10 d.

Herein, we investigated the effects of aging time and temperature on the performance of co-precipitation–prepared Cu-Zn-Al catalysts in the low-temperature water-gas shift (LT-WGS) reaction. The highest CO conversion within the employed temperature range as well as very stable activity over 200 h were observed for the catalyst prepared at 80 °C and aged for 72 h, which was ascribed to its high surface area and close-to-100% degree of CuO reduction. Conversely, catalysts aged at temperatures below 80 °C had poor physical properties, while aging for

Because the whole world is under threat from climate change, 195 countries decided to reduce greenhouse gas (GHG) emissions by adopting the “Paris Agreement”. The mitigation and utilization of GHG have become the most significant challenges in the area of green energy research. One feasible solution is the reforming of methane with carbon dioxide (called dry reforming of methane, DRM) that converts the two main GHGs (CO2 and CH4) into synthesis gas (H2 and CO), which is a resource for the manufacture of useful value-added products. The main issue that needs to be addressed for DRM is the deactivation of catalysts by sintering and carbon formation. Design of a viable catalyst that exhibits high catalytic activity and stability, as well as resistance against deactivation, could be accomplished by making appropriate choices of active metal, support, promoter, structure and methods for preparation and activation. Numerous studies and reviews have dealt with various aspects of DRM. This review focuses on the physicochemical properties of the pertinent catalysts and their role in the catalytic performance needed for DRM. Specifically, the interaction between components, dispersion, particle size, basicity, oxygen storage capacity, reducibility, porosity and surface area are discussed. This study provides the understanding of catalytic properties and their correlation with catalytic performance needed for the rational design of catalysts and suitable for DRM.

A comprehensive ecotoxicological evaluation of a sulfamethazine (SMZ) and sulfamethoxazole (SMX) mixture was conducted using an indicator microalga, Scenedesmus obliquus. The toxicological effects of this mixture were studied using microalgal growth patterns, biochemical characteristics (total chlorophyll, carotenoid, carbohydrate, fatty acid methyl ester), and elemental and Fourier-transform infrared spectroscopy analyses. The 96-h half maximal effective concentration (EC50) of the SMZ and SMX mixture was calculated to be 0.15 mg L−1 according to the dose-response curves obtained. The chlorophyll content decreased with elevated SMZ and SMX concentrations, while the carotenoid content initially increased and then decreased as concentration raised. The unsaturated fatty acid methyl esters (FAMEs) content was enhanced with higher SMZ and SMX concentrations, while that of saturated FAMEs simultaneously decreased due to SMZ and SMX stress. Elemental analyses showed an improved percentage of nitrogen and sulfur in the microalgal biomass as SMZ and SMX concentrations increased. The microalga S. obliquus was shown to biodegrade the chemicals tested and removed 31.4–62.3% of the 0.025–0.25 mg SMZ L−1 and 27.7–46.8% of the 0.025–0.25 mg SMX L−1 in the mixture after 12 days of cultivation. The greater biodegradation observed at higher SMZ and SMX concentrations indicates that microalgal degradation of SMZ and SMX could act as an efficient adaptive mechanism to antibiotics.

To investigate the effect of support materials on catalytic performance in carbon dioxide reforming of coke oven gas, Ni-based catalysts supported on various metal oxides with various properties are prepared and evaluated. The support material affects the important properties related to the catalytic performance such as surface area, Ni dispersion, basicity, oxygen storage capacity, and interaction between Ni and support. Among the various catalysts on different metal oxides, Ni/MgO Al2O3 catalyst exhibits the highest CH4 conversion due to its high Ni dispersion, large surface area, and strong basicity. Hence, the Ni loading in the Ni/MgO Al2O3 catalyst is optimized. Ni loading performs the important roles to determine the Ni dispersion, the amount of Ni active sites, and basicity. 15 wt% Ni/MgO Al2O3 catalyst shows the highest catalytic activity even at a high gas hourly space velocity (GHSV) of 1,500,000 h−1, owing to the large amount of Ni active sites which related to Ni loading, Ni dispersion, and reduction degree. To confirm the stability of the 15 wt% Ni/MgO Al2O3 catalyst, catalytic reaction has been carried out for 50 h and noticeable catalytic deactivation is not observed for 50 h.

Lipidic-waste such as fat, oil, and grease (FOG) are promising substrates for achieving higher bioenergy yields. An inadequate presence of an effective microbiome in the anaerobic digesters is the bottleneck for the proper utilization of FOG. Gradual introduction of FOG (0.2%, 1.2%, and 2.4% as volatile solids) in acidogenic fermentation showed a significant improvement in hydrogen yield (72%), compared to the control, after 2.4% FOG loading. Volatile solid (VS) reduction reached up to 65% in high FOG reactors with complete removal of major unsaturated fatty acids. Removal of saturated fatty acids increased to 90%. Improvement in hydrogen productivity (46 mL d−1) occurred during step-wise loading of 2.4% FOG to the acclimatized microbiome. The metabolic shift toward carboxylic chain elongation produced C4 and C6 fatty acids at concentrations of 1.61 mM and 0.90 mM, respectively in the acidogenic reactors. High-throughput sequencing of 16S rRNA amplicons revealed that the acclimatization process enriched the phylum Firmicutes (90%), followed by Bacteroidetes (12%) and Cloacimonetes (11%). The abundance of these phyla and their respective genera confirmed their preeminent role in hydrolysis, hydrogenogenic acidogenesis, and carboxylic chain elongation to produce hydrogen and C4–C7 fatty acids. Thus, we suggest that the improvement of hydrogen production using a microbiome acclimatized to FOG, and simultaneous production of high value organics (C4–C7 fatty acids), could facilitate the greater efficacy of the acidogenic fermentation.

Ni/MgO-Al2O3 (Ni/MG70) catalysts were developed for the deoxygenation reaction to produce green diesel from non-edible fatty acids. As the Ni loading amount was increased from 5% to 30%, the characteristics of the catalysts, such as Brunauer–Emmett–Teller (BET) surface area, Ni dispersion, reducibility, number of Ni active sites, and acidity, varied. Among the prepared catalysts, the 20% Ni/MG70 catalyst showed excellent deoxygenation performance owing to its highest number of Ni active sites, easier reducibility, and appropriate acidity. Furthermore, it was confirmed that deoxygenation in this study was carried out via the hydrodeoxygenation reaction pathway to remove oxygen species as H2O. In addition, the basic fuel properties, calorific value and viscosity, were analyzed for produced green diesel.

Support- and sulfide-free cobalt molybdenum catalysts are prepared via different synthetic procedures for catalytic deoxygenation of oleic acid under inert (N2) and solvent-free conditions. Among the tested catalysts, the CoMo catalyst prepared via a sol-gel method achieves the highest catalytic performance, namely, 88.9% oleic acid conversion, with 48.1% C9–C17 selectivity, and 69.6% oxygen removal rate, owing to its excellent physical properties. Additionally, oxygen vacancy is formed in CoMo catalyst during sol-gel synthesis process and it also effect on the catalytic activity. Examination of the deoxygenation reaction over pre-reduced catalysts reveals that the CoMoO4 species is the active species in the CoMo catalysts. The fuel properties of the resultant products are affected strongly by the catalytic performances of the CoMo catalysts. The biofuel produced using the CoMo catalyst prepared via the sol-gel method showed the highest calorific value (10,119 cal/g) and the lowest viscosity (31.5 cP), and, consequently, this CoMo catalyst exhibits the highest catalytic activity and has significant potential for application in biofuel production.