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Severe ecological and environmental problems such as acid rain, greenhouse gas emission, atmospheric pollution etc. emerged with the wide application of fossil fuels force human beings to seek new green energy to alleviate the heavy dependency on those petrochemical products. Converting renewable microalgae biomass into liquid fuels is one of the promising way. However, the existence of nitrogen heteroatom and metal elements in microalgal bio-crude oil will extremely deteriorate the quality and inhibit the commercial utilization of microalgal bio oil. It is highly necessary to remove those nitrogen and metal elements from microalgal bio oil phase to meet the strict environmental and clean production requirements. Therefore, this paper extensively reviewed the updated results on catalytic denitrogenation and demetallization of microalgal bio-crude oil, including summary on the mechanism of C–N bond breaking, reaction pathways of major N-containing and metalloporphrins model compounds. Besides, the challenges facing the catalytic process, for example, catalyst stability and operating conditions during the denitrogenation and demetallization reactions were appraised as well.

Nitrogen (N) in sewage sludge (SS) should be reduced if it is to be used to produce clean solid fuels. However, the N transformation during hydrothermal carbonization (HTC) of SS is not yet fully understood. Since the composition of SS is complex, it is wise to study a model compound, which should have typical functional groups of organic components. Hence, in this study, six model components (protein, lipid, cellulose, hemicellulose, humic acid, and lignin) representing the main organic components in SS were mixed with SS and treated at 150-270 °C for 1 h. The influence of the organic component and reaction temperature on hydrochar yield, hydrochar characterization, and N distribution in the products was investigated. Except for proteins and lipids, all the other components were found to contribute to the N content and aromatization of the hydrochar. Humus shows the best comprehensive performance in terms of both reducing the N content and increasing the aromaticity. The strongest effects of hemicellulose and cellulose on N retention in hydrochar are found to occur at 210 °C and 240 °C, respectively. The N retention caused by lignin is correlated with the Mannich reaction at 240 °C, while humus significantly promotes N transformation at 240 °C. For carbohydrates, lignin, and humus, the temperatures required for increasing the N content and aromaticity maintain a high degree of consistency. Although protein pulls down the energy recovery (ER) and yield of the hydrochar, observations indicate that it favors the carbonization process. This finding can be used for estimating the N content and quality of hydrochar and provides references for future research targeting the upgrading of hydrochar.

Hydroxychloroquine sulfate is effective in the treatment of malaria and autoimmune diseases and as an antiviral drug. However, unreported impurities are often detected in this drug, which pose a health risk. In this study, the structures of hydroxychloroquine and six unknown impurities were analyzed using ultra-high-performance liquid chromatography-quadrupole/time-of-flight-tandem mass spectrometry (UHPLC-Q/TOF/MS/MS), and the structures were characterized using liquid chromatography-solid-phase extraction-nuclear magnetic resonance (LC-SPE-NMR) spectroscopy.An Agilent InfinityLad Poroshell HPH-C18 column (100 × 4.6 mm, 2.7 μm) was used. For the analysis of hydroxychloroquine and six unknown impurities, the mobile phase was 20 mM ammonium formate aqueous solution and methanol/acetonitrile (80:20, v/v) using gradient elution. Full-scan MS and MSThe MSBased on the identification and characterization of these impurities, this study also describes the cause of the production of the impurities and provides insights for companies to improve their production processes and a scientific basis for the improvement of the related pharmacopoeias.

Hydrothermal liquefaction of the third-generation biomass represented by microalgae can produce biocrude. However, the directly obtained biocrude has a high heteroatom content and a low higher heating value (HHV), which cannot meet the standards of biofuel. In this work, water-insoluble biocrude which was directly gained from microalgae hydrothermal liquefaction (HTL) was upgraded under four kinds of solvents (i.e., methanol, ethanol, acetone, and H₂O) and one type of catalyst (H₂O + Ru/C) at 240–400 °C for 1 h. The results show that the HHV and C and H contents of upgraded bio-oil increased and the O/C ratio decreased significantly after solvent upgrading. The highest upgraded bio-oil yield appeared in the case of ethanol upgrading and reached the maximum value of 82.8 wt % at 360 °C. The upgraded bio-oil yield of acetone upgrading increased from 45.8 to 68.2 wt % as the temperature increased within 240–400 °C. Also, esterification reactions between alcohol and acid in the supercritical system remarkably reduced the content of carboxyl-containing organic matter.

In this paper, the treatment characteristics of glyphosate wastewater based on supercritical water oxidation (SCWO) technology is studied both in spiral coiled tube reactor and tank reactor, including the influences of operating parameters such as reaction temperature, reaction pressure, oxidation coefficient, residence time, and initial properties of wastewater such as organic concentration, pH value on the degradation of COD and NH3-N with H2O2 as oxidant, and the different reaction characteristics in different batch reactors are also analyzed in detail. Furthermore, the simplified SCWO reaction pathway of glyphosate wastewater is also proposed to understand the degradation process better. Finally, a comprehensive SCWO system for treating glyphosate wastewater efficiently, and transforming and utilizing organic nitrogen as well as organophosphorus directionally is proposed and designed, including SCWO unit, ammonia distillation unit, phosphate recovery unit, and biochemical treatment unit, which can enhance the treatment efficiency and economic benefits synergistically, and provide basic data for the industrialization of glyphosate wastewater degradation based on SCWO technology.

The imbalance between the energy demand and supply and environmental pollution makes it necessary to develop renewable energy as an alternative energy source. Hydrothermal liquefaction (HTL) of biomass is a promising method to produce a crude bio-oil (biocrude), and upgrading biocrude by catalytic hydrogenation can improve its quality. This article systematically describes chemical reactions in biomass HTL and the catalytic hydrogenation upgrading of the obtained biocrude. We comprehensively analyze the effects of operating parameters on chemical reactions in HTL and catalytic hydrogenation upgrading processes, such as reaction temperature, residence time, and catalyst type. We also propose the future development directions of biomass HTL and biocrude upgrading. This information can help in selecting the reaction routes and reaction parameters such that the yield and quality of bio-oil can be improved.

This article focuses on the kinetic modeling and catalytic performance of hydrodenitrogenation of pyridine under hydrothermal conditions. Piperidine derivatives are the major nitrogen-containing in...

Aiming at the problems of soil column forming near the plastic vertical drains and soil cracking during electro-osmosis stage in the treatment of dredged slurry by vacuum pre-loading combined with ...

Corrosion continues to be a major challenge in developing supercritical water-cooled reactor and supercritical water oxidation system. Corrosion behaviors of candidate alloy materials used in these...

Supercritical hydrothermal synthesis of nanosized metal oxides is of great interest for scholars due to its one-pot and readily realizing commercial production process. Hydrothermal synthesis of nanosized TiO2 in subcritical and supercritical water was investigated with different reaction temperatures (250–450°C), time (3–10 min), precursor species (Ti(SO4)2, TiCl4), and the addition of a surfactant (CH3(CH2)5NH2). TiO2 synthesized under supercritical state has a higher degree of crystallinity when compared with TiO2 obtained from subcritical state, which is attributed to a higher reaction rate. Extending reaction time from 3 to 10 min leads to the growth of crystal and broader size distribution (36.66 ± 8.5 nm). More uniform products can be obtained when Ti(SO4)2 acting as the precursor compared with TiCl4 being the precursor. The application of surfactant CH3(CH2)5NH2 in the synthesis makes chemical bonding between the particle surface and organic ligand. It affects the growth direction of TiO2 crystal; as a result, rod-like TiO2 crystal is obtained.

Corrosion has severely hindered the development and application of high-temperature hydrothermal oxidation technologies for disposing of chloride-containing organic wastewater. This study explored the early corrosion behaviors of 316 stainless steel (316 SS) (UNS S31600), passivated by sodium phosphate (Na3PO4) in supercritical water in advance, in subcritical water (at 100, 160, 230, and 300 °C and 25 MPa) having high contents of oxygen (O2) and sodium chloride (NaCl) for 50 h. The results show that the corrosion rate of the phosphate-passivated 316 SS was approximately half of that of the passivated 316 SS (pretreated in supercritical water without Na3PO4) under the same conditions. The surface oxides of the phosphate-passivated 316 SS consisted of Cr2O3, Fe2O3, CrPO4, FePO4, and Ni3(PO4)2. The passivation pretreatment of 316 SS in supercritical water with Na3PO4 could form a stable and protective oxide film containing phosphates. These phosphates significantly improved the corrosion resistance of 316 SS in subcritical water (containing oxygen and chloride) by preventing corrosive substances from contacting the alloy substrate.

In this study, the oxidation behaviour of alloy 617, alloy 740, alloy HR6W and Sanicro 25 was investigated in SCW and vapour environment at 650°C for 320 h. The weight gain and the thickness of the...

Hydrothermal liquefaction (HTL) and supercritical water gasification (SCWG), two effective thermochemical approaches converting biomass into biofuels, have received increasing attention due to their advantages of a fast reaction rate and the use of wet feedstocks without the need for an energy-intensive drying process. In this review, we first summarize the physical properties of the biocrude oil obtained from HTL and then examine the catalytic hydrotreatment of the biocrude oil with or without solvents. The experimental studies on the SCWG of sewage sludge, microalgae, black liquor, and food wastes are analyzed, and the corrosion and salt-deposition problems associated with the solutions are discussed. Finally, to fully comprehend the reaction mechanism of biomass components in hydrothermal media, the conversion of model compounds (cellulose, hemicellulose, lignin, lipid, protein, and their derivatives) is reviewed.

Hydrothermal treatment (HTT) (i.e., hydrothermal carbonization, liquefaction, and gasification) is a promising technology for biomass valorization. However, diverse variables, including biomass compositions and hydrothermal processes parameters, have impeded in-depth mechanistic understanding on the reaction and engineering in HTT. Recently, machine learning (ML) has been widely employed to predict and optimize the production of biofuels, chemicals, and materials from HTT by feeding experimental data. This review comprehensively analyzed the application of ML for HTT of biomass and systematically illustrated basic ML procedure and descriptors for inputs and outputs of ML models (e.g., biomass compositions, operation conditions, yield and physicochemical properties of derived products) that could be applied in HTT. Moreover, this review summarized ML-aided HTT prediction of yield, compositions, and physicochemical properties of HTT hydrochar or biochar, bio-oil, syngas, and aqueous phase. Ultimately, future prospects were proposed to enhance predictive performance, mechanistic interpretation, process optimization, data sharing, and model application during ML-aided HTT.