N-containing Chemicals Research Articles

Hydrothermal co-carbonization of medium-density fiberboard with N-rich compounds to produce N-containing compounds and N-doped biochar: Product distribution, nitrogen transformation pathway and electrochemical performance

High-value utilization of waste resources has received widespread attention. In this study, N- containing chemicals (NCCs) and nitrogen-enriched hydrochars were prepared by co-hydrothermal carbonization (Co-HTC) of waste medium-density fiberboard (MDF) and various nitrogen carriers. The influence of the nitrogen carrier type (chitosan, urea, or melamine) and the MDF: nitrogen carrier mass ratio on yield and production distribution were investigated. The formation mechanism and possible reaction pathways of NCCs in bio-oil and N-doped biochar were elucidated, and the electrochemical performance of N-rich hydrochar as a precursor for supercapacitor materials was explored. The results indicated that the introduction of an ammonia source during hydrothermal carbonization obviously increased the NCC content via the Maillard reaction and decreased the hydrochar yield, resulting in structures disordered and poor microporosity. The introduction of chitosan significantly promoted pyridine (35.50 %) and hydrochar (36.95 %) generation owing to the nitrogen fixation effect (N: 6.27 ∼ 15.56 %). Urea addition facilitated the formation of NCCs (89.92 %) and imidazoles/pyrazines (39.46 %). The addition of melamine, which has the most amino functional groups, significantly increased aniline compound formation. Moreover, the activated hydrochar derived from the ammonia source Co-HTC exhibited great electrochemical performance, and the prepared electrode material derived from MDF: chitosan = 1:5 achieved highest reversible specific capacitance of 174.5F/g at 0.5 A/g and 96.46 % initial capacitance retention after 10,000 cycles at 10 A/g due to developed mesoporosity, high specific surface area and enriched N/O functional groups. This study provides a novel sustainable strategy for the efficient and high-value utilization of waste MDF and improved the economic viability of MDF biorefineries.

Study of KOH-activated hydrochar for CO2 adsorption

The use of solid porous materials for CO2 capture is a more environmentally benign approach than conventional wet scrubbing using amine-based solutions. Therefore, in this study, porous carbon materials were prepared using sawdust through hydrothermal carbonization (HTC) to produce hydrochar, followed by KOH activation. The results showed that KOH-activated hydrochar had a specific surface area of 646–1195 m2/g, and a micropore area of 547–1059 m2/g, indicating a microporous structure was developed. The highest CO2 adsorption capacity at tested adsorption temperatures was achieved from activated hydrochar obtained at 750 °C (40 °C: 0.95 mmolCO2/gsample; 75 °C: 0.80 mmolCO2/gsample), which is higher than pristine hydrochar (40 °C: 0.05 mmolCO2/gsample; 75 °C: 0.04 mmolCO2/gsample). Physisorption through pore diffusion and surface coverage and chemisorption involving formation of covalent bonds between adsorbent’s surface functionality and CO2 both contributed to CO2 adsorption. Importantly, the presence of N-containing chemicals, particularly the presence of N-containing functional groups on the surface, played an important role in CO2 adsorption capacity. Based on the current results and relevant literature, the development of ultra-micropore and the introduction of more N-containing functional groups to the surface would be the research focuses to further increase the CO2 adsorption capacity.

Extraction and Analysis of Medicinal Property in Secondary Metabolites Obtained from Selected Plant Species

Medical plants have been used from thousands of years to treat and prevent many diseases. Wockhardt global school Consist various plants variety and for this study three medicinal plants were selected and these plants are Tridax procumbiens (Tantani), Ficus racemosa (Umbar), Nyctanthes abortiristis (Parijat). The primary aim of this study was to extract and identify the presence of phytochemicals and to determine their medicinal uses for human beings. From Vedic era the traditional plant medicines has been considered as a primary healthcare for human beings. In the given study the presence of flavonoids, alkaloids, N-Containing chemicals were determined by using phytochemical extraction method. The chemicals were identified based upon various qualitative tests. The selected plants consist glycosides, alkaloids, saponins, flavonoids and carbohydrates. This phytochemicals are responsible for anti-inflammatory properties hence the selected medicinal plants can be used for inflammation, bone pain, joint pain, swelling, and common cough etc. Keywords: Medicinal plants, secondary metabolites, phytochemicals, flavonoids, alkaloids, leaf extract.

Amorphous Bismuth-Tin Oxide Nanosheets with Optimized C-N Coupling for Efficient Urea Synthesis.

Closing the carbon and nitrogen cycles by electrochemical methods using renewable energy to convert abundant or harmful feedstocks into high-value C- or N-containing chemicals has the potential to transform the global energy landscape. However, efficient conversion avenues have to date been mostly realized for the independent reduction of CO2 or NO3-. The synthesis of more complex C-N compounds still suffers from low conversion efficiency due to the inability to find effective catalysts. To this end, here we present amorphous bismuth-tin oxide nanosheets, which effectively reduce the energy barrier of the catalytic reaction, facilitating efficient and highly selective urea production. With enhanced CO2 adsorption and activation on the catalyst, a C-N coupling pathway based on *CO2 rather than traditional *CO is realized. The optimized orbital symmetry of the C- (*CO2) and N-containing (*NO2) intermediates promotes a significant increase in the Faraday efficiency of urea production to an outstanding value of 78.36% at -0.4 V vs RHE. In parallel, the nitrogen and carbon selectivity for urea formation is also enhanced to 90.41% and 95.39%, respectively. The present results and insights provide a valuable reference for the further development of new catalysts for efficient synthesis of high-value C-N compounds from CO2.

Ball milling boosted hydrothermal N-doped sludge-derived biochar towards efficiently adsorptive removal of sulfamethoxazole from waters: Behavior, mechanism and DFT study

Developing an efficient adsorbent is of great significance to eliminate the adverse impacts on human and animals health caused by environmental concentration sulfamethoxazole (SMX). Various N-containing chemicals (ammonium chloride (NH4Cl), thiourea (CH4N2S), urea (CO(NH2)2), and melamine (C3H6N6)) were employed to activate sludge biochar (SBC) under hydrothermal condition. Afterward, the optimum hydrothermal N-doped SBC (NSBC-0.5) (C3H6N6 was confirmed as the perfect N-containing chemical) was further modified by ball milling to prepare BNSBC-0.5. The maximum adsorption capacity of BNSBC-0.5 for SMX calculated from Langmuir was 6.86 × 104 μg/g. The physicochemical properties analysis, adsorption experiments, together with density functional theory (DFT) calculation confirmed that the process of SMX adsorption onto BNSBC-0.5 was dominantly by Lewis acid-base, π-π conjugation, pore filling and electrostatic interactions. The multiple adsorption mechanism guaranteed the high anti-interference of BNSBC-0.5 to inorganic salts/strength and organic matter concentrations range and enabled it to be a promising adsorbent for efficiently eliminating SMX in various actual waters (Yangtze River water (88.5 %), lake water (89.3 %), running water (89.2 %), pure water (92.7 %), and deionized water (92.5 %)). The regenerated (via NaOH desorption) BNSBC-0.5 was capable of sustainably and effectively adsorbing SMX in recycles. Additionally, BNSBC-0.5 exhibited the satisfactory environmental safety in view of the low leaching levels of total nitrogen (TN) over a board pH range. This work synthesized a prospective adsorbent for SMX elimination, also the harmless disposal and waste utilization of sludge were accomplished.

Synergy of heterogeneous Co/Ni dual atoms enabling selective C–O bond scission of lignin coupling with in-situ N-functionalization

Selective cleavage of Csp2OCH3 bond in lignin without breaking other types of CO bonds followed by N-functionalization is fascinating for on-purpose valorization of biomass. Here, a Co/Ni-based dual-atom catalyst CoNiDA@NC prepared by in-situ evaporation and acid-etching of metal species from tailor-made metal–organic frameworks was efficient for reductive upgrading of various lignin-derived phenols to cyclohexanols (88.5%–99.9% yields), which had ca. 4 times higher reaction rate than the single-atom catalyst and was superior to state-of-the-art heterogeneous catalysts. The synergistic catalysis of Co/Ni dual atoms facilitated both hydrogen dissociation and hydrogenolysis steps, and could optimize adsorption configuration of lignin-derived methoxylated phenols to further favor the Csp2–OCH3 cleavage, as elaborated by theoretical calculations. Notably, the CoNiDA@NC catalyst was highly recyclable, and exhibited excellent demethoxylation performance (77.1% yield) in real lignin monomer mixtures. Via in-situ cascade conversion processes assisted by dual-atom catalysis, various high-value N-containing chemicals, including caprolactams and cyclohexylamines, could be produced from lignin.

A 2D Ba2N Electride for Transition Metal-Free N2 Dissociation under Mild Conditions.

N2 activation is a key step in the industrial synthesis of ammonia and other high-value-added N-containing chemicals, and typically is heavily reliant on transition metal (TM) sites as active centers to reduce the large activation energy barrier for N2 dissociation. In the present work, we report that a 2D electride of Ba2N with anionic electrons in the interlayer spacings works efficiently for TM-free N2 dissociation under mild conditions. The interlayer electrons significantly boost N2 dissociation with a very small activation energy of 35 kJ mol-1, as confirmed by the N2 isotopic exchange reaction. The reaction of anionic electrons with N2 molecules stabilizes (N2)2- anions, the so-called diazenide, in the large interlayer space (∼4.5 Å) sandwiched by 2 cationic slabs of Ba2N as the main intermediate.

Imidazo[1,2-a]pyridine derivatives synthesis from lignin β-O-4 segments via a one-pot multicomponent reaction

The catalytic conversion of lignin into N-containing chemicals is of great significance for the realization of value-added biorefinery concept. In this article, a one-pot strategy was designed for the transformation of lignin β-O-4 model compounds to imidazo[1,2-a]pyridines in yields up to 95% using 2-aminopyridine as a nitrogen source. This transformation involves highly coupled cleavage of C-O bonds, sp3C-H bond oxidative activation, and intramolecular dehydrative coupling reaction to construction of N-heterobicyclic ring. With this protocol, a wide range of functionalized imidazo[1,2-a]pyridines sharing the same structure skeleton as those commercial drug molecules, such as Zolimidine, Alpidem, Saripidem, etc., were synthesized from different lignin β-O-4 model compounds and one β-O-4 polymer, emphasizing the application feasibility of lignin derivatives in N-heterobicyclic pharmaceutical synthesis.

Synergistic catalysis of mesoporous Cu/Co3O4 and surface oxygen vacancy for CO2 fixation to carbamates

As one of the most important defects, oxygen vacancy (OV) on the surface of transition metal oxides can function as catalytic reactive site for various reactions. Herein, Cu-doped Co3O4 (Cu/Co3O4) catalyst with rich surface OV was developed for efficient and quantitative transformations of CO2, primary amines, and propargyl alcohols to oxazolidinones at mild reaction conditions. Both initial formation rate of oxazolidinone and surface acidity on the Cu/Co3O4 increased with its surface OV concentration. The doped Cu species in Cu/Co3O4 functioned as an active site for propargyl alcohol activation, enhanced the surface OV concentration for CO2 activation, and improved the surface acidity to promote the rate-determining step in CO2-to-oxazolidinone transformation. In addition to oxazolidinones, Cu/Co3O4 was applicable to various β-oxopropylcarbamates syntheses by coupling CO2, propargyl alcohols and secondary amines. This research demonstrates a synergistic cooperative catalysis between Cu and surface OV for CO2 transformation to high-valuable N-containing chemicals.

Renewable nitrogen-containing products by Maillard reaction of sewage sludge and glucose. Part II. Fixed-bed co-pyrolysis of sewage sludge and glucose

Sewage sludge (SS) are extremely promising sustainable feedstock for fuels and chemicals. However, their high nitrogen content may result in nitrogen emissions during the pyrolysis. In this study, the fixed-bed co-pyrolysis (FBCP) of SS and glucose was carried out to obtain N-containing chemicals and N-doped bio-char. The transformation and production of nitrogen-containing compounds (NCCs) by Maillard reaction were investigated. Additionally, strategies to optimize experimental conditions were studied. Results show that keeping 50.0 wt% glucose in blended feedstock with the gas flow rate of 0.75 L/min and the final temperature of 450 °C is beneficial to maximize heterocyclic amines yield in bio-oil and limit the NH3 and NOx release. With the addition of glucose, carbonyl groups of glucose reacted with the amino groups of dried sewage sludge (DSS). A large number of amine/amide-N, pyridinic-N, pyrrolic-N, and quaternary-N enriched in bio-oil and surfaces of bio-char (over 95 wt% of total nitrogen) were generated, while significantly decreasing the nitrogen content in gas products (from 49.3 % to 3.9 %). Based on experiment results, the mechanism of nitrogen transformation during FBCP of DSS and glucose was finally proposed.

A decision support tool for the selection of 15 N analysis methods of ammonium and nitrate

The stable nitrogen isotope (15 N) analysis of ammonium (NH4+) and nitrate (NO3–) is widely used in ecological research, providing insights into N cycling and its underlying regulating mechanisms in both aquatic and terrestrial ecosystems. To date, a large number of methods have been developed for the preparation and measurement of 15 N abundance of NH4+ and NO3– in liquid environmental samples at either natural abundance or enriched levels. However, these methods are all subject to certain specific advantages and limitations, and ecologists might be looking for an efficient way to select the most suitable methods in face of shifting sampling and analytical conditions. Based on our extensive review of these 15 N analysis methods we developed a decision support tool (DST) to provide quick and proper guidance for environmental researchers in finding the optimal method for preparing their liquid samples for 15 N analysis in NH4+ or NO3–. The DST is a decision tree based on several key criteria that users need to take into account when choosing the preferred sample preparation method for their samples. The criteria concern: the sample matrix, the 15 N abundance and the concentration of the target N species, the contamination by other N-containing chemicals, the isotopic fractionation, the availability of equipment, concerns about toxicity of reagents, and the preparation time. This work links field-scale experiments and laboratory 15 N analysis. Potential applications of our decision trees include 15 N studies ranging from natural abundance to tracer level in a wide range of terrestrial, freshwater and marine ecosystems.

Ammonia (NH3)/nitrogen (N2) torrefaction pretreatment of waste biomass for the production of renewable nitrogen-containing chemicals via catalytic ammonization pyrolysis: Evolution of fuel-N under a N2/NH3-rich atmosphere

To investigate the nitrogen migration and transformation mechanisms that produce high value-added N-containing chemicals, the NH3/N2 torrefaction pretreatments of waste biomass for the production of renewable N-containing compounds were explored, and the effects of torrefaction temperature (200, 225, 250, 275, 300 °C) on fuel properties, structure, crystallinity, surface functional groups and thermal kinetics were evaluated by element analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier infrared spectroscopy (FTIR) and thermogravimetric analysis (TG-DTG). The effects of subsequent catalytic ammonization pyrolysis upgrading of the torrefied biomass with Co/HZSM-5/HZSM-5 catalysts under an NH3/N2 atmosphere on product yield and N-containing compound selectivity were also evaluated with GC/MS and UV-fluorescence spectrometry. Furthermore, nitrogen fixation and migration mechanisms were also proposed in depth. The results showed that NH3 torrefaction was more effective in enhancing N fixation and retarding the release of N-containing volatiles in torrefied biochar (0.26%–9.43%) and reducing the oxygen content (43.18%–21.81%) via Maillard reactions compared with N2 torrefaction. With increasing torrefaction severity, the N-containing compound content, higher heating values (HHV), deoxygenation ratio (DEO) and nitrogen-doping ratio (NDR) increased, which were much higher than those of conventional N2 torrefaction. Higher temperatures promoted the evolution of graphitic-N and oxidized-N and reduced pyrrolic-N and pyridinic-N group formation in torrefied biochar. The maximum content of N-containing compounds of 88.71% was obtained at a torrefaction temperature of 275 °C under NH3 pyrolysis coupled with the Co/HZSM-5 catalyst, and was achieved via substrate interaction with the -Co-O-Si- catalyst sites and Maillard reactions. Furthermore, the N2 atmosphere combined with the HZSM-5 catalyst significantly promoted the conversion of HC compounds (∼56.97% at 225 °C during N2 torrefaction), while the Co/HZSM-5 catalyst combined with the NH3 atmosphere significantly improved N-containing compound formation. NH3 pyrolysis facilitated the formation of pyrroles and pyrazines while reducing the formation of amides by deamination and dehydrogenation reactions. Cellulose was conducive to the transformation of pyrrole in NH3 pyrolysis, while lignin was conducive to the formation of aniline. These results could offer strategies to regulate nitrogen functional groups to enhance N-containing chemicals.

The importance of utilizing nitrate (NO3-) over ammonium (NH4+) as nitrogen source during detoxification of exogenous thiocyanate (SCN-) in Oryza sativa.

Thiocyanate (SCN-) is a nitrogen-containing pollutant, which can be involved in the nitrogen (N) cycle and interferes with plant growth. The current study highlights a new insight into the N (nitrate [NO3-] and ammonium [NH4+]) utilization ways in rice seedlings under SCN- exposure to clarify the interactive effect on uptake and assimilation between these N-containing chemicals. Phenotypically, relative growth rates (RGR) of NO3--fed seedlings were significantly higher than NH4+-fed rice seedlings at the same SCN- concentration. Both N fertilizations have no significant influence on SCN- content and its assimilation in rice seedlings. However, significant accumulation of NO3- and NH4+ were detected in shoots prior to roots under SCN- stress. Enzymatic assay and mRNA analysis showed that the carbonyl sulfide (COS) pathway of SCN- degradation occurred in both roots and shoots of NO3--fed seedlings but only evident in roots of NH4+-fed seedlings. Moreover, the effect of SCN- on the activity of nitrate reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT) was negligible in NO3--fed seedlings, while GOGAT activity was significantly inhibited in shoots of NH4+-fed seedlings. Nitrogen use efficiency (NUE) estimation provided positive evidence in utilizing NO3- over NH4+ as the main N source to support rice seedling growth during detoxification of exogenous SCN-. Overall, SCN- pollution has unexpectedly changed the rice preference for N source which shifted from NH4+ to NO3-, suggesting that the interactions of SCN- with different N sources in terms of uptake and assimilation in rice plants should not be overlooked, especially at the plant N nutritional level.

HPLC method development for chitin and chitosan valorisation chemistry

Recently, chitin/chitosan chemistry is gaining huge attention to yield chemicals like oligomers, monomers, N-containing chemicals and furan derivatives. However, due to lack of proper analytical technique to separate them due to their almost similar size and polarity hamper the further progress in this domain. In this work, a high performance liquid chromatography method with a variable wavelength and refractive index detector is optimised for simultaneous separation and quantification of amino sugars (D (+)- glucosamine, N-acetyl-D-glucosamine, Glucosamine hydrochloride dimer), other sugars (D (+)-glucose, D-(+)-fructose, 2-Deoxy-D-glucose), N-containing chemicals (D-glucosaminic acid, 2-Aminoethanol, N-acetylethanolamine, Acetamide) and furan derivative (5-Hydroxymethylfurfural). While non-polar C18 column with isocratic elution [acetonitrile/water (1/9v/v)] could show separation of few compounds, but best results were achieved with RPM-Monosaccharide Pb2+ column with water as a mobile phase. The regression equation revealed good linear relationship (R2=0.9904-0.9974) within test ranges. Repeatability of the method and column stability was found to be within acceptable limits.

Catalytic co-pyrolysis of cellulose and waste polyoxymethylene to improve producing pyridines compounds over commercial HZSM-5 zeolites under ammonia atmosphere

Polyoxymethylene resin, one of the five major engineering materials with excellent comprehensive performance, was widely used in the industry. Pyridines, a kind of important heterocyclic compounds, were widely used as substrates for synthesis pharmaceutical, agro-chemical and dye industries. In this study, N-containing chemicals could be produced from waste polyoxymethylene (POM) plastic and cellulose via catalytic pyrolysis over commercial zeolite under ammonia atmosphere. Zeolite acidity and pyrolysis temperature affected product distribution significantly. Suitable catalyst for pyridines production was HZSM-5 (Si/Al = 83.3), and lower temperature (500 °C) prefer to form pyridines, nitriles and pyrroles and higher temperature could increase pyridines selectivity while decreased its yield. In addition, significant synergetic effects have been observed when cellulose was added, which improved pyridines yield by 40.64 % to 11.32 C% at the mixing weight ratio of cellulose to POM of 5:1. The synergistic effect between cellulose and POM for enhancing pyridines production were that POM pyrolytic intermediate (HCHO) can be used not only as substrate to form pyridines but also as an alkylation reagent to produce alkylation substituted pyridines. Catalytic pyrolysis with ammonia process has been proved to be a promising method for producing N-containing chemicals from biomass and wasted oxygen-containing plastics.

Valorization of chitin derived N-acetyl-D-glucosamine into high valuable N-containing 3-acetamido-5-acetylfuran using pyridinium-based ionic liquids

Chitin and its derivatives contain biologically fixed nitrogen elements, which can provide nitrogen sources for N-containing chemicals. Herein, a series of pyridinium-based ionic liquids were synthesized to directly catalyze the conversion of N-acetyl-D-glucosamine (NAG, the monomer of chitin) to 3-acetamido-5-acetylfuran (3A5AF). The yield of 3A5AF in 1-carboxymethyl pyridinium chloride ionic liquid reached 37.49%, without any additives. Using B2O3 and CaCl2 as additives, the optimum yield increased to 67.37% at 180 °C in 20 min. In addition, HPLC-MS analysis has been utilized to elucidate the reaction mechanism. This research on turning “waste” into “wealth” opens up new ways for the utilization of biomass waste, which not only reduces environmental pollution but also has potential economic value.

Selective Utilization of N-acetyl Groups in Chitin for Transamidation of Amines

The selective transformation of chitin into various renewable N-containing chemicals and medicines has attracted increasing attention. However, the N-acetyl groups in chitin construct strong hydrogen bond networks, which restricts its depolymerization and transformation. The selective conversion of robust chitin commonly requires considerable base catalysts to remove the N-acetyl group as a byproduct in advance, which is non-compliance with the principle of atomic economy. Herein, for the first time we demonstrate a novel approach to achieve the selective utilization of the N-acetyl group in chitin for transamidation of chitin with amines. A series of amine derivatives, mainly including aliphatic amine, cyclic amine and functionalized aromatic amine, could be selectively converted into the corresponding amide products frequently found in pharmaceuticals. Furthermore, the solid residue after removing the acetyl group (denoted as De-chitin) with the sufficient exposure of -NH2 groups as a solid base catalyst shows excellent performance in the aldol condensation reaction of furfural and acetone to produce fuel precursors. Our process provides a strategy that exploiting every functional group adequately in substrates to obtain value-added chemicals.

Synthesis of arylamines and N-heterocycles by direct catalytic nitrogenation using N2

Ammonia and nitric acid are two key platform chemicals to introduce nitrogen atoms into organic molecules in chemical industry. Indeed, nitric acid is mostly produced through the oxidation of ammonia. The ideal nitrogenation would involve direct use of dinitrogen (N2) as a N source to construct N-containing organic molecules. Herein, we report an example of direct catalytic nitrogenation to afford valuable diarylamines, triarylamines, and N-heterocycles from easily available organohalides using dinitrogen (N2) as the nitrogen source in a one-pot/two-step protocol. With this method, 15N atoms are easily incorporated into organic molecules. Structurally diversified polyanilines are also generated in one pot, showing great potential for materials chemistry. In this protocol, lithium nitride, generated in situ with the use of lithium as a reductant, is confirmed as a key intermediate. This chemistry provides an alternative pathway for catalytic nitrogenation to synthesize highly valuable N-containing chemicals from dinitrogen.

Optimization of the nitrogen and oxygen element distribution in microalgae by ammonia torrefaction pretreatment and subsequent fast pyrolysis process for the production of N-containing chemicals

In this work, ammonia (NH3) torrefaction pretreatment (ATP) was developed to optimize the nitrogen and oxygen element distribution of microalgae via the N-doping and oxygen removal reaction, which could obviously improve the potential use of microalgae as a feedstock for the production of N-heterocyclic chemicals through fast pyrolysis technology. The nitrogen content increased from 8.3% of raw microalgae to 11.51% at 300 °C of ATP, while the oxygen content decreased from 35.96% to 21.61%, because of the Maillard reactions. In addition, the nitrogen-doping ratio and oxygen removal ratio of ATP was much higher than the conventional nitrogen torrefaction pretreatment (NTP). With the increase of ATP torrefaction temperature or the pyrolysis temperature, the relative content of the N-containing compounds increased, while the O-containing compounds decreased. For the N-heterocyclic chemicals, higher pyrolysis temperature favored the formation of pyrroles, while inhibited the formation of pyridines and indoles.

Evolution of N-Containing Compounds during Hydrothermal Liquefaction of Sewage Sludge

In this study, complementary techniques, including ultrahigh-resolution Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) and X-ray photoelectron spectroscopy (XPS), were applied to characterize the transformation of nitrogen components during hydrothermal liquefaction (HTL) of sewage sludge. Results showed that 3–35% of nitrogen in sludge was transferred into the biocrude product when using HTL reaction temperatures ranging from 200 to 350 °C, with the remaining nitrogen partitioning to aqueous, solid, and gaseous coproducts. N-containing organics in biocrude shifted to structures with higher H:C ratios when HTL reaction temperatures were increased, whereas an opposite trend was observed for O:C ratios of N-containing chemicals in biocrude and aqueous products. Accordingly, weighted averages of double-bond equivalents (DBEw) and aromatic index (AImod,w ) of N-containing products in biocrude decreased as reaction temperature increased, while AImod,w increased for products in the aqueous phase. These trends are consistent with cyclization/aromatization reactions, promoting the formation of N-containing products that partition predominantly to the aqueous phase. XPS analysis revealed that the proportion of amine-N in biocrude increased sharply with reaction temperature, whereas heterocyclic-N (pyridinic-N and pyrrolic-N) and nitrile-N structures were mainly concentrated in solid residues. Improved molecular insights can serve as the basis for optimizing nitrogen management and recovery operations during HTL of sewage sludge.