查找使用阿拉丁产品的科研文献

ReaxFF-based molecular dynamics simulation of the impact of potassium on the formation of NH3 during protein pyrolysis

Shuai Guo,Yu Wang,Li Yang,Baizhong Sun,Hongwei Qu,Xingcan Li,Deng Zhao

The study used ReaxFF MD (Reactive Force Field Molecular Dynamics) to investigate the migration behavior and mechanisms of nitrogen in the pyrolysis process of biomass, specifically focusing on the effect of the alkali metal potassium on the main nitrogen-containing substance, proteins. This research primarily centers on the conversion mechanisms of nitrogen in the three-phase products (char, tar, and gas) during the pyrolysis of proteins, as well as the impact on NH 3 formation. The findings reveal several key insights: First, the introduction of potassium significantly enhances the cleavage activity of protein macromolecules by promoting the breaking of carbon-carbon and carbon-nitrogen bonds, which accelerates the degradation process of protein molecules and subsequently increases the conversion rate of nitrogen from proteins to the nitrogen in char, tar, and gas. Second, the addition of potassium alters the sources of gaseous nitrogen (gas-N); initially derived mainly from the secondary cracking of tar nitrogen (tar-N), gas-N predominantly originates from the conversion of char nitrogen (char-N) under the influence of potassium. Lastly, the introduction of potassium affects NH 3 production by significantly altering the trend of nitrogen-hydrogen bond variation during the pyrolysis of proteins. This is primarily attributed to potassium's facilitation of dehydration reactions, which disrupt nitrogen-hydrogen bonds during protein pyrolysis. Additionally, it allows NH 3 produced in the later stages of pyrolysis to participate in the formation of other nitrogen-containing compounds, particularly HCN. Potassium also promotes the dehydrogenation of the large number of HCN molecules generated during protein pyrolysis, forming CN radicals that subsequently react with NH 3 to produce new compounds. This is the main reason for the variation in NH 3 yield.

Synthesis of a chabazite-supported copper catalyst with full mesopores for selective catalytic reduction of nitrogen oxides at low temperature

Jixing Liu,Jian Liu,Zhen Zhao,Weiyu Song,Yuechang Wei,Aijun Duan,Guiyuan Jiang

A series of meso-microporous copper-supporting chabazite molecular sieve (Cu-SAPO-34) catalysts with excellent performance in low-temperature ammonia selective catalytic reduction (NH 3 -SCR) have been synthesized via a one-pot hydrothermal crystallization method. The physicochemical properties of the catalysts were characterized by scanning electron microscopy, transmission electron microscopy , N 2 adsorption-desorption measurements, X-ray diffraction, 27 Al magic angle spinning nuclear magnetic resonance , diffuse reflectance ultraviolet-visible spectroscopy, inductively coupled plasma-atomic emission spectroscopy, X-ray photoelectron spectroscopy , temperature-programmed reduction measurements, and electron paramagnetic resonance analysis. The formation of micro-mesopores in the Cu-SAPO-34 catalysts decreases diffusion resistance and greatly improves the accessibility of reactants to catalytic active sites. The main active sites for NH 3 -SCR reaction are the isolated Cu 2+ species displaced into the ellipsoidal cavity of the Cu-SAPO-34 catalysts.

Highly selective preparation of valuable dinitronaphthalene from catalytic nitration of 1-nitronaphthalene with NO2 over HY zeolite

Renjie Deng,Kuiyi You,Fangfang Zhao,Pingle Liu,He'an Luo

In this work, a simple method for the highly selective preparation of valuable dinitronaphthalene from 1-nitronaphthalene employing NO 2 as a nitrating agent has been developed. The results demonstrated that HY zeolite as an eco-friendly and stable catalyst exhibits good catalytic performances. The total selectivity to valuable dinitronaphthalene compounds including 1,5-, 1,4-, and 1,3-dinitronaphthalene can reach 87.6 % in our present nitration reaction. Meanwhile, the physico-chemical properties of catalysts were characterized by XRD, FTIR, TG/DTG, BET, and NH 3 -TPD, and the probable nitration reaction mechanism was also suggested in this paper. The present nitration process seems to be a mild, eco-friendly, and economical route for the preparation of valuable dinitronaphthalene compounds.

A comparative study of hydrothermal aging effect on cerium and lanthanum doped Cu/SSZ-13 catalysts for NH3-SCR

Di Deng,Shujun Deng,Dandan He,Zhiheng Wang,Zhipeng Chen,Yi Ji,Guoping Yan,Guangjin Hou,Licheng Liu,Hong He

Ce- or La-doped Cu/SSZ-13 catalysts were prepared by a hydrothermal method and Cu, Ce or La ions were incorporated through stepwise ion exchange. The catalyst activity was measured for the ammonia selective catalytic reduction reaction. The structure and composition of catalyst were characterized by using X-ray diffraction, scanning electron microscopy, inductively coupled plasma mass spectrometry solid-state NMR, NH 3 -TPD techniques, and the active components were examined by XPS and XANES . The results indicate that the Ce and La doping can both completely preserve the SCR activity of Cu/SSZ-13 above 300 °C, but there is also a decrease of activity below 200 °C. On the other hand, Ce doping is beneficial to the formation of framework aluminum , stabilizes molecular sieve framework and Cu active sites of Cu/SSZ-13, thereby improves the catalyst hydrothermal stability. But La doping will decrease the amount of framework aluminum and Cu active sites of Cu/SSZ-13 after hydrothermally aging, even destroy zeolite CHA structure. This is quite harmful to the catalyst hydrothermal stability.

Low-temperature SCR of NOx by NH3 over MnOx/SAPO-34 prepared by two different methods: a comparative study

Chenglong Yu,Lifu Dong,Feng Chen,Xiaoqing Liu,Bichun Huang

Cauliflower-like Sn-ZnO/ZIF-67 for highly sensitive and selective NH3 detection, and monitoring freshness of soy products

Weili Ye,Lihan Deng,Jin Li,Chu Chen

Accurate detection of ammonia (NH 3 ) is a key indicator for evaluating the deterioration of high-protein foods and is of great significance for food safety. In this study, we modified Sn-ZnO using a Co-based metal–organic framework (MOF) material (ZIF-67) to prepare cauliflower-shaped Sn-ZnO/ZIF-67 (SZZ67) for NH 3 sensors at room temperature (25 °C). By regulating Co 2+ , it was found that the sensor's response to NH 3 decreased with the increase in Co 2+ content, while the desorption ability was significantly enhanced. When the mass ratio of Sn-ZnO to the added C 4 H 6 CoO 4 ∙4H 2 O was 1:1, its response was 13.46 times that of Sn-ZnO, the response/recovery time was 63.78/7.99 s, and good moisture resistance was observed. Density functional theory (DFT) confirmed that SZZ67 can adsorb more NH 3 and release more conductive electrons, thereby increasing its response value. The sensors prepared using SZZ67 could more effectively monitor NH 3 , which is applicable for monitoring the freshness of soy products.

Investigation of NH3 absorption by protic imidazolium thiocyanate-based deep eutectic solvents with multiple binding sites and low viscosity

Ziyue Zhou,Ke Li,Kai Zong,Xiaoxia Deng,Dongshun Deng

Ammonia (NH3) is not only an important basic chemical raw material but also a typical polluting gas. The separation and recovery of NH3 from tail gas is of great significance for human health and the environment. In this study, a series of protic ionic liquid-based deep eutectic solvents (PIL-based DESs) were constructed by pairing imidazolium thiocyanate ([Im][SCN]) as the hydrogen-bond acceptor (HBA) with various hydrogen-bond donors (HBDs) [glycerol (Gly), ethylene glycol (EG), formamide (FM), acetamide (AT), and caprolactam (CL)]. Their physical properties and NH3 absorption performance were systematically investigated. The results showed that [Im][SCN] played a role in chemical NH3 absorption in the PIL-based DESs, while the HBDs mainly contributed to physical NH3 capture. HBDs containing hydroxyl groups demonstrated an evident improvement in NH3 absorption capacity compared to those with amide groups. [Im][SCN]–EG (1 : 3) demonstrated the highest mass capacity of 0.233 g NH3/g DES, which exceeded those of all the other IL-based DESs and originated from the multiple interactions between the acidic H as well as the hydroxyl groups in the DES and NH3, according to the 1H NMR and FTIR spectral analysis. Furthermore, [Im][SCN]–EG (1 : 3) indicated a high NH3/CO2 selectivity of 632.2, satisfactory thermal stability and excellent recyclability. [Im][SCN]–EG DESs possess great potential as attractive absorbents in NH3 separation and recovery.

Unlocking the potential of organic-inorganic hybrids in microwave gas sensors: Rapid and selective NH3 sensing at room-temperature

Ningyi Wang,Wei Tao,Nan Zhang,Tianshuang Wang,Xiaolong Wang,Fangmeng Liu,Xu Yan,Fengmin Liu,Xishuang Liang,Peng Sun,Geyu Lu

Microwave gas sensor (MGS), being as a kind of new-developed sensing device, possesses the ability to resolve the poor stability, imprecise selectivity, slow response speed and other problems plaguing room-temperature gas sensors. However, the nature of gas sensing mechanism of MGS has not yet been revealed, and the sensitive materials currently applied on MGS are relatively unstable and insensitive under high humidity. Here we have for the first time reported a highly sensitive, selective, and stable MGS composed of ultra-narrowband microwave filter transducer and organic-inorganic hybrid sensitive material (multilayered structured polyaniline (PANI)-SnO 2 ). Owing to the standout capacity of ammonia (NH 3 ) adsorption, the high resistance to water poisoning, and the efficient tuning of relative permittivity ascribed to p-n (PANI-SnO 2 ) heterojunction , the organic-inorganic hybrid based MGS operating at room-temperature can selectively detect low concentration of NH 3 with high sensitivity, fast response speed, and anti-humidity capacity, which has never been reported before. This work develops a new class of microwave sensing functional materials, and demonstrates that the concept in tuning relative permittivity for constructing outstanding performance microwave gas sensor.

A Highly Sensitive and Selective NH3 Sensor Based on a Spherical In2O3-Sensing Electrode Prepared Using the Hydrothermal Method

Dongxing Zhang,Jie Zou,Xuebin Li,Fuan Li,Chunyue Bi,Zhenyan Wang,Yuanjie Su,Jiawen Jian

In2O3 material with special morphology was synthesized using the hydrothermal method and was used as the sensing electrode for a mixed potential ammonia sensor based on yttria-stabilized zirconia electrolyte. The In2O3 sensing electrode (In2O3-SE) was sintered at different temperatures and was characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (SEM). The influence of the In2O3-SE sintering temperature on the performance of the sensor was investigated by testing the NH3 response at 500 °C. The results showed that the sensor attached with In2O3-SE sintered at 900 °C exhibited the largest response value (–102.1 mV for 250 ppm NH3) at 500 °C. Moreover, the response value of the sensor varied almost linearly with the logarithm of NH3 concentration in the range of 20–400 ppm, which was consistent with the mixed potential mechanism, as verified by polarization and electrochemical impedance spectroscopy (EIS) tests. Furthermore, the sensor also displayed high sensitivity to NH3, but weak cross-sensitivities to various interfering gases (CHs, NOx, CO, CO2 and H2O) at 500 °C. It exhibited slight signal drifts both in the continuous 26-h test and in the interval test over a period of one month, which showed that the sensor attached with 900 °C-sintered In2O3-SE has acceptable short- and long-term stability.

Investigation of electrode-free, room temperature, flexible NH3 sensors with high stability and sensitivity using MXene@PANI-MWCNTs ink

Jiahui Zheng,Bochao Ma,Xiaoqing Cui,Rui Wang,Li An,Bin Guo,Hongyan Zhang

Detecting ammonia (NH 3 ) is crucial for both the atmospheric environment and human health. However, developing low-cost, high-sensitivity, and flexible sensors for NH 3 is a significant challenge. Herein, we report a flexible, electrode-free NH 3 sensor based on an ink of polyaniline-covered MXene and multi-walled carbon nanotubes (MXene@PANI-MWCNTs), which was developed on cotton fabric using a dispensing print method. After optimizing the MXene@PANI-MWCNTs concentration, the number of sensor arms and the printed layers, the sensor exhibited a high response in the range of 0.5–25 ppm and can detect as low as 0.5 ppm NH 3 at 40% relative humidity (RH), room temperature (25°C). The response values were significantly higher than those for other interfering gases including H 2 , CO, H 2 S, and NO 2 . Furthermore, the sensor demonstrated excellent mechanical stability, with its response dropping by only 3.7% after 1000 bending cycles. When covered with expanded polytetrafluoroethylene (e-PTFE) film, the sensor showed stable performance in the ranging of 30%–90% RH at 25°C. Additionally, MXene@PANI-MWCNTs ink was printed on masks to detect NH 3 levels in breath, offering potential for medical diagnostics and personal health monitoring.

MgO/N-doped carbon synthesized via facile NH3·H2O-modulated citric acid complexation for efficient room-temperature H2S oxidation

Kunlin Li,Wei Guo,Yu Tian,Kai Li,Ping Ning,Xueyan Chen,Fei Wang,Changbin Zhang

Carbon-based materials are widely used for H 2 S oxidation, yet their performance under ambient conditions requires further improvement via precise structural engineering. In particular, existing MgO-modified carbon materials still suffer from suboptimal H 2 S removal capacity, limited regenerability, and/or complicated synthesis processes, which restrict their practical application in room-temperature desulfurization. In this work, we report MgO/N-doped carbon catalysts synthesized by an NH 3 ·H 2 O-modulated citric acid complexation method, which demonstrated superior activity for ambient H 2 S oxidation. It was shown that the introduction of NH 3 ·H 2 O induced the formation of NH 4 NO 3 in pyrolysis precursors, and the decomposition of NH 4 NO 3 during pyrolysis created abundant carbon defects and also incorporated pyridinic/pyrrolic N species. These defects anchor Mg ions, leading to the formation of well-dispersed MgO nanosheets that enhanced surface basicity and facilitated H 2 S dissociation. Meanwhile, the defect-rich structure significantly improved O 2 activation to generate reactive 1 O 2 species for efficient H 2 S oxidation. The optimized MNC-3 delivered an exceptional H₂S capacity of 2.41 g/g cat. with 55 h breakthrough time at room temperature, and retained 0.78 g/g cat. after three regeneration cycles. This work provides a rational design strategy for high-performance, cost-effective room-temperature desulfurization materials through integrated modulation of active phase morphology, nitrogen doping, and carbon defects.

Phosphate Modification Promotes Low-Temperature NH3-SCO over Cu/CeO2 Through Coupled Regulation of Surface Acidity and Oxygen Species

Shiqi Ma,Haoyang Li,Yuchen Huang,Kai Sun,Yuejia Huang,Yarong Fang,Yan Du

Selective catalytic oxidation of ammonia (NH3-SCO) is a promising technology for ammonia abatement. Cu/CeO2catalysts have attracted extensive attention because of their strong metal–support interaction and favorable redox properties. However, their practical application is still limited by insufficient low-temperature catalytic activity and unsatisfactory control of by-product formation. Herein, phosphate-functionalized Cu/CeO2catalysts were fabricated to regulate surface acidity and oxygen species behavior, thereby promoting low-temperature NH3-SCO activity. The optimal Acid-Cu/CeO2catalyst achieved 90% NH3conversion at 260 °C, corresponding to a 192 °C decrease in T90compared with pristine Cu/CeO2(452 °C). Kinetic analysis showed that the apparent activation energy decreased from 125.78 to 84.70 kJ mol−1after phosphoric acid modification. In addition, Acid-Cu/CeO2maintained relatively high N2selectivity and lower NOxselectivity over the tested temperature range, indicating that phosphate modification suppresses the deep oxidation of NH3to NOxby-products. Structural and surface characterization results demonstrated that Cu species remained highly dispersed on CeO2after modification, while surface phosphate species modified the local electronic environment and redistributed oxygen species. O 1s XPS and O2-TPD results revealed that phosphate modification decreased the static surface adsorbed/defect-related oxygen fraction but improved the accessibility and mobility of labile surface/subsurface or weakly bound lattice oxygen species. Py-IR and DRIFTS results further showed that phosphate modification increased Brønsted/Lewis acidity, enhanced NH3adsorption and N-H activation, and facilitated the formation and subsequent consumption of NHx/-NHO-related intermediates under reaction conditions. This work provides insights into phosphate-mediated regulation of surface acidity and oxygen mobility and offers a strategy for designing efficient low-temperature Cu/CeO2-based NH3-SCO catalysts.