Ammonia Chemisorption Research Articles

Gas permeable membrane electrode assembly with in situ utilization of authigenic acid and base for transmembrane electro-chemisorption to enhance ammonia recovery from wastewater

Ammonia recovery from wastewater is of great significance for aquatic ecology safety, human health and carbon emissions reduction. Electrochemical methods have gained increasing attention since the authigenic base and acid of electrochemical systems can be used as stripper and absorbent for transmembrane chemisorption of ammonia, respectively. However, the separation of electrodes and gas permeable membrane (GPM) significantly restricts the ammonia transfer-transformation process and the authigenic acid-base utilization. To break the restrictions, this study developed a gas permeable membrane electrode assembly (GPMEA), which innovatively integrated anode and cathode on each side of GPM through easy phase inversion of polyvinylidene fluoride binder, respectively. With the GPMEA assembled in a stacked transmembrane electro-chemisorption (sTMECS) system, in situ utilization of authigenic acid and base for transmembrane electro-chemisorption of ammonia was achieved to enhance the ammonia recovery from wastewater. At current density of 60 A/m2, the transmembrane ammonia flux of the GPMEA was 693.0 ± 15.0 g N/(m2·d), which was 86 % and 28 % higher than those of separate GPM and membrane cathode, respectively. The specific energy consumption of the GPMEA was 9.7∼16.1 kWh/kg N, which were about 50 % and 25 % lower than that of separate GPM and membrane cathode, respectively. Moreover, the application of GPMEA in the ammonia recovery from wastewater is easy to scale up in the sTMECS system. Accordingly, with the features of excellent performance, energy saving and easy scale-up, the GPMEA showed good prospects in electrochemical ammonia recovery from wastewater.

Impregnated fibrous ammonia chemisorbent based on citric acid. Prediction of protective characteristics

The influence of relative humidity (RH) of the gas-air environment on the ammonia chemisorption by impregnated fibrous chemisorbent (IFCS) is studied. IFCS was obtained by impregnating nonwoven needle-punched material from polyester fibers with an aqueous solution of citric acid (40 w%) with modifiers (glycerin, sodium chloride and ethanol) to uniformly distribute the chemisorbent on the surface of the fibers and increase adhesion to the composition of the impregnating solution. It is shown that for all values of relative humidity the curves of ammonia breakthrough through a fixed layer of IFCS спр(tпр) in the coordinates ln(c0/спр -1), tпр are reliably R2 > 0.95 approximated by straight lines and the Wheeler-Jonas theoretical model can be used for the quantitative description of the ammonia-IFCS system. By comparing the experimental and theoretical curves спр(tпр) in the coordinates ln(c0/спр -1), tпр the unknown model parameters were determined: the chemisorption rate constant and the sorption capacity of the IFCS unit mass and their dependence on the relative humidity of the gas-air environment (GAE). It has been established that the IFCS sorption capacity increases linearly with increasing, and the chemisorption rate constant of the ammonia-IFCS system does not depend on the GAE relative humidity and is equal to . The influence of the GAE relative humidity and the thickness of the IFCS layer on the ammonia breakthrough time is experimentally investigated and the adequacy of using the Wheeler-Jonas model for predicting the service life of IFCS for real use conditions is substantiated.

Linear scaling of charge transfer versus work function of Ammonia chemisorption on X-metal (X = Ag, Au, Pd, and Pt) surface

Although the d-band center theory can efficiently describe the interaction between gas molecules and transition metal surfaces, the specific reaction process and detailed adsorption criteria remain unclear. Therefore, we systemically investigated the adsorption process and mechanism of Ammonia (NH3) molecules on transition metal (i.e., Ag, Au, Pd and Pt) surfaces using first-principles calculations. Results indicate that the NH3 molecule undergoes chemisorption on the Pt (111) surface with considerable charge transfer and adsorption energy, indicating that Pt metal is a promising NH3-sensitive material. Furthermore, the chemisorption primarily entails the highest-occupied molecular orbital (HOMO) of NH3, and the metal atoms conform perfectly to the principles of energy-level matching, wave function matching, and maximal orbital wave function overlap. Notably, a linear relationship exists between the charge transfer of NH3 and the work function of X-metal substrates. Our findings provide a feasible way to efficiently design NH3-sensitive materials for experiments.

Synthesis and Acidity Study of Mixed MFI-MORD Type Zeolite

Zeolites of various nature are widely used in the chemical industry, the fuel and energy sector of the economy as sorbents, catalysts and materials for the creation of inorganic membranes for various purposes. At the same time, it is possible to change the acid properties of the surface of zeolites both by varying the ratio of silicon to aluminum or silicon to phosphorus, and by joint synthesis of zeolites of various types with different acidic properties. The presented article provides a method for the sequential production of a zeolite of a mixed structure type MFI and mordenite. Synthesis of the original MFI type zeolite was carried out using seed grains by the hydrothermal method for 72 hours, followed by washing and drying of the zeolite. To obtain a layer of mordenite on the surface of the MFI type zeolite, the initial zeolite was pretreated with alkali and then treated with n-butylamine. In this way, nine samples of zeolite with different acidic surface properties were obtained. Determination of the acidic properties of the surface was carried out by the method of ammonia chemisorption followed by its desorption from the surface of the zeolite. For this purpose, the test sample was loaded into a quartz cuvette, purged with argon at a temperature of 800°С, after which the temperature dropped to 150°С, and the surface of the zeolite was treated with ammonia. Subsequently, the test sample was heated up to 800°С with registration of desorption curves. The amount of adsorbed ammonia was carried out according to previously prepared calibration curves. The synthesized samples of zeolites had different acidity from 0.48 to 0.72 mmol(NH3)/g(sample). In this case, the total acidity of the samples correlated with the ratio of silicon to aluminum in the zeolite samples. Also, depending on the ratio of the MFI and mordenite structures in the zeolite sample, it is possible to vary not only the number, but also the strength of the formed acid sites. So, an increase in the content of mordenite contributes to an increase in the strength of acid centers. The developed method for the synthesis of mixed structure zeolites of the MFI type mordenite made it possible to control the surface acidity of the synthesized samples.

Stoichiometric metal nitration based novel green synthesis of mesoporous metal oxides and their enhanced heterogeneity

In this work, a general and novel method for the green synthesis of mesoporous metal oxides via stoichiometric metal nitration has been demonstrated. Pluronic surfactants and their effect on synthesis procedures in terms of surface area have been experimentally studied in detail. Contrary to the traditional synthesis procedure, water has been utilized as the solvent and in several cases, such as tin oxide, manganese oxide, aluminum oxide, antimony oxide, zinc oxide, cobalt oxide, copper oxide, yttrium oxide, lanthanum oxide, and silver either the highest or comparable surface areas have been successfully synthesized. Through XRD, and TEM, all materials were observed to be crystalline except silver and magnesium oxide. SEM shows that with an increase in surfactant molar mass agglomeration decreases. Ammonia chemisorption on acidic materials gives quantitative amounts of ammonia chemical bonding with catalysts, whereas carbon dioxide chemisorption gives a quantitative value of CO2 chemical binding with basic sites. As high as 1901.8 μmol/g and 994.6 μmol/g ammonia chemisorption values for oxides of vanadium and tin were achieved. Amphoteric materials give both acidic and basic enhanced adsorption. Finally, all synthesized materials are studied under organic catalytic transformations. Benzyl bromide is theoretically more active compared with benzylamine and benzyl alcohol which was also experimentally shown through the conversion.

Highly Mesoporous MoO3 Catalysts for Electrophilic Aromatic Substitution.

Herein, a straightforward synthesis method for highly mesoporous molybdenum oxide has been demonstrated via use of inverse micelles and molybdenum-oxo cluster formation. The synthesized catalyst is stable, crystalline, and MoO3 phase pure, as confirmed through thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. Further results from electron paramagnetic resonance, Raman spectroscopy, and UV-vis spectroscopy confirm the MoO3 phase purity. Chemisorption studies reveal that the synthesized material is 65 times more active than its commercial parts. The quantitative value of ammonia chemisorption for the synthesized catalyst is 1270 μmol/g, whereas the commercial catalyst only gives 22 μmol/g. These materials were tested for electrophilic substitution reactions since they are excellent solid acid. Electrophilic substitution of benzyl alcohol with toluene gives a >99% conversion with ∼80% of selectivity toward the methyl diphenylmethane product. The turnover number and turnover frequency values were calculated to be as high as 115 and 38, respectively. A substrate scope study shows that the reaction has preference toward electron-donating groups, whereas electron-withdrawing groups block the reaction. Based on the obtained results, a mechanism has been proposed.

Ammonia removal in selective catalytic oxidation: Influence of catalyst structure on the nitrogen selectivity

Selective catalytic oxidation is regarded as an effective and favored method for the removal of hazardous ammonia. A number of M-Pt/USY (M=Mn, Fe, Ce and Pr) catalysts were prepared and the resulting materials were characterized using N2 adsorption/desorption, XRD, TEM, NH3-TPD, XPS and H2-TPR. It was found that the addition of non-stoichiometric metal oxides to Pt/USY leads to the generation of additional acid sites for ammonia chemisorption and that N2 selectivity improved with increased strong acidity of the bi-functional catalysts. The oxidation state of active Pt could be adjusted by the introduction of non-stoichiometric metal oxides with increased concentrations of oxidized Ptδ+ species observed in the order of FeOx >CeO2-x >MnO2-x >Pr6O11. High valence platinum surrounded by atomic oxygen that can act as a proton scavenger to drive ammonia activation, inhibiting O2 dissociation and therefore improve N2 selectivity. Fe-containing USY zeolite is demonstrated to be a preferred catalyst for the removal of ammonia, due to its high N2 selectivity and good hydrothermal stability.

Curious Mechanism of the Dissociative Chemisorption of Ammonia on Ru(0001)

Dissociative chemisorption of polyatomic molecules on metals, which is relevant to heterogeneous catalysis, usually proceeds through a rotationally adiabatic or rotational sudden mechanism. The reaction is usually either direct or proceeds through a trapped molecular chemisorbed state. Here, ab initio molecular dynamics is used to model the dissociative chemisorption of ammonia on Ru(0001). The reaction mechanism is neither rotationally adiabatic nor rotational sudden, with clearly distinct and nonstatistical initial and time-of-reaction orientation distributions. A reasonably good agreement is obtained between the computed and previously measured sticking probabilities. Under the conditions investigated, the reaction of NH3 goes through a molecular chemisorption-like state, but the reaction is direct.

Functionalized carbon nanotube immobilized membrane for low temperature ammonia removal via membrane distillation

Enhanced ammonia separation via direct contact membrane distillation (DCMD) using carbon nanotube immobilized membranes (CNIMs) is presented. The CNIMs were prepared using raw carbon nanotubes (CNTs) as well as more polar carboxylated carbon nanotubes referred to as f-CNTs. The ammonia removal by both CNIMs were markedly superior to that of the original PTFE membrane, while functionalized CNIM (CNIM-f) showed the best performance in terms of flux, mass transfer coefficients and selectivity. The flux with f-CNTs was 63% higher than the PTFE membrane and 22% higher than raw CNTs. Similar trends were observed for ammonia removal efficiency and mass transfer coefficients that were also significantly higher for the f-CNTs. The ammonia selectivity with respect to water vapor decreased with temperature for the PTFE and CNIM with raw CNTs, but in the presence of f-CNTs the selectivity did not show any decrease with temperature. The enhancement in ammonia removal with f-CNTs is attributed to the favored chemisorption of ammonia on the f-CNTs which was evident from contact angle measurements that showed a dramatic decrease for aqueous ammonia in the presence of the carboxylic groups.

Reversible and Vapochromic Chemisorption of Ammonia by a Copper(II) Coordination Polymer

The single crystal X-ray structure determination of {[Cu(tpt)(o-phthalate)]·31/3(C2H2Cl4)}n (tpt=2,4,6-tri-4-pyridyl-1,3,5-triazine, C2H2Cl4=1,1,2,2-tetrachloroethane=TCE) shows a 3D network in which CuII centres are linked by 3-connecting tpt ligands with the topology of a 12,3 net. CuII centres are further linked by o-phthalate dianions. The copper coordination geometry is square pyramidal, with o-phthalate oxygen donors trans to each other in the basal plane and the remaining positions taken by the pyridines of three linking tpt units. The solvent accessible void space is ~65%. The pale blue-green crystalline desolvate, obtained by heating to 200°C or washing the TCE solvate with acetone is formulated as [Cu(tpt)(o-phthalate)]n. Powder X-ray diffraction and electron paramagnetic resonance spectroscopy show that the crystal structure and the CuII geometry changes upon desolvation. The crystalline desolvated phase sorbs two equivalents of ammonia per copper ion. The adduct, mauve [Cu(tpt)(o-phthalate)(NH3)2]n, shows reasonable crystallinity and is stable up to ~150°C under ambient conditions before the reversible desorption (minimum 10 cycles) of the guest ammonia. The colour change and high desorption temperature, along with changes in g values, is suggestive of chemisorption in two steps with Cu–ammine bonding in the loaded phase.

PECULIARITIES OF SMALL STRAINED ALICYCLE COMPOUNDS FORMATION IN CATALYTIC TRANSFORMATION OF METHANOL OVER ZEOLITE H-ZSM-5

The article presents the results of strained hydrocarbons formation study during the catalytic transformation of methanol into hydrocarbons on zeolite H-ZSM-5. The formation of the following strained cyclic compounds was determined: 1,1-dimethylcyclopropane, 1,2-dimethyl-cyclopropane, 1,1,2-trimethylcyclopropane, 1,2,3-trimethylcyclopropane, 1,1,2,2-tetramethylcyclo-propane, 1,1,2 , 3-tetramethylcyclopropane. The non-stationary character of strained cyclic hydrocarbons formation with a pronounced hydrocarbons formation rate maximum and subsequent deactivation of the catalyst was found. The temperature effect on strained hydrocarbons yield was evaluated. Thus, with an increase in the process reaction temperature up to 400 °C, a maximum of strained hydrocarbons accumulation rate was achieved as 8-8.5 g(Hyd)/(kg(Cat)·h) on 350 h of reaction, and a further increase in the reaction temperature leads to a decrease in the strained hydrocarbons accumulation rate. The effect of the methanol feed rate on the strained hydrocarbons formation rate was also studied. An increase in the methanol feed rate from 0.02 ml/min to 0.16 ml/min results in increase in the strained hydrocarbons formation rate up to 37 g (Hyd)/(kg(Cat)·h). The article presents results of H-ZSM-5 physicochemical study used by ammonia chemisorption, nitrogen phisisorption, X-ray photoelectron spectroscopy. Physicochemical studies of catalyst samples after the methanol transformation process to form strained hydrocarbons showed a twofold decrease in the number of acid sites from 1.2 mmol(NH3)/g (sample) to 0.3 mmol (NH3)/g(sample) and a significant decrease in surface area of micropores from 294 m2/g for the initial sample to 16 m2/g for the sample after the reaction. The X-ray diffraction spectroscopy method showed that the composition of the catalysts H-ZSM-5 surface includes carbon, oxygen, silicon and aluminum. Carbon concentration was found to be 4.3 at.% on the surface of the initial catalyst. While the carbon concentration increases up to 14.1 at.% during the reaction. Also oxygen content on the catalysts surface decreases from 59.9 to 53.4 at%, silica concentration decreases from 35.5 to 32.1 at.%. The following indicates the formation of a carbon surface layer over the catalysts.

Highly selective PbS thin film based ammonia sensor for inert ambient: In-situ Hall and photoelectron studies

Granular thin films of p-type semiconducting PbS (Cubic) with predominantly a-axis oriented grains having an average grain size of about 300 nm were deposited on polycrystalline alumina by pulsed laser deposition technique. Optical measurements show a band gap of 2.25 eV. The thin films were highly selective to ammonia at 473 K even in the presence of hydrogen and they operate in inert ambient with a typical response and recovery times of about 25 s and 120 s respectively. In-situ Hall measurements show an exponential decrease in hole carrier concentration with increasing NH3 level. XPS analysis of Pb 4f and S 2p levels reveals that the valence state of Pb and Sulphur remain in +2 and −2 respectively after exposure to the reducing ammonia and the appearance of N 1s peak at 398.1 eV confirms dissociative chemisorption of ammonia on PbS surface.

Polymer Composite Optically Integrated Lab on Chip for the Detection of Ammonia

This paper reports a novel method to detect ammonia by using the ninhydrin – PDMS composite. The polymer composite film is prepared by integrating ninhydrin into the PDMS polymer matrix. Further, an optical lab-on-a-chip device is developed by integrating the ninhydrin-polymer composite into a microfluidic device for the detection of ammonia. The chemisorption of ammonia onto the composite resulted in the change in its optical absorption property. The proposed device has an integrated light emitting diode and photoresistor in order to measure the change in absorption and hence the detection and quantification of ammonia are performed. The response time of the sensor was found to be linear for a wide range of ammonia concentrations and it is shortest for the thin (100 μm) composite film. The limit of detection of the proposed device is found to be as low as 2ppm. The proposed sensor platform is also demonstrated for the detection of amino acids.

Carbon-free H2 production from ammonia triggered at room temperature with an acidic RuO2/γ-Al2O3 catalyst.

Ammonia has been suggested as a carbon-free hydrogen source, but a convenient method for producing hydrogen from ammonia with rapid initiation has not been developed. Ideally, this method would require no external energy input. We demonstrate hydrogen production by exposing ammonia and O2 at room temperature to an acidic RuO2/γ-Al2O3 catalyst. Because adsorption of ammonia onto the catalyst is exothermic, the catalyst bed is rapidly heated to the catalytic ammonia autoignition temperature, and subsequent oxidative decomposition of ammonia produces hydrogen. A differential calorimeter combined with a volumetric gas adsorption analyzer revealed a large quantity of heat evolved both with chemisorption of ammonia onto RuO2 and acidic sites on the γ-Al2O3 and with physisorption of multiple ammonia molecules.

An operando DRIFTS-MS study of NH3 removal by supported ionic liquid phase (SILP) materials

Abstract A novel gas purification material using a supported ionic liquid phase (SILP) has been investigated for removal of NH3 from ambient gas streams (1500 ppm NH3 in Ar). The SILP material is made of a thin film of an imidazolium based ionic liquid and a dissolved copper metal complex ([C2C1Im]Cl/CuCl2), which were dispersed in the pores of a silica 100 support. Diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) was used to investigate the irreversible absorption from a 1500 ppm NH3 gas stream and to identify species formed upon physisorption and chemisorption of ammonia. Additionally, temperature-programmed DRIFTS combined with in situ mass spectrometry were used to evaluate the reversibility and regenerability of the system.

Gas Protection of Two-Dimensional Nanomaterials from High-Energy Impacts.

Two-dimensional (2D) materials can be produced using ball milling with the help of liquid surfactants or solid exfoliation agents, as ball milling of bulk precursor materials usually produces nanosized particles because of high-energy impacts. Post-milling treatment is thus needed to purify the nanosheets. We show here that nanosheets of graphene, BN, and MoS2 can be produced by ball milling of their bulk crystals in the presence of ammonia or a hydrocarbon ethylene gas and the obtained nanosheets remain flat and maintain their single-crystalline structure with low defects density even after a long period of time; post-milling treatment is not needed. This study does not just demonstrate production of nanosheets using ball milling, but reveals surprising indestructible behaviour of 2D nanomaterials in ammonia or hydrocarbon gas under the high-energy impacts; in other milling atmospheres such as air, nitrogen or argon the same milling treatment produces nanosized particles. A systematic study reveals chemisorption of ammonia and hydrocarbon gases and chemical reactions occurring at defect sites, which heal the defects by saturating the dangling bonds. Density functional theory was used to understand the mechanism of mechanochemical reactions. Ball milling in ammonia or hydrocarbon is promising for mass-production of pure nanosheets.

Experimental evidence of NO SCR mechanism in the presence of the BEA zeolite with framework and extra-framework cobalt species

Temperature-programmed desorption (TPD), temperature-programmed surface reaction (TPSR) and stop flow-TPD techniques as well as FT-IR spectroscopy of pre-adsorbed NH3 and NO are applied to characterize active sites present in Co-containing BEA zeolites. Cobalt is introduced into BEA zeolite by different methods: (i) two-step postsynthesis – PS, (ii) conventional wet impregnation – Imp and (iii) ion-exchange – IE. The obtained catalysts are labelled as Co(PS)SiBEA (postsynthesis), Co(IMP)AlBEA (wet impregnation) and Co(IE)AlBEA (ion exchange). All the obtained catalysts are found to be active in the process of selective catalytic reduction (SCR) of NO with ammonia. The catalytic activity depends on the method used for cobalt introduction and thus on cobalt centres speciation. The reactivity of NH3 and NO adsorbed on Co(IMP)AlBEA and Co(IE)AlBEA is higher than that measured for the Co(PS)SiBEA catalysts. The temperature-programmed studies and FT-IR with NO and/or NH3 adsorption for the Co-containing samples show that during SCR reaction NO and NH3 molecules compete for the same adsorption sites. The main reaction pathways of the DeNOx process performed in the presence of Co(IMP)AlBEA and Co(IE)AlBEA involves the reaction between chemisorbed ammonia and NO from gas phase, according to the Eley-Riedel mechanism.

FIBROUS CHEMISORBENTS-AMPHOLYTE BASED ON THE COMPLEX COMPOUND OF NICKEL(II) CHLORID AND MONOETHANOLAMINE

The water vapor adsorption by complex compounds of nickel(II) chloride and monoethanolamine with different molar ratio metal : ligand, deposited on a fibrous carrier from nonwoven web on the basis of polyester fiber has been investigated under static conditions. Water vapor adsorption isotherms were analyzed in the framework of Brunauer-Emmett-Teller (BET) adsorption theory, monolayer capacitance values and the heats of water molecules adsorption in the first layer were determined. Sulphur dioxide and ammonia chemisorptions under static and dynamic conditions with obtained chemisorbents has been investigated. It was found the process of chemisorption of sulfur dioxide can take place only in the presence of «free» water formed on the fiber surface after formation of the monolayer, when the value of water vapor relative pressure of reaches P/PS = 0,25÷0,30. Under these conditions the destruction of the donor-acceptor bond in the cation complex between the nickel ions and monoethanolamine molecules within the domestic sphere of aminocomplexes takes place followed by the formation of more stable «onium» sulphites, hydrosulphites and pyrosulphite. It is found in the case of ammonia chemisorption by above mentioned material prewetting of the sample does not significantly increase ammonia absorption. In this case the displacement of the water molecules from inner-aquaaminocomplexes composition and replacing it with an equivalent amount of ammonia molecules take place to form a mixedligand complex of the composition: [Ni(HOCH2CH2NH2)n(NH3)6‑2n]Cl2. It is shown that the designed fibrous chemisorbent carries out a combined air purification both on sulfur dioxide and ammonia and may be used for the equipment of personal respiratory protection – lightweight respirators for dust and gases.

Fabrication, characterization and statistical investigation of a new starch-based hydrogel nanocomposite for ammonium adsorption

This work investigates a new starch-based hydrogel nanocomposite made from starch and poly vinyl alcohol blend as polymeric matrix and fumarate-alumoxane (Fum-A) and maleic anhydride (MA) as cross-linking agents, for its use in NH4+ removal from aqueous solutions.The adsorption performance of the hydrogel nanocomposite and also, nanocomposite's maximum adsorption capacity for ammonium adsorption via isotherm studies are examined. Box–Behnken experimental design is used to evaluate performance of hydrogel nanocomposite in the adsorption process. A mechanism was proposed for the chemisorption of ammonia. The water adsorption degree of cross-linked hydrogel nanocomposites decreased with increasing the amount of nanoparticles. The swelling degree of hydrogel nanocomposite (3.6 wt%) was improved about 1.5 units as compared with the hydrogel alone. The maximum removal efficiency (R%) of ammonium ion by hydrogel nanocomposite was 97.99%. The Langmuir isotherm model agrees well with the experimental data and its correlation coefficient value was close to adjust the correlation coefficient value, as compared with Temkin and Freundlich isotherm models. The maximum capacity of the model being 19.01 mg/g was improved compared with the maximum capacity of the Langmuir isotherm (7.43 mg/g).

Chemisorption of ammonia molecules on ytterbium nanofilms deposited on silicon Si(111) at room temperature

The interaction of ammonia molecules with the surface of ytterbium nanofilms of uniform thickness grown on a Si(111) 7 × 7 substrate and forming a chemically sharp interface with it has been investigated. It has been found that this interaction depends significantly on the thickness of nanofilms. For a film thickness equal to 5 monoatomic layers, chemisorption of ammonia has an essentially nondissociative character and the molecules form a donor-acceptor bond with ytterbium; as a result, the metal transforms from the divalent state into a new nonautonomous trivalent state. For other film thicknesses, the adsorbed molecules dissociate, nitrogen atoms diffuse into the bulk of the film and enter into the reaction with silicon, and ytterbium remains in the initial divalent state. It has been shown that the character of the interaction of ammonia molecules with ytterbium nanofilms and the stability of the NH3-Yb-Si(111) structures are determined by the standing waves of electron density (Friedel oscillations) generated by the interface between the metal and silicon substrate.