Infrared spectra of nitric oxide adsorbed on cobalt-alumina catalyst

Nitric oxide adsorption on the surface of a Co–Al catalyst was investigated using infrared technique. The presence of two kinds of adsorbed species was confirmed by N–O stretching frequencies at 1780 and 1855 cm^–1. The effect of potassium added to the Co–Al catalyst was examined.

---

Co–Al . N–O : 1780 1855 ^–1. , Co–Al.

     

Infrared spectra of nitric oxide adsorbed on photoreduced V/SiO2 catalyst

Studies of the IR spectra of surface species produced via NO adsorption on selectively photoreduced V/SiO₂ catalysts indicate that at low coverages NO is adsorbed on V³⁺ ions to form strongly bonded mononitrosyl species V³⁺...... NO. With increasing NO coverage, V³⁺ is oxidized to V⁴⁺, which is accompanied by the appearance of gaseous N₂O and weak adsorption of NO on V⁴⁺.

---

- , NO V/SiO₂ . , V³⁺ NO V³⁺... NO. V³⁺ V⁴⁺, N₂O NO V⁴⁺.

     

A surface potential study of adsorbed oxygen species on a Bi2Mo3O12 catalyst

Bi₂Mo₃O₁₂ is a selective oxidation catalyst of propylene into acrolein. Surface potential measurements proved the presence of an equilibrium between gaseous oxygen and the O^2– species adsorbed on the surface of the catalyst, under oxygen atmosphere, in the range 538K–673K. This is in accordance with the fact that O^2– is a selective oxidation species. An oxygen adsorption mechanism is also discussed.

---

Bi₂Mo₃O₁₂ . O^–2, , 538–613 . , O^–2 . .

     

Influence of adsorbed molecules on the permeation properties of silicalite membranes

Gas permeation through zeolite membranes can be extremely sensitive to organics or moisture, adsorbed from feed impurities or from the atmosphere during storage, and thus, thermal pretreatment is necessary to obtain reliable permeation rates. Altered adsorption properties of the external surface and selective pore blockage might have caused the observed trends.     

Infrared study of adsorbed species on electrodes: Adsorption of carbon monoxide on Pt,Rh and Au

Infrared spectra of adsorbed species at the solid/aqueous electrolyte interface are reported, following the adsorption of CO on platinum, rhodium and gold electrodes using in situ electrochemically modulated IR spectroscopy. Similarities exist with the corresponding solid-gas interfaces, i.e:

• (1)a linearly bonded species is formed absorbing near 2080 cm⁻¹ on Pt, 2030 cm⁻¹ on Rh and 2120 cm⁻¹ on Au;
• (2)bridged bonded or multibonded CO species are also present and detected at 1860 cm⁻¹ (Pt), 1900 cm⁻¹ (Rh) and 1930 cm⁻¹ (Au);
• (3)CO₂ produced by CO oxidation is detected near 2360 cm⁻¹ at potentials as low as 0.35 V (vs. SHE).

     

Infrared and Raman spectroscopic study of 1,2-benzenedithiol adsorbed on silver

Adsorption of 1,2-benzenedithiol (1,2-BDT) on a silver surface has been investigated by surface-enhanced Raman (SER) and reflection-absorption infrared (RAI) spectroscopy. The molecule was adsorbed on silver very favorably by forming two Ag---S bonds after deprotonation. From the RAI spectral pattern, the benzene ring of adsorbed 1,2-BDT was presumed to be tilted by ca. 38° from the surface normal. This RAI information was used to test the validity of various proposed SER selection rules. Being frequently quoted in the literature, the presence or absence of the benzene ring CH stretching vibration in the SER spectrum seemed, in fact, to be a very useful indicator in judging the perpendicular or parallel orientation of the benzene ring with respect to the surface. However, the so-called in-plane/out-of-plane dichotomy as well as the more elaborate symmetry-based electromagnetic selection rule was found not to work in the present system.     

Reaction of oxygen with adsorbed hydrogen species of a reduced Pt/TiO2 catalyst

Reaction of oxygen with the adsorbed hydrogen species of Pt/TiO₂ catalysts reduced in the temperature range of RT-773 K has been studied by temperature-programmed oxidation (TPO). It is obtained that the Pt-assisted reaction of oxygen with both the surface hydroxy groups and titanium hydride species occurs in the temperature range of 320–450 K; direct oxidation of the surface hydrogen species takes place on the surface of TiO₂ in the temperature range of 500–600 K; and oxygen reacts with the stored hydrogen species in the sublayer and bulk of the TiO₂ support when the temperature was increased to above 600 K.     

Initial steps in the production of H2 from ethanol: A FT-IR study of adsorbed species on Ni/MgO catalyst surface

Reactivity of pure ethanol and acetaldehyde on Ni/MgO catalyst at different reaction temperatures was investigated confirming that hydrogen production is ascribable to a series of consecutive and/or parallel reactions. FT-IR studies on adsorbed dry molecules (ethanol or acetaldehyde) showed that ethanol decomposition occurs on catalyst surface through formation of acetaldehyde, which is converted to acetates and then to carbonates, or decomposes to CO, C and H₂.     

Infrared study of the interaction between adsorbed molecules in the Co/ZnO system

The dependence of spectra on the surface coverage and data on isotope substituted CO molecules permit to reveal the resonance interaction of vibrating dipoles and the effect of induced heterogeneity, i.e. weakening of the electron-accepting properties of Zn²⁺ ions in the occupation of adjacent sites by adsorbed molecules.

---

- CO , . . Zn²⁺ .

     

A quantum-chemical study of para/ortho-toluene alkylation by adsorbed methoxy species on zeolites

MNDO and PM3 semiempirical methods have been employed to study the mechanism of toluene alkylation by methanol on zeolites, by means of the cluster (H)₃SiO(CH₃)T(H)₂OSi(H)₃ in were T = Al, B, Ga. Two possible reaction mechanisms have been found. The first one corresponds to the classical process of aromatic electrophilic substitution, in which the transition state of the reaction shows distances and angles according to the precursor of the Wheland intermediate. The second mechanism proceeds in one concerted step, in which the transfer of the proton from the toluene to the basic oxygen of the zeolite is simultaneous to the transfer of the methyl cation from the zeolite to the toluene. The effect of chemical composition of the cluster on regioselectivity has been studied, and perturbed molecular orbital (PMO) analysis of the system at the ab initio HF/STO-3G level has shown that covalent interactions are important. The energy of the covalent interaction between the molecular orbitals of the toluene and the cluster mainly HOMO-LUMO, are more important in para than in ortho positions.     

Infrared study of photooxidation of nitrogen oxides and ammonia adsorbed on alumina

Changes in the IR spectra of nitrogen oxides and ammonia adsorbed on Al₂O₃ caused by UV irradiation indicate that in the presence of gaseous or liquid (–196°C) O₂ photooxidation takes place, resulting mostly in the formation of surface NO ₃ ^– ions.

---

- - , Al₂O₃, , (–196°C) NO ₃ ^– .

     

Infrared study of the bonding of adsorbed nitriles to metals

The ability of the surface of Pt, Pd, Ru, Rh and Ni to form coordinate and covalent bonds with adsorbed molecules has been studied.

---

Pt, Pd, Rh, Ru Ni .

     

Theoretical study of the formation of adsorbed dicarbonyl species

The formation of mono- and dicarbonyl species during CO adsorption has been theoretically studied in order to obtain a mathematical model of the adsorption isotherms. The dependences proposed describe well the results of other authors and allow better utilization of the experimental data.

---

- CO . .

     

Kinetics of the hydrogenation of co on an Fe/Al2O3 catalyst

A study was carried out on the effect of temperature and reaction mixture composition on the activity and selectivity of an Fe/Al₂O₃ CO hydrogenation catalyst relative to lower olefins at atmospheric pressure. An increase in the CO concentration was found to lead to increased selectivity relative to olefins not only due to a diminution in the hydrogenating capacity of the catalyst but also an increase in the rate of the reaction step yielding olefins.L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Nauka Prospekt, 252039 Kiev, Ukraine. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. I, pp. 36–39, January–February, 1996. Original article submitted May 22, 1995.     

Behavior of adsorbed diphenyl-sulfide on the Pd/C catalyst for o-chloronitrobenzene hydrogenation

A series of diphenyl-sulfide（Ph₂S）-immobilized Pd/C catalysts(Pd-Ph₂S_（X）/C) were prepared using the wetness-impregnation and immobilization method.Pd-Ph₂S_（x）w/C catalysts employed for the hydrogenation of o-chloronitrobenzene showed very high selectivity.The structure of Pd-Ph₂S_（x）/C with different molar ratio of ligand（x-values） was characterized by XPS and TG-DSC-MS.The results suggest a "saturated" surface ratio of Ph₂S/Pd（about 0.3） was formed on the Pd-Ph₂S_（x）/C catalysts surface.The Ph₂S immobilized on the Pd particle is quite stable,and the desorption of Ph₂S or dissociative loss of phenyl group was only found at temperatures above 500 K.The possible catalytic mechanism of the Pd-Ph₂S_（x）/C catalyst was also discussed.     

Infrared spectroscopic studies of dihydrogen adsorbed on oxide surfaces

The complex structure of the IR spectra of dihydrogen adsorbed at 60–77 K on several oxide adsorbents, in the 4300–4000 cm^–1 region, is supposed to be due to the combination of ^v H-H with a low-frequency vibration of the H₂ molecule with respect to the surface.

---

4300–4000 ^–1 - H₂, 60–77 . , ^v H-H .