The lewis base properties of metal oxides have been investigated by using infrared spectra,surface lewis base sites and their basic strength of MgO,CaO,ZrO2,TiO2,SnO2 and Sb2O5 have been characterized by using boric acid trimethyl ester as a probe molecule.
Furthermore,the binding energies of Al 2S and O 1S of the samples determined by XPS are found to be proportional to the strength of surface acid and base sites of the samples
Microcalorimetric adsorption was used to determine quantitatively the number and strength of acid/base sites on the oxide samples of Eu 2O 3, CeO 2, MgO, ZnO, Al 2O 3 and NiO. The initial heats of NH 3 and CO 2 adsorption were found to be proportional to Sanderson electronegativities of the samples.
Microcalorimetric measurements of NH 3 and CO 2 adsorptions were used to determine the strength of acid and base sites on copper aluminium composite oxides,and adsorption curves were given coneurently.
Specifically, the strength and number of surface acid and base sites can be quantitatively titrated by the microcalorimetric adsorption of NH 3 and CO 2 as probe molecules.
The basic sites of MgO surface are covered with Cu, therefore there are only one NO adsorption on Cu/MgO catalyst surface except Cu/MgO (1%), which is attributed to metal Cu.
CO 2 TPD analysis of a series of Li Sn O catalysts indicated that the surface basic sites were formed when SnO 2 is transformed into Li 2SnO 3 in catalyst, which favored the desorption of isobutene from catalysts.
The conversion of acetonitr ile and the selectivity to acrylonitrile decrease when CeO2 or KCl are added to BaCO3.The NH3-TPD and CO2-TPD results indicate that the surface acid sites and basic sites of the catalysts decrease after the addition of CeO2 or KCl. Therefo re,the activity of Mn/BaCO3 attributes to the co-operation of the acid sites and basic sites of the catalysts surface.
The activity of some catalysts for preparation of methylcyclopentadiene through fixed bed was studied. In the reaction, methanol is used as methylation reagent. The influence of strength of acidic and basic center in catalysts on the reaction was discussed.
The FTIR results of CS 2 and H 2O coadsorption on γ alumina show that the CS 2 hydrolysis on alumina follows Langmuir Hinshelwood mechanism, and that the adsorbed CS 2 reacts with the H 2O on Lewis basic centers of alumina.
The work described in this Thesis involves the introduction of aluminum ions and basic centers into the MCM-41 framework in order to modify its structural and surface properties in a controllable fashion.
There arc at least two kinds of basic centers on catalyst surface, of which the stronger "b" basic centers have greater contribution to dehydrogenation of ethylbenzene than the weaker "a" basic centers.
CO2-Tem-perature-Programmed Desorption showed that the basic centers on the surface of catalysts were beneficial to activation of methane and capable of enhancing the catalysts ability of resistance a-gainst carbon deposition.
It was found that the state of a hydroxyl cover and the concentrations of surface acid-base sites and chlorine impurity atoms can be regulated by changing the conditions of oxide irradiation.
The concentrations and strength distributions of surface OH groups, Lewis acid sites, and Lewis base sites depend on the nature and concentration of rare earth elements in the binary samples.
The formation of a hydroxyl cover and acid-base sites on the surfaces of electrochemically coprecipitated binary aluminum and zirconium oxides is studied.
The rate of reaction decreased with decreasing strength of Lewis acid sites and with increasing strength of basic sites; however, the selectivity of thiol formation increased.
The total concentration of basic sites in aluminum oxides prepared by boehmite dehydration at 600, 800, and 1000°C decreases from 4.86 to 3.72 μmol/m2.
As a consequence, the surface has high concentrations of strong aprotic acid and strong basic sites and is characterized by a high surface oxygen binding energy.
The product distribution for the conversion of methylbutynol, a test catalytic reaction, on the surface of the minerals studied shows that it contains both acidic and basic sites.
MNDO-PM3 and AMI quantum chemical calculations of the molecular structure of N,N'-diphenylguanidine (DPG) prove that the molecule preferably exists as an asymmetric tautomer with a basic center C=N-.
The basic center may be composed of the oxygen anions liberated from the decomposition of the nitrate or carbonate anions that are dissociatively adsorbed on the support surface during the preparation.
The cyclodehydration reaction is effected by conversion of a semicyclic conformer of the protonated diol molecule at a basic center of the catalyst by a concerted mechanism.
Thus, in the N-hydroxyurea, N-hydroxythiourea, and N-hydroxysilaurea, both protonation at the double bonded (C=O, C=S and Si=O) oxygen and sulfur atoms, as well as the protonation at the N(H)OH nitrogen basic center is equally probable.
Amounts of CO2 and NH3 adsorption on ZSM-5 zeolites were measured by temperature programmed desorption (TPD), and the activity and selectivity of ZSM-5 zeolites for ethanol dehydration were determined with a pulse microreactor. Two peaks (peak Ⅰ and peak Ⅱ) appeared on the TPD profile of HZSM-5 after NH3 adsorption, and the TMs corresponding to peak Ⅰ and Ⅱ were 296 and 500℃ respectively. The amount of NH3 adsorption increased with the increasing of degree of exchange, the peak Ⅱ began to arise at 40-50% de...
The effects of preparation factors of Ni-Mo catalyst with DX-30 active carbon as carrier on hydro-desulfurization and hydro-denitrification of coal liquefaction oil were studied. The results show that the catalyst of 99.8% desulfurization efficiency and 63.2% denitrification efficiency were obtained. They are higher than those by commercial petroleum refining catalyst with Al_2O_3 or SiO_2 as carrier. It was found that the soaking order of active components in the catalyst,content of components,atomic ratio...
The paper investigates the performance of catalyst Ni-Mo,which uses activatedcarbon DX-30 as a carrier for hydrogenation of Liquid products from coal Lique-faction,and preparation factors that influence the performance of catalyst.Expe-rimental results indicate that under the same reaction conditions,catalyst Ni-Mo/DX-30 is better than catalysts 3665 and 3822 in hydro-desulfurization and hydro-denitrogenation,both of which are regarded as effective catalysts in this country.It is found that performance of c...
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