Calcination at temperature >300℃ would lead to the complete decomposition of the precursor to Nb_2O_5. The surface acidic sites on the calcined samples studied were all Lewis type, and no Bronsted acid sites were observed.
The results show that the average pore diameter of the synthesized sample is 2.86 nm which belongs to the range of mesopores(2～50 nm) defined by IUPAC,pore distribution is narrow. The BET specific area is 625 m~2·g~(-1) and the surface owns both of brnsted and lewis acidic sites.
In TPR process, the 2Mg/Al sample is not reduced, while the reduction of the Co-containing mixed oxide is via a path of Co3+ to Co2+ and then to Co0. The surface of the mixed oxide was s howed to contain the acidic sites and the basic sites, and with the change of th e Co content in sample the acidic sites and the basic sites were gained some adj ustments.
In TPR process, the 4Mg/Al sample was not reduced, while the reduction of the Ni-containing mixed oxide was via a path from Ni2+ to Ni0. The surface of the mixed oxide was showed to contain the acidic sites and the basic sites, and with the change of the Ni2+ content in the sample some adjustments were gained with the acidic sites and the basic sites.
Firstly, the OHgroup of the acidic site of zeolite adsorbs the double-bond of 1-butene and forms a π-complex. Secondly, thedouble-bond isomerization reaction shows a concerted mechanism and yields the adsorbed trans-2-butene. Lastly,trans-2-butene is produced by desorption and the zeolite active site is restored.
The results indicated that by substituting Mg, Mn and Ni into the framework of SAPO-11, some new acid sites on SAPO-11 were generated and the acidity of SAPO-11 was increased.
Calcination at temperature >300℃ would lead to the complete decomposition of the precursor to Nb_2O_5. The surface acidic sites on the calcined samples studied were all Lewis type, and no Bronsted acid sites were observed.
In contrast, the water-butanol biphase media were unfavorable for the Mg substitution into the framework, and thus the acid sites and the catalytic activity of Pt/MgAPO-11 decreased.
Temperatured-programmed reduction(TPR) of hydrogen was used to investigate the reducibility of Mo species on Mo/HZSM-5 catalysts prepared by different methods,and the possible six H_2-consumption peaks were assigned precisely with the help of()~1H MAS NMR. The TPR peaks corresponding to the reduction of Mo species associated with Brnsted acid sites were first identified.
采用H2-TPR技术研究了不同方法制备的Mo/HZSM-5催化剂,并借助1H MAS NMR等表征手段对Mo/HZSM-5催化剂还原过程中可能出现的6个TPR谱峰进行了详细归属,首次指认了分布于分子筛孔道内并与B酸性位相互作用的Mo物种的还原峰.
By using TPR, TPD and EPR techniques, the influence of titanium addition on the surface acidity andalkality and reducibility for Cu-Co-Zn/Al2O3 catalyst were studied. The results show that addition of titaniumcan effectively promote the reduction of Cu2+ and modify the intensity and number of acidic and basic sites,which favours the reaction.
Using density functional theory(DFT), the double-bond isomerization of 1-butene to trans-2-butene overzeolites is investigated with a 3T cluster model simulating zeolite.
The presence of water vapor in the feed stream remarkably reduced the catalytic activity, which could be due to the blockage of acidic sites on the surface of catalyst by water molecules.
Furthermore, specific surface area, acid strength, the amount of acidic sites, and the catalytic activities for the decomposition of trifluoromethane of these salts were investigated.
The catalytic activity for decomposition of CHF3 was related with a certain degree of specific surface area, acid strength, and the amount of acidic sites.
To separate the influence of plant community composition from that of the soil environment, we decomposed the same nine substrates at a moist acidic and a moist non-acidic site located less than 2?km apart.
Based on the proportion of test characters that received positive responses, the organisms from the acidic site were more general in their abilities (47.6% positive) as compared with the neutral counterparts (18.7% positive).
The strongest Bronsted acid sites were produced on SO42-/TiO2 promoted with H2SO4, while Lewis acid sites on S2O82-/TiO2 even stronger than those on SO42-/ZrO2/MCM-41 were generated when persulfate solution was used as sulfating agent.
The preparation of methylamine on NZSM-5 and PZSM-5 zeolite has been studied in a fixed-bed flow reactor. It has been found that the ZSM-5 catalyst has high activity and apparent sharpselectivity,and can effectively inhibit the formation of trimethylamine.Pmodification of ZSM-5enhances the inhitory action.THe sorption profiles show that the modification by P has in-creased the acid sites on which monomethylamine and ammonia chemisorb,and decreased the acidsites on which diinethylamine and trimethylamine che...
NaY zeolites containing different types of nickel species were prepared. The effects of temperature, time and H2S concentration on sulfidation of the zeolites were investigated. The NiO impregnated zeolite samples are sulfided most readily, while the isomorphous substituted Ni heteroatom bearing zeolite is the hardest to be sulfided. The thermal and hydrothermal stabilities of the sulfide species formed on the zeolite surface were studied. Water desorbed from the zeolite at elevated temperature may cause th...
The combination method of temperature programmed decomposition of tetraethylammonium (template) after calcined at lower temperature was studied by TPDE, TPD and XRD. It is shown that the different combination methods may modify the surface acidity of zeolite β, and the choice of suitable temperature for combination de amine may change acidity to a great extent, in which zeolite β emerges an acidic site of medium strength with great acid amount other than two acidic sites with the conventional de amine me...
酸性位
acidic sites
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