Characterization of acid catalysts by means of model reactions

Concepts and Analysis of Surface Acidity and Basicity

“…6 Characterization of Brønsted acid strength of zeolite catalysts through various reactions [208] conditions. Its qualitative identification is largely routine work and in most cases reliable.…”

“…The fact that the straight line in Fig. Table 6) requiring different activation energies or reaction temperatures under otherwise standardized conditions were suggested by Guisnet and coworkers [208] in order to measure the different acid strengths of the zeolites employed to catalyze these reactions ( Table 6). Sigl et al [206] Several other test reactions have been proposed, such as conversion of toluene, xylene isomerization [207] and dehydration of cyclohexanol.…”

Mechanism of carbon?nitrogen bond scission in the presence of H2S on Pt Supported catalysts

“…Overall amine conversion and product distribution were determined after a period of at least 15 h on stream, which was enough for reaching stable conversions. The acidity of the catalysts was evaluated by hydrocracking of 2,2,4-trimethylpentane (isooctane) [17,9]. The reaction was carried out at 523 K at atmospheric pressure, with an isooctane partial pressure of 1.7 kPa, a hydrogen flow rate of 0.67 mL/s and a catalyst weight 0.05-0.75 g. No deactivation was observed during the experiments.…”

“…Then, the acidic properties of the silica-alumina support were determined from the hydrocracking of isooctane, which is sensitive to Bro¨nsted acidity [17] (see figure 3). It evidences the strong acidity of the silica-alumina as compared to the two other supports.…”

Caracterização e propriedades catalíticas da zeolita HZSM5 modificada com nióbio

“…Esta maior atividade isomerizante se deve a um provável aumento da força ácida. Este aumento de acidez, confirmado pelos resultados das reações pode ser explicado se admitirmos que a isomerização do m-xileno ocorre de acordo com o mecanismo descrito abaixo 15,16 . Inicialmente, ocorre a formação de um íon "benzenium" pela abstração de um próton fortemente ácido da zeólita na etapa 1, com uma posterior transferência intramolecular do Tabela 2.…”