Temperature-programmed desorption of n-propylbenzene from HNaZSM-5 and Na(Li, K, Rb, Cs) ZSM-5 type zeolites

Analysis of Toluene Adsorption on Na-Form Zeolite with a Temperature-Programmed Desorption Method

“…It can be concluded that the low-temperature peak is mainly ascribed to toluene adsorbed on H + , whereas the high-temperature peak can be attributed to toluene adsorbed on Na + . Stronger adsorption of an aromatic compound on Na-form zeolite than that on H-form, i.e., stronger interaction of an aromatic ring with Na + cation than that with Brønsted acid site, has been well-known. − , …”

“…Stronger adsorption of an aromatic compound on Na-form zeolite than that on H-form, i.e., stronger interaction of an aromatic ring with Na + cation than that with Brønsted acid site, has been wellknown. [11][12][13][14]27 Then, the amounts of toluene corresponding to low-and hightemperature peaks were determined from the peak areas, as shown in Table 1. For Na-MFI, HNa-MFI, and Na-BEA where two peaks overlapped on each zeolite, deconvolution of the TPD peak was carried out by using eq 2, as shown in Figure 6.…”

“…There are several candidates such as CO, N 2 , Ar, and aromatic hydrocarbon as nucleophilic probes for acidity evaluation of solids including zeolites. − These compounds are physically adsorbed on acid sites. However, adsorption of these compounds on such a cation as Na + stronger than that on H + in zeolite sometimes disturbs the analysis of acidity of a practical catalyst usually containing multiple components; in the case of aromatic hydrocarbons, an alkaline cation acts as a Lewis acid to form a strong interaction with π electrons. − In contrast, a typically basic molecule, ammonia is chemisorbed on acid sites more strongly than on nonacidic sites, and therefore we can count the number of acid sites (acid amount) through the number of strongly adsorbed ammonia molecules …”

“…Thermodynamic parameters concerning the adsorption of aromatic compounds on zeolites have been collected by direct equilibrium measurements − and calorimetry . To obtain the same parameters, this study proposes the effective use of TPD, which is easy and reliable for systematic study on many zeolites, as supported by the presence of many attempts with TPD as a tool to study the adsorption of aromatic compounds on zeolites for various applications as mentioned below. ,,,− For this purpose, we introduce a theoretical analysis of toluene TPD, which has been established in the ammonia TPD 18 as above. The TPD process is classified into three cases, kinetics control, equilibrium control with free readsorption, and diffusion control; experimental classification of toluene TPD on zeolites has been carried out in this study for the first time.…”

“…However, adsorption of these compounds on such a cation as Na + stronger than that on H + in zeolite sometimes disturbs the analysis of acidity of a practical catalyst usually containing multiple components; in the case of aromatic hydrocarbons, an alkaline cation acts as a Lewis acid to form a strong interaction with π electrons. [11][12][13][14] In contrast, a typically basic molecule, ammonia is chemisorbed on acid sites more strongly than on nonacidic sites, and therefore we can count the number of acid sites (acid amount) through the number of strongly adsorbed ammonia molecules. 15 Frequently, different conclusions are derived from experiments based on different probe molecules, and therefore, there is a controversy about the validity of the use of these probes.…”