TY - JOUR

T1 - Effect of the Initial Form of the Zeolite Support on the State of Mo in the Mo/ZSM-5 Catalyst and Its Activity in the Course of Methane Dehydroaromatization

AU - Stepanov, A. A.

AU - Zaikovskii, V.

AU - Korobitsyna, L. L.

AU - Vosmerikov, A. V.

N1 - The work was carried out within the State Assignment for the IPC SB RAS financed by the Ministry of Science and Higher Education of the Russian Federation.

PY - 2021

Y1 - 2021

N2 - The physicochemical and catalytic properties of Mo/ZSM-5 catalysts for methane dehydroaromatization prepared using different (NH4- and H-) zeolite forms and nanosized Mo powder are studied. It is shown that the properties of the samples under study depend on the initial form of the zeolite used for their preparation. According to the data of electron microscopy and EDS analysis, the morphology and elemental composition of particles in the Mo/H-ZSM-5 and Mo/NH4-ZSM-5 samples are practically similar, and molybdenum is stabilized in the zeolite matrix in the form of the aggregates of atoms. The distribution profiles of silicon and molybdenum in the catalysts indicate that a more uniform distribution of molybdenum in the zeolite is observed for the Mo/NH4-ZSM-5 sample. Changes in molybdenum localization after methane dehydroaromatization were revealed. Molybdenum migration to the zeolite surface was observed, with the formation of MoCx particles up to 100 nm in size, coated with a carbon layer about 3 nm thick. It was established by means of the thermal desorption of ammonia that the concentration of strong acid sites in the catalyst prepared using the hydrogen form of the zeolite was lower than that for the catalyst prepared on the basis of the ammonium form of the zeolite. This difference in the acidic characteristics of the obtained Mo/ZSM-5 catalysts depends on the conditions of their preparation. The number of thermal treatments increased in the course of catalyst preparation using the hydrogen form of the zeolite, which resulted in the partial destruction of the zeolite crystal lattice with the formation of the Al-2(MoO4)(3) phase. Studies of the catalytic properties of the samples showed that the Mo/ZSM-5 catalyst prepared on the basis of ammonium zeolite exhibited the highest activity in the course of the nonoxidative conversion of methane to aromatic hydrocarbons.

AB - The physicochemical and catalytic properties of Mo/ZSM-5 catalysts for methane dehydroaromatization prepared using different (NH4- and H-) zeolite forms and nanosized Mo powder are studied. It is shown that the properties of the samples under study depend on the initial form of the zeolite used for their preparation. According to the data of electron microscopy and EDS analysis, the morphology and elemental composition of particles in the Mo/H-ZSM-5 and Mo/NH4-ZSM-5 samples are practically similar, and molybdenum is stabilized in the zeolite matrix in the form of the aggregates of atoms. The distribution profiles of silicon and molybdenum in the catalysts indicate that a more uniform distribution of molybdenum in the zeolite is observed for the Mo/NH4-ZSM-5 sample. Changes in molybdenum localization after methane dehydroaromatization were revealed. Molybdenum migration to the zeolite surface was observed, with the formation of MoCx particles up to 100 nm in size, coated with a carbon layer about 3 nm thick. It was established by means of the thermal desorption of ammonia that the concentration of strong acid sites in the catalyst prepared using the hydrogen form of the zeolite was lower than that for the catalyst prepared on the basis of the ammonium form of the zeolite. This difference in the acidic characteristics of the obtained Mo/ZSM-5 catalysts depends on the conditions of their preparation. The number of thermal treatments increased in the course of catalyst preparation using the hydrogen form of the zeolite, which resulted in the partial destruction of the zeolite crystal lattice with the formation of the Al-2(MoO4)(3) phase. Studies of the catalytic properties of the samples showed that the Mo/ZSM-5 catalyst prepared on the basis of ammonium zeolite exhibited the highest activity in the course of the nonoxidative conversion of methane to aromatic hydrocarbons.

KW - methane

KW - dehydroaromatization

KW - benzene

KW - ZSM-5 zeolite

KW - Mo-containing catalyst

KW - acidity

KW - activity

KW - CONVERSION

KW - MOLYBDENUM

UR - https://elibrary.ru/item.asp?id=46370905

U2 - 10.15372/CSD2021296

DO - 10.15372/CSD2021296

M3 - Article

VL - 29

SP - 190

EP - 197

JO - Химия в интересах устойчивого развития

JF - Химия в интересах устойчивого развития

SN - 0869-8538

IS - 2

M1 - 13

ER -