Cadmium Modified HZSM-5: A Highly Efficient Catalyst for Selective Transformation of Methanol to Aromatics

Abstract

Cadmium modified HZSM-5 catalyst (Cd/ZSM-5) prepared by incipient wetness impregnation shows markedly high selectivity of aromatics and low selectivity of light alkanes and C5–C9 nonaromatics in the methanol-to-aromatics (MTA) transformation. The majority of the introduced Cd cations can exchange with protons of the bridged hydroxyl groups of HZSM-5, leading to a reduced number of Brønsted acid sites while generating new Lewis acid sites on the catalysts. The selectivity of aromatics with the Cd/ZSM-5 is found to be linearly correlated with the concentration of the strong Lewis acid sites. Compared to Zn/ZSM-5, the most extensively investigated catalyst thus far for the MTA, Cd/ZSM-5 is found to be more effective in promoting the aromatics formation. The different catalytic behavior observed for Cd/ZSM-5 and Zn/ZSM-5 catalysts is most likely due to the difference in ionic radius of Cd and Zn.

Controlling the product selectivity in the conversion of methanol to the feedstock for phenol production

“…In the literatures, the HZSM-5 used for methanol to aromatics contained high amount of Brønsted acid sites (BAS) compared to that of Lewis acid sites (LAS). 3,9,10,13 Zn impregnation on such HZSM-5 decreased BAS and increased LAS significantly. 3,9,10,13 This resulted in an increase in the aromatics selectivity and a decrease in alkanes selectivity.…”

“…3,9,10,13 Zn impregnation on such HZSM-5 decreased BAS and increased LAS significantly. 3,9,10,13 This resulted in an increase in the aromatics selectivity and a decrease in alkanes selectivity. 3,9,10,13 The increase in the aromatic selectivity was attributed to Zn-LAS (ZnOH + ) that could accelerate aromatization and dehydrogenation reactions.…”

“…Among all the metal species, zinc has received considerable attention due to its good selectivity toward aromatics, relatively low cost, and being less toxic. [8][9][10][11][12][13][14][15] In the appendix, Table 7 lists the catalytic performances of HZSM-5, zinc-impregnated HZSM-5 (Zn/ HZSM-5), silica-deposited HZSM-5 (Si/HZSM-5), and zincimpregnated silica deposited HZSM-5 (Zn/Si/HZSM-5) found in the literatures. The impregnation of Zn on HZSM-5 in general increased aromatics selectivity and decreased alkanes (methane, ethane, propane, butanes) selectivity.…”

Conversion of Methanol to Hydrocarbons on Bimetallic Catalysts on the Basis of ZSM-5

“…Regarding olefin selectivity the catalysts may be placed in the following: HZSM-5 < Cr-ZSM-5<V-ZSM-5<Mn-ZSM-5<Ni-ZSM-5<Zr-ZSM-5 = Ti-ZSM-5< Fe-ZSM-5< Co-ZSM-5 [2,17,18].…”

Synthesis of ZSM‐5 by hydrothermal method with pre‐mixing in a stirred‐tank reactor

“…It presents a well‐defined porosity, which enables reactants and products to cross channels easily . Therefore, ZSM‐5 has been widely used in many processes including methanol to gasoline (MTG), methanol to propylene (MTP), aromatic selective transformation, alkanes selective cracking, etc.…”