ZSM-5 Catalysts for MTO: Effect and Optimization of the Tetrapropylammonium Hydroxide Concentration on Synthesis and Performance

Abstract

Light olefin production from methanol using various zeolite catalysts has industrial and economic importance considering the growth of the petrochemical market. Zeolites are generally synthesized using various organic templates as structure-directing agents (SDAs). In this study, synthesis of a series of ZSM-5 zeolites was performed systematically using the microwave-assisted crystallization method, and these samples were analyzed in detail to understand the effect of the SDA concentration. Powder diffraction, N 2 adsorption, scanning electron microscopy, ammonia adsorption desorption, and 27 Al and 29 Si NMR spectroscopies were used for the characterization. The organic SDA tetrapropyl ammonium hydroxide (TPAOH/SiO 2 mole ratio = 0.0500) is found to have an optimum concentration against the silica precursor for achieving the highest crystallinity, suitable morphology, ideal pore size, effective pore volume, and tuned microporous/mesoporous area. For samples with a template concentration ratio of 0.050 or higher, 29 Si and 27 Al NMR data revealed the presence of an intact ZSM-5 structure. Using a fixed bed reactor at 500 °C and atmospheric pressure, the catalytic performance of the selected catalysts from the series is investigated for the methanol-to-olefin conversion reaction. The sample with the highest crystallinity showed the best conversion, selectivity toward light olefins, and time on stream stability. It is also worth noting that the highest crystallinity, micropore area, and micropore volume are reached for the optimum value rather than the highest template concentration. This allows for a reduction in the template concentration and a move closer to a synthesis pathway benign to environment and economics.

Review on the Catalytic Conversion of Naphtha to Aromatics: Advances and Outlook

“…Different preparation methods and the complexity of the metal−zeolite interaction throughout the preparation led to the variances in nature, position, and characteristics. 14 The presence of shorter diffusion path lengths and more channels is advantageous for both the diffusion of aromatics (produced) and the suppression of coking inside the channels. ZSM-5 with smaller particle sizes, larger external surfaces, and weaker Brønsted acid sites exhibit excellent activity, selectivity, and stability.…”

One‐pot Synthesis of Phosphorus‐modified ZSM‐5 Zeolite by Solid‐state Method and its MTO Catalytic Performance

“…As we all know, the evolution of light olefin industry is one of the key indicators to assess a country‘s economic power, and also plays an important role in national economic development [1,2] . Light olefins are primarily produced by hot steam cracking of light naphtha above 1073 K, which is a pyrolysis process and high energy consumption, leading to an increase in carbon dioxide emissions eventually [3–5] . The methanol to olefin (MTO) catalytic reaction, which offers an alternative platform for the production of basic petrochemicals from nonoil resources under atmospheric pressure, and is believed to be a more green and environmentally friendly method, making it an interesting and important reaction in both industry and academic area [6,7] …”

“…[1,2] Light olefins are primarily produced by hot steam cracking of light naphtha above 1073 K, which is a pyrolysis process and high energy consumption, leading to an increase in carbon dioxide emissions eventually. [3][4][5] The methanol to olefin (MTO) catalytic reaction, which offers an alternative platform for the production of basic petrochemicals from nonoil resources under atmospheric pressure, and is believed to be a more green and environmentally friendly method, making it an interesting and important reaction in both industry and academic area. [6,7] At present, acidic zeolite has been extensively used in petrochemical and oil refining processes, as well as in the production of light olefins.…”

Preparation of a High-Silicon ZSM-5 Molecular Sieve Using Only Coal Gangue as the Silicon and Aluminum Sources

“…The special framework structure of the ZSM-5 molecular sieve provides it with unique shape selectivity, thermal stability, and acid resistance [ 5 , 6 , 7 ]. It is widely used in the field of traditional chemical catalysis [ 8 , 9 , 10 , 11 , 12 ]. ZSM-5 molecular sieves have been modified, showing good durability in catalytic cracking reactions using n-hexane and isopropyl-benzene [ 13 , 14 , 15 ] and excellent selectivity in the reaction of methanol to aromatics, gasoline, and olefin [ 16 , 17 ].…”