Umwandlung von Methanol in Kohlenwasserstoffe: Wie Zeolith‐Hohlräume und Porengröße die Produktselektivität bestimmen

Abstract

Flüssige Kohlenwasserstoffe nehmen aufgrund ihrer hohen Energiedichte und guten Transportfähigkeit eine Schlüsselrolle in der globalen Energieversorgung ein. Eine vergleichbare Bedeutung haben niedere Alkene wie Ethylen und Propylen in der Produktion von Verbrauchsgütern. In einer Gesellschaft der Nach‐Erdöl‐Zeit wird die Produktion von Kraftstoffen und Alkenen auf alternative Quellen wie Biomasse, Kohle, Erdgas und CO2 angewiesen sein. Die Umwandlung von Methanol in Kohlenwasserstoffe, bekannt als Methanol‐to‐ Hydrocarbons(MTH)‐Reaktion, könnte eine zentrale Rolle auf diesem Weg einnehmen, weil je nach Wahl des Katalysators und der Reaktionsbedingungen gezielt Benzin (Methanol‐to‐Gasoline, MTG) oder Alkene (Methanol‐to‐Olefins, MTO) hergestellt werden können. Dieser Aufsatz beschreibt eine Reihe von industriellen MTH‐Projekten, die in den letzten Jahren realisiert wurden, sowie den aktuellen Stand der Grundlagenforschung zur Synthese und Anwendung von mikroporösen Materialien für die gezielte Veränderung von Selektivität und Lebensdauer der Katalysatoren.

Shape-Selective Diffusion of Olefins in 8-Ring Solid Acid Microporous Zeolites

“…[4][5][6][7][8] In this area, the methanol-to-olefins (MTO) process is one of the most important alternatives to the oil-based routes. [9][10][11] It is now already commercialized at large scale in various places worldwide. 10 H-ZSM-5 and SAPO-34 are the archetypal industrially applied catalysts for methanol conversion.…”

“…[9][10][11] It is now already commercialized at large scale in various places worldwide. 10 H-ZSM-5 and SAPO-34 are the archetypal industrially applied catalysts for methanol conversion. H-ZSM-5 has the MFI topology and is an aluminosilicate whereas SAPO-34 has the CHA topology and is a siliocoaluminophosphate material.…”

“…[12][13][14] In the search for optimal catalysts for the MTO process, other potential candidates have been explored, which have a tunable ethene/propene ratio and low deactivation rates. 10 The overall reaction mechanism is nowadays accepted to be based on a hydrocarbon pool (HP), which co-catalyzes the reactions. [15][16][17] In this paper we have selected three classes of small ring zeotype materials, bearing the AEI, CHA and AFX topology with 8-ring channels at largest, as displayed in Fig.…”

Direct Observation of Cyclic Carbenium Ions and Their Role in the Catalytic Cycle of the Methanol‐to‐Olefin Reaction over Chabazite Zeolites

“…To date, the methanol-to-olefins (MTO) process has been one of the most successful non-petrochemical routes for the production of light olefins from abundant resources of natural gas or coal. [1][2][3] Considering the essential role of the products of the MTO reaction in the global energy chain and chemical industry, [4] investigations of the MTO reaction mechanism are crucial for both of the fundamental science and industrial application. Catalysts used in the MTO process are typically microporous solid acids, including zeolites and zeotype molecular sieves, among which the H-ZSM-5 zeolite with framework type MFI and SAPO-34 with framework type CHA deliver the best catalytic performance in the MTO reaction.…”

“…Catalysts used in the MTO process are typically microporous solid acids, including zeolites and zeotype molecular sieves, among which the H-ZSM-5 zeolite with framework type MFI and SAPO-34 with framework type CHA deliver the best catalytic performance in the MTO reaction. [1][2][3][4] Despite the tremendous research efforts over the past 30 years, [4][5][6][7][8] the reaction mechanism of the first C À C bond in the MTO process remains elusive. In general, the hydrocarbon pool (HCP) mechanism, [9] that is, that cyclic organic species confined in the zeolite cage or intersection of channels act as co-catalysts, has been generally accepted as a rational explanation for the olefins production from the C 1 reactant, methanol.…”