Ethanol to Aromatics on Modified H‐ZSM‐5 Part I: Interdependent Dealumination Actions

Abstract

In this study a H‐ZSM‐5 zeolite (Si/Al=11) was modified by a stepwise treatment with steam, sodium hydroxide and hydrochloric acid. During progressing dealumination by various treatment methods, the drawbacks of initial post‐synthetic steps, e. g. pore‐filling by steam dealumination, are compensated by subsequent steps, e. g. washing by acid, which leads to a scientifically based preparation of required ZSM‐5 zeolite. Solid‐state properties of as‐synthesized and modified zeolites are determined by structural (XRD, ICP‐OES, NMR), textural (physisorption, laser scattering) and acid sites analysis (TPAD). Consequently, extended dealumination without structural damage is demonstrated. Its origin by framework dealumination and pore cleaning is verified in ethanol to hydrocarbon process (ETH) by shape‐selective formation of coke and aromatics, characterized by “aromatics index” (AI).

Ethanol to Aromatics on Modified H‐ZSM‐5 Part II: An Unexpected Low Coking

“…ICP‐OES results as well as ( AI ) indicate an increase of the Si/Al ratio as well as cleaned pores. This is described in more detail in recent work [10] . For ammonia desorption data, powder diffraction patterns and N 2 physisorption data, please consult the supplementary information, Figure S1–S3.…”

“…Previous investigations revealed scientifically based combinations of dealumination methods to reduce acid site density, to clean pore channels from residual extra-framework species (EFSPE) and to enhance aromatics yields. [9,10] The main goal of this work now is to study short-term durability behavior of H-ZSM-5 zeolites during conversion of ethanol to aromatics by variation of inert gas flow and contact time, respectively. Based on a commercial and modified H-ZSM-5 zeolite durability and selectivity trends with varying inert gas flow reveal unexpected distinct product formation parameters for aromatics and coke formation and a decoupling of catalyst decay from coking.…”

“…Previous investigations revealed scientifically based combinations of dealumination methods to reduce acid site density, to clean pore channels from residual extra‐framework species (EFSPE) and to enhance aromatics yields [9,10] . The main goal of this work now is to study short‐term durability behavior of H‐ZSM‐5 zeolites during conversion of ethanol to aromatics by variation of inert gas flow and contact time, respectively.…”

Deactivation Kinetics of ZSM‐5 by Coke in Ethanol‐to‐Hydrocarbons Process

“…8 A standardization of individual product streams to the current status of deactivation of the secondary conversion of C 2 (mainly ethylene) has been described for gas‐phase products C 2 , C 3 , C 4 and C 5+ in ethanol conversion process at almost complete ethanol conversion. 14, 15 An easy triangular plot is used to display changes in standardized C 3 *, C 4 * and C 5+ * with ToS and ongoing catalyst deactivation (see Fig. 1).…”

“…C 5+ is a measure for further build‐up and interconversion processes of hydrocarbon molecules. 14, 15…”