Synthesis of an excellent MTP catalyst: hierarchical ZSM-5 zeolites with great mesoporosity

Abstract

A unique organosiloxane-polyether amine (OPA) was produced and used as mesoporogen to efficiently synthesize hierarchical ZSM-5 zeolites with great mesoporosity. We have employed silica sol and tetraethylorthosilicate, respectively, to investigate the influence of different silicon sources on hierarchical zeolites in the presence of OPA. The mesopores of synthesized samples focused on 6–15 nm, and the external surface area varied from 185 to 463 m2 g−1 where the micropore surface area was maintained at 245–334 m2 g−1. Benefiting from the superior structure properties, these samples were used as catalysts in the reaction of methanol to propylene, and the optimal one catalysed for 180 h with methanol conversion above 95%. The as-produced OPA could connect steadily with zeolite frameworks through covalent bonds (–Si–O–Si–) during the hydrothermal crystallization process. This type of connection mode could effectively avoid the formation of amorphous phase and the special molecular structure of OPA could efficiently introduce abundant mesopores with few micropores being consumed. The samples synthesized with silicon sol were made up of quasi-circular particles of about 800 nm in size and further consisted of nanocrystals of 40 nm, and the samples produced with TEOS have a particle size of about 1–2 µm aggregated with nanocrystals of 300 nm.

State of the Art and Perspectives of Hierarchical Zeolites: Practical Overview of Synthesis Methods and Use in Catalysis

“…This catalyst showed better performances in the MTA reaction compared to a commercial ZSM-5. [108] Several other authors studied the use of similar templates, such as an organosilane quaternary ammonium salt with double-oxycarbonyl carbon chains (resulting in mesopores of 4 nm), [109] triethoxyvinylsilane (resulting in mesopores of 2.7 nm), [110] organosiloxane-polyether amine (resulting in mesopores of 6-15 nm), [111] an organosiloxane (C 24 H 57 O 12 NSi 3 ) (resulting in mesopores of 3-6 nm), [112] and phenylaminopropyltrimethoxysilane (PATMOS) (resulting in mesopores of 3-6 nm). [113] Soluble polymers are another popular soft template.…”

Optimization of hierarchical ZSM-5 structure from kaolin as catalysts for biofuel production

“…Therefore, the template method has been preferred because it produces a larger mesopores between 3-12 nm while maintaining crystalline framework. 21 Hierarchical ZSM-5 was obtained by self-assembly of the aluminosilicate gel to form large pores 21 employing various templates such as tetrapropylammonium hydroxide (TPAOH), 25 tetraethylammonium hydroxide (TEAOH), 26 carbon nano tube, 27 graphene, 28 organosilanes ( [3-(trimethoxysilyl)propyl] ammonium chloride (TPHAC)), 29,30 surfactants (CTAB), [31][32][33] or polymers (polyacrylic acid). 7,34 TPAOH is the most widely employed template for forming hierarchically hollow mesoporous ZSM-5 via a dissolution-recrystallization mechanism.…”

Size controllable synthesis of ZSM-5 zeolite and its catalytic performance in the reaction of methanol conversion to aromatics

“…The reaction of methanol to hydrocarbons (MTHs) over a zeolite catalyst discovered in the 1970s is a non-petroleum route for the production of various hydrocarbons [9][10][11][12][13]. ZSM-5 zeolite is one of the most concerned materials in the MTH reaction.…”