Fast and Selective Solvent-Free Branching of Unsaturated Fatty Acids with Hierarchical ZSM-5

Abstract

Branched fatty acids are of great interest in the oleochemical industry for many high-end applications due to their interesting physicochemical properties. In the last decades, research has focused mainly on the use of ferrierite (FER) as catalyst for the isomerization of fatty acids into these branched fatty acids. With the use of FER, high yields of branched fatty acids can be obtained. FER is however expensive, and additives are necessary to obtain a high selectivity toward branched fatty acids. In this letter, we focus on the use of ZSM-5, a much cheaper zeolite, which has been extensively studied in the past for other reactions. Five commercial ZSM-5 samples and one hierarchical ZSM-5 sample were tested for the isomerization of fatty acids into branched fatty acids. The results clearly show that the accessibility of Brønsted acid sites is of utmost importance for their catalytic activity. Thanks to the introduction of mesopores in the zeolite crystals of ZSM-5, creating a hierarchical zeolite, a superior catalyst was obtained with a multifold activity increase, without compromising in branched fatty acid selectivity, that is capable of competing against the state-of-the-art FER zeolite.

Constructing single-crystalline hierarchical plate-like ZSM-5 zeolites with short b-axis length for catalyzing MTO reactions

“…, preparing zeolites with meso–microporous, macro–microporous or macro–meso–microporous structures, to shorten the intrinsic channels of zeolites, and thus accelerating mass transfer inside ZSM-5 crystals. 12–15 (3) Preparing thin lamellar crystals in the b -axis direction to shorten the primary diffusion path of the mass transfer within zeolite crystals. 16–18…”

“…[9][10][11] (2) Introducing some meso-and/or macro-pores into zeolite crystals, i.e., preparing zeolites with meso-microporous, macro-microporous or macro-meso-microporous structures, to shorten the intrinsic channels of zeolites, and thus accelerating mass transfer inside ZSM-5 crystals. [12][13][14][15] (3) Preparing thin lamellar crystals in the b-axis direction to shorten the primary diffusion path of the mass transfer within zeolite crystals. [16][17][18] For the ZSM-5 zeolite catalyst with nano-size crystallites, although the diffusion limitation problem could be solved well as expected, it still suffers from low thermal stability.…”

Catalytic amination of lactic acid using Ru–zeolites

“…23,24 Zeolites are well known for their high thermal stability and ability to well disperse the functional metals. [25][26][27] Furthermore, ruthenium-based zeolites have been used in a variety of catalytic reactions from the epoxidation of styrene, conversion of glucose and sorbitol to glycols and ammonia synthesis. [28][29][30] Also, the activity of Ru catalysts has been documented in the direct amination of alcohols to produce primary amines.…”

Enhancement of p-xylene selectivity in the reaction between 2,5-dimethylfuran and ethanol over an ammonium fluoride-modified ZSM-5 zeolite

“…27,28 Despite these remarkable achievements, the intrinsic microporosity of HZSM-5 leads to steric and diffusion limitations in many reactions. To alleviate the issues, several studies have been focused on the synthesis of hierarchical zeolites, [29][30][31][32][33] including direct synthesis, postsynthesis (such as dealumination or desilication), and novel dual templating methods. [34][35][36][37][38] Among the many procedures, the modification using fluorine agent (HF, NH 4 F) is an ideal modification method for ZSM-5 (abbreviated as FZ5), which can not only enlarge the pore size but also modify the acidity under an appropriate dealumination and desilication condition.…”