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7784 KiB

Open AccessArticle

Hydrodeoxygenation of Methyl Laurate over Ni Catalysts Supported on Hierarchical HZSM-5 Zeolite

by Nana Li, Yadong Bi, Xiaoqiang Xia, Hui Chen and Jianli Hu

Catalysts 2017, 7(12), 383; https://doi.org/10.3390/catal7120383 - 11 Dec 2017

Cited by 13 | Viewed by 4417

The hierarchical HZSM-5 zeolite was prepared successfully by a simple NaOH treatment method. The concentration of NaOH solution was carefully tuned to optimal the zeolite acidity and pore structure. Under NaOH treatment conditions, a large number of mesopores, which interconnected with the retained [...] Read more.

The hierarchical HZSM-5 zeolite was prepared successfully by a simple NaOH treatment method. The concentration of NaOH solution was carefully tuned to optimal the zeolite acidity and pore structure. Under NaOH treatment conditions, a large number of mesopores, which interconnected with the retained micropores, were created to facilitate mass transfer performance. There are very good correlations between the decline of the relative zeolite crystallinity and the loss of micropores volume. The Ni nanoclusters were uniformly confined in the mesopores of hierarchical HZSM-5 by the excessive impregnation method. The direct deoxygenation in N₂ and hydrodeoxygenation in H₂ of the methyl laurate were compared respectively over the Ni/HZSM-5 catalysts. In the N₂ atmosphere, the deoxygenation rate of the methyl laurate on the Ni/HZSM-5 catalyst is relatively slow. In the presence of H₂, the synergistic effect between the hydrogenation function of the metal and the acid function of the zeolite supports can make the deoxygenation level more obvious. The yield of hydrocarbon products gradually reached the maximum with the appropriate treatment concentration of 1M NaOH, which could be attributed to the improved mass transfer in the hierarchical HZSM-5 supports. Full article

(This article belongs to the Special Issue Zeolites and Catalysis)

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12708 KiB

Open AccessArticle

Fine-Tuning Synthesis and Characterization of Mono-Sized H-Beta Zeolite-Supported Palladium-Iridium Nanoparticles and Application in the Selective Hydrogenation of Acetylene

by Masood Sahooli, Mohammad Reza Rahimpour and Mohammad Khorram

Catalysts 2017, 7(11), 343; https://doi.org/10.3390/catal7110343 - 13 Nov 2017

Cited by 5 | Viewed by 5360

Abstract

In this research, a mono-sized Beta zeolite support synthesized by the solvothermal method was used in the selective acetylene to ethylene hydrogenation reaction with minimum coke build up on the catalyst surface. Tetrapropylammonium hydroxide (TPAOH), tetrapropylammonium bromide (TPABr), n-butylamine, and morpholine were [...] Read more.

In this research, a mono-sized Beta zeolite support synthesized by the solvothermal method was used in the selective acetylene to ethylene hydrogenation reaction with minimum coke build up on the catalyst surface. Tetrapropylammonium hydroxide (TPAOH), tetrapropylammonium bromide (TPABr), n-butylamine, and morpholine were used as structure direct agents (SDA) in the support to obtain various shapes. The characterization results show that although the Si/(Al+SDA) ratio has no effect on the phase purity of support, it has a remarkable effect on porosity, crystal size, shape, and structure of micropores. After comparing characterization results, the developed support, based on TPAOH, was selected and modified by different metals (Ce, Ir, Ag, and Pd) using the incipient wetness co-impregnation method. Since there is an interaction between selectivity and conversion, the optimum metal content in the synthesized catalysts and reaction condition were determined to achieve the desired acetylene conversion and ethylene selectivity. The physicochemical transformation of the developed optimum catalysts was determined using different techniques. Based on the characterization and cata-test results, the catalyst which contains 0.29% Ir and 0.08% Pd presents a better performance and higher stability compared to the other catalysts due to the moderate size and mono layer dispersion of the metals on the support. The experimental results show that acetylene conversion and ethylene selectivity approach 97% and 92% at 55 °C, respectively. Full article

(This article belongs to the Special Issue Zeolites and Catalysis)

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3973 KiB

Open AccessArticle

Highly Selective Catalytic Properties of HZSM-5 Zeolite in the Synthesis of Acetyl Triethyl Citrate by the Acetylation of Triethyl Citrate with Acetic Anhydride

by Kyong-Hwan Chung, Sangmin Jeong, Hangun Kim, Sun-Jae Kim, Young-Kwon Park and Sang-Chul Jung

Catalysts 2017, 7(11), 321; https://doi.org/10.3390/catal7110321 - 30 Oct 2017

Cited by 11 | Viewed by 6292

Abstract

The catalytic activities of acid catalysts for the acetylation of triethyl citrate with acetic anhydride in the preparation of acetyl triethyl citrate were evaluated. Microporous zeolites such as HZSM-5 and HY zeolites catalysts were introduced as heterogeneous acid catalysts. HZSM-5 zeolite catalysts showed [...] Read more.

The catalytic activities of acid catalysts for the acetylation of triethyl citrate with acetic anhydride in the preparation of acetyl triethyl citrate were evaluated. Microporous zeolites such as HZSM-5 and HY zeolites catalysts were introduced as heterogeneous acid catalysts. HZSM-5 zeolite catalysts showed a high conversion of triethyl citrate and excellent selectivity of acetyl triethyl citrate. The catalytic activities of HZSM-5 zeolites were superior to those of the HY zeolites. In particular, the selectivity of acetyl triethyl citrate on HZSM-5 zeolites exceeded 95%. The moderate acid strength of HZSM-5 (Si/Al = 75) zeolite led to the highest catalytic activities among the HZSM-5 zeolite catalysts, which have various acid strengths. Full article

(This article belongs to the Special Issue Zeolites and Catalysis)

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6510 KiB

Open AccessFeature PaperArticle

The Role of Non-Framework Lewis Acidic Al Species of Alkali-Treated HZSM-5 in Methanol Aromatization

by Po-Chen Lai, Chi-Ying Hsieh, Chao-Huang Chen and Yu-Chuan Lin

Catalysts 2017, 7(9), 259; https://doi.org/10.3390/catal7090259 - 01 Sep 2017

Cited by 10 | Viewed by 4269

Abstract

Mesoporous HZSM-5 prepared by alkaline treatment (also termed desilication) has drawn significant attention due to its potential in large-scale production and in versatile applications, such as separation and catalysis. Alkali-treated HZSM-5 contains considerable amounts of non-framework (amorphous) Lewis acidic Al species on the [...] Read more.

Mesoporous HZSM-5 prepared by alkaline treatment (also termed desilication) has drawn significant attention due to its potential in large-scale production and in versatile applications, such as separation and catalysis. Alkali-treated HZSM-5 contains considerable amounts of non-framework (amorphous) Lewis acidic Al species on the external surface, and is deemed to be essential in affecting its catalytic performances. This study intends to clarify the catalytic nature of amorphous Al species of alkali-treated HZSM-5 in methanol aromatization. Physicochemical characterizations, including N₂ adsorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), magic-angle-spinning nuclear magnetic resonance (MAS NMR), inductively coupled plasma (ICP) analysis, NH₃ temperature-programmed desorption (TPD), and methanol-TPD, were performed. The outcomes showed that non-framework Al promotes the hydride transfer in mesoporous HZSM-5, thereby facilitating the aromatization reaction. Among aromatic products, durene can be promoted by non-framework Al through methylation/transalkylation of other aromatics, particularly xylenes, instead of being promoted by reduced space confinement in mesoporous HZSM-5. Full article

(This article belongs to the Special Issue Zeolites and Catalysis)

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1155 KiB

Open AccessArticle

Nature and Location of Carbonaceous Species in a Composite HZSM-5 Zeolite Catalyst during the Conversion of Dimethyl Ether into Light Olefins

by María Ibáñez, Paula Pérez-Uriarte, Miguel Sánchez-Contador, Tomás Cordero-Lanzac, Andrés T. Aguayo, Javier Bilbao and Pedro Castaño

Catalysts 2017, 7(9), 254; https://doi.org/10.3390/catal7090254 - 30 Aug 2017

Cited by 39 | Viewed by 6184

Abstract

The deactivation of a composite catalyst based on HZSM-5 zeolite (agglomerated in a matrix using boehmite as a binder) has been studied during the transformation of dimethyl ether into light olefins. The location of the trapped/retained species (on the zeolite or on the [...] Read more.

The deactivation of a composite catalyst based on HZSM-5 zeolite (agglomerated in a matrix using boehmite as a binder) has been studied during the transformation of dimethyl ether into light olefins. The location of the trapped/retained species (on the zeolite or on the matrix) has been analyzed by comparing the properties of the fresh and deactivated catalyst after runs at different temperatures, while the nature of those species has been studied using different spectroscopic and thermogravimetric techniques. The reaction occurs on the strongest acid sites of the zeolite micropores through olefins and alkyl-benzenes as intermediates. These species also condensate into bulkier structures (polyaromatics named as coke), particularly at higher temperatures and within the meso- and macropores of the matrix. The critical roles of the matrix and water in the reaction medium have been proved: both attenuating the effect of coke deposition. Full article

(This article belongs to the Special Issue Zeolites and Catalysis)

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1982 KiB

Open AccessArticle

Functionalization of SSZ-13 and Fe-Beta with Copper by NH₃ and NO Facilitated Solid-State Ion-Exchange

by Alexander Shishkin, Soran Shwan, Torben Nilsson Pingel, Eva Olsson, Anna Clemens, Per-Anders Carlsson, Hanna Härelind and Magnus Skoglundh

Catalysts 2017, 7(8), 232; https://doi.org/10.3390/catal7080232 - 08 Aug 2017

Cited by 11 | Viewed by 6023

Abstract

We show that functionalization of SSZ-13 (CHA) and Fe-beta (*BEA) with copper using a recently reported solid-state ion-exchange method, facilitated by NH

_{3}

and nitrogen oxides (NO), is a viable route to prepare Cu-SSZ-13 and (Cu + Fe)-beta catalysts, starting from H-SSZ-13 and [...] Read more.

We show that functionalization of SSZ-13 (CHA) and Fe-beta (*BEA) with copper using a recently reported solid-state ion-exchange method, facilitated by NH

_{3}

and nitrogen oxides (NO), is a viable route to prepare Cu-SSZ-13 and (Cu + Fe)-beta catalysts, starting from H-SSZ-13 and Fe-beta, respectively. The physicochemical properties of the prepared catalysts are characterized by XRD, UV-Vis-spectroscopy and STEM-EDS, confirming that copper originally present in the physical mixture of CuO and H-SSZ-13, and CuO and Fe-beta, is inserted into the micropores of SSZ-13 and Fe-beta, respectively. Activity measurements in gas-flow reactor show that the samples are active for NO reduction by NH

_{3}

-SCR over a broad temperature range, i.e., 150–500

^{\circ}

C. For the Cu-SSZ-13 catalysts, which have a copper loading range of 0.5–4 wt. %, the sample prepared from the physical mixture with a CuO/SSZ-13 ratio corresponding to 2 wt. % Cu is the most active catalyst for NH

_{3}

-SCR under the present reaction conditions. Furthermore, the (Cu + Fe)-beta catalyst shows higher NH

_{3}

-SCR activity over a broader temperature range and especially at low temperature as compared to the Fe-beta and Cu-beta counterparts. The results encourage further elaboration on sequential ion-exchange procedures for bimetallic functionalization of zeolites. Full article

(This article belongs to the Special Issue Zeolites and Catalysis)

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4022 KiB

Open AccessFeature PaperArticle

Mesoporous ZSM-5 Zeolites in Acid Catalysis: Top-Down vs. Bottom-Up Approach

by Pit Losch, Thomas C. Hoff, Joy F. Kolb, Claire Bernardon, Jean-Philippe Tessonnier and Benoît Louis

Catalysts 2017, 7(8), 225; https://doi.org/10.3390/catal7080225 - 26 Jul 2017

Cited by 23 | Viewed by 7714

Abstract

A top-down desilication of Al-rich ZSM-5 zeolites and a bottom-up mesopores creating method were evaluated in this study. Three liquid–solid and one gas–solid heterogeneously-catalysed reactions were chosen to establish relationships between zeolites textural properties and their catalytic behavior in acid-catalysed model reactions that [...] Read more.

A top-down desilication of Al-rich ZSM-5 zeolites and a bottom-up mesopores creating method were evaluated in this study. Three liquid–solid and one gas–solid heterogeneously-catalysed reactions were chosen to establish relationships between zeolites textural properties and their catalytic behavior in acid-catalysed model reactions that are influenced by shape selectivity: Diels-Alder cyclization between isoprene and methylacrylate, Methanol-to-Olefins (MTO) reaction, chlorination of iodobenzene with trichloroisocyanuric acid (TCCA), and Friedel-Crafts acylation of anisole by carboxylic acids with differing sizes. It is found amongst others that no optimal mesoporosity for all the different reactions can be easily obtained, but depending on the chosen application, a specific treatment has to be set to achieve high activity/selectivity and stability. Full article

(This article belongs to the Special Issue Zeolites and Catalysis)

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Review

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8580 KiB

Open AccessReview

Strategies to Enhance the Catalytic Performance of ZSM-5 Zeolite in Hydrocarbon Cracking: A Review

by Yajun Ji, Honghui Yang and Wei Yan

Catalysts 2017, 7(12), 367; https://doi.org/10.3390/catal7120367 - 29 Nov 2017

Cited by 95 | Viewed by 13645

Abstract

ZSM-5 zeolite is widely used in catalytic cracking of hydrocarbon, but the conventional ZSM-5 zeolite deactivates quickly due to its simple microporous and long diffusion pathway. Many studies have been done to overcome these disadvantages recently. In this review, four main approaches for [...] Read more.

ZSM-5 zeolite is widely used in catalytic cracking of hydrocarbon, but the conventional ZSM-5 zeolite deactivates quickly due to its simple microporous and long diffusion pathway. Many studies have been done to overcome these disadvantages recently. In this review, four main approaches for enhancing the catalytic performance, namely synthesis of ZSM-5 zeolite with special morphology, hierarchical ZSM-5 zeolite, nano-sized ZSM-5 zeolite and optimization of acid properties, are discussed. ZSM-5 with special morphology such as hollow, composite and nanosheet structure can effectively increase the diffusion efficiency and accessibility of acid sites, giving high catalytic activity. The accessibility of acid sites and diffusion efficiency can also be enhanced by introducing additional mesopores or macropores. By decreasing the crystal size to nanoscale, the diffusion length can be shortened. The catalytic activity increases and the amount of carbon deposition decreases with the decrease of crystal size. By regulating the acid properties of ZSM-5 with element or compound modification, the overreaction of reactants and formation of carbon deposition could be suppressed, thus enhancing the catalytic activity and light alkene selectivity. Besides, some future needs and perspectives of ZSM-5 with excellent cracking activity are addressed for researchers’ consideration. Full article

(This article belongs to the Special Issue Zeolites and Catalysis)

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