Catalysts

Editorial

5 pages, 173 KiB

Open AccessEditorial

Editorial Special Issue “Heterogeneous Catalytic Materials: Synthesis, Characterization and Applications for Energetic Purposes”

by Catia Cannilla

Catalysts 2020, 10(10), 1174; https://doi.org/10.3390/catal10101174 - 13 Oct 2020

Cited by 1 | Viewed by 1369

Abstract

Solid catalytic materials play a key role in the development of industrial chemistry, showing important advantages over liquid materials thanks to their easier separation from the reaction liquid medium, their reusability and stability, and their environmentally friendly character [...] Full article

(This article belongs to the Special Issue Heterogeneous Catalytic Materials: Synthesis, Characterization and Applications for Energetic Purposes)

Research

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12 pages, 3650 KiB

Open AccessFeature PaperArticle

CuZnZr-Zeolite Hybrid Grains for DME Synthesis: New Evidence on the Role of Metal-Acidic Features on the Methanol Conversion Step

by Massimo Migliori, Antonio Condello, Francesco Dalena, Enrico Catizzone and Girolamo Giordano

Catalysts 2020, 10(6), 671; https://doi.org/10.3390/catal10060671 - 15 Jun 2020

Cited by 8 | Viewed by 2945

Abstract

The assessment of the catalytic performance of “hybrid” metal/zeolite catalysts (based on FER or MFI structure and CuZnZr metal complexes) in the methanol dehydration step to DME has been studied in this work. The results clearly show that there is an important effect [...] Read more.

The assessment of the catalytic performance of “hybrid” metal/zeolite catalysts (based on FER or MFI structure and CuZnZr metal complexes) in the methanol dehydration step to DME has been studied in this work. The results clearly show that there is an important effect of the interaction between metal and acid sites affecting the acid catalyst performances. Additionally, deactivation, studied by means of a Timo-on-Stream (TOS) test, was affected by the type of zeolite structure used for hybrid catalyst preparation. The decrease in DME selectivity can be attributed to the cooperation of metal and acid sites in the production of different compounds (mainly methyl formate and dimethoxy methane) converting methanol and DME. The presence of these compounds (indicating different reaction pathways active) was found to be dependent on the zeolite structure and on the type of co-precipitation medium (water or ethanol) used to prepare the hybrid catalyst. Full article

(This article belongs to the Special Issue Heterogeneous Catalytic Materials: Synthesis, Characterization and Applications for Energetic Purposes)

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25 pages, 3690 KiB

Open AccessArticle

Lab-Scale Investigation of Palm Shell Char as Tar Reforming Catalyst

by Yen-Hau Chen, Max Schmid, Chia-Chi Chang, Ching-Yuan Chang and Günter Scheffknecht

Catalysts 2020, 10(5), 476; https://doi.org/10.3390/catal10050476 - 27 Apr 2020

Cited by 16 | Viewed by 3427

Abstract

This research investigated the application of palm shell char as a catalyst for the catalytic steam reforming of tar after the sorption enhanced gasification (SEG) process. The catalytic activities of palm shell char and metal-supported palm shell char were tested in a simulated [...] Read more.

This research investigated the application of palm shell char as a catalyst for the catalytic steam reforming of tar after the sorption enhanced gasification (SEG) process. The catalytic activities of palm shell char and metal-supported palm shell char were tested in a simulated SEG derived syngas with tar model compounds (i.e., toluene and naphthalene) at a concentration of 10 g m⁻³ _NTP. The results indicated that palm shell char had an experimentally excellent catalytic activity for tar reforming with toluene and naphthalene conversions of 0.8 in a short residence time of 0.17 s at 900 °C. A theoretical residence time to reach the complete naphthalene conversion was 1.2 s at 900 °C for palm shell char, demonstrating a promising activity similar to wood char and straw char, but better than CaO. It was also found that potassium and iron-loaded palm shell chars exhibited much better catalytic activity than palm shell char, while the parallel reaction of gasification of K-loaded palm shell char influenced the conversion with its drastic mass loss. Moreover, contrary to CaO, palm shell char presented relatively low selectivity to benzene, and its spontaneous gasification generated extra syngas. In summary, the present study demonstrated that the low-cost material, palm shell char, can successfully be used as the tar-reforming catalyst after SEG process. Full article

(This article belongs to the Special Issue Heterogeneous Catalytic Materials: Synthesis, Characterization and Applications for Energetic Purposes)

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15 pages, 4997 KiB

Open AccessFeature PaperArticle

Tailoring of Hydrotalcite-Derived Cu-Based Catalysts for CO₂ Hydrogenation to Methanol

by Leone Frusteri, Catia Cannilla, Serena Todaro, Francesco Frusteri and Giuseppe Bonura

Catalysts 2019, 9(12), 1058; https://doi.org/10.3390/catal9121058 - 12 Dec 2019

Cited by 19 | Viewed by 4016

Abstract

Ternary Cu_xZn_yAl_z catalysts were prepared using the hydrotalcite (HT) method. The influence of the atomic x:y:z ratio on the physico-chemical and catalytic properties under CO₂ hydrogenation conditions was probed. The characterization data of [...] Read more.

Ternary Cu_xZn_yAl_z catalysts were prepared using the hydrotalcite (HT) method. The influence of the atomic x:y:z ratio on the physico-chemical and catalytic properties under CO₂ hydrogenation conditions was probed. The characterization data of the investigated catalysts were obtained by XRF, XRD, BET, TPR, CO₂-TPD, N₂O chemisorption, SEM, and TEM techniques. In the “dried” catalyst, the typical structure of a hydrotalcite phase was observed. Although the calcination and subsequent reduction treatments determined a clear loss of the hydrotalcite structure, the pristine phase addressed the achievement of peculiar physico-chemical properties, also affecting the catalytic activity. Textural and surface effects induced by the zinc concentration conferred a very interesting catalyst performance, with a methanol space time yield (STY) higher than that of commercial systems operated under the same experimental conditions. The peculiar behavior of the hydrotalcite-like samples was related to a high dispersion of the active phase, with metallic copper sites homogeneously distributed among the oxide species, thereby ensuring a suitable activation of H₂ and CO₂ reactants for a superior methanol production. Full article

(This article belongs to the Special Issue Heterogeneous Catalytic Materials: Synthesis, Characterization and Applications for Energetic Purposes)

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12 pages, 2489 KiB

Open AccessArticle

Effect of Preparation Method on ZrO₂-Based Catalysts Performance for Isobutanol Synthesis from Syngas

by Yingquan Wu, Li Tan, Tao Zhang, Hongjuan Xie, Guohui Yang, Noritatsu Tsubaki and Jiangang Chen

Catalysts 2019, 9(9), 752; https://doi.org/10.3390/catal9090752 - 6 Sep 2019

Cited by 9 | Viewed by 3136

Abstract

Two types of amorphous ZrO₂ (am-ZrO₂) catalysts were prepared by different co-precipitation/reflux digestion methods (with ethylenediamine and ammonia as the precipitant respectively). Then, copper and potassium were introduced for modifying ZrO₂ via an impregnation method to enhance the catalytic [...] Read more.

Two types of amorphous ZrO₂ (am-ZrO₂) catalysts were prepared by different co-precipitation/reflux digestion methods (with ethylenediamine and ammonia as the precipitant respectively). Then, copper and potassium were introduced for modifying ZrO₂ via an impregnation method to enhance the catalytic performance. The obtained catalysts were further characterized by means of Brunauer-Emmett-Teller surface areas (BET), X-ray diffraction (XRD), H₂-temperature-programmed reduction (H₂-TPR), and In situ diffuse reflectance infrared spectroscopy (in situ DRIFTS). CO hydrogenation experiments were performed in a fixed-bed reactor for isobutanol synthesis. Great differences were observed on the distribution of alcohols over the two types of ZrO₂ catalysts, which were promoted with the same content of Cu and K. The selectivity of isobutanol on K-CuZrO₂ (ammonia as precipitant, A-KCZ) was three times higher than that on K-CuZrO₂ (ethylenediamine as precipitant, E-KCZ). The characterization results indicated that the A-KCZ catalyst supplied more active hydroxyls (isolated hydroxyls) for anchoring and dispersing Cu. More importantly, it was found that bicarbonate species were formed, which were ascribed as important C₁ species for isobutanol formation on the A-KCZ catalyst surface. These C₁ intermediates had relatively stronger adsorption strength than those adsorbed on the E-KCZ catalyst, indicating that the bicarbonate species on the A-KCZ catalyst had a longer residence time for further carbon chain growth. Therefore, the selectivity of isobutanol was greatly enhanced. These findings would extend the horizontal of direct alcohols synthesis from syngas. Full article

(This article belongs to the Special Issue Heterogeneous Catalytic Materials: Synthesis, Characterization and Applications for Energetic Purposes)

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20 pages, 2672 KiB

Open AccessArticle

Co-precipitation Synthesized MnO_x-CeO₂ Mixed Oxides for NO Oxidation and Enhanced Resistance to Low Concentration of SO₂ by Metal Addition

by Jiaming Shao, Fawei Lin, Yan Li, Hairong Tang, Zhihua Wang, Peixi Liu and Guanyi Chen

Catalysts 2019, 9(6), 519; https://doi.org/10.3390/catal9060519 - 12 Jun 2019

Cited by 23 | Viewed by 4108

Abstract

NO oxidation was conducted over MnO_x-CeO₂ catalysts, which were synthesized by the co-precipitation method. The calcination temperature and third metal doping were the main considerations. MnCe catalysts calcined at 350 °C and 450 °C attained the highest NO conversion efficiency, [...] Read more.

NO oxidation was conducted over MnO_x-CeO₂ catalysts, which were synthesized by the co-precipitation method. The calcination temperature and third metal doping were the main considerations. MnCe catalysts calcined at 350 °C and 450 °C attained the highest NO conversion efficiency, compared to 550 °C. XRD results suggested that the higher the calcination temperature, the higher the crystallization degree, which led to a negative effect on catalytic activity. Subsequently, Sn, Fe, Co, Cr, and Cu were separately doped into MnCe composites, but no improvement was observed for these trimetallic catalysts in NO conversion. Nevertheless, MnCeSn, MnCeFe, and MnCeCo still exhibited a desirable NO conversion efficiency, so they were tested under SO₂ addition together with MnCe catalyst. Among them, MnCeFe exhibited the highest NO conversion after whole poisoning testing. XPS results indicated that Fe could protect Mn and Ce metal oxides from being reduced during SO₂ poisoning process. Furthermore, in in-situ DRIFTS measurement, part of nitrate species maintained undestroyed on the MnCeFe catalyst surface after SO₂ poisoning. These characteristics reinforced that Fe dropping would achieve better performance under SO₂ atmosphere. Full article

(This article belongs to the Special Issue Heterogeneous Catalytic Materials: Synthesis, Characterization and Applications for Energetic Purposes)

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14 pages, 3796 KiB

Open AccessCommunication

Ultra-Small Pd Nanoparticles on Ceria as an Advanced Catalyst for CO Oxidation

by Andrei Tereshchenko, Vladimir Polyakov, Alexander Guda, Tatiana Lastovina, Yulia Pimonova, Alexey Bulgakov, Andrey Tarasov, Leonid Kustov, Vera Butova, Alexander Trigub and Alexander Soldatov

Catalysts 2019, 9(4), 385; https://doi.org/10.3390/catal9040385 - 24 Apr 2019

Cited by 20 | Viewed by 5771

Abstract

In this study, we demonstrate the preparation and characterization of small palladium nanoparticles (Pd NPs) on modified ceria support (Pd/CeO₂) using wet impregnation and further reduction in an H₂/Ar flow. The obtained particles had a good dispersion, but their [...] Read more.

In this study, we demonstrate the preparation and characterization of small palladium nanoparticles (Pd NPs) on modified ceria support (Pd/CeO₂) using wet impregnation and further reduction in an H₂/Ar flow. The obtained particles had a good dispersion, but their small size made it difficult to analyze them by conventional techniques such as transmission electron microscopy (TEM) and X-ray powder diffraction (XRPD). The material demonstrated a high catalytic activity in the CO oxidation reaction: the 100% of CO conversion was achieved at ~50 °C, whereas for most of the cited literature, such a high conversion usually was observed near 100 °C or higher for Pd NPs. Diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy in combination with CO probe molecules was used to investigate the size and morphology of NPs and the ceria support. On the basis of the area ratio under the peaks attributed to bridged (B) and linear (L) carbonyls, high-dispersion Pd NPs was corroborated. Obtained results were in good agreement with data of X-ray absorption near edge structure analysis (XANES) and CO chemisorption measurements. Full article

(This article belongs to the Special Issue Heterogeneous Catalytic Materials: Synthesis, Characterization and Applications for Energetic Purposes)

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13 pages, 2228 KiB

Open AccessArticle

Heteropolyacid Salt Catalysts for Methanol Conversion to Hydrocarbons and Dimethyl Ether: Effect of Reaction Temperature

by Yuehong Yu, Daoming Sun, Shuanjin Wang, Min Xiao, Luyi Sun and Yuezhong Meng

Catalysts 2019, 9(4), 320; https://doi.org/10.3390/catal9040320 - 1 Apr 2019

Cited by 19 | Viewed by 4399

Abstract

Phosphotungstic and silicotungstic acid salt catalysts (CuPW, CuSiW, FePW, FeSiW) were synthesized by substitution of protons with ferric and copper ions through a simple replacement reaction. The structure and thermal stability were characterized by IR, XRD and TG, and the salts showed a [...] Read more.

Phosphotungstic and silicotungstic acid salt catalysts (CuPW, CuSiW, FePW, FeSiW) were synthesized by substitution of protons with ferric and copper ions through a simple replacement reaction. The structure and thermal stability were characterized by IR, XRD and TG, and the salts showed a keggin structure and a thermal tolerance near 450 °C. Temperature programmed reactions indicated that the four catalysts showed similar trends in the change of methanol conversion, DME selectivity, and light olefins selectivity at 100–400 °C. Copper salt catalysts showed a 100% DME selectivity at temperatures ranging from 100–250 °C, while FeSiW and FePW catalysts had a 100% DME selectivity near 250 °C. Moreover, the heteropolyacid salt catalysts also produced a certain number of light olefins at the temperature ranging from 250–350 °C, and the CuSiW catalyst exhibited the highest ethylene and propylene selectivity of 44%. In the stability test evaluated at 200 °C, the catalysts showed different tendencies during the induction period and the same trends during the reduction period for the methanol conversion to DME, due to the differences in the strengths of the strong acid sites. Finally, the silicotungstic acid salt catalysts showed the longest lifetime of 120 h, much longer than the heteropolyacids. This approach provides an effective way to synthesize hydrocarbons through methanol, especially DME, at different temperatures using one catalyst. Full article

(This article belongs to the Special Issue Heterogeneous Catalytic Materials: Synthesis, Characterization and Applications for Energetic Purposes)

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Review

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21 pages, 2340 KiB

Open AccessReview

Copper–Zirconia Catalysts: Powerful Multifunctional Catalytic Tools to Approach Sustainable Processes

by Nicola Scotti, Filippo Bossola, Federica Zaccheria and Nicoletta Ravasio

Catalysts 2020, 10(2), 168; https://doi.org/10.3390/catal10020168 - 1 Feb 2020

Cited by 41 | Viewed by 6939

Abstract

Copper–zirconia catalysts find many applications in different reactions owing to their unique surface properties and relatively easy manufacture. The so-called methanol economy, which includes the CO₂ and CO valorization and the hydrogen production, and the emerging (bio)alcohol upgrading via dehydrogenative coupling reaction, [...] Read more.

Copper–zirconia catalysts find many applications in different reactions owing to their unique surface properties and relatively easy manufacture. The so-called methanol economy, which includes the CO₂ and CO valorization and the hydrogen production, and the emerging (bio)alcohol upgrading via dehydrogenative coupling reaction, are two critical fields for a truly sustainable development in which copper–zirconia has a relevant role. In this review, we provide a systematic view on the factors most impacting the catalytic activity and try to clarify some of the discrepancies that can be found in the literature. We will show that contrarily to the large number of studies focusing on the zirconia crystallographic phase, in the last years, it has turned out that the degree of surface hydroxylation and the copper–zirconia interphase are in fact the two mostly determining factors to be controlled to achieve high catalytic performances. Full article

(This article belongs to the Special Issue Heterogeneous Catalytic Materials: Synthesis, Characterization and Applications for Energetic Purposes)

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