ISOMERIZATION OF C5-C7 LINEAR ALKANES OVER WO3-ZRO2 UNDER HELIUM ATMOSPHERE

The effect of WO3 on the properties and catalytic isomerization of C5-C7 linear alkanes over ZrO2 was studied under helium atmosphere. The WO3-ZrO2 was prepared by impregnation of Zr(OH)4 with an aqueous (NH4)6[H2W12O40], followed by calcination at 1093 K for 3 h in air. The amount WO3 was 10 wt%. XRD and BET studies showed that the introduction of WO3 stabilizes the tetragonal phase of ZrO2, leading to larger surface area and stronger acidity of ZrO2. Pyridine FTIR study verified the interaction of WO3 with ZrO2 formed strong Lewis and Bronsted acid sites. The presence of WO3 increased the catalytic isomerization of C5-C7 linear alkanes. The conversion of C5, C6 and C7 reached 1.3, 2.6 and 5.1 %, respectively. While the selectivity of isopentane, isohexane and isoheptane reached 15.6, 20.5 and 19.5 %, respectively. The high activity of WO3-ZrO2 was due to the ability of WO3 to adsorb and dissociate linear alkane to form hydrogen and alkane radical in which the atomic hydrogen underwent to the formation of protonic acid sites and hydride. The presence of protonic acid sites and hydride determined the activity of WO3-ZrO2.

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Lanthanum Exchanged Keggin Structured Heteropoly Compounds for Biodiesel Production

Catalysts ◽

10.3390/catal9120979 ◽

2019 ◽

Vol 9 (12) ◽

pp. 979 ◽

Cited By ~ 1

Author(s):

Badriah Al-Shammari ◽

Qana A. Alsulami ◽

Katabathini Narasimharao

Keyword(s):

High Activity ◽

Surface Area ◽

Photoelectron Spectroscopy ◽

Physical Adsorption ◽

Acid Sites ◽

Biodiesel Production ◽

One Pot ◽

Exchange Method ◽

X Ray ◽

Basic Sites

La-exchanged 12-tungstophosphoric acid (LaxTPA) and 12-molybdophosphoric acid (LaxMPA) salts (x = 0.25, 0.50, 0.75 and 1.00) were prepared via an ion exchange method. The physico-chemical characteristics of the materials were analyzed by using elemental analysis, X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), N2-physical adsorption, X-ray photoelectron spectroscopy (XPS), and acidity-basicity measurements. The results indicated that La was introduced into the secondary structure of heteropolyacid (HPA) and have not influenced the primary structure, which effectively improved the surface area and pore size. Acidity-basicity studies indicated that incorporation of La resulted in a decrease in the number of acid sites and an increase in the number of basic sites. The catalytic activity of samples was studied in transesterification of glyceryl tributyrate with methanol and LaxTPA samples which exhibited high activity compared to LaxMPA samples due to having more active basic sites and a larger surface area. Calcined LaxTPA samples showed excellent stability, outstanding recyclability, and high activity for one pot transesterification and esterification processes. This outcome was attributed to the presence of balanced acidic and basic sites.

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On the Role of Protonic Acid Sites in Cu Loaded FAU31 Zeolite as a Catalyst for the Catalytic Transformation of Furfural to Furan

Molecules ◽

10.3390/molecules26072015 ◽

2021 ◽

Vol 26 (7) ◽

pp. 2015

Author(s):

Łukasz Kuterasiński ◽

Małgorzata Smoliło-Utrata ◽

Joanna Kaim ◽

Wojciech Rojek ◽

Jerzy Podobiński ◽

...

Keyword(s):

Active Sites ◽

Acid Sites ◽

Bronsted Acid ◽

Brønsted Acid ◽

Brønsted Acid Sites ◽

Protonic Acid ◽

Brönsted Acid ◽

Brönsted Acid Sites ◽

Bronsted Acid Sites

The aim of the present paper is to study the speciation and the role of different active site types (copper species and Brønsted acid sites) in the direct synthesis of furan from furfural catalyzed by copper-exchanged FAU31 zeolite. Four series of samples were prepared by using different conditions of post-synthesis treatment, which exhibit none, one or two types of active sites. The catalysts were characterized by XRD, low-temperature sorption of nitrogen, SEM, H2-TPR, NMR and by means of IR spectroscopy with ammonia and CO sorption as probe molecules to assess the types of active sites. All catalyst underwent catalytic tests. The performed experiments allowed to propose the relation between the kind of active centers (Cu or Brønsted acid sites) and the type of detected products (2-metylfuran and furan) obtained in the studied reaction. It was found that the production of 2-methylfuran (in trace amounts) is determined by the presence of the redox-type centers, while the protonic acid sites are mainly responsible for the furan production and catalytic activity in the whole temperature range. All studied catalysts revealed very high susceptibility to coking due to polymerization of furfural.

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Two-Dimensional Transition Metal Borides as High Activity and Selectivity Catalysts for Ammonia Synthesis

Nanoscale ◽

10.1039/d1nr05774j ◽

2021 ◽

Author(s):

Haona Zhang ◽

Shuhua Wang ◽

Hao Wang ◽

Baibiao Huang ◽

Shuping Dong ◽

...

Keyword(s):

Transition Metal ◽

Specific Surface ◽

High Activity ◽

Surface Area ◽

Active Site ◽

Ammonia Synthesis ◽

Two Dimensional ◽

Large Specific Surface Area ◽

Site Density ◽

Metal Borides

In comparison to defect/doping induced activity in materials, transition metal borides with exposed metal atom, large specific surface area and high active site density show advantages as durable and efficient...

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Solid Acids from Persulphated and Perchlorated Physical Mixtures of Zirconium and Titanium Hydroxides

Adsorption Science & Technology ◽

10.1260/026361702321705267 ◽

2002 ◽

Vol 20 (10) ◽

pp. 977-993

Author(s):

Gamal M.S. El Shafei ◽

Christine A. Philip

Keyword(s):

Tetragonal Phase ◽

Anatase Phase ◽

Nitrogen Adsorption ◽

Rutile Phase ◽

Acid Sites ◽

Solid Acids ◽

Monoclinic Zirconia ◽

Anion Adsorption ◽

Physical Mixtures ◽

Structural Aspects

Calcination at 650°C of a physical mixture of zirconium and titanium hydroxides led to the formation of the corresponding oxides, monoclinic zirconia and anatase. The adsorption of perchlorate or persulphate anions (as 0.05, 0.1, 0.2 or 0.4 M aqueous solutions) before calcination did not inhibit crystallization; however, perchlorate anions activated the formation of rutile in addition to the predominant anatase phase. Indeed, the adsorption of perchlorated anions prior to calcination allowed the thermodynamically less stable tetragonal phase of zirconia to be detected in addition to monoclinic zirconia at ambient temperature. In contrast, the adsorption of persulphate anions before calcination stabilized the tetragonal phase with no rutile phase being detected in this case. Infrared spectroscopy showed that adsorbed S2O82– anions were held more strongly by the solid than ClO4− anions which tended to decompose when the solid was calcined. The acidities of the solid acids produced because of S2O82– or ClO4−anion adsorption were studied via the adsorption of pyridine (pKa = 5.3) from cyclohexane solution. The amounts and strengths of the acid sites formed during persulphate treatment were higher than those resulting from perchlorate adsorption. The strength of the acid sites formed on samples calcined before loading with S2O82– or ClO4− anions showed no significant differences. Variations detected in the structural aspects arising from S2O82– or ClO4− anion adsorption were reflected in the texture as assessed by nitrogen adsorption at −196°C.

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Synthesis of Uniform Mesoporous Zeolite ZSM-5 Catalyst for Friedel-Crafts Acylation

ChemEngineering ◽

10.3390/chemengineering3020035 ◽

2019 ◽

Vol 3 (2) ◽

pp. 35 ◽

Cited By ~ 10

Author(s):

Heman Smail ◽

Mohammad Rehan ◽

Kafia Shareef ◽

Zainab Ramli ◽

Abdul-Sattar Nizami ◽

...

Keyword(s):

Surface Area ◽

Surface Acidity ◽

Analytical Techniques ◽

Acid Sites ◽

Zeolite Catalysts ◽

Gas Chromatography Mass Spectrometry ◽

Crystallographic Structure ◽

Mesoporous Zeolite ◽

Mesoporous Zeolites ◽

Surfactant Templates

This work highlights how the treatment of ZSM-5 (parent Zeolite Socony Mobil–5, Si/Al = 23) with different surfactant templates and alkaline solution, improved the catalytic performance in the Friedel-Crafts acylation of anisole with a propionic anhydride to obtain p-methoxypropiophenone. The modified microporous to mesoporous zeolite catalysts were characterized using different analytical techniques, including X-ray diffraction (XRD), nitrogen porosimetry, Fourier-transform infrared spectroscopy (FT-IR), temperature-programmed desorption (ammonia-TPD) and field emission scanning electron microscopy (FE-SEM) to analyze the crystallographic structure, surface acidity, surface area, porosity, morphology, and particle size. The results showed that the formed mesoporous zeolite by NaOH solution had smaller mesopores (ca. 3.7 nm) as compared to the mesoporous zeolites obtained by surfactant templates, such as, CTAB (ca. 14.9 nm), TPAOH (ca. 11.1 nm) and mixture of CTAB/TPAOH (ca. 15.2 nm). The catalytic acylation reaction was conducted in a batch glass reactor at various temperatures and the products were analyzed using off-line gas chromatography–mass spectrometry (GC-MS). It was found that the activity of treated ZSM-5 with mixed surfactant templates (CTAB/TPAOH) exhibited enhanced selectivity towards the main product (p-methoxypropiophenone) by a factor 1.7 or higher than unmodified ZSM-5 due to its increased surface area by 1.5 times and enhanced acid sites.

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Impact of Thermal Treatment of Nb2O5 on Its Performance in Glucose Dehydration to 5-Hydroxymethylfurfural in Water

Nanomaterials ◽

10.3390/nano10091685 ◽

2020 ◽

Vol 10 (9) ◽

pp. 1685

Author(s):

Katarzyna Morawa Eblagon ◽

Anna Malaika ◽

Karolina Ptaszynska ◽

Manuel Fernando R. Pereira ◽

José Luís Figueiredo

Keyword(s):

Thermal Treatment ◽

Surface Area ◽

Pure Water ◽

High Surface ◽

High Surface Area ◽

Acid Sites ◽

High Ratio ◽

Total Acidity ◽

One Pot ◽

Niobic Acid

The cascade dehydration of glucose to 5-hydroxymethylfurfural (HMF) was carried out in water over a series of Nb2O5 catalysts, which were derived from the thermal treatment of niobic acid at 300 and 550 °C, under air or inert atmosphere. Amorphous niobic acid showed high surface area (366 m2/g) and large acidity (2.35 mmol/g). With increasing the temperature of the thermal treatment up to 550 °C, the amorphous Nb2O5 was gradually transformed into a pseudohexagonal phase, resulting in a decrease in surface area (27–39 m2/g) and total acidity (0.05–0.19 mmol/g). The catalysts’ performance in cascade dehydration of glucose realized in pure water was strongly influenced by the total acidity of these materials. A remarkable yield of 37% HMF in one-pot reaction in water was achieved using mesoporous amorphous niobium oxide prepared by thermal treatment of niobic acid at 300 °C in air. The best-performing catalyst displayed a total acidity lower than niobic acid (1.69 mmol/g) which afforded a correct balance between a high glucose conversion and limited further conversion of the target product to numerous polymers and humins. On the other hand, the treatment of niobic acid at 550 °C, independently of the atmosphere used during the sample preparation (i.e., air or N2), resulted in Nb2O5 catalysts with a high ratio of Lewis to Brønsted acid sites and poor total acidity. These materials excelled at catalyzing the isomerization step in the tandem process.

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Parabens Adsorption onto Activated Carbon: Relation with Chemical and Structural Properties

Molecules ◽

10.3390/molecules24234313 ◽

2019 ◽

Vol 24 (23) ◽

pp. 4313 ◽

Cited By ~ 1

Author(s):

Astrid Roxanna Moreno-Marenco ◽

Liliana Giraldo ◽

Juan Carlos Moreno-Piraján

Keyword(s):

Aqueous Solution ◽

Activated Carbon ◽

Surface Area ◽

Endocrine Disruptor ◽

Emerging Contaminants ◽

Activated Carbons ◽

Elaeis Guineensis ◽

Acid Sites ◽

Co2 Atmosphere

Parabens (alkyl-p-hidroxybenzoates) are antimicrobial preservatives used in personal care products, classified as an endocrine disruptor, so they are considered emerging contaminants. A raw version of activated carbons obtained from African palm shell (Elaeis guineensis) modified chemically by impregnation with salts of CaCl2 (GC2), MgCl2 (GM2) and Cu(NO3)2 (GCu2) at 2% wt/v and carbonized in CO2 atmosphere at 1173 K was prepared. The process of adsorption of methyl (MePB) and ethylparaben (EtPB) from aqueous solution on the activated carbons at 18 °C was studied and related to the interactions between the adsorbate and the adsorbent, which can be quantified through the determination of immersion enthalpies in aqueous solutions of corresponding paraben, showing the lowest-value carbon GM2, which has a surface area of 608 m2 × g−1, while the highest values correspond to the activated carbon GCu2, with a surface area of 896 m2 × g−1 and the highest content of surface acid sites (0.42 mmol × g−1), such as lactonic and phenolic compounds, which indicates that the adsorbate–adsorbent interactions are favored by the presence of these, with interaction enthalpies that vary between 5.72 and 51.95 J × g−1 for MePB adsorption and 1.24 and 52.38 J × g−1 for EtPB adsorption showing that the process is endothermic.

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One-pot aerobic oxidative sulfonamidation of aromatic thiols with ammonia by a dual-functional β-MnO2 nanocatalyst

Chemical Communications ◽

10.1039/c9cc09411c ◽

2020 ◽

Vol 56 (14) ◽

pp. 2095-2098 ◽

Cited By ~ 2

Author(s):

Eri Hayashi ◽

Yui Yamaguchi ◽

Yusuke Kita ◽

Keigo Kamata ◽

Michikazu Hara

Keyword(s):

High Activity ◽

Surface Area ◽

High Surface ◽

High Surface Area ◽

One Pot ◽

Dual Functional ◽

Aromatic Thiols ◽

The One

High-surface-area β-MnO2 nanoparticles exhibited high activity for the one-pot oxidative sulfonamidation of thiols to sulfonamides using O2 and NH3.

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Modification of ZSM-5 Zeolite in order to Improve the Yield of Light Olefins during Cracking of Oil and Plant Materials

Kataliz v promyshlennosti ◽

10.18412/1816-0387-2018-4-31-40 ◽

2018 ◽

Vol 18 (4) ◽

pp. 31-40

Author(s):

V. P. Doronin ◽

P. V. Lipin ◽

O. V. Potapenko ◽

V. V. Vysotsky ◽

T. I. Gulyaeva ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Alkali Treatment ◽

Total Yield ◽

Acid Sites ◽

Vacuum Gasoil ◽

Light Olefins ◽

Plant Oil ◽

Plant Materials

The influence of modifying HZSM-5 zeolite as a component of a bizeolite catalyst in transformations of hydrotreated vacuum gasoil, plant oil, and a mixture of vacuum gasoil and plant oil was studied. The modification with phosphorus was established to decrease the specific surface area and meso- and macropore volumes in HZSM-5 zeolite; the higher phosphorus content, the lower main characteristics of the zeolite porous structure. A decrease in the total acidity of P/HZSM-5 and quantitative redistribution between weak and moderate acid sites also was observed. Testing of the zeolites in catalytic cracking revealed that the phosphorus modification favored an increase in the total yield of propane-propylene and butane-butylene fractions containing olefins in high proportions. Alkali treatment of HZSM-4 zeolite with a high silicate module resulted in a higher silicon extraction and in a considerable increase in the specific surface area of mesopores. In addition, strong acid sites of the zeolite were transformed to weaker ones and/or their exposure changed due to partial silicon removal.

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