scholarly journals Influence of Boron, Tungsten and Molybdenum Modifiers on Zirconia Based Pt Catalyst for Glycerol Valorization

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 509 ◽  
Author(s):  
Manuel Checa ◽  
Vicente Montes ◽  
Jesús Hidalgo-Carrillo ◽  
Alberto Marinas ◽  
Francisco Urbano
Keyword(s):  
Active Catalyst ◽  
Acid Sites ◽  
Lewis Acidity ◽  
Pt Catalyst ◽  
Chloroplatinic Acid ◽  
Pt Catalysts ◽  
Reaction Products ◽  
Acidic Properties ◽  
Glycerol Hydrogenolysis ◽  
Zro2 Catalyst

The influence of boron, tungsten and molybdenum modifiers on zirconia-based Pt catalyst was studied for glycerol valorization. Zirconia modified supports were prepared by impregnation of ZrO2 with either boric, silicontungstic or phosphomolybdic acids to obtain supports with enhanced Brönsted acidic properties. The modified supports were subsequently impregnated with chloroplatinic acid to obtain Pt-based catalysts. Pt incorporation resulted in the increase in Lewis acidity of the solids, being more significant for the Pt//W/ZrO2 catalyst. Reduced Pt catalysts were tested for the liquid-phase glycerol hydrogenolysis, observing a synergistic effect between catalyst acid sites and metal function that proved to be crucial in glycerol hydrogenolysis. The Pt//W/ZrO2 catalyst was the most active catalyst in this reaction, being the only leading to 1,3-PDO (45% sel., 160 °C) while Pt//Mo/ZrO2 is the best option for 1,2-PDO (49% sel., 180 °C). Reusability studies carried out for Pt//W/ZrO2 showed that catalytic activity dropped after the first use, remaining constant for the second and subsequent ones. Selectivity to reaction products also changes during reuses. Therefore, the selectivity to 1,2 PDO increases in the first reuse in detriment to the selectivity to n-propanol whereas the selectivity to 1,3-PDO remains constant along the uses. This behavior could be associated to the lixiviation of W species and/or catalyst fouling during reaction runs.

scholarly journals Hydrogenolysis of Glycerol on the ZrO2-TiO2 Supported Pt-WOx Catalyst

Catalysts ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 312 ◽  
Author(s):  
Zhiwen Xi ◽  
Zhe Hong ◽  
Fangtao Huang ◽  
Zhirong Zhu ◽  
Wenzhi Jia ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Self Assembly ◽  
Catalyst Surface ◽  
Acid Sites ◽  
Acidic Properties ◽  
Lewis Acid Sites ◽  
Molar Ratios ◽  
Assembly Method ◽  
Evaporation Induced Self Assembly ◽  
Glycerol Hydrogenolysis

A series of Pt/WOx-ZrO2-TiO2 catalysts with different Ti/Zr molar ratios was prepared by an evaporation induced self-assembly method, and used to efficient hydrogenolysis of glycerol to 1-PO and 1,3-PDO. BET, XRD, Raman, TEM, XPS and Py-IR were employed to characterize the physicochemical properties of the catalysts. The structural and acidic properties of the catalysts were affected by the Ti/Zr ratio of the support ZrO2-TiO2. Two new crystalline phases of ZrTiO4 and Ti2ZrO6 and the amount of acid sites were detected in the Pt/WOx-ZrO2-TiO2 catalysts. 1-PO is dominant in all products of glycerol hydrogenolysis over the supported Pt-WOx catalysts, which is attributed to more Lewis acid sites on the catalyst surface. The Pt/WOx-ZrO2-TiO2 catalyst with a Ti/Zr ratio of 7/3 showed the highest 1,3-PDO yield (25.3%) and 1-PO yield (42.3%), due to its more acid sites including Brønsted and Lewis, and higher concentration of surface Pt0.

scholarly journals Hollow MFI Zeolite Supported Pt Catalysts for Highly Selective and Stable Hydrodeoxygenation of Guaiacol to Cycloalkanes

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 362 ◽  
Author(s):  
Xiaopo Niu ◽  
Fuxiang Feng ◽  
Gang Yuan ◽  
Xiangwen Zhang ◽  
Qingfa Wang
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Acid Sites ◽  
Pt Catalyst ◽  
Pt Catalysts ◽  
Mfi Zeolite ◽  
Long Term Stability ◽  
Supported Pt Catalysts ◽  
Hierarchical Porous ◽  
Ft Ir

Hollow Silicalite-1 and ZSM-5 zeolites with hierarchical porous shells have been synthesized by using a dissolution-recrystallization method. The morphology, structure, and acidity of these zeolites supported Pt catalysts were characterized by XRD, FT-IR, MAS-SSNMR, FE-SEM, FE-TEM, N2-BET, XPS, NH3-TPD, and CO pulse chemisorption. Compared to the conventional ZSM-5 supported Pt catalyst, the special structure in hollow ZSM-5 zeolite significantly promotes the dispersion of metallic Pt and the synergistic effect between metal active sites and acid sites. These boost the catalytic activity, selectivity of guaiacol hydrodeoxygenation toward cycloalkanes and long-term stability over the Pt/hollow ZSM-5 catalyst combined with improved mass transfer of products and reactants derived from the hierarchical hollow porous structure. Moreover, the Pt/hollow ZSM-5 catalyst exhibits excellent low temperature catalytic activity to completely transform guaiacol into cycloalkanes with the cyclohexane selectivity of more than 93% at 220 °C, suggesting that hollow ZSM-5 zeolite is a promising support for upgrading of bio-oils.

Hydrogenolysis of glucose and fructose in glycol solutions over CuO-MgO-ZrO2 catalyst

2020 ◽  
pp. 48-55
Author(s):  
M.E. Sharanda ◽  
◽  
E.A. Bondarenko ◽  
Keyword(s):  
Ethylene Glycol ◽  
Propylene Glycol ◽  
Flow Reactor ◽  
General Trend ◽  
Raw Materials ◽  
Reaction Products ◽  
Renewable Raw Materials ◽  
High Partial Pressure ◽  
Zro2 Catalyst ◽  
Phase Process

Ethylene glycol and propylene glycol are important representatives of polyols. On an industrial scale, they are obtained from petrochemical raw materials. Within a decade, significant efforts were made for the producing of polyols from biologically renewable raw materials - carbohydrates. The general trend for carbohydrate hydrogenolysis includes application of liquid-phase process with the use of modified metal-oxide catalysts, at 120-120 ° C and pressure of 3MPa or above. So high pressure is used for the reason to increase hydrogen solubility, and also due to the high partial pressure of low boiling solvents. We supposed that usage of high boiling solvents could allow hydrogenolysis to be performed at the lower pressure. Ethylene glycol and propylene glycol are of particular interest as such kind of solvent since they are both the main products of glucose hydrogenolysis. In this work, the process of hydrogenolysis of glucose and fructose over Cu / MgO-ZrO2 catalyst have been studied at temperature range of 160-200 °C and a pressure of 0.1-0.3 MPa in a flow reactor. The solvents were simultaneously the target products of the reaction - ethylene glycol and / or propylene glycol. Gas chromatography and 13C NMR were used for the reaction products identification. It was found that the solubility of glucose in propylene glycol is 21 % by weight, and in ethylene glycol 62% by weight. It was pointed out that the process of hydrogenolysis can take place at a pressure close to atmospheric. Under these conditions, the conversion of hexoses reaches 96-100 %. The reaction products are preferably propylene glycol and ethylene glycol. The total selectivity for C3-2 polyols is 90-94 %, that is higher than in the hydrogenolysis of glucose in aqueous solution.

The Effect of Acidity of Al and Fe Silicates with MFI Structure on Benzene and Toluene Alkylation with Isopropyl Alcohol

1996 ◽  
Vol 61 (8) ◽  
pp. 1115-1130 ◽  
Author(s):  
Jiří Čejka ◽  
Naděžda Žilková ◽  
Blanka Wichterlová
Keyword(s):  
Kinetic Study ◽  
Molecular Sieves ◽  
Isopropyl Alcohol ◽  
Acid Sites ◽  
Transport Rate ◽  
Reaction Products ◽  
Oh Groups ◽  
Benzene Alkylation ◽  
Toluene Alkylation ◽  
Low Strength

Kinetic study of toluene and benzene alkylation with isopropyl alcohol on alumo- and ferrisilicates of MFI structure has shown that the alkylation activity does not follow the acidity (both the number and strength of bridging OH groups) of these molecular sieves. The rate of the overall reaction is controlled by the desorption/transport rate of bulky, strongly adsorbed cymenes and cumene. A higher concentration of n-propyltoluenes compared to n-propylbenzene, both undesired reaction products, formed via a bimolecular isomerization of isopropyl aromate with benzene or toluene, was due to the higher reactivity of isopropyltoluene with toluene in comparison with that of cumene with benzene. It is concluded that ferrisilicates of MFI structure possessing low strength acid sites appear to be promising catalysts for achieving both a high isopropyl- and para-selectivity in toluene alkylation to p-cymene.

scholarly journals Glucose Conversion into 5-Hydroxymethylfurfural over Niobium Oxides Supported on Natural Rubber-Derived Carbon/Silica Nanocomposite

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 887
Author(s):  
Rujeeluk Khumho ◽  
Satit Yousatit ◽  
Chawalit Ngamcharussrivichai
Keyword(s):  
Natural Rubber ◽  
Lewis Acid ◽  
Value Added ◽  
Acid Sites ◽  
Superior Performance ◽  
Lewis Acidity ◽  
Lewis Acid Sites ◽  
Niobium Oxides ◽  
Silica Nanocomposite ◽  
Loading Amount

5-Hydroxymethylfurfural (HMF) is one of the most important lignocellulosic biomass-derived platform molecules for production of renewable fuel additives, liquid hydrocarbon fuels, and value-added chemicals. The present work developed niobium oxides (Nb2O5) supported on mesoporous carbon/silica nanocomposite (MCS), as novel solid base catalyst for synthesis of HMF via one-pot glucose conversion in a biphasic solvent. The MCS material was prepared via carbonization using natural rubber dispersed in hexagonal mesoporous silica (HMS) as a precursor. The Nb2O5 supported on MCS (Nb/MCS) catalyst with an niobium (Nb) loading amount of 10 wt.% (10-Nb/MCS) was characterized by high dispersion, and so tiny crystallites of Nb2O5, on the MCS surface, good textural properties, and the presence of Bronsted and Lewis acid sites with weak-to-medium strength. By varying the Nb loading amount, the crystallite size of Nb2O5 and molar ratio of Bronsted/Lewis acidity could be tuned. When compared to the pure silica HMS-supported Nb catalyst, the Nb/MCS material showed a superior glucose conversion and HMF yield. The highest HMF yield of 57.5% was achieved at 93.2% glucose conversion when using 10-Nb/MCS as catalyst (5 wt.% loading with respect to the mass of glucose) at 190 °C for 1 h. Furthermore, 10-Nb/MCS had excellent catalytic stability, being reused in the reaction for five consecutive cycles during which both the glucose conversion and HMF yield were insignificantly changed. Its superior performance was ascribed to the suitable ratio of Brønsted/Lewis acid sites, and the hydrophobic properties generated from the carbon moieties dispersed in the MCS nanocomposite.

scholarly journals Tuning the Reaction Selectivity over MgAl Spinel-Supported Pt Catalyst in Furfuryl Alcohol Conversion to Pentanediols

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 415
Author(s):  
Xinsheng Li ◽  
Jifeng Pang ◽  
Jingcai Zhang ◽  
Xianquan Li ◽  
Yu Jiang ◽  
...  
Keyword(s):  
Furfuryl Alcohol ◽  
Pt Nanoparticles ◽  
Catalytic Performance ◽  
Major Product ◽  
Pt Catalyst ◽  
Reaction Products ◽  
Strong Base ◽  
Reaction Selectivity ◽  
Supported Pt Catalysts ◽  
Alcohol Conversion

Catalytic conversion of biomass-derived feedstock to high-value chemicals is of remarkable significance for alleviating dependence on fossil energy resources. MgAl spinel-supported Pt catalysts were prepared and used in furfuryl alcohol conversion. The approaches to tune the reaction selectivity toward pentanediols (PeDs) were investigated and the catalytic performance was correlated to the catalysts’ physicochemical properties based on comprehensive characterizations. It was found that 1–8 wt% Pt was highly dispersed on the MgAl2O4 support as nanoparticles with small sizes of 1–3 nm. The reaction selectivity did not show dependence on the size of Pt nanoparticles. Introducing LiOH onto the support effectively steered the reaction products toward the PeDs at the expense of tetrahydrofurfuryl alcohol (THFA) selectivity. Meanwhile, the major product in PeDs was shifted from 1,5-PeD to 1,2-PeD. The reasons for the PeDs selectivity enhancement were attributed to the generation of a large number of medium-strong base sites on the Li-modified Pt catalyst. The reaction temperature is another effective factor to tune the reaction selectivity. At 230 °C, PeDs selectivity was enhanced to 77.4% with a 1,2-PeD to 1,5-PeD ratio of 3.7 over 4Pt/10Li/MgAl2O4. The Pt/Li/MgAl2O4 catalyst was robust to be reused five times without deactivation.

Ir–Re alloy as a highly active catalyst for the hydrogenolysis of glycerol to 1,3-propanediol

2015 ◽  
Vol 5 (3) ◽  
pp. 1540-1547 ◽  
Author(s):  
Chenghao Deng ◽  
Xuezhi Duan ◽  
Jinghong Zhou ◽  
Xinggui Zhou ◽  
Weikang Yuan ◽  
...  
Keyword(s):  
Active Catalyst ◽  
Structured Catalyst ◽  
Highly Active ◽  
Enhanced Resistance ◽  
Glycerol Hydrogenolysis ◽  
First Time ◽  
Alloy Catalyst

We report for the first time the synthesis of a Ir–Re alloy catalyst, which exhibits significantly improved activity in glycerol hydrogenolysis and enhanced resistance against particle sintering compared with a Ir–ReOx structured catalyst.

scholarly journals Regenerable Acidity of Graphene Oxide in Promoting Multicomponent Organic Synthesis

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Virgilio D. Ebajo ◽  
Cybele Riesse L. Santos ◽  
Glenn V. Alea ◽  
Yuya A. Lin ◽  
Chun-Hu Chen
Keyword(s):  
Graphene Oxide ◽  
Organic Synthesis ◽  
Lewis Acid ◽  
Photoelectron Spectroscopy ◽  
Acid Sites ◽  
Lewis Acidity ◽  
Epoxide Ring ◽  
Multicomponent Synthesis ◽  
Lewis Acid Sites ◽  
Toxic Reaction

Abstract The Brønsted acidity of graphene oxide (GO) materials has shown promising activity in organic synthesis. However, roles and functionality of Lewis acid sites remain elusive. Herein, we reported a carbocatalytic approach utilizing both Brønsted and Lewis acid sites in GOs as heterogeneous promoters in a series of multicomponent synthesis of triazoloquinazolinone compounds. The GOs possessing the highest degree of oxidation, also having the highest amounts of Lewis acid sites, enable optimal yields (up to 95%) under mild and non-toxic reaction conditions (85 °C in EtOH). The results of FT-IR spectroscopy, temperature-programed decomposition mass spectrometry, and X-ray photoelectron spectroscopy identified that the apparent Lewis acidity via basal plane epoxide ring opening, on top of the saturated Brønsted acidic carboxylic groups, is responsible for the enhanced carbocatalytic activities involving Knoevenagel condensation pathway. Recycled GO can be effectively regenerated to reach 97% activity of fresh GO, supporting the recognition of GO as pseudocatalyst in organic synthesis.

Oligomerization of pent-1-ene over zeolite catalysts

2019 ◽  
Vol 19 (4) ◽  
pp. 307-315
Author(s):  
N. G. Grigoryeva ◽  
D. V. Serebrennikov ◽  
S. V. Bubennov ◽  
B. I. Kutepov
Keyword(s):  
Catalytic Properties ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Main Reaction ◽  
Reaction Products ◽  
High Concentration ◽  
Reaction Conditions ◽  
One Dimensional ◽  
Fuel Components ◽  
Channel Systems

Oligomerization of pent-1-ene is an effective process for synthesis of high-quality environmentally friendly fuel components. Catalytic properties of H-zeolites FAU, OFF, MOR, ВЕА, MTW and MFI were studied for synthesis of pentene oligomers in an autoclave at 110–200 °C. The wide-pore structure of H-Y and H-Beta (18) zeolites and the high concentration of acid sites were established to cause the high oligomerization activity to obtain 97–100 % yields of oligomers. Oligomers obtained over these catalysts comprised, depending on the reaction conditions, 30–73 % dimers, 25–50 % trimers and 2–14 % oligomers with more than three monomer units (n > 3). Fine-pore zeolites (H-ZSM-5) and zeolites with one-dimensional channel systems (H-OFF, H-MOR, H-ZSM-12) were less active to oligomerization of pent-1-ene, decenes being the main reaction products.

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