Synergetic effects of hydrogenation and acidic sites in phosphorus-modified nickel catalysts for the selective conversion of furfural to cyclopentanone

2021 ◽  
Author(s):  
Guoming Gao ◽  
Yuewen Shao ◽  
Yong Gao ◽  
Tao Wei ◽  
Guanggang Gao ◽  
...  
Keyword(s):  
Nickel Catalysts ◽  
Acid Sites ◽  
Nickel Phosphide ◽  
Selective Conversion ◽  
Synergetic Effects ◽  
Balanced Distribution ◽  
Acidic Sites

Nickel phosphide species can tailor the selectivity of hydrogenation sites. The yields of CPO and CPL reached 93.5% over 15%Ni–25%P/Al2O3. The balanced distribution of hydrogenation/acid sites maximizes the yield of CPO.

Balanced distribution of Brønsted acidic sites and Lewis acidic sites for highly selective conversion of xylose into levulinic acid/ester over Zr-beta catalysts

2019 ◽  
Vol 21 (24) ◽  
pp. 6634-6645 ◽  
Author(s):  
Yuewen Shao ◽  
Kai Sun ◽  
Lijun Zhang ◽  
Qing Xu ◽  
Zhanming Zhang ◽  
...  
Keyword(s):  
Acid Ester ◽  
Levulinic Acid ◽  
Selective Conversion ◽  
Balanced Distribution ◽  
Lewis Acidic Sites ◽  
Acidic Sites

Highly selective conversion of xylose into levulinic acid/ester was achieved over the Zr-beta catalyst with balanced distribution of acidic sites.

scholarly journals Insight into Active Centers and Anti-Coke Behavior of Niobium-Containing SBA-15 for Glycerol Dehydration

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 488
Author(s):  
Katarzyna Stawicka ◽  
Maciej Trejda ◽  
Maria Ziolek
Keyword(s):  
Coke Formation ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Silica Matrix ◽  
High Concentration ◽  
Active Centers ◽  
Acidic Sites ◽  
Glycerol Dehydration ◽  
Adsorption Desorption ◽  
Insight Into

Niobium containing SBA-15 was prepared by two methods: impregnation with different amounts of ammonium niobate(V) oxalate (Nb-15/SBA-15 and Nb-25/SBA-15 containing 15 wt.% and 25 wt.% of Nb, respectively) and mixing of mesoporous silica with Nb2O5 followed by heating at 500 °C (Nb2O5/SBA-15). The use of these two procedures allowed obtaining materials with different textural/surface properties determined by N2 adsorption/desorption isotherms, XRD, UV-Vis, pyridine, and NO adsorption combined with FTIR spectroscopy. Nb2O5/SBA-15 contained exclusively crystalline Nb2O5 on the SBA-15 surface, whereas the materials prepared by impregnation had both metal oxide and niobium incorporated into the silica matrix. The niobium species localized in silica framework generated Brønsted (BAS) and Lewis (LAS) acid sites. The inclusion of niobium into SBA-15 skeleton was crucial for the achievement of high catalytic performance. The strongest BAS were on Nb-25/SBA-15, whereas the highest concentration of BAS and LAS was on Nb-15/SBA-15 surface. Nb2O5/SBA-15 material possessed only weak LAS and BAS. The presence of the strongest BAS (Nb-25/SBA-15) resulted in the highest dehydration activity, whereas a high concentration of BAS was unfavorable. Silylation of niobium catalysts prepared by impregnation reduced the number of acidic sites and significantly increased acrolein yield and selectivity (from ca. 43% selectivity for Nb-25/SBA-15 to ca. 61% for silylated sample). This was accompanied by a considerable decrease in coke formation (from 47% selectivity for Nb-25/SBA-15 to 27% for silylated material).

scholarly journals Inside Back Cover: Lewis Acid Sites Stabilized Nickel Catalysts for Dry (CO2 ) Reforming of Methane (ChemCatChem 24/2016)

ChemCatChem ◽  
2016 ◽  
Vol 8 (24) ◽  
pp. 3814-3814
Author(s):  
Jun Ni ◽  
Jia Zhao ◽  
Luwei Chen ◽  
Jianyi Lin ◽  
Sibudjing Kawi
Keyword(s):  
Lewis Acid ◽  
Nickel Catalysts ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Co2 Reforming ◽  
Back Cover ◽  
Co2 Reforming Of Methane

scholarly journals Nickel-Catalysed Vapour-Phase Hydrogenation of Furfural, Insights into Reactivity and Deactivation

2020 ◽  
Vol 63 (15-18) ◽  
pp. 1446-1462 ◽  
Author(s):  
Kathryn L. MacIntosh ◽  
Simon K. Beaumont
Keyword(s):  
Furfuryl Alcohol ◽  
Copper Chromite ◽  
Catalyst Support ◽  
Nickel Catalysts ◽  
Vapour Phase ◽  
X Ray Diffraction ◽  
Temperature Programmed Oxidation ◽  
Acidic Sites ◽  
Supported Nickel Catalysts ◽  
Temperature Programmed

AbstractFurfural is a key bioderived platform molecule, and its hydrogenation affords access to a number of important chemical intermediates that can act as “drop-in” replacements to those derived from crude oil or novel alternatives with desirable properties. Here, the vapour phase hydrogenation of furfural to furfuryl alcohol at 180 °C over standard impregnated nickel catalysts is reported and contrasted with the same reaction over copper chromite. Whilst the selectivity to furfuryl alcohol of the unmodified nickel catalysts is much lower than for copper chromite as expected, the activity of the nickel catalysts in the vapour phase is significantly higher, and the deactivation profile remarkably similar. In the case of the supported nickel catalysts, possible contribution to the deactivation by acidic sites on the catalyst support is discounted based on the similarity of deactivation kinetics on Ni/SiO2 with those seen for less acidic Ni/TiO2 and Ni/CeO2. Powder X-ray diffraction is used to exclude sintering as a primary deactivation pathway. Significant coking of the catalyst (~ 30 wt% over 16 h) is observed using temperature programmed oxidation. This, in combination with the solvent extraction analysis and infrared spectroscopy of the coked catalysts points to deactivation by polymeric condensation products of (reactant or) products and hydrocarbon like coke. These findings pave the way for targeted modification of nickel catalysts to use for this important biofeedstock-to-chemicals transformation.

scholarly journals The ZSM-5-Catalyzed Oxidation of Benzene to Phenol with N2O: Effect of Lewis Acid Sites

Catalysts ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 44
Author(s):  
Cui Ouyang ◽  
Yingxia Li ◽  
Jianwei Li
Keyword(s):  
Active Sites ◽  
Acid Sites ◽  
X Ray Diffraction ◽  
Remarkable Feature ◽  
Chemisorbed Oxygen ◽  
Lewis Acidic Sites ◽  
Acidic Sites ◽  
Adsorption Desorption ◽  
Oxidation Of Benzene ◽  
N2o Selectivity

The oxidation of benzene to phenol (BTOP) with N2O as the oxidant has been studied with a variety of Fe/ZSM-5 catalysts. The literature has conclusively proven that Fe2+ sites are the active sites. However, some studies have suggested that the Lewis acidic sites (LAS) are responsible for the generation of the active chemisorbed oxygen. Nevertheless, there is no clear relationship between the LAS and the N2O selectivity to phenol. In an effort to elucidate the effects of LAS on BTOP with various ZSM-5 catalysts, we investigated the initial N2O selectivity to phenol. Here we show that the initial N2O selectivity to phenol is negative with the amount of LAS over a certain range. The catalyst H-ZSM-5-ST (H-ZSM-5 treated with water vapor) showed a remarkable initial N2O selectivity to phenol as high as 95.9% with a 0.021 mmol g−1 LAS concentration on the surface of the catalyst, while the Fe/ZSM-5 catalyst demonstrated the lowest initial N2O selectivity to phenol (11.7%) with the highest LAS concentration (0.137 mmol g−1). Another remarkable feature is that steaming was more effective than Fe ion exchange and high temperature calcining. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), N2-adsorption-desorption, UV-vis, NH3-TPD and pyridine Fourier transform infrared (FT-IR) techniques. Our results demonstrate how the concentration of LAS is likely to affect the initial N2O selectivity to phenol within a certain range (0.021–0.137 mmol g−1). This research has demonstrated the synergy between the active Fe2+ sites and LAS.

Study on Preparation and Catalytic Properties of Pd/γ-Al2O3 Catalysts in One-Step Synthesis of Dimethyl Ether

2011 ◽  
Vol 66-68 ◽  
pp. 1404-1409 ◽  
Author(s):  
Rui Zhi Chu ◽  
Zhong Cai Zhang ◽  
Ya Fei Liu ◽  
Xian Liang Meng ◽  
Zhi Min Zong ◽  
...  
Keyword(s):  
Dimethyl Ether ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Co Conversion ◽  
Dimethyl Ether Synthesis ◽  
Acidic Sites ◽  
One Step ◽  
Space Time Yield ◽  
Ether Synthesis ◽  
Synthesis Of Dimethyl Ether

A series of Pd/γ-Al2O3 catalysts with different additons of Pd were prepared by impregnation. The effect of calcination condition and Pd loading on catalytic performance of catalysts for one-step dimethyl ether synthesis has been investigated. The physic-chemical performance and structure of Pd/γ-Al2O3 catalysts were characterized by CO-TPD, TGA and nitrogen physisorption. The results show that the dispersion of Pd and the amount of adsorbration on the CO-bridge of Pd could be increased to by the moderate microwave heating on the catalysts, and the catalyst performance can be improved. But a large number of surface acidic sites of Pd/γ-Al2O3 are covered by highly fragmented Pd-grain, it causes DME selectivity reduced. And the excessive Pd can reduce the samples’ surface acid, decrease the dispersion of the metal Pd and block up the pore of γ-Al2O3. The CO conversion rate and DME space-time yield could reach 60.1% and 28.76 mmol·g-1·h-1 respectively at 2% Pd loading, at this time Pd/γ-Al2O3 has a high Pd activity surface and ideal acid sites.

Dehydration of lactic acid to acrylic acid over lanthanum phosphate catalysts: the role of Lewis acid sites

2016 ◽  
Vol 18 (34) ◽  
pp. 23746-23754 ◽  
Author(s):  
Zhen Guo ◽  
De Sheng Theng ◽  
Karen Yuanting Tang ◽  
Lili Zhang ◽  
Lin Huang ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Acrylic Acid ◽  
Lewis Acid ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Lanthanum Phosphate ◽  
Lewis Acidic Sites ◽  
Acidic Sites ◽  
Nano Rods

Lewis acidic sites on the surface of lanthanum phosphate nano-rods play a crucial role on the catalytic dehydration of lactic acid to acrylic acid.

scholarly journals Highly selective conversion of guaiacol to tert-butylphenols in supercritical ethanol over a H2WO4 catalyst

RSC Advances ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 2764-2771 ◽  
Author(s):  
Fuhang Mai ◽  
Kai Cui ◽  
Zhe Wen ◽  
Kai Wu ◽  
Fei Yan ◽  
...  
Keyword(s):  
High Selectivity ◽  
Acid Sites ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Brønsted Acid Sites ◽  
Effective Catalyst ◽  
Selective Conversion ◽  
Brönsted Acid ◽  
Brönsted Acid Sites ◽  
Supercritical Ethanol

H2WO4 is an effective catalyst for the conversion of guaiacol, and the Brønsted acid sites on H2WO4 surface promote a high selectivity of tert-butylphenols.

scholarly journals NO-CH4-SCR Over Core-Shell MnH-Zeolite Composites

2019 ◽  
Vol 9 (9) ◽  
pp. 1773 ◽  
Author(s):  
Yixiao Li ◽  
Quanhua Wang ◽  
Ding Wang ◽  
Xiaoliang Yan
Keyword(s):  
Catalytic Reduction ◽  
Acid Sites ◽  
Relative Mass ◽  
Excess Oxygen ◽  
Core Shell ◽  
Composite Catalysts ◽  
Beta Zeolites ◽  
Acidic Sites ◽  
New Type ◽  
Zeolite Composite

Selective catalytic reduction of NO with methane (NO-CH4-SCR) in the presence of excess oxygen was investigated over the synthesized MnH-ZZs-n zeolite composite catalysts with FAU (as core) and BEA (as shell) topologies. XRD, SEM, and NH3-TPD technologies were employed to characterize the catalysts. It is found that the topological structure of the zeolite affected the catalytic properties and H2O/SO2 tolerances considerably. MnH-ZZs-n catalysts exhibited much higher NO-CH4-SCR activity than the physical mixture catalysts with comparable relative mass content of Y and Beta zeolites, particularly the ratio of Y and Beta at the range of 0.2–0.5 than the MnH-Beta catalysts with single topology. NH3-TPD results showed that one new type of strong acidic sites formed in H-ZZs-n and remained in MnH-ZZs-n resulted from the interaction between the Lewis and Brönsted acid sites under a particular environment. The special zeolite-zeolite structure with ion-exchanged Mn ions in the core-shell zeolite composite catalysts contributed to the novel NO-CH4-SCR properties.

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