Effect of different seed sources on the hydrothermal crystallization of MCM-22 zeolite catalysts

CrystEngComm ◽  
2018 ◽  
Vol 20 (25) ◽  
pp. 3467-3475 ◽  
Author(s):  
Mariana V. Rodrigues ◽  
Luiz H. Vieira ◽  
Guilherme P. Campos ◽  
Leandro Martins
Keyword(s):  
Mother Liquor ◽  
Zeolite Catalysts ◽  
Hydrothermal Crystallization ◽  
Considerable Decrease ◽  
Seed Sources ◽  
Crystallite Sizes

Ball-milled MCM-22 and dried mother liquor seeds proved to be effective in the synthesis of the MCM-22P lamellar precursor with a low Si/Al ratio. Crystallization times were reduced from 25 to 2–4 days with a considerable decrease in crystallite sizes.

Temperature-regulated construction of hierarchical titanosilicate zeolites

2020 ◽  
Vol 7 (9) ◽  
pp. 1872-1879
Author(s):  
Yue Song ◽  
Risheng Bai ◽  
Yongcun Zou ◽  
Zhaochi Feng ◽  
Jihong Yu
Keyword(s):  
Zeolite Catalysts ◽  
Organic Template ◽  
Hydrothermal Crystallization ◽  
Tetrabutylammonium Hydroxide

A temperature-regulated method was developed to construct anatase-free hierarchical TS-1 zeolite catalysts by utilizing a two-step hydrothermal crystallization strategy with tetrabutylammonium hydroxide as the sole organic template.

scholarly journals Effects of Crystallite Sizes of Pt/HZSM-5 Zeolite Catalysts on the Hydrodeoxygenation of Guaiacol

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2246
Author(s):  
Haonan Duan ◽  
Yajie Tian ◽  
Siyuan Gong ◽  
Bofeng Zhang ◽  
Zongjing Lu ◽  
...  
Keyword(s):  
Reaction Rate ◽  
Reaction Pathway ◽  
Zeolite Catalysts ◽  
Reaction Pathways ◽  
Bulk Crystals ◽  
Support Interaction ◽  
Metal Support Interaction ◽  
Metal Support ◽  
Acidic Sites ◽  
Crystallite Sizes

Herein, Pt/HZSM-5 zeolite catalysts with different crystallite sizes ranging from nanosheet (~2 nm) to bulk crystals (~1.5 μm) have been prepared for the hydrodeoxygenation of guaiacol, and their effects on the reaction pathway and product selectivity were explored. HZSM-5 zeolites prepared by seeding (Pt/Z-40: ~40 nm) or templating (Pt/NS-2: ~2 nm) fabricated intra-crystalline mesopores and thus enhanced the reaction rate by promoting the diffusion of various molecules, especially the bulky ones such as guaiacol and 2-methoxycyclohexanol, leading to a higher cyclohexane selectivity of up to 80 wt % (both for Pt/Z-40 and Pt/NS-2) compared to 70 wt % for bulky HZSM-5 (Pt/CZ: ~1.5 μm) at 250 °C and 120 min. Furthermore, decreased crystallite sizes more effectively promoted the dispersion of Pt particles than bulky HZSM-5 (Pt/Z-400: ~400 nm and Pt/CZ). The relatively low distance between Pt and acidic sites on the Pt/Z-40 catalyst enhanced the metal/support interaction and induced the reaction between the guaiacol molecules adsorbed on the acidic sites and the metal-activated hydrogen species, which was found more favorable for deoxygenation than for hydrogenation of oxygen-containing molecules. In addition, Pt/NS-2 catalyst with a highly exposed surface facilitated more diverse reaction pathways such as alkyl transfer and isomerization.

Advances in ultramicrotomy for physical sciences applications

1993 ◽  
Vol 51 ◽  
pp. 710-711
Author(s):  
G. McMahon ◽  
T. Malis
Keyword(s):  
Particle Surface ◽  
Zeolite Catalysts ◽  
Physical Sciences ◽  
Pull Out ◽  
Large Particles ◽  
Novel Applications ◽  
Metal Wires ◽  
Frequent Problem ◽  
Specific Orientation ◽  
Diamond Knife

As with all techniques which are relatively new and therefore underutilized, diamond knife sectioning in the physical sciences continues to see both developments of the technique and novel applications.Technique Developments Development of specific orientation/embedding procedures for small pieces of awkward shape is exemplified by the work of Bradley et al on large, rather fragile particles of nuclear waste glass. At the same time, the frequent problem of pullout with large particles can be reduced by roughening of the particle surface, and a proven methodology using a commercial coupling agent developed for glasses has been utilized with good results on large zeolite catalysts. The same principle (using acid etches) should work for ceramic fibres or metal wires which may only partially pull out but result in unacceptably thick sections. Researchers from the life sciences continue to develop aspects of embedding media which may be applicable to certain cases in the physical sciences.

Development of a method for multielemental determination in water by EDXRF with radioisotopic source of 238Pu.

2019 ◽  
Vol 7 (2A) ◽  
Author(s):  
Camilo Fuentes Serrano ◽  
Juan Reinaldo Estevez Alvares ◽  
Alfredo Montero Alvarez ◽  
Ivan Pupo Gonzales ◽  
Zahily Herrero Fernandez ◽  
...  
Keyword(s):  
Thin Layer ◽  
Expanded Uncertainty ◽  
Considerable Decrease ◽  
X Ray ◽  
Precipitation Efficiency ◽  
Method Of Determination ◽  
Sensitivity Curves ◽  
Order Of Magnitude ◽  
Metrological Parameters

A method for determination of Cr, Fe, Co, Ni, Cu, Zn, Hg and Pb in waters by Energy Dispersive X Ray Fluorescence (EDXRF) was implemented, using a radioisotopic source of 238Pu. For previous concentration was employed a procedure including a coprecipitation step with ammonium pyrrolidinedithiocarbamate (APDC) as quelant agent, the separation of the phases by filtration, the measurement of filter by EDXRF and quantification by a thin layer absolute method. Sensitivity curves for K and L lines were obtained respectively. The sensitivity for most elements was greater by an order of magnitude in the case of measurement with a source of 238Pu instead of 109Cd, which means a considerable decrease in measurement times. The influence of the concentration in the precipitation efficiency was evaluated for each element. In all cases the recoveries are close to 100%, for this reason it can be affirmed that the method of determination of the studied elements is quantitative. Metrological parameters of the method such as trueness, precision, detection limit and uncertainty were calculated. A procedure to calculate the uncertainty of the method was elaborated; the most significant source of uncertainty for the thin layer EDXRF method is associated with the determination of instrumental sensitivities. The error associated with the determination, expressed as expanded uncertainty (in %), varied from 15.4% for low element concentrations (2.5-5 μg/L) to 5.4% for the higher concentration range (20-25 μg/L).

A Guide to Southern Pine Seed Sources

1987 ◽  
Author(s):  
Clark W. Lantz ◽  
John F. Kraus
Keyword(s):  
Southern Pine ◽  
Seed Sources

FORCE CONDITIONS OF TRANSITION TO ONE-ZONE PROCESS OF BACKWARD SLIP DURING COLD ROLLING OF STRIPS

2020 ◽  
pp. 45-53
Author(s):  
L.S. Kokhan ◽  
◽  
A.V. Aldunin ◽  
Keyword(s):  
Service Life ◽  
Cold Rolling ◽  
Considerable Decrease ◽  
Steel Strips ◽  
Increase Service Life

Results of analytical researches of power parameters of cold rolling of thin and average steel strips with a back tension are presented. Considerable decrease in average relative tension on a surface of contact with rolling rolls upon transition is established from two-zonal to one-zonal rolling of lag. It allows to increase service life of rolling rolls.

Analysis of crystallite size changes in a hematite and magnetite formed on steel used in the power idustry

2017 ◽  
Vol 1 (21) ◽  
pp. 65-73
Author(s):  
Monika Gwoździk
Keyword(s):  
Elevated Temperature ◽  
Oxide Layer ◽  
Cross Section ◽  
X Ray ◽  
Term Operation ◽  
Diffraction Line Profile ◽  
Crystallite Sizes ◽  
Scherrer Formula ◽  
Pipe Outlet

The paper presents results of studies on the crystallite sizes of oxide layer formed during a long-term operation on 10CrMo9-10 steel at an elevated temperature (T = 545° C, t = 200,000 h). This value was determined by a method based on analysis of the diffraction line profile, according to a Scherrer formula. The oxide layer was studied on a surface and a cross-section at the outer and inner site on the pipe outlet, at the fire and counter-fire wall of the tube. X-ray studies were carried out on the surface of a tube, then the layer’s surface was polished and the diffraction measurements repeated to reveal differences in the originated oxides layer.

Performance of Ag-HZSM-5 Zeolite Catalysts in n-heptane Conversion

2017 ◽  
Vol 68 (1) ◽  
pp. 116-120
Author(s):  
Iuliean Vasile Asaftei ◽  
Neculai Catalin Lungu ◽  
Lucian Mihail Birsa ◽  
Ioan Gabriel Sandu ◽  
Laura Gabriela Sarbu ◽  
...  
Keyword(s):  
Aromatic Hydrocarbons ◽  
Metal Content ◽  
Pulse Method ◽  
Acid Strength ◽  
Strength Distribution ◽  
Zeolite Catalysts ◽  
Benzene Toluene ◽  
Acid Strength Distribution ◽  
Silver Cations ◽  
Heptane Conversion

The conversion of n-heptanes into aromatic hydrocarbons benzene, toluene and xylenes (BTX), by the chromatographic pulse method in the temperature range of 673 - 823K was performed over the HZSM-5 and Ag-HZSM-5 zeolites modified by ion exchange with AgNO3 aqueous solutions. The catalysts, HZSM-5 (SiO2/Al2O3 = 33.9), and Ag-HZSM-5 (Ag1-HZSM-5 wt. % Ag1.02, Ag2-HZSM-5 wt. % Ag 1.62; and Ag3-HZSM-5 wt. % Ag 2.05 having different acid strength distribution exhibit a conversion and a yield of aromatics depending on temperature and metal content. The yield of aromatic hydrocarbons BTX appreciably increased by incorporating silver cations Ag+ into HZSM-5.

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