Mohd Nazlan Mohd Muhid

29Si MAS NMR, XRD and FESEM studies of rice husk silica for the synthesis of zeolites

We have used rice husk ash as a silica source for the synthesis of zeolites. Amorphous silica is a highly reactive silicon source, but not all silica which is amorphous to XRD is equally suitable. The local structure of amorphous silica was investigated by 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) and field emission scanning electron microscopy (FESEM) in order to optimize the process. The results show that amorphous silica extracted by physical combustion with controlled temperature contains only ∗Si(OSi)4 tetrahedral units and is the most reactive silica source in the synthesis of zeolite Y, compared to other silica samples prepared by chemical extraction and uncontrolled burning. The presence of crystalline cristobalite and trydimite phases and SiOH groups render the silica less active.

The reuse of wastepaper for the extraction of cellulose nanocrystals

The study reports on the preparation of cellulose nanocrystals (CNCs) from wastepaper, as an environmental friendly approach of source material, which can be a high availability and low-cost precursor for cellulose nanomaterial processing. Alkali and bleaching treatments were employed for the extraction of cellulose particles followed by controlled-conditions of acid hydrolysis for the isolation of CNCs. Attenuated total reflectance Fourier Transform Infrared (ATR FTIR) spectroscopy was used to analyze the cellulose particles extracted while Transmission electron microscopy images confirmed the presence of CNCs. The diameters of CNCs are in the range of 3-10nm with a length of 100-300nm while a crystallinity index of 75.9% was determined from X-ray diffraction analysis. The synthesis of this high aspect ratio of CNCs paves the way toward alternative reuse of wastepaper in the production of CNCs.

Alumination of the purely siliceous mesoporous molecular sieve MCM-41 and its hydrothermal conversion into zeolite Na-A

Purely siliceous mesoporous [Si]-MCM-41 has been aluminated using an aqueous solution of sodium aluminate, NaAlO2, to form [Si,Al]-MCM-41 with the framework Si/Al ratio as low as 1.9. 27Al and 29Si magic-angel-spinning (MAS) NMR show that all aluminium is incorporated in the framework. The well resolved X-ray diffraction (XRD) pattern of calcined [Si,Al]-MCM-41 indicates that the mesopore system is stable and that the channel diameter decreases with the increased degree of incorporation of Al. The intensity of lines corresponding to Si(nAl) building blocks in the 29Si MAS NMR spectra reflect changes in the local atomic arrangement upon alumination. Increased reaction temperature at a constant concentration of NaAlO2 enhances the efficiency of the alumination, but increased concentration at constant temperature disrupts the framework structure. Upon treatment with a concentrated (>1 mol 1–1) solution of NaAlO2 at moderate temperatures (100 ± 20 °C), [Si]-MCM-41 is transformed into crystalline zeolite Na-A.

Novel Nanostructured Photocatalyst of Vanadium‐Doped Silica‐Titania Aerogel

An excellent UV and visible irradiation response of vanadium‐doped silica‐titania photocatalysts has been successfully prepared. The designed photocatalyst possesses high surface areas of 610 m2/g. Its outstanding photocatalytic activity is attributed to the presence of tetrahedrally coordinated vanadia species in forms of Ti–O–V bonding. Besides, the incorporation of V extends the light adsorption edge of V‐doped silica titania aerogels and resulting in reduced band gap energy.

Insulator-to-Metal Transition in Potassium-Loaded Zeolite P

Potassium metal was loaded into porous crystals of potassium-form maximum aluminum zeolite P (K-MAP), and optical absorption, electrical resistivity, and magnetic susceptibility measurements were performed. The average loading density of potassium atoms per GIS cage of zeolite P, n, was systematically changed up to 1.09. Optical absorption bands are observed around 1.3–2 eV and grow to dominate the spectrum with increasing n. These absorption bands are assigned to the optical excitations of s-electrons confined in the zigzag channels of GIS cages. The temperature dependence of electrical resistivity ρ indicates insulating properties for \(n \lesssim 1.05\). At n = 1.09, ρ suddenly decreases by several orders of magnitude, and shows metallic properties indicating that an insulator-to-metal transition occurs between n = 1.05 and 1.09. The samples are basically nonmagnetic at any n. The nonmagnetic and insulating phase at \(n \lesssim 1.05\) is explained by the formation of small bipolarons in the spin-singl...

Visible light enabled v and Cr doped titania-silica aerogel photocatalyst

A series of high surface area (~700 m2/g) nanostructured coupled semiconductor photocatalysts (NCSP) based on transition metals (M = Cr, V) doped titania-silica aerogel of various molar ratios of Ti:Si (1:25, 1:33 and 1:50) were synthesized via direct synthesis and wet impregnation methods. All samples reveal well-dispersed TiO2 with three different types of Ti coordination namely isolated Ti, non-isolated Ti and octahedrally coordinated Ti species. Cr and V (5 wt%)-titania silica aerogel under visible light irradiation reduced the bandgap energy of T25 to 2.9 eV. The photocatalytic activity of NCSP is 3 fold more active than photocatalyst supported on amorphous silica. Cr (5 wt%)-titania silica aerogel photocatalyst gives the highest conversion of styrene under both UV and visible light irradiation (55% and 47% respectively).

Maerogel: Alternative for Thermal Barrier Coating Topcoat

Thermal barrier coating (TBC) system has been developed for high temperature applications along with the used of yttria stabilized zirconia (YSZ) as topcoat. Recently, developing coating material made from nanoparticles is widely explored. Thus, maerogel could become a potential candidate for this purpose because it consists of nano porous particle with low in density and low in thermal conductivity. The coating is expected to improve the formation of thermally grown oxide (TGO), thermal stability and increase the insulating capability. However, maerogel need agglomeration process before coating can be made because of it has low mass and high specific area.

25-P-12-Catalytic activity of secondary aluminated mesoporous molecular sieve ALMCM-41 in the Friedel-Crafts reaction of bulky aromatic compounds

Publisher Summary This chapter presents the catalytic activity of secondary aluminated mesoporous molecular sieve AlMCM-41 (AlMCM-41(sec)) in the Friedel–Crafts reaction of bulky aromatic compounds. Characterization indicates that secondary alumination incorporates aluminium into the framework without affecting the long-range order of the mesopores and structural stability of the framework. Friedel–Crafts alkylation of 2,4-di- t -butylphenol with cinnamyl alcohol catalyzed by the A1MCM-41 (sec) catalyst gives a high conversion. 29 Si magic angle spinning nuclear magnetic resonance (MAS NMR) shows a different distribution of aluminium in the framework of MCM-41 by secondary synthesis as compared to direct synthesis. AlMCM-41 (sec) possesses Lewis and Bronsted acidity and is a more efficient catalyst for the reaction of large compounds.

Zeolite-Rubber Blend: A composite with improved mechanical and conducting properties

This paper presents for the first time the study on the effect of compounding zeolites into NR/HDPE blends on the structure, mechanical properties with respect to tensile strength, thermal stability and electrical resistivity. The increase in efficiency of compounding and improved mechanical properties observed are associated with the particle size and framework structure of the zeolites. The particle size of zeolites influences the distribution and homogeneity of the resulting NR/HDPE composite. The mechanical properties such as modulus, tensile strength and % elongation at break also depend on the amount and type of zeolite added. Characterization studies by MAS NMR and TG indicate that the mixing process is physical in nature and has no effect on the structure and temal properties of the resulting composite. Incorporation of zeolites strongly increases the electrical resistivity of the resulting composite.

Eco-Friendly Synthesis of Nanozeolite NaA from Rice Husk Ash and its Efficiency in Removing Ammonium Ions

The eco-friendly synthesis of nanozeolite need to be developed in order to minimize the consumption of unwanted excess extracted solutions or solvents and maximize the utilization of beneficial wastes as its raw materials. Thus, the synthesis of nanozeolite NaA from rice husk ash (RHA) without extraction of silica from RHA and without organic template has been successfully achieved. Nanozeolite NaA was synthesized from rice husk ash (RHA) via this main step: aging the aluminosilicate suspension (3.190 Na2O: Al2O3: 1.4SiO2:235.07H2O) for 3 days at room temperature with agitation rate of 150 rpm followed by heating at 55 °C for 18 hours. The nanozeolite NaA was confirmed by XRD, FTIR, FESEM and particle size distribution analysis where the highest particle size was in the range of 100 to 400 nm. Its efficiency in removing ammonium ions in aqueous solution was found to be better than that of microsized zeolite NaA thus proved that the lower particle sizes of zeolite NaA (nanosize) tended to have higher adsorption sites and higher exchange capacity.