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1.
Hydrothermal conversion of rice husk ash to faujasite-types and NaA-type of zeolites 总被引:1,自引:0,他引:1
The faujasite-type of zeolites (NaX and NaY) and NaA-type of zeolite were synthesized from rice husk ash (RHA) via the hydrothermal
conditions. The combustion of rice husk at controlled temperature of 600 °C for an hour in open air produce more than 90%
of amorphous silica in the ash which was reactive towards the synthesis of zeolites. The formation of zeolite NaY from RHA
is metastable and thus, the seeding and ageing effects in the synthesis of zeolite NaY were investigated to avoid the formation
of zeolite A or P as the impurities in zeolite NaY. Zeolites NaX and NaA were also successfully synthesized with high purity,
absence of impurities and other phases, and high reproducibility. Thus, the amorphous forms of silica in RHA can be used as
a source of silica for the synthesis of faujasite-types and NaA-type of zeolites. 相似文献
2.
Ghazale Mehmandoust Afshin Pourahmad 《Journal of Inorganic and Organometallic Polymers and Materials》2018,28(6):2213-2220
White rice husk silica (RHS), an agriculture waste, was used as a silica source for ZSM-12 (MTW) zeolite synthesis. The ZSM-12 zeolite derived from RHS was prepared by hydrothermal method at 150 °C in the presence of tetraethylammonium hydroxide. Zinc oxide nanoparticles (NPs) were grown in zeolite substrates using a solid state reaction. The crystallization of ZSM-12 zeolite and ZnO/ZSM-12 nanocomposite (NC) was monitored by XRD, FTIR and SEM, TEM, and BET techniques. It was found that complete crystallization of ZSM-12 zeolite phase was achieved after 6 days. The XRD patterns declared the presence of both ZnO NPs and ZSM-12 zeolite in NC. The SEM image of ZSM-12 and NC demonstrated large spherical aggregates with size diameter of 2.5 µm. The TEM image of ZSM-12 showed formation of ZnO NPs with particle size ~?35 nm on ZSM-12 zeolite. The BET results indicated that pore volume and surface area of ZnO/ZSM-12 NC was bigger than ZSM-12 zeolite. On the basis of the obtained experimental results, it was founded that ZnO NPs were encapsulated into channels of ZSM-12 zeolite.
相似文献
3.
Jan-Jezreel F. Saceda Kamolwan Rintramee Supattra Khabuanchalad Sanchai Prayoonpokarach Rizalinda L. de Leon Jatuporn Wittayakun 《Journal of Industrial and Engineering Chemistry》2012,18(1):420-424
Zeolite Y in sodium form (NaY) was synthesized using silica source from rice husk, transformed to ammonium form (NH4Y), and calcined to convert to proton form (HY). The direct conversion of NH4Y to HY resulted in loss of the zeolite crystallinity and lower surface area. Thus, the NH4Y was further used in the preparation of cerium (Ce) catalysts. The NH4Y was also treated with a basic solution in an attempt to generate mesopores but only site defects were likely formed. The supported Ce catalysts with good Ce dispersion were prepared by wetness impregnation of Ce precursor solution on NaY, NH4Y, and base-treated NH4Y. Upon calcination, the generated catalysts were notated as Ce/NaY, Ce/HY, and Ce/YB. In catalytic testing on ethanol oxidation at varying temperature in a continuous laboratory-scale fixed-bed reactor, all the zeolites gave low ethanol conversion at 100–300 °C. The catalytic activity significantly improved with the presence of Ce. The Ce/YB showed the higher ethanol conversion and CO2 yield than Ce/NaY and Ce/HY probably because of the presence of more local site defects on the zeolite. 相似文献
4.
Chaiwat Prompubess Lursuang Mekasut Pornpote Piumsomboon Prapan Kuchontara 《Korean Journal of Chemical Engineering》2007,24(6):989-995
In this research, co-combustion of coal and rice husk was studied in a circulating fluidized bed combustor (CFBC). The effects
of mixed fuel ratios, primary air and secondary air flow rates on temperature and gas concentration profiles along riser (0.1
m inside diameter and 3.0 m height) were studied. The average particle size of coal from Maetah used in this work was 1,128
mm and bed material was sand. The range of primary air flow rates was 480–920 l/min corresponding to U
g
of 1.0–2.0 m/s for coal feed rate at 5.8 kg/h. The recirculation rate through L-valve was 100 kg/hr. It was found that the
temperatures along the riser were rather steady at about 800–1,000 degrees Celsius. The introduction of secondary air improved
combustion and temperature gradient at the bottom of the riser, particularly at a primary air flow rate below 1.5 m/s. Blending
of coal with biomass, rice husk, did improve the combustion efficiency of coal itself even at low concentration of rice husk
of 3.5 wt%. In addition, the presence of rice husk in the feed stocks reduced the emission of both NO
x
and SO2. 相似文献
5.
N.A. Oladoja I.A. OloladeO.A. Alimi T.A. AkinnifesiG.A. Olaremu 《Chemical Engineering Research and Design》2013
An environmentally benign metal oxide, Fe, was incorporated into silica derived from rice husk via the sol gel route and the physiognomies of both the modified (IRS) and raw rice husk derived silica (RHS) were studied via FTIR and XRD analysis and pHPZC and surface area determinations. The stability of the Fe incorporated into the silica matrix, determined via the toxicity characteristic leaching procedure, showed that the integrity of the sorbent was intact only in basic medium but got vitiated in acidic medium. The sorption process conformed to the pseudo second order model than reversible first order and pseudo first order kinetic models and the rate of sorption of Cr(VI) onto either sorbents was determined by film diffusion. Process variables optimization showed that the amount of Cr(VI) removed per gram of sorbent reduced with increase in initial solution pH and the negative impact of the anionic interference was more in the presence of SO32− than NO32− and Cl−. The predicted Langmuir monolayer sorption capacity (mg/g) of the IRS (63.69) was higher than that of the RHS (61.35). The value of the mean free energy (kJ/mol) of sorption, obtained for IRS (267.26) and RHS (100.00), and the significant changes in the peak positions of specific functional groups on the Cr(VI) laden sorbents showed that chemisorption was the dominant mechanism of Cr(VI) uptake. 相似文献
6.
This paper focuses on the synthesis of NaY zeolite crystals by using microwave-hydrothermal (M-H) processing. NaY zeolites were synthesized from colloidal silica, sodium aluminate, sodium hydroxide and deionized water at 100°C, and some properties were studied. NaY zeolite crystals with high surface area, in the range of 439 to 716 m2/g, have been prepared at 100°C for 1 to 3 hrs. Compared to the formation of NaY zeolite via conventional-hydrothermal (C-H) treatment, the M-H treatment led to increased rate of formation by 3 to 4 times. 相似文献
7.
采用物理法将稻壳炭化,炭化料用酸碱处理,固体残渣经高温水蒸汽活化制备活性炭,脱灰液体采用沉淀法制备SiO2. 结果表明,用2.5 mol/L NaOH溶液按液固比10 mL/g脱灰的炭化料所制活性炭比表面积为961.8 m2/g,比不脱灰炭化料所制活性炭增加136%,总孔容积增加103.8%,对碘和亚甲基蓝的吸附容量分别为1270和300 mg/g. 在10% HCl、煅烧温度600℃条件下所制SiO2粒径为40~60 nm,为无定型结构,比表面积达330 m2/g,纯度达99.84%. 相似文献
8.
9.
Khalil Ahmed Shaikh Sirajuddin Nizami Nudrat Zahid Raza 《Journal of Industrial and Engineering Chemistry》2013,19(4):1169-1176
This paper discusses an extensive overview of characterization of marble sludge (MS) with carbon black (CB) and rice husk derived silica (RHS) in hybrid natural rubber (NR) composite. Cure characteristics, mechanical and swelling properties of MS/CB and MS/RHS hybrid NR composite were investigated. As CB and RHS content increases in weight ratio of MS/CB and MS/RHS a decrease in scorch and cure time and increase in the torque, tensile, tear, modulus, hardness, crosslink density were observed, while elongation at break and swelling coefficient decreased. The aging behavior of corresponding hybrid composite materials was also evaluated at two different temperatures. 相似文献
10.
Amit Kumar Milan K. Naskar 《International Journal of Applied Ceramic Technology》2019,16(4):1525-1532
Dice-shaped zeolite A (NaA) was prepared via direct dissolution of rice husk ash (96.5% SiO2) in the presence of NaOH and sodium aluminate solution by autoclave process at 90°C/6 h without using any templating agent. The prepared particles were characterized by DTA/TG, XRD, FTIR, N2 adsorption-desorption physisorption analysis, FESEM, and TEM. XRD results confirmed crystallization of pure NaA zeolite phase. FTIR study shows the characteristic bands at 554 cm−1 for double 4 membered ring (D4R) of NaA zeolite. The total BET surface area of the product was found to be 31.6 m2 g−1. FESEM and TEM images show dice shaped NaA particles of size around 1 μm which is formed via oriented crystalline aggregation of primary particles (30-40 nm). A tentative mechanism was proposed for the formation of NaA crystals through direct dissolution of rice husk ash. The synthesized NaA zeolite could be used for purification of alcohol and separation of toxic and radioactive ions from waste water via a cost-effective process. 相似文献
11.
Dhinasekaran Durgalakshmi Rajendran Ajay Rakkesh Balakumar Subramanian 《International Journal of Applied Ceramic Technology》2020,17(4):1976-1984
The sol-gel route of synthesizing bioactive glasses of composition 45S5 has shown higher compatibility than the melt casting method. In bioactive glass synthesis, a major silica source is derived from the synthetic tetraethyl orthosilicate precursor. This work demonstrates the sol–gel-derived bioactive glass prepared from rice husk and TEOS as silica sources. In this study, the effect of crystallization with respect to the silica source in bioactive glass composition was investigated to gain further understanding on the processes involved in the fabrication of bioglass. The in vitro biodegradation and apatite formation of the bioactive glass in simulated body fluid was investigated by spectroscopic and morphological studies. Both the bioactive glasses show a change in morphology toward nanostructured apatite formation after in vitro immersion studies. Further, the hemocompatibility of bioactive glass prepared using rice husk is similar to bioactive glass prepared from organic silica sources. This promises the possibility of synthesizing low cost and biocompatible bioactive glass 45S5 system for tissue engineering applications. 相似文献
12.
Bijan Bihari Nayak Bishnu Charanarabinda Mohanty Saroj Kumar Singh 《Journal of the American Ceramic Society》1996,79(5):1197-1200
SiC particles have been synthesized in the α-phase from a mixture of boiler-burnt rice husk and graphite powder in a dc extended arc plasma reactor on a 200–250 g scale. A SiC yield as high as 72% was achieved at a 3.03:1 carbon-to-silica ratio. 21R polytypism, which is rare to grow, was observed in the SiC. About 90% of the SiC particles produced were found to lie under 163 μm, 50% under 90 μm, and 10% under 28 μm size. Very fine particles under 10 μm size occurred to the extent of 3%. XRD and SEM characterizations were carried out to study the phase and morphology of the particles. Heterogeneous gas-phase reactions seem to be responsible for intermediate-size SiC particle growth in the multitemperature zone dc extended arc plasma reactor. 相似文献
13.
Mesoporous silica SBA-15 samples were subjected to microwave heating for 10–40 min at 393 and 443 K after dry-impregnation
with TPAOH (tetrapropylammonium hydroxide) to prepare a mesoporous material with zeolytically ordered pore walls. Physicochemical
properties of the materials prepared were characterized by XRD, N2 adsorption at 77 K, SEM, TEM, UV–vis and FT-IR spectroscopies. These investigations revealed that selective transformation
of amorphous pore walls of SBA-15 to crystalline zeolytic phase is difficult to be achieved and a mixed phase of mesoporous
silica/zeolite composite material was obtained, instead. Microwave heating time, temperature, TPAOH concentration, and hydrothermal
stability of the mesoporous host materials tested (MCM-41, HMS, and SBA-15) were important factors to maintain the mesopore
structure of the host materials during the post-synthetic microwave heating treatment. 相似文献
14.
Silica powder at nanoscale was obtained by heat treatment of Vietnamese rice husk following the sol–gel method. The rice husk ash (RHA) is synthesized using rice husk which was thermally treated at optimal condition at 600°C for 4 h. The silica from RHA was extracted using sodium hydroxide solution to produce a sodium silicate solution and then precipitated by adding H2SO4 at pH = 4 in the mixture of water/butanol with cationic presence. In order to identify the optimal condition for producing the homogenous silica nanoparticles, the effects of surfactant surface coverage, aging temperature, and aging time were investigated. By analysis of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, the silica product obtained was amorphous and the uniformity of the nanosized sample was observed at an average size of 3 nm, and the BET result showed that the highest specific surface of the sample was about 340 m2/g. The results obtained in the mentioned method prove that the rice husk from agricultural wastes can be used for the production of silica nanoparticles. 相似文献
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17.
Local rice husk was precleaned and properly heat treated to produce high purity amorphous SiO2 for use in the synthesis of ZSM-5 zeolite and silicalite by hydrothermal treatment (150 °C) of the precursor gels (pH 11) under autogenous pressure in a short reaction time (4–24 h). A wide range of SiO2/Al2O3 molar ratios (30–2075) and a small template content were employed to fully exploit the potential of rice husk ash (RHA). The mineralogical phases, morphology, specific surface area and pore volume of the synthesized products were investigated by XRD, FT-IR, SEM and BET analyses, respectively. Under the employed conditions, it was found that the gels with a low range of SiO2/Al2O3 molar ratios (<80) produced an amorphous phase to poorly crystalline ZSM-5 zeolite; those with a medium range (80–200) favored well crystalline ZSM-5 zeolite production with a large surface area; whilst those with a high range of SiO2/Al2O3 molar ratios (>200) yielded silicalite. The increase in Na2O content, which was derived from the addition of NaAlO2 to attain the desired SiO2/Al2O3 molar ratio of the gel, did not significantly enhance the crystallization rate, crystallinity, or yield of products. On the contrary, these properties were greatly affected by the increase in the SiO2/Al2O3 molar ratio. 相似文献
18.
Roghayeh Khaleghian-Moghadam Fakhry Seyedeyn-Azad 《Microporous and mesoporous materials》2009,120(3):285-293
Pure and high crystalline low silica X-type zeolite with Si/Al ratio of 1 was synthesized under specific hydrothermal conditions. After preparation and characterization of Na form of the zeolite (Na-LSX) from the synthesized zeolite, Na cations were exchanged by three alkaline earth cations. The amount of the exchanged cations per 1 g of the zeolite for each cation was determined by wet chemical method. Among the various prepared samples, those containing approximately equal amount of different cations were selected and characterized by XRD, IR, and XRF techniques. TGA/DTG/DTA and XRD techniques were employed to investigate thermal behavior of the cation exchanged zeolites. 相似文献
19.
Paola Catalfamo Letterio Mavilia Patrizia Primerano Francesco Corigliano 《Journal of Porous Materials》2007,14(3):285-289
Ascorbic acid is commonly used as an antioxidant agent in form of a powder. This allows the immediate availability of the
molecule but cannot avoid the rapid inactivation of the excess. Sodium zeolites have frequently been proposed as agents for
the controlled release of absorbed molecules. In order to prepare controlled release antioxidant agents, we treated sodium
X and Y zeolites with ascorbic acid dissolved in organic solvents in order to establish how much acid they were able to retain
and understand the retention and release mechanism. We found that the acid: (i) undergoes a dissociation and H+/Na+ exchange with zeolite; (ii) is retained as sodium salt while the zeolite is protonated; (iii) is released as a function of
the sodium salt solubility into the solvent used. Thus, the imbibition was function of the nature of the solvent and, in aqueous-organic
solvent mixtures, it was a direct function of the water concentration in the range 0–1% and an inverse function in the range
1–11%. It follows from above that, when sodium zeolite is used as a support for ascorbic acid, water percent in the range
0–11% may control the release as the ascorbate salt into aqueous–organic solvent mixtures. 相似文献
20.
Tao Zhu Seil Yang Dae Ki Choi Kyung Ho Row 《Korean Journal of Chemical Engineering》2010,27(6):1910-1915
To find an ideal adsorbent for carbon dioxide capture, a new polyethyleneimine modified silica gel material was synthesized
with a simple procedure. Three silica gel materials with various particle sizes (15, 25 and 40–63 μm) were prepared and functionalized
with polyethyleneimine. The carbon dioxide adsorption amounts of modified silica gel and non-modified silica gel were calculated
using a mass balance equation at three different temperatures (298.15, 308.15 and 318.15 K), respectively, and the influence
of gas pressure and particle size on adsorption was discussed. Experimental data showed that the carbon dioxide adsorption
capacity of modified silica gel was better than non-modified silica gel, and the adsorption capacity gradually decreased with
increasing particle size. The smaller particle size (15 μm) PEI modified silica gel had the largest adsorption capacity, at
298.15 K, and the adsorption amounts of various particle sizes of PEI-silica better fit the Langmuir isotherm model. 相似文献