Silica-alumina Ratio Research Articles

FactSage Studies to Identify the Optimum Slag Regime for Blast Furnace Operation

Decreasing the slag rate can lead to a lower fuel rate and higher productivity in the blast furnace (BF). Indian iron ore is known to have adverse alumina–silica ratio. Therefore, to reduce the slag rate there is a need to either remove alumina from the iron ore or to add more silica to dilute the effect of alumina in slag. The latter would increase the slag rate, while the other option is not cost effective. The slag rate can be reduced by operating the BF at high Al2O3%. However, high Al2O3% in BF slag has an adverse impact on liquidus temperature and viscosity. Therefore, there is a prerequisite to identify a slag regime that has low liquidus temperature and low viscosity. In the present work, the FactSage studies of 275 no. of BF slags at wide chemistry variation (Al2O3 = 17–25%, MgO = 8–16%, slag basicity = 0.96–1.2) are conducted to calculate the liquidus temperature and viscosity of slag. Based on the FactSage calculation, it has been identified that 12% MgO coupled with slag basicity ~ 1.0 is the most favorable composition for 22% Al2O3 in slag operation to achieve a lower liquidus temperature and lower viscosity which is essential for efficient BF operation.

Nuclear spin relaxation as a probe of zeolite acidity: a combined NMR and TPD investigation of pyridine in HZSM-5.

The relative surface affinities of pyridine within microporous HZSM-5 zeolites are explored using two-dimensional 1H nuclear magnetic resonance (NMR) relaxation time measurements. The dimensionless ratio of longitudinal-to-transverse nuclear spin relaxation times T1/T2 is shown to exhibit strong sensitivity to the silica/alumina ratio (SAR) of these zeolites, which is indicative of material acidity. This trend is interpreted in terms of increased pyridine surface affinity with decreasing SAR. Temperature programmed desorption (TPD) analysis corroborates this observation, revealing a distinct increase in the heat of desorption associated with adsorbed pyridine as a function of decreasing SAR. A direct correlation between NMR and TPD data suggests NMR relaxation time analysis can be a valuable tool for the non-invasive characterisation of adsorption phenomena in microporous solids.

Effect of Silica-Alumina Ratio of Catalysts on NO Decomposition Rate in Cement Kiln Exhaust

In order to deal with the pollution of NO in cement kiln exhaust, the study of NO catalytic decomposition catalyst obtained much more attention. The effect of silica-alumina ratio on NO decomposition rate in cement kiln without other reductant was studied. The NO decomposition rate of catalysts with different silica-alumina ratio was determined by infrared spectrometer. And pore structures and the microstructure of the catalyst were characterized separately by BET surface area, nitrogen adsorption-desorption and XRD. The results show that silica-alumina ratio of catalyst was preferred to be 50 with the best NO decomposition rate when the temperature was below 300 °C. The catalyst with silica-alumina ratio of 60 has the higher catalytic activity when the temperature was higher than 300 °C, and the decomposition rate achieved 70% at 600 °C. XRD results shows the crystallinity of catalysts increased as the silica-alumina ratio increased. BET surface area and the cumulative pore volume of catalysts gradually increased, and the average pore diameter gradually reduced with the increase of silica-alumina ratio.

Exploring the Potential of Acid Treated Bentonite Clay for Various Catalytic Applications

Clays are widely used as catalysts and catalyst supports for a broad range of chemical processes due to their unique layered structure and low cost. Potential of Bentonite clay from Gujarat region (India) as a catalyst is evaluated in this work. Beneficial properties such as high cation exchange capacity, high absorption capacity, stickiness, expandable layer etc. makes Bentonite clay suitable for a wide range of catalytic applications in chemical process industries. Treatment of Bentonite clay with 5 - 10M sulphuric acid (H2SO4) followed by calcination at 600 0C showed removal of metallic impurities which increased porosity. The physical and chemical characteristics of modified clay were checked by WET process analysis and FTIR. Results showed that increase in acid strength led to better removal of Al3+ ion and other metal oxides thereby increasing silica-alumina ratio. Better surface characteristics indicate that Gujarat Bentonite clay is suitable for use as catalysts and catalyst supports.

Prediction method of coal slagging property in layer-fired boiler

In this article, different coal samples are selected and their physicochemical properties are analyzed. Study and comprehensively analyze various factors affecting slagging. Prediction of coal slagging properties using 12 influencing factors, include: softening temperature, the difference between deformation temperature and flow temperature, characteristic of char residue, sodium oxide content, silicon ratio, silica-alumina ratio, iron-calcium ratio, acid-base oxide ratio, sulfur slagging index, contamination index, chlorine content, inorganic mineral content. The fuzzy clustering analysis method was used to classify and quantify all the influencing factors, and the coal slagging prediction method of layer fired boiler was proposed and verified by application.

Synthesis of Zeolite X from Locally Sourced Kaolin Clay from Kono-Boue and Chokocho, Rivers State, Nigeria

This work describes the development of a process to produce zeolite X from mined kaolin clay from Kono-Boue and Chokocho, Rivers State, Nigeria. The procedures involved the beneficiation of the raw kaolin and calcinations at 850°C, to transform the kaolin to a more reactive metakaolin. Afterwards, the extremely reactive metakaolin was purge with sulphuric acid to obtain the much needed silica-alumina ratio for zeolite X synthesis. An alkaline fusion stage was then carried out to transform the metakaolin into zeolite by mixing with aqueous NaOH to form gel then allowed to stay for a duration of seven days at room temperature. The samples were then charged into a propylene container and placed in an oven at a temperature of 100°C for the reaction to take place for 6 h. Identification of the crystalline phases by X-ray Diffraction (XRD), chemical/elemental compositions by X-ray Fluorescence (XRF)/Energy Dispersive Spectroscopic analyses (EDS), surface morphology by Scanning Electron Microscopy (SEM) and molecular vibration of units by Fourier Transform Infrared Spectrophotometry (FT-IR) were done. The results showed that the zeolite synthesized from Chokocho kaolin (CK) was more crystalline/larger with sharper peaks on both XRD and FTIR than that from Kono-Boue. This was also supported by slightly rougher surface morphology of CK over KK on SEM. XRF Si:Al ratios of 10.73 and 14.36 were obtained for KK and CK respectively. EDS results supported the XRF ratios. Sharper zeolitic characteristic O-H stretching bands at 3488 and 3755 cm-1 were recorded for CK than KK. However, both results showed that zeolite X have been produced from both Kono-Boue and Chokocho kaolin clays respectively.

Kinetic and thermodynamic study of potassium recovery from silicate rocks

ABSTRACT Silicate rocks (mica, feldspar, glauconite, and sericite) having potash values of 7–11% are evaluated as an alternative potash source. Direct leaching of the feed sample in different lixiviants yielded very less potash extraction (1–5%). Heat treatment with suitable flux such as calcium chloride resulted in 100% potash recovery from mica and glauconite, whereas it was limited to 71% and 65% for feldspar and sericite. The activation energy for CaCl2 reaction with mica, feldspar, glauconite, and sericite is 64.35, 70.14, 69.17 and 86.63 kJ/mol. K – extraction is a function of silica-alumina ratio and association of K – bearing phase.

Conversion of Y into SSZ-13 zeolite, in the absence of extra silica, alumina and seed crystals, with N,N,N-dimethylethylcyclohexylammonium bromide, and application of the SSZ-13 zeolite in the propylene production from ethylene

SSZ-13 zeolite (CHA structure) with small pore or 8-membered ring has been widely studied in catalysis and adsorption. Even SSZ-13 might be very useful in such applications, the synthesis usually relies on expensive organic templates. In this study, SSZ-13 was obtained, with a relatively inexpensive template, N,N,N-dimethylethylcyclohexylammonium bromide, from conversion of Y zeolites with wide silica/alumina ratios (SARs), especially in the absence of any crystal seed, additional silica and alumina. The obtained SSZ-13 s have relatively wide SAR of 6.9–36.7; and phase-pure SSZ-13 s could also be obtained from mixture of Y zeolites. The obtained SSZ-13 s, in proton form, were applied in ethylene-to-propylene (ETP) reaction, and the SSZ-13 with suitable SAR (18.8) had not only high propylene yield but also stable propylene production compared with other SSZ-13 s, showing the possible application of the SSZ-13 in ETP reaction.

Synthesis of MOR Zeolite/Magnetite Composite via Seed Assisted Method.

MOR zeolite is an effective adsorbent for separating organic molecules from various solutions owing to its large windows of 0)65 × 0)70 nm and its relatively high silica-alumina ratio which provides higher hydrophobicity. Fine powdery MOR zeolite is desirable for adsorption of organic molecules considering its larger surface area; however, fine particles are difficult to remove from solutions after treatment. Intensification of magnetic susceptibility through combination with magnetic particles ensure quick and easy removal of fine adsorbents by magnetic force. Meanwhile, seed assisted method is a powerful technique to direct and accelerate zeolite synthesis by adding seed crystals into the precursor sol prior to hydrothermal synthesis. In this work, we selected magnetite as the magnetic particle and propose the hydrothermal synthesis of MOR zeolite/magnetite composite via seed assisted method for the first time. MOR zeolite/magnetite composite with high MOR zeolite crystallinity was obtained by synthesizing for only 6 hours at 463 K when adding seed crystals, while no sign of crystallization was observed even after 24 hours in their absence. In addition, pre-milling of seed crystals together with magnetite was found to be effective to incorporate magnetite into MOR zeolite during crystallization and to decrease the primary crystal size of the crystallized MOR zeolite.

Calcination of calcium sulphoaluminate cement using flue gas desulfurization gypsum as whole calcium oxide source

Flue gas desulfurization (FGD) gypsum is an industrial by-product of the desulfurization process. The gross product of FGD gypsum has reached 550 million tons in China by 2016 and quite a portion was discarded. The purpose of this study is to investigate the feasibility of an innovative concept of producing the CSA cement based on sulfur recovery and entirely made of the FGD gypsum to replace natural gypsum and limestone as CaO and SO3 sources. A mixture of industrial solid waste was calcined under different calcination conditions to study the decomposition behavior of FGD gypsum and properties of CSA cement made from the FGD gypsum. Experimental results show that it is feasible to use the FGD gypsum to entirely supply the CaO and SO3 of this cement, the optimized calcination temperature is between 1270 and 1310 °C, and the suitable retention time is 60–100 min. The highest compressive strengths of 63.3, 85.3, 102.8 MPa were attained at 1, 3, and 28 d, respectively when the temperature was kept at 1310 °C for 60 min. Results also indicate that the FGD gypsum decomposition, which is mainly influenced by calcination temperature, retention time and alumina–silica ratio, has a significant impact on the clinker mineral phase formation. The novel technical idea developed in this research can greatly improve the utilization of FGD gypsum and may reduce about 50% of CO2 emission in routine production.

Alumina-silica nano-sorbent from plant fly ash and scrap aluminium foil in removing nickel through adsorption

The alumina-silica nano-sorbent with different alumina-silica ratio were synthesized from thermal power plant fly ash and scrap aluminium foil by alkali extraction, followed by precipitation and calcination. The adsorbent were used successfully for Ni(II) adsorption. The nano-sorbent was characterized by X-ray fluorescence analysis (XRF), X-ray diffraction analysis (XRD), Fourier Transform Infrared spectroscopy (FTIR), Brunauer-Emmet-Teller (BET) analysis, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM). In the BET analysis, the proposed nano-sorbent was found to be mesoporous type with a surface area of 136.18 m2/g, which was about 65 times greater than that of fly ash. The adsorption isotherm confirmed a monolayer adsorption and the kinetic result explained that the chemisorption was predominating in presence of external film and intra-particle pore diffusion. The nature of the adsorption process was observed to be spontaneous and endothermic, at low Ni(II) initial concentration by thermodynamic analysis. The optimal values of the process parameters of equilibrium isotherms, namely pH, initial concentration and temperature were determined. The maximum adsorption capacity of proposed alumina-silica adsorbent for Ni(II) was found to be of 49.754 mg/g.

Synthesis of micro-mesoporous molecular sieve ZSM-5/SBA-15: tuning aluminium content for tert-butylation of phenol

Micro-mesoporous ZSM-5/SBA-15 molecular sieve was derived from mesoporous molecular sieves SBA-15 by hydrothermal crystallization approach. The silica-alumina ratio significantly affects the structure and catalytic performance of ZSM-5/SBA-15. When the $$\hbox {n}_{\mathrm{Si}}\hbox {/n}_{\mathrm{Al}}$$ is less than 25, the two-dimensional hexagonal pore structure of SBA-15 keeps intact with relatively low crystallinity of the pore wall. However, when the $$\hbox {n}_{\mathrm{Si}}\hbox {/n}_{\mathrm{Al}}$$ is larger than 50, the SBA-15 pores are severely damaged. When $$\hbox {n}_{\mathrm{Si}}\hbox {/n}_{\mathrm{Al}}$$ is 25, the catalyst ZSM-5/SBA-15 retains relatively good pore structure and shows excellent catalytic performance with 96.2% phenol conversion and 53.5% selectivity to 2,4-ditert-butyl phenol in the tert-butylation of phenol. SYNOPSIS Micro-mesoporous ZSM-5/SBA-15 molecular sieve was derived from mesoporous molecular sieve SBA-15 by hydrothermal crystallization approach. ZSM-5/SBA-15 ( $$\hbox {n}_{\mathrm{Si}}\hbox {/n}_{\mathrm{Al}}=25$$ ) retains relatively good pore structure and shows excellent catalytic performance with 96.2% phenol conversion and 53.5% selectivity to 2,4-ditert-butyl phenol in the tert-butylation of phenol. Effect of silica-alumina ratio of micro-mesoporous silica ZSM-5/SBA-15 on the catalytic performance of tert-butylation of phenol

Characterization of Kenyan ceramics for production of medium duty alumina firebrick incinerator linings

The aim of this study was to evaluate locally available ceramic raw materials for the manufacture of Medium Duty Alumina Refractory Firebrick for incinerator lining.The clays were collected from two sites, Eburru in Nakuru County and Mukurwe-ini in Nyeri County in Kenya. Atomic Absorption Spectrophotometer and X-Ray Diffraction analytical methods were used to determine the chemical composition of the respective clays before and after firing at 1000OC for two hours.Atomic Absorption Spectrophotometer results revealed that Eburru Kaolin contained the highest amount of silica at 72.64% SiO2 but had the lowest of all other oxides. All the three raw materials were found to increase their oxide percentages after firing due to the loss in moisture and organic matter and reflected on their aluminasilica ratio. The X-Ray Diffraction results showed that the refractory formulated using the clays at a ratio of 2:2:1 Eburru Kaolin : Eburru Fireclay: Mukuruweini Ballclay attained good structural properties after firing at 1000OC for two hours and was comparable to commercial products in the market in addition to meeting the standards of a Medium Duty Refractory Firebrick.This is suitable for manufacture of incinerator linings.Keywords: Incinerator linings, Kaolin, Firebrick, Refractory

Conversion of ethylene into propylene with the siliceous SSZ-13 zeolite prepared without an organic structure-directing agent

The SSZ-13 zeolite was synthesized via seed-assisted method without an organic structure-directing agent (OSDA) from sodium silicate, sodium aluminate, and seed crystals using a wide range of silica/alumina ratios (SARs) in the precursor gels. The SAR of the SSZ-13 was quite high (10) when the SAR of the precursor gel was 40, which was the optimum ratio for high crystallinity. The zeolite was steamed at a high temperature to further increase the SAR via dealumination. The crystal structure of SSZ-13 was stable during steaming because of its high SAR, quite different from another SSZ-13 zeolite obtained from the conversion of zeolite Y in K+ ion in the absence of an OSDA. Steaming at 800 °C and further washing with acid led not only to an increase in the SAR up to 21, but also to a steady increase in porosity. However, the concentration of acid sites, especially strong ones, decreased steadily with increasing steaming time, and octahedral aluminum was removed successfully after adequate steaming. Both pristine and steamed SSZ-13 zeolites were applied to the ethylene-to-propylene (ETP) reaction. With increased steaming time, both the stability of the ethylene conversion and the maximum propylene yield increased. Compared to conventional SSZ-13 zeolites synthesized using expensive OSDAs, adequately steamed SSZ-13 zeolites were competitive for catalyzing the ETP. The exceptional performance of the SSZ-13 zeolite obtained in this study may be understood in terms of its adequate SAR and the decreased number of acid sites (especially strong acid sites), which might be active for hydrogen transfer and ethylene oligomerization. Therefore, it could be suggested that the SSZ-13 zeolite synthesized without an OSDA can be effective in the ETP reaction when steam-treated under suitable conditions.

Effect of the promoter presence in catalysts on the compositions of Fischer–Tropsch synthesis products

The effects of alkali promoters namely potassium, copper, and manganese, on the performance of the bi-functional iron–low acidity ZSM-5 catalysts in the Fischer–Tropsch (FT) synthesis were studied. ZSM-5 with very high silica alumina ratio (SAR) of 280 was used to take advantage of its shape selectivity and suppressing the effect of alkali migration on zeolite cation exchange sites. One bi-functional iron base catalyst (FeZ), three single promoted (KFeZ, CuFeZ, MnFeZ) and four multiple promoted (CuKFeZ, CuMnFeZ, KMnFeZ, CuKMnFeZ) catalysts were synthesized by the incipient to wetness impregnation method. They were characterized by XRD, BET, TPR, TEM and TPD analyses methods and tested for their FT synthesis activities.Promoters had considerable impacts on the compositions and the hydrocarbon distributions of the FT synthesis products. Addition of promoters resulted in an increase of up to 8.5–56% and 20–743% in the synthesis of gasoline and diesel range hydrocarbons, respectively. Consequently, the production of the total liquid fuel (gasoline+diesel) also increased from 48% (base catalyst) to 64–79% (promoted catalysts). The highest gasoline range hydrocarbon production was obtained from MnFeZ and CuKMnFeZ (≈70%) while CuKMnFeZ produced a FT product having the highest total liquid fuel (≈79%).

The Effect of Metal Loading and Alkaline Treatment on The Zeolites Toward Catalytic Pyrolysis of γ-Valerolactone

γ-Valerolactone (GVL) is a glucose derivatives and its utilization as organic solvent has been developed to extract lignin from biomass. Both GVL and lignin can be used for producing aromatic chemicals (Bezene, Toluene, Xylene – BTX) via catalytic pyrolysis. We present a study focused on the catalyst modification of the zeolites to produce BTX from GVL. The catalysts were modified using wet impregnation method and alkaline treatment using NaOH solution. The addition of metal oxides were examined. Catalyst performance test were carried out in a fixed bed reactor. The feed was flowed at flowrate of 0.2 ml/min in 50 ml/min N2. The operating temperature was maintained at 500°C with catalyst-to-GVL ratio of 1:1.5. The results showed that adition of Fe-metal improves zeolites activity compared with parent zeolites. Alkaline treatment had negative impact on HZSM-5 activity because of the change of silica-alumina-ratio (SAR) and average pore diameter.

Selective and stable production of ethylene from propylene over surface-modified ZSM-5 zeolites

This study is the first to examine the selective production of ethylene from propylene (propylene-to-ethylene, PTE) with using various structural types of zeolites. The catalytic performances of these zeolite catalysts were tested in a continuous fixed-bed reactor system with respect to ethylene selectivity and catalyst stability during the overall reaction period. Among these zeolite catalysts, ten-membered ring zeolites with three-dimensional pore structures (ZSM-5 and ZSM-11) exhibited stable catalytic performances with considerable ethylene selectivity compared to other zeolite catalysts. The ZSM-5 zeolite, thus selected, was further studied in the PTE reaction with different silica-alumina ratios (Si/Al2, SARs), a surface modification with phosphorus, and under different reaction conditions in order to investigate the effect of acidity, surface properties, and process variables on the catalytic activity as well as to additional improve the ethylene selectivity. From these studies, the PTE reaction was found to depend strongly on the reaction condition, SAR and surface P modification in the ZSM-5 zeolite. The phosphorous-modified ZSM-5 catalyst exhibited the highest ethylene selectivity of more than 70% with moderate propylene conversion of 36.3% at a low propylene space velocity and a low partial pressure condition.

An Evaluation of the Environmental Safety and Geochemical Characteristics of Coal Combustion Products

In this study, the environmental safety and geochemical properties of Coal Combustion Products (CCPs) produced coal-fired power plants were investigated. Samples of CCPs were taken from all of the coal-fired power plants of Korea. Heavy metal concentration, Electrical Conductivity (EC), and pH measurements were conducted to evaluate the environmental stability and geochemical properties of the CCPs. X-ray fluorescence and X-ray diffraction analyses were performed and enrichment factors and an index of geo-accumulation were calculated to evaluate the levels of contamination in the CCPs. The pH value of the CCPs ranged from 7.6 to 9.3, slightly alkaline, and the EC ranged between 110 and 4,940 μS/cm. CCPs from anthracite coal had a lower silica-alumina ratio and lower proportions of CaO and MgO, and greater proportions of K2O, than CCPs from bituminous coal. The EF value of Fe, Ti, and P in some CCP samples classified moderate enrichment category, all other elements in the samples were classified in the deficiency to minimal enrichment category. Also, the heavy metal concentrations in all CCP samples were lower than the environmental standards, indicating that the CCPs satisfied environmental regulations.

Targeted Synthesis of Ultrastable High-Silica RHO Zeolite Through Alkali Metal-Crown Ether Interaction.

High-silica RHO zeolite was directly synthesized using an alkali metal-crown ether (AMCE) complex as organic structure-directing agent (OSDA). Derived from the UV-vis spectra and zeolite patterns, the crown ether-cesium cation interaction was found to have crucial effect on the enhancement of silica content within the zeolite framework. The synthesized RHO zeolites possess up to four times larger silica/alumina ratio (SAR) values than that in their conventional form, which gives them extraordinarily rigid frameworks even after hydrothermal aging under 800 °C. Compared to commercial zeolites, copper-exchanged high-silica RHO zeolites demonstrate considerably high reaction activity in NOX removal, making them promising candidates for diesel exhaust treatment.

Effect of Silica Alumina Ratio and Thermal Treatment of Beta Zeolites on the Adsorption of Toluene from Aqueous Solutions

The adsorption of toluene from aqueous solutions onto hydrophobic zeolites was studied by combining chromatographic, thermal and structural techniques. Three beta zeolites (notated BEAs, since they belong to BEA framework type), with different SiO2/Al2O3 ratios (i.e., 25, 38 and 360), before and after calcination, were tested as adsorbents of toluene from aqueous media. This was performed by measuring the adsorbed quantities of toluene onto zeolites in a wide concentration range of solute. The adsorption data were fitted with isotherms whose models are based on surface heterogeneity of the adsorbent, according to the defective structure of beta zeolites. The thermal treatment considerably increases the adsorption of toluene, in the low concentration range, on all BEAs, probably due to surface and structural modifications induced by calcination. Among the calcined BEAs, the most hydrophobic zeolite (i.e., that with SiO2/Al2O3 ratio of 360) showed the highest binding constant, probably due to its high affinity for an organophilic solute such as toluene. The high sorption capacity was confirmed by thermogravimetric analyses on BEAs, before and after saturation with toluene.