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Some important steps have taken as described below when the laboratory work was carried out for synthesis zeolite-A, zeolite-Y and coating the colloidal of zeolite-Y on the diatom surfaces. The safety instructions such as lab coat, goggles and gloves were worn all times in during laboratory work to prevent any contacts with spills of chemical materials with the skin and eyes. These instructions were done with all synthesis process. The risk assessment and COSHH forms for the synthesis of zeolite-A, zeolite Y are attached in appendix -A.
3.2 Pre-treatment of Teflon lined autoclaves:
The Teflon-lined autoclaves were used in this experiments has been washed with deionised water and then with sodium hydroxide (NaOH) with 2M solution .The mixture was shacked for sufficient time to ensure good dissolving in D.W. Is essential to ensure that the volume of the NaOH solution it most not more tow third (2/3) of the volume of the autoclaves .That instruction has taken to ensure the autoclaves was not explode under the temperature and pressure. The autoclaves were sealed tightly and put it into oven under 170°C for 12hrs (minimum 3h).After that time, the autoclaves were taken out and then left out to cool down into the sink .After 20 minutes of cooling, these autoclaves were opened and the NaOH solutions were removed, then the Teflon lined autoclaves were washed with D.I and they were left to dry at room temperature.
3.3.1 Syntheses of Zeolite-A:
The crystallization of zeolite-A was carried out in linear tube crystallizer by using batch reactor mode .The formation of zeolites depends on crystallization, alkalinity and temperature. In this study, zeolite-A was synthesised by usin the following recipe ,
3.165 Na2O : Al2O3 : 1.926SiO2 : 128H2O
The objective of this experiment was to obtain the expertise required for further experiments using same technique by following the gradually growth of zeolite-A and to be familiar with the equipments which will used in the future such as autoclaves ,ovens , XRD ,SEM and deferent Chemical materials .
The Synthesis was carried out at temperature of 1000C in stainless steel batch reactor under autogenously pressure .Sources of Aluminium and Silicon is needed to prepare Zeolite-A .Details of calculation of the reactants required in the experiment is shown later (Calculation of Zeolite A (see appendix-B). Table (3.1) show the growth gel ingredients of Zeolite-A.
Table (3.1): Zeolite A growth gel ingredients, amount in grams and suppliers.
Sodium Hydroxide,NaOH 99.6%
Sodium Silicate ,(Na2SiO3), 47% wt of SiO2 and 52% wt of Na2O
The materials used in the experimental work were
Sodium Hydroxide [supplied by sigma-Aldrich CHEMIE GmbH, Germmany] with composition 99.6% wt NaOH was used as a source of Na2O by adding 0.787 gm to 25 gm of distilled water ,the solution was shacked for suitable time to ensure the dissolving of all NaOH in the deionized water . Then the solution was divided into two equal halves.
Sodium Aluminates [supplied by sigma-Aldrich CHEMIE GmbH, Germmany ] with composition of 55% wt Al2O3 and 45% wt of Na2O used as a source of sodium and Aluminium to prepare Sodium Aluminates solution ,2.026 gm of the solid were dissolved in 12.5 gm of distilled water and shaked gently for sufficient time to make the homogenous situation .
Sodium silicate[supplied by sigma-Aldrich CHEMIE GmbH, Germmany ] with compositions of 47% wt SiO2 and 52% wt Na2O was used as a source of Silicon Sodium, Sodium Silicate solution was prepared by adding 2.687 gm from Na2Sio3 to 12.5 gm D.W and shacked gently for a sufficient time to ensure good mixing .
Distilled Water with NaOH was used to clean the reaction vessels before (as described later) and after the synthesis.
Whitman membrane filter type PTFE of diameter 90 mm pore size of 0.2 µm and filter holder with 500 ml capacity were used to separate the solid from liquid solution of the sample.
3.3.2 Experimental Procedure:
Zeolite-A was synthesized hydrothermally using sodium Aluminates, Sodium Silicate and Sodium Hydroxide. The initial composition of the reactant mixture [80, 61].
3.165Na2O: Al2O3 :1.926SiO2:128H2O
The crystallization was carried out in liner tube of autoclave in batch mode; the temperature of synthesis was kept at 100 ±1 0C for (30, 60, 90,150 and180) minutes.
Before the Zeolite crystallization, the autoclave was washed by 10% of NaOH solution as described above .Zeolite-A was synthesized by adding 0.787 gm of NaOH with 25 gm distilled water (assume ΡH2O=1 gm/m3), then the solution divided into two equal halves. The first half was mixed with 2.05 gm of Sodium Aluminates and shacked for sufficient time to ensure completely dissolving the materials. The second half was used (12.5 gm NaOH solution) to dissolve 2.687 gm of Sodium metasilicate and shacked gently for sufficient time to ensure the proper mixing. The solution of Silicate was poured into the solution of Aluminates; a thick gel was composed quickly and shacked gently for a suitable time to ensure the homogenous between them. This product was put into oven under 1000C for different times (60,90, 120, 150and 180) minutes after that, the autoclave cooled has done into 20 minutes under tap water in the sink. Vacuum method was used to separate the solid from solution by poured the solution into Whitman membrane filter with 500 ml capacity of filter holder .The pH meter was used to check the pH of solution when it became under 9 (pH =8.76-8.9 in this work) by washed the filter with distilled water with continues vacuum .Finally, the filter with separated solid was put in oven under 900C overnight for drying. The percent of crystalline as describe below was calculated:
% Crystalline =
The sample was analysed by XRD, X-ray diffractometer to study the crystallinity of the zeolite products. The crystalline is calculated by using the above formula by counting the most intensity for peaks of sample and most intensity for peaks from standard (commercial Zeolite A assuming 100% crystal of zeolite-A) supplied by sigma Aldrich [ 83].The same method of calculation will used to prepare other samples in the future. In addition, Scanning Electron Microscopy (SEM) was used to determine the crystal size and the morphology of Zeolite structure.
3.4 Experimental ÐŸ
3.4.1 Synthesis of standard Zeolite-Y:
This experiment for zeolie Na-Y type FAU reproduced the work by D. M. Ginter, A. T. Bell and C. J. Radke which was reported in the verified synthesis handbook (2001). The chemical compositions for the synthesis procedure are described below :
Type material: Na56[Al56 Si136 O384]:250H2O
a- Seed Gel (5% of Al): 10.67 Na20 : Al2O3 : 10 Si02 :180 H2O
b- Feed Stock Gel (95% of Al): 4.30 Na20 : AI2Q : 10 Si02 : 180 H2O
c- Overall Gel: 4.62 Na20 : Al2O3 : 10 Si02 : 180 H2O
The proper materials were used in this experiment using batch reactor mode, to make same recipe. The Sources of materials which were used in this experiment are for seed gel and feed stock gel:
NaOH 99.6% supplied by Fisher scientific.
Sodium Aluminates (strem chemical 1.27 Na/Al ,6.1% H2O)
The calculation for each material has done to get the required amount of each substance, (see Appendix-C), show the calculation for seed gel, feed stack gel and overall gel. Five samples have been done to follow the gradually growth of the crystallization in different times (5, 20, 20, 24 and 45) h. The flow diagram figure (3.1) shows the main steps in the synthesis of Na-Y zeolite.
An aqueous basic medium were used to dissolve the reactant components in hydrothermal zeolite Y synthesis, then the reactants have heated at 100°C. The crystallization phase were growth gradually with heating time into more thermodynamically stable phase .The products of synthesis zeolite-Y have compared with typical Faujasite to ensure the product crystanillity.
Feed Stack Gel
Product of zeolite Y
Figure (3.1): The flow diagram show the main steps in the synthesis of Na-Y zeolite.
3.4.2 The Synthesis Procedure:
The suitable method to prepare Na-Y zeolite has been used, this method includes six main pointes as shown in diagram figure (3.1).
Preparation of Seed Gel: (Step 1)
The composition batch formula for seeding gel is:
(5% of Al): 10.67 Na20: Al2O3: 10 Si02:180 H2O
Table (3.2 ): Zeolite Y growth seeding gel ingredients, amount in g and suppliers.
Sodium Hydroxide,NaOH 99.6%
Sodium Aluminates , anhydrous, 55% wt of Al2O3 and 45%wt of Na2O
The amounts of materials were prepared from its sources are shown in table ( 3.2 ) after calculation process, sodium aluminates (NaAl2O3) were used as alumina source, the D.I water were used as solvent source and sodium hydroxide NaOH as a minerals source. All these reactants were mixed together in a beaker or a plastic bottle and then stirred for sufficient time to ensure totally dissolved, the Ludox-40 were used with required amount as silica source .The Ludox -40 were added very carefully to the mixture to confirm the reaction with the mixture by using a plastic pipette. The whole mixtures were mixed slightly for 10 minutes using magnetic stirrer. After stirred time, the plastic bottle was capped tightly and the slurry was left for 24hrs at room temperature.
220.127.116.11 Preparation of Feed Stack Gel: (Step2)
The feed stock gel formula is :
(95% of Al): 4.30 Na2O : AI2O3 : 10 SiO2 : 180 H2O
Table (3.3): Zeolite Y growth seeding gel ingredients, amount in g and suppliers.
Sodium Hydroxide,NaOH 99.6%
Sodium Aluminates , anhydrous, 55% wt of Al2O3 and 45%wt of Na2O
The amounts of materials were prepared from table (3.3). Similar to the seed gel procedure, the required amounts of chemical materials for feed stock gel were prepared and weighted in a sensitive balance. The chemical materials , sodium aluminate NaAl2O3 , D.I water and NaOH in separate plastic bottle were mixed gently until completely dissolved .Then Ludox-40 were added slightly to the other material as SiO2 source .Smooth gel have gotten after 10 minutes of vigorously stirred .
Preparation of overall gel: (Step 3)
1. The composition formula for overall gel is:
4.62 Na2O: Al2O3: 10 SiO2: 180 H2O
2. The essential amount of the seeding gel in step (1) was added to the feed stock gel in step
(2); the entire constituent were stirred for nearly 20 minutes to confirm good mixing for
reactants .After that, the mixture was divided into five Teflon- lined autoclaves. These
Autoclaves were transferred into the oven at100°C under autogenes pressure for different
crystallization time (5, 20, 20, 24 and 45) h.
3. After each time, the autoclaves were taken out the oven and put in the sink to cool for 20
minutes under tap water. The washing process has been done with D.W using 90 mm
diameter Whitman filter with 500 ml filter holder until the pH slight down below 9.
The products of zeolite Y were dried overnight at 110°C.
Finally, The analyses of the structure for the sample products of zeoliteY have been done to
study the structures using X-Ray diffraction (Philips Expert Pro MPD) and scanning electron microscopy (FEI Quanta 200 ESEM) .
3. 6 EXPERIMENT Ð¨
3.6.1 Synthesis of Celatom/Zeolite-Y Hierarchical Porous Material
The synthesis of zeolite-Y was carried out using three main steps,
Pre-treatment of autoclaves and equipments were used in laboratory work.
Syntheses of colloidal zeolite-Y as seeds were done using two methods,
Colloidal of zeolite -Y was made using synthesis process.
Colloidal of zeolite-Y was made using ball mill from a commercial source.
The synthesis of zeolite Y on a diatomite surface is reproduced the work by Anderson, Holmes (81), Oscar Hernandez as a part of his PhD degree, 2007 (82).
The main objectives of experiment is to gain experience in the field of zeolite synthesis ,which will be used as the research development .
Synthesis of Colloidal of Zeolite-Y:
The molar composition of zeolite Y seeding gel is (82)
2.46 (TMA) 2O: 0.032 Na2O : Al2O3 : 3.4 SiO2 : 370 H2O : 13.6 EtOH
The calculation process of the required amounts of chemical materials was carried out , (see appendix-D).
Table (3.4) shows details of chemical used as a source, suppliers and amounts .The final composition formula as shown below,
4.92TMAOH: 0.08 NaOH : 2 Al(OH)3 : 3.4 SiO2 : 364.53 H2O
Table (3.4): The Colloidal of Zeolite-Y ingredients, amounts and suppliers.
Sodium hydroxide, NaOH pellets was used to prepare the alkaline media. Tetraethoxysilane (C8H20O4Si) TEOS, was used as silica source .The aluminium source was provided by Aluminium isopropoxide (9H21AlO3).While the template source was Tetamethylammonium hydroxide TMA2O (25% Wt solution) (C4H12N.OH).
Template solution was then prepared by dissolving 89.7 gm of (TMA)2O in 263 ml of D.I. The template solution was divided into two equal halves .A 0.128g of NaOH was dissolved in one half of template solution and sufficient time was allowed for mixing and dissolution as a first component .Then was them followed by adding 20.4g of aluminium isopropxide and was also stirred to ensure good mixing .
The second precursor was prepared by dissolving (35.4 gm) source of silica (TEOS) in the second half of the template solution. The two first solutions were mixed and stirred for 24 h resulted a clear homogenous solution.
The Teflon-lined autoclave was prepared as a previous describes, the homogenous solution was transferred in it to covere two-third volume. The autoclave was sealed tightly and put in oven for six days at 100°C for any synthesis to take place.
The solution was dialyzed figure (3.2) in large excess of deionised water for two days; the water was changed four times. pH in the range of 8.5-7.5 was obtained . A small sample of colloidal zeolite-Y was dried to determine the solid percentage (wt %). XRD analysis and SEM images of the samples were used to verify the crystalline structure.
Figure (3.2): Dialyses Process for colloidal-Y for 2 days .
18.104.22.168 Seeding process:
The product of colloidal zeolite -Y was mixed with Celatom FW-14 (supplied by Aldrich) for 6 hours in a sonic bath figure (3.3), which forces the molecules in the mixture to move and attach to the surface of celatom by electrostatic effects, After six hours the celatom with colloidal was removed from the sonic bath, filtered using Whitman filter (90 mm Ï•) and dried overnight at 40°C. The zeolite seeds nucleate on the surface of Celatom during this process.
Figure ( 3.3 ) : Sonic bath for 20:1 Celatom: colloidal of zeoilite-Y .
22.214.171.124 Crystal Growth :
While the Celatom FW-14 was seeded with colloidal of zeolite Y, the growth gel was prepared from the initial composition .
14 Na2O: Al2O3: 10 SiO2: 798 H2O: 3 Na2SO4
The silica source was sodium metasilicate (supplied by ACROS).Sodium hydroxide and aluminium octadecahydrate were used as source for the else elements .Soduim hydroxide was used to provide the alkaline medium. The calculation was explained in Appendix-E .The molar ratio of the ingredients for the growth gel was adjusted to:
14 NaOH : Al2(SO4)3·18H2O : 10 Na2SiO3·9H2O : 683H2O
Table ( 3.5) show the amount of each ingredient for the formation of the growth gel.
Table ( 3.5 ): Crystal growth ingredients, amounts and suppliers.
The values were multiplied by factor 0.0004167 to obtain the required amount of the synthesis process (the amounts of reactant has been reduced after multiplied by the factor due to the required amount in this experiment).
In this experiment the Celatom FW-14 was used as silica source with celatom : silica molar ratio 4:1 .It was estimated that celatom was slowly composed of silica , as appear in the syntheses gel formula :
30 NaOH: Al2(SO4)3·18H2O : 2 Na2SiO3·9H2O : 8 SiO2 : 747H2O
Deionised water with 5.59 gm was weighed and divided into two equal parts .Sodium hydroxide was weighted (0.5gm) and added into one of the D.I under stirrer at medium rate .0.277 gm of aluminium sulphate octadehydrate powder was weighted and added to the sodium hydroxide solution at the plastic bottle to make the first precursor .
The plastic bottle was sealed and the mixture was stirred by magnetic stirrer at medium rate.0.236 gm of sodium metasilicate was used to prepare the second precursor by dissolving in the second half of D.I. The mixture was stirred to ensure dissolve all amount of sodium silicate after sealing the plastic bottle to prepare the second precursor. The first and second precursor were mixed and the mixture were stirred for 2 hours in the plastic bottle , the mixture was transferred to the Teflon-lined autoclave , 0.2 gm of seeded celatom FW-14 was added to the mixture . The mixtures were covered two-third volume of the autoclave, sealed tightly and left in the oven for (75, 120 and 180) minute at 100°C
After each time the autoclave was taken out of the oven and left to cool down for 20 minutes .The autoclaves was opened and the gel was emptied out of the autoclaves. The growth gel was washed with deionised water, filtered by Whitman filter and dried overnight at 40°C.
The dried sample were analysed by XRD [Philps Expert pro MPD] powder diffraction and SEM, Scanning Electron Microscopy (FEI Quanta 200ESEM] .
3.7 EXPERIMENTAL ÐŸÐŸ
3.7.1 Colloidal of Zeolite-Y Using Ball Mill Technique:
The commercial of zeolite-Y was used to make the seeding. Sufficient amount of commercial zeolite-Y was taken and mixed with D.I. This solution was placed into the ball mill which it made from a ceramic media (the grinder) figure (3.4 ) .The solution was lasted for 24hours in the grinder and the colloidal l zeolite-Y mixture was collected for seeding process.
Figure (3.4): The ball mill instrument.
The ball mill was used in this work to convert the commercial zeolite-Y pellets into extremely fine powder. It is rotates horizontally with cylindrical shape, includes the material which was grinded together with grinding media. The media of grinding can were ceramic ball figure (3.5). .
Figure (3.5): Ceramic ball (media of grinding).
The ball mill which used in this experiment was small and consists of a cylindrical capped container which sits on two drive shafts (belts and pulleys are used to convert rotary motion).
Zeolite-Y seeding gel is usually synthesised by mixing the ingredients in the required amount. Colloidal ol zeolite-Y from commercial source was used to make seeding gel in this project to compare with the synthesis colloidal of zeolite -Y. The commercial zeolite-Y was mixed with D.I water and placed in the grinder for 24 hours while the other parameter was fixed is :
Vessel: A 500 ml plastic bottle was used with (3cm) radius.
Speed: 172 rpm, calculated according to the vessel's radius using the empirical formula (82)
V= speed, given in rpm and
r= mill radius, given in feet
Grinding media: Ceramic (zircon oxide) Beads, D=5mm.
Amount of material: 250ml (measured in volume to keep the proportion)
Wetting agent: 250ml of deionised water.
This technique is novel as it is not conventionally followed. In addition, saves the time and cost for synthesis of the seeding gel, due to the conventional synthesis process (as described in previous experiment) when the seeding gel required long time for heating (6 days at 100°C) and 2 days for dialyses, which is more time consummated .Also, as the conventional synthesis process for seeding gel is too long, it might be gotten some mistake.
A 250ml of commercial zeolite-Y has mixed with 250ml of D.I in 500 ml plastic bottle to confirm the ratio 1:1 .The ceramic balls with 5mm diameter figure (3.5) were used for grinding the zeolite-Y with D.I. The ball mill was installed with known parameters according to the radius and the type of mixture, the speed of rotate has been used with 172 r.p.m for 24 hours.
After that, the mixture was sieved to separate the grinding media and the remaining of commercial zeolite-Y was analysed using XRD and SEM after drying small amount overnight at 24°C to investigate the effective of the grinding to the crystalline and morphology of the zeolite.
The particle size and seed morphology of the colloidal of zeolite-Y was measured using dynamic light scattering (DLS) and SEM. The solid ratio of the colloidal solution was measured by putting it in small beaker and dried over night at 40°C.
3.7.2 Seeding Hydrothermal Growth:
Seeding of Celatom FW-14 was conducted as same procedure in section (126.96.36.199) using sonic bath for six hours with Celatom: colloidal ratio 20:1. The amount of Celatom seeded with ground zeolite (1g) was used as silica source for 3h at 100 °C in hydrothermal treatment process.