;+ctc. INTRODUCTION In the last report, we have described the conversion of Conemiaugh fly ash into mesoporous EXPERIMENTAL PROCEDURE

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1 . ~ QUARTERLY PROGRESS REPORT (//97-3/3/97) -.?. Contract No. DE-FG22-94PC9425 Project Title : Conversion of Coal Wastes into Waste-Cleaning Materials Principal nvestigator : Wei-Heng Shih Graduate Student : Hsiao-Lan Chang - P t. - i ;+ctc p Flf 2: **.?L ri. * -.; f t$* ; NTRODUCTON n the last report we have described the conversion of Conemiaugh fly ash into mesoporous materials (MCM-4) using the fusion process followed by hydrothermal treatment. n this report we present more detailed study on the microstructure and chemical compositionsof the MCM-4 phase converted from Conemiaugh ash. The converted mesoporous material was analyzed by TEM and the Energy Dispersive X-ray Spectroscopy in the TEM. This part of the work was done in collaboration with Prof.. Aksays group at Princeton University. The hexagonal mesoporous structure was found to have a pore size about 26. A with a SUA mole ratio of 3.4. n addition we studied the conversion of several other fly ashes with a wide range of chemical compositions to mesoporous aluminosilicates. t was found that both Eddystone and Goudey fly ashes can be successfully converted into MCM-4 aluminosilicates.moreover besides working on the synthesis of aluminosilicatemesoporous materials by fusion of fly ash and NaOH powder a mesoporous materials was successfully synthesized by fusion of fly ash and Ca(OH)2powder. The nitrogen adsorptioddesorption isotherms and XRD patterns of this mesoporous material using Ca(OH)2 were similar to those of mesoporous material using NaOH. t is not clear at the moment whether the mesoporous materials using Ca(OH)2 contains any Ca or not. f it does then the mesoporous materials synthesizedwith Ca(OH)2 may be very useful for SO2/NOgas adsorption in pollutant emission control by the reaction between those gases with Ca. EXPERMENTAL PROCEDURE TE The structure pore size and local chemical compositionof the mesoporous materials mentioned in the previous report were examined in detail by TEM-EDXS in Princeton University. EDXS analysis was typically performed at 200 kev accelerating voltage with a 50 nm spot size. The data of EDXS in mesoporous materials were averaged from 0 points taken from 3 different particles. Three fly ashes: Eddystone Goudey and Conemiaugh were used as the raw materials in the study. The raw material was first mixed with NaOH powder and poured into steel crucibles which were heated at 550 C for hour in the air. For the synthesis of Ca-aluminosilicatematerials from Conemiaugh ash the fusion process involved mixing different weight ratios of fly ash to Ca(OH)2 powder. The ratios studied were :.2 :2.4 and :0.6 respectively. The mixture of fly ash and Ca(OHJ2powder was poured into steel crucibles and treated at 8 0 C for hour in the air. After fusion process the powders of NaOH with fly ash or Ca(Ow2 with fly ash were ground and dissolved in distilled water for day at room temperature and ambient pressure. The sediments by the centrifugation of fly ash solutions were taken out and more distilled water was added followed by aging at room temperature and ambient pressure for day. After aging the supernatants separated from the fused fly ash solutions by centrifugationwere ready to be used. The surfactant solution was prepared by the following procedures: First g of surfactant C6H33(CH3)3NBr were mixed with.32 g distilled water and stirred for 5 minutes at room temperature. Second the mixture was added 0.25 ml of 4.96 N NH40H and 7 ml of distilled water and stirred for 30 minutes at room temperature. Once the surfactant solution was prepared the supernatantprepared from the fly ash DSTREUTOM OF MS DOCUMENT S UNLMTED

2 solution was poured into it. The mixture solution was stirred for 40 minutes at room temperature and then cured at 00 C in a 250 ml boiling flask topped with a reflux condenser. At various curing times samples were taken from the solid precipitates by centrifugation of the solutions after the boiling flask cooled down to room temperature. Samples were washed with distilled water and centrifuged twice. The centrifuged sediments were dried at 80 C for 2 hours in the air.after grinding the powders were calcined at 540 C for 7 hours in the air. The calcined powders were characterized with X-ray diffractometer and BET surface area analyzer. RESULTS and DSCUSSON The TEM micrograph of the mesoporous material converted from Conemiaugh ash and NaOH is shown in Fig.. Clear hexagonal patterns of the pores can be seen. The TEM micrograph shows that the size of the pores and the distancesbetween the pores varies in different part of the micrograph. These variations are due to different projection angels from the different areas. The average lattice constant and the average pore size of hexagonal pattern calculated from different parts of the micrograph are 3.95 nm and 2.6 ntn respectively. The EDXS analysis of the mesoporous material shows that it is mainly an aluminosilicate with the average chemical compositions of Si02 (90.3wt%) A203 (6.5wt%) Fe30 (.6wt%) respectively and small amounts of Ca K S P. The EDXS results were shown in Fig. as well. t should be noted that although there were many Na elements in the solution no Na was detected in the MCM-4 aluminosilicates. Apparently Na is not compatible with the alminosilicatemesoporous phase. The SUA molar ratio of the mesoporous material is 3.4 which is much higher than the Si/A molar ratio of.76 of the as-received Conemiaugh ash. This result indicated that the incorporation of Al in the MCM-4 phase in the current process is not easy. So far aluminosilicates with SUA ratio less than 29 has been conclusively shown using the CTAB surfactant that we used here. The XRD patterns of the precipitates from the three fly ashes are showed in Fig.2. Although the chemical compositions of these fly ashes are different as shown in the previous report it is believed that the amounts of dissolved silicates and aluminates in the solution are the critical factors in the synthesis. Our results show that the fusion process can be applied to the conversion of many fly ashes into mesoporous materials due to the increase of soluble silicates and aluminates. The XRD patterns of the precipitates from solutions with different weight ratios of fly ash to Ca(OH)2 are showed in Fig.3. When the content of Ca(OH)2powder increased the intensity of the dloopeak decreased. t is clear that the high concentration of calcium may be detrimental to the synthesis of mesoporous materials. This is similar to our previous results about the detrimental effects of Na on the synthesis of mesoporous materials. The dlm-spacing of mesoporous material using Ca(OH)2 was z 4.2 nm which is larger than that of mesoporous material synthesized from NaOH. The nitrogen adsorption/ desorption isotherms for the mesoporous material obtained from the solution with the weight ratio of fly ash to Ca(OH)2= : 0.6 are shown in Fig.4. The adsorption/desorption isotherm is typical of MCM-4 phase with a surface area 702 m2/g which is a little bit smaller than that of mesoporous material using NaOH. The pore size distribution of the me$oporousmaterial using Ca(OH)2 shown in Fig.5 is quite uniform with an average pore size of 30.9 A. Similar results were obtained for other weight ratios of fly ash to Ca(OW2.

3 CONCLUSONS and FUTURE PLAN t was shown that the mesoporous materials formed using NaOH is mainly aluminosilicate with a Si/A ratio of 3.4. The mesoporous aluminosilicate contained small amount of other elements existing in fly ash but does not contain Na. Furthermore it was shown that the mesoporous materials can be converted from other fly ashes by the fusion process. t is believed that the fusion process increases the amounts of silicates and aluminates in the precursor solution thereby increases the chance of forming mesoporous materials. On the other hand the successful synthesis of mesoporous materials from Ca(0W2 powder and fly ash showed that mesoporous materials containing Ca may be possible. The Ca-containing mesoporous material may greatly increase its potential as a SO2/NOgas adsorbent since Ca has been shown to remove SO2/NO gas effectively. More work in chemical composition analysis on the mesoporous materials using Ca(OH)2 will be performed. Furthermore the role of the fusion process needs to be addressed. For example the effect of Si/A molar ratio in the precursor solution on the formation of mesoporous materials is not known. Since the synthesis of zeolite is simpler than that of mesoporous material because of no surfactant involved we will address the effect of Si/N molar ratio in the fly ash solution on the synthesis of zeolite first. t is hoped that the detail chemical analysis of silicon a l e u m and sodium species in the three fly ash solutions during synthesis will elucidate the role of the fusion process. DSCLAMER This report was p r c p a d as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof nor any of their employees makes any warranty express or implied or assumes any legal liability or responsibility for the accuracy completeness or usefulness of any information apparatus product or process disclosed. or represents that its use would not infringe privately owned rights. Reference herein to any spccific commercial product process or service by trade name trademark manufacturer or otherwise does not necessarily constitute or imply its endorsement mommcndation or favoring by the United States Government or any agency thereof. The Views and opinions of authors expressed herein do not nccessarily state or reflect those of the United States Government or any agency thereof.

4 Si Ka Si/A molar ratio = 3.4 Average pore size = A key Fig. TEM micrograph of the sodium-aluminosilicatemesopomus phase precipitated from Conemiaugh ash solution. The EDXS results are also included. The unlabelled peaks belong to the Cu grid.

5 Goudey Conemiaugh l l 5 6 l ( degree ) Fig.2. XRD patterns of sodium-aluminosilicate mesoporous phases precipitated after 7 days of curing. 9 0

6 = :.2 Fly ash : Ca(OH)2 = : 2.4 h Ca(OH)2 = : 0.6 Fly ash ( degree) Fig.3. XRD patterns of calcium-aluminosilicatemesopomus phases precipitated after 7 days of curing. 9 0

7 O.Oo PPO Ooo Fig.4. Nitrogen admrption/desorption isotherms fm the calcium-aluminosilicate mesopairous phase precipitated after 7 days of curing. Squares indicate desorption data and cixxles are for adsorption.

8 c BJH dv/dd (Adsorption) W.OOO x o.oo0 O.oO0 O.OOO Pore Diameter [A] Fig5 Pore size distribution of the calcium-aluminosilicatemesoporousphase precipitated after7 days of curing

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