Project report
Production/Synthesis of Zeolite Y
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- Bu səhifədəki naviqasiya:
- CHAPTER FOUR RESULTS AND DISCUSSION 4.1 Chemical Analysis of raw kaolin
- 4.2 Discussion on Refining the raw kaolin
- 4.3 Result of Dehydroxylation/Metakaolinization of Okpella Kaolin Clay.
- Table 4.2 Dehydroxylation/Metakaolinization at Temperature of 550˚C
- Table 4.3 Dehydroxylation/Metakaolinization at Temperature of 600 o C
- Table 4.4 Dehydroxylation/Metakaolinization at Temperature of 650 o C
- Table 4.5 Dehydroxylation/Metakaolinization at Temperature of 700 o C
- Table 4.6 Dehydroxylation/Metakaolinization at Temperature of 750 o C
3.3.4 Production/Synthesis of Zeolite Y The method used in the synthesis of zeolite Y was carried out in a manner similar to that as reported by Kovo (2010). In the synthesis of zeolite Y from Okpella kaolin, the use of external silica source was used and three factors were carefully studied, these are ageing time at room temperature, crystallization time and crystallization temperature. According to Chandrasekhar and Pramada, (2004) as reported by Kovo (2010), the aluminosilica gel used to synthesize zeolite Y was produced based on the following molar ratio, 15Na2O: Al2O3: 15SiO2: 450H2O Sodium hydroxide pellets (99% w/w) and anhydrous sodium metasilcate (Qualikems) which serves as a source of additional silica were both supplied by Qualikems Laboratory. The Okpella metakaolin served as a combined source of alumina and silica. 193.9590g (0.1939litres) of deionised water was measured and was divided into two equal parts in separate beakers. 1.9740g of sodium hydroxide pellets were measured and were added into the first half of the deionised water and was stirred until it dissolved completely. 5.3313g of Okpella metakaolin was measured and was also dissolved in the first half of the deionised water. 40g of sodium metasilicate was measured and dissolved in the second half of the deionised water. After proper stirring and mixing of the two sets of precursors, they were then mixed together to form a homogeneous aluminosilicate gel. The gel(s) was then aged at room temperature at varying ageing time of 24hours, 12hours, 6hours, and 3hours respectively with intermittent stirring. The aged gel(s) were then crystallised using the oven at different crystallization temperature and crystallization time of 9hours (i.e. different synthesis conditions). This is presented in the table below. Upon crystallization and or hydrothermal treatment, the sample(s) were removed in the oven, allowed to cool and were washed using the deionised water until the pH of the sample(s) were between 7 and 9. This was followed with drying of the sample(s) at 70oC using the oven for 10hours.
(a) SAMPLE A
(b) SAMPLE B
(c) SAMPLE C
(d) SAMPLE D
The products obtained from the above synthesis of zeolite Y were characterised with XRD and SEM. CHAPTER FOUR RESULTS AND DISCUSSION 4.1 Chemical Analysis of raw kaolin Table 4.1 below shows the elementary analysis of the raw Okpella kaolin clay. From literature, faujasites zeolites comprising of zeolite X and Y have a high silicate to alumina ratio hence the starting clay material for development of such zeolites has got to have a silicate to aluminate ratio of 1 or above to be able to synthesize the zeolite. Table 4.1. XRF Analysis of Okpella Kaolin Clay
LOI = Loss on Ignition. The raw Okpella kaolin clay has a silicate to aluminate ratio of 2.177, which implies it satisfies the ratio condition for production of zeolites. The table also shows the percentage composition of the minerals in the kaolin as percentage oxides, it is evident that the kaolin has a lot of impurities like SO3, CaO, TiO2 , V2O5, Fe2O3 , ZnO and so on. These oxides affect the kaolin as they reduce its plasticity in preparation of the catalyst, hence various methods are used to refine the kaolin and make it active for preparation. The LOI of 13.2% shows the maximum amount of water that could be removed from the kaolin, which in turn tells the maximum mass loss possible with the kaolin. 4.2 Discussion on Refining the raw kaolin The raw kaolin containing those impurities as stated in table 4.1 have to be removed by employing the beneficiation technique, which is the use of solvent like water or other chemicals to remove the impurities. Settling tanks were used to refine the raw kaolin to particle size of 20µm and some of the impurities are washed off with the heavier component, quartz. A new XRF on the refined kaolin would have shown a drop in the amount of impurities present in the kaolin. 4.3 Result of Dehydroxylation/Metakaolinization of Okpella Kaolin Clay. The refined kaolin by itself cannot be used to develop the zeolite as it still is in its ground or unexcited stage. Dehydroxylation is used to remove the water in bound of the kaolin which then reorganizes the structure making it have an octahedral structure that allows for the synthesis of the zeolite. This activation procedure is depicted in tables 4.2 – 4.6 as mass loss increases with respect to time and temperature. The dehydroxylation/metakaolinization of Okpella kaolin at different heating temperatures and time are presented in table 4.2 – 4.6.
OMK = Okpella Metakaolinization g = gram In table 4.2 above, the heating time for the kaolin was 550˚C at different heating times 5, 10, 15, 30, 60 and 90minutes. When it was heated for 5minutes, the mass loss was 0.17g which is 1.7% of the original mass, with an increase in heating time to 10minutes, the mass loss increased to 0.25g meaning that more of water inbound in the kaolin was liberated. The increase in mass loss continued that way to the heating time of 90minutes where it was highest at 1.10g and 11% of the original mass of kaolin. Since the LOI is 13.2% from table 4.1, it means that the maximum mass loss possible from 10g of kaolin is 1.32g. The results in this table so far aren’t up this value meaning that complete dehydroxylation hasn’t been achieved.
OMK = Okpella Metakaolinization g = gram In table 4.3 above, the same phenomenon continues as an increase in heating time corresponds to an increase in mass loss. The temperature in the furnace here was 600˚C, at heating time of 5minutes, the mass loss was 0.3g and at 10minutes it dropped to 0.07g before it then increased to 0.84g for 15minutes and continued increasing steadily to 1.30g for 90minutes. The unexpected drop in mass loss in 10minutes heating time can be analyzed as an experimental error in the furnace as heating in the furnace wasn’t constant due to an erratic power supply to the furnace at that time. The maximum mass loss recorded at the temperature of 600˚C was 1.30g gotten at 90minutes. This makes it clear that an increase in heating time allows for more dehydroxylation of the kaolin.
OMK = Okpella Metakaolinization g = gram In table 4.4 above, the dehydroxylation was carried out at 650˚C. There was an increase of mass loss with an increase of heating time as seen in other tables. For 5minutes heating time, the mass loss was 0.21g increased to 0.99g for 10minutes and 1.15g for 15minutes but at 30minutes, the mass loss reduced to 0.91g which can also be analyzed as an experimental error. When the heating time was 60minutes, the mass loss then increased to 1.24g and at 90minutes, the mass loss reduced to 1.07g which shows that we got to the optimum condition at 60minutes, hence an increase in heating time may not have any effect on the kaolin. Table 4.5 Dehydroxylation/Metakaolinization at Temperature of 700oC
OMK = Okpella Metakaolinization g = gram 700˚C was the heating temperature for dehydroxylation in table 4.5, the expected trend continued in this heating temperature. At 5minutes heating time, the mass loss was 0.66g, it increased to 1.11g for 10minutes and continued that way to 1.30g for 90minutes. Table 4.6 Dehydroxylation/Metakaolinization at Temperature of 750oC
OMK = Okpella Metakaolinization g = gram In table 4.6, the heating time was 750˚C, there was an increase in mass loss too as heating time increased steadily. At 5minutes heating time, mass loss was 0.90g it increased to 1.22g for 10minutes and 1.27g for 15minutes before it dropped to 1.24g for 30minutes and continued increasing to 1.30g at 90minutes. This shows one can take heating time of 15minutes as an optimum for synthesis of zeolite as after that time, there was a decline in mass loss before it started increasing. Table 4.7 Percentage (%) mass loss of Okpella kaolin clay for different calcination temperature and times
Table 4.7 above shows the effect of heating time and heating temperature on mass loss of kaolin. It is noticed that at elevated temperatures, there was an increased mass loss corresponding to better dehydroxylation of the kaolin, also with higher heating times, the mass loss increases too. This depicts that an increased temperature and increased time favours better dehydroxylation as mass loss increases. Also, an extended increase in heating time or temperature may end up not having an effect on the kaolin as it may not go above the LOI value. As is seen in the table, the maximum mass loss was 13.0 gotten at heating time of 90minutes for temperature of 750oC, 700oC and 600oC In table 4.8 in the appendix, the effect of heating time and heating temperature was evaluated on the degree of dehydroxylation. As it was in the table for mass loss, degree of dehydroxylation increases with respect to increased heating time and temperature. Degree of dehydroxylation was highest at 90minutes for 600oC, 700oC, 750oC heating temperatures, this is also made clearer with the graphs of degree of dehydroxylation against heating time for different temperatures as shown in figure 4.1 below
The curve for 750˚C shows the highest degree of dehydroxylation, followed by that of 700˚C that way down to the curve for 550˚C. it also showed that none of the curves got to a degree of 1, hence an optimum is picked based on a temperature and heating time that is easy to reach. In our case, heating time of 60minutes and temperature of 650oC were used. Yüklə 357,43 Kb. Dostları ilə paylaş:
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