Project report

CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

5.1 Conclusion

The synthesis of zeolite from kaolin was successful as we have good crystals of supposed zeolite Y. The crucial stages of the preparation of zeolites are dehydroxylation and zeolitization. The optimum conditions for preparation of metakaolin were temperature and time of 650˚C and 60minutes respectively. Various conditions, different ageing times and crystallization temperatures, for ageing and crystallization were evaluated. The conditions of 3hours ageing time, 80˚C and 9hours crystallization temperature and time respectively appear to be the best as they produced the best zeolite crystals.

Okpella kaolin clay is a good material for development of zeolites in Nigeria.
5.2 Recommendations

Based on the issues encountered during experimentation, the following recommendations are suggested

1) Characterization of samples should be done after each stage to enhance better results.

2) Steady power supply will enhance performance and speed of reaction during operation of the furnace, ovens (autoclave reactor) and other equipment.

3) Smaller particle size during refining should be used as it provides for larger catalyst surface area due to the particle-size and surface area relationship.

4) Metakaolin could be used as a single starter material by dealuminating with acids.

5) Factorial designs should be implemented to assist with modeling of the zeolitization process so it becomes easy and less complicated to achieve.
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APPENDIX A

MASS LOSS

The mass loss values in percentage were calculated as follows:

Mass loss percentage =

Initial mass = 10g

For table 4.2a;

550˚C

For 5 mins: mass loss= 0.17

Mass loss =1.7%

For 10 mins: mass loss= 0.25

Mass loss =2.5%

For 15 mins: mass loss= 0.42

Mass loss =4.2%

For 30 mins: mass loss= 0.82

Mass loss =8.2%

For 60 mins: mass loss= 1.02

Mass loss =10.2%

For 90 mins: mass loss= 1.10

Mass loss =11%

For table 4.2b

600˚C

For 5 mins: mass loss= 0.30

Mass loss =3%

For 10 mins: mass loss= 0.07

Mass loss =0.7%

For 15 mins: mass loss= 0.84

Mass loss =8.4%

For 30 mins: mass loss= 1.10

Mass loss =11%

For 60 mins: mass loss= 1.15

Mass loss =11.5%

For 90 mins: mass loss= 1.30

Mass loss =13%

For table 4.2c

650˚C

For 5 mins: mass loss= 0.21

Mass loss =2.1%

For 10 mins: mass loss= 0.99

Mass loss =9.9%

For 15 mins: mass loss= 1.15

Mass loss =11.5%

For 30 mins: mass loss= 0.91

Mass loss =9.1%

For 60 mins: mass loss= 1.24

Mass loss =12.4%

For 90 mins: mass loss= 1.07

Mass loss =10.7%

For table 4.2d

700˚C

For 5 mins: mass loss= 0.66

Mass loss =6.6%

For 10 mins: mass loss= 1.11

Mass loss =11.1%

For 15 mins: mass loss= 1.20

Mass loss =12%

For 30 mins: mass loss= 1.20

Mass loss =12%

For 60 mins: mass loss= 1.26

Mass loss =12.6%

For 90 mins: mass loss= 1.30

Mass loss =13%
For table 4.2e

750˚C

For 5 mins: mass loss= 0.90

Mass loss =9%

For 10 mins: mass loss= 1.22

Mass loss =12.2%

For 15 mins: mass loss= 1.27

Mass loss =12.7%

For 30 mins: mass loss= 1.24

Mass loss =12.4%

For 60 mins: mass loss= 1.28

Mass loss =12.8%

For 90 mins: mass loss= 1.30

Mass loss =13%

APPENDIX B

DEGREE OF DEHYDROXYLATION

The degree of dehydroxylation(Dtg) was calculated using the formula

Dtg =

Where

M= mass loss in %

M_max = Loss on Ignition, LOI = 13.2%

For 550˚C

For 5mins, M=1.7%

Dtg =

For 10mins, M=2.5%

Dtg =

For 15mins, M=4.2%

Dtg =

For 30mins, M=8.2%

Dtg =

For 60mins, M=10.2%

Dtg =

For 90mins, M=11%

Dtg =
For 600˚C

For 5mins, M=3%

Dtg =

For 10mins, M=0.7%

Dtg =

For 15mins, M=8.4%

Dtg =

For 30mins, M=11%

Dtg =

For 60mins, M=11.5%

Dtg =

For 90mins, M=13%

Dtg =

For 650˚C

For 5mins, M=2.1%

Dtg =

For 10mins, M=9.9%

Dtg =

For 15mins, M=11.5%

Dtg =

For 30mins, M=9.1%

Dtg =

For 60mins, M=12.4%

Dtg =

For 90mins, M=10.7%

Dtg =
For 700˚C

For 5mins, M=6.6%

Dtg =

For 10mins, M=11.1%

Dtg =

For 15mins, M=12%

Dtg =

For 30mins, M=12%

Dtg =

For 60mins, M=12.6%

Dtg =

For 90mins, M=13%

Dtg =
For 750˚C

For 5mins, M=9%

Dtg =

For 10mins, M=12.2%

Dtg =

For 15mins, M=12.7%

Dtg =

For 30mins, M=12.4%

Dtg =

For 60mins, M=12.8%

Dtg =

For 90mins, M=13%

Dtg =

APPENDIX C

Settling time Calculation

Refining or beneficiation of the raw Okpella kaolin was aided by the use of Stoke’s law of sedimentation already discussed in the literature.

The equation is as follows:

Where ρ is the density of the particle = 2650kg/m³

ρ_o is the density of the solvent = 1000kg/m³

η is the viscosity of solvent at 30^oC = 7.98 x 10^-6Ns/m³

d is particle diameter = 20µm

h= given distance of settling tube = 34cm = 0.34m

g= gravitational acceleration = 9.81m/s²

hence, settling time, t_s for quartz of 20µm

t_s =

= 12minutes and 57 seconds

APPENDIX D

Formulation of Zeolite Y by the use of external silica material

The molar composition of the aluminosilicate gel used for the formulation or synthesis of zeolite Y was taken based on the work of Kovo (2010) as

15Na₂O:Al₂O₃:15SiO₂:450H₂O

The mole ratio are Na₂O = 15

Al₂O₃ = 1

SiO₂ = 15

H₂O = 450

From literature, metakaolin has the formula Al₂Si₂O₇

Metakaolin has mole ratio of 1 aluminate, Al₂O₃ and 2 silicate, SiO₂

From the molar composition of the growth gel for the synthesis of zeolite Y, the mole ratio of SiO₂ is 15, hence, there arises the need to increase the SiO₂ in the metakaolin up to 15, this will be done by getting the extra 15- 2= 13moles from the external silica source, say sodium metasilicate (Na₂SiO₃).

Metakaolin used for the process

The mass of the metakaolin is gotten as follows:

Molecular formula of metakaolin is Al₂Si₂O₇

The relative molecular masses of individual elements are:

Al = 26.98; Si = 28.09; O = 16.00; Na= 23.00; H = 1.00

Molecular weight of metakaolin is calculated as:

= (2 x 26.98) + (2 x 28.09) +(16 x 7)

= 53.96 + 56.18 + 112

= 222.14g

mass of metakaolin = 222.14g
Amount of Additional Silica

Using sodium metasilicate (Na₂SiO₃), as external silica source, containing 47% SiO₂ and 52% Na₂O, the remaining 1% serves as impurities.

Na₂SiO₃ → Na₂O + SiO₂

Molar mass of Na₂SiO₃ = (2 x 23) +28.09 + (3 x 16)

= 46 + 28.09 +48

= 122.09g/mole

If 100g of Na₂SiO₃ is used, 47g will be SiO₂

Molar mass of SiO₂ = 28.09 +32 = 60.09g/mole

Amount of SiO₂=

100g of Na₂SiO₃ = 0.78mole of SiO₂

13moles will then be gotten from

= 1667.67g of Na₂SiO₃

Since 52% of Na₂SiO₃ is Na₂O

Then

= 866.67g of Na₂O

Converting to molar mass

Molar mass of Na₂O = (23 x 2) + 16

= 62g/mole

Amount of Na₂O = = 13.98 mole of Na₂O

Thus remaining amount of Na₂O required for the gel is 15 – 13.98 = 1.02mole of Na₂O.
Additional Na₂O

Additional Na₂O is gotten from NaOH since Na₂O does not exist naturally alone.

Thus, Na₂O + H₂O →2NaOH

Molar mass of NaOH = 23+16+1= 40g/mole

If 10g of NaOH is taken, then the actual amount of NaOH is 99% of 10 = 9.9g which is equivalent to = 0.248NaOH

10g = 0.248mole of NaOH

We require 1.02mole of NaOH but from the stoichiometry equation above

1mole of Na₂O gives 2moles of NaOH

Hence, the required 1.02mole of Na₂O will be gotten from 2 x 1.02 of NaOH = 2.04mole NaOH

10g of NaOH = 0.248mole of NaOH

x_g = 2.04mole of NaOH

x_g = = 82.25g of NaOH pellets
Additional H₂O

1.02mole of H₂O is gotten from NaOH, hence the remaining water is gotten as 450- 1.02= 448.98mole of H₂O

Molar mass of H₂O = 16 +2 =18g/mol

Mass of H₂O required = 18 x 448.98 = 8081.64g of H₂O

Thus the total amount of individual reagents required for the synthesis of zeolite Y with molar composition of 15Na₂O:Al₂O₃:15SiO₂:450H₂O are as follows:

Metakaolin= 222.14g

Na₂SiO₃ = 1667.67g

NaOH = 82.25g

H₂O = 8081.64g

Scaling down to 40g of metakaolin, we will use

Scaling factor =

Metakaolin=

Na₂SiO₃ = 40g

NaOH =

H₂O =

= 0.1939litres

Hence the following amount of precursor were used to synthesize zeolite Y:

Metakaolin= 5.3313g

Na₂SiO₃ = 40g

NaOH = 1.9740g

H₂O = 193.959g = 0.1939litres

APPENDIX E

Table 4.8 Degree of dehydroxylation of Okpella kaolin clay for different

calcination temperature and times

		Temperatures ^oC
Heating time, (min)
	550	600	650	700	750
5	0.13	0.23	0.16	0.50	0.68
10	0.19	0.05	0.75	0.84	0.92
15	0.32	0.64	0.87	0.91	0.96
30	0.62	0.83	0.69	0.91	0.94
60	0.77	0.87	0.94	0.95	0.97
90	0.83	0.97	0.81	0.98	0.98