The Shown Stirring Effect Observed in the (FAU structure) X Zeolite Synthesis with Carbon Nanoparticles Occluded

The shown stirring effect observed in the (FAU structure) X zeolite synthesis with carbon nanoparticles occluded.

Zeolites have found wide application as heterogeneous catalysts, particularly in refineries and petrochemicals. However, in many applications, a problem encountered is that the zeolites has only micropores, which imposes diffusion limitations on the molecules of reactants and products. One of the most widely employed zeolites in refineries and mainly in fluid catalytic cracking process is the Y zeolite. Some great depths oil fields has shown an increase in the size of its molecules, making difficult its processing with existing zeolitic industrial catalysts. Oil refiners have been spent research efforts of other zeolites with bigger microporous and mesoporous material. An example is the Beta zeolite, which has larger pores than the traditional zeolite Y, but it's hard to be synthetized. Thus, the synthesis of mesoporous zeolites aims to increase accessibility to active sites by reducing the restrictions of molecules of reactants and products in the bulk of the catalyst.

In order to determine the variables that had the more influence on the FAU X zeolite synthesis with low SiO2/Al2O3, the Plackett-Burman statistical method was used. The selected variables were impeller type and speed, mixing time, order of reagent addition , stirring time, ageing time in low temperature, crystallization time and presence of crystal seeds.

We opted for conducting 12 experiments, including 3 fictitious variables. These fictitious variables should present low influence in the procedure. The levels for each variable were delimited adopting the higher levels for the lower and higher values for minors see Table 1.

Table 1: Ramdomly selected variables for Plackett-Burman method

	Variable	-	+
F1	Fictitious 1
F2	Fictitious 2
F3	Fictitious 3
V1	Impeller speed rotation	800-1000	300-500
V2	Stirring time	2 minute	5 minutes
V3	Ageing time	24 h	< 5 min
V4	Impeller type	Toothed dispersor	Axial flow impeller
V5	Crystallization time	22-24 h	4 h
V6	Mixing time	5 minutes	< 1 minute
V7	Mixing order	Aluminate on silicate	Silicate on aluminate
V8	Seeding	Yes ( 0,1 g )	No

Following the implementation of the method, Table 2, presents the order distribution of the variables and the respective levels to be used in the numbered experiments.

 Table 2: Distribution of levels depending on the variables for each experiment.

	F2	F1	V3	V4	V5	V6	V1	F3	V2	V7	V8
1	+	+	-	+	+	+	-	-	-	+	-
2	+	-	+	+	+	-	-	-	+	-	+
3	-	+	+	+	-	-	-	+	-	+	+
4	+	+	+	-	-	-	+	-	+	+	-
5	+	+	-	-	-	+	-	+	+	-	+
6	+	-	-	-	+	-	+	+	-	+	+
7	-	-	-	+	-	+	+	-	+	+	+
8	-	-	+	+	+	+	-	+	+	+	-
9	-	+	-	+	+	-	+	+	+	-	-
10	+	-	+	+	-	+	+	+	-	-	-
11	-	+	+	-	+	+	+	-	-	-	+
12	-	-	-	-	-	-	-	-	-	-	-

After the elaboration of the planning, the twelve experiments variables were carried out using a common methodology. The adsorption of toluene of the twelve samples were determined in a dissector where the silica gel has been replaced with a solution of vaseline and toluene. The samples were weighted during 20 days up to constant weight (Figure 1). According to the adsorption measurements (Table 3) samples 1, 2, 3, 6, 9 and 11 presented better adsorption of toluene.

Figure 1 - Toluene adsorption for Sample 9

Table 3 - Toluene adsorption measurement

Sample	Adsorbed toluene (%)
1	14,85
2	14,75
3	12,26
4	2,23
5	0,42
6	16,10
7	0,11
8	1,01
9	16,32
10	0,14
11	12,10
12	0,36

Based on a hypothesis test we concluded that the variables that shown more influence on adsorption capacity were stirring time (higher is better), mixing time (lower is better), crystallization time (largest effect), impeller type (toothed disperser is better) and the presence of seeds. One dummy variable presented a large effect, which means that possibly it has confused with other studied variables.

According to this study, the samples that presented high toluene adsorption capacity were crystallized with 24 h, with a mixing time lower than one minute, with a stirring time of 5 minutes using the toothed disperser and seeds of FAU X zeolite.

Powder diffraction X-ray has shown pure crystalline FAU X zeolite for all samples that presented high toluene adsorption capacity, which means validate the utilized methodology.

In the next step of this study treated carbon nanoparticle will be included in the synthesis batches to verify if they get occluded in crystal zeolites, making possible to obtain mesoporous materials useful for heavy oil cracking.

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