CHARACTERIZATION K3PO4/NaZSM-5 USING XRD AND FTIR AS A CATALYST TO PRODUCE BIODIESEL

Samik¹, Ratna Ediati², and Didik Prasetyoko³

^{Proceeding of International Conference On Research, Implementation And Education
Of Mathematics And Sciences 2014, Yogyakarta State University, 18-20 May 2014}

¹Chemistry Department, Mathematical and Natural Sciences Faculty,

Surabaya State University (samikunesa@gmail.com, Tel.: +6285731160005), Indonesia
^2,3Chemistry Department, Mathematical and Natural Sciences Faculty,

Institute of Technology Sepuluh Nopember, Indonesia

Abstract

Synthesis of NaZSM-5 and impregnation of K₃PO₄ catalyst with concentration 5, 10, and 15 wt.% on the resulting NaZSM-5 as a catalyst to produce biodiesel have been done in this study. This study is an experimental study, the research stages include the synthesis and characterization NaZSM-5 and K₃PO₄/NaZSM-5. Characterization by X-Ray Diffraction (XRD) was conducted to determine the X-ray diffraction patterns and the percentage crystallinity of the samples. X-ray diffraction pattern of the resulting sample showed the emergence of diffraction peaks with high intensity at 2θ = 7.8; 8.8; 23.0; 23.2, and 24.3° are specifically indexed to the structure of the MFI topology. The percentage crystallinity of the sample becomes smaller with increasing number of K₃PO₄ impregnated on NaZSM-5 synthesis. Characterization of the samples by Fourier Transform Infra Red (FTIR) aims to determine the type of functional groups present in a compound. FTIR spectra of samples NZ, NZK5, NZK10 and NZK15 have absorption bands in the region 1220 and 547 cm^-1 which shows the absorption characteristics of vibration T - O - T on NaZSM-5 type zeolite which distinguish the other and sensitive to changes in structure. The results of characterization using XRD and FTIR showed that the structure of NaZSM-5 remained unchange after impregnated with K₃PO₄.

Keyword: K₃PO₄/NaZSM-5, the diffraction pattern, the percentage crystallinity,  

                                   absorption characteristics

INTRODUCTION

Biodiesel, a mixture of fatty acid alkyl esters, has been developed as one of the most promising alternative fuel for fossil fuels regarding the limited resources of fossil fuels and the environmental concerns [1]. Almost all commercial biodiesel is currently produced by using homogeneous catalyst (i.e., KOH, NaOH and H₂SO₄). Even though homogeneous catalyzed biodiesel production processes are relatively fast and achieve high conversions, the removal of the homogeneous catalyst after reaction may be a significant problem. This is a concern, since aqueous quenching causes the formation of stable emulsions and saponification, making separation of alkyl-esters difficult, resulting in the generation of large amounts of waste water, and  need a high cost in operation especially for waste water treatment [1-3]. For this reason, heterogeneous catalyst is likely to be used replacing homogeneous catalyst in the near future.

Heterogeneous base catalysts are more effective than acid catalysts and enzymes. From the economic standpoint, it would be ideal if solid base catalysts could work efficiently at temperatures below 150^oC and low pressure. On the other hand, solid acid catalysts, enzymes and non-catalytic supercritical transesterification have been largely ignored in biodiesel research due to pessimistic expectations in terms of reaction rates, undesirable side reactions and high costs [4].

Several heterogeneous base catalysts that used for biodiesel production are ZnO-Al₂O₃/ZSM-5 yield 99,00% [2], K₃PO₄ yield 97,30% [5], KF/Ca-Al hidrotalcite yield 97,14% [6], Mg/MCM-41 yield  85,00% [7], KI/ mesoporous silica yield 90,09% [3]. In this experiment, K₃PO₄ is chosen as catalysts because yield of biodiesel 97,30%, relatively insoluble in methanol and oil [5]. NaZSM-5 supported K₃PO₄ were prepared by impregnation. Thus the aim of this work is to evaluate character of NaZSM-5 and K₃PO₄/NaZSM-5 by XRD and FTIR.

RESEARCH METHOD

Synthesis

The NaZSM-5 crystals were prepared by procedure similar to that described by Khalifah [8]. The seeding gels were prepared by dissolving 1.28 gram sodium aluminate in a solution (12.6 mL TPAOH and 62.5 mL water). After its complete dissolution, 28.2 ml TEOS was added in a solution. This solution  was stirred for 15 min and heated at 60 ^oC for 6 h. After gel formed, was added 11.952 gram CTABr little by little and was stirred until its complete dissolution. Subsequently the crystallisation of the seeding gels was carried out using autoclave for 24 h at 150 ^oC. Finally the solid was separated by filtration, washed with distilled water until pH neutral and dried, firstly for 24 h at 60 ⁰C and subsequently for 24 h at 110 ⁰C. The occluded surfactant (CTA⁺) and the organic template (TPA⁺) were removed by calcination in air at 550 ^oC for 10 h.

The K₃PO₄ solution was impregnated on NaZSM-5 by impregnation with concentration of K₃PO₄ at 5, 10, and 15 wt.%. The catalyst was dried at 110 °C for 24 h followed by calcining at 550 °C for 10 h so that produce K₃PO₄/NaZSM-5 catalyst. The resulting NaZSM-5 and K₃PO₄/NaZSM-5 catalyst with concentration of K₃PO₄ at 5, 10, and 15 wt.% are labeled NZ, NZK5, NZK10 and NZK15.

Characterisation

The X-ray diffraction patterns and the percentage of crystallinity of NZ, NZK5, NZK10 and NZK15 were characterized by Phillips Expert X-Ray Diffraction (XRD) with Cu K_a radiation (40 kV, 30 mA) at scale  2θ  =  5-40^o and rate of scan 0,04 ^o/second. The infrared spectra were recorded using the KBr pellets and Shimadzu Instrument Spectrum One 8400S Fourier Transform Infrared (FTIR) Spectrometer in the range between 4000 and 400 cm^-1.

RESULT AND DISCUSSION

X-ray Diffraction

The X-ray diffraction pattern of K₃PO₄, the resulting samples (NZ, NZK5, NZK10 and NZK15) and ZSM-5 was producted by Zhu et al. [9]  are shown in Fig. 1. The XRD pattern of the resulting sample showed the emergence of diffraction peaks that similar with high intensity at 2θ = 7.8; 8.8; 23.0; 23.2, and 24.3°.

This XRD resulting is similar as the XRD patterns of  ZSM-5 was reported by Zhu et al. [9] with high intensity at 2θ = 7.8; 8.8; 23.1; 23.4, and 24.4° are specifically indexed to the structure of the MFI topology. On the basis of this characterization, NZ, NZK5, NZK10 and NZK15 included the structure of the MFI topology and not be found the another ZSM-5 type.

Fig. 1 also show diffraction pattern of the K₃PO₄ with high intensity at 2θ = 31.8^0­­. The presence of K₃PO₄  impregnated on NaZSM-5 does not show new peak of K₃PO₄ at NZ, NZK5, NZK10 and NZK15, suggesting that the structure of NaZSM-5 is not destroyed during the process of catalyst preparation and K₃PO₄ has well dispersed on NaZSM-5. Zhang et al. [10] observe nothing diffraction peak of PtSnNa catalyst after impregnated on ZSM-5, suggesting that the structure of ZSM-5 is not destroyed during the process of catalyst preparation. Some parts of Na⁺ and Sn⁴⁺ could enter the zeolite main channels, while Pt particles were located mainly on the external surface of the zeolite.

Fig. 1. The X-ray diffraction pattern of K₃PO₄, the resulting samples (NZ, NZK5, NZK10 and NZK15) and ZSM-5 was producted by Zhu et al. [9]

The intensities of NaZSM-5 characteristic peaks were decreasing caused by increasing of K₃PO₄ concentration. The phenomenon decreasing of the intensities of ZSM-5 characteristic peaks also reported by Kim et al. [2] after ZnO-Al₂O₃ and SnO-Al₂O₃ was impregnated on ZSM-5.

Table 1 show relationship percentage crystallinity with percentage K₃PO₄ impregnated on NaZSM-5, that calculated based on intensity main peak at 2θ = 23° using highest intensity sample (NaZSM-5) as comparator standard that assumed has percentage crystallinity = 100. The percentage crystallinity of the samples becomes smaller with increasing number of K₃PO₄ impregnated on NaZSM-5 synthesis.

Table 1. Relationship percentage crystallinity with percentage K₃PO₄ impregnated on NaZSM-5

Sample	2θ	Intensity, I	I/Io	% Crystallinity
NZ	23.10	376.70*	1.00	100
NZK5	23.00	334.18	0.89	89
NZK10	23.01	314.18	0.83	83
NZK15	23.00	271.50	0.72	72

* comparator standard (Io)

FTIR Spectra

FTIR spectra between 400–1300 cm^-1 of K₃PO₄ and the resulting samples (NZ, NZK5, NZK10 and NZK15) are shown in Fig. 2. In this range all resulting samples possess one broad band at 1000–1200 cm^-1, and three bands around 795, 547, and 455 cm^-1. FTIR spectra of samples NZ, NZK5, NZK10 and NZK15 have absorption bands in the region 1220 and 547 cm^-1 which shows the absorption characteristics of vibration T-O-T on NaZSM-5 type zeolite which distinguish the other and sensitive to changes in structure.

Fig. 2. FTIR spectra of K₃PO₄ and the resulting samples (NZ, NZK5, NZK10 and NZK15)

Traditionally [8,11], the bands in the range at around 1000–1200 and 455 cm^-1 are attributed to the structure insensitive internal tetrahedron asymmetric stretching vibrations T-O-T and bending vibrations Si-O-Si, respectively. The band at around 795 cm^-1 can be attributed to both structure insensitive internal tetrahedron and structure sensitive external tetrahedron symmetric stretching vibrations Si-O-Si. The structure sensitive band, appearing in the presented spectra around 547 cm^-1, is attributed to five-ring units in the structures of pentasil zeolites like ZSM-5 (Table 2).

FTIR spectra of K₃PO₄ have absorption bands in the region 1396, 1000 and 551 cm^-1. The bands at 1396 and 879 cm^-1 is attributed to vibrations of carbonate ion from CO₂ gas adsorbed by K₃PO₄ [12-14]. The bands at 1000 and 551 cm^-1 is attributed to stretching vibrations and bending vibrations of phosphate ion on K₃PO₄ [12]. 

Building on FTIR spectra, the presence of K₃PO₄  impregnated on NaZSM-5 does not show new bands of K₃PO₄ at NZ, NZK5, NZK10 and NZK15. So, the analysis resulting of characterization using XRD and FTIR show that the structure of NaZSM-5 remained unchange after impregnated with K₃PO₄.

Table 2. Wave number of of K₃PO₄, ZSM-5 and the resulting samples

                                 (NZ, NZK5, NZK10 and NZK15)

Bands	Wave number (cm-1)						Absorption characteristics
	K3PO4	ZSM-5 Gonçalves, et al [11]	NZ	NZK 5	NZK 10	NZK 15
V1	1396	-	-	-	-	-	Vibrations of carbonate ion
V2	1014	-	-	-	-	-	Stretching vibrations of phosphate ion
V3	879	-	-	-	-	-	Vibrations of carbonate ion
V4	551	-	-	-	-	-	Bending vibrations of phosphate ion
V5	-	1220	1222	1219	1215	1215	Structure insensitive internal tetrahedron asymmetric stretching vibrations T-O-T
V6	-	1100	1103	1103	1099	1099	Structure insensitive internal tetrahedron asymmetric stretching vibrations Si-O-T
V7	-	795	802	795	795	795	Structure insensitive internal tetrahedron and structure sensitive external tetrahedron symmetric stretching vibrations Si-O-Si
V8	-	546	547	547	548	548	Five-ring units in the structures of pentasil
V9	-	450	455	455	459	459	Bending vibrations Si-O-Si

CONCLUSION AND SUGGESTION

Characterization by XRD and  FTIR of the NaZSM-5 and K₃PO₄/NaZSM-5 catalyst with concentration of K₃PO₄ at 5, 10, and 15 wt.% was investigated. The XRD pattern of the resulting sample (NZ, NZK5, NZK10 and NZK15) showed the emergence of diffraction peaks that similar with high intensity at 2θ = 7.8; 8.8; 23.0; 23.2, and 24.3° that are specifically indexed to the structure of the MFI topology and not be found the another ZSM-5 type. The percentage crystallinity of the sample becomes smaller with increasing number of K₃PO₄ impregnated on NaZSM-5 synthesis. FTIR spectra of resulting samples  have absorption bands in the region 1220 and 547 cm^-1 which shows the absorption characteristics of vibration T-O-T on NaZSM-5 type zeolite which distinguish the other and sensitive to changes in structure. The analysis resulting of characterization using XRD and FTIR show that the structure of NaZSM-5 remained unchange after impregnated with K₃PO₄.

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