Conversion of waste cooking oil into useful chemicals. The use of a zeolite catalyst and a clay catalyst


Academic Paper, 2020
28 Pages

Excerpt

Table of Contents

List of Figures

List of Tables

1. Introduction
1.1. Catalyst Identification:

2. Waste Cooking Oil (WCO): Characterization
2.1. Transesterification Reaction Mechanism

3. Literature: Biofuel Synthesis

4. Biofuels from Waste Cooking Oil Using Zeolite/Clay Catalyst
4.1. The Synthesis
4.2. Catalyst Characterization: Zeolite or Clay
4.3. Product Characterization

5. Conclusion

6. References

EKPUKA JOSEPH ERONMONSELE

MASTERS OF SCIENCE (M.Sc.) IN INDUSTRIAL CHEMISTRY.

Abstract: Waste or Second used Vegetable oil contains high fatty acid content. This second used oil is better utilized for the production of biodiesel among other useful chemicals. Biodiesel or in general biofuels can be produced in the complex process of transesterification or in hydrotreatment. To do this a catalyst is required. The conversion process is the aim of this paper. This paper identifies clay or zeolite as catalyst material which is required to convert second used cooking oil into useful chemicals. The information presented forward offers a deep insight of products that are obtainable from the conversion of waste vegetable oil.

Keywords: Waste cooking oil, Vegetable oil, Zeolite, Catalyst

List of Figures

Figure 1. XRD – X Ray Diffraction Pattern of Kaolin

Figure 2. NH3-Temperature Profile Desorption Profiles of Various Solid Supports ( NH3-TPD is a strong tool for estimating the acidic property of a solid surface)

Figure 3: Pretreatment of High Free Fatty Acid (FFA) Feed-Stock with Acid-Catalzed Reactor

Figure 4: Species of Free Fatty Acids

Figure 5: FTIR Spectrum of Zeolite-Based Catalyst

Figure 6: FTIR Spectra of Kaolinite

Figure 7: Flame Ionization Detector Gas Chromatography Chart of Liquid Products in Hydrotreatment of Waste Cooking oil over Ru/Al13-Mont under various H2/Oil ratios (T: 350 °C; H2 pressure: 2 MPa;LHSV- Liquid Hourly Space Velocity : 15.2 h–1)

Figure 8: Flame Ionization Detector Gas Chromatography Charts of Liquid Products in Hydrotreatment of Waste Cooking oil over Ru/Al13-Mont under various H2 Pressures (T: 350 °C; H2/oil: 400;LHSV:15.2 h–1)

List of Tables

Table 1: Composition and Properties of a Waste Cooking oil

Table 2: Product Yield over Various Catalysts at Liquid Hourly Space Velocity LHSV

Table 3: Composition and Properties of Liquid Hydrocarbon (C5+) from a Hydrotreatment Process of Waste Cooking Oil over Different Catalysts

1. Introduction

Waste Cooking Oil (WCO) is used vegetable oil obtained from cooking food. Although, waste cooking oil is low cost, environmental and soil degradation occur from the disposal of waste oil. To better control this effect, waste vegetable oil can be better utilized as a feedstock to produce biofuel (Filho et al., 1993; Morais et al., 2010).

Biofuel is FAME. FAME is Fatty - Acid – Methyl – Ester resultant from a transesterification reaction. Transesterification is a reaction occurring as a result from the reactant oil (triglyceride) and alcohol. Biofuel synthesis uses 1:1 group clay minerals as catalyst. Clay catalyst is largely restricted to kaolinite. Kaolinite can serve as a support to the actual catalyst or as a precursor to other ceramic material catalysts or Zeolites.

Transesterification of WCO to fatty acid methyl ester will use catalyst. Although this conversion at high temperatures and pressures can be carried out without catalyst, the product yield usually contains a comparatively substantial amount of fatty acids (Li et al., 2010). Thus, solid acid catalysts are favourable for biofuel synthesis (Yanyong et al., 2012).

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Figure 1. XRD – X Ray Diffraction Pattern of Kaolin (Htay and Mya Oo, 2008)

This review uses Zeolite and or Clay as catalyst with or without a catalyst support. Clay catalysts can be obtained from Kaolin. XRD pattern above shows components of clay. Clay catalysts can also be doped with trace amounts of Magnesium (Mg), Calcium (Ca) and Ruthenium (Ru) for support. A clay mineral is Al2Si2O5(OH)4 (Myat Mon, 2003). Al2Si2O5(OH)4 is kaolinite. The sheet structure for Al2Si2O5(OH)4 in a 1:1 proportion is composed of tetrahedral sheets of SiO4 and octahedral sheets of Al(O,OH)6. Hence, Al2Si2O5(OH)4 has a pseudo-hexagonal symmetry (Htay and Mya Oo, 2008) .

1.1. Catalyst Identification: XRD pattern above of Kaolin shows Kaolinite major Al2(Si205)(OH)4 and Quarts low major SiO2. A minor which may be metakaolinite also appears in the figure. A typical zeolite synthesis can be obtained from clay (Myat Mon, 2003). The inactive structures of Silicon-Oxygen or Aluminium-Oxygen in kaolinite are difficult to be directly synthesized to zeolite. However, Zeolite can be obtained from Kaolinite by the addition of NaOH (Kaolinite / NaOH= 1:1.5 by weight) at 850˚C for a time frame of three hours.

Meso-Y (Mesoporous Y), SAPO-34 (Silicoaluminophosphate 34), and HY are examples of zeolite type that can be loaded on with catalyst support like nickel in a transformational process of waste oil to generate bio-jet fuel (Li, 2015). Mostly, synthetic zeolites are widely applied commercially. Zeolite structures of keen attentive interests are that of large pores zeolite. Large pore zeolites encompass of type X, Y, L and type omega and mordenite. These zeolites are used in hydrocarbon conversion catalysis (Htay and Mya Oo, 2008).

Hydrocarbon conversion most commonly use solid acid catalysts. Infrequently, Zeolite Y catalyst is most commercially used as catalyst because it exhibits a high concentration of active activity on an acid site. In 2017, Zongwei et al investigated a synthesis of zeolite NaY from kaolinite. HY can be prepared from NaY by ion exchange (Zongwei et al., 2017).

A catalyst active on acid site is by nature influenced mainly by the acid sites. For example, the figure below shows an NH3-TPD profile with the peak position relative to maximum temperature for different catalyst supports with various acidic strengths. The descending directive of acidity is HY > Al13-Mont > SiO2 (no acidity).

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Figure 2. NH3-Temperature Programming Desorption Profiles of Various Solid Supports (NH3-Temperature Programming Desorption is a strong tool for estimating the acidic property of a solid surface) (Yanyong et al., 2012).

2. Waste Cooking Oil (WCO): Characterization

Waste cooking oil or waste vegetable oil is used vegetable oil which doesn’t meet consumption appropriateness because of its elevated level of free fatty acids (FFA) concentration. A high FFA concentration greatly increases the production cost. Waste cooking oil is used to produce FAME type bio-diesel and additives for lubricating oil. Cooking vegetable oil can be sunflower oil, peanut oil or olive oil (Filho et al., 1993; Morais et al., 2010).

Waste oil feedstock utilized for biofuel production is different from fresh cooking oil due to hydrolysis and oxidation. Hydrolysis and oxidation occur in frying of oil in the presence of heat and water. Fresh vegetable oil contains unsaturated hydrocarbons (Triglyceride). Triglyceride form Diglyceride, Monoglycerid and FFA when vegetable oil is subjected to thermal stress in frying or cooking process. This oil from frying and cooking is Waste Cooking Oil (WCO). A typical example of the configuration and dexterity of a used vegetable oil is specified in the table below.

Table 1: Composition and Properties of a Waste Vegetable oil (Yanyong et al., 2012)

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Fatty acid composition for used vegetable oil will be dominated by oleic (C18 structure) and linoleic acid (C18 structure). Waste cooking oil yields a lot of products over various catalysts during hydrotreatment. The hydrotreatment conversion will not decline after treatment reaction over each catalyst if lipids and free fatty acids are absent (Morais et al., 2010).

Product yield over catalysts include fuel gas (C1 + C2) (<1.0 weight %), liquid fuel (C5+ hydrocarbons) (82.1–84.0 weight %) and LPG (C3 + C4) (4.8–5.6 weight %) See Table 2. C5+ liquid hydrocarbons and C3 + C4 LPG fit profiles to meet an energy source for automobiles. Shown also in table 2 is Water (% proportional range yield: 7.7–8.0 weight %) included with COx (as CO and CO2, % proportional range yield: 3.2–3.4 weight %) which will produced similarly in the hydrotreatment process over various catalyst.

Propane in the formed LPG (C3 + C4) will occupy above 90 weight % over various catalysts. For the reason that all C=O bonds triglycerides are broken during the hydrotreatment process. Hence, propane is formed.

Table 2: Product Yield over Various Catalysts at Liquid Hourly Space Velocity LHSV (Yanyong et al., 2012)

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Some hydrocarbons formed over various catalysts say Ru/SiO2 contain large aggregates of C11–C20 better known as diesel-distillate (98.9 weight % shown in Table 3) with a low isomerization/cracking ratio (0.08 shown in Table 3) among different catalysts. It is important to note that a 20 °C pour point for a product yield is too high to be used as a diesel fuel. Ru/HY is not a suitable catalyst for conversion of waste oil to Bio-Hydrogenated Diesel BHD. Because BHD fuel contains large aggregates of gasoline-distillate (C5 - C10 by 42.8 weight %) on strong acid sites (Myat Mon, 2003).

Table 3: Composition and Properties of Liquid Hydrocarbon (C5+) from a Hydrotreatment Process of Waste Cooking Oil over Different Catalysts (Yanyong et al., 2012).

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In an increasing order, n -C15H32, n -C16H34, n -C17H36, and n -C18H38 has melting points as 10, 18, 22 and 28°C correspondingly. A considerable amount of n -paraffins (C15–C18) gives at 20 °C a high pour point value typically for liquid hydrocarbon products over Ru/SiO2 (Table 3). Pour point is also known as liquid flow. Liquid flow is an important factor for liquid diesel. Better utilized to fit current diesel engines, liquid hydrocarbon pour points should be decreased especially over Ru/SiO2 products.

The relative melting points of Iso -paraffins with those of light paraffins are low. Some examples paraffins and their melting points in degree celsius (°C) are n -C11H24: −25, 3-methyl-pentadecane: −22, 2-methyl-pentadecane: −11, 2-methyl-tetradecane: −8, 3-methyl-heptadecane: −6 and 2-methyl-hexadecane: 5. Solid acids (Al13-Mont and HY) can use Ru as a catalyst support to improve the fluidity of liquid hydrocarbon products. These products are formed from the hydrotreatment of waste oil in an isomerization/cracking activity of C15H32–C18H38 n -paraffins.

Obviously, fuels can be generated from biological feed stocks (WCO) using catalyst. These fuels are termed “biofuels”. Biofuels can be categorized as first generation fuels and second-generation fuels. Catalysts used in transesterification or dehydrogenation process of WCO can be homogeneous or heterogeneous.

Heterogeneous catalysts alternatively are less corrosive, reusable, generate less amount of wastewater and easy to separate from mixture product. Homogeneous catalysts are corrosive, nonreusable, generate many toxic wastewaters and difficult to separate from reaction mixture. The biodiesel production cost can be reduced, thus the chosen catalysts should have low price and be available in large quantity (Ma and Hanna , 1999).

2.1. Transesterification Reaction Mechanism

The reaction mechanism for converting waste cooking oil into usable chemicals is transesterification (Freedman et al., 1986) or hydrodeoxygenation using catalyst. The hydrotreatment process for waste vegetable oil proceeds via deoxygenation reaction of saturated fatty acids.

Alkanes produced that have a reduced carbon atom than the reactant fatty acid will be produced via Decarbonylation (DCO) and decarboxylation (DCO2). However, alkanes with identical carbon atoms will be produced by means of hydrodeoxygenation (HDO) process. Thus, a molar ratio proportion of say C17/C18 can reflect an inclination of DCOx/HDO reactions. For biodiesel production, the availability of active sites can be increased in line with catalyst concentration.

Biodiesel is produced via transesterification reaction.

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Transesterification reaction

FAME - Fatty acid methyl ester can be categorized as first generation biofuel. FAME is produced via transesterification reaction. Transesterification reaction is between oil and methanol (alcohol) using a catalyst (Freedman et al., 1986). Furthermore, a typical deoxygenation process for saturated fatty acids (such as C17H35COOH) encompass of a trio reaction: reduction, decarbonylation, and decarboxylation.

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Title
Conversion of waste cooking oil into useful chemicals. The use of a zeolite catalyst and a clay catalyst
Author
Year
2020
Pages
28
Catalog Number
V519978
ISBN (eBook)
9783346136374
ISBN (Book)
9783346136381
Language
English
Tags
conversion
Quote paper
Joseph Ekpuka (Author), 2020, Conversion of waste cooking oil into useful chemicals. The use of a zeolite catalyst and a clay catalyst, Munich, GRIN Verlag, https://www.grin.com/document/519978

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