Production of biodiesel from native microalgae of Mazandaran province using alumina zirconia catalysts

PhD Dissertation in Chemical Engineering

Abstract

With the increase in population, the need for energy sources for mankind has also increased. Diesel, as an effective fuel, fulfills the need for transportation fuel in the world. Biodiesel, which is considered a renewable fuel and produces less harmful environmental effects, is produced from various sources, among which edible oil plants such as sunflower oil, soybean oil, olive oil, etc., agricultural waste and microalgae can be mentioned. In the current research, the production of biodiesel from algae is considered because, compared to other sources, algae produce more lipids in their biomass and are not used as human food sources. In this research, Sandesmus microalga species was investigated due to its abundance in Caspian sea water and its availability. Microalgae were cultivated in TMRL medium and the effect of light and reduction of nitrogen source on their growth was investigated. The results showed that the amount of excess nitrogen has no effect on the growth of microalgae. However, when low light intensity is used, reducing the amount of nitrogen in the culture medium is considered a trick to increase the amount of biomass. The logistic model was successfully used to predict the growth curve and maximum biomass. After extracting oil from cultivated microalgae, whose oil content was calculated as 25.8% of their dry weight, oil analysis was done using a gas chromatography device. The results showed that about 81.84% of the total fatty acids in microalgae oil are composed of C16 and C18 fatty acids, which are suitable for the production of high-quality biodiesel. In the next step, catalyst synthesis was done and their characteristics were determined using FTIR, XRD, BET, SEM and TEM tests. The specific surface area of ??gamma alumina zirconia, amorphous alumina, and zirconia catalysts was 389, 312, and 148 square meters/g, respectively. The size of the holes was calculated as 21.243, 18.991 and 20.664 nm, respectively, which indicates the mesoporous structure of the synthesized catalysts. In order to find the maximum efficiency of biodiesel production, the parameters of molar ratio of alcohol to oil, duration of reaction, reaction temperature and amount of catalyst were optimized. After finding the optimal conditions, the transesterification reaction was carried out in the presence of different catalysts and under the following conditions: molar ratio of alcohol to oil equal to 12, duration of 4 hours, temperature of 70 degrees Celsius, amount of catalyst 2% by weight of oil, mechanical stirrer speed of 600 rpm and volume ratio of hexane to methanol was 2 to 5. Biodiesel production efficiency under these conditions for gamma alumina zirconia, amorphous alumina and zirconia catalysts is equal to: 97.8, 94.6 and 81.5%, respectively. Gamma alumina zirconia and amorphous alumina catalysts can be reused at least 5 times after the reduction process.

Key words:

biodiesel, microalgae, fatty acid, zirconia alumina catalyst, transesterification

Introduction

Sustainability is a key principle in natural resource management, which includes considering operational efficiency, minimizing harmful environmental impacts, and socio-economic considerations. Considering the depletion of global reserves of fossil fuels and the emission of greenhouse gases resulting from their use, trusting and relying on the continuous use of fossil fuel energy sources does not seem wise and logical. As a result, extensive research aimed at the development and production of carbon-free renewable gas, liquid and solid biofuels as alternative energy sources is being carried out all over the world.

Alternative energy sources related to the first generation biofuels that are obtained from soil products such as sugarcane, sugar beet, corn and rapeseed have a special place in the global food market, and their indiscriminate cultivation and harvesting causes water shortages. And the destruction of forests will be all over the world. Second generation biofuels, which are obtained from the remains of forest trees and lignocellulosic materials of agricultural products and non-edible food, also have some disadvantages of first generation biofuels. Therefore, according to the current level of knowledge and technology, third generation biofuels, especially fuels from microalgae, are an option..

Therefore, according to the level of current knowledge and technology, the third generation biofuels, especially the fuels derived from microalgae, are a good option to replace fossil fuels. Third generation biofuels do not have the disadvantages of using first and second generation fuels. Microalgae are photosynthetic microorganisms that require simple substances (light, sugars, carbon dioxide, nitrogen, phosphorus, and potassium) and can produce large amounts of fats, proteins, and carbohydrates in their short growth period. These products can be converted into biofuels as well as valuable by-products.

The purpose of this research is to produce biodiesel from native microalgae of Mazandaran province using alumina-zirconia catalysts on a laboratory scale. In this research, the high efficiency of biodiesel production using the synthesized catalyst will be shown compared to other studies. The results of this research show that biodiesel obtained from microalgae can gradually replace a significant part of fossil fuels and meet the growing needs of the energy sector. It is hoped that by conducting this research, we have taken a small step towards the advancement of new technologies in our beloved country.

In order to achieve the above goals, the following items will be discussed and examined in this thesis:

- Chapter 1: History of biodiesel production, applications of biodiesel, disadvantages and advantages of biodiesel, methods of biodiesel production and the use of algae as the primary source of production. Biodiesel

- The second chapter: materials, equipment used, laboratory methods and measurements

- The third chapter: Review and discussion of the results of the experiments which include the following:

(1) Investigation of light intensity and reduction of nitrogen source on microalgae growth

(2) Checking the oil extraction method

(3) Analysis of the oil obtained from algae

(4) Checking the analyzes performed on the synthesized catalysts

(5) Determining the functional groups of the catalysts

(6) Determining the surface area and Particle size of catalysts

(7) Examining photos taken from the surface of catalysts

(8) Examining parameters affecting the transesterification reaction

(9) Determination of biodiesel production efficiency in the presence of catalysts

(10) Examining recovery and use Again from Catalysts

- Chapter Four: Conclusion and Suggestions

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Chapter One: Review of previous studies

1-1- Introduction

At the end of 2011, the world's annual energy consumption was estimated to be equivalent to 12274.6 million tons of oil. became [1]. Fossil fuels [1] provide 87% of the world's energy consumption, among which the share of oil is 33.1%, coal 30.3%, natural gas 23.6%, nuclear energy 4.4% and hydroelectricity 6.5% [1]. Due to extensive technological advances, the existence of high-potential reserves, and increased extraction of new reserves such as natural gas, it is believed that fossil fuels will be available at low prices for a considerable period of time [2]. Unfortunately, the potential threats of global climate change have increased, and most of it is related to greenhouse gas emissions [2] from burning fossil fuels [3]. The change in the aforementioned climate conditions can have great consequences for nature and mankind [4]. As a result, the sustainable use of fossil fuels does not seem logical from the point of view of their limited resources and the negative effects of carbon dioxide emissions.

Fossil fuels are the largest distributors of greenhouse gases in the biosphere [3] and at the end of 2011, the emission of carbon dioxide gas from the combustion of these fuels was 32.578 gigatons [5]. Natural processes are able to remove only about 12 gigatons of carbon dioxide gas.