BIODIESEL December 2015

Biodiesel What….Why……..How……….

What is biodiesel ?

• Diesel oil made of vegetable oil. It has comparable properties with a “fossil diesel oil”

Why use biodiesel ?To reduce the consumption of fossil diesel. To use renewable sources.

How to prepare biodiesel ?Esterification

Biodesel is made from :

waste vegetable oil (WVO) or straight vegetable oil (SVO).Lipid from algae

Oil is Fatty acid. (Long chain Carboxylic Acid)

What is oil?

Cant we just use oil directly without converting into biodesel?

Raw materials

Straight vegetable oils (SVO):

- Too viscous - -Low cetane number-High freezing point (easy to freeze)

Viscosity At 40 C:

Petrodiesel : 4 to 5 mm2/s, vegetable oils: 30 and 40 mm2/s.

Cetane number is a measure of how quickly a fuel will ignite in acompression ignition engine.

Cetane is very quickly ignited, and its number is set to 100.

The cetane number of the fuel should be above 41. Most vegetable oils have an adequate cetane number, but, if necessary, additives can be mixed with the oil. Small amounts of acetone have been used.

Cetane number

(C16H34), also called hexadecane,

Viscocity and Cetane Number

Freezing Point of Veg Oil

• corn oil - 20 deg. C• sunflower oil - 17 deg. C• olive oil - 6 deg. C• sesame oil - 6 deg. C• peanut oil 3 deg. C• palm oil 24.1 deg. C• coconut oil 25.1 deg. C

What to do ?????

Solutions :

a. Blend with Diesel oil or kerosene.b. Preheat (65 C)c. Transesterification --> biodiesel

Oil = Fatty Acid

Oil content (wt%) of oil fruits and oil seeds

ESTERIFICATION

Transesterification of triglycerides with alcohol

Transesterification

CH2

|

CH

|

CH2

CH3OCOR”

OCOR”’

OCOR’

OH

CH3

CH3

OH

OH

Transesterification of rapeseed oil using

Transesterification of rapeseed oil

Flow diagram of the Jatropha Energy System

For biodiesel, methanol is currently popular,But ethanol is the better choice because it isProduced from biomass

Methanol is usually obtained from petroleum although it can be produced from biomass.Methanol is toxic

Methanol or ethanol ?

C16H32O2

Molar mass 256.42 g/mol

You have 1000 kg of a vegetable oil that happens to consist of a single triglyceride (not a mixture of triglycerides). The three acids in each molecule are all palmitic acid (C16:0).

What is the proper chemical name of this triglyceride?What is the molecular mass of the triglyceride?Estimate the number of kilograms of glycerine produced when the above vegetable oil is transesterified with ethanol.

Glycerol C 3H5(OH)3Molar mass92.09382 g/mol

Molecular formula C16H32O2Molar mass 256When make a bond, loss 1 H → 255Tri → 255 x 3 = 765CH2-CH-CH2 = 41Total = 806

This is a triple palmitate of glycerine hence it is glyceryl tri-palmitate.

Each mole of triglyceride releases 1 mole of glycerine upon beingesterified. 1000 kg of oil correspond to 1000/806 = 1.24 kilomoles. Henceglycerine produced : 1.24 kilomolesWeight of glycerine produced : 1.24 × 92 = 114 kg.

Example 2:

To produce biodiesel, ethyl or methyl esters from rapeseed oil, ethanol or methanol, and potassium hydroxide are used in the reaction:

a. Determine the theoretical conversion efficiency of the biodiesel reaction

b. Determine the amount of ethanol required to convert 1 L of rapeseed oil reacted with 1 percent potassium hydroxide.

Base your calculations on triolein since this is often the predominant triglyceride in vegetable-based oils: C57H98O6,

C57H98O6, MW 878 g/gmol, density 0.88 kg/LEthanol: C2H5OH, MW: 46 g/mol, density 0.794 kg/LMethanol: CH3OH, MW: 32 g/mol, density: 0.796 kg/LPotassium hydroxide in alcohol (1 wt %/vol):

Oleic acid 18:1 cis-9

C18H34O2

Fuel Density (kg/L)

Energy (MJ/L)

Biodiesel 0.88 36.6

Methanol 0.79 22.7

CH2-CH-CH2 = 413 Oxygen = 3 X 16 = 483 Carbonyl (CO) = 3 x 28 = 843 oleic = 3 [( 17x12 )+(33 x 1)] = 3[ 237]= 711

Total = 711+84+48+41 = 884

Molecular formula C57H104O6

57*12+104+6*16 = 884 Molecular weight

C3H5OOCR)3 + 3 C2H5OH → 3 RCOOC2H5 + C3H5(OH)3

884 46

R= C17H33 -->237

237 + 12+32+24+5 36+5+3(17)

310 92

36+5+(16+16+12+237)3

a. Conversion efficiency : 105 %

1000 gram = 1.13 mol

3 x 1.13=3.39 mol=1050 gram

b. The weight of 1 litre oil = volume x density , ------>0.88 kg = 0.995 mol ------> ethanol = 3 x 0.99 mol

= 3 mol = 3 x 46 gram= 138 gram

Every 1 litre ( or 880 gram) oil needs 138 gram ethanol. Every 1 gram of ethanol will convert 880/138 = 6.4 gram 0f oil

b. Molar ratio for alcohol to triglyceride molecule is 3 to 1; → 3 mol EtOH × 46 g/mol = 138 g So 138 g of ethanol per gmol of triglyceride are needed. 1 gmol of triolean × 878 g/gmol = 878 g triolean;

EtOH needed for compl conversion =

878 g triolean/138 g EtOH = 6.4 g oil/1 g

If methanol is used instead of ethanol :a. Stoichiometrically, how many kg of methanol are required for each kg of vegetable oil?b. If the methanol, were used directly as fuel, how much energy would be released?c. If 1 liter of biodiesel is used as fuel, how much energy is released?

d. What is the methanol-to-biodiesel enegy ratio?

Fuel Density (kg/L)

Energy (MJ/L)

Biodiesel 0.88 36.6

Methanol 0.79 22.7

C3H5(OOCR)3 + 3 CH3OH → 3 RCOOCH3 + C3H5(OH)3

a. 1 litre oil = 0.88 kg = 0.995 mol ------> Methanol = 3 x 0.99 mol

= 3 mol = 3 x 32 gram= 96 gram

Every 1 litre ( or 880 gram) oil needs 96 gram Methanol. Every 1 gram of Methanol will convert 880/96 = 9.16 gram 0f oil (compare with that of ethanol)

b. ref to table in question, methanol energy = 22.7 MJ / LMethanol density = 0.8 kg/L. Every 1 L methanol will produce 22.7 MJ energyOr, every 0.8 kg ( 800 gr) methanol will produce 22.7 MJ energyFor every 96 gr methanol – > 96/800 x 22.7

= 2.72 MJ

C3H5(OOCR)3 + 3 CH3OH → 3 RCOOCH3 + C3H5(OH)3

c. Mw biodiesel = 237+12+32+15 = 2961 mol oil will produce 3 mol biodesel. 3 mol biodesel= 3 x 296 gr= 888 gr

ref to table , biodiesel energy = 36.6 MJ / LBiodiesel density = 0.88 kg/L. Every 1 L methanol will produce 36.6 MJ energyOr, every 0.88 kg ( 880 gr) methanol will produce 36.6 MJ energyFor every 888 gr biodiesel – > 888/880 x 36.6

= 37 MJ

Fuel Density (kg/L)

Energy (MJ/L)

Biodiesel 0.88 36.6

Methanol 0.79 22.7

What is the main reason to prefer biodiesel tostraight vegetable oils (SVO) as fuel for diesel engines?

What should you do to make SVOs more acceptable as diesel fuel (other than making biodiesel out of them)?