DE20305164U1 - Rapidly biodegradable base oil for eco-friendly lubricants is based on animal or waste edible fatty alkyl esters transesterified with alcohols of up to 8C - Google Patents

Abstract

A base oil for a lubricant is rapidly biodegradable and is based on animal or waste edible transesterified fatty alkyl esters and alcohols of up to 8C.

Description

Rapidly biodegradable lubricant base oil based on animal fat and used cooking oil alkyl esters with alcohols with up to 8 carbon atoms

In Germany, around 1.1 million tonnes of mineral oil-based lubricants are used each year. Around 50% of this is released into the environment as a result of the system or accidents and leaks. The group of lost lubricants, such as cooling lubricants, saw chain oils or wire rope lubricants, are almost completely lost due to use. The hydrocarbons contained in mineral oil products in particular are toxic to mammals, fish and bacteria.

Rapidly biodegradable lubricants, on the other hand, cause little or no environmental impact when they enter the environment. These lubricants are generally divided into four classes of substances:

• Natural esters

• Synthetic esters

• Polyalkylene glycols

• Polyalphaolefins

The group of synthetic esters also includes the alkyl esters of natural fatty acids. ¹ These products are characterized by relatively good hydrolysis resistance compared to natural esters and by their biological origin. These esters are usually produced by esterifying fatty acids with the corresponding alcohols. To do this, native fat must first be split into fatty acids and glycerin with water at high temperatures and pressures (e.g. 250 ⁰ C ₁ 50 bar). The fatty acids are then esterified under high pressure and high temperature (e.g. 240 ⁰ C, 100 bar). The products obtained are therefore relatively expensive and hardly competitive with mineral oil lubricants.

On the other hand, the biodiesel industry produces large quantities of fatty acid methyl esters at relatively low costs. The production costs of these methyl esters can be reduced even further, especially when inexpensive used cooking oils or animal fats are used as raw materials.

The lubricant base oil described here is a fatty acid alkyl ester, which is produced by transesterification from the above-mentioned raw material fatty acid methyl ester, in particular with the alcohols (1- and 2-) propanol, (1- and 2-) butanol and 2-ethyl-1-hexanol.

¹ Federal Ministry of Consumer Protection, Food and Agriculture: Report on biologically fast
degradable lubricants and hydraulic fluids«», 2002 . .

In order to improve the oxidation stability of these lubricants, a stearin fraction obtained from the fatty acid methyl ester by cold fractionation is preferably used as a raw material for the transesterification.

The following table shows examples of physical properties of the lubricant base oil depending on the alcohol used for transesterification.

Properties of the lubricant base oil:

Alkyl esters with
Alcohol: Flash point
[ ⁰ C] viscosity
[ ^mm2 /s] PourPoint
[ ⁰ C] Solubility in
Isohexane 2-Ethyl-1-hexanol 180-220 7.5 -8.5 0-6 Yes 1-Butanol 170-190 5.5-6.5 10-14 Yes 1-Propanol 160-180 5.3-6.3 10-16 Yes

The product described here is a fatty acid alkyl ester which is produced by transesterification from the above-mentioned raw material fatty acid methyl ester, in particular with the alcohols (1- and 2-) propanol, (1- and 2-) butanol and 2-ethyl-1-hexanol.

Description of the laboratory tests:

In laboratory-scale transesterification experiments, it was found that a low water content is crucial for the course of the reaction. The water of reaction, which is formed when the basic catalyst (KOH or NaOH) is dissolved in the alcohol and the corresponding alcoholate is formed (see equation 3.1), also has a disruptive effect on the transesterification reaction.

KOH + R-OH -► K ⁺ + RO- + H ₂ O
Equation 1 : Reaction alcohol/catalyst

By distillation or drying agents, this water can be largely removed and the transesterification reaction can thus be led to a more complete conversion.
For the reaction, heated alcohol/catalyst mixture is mixed with fatty acid methyl ester at the same temperature in a stirred reactor after distillation or drying. If there is an excess of alcohol, the transesterification reaction takes place spontaneously with slight foam development (due to outgassing methanol vapors). The methanol vapors are condensed and can be recycled. After 15-45 minutes, the transesterification reaction is complete and the reaction mixture is cooled to 25 - 70 ^° C for washing. It is washed with acidified water to neutralize the catalyst residues and with neutral water to remove acid residues. The washing water is separated by static or mechanical decanting. In the subsequent vacuum distillation, water and excess stoichiometric alcohol are removed. The alcohol can be recycled after processing. Table 1 shows suitable reaction conditions for the transesterification with the corresponding alcohols.

Tab.1: Suitable reaction conditions

.. Pressure
[mbar] Propanol (1- or 2-) 75-95 800-1500 Butanol (1- or 2-) 95-113 800-1500 2-Ethyl-i-Hexahoj 140-160 800-1500 temperature
[ ⁰ C] Transesterification 25 1000 Transesterification 25 1000 Transesterification 70 1000 Washing 100 2-100. Washing 100 2-100 Washing 160 2-100 Distillation (removal
Propanol) Distillation (removal
Butanol) Distillation (removal
2-EH)

All production steps can be carried out in an industrial biodiesel plant after minor modifications. In this way, synergy effects are exploited and a cost-effective product with a good ecological balance is obtained.

Figure 1 shows the production scheme for the transesterification of fatty acid methyl esters to the corresponding alkyl esters found on the basis of laboratory tests.

Claims (3)

1. Lubricant base oil, characterized in that it is rapidly biodegradable. 2. Lubricant base oil according to claim 1, characterized in that it contains animal and used cooking oil alkyl esters with alcohols having up to 8 C atoms as a base. 3. Lubricant base oil according to claim 1 and 2, characterized in that of these raw materials (animal and used cooking fat alkyl esters) only selected fatty acid fractions, in particular palmitic and stearic fractions, are contained.