PL215958B1 - Method for obtaining second generation fuel from the glycerine fraction formed during production of biodiesel from vegetable oils or animal fats - Google Patents

Description

The subject of the invention is a method of producing a second generation fuel from the crude glycerin phase obtained in the production of methyl esters of higher fatty acids from vegetable oils extruded from seeds and fruits of oil plants, as well as from waste vegetable and animal fats.

Known methods of producing bioesters (first generation fuels) do not use the fuel of the glycerin phase obtained in the production of bioesters, obtained in the form of; solid, quasi-solid and liquid. The glycerin phase, e.g. from rapeseed oil, contains approx. 50% pure glycerin, mono- and diglycerides, catalyst, phospholipids, tocopherols, colored substances, soaps, alkyl alcohol, usually methanol, and approx. 30% by weight. water.

The management of the glycerin phase in large enterprises usually involves the recovery of pure glycerin for the raw material intended for the cosmetics and pharmaceutical industries. Despite the high financial costs necessary to obtain pure glycerine, its prices are still decreasing. The sharp increase in the production of biodiesel in the world caused the price of glycerin to fall. The saturation of the market with this product forces producers of "bioesters" to look for cheap, ecologically safe, new methods of processing and managing the glycerin phase. Purification of the glycerin phase into technical glycerin in small facilities by the known methods is unjustified and unprofitable due to the significant investment costs and energy-consuming technological operations related to the refining of the glycerin phase. On the other hand, the demand for small and medium-sized installations for the production of biofuels is significant, e.g. in rural municipalities, but the currently offered processes and technological and design solutions do not have simple solutions that would enable the fuel management of the glycerin phase at the bioester producer, regardless of the type of raw material used and the origin fats.

The currently used technologies for the production of "bioesters" do not have a simple, ie technologically uncomplicated, method of fuel management of the waste glycerin phase that arises during the production of esters.

Known methods of managing the waste glycerol phase consist in carrying out the etherification process of glycerol contained in the waste glycerol phase, e.g. in the presence of solid catalysts, such as: amberlite-15 in US Patent 6,015,440; amberlite-35 in the patent description PL 206797; polystyrene resins containing Dowex-50 sulfonic acid or Lewis acids in US Patent 5,578,090, and zeolites with an internal aluminum content, e.g. in DE 4222183.

The essence of the second generation fuel production method from the crude glycerin phase obtained in the production of methyl esters of higher fatty acids according to the invention consists in the fact that the crude glycerin phase containing potassium glycerate is subjected to catalytic etherification in a heterogeneous liquid-liquid system consisting in mixing alkyl sulphate, preferably methyl or with an excess of sulfuric acid as a catalyst, in a 1: 1 volume ratio, the etherification reaction being most preferably carried out at a temperature of 50 ° C and ending at a pH of 2.5, at which the precipitate of potassium bisulfate is separated from the reaction medium .

In the present invention, the process of catalytic etherification of the waste crude glycerol phase is carried out with an aliphatic alcohol dissolved in an excess of sulfuric acid H2SO4 as catalyst, with a mixing ratio of 1: 1. When using an aliphatic alcohol in the form of methyl alcohol in excess of sulfuric acid, sulfuric acid methyl ester is formed in the form of methyl bisulfate CH3O-SO3H:

CH3OH + HOSO3H> CH3O-SO3H + H2O (1) which in excess of concentrated sulfuric acid is converted to the following oxonium salt:

(CH3OH2) ⁺ + ^- (OSO3H) (2)

Thus, the course of the catalytic etherification reaction of potassium glycerate contained in the glycerin phase can generally be described by the following reaction equation:

_{+ -} H +

C3H5 (OK) 3 + 3 (CH3OH2) + + 3 (OSO3H) ^- _{; [[Q} CsHsCOCHsb + 3KHSO4 (3)

As a result of reaction (3), a non-uniform liquid product is obtained, containing glycerol alkyl ethers: 1 methoxy 2, 3 propanediol and 2 methoxy 1,3 propanediol, as well as methyl esters of higher fatty acids from fats unreacted in the transesterification process, especially fats

PL 215 958 B1 containing -C = C- double bonds and soaps, e.g. potassium and free fatty acids, as well as the solid product in the form of potassium bisulfate KHSO4.

The fuel produced in this way was called the second generation fuel obtained from the waste glycerin phase. Due to the presence in the fuel of glycerol ethers and methyl esters of higher fatty acids from unreacted glycerides in the transesterification process, this fuel has a significant calorific value, amounting to 36.185 MJ / kg.

A simplified flow diagram of the crude glycerol etherification process according to the invention is shown in the drawing.

₃

1000 dm ^{3 of} raw, waste glycerin phase with a pH value of 8, containing 50 wt. potassium glycerate C3H5O3K3 along with unreacted in the transesterification process: KOH, CH3OH, mono- and diglycerides, phospholipids, tocopherols, color substances and potassium soap, which constitute 40 wt. of the glycerol phase and the remaining 10 wt.% is water. The contents of the reactor are heated to 50 ° C while being continuously stirred at a speed of 120 rpm. Then added to the reactor over 80 minutes ₃

120 dm ^{3 of a} solution containing methyl sulfate in excess sulfuric acid, obtained by mixing 99.8% CH3OH and 96% H2SO4 in a 1: 1 volume ratio, with sulfuric acid being the catalyst for the etherification reaction. The etherification reaction is completed at pH = 2.5, in which the crystalline KHSO4 precipitate separates from the reaction medium, with the simultaneous change of the color of the liquid in the reactor from brown to light yellow. In the final stage of the etherification reaction, 60 vol.% Is obtained. glycerin ethers: (1 methoxy 2,3 propanediol and 2 methoxy 1,3 propanediol), as well as 20 vol. methyl esters of higher fatty acids obtained from glycerides contained in the glycerol phase and a water fraction containing 20% vol. H2O with dissolved, unreacted glycerol and a precipitate of 15 kg of KHSO4 crystal salt. The produced liquid product is not chemically uniform.

The next technological step is phase separation, consisting in gravity sedimentation of the obtained solid product (sludge), or mechanical sedimentation with the use of a sedimentation centrifuge or filter press. In this way, the precipitate of potassium hydrogen sulphate (VI) is separated from the liquid products. The sediment is directed to the drying tray and the fuel fraction washed with water. Water does not dissolve in the fuel fraction.

The obtained precipitate containing 29.8 wt. K2O in dry matter does not dissolve in the environment of fatty acid methyl esters and glycerin ethers and can be used, for example, as a fertilizer in agriculture.

The produced fuel of the second generation can be dissolved in any ratio with the fuel of the first generation, i.e. methyl esters of higher fatty acids, as well as with naphtha fuels.

Claims (1)

The method of producing the second generation fuel from the crude glycerol phase obtained in the production of methyl esters of higher fatty acids, characterized in that the crude glycerin phase containing potassium glycerate is subjected to catalytic etherification in a heterogeneous liquid-liquid system consisting in mixing alkyl sulphate, preferably methyl or ethyl sulphate, with with an excess of sulfuric acid as catalyst in a 1: 1 volume ratio, the etherification reaction being most preferably carried out at a temperature of 50 ° C and ending at a pH of 2.5, in which the precipitate of potassium bisulfate is separated from the reaction medium.