CZ220892A3 - Improved process for producing diesel fuel of biological origin from rape seed oil - Google Patents

Abstract

Rape oil is elaborated by reesterification by methanol in presence of hydroxide potassium as catalyst. In reactive mixture created after reesterification, is added the concentrate phosphoric acid. Original matters are leaded to reaction in ratio rape oil:methanol:hydroxide potassium = 1:3,3 to 5,25 : 0,16 to 0,25 mol. Phosphoric acid is added as 1,1 to 1,5 molar multiple of used matter mass of hydroxide potassium. Reaction is realized at temperature 20 to 25 degrees of Celsius and at atmospheric pressure. After adding of phosphoric acid is in reactive mixture created precipitate containing prevailingly dihydrogenphosphate potassium which is mechanically separated from liquid phase. From liquid phase is eliminated methanol by vacuum elimination or bubbling by air at temperature 20 to 50 degrees of Celsius. Methanol steams are collected in condenser. Liquid phase created in this way is spontaneous divided into upper layer bionapht and upper layer very concentrated solution almost pure glycerol in water.

Description

Technical Field '-. * · ----... ⁽ _____________________

The invention relates to a process for the production of biodiesel and glycerin from rapeseed oil by re-esterification with methanol under catalysis with potassium hydroxide and with the addition of a suitable acid.

BACKGROUND OF THE INVENTION

Biodiesel (Biodiesel) is a mixture of fatty acid esters, derived from natural materials (vegetable and animal fats and oils) and is a propellant in diesel (Diesel) engines. In Europe the most common starting material is rapeseed oil. This can be used as biodiesel after previous filtration, eventually. refining in its original form, which requires considerable and expensive treatment of diesel engines designed for conventional diesel. The product of its catalytic re-esterification with a suitable monohydric alcohol is more frequently used. This reaction produces biodiesel as a mixture of alkyl esters of rapeseed oil fatty acids and glycerin. For such biodiesel there is no need to modify conventional diesel engines.

The most commonly used alcohol and catalyst are methanol and potassium hydroxide.

Various processes for producing this type of biodiesel are the subject of a number of patents. A review is given in our patent CS No. 27811D (PV 524-92). They differ from each other by a) temperature b) ratio of starting components c) reesterification d) separation of biodiesel from glycerine phase,

e) purifying the biodiesel from catalyst residues, alcohol and glycerin; f) treating the glycerin phase.

A considerable disadvantage of all the prior art processes known is that part of the biodiesel goes into the glycerine phase together with the bulk of the unreacted alcohol and the bulk of the catalyst used. Processing of this phase is then difficult and obtaining pure glycerin, eventually. the resulting biodiesel is complicated and therefore expensive - see patent application 908-92.

According to CS patent No. 278110, the rapeseed oil reesterification according to the invention is carried out at a ratio of rapeseed oil: methanol: potassium hydroxide = 1: 1.1 - 1.5 equivalents: 1.0 - 1.6 weight percent (based on rapeseed) oil) at room temperature preferably in the range of 20-25 ° C. This is done by introducing into the present intensively mixed rapeseed oil a solution of potassium hydroxide in methanol prepared in the stated ratio of the components according to the invention. The resulting mixture was stirred vigorously for 2-5 minutes and then allowed to settle for about 1-2 hours until two sufficiently sharply differentiated layers were formed and separated. The top layer contains a major proportion of biodiesel, as well as methanol and potassium hydroxide. It is subjected to further processing. The backsheet contains glycerin as the major component.

The process according to the invention is not processed.

The treatment of the upper layer consists in separating the residual methanol and the catalyst. According to the invention, the methanol separation is carried out by vacuum evaporation of methanol, preferably at a pressure of 666-1333 Pa and at the above-mentioned room temperature. Preferably, this vacuum evaporation is carried out as the biodiesel level increases, for example by stirring or spraying. A precipitate is formed which contains the major part of the upper layer of the initially dissolved potassium hydroxide. This precipitate can be easily mechanically separated from the biodiesel.

Methanol vapors are collected in a condenser.

SUMMARY OF THE INVENTION

It consists in performing the initial part of the reaction according to our patent CS No. 278110 and then chemical and physical intervention in the reaction mixture, which causes successively: separation of excess methanol (as liquid), separation of catalyst (in the form of solid inorganic fertilizer) and separation of the resulting liquid reaction. blends on biodiesel and a practically pure solution of glycerin in water. The rapeseed oil reesterification according to the invention is carried out initially as described in patent No. 278110 (see previous chapter) until the reaction mixture is stirred vigorously for 2-5 minutes. The mixture was then stirred gently for a further 58-55 minutes. Then, to the vigorously stirred reaction mixture, an amount of concentrated phosphoric acid (85%) corresponding to 1.1-1.5 times moles of the potassium hydroxide substance used is gradually added. The total addition time of the phosphoric acid is about 10 minutes. In this neutralization step, a white precipitate gradually forms in the reaction mixture, which is initially tacky, settles on the bottom and walls of the reactor, and requires a powerful stirrer to stir it throughout the volume of the liquid. After completion of the neutralization (pH 6-7), the unreacted methanol is removed from the reaction mixture by vacuum evaporation, preferably at a pressure of 666-1533 Pa or by bubbling the reaction mixture through air at 20-50 ° C and appropriately increasing the surface area of the reaction mixture. mixing or spraying. Evacuation, resp. it takes 2-3 hours for the methanol to bubble. Methanol vapors are frozen in a condenser. During evacuation, the white precipitate coarsens and becomes sticky. Therefore, after evacuation, it can be easily separated by filtration or centrifugation from the liquid part by the reaction mixture. This liquid, after filtration, spontaneously separates over approximately 2 hours into the upper methyl ester phase - biodiesel and the lower phase - an almost colorless, practically pure solution of glycerin in water. The water comes from the used 85¾ phosphoric acid and it is produced by neutralization. In this procedure, the amount of glycerin obtained corresponds to the theoretically expected amount (based on the amount of rapeseed oil used) and this glycerin is not contaminated with either biodiesel or plant dyes, such as in the process described in U.S. Pat. - 200% of the theoretical volume of glycerin produced by the effect of the overrun of biodiesel, methanol, catalyst and plant dyes. The glycerin phase is not processed in the process of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

To a 1000 cm @ 3 glass batch reactor equipped with a stirrer was charged 500 cm @ 3 (0.455 g) of crude sedimented rapeseed oil. Under vigorous stirring, a solution of 6.6 g of 90¾ KOH in 93 cm @ 3 of methanol was added in one portion. The mixture was stirred vigorously for 2 minutes, then gently for 58 minutes. Then, 6.7 cm @ 3 of concentrated (85% phosphoric acid) was added to the vigorously stirred reaction mixture for 10 minutes. During the addition of the acid, a sticky white precipitate formed in the reaction mixture. evacuated at about 1000 Pa at 20-22 [deg.] C. The volatile methanol was collected in a condenser After the evacuation was complete, the white precipitate was collected from the reaction mixture by filtration. Two layers were formed after 2 hours of sedimentation: a top of 520 ci? containing biodiesel, a bottom of a highly concentrated and almost colorless solution of glycerin in water.

99.6 wt. % to rapeseed oil, conversion of 92.7% to rapeseed oil (HPLC), = - 95 wt. % (HPLC), respectively. = - 95 wt. % (GC) for rapeseed oil methyl esters, density 0.875 g.cm (20 ° C), viscosity 7.43 mm ² · s ^- ^ (20 ° C), methanol content 0.19 wt. %, flash point in a closed crucible 160 ° C, potassium content <* = 2 mg / ciP ME, pour point -15 ° C, pH 6-7, sulfur content 0.037 wt. %. Glycerin phase: density 1.235 g.cm &lt; -1 &gt; % (GC), water content 9 wt. % (GC), pH a * 7, potassium content 0.40 wt. % methanol content 0.7 wt. % Solid phase: crystalline potassium dihydrogen phosphate with traces of biodiesel and glycerin, yield 16 g, ie practically 100 wt. % of theory - given the amount of KOH added.

Industrial applicability

The process according to the invention leads to the conversion of rapeseed oil into three practicable and environmentally acceptable products, namely biodiesel, an almost pure, highly concentrated solution of glycerin in water and potassium dihydrogen phosphate with traces of glycerin and biodiesel. Further, virtually all unreacted methanol is recovered. All these products are formed separately and in almost theoretical yield. The biodiesel parameters comply with international regulations except for the sulfur content given by its content in rapeseed oil which cannot be influenced. The glycerin layer can be easily converted to pure glycerin. Solid potassium dihydrogen phosphate can be used as an inorganic fertilizer. The recovered unreacted methanol can be used for further reesterification. The process according to the invention is therefore practically waste-free technology.

Claims (6)

1. A process for producing biodiesel from rapeseed oil by reesterification with methanol under catalysis with potassium hydroxide and treating the reaction mixture formed with reesterification, characterized in that phosphoric acid is added to the reaction mixture resulting from the reesterification in an amount of 1.1 times the amount of iftoTrtl · hydroxide used. potassium, that methanol is removed from the reaction mixture by vacuum evaporation or air blowing, that the precipitate is separated mechanically and that the liquid phase is separated into biodiesel and a lower glycerol phase. Process for the production of biodiesel according to claim 1, characterized in that during the re-esterification the reaction mixture is first X z The mixture was stirred vigorously for 2 55 minutes and stirred gently for a further 58 ^55 minutes. 3. The process for producing biodiesel according to claims 1 and 2, characterized in that concentrated phosphoric acid is added to this intensively stirred reaction mixture at a rate of about 5% by weight. per minute. A process for producing biodiesel according to claims 1-3, characterized in that the suspension thus formed is mechanically charged. filtration or centrifugation - separates into solid phase and liquid phase. A process for producing biodiesel according to claims 1-4, characterized in that methanol is removed from the liquid phase by evacuation or air at a temperature of 20 ° C to 50 ° C while increasing its surface by stirring or spraying, for example. by the knnrlRn7á + nr '· ^ A process for the production of biodiesel according to claims 1-5, characterized in that the demethanolized liquid phase is separated spontaneously into a top layer of biodiesel and a bottom glycerone layer.