FR2783822A1 - PROCESS FOR THE MANUFACTURE OF FATTY ALCOHOLS - Google Patents

Abstract

There is proposed a process for the manufacture of fatty alcohols, in which fatty acids or fatty acid esters are heated with an excess of hydrogen at pressures of 50 to 350 bar at temperatures of 200 to 250 degrees Celsius. The fat / hydrogen mixture is carried over to a fixed catalyst bed, the resulting mixture consisting of fatty alcohol, methanol and unreacted hydrogen is cooled, it is separated in a separator into a liquid phase and into a gas phase, the liquid phase containing the fatty alcohol and the methanol is relaxed, evacuated and treated separately, while the unreacted hydrogen is compressed with fresh hydrogen, in passing it through a gas recycle pump at the reaction pressure, and it is introduced into the hydrogenation.Process characterized in that at least a partial stream of non-hydrogenated hydrogen is passed through the reactor vessel. heated (quench hydrogen) and thus cooled. By this measurement, the qu The amount of recycled gas is significantly reduced and the flow rate is correspondingly increased.

Description

Field of the Invention The present invention relates to the field of

  hydrogenation of fats and relates to a process

  perfected manufacturing of fatty alcohols using the tech-

  tank reactor. State of the art

  In the manufacture of fatty alcohols by hydrogenation

  Nation of fatty acids or fatty acid esters, preferably methyl esters, the actual hydrogenation reaction is carried out in one or more fixed bed reactors one after the other at temperatures of 200 to 250 C and at a hydrogen pressure of 50 to 300, preferably from 300 bars. For this purpose, for example, the methyl ester is compressed with pumps in the installations, where it is

  mixture with compressed hydrogen, it is heated with this-

  it at reaction temperature and then we introduce it

  in the reactor. After crossing the reactor (s),

  the reaction mixture cools and the liquid phase and the gas phase are separated in a separator. The liquid phase is expanded and conducted for the separation of methanol,

  while the gaseous phase, which consists mainly of

  of hydrogen, on a compressor in a cycle. In the

  separation of methanol arranged in an evaporator installation

  tion, we rid the fatty alcohol of methanol and we can without

  other purification use it for its application. Pro

  hydrogenation esters of fatty acid esters in reactants

  tube bundle torers are described for example in

  the two German patent applications DE-A1-3 913 387 and DE-

  Al-4,242,466 (Henkel); furthermore we know from the docu-

  ment DE-A1-43 421 837 (Henkel) the procedure in parallel-

in two reactors.

  At elevated temperatures during hydrogenation

  nation, we end up with the formation of secondary byproducts

  desirable, e.g. hydrocarbons, and this shortens the life of the catalyst. In catalytic hydrogenation

  fats, oils and fatty derivatives in al-

  fatty cools in the fixed bed reactor (procedure with

  flow bed), especially when the reaction

  tion is conducted adiabatically, an excess of hydro-

  gene located 10 to 100 times above the stoichiometric need

  metric. In the case of tube bundle reactors, the problem can be overcome, since a large part of the heat can be removed by intensive cooling.

  sif of the envelope of different tubes. The amount of hydro-

  gene introduced into the cycle therefore only serves secondary cooling, and rather the excess hydrogen is chosen so as to produce an optimum increase in the hydrogenation power. The downside, however, is that

  It is very expensive to get tubular reactors. The re-

  cooling of the envelope with oil at temperature

  high is also technically very expensive.

  A much more economical alternative

  that is represented by the reactor vessels which represent the particular case of a tubular reactor comprising a tube. Due to their much larger section, the reactor vessels cannot be cooled sufficiently by the jacket. Cooling must therefore be produced here also by a significantly greater amount of recycling gas compared with the tube bundle reactor. However, large quantities of recycle gas produce high gas flow rates, which from a certain order of magnitude separate droplets from the trickle phase which are accelerated with the gas phase and conducted through the catalyst. The

  transformation into fatty alcohol is not carried out in

  lettes only incompletely by comparison with the runoff phase, and the saponification index of the final product increases, while the hourly liquid flow rate drops significantly.

  In this respect we will also refer to the de-

  German patent application DE-A1-4 005 629 (Henkel), in the-

  which it is recommended to conduct the hydrogen through at least two fixed bed reactors arranged one after the

  the other, without cooling the gas leaving the reactors and penetrating

  trant in the following reactors, and by introducing the ma-

  fat, oil or parallel fat derivative

also in the reactors.

  Consequently, the object of the invention was to remedy the problems described herein and to find a process for hydrogenation of fatty substances in tank reactors, in which the quantity of recycling gas can be reduced without reducing the flow and increasing

  the saponification index of the resulting alcohols.

Description of the invention

  The invention relates to a process for the production of fatty alcohols in which fatty acids are heated to pressures of 50 to 350 bars at temperatures of 200 to 250 ° C.

  esters of fatty acids with an excess of hydrogen, it is known

  mixes the fat / hydrogen mixture on a fixed bed of catalyst, the resulting mixture consisting of fatty alcohol, methanol and unreacted hydrogen is cooled, separated in a separator into a liquid phase and

  a gas phase, the liquid phase containing the al

  cool fat and methanol, we evacuate and treat it

  separate lesson while compressing unreacted hydrogen with fresh hydrogen, by a gas recycling pump, at the reaction pressure and it is introduced into the hydrogenation, which is characterized by what we pass

  in the tank reactor at least a partial stream of the hy-

  unheated drogen and thus cooled.

  Surprisingly, we have found that in cooling

  Dosing the tank reactor with unheated hydrogen (at around 50 to 60 C), the quantity of

  recycling gas and correspondingly increase the flow

  dante. The resulting fatty alcohols have a low

  dice of saponification and carbonyl. The advantages of

  process are also due to the fact that we can reduce the consumption

  energy in the advanced heating appliance or, as the case may be, the heat exchanger, that the quantity of cooling water is reduced, and that the power of the

  gas circulation pump required is weaker.

  Hydrogenation The hydrogenation of the starting materials, therefore

  fatty acids and their esters with glycerin, al-

  cool and preferably methanol, can be carried out in a known manner at temperatures between 200 and 250 C and at

  pressures between 50 and 150 (low pressure process

  pressure) as well as between 150 and 350 bars (high pressure process

  if we). As catalysts, mention should be made of the known Adkins catalysts based on copper / chromium spinels or the

  copper / zinc oxides or, depending on the case, copper / aluminum.

  The other principle of hydrogenation has already been mentioned more

  above and is detailed in the documents below

  tees as well as for example in the monograph "fatty alcohols" Cooling by quenching gas The principle of the invention is due to the use of part of the unheated hydrogen introduced into the cycle to regulate the evacuation of heat the tank reactor in the sense of a heat exchange. To this end, in the

  in the simplest case, a current is blown laterally

  tiel of hydrogen soaking in the tank reactor. For this purpose, it is recommended that the reactors be equipped with corresponding devices for the admission of gas (for example lances). Preferably, we do not proceed

  only by quenching at one place in the reactor, but we have

  on continuous cooling. To this end, it is recom-

  instructed to introduce gas into the tank reactor throughout

  its length with 2 to 10, preferably 3 to 4 currents per

  tiels. In a preferred embodiment of the invention, the hydrogenation is carried out in two tank reactors arranged one after the other, and in the first reactor a conversion rate of 80 to 90% is reached. the theoretical amount, and the resulting hydrogenation product, consisting of fatty alcohol, methanol as well as unreacted fat and hydrogen, is then added to the second reactor, and a reaction is carried out. complete. In this case, it has been found to be advantageous to mix another partial stream of the quenching hydrogen with the output product.

  of the first reactor before introduction into the second reaction

  tor. In short, we prefer to limit the amount of hydrogen

  troduit in the cycle at 1500 to 2500, in particular 1800 to

2200 m3 / hour.

Examples

Comparative example Vl.

  We continuously transform in an instal-

  lation according to Figure 1 of the methyl ester of coconut fatty acid into coconut fatty alcohol. To this end, the ester is first of all compressed by a pump (1) with a power of 6 tonnes per hour, at a pressure of 300 bars, and it is brought to

  the reaction temperature of 250 C with hydrogen (hy-

  fresh drogen and recycling hydrogen) first in a heat exchanger (2) then in an advanced heating device (3). The mixture is delivered to the head of the tank reactor (4), which is filled with a fixed bed of copper / zinc catalyst. The primary hydrogenation product is brought (conversion rate approximately 90%) to the head of the second

  tank reactor (5) and is reacted therein entirely

  cool fat and methanol. The mixture is conducted with the excess hydrogen (hydrogen from the recycling gas) through the exchanger

  heat (2) and the refrigeration unit (6) in a dryer

  separator (7) and it is separated therein into a liquid phase and a gaseous phase. The liquid phase is relaxed and transferred

  in a methanol separation installation (8). We know

  draws the recycling hydrogen into a gas recycling pump (9) and it is again compressed there at the pressure of the

  reaction with fresh hydrogen. The results are short

appear in Table 1.

Example 1.

  We repeat the example Vl, but we instill a cost

  partial rant of hydrogen after it has passed through the gas recycling pump at a temperature of 60 C, laterally

  in the tank reactor (4). Another current is mixed by-

  with the reaction mixture leaving the tank reactor

  (4) consisting of ester, fatty alcohol, methanol and hydro-

  gene heated before introduction into the reactor (5) (cf.

  figure 2). The results are collated in Table 1.

  EXAMPLES 2 AND 3 Example 1 is repeated, but partial hydrogen flows are blown over the entire length of the reactor.

  tank divided in two or three places (see fig.

  gure 2) Table 1 Hydrogenation in the tank reactor with and without quenching gas cooling Characteristic data Vi 1 2 3 Number of places of introduction of - 2 3 4 tion of quenching hydrogen Amount of recycling 345 153 98 70 to limit the temperature increase over the length of the reactor [4] to 10 C [m3 / hour] Rise in temperature over the length of the reactor (4) to 22 22 13 10 to a quantity of recycling gas of 70 m3 / hour [C] Specific energy consumption 750 266 120 45 than in the advanced heating appliance (3) [kJ / kg of load] Required power of the 45 20 10 5 recycling pump gas [kW] Specific water consumption 1000 590 350 210 refrigeration in the refrigeration unit 6 [kJ / kg load]

Claims (4)

R E V E N D I C A T I ON S   1) Process for the production of fatty alcohols, in which fatty acids or fatty acid esters are heated with a   excess hydrogen at pressures of 50 to 350 bars at tem-   peratures from 200 to 250 C, the fat / hydrogen mixture is conducted on a fixed catalyst bed, the resulting mixture is cooled, consisting of fatty alcohol, methanol and   unreacted hydrogen, it is separated in a separator   In a liquid phase and in a gaseous phase, the liquid phase containing the fatty alcohol and methanol is relaxed.   it is evacuated and treated separately, while   prime the unreacted hydrogen with fresh hydrogen, by passing it through a gas recycling pump   at the reaction pressure, and it is introduced into the hydro-   genation, characterized in that at least one partial stream of unheated hydrogen (quenching hydrogen) is passed through the tank reactor and so we cool it.   2) Process according to claim 1, characterized in that the tank reactor is cooled over its entire length with 2 to 10 partial streams of quenching hydrogen, preferably 3 to 4 partial currents.   3) Method according to claims 1 and 2, characterized in that   the hydrogenation is carried out in two tank reactors available one after the other.   4) Method according to claim 3, characterized in that   another partial stream of tremendous hydrogen is mixed   page with the output of the first reactor before   introduction into the second reactor.    ) Method according to at least one of claims 1 to 4,   characterized in that the quantity of hydrogen recycled is limited to 1500 to 2500   m 3 / hour, in particular 1,800 to 2,200 m / hour.   m / hour, in particular 1,800 to 2,200 m / hour.