FR2514665A1 - SPECIAL CATALYST FOR THE SYNTHESIS OF METHANOL - Google Patents

Abstract

THE SUBJECT OF THE PRESENT INVENTION IS A CATALYST CONTAINING, IN THE UNREDUCTED STATE, COPPER OXIDE, ZINC OXIDE, CHROME OXIDE AND MORE PARTICULARLY AT LEAST 10 BY WEIGHT OF CUO, AT LEAST 10 DE CRO ALONGSIDE ANY QUANTITY NOT EXCEEDING 2.5 GRAPHITE. THIS CATALYST IS CHARACTERIZED BY THE FACT THAT IT CONTAINS 1 TO 10 ALUMINA AND 39 TO 70 ZNO. IT RELATES TO A SPECIAL CATALYST FOR THE SYNTHESIS OF METHANOL.

Description

SPECIAL CATALYST FOR THE SYNTHESIS OF METHANOL

  The subject of the present invention is catalysts with high activity under favorable energy conditions (that is to say at low pressure and at a temperature below 2800 C) for the synthesis, in particular of methanol, and containing in the non-reduced state of the Copper oxide, zinc oxide, chromium oxide and aluminum oxide The invention also relates to the process for the preparation of these high activity catalysts.

  and their application to the synthesis of methanol It is known that metha-

  nol is produced by synthesis by combining carbon monoxide or carbon dioxide with hydrogen in the presence of catalysts containing zinc and chromium oxides or oxides of copper, zinc and chromium in the unreduced state. or oxides of copper, zinc and aluminum; in

  in many cases manganese is also added.

  Catalysts according to the prior art frequently require high synthesis pressures and may have, besides an activity which is not exceptional, a low selectivity with regard to methanol; in their preparation, moreover, it is usually necessary

  to use compounds such as Na 2 CO 3, NaHCO 3, NH 4 -OH, amine chloride,

  monium, etc. to maintain the pH above 7 (and thereby cause coprecipitation), and / or precipitants which can pollute the catalyst or require particularly intense washing. In German Patent No. 2,122,952, the applicant has already described catalysts which are very advantageous compared to those obtained in the prior art

  and particularly efficient processes with regard to their pre-

  The catalysts described in this patent contain (in the unreduced state) from 10 to 20% by weight of Cu O, from 60 to 80% of ZnO, from 10 to 20% of CrO 3 and approximately 1% of graphite, and they are prepared by melting copper acetate in water, by heating this solution to 7080 ° C, by suspending zinc oxide and

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  graphite, precipitating this suspension with stirring, adding an aqueous solution of chromic anhydride, filtering, washing and drying the precipitate at 100 to 1100 C, compressing the product thus

  obtained by treating it at about 300 ° C in the presence of nitrogen and

  The catalysts thus obtained have a good degree of activity, a good shelf life and can be used for

low synthesis pressures.

  Despite these benefits, the recent oil crisis has highlighted the need to synthetically produce methanol in ever-increasing quantities and for that with ever-increasing yields

  and ever decreasing energy consumption.

  Continuing its uninterrupted research in this field, the Applicant has now developed advanced catalysts which

  precisely meet the urgent needs in methane production.

  with better yields, better selectivity and

  a more advantageous energy consumption The catalyst according to the present invention

  The present invention is characterized in that the copper acetate and the aluminum acetate are dissolved in deionized water at the best solubilization temperature (75 to 850 C) and after having suspended the oxide stirred with zinc in this solution, the oxide is left

  of zinc to hydrate for a period of 18 to 30 hours, the suspension

  The hydrate is heated from 75 to 850 ° C. while keeping the pH only slightly below 7 during all these phases. The hydrated suspension is then reacted under heating with chromic anhydride for the time required for becomes slightly above 7, and after having filtered, washed, dried, compressed and heated under a stream of nitrogen the product thus obtained, the resulting product is subjected to a heat treatment at a temperature of 300 to 400 ° C under current nitrogen and

  air before putting it in the form of granules or pellets.

  The lysing agent according to the present invention contains in the reduced state from 10 to 40% (by weight) of CuO, from 10 to 20% of CrO, from 70 to 38% of ZnO and from 10 to 20% of A 1203. ; preferably, the catalyst contains a minimum amount

  (about 1 to 1.5%) graphite.

  Various aspects and advantages of the invention will be better illustrated

  the following description with the appended drawings and the examples

  following examples given by way of non-limiting illustration.

  FIG. 1 represents an illustrative and not limited block diagram

  of a process for the preparation of catalysts for the synthesis of

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  methanol which are highly active at low pressure and at a temperature of about 220 to 2700 C. Figure 2 shows a comparison chart of the catalyst activities according to the present invention and according to the German patent cited above. In phase 1 (FIG. 1) an aqueous solution is prepared with copper acetate Cu Ac and basic aluminum acetate Al Ac by adding these compounds to H 20 base water and heating to R at a temperature of about 50 to 60% C (for example by the passage of steam V in a coil placed at the bottom of the container containing the solution).

  solution is transferred from 1 to 2 o, while being maintained under

  tation (using stirrer 2 'for example), zinc oxide Zn O is added and preferably also graphite (which as can be seen

  can also be added to the product in the dry state).

  The addition in 2 takes place with stirring also with contribution of

  their R 'so that the suspension is maintained at a temperature of eg 50 to 60' C for a period of time, for example during

  The SOS suspension thus obtained at 2 is left standing for

  for a certain time (e.g. 18 to 30 hours and preferably 24 hours) so as to promote, at room temperature, the hydration of the zinc oxide. Once this hydration has been completed, the suspension (with the hydrated Zn O ) is again submitted to 4 heat treatment which is conducted preferably at a temperature between 75 and 850 C for about an hour It should be noted that at this stage, the p H of

  the solution in 1 and in the suspensions in 2, 3 and 4, is always less than

  at 7 and therefore still slightly acidic, for example at p H = 6.

  In the suspension (slightly acidic), heated to 4, then

  CrO 3 chromic anhydride where a reaction takes place between the

  SOS hot-bed and fresh CrO 3 at a temperature (preferably between 75 and 85% C and better still at 80 ° C) and for the time necessary for the

  in a slightly alkaline value, for example, about 7.5.

  At the moment this value of p H is reached, it means that the reaction

  is complete so that the heating R "can be interrupted and that

  the filtration (step 6) of the precipitate at room temperature can be

menced.

  The filtered product from 6 passes to 7 to be subjected to a

  with deionized water and is then dried at 8 at a

  for example from 100 to 1100 C, it is then pressed at 9; the processes

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  7, 8 and 9 are substantially conventional treatments.

  On the contrary, according to the particularly advantageous embodiment

  In accordance with the invention, the compressed product from 9 is subjected to a high temperature heat treatment for example at about 3500 C under nitrogen circulation and then to a second heat treatment, for example still at 350% C but under nitrogen circulation containing between 1

  and 5% air to produce a catalyst in the oxidized state.

  It is then granulated at 12 and put into pellets.

  The final catalytic product PFR is thus obtained in the unreduced state.

  As mentioned, the granulated product (at dimensions, for example, between 0.3 and 1.5 mm) can receive an addition of graphite GRA before forming depastilles and this graphite completely or partially replacing the graphite GRA added in 2 It will be noted that the block diagram of FIG. 1 indicates the treatments more than the treatment steps; treatments can indeed be performed on

  more often in several stages and in several containers or reactors.

EXAMPLE 1

  A solution is prepared by dissolving 400.6 g of deionized water

  of copper acetate and 81.9 g of aluminum acetate.

  SOL solution, is heated (by steam circulating in a

  coil) at a temperature of about 60% C to make it easier to

  elution of copper and aluminum acetates (phase 1) 650 g of zinc oxide and 10 g of GRA graphite 2 were added to this solution with stirring. In 2, the SOS suspension was obtained in 800 cm 3 of deionized water. maintained for one hour at 800 C The suspension SOS is then left at rest

  (in 3) for 24 hours, during which time the temperature falls naturally

  800 C, the temperature it had at 2, at room temperature

  so that Zn O can be completely hydrated after hydration.

  After 24 hours, the suspension is again heated to 4 ° to 800 ° C. with continuous stirring (4 '). In all the treatments from 1 to 4, the pH of the SOL solution and of the hydrated and heated suspension SOS is always

  less than 7 and preferably of the order of 6.

  The heated suspension (at about 80% C) and stirred from 4 is reacted (at 5) with a solution consisting of 210.5 g of chromic anhydride in 500 cm 3 of deionized water and this until that its p H is slightly greater than 7 for example up to 7.3 In

  these conditions, a complete precipitation takes place The precipitate is fil-

  at 6, washed under normal conditions at 7, dried in 8 at 100-110 ° C.

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  The product thus obtained is treated for 5 hours with a stream of nitrogen at 3500 C at 10 and then for 1 hour with a stream of nitrogen containing 1 to 5% of air at the same temperature of 350 ° C. C (treatment indicated by 11 in the block diagram) The product is then granulated and put into pellets in 12 Its composition after reduction is: Cu O 15% Zn O 65% Cr 203 16%

A 23 3%

  It should be emphasized that during all the treatments from 1 to 12, no p H regulators or precipitation agents are used: the absence of these chemical agents and in particular precipitating agents is very important since it does not lead to polluting traces. in the catalyst, which

  avoids intensive and expensive washes.

EXAMPLE 2

  By operating as in Example 1, a solution is prepared with 801.2 g of copper acetate and 81.9 g of aluminum acetate, solution

  in which 500 g of ZnO and 10 g of graphite are suspended.

  After hydration of the Zn O for 24 hours and heating to 800 ° C.

  hydrated board, the suspension is reacted with 210.5 g of anhy-

  chromic druid until p H = 7.6.

  After filtration, washing, drying, compression, heat treatment

  at 350 ° C with first circulation of nitrogen and then of nitrogen and oxygen, the catalytic product thus obtained has the following composition: Cu O 30% Zn O 50% Cr 2 O 3 16%

A 1203 3%

EXAMPLES 3 (COMPARISON) 4 and 5

  Use of the catalyst produced for the synthesis of methanol.

  The tests were conducted substantially in the same way as

  the operating conditions defined in German Patent No. 2,122,952.

  Each time, a catalyst sample was taken and reduced to a temperature of 220% C and at ordinary pressure. When the catalyst could be assumed to be in an advanced state of reduction, its temperature was increased to 290% C while that the gas pressure was brought to

bars.

TABLE 1

  TYPE Dimension Volume Weight Pressure Temperature Speed Production Concentra-

  CATALYST N catalytic in space C in Kg CH 30 H in cm 3 catalyst bar in per liter CH 30 H l in g% by weight

it is a catalyst.

  1) according to German Patent No. 2 122952 Cu / Cr / Zn 15% Cu O 2) According to the invention

(Example 1)

  Cu / Cr / Zn / A 1 15% Cu O 3) According to the invention

(Example 2)

Cu / Cr / Zn / A 1 30% Cu O 0.75 t 1

0.75 1

0.75 e 1 9.29

6 9.29

8.14

12,500

12,500

12,500

0.5 0.7 vi 0 n 1 i os N cs Cn

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  The methanol synthesis reactor was filled with synthesis gas during the reaction and the activity was measured using a feed mixture having the same composition as the mixture used during the reduction and consisting of H 2 : 65%, CO: 6.8%, CO 2: 11.3%,

N 2: 16.8%.

  The catalyst activity was measured after a period of stabilization.

  during 120 hours, when, when two

  taken under the same experimental conditions gave the same specific results of production by weight of pure methanol by

  1 liter of catalyst, that is to say in kg of pure CH 3 H / H / liter of catalyst.

  The following table 1 and the diagram of FIG. 2 in the appendix show the conditions and the results obtained with a catalyst according to

  the German patent (Comparative Example 3), with the catalyst according to

  1 according to the invention (example 4) and with a catalyst according to the previous example 2 according to the present invention (example 5 ') The two catalysts according to the invention which have been used are all the

  two of Cu / Cr / Zn / Al type with this difference that the catalyst of the example

  pl 4 is at 15% Cu O and the catalyst of Example 5 at 30% Cu O. The catalyst according to German Patent 2,122,958 used for comparison (i.e. Cr / Zn with 15% Cu O) is a catalyst usually used industrially in a plant of

CASALE.

  Among all the remarkable features of the invention, we will mention only the following: no precipitation agents are used; 2. The variation of p H naturally takes place (without regulators) during

  reduction of Cu O with ZnO in copper acetate and acetone

  aluminum tate; at a temperature of 800 ° C., the pH is about 6 until Cr 3 O 3 is added and during the reaction after 3 hours, it rises to 7.3; 3. pyrolysis: the thermal decomposition of the acetates and then their subsequent oxidation with N 2 + O 2 (air); 4. the catalyst with a low Cu O content is highly active and can be expensive; The catalyst is selective for the synthesis of methanol (there are no alkaline ions to form secondary products). It is then possible to: a. Perform a non-intensive washing of the filter;

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  6. by this particular catalyst manufacturing process, we obtain

  a finely dispersed copper oxide.

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Claims (6)

REVENDI CATIONS   1. Catalyst containing, in a non-reduced state, the oxide of   vre, zinc oxide, chromium oxide and more particularly at least 10% by weight of Cu O, at least 10% of Cr O 3 beside a possible amount of not more than 2.5% graphite, characterized in that it contains 1 to 10% alumina and 39 to 70% Zn O. 2. Catalyst according to claim 1, characterized in that it contains: from to Cu O 10% 40% Cr O 3 10% 20% Zn O 70% 38% A 1203 10% 2%   3. Catalyst according to one of claims 1 or 2, characterized   in that a solution is prepared in deionized water containing 400 to 800 g of copper acetate, 70 to 90 g of aluminum acetate, which is then heated to a temperature between 70 and 80 ° C., 650 g of zinc oxide are added to form a suspension, and the zinc oxide is allowed to hydrate for at least 18 hours, which is heated.   the suspension at 75-80 ° C, that the p K of the solution and suspensions sub-   sequents is slightly less than 7, that the suspension is reacted   with a solution also in deionized water containing from 190 to   230 g of chromic anhydride at a temperature and for a sufficient time   In order for the pH to be slightly greater than -7, and after filtration, washing, drying, compression and thermal treatment, of the product thus obtained under nitrogen circulation, it is heat-treated again at a temperature of at least 300.degree. 'C under nitrogen circulation and front air   to put it in the form of granules and pellets.   4. Catalyst according to one of the preceding claims, characterized   in that its graphite content is between 0.5 and 1.5%.   5. Process for the preparation of a catalyst according to the   1 to 3, characterized by the fact that a solution of   and aluminum acetate is prepared in deionized water and is then suspended in zinc oxide with air stirring,   the zinc oxide is then allowed to hydrate for at least 18 hours.   at room temperature, the suspension-being then heated to 75-    C keeping the H slightly less than 6, after which the suspension   is reacted with a quantity of chromic anhydride solution   in deionized water at a temperature and for a sufficient time   In order for the pH to be slightly greater than 7 (in the complete absence of pH regulators) and after filtering, washing, drying, pressing and heat-treating at about 350 ° C. under nitrogen circulation, the product obtained is again treated at about 350 to 40 ° C under nitrogen circulation   and air before granulation and tableting.   6. Application of the catalysts according to one of claims 1   at 4, obtained by the process according to claim 5 for the synthesis of methanol.