IE45188B1 - An ammoxidation catalyst for preparing 4-cyanothiazole - Google Patents

Description

This invention relates to the production of 4-cyanothiasole from A3-4-methylthiazole or 4-methylthiazole and catalysts for such production.

One of the problems inherent in an ammoxidation system for making cyanothiazole from 4-methylthiazole or A3-4-methylthiazoline, particularly in a system using an excess of oxygen in the reactant stream, is undesirable combustion of organic reactant and ammonia to unwanted byproducts. This, of course, adds to process costs in that more reactant is required to produce a given amgiint of cyanothiazole (i.e. yields are reduced) and also larger capital investment is required to build a plant for a given capacity. Thus, a reduction in the undesired combus tion of ammonia and organic reactant will result in an increase in yield.

The present invention is based on the discovery that in the catalytic vapour phase ammoxidation ofΔ3-4methylthiazoline or 4—methylthiazole to 4-cyanothiazole, the yield of 4-cyanothiazole can be significantly increased and ammonia and hydrocarbon decomposition mitigated by using a chromium cobalt molybdate catalyst in which the atomic ratio of molybdenumscobalt is in the range 1.20:1.00 to 1.05:1.00 and the atomic ratio of chromiumscobalt is in the range 0.6:1.0 to 1.4:1.0.

Such a catalyst constitutes one embodiment of the present invention. gg Zxiso in accordance v/ith the present invention, there is provided a method of preparing 4-cyanothiazole from dimethyl thiazole or A3-4-methylthiazoline that comprises passing, as a reactant stream, a gaseous mixture comprising 4-methylchiazole or d3-4~methylthiazcline, ammonia, oxygen and water ae steam, over such a catalyst at a temperature of 360 to 450°c.

The catalysts of the present invention are more selective for production of the desired --cyanothiazole, and can be uses in an adiabatic or isothermal-type reactor, which results in allowance of temperature fluctuations without any significant decrease in the high selectivity for 4-cyanothiasole. Also, whan Δ3-4-methylthiazoline is used in the reactant stream, l-msthylthiazoie is produced first, and when not all of the 4-raethylthiazole is converted to 4-cyanothia3Oi&, it is not decomposed by the catalyst of this invention to undesirable by-products.

In. a preferred aspect of this invention, one or more of the following additives: potassium hydroxide (KOH), ferric chloride (FaCl3), ammonium orthophosphate (KH^HPO^, telluric acid ^^04), potassium sulphate (K.,SCr), and vanadyl sulphate (VOSO^) is or are added during preparation cf che catalyst.

Pref jrably the mols ratios of the reactant stream are ammoniai(4-methylthiazole or Δ3-4-methylthiazoline) 1:1 to 2 r 1; oxygen:(4-methyltniazoline orA3-4-methylthia2oline) 0.5sl to 200:1? (water as steam):(4-methylthiazole orΔ3-4-methyl30 thiazoline) 0.001:1 to 10:1.

Preferably the chromium chloride:cobalt molybdate molar ratio in tha catalyst is from 0.8:1 to 1.1:1. 4318 8 Preferred ranges for the molar ratios of additives to the cobalt molybdate are: potassium hydroxide from 0.01:1 to 0.08:1; ferric chloride from 0.001:1 to 0.01:1; ammonium orthophosphate from 0.001:1 to 0.04:1; telluric acid from 0.01:1 to 0.05:1; potassium sulphate 0.01:1 to 0.08:1; and vanadyl sulphate from 0.01:1 to 0.08:1.

The catalyst may be prepared by contacting solid cobalt molybdate having a particle size of less than 10μ with chromic chloride, preferably in aqueous solution.

This is in effect a slurrying of the cobalt molybdate with chromic chloride solution, and is so referred to in describing this invention. The slurry is concentrated to a thick paste, dried and then fired, preferably for about 12 hours at about 45O°C.

The resulting catalyst can then be supported on one of the commercially available inert supports such as silica (SiO^), alumina, pumice, calcium sulfate or magnesium oxide. The preferred inert support is silica. By the term inert'1 is meant that the support does not have any deleterious effects on the catalyst. The catalyst is supported by jet atomizing the catalyst to a powder and then mixing it with aqueous colloidal silica to obtain a catalyst with high physical strength. The catalyst can be up to 8C% by weight of the total weight of catalyst plus support. A more desirable weight range of the catalyst is 55-65%.

In carrying out the process of the invention, the reactor and attendant equipment are prepared in the usual way, the reactor being charged with catalyst and otherwise prepared for start-up, including the heating up of the J 2 G 8 - 5 catalyst if desired. The 4-m&thylthiazole or A3-4-methylthiazolint',aflK!OGia,oxygen and water (steam) are passed over the catalyst at reaction conditions and at certain mole percent ratios. For an isothermal reactor system, the o o temperature range can be from 360 C. to 430 C. A more desired range for an isothermal reactor system is 395°C, to 4O5°C. For an adiabat.ic reactor system, the outlet temperature rance is from about 39O°C. to 450vC. & more desirab?e temp?rat-’re range for an adiabatic reactor system is 420¼ to 440°C.

The contact time for a reactant stream is the time that the reactants are in contact ’.vith the catalyst composition. For an isothermal or adiabatic reactor system? the contact time can ba from O.-i to l.o second. A more 2.5 desirable range is 0.2S to 0.3» second. iht following examples are given for the purpose or illustration and not for t.;e purpose of limiting the scope .,: the .·.'.·,'(·.ηί. h ·'. . iM&SJ, This example illustrates the preparation of the chromium ccbalt molybdate catalyst. The cobalt molybdate may he prepared by known techniques, i.e. cobalt molybdate in precipitated by reacting cobalt sulfate or nitrate with ammonium n.olybr.ar.a cs follows; 2f ·. Ts 200 milliliters (ml.) of water is added 145.0 grams »#£.; of ..olict ni~rate «θ^Ο) and the mixture is hsat-xi to 40°C. with stirring until all the material ia in solution. 2. To 2-0 mi. of water is added 90 gm. of ammonium JO psramclybdste (NE ) and the mixture is heated to 40ν·3» ui;h stirring until all the material is in solution. dSiss - 6 Solutions obtained in Steps 1. and 2. above are mixed together and then 8H ammonium hydroxide (ΙίΗ^ΟΗ) is added until the pH remains at 5.8 for one hour. A purple material precipitates from the solution.

The resulting precipitate is filtered and washed with 200 ml. of water to remove the excess of cobalt nitrate and ammonia, then the filter cake is dried to about 5% water in a vacuum oven at 15-20 millimeters Hg at 80-90°C, The filter cake is fired for 16 to 24 hours in air at 45O°C., and then the catalyst is jet atomized to a particle size of about 1-2μ,. A phase change occurs during jet atomization forming a low-density green powder. By jet atomizing is meant fluid energy milling using air or nitrogen to obtain particle sizes less than lop. and typically in the 0.5p. to 5μ, particle size range. The molar ratio of molybdenum:cobalt is 1.15:1.00.

Chromium Cobalt Molybdate Catalyst To 20 ml, of water is added 40 gm. of chromium chloride (CrCl^.SHgO) with heating to 50°C. while stirring until all the material is in solution; then 40 gm. of the cobalt molybdate is added. It is at this stage of the catalyst preparation that the additive agents described above can be added to the catalyst. In this catalyst preparation, 0.8 gm. of potassium sulfate is added.

The resulting mixture is made into a thick paste by evaporating the water, dried in a vacuum oven at 15-20 mm. Hg at 80-95°C., and finally fired for 12 hours at 450°C. The finished catalyst is sized to 16-30 mesh (Handbook of Chemistry and Physics, 40th Edition, pg. 3357, U.S. Standard Sieve Series). - Ί ·ΐ» S1 g g EXAMPLE 2 In tills example, the catalyst prepared according to Example I is utilized. 3.0 cc of catalyst is loaded into a stainless steel isothermal reactor tube of 0.635 cm inner diameter. The isothermal reactor is connected to an on-line gas chromatograph to analyse the reactants and products.

The feed composition is adjusted te enter the reactor at ihe rate X. 0.L2 cc./minute or £3-4-methyithiazoiine; air at 625 cc./minute? and concentrated ammonium hydroxide (23%) at 0.02 cc./minute. The reactor temperature is 415°c. At this temperature, 43-4-methylthia2oline is quantitatively converted tc 4-methylthiazolo in tiie attendant equipment before it come·'· into contact with the catalyst bed. Of the 4-merhylthiazole that comes into contact witn the catalyst. 50% is converted into products. Of the 4-methy!thiazole that. is converted into products, 75% xs converted to 4-c?anochiazole, 10% is converted to thiazole, and the remaining 15% is converted to by-products. Thus,, ths selectivity. -:o 4-cyanothiazole xs 755'..

BSAMang 3.

The catalyst utilized in this example is similar to that prepared in Example 1 except that vanadyl sulfate (7080^) and telluric acid (HgTeO^) instead of potassium sulfate are utilized as the additives. The reactor conditions ara ths same as those it. Example 2. 3.6 cc. of catalyst is loaded into the reactor tube. Ths feed composition is adjusted tc enter the reactor at the race of 0,02 cc./minut-· of 4-methylthiazole? air at GOO cc ./aixiiate and concentrated ammonium hydroxide (28%) at 0.02 cc./minute. The conversion and selectivity to 4-cy-;iiuthi.azole is given in the Tab3.es below.

Table I Catalyst (molar ratios) VOSO^, O.Ol/Cr 0.13/Co 1.00/Mo 1.15 (%) Selectivity (%) Reactor Temp. .ο » . ( CJ Conversion 420 56 70 410 44 73 400 32 76 390 23 81 380 14 87 Table II Catalyst (molar ratios) Te 0.03/Cr 0. ,80/Co 1.00/Mo 1.15 Reactor Temp. , (°C.) Conversion Selectivity 420 50 70 410 36 73 400 26 76 390 17 78 380 12 80 EXAMPLE 4 The catalyst utilized in this example is similar to that prepared in Example 1 except that ammonium orthophosphate and ferric chloride are added in addition to potassium sulfate. The atomic ratios of the additives to the cobalt molybdate are phosphorus:cobalt, 0.005:1; ironzcobalt, 0.004:1; and potassium:cobalt 0.02:1.

The same reactor conditions and feed composition are used in this example as in Example 3. The conversion and selectivity to 4-cyanothiasole is given in Table III. 313 8 Tabla III Reactor Temp. (°C.) Conversion (¾ Selectivity .(%) 420 73 63 410 56 70 400 41 74 390 29 77 3 SO 21 30 EXAMPLE 5 1C This example illustrates the catalyst whan the molar ratios of the components are chromium chloride 0.80:cobalt l.OOzmolybdenum 1.10:potassium sulfate 0.075. Also, gaseous is used rather than concentrated KH.OH.

The feed composition contains 4-methylthiazole as the organic reactant. The feed enters tha reactor at tha rate oi 0.02 ce,/minute cf v-methyithiazolej air 600 ec./ minute and 1.3 moles of S5 per mole of 4-methylthiazole. The conversion and selectivity to 4-cyanothiazole are given in Table IV.

Table IV Reactor Temp.

Conversion (¾) Seleativity (%) 420 68 69 41C ΰ5 71 400 42 73 390 31 75 380 22 77 comparative: example This example illustrates the use of cobalt molybdate catalyst. The selectivity is lower than that of the catalyst of the present invention. gS Into a stainless steel reactor tube of 0.635 cm inner diameter is loaded 3.6 cc. of cobalt molybdate catalyst.

The reactor is placed in an isothermal gas chromatographic reactor system. The feed composition is adjusted to enter the reactor at 0.018 cc./minute of 4-methylthiazole, 0.013 cc./minute of concentrated HH^OH (28%) and 600 cc./minute of dry air. Under the temperature conditions as shown in Table V, the following conversion and selectivity to 4-cyano thiazole is given.

Table V Reactor Temp. (°C,) Conver sion (%) Selectivity (%) 420 69 43 410 54 54 400 43 57 390 34 60 380 23 64 4S18S

Claims (11)

1. CLAIMS;1, A chromium cobalt molybdate cafcaxyst in which the atomic ratio cf moiybdenum:cobalt is in the range 1.20:1.00 to 1.05:1.00 and the atomic ratio of chromium:cobalt is in

2. , A catalyst as claimed in claim 1, in which the atomic ratio cf chromium:cobalt is in the range 0.8:1.0 to 1.1:1.0.

3. A chromium cobalt molybdate catalyst in which 10 one or more of additives from potassium hydroxide, ferric chloride, ammonium orthophosphate, telluric aoid, potassium, sulphate and/or vanadyl sulphate, is or are added during preparation of the catalyst; the atomic ratio of molybdenum: cobalt is in the range 1.20:1 co to 1.05:1.00; the atomic 15 ratio of chromiumscobalt it a.; tbe range 0,6:1 to 1.4:1 and the molar ratio of total additive tc cobalt molybdate is in the range 0,001:1 to 0.08:1.

4. A method of p.rca-'.ring a catalyst as claimed xn claim 1, substantially as hereinbefore described in Example 1. 20 5. A catalyc.. aa claimed in claim 1 when prepared by a method an claimed in claim 4.

5. Oxygen:4-methylthiazole or A3-4-methylthiazoline in the range 0.5:1 to 200:1; and water as steam:4-methylthiazole or A3-4-methylthiazoline in the range 0.001:1 to 10:1. 5 the range 0.6:1.0 to 1.4:1.0.

6. A method of preparing 4-cyanothiazole from 4methylthiuzoie or Λ'ί-4-mcthylthiasoline that comprises passing, as a reactant stream, a gaseous mixture comprising 4-methylthiazole or ZJ3-4~methylthi£tzoline, ammonia, oxygen, and vater as steam, over a catalyst as claimed in claim 1 at a temperature of 360 to 450' O.

7. A method as claimed in claim 6, in which the catalyst ic a catalyst as claimed in claim 3.

8. , ϋ method as claimed in claim 6, in which the catalyst is a catalyst as claimed in claim 2 or 5.

9. A method as claimed in claim 6, 7 or 8, in which the mole ratios of the reactant in the stream are: ammonia:4-methylthiazole or A3-4-methylthiazoline in the range 1:1 to 2:1;

10. A method as claimed in claim 6, substantially as 10 hereinbefore described in any one of Examples 2 to 5.

11. 4-Cyanothiazole, when prepared by a method as claimed in any one Of claims 6 to 10.