KR800001030B1 - Method for preparation of dimethyl ether - Google Patents

Abstract

Me2O was prepd. in high conversion and yield by hydrogenation of CO over Si compd. stabilized catalysts contg. Al, Cr, Ta, Mn, Cu, and/or Zn at 300-330≰C, 50-100 kg/cm2, and space velocity 1,000-10,000/h. Thus, passing 3:1 H- CO over a Cu-Zn-Cr catalyst on stabilized Al2O3 at 300≰C, 50kg/cm2, and space velocity 3,500/h gave CO conversion 56% and selectivity for Me2O 61.3, MeOH 3.3, and CO2 35.4%

Description

Method for preparing dimethyl ether

The present invention relates to a method for preparing dimethyl ether using a novel catalyst.

It is known that dimethyl ether can be prepared by reacting carbon monoxide with hydrogen.

In addition to dimethyl ether, the main products of the reaction are methanol, carbon dioxide and water accompanied by the unreacted gas fraction.

The reaction is generally carried out in the presence of a complex catalyst system comprising oxidized derivatives of the elements used in the synthesis and dehydration of methanol. P.H Emmet's book, Catalyst, published in 1955 by Lennold, Inc., describes the proposed system for the synthesis of methanol in volume 3, pages 356-380.

Catalytic systems for the synthesis of dimethyl ether have been described in France in particular specification 641,580 since 1927 and are given in the same assignee for example in Italian patent No. 927,655 for use in the preparation of dimethyl ether.

The catalyst systems described so far have good results in yield and conversion to dimethyl ether, but have shortcomings that have shortcomings that do not allow industrial use.

The method in Korean Patent Specification No. 2,468 prepares ethers starting from alcohols, wherein the catalyst is composed of activated alumina modified by reacting alumina with a silicon compound. Although such catalysts allow the production of dimethyl ether from methanol, they are listed in relatively low yields per material passing through the catalyst and have significant drawbacks that require recovery recycle and product separation. When using methanol as the starting material, the catalysts described in the cited patents have an acceptable service life but cannot provide more than 84% methanol conversion under the most suitable conditions.

Taken together, conventional catalysts cannot provide unacceptable water levels or provide acceptable conversions and in some cases have both drawbacks.

It is an object of the present invention to provide a process for producing dimethyl ether in high yield and high conversion using a catalyst which has a long service life under the reaction conditions and allows for good industrial use from an industrial standpoint.

In particular, the catalyst of the present invention is stable under the reaction conditions and can be used for the synthesis of dimethyl ether for a long time of thousands of hours.

The process of the present invention consists of injecting a gas mixture consisting of CO, H ₂ and possibly CO ₂ into a reaction vessel and reacting CO and H ₂ in the presence of the catalyst described below in the reaction vessel and dimethyl ether yields a quantitative yield. Recovered from the mixture obtained and obtained from the reactor by conventional methods.

The catalyst according to the invention consisted of metal oxides and salts which undergo a stabilization process.

The term “stabilization process” refers to a compounding process received by the catalyst or by several components of the catalyst to withstand fluidic action at high temperatures as well as heat and mechanical tension.

Particularly suitable are treatments with silicone compounds as described for stabilization of alumina in Italian Patent Specification No. 1,001,614 and Italian Patent 27,455 / A 74, which have the following general formula.

In the above formula

X, Y, Z, W are -OR, -Cl, -BR, -SiH ₃ , -COOR, and -SiHnClm wherein R is hydrogen, alkyl having 1-30 carbon atoms, cycloalkyl, aromatic, alkylaromatic or Alkyl cycloalkyl groups, in particular methyl, ethyl, isopropyl, n-propyl, n-butyl, isobutyl, cyclohexyl, cyclopenyl, phenyl, phenylcyclohexyl, alkyl phenyl, n and m being 1-3 Appointment.

The term “mixture of metal oxides and metal salts” refers to compositions consisting of oxides or salts of aluminum, proium, lanthanum, manganese, copper, zinc and mixtures thereof.

Since the stabilizing effect of the silicone derivatives is carried out in particular on aluminum oxide, the presence of aluminum in the catalyst mixture is limited and in order to have the properties necessary for the catalyst to maintain its catalytic activity which does not change for a long time, 10-70% of alumini Requires the content of lithium.

The combination of metal oxides and salts can be obtained according to technical conventional processes while stabilization can be carried out before or after mixing all the components together.

By changing the pH, for example, all metals constituting the catalyst can be processed starting from their salts, in particular from solutions of nitrates or vinegar oxides. The precipitates precipitated by filtration and washing are dried and heated at 400 ° C. to powder. In addition to nitrates and vinegar oxides, mixtures of basic carbonates, oxides and hydroxides of metals can be used.

In addition to drying, the filtrate is washed and then slurried in water and atomized. The catalyst powder thus obtained can be treated with a silicone compound such as tetraethyl orthosilicate at a temperature of 0-120 ° C. The excess silicon compound is removed by heating at 170 ° C or higher.

The stabilized catalyst is made into a suitable form by conventional methods such as alcohol, tableting, ferretization and the like.

Treatment with tetraethyl ortho-silicate may be carried out before heat treatment or after the catalyst is made in a constant form and, if necessary, changed.

Another production method is oxidation of the metal constituting the catalyst with the extrusion of alumina, followed by precipitation, drying and atomization, followed by stabilization by treatment with a silicon derivative such as tetraethyl orthosilicate, silicon tetra chromide and the like. It consisted of mixing with aluminum.

Mixing with stabilized aluminum oxide can be carried out after heat treatment.

Prior to the full activity, the catalyst obtained above is reduced by passing a mixture of hydrogen diluted with nitrogen on the catalyst, gradually increasing the temperature until a preselected reaction temperature is reached. Reduction time and temperature are selected as a function of the form to be produced.

Without seeking a reaction mechanism and without limitation the present invention, dimethyl ether synthesis does not involve the formation of intermediates of free methanol in the gas phase. The reaction is carried out over a wide range of temperatures and pressures, in particular operating under conditions of 30-400 atm and 200-500 ° C., more preferably at 40-150 atm and 230-350 ° C.

The ratio between reactants is not limited. Suitable molar ratios of CO / H ₂ are between 1:10 and 3: 1. The space velocity can vary between 1,000 hours ^-1 10,000 ^-1 hours but with higher space velocity a satisfactory result can be obtained.

The reaction mixture may also include gases that are inert to the associated reaction.

The examples are described without limiting the invention.

Before describing an embodiment, several definitions will be made.

Example 1

Catalysts based on Cu, Zn, Cr and Al, in which metals are present in an atomic ratio of 20/12/8/60, are prepared according to the following process.

Dissolve 1,600 g of Cu (NO ₃ ) ₂ 3H ₂ O, 17,180 g of Zn (NO ₃ ) ₂ 6H ₂ O, and 1,060 g of Gr (NO ₃ ) ₂ 9H ₂ O in 20 L of water and the solution at 85 ° C. 20 L of a solution obtained by dissolving 1,300 g of caustic soda in water with stirring is added. On cooling, the precipitate falls, which is washed with water, filtered and washed again with water, and the obtained precipitate is dried in an oven at 120 ° C.

The obtained material was ground to a particle size of 20 mesh ASTM or less and then 1000 g of gamma-alumina having a particle size of 20-100 mesh ASTM prepared according to the process described in Example 1 of Italian Patent Specification No. 1,001,614; Mix.

The composition is made into tablets having a straightness of 4 mm and a length of 6 mm.

The thermocouple having an outer diameter of 8 mm is placed in the central axis of the reactor in a tubular reactor having a diameter of 254 mm in which 100 mm of the catalyst is placed in an electrically heated annular oven. In order to reduce the catalyst under the formed conditions, a mixture of hydrogen and nitrogen is injected into the reactor to gradually increase the temperature. When the temperature reaches 260 ℃ no heat is generated due to the reduction reaction of the catalyst. The pressure is raised to 50 kg / cm 2 and the hydrogen-nitrogen mixture is replaced with a mixture of CO and H ₂ in a ratio of 25% CO and 75% H ₂ at a space velocity of 3,500 hours ⁻¹ . At this time, the temperature of the catalyst is stabilized to 300 ℃.

The condenser downstream of the reactor condenses methanol and water together with some of the dimethyl ether produced in the reactor. Water, methanol and condensed dimethyl ether are recovered from the device under pressure and analyzed. The gas from the reactor is analyzed by passing the chromatographic sampling valve and then sent to the flow meter to measure the flow rate.

Table 1 lists the results of the sustained tests conducted for 475 hours under the conditions described above. By-products present at concentrations below 1% were not considered.

Example 2 (Comparative Test)

A catalyst prepared by the above-described process with the same composition as in Example 1 but replaced by gamma-alumina that did not stabilize stabilized gamma-alumina was subjected to a sustained test under the conditions described in Example 1, and the results are shown in Table 2. It is listed in.

This example is for comparison purposes and decreases with time when using gamma-alumina that does not stabilize CO conversion and DME selectivity.

TABLE 1

TABLE 2

Example 3

Prepare a catalyst of Cu, Zn and Cr with an atomic ratio of 25/37/38. For this purpose, dissolve 800 g of Cu (NO ₃ ) ₂ 3H ₂ O 1,500 g of Zn (NO ₃ ) ₂ 6H ₂ O and 2050 g of Cr (NO ₃ ) ₂ 9H ₂ O in 20 liters of water and The oxide is precipitated by heating to 850 ° C. and stirring while adding 10% aqueous sodium carbonate solution until reaching a pH of 7.0-7.2. After cooling, the precipitate is washed with water, the precipitate is washed with water, collected by filtration, washed with water and dried in an oven at 120 ° C.

Identical amounts of spherical stabilized gamma-alumina with a 3 mm direct connection made of the dried powder into tablets having a diameter of 3 mm and a length of 5 mm making this catalyst according to the examples of Italian Patent Specification 1,001,614. It is mixed with (by weight). 100 ml of the solid mixture is used for the sustained test according to the process described in Example 1 but under a pressure of 90 kg / cm ₂ and a flow rate of 500 L / hr of CO and H ₂ mixtures. The reaction temperature is 330 ℃ and the results are listed in Table 3.

TABLE 3

EXAMPLE

A catalyst was prepared according to the process described in Example 1 with a molar ratio of Cu, Zn, Cr and Al of 15/10/5/10. The continuous test is carried out according to Example 1 under a pressure of 90 kg / cm 2 and a temperature of 310 ° C.

The performance of the catalyst after 500 hours of use with the new catalyst is reported below.

Example 5

A catalyst is prepared according to the same composition and process as in Example 1 using stabilized gamma-alumina obtained according to the process of Example 10 of Italian Specification No. 1,001,641.

As indicated in Example 1, a duration test is conducted under a pressure of 70 kg / cm 2, a CO and H ₂ flow rate of 3501 / hr, and a reaction temperature of 280 ° C.

The performance of the catalyst at the start of the test and after 496 hours is as follows.

Example 6

1.449 g of Cu (NO ₃ ) ₂ · 3H ₂ O 960.4 g of Cr (NO ₃ ) ₃ · 9H _{2 in an} atomic ratio of 30/18/12/40 Cu / Zn / Cr / Al in 20 L of water at 85 ° C Dissolve 1.071 g of Zn (NO ₃ ) ₂ 6H ₂ O and 3.000.1 g of Al (NO ₃ ) ₃ .9H ₂ O.

Ammonia was added to the solution obtained above at pH 85 at 85 ° C., and then filtered to recover the precipitate, washed with water and then slurried in water to make fine particles and dried. The dried powder obtained is treated with tetraethyl orthosilicate according to the procedure set forth in Italian Patent Specification No. 1,001,614 and then the excess tetraethyl orthosilicate is removed and made into tablets having a diameter of 4 mm and a length of 6 mm.

The catalyst obtained is heat treated at 350 ° C. and 100 ml of the catalyst is placed in a reactor as described in Example 1 and reduced as in Example 1. A reaction mixture consisting of 75% hydrogen and 25% carbon monoxide was injected at a space velocity of 7,500 hours ⁻¹ at a temperature of 320 ° C. and a pressure of 90 atm. 540 hours of continuous testing was performed. Initial and final performance was as follows.

Example 7

A mixture of 50% by volume of carbon monoxide and 50% by volume of hydrogen was injected at a space velocity of 3,500 hours ^-1 under a pressure of 90 atm and a temperature of 300 ° C on the same catalyst as in Example 1.

The performance of the catalyst was obtained after 580 hours of use with the new catalyst.

Claims (1)

Reaction pressure of 50-100 kg / cm 2 using a novel catalyst which stabilizes oxides and salts of metals selected from aluminum, chromium, tartanium, manganese, copper and zinc with a silicon compound represented by the following general formula And reacting hydrogen and carbon monoxide under reaction conditions of a space velocity of 1,000-10,000 ^h-1 , and then separating dimethyl ether obtained from the reactant.

Wherein X, Y, Z and W are -R, -OR, -Cl, Br, -SiH ₃ , -COOR, SiHnClm and R is hydrogen, alkyl, cycloalkyl, aromatic alkylaromatic, having 1-30 carbon atoms Alkylcycloalkyl, where n and m are integers from 1-30.