KR100505531B1 - Pd-La-Si catalyst for selective hydrogenation of acetylene and production method of the same - Google Patents

Abstract

The present invention relates to a palladium-lanthanum-silicon (Pd-La-Si) catalyst for producing hydrogen with high purity by selectively hydrogenating acetylene in ethylene containing acetylene, and after preparing or regenerating the catalyst, An object of the present invention is to provide a selective hydrogenation catalyst of acetylene which has high ethylene selectivity and reaction activity even at a low temperature, and a method for producing the same.

The acetylene selective hydrogenation catalyst of the present invention contains 0.05 to 2.0% by weight of palladium, 0.07 to 2.6% by weight of lanthanum, and 0.0001 to 0.065% by weight of silicon (the remaining portion is a carrier), and (1) the carrier is an aqueous tetraaminepalladium hydroxide solution. After impregnating with it, drying and firing to support palladium; (2) impregnating the palladium-supported carrier (Pd catalyst) into the lanthanum aqueous solution, followed by drying and calcining to support the lanthanum; (3) reducing the palladium and lanthanum-supported carrier (Pd-La catalyst) under a stream of hydrogen at 350 to 700 ° C., and then depositing a silicon compound at 200 to 300 ° C .; And (4) reducing the carrier on which palladium and lanthanum on which the silicon compound is deposited is carried out at 300 to 600 ° C. for 1 to 5 hours.

Description

Pd-La-Si catalyst used for selective hydrogenation of acetylene and its preparation method {Pd-La-Si catalyst for selective hydrogenation of acetylene and production method of the same}

The present invention relates to a palladium-lanthanum-silicon (Pd-La-Si) catalyst for selectively hydrogenating acetylene in ethylene containing acetylene to obtain high purity ethylene, and a method for preparing the same.

Ethylene for polymer polymerization is mainly produced by thermal decomposition of naphtha or catalytic cracking of petroleum gas such as ethane, propane, butane, etc. The ethylene produced by the above method contains about 0.5 to 2.0% by weight of acetylene. However, since acetylene contained in ethylene not only lowers the activity of the catalyst but also lowers the physical properties of the polymer, the acetylene content should be lowered to 2 ppm or less.

Currently, high-purity ethylene is produced by selectively hydrogenating acetylene contained in ethylene using a hydrogenation catalyst. The most important factor in the hydrogenation catalyst is reactivity (activity), and selectivity in which acetylene is hydrogenated to ethylene and ethylene is not hydrogenated to ethane. (selectivity).

In the reaction for selectively hydrogenating acetylene, noble metal catalysts are generally used. In particular, palladium is known to be excellent in reactivity and selectivity. According to Bond et al. ("Catalysis by metals" Academic Press, New York, 281-309, 1962), the selectivity of the transition metal catalyst is lowered in the order of Pd> Rh, Pt> Ni> Ir.

In the hydrogenation of acetylene, heat of 30-40 kcal per mole is generated. When the reaction temperature is increased, the conversion of acetylene is increased, but the ethylene conversion is also increased and the selectivity is changed. Therefore, it is necessary to maintain the reaction temperature in an appropriate range. The catalyst and reactor are preferably designed to rise to within 15 ° C. when acetylene is fully converted to ethylene.

US Pat. No. 4,387,258 discloses a method for preparing a catalyst by supporting palladium on silica, and US Pat. No. 4,839,329 discloses a method for preparing a catalyst by supporting palladium on titanium dioxide.

In addition to silica and titanium dioxide, alumina is commercially used as a carrier. The supported catalyst is a side reaction of the carrier, and thus, oligomers having 4 or more carbon atoms are formed to form pores of the carrier. There is a problem of reducing the regeneration cycle and life of the catalyst by blocking or surrounding the active site.

Another important problem in hydrogenation catalysts is to increase the selectivity of the catalyst in addition to the regeneration cycle and lifetime of the catalyst.

Although the hydrogenation rate of ethylene is 10-100 times faster than the hydrogenation rate of acetylene ( Adv. In Catal ., 15, 91-226 (1964)), the selective hydrogenation of acetylene is more selective to the reaction site than ethylene. This is because it is adsorbed by. As a result of examining adsorption characteristics of acetylene, methylacetylene, propadiene, ethylene, and propylene to palladium, it was found that the adsorption rate was in the order of acetylene>diolefin>olefin> paraffin, and the desorption rate was in the reverse order. (The Oil and Gas Journal, 27, 66 (1972))

Therefore, when diolefin is added when hydrogenating acetylene contained in ethylene, the diolefin interferes with the adsorption of ethylene, thereby selectively hydrogenating acetylene without hydrogenating ethylene. In other words, by interfering with the adsorption of ethylene to increase the selectivity of acetylene, a material having a moderate adsorption characteristics such as diolefin is called a modulator. Carbon monoxide also acts as a moderator in the hydrogenation of acetylene like diolefins. Carbon dioxide is more suitable because the diolefin itself becomes a green oil and there is a problem of separating the unreacted diolefin after the reaction.

U.S. Patent Nos. 3,325,556 and 4,906,800 disclose methods for increasing the selectivity of acetylene hydrogenation by adding trace amounts of carbon monoxide.

However, even when carbon monoxide is used as a moderator, carbon monoxide generates a carbonylation reaction to generate green oil, thereby reducing the regeneration cycle and life of the catalyst.

As a catalyst to solve the problem that the regeneration cycle and life of the catalyst is shortened by the production of green oil, Korean Patent Laid-Open No. 2000-0059743 discloses a palladium titanium (Pd-Ti) catalyst in which titanium is supported by a palladium catalyst. Is disclosed.

The palladium titanium catalyst utilizes a strong metal support interaction (SMI) between titanium dioxide and palladium, which occurs during a high temperature reduction process of about 500 ° C. SMSI phenomenon means that the carrier is partially reduced during the high temperature reduction process and the metal surface is modified and electrons are transferred from the support to the metal to enrich the electronic state of the metal. This SMSI effect can reduce the amount of green oil produced on the surface of Pd, consequently extending the lifetime of the catalyst and improving the selective hydrogenation of acetylene to ethylene.

As a hydrogenation catalyst using a material having such a strong metal-carrier interaction (SMSI), the prior application patent Korean Patent Application No. 2003-0018888 of the inventors of the present invention discloses a palladium-lanthanum catalyst carrying lanthanum (La) as a promoter It is.

However, this strong metal-carrier interaction has a disadvantage in that when the catalyst is regenerated and exposed to an oxidizing atmosphere, the deformation effect of the metal surface is also lost. In other words, in a commercial process, when the catalyst is deactivated, it is regenerated at about 400 ° C. using hot air, and in this process, the deformation effect of the metal surface due to the SMSI action disappears.

Therefore, in order to restore the catalytic performance, a high temperature reduction process of about 500 ° C. is required again as in the case of preparing a catalyst. However, since the temperature that can be raised in a commercial hydrogenation reactor is only about 300 ° C., it is difficult to apply the catalyst in an actual process.

It is an object of the present invention to provide a selective hydrogenation catalyst of acetylene which has high acetylene selectivity and reaction activity even when the catalyst is reduced or reduced at low temperatures, and a method for producing the catalyst.

The catalyst of the present invention for achieving the above object is characterized in that the palladium content of 0.05 to 2.0% by weight, the lanthanum content of 0.07 to 2.6% by weight, the silicon content of 0.0001 to 0.065% by weight (residue is a carrier) .

The selective hydrogenation catalyst of acetylene,

(1) a step of impregnating a carrier with an aqueous tetraamine palladium hydroxide solution, followed by drying and baking to support palladium;

(2) impregnating the palladium-supported carrier (Pd catalyst) into the lanthanum aqueous solution, followed by drying and calcining to support the lanthanum;

(3) reducing the palladium and lanthanum-supported carrier (Pd-La catalyst) under a stream of hydrogen at 350 to 700 ° C., and then depositing a silicon compound at 200 to 300 ° C .; And

(4) The palladium and the lanthanum-supported carrier on which the silicon compound is deposited are prepared by a process including reducing the carrier on 300 to 600 ° C. for 1 to 5 hours.

Hereinafter, each step will be described in more detail.

(1) is a process for producing a palladium catalyst (Pd catalyst), so that palladium is supported by 0.05 to 2.0% by weight.

The method for preparing the Pd catalyst is a known method, for example, a carrier (silica, titanium dioxide, alumina) is added to the aqueous solution of tetraamine palladium hydroxide in accordance with the desired amount of palladium, and stirred at room temperature for about 12 hours, Wash several times with distilled water. Subsequently, the washed catalyst is dried by vacuum drying at room temperature, dried at 50 to 150 ° C., and then calcined at 400 to 600 ° C. under an air stream for 1 to 5 hours.

(2) is a process for preparing a palladium lanthanum catalyst (Pd-La catalyst) by supporting lanthanum (La) on the Pd catalyst prepared in (1), so that the lanthanum is 0.07 to 2.6% by weight.

The lanthanum supported as a cocatalyst has a strong interaction with palladium at a high temperature reduction of about 500 ° C. to increase the selectivity of the catalyst, and the lanthanum supported method is essentially the same as the method for preparing the Pd catalyst of (1). not different.

(3) is a process of depositing a silicon compound on a Pd-La catalyst, which constitutes a feature of the present invention with step (4) described below when compared with the known art.

Silicon is supported by 0.0001 to 0.065% by weight, and oxygen is removed from the reactor containing Pd-La catalyst by nitrogen stream, followed by a process of reducing the catalyst under a hydrogen stream at 350 to 700 ° C. In the reduction process, it is believed that some of the lanthanum migrates to the palladium surface and partially covers the palladium surface to modify the palladium.

As the silicone compound, tetrahydrosilane, triethylsilane, tripropylsilane, phenylsilane or a mixture thereof can be used, which is placed in a carrier gas (hydrogen) and brought into contact with the catalyst at 200 to 300 ° C.

(4) is a step of reducing the Pd-La catalyst on which the silicon compound is deposited in the step (3), and is performed at 300 to 600 ° C. for 1 to 5 hours.

Silicon supported through steps (3) and (4) maintains the interaction between lanthanum and palladium even after regenerating the catalyst and reducing it at low temperatures.

The hydrogenation catalyst of the present invention prepared by the above method selectively hydrogenates acetylene from ethylene containing acetylene. In the case of ethylene containing 0.5 to 2.0 wt% of acetylene, 400 to 2,400 ml / ( Contact) at the reactant flow rate in minutes (gram catalyst).

The configuration of the present invention will become more apparent by the examples described below, and the effect will be proved by the comparative examples.

<Example 1>

A. Preparation of Palladium Catalyst

Palladium catalysts were prepared by known methods. 20 g of silica was added to 200 ml of 0.33 wt% tetraamine palladium hydroxide aqueous solution, and stirred for 12 hours to carry palladium, followed by vacuum drying. Subsequently, it was dried in an oven at 100 ° C. for 12 hours and calcined for 2 hours under an air stream of 300 ° C., whereby a palladium catalyst having a palladium content of 1% by weight was prepared.

B. Support of Lanthanum

3 ml of 2 wt% lanthanum nitrate hydrate aqueous solution was used to prepare lanthanum by incipient wetness impregnation in the palladium catalyst prepared above, followed by drying in an oven at 100 ° C. for 6 hours and under 300 ° C. air stream. After firing for 2 hours, a palladium-lanthanum catalyst having a lanthanum / palladium molar ratio of 1 was prepared.

C. Reduction and Deposition of Silicon

3 g of the palladium-lanthanum catalyst prepared above was charged into a fixed bed tube, reduced by passing hydrogen at 500 ° C. for 1 hour, and then passed through nitrogen to lower the temperature to 250 ° C., followed by 1% SiH ₄ / Ar gas (1% SiH _4). And 99 ml of mixed gas of 99% Ar) were deposited by pulse injection through a sampling loop, and the amount of Si deposited was controlled by the number of pulse injections. Hydrogen was used as the carrier gas and the flow rate of hydrogen was 20 ml per minute. Subsequently, oxygen was passed through 25 ° C. for 2 hours.

D. Reduction

The palladium-lanthanum catalyst on which the silicon deposited above was deposited was reduced by passing hydrogen at 300 ° C. for 1 hour. The silicon / palladium molar ratio of the catalyst thus prepared is 0.012.

<Example 2>

A hydrogenation catalyst was prepared in the same manner as in Example 1, except that the silicon / palladium molar ratio was 0.006.

<Example 3>

A hydrogenation catalyst was prepared in the same manner as in Example 1, except that the silicon / palladium molar ratio was 0.12.

Comparative Example 1

A catalyst was prepared in the same manner as in Example 1, except that the lanthanum supporting step (B) and the reducing and silicon deposition steps (C) were not performed.

That is, palladium was supported on silica to prepare a palladium catalyst having a palladium content of 1% by weight (step A), and then reduced by passing hydrogen at 300 ° C. for 1 hour (step D).

Comparative Example 2

A catalyst was prepared in the same manner as in Comparative Example 1 except that the reduction process was performed at 500 ° C.

Comparative Example 3

A catalyst was prepared in the same manner as in Example 1, except that the reduction and deposition of silicon (C) were not carried out.

That is, palladium is supported on silica to prepare a palladium catalyst having a palladium content of 1% by weight (step A), and then a palladium-lanthanum catalyst having a lanthanum / palladium molar ratio of 1 is prepared (step B), 300 Hydrogen at 캜 was passed through for 1 hour to reduce (step D).

<Comparative Example 4>

A hydrogenation catalyst was prepared in the same manner as in Comparative Example 3 except that the reduction process was performed at 500 ° C.

<Example 4>

Hydrogenation of acetylene was carried out using the catalysts prepared in Examples 1-3 and Comparative Examples 1-4.

A. Sample Gas

An ethylene-acetylene mixed gas having an acetylene content of 1.02 mol% was used.

B. Experiment

Fill the 1/4 inch glass tubular reactor with 0.03 g of catalyst each, and mix the sample gas and hydrogen, changing the space velocity to 400, 800, 1200, 1600, 2000, 2400 (ml / min / gram catalyst). Passed. Hydrogen was fed twice the acetylene on a molar basis and the reaction was carried out at 60 ° C.

C. Results

Acetylene conversion and ethylene selectivity were calculated according to [Equation 1] and [Equation 2], respectively, and the results are shown in FIG. 1.

Acetylene conversion = ΔA / A ₀

Ethylene Selectivity = ΔB / ΔA = ΔB / (ΔB + ΔC)

Where A ₀ = initial concentration of acetylene, ΔA = change in acetylene, ΔB = change in ethylene, and ΔC = change in ethane.

According to FIG. 1, when the reduction was performed at 300 ° C., the reaction selectivity was slightly higher than that of the Pd-La catalyst (Comparative Example 3) on which lanthanum was supported (Comparative Example 1). In the case of reducing at, the reaction selectivity of the lanthanum-supported Pd-La catalyst (Comparative Example 4) increased rapidly, and the lanthanum-supported Pd-La catalyst (Comparative Example 3) or unsupported Pd catalyst was reduced at 300 ° C. It can be seen that the reaction selectivity is higher than that of (Comparative Example 1). On the contrary, the lanthanum-free Pd catalyst reduced at 500 ° C. (Comparative Example 2) has a very low reaction selectivity. The lanthanum-supported Pd-La catalyst (Comparative Example 4) reduced at 500 ° C. is modified with palladium surface by lanthanum due to strong metal-supporting interaction (SMSI phenomenon) when reducing at high temperature. It is interpreted that the production of 1,3-butadiene, which is known as a precursor for deactivating the catalyst, is suppressed due to the suppression of the production of ethylidine, which requires a point, and the generation of ethane.

On the other hand, the reaction selectivity of the lanthanum-supported Pd-La catalyst (Comparative Example 3) reduced at 300 ° C is relatively lower than that of the Pd-La catalyst (Comparative Example 4) reduced at 500 ° C. It is interpreted that SMSI phenomenon did not sufficiently occur between lanthanum and palladium.

The Pd-La-Si catalyst supported on lanthanum and silicon and reduced at 300 ° C. (Example 1) was a Pd-La catalyst supported only on lanthanum reduced at 300 ° C., despite being reduced at a relatively low temperature of about 300 ° C. It can be seen that the reaction selectivity was higher than that of (Comparative Example 3), and the reaction selectivity was almost similar to that of the Pd-La catalyst (Comparative Example 4) loaded with only lanthanum reduced at 500 ° C. This is because when the silicon is supported on the Pd-La catalyst, although the catalyst is reduced at a relatively low 300 ° C after exposure to oxygen in the regeneration process (Example 1), the improved performance of the reduced Pd-La catalyst at a high temperature (500 ° C) It can be maintained as it is. It is interpreted that this is because the silicon is supported to fix lanthanum to the Pd surface to some extent.

On the other hand, Pd catalyst (Comparative Example 2), which is not loaded with lanthanum reduced at 500 ° C., causes palladium to agglomerate in the reduction process, so that the production of ethylidine, which requires many adsorption points, is relatively accelerated. It is interpreted that the production of butadiene is promoted and the ethylene selectivity is reduced.

Example 5

The same conditions as in Example 4 were applied to the catalysts having different silicon contents, that is, the catalysts prepared in Examples 1, 2, 3, and 3 and 4 (comparative example, the silicon content was 0). Hydrogenation of acetylene at was carried out, and the results are shown in FIG. 2.

Pd-La-Si catalyst (Example 2) reduced at 300 ° C with Si / Pd of 0.006 on a molar basis showed almost the same reaction selectivity as Pd-La catalyst (Comparative Example 3) reduced at 300 ° C. As a reference, the Pd-La-Si catalyst (Example 1), which had a Si / Pd of 0.012 and was reduced at 300 ° C, was higher than the Pd-La catalyst (Comparative Example 3) reduced at 300 ° C, and reduced at 500 ° C. Pd-La-Si catalyst (Example 3), which has a reaction selectivity similar to that of the catalyst (Comparative Example 4) and has an increased silicon content of 0.12 Si / Pd on a molar basis and is reduced at 300 ° C. (Example 3), is reduced to Pd at 300 ° C. The reaction selectivity is lower than that of the -La catalyst (Comparative Example 3), and the reaction activity is also drastically reduced.

In Example 2, since the amount of the supported silicon is small to effectively fix the lanthanum, the result is similar to that in which the silicon is not supported. On the contrary, in the case of Example 3, the amount of the supported silicon is too large to be the active metal. Since almost all active points of palladium are covered, it is interpreted that the reaction selectivity and the reaction activity decrease rapidly at the same time. Therefore, it can be seen from the above results that there is a silicon loading showing optimum reaction selectivity.

The hydrogenation catalyst of the present invention has excellent selectivity for hydrogenating acetylene to ethylene without hydrogenating ethylene to ethane, saturated hydrocarbon, and having similar reaction activity and selection as Pd-La catalyst reduced at high temperature even at low temperature. Shows a figure.

In addition, since the high performance is recovered even when the catalyst is regenerated at a low temperature, the reduction process can be performed while the catalyst is contained in the hydrogenation reactor, which is practical.

FIG. 1 shows the results of acetylene selective hydrogenation of the palladium (Pd) catalyst, the palladium-lanthanum (Pd-La) catalyst, and the palladium-lanthanum-silicon (Pd-La-Si) catalyst prepared in Examples and Comparative Examples. (The six values in each example or comparative example were obtained by mixing sample gas and hydrogen from the left side to change the space velocity to 400, 800, 1200, 1600, 2000, 2400 (ml / min.gram catalyst).)

Figure 2 shows the selectivity in the acetylene hydrogenation of the catalyst prepared by varying the silicon content. (In each Example or Comparative Example, six values are obtained by mixing sample gas and hydrogen from the front and changing the space velocity to 400, 800, 1200, 1600, 2000, 2400 ml / (min) (gram catalyst). )

Claims (5)

A hydrogenation catalyst for selectively hydrogenating acetylene from ethylene containing acetylene having a palladium content of 0.05 to 2.0% by weight, a lanthanum content of 0.07 to 2.6% by weight, and a silicon content of 0.0001 to 0.065% by weight (the remainder being a carrier). (1) a step of impregnating a carrier with an aqueous tetraamine palladium hydroxide solution, followed by drying and baking to support palladium; (2) impregnating the palladium-supported carrier (Pd catalyst) into the lanthanum aqueous solution, followed by drying and calcining to support the lanthanum; (3) reducing the palladium and lanthanum-supported carrier (Pd-La catalyst) under a stream of hydrogen at 350 to 700 ° C., and then depositing a silicon compound at 200 to 300 ° C .; And (4) A method for producing a hydrogenation catalyst for selectively hydrogenating acetylene with ethylene, comprising the step of reducing the carrier on which palladium and lanthanum on which the silicon compound is deposited are carried out at 300 to 600 ° C. for 1 to 5 hours. The method for producing a hydrogenation catalyst according to claim 2, wherein lanthanum nitrate hydrate is used as the lanthanum compound. The method for producing a hydrogenation catalyst for selectively hydrogenating acetylene according to claim 2, wherein the silicon compound deposited in step (3) is selected from tetrahydrosilane, triethylsilane, tripropylsilane, or phenylsilane. A method for selectively hydrogenating acetylene by contacting ethylene containing 0.5 to 2.0% by weight of acetylene at a reaction temperature of 30 to 120 ° C. at a rate of a reactant flow rate of 400 to 2,400 ml / min gram catalyst.