JPS5959634A - Selective hydrogenation of acetylene - Google Patents

Abstract

PURPOSE:To hydrogenate acetylene selectively, by bringing a mixed gas containing ethylene as a main component, H2 and a very small amount of acetylene into contact with CO using a Pd catalyst treated with a specified amount of CO so tat acetylene is selectively hydrogenated andd the reaction is advanced smoothly. CONSTITUTION:A mixed gas obtained by distilling and separating a cracking gas of hydrocarbon, removing >=3D heavy fractions, comprising low-boiling fractions containing ethylene as a main component, a very small amount of acetylene and >=10 times as much H2 as acetylene by molor amount is brought into contact with CO in the presence of a Pd catalyst supported preferably on an alpha-alumina carrier at 40-90 deg.C at 10-50kg/cm<2>G at a space velocity (SV) of 3,000-6,000/hr, and acetylene is selectively hydrogenated. The Pd catalyst is obtained by bringing CO into contact with the Pd catalyst in an inert gas such as N2, etc. at 0-40 deg.C at 5-100mm.Hg partial pressure of CO for 5-70hr in such a way that >=70ml (calculated in a standard state) is adsorbed per g Pd catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for selective hydrogenation of acetylene. More specifically, it relates to a method for selectively hydrogenating acetylene contained in a mixed gas containing ethylene as a main component.◇ The permissible limit of acetylene as an impurity contained in ethylene used as a raw material for producing polyethylene resin is: It is usually about 10 ppm in molar exchange. By the way, ethylene is usually obtained by thermally decomposing naphtha, ethane, butane, etc. and then separating it by distillation to obtain the ethylene fraction.
Contains acetylene generated during thermal decomposition in ethylene fraction; 4
It is impossible to reduce J'# to 1.0 ppm or less by distillation separation method.

Therefore, it becomes necessary to remove acetylene by means other than distillation separation method, for example, U.S. Patent No. 3, 308
, No. 180, when hydrogenating 0.5 to 1% acetylene contained in a mixed gas containing ethylene as a main component with hydrogen using a palladium catalyst, 1 mole of acetylene in the mixed gas is hydrogenated. It has been proposed to carry out the hydrogenation in the presence of 5 to 4 ppm of hydrogen oxide to .5 to 5 moles of hydrogen and the gas mixture.

Although this method of selectively hydrogenating acetylene is a very excellent method, there are cases where the jJ-method cannot be used as is. That is, in the light boiling point fraction containing ethylene, which is obtained by distilling and separating hydrocarbon pyrolysis gas to remove heavy fractions with carbon atoms of 3 or more, there are originally other substances in addition to ethylene.
Acetylene and more than 10 times the molar amount of hydrogen are present, and because of this relatively large amount of hydrogen, if the known method described in 011 is applied as is, acetylene will only be hydrogenated, resulting in hydrogenation. However, ethylene is also hydrogenated to some extent to form ethane. This not only means a loss of ethylene, but also makes it impossible to control the crystallinity due to the heat generated by the hydrogenation reaction of ethylene, creating an extremely dangerous situation that makes it difficult to continue the hydrogenation process. This results in wool spinning in which the desired hydrogenation of acetylene cannot be carried out sufficiently.

As a result of various studies on how to avoid such a mold part and allow the hydrogenation process to proceed smoothly, the inventors of the present invention found that, prior to the hydrogenation reaction, the palladium catalyst used was treated with carbon monoxide, By adsorbing it more than a certain amount,
It has been found that the selectivity of the catalyst can be further improved and the above problems can be solved all at once. This indicates that the above-mentioned U.S. patent specifies that, before the hydrogenation reaction, directly -
・Although it is possible to pass carbon acetate, it is stated that this method is not so effective (2H lines 60-65).
'.

1' IC (target)

Therefore, the present invention relates to a selective swimming method of acetylene, in which a mixed gas containing ethylene as the main component, NNtit acetylene, and hydrogen in an amount of about 1.0 times or more mole relative to it is oxidized with a palladium catalyst. Contact in the presence of carbon!! - When selectively hydrogenating acetylene and acetylene, 70 ml of carbon monoxide is adsorbed per 17 palladium catalysts (converted to standard conditions) prior to the hydrogenation reaction. It is characterized by contact treatment of palladium catalyst Q'X with carbon monoxide.

The mixed gas to be treated in the method of the present invention has ethylene as its main component and is very low in cost (fi!+ Jooo in terms of mole).

ppm or less) and about 10 times or more, preferably 10 to 100 times the mole of hydrogen, and in addition to these, saturated hydrocarbons such as methane and ethane, or carbon oxides. may contain. To give a specific example, a light boiling point fraction containing ethylene as a main component is obtained by distilling and separating the thermal decomposition gas of hydrocarbons such as Navvu and removing the heavy fraction of charcoal 3 or more. For example, those having the following composition are used.

Ethylene 40-50 mol% Nok element 10-30 mol% Sedilene (), 3-0.5T Nyl% Methane 20-35 mol% Ethane 7-15 mol% Carbon monoxide 300 to 500 ppm (%, ) Palladium catalyst used as a catalyst for the hydrogenation reaction, a carrier such as alumina or silica, preferably an alumina carrier, and preferably an α-alumina 111 body, about 0.01 to 0 It is generally used as having a specific surface area of 1 to 50 rrV with a supporting nail of 1% by weight.

The catalytic R11 treatment of the palladium catalyst with carbon monoxide is carried out prior to the hydrogenation reaction of the R5 mixture gas.

This contact treatment can be carried out for 7J depending on various conditions, but for example, palladium is added to the hydrogenation reactor for 1.7J. After filling the tank with nitrogen, the air was replaced by a sufficient supply of nitrogen.In the presence of an inert gas such as nitrogen, the temperature
Under the temperature condition F, the partial pressure of -carbon oxide is approximately 5 to 100 mm.
Supply oxidation so that it becomes Hg, about 5 to 70
Time palladium touch l14! It can be understood by connecting (?) with -carbon oxide.

Through this contact treatment, the partial pressure of carbon monoxide in the reaction tank is reduced by adsorption onto the palladium catalyst, but the amount of adsorption is approximately 70+n/! per q of palladium catalyst! Above, preferably about 70 to 150 m1! (standard state conversion). If the amount of carbon oxide adsorbed on the catalyst is less than this, selective hydrogenation of acetylene will become difficult.
There is a risk that anti-b6 will develop in an unfavorable direction, such as hydrogenation of ethylene.

In this way, the hydrogenation reaction of C-carbon oxide and catalytic (mixture of C using treated Snipalladium) gas is as follows:
- The presence of oxidized carbon 11'r is carried out. - Carbon oxide is water 2 part/) 11, (+:, f, and there are many supports, plus ° 11 19, so it is about] 0 () ~ 50 for the mixed gas)
Make sure that 0 ppm (11 moles) is present.
c III], add enough Ni to the mixed gas.
1rr: 'rrI, p or l (I do not publish the addition as Shinta?, -riφ conversion 1.) element is present in the mixed gas, and when 4C and tl are present, it is separately explained. supply.

The water-free treatment of the mixed gas is carried out according to the general method of hydrogenation using palladium, specifically at a temperature of about 40 to 90°C, preferably at about 50 to 80°C. , about JO ~ 50 list - Luke condition 1.5 and about 3 of ()
000-6000. 'Performed at superficial velocity (SV) of time.

Through this hydrogenation reaction 1), the acetylene in the mixed residue is selectively converted to ethylene. There is no loss of i, and there is no usual heat generation, so the reaction is smooth.
(Removes the effect of getting it.

Next, we will explain the present invention on the actual 1111i example. 1
Do 1.

Example Palladium catalyst using α-alumina as a carrier (contains palladium, rr) NO, 04K m%, Jt surface area 1
8 nVQ) 10 tons filled capacity 33 nr”
Nitrogen gas is supplied into the reaction tank, and the air (C is 1σ per minute) is supplied.
After exchange, the JJII pressure was applied to about 1-G.

In a reaction vessel with such a condition, 0.42
When ky was added, the partial pressure of -.carbon oxide was 15ff1 mHg at a temperature of 30°C. While circulating the -carbon oxide mixed gas, contact between the -C, palladium-III medium and the -carbon oxide was carried out for 15 hours. The partial pressure of carbon monochloride after 15 hours was approximately 7: nmIIg, 1.5 nm of monoacid per q of palladium. One mouse is 90 in the standard condition.
It was ml.

Next, 45 mol% of ethylene was added to this anti-1i15i container.
, -7' 10tl/ > 0.5-T-, Ilz %,
Water! f: 12-T: Le%, -4j@carbon 500
A mixed gas containing fV of ppm, I, Mekun, Jtan, etc. was introduced. At this time, the gas pressure rJ, 30'
(f; I G.

The reaction vessel population temperature is 15℃, and the gas supply IVk is empty.
J was set at 6000 degrees/hour.

After that, the temperature of the gas introduced into the reaction vessel was adjusted at a rate of 15°C/hour! ￥ After about 3 hours, it will be wet.
degree 60℃, outlet temperature +<r 70℃Te1: IA I! j difference kl: 10°C, ethylene concentration jβi1 at the outlet
``F454 mol%, mild acetylene i':, '1 degree is 5
ppm and 1. ``At this point, we stopped the -t7. wetting of the gas and were able to stably perform i'i81 selective hydrogenation of acetylene under the conditions specified.

Comparative Example 〃j1; In the example, the operation of bringing carbon monoxide into contact with Barajiuno\friB deaf; '14: <
, ilj, /l of acetylene in the combined gas (added, -l 11j 6 open?r + 1.5 hours after addition D
y+i Iσ37.5℃, out ['l li, i! rr
E 45 T: T"pX 1 degree difference was 7.5°C, so the rising speed was reduced by 10I;/' waiting time was reduced by 14,
Person [1n:il'+ I'j When temperature is 40℃, exit 8th Q
The temperature was extremely high at 53°C.

SoL-L-c 9+ 4<IL Tf stop temperature d-;,
l Taka, Ill l J Warm Irl & J rapidly 1-F
/, t reached 90 degrees Celsius, so Nshinada control became impossible, and a dangerous condition occurred, so tl7, the supply of //s was stopped +) 11:! 1″ and bu,
:.

Claims (1)

[Claims] 13 A mixed gas containing ethylene as a main component, acetylene as shown in the figure, and hydrogen in an amount more than about 10 times its molar amount is brought into contact with a palladium catalyst in the presence of carbon monoxide to select acetylene. During hydrogenation, approximately 7 carbon monooxides are added per 1 g of palladium catalyst prior to the hydrogenation reaction.
A method for selective hydrogenation of acetylene, which comprises contacting a palladium catalyst with carbon monoxide so that 0 me or more (standard state equivalent) is adsorbed. 2. Claim 1, wherein the mixed gas is a 1iW boiling point fraction containing ethylene as a main component, obtained by distilling and separating hydrocarbon pyrolysis gas and removing heavy fractions having 3 or more carbon atoms.
The method for selective hydrogenation of acetylene according to No.6.