JPS5896682A - Selective hydrogenation of acetylene compound - Google Patents

Abstract

PURPOSE:To carry out the selective hydrogenation of acetylene compound in a 3-4C fraction in a liquid phase under pressure stable for a long period, in high selectivity, suppressing the side reactions, by using a Pd-type solid catalyst and adding O2 to the reaction system. CONSTITUTION:In the selective hydrogenation of acetylene compound in the fraction composed mainly of 3-4C olefinic hydrocarbons (e.g. propylene, n-butene, butanes, etc.) (obtained e.g. by the cracking of petroleum) in liquid phase under pressure, the reaction is carried out in the presence of >=1ppb of O2 using a Pd- type solid catalyst (preferably 0.1-2wt% Pd supported on a carrier such as alumina). EFFECT:The addition of a slight amount of O2 improves the initial activity and the selectivity of the catalyst, and remarkably improves the stability of the catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to the production of acetylene in a fraction mainly composed of olefinic hydrocarbons having 3 to 4 carbon atoms (hereinafter referred to as 03-4 fraction) obtained by cracking petroleum products, etc. A method of selectively hydrogenating a compound under pressurized liquid phase conditions, characterized in that the reaction is carried out using a palladium-based solid catalyst as a catalyst and containing at least i ppb of oxygen in the reaction system. and how to do so.

-・ ・ ~ The C3-4 fraction obtained by cracking petroleum products mainly contains propylev, 1,3-butadiene, isobutyne, n-butene (butene-1, butene-2), propane,
It consists of butanes, and contains small amounts of acetylene compounds such as acetylene, methylacetylene, ethylacetylene, and vinylacetylene as impurities, and in some cases diene compounds such as allene (propadiene) and methylarene as impurities. It may also contain.

When separating these 03-4 fractions and using them as raw materials for rubber, plastic, and other chemical industries, the acetylene compounds contained as impurities pose various obstacles.
It must be removed by appropriate treatment in advance so that the concentration is below a certain level.

Conventionally, as a method for removing acetylene compounds in the C3-4 fraction, acetylene compounds are selected by suppressing hydrogenation of the main components olefins and diolefins as much as possible under gas phase or liquid phase conditions in the presence of a catalyst. A method of hydrogenation is currently being used. However, in the conventionally known methods, it is very difficult to selectively and sufficiently hydrogenate only the acetylene compound while suppressing the hydrogenation of the main components, olefins and diolefins, as much as possible. Particularly in the case of C4 fractions, there is generally little difference in reactivity between 1,3-butadiene and impurity acetylene compounds, and the concentration of acetylene compounds to be hydrogenated is extremely low compared to the concentration of butadiene. Therefore, it is very difficult to selectively and sufficiently hydrogenate only the acetylene compound while suppressing the hydrogenation of butadiene as much as possible.

For example, in the gas phase method, the reaction is usually carried out at a temperature of about 150 to 200°C, but in the reaction at such a high temperature, hydrogenation and polymerization of butadiene are severe, and a considerable amount of butadiene is inevitably lost. Deterioration of the catalyst due to adhesion of substances is also significant. On the other hand, in the liquid phase method, the reaction is usually carried out at a relatively low temperature of 100°C or less, so there are fewer drawbacks such as catalyst deterioration compared to the gas phase method, but on the other hand, hydrogenation of the acetylene compound is completely carried out, It is also difficult to avoid the disadvantage that it is necessary to use a considerably large amount of hydrogen, and the proportion of hydrogenation of butadiene increases accordingly.

In view of the current situation, the inventors of the present invention have decided to proceed from 03 to 2003. As a result of various studies to develop an effective method for selectively hydrogenating acetylene compounds in the distillate, we found that a trace amount of the raw material C3-4 fraction to be subjected to the reaction using a palladium catalyst was found. It has been found that the incorporation of oxygen of 50% yields an excellent effect. When selective hydrogenation of an acetylene compound in a C3-4 fraction is carried out using a palladium-based catalyst, even if the reaction is carried out using a C3-4 fraction that does not contain any oxygen, the catalyst is initially Although its activity and selectivity are relatively good,
There is a problem with stability when used for a long period of time. However, when the 03-4 fraction mixed with a trace amount of oxygen was used, it was found that the initial activity and selectivity of the catalyst were improved, and the Ω stability of the catalyst was significantly improved.

Although the mechanism by which oxygen mixed into the reaction system improves catalyst stability is unknown, its effect is extremely significant.

In the present invention, the method of mixing a trace amount of oxygen into the reaction system is not necessarily limited, but in practice, pure oxygen or an oxygen-containing gas such as air or an inert gas containing oxygen is mixed into a raw material component, such as A certain amount may be mixed into the 03-4 fraction. Air can be particularly preferably used in consideration of safety and the like.

The oxygen concentration added into the reaction system is as follows: Raw materials 03-.
The concentration in the fraction is preferably 1 ppb to 10 ppm, particularly preferably 10 ppb to 1 ppm.

Although the state of existence of oxygen added in the reaction system or in the raw material hydrocarbon fraction is not clear, it may be converted into molecular oxygen, that is, dissolved oxygen in the raw material hydrocarbon, or oxygen-containing compounds such as aldehydes and peroxides. It is expected that it will exist in the form of a state, etc. Furthermore, although the mechanism of action of oxygen in the method of the present invention is not clear, it is presumed that oxygen has the following action and therefore produces a remarkable effect.

That is, molecular oxygen acts as a polymerization inhibitor and prevents polymer by-products on the catalyst surface, or stabilizes components in the 03-4 fraction that are poisonous substances for palladium-based catalysts, or hydrogen, It is possible to consider effects such as increasing catalyst activity and stability by controlling the adsorption power of acetylenes on the catalyst surface. The catalyst used in the present invention has palladium as a main component or palladium as a co-catalyst. Preferably, these contain other metal salts, such as inorganic or organic acid salts of copper, silver, gold, tin, zinc, cadmium or lead. Various metal oxides can be used as the carrier, but alumina is particularly preferred, and among them γ-M208, η-M 20g, θ-
U2O8 etc. are suitable. As for the catalyst composition, the ratio of palladium to support is 0.05 to 5% by weight, preferably O
, 1 to 2% by weight, and the ratio of the cocatalyst component to palladium is 0.1 to 10 as the atomic ratio of the metal, preferably 0.
．． It is in the range of 5-8. There are no particular restrictions on the method for preparing the catalyst, and any method commonly used for this type of catalyst may be used as appropriate. - For example, it can be prepared by the following methods. After impregnating the alumina carrier with a predetermined amount of a solution of acid or water-soluble salts such as palladium chloride, palladium nitrate, palladium acetate, and sodium palladium chloride,
This palladium salt is reduced to metallic palladium by a dry or wet method using a suitable reducing agent such as hydrogen, hydrazine, formaldehyde, or sodium formate. Next, the alumina supporting metallic palladium is thoroughly washed with water and dried in vacuum. When using a co-catalyst component, it is further immersed in a solution containing soluble salts of the metals at a predetermined concentration to support these salts, subjected to reduction treatment if necessary, and vacuum-dried to form the desired product. Get the catalyst.

There are no strict limitations on the reaction conditions when carrying out the method of the present invention, but the reaction is generally carried out under the following conditions.

The reaction temperature is in the range of 0 to 80°C, preferably 5 to 60°C, and the reaction pressure is in the range of 2 to 3oky/crlG - preferably,
In the range of 3 to 20 jcg/dlG, the molar ratio of L and acetylene compound is in the range of 0.1 to 15, preferably in the range of 0.5 to 10, LH8V is in the range of 2 to 80 hr', preferably 4 to 40
The reaction temperature and reaction pressure are set within the range of hr-1 and at which the reaction system can substantially maintain a liquid phase. Pretreatment for dehydration of feedstock hydrocarbons is 0.1 to 80 hr at LH8V.
', preferably 0.1 to 40 hr=Other conditions are carried out within a range similar to the reaction conditions.

The H2 used in the present invention may be pure or diluted with an inert gas such as methane.

The content of the 04 acetylene compound in the C3-4 fraction used in the present invention is not particularly limited, but hydrogenation removal is possible even when the total concentration of various coexisting acetylene compounds is in the range of 0.5 to 3 wt%.

The reaction type in carrying out the method of the present invention is a fixed bed reaction, and either a flowing type or an overflow type can be adopted to carry out a fixed bed reaction in a liquid phase. Further, as the reactor, either an isothermal type or an adiabatic type can be used.

According to the method of the present invention, selective hydrogenation is promoted, the removal rate of acetylenes is extremely high, and the hydrogenation of the main component mono- or diolefin, which occurs as a side reaction, is significantly reduced, so that its loss can be minimized. Moreover, it has the excellent advantage of being able to maintain a stable reaction over a long period of time.

Hereinafter, the method of the present invention will be explained in more detail by showing typical examples. However, these are merely examples, and it goes without saying that the present invention is not limited thereto.

Example 1 (1) Feedstock hydrocarbon composition Butanes 7.1 wt% Butenes
21.6 Ibutene 243 1.3-Butadiene 45.9 1.2-Butadiene 0.1 Ethylacetylene 0.2 Vinyl acetylene 0.8 Methylacetylene Trace amount of propadiene (2) Oxygen concentration in C4 fraction of a given amount Air is mixed into the C4 fraction to increase the oxygen concentration to 2.
It was set as sppm.

(3) Hydrogenation conditions catalyst: Pd-Pb(OH3COO)2-I'd;!
20sPb/Pd atomic ratio -2 Pd content (relative to A720g) "" O-35wt% Temperature: 21°C Pressure: ] Okg/crIG H2 molar ratio: 5 LH8V: 37.5 hr = C4 distillate containing this oxygen The table shows the results of the hydrogenation removal reaction of 04 acetylenes under different hydrogenation conditions.

Example 2 A hydrogenation reaction was carried out in the same manner as in Example 1 except that the oxygen concentration in the C2 fraction was set to 0.15 ppm.

The results are shown in the table.

Comparative Example I A hydrogenation reaction was carried out in the same manner as in Example except that no oxygen was mixed into the C4 fraction. The results are shown in the table.

reaction results Patent applicant: Showa Denko Co., Ltd. Agent Sei Kikuchi

Claims (1)

[Claims] In a method of selectively hydrogenating acetylene compounds in a fraction mainly composed of olefinic hydrocarbons having 3 to 4 carbon atoms under pressurized liquid phase conditions in the presence of a palladium solid catalyst, the reaction system A method characterized in that the reaction is carried out in the presence of at least i T) pb of oxygen.