KR100365688B1 - Catalyst composition for dehydrogenating paraffin based hydrocarbon - Google Patents

Abstract

PURPOSE: A catalyst composition for suppressing generation of secondary reaction in the dehydrogenation process, increasing selectivity of a target product and improving stability of the catalyst is provided. CONSTITUTION: The catalyst composition for dehydrogenating paraffin based hydrocarbon is characterized in that 0.2 to 1.0 wt.% of platinum, 0.05 to 0.5 wt.% of tin, 0.05 to 0.5 wt.% of titanium and 0.2 to 2.0 wt.% of alkali metal are supported onto a porous metal oxide support comprising a principal constituent of spherical alumina and having surface area of 85 m¬2/g or less, total pore volume of 0.4 to 0.8 cc/g and average pore radius of 100 to 150 Å, wherein a weight ratio of indium/zinc is 0.1 to 10, a weight ratio of platinum/(indium+zinc) is 0.2 to 10, a weight ratio of platinum/alkali metal is 0.1 to 5.0, and the alkali metal is a mixture of potassium and lithium satisfying that a weight ratio of potassium/lithium is 0.1 to 10.

Description

Catalyst composition for paraffinic hydrocarbon dehydrogenation.

The present invention relates to a process for dehydrogenating paraffinic hydrocarbons to olefinic hydrocarbons using heterogeneous catalysts. More particularly, the present invention relates to a catalyst composition for dehydrogenation having high activity, selectivity and stability.

Dehydrogenated hydrocarbons are highly economical compounds that are used as raw materials for fine chemicals, as raw materials for polymer materials and as additives for the production of high performance gasoline, and demand for them is increasing day by day.

The process of dehydrogenating normal paraffins to normal olefins is already known, which involves contacting hydrogen and paraffins with a dehydrogenation catalyst and reacting at high temperatures at atmospheric or higher pressures. Examples of the dehydrogenation catalyst used in this reaction include those in which a metal belonging to platinum or other Group B noble metal element is supported on alumina, silica, silica-alumina, or the like.

In general, however, dehydrogenation may yield other than the desired product due to secondary reactions such as pyrolysis, isomerization, and cyclization, and the dehydrogenation itself proceeds further to produce diolefins other than monoolefins. There is also a case.

In addition, catalyst deactivation progresses prematurely, which shortens the life of the catalyst, and when the reaction is carried out at a high temperature, metal particles such as platinum distributed on the surface of the carrier are sintered to reduce the surface area of the active metal, which is also a factor of catalyst deactivation. Therefore, the dehydrogenation has been a big burden when applied to commercial scale processes.

Accordingly, catalyst compositions in which at least one other metal component is combined with platinum or other Group VIII precious metal elements have been conventionally proposed to improve the activity and selectivity of the catalyst in the dehydrogenation process.

British Patent 1,497,297 describes a catalyst in which alumina is supported on platinum and alkali metals with at least one element selected from gallium, indium, and thallium, and British Patent 1,499,297 uses platinum, potassium, indium and alkali metals. A catalyst system is used. In addition, US Pat. No. 4,551,574 describes a catalyst composition in which platinum, tin, indium and alkali or alkaline earth metals are supported on a porous support, and US Pat. No. 4,762,960 discloses platinum, tin, germanium, rhenium and alkali or alkaline earth metals as oxide supports. And dehydrogenation catalysts impregnated in US Pat. No. 4,880,674, which mentions dehydrogenation catalyst compositions co-precipitated with platinum, palladium, iridium, osmium and Group IV A elements.

However, the catalysts prepared by the above techniques were not all satisfactory in terms of activity in dehydrogenation of normal paraffin, selectivity of useful reaction products, and stability of the catalyst.

The present invention has been made to solve the problems of the prior arts, and an object of the present invention is to provide a catalyst composition that suppresses the occurrence of secondary reactions in the dehydrogenation process, increases the selectivity of the desired product and improves the stability of the catalyst.

The present inventors earnestly studied in order to achieve the above object, and when the critical bonding of platinum (Pt), indium (In), zinc (Zn) to each other critically dehydrogenated normal paraffins to convert to normal olefins, The present invention has been accomplished by knowing that it can lead to long-term maintenance of activity.

That is, the present invention is a porous metal oxide carrier mainly composed of spherical alumina, 0.2-1.0 wt% platinum, 0.05-0.5 wt% indium, 0.05-0.5 wt% zinc and 0.2-2.0 wt% alkali metal, based on the element content. It characterized in that the preparation for the supported paraffinic hydrocarbon dehydrogenation catalyst.

Hereinafter, the present invention will be described in detail.

The catalyst of the present invention is a porous metal oxide carrier mainly composed of spherical alumina, 0.2-1.0 wt% platinum, 0.05-0.5 wt% indium, 0.05-0.5 wt% zinc, and 0.2-2.0 wt% alkali metal on an elemental basis. In this case, the weight ratio of indium / zinc is 0.1-10, the weight ratio of platinum / (indium + zinc) should be in the range of 0.2-10, and the weight ratio of platinum / alkali metal is preferably 0.1-5.0.

Suitable supports for the catalysts according to the present invention are catalysts which, unlike alumina having a high specific surface area of more than 200 m 2 / g and a total pore volume of 0.5 cc / g-1.5 cc / g, are generally used. Alumina having a surface area of 85 m 2 / g or less and a total pore volume of 0.4 cc / g-0.8 cc / g is used to improve the efficiency of the catalyst. On the other hand, the shape preferable as a support body is a spherical particle with a diameter of 1.0-2.0 mm or less.

In order to manufacture alumina into a spherical shape, a known sol-gel method can be applied. That is, the aluminum starting material is reacted with a suitable peptizing agent and water to convert to a sol, and the sol mixture is dropped into an oil bath to form spherical particles of the gel. In addition, the prepared spherical particles are heat-treated at a high temperature of 1000 ° C. or more in order to have physical properties such as surface area and pore volume mentioned above.

In order to prepare the catalyst of the present invention, first, an indium, zinc-containing alumina is prepared by cogelation of indium, zinc and alumina, and the catalyst is prepared by co-impregnation or two-stage impregnation with platinum and alkali metal. It can be mentioned.

As the main metal of the catalyst composition of the present invention, Group VIII precious metal elements, that is, platinum, palladium, iridium, rhodium, osmium, ruthenium, and the like may be used. As mentioned above, platinum is used as the most preferable element. Platinum is preferably dispersed evenly throughout the catalyst, and water-soluble compounds such as chloroplatinic acid, platinum cyanide and platinum complex salts are mixed with a very small amount of nonionic surfactants, which are less than 0.05%, which affect the platinum dispersion, and impregnated in alumina. . Doing so ensures that the platinum is uniformly dispersed or fixed in the final composite.

Another important component constituting the catalyst composition of the present invention is an alkali metal, which includes lithium, sodium, potassium, cesium, rubinium, and the like. Among them, in the present invention, potassium (K) and lithium (Li) are used simultaneously in the ratio of potassium / lithium = 0.1-10.

Dehydrogenation reaction conditions using the catalyst prepared according to the present invention, the temperature is 400 ℃-700 ℃, the reaction pressure can be in the range of 0.1-5 atm, and the catalyst and the mixed gas of the hydrocarbon diluted with nitrogen or hydrogen When the contact time is expressed as Liquid Hourly Space Velocity (LHSV), 0.1-30 hr ^-1 , and the mixing ratio or partial pressure of atmospheric gases such as nitrogen and hydrogen used to dilute hydrocarbons to suppress coke formation, The mixing ratio is in the range of 0.1-5 mole ratio (hydrogen or nitrogen / hydrocarbon) to hydrocarbon and 0-1.0 atm for partial pressure.

Emphasizing in the present invention in the preparation of the carrier is the coprecipitation of some effective metals of the catalyst composition in the preparation of alumina and the firing conditions of the carrier.

That is, the characteristics of the carrier highlighted in the present invention have a significant influence on the properties of the entire catalyst, and the following carrier production process is emphasized.

The specification of the carrier exhibiting excellent effect in the present invention is 85m 2 / g or less, the total pore volume of 0.4-0.8cc / g, the average pore radius of 100-150Å as measured by the BET method, the powder form, spherical, plate-like Etc., Preferably, the powder density of 200 mesh or less or the spherical carrier having a diameter of about 1-2 mm is suitable in the reactor with a packing density of 0.5-1 cc / g.

In order to suppress deactivation due to coke formation of the catalyst, the catalyst of the present invention is added to react with 10 to 100 ppm by weight of sulfur in organic sulfur based on the reactant gas.

The catalyst prepared by the present invention has high activity and selectivity in the dehydrogenation of C ₃ -C ₂₀ hydrocarbons, and shows stability of activity and selectivity even after long use.

Hereinafter, the reaction effects of the present invention and specific application methods thereof will be described in the following examples. In order to demonstrate the advantages obtained by the present invention, the catalysts of the present invention are prepared in Examples, and Comparative Examples Prepared a catalyst different from the present invention.

Example 1-3

First, a carrier for supporting a metal component was prepared. Indium and zinc starting materials were mixed with 50 ml of alumina sol, gelled by adding 9.3 g of weak base di-allyl amine, and then dropped in an oil bath to obtain a carrier having a constant shape.

This was dried at 120 ° C. and calcined at 1000 ° C. or more to prepare indium and zinc-containing alumina. Thus prepared alumina was impregnated with platinum and alkali metal to prepare various catalysts, which are shown in Table 1.

Reaction test for comparing the performance of each catalyst was tested using a propane (purity: 99.9 wt%) of dehydrogenation reaction at 600 ℃, atmospheric pressure, LHSV is 3hr ^-1 , the amount of catalyst was based on 3g. The reactor used a fixed bed reactor made of quartz with almost no catalysis, and the partial pressure of hydrogen was fixed at 0.5 atm, ie the molar ratio of hydrogen to propane was 1.

[Comparative Examples 1,2]

Catalysts as shown in Table 1 were prepared using the composition according to the existing technology, and tested in the same conditions and methods as above, and the results are shown in Table 1.

X: Propane Conversion Rate (wt%)

S: Selectivity of propylene in the product (% by weight)

Claims (3)

Platinum 0.2-1.0 wt%, tin 0.05 based on the elements contained in a porous metal oxide carrier having a surface area of 85 m2 / g or less, a total pore volume of 0.4 to 0.8 cc / g, and an average pore radius of 100 to 150 microns. A catalyst composition for paraffinic hydrocarbon dehydrogenation reaction, characterized in that -0.5% by weight, 0.05-0.5% by weight of titanium, and 0.2-2.0% by weight of alkali metal are supported. The paraffin according to claim 1, wherein the weight ratio of indium / zinc is 0.1 to 10, the weight ratio of platinum / (indium + zinc) is in the range of 0.2 to 10, and the weight ratio of platinum / alkali metal is 0.1 to 5.0. Catalyst composition for hydrocarbon dehydrogenation. The catalyst composition for paraffinic hydrocarbon dehydrogenation according to claim 1, wherein the alkali metal is a mixture of potassium and lithium having a potassium / lithium ratio of 0.1 to 10.