KR960010901B1 - Process for preparing catalyst support of spherical alumina - Google Patents

Abstract

The catalyst supporter is made by (a) mixing aluminasol and aqueous solution containing 5-30% diallylamine showing buffering action between pH 6-8 at the volume ratio of 1:5-1.5:1; (b) titrating the mixture into glass tube filled with suspension agent. maintained at above 50 deg.C. This alumina has 80-200 m2/g surface area and 0.1g/cm3 apparent bulk density(ABD) and is used as catalyst supporter for dehydrogenation of saturated hydrocarbon.

Description

Method for producing spherical alumina catalyst support itself

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing alumina used as a support in a catalyst composite used to dehydrogenate a hydrocarbon capable of dehydrogenation, and more particularly, to a method for producing an alumina catalyst support having a substantially spherical form.

In general, the dehydrogenation of hydrocarbons is commercial because dehydrogenated hydrocarbons are increasing in demand in the manufacture of various chemical products such as detergents, high octane gasoline, pharmaceutical plastics, synthetic rubbers and other products known in the art. As an important process. One example of this process is the dehydrogenation of low molecular weight saturated hydrocarbons, such as ethane and propane, which are very important industrial reactions. From this, ethylene and propylene are polymerized to be useful for polymer materials such as polyethylene and polypropylene. do.

The catalyst complex used for the dehydrogenation of hydrocarbons is formed on the alumina support, and the prior art of preparing the alumina support includes a precipitation method using a precipitant such as ammonium hydroxide, aluminum chloride hexahydrate, aluminum nitride, and the like. This precipitation method, however, produces a relatively high purity, high surface area alumina support but has the disadvantage of taking irregularly shaped powders.

Another method for preparing the alumina support is sol gel development, in which alumina sol made of a solution containing aluminum in a sol form is added dropwise to an insoluble liquid, but in this case, the appropriate time and pH required for gelation are applied. Hard to maintain. To compensate for this, bases such as ammonium hydroxide and ammonium carbonate were mixed with the alumina sol, but the former was not applicable to the production of spherical alumina of the desired size as the sol immediately gelled away. There is a disadvantage that spherical alumina in the resulting process is broken up.

In order to solve this problem, the present invention is characterized in that it is possible to prepare a spherical alumina catalyst support of a uniform diameter by mixing an appropriate weak salt in alumina sol.

That is, according to the present invention, in the method for preparing a catalyst support for dehydrogenation of low molecular weight saturated hydrocarbon, after mixing an aqueous solution in which 5 to 30% of weak base is dissolved in alumina sol, the mixed sol solution is suspended while maintaining at 50 ° C. or higher. The present invention is to provide a method for producing a catalyst support for dehydrogenation of low molecular weight saturated hydrocarbons by dropping a glass tube filled with a medium to obtain spherical alumina of uniform diameter.

In particular, the present invention includes a platinum group metal component, an IVA group metal component, and an alkali metal or alkaline earth metal component, and has a surface area of 85 to 200 m 2 / g used as a support for a catalyst for dehydrogenation of a low molecular weight saturated hydrocarbon capable of dehydrogenation and ABD. Is to provide a method for producing a spherical alumina having a range of 0.1 or more and a uniform size having a diameter of 1-10mm.

The weak base used in the present invention is water soluble and the sol mixture should be gelled within an appropriate time to maintain the gelation time until the desired shape and size, and has a strong buffering effect at pH 6-8, so that a relatively large amount in this range It must be mixed with the amount of acid and not substantially reduce the pH of the mixture.

In addition, the weak base used in the present invention should be able to properly increase the gas decomposition rate as the temperature rises without evaporation of the gas. For example, when alumina sol is mixed with a weak base composed of hexamethylenetetramine, gelation proceeds at about 20 ° C. for about 3 to 5 hours, but when heated to 90 ° C., all gelation occurs for 1 to 2 seconds. This is because the gel can not be gelated for 5 days when cooled to -3 ℃.

In the present invention, aluminum-tri-secondary-butoxide was used as the starting metal alkoxide, and secondary-butanol or yellow-propanol was used as the solvent. 1 mol of aluminum-tri-secondary-butoxide was dissolved in 2 to 4 mol of secondary-butanol or normal-propanol as solvents under a sealed nitrogen atmosphere, and the temperature was maintained at about 70 to 90 ° C. Mix for about 4-10 hours. After sufficient mixing, distilled water is slowly dropped to cause hydrolysis. At this time, distilled water is added dropwise with respect to aluminum-tri-secondary-butoxide in a volume ratio of about 0.3: 1 to 2: 1. The solution in which distilled water is dripped is mixed while maintaining the temperature of about 70-90 degreeC for about 2 to 24 hours.

An appropriate weak salt is mixed with the alumina sol solution thus prepared. In the present invention, diallylamine is selected and used as a particularly suitable weak base. This weak base is also nicknamed di-2-propenylamine and has the formula (H2C = CHCH2) 2NH. It can be easily obtained by reacting diallylamine with allylbromide or allylchloride. It is prepared in the form of an aqueous solution dissolved in water at a concentration of 5 to 30%, and an aqueous solution of 10% is convenient to handle.

When mixing the alumina sol solution and the diallylamine solution, the mixing volume ratio is preferably about 1: 5 to 1.5: 1. As the volume of the diallylamine solution is smaller, the hardness of the spherical alumina is weaker, whereas the diallylamine solution is used. The higher the volume, the more spherical alumina cracks.

The mixture of two aqueous solutions thus obtained is passed through a suspension medium. In a preferred method, the mixed liquid is dispersed in the form of droplets through a nozzle or an orifice. At this time, the size of the diameter of the spherical alumina is determined according to the size of the nozzle or the orifice. Spherical alumina of very small size can also be dispersed in a rotating disk.

The mixed solution of the two aqueous solutions is added dropwise to a suspension medium heated to 50 ° C. or higher to allow gelation to proceed for an appropriate time. The suspension medium used in the present invention has a lower density than the gelled spherical alumina as soybean oil, so that the spherical alumina can be extracted from the bottom of the gel formation region. Spherical alumina extracted from the bottom of the gel formation region is aged at a temperature of 50 to 120 ℃ for 10 to 36 hours. At this time, the mold alumina is aged while submerged in the suspension medium to remove the diallylamine which is a weak component remaining in the spherical alumina after gel formation.

After the flash treatment, the spherical alumina can be washed using any suitable method. Preferably it is a method of flowing water upstream or downstream. After the washing is finished, it is dried for about 1 to 36 hours at a temperature range of about 90 ~ 350 ℃, and then fired for about 1 to 24 hours at a temperature range of about 400 ~ 900 ℃. In the drying process, it proceeds slowly in an atmosphere containing some moisture to prevent the spalling of spherical alumina. Depending on the catalyst to be prepared finally, spherical alumina may be dried and calcined with other catalyst components.

The surface area of the catalyst in the present invention was measured by known physical adsorption methods. This method can be used to measure surface area, pore volume, and pore volume distribution by using Micrometrics Chemisorb 2700. At this time, the physical adsorption technique is implemented by adopting the dynamic gas flow technique. In this technique, an adsorbable, ie condensable, gas is extracted from an inert gas and a non-adsorbed, ie, non-condensable, gas flows past the sample at low temperature. The surface area, pore volume, and pore volume distribution are calculated by calculation of the amount of gas extracted by a well-chosen relationship.

According to the present invention, the obtained alumina is a catalyst used in the conversion of organic compounds such as dehydrogenation of hydrocarbons or forms the main component of the catalyst, and various advantages can be obtained by using a substantially spherical alumina support. That is, when used as a filling material of the reaction zone or contact zone in a fixed bed reactor, the use of a spherical support enables more uniform filling, thereby reducing the pressure change in the fixed bed and passing the fixed bed without contact or reaction. Can be prevented. Another advantage is that since there is no protrusion on the surface of the support, there is less wear and tear during the process or during transportation, thereby preventing the blockage of various devices of the process by the small grains worn and broken. In particular, this latter advantage can be seen when the alumina support is used in a fluidized bed in which the support is moved from one zone to another by means of additional carrier media, rather than the bottom bed.

Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1

120 g of aluminum-tri-secondary-butoxide was dissolved in 58.5 g of normal-propanol as a solvent, and then mixed for 5 hours while maintaining the temperature at about 80 ° C. in a magnetic thermostirrer. 4.4 g of distilled water is slowly added dropwise to the mixed solution sufficiently mixed to hydrolyze to obtain alumina sol. In addition, a sufficient amount of water is added to 91 g of diallylamine to form a 20% aqueous solution.

The alumina sol solution and 20% aqueous solution are each administered to a mixer with a baffle while stirring by an electric motor at a flow rate of 100 cc per minute. The sufficiently stirred liquid mixture is dropped into a glass tube 1 m in diameter and 2 cm in diameter. In this case, a disc with a small hole with a diameter of 3 mm is attached to the upper part of the glass tube, and soybean oil is filled up to 4 cm from the disc.

The glass tube is heated to 90 to 100 ° C by an asbestos spigot that surrounds the glass tube. In this state, the mixed liquid dropped into the glass tube is spherical alumina in the form of 150 g and is accumulated at the bottom of the glass tube and aged together with soybean oil at the same temperature for 16 hours. After aging, soybean oil is removed and spherical alumina is washed with water. The washed spherical alumina is dried at a temperature of 110 ° C. and immediately calcined at 700 ° C. Care should be taken to ensure that the spherical alumina does not cool down as it moves from the drying process to the firing process to prevent cracking by absorbing moisture in the meantime. The properties of the finally prepared spherical alumina are shown in Table-1. Spherical alumina prepared by the above method has a relatively significant spherical shape and is durable and does not substantially break even when exposed to air or moisture.

Comparative Example 1

In order to form an alumina mixture which can be gelled for an appropriate time, an ammonia OH hydroxide solution is mixed with an alumina sol containing aluminum chloride hexahydrate, and then the mixture is passed through a suspension medium. At this time, the gelation rapidly proceeds to precipitate, thereby producing alumina in a very small diameter and irregularly shaped powder form. Thus, ABD becomes very similar to the true density, meaning that the measurement is meaningless, and the properties are shown in Table-1.

Claims (2)

In the method for producing a catalyst support for dehydrogenation of low molecular weight saturated hydrocarbon, an aqueous solution containing 5 to 30% of a diallylamine having a buffering action in alumina sol at a pH of 6 to 8 is mixed at a volume ratio of 1: 5 to 1.5: 1. And then dropping the mixed sol solution on a glass tube filled with a suspension medium while maintaining the mixed sol solution at 50 ° C. or higher to obtain spherical alumina of uniform diameter, wherein the catalyst support for dehydrogenation of low molecular weight saturated hydrocarbon. 2. The dehydration of low molecular weight saturated hydrocarbons according to claim 1, wherein the spherical alumina is a spherical alumina catalyst support of uniform diameter having a surface area of 80 to 200 m < 2 > / g and a corresponding apparent bulk density (ABD) of at least 0.1 g / cm < 3 >. Method of producing a catalytic support for use.