WO2008023871A2

WO2008023871A2 - Process for co-production of isopropanol and normal paraffins having high purity

Info

Publication number: WO2008023871A2
Application number: PCT/KR2007/000626
Authority: WO
Inventors: In-Chul Oh; Chang-Gook Kim; Dae-Yong Rhie; Lee-Ho Kim; Jun-Soo Kim; Soo-Hyun Kim; Chan-Koo Hwang
Original assignee: Isu Chemical Co., Ltd.
Priority date: 2006-08-21
Filing date: 2007-02-06
Publication date: 2008-02-28
Also published as: WO2008023871A3; KR100874774B1; KR20080017595A

Abstract

The present invention relates to a process for co-producing isopropanol and normal paraffins of high purity, and, more particularly, to a process including the stage of conducting liquid-phase hydrogenation of a mixture comprising hydrogen, acetone, and normal paraffins containing aromatic compounds as impurities, in the presence of a hydrogenation catalyst.

Description

TITLE OF THE INVENTION

PROCESS FOR CO-PRODUCTION OF ISOPROPANOL AND NORMAL PARAFFINS HAVING HIGH PURITY

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2006-0078870 filed in the Korean Intellectual Property Office on August 21, 2006, the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a process for co-producing isopropanol and normal paraffins with high purity. More particularly, the present invention relates to a method that can effectively control the heat of liquid-phase hydrogenation of acetone by adding normal paraffins to the reactant of hydrogenation, thereby continuously preparing the isopropanol and normal paraffins with high purity at the same time.

(b) Description of the Related Art Normal paraffins are very useful raw materials for the production of various compounds, such as linear alkylbenzenes secondary alcohols, paraffin sulphonates for the synthetic detergents, and chlorinated paraffins for the lubricating additives.

Generally, normal paraffins are produced from kerosene as the raw material using a molecular sieve. Generally, commercially available normal paraffins are containing aromatic compounds as impurities from hundreds to thousands of parts per million (ordinarily 800--1500 ppm). Accordingly, when normal paraffins containing a large amount of impurities are used as the raw materials, various problems can be generated.

For example, when linear alkylbenzenes are manufactured by using the normal paraffins containing a large amount of aromatic compounds, the aromatic compounds increase harmful effects on the dehydrogenation catalyst so that the catalyst activity becomes lower quickly and the lifetime of the catalyst is shortened. In addition, the aromatic compounds are converted into by-products during the alkylation reaction. Moreover, when secondary alcohols, paraffin sulphonates, and chlorinated paraffins are manufactured by using the normal paraffins with high impurities, the yield of the desired products is lowered, since the aromatic compounds absorb the free radicals in the free radical reaction.

Further, isopropanol is a very useful intermediate in organic synthesis as well as a commercially important solvent and a raw material for preparing cumene, isopropylamine, and isopropylether.

The manufacturing method of the isopropanol, for example, includes hydration of propylene and hydrogenation of acetone, and etc.

Among the manufacturing methods, the hydrogenation of the acetone is an exothermic reaction so that the controllability of the temperature in a reactor is limited. Accordingly, there are problems of difficulty in controlling the reaction temperature. The conversion rate of the acetone to isopropanol is reduced because of by-products produced from side-reactions caused by high reaction temperature, and the safety of the process is lowered because of a sudden increase of the reactor temperature.

In order to solve the problems, U.S. Pat. No. 6,930,213 discloses a process for preparing isopropanol that includes conducting the hydrogenation of acetone in at least two hydrogenation process stages in serially connected reactors having the ability to recycle product. However, the process of U.S. Pat. No. 6,930,213 has disadvantages in that the reaction process and equipment are complicated because of multiple stages, and the process becomes less economical and the amount of by-products can increase by recycling reaction products containing a large amount of isopropanol.

Furthermore, U.S. Pat. No. 6,878,851 disclosures a process for preparing the isopropanol using the multi-tubular reactor for controlling the heat of reaction. However, the process of U.S. Pat. No. 6,878,851 has disadvantages in that the structure of the reactor is complicated, and it is difficult to load and unload of a catalyst, and it is difficult to evenly inject the reactants.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY OF THE INVENTION In order to solve the problems of the prior art described hereinabove, the present invention provides a method that can control the heat of liquid-phase hydrogenation of acetone by adding normal paraffins to the reactant of the hydrogenation, thereby continuously preparing isopropanol and normal paraffins of high purity at the same time. The present invention provides a process of preparation for isopropanol comprising a step of conducting liquid-phase hydrogenation of acetone in the presence of a hydrogenation catalyst, the process being characterized in that the heat of hydrogenation is lowered by adding normal paraffins to the reactant of the hydrogenation. While researching a preparation method of isopropanol and conducting liquid-phase hydrogenation of acetone, the inventors of the present invention found that if normal paraffins are added to the reactant of hydrogenation, the heat of reaction may be lowered. Therefore, the side reactions of the hydrogenation of the acetone may be reduced, and the application of a continuous mass-production process is facilitated. At the same time, normal paraffins of high purity may be manufactured by hydrogenation. Based on these findings described hereinabove, the present invention may be accomplished.

DETAILED DESCRIPTION OF THE EMBODIMENTS The term "normal paraffins with high purity" as used herein means normal paraffins containing aromatic contents of less than or equal to 500 ppm as impurities.

The present invention provides a process for co-producing isopropanol and normal paraffins including a stage of conducting liquid-phase hydrogenation of a mixture including hydrogen, acetone, and normal paraffins containing aromatic compounds as impurities, in the presence of a hydrogenation catalyst.

The said step is a gas-liquid chemical reaction in which the acetone in liquid phase and the normal paraffins in liquid phase are reacted with the hydrogen in gas phase in the presence of a hydrogenation catalyst.

Among the reactants of said step, the hydrogen and acetone are pure or contain impurities, considering that even if the hydrogen and acetone contain impurities, the effect of the present invention is not affected by the impurities of said reactants. More preferably, the pure hydrogen and pure acetone do not contain impurities.

For example, pure hydrogen can be used, or hydrogen containing impurities including methane, ethane, nitrogen, etc., can be used.

Further, pure acetone, for example, can be used, or unreacted acetone recovered from the hydrogenation of the present invention can be reused. As the acetone is obtained generally as a by-product of the phenol preparation process, an aromatic compound such as benzene is contained in the acetone as an impurity. Said normal paraffins may be ones that are typically used in the art to which the present invention pertains. Preferably, the normal paraffins may be at least one selected from the group consisting of C7-C22 linear alkanes, and a combination thereof.

According to the present invention, the hydrogenation may be conducted preferably at a volume ratio of normal paraffins to acetone ranging from 0.1 : 1 to 3 : 1. That is, the normal paraffins are preferably present at more than or equal to 0.1 volume to 1 volume of acetone in order to achieve the minimum effect of controlling the heat of reaction. And the normal paraffins are preferably present at less than or equal to 3 volumes to 1 volume of acetone in consideration of the increasing rate of the effect and the productivity of the isopropanol. The hydrogenation may be preferably conducted at a molar ratio of hydrogen to acetone ranging from 1:1 to 3:1.

That is, the hydrogen is preferably present at more than or equal to 1 mole to

1 mole of acetone in order to achieve the minimum conversion rate and selectivity of the hydrogenation. And the hydrogen is preferably present at less than or equal to 3 moles to 1 mole of acetone in consideration of the productivity of the isopropanol and profitability of the process.

Said hydrogenation catalyst may one that is typically used in the art to which the present invention pertains Preferably, the hydrogenation catalyst may include at least one catalytically active metal selected from the group consisting of nickel, platinum, palladium, ruthenium, rhodium, and a combination thereof.

More preferably, the hydrogenation catalyst may include a neutral support selected from the group consisting of alumina, silica, zirconia, titania, and a combination thereof to increase the structural stability of the catalyst.

According to the process of the present invention, the conversion rate of the acetone to the isopropanol is preferably more than or equal to 99.0%, and the hydrogenated normal paraffins preferably have impurities (aromatic compounds) less than or equal to 500 ppm. In addition, the process of the present invention has the advantage that the heat of reaction is controlled excellently by mixing appropriate amounts of the acetone and normal paraffins and performing hydrogenation process, such that the application of the continuous mass-production process is facilitated.

In another aspect of the present invention, the process of the present invention may be a continuous process further including steps after the hydrogenation stage: obtaining the liquid product by separating excess of hydrogen from the hydrogenation product; obtaining refined isopropanol and normal paraffins with high purity by separating unreacted acetone from the liquid products; and recycling the unreacted acetone to the hydrogenation step. However, said steps (continuous process) can be assembled by any of the steps well-known in the art, and they are not limited thereto.

The flow rate of the mixture stream through the continuous reactor is adjusted in accordance with the quantity of catalyst within the reactor such that the weight hourly space velocity (WHSV) may be the range from 0.1 to 5.0 hr^'1. That is, the WHSV is preferably more than or equal to 0.1 hr^"1 in consideration of the minimum productivity of the process, and the WHSV is preferably less than or equal to 5.0 hr^"1 in consideration of the conversion rate of the hydrogenation.

The hydrogenation may be conducted preferably at a temperature of 70 ^°C to 150 ^°C , and a pressure of 1 MPa to 5 MPa.

That is, the temperature is preferably more than or equal to 70 ^°C in order to supply the minimum activation energy of reaction. The temperature is preferably less than or equal to 150 ^"C in order to prevent the acetone from decomposing and the isopropanol from transforming to by-products. The pressure is preferably more than or equal to 1 MPa in consideration of the minimum conversion rate of the hydrogenation, and the pressure is preferably less than or equal to 5 MPa in consideration of the profitability of the process and the conversion rate of the hydrogenation.

To convert acetone and hydrogen into isopropanol, the feed mixture may be supplied either through the top of the reactor (top-down) or through the bottom of the reactor (bottom-up) and passed through the reactor. However, the flow direction is not limited thereto.

The following will describe examples of the present invention and comparative examples. The examples will enable those skilled in the art to more clearly understand how to practice the present invention. It is to be understood that, while the invention has been described in conjunction with the preferred specific embodiments thereof, that which follows is intended to illustrate and not limit the scope of the invention. Other aspects of the invention will be apparent to those skilled in the art to which the invention pertains. Example 1 A reactor tube having a length of 15.24 cm, an internal diameter of 2.54 cm was provided with a fixed bed containing 70 grams of a catalyst (KL-6564, nickel 18%, alumina 82%, KATA LEUNA). The reactor was equally delineated into three sections of upper section, middle section, and lower section, and the initial temperature of each section was measured. In order to observe the intrinsically generated heat of the reaction, the hydrogenation was progressed without supply of additional heat.

At this time, the liquid reactants of acetone and normal paraffins (C 10-Cl 3 alkanes, the content of aromatic compounds: 912 ppm) were fed respectively into the top of the reactor at a weight hourly space velocity (WHSV) 1.0 hr^"1, while maintaining the volume ratio of acetone : normal paraffins = 1:0.5.

The molar ratio of the hydrogen to acetone was maintained at 1:1, and the reaction pressure was maintained at 3 MPa.

The maximum temperature of each section of reactor (upper section, middle section, and lower section) was measured while reacting according to the conditions. The conversion rate of the acetone to isopropanol was analyzed by gas chromatography, and the content of aromatic compounds in the normal paraffins was measured by ultraviolet absorption spectrometry. The results are shown in TABLE 1. Examples 2-6

As shown in TABLE 1, Examples 2-6 were performed with the same method as in Example 1, except for the kind of catalyst, the volume ratio of the liquid reactants, or the molar ratio of hydrogen. Comparative Examples 1-2 As shown in TABLE 1, Comparative Examples 1-2 were performed with the same method as in Example 1, except for the liquid reactant (only acetone) and the kind of catalyst. [TABLE 1]

As shown in TABLE 1, the reaction temperature of Examples 1-6 was reduced over 20 ^°C in comparison with Comparative Examples 1-2, which did not use normal paraffins. These result indicated that the addition of the normal paraffins to the reaction mixture was advantageous for the control of heat of reaction.

Moreover, as to Examples 1-6, the conversion rate of the acetone to isopropanol was more than 99.0 %. At the same time, Examples 1-6 could obtain normal paraffins of high purity in which the impurity content was less than 250 ppm.

As described hereinabove, the process for co-producing isopropanol and normal paraffins of the present invention includes controlling the heat of liquid-phase hydrogenation of the acetone by adding normal paraffins to the reactant of the hydrogenation, and continuously preparing the isopropanol and normal paraffins of high purity at the same time.

While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A process for co-producing isopropanol and normal paraffins comprising a step of conducting liquid-phase hydrogenation of a mixture comprising hydrogen, acetone, and normal paraffins containing aromatic compounds as impurities, in the presence of a hydrogenation catalyst.

2. The process of claim 1, wherein the hydrogenation is conducted at a volume ratio of normal paraffins to acetone ranging from 0.1 : 1 to 3 : 1.

3. The process of claim 1, wherein the hydrogenation is conducted at a molar ratio of hydrogen to acetone ranging from 1:1 to 3:1.

4. The process of claim 1, wherein the normal paraffins are at least one selected from the group consisting of C7-C22 linear alkanes, and a combination thereof.

5. The process of claim 1, wherein the hydrogenation is conducted at a temperature from 70 ^°C to 150 ^°C, and a pressure from 1 MPa to 5 MPa.

6. The process of claim 1 which further comprises, after the hydrogenation step, the steps of: obtaining a liquid product by separating excess of hydrogen from a hydrogenation product; obtaining refined isopropanol and normal paraffins with high purity by separating unreacted acetone from the liquid product; and recycling the unreacted acetone to the hydrogenation step.

7. The process of claim 6, wherein the hydrogenation is conducted in a continuous reactor at a weight hourly space velocity (WHSV) from 0.1 to 5.0 hr^" .

8. The process of claim 1, wherein the content of aromatic compounds in normal paraffins is less than or equal to 500 ppm after the hydrogenation.

9. The process of claim 1, wherein the hydrogenation catalyst comprises at least a catalytically active metal selected from the group consisting of nickel, platinum, palladium, ruthenium, rhodium, and combinations thereof.

10. The process of claim 9, wherein the hydrogenation catalyst further comprises a neutral support selected from the group consisting of alumina, silica, zirconia, titania, and combinations thereof.

11. A process of preparation for isopropanol comprising a step of conducting liquid-phase hydrogenation of acetone in the presence of a hydrogenation catalyst, being characterized in that the heat of hydrogenation is lowered by adding normal paraffins to the reactant of the hydrogenation.