JPS6244529B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for dehydrating methanol to produce hydrocarbons using a special catalyst. More specifically, the present invention relates to a method for dehydrating methanol to produce hydrocarbons by using highly acidic aluminum dihydrogen tripolyphosphate alone or in combination with other substances as a catalyst. Gasoline, petrochemical raw materials, etc. are made of hydrocarbons, which are derived from petroleum, a natural resource. However, now that the depletion of petroleum resources is being viewed as a problem, a method for producing hydrocarbons from methanol is attracting attention as a new alternative raw material source. That is, methanol is first synthesized from carbon monoxide and hydrogen obtained from coke, coal, natural gas, etc. through a high-pressure catalytic reaction. If hydrocarbons can be produced from this methanol, it will be possible to obtain a new energy source and raw material source for the chemical industry to replace petroleum, which is why this is considered important as so-called _C1 chemistry. An object of the present invention is to provide a method for more effectively producing hydrocarbons by dehydrating methanol using a new catalyst. Research on catalysts for synthesizing hydrocarbons from methanol is relatively new. Catalysts that have been announced so far include zeolite, polyphosphoric acid, metal orthophosphates such as monobasic aluminum phosphate, metal sulfates such as nickel sulfate, zinc halides such as zinc chloride and zinc iodide, AlCl ₃ 3 H ₃ PO ₄ , 12-tungstophosphoric acid, 12-tungstosilicic acid, and strongly acidic cation exchange resins. Looking at these catalysts, 1. The conversion rate of methanol to hydrocarbons is low. 2. Catalytic activity decreases quickly and catalyst life is short. 3. It is difficult to regenerate some deteriorated catalysts. 4. The catalyst preparation method is complicated and the reproducibility of catalyst activity may be lacking. 5. There are many side reaction products such as carbon monoxide and dimethyl ether. Due to these problems, it has become urgent to develop a superior catalyst. A mechanism has been proposed in which the reaction in which methanol is dehydrated to form hydrocarbons occurs at acid sites on the catalyst. That is, when the catalyst is a protic acid, methanol is first dehydrated to form a methoxy group, which is polarized and converted to a methyl carbonium ion, which then reacts with methanol to form a carbon-carbon bond. As a catalyst for dehydrating methanol to produce hydrocarbons, it is presumed that a solid acid having as high acidity as possible is preferable based on the above reaction mechanism. It has been found that aluminum dihydrogen tripolyphosphate, which is highly insoluble and nonvolatile, is extremely suitable for this purpose, and the present invention has been achieved. The present invention relates to a method for dehydrating methanol to produce hydrocarbons using a catalyst made of aluminum dihydrogen tripolyphosphate alone or in combination with other substances. More specifically, it relates to a method for producing hydrocarbons by dehydrating methanol at a temperature of 200 to 500°C using a catalyst consisting of aluminum dihydrogen tripolyphosphate, which has extremely high acidity, alone or in combination with other substances. be. The acid strength of a solid acid is expressed in pKa, and acidity is the number of acid sites or acidic centers in a solid acid, and is usually expressed as the number of milligram equivalents of n-butylamine molecules per unit weight of solid (meq/g). is displayed.
That is, high acidity means that the acid content of the solid acid is high, or in other words, that the catalyst has many active sites. The acidity of commonly used insoluble and nonvolatile solid acids is at most 0.02 to 0.5meq/
The aluminum dihydrogen tripolyphosphate used in the present invention has a very small value in g, but the aluminum dihydrogen tripolyphosphate used in the present invention has a
It has extremely high acidity of 20meq/g. Moreover, this aluminum dihydrogen tripolyphosphate is insoluble and nonvolatile, exists stably at temperatures below 500°C, has almost no change in catalytic activity over time, and has a longer lifespan than other catalysts. The raw material for aluminum dihydrogen tripolyphosphate used in the present invention consists of aluminum or an aluminum-containing substance and a phosphoric acid-containing substance.
A mixture with a P ₂ O ₅ /Al ₂ O ₃ molar ratio of 1 to 6 is 90 to
It is characterized in that it is manufactured by heating and crystallizing at a temperature of 450°C, and for example,
It is described in detail in JP-A-49-109298 and JP-A-50-52584. Aluminum metal, aluminum hydroxide, aluminum oxide, etc. can be used as aluminum or an aluminum-containing substance, but it is convenient to use aluminum hydroxide or aluminum oxide in practice. Further, as the phosphoric acid substance, phosphoric acid, ammonium phosphate, phosphorus pentoxide, etc. can be used, but it is usually convenient to use 85% phosphoric acid, which is easy to obtain and handle. These raw materials have a P ₂ O ₅ /Al ₂ O ₃ molar ratio of 1 to 6,
It is preferably mixed in a range of 2 to 5, more preferably 2 to 3. Outside the above molar ratio range, A, B, and C types of aluminum metaphosphate or berlinite type aluminum orthophosphate are produced, and highly acidic aluminum dihydrogen tripolyphosphate used in the present invention cannot be obtained. Next, add the above mixture
Crystallization is carried out by heating to a temperature of 90 to 500°C, preferably 150 to 300°C. If the temperature is low, it will not crystallize, and
If the temperature is higher than 500°C, A, B, and C types of aluminum metaphosphate or berlinite type aluminum orthophosphate will be produced, which is not preferable. The thus obtained aluminum dihydrogen tripolyphosphate is water-insoluble and nonvolatile, and shows a clear peak at 2θ = 11.2° in the X-ray diffraction diagram, and
Since it has an extremely high acidity of 20 meq/g, it becomes a highly active catalyst when used in the process of the present invention. Although there are no particular limitations on the concentration of methanol that can be used in the method of the present invention, since the reaction of the present invention is a dehydration reaction of methanol, it is desirable that the water content in methanol is low. However, since the reaction temperature is high, the influence of moisture is small, so a sufficient conversion rate can be obtained even with 90-95% methanol. Therefore, even if the concentration of raw methanol is low, it is sufficient to concentrate it by simple distillation, and there is no particular need to convert it into anhydrous methanol. The dehydration reaction of methanol using the catalyst of the present invention can be carried out using a conventional flow reactor. For example, using a fixed bed reactor, methanol that has been evaporated in advance in an evaporator can be supplied to a catalyst layer heated to a predetermined temperature, but it is also possible to supply methanol as a liquid just before the catalyst layer and turn it into vapor. can. The reaction can also be carried out in the same manner using a fluidized bed reactor. The reaction temperature is such that the catalyst layer temperature is generally 200 to 500°C, preferably 230 to 470°C.
C, more preferably 250 to 440 C. At lower temperatures, the reaction rate decreases and unreacted methanol increases, and dimethyl ether is produced as a by-product and mixed into the hydrocarbon. Further, temperatures higher than this are not only uneconomical thermally, but are also undesirable because carbon may be deposited on the catalyst or carbon monoxide or carbon dioxide may be mixed into the hydrocarbons. Furthermore, it goes without saying that the aluminum dihydrogen tripolyphosphate according to the present invention may be used in combination with other substances, and examples of other substances used in combination include aluminum oxide, aluminum hydroxide,
Bauxite, activated carbon, diatomaceous earth, acid clay, activated clay, aluminum phosphate, aluminum sulfate, thorium oxide, zirconium oxide, titanium oxide, yttrium oxide, molybdenum oxide, tungsten sulfide, zeolite, etc. They can be combined and used together as appropriate. Next, specific examples of the present invention will be described, but first, examples of manufacturing the catalyst will be described as follows. Catalyst production example 1 α-aluminum oxide 78.7g and 85% phosphoric acid 650g
(P ₂ O ₅ /Al ₂ O ₃ =3.7) and gradually heated in a porcelain crucible to 262° C. after 2 hours. After cooling the semi-solid material obtained here to room temperature, further
It was heated and crystallized in an electric furnace adjusted to 300°C. After leaving it to cool, crush it, wash it with water, dry it, and then
Aluminum dihydrogen tripolyphosphate having the acidity shown in the table was obtained.

[Table] Catalyst production example 2 Aluminum hydroxide containing 65% as Al ₂ O ₃
61.5g and 385g of 85% phosphoric acid (P ₂ O ₅ /
Al ₂ O ₃ =4.3) and heated at 380°C in a porcelain crucible.
This was left to cool, then pulverized, washed with water, and dried to obtain aluminum dihydrogen tripolyphosphate having the acidity shown in Table 2 below.

[Table] Catalyst production example 3 Aluminum hydroxide 80 containing 65% as Al ₂ O ₃
g and 500 g of 85% phosphoric acid (P ₂ O ₅ /Al ₂ O ₃
= 4.3), and 40 g of powdered silicon oxide was added and gradually heated to crystallize at 320°C. This was left to cool, then pulverized, washed with water, and dried to obtain aluminum dihydrogen tripolyphosphate having the acidity shown in Table 3 below.

[Table] Examples of the method of the present invention are shown below. Example 1 40 g of aluminum dihydrogen tripolyphosphate obtained in Catalyst Production Example 1 was pelletized, filled into a reaction tube with an inner diameter of 30 m/m, and heated to 275°C. The length of the catalyst packed bed was about 10 cm. Approximately 90ml of 95% methanol
was prepared and gradually heated to evaporate at an average rate of 4 ml/hr, and gaseous methanol was introduced into the reaction tube for heating and dehydration. Total reaction time was 23 hours. When the reaction products were analyzed using a gas chromatograph 2 hours after the start of the reaction, when the reaction seemed to have become steady, and 20 hours later, there was no difference between the two within the error range, and the conversion rate of methanol was It was 98.4%. The distribution of the hydrocarbons produced was as shown in Table 4 below. Further, only traces of dimethyl ether could be observed.

[Table] Example 2 30 g of aluminum dihydrogen tripolyphosphate obtained in Catalyst Production Example 2 was pelletized, filled into a reaction tube with an inner diameter of 30 m/m, and heated to 340°C. The length of the catalyst packed bed was about 8 cm. Place a small amount of glass wool on the methanol introduction side of the catalyst packed bed in the reaction tube, and
Approximately 50 ml of methanol was gradually introduced as a liquid into the glass wool section at an average rate of 5 ml/hr and evaporated.
The methanol that had become a gas was subjected to a dehydration reaction on the catalyst. Total reaction time was 10 hours. The reaction product 5 hours after the start of the reaction was analyzed using a gas chromatograph, and a methanol conversion rate of 97.4% was obtained. The distribution of the hydrocarbons produced was as shown in Table 5 below. Almost no by-products of dimethyl ether, carbon monoxide, or carbon dioxide gas were observed.

[Table] Example 3 3 g of the sodium dihydrogen tripolyphosphate-silicon oxide catalyst obtained in Catalyst Production Example 3 was placed in a porcelain boat, placed in a reaction tube, and heated to 430°C. Separately, prepare about 50 ml of anhydrous methanol, and add 25 ml of nitrogen to it.
A mixed gas of methanol and nitrogen was created by blowing in at a rate of 1.5 m, and this was introduced into the reaction tube to cause the methanol to undergo a dehydration reaction. The average evaporation rate of methanol
It was 1.5ml/hr. The total reaction time was 35 hours. The reaction product was sampled every 5 hours from the start of the reaction and analyzed using a gas chromatograph to obtain an average methanol conversion of 96.7%. The average distribution of the hydrocarbons produced was as shown in Table 6 below. There was almost no difference in the analysis results every 5 hours from the start of the reaction. Furthermore, no traces of carbon monoxide or carbon dioxide gas could be detected.

[Table] In the three examples above, the activity of this aluminum dihydrogen tripolyphosphate catalyst did not change dramatically even if it was used for long-term reactions or left in the air after being used for reactions. Nakatsuta. Also,
Dimethyl ether and carbon monoxide are present in the reaction products.
Only traces of side reaction products such as carbon dioxide gas could be observed within the range of the present experimental conditions. That is, according to the present invention as described above, a catalyst is used which is made of aluminum dihydrogen tripolyphosphate, which has extremely high acidity, alone or in combination with other substances, and this catalyst has a reproducible activity during preparation. has good activity, long life, and
It has the characteristics that its activity does not decrease even if it is left in the air. In addition, because it has a high acidity as a solid acid, it has a high reaction rate and can be used for methanol dehydration and can withstand long-term continuous use. It has the effect of producing hydrocarbons with almost no products. Furthermore, the method of the present invention does not require high pressure as in the Fischier-Tropsch method, which is known as a method for producing hydrocarbons, and the reaction proceeds at normal pressure, thus providing an industrially extremely useful method. It is.

Claims (1)

[Claims] 1 Aluminum dihydrogen tripolyphosphate alone,
A method for producing hydrocarbons by dehydrating methanol and producing hydrocarbons using a catalyst or a catalyst used in combination with other substances.