Preparation method of p-cymene

Abstract

The invention discloses a method for preparing p-cymene, which belongs to the field of cymene preparation. The method for preparing p-cymene comprises the following steps: loading a prepared activated carbon-loaded ZnSO4 / NiSO4 catalyst into a reactor, heating the reactor, and continuously passing a mixed olefin whitening liquid into the reactor using an inert gas, and collecting the liquid after the reaction from the upper outlet of the reactor to obtain p-cymene. The method for preparing p-cymene of the invention does not use precious metals, and the catalyst is cheap; the catalyst has good selectivity, and the selectivity of p-cymene reaches more than 99%; the requirements for raw materials are simple, and the mixed olefin whitening liquid of the factory can be used as the raw material, thereby improving the utilization rate of the raw materials and reducing the cost.

Description

Technical Field

[0001] The invention belongs to the field of p-cymene preparation, and in particular relates to a method for preparing p-cymene. Background Art

[0002] p-Cymene, also known as p-isopropyltoluene, has the chemical name 1-methyl-4-isopropylbenzene. It is a colorless, transparent liquid with an aromatic odor, which exists in many natural essential oils. p-Cymene is also a derivative of turpentine, a major forest chemical product in my country. It is a very important chemical product and organic synthesis intermediate with a wide range of uses, such as being used to prepare citrus, vegetable and condiment flavors, used in the preparation of soft drinks, iced foods, candies, and chewing gums, and can also be used to prepare cosmetics, soaps, and detergent flavors; used to make soft capsules, used as antitussives, expectorants, and treatments for chronic bronchitis; and can also be used to synthesize a variety of polycyclic musk-type fragrances and aromatic ring-containing fragrances, drugs, herbicides, fungicides, etc.

[0003] The preparation of p-cymene by catalytic dehydrogenation of industrial dipentene as raw material has always attracted people's attention. my country has a large output of turpentine. In the production process of synthesizing camphor and terpineol using turpentine as raw material, a large amount of by-product dipentene will be produced. It is mainly a mixture of several monocyclic and bicyclic terpenes with similar molecular structures and the same relative molecular weight, also known as industrial dipentene. The catalytic dehydrogenation of dipentene usually has gas phase catalytic reaction method and liquid phase catalytic reaction method, and the gas phase catalytic reaction method is the main one. This method has been industrialized abroad many years ago, but the catalyst used in this method is mainly precious metal catalysts, such as palladium carbon and platinum carbon. Although the dehydrogenation efficiency is high, in addition to p-cymene, there are also more by-products p-menthane. The catalysts used for industrial dipentene dehydrogenation can be divided into metal catalysis and non-metal catalysis according to their types, and metal catalysis is the main one. Metal catalysts such as nickel, nickel / copper, platinum / carbon, palladium, palladium / silicon dioxide, palladium oxide-sulfur / carbon, palladium nanoparticles, etc.; non-metal catalysts such as sulfur / diphenylthiourea, solid acid, silicon / aluminum oxide, etc.

[0004] In the production process, enterprises use a wide variety of raw materials from a wide range of sources. While producing qualified products, some intermediates are also produced. The components of these intermediates are distributed in a mixed manner and cannot be sold as products. They can only be sold at a low price as scraps. Analysis has found that in the large amount of mixed olefin white liquid produced in the production process of enterprises, in addition to p-cymene and eucalyptol, there are also p-menene, pinolene, limonene and carene, which are difficult to separate. The presence of these difficult-to-separate components makes it difficult to separate p-cymene from mixed olefin white liquid, especially p-cymene with higher purity. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing p-cymene to overcome at least one of the above-mentioned defects in the prior art.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The preparation method of para-cymene provided by the present invention comprises the following steps: loading the prepared activated carbon-loaded ZnSO4 / NiSO4 catalyst into a reactor, the reactor being a tubular reactor, heating the tubular reactor, and continuously passing the mixed olefin whitening liquid into the tubular reactor by using an inert gas, and collecting the liquid after the reaction from the upper end outlet of the tubular reactor to obtain para-cymene.

[0008] Preferably, the preparation method of activated carbon-loaded ZnSO4 / NiSO4 catalyst comprises the following steps: dissolving ZnSO4 and NiSO4 in water to prepare a ZnSO4 / NiSO4 aqueous solution, adding pre-treated activated carbon and stirring, soaking, filtering, washing and drying to obtain an activated carbon-loaded ZnSO4 / NiSO4 catalyst.

[0009] Preferably, the pretreatment of activated carbon includes the following steps: grinding and screening the activated carbon, soaking the screened activated carbon in sodium hydroxide solution and hydrochloric acid solution successively, filtering, then placing the activated carbon in nitric acid solution and heating to reflux for 1.7-2.1h, filtering, washing with water until neutral, and drying for later use.

[0010] Preferably, in the pretreatment of the activated carbon, a molecular sieve of 80-100 mesh is used for screening, and the screened activated carbon is soaked in both a sodium hydroxide solution and a hydrochloric acid solution for 1.8-2.2 hours.

[0011] Preferably, in the pretreatment of activated carbon, the concentrations of the sodium hydroxide solution and the hydrochloric acid solution are both 0.1-0.3 mol / L, and the volume fraction of the nitric acid solution is 18-22%.

[0012] Preferably, in the preparation of the activated carbon-supported ZnSO4 / NiSO4 catalyst, the activated carbon is columnar coal-based activated carbon, the stirring and soaking time is 1.8-2.2h, the washing times are 2-4 times, and the drying temperature is ≤90°C.

[0013] Preferably, in the preparation of the activated carbon-supported ZnSO4 / NiSO4 catalyst, the mass ratio of ZnSO4, NiSO4 and water is 1:0.8-1.2:3-5, and the mass ratio of the ZnSO4 / NiSO4 aqueous solution and the activated carbon is 2:0.7-1.3.

[0014] Preferably, the chromatographic content of p-cymene in the heteroolefin white liquor is 24.8%-31.35%.

[0015] Preferably, the tubular reactor is heated at 260° C.-290° C., the flow rate of the inert gas is 1900-2100 L / h, and the continuous feeding rate of the heteroolefin white liquor is 30 Kg / h-35 Kg / h.

[0016] Preferably, the inert gas is nitrogen, helium, neon or argon.

[0017] The beneficial effects of the present invention are:

[0018] No precious metals are used, and the catalyst is cheap; the catalyst has good selectivity, and the selectivity for cymene reaches more than 99%; the requirements for raw materials are simple, and the factory's mixed olefin white liquid can be used as raw material, which improves the utilization rate of raw materials and reduces costs. DETAILED DESCRIPTION

[0019] The present invention will now be further described in conjunction with specific implementation methods.

[0020] Embodiment 1:

[0021] Activated carbon pretreatment: Grind the activated carbon. Activated carbon is preferably columnar coal-based activated carbon. Other activated carbons may also be used. After screening with a molecular sieve of 80-100 mesh, weigh 5 kg of the screened activated carbon, soak it in 10 L 0.2 mol / L sodium hydroxide solution and 10 L 0.2 mol / L hydrochloric acid solution for 2 h respectively, filter it, then place the activated carbon in a 20% nitric acid solution by volume, heat it under reflux for 2 h, filter it, wash it with water until it is neutral, and dry it for later use.

[0022] Dissolve 5Kg ZnSO4 and 5Kg NiSO4 in 20Kg water to prepare a ZnSO4 / NiSO4 aqueous solution, then add 15Kg pre-treated activated carbon and stir and soak for 1.8h, filter, wash with water 3 times, and dry at 90℃ to obtain activated carbon loaded with ZnSO4 / NiSO4.

[0023] 5.8 kg of the prepared activated carbon-supported ZnSO4 / NiSO4 catalyst was loaded into a tubular reactor.

[0024] The mixed ene white liquor (containing 1-p-menene 10.28%, 1,4-cineole 2.26%, α-terpinene 5.94%, limonene 15.22%, 1,8-cineole 10.5%, r-terpinene 1.92%, p-cymene 31.35%, terpinene 11.85% and 4-carene 10.63%) is heated to 260 ℃, and continuously enters a tubular reactor at a speed of 30Kg / h under the driving of nitrogen at a flow rate of 1900L / h, reacts at 260 ℃, and the reacted liquid is collected from the upper end outlet of the tubular reactor. The reacted liquid contains 0.11% of 1-p-menene, 1,4-cineole 1.78%, camphene 0.14%, limonene 0.18%, 1,8-cineole 6.98%, p-cymene 90.38% and terpinene 0.31% through gas chromatography detection. The total olefin content in the mixed olefin white liquid before the reaction is 55.84%, and the remaining mixed olefin content in the reaction liquid after the reaction is 0.74%. The conversion rate is as high as 98.7%, and the selectivity of cymene reaches 99.8%.

[0025] Embodiment 2:

[0026] Activated carbon pretreatment: Grind the activated carbon. Columnar coal-based activated carbon is preferred. Other activated carbons may also be used. After screening with a molecular sieve of 80-100 mesh, weigh 5 kg of the screened activated carbon, soak it in 10 L 0.1 mol / L sodium hydroxide solution and 10 L 0.1 mol / L hydrochloric acid solution for 2.2 h respectively, filter it, then place the activated carbon in a 18% nitric acid solution by volume, heat it under reflux for 2 h, filter it, wash it with water until it is neutral, and dry it for later use.

[0027] Dissolve 5Kg ZnSO4 and 6Kg NiSO4 in 25Kg water to prepare a ZnSO4 / NiSO4 aqueous solution, then add 23.4Kg pre-treated activated carbon and stir and soak for 2h, filter, wash with water twice, and dry at 90℃ to obtain activated carbon loaded with ZnSO4 / NiSO4.

[0028] 5.8 kg of the prepared activated carbon-supported ZnSO4 / NiSO4 catalyst was loaded into a tubular reactor.

[0029] The mixed ene white liquor (containing 10.28% of 1-p-menene, 2.26% of 1,4-cineole, 5.94% of a-terpinene, 15.22% of limonene, 10.5% of 1,8-cineole, 1.92% of r-terpinene, 31.35% of p-cymene, 11.85% of terpinene and 10.63% of 4-carene) is heated to 290° C., and driven by nitrogen at a flow rate of 2100L / h, enters a tubular reactor at a speed of 35Kg / h, reacts at 290° C., and the reacted liquid is collected from the upper outlet of the tubular reactor. The reacted liquid contains 0.13% of 1-p-menene, 1.76% of 1,4-cineole, 0.17% of camphene, 0.22% of limonene, 7.5% of 1,8-cineole, 89.78% of p-cymene and 0.37% of terpinene through gas chromatography detection. The total olefin content in the mixed olefin white liquid before the reaction is 55.84%, and the remaining mixed olefin content in the reaction liquid after the reaction is 0.89%. The conversion rate is as high as 98.4%, and the selectivity for cymene reaches 99.9%.

[0030] Embodiment three:

[0031] Activated carbon pretreatment: Grind the activated carbon. Activated carbon is preferably columnar coal-based activated carbon. Other activated carbons may also be used. After screening with a molecular sieve of 80-100 mesh, weigh 5 kg of the screened activated carbon, soak it in 10 L 0.3 mol / L sodium hydroxide solution and 10 L 0.3 mol / L hydrochloric acid solution for 1.8 h respectively, filter it, then place the activated carbon in a 22% nitric acid solution by volume, heat it under reflux for 2 h, filter it, wash it with water until it is neutral, and dry it for use.

[0032] Dissolve 5Kg ZnSO4 and 4Kg NiSO4 in 15Kg water to prepare a ZnSO4 / NiSO4 aqueous solution, then add 8.4Kg pre-treated activated carbon and stir and soak for 2.2h, filter, wash with water 4 times, and dry at 90℃ to obtain activated carbon loaded with ZnSO4 / NiSO4.

[0033] 5.8 kg of the prepared activated carbon-supported ZnSO4 / NiSO4 catalyst was loaded into a tubular reactor.

[0034] The mixed olefin white liquor (containing 12.1% of 1-p-menene, 3.5% of 1,4-cineole, 7.6% of a-terpinene, 14.34% of limonene, 12.53% of 1,8-cineole, 3.44% of r-terpinene, 24.8% of p-cymene, 11.55% of terpinene and 10.1% of 4-carene) is heated to 280° C., and driven by nitrogen at a flow rate of 2000 L / h, enters a tubular reactor at a speed of 32 Kg / h, reacts at 280° C., and collects the reacted liquid from the upper outlet of the tubular reactor. The reacted liquid contains 0.18% of 1-p-menene, 2.9% of 1,4-cineole, 0.23% of camphene, 0.15% of limonene, 7.65% of 1,8-cineole, 88.4% of p-cymene and 0.42% of terpinene through gas chromatography detection. The total olefin content in the mixed olefin white liquid before the reaction is 59.13%, and the remaining mixed olefin content in the reaction liquid after the reaction is 0.98%. The conversion rate is as high as 98.3%, and the selectivity for cymene reaches 99.9%.

[0035] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, it should be understood by those skilled in the art that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing p-cymene, characterized in that: The following steps are involved: The prepared activated carbon-supported ZnSO4 / NiSO4 catalyst is loaded into a reactor, the reactor is heated, and the heteroolefin whitening liquid is continuously introduced into the reactor by using an inert gas, and the liquid after the reaction is collected from the upper outlet of the reactor to obtain para-cymene. The heteroolefin whitening liquid is: Contains 10.28% 1-p-menene, 2.26% 1,4-cineole, 5.94% a-terpinene, 15.22% limonene, 10.5% 1,8-cineole, 1.92% r-terpinene, 31.35% p-cymene, 11.85% terpinene and 10.63% 4-carene; Or contains 1-p-menene 12.1%, 1,4-cineole 3.5%, a-terpinene 7.6%, limonene 14.34%, 1,8-cineole 12.53%, r-terpinene 3.44%, p-cymene 24.8%, terpinene 11.55% and 4-carene 10.1%.

2. The method for preparing p-cymene according to claim 1, characterized in that: The preparation method of the activated carbon-supported ZnSO4 / NiSO4 catalyst comprises the following steps: Dissolve ZnSO4 and NiSO4 in water to prepare a ZnSO4 / NiSO4 aqueous solution, then add pre-treated activated carbon and stir, soak, filter, wash and dry to obtain an activated carbon-loaded ZnSO4 / NiSO4 catalyst.

3. The method for preparing p-cymene according to claim 2, characterized in that: The pretreatment of activated carbon includes the following steps: The activated carbon is ground and screened, and the screened activated carbon is soaked in sodium hydroxide solution and hydrochloric acid solution successively, filtered, and then placed in nitric acid solution, heated and refluxed, filtered, washed with water until neutral, and dried for use.

4. The method for preparing p-cymene according to claim 3, characterized in that: In the pretreatment of the activated carbon, a molecular sieve of 80-100 mesh is used for screening, and the screened activated carbon is soaked in both a sodium hydroxide solution and a hydrochloric acid solution for 1.8-2.2 hours.

5. The method for preparing p-cymene according to claim 3, characterized in that: In the pretreatment of activated carbon, the concentrations of the sodium hydroxide solution and the hydrochloric acid solution are both 0.1-0.3 mol / L, and the volume fraction of the nitric acid solution is 18-22%.

6. The method for preparing p-cymene according to claim 2, characterized in that: In the preparation of activated carbon-supported ZnSO4 / NiSO4 catalyst, the activated carbon adopts columnar coal-based activated carbon, the stirring and soaking time is 1.8-2.2h, the washing times are 2-4 times, and the drying temperature is ≤90°C.

7. The method for preparing p-cymene according to claim 2, characterized in that: In the preparation of activated carbon-supported ZnSO4 / NiSO4 catalyst, the mass ratio of ZnSO4, NiSO4 and water is 1:0.8-1.2:3-5, and the mass ratio of the ZnSO4 / NiSO4 aqueous solution and activated carbon is 2:0.7-1.

3.

8. The method for preparing p-cymene according to claim 1, characterized in that: The reactor is heated at 260-290°C, the flow rate of the inert gas is 1900-2100 L / h, and the continuous feeding rate of the heteroolefin white liquid is 30 Kg / h-35 Kg / h.

9. The method for preparing p-cymene according to claim 1, characterized in that: The inert gas is nitrogen, helium, neon or argon.