Patent Application
20250223251
The present invention relates to a method for preparing methylphenol and homologue by catalytic conversion of low carbon alcohol ketone, in particular to a method for preparing methylphenol and homologue from methanol, ethanol and acetone as reactants, and belongs to the technical field of chemical catalysis.
Methylphenol (cresol for short) and homologue are indispensable raw materials in chemical production, and are widely used in many fields such as medicine, dye, pesticide, resin and paint. M-cresol is a raw material for synthesis of a pesticide permethrin, 2,5-dimethylphenol is a flavoring agent and also a raw material for production of the drug Gemfibrozil, and 2,3,6-trimethylphenol is an essential substrate for synthesis of vitamin E.
At present, main production methods for cresol include coal tar extraction, isopropyltoluene oxidation and direct aromatics oxidation, wherein isopropyltoluene oxidation is currently the main method for producing methylphenol in the industry. Since isopropyltoluene isopropyl peroxide (tertiary CHP) is obtained by means of catalytic oxidation in the method, and both isopropyl and methyl of isopropyltoluene are likely to be oxidized, a mixture of tertiary CHP and isopropyltoluene methyl peroxide (primary CHP) is generally obtained in the oxidation step of the method. Tertiary CHP will produce cresol and acetone in the acid hydrolysis step, and primary CHP will produce isopropyl phenol and formaldehyde in the acid hydrolysis step, while formaldehyde can form a resinous substance which is difficult to handle with phenolic substances, and consume the target product cresol, resulting in reduced selectivity [Petrochemical Industry Trends, 1993, 3, 39-42]. High carbon phenol such as 2,3,6-trimethylphenol and 2,3,5-trimethylphenol is produced by methylation of cresol and obtained by reaction of cresol and methanol under catalysis, and while the substrate depends on the cresol production route, the reaction path needs to be obtained by two-step reaction [CN102976903A], so the cost is high. Isopropyltoluene in the cumene oxidation route is obtained by hydrocarbylation reaction of petroleum products toluene and propylene, and arene materials are in shortage due to increasing focus of refineries on the production of light gasoline [Science 2014, 344, 616; Angew. Chem. Int. Ed. 2013, 52, 11980]. For the above routes, methylphenol and homologue are obtained by oxidation of arene materials.
In recent years, high-value conversion and utilization of low carbon resources has attracted wide attention. The preparation of high carbon alcohol [ACS Catal. 2022, 12, 12045-12054], high carbon ketone [Angew Chem Int Ed. 2020, 59(34): 14550-14557] and aromatic alcohol [U.S. Pat. Nos. 10,960,386 B2, 11,338,275 B2] from ethanol has been reported. In addition, the conversion from ethanol to phenolic products has been sporadically reported, for example, with hydrotalcite as a catalyst, the selectivity of phenolic products obtained by ethanol conversion is 35% at high temperature of 450° C. [Catalysis Today. 2016, 269 (1):82-87]; and with Ce(OH)SO4·xH2O as a catalyst, ethanol can be converted into phenolic products at 420° C. and at low space velocity <10 min−1 [ACS Catal. 2021, 11, 6162-6174]. In the above reports, ethanol is used as a single reactant to produce phenolic products through a path of rearrangement, condensation and aromatization at high temperature of 400-450° C., which results in a large number of alkene by-products in the products.
A new way for preparing methylphenol and homologue from methanol, ethanol and acetone through a path of cross coupling-aromatization is developed. The route is highly innovative, which can expand a new way of green production of fine chemicals and realize the high-value comprehensive utilization of low carbon micromolecules.
The purpose of the present invention is to provide a route for preparing methylphenol and homologue from methanol, ethanol and acetone as reactants through dehydrogenation-cross coupling-aromatization reaction and to provide a catalyst required for the catalytic conversion route, which is specially emphasized to be the first reported synthesis route of methylphenol and homologue, with notable creativity. The route has the most important characteristic that target products methylphenol and homologue are produced with a catalyst at low temperature (≤300° C.) in one step, which is a new green route to produce methylphenol and homologue and meets the needs of energy conservation, consumption reduction and sustainable development strategies.
The reaction network of a preparation method for methylphenol and homologue is as follows:
The present invention creatively proposes use of three low carbon molecules as reactants for production of methylphenol and homologue through a new reaction path. The synthesis of cresol and homologue by catalytic conversion of low carbon micromolecules has the advantages of less pollution, less three wastes and easy product separation, and avoids use of petroleum-based raw materials. The reaction temperature of the reaction path is low, the selectivity of total cresol is up to 34.0%, and the selectivity of 2,3,6-trimethylphenol is up to 7.1%, with a good industrial application prospect. The innovation points of this patent include innovation of the reaction path and innovation of the catalyst system.
The technical solution of the present invention is as follows:
A preparation method for methylphenol and homologue comprises the following steps:
Under the conditions of reaction temperature of 150-350° C. and reaction pressure of 1-50 atm, a mixed material of methanol, ethanol and acetone is fed into a reactor containing a catalyst by a carrier gas at the total flow of the reaction gas of 20-200 mL/min to produce methylphenol through coupling-aromatization reaction.
The ranges of partial pressures of the reactants methanol, ethanol and acetone are respectively 0.1-10 kPa, and the ratio of partial pressures of methanol, ethanol and acetone is (0.5-40):(0.5-40):1 and preferably (0.5-15):(0.5-15):1. The total flow of the reaction gas is preferably 30 mL/min.
The reactor is preferably a fix bed reactor and a normal pressure reactor.
The weight hourly space velocity of the reaction is 0.01-3 h−1 and preferably 0.2-1.5 h−1.
The carrier gas is an inert gas such as nitrogen, argon and helium.
The catalyst is a hydroxyphosphate catalyst, with the chemical formula of AxByCzDmEn(OH)2(PO4)6, wherein x+y+z+m+n=9-10, 9-10≥x,y,z,m,n≥0, A, B, C, D and E are the same or different, and are selected from one or a combination of more than one of Mg, Ca, Sr, Ba and Pb, and hydroxyphosphate is one or a mechanical mixture of more than one.
The hydroxyphosphate is preferably is Ca10(OH)2(PO4)6.
The catalyst is a hydroxyphosphate catalyst modified by transition metal, comprising components by weight percent; transition metal comprises non-noble metal and/or noble metal; the non-noble metal is selected from one or a combination of more than one of Co, Ni, Cu, Zn and Y; the noble metal is selected from one or a combination of more than one of Ag, Pt and Ir; the transition metal is in an oxidation state or metallic state; and nitrate, chloride, levulinate, sulfate or acetate of the metal is used as a precursor, the concentration of a precursor solution is 0.05 g/mL-0.75 g/mL, and the modification amount of the transition metal is 0.01-50 wt % of the weight of hydroxyphosphate.
The transition metal is preferably Ag and Cu, and the modification amount is 0.1-10 wt % of the hydroxyphosphate.
The hydroxyphosphate catalyst modified by transition metal is reduced for 1-5 h at 350-750° C. in hydrogen atmosphere before reaction, and the concentration of the hydrogen atmosphere is one of 5-30 vol % H2/N2, 5-30 vol % H2/He and 5-30 vol % H2/Ar.
The catalyst is a mixture of a hydroxyphosphate catalyst and a hydroxyphosphate catalyst modified by transition metal.
The present invention has the following beneficial effects: compared with the prior art, the present invention provides a reaction path for directly producing methylphenol and homologue from low carbon micromolecular alcohol and ketone through coupling-aromatization reaction, the maximum selectivity of total cresol is 34.0%, and the selectivity of 2,3,6-trimethylphenol is up to 7.1%. The by-product hydrogen of the reaction path can be used as a chemical material. Other by-products such as high carbon alcohol and ketone (C3-C8) whose melting and boiling points are quite different from those of methylphenol and which are easy to be separated by rectification can be used as fuel additives to partially replace petroleum-based products, which provides an alternative path for synthesis of methylphenol products, has great strategic significance for energy security and has a high industrial application prospect.
The FIGURE shows a reaction path for producing methylphenol by coupling of methanol, ethanol and acetone proposed in the present invention, and MPV reaction is Meerwein-Ponndorf-Verley hydrogenation reaction.
The present invention is described below in detail through some embodiments. However, the present invention is not limited to these embodiments.
Hydroxyphosphate is represented by HAP-M, wherein HAP indicates metal hydroxyphosphate, and M indicates metal which is one or several of Mg, Ca, Sr, Ba and Pb.
Hydroxyphosphate modified by metal is represented by an xMetal-HAP-M carrier, wherein Metal indicates loaded transition metal and is one or several of non-noble metal such as Co, Ni, Cu, Zn and Y and/or noble metal such as Pt, Ag and Ir, and x is the percentage of the Metal modification amount in the total weight of the catalyst multiplied by 100.
The preparation conditions and process of other catalysts are the same as those in embodiment 1. The corresponding relation between sample numbers and preparation conditions is shown in Table 1.
The preparation conditions and process of other catalysts are the same as those in embodiment 2. The corresponding relation between sample numbers and preparation conditions is shown in Table 2.
Methanol, ethanol and acetone as reactants are subjected to coupling-aromatization reaction in a fix bed reactor. Reaction conditions are as follows: the catalyst is filled in a fix bed reactor with an inner diameter of 8 mm at normal pressure and reaction temperature of 300° C., the weight hourly space velocity is 1 h−1, the total flow of the reaction gas is 30 mL/min, the total partial pressure of methanol and ethanol is 6 kPa, the partial pressure of acetone is 1 kPa, the ratio of the partial pressures of methanol, ethanol and acetone is (1-5):(1-5):1, and the partial pressures of the reactants are adjusted by adjusting the feed flow of methanol, ethanol and acetone. After the reaction is steady, the reaction materials and products are analyzed by on-line chromatogram. The conversion rates of methanol and ethanol and the selectivity of methylphenol at different partial pressures are shown in Table 3, and the selectivity of acetone is close to 100% which is not listed in Table 3.
Methanol, ethanol and acetone as reactants are subjected to coupling-aromatization reaction in a fix bed reactor. Reaction conditions are as follows: the catalyst is filled in a fix bed reactor with an inner diameter of 8 mm at normal pressure and reaction temperature of 300° C., the weight hourly space velocity is 1 h−1, the total flow of the reaction gas is 30 mL/min, the partial pressure of methanol is 4 kPa, the partial pressure of ethanol is 2 kPa, the partial pressure of acetone is adjusted between 0.33 kPa and 3 kPa and adjusted by changing the feed flow of acetone, and the ratio of the partial pressures of methanol, ethanol and acetone is (1.33-12.12):(0.67-6.06):1. The conversion rates of methanol and ethanol and the selectivity of methylphenol at different partial pressures of acetone are shown in Table 4. The selectivity of acetone is close to 100% which is not listed in Table 4.
Catalytic Conversion Performance of xMetal-HAP-M Catalyst.
Methanol, ethanol and acetone as reactants are subjected to coupling-aromatization reaction in a fix bed reactor. Reaction conditions are as follows: the catalyst is filled in a fix bed reactor with an inner diameter of 8 mm at normal pressure and reaction temperature of 300° C., the weight hourly space velocity is 1 h−1, the total flow of the reaction gas is 30 mL/min, the partial pressure of methanol is 4 kPa, the partial pressure of ethanol is 2 kPa, the partial pressure of acetone is 1 kPa, and the ratio of the partial pressures of methanol, ethanol and acetone is 4:2:1. Different xMetal-HAP-M materials are used as catalysts for the reaction, and the preparation method for the xMetal-HAP-M catalyst is shown in embodiment 2. The conversion rates of methanol and ethanol and the selectivity of methylphenol for different catalysts are shown in Table 5. The selectivity of acetone is close to 100% which is not listed in Table 5.
Methanol, ethanol and acetone as reactants are subjected to catalytic reaction testing in a fix bed reactor. Reaction conditions are as follows: the catalyst is filled in a fix bed reactor with an inner diameter of 8 mm at normal pressure and reaction temperature of 300° C., the weight hourly space velocity is 1 h−1, the total flow of the reaction gas is 30 mL/min, and the partial pressures of ethanol, methanol and acetone are all 6 kPa. The product distribution during the reaction of different reactants is shown in Table 6.
As shown in Table 6, when raw materials are fed separately in the reaction, the product distribution of the three substrates is different, and the products do not contain methylphenol, which indicates that methylphenol cannot be obtained by separate feeding at low temperature.
Methanol, ethanol and acetone mixedly fed in pairs are subjected to catalytic reaction testing in a fix bed reactor. Reaction conditions are as follows: the catalyst is filled in a fix bed reactor with an inner diameter of 8 mm at normal pressure and reaction temperature of 300° C., the weight hourly space velocity is 1 h−1, the total flow of the reaction gas is 30 mL/min, and the conversion rates of methanol and ethanol and the selectivity of methylphenol under different reactant feeding are shown in Table 7.
As shown in Table 7, when methanol and ethanol are fed in a mixed manner, only aliphatic alcohols are produced, and no methylphenol is detected. When acetone is fed together with methanol and ethanol respectively in a mixed manner, only a small amount of methylphenol is detected in the product, which indicates that acetone exists as a substrate that can form cresol, but methylphenol can be produced in a large amount only when three substrates are cross-coupled.
Methanol, ethanol and acetone as reactants are subjected to coupling-aromatization reaction in a fix bed reactor. Catalytic reaction testing is carried out in the fix bed reactor. Reaction conditions are as follows: 200 mg of catalyst is filled in a fix bed reactor with an inner diameter of 8 mm at normal pressure and reaction temperature of 300° C., the weight hourly space velocity is 1 h−1, the total flow of the reaction gas is 30 mL/min, the partial pressure of methanol is 4 kPa, the partial pressure of ethanol is 2 kPa, the partial pressure of acetone is 1 kPa, and the ratio of the partial pressures of methanol, ethanol and acetone is 4:2:1. The conversion rates of methanol and ethanol and the selectivity of methylphenol under different catalysts are shown in Table 8.
As shown in Table 8, no reaction occurs in the absence of a catalyst. When other recognized acid-base catalysts are used, high carbon alcohol, alkene and high carbon ketone are more inclined to form in the products due to mismatch of acid-base sites, so the hydroxyphosphate catalyst is preferred in the reaction.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2023/088278 | 4/14/2023 | WO |
