A method for preparing hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime

Abstract

A method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime belongs to the technical field of hydroxylamine aqueous solution preparation. Specifically, cyclohexanone oxime and deionized water are added to a hydrolysis kettle to completely dissolve the cyclohexanone oxime, and an appropriate amount of a bisphenol-based solid acid catalyst is added. The mixture is stirred, refluxed, and condensed to obtain a reaction solution containing hydroxylamine. An extractant is added to the reaction solution, and the organic phase in the reaction solution is separated to obtain cyclohexanone; the residual aqueous phase is centrifuged to obtain the product hydroxylamine aqueous solution and the bisphenol-based solid acid catalyst, respectively, and the catalyst is recovered and recycled. This method significantly improves the conversion rate of the catalytic hydrolysis of cyclohexanone oxime, has a simple process route, simple operation, mild reaction conditions, and low energy consumption, and is a green and environmentally friendly production process.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of hydroxylamine aqueous solution, in particular to a method for preparing hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime. Background Art

[0002] The molecular formula of hydroxylamine is NH2OH, which can be regarded as a derivative formed by replacing a proton in NH3 with a hydroxyl group. It is an unstable white crystal at room temperature, easily deliquesces, and often exists in the form of an aqueous solution.

[0003] High-purity, concentrated aqueous hydroxylamine solutions are particularly useful in the electronics industry, for example, in combination with other substances for cleaning printed circuit boards or silicon wafers. For use in the electronics industry, impurity concentrations, particularly metal ions, are typically required to be well below 1 ppm, i.e., electronic-grade products are required. Purity requirements for aqueous hydroxylamine solutions are constantly increasing.

[0004] Chinese Patent Publication No. CN107089924A discloses a combined production process for hydroxylamine, hydroxylamine salt, and cyclohexanone oxime. The raw materials are subjected to ammoximation reaction and hydroxylamine reaction, and the reaction solution obtained is subjected to extraction and separation to obtain an organic phase. The organic phase is used to prepare the product cyclohexanone oxime, or a portion of the organic phase and a portion of the product cyclohexanone oxime are hydrolyzed as raw materials for an oxime hydrolysis reaction. The organic phase in the hydrolyzed solution is recycled back to the oximation reactor, and a portion of the inorganic phase in the hydrolyzed solution is recycled back to the hydroxylamine oximation reactor as raw material. The other portion of the inorganic phase is used to prepare a hydroxylamine aqueous solution and a hydroxylamine salt. The process flow of the present invention is simple, reduces the requirements of the ammoximation reaction for the purity of the raw material cyclohexanone and the performance of the catalyst, and obtains a high-quality cyclohexanone oxime product that does not contain cyclohexanone, which is beneficial to the simplification and product quality of the downstream caprolactam process, while obtaining high-value-added hydroxylamine and hydroxylamine salt products.

[0005] International Patent Publication No. PCT / EP1996 / 005773 discloses a method for preparing an aqueous solution of free hydroxylamine. The solution obtained by treating a hydroxylammonium salt with an alkali is then treated with water or steam at 80°C to separate the solution into an aqueous hydroxylamine fraction and a salt fraction. This process is flexible and easily scalable. The risk of decomposition is minimized due to low thermal stress, low hydroxylamine concentration, and short residence time during process implementation.

[0006] Chinese Patent Publication No. CN101049919A discloses a method for producing high-purity hydroxylamine and its active alkaline aqueous solution. Hydroxylamine phosphate is thermally decomposed under a pressure of less than 30 mmHg and a temperature of 80-150°C, and the sublimates are collected to produce high-purity hydroxylamine crystals. These high-purity hydroxylamine crystals can be prepared to any desired concentration of the active alkaline aqueous solution, and their metal ion content is extremely low, fully meeting the needs of the pharmaceutical and electronics industries. The method utilizes simple equipment and operation, avoids the high-vacuum distillation and concentration process of low-concentration aqueous solutions, and eliminates the explosion hazard associated with the concentration process.

[0007] However, existing technologies for preparing hydroxylamine either have difficulties in continuous production, equipment corrosion makes industrial production difficult, or the process methods are complex and expensive, and have not been accepted by the industry to this day, or the metal ion concentration is too high, making it difficult to produce electronic-grade products. Summary of the Invention

[0008] To solve at least one of the technical problems in the above technical background, the present invention proposes a method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime. The hydroxylamine aqueous solution is obtained by catalytic hydrolysis of cyclohexanone oxime at room temperature and extraction and separation. The catalyst is stable and recyclable, which has environmental and economic benefits.

[0009] The technical solution of the present invention is:

[0010] A method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime, the operating steps of which are:

[0011] A1: Add 1-5 parts by mass of cyclohexanone oxime and deionized water to a hydrolysis kettle to completely dissolve the cyclohexanone oxime. Add an appropriate amount of catalyst, stir, reflux, and condense to obtain a reaction solution containing hydroxylamine.

[0012] A2: adding an extractant to the reaction solution containing hydroxylamine, separating the organic phase from the reaction solution to obtain cyclohexanone; and centrifuging the raffinate aqueous phase to obtain the product hydroxylamine aqueous solution and the catalyst, respectively.

[0013] In some embodiments of the present invention, the reaction temperature in A1 is 12-28° C., and the reaction time is 0.1-2 h.

[0014] In some embodiments of the present invention, the reaction pressure in A1 is normal pressure.

[0015] In some embodiments of the present invention, the molar ratio of cyclohexanone oxime to deionized water in A1 is 1:20-200.

[0016] In some embodiments of the present invention, the amount of the catalyst added in A1 is 0.1-2 wt % of the hydrolysis system.

[0017] In some embodiments of the present invention, the extractant in A2 is at least one selected from butyl acetate, ethyl acetate, chloroform, and toluene.

[0018] In some embodiments of the present invention, the extraction temperature in A2 is 10-30°C.

[0019] In some embodiments of the present invention, the catalyst in A1 is a bisphenol-based solid acid catalyst, and its preparation method is:

[0020] B1: Add 6.5-9 parts of 2-cyclohexene-1-one to 100-300 parts of DMF, add 2.27-3 parts of methylamino nitrate, and 2-5 parts of sodium methoxide, heat to 55-70°C, and react for 50-100 minutes;

[0021] B2: Add 50-70 parts of macroporous styrene mercapto resin, 0.01-0.3 parts of diallyl bisphenol, and 0.8-2.6 parts of sodium methoxide to the prefabricated solution of B1, react for 100-150 minutes under a flowing state, and filter to obtain a bisphenol-based styrene resin;

[0022] B3: The bisphenol-based styrene resin obtained in step B2 is placed in a stirred tank, 500-800 parts of 70%-80% sulfuric acid is introduced, and the mixture is stirred at 30-50° C. for 10-16 hours, filtered, and dried to obtain a bisphenol-based solid acid catalyst.

[0023] The preparation mechanism of the bisphenol-based solid acid catalyst in the present invention is as follows:

[0024] First, in step 1, 2-cyclohexene-1-one and methylamino nitrate undergo amino addition reaction under the action of sodium methoxide as a catalyst; in step 2, macroporous styrene mercapto resin and diallyl bisphenol undergo addition reaction under the action of sodium methoxide as a catalyst, and the product undergoes mercapto addition reaction with the material in step 1 to obtain bisphenol-based styrene resin; and finally, in step 3, sulfuric acid is introduced to obtain a bisphenol-based solid acid catalyst.

[0025] Technical effects:

[0026] The method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime of the present invention has the following significant effects compared with the prior art:

[0027] (1) The process of the present invention is simple in process route, simple in operation, mild in reaction conditions, and low in energy consumption, and is a green and environmentally friendly production process;

[0028] (2) The present invention prepares a hydroxylamine aqueous solution by direct catalytic hydrolysis of cyclohexanone oxime, eliminating the hydroxylamine salt separation process, simplifying the process steps, and improving the product purity;

[0029] (3) The present invention prepares a bisphenol-based solid acid catalyst, which significantly improves the conversion rate of cyclohexanone oxime catalytic hydrolysis, and the bisphenol-based solid acid catalyst can be recycled and reused after the reaction is completed, thereby reducing production costs. DETAILED DESCRIPTION

[0030] The essential features and significant effects of the present invention can be reflected in the following embodiments, but they do not limit the present invention in any way. Those skilled in the art can make some non-essential improvements and adjustments based on the content of the present invention. The present invention is further described below through specific embodiments.

[0031] The hydroxylamine in the aqueous phase was analyzed by potassium permanganate redox titration. The cyclohexanone composition in the organic phase was qualitatively analyzed by pure substance retention method and chromatography-mass spectrometry, and the conversion rate of cyclohexanone oxime was quantitatively analyzed by gas chromatography.

[0032] Example 1

[0033] A method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime, the operating steps of which are:

[0034] A1: Add 1 kg of cyclohexanone oxime and deionized water to a hydrolysis reactor to completely dissolve the cyclohexanone oxime. Add an appropriate amount of catalyst, stir, reflux, and condense to obtain a reaction solution containing hydroxylamine.

[0035] A2: adding an extractant to the reaction solution containing hydroxylamine, separating the organic phase from the reaction solution to obtain cyclohexanone; and centrifuging the raffinate aqueous phase to obtain the product hydroxylamine aqueous solution and the catalyst, respectively.

[0036] The reaction temperature in A1 is 12° C. and the reaction time is 0.1 h.

[0037] The reaction pressure in A1 is normal pressure.

[0038] The molar ratio of cyclohexanone oxime to deionized water in A1 is 1:20.

[0039] The amount of catalyst added in A1 is 0.1 wt% of the hydrolysis system.

[0040] The extractant in A2 is selected from butyl acetate.

[0041] The extraction temperature in A2 is 10°C.

[0042] The catalyst in A1 is a bisphenol-based solid acid catalyst, and its preparation method is as follows:

[0043] B1: Add 6.5 g of 2-cyclohexene-1-one to 100 g of DMF, add 2.27 g of methylamino nitrate, and 2 g of sodium methoxide, heat to 55°C, and react for 50 minutes;

[0044] B2: Add 50 g of macroporous styrene-mercapto resin, 0.1 g of diallyl bisphenol, and 0.8 g of sodium methoxide to the prefabricated solution of B1, react for 100 minutes under a flowing state, and filter to obtain a bisphenol-based styrene resin;

[0045] B3: The bisphenol-based styrene resin obtained in step B2 was placed in a stirred tank, 500 g of 70% sulfuric acid was introduced, and the mixture was stirred at 30° C. for 10 hours, filtered, and dried to obtain a bisphenol-based solid acid catalyst.

[0046] According to analysis and testing, the conversion rate of cyclohexanone oxime in this example was 67.8%, and the selectivity of hydroxylamine was 99.1%.

[0047] Example 2

[0048] A method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime, the operating steps of which are:

[0049] A1: Add 2.5 kg of cyclohexanone oxime and deionized water to a hydrolysis kettle to completely dissolve the cyclohexanone oxime. Add an appropriate amount of catalyst, stir, reflux, and condense to obtain a reaction solution containing hydroxylamine.

[0050] A2: adding an extractant to the reaction solution containing hydroxylamine, separating the organic phase from the reaction solution to obtain cyclohexanone; and centrifuging the raffinate aqueous phase to obtain the product hydroxylamine aqueous solution and the catalyst, respectively.

[0051] In the A1, the reaction temperature is 16° C. and the reaction time is 0.6 h.

[0052] The reaction pressure in A1 is normal pressure.

[0053] The molar ratio of cyclohexanone oxime to deionized water in A1 is 1:80.

[0054] The amount of catalyst added in A1 is 0.6 wt% of the hydrolysis system.

[0055] The extractant in A2 is selected from ethyl acetate.

[0056] The extraction temperature in A2 is 15°C.

[0057] The catalyst in A1 is a bisphenol-based solid acid catalyst, and its preparation method is as follows:

[0058] B1: Add 7.5 g of 2-cyclohexene-1-one to 150 g of DMF, add 2.47 g of methylamino nitrate, and 3 g of sodium methoxide, heat to 60°C, and react for 65 minutes;

[0059] B2: Add 55 g of macroporous styrene mercapto resin, 0.2 g of diallyl bisphenol, and 1.4 g of sodium methoxide to the prefabricated solution of B1, react for 120 minutes under a flowing state, and filter to obtain a bisphenol-based styrene resin;

[0060] B3: The bisphenol-based styrene resin obtained in step B2 was placed in a stirred tank, 600 g of 70% sulfuric acid was introduced, and the mixture was stirred at 35° C. for 12 hours, filtered, and dried to obtain a bisphenol-based solid acid catalyst.

[0061] According to analysis and testing, the conversion rate of cyclohexanone oxime in this example was 71.1%, and the selectivity of hydroxylamine was 99.5%.

[0062] Example 3

[0063] A method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime, the operating steps of which are:

[0064] A1: Add 3.8 kg of cyclohexanone oxime and deionized water to a hydrolysis kettle to completely dissolve the cyclohexanone oxime. Add an appropriate amount of catalyst, stir, reflux, and condense to obtain a reaction solution containing hydroxylamine.

[0065] A2: adding an extractant to the reaction solution containing hydroxylamine, separating the organic phase from the reaction solution to obtain cyclohexanone; and centrifuging the raffinate aqueous phase to obtain the product hydroxylamine aqueous solution and the catalyst, respectively.

[0066] In the A1, the reaction temperature is 24° C. and the reaction time is 1.2 h.

[0067] The reaction pressure in A1 is normal pressure.

[0068] The molar ratio of cyclohexanone oxime to deionized water in A1 is 1:145.

[0069] The amount of catalyst added in A1 is 1.2 wt% of the hydrolysis system.

[0070] The extractant in A2 is selected from chloroform.

[0071] The extraction temperature in A2 is 25°C.

[0072] The catalyst in A1 is a bisphenol-based solid acid catalyst, and its preparation method is as follows:

[0073] B1: Add 8.5 g of 2-cyclohexene-1-one to 250 g of DMF, add 2.77 g of methylamino nitrate, and 4 g of sodium methoxide, heat to 75°C, and react for 80 minutes;

[0074] B2: Add 65 g of macroporous styrene-mercapto resin, 0.3 g of diallyl bisphenol, and 2.3 g of sodium methoxide to the prefabricated solution of B1, react for 140 minutes under a flowing state, and filter to obtain a bisphenol-based styrene resin;

[0075] B3: The bisphenol-based styrene resin obtained in step B2 was placed in a stirred tank, 700 g of 80% sulfuric acid was introduced, and the mixture was stirred at 45° C. for 14 hours, filtered, and dried to obtain a bisphenol-based solid acid catalyst.

[0076] According to analysis and testing, the conversion rate of cyclohexanone oxime in this example was 72.4%, and the selectivity of hydroxylamine was 99.6%.

[0077] Example 4

[0078] A method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime, the operating steps of which are:

[0079] A1: Add 5 kg of cyclohexanone oxime and deionized water to a hydrolysis reactor to completely dissolve the cyclohexanone oxime. Add an appropriate amount of catalyst, stir, reflux, and condense to obtain a reaction solution containing hydroxylamine.

[0080] A2: adding an extractant to the reaction solution containing hydroxylamine, separating the organic phase from the reaction solution to obtain cyclohexanone; and centrifuging the raffinate aqueous phase to obtain the product hydroxylamine aqueous solution and the catalyst, respectively.

[0081] The reaction temperature in A1 is 28° C. and the reaction time is 2 h.

[0082] The reaction pressure in A1 is normal pressure.

[0083] The molar ratio of cyclohexanone oxime to deionized water in A1 is 1:200.

[0084] The amount of catalyst added in A1 is 2 wt% of the hydrolysis system.

[0085] The extractant in A2 is selected from toluene.

[0086] The extraction temperature in A2 is 30°C.

[0087] The catalyst in A1 is a bisphenol-based solid acid catalyst, and its preparation method is as follows:

[0088] B1: Add 9 g of 2-cyclohexene-1-one to 300 g of DMF, add 3 g of methylamino nitrate, and 5 g of sodium methoxide, heat to 70°C, and react for 100 minutes;

[0089] B2: Add 70 g of macroporous styrene-mercapto resin, 0.3 g of diallyl bisphenol, and 2.6 g of sodium methoxide to the prefabricated solution of B1, react for 150 minutes under a flowing state, and filter to obtain a bisphenol-based styrene resin;

[0090] B3: The bisphenol-based styrene resin obtained in step B2 was placed in a stirred tank, 800 g of 80% sulfuric acid was introduced, and the mixture was stirred at 50° C. for 16 hours, filtered, and dried to obtain a bisphenol-based solid acid catalyst.

[0091] According to analysis and testing, the conversion rate of cyclohexanone oxime in this example was 69.6%, and the selectivity of hydroxylamine was 99.4%.

[0092] Comparative Example 1

[0093] A method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime, the operating steps of which are:

[0094] A1: Add 1 kg of cyclohexanone oxime and deionized water to a hydrolysis reactor to completely dissolve the cyclohexanone oxime. Add an appropriate amount of catalyst, stir, reflux, and condense to obtain a reaction solution containing hydroxylamine.

[0095] A2: adding an extractant to the reaction solution containing hydroxylamine, separating the organic phase from the reaction solution to obtain cyclohexanone; and centrifuging the raffinate aqueous phase to obtain the product hydroxylamine aqueous solution and the catalyst, respectively.

[0096] The reaction temperature in A1 is 12° C. and the reaction time is 0.1 h.

[0097] The reaction pressure in A1 is normal pressure.

[0098] The molar ratio of cyclohexanone oxime to deionized water in A1 is 1:20.

[0099] The amount of catalyst added in A1 is 0.1 wt% of the hydrolysis system.

[0100] The extractant in A2 is selected from butyl acetate.

[0101] The extraction temperature in A2 is 10°C.

[0102] The catalyst in A1 is a bisphenol-based solid acid catalyst, and its preparation method is as follows:

[0103] B1: Add 6.5 g of 2-cyclohexene-1-one to 100 g of DMF, add 2.27 g of methylamino nitrate, and 2 g of sodium methoxide, heat to 55°C, and react for 50 minutes;

[0104] B2: Add 50 g of macroporous styrene-mercapto resin and 0.8 g of sodium methoxide to the prefabricated solution of B1, react for 100 minutes under a flowing state, and filter to obtain a bisphenol-based styrene resin;

[0105] B3: The bisphenol-based styrene resin obtained in step B2 was placed in a stirred tank, 500 g of 70% sulfuric acid was introduced, and the mixture was stirred at 30° C. for 10 hours, filtered, and dried to obtain a bisphenol-based solid acid catalyst.

[0106] According to analysis and testing, the conversion rate of cyclohexanone oxime in this example was 54.8%, and the selectivity of hydroxylamine was 97.7%.

[0107] Comparative Example 2

[0108] A method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime, the operating steps of which are:

[0109] A1: Add 1 kg of cyclohexanone oxime and deionized water to a hydrolysis reactor to completely dissolve the cyclohexanone oxime. Add an appropriate amount of catalyst, stir, reflux, and condense to obtain a reaction solution containing hydroxylamine.

[0110] A2: adding an extractant to the reaction solution containing hydroxylamine, separating the organic phase from the reaction solution to obtain cyclohexanone; and centrifuging the raffinate aqueous phase to obtain the product hydroxylamine aqueous solution and the catalyst, respectively.

[0111] The reaction temperature in A1 is 12° C. and the reaction time is 0.1 h.

[0112] The reaction pressure in A1 is normal pressure.

[0113] The molar ratio of cyclohexanone oxime to deionized water in A1 is 1:20.

[0114] The amount of catalyst added in A1 is 0.1 wt% of the hydrolysis system.

[0115] The extractant in A2 is selected from butyl acetate.

[0116] The extraction temperature in A2 is 10°C.

[0117] The catalyst in A1 is a bisphenol-based solid acid catalyst, and its preparation method is as follows:

[0118] B1: Add 6.5 g of 2-cyclohexene-1-one to 100 g of DMF and 2 g of sodium methoxide, heat to 55°C, and react for 50 minutes;

[0119] B2: Add 50 g of macroporous styrene-mercapto resin, 0.1 g of diallyl bisphenol, and 0.8 g of sodium methoxide to the prefabricated solution of B1, react for 100 minutes under a flowing state, and filter to obtain a bisphenol-based styrene resin;

[0120] B3: The bisphenol-based styrene resin obtained in step B2 was placed in a stirred tank, 500 g of 70% sulfuric acid was introduced, and the mixture was stirred at 30° C. for 10 hours, filtered, and dried to obtain a bisphenol-based solid acid catalyst.

[0121] After analysis and testing, the conversion rate of cyclohexanone oxime in this example was 56.6%, and the mass concentration of hydroxylamine was 98.1%.

[0122] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention are possible without inventive effort by those skilled in the art. Therefore, any technical solution that can be derived by one skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime, the operating steps of which are: A1: Add 1-5 parts by mass of cyclohexanone oxime and deionized water to a hydrolysis kettle to completely dissolve the cyclohexanone oxime. Add an appropriate amount of catalyst, stir, reflux, and condense to obtain a reaction solution containing hydroxylamine. A2: adding an extractant to the reaction solution containing hydroxylamine, separating the organic phase from the reaction solution to obtain cyclohexanone; and centrifuging the raffinate aqueous phase to obtain the product hydroxylamine aqueous solution and the catalyst, respectively; The catalyst in A1 is a bisphenol-based solid acid catalyst, and its preparation method is as follows: B1: Add 6.5-9 parts of 2-cyclohexene-1-one to 100-300 parts of DMF, add 2.27-3 parts of methylamino nitrate, and 2-5 parts of sodium methoxide, heat to 55-70°C, and react for 50-100 minutes; B2: Add 50-70 parts of macroporous styrene mercapto resin, 0.01-0.3 parts of diallyl bisphenol, and 0.8-2.6 parts of sodium methoxide to the prefabricated solution of B1, react for 100-150 minutes under a flowing state, and filter to obtain a bisphenol-based styrene resin; B3: The bisphenol-based styrene resin obtained in step B2 is placed in a stirred tank, 500-800 parts of 70%-80% sulfuric acid is introduced, and the mixture is stirred at 30-50° C. for 10-16 hours, filtered, and dried to obtain a bisphenol-based solid acid catalyst.

2. The method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime according to claim 1, characterized in that: The reaction temperature in A1 is 12-28° C., and the reaction time is 0.1-2 h.

3. The method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime according to claim 1, characterized in that: The reaction pressure in A1 is normal pressure.

4. The method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime according to claim 1, characterized in that: The molar ratio of cyclohexanone oxime to deionized water in A1 is 1:20-200.

5. The method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime according to claim 1, characterized in that: The amount of the catalyst added in A1 is 0.1-2 wt% of the hydrolysis system.

6. The method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime according to claim 1, characterized in that: The extractant in A2 is at least one selected from butyl acetate, ethyl acetate, chloroform, and toluene.

7. The method for preparing a hydroxylamine aqueous solution by catalytic hydrolysis of cyclohexanone oxime according to claim 1, characterized in that: The extraction temperature in A2 is 10-30°C.