A process for removing o-(p-)chlorobenzyl alcohol as an impurity in o-(p-)chlorobenzaldehyde products

Abstract

The present invention proposes a process for removing o-chlorobenzyl alcohol as an impurity in an o-chlorobenzaldehyde product, which comprises three steps of a hydrolysis reaction, a conversion reaction and an alkaline hydrolysis reaction. The present invention converts the o-chlorobenzyl alcohol as an impurity in the o-chlorobenzaldehyde product into o-chloromonobenzyl chloride using a Lucas reagent, and then adds a catalyst triethylamine in the alkaline hydrolysis process to complex the o-chloromonobenzyl chloride into a water-soluble quaternary ammonium salt, thereby converting the impurity into a water-soluble component, and then removing the impurity by oil-water separation, and finally realizing the refining and purification of the product o-chlorobenzaldehyde by vacuum distillation, thereby greatly improving the purity of the prepared o-chlorobenzaldehyde product and obtaining a high-quality product.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, in particular to a process for removing o-chlorobenzyl alcohol (p-chlorobenzyl alcohol) as an impurity in o-chlorobenzaldehyde (p-chlorobenzyl alcohol) products. Background Art

[0002] o-(p-)chlorobenzaldehyde is an important chemical raw material, a colorless transparent liquid, and is mainly used in organic synthesis, pesticides, pharmaceuticals and dye industries. At present, the main production process at home and abroad is the chlorination hydrolysis process, which uses o-(p-)chlorotoluene and chlorine as raw materials, synthesizes o-(p-)chlorobenzylidene dichloride through catalytic chlorination, and obtains the crude o-(p-)chlorobenzylidene dichloride (referred to as dichlorobenzyl) through vacuum distillation, and then obtains the finished o-(p-)chlorobenzylaldehyde through hydrolysis, alkaline hydrolysis reaction and vacuum distillation, and the total yield is about 90%.

[0003] In actual industrial production, the hydrolysis and alkaline hydrolysis reactions of the production process are difficult to avoid side reactions and Cannizzaro disproportionation reactions in the production process, as a small amount of monobenzyl chloride and tribenzyl chloride (the content of dichlorobenzyl is about 93.5%, of which monobenzyl chloride is about 0.5% and tribenzyl chloride is about 6.0%) is present in the crude dichlorobenzyl chloride intermediate raw material of the hydrolysis reaction. A small amount of o-(p-)chlorobenzyl alcohol (about 0.5-1.0%) is produced in the production process. In the subsequent vacuum distillation, since the boiling points of o-(p-)chlorobenzyl alcohol and the product o-(p-)chlorobenzaldehyde differ very little (the boiling point difference is less than 2° C.), it is difficult to separate them in the vacuum distillation purification process of the product, resulting in the purity of the o-(p-)chlorobenzaldehyde product failing to reach more than 99.5%, and it is difficult to obtain a high-quality o-(p-)chlorobenzaldehyde product. This process is aimed at removing the impurity o-chlorobenzyl alcohol (p-chlorobenzyl alcohol) in the o-chlorobenzaldehyde product. Through process optimization design, the content of the impurity o-chlorobenzyl alcohol (p-chlorobenzyl alcohol) in the o-chlorobenzaldehyde product is controlled to be less than 0.20%, thereby achieving the purpose of improving the quality of the o-chlorobenzaldehyde product (main content ≥99.5%). Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a process for removing o-chlorobenzyl alcohol (p-chlorobenzyl alcohol) as an impurity in o-chlorobenzaldehyde (p-chlorobenzyl alcohol) products, thereby solving the problem that the purity of o-chlorobenzyl alcohol (p-chlorobenzyl alcohol) is not high enough and the product quality is not good enough due to the presence of o-chlorobenzyl alcohol impurities in the prior art.

[0005] According to an embodiment of the present invention, the present invention proposes a process for removing the impurity o-(p-)chlorobenzyl alcohol in an o-(p-)chlorobenzaldehyde product, comprising the following steps:

[0006] Hydrolysis reaction:

[0007] The crude benzyl dichloride product after distillation and purification is pumped from the liquid tank of the distillation tower to the benzyl dichloride high-level tank, and then put into the hydrolysis kettle through the feed, and then add a catalyst with a mass fraction of 0.15%-0.3%, start stirring, turn on the cooling water of the condenser, raise the temperature to 120-130°C, then open the outlet valve of the water high-level tank, and continuously add water by metering. When the content of benzyl dichloride is ≤0.2%, stop the hydrolysis and cool down to no more than 80°C;

[0008] Conversion reaction:

[0009] Add the prepared Lucas reagent to the o-chlorobenzyl alcohol (p-chlorobenzyl alcohol) in a 1:1 molar ratio to the o-chlorobenzyl alcohol (p-chlorobenzyl alcohol), stir at a temperature of 80-100° C., keep warm for 3-5 hours, take samples for analysis, and terminate the conversion reaction when the o-chlorobenzyl alcohol (p-chlorobenzyl alcohol) is ≤0.20%, and separate the o-chlorobenzaldehyde (p-chlorobenzyl alcohol) oil phase;

[0010] Alkaline hydrolysis reaction:

[0011] To the o-chlorobenzaldehyde (p-chlorobenzyl) oil phase obtained by the conversion reaction, a soda ash solution and triethylamine are quantitatively added, the reaction temperature is controlled at 90-100° C., and a reflux reaction is carried out under stirring. After the reaction for 4-6 hours, sampling is performed for analysis, and the alkaline hydrolysis reaction is terminated when the o-chlorobenzyl (p-chloro) chloride is ≤0.20%. After the reaction is completed, the o-chlorobenzaldehyde (p-chlorobenzyl) oil phase is separated, and the oil phase is subjected to reduced pressure distillation to obtain the o-chlorobenzaldehyde finished product.

[0012] Preferably, in the hydrolysis reaction, the catalyst used is zinc oxide.

[0013] Preferably, in the hydrolysis reaction, sampling and analysis are performed after the reaction is completed. When the content of the impurity o-(p-)chlorobenzyl alcohol in the o-(p-)chlorobenzylaldehyde hydrolyzate product is ≥0.2%, the next step of conversion reaction is carried out, otherwise, the reduced pressure distillation treatment is directly performed.

[0014] Preferably, after the conversion reaction and alkaline hydrolysis reaction are completed, water washing and separation are carried out, excess water is added to the product and stirred for washing for 30-45 minutes, and the product is allowed to stand for not less than 1 hour. After the oil and water are separated, the oil phase is extracted to separate the o-(p-)chlorobenzaldehyde and enter the next step of the process.

[0015] Preferably, after the alkaline hydrolysis reaction, the separated water phase is sent to a sewage treatment workshop, and o-(p-)chlorobenzoic acid is recovered by acid precipitation and centrifugation.

[0016] Preferably, in the alkaline hydrolysis reaction, after separating the o-chlorobenzaldehyde (p-chlorobenzaldehyde) oil phase, the oil phase is first washed with water for a second time for separation, and then subjected to reduced pressure distillation.

[0017] Preferably, in the alkaline hydrolysis reaction, the soda ash solution added is a soda ash solution with a weight fraction of 15-20%.

[0018] The technical principle of the invention is as follows: o-(p-)chlorobenzyl alcohol, an impurity in an o-(p-)chlorobenzylaldehyde product, is converted into o-(p-)chloromonobenzyl chloride by using a Lucas reagent, and then a catalyst triethylamine is added in an alkaline hydrolysis process to complex the o-(p-)chloromonobenzyl chloride into a water-soluble quaternary ammonium salt, thereby converting the impurities into water-soluble components, and then the impurities can be removed by oil-water separation, and finally the o-(p-)chlorobenzylaldehyde product is refined and purified by reduced pressure distillation.

[0019] The corresponding chemical reaction principle equation is as follows:

[0020] C6H4Cl—CH2OH+ZnCl2(HCl)=C6H4Cl—CH2Cl+H2O

[0021] (o-chlorobenzyl alcohol) + (Lucas reagent) = (o-chlorobenzyl chloride)

[0022] C6H4Cl—CH2Cl+N(CH2CH3)3=C6H4Cl—CH2N(CH2CH3)3Cl

[0023] (o-chlorobenzyl chloride) + (triethylamine) = (benzyltriethylammonium chloride)

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. In the present invention, the steps of conversion reaction and alkaline hydrolysis reaction are added after the traditional o-(p-)chlorobenzylaldehyde hydrolysis preparation process, firstly, the o-(p-)chlorobenzyl alcohol impurity in the o-(p-)chlorobenzylaldehyde product is converted into o-(p-)chloromonochlorobenzyl by Lucas reagent, and then the o-(p-)chloromonochlorobenzyl is complexed with triethylamine in an alkaline environment to form a water-soluble quaternary ammonium salt, thereby realizing the process of converting fat-soluble impurity components into water-soluble components, and then the impurities can be removed by oil-water separation, and finally the o-(p-)chlorobenzylaldehyde product is refined and purified by reduced pressure distillation, thereby greatly improving the purity of the prepared o-(p-)chlorobenzylaldehyde product and obtaining a high-quality product;

[0026] 2. The alkaline hydrolysis reaction carried out in the present invention can also react o-(p-)chlorobenzoic acid into sodium o-(p-)chlorobenzoate, which is also a water-soluble component, thereby removing a small amount of o-(p-)chlorobenzoic acid impurities generated by oxidation of o-(p-)chlorobenzaldehyde during the reaction, further improving the purity of the product. At the same time, the generated o-(p-)chlorobenzoic acid is recovered, reducing the amount of raw materials used and improving the economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0029] Embodiment 1:

[0030] This embodiment includes the following steps:

[0031] Hydrolysis reaction:

[0032] The crude benzyl dichloride product after distillation and purification is pumped from the liquid tank of the distillation tower bottom to the benzyl dichloride high-level tank, and then put into the hydrolysis kettle through the feed, and then 0.15%wt of zinc oxide is added as a catalyst, stirring is started, the cooling water of the condenser is turned on, the temperature is raised to 120-130°C, and then the outlet valve of the water high-level tank is opened, and water is continuously added dropwise by metering. When the content of benzyl dichloride is ≤0.2%, the hydrolysis is stopped, and the temperature is lowered to not higher than 80°C; after the reaction is completed, sampling and analysis are carried out. When the content of the impurity ortho-chlorobenzyl alcohol in the ortho-chlorobenzaldehyde hydrolyzate product is ≥0.2%, it is an unqualified product and is transferred to the next step of conversion reaction. Otherwise, it is a qualified product and is directly subjected to reduced pressure distillation treatment.

[0033] A total of 3.6 tons of unqualified o-chlorobenzaldehyde were detected, of which the content of o-chlorobenzyl alcohol was 0.50%wt.

[0034] Conversion reaction:

[0035] Prepare Lucas reagent by mixing 150 kg of zinc chloride and 130 kg of 30% hydrochloric acid.

[0036] The Lucas reagent is added to the o-chlorobenzaldehyde hydrolyzate product, stirred at a temperature of 80-100°C, kept warm for 3 hours, and sampled for analysis. When o-chlorobenzyl alcohol is ≤0.20%, the conversion reaction is terminated, and the o-chlorobenzaldehyde oil phase is separated. After the reaction is completed, water washing and separation are carried out. 1 ton of water is added to the product and stirred for 30 minutes, and then it is allowed to stand for 1 hour. After the oil and water are separated, the oil phase is extracted to separate the o-chlorobenzaldehyde and enter the next process.

[0037] Sampling and analysis showed that the content of o-chlorobenzyl alcohol was 0.12%wt.

[0038] Alkaline hydrolysis reaction:

[0039] Use 200 kg of soda ash and add water to make a 15% aqueous solution (PH = 8-9).

[0040] To the o-chlorobenzaldehyde oil phase obtained by the conversion reaction, a soda solution and 7 kg of triethylamine were quantitatively added, the reaction temperature was controlled at 90-100° C., and a reflux reaction was carried out under stirring. After reacting for 4 hours, samples were taken for analysis. When the o-chlorobenzyl chloride content was ≤0.20%, the alkaline hydrolysis reaction was terminated.

[0041] Sampling and analysis showed that the content of o-chlorobenzyl chloride was 0.10%wt.

[0042] Separation and purification:

[0043] After the reaction is completed, the product is washed and separated. 1 ton of water is added to the product and stirred and washed for 30 minutes. After standing for 1 hour, after the oil and water are separated, the oil phase is extracted to separate the o-chlorobenzaldehyde, and the oil phase is washed and separated twice in the same way, and then the oil phase is subjected to reduced pressure distillation to obtain the o-chlorobenzaldehyde product. The separated water phase is sent to the sewage treatment workshop, and o-chlorobenzoic acid is recovered by acid precipitation centrifugation.

[0044] The purity of the finally obtained o-chlorobenzaldehyde product is 99.75%.

[0045] Embodiment 2:

[0046] This embodiment includes the following steps:

[0047] Hydrolysis reaction:

[0048] The crude dichlorobenzyl product after distillation and purification is pumped from the liquid tank of the distillation tower bottom to the dichlorobenzyl high-level tank, and then put into the hydrolysis kettle through the feed, and then 0.2% of zinc oxide is added as a catalyst, stirring is started, the cooling water of the condenser is turned on, the temperature is raised to 120-130° C., and then the outlet valve of the water high-level tank is opened, and water is continuously added dropwise by metering. When the content of dichlorobenzyl is ≤0.2%, the hydrolysis is stopped, and the temperature is lowered to not higher than 80° C. After the reaction is completed, sampling and analysis are carried out. When the content of the impurity o-chlorobenzyl alcohol in the o-chlorobenzaldehyde hydrolyzate product is ≥0.2%, it is an unqualified product and is transferred to the next step of conversion reaction. Otherwise, it is a qualified product and is directly subjected to reduced pressure distillation treatment.

[0049] A total of 3.6 tons of unqualified o-chlorobenzaldehyde were detected, of which the content of o-chlorobenzyl alcohol was 0.75%wt.

[0050] Conversion reaction:

[0051] Prepare Lucas reagent by mixing 150 kg of zinc chloride and 130 kg of 30% hydrochloric acid.

[0052] The Lucas reagent was added to the o-chlorobenzaldehyde hydrolyzate product, stirred at a temperature of 80-100°C, kept warm for 4 hours, and sampled for analysis. When o-chlorobenzyl alcohol was ≤0.20%, the conversion reaction was terminated, and the o-chlorobenzaldehyde oil phase was separated. After the reaction was completed, water washing and separation was performed. 1 ton of water was added to the product and stirred for 35 minutes, and then allowed to stand for 1.5 hours. After the oil and water were separated, the oil phase was extracted to separate the o-chlorobenzaldehyde and enter the next process.

[0053] Sampling and analysis showed that the content of o-chlorobenzyl alcohol was 0.15%wt.

[0054] Alkaline hydrolysis reaction:

[0055] Use 200 kg of soda ash and add water to make an 18% aqueous solution (PH = 9-11).

[0056] To the o-chlorobenzaldehyde oil phase obtained by the conversion reaction, a soda solution and 7 kg of triethylamine were quantitatively added, the reaction temperature was controlled at 90-100° C., and a reflux reaction was carried out under stirring. After the reaction lasted for 5 hours, samples were taken for analysis. When the o-chlorobenzyl chloride content was ≤0.20%, the alkaline hydrolysis reaction was terminated.

[0057] Sampling and analysis showed that the content of o-chlorobenzyl chloride was 0.10%wt.

[0058] Separation and purification:

[0059] After the reaction is completed, the product is washed and separated. 1 ton of water is added to the product and stirred and washed for 35 minutes. After standing for 1.5 hours, the oil phase is extracted to separate the o-chlorobenzaldehyde, and the oil phase is washed and separated twice, and then the oil phase is subjected to reduced pressure distillation to obtain the o-chlorobenzaldehyde product. The separated water phase is sent to the sewage treatment workshop, and o-chlorobenzoic acid is recovered by acid precipitation centrifugation.

[0060] The purity of the finally obtained o-chlorobenzaldehyde product is 99.60%.

[0061] Embodiment 3:

[0062] This embodiment includes the following steps:

[0063] Hydrolysis reaction:

[0064] The crude benzyl dichloride product after distillation and purification is pumped from the liquid tank of the distillation tower bottom to the benzyl dichloride high-level tank, and then put into the hydrolysis kettle through the feed, and then 0.3% of zinc oxide is added as a catalyst, stirring is started, the cooling water of the condenser is turned on, the temperature is raised to 120-130° C., and then the outlet valve of the water high-level tank is opened, and water is continuously added dropwise by metering. When the content of benzyl dichloride is ≤0.2%, the hydrolysis is stopped, and the temperature is lowered to not higher than 80° C. After the reaction is completed, sampling and analysis are carried out. When the content of impurity p-chlorobenzyl alcohol in the p-chlorobenzaldehyde hydrolyzate product is ≥0.2%, it is an unqualified product and is transferred to the next step of conversion reaction. Otherwise, it is a qualified product and is directly subjected to reduced pressure distillation treatment.

[0065] A total of 3.5 tons of unqualified p-chlorobenzaldehyde were detected, of which the content of p-chlorobenzyl alcohol was 0.60%wt.

[0066] Conversion reaction:

[0067] Prepare Lucas reagent by mixing 150 kg of zinc chloride and 130 kg of 30% hydrochloric acid.

[0068] The Lucas reagent is added to the p-chlorobenzaldehyde hydrolyzate product, stirred at a temperature of 80-100°C, kept warm for 5 hours, and sampled for analysis. When p-chlorobenzyl alcohol is ≤0.20%, the conversion reaction is terminated, and the p-chlorobenzaldehyde oil phase is separated. After the reaction is completed, it is washed and separated. 1 ton of water is added to the product and stirred and washed for 45 minutes, and then allowed to stand for 1 hour. After the oil and water are separated, the oil phase is extracted to separate the p-chlorobenzaldehyde and enter the next process.

[0069] Sampling and analysis showed that the content of p-chlorobenzyl alcohol was 0.10%wt.

[0070] Alkaline hydrolysis reaction:

[0071] Use 200 kg of soda ash and add water to prepare a 20% aqueous solution (PH = 10-12).

[0072] To the p-chlorobenzaldehyde oil phase obtained by the conversion reaction, a soda solution and 7 kg of triethylamine were quantitatively added, the reaction temperature was controlled at 90-100°C, and a reflux reaction was carried out under stirring. After the reaction for 6 hours, samples were taken for analysis. When p-chlorobenzyl chloride was ≤0.20%, the alkaline hydrolysis reaction was terminated.

[0073] Sampling and analysis showed that the content of p-chlorobenzyl chloride was 0.08%wt.

[0074] Separation and purification:

[0075] After the reaction is completed, the product is washed and separated. 1 ton of water is added to the product and stirred and washed for 45 minutes. After standing for 1 hour, the oil phase is extracted to separate the p-chlorobenzaldehyde after the oil and water are separated. The oil phase is washed and separated twice, and then the oil phase is subjected to reduced pressure distillation to obtain the p-chlorobenzaldehyde product. The separated water phase is sent to the sewage treatment workshop, and p-chlorobenzoic acid is recovered by acid precipitation centrifugation.

[0076] The purity of the finally obtained p-chlorobenzaldehyde product is 99.70%.

[0077] Embodiment 4:

[0078] This embodiment includes the following steps:

[0079] Hydrolysis reaction:

[0080] The crude benzyl dichloride product after distillation and purification is pumped from the liquid tank of the distillation tower bottom to the benzyl dichloride high-level tank, and then put into the hydrolysis kettle through the feed, and then 0.15% of zinc oxide is added as a catalyst, stirring is started, the cooling water of the condenser is turned on, the temperature is raised to 120-130° C., and then the outlet valve of the water high-level tank is opened, and water is continuously added dropwise by metering. When the content of benzyl dichloride is ≤0.2%, the hydrolysis is stopped, and the temperature is lowered to not higher than 80° C. After the reaction is completed, sampling and analysis are carried out. When the content of impurity p-chlorobenzyl alcohol in the p-chlorobenzaldehyde hydrolyzate product is ≥0.2%, it is an unqualified product and is transferred to the next step of conversion reaction. Otherwise, it is a qualified product and is directly subjected to reduced pressure distillation treatment.

[0081] A total of 3.6 tons of unqualified p-chlorobenzaldehyde were detected, of which the content of p-chlorobenzyl alcohol was 1.0%wt.

[0082] Conversion reaction:

[0083] Prepare Lucas reagent by mixing 150 kg of zinc chloride and 130 kg of 30% hydrochloric acid.

[0084] The Lucas reagent is added to the p-chlorobenzaldehyde hydrolyzate product, stirred at a temperature of 80-100°C, kept warm for 4 hours, and sampled for analysis. When p-chlorobenzyl alcohol is ≤0.20%, the conversion reaction is terminated, and the p-chlorobenzaldehyde oil phase is separated. After the reaction is completed, water washing and separation are performed, 1 ton of water is added to the product and stirred for 30 minutes, and then allowed to stand for 1 hour. After the oil and water are separated, the oil phase is extracted to separate the p-chlorobenzaldehyde and enter the next process.

[0085] Sampling and analysis showed that the content of p-chlorobenzyl alcohol was 0.10%wt.

[0086] Alkaline hydrolysis reaction:

[0087] Use 200 kg of soda ash and add water to make a 15% aqueous solution (PH = 8-9).

[0088] To the p-chlorobenzaldehyde oil phase obtained by the conversion reaction, a soda solution and 7 kg of triethylamine were quantitatively added, the reaction temperature was controlled at 90-100°C, and a reflux reaction was carried out under stirring. After reacting for 4 hours, samples were taken for analysis. When p-chlorobenzyl chloride was ≤0.20%, the alkaline hydrolysis reaction was terminated.

[0089] Sampling and analysis showed that the content of p-chlorobenzyl chloride was 0.10%wt.

[0090] Separation and purification:

[0091] After the reaction is completed, the product is washed and separated. 1 ton of water is added to the product and stirred and washed for 30 minutes. After standing for 1 hour, the oil phase is extracted to separate the p-chlorobenzaldehyde after the oil and water are separated. The oil phase is washed and separated twice, and then the oil phase is subjected to reduced pressure distillation to obtain the p-chlorobenzaldehyde product. The separated water phase is sent to the sewage treatment workshop, and p-chlorobenzoic acid is recovered by acid precipitation centrifugation.

[0092] The purity of the finally obtained p-chlorobenzaldehyde product is 99.65%.

[0093] The parameters of the products prepared in the above examples are shown in Table 1:

[0094]

[0095] Table 1

[0096] As can be seen from the background technology, the purity of the o-(p-)chlorobenzaldehyde product in the prior art is less than 99.5%. At the same time, as can be seen from Table 1, the final purity of the product in all embodiments of the present invention is not less than 99.60%, which fully illustrates the effectiveness of the purification process.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A process for removing the impurity o-,p-chlorobenzyl alcohol in o-,p-chlorobenzaldehyde products, characterized in that: The steps include: Hydrolysis reaction: put the crude dichlorobenzyl raw material after distillation and purification into the hydrolysis kettle, add 0.15%-0.3% of the catalyst by mass, stir well, and heat to 120-130°C, continuously add water by metering, stop the hydrolysis when the content of dichlorobenzyl is ≤0.2%, and cool to no more than 80°C; Conversion reaction: quantitatively add the prepared Lucas reagent into the o-, p-chlorobenzyl alcohol hydrolyzate product in a molar ratio of 1:1, stir at a temperature of 80-100°C, keep warm for 3-5 hours, take samples for analysis, and terminate the conversion reaction when the o-, p-chlorobenzyl alcohol is ≤0.20%, and separate the o-, p-chlorobenzaldehyde oil phase; Alkaline hydrolysis reaction: add soda solution and excess triethylamine to the o-, p-chlorobenzaldehyde oil phase obtained by the conversion reaction, control the reaction temperature to 90-100°C, and perform reflux reaction under stirring. After reacting for 4-6 hours, take samples for analysis. When o-, p-chlorobenzyl chloride is ≤0.20%, the alkaline hydrolysis reaction is terminated. After the reaction is completed, separate the o-, p-chlorobenzaldehyde oil phase, and then perform reduced pressure distillation on the oil phase to obtain the o-, p-chlorobenzaldehyde finished product.

2. A process for removing the impurity o-, p-chlorobenzyl alcohol in o-, p-chlorobenzaldehyde products as claimed in claim 1, characterized in that: In the hydrolysis reaction, the catalyst used is zinc oxide.

3. A process for removing the impurity o-, p-chlorobenzyl alcohol in o-, p-chlorobenzaldehyde product as claimed in claim 1, characterized in that: In the hydrolysis reaction, sampling and analysis are performed after the reaction is completed. When the content of the impurity o-,p-chlorobenzyl alcohol in the o-,p-chlorobenzylaldehyde hydrolyzate product is ≥0.2%, the next step of conversion reaction is carried out, otherwise, the reduced pressure distillation treatment is directly performed.

4. A process for removing the impurity o-, p-chlorobenzyl alcohol in o-, p-chlorobenzaldehyde product as claimed in claim 1, characterized in that: After the conversion reaction and alkaline hydrolysis reaction are completed, water washing and separation are carried out. Excess water is added to the product and stirred for washing for 30-45 minutes, and it is allowed to stand for not less than 1 hour. After the oil and water are separated, the oil phase is extracted to separate the o- and p-chlorobenzaldehyde to enter the next process.

5. A process for removing the impurity o-,p-chlorobenzyl alcohol in o-,p-chlorobenzaldehyde product as claimed in claim 1, characterized in that: After the alkaline hydrolysis reaction, the separated water phase is sent to a sewage treatment workshop, and the o- and p-chlorobenzoic acid are recovered by acid precipitation and centrifugation.

6. A process for removing the impurity o-, p-chlorobenzyl alcohol in o-, p-chlorobenzaldehyde product as claimed in claim 1, characterized in that: In the alkaline hydrolysis reaction, after the o- and p-chlorobenzaldehyde oil phase is separated, the oil phase is firstly washed and separated twice with water, and then subjected to reduced pressure distillation.

7. A process for removing the impurity o-, p-chlorobenzyl alcohol in o-, p-chlorobenzaldehyde product as claimed in claim 1, characterized in that: In the alkaline hydrolysis reaction, the added soda ash solution is a soda ash solution with a weight fraction of 15-20%.

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