A method for recycling carbide slag to produce neopentyl glycol and calcium formate

Abstract

The present invention provides a production method for recycling carbide slag to produce neopentyl glycol and calcium formate. The method uses carbide slag slurry containing calcium hydroxide solution, which is made from carbide slag produced by the acetylene method for producing PVC, as a catalyst and adds it to the condensation reaction for preparing neopentyl glycol using isobutyraldehyde and formaldehyde as raw materials. The present invention uses a large amount of solid waste carbide slag containing calcium hydroxide produced by the acetylene method for producing PVC as a catalyst for the disproportionation method, solving the problem of difficult utilization of carbide slag. At the same time, it solves the problem that when directly adding calcium hydroxide solution as a catalyst, calcium formate wall sticking is likely to occur. The solid formed by calcium formate wall sticking has the characteristics of strong adhesion and compactness, which is difficult to clean. The cleaning cost is high and it is easy to cause equipment blockage and shutdown. In severe cases, the equipment cannot be cleaned and is abandoned. In addition, by adding a crystal form finishing agent to the condensation reaction solution, the crystallization mode of calcium formate and the size of crystallization particles can be changed, improving the purity and quality of calcium formate and neopentyl glycol.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical production, and particularly relates to a method for recycling carbide slag to produce neopentyl glycol and calcium formate. Background Art

[0002] Neopentyl glycol C5H 12 O2 is an organic compound commonly used in the synthesis production processes of chemical fibers, coatings, lubricants, etc. The currently commonly used production method uses formaldehyde and isobutyraldehyde as raw materials, undergoes condensation under the catalysis of an alkali to obtain hydroxy-tert-butyl aldehyde, and is reduced to neopentyl glycol with excessive formaldehyde under strong alkali conditions, while formaldehyde is oxidized and reacts with the alkali to form formate. Chinese Patent CN105175228B discloses a process for preparing neopentyl glycol by the calcium method, which uses isobutyraldehyde and formaldehyde as raw materials, uses industrial-grade calcium hydroxide as a catalyst, and prepares neopentyl glycol through condensation, evaporation, and distillation processes, improving the conversion rate of neopentyl glycol and the purity of by-products. However, it is found that when preparing neopentyl glycol by the calcium method, the by-product calcium formate is prone to wall caking, causing equipment blockage, and in severe cases, directly causing a shutdown, seriously restricting the production efficiency of neopentyl glycol; at the same time, how to separate impurities in the reaction raw materials, reaction by-products from the neopentyl glycol product is also one of the main restricting factors.

[0003] Carbide slag is a waste generated during the preparation of PVC by the acetylene method. Its main component is calcium hydroxide, and the impurities are mainly various metal oxides such as silicon and aluminum. The large amount of calcium hydroxide contained therein can be used as a catalyst in the reaction for preparing neopentyl glycol and oxidize formaldehyde to react to form calcium formate, reducing the production cost of neopentyl glycol. However, the carbide slag has a large amount of impurities and complex impurity types, making it difficult to effectively separate from the product. At the same time, the crystal form of the generated calcium formate is difficult to control, seriously affecting the effective separation of calcium formate and neopentyl glycol. Therefore, how to use the effective components in carbide slag to prepare high-quality calcium formate and neopentyl glycol and separate the impurities from each product has become an urgent problem to be solved. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for recycling carbide slag to produce neopentyl glycol and calcium formate. This method produces neopentyl glycol and calcium formate by recycling calcium hydroxide in carbide slag, reducing the production cost and reducing the waste of effective components in carbide slag.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A method for recycling carbide slag to produce neopentyl glycol and calcium formate specifically includes the following steps:

[0007] S1: Dilute the carbide slag with water to form a carbide slag slurry with a pH value of 10 - 12;

[0008] S2: Add formaldehyde and carbide slag slurry into the reactor at one time, mix them evenly, add formaldehyde polysaccharide inhibitor, and then add isobutyraldehyde evenly according to the reaction time, and react at 25-48°C for 2-5h to obtain a condensate;

[0009] S3: Add the composite crystal finishing agent to the condensed liquid, stir and disperse at 20-40°C for 0.5-2h to obtain a mixed liquid; then filter after sufficient precipitation to obtain a filter residue and a clear liquid;

[0010] S4: filtering the filter residue for a second time, recovering the secondary filtrate and mixing it with the clear liquid, and then distilling it to obtain a preliminary distillate; the product after distillation is filtered to obtain a crude calcium formate product and a filtrate;

[0011] S5: washing the obtained crude calcium formate with 50-100° C. water, and drying at 100-120° C. for 1-5 hours to obtain a finished calcium formate; mixing the filtrate with the preliminary distillate, distilling it again, and then cooling and crystallizing to obtain a finished neopentyl glycol.

[0012] Preferably, the carbide slag described in step S1 has a particle size of 150-300 mesh and a content of 70%-80%, and a calcium hydroxide content of 50%-60%; the mass ratio of carbide slag to water is 1:(2-10).

[0013] Preferably, the mass ratio of the carbide slag slurry to isobutyraldehyde in step S2 is (0.5-5):1, and the molar ratio of formaldehyde to isobutyraldehyde is (2.5-4.5):1.

[0014] Preferably, the formose inhibitor in step S2 is manganese molybdate, and the dosage is 5-15 ppm based on the mass of the formaldehyde solution.

[0015] Preferably, the composite crystal finishing agent in step S3 is composed of the following raw materials counted by total mass fraction 100%: 20%-30% sodium alkylbenzene sulfonate, 10%-20% sodium polyacrylate, 20%-30% organosilicon, and 30%-40% water; preferably, the organosilicon is polydimethylsiloxane, cyclic (CH3) 10 Si5O5 or linear (CH3) 12 Si5O4.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The large amount of solid waste calcium hydroxide carbide slag produced by the acetylene process for producing PVC is recycled, which reduces the pollution of the environment by the strong alkaline waste liquid in the carbide slag. At the same time, the sulfide and phosphide contained in the carbide slag can be separated and recycled, which reduces the difficulty of treating the carbide slag. In addition, the calcium hydroxide in the carbide slag is used in the production of neopentyl glycol and calcium formate, and hundreds of millions of tons of carbide slag can be used and treated every year, which will produce huge benefits.

[0018] 2. By adding a formose inhibitor during the reaction process, the glycation reaction of formaldehyde is inhibited. At the same time, the formose inhibitor can also inhibit the reaction between impurity aluminum in carbide slag and raw materials to generate aluminum salt impurities, reducing the impurity content in neopentyl glycol. Meanwhile, it can greatly alleviate the wall - sticking phenomenon of calcium formate and avoid blockage.

[0019] 3. By adding a composite crystal form finishing agent to the condensation liquid, the particle size of calcium formate crystals can be increased from 50 - 90 mesh to 40 - 60 mesh. The crystal grains are larger and the particle size is more stable, reducing the separation difficulty between calcium formate and neopentyl glycol. The content of neopentyl glycol in calcium formate and the preliminary distillate is increased from about 75% to about 98% and 96% respectively. At the same time, the whiteness of the calcium formate finished product is increased from 50% - 70% to more than 85%, improving the economic value of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the reaction process of the present invention.

[0021] Figure 2 It is a comparison diagram of the wall - hanging situation on the inner wall of the calcium formate bottle when the formose inhibitor is not added and when it is added in Example 1. In the figure, a is the wall - hanging situation when the formose inhibitor is not added, and b is the wall - hanging situation when the formose inhibitor is added. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] In the embodiment of the present invention, the carbide slag is from the chlor - alkali branch of Hubei Yihua Chuxing Co., Ltd. Its main component is calcium hydroxide, with a content of 57.4%. The mass fraction of carbide slag with a particle size of 150 - 300 mesh is 77.6%, the mass fraction less than 150 mesh is 13.6%, and the mass fraction greater than 300 mesh is 8.8%.

[0024] Example 1

[0025] A method for recycling carbide slag to produce neopentyl glycol and calcium formate specifically includes the following steps:

[0026] S1: Add 4 times the mass of water to the carbide slag and dilute it into a paste to prepare a carbide slag slurry containing calcium hydroxide;

[0027] S2: Add a formaldehyde polysaccharide inhibitor at 10 ppm to a 160 g / L formaldehyde solution, and add the carbide slag slurry obtained in step S1. After mixing evenly, add isobutyraldehyde to the solution uniformly according to a reaction time of 120 min, control the reaction temperature at 40 °C, and obtain a condensation liquid after the reaction; the molar ratio of formaldehyde to isobutyraldehyde in the feed is 3.5:1, the mass ratio of carbide slag to isobutyraldehyde is 4:1, and the formaldehyde polysaccharide inhibitor is manganese molybdate;

[0028] S3: Subject the condensation liquid to precipitation and filtration to obtain a clear liquid and a filter residue;

[0029] S4: Filter the filter residue a second time, recover the filtrate and mix it with the clear liquid in step S3. Distill the mixed clear liquid at 70 °C to obtain a preliminary distillate, and then subject the distilled product to suction filtration to obtain a crude calcium formate product and a filtrate;

[0030] S5: Wash the crude calcium formate product obtained in step S4 with deionized water at 60 °C, and then dry it for 4 h to obtain a finished calcium formate product; mix the filtrate and the preliminary distillate obtained in step S4, then distill at 70 °C, and then cool and crystallize to obtain a finished neopentyl glycol product.

[0031] In step S2, no formaldehyde polysaccharide inhibitor is added as a control to compare the wall - sticking situation on the inner wall of the bottle during the distillation of calcium formate.

[0032] As Figure 2 shown, Figure 2 a in the figure is the situation where no formaldehyde polysaccharide inhibitor is added during distillation. It is found that calcium formate adheres significantly to the inner wall of the bottle. b is the situation where a 10 ppm formaldehyde polysaccharide inhibitor is added during distillation. It is found that the wall - sticking phenomenon of calcium formate is significantly improved, and almost no wall - sticking phenomenon occurs.

[0033] Example 2

[0034] On the basis of Example 1, under the conditions that the concentration of the formaldehyde solution in step S2 is 160 g / L and the molar ratio of formaldehyde to isobutyraldehyde in the feed is 3.5:1, compare the content of neopentyl glycol and the content of impurities in the preliminary distillate with and without adding a formaldehyde polysaccharide inhibitor; the formaldehyde polysaccharide inhibitor is manganese molybdate, and the impurities are formaldehyde saccharides (hexose - like substances) and aluminum salts (carried by the carbide slag).

[0035] Table 1 Influence of formaldehyde polysaccharide inhibitor on the content of neopentyl glycol

[0036] Item Content of neopentyl glycol in the preliminary distillate (%) Impurity content (%) Adding formaldehyde glycan inhibitor 96.5 3.5 Without adding formaldehyde glycan inhibitor 91.6 8.4

[0037] As can be seen from Table 1, under the same conditions, when a formose inhibitor is added during the reaction process, the impurity content in the neopentyl glycol product in the preliminary distillate is 3.5%, and the impurity content without adding the formose inhibitor is 8.4%, a year-on-year decrease of 4.9%. This indicates that during the production of neopentyl glycol and calcium formate using carbide slag, the formose inhibitor can significantly reduce the impurity content in the neopentyl glycol product in the preliminary distillate and increase the content of neopentyl glycol in the preliminary distillate.

[0038] Example 3

[0039] On the basis of Example 1, control the concentration of the formaldehyde solution to be 160 g / L, the molar ratio of formaldehyde to isobutyraldehyde in the feed to be 3.5:1, and the mass ratio of carbide slag to isobutyraldehyde to be 3:1. Add a composite crystal form finishing agent to the condensation liquid obtained in step S2, then stir and disperse to obtain a mixed liquid, and then perform filtration, distillation, etc. on the mixed liquid to obtain calcium formate finished product and neopentyl glycol finished product, and change the ratio of the composite crystal form finishing agent to affect the content of calcium formate finished product and neopentyl glycol finished product in the preliminary distillate.

[0040] Example 3-1: Add a composite crystal form finishing agent prepared from 20% sodium alkylbenzene sulfonate, 15% sodium polyacrylate, 30% polydimethylsiloxane and 35% water to the condensation liquid obtained in step S2, with a dosage of 20 ppm of the calcium formate content. The mixture is stirred and dispersed at 30 °C for 1 h to obtain a mixed liquid; then the mixed liquid is filtered twice to obtain a clear liquid, and the clear liquid is distilled in a vacuum system at 60 °C, and the calcium formate crude product, filtrate and preliminary distillate are obtained by suction filtration; then the calcium formate crude product is washed with deionized water at 80 °C and then dried at 120 °C for 2 h to obtain a calcium formate finished product with a particle size between 40 and 60 mesh and a whiteness of more than 85%; the preliminary distillate and the filtrate are mixed and then distilled and cooled to crystallize to obtain a neopentyl glycol finished product.

[0041] Example 3-2: Add a composite crystal form finishing agent prepared from 30% sodium alkylbenzene sulfonate, 20% sodium polyacrylate, 20% cyclic (CH3) 10 Si5O5H and 30% water to the condensation liquid obtained in step S2, with a dosage of 20 ppm of the calcium formate content. The mixture is stirred and dispersed at 40 °C for 1 h to obtain a mixed liquid; then the mixed liquid is filtered twice to obtain a clear liquid, and the clear liquid is distilled in a vacuum system at 65 °C, and the calcium formate crude product, filtrate and preliminary distillate are obtained by suction filtration; then the calcium formate crude product is washed with deionized water at 85 °C and then dried at 120 °C for 2 h to obtain a calcium formate finished product with a particle size between 40 and 60 mesh and a whiteness of more than 85%; the preliminary distillate and the filtrate are mixed and then distilled and cooled to crystallize to obtain a neopentyl glycol finished product.

[0042] Example 3-3: Add a composite crystal form finishing agent prepared from 30% sodium alkylbenzene sulfonate, 10% sodium polyacrylate, 30% linear (CH3) 12 Si5O4 and 30% water to the condensation liquid obtained in step S2, with a dosage of 20 ppm of the calcium formate content. The mixture is stirred and dispersed at 40 °C for 1 h to obtain a mixed liquid; then the mixed liquid is filtered twice to obtain a clear liquid, and the clear liquid is distilled in a vacuum system at 65 °C, and suction filtration is carried out to obtain crude calcium formate, filtrate and preliminary distillate; then the crude calcium formate is washed with deionized water at 85 °C and then dried at 120 °C for 2 h to obtain a finished calcium formate product with a particle size between 40 and 60 mesh and a whiteness of more than 85%; the preliminary distillate and the filtrate are mixed and then distilled and cooled to crystallize to obtain a finished neopentyl glycol product.

[0043] Comparative Example 1: Do not add the composite crystal form finishing agent to the condensation liquid obtained in step S2, directly filter, mix the clear liquid obtained by secondary filtration for distillation and suction filtration to obtain crude calcium formate, filtrate and preliminary distillate; wash the crude calcium formate with deionized water at 85 °C, and then dry at 120 °C for 2 h to obtain a finished calcium formate product with a particle size between 50 and 90 mesh and a whiteness between 50% and 70%; the preliminary distillate and the filtrate are mixed and then distilled and cooled to crystallize to obtain a finished neopentyl glycol product.

[0044] Comparative Example 2: Add a crystal form finishing agent prepared from 30% sodium alkylbenzene sulfonate and 70% water to the condensation liquid obtained in step S2, with a dosage of 20 ppm of the calcium formate content. The other steps are the same as in Example 3-2. The prepared finished calcium formate product has a particle size of 50-70 mesh and a whiteness of 70%-80%.

[0045] Comparative Example 3: Add a crystal form finishing agent prepared from 20% sodium polyacrylate and 80% water to the condensation liquid obtained in step S2, with a dosage of 20 ppm of the calcium formate content. The other steps are the same as in Example 3-2. The prepared finished calcium formate product has a particle size of 60-80 mesh and a whiteness of 70%-90%.

[0046] Comparative Example 4: Add 40% linear (CH3) 12 Si5O4 and 60% water to the condensation liquid obtained in step S2, with a dosage of 20 ppm of the calcium formate content. The other steps are the same as in Example 3-2. The prepared finished calcium formate product has a particle size of 50-80 mesh and a whiteness of 60%-85%.

[0047] Table 2 Influence of the composite crystal form finishing agent on the calcium formate and neopentyl glycol contents

[0048] Item Content of calcium formate Content of neopentyl glycol in the preliminary distillate Example 3-1 98.5％ 95.2％ Example 3-2 98.8％ 95.4％ Example 3-3 98.7％ 95.1％ Comparative Example 1 66.8％ 63.8％ Comparative Example 2 80.2％ 78.6％ Comparative Example 3 79.6％ 80.3％ Comparative Example 4 80.9％ 79.4％

[0049] As can be seen from Table 2, using composite crystal form finishing agents with different ratios has little effect on the content of calcium formate and the content of neopentyl glycol in the calcium formate finished product. The content of calcium formate remains above 98.5%, and the content of neopentyl glycol is above 95%. However, adding the composite crystal form finishing agent and not adding it have a greater impact on the calcium formate content and neopentyl glycol content. When the crystal form finishing agent is not added, the content of calcium formate decreases significantly, only being 66.8%, and the content of neopentyl glycol decreases to 63.8%. In addition, the particle size of the obtained calcium formate finished product has a large gap and low whiteness. At the same time, using sodium polyacrylate, sodium alkylbenzene sulfonate, and silicone ((CH3) 12 Si5O4) as crystal form finishing agents respectively for the preparation of calcium formate, it is found that the particle size of the obtained calcium formate increases to a certain extent, and the whiteness also increases. At the same time, the content of neopentyl glycol in calcium formate and the preliminary distillate is significantly increased compared with when the crystal form finishing agent is not added, but there is still a large difference compared with the content of calcium formate and neopentyl glycol after adding the composite crystal form finishing agent. In summary, the compounding of sodium polyacrylate, sodium alkylbenzene sulfonate, silicone and water can synergistically control the crystal form of calcium formate, jointly increase its whiteness, and help the separation of calcium formate and neopentyl glycol.

[0050] Example 4

[0051] On the basis of Example 1, control the mass ratio of carbide slag to deionized water to be 1:4, control the reaction time to be 100 min, uniformly add isobutyraldehyde to the solution, and change the concentration of the formaldehyde solution and the feeding molar ratio of formaldehyde to isobutyraldehyde to study the influence on the content of neopentyl glycol in the preliminary distillate.

[0052] Table 3 Influence of formaldehyde concentration and feeding molar ratio of formaldehyde to isobutyraldehyde on the content of neopentyl glycol

[0053]

[0054] The results in Table 1 show that when the feeding ratio of formaldehyde to isobutyraldehyde remains unchanged, as the formaldehyde concentration gradually increases from 120 g / L to 160 g / L, the content of neopentyl glycol in the preliminary distillate gradually increases; when the formaldehyde concentration remains unchanged, as the feeding ratio of formaldehyde to isobutyraldehyde gradually increases from 2.5:1 to 4.5:1, the content of neopentyl glycol in the preliminary distillate also gradually increases. Among them, when the formaldehyde concentration is 160 g / L and the feeding ratio of formaldehyde:isobutyraldehyde is 4.5:1, the content of neopentyl glycol in the preliminary distillate is the highest, being 96.5%.

[0055] Example 5

[0056] On the basis of Example 1, control the formaldehyde concentration to be 160 g / L, the molar ratio of formaldehyde:isobutyraldehyde to be 4.5:1, and change the mass ratio of carbide slag to deionized water to study the influence on the content of neopentyl glycol in the preliminary distillate.

[0057] Table 4 Influence of mass ratio of carbide slag to deionized water on content of neopentyl glycol in preliminary distillate

[0058] Calcium carbide slag: deionized water Content of neopentyl glycol in the preliminary distillate (%) 1∶2 93.9 1∶3 95.2 1∶4 96.5 1∶5 96.1 1∶10 94.3

[0059] It can be seen from Table 2 that as the content of carbide slag in deionized water gradually decreases, the content of neopentyl glycol in the preliminary distillate shows a trend of first increasing and then decreasing. Among them, when the mass ratio of carbide slag to deionized water is 1:4, the content of neopentyl glycol in the preliminary distillate is the highest, which is 96.5%.

Claims

1. A method for recycling carbide slag to produce neopentyl glycol and calcium formate, characterized in that: The method includes the following steps: S1: Dilute carbide slag with water to form carbide slag slurry; S2: Add the carbide slag slurry obtained in step S1 to a formaldehyde solution in proportion, and add a formaldehyde polysaccharide inhibitor and isobutyraldehyde, and react to obtain a condensation liquid; S3: Add a composite crystal form finishing agent to the condensation liquid obtained in step S2, and stir and disperse to obtain a mixed liquid; S4: Filter the mixed liquid obtained in step S3 by precipitation to obtain a filter residue and a clear liquid; S5: Filter the filter residue obtained in step S4 for the second time, recover the filtrate and mix it with the clear liquid in S4, and distill the mixed clear liquid to obtain a preliminary distillate; the product after distillation is filtered by suction to obtain crude calcium formate and a filtrate; S6: Wash and dry the crude calcium formate obtained in step S5 to obtain a finished calcium formate product; mix the filtrate and the preliminary distillate obtained in step S5, and then distill and cool and crystallize to obtain neopentyl glycol; The mass ratio of the carbide slag slurry to isobutyraldehyde in step S2 is (0.5 - 5):1, and the molar ratio of formaldehyde to isobutyraldehyde is (2.5 - 4.5):1; The composite crystal form finishing agent in step S3 is composed of the following raw materials counted by the total mass fraction of 100%: 20% - 30% of sodium alkylbenzene sulfonate, 10% - 20% of sodium polyacrylate, 20% - 30% of organosilicon, 30% - 40% of water; The formaldehyde polysaccharide inhibitor in step S2 is manganese molybdate, and the dosage of the formaldehyde polysaccharide inhibitor is 5 - 15 ppm of the mass of formaldehyde; The silicone is polydimethylsiloxane, cyclic (CH3) 10 Si5O5H or linear (CH3) 12 Si5O4.

2. A method for recycling carbide slag to produce neopentyl glycol and calcium formate according to claim 1, characterized in that: The carbide slag in step S1 contains 50% - 60% of calcium hydroxide by mass fraction; the mass ratio of carbide slag to water is 1:(2 - 10).

3. A method for recycling carbide slag to produce neopentyl glycol and calcium formate according to claim 1, characterized in that, The condensation reaction temperature in step S2 is 25 - 48 °C.

4. A method for recycling carbide slag to produce neopentyl glycol and calcium formate according to claim 1, characterized in that, The stirring and dispersing temperature in step S3 is 20 - 40 °C, and the dispersing time is 0.5 - 2 h.

5. A method for recycling carbide slag to produce neopentyl glycol and calcium formate according to claim 1, characterized in that, The heating and distillation temperature in steps S5 and S6 is 40 - 90 °C.

6. A method for recycling carbide slag to produce neopentyl glycol and calcium formate according to claim 1, characterized in that, The water washing temperature in step S6 is 50 - 100 °C, the drying temperature is 100 - 120 °C, and the drying time is 1 - 5 h.

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