Calcium method trimethylolpropane preparation method beneficial to separation of calcium formate and organic matter aqueous solution

Abstract

The invention discloses a calcium-process trimethylolpropane preparation method beneficial to separation of calcium formate and an organic matter aqueous solution. The method comprises the following steps: 1) carrying out condensation reaction on formaldehyde, n-butyraldehyde and calcium hydroxide to obtain a condensation solution; 2) mixing the condensation liquid with acetonitrile according to a volume ratio of 1: 1 to separate out calcium formate with a separation rate of 60%; (3) filtering and separating by a plate frame, and refining a filter cake to prepare a calcium formate product; 4) rectifying the filtrate to remove a solvent and part of water; 5) mixing the filtrate without the solvent with acetonitrile according to a volume ratio of 1: 1, and separating residual calcium formate in the solution; (6) filtering and separating by a plate frame, and refining a filter cake to prepare a calcium formate product; the method has the advantages that distillation and concentration steps are omitted, accordingly, evaporation energy consumption can be reduced, colored impurities generated by distillation and concentration at high temperatures can be prevented, the stability of production systems can be improved, the content of impurity calcium formate in the filtrate after extraction can be reduced, and the method is favorable for improving the extraction yield of the trimethylolpropane.

Description

Technical Field

[0001] The invention relates to the technical field of calcium-based trimethylolpropane preparation methods, and in particular to a calcium-based trimethylolpropane preparation method which is beneficial to the separation of calcium formate and an organic aqueous solution. Background Art

[0002] Trimethylolpropane is usually produced by a calcium condensation process, which produces calcium formate as a by-product. During the production process, calcium formate is crystallized by distilling and concentrating the condensed liquid, and calcium formate is separated from the organic aqueous solution by centrifugal sedimentation. The separated solution is then extracted with isooctyl alcohol, and then separated and refined to obtain trimethylolpropane.

[0003] The existing trimethylolpropane has the following production problems: (1) During the distillation and concentration process, as the temperature rises, other side reactions occur in the condensation liquid, resulting in colored impurities; (2) Calcium formate precipitates during the distillation and concentration process, and the evaporator is easily blocked by calcium formate, requiring regular cleaning, resulting in reduced equipment stability; (3) Due to the presence of organic impurities in calcium formate during the refining process, the calcium formate product has a strong odor and low purity, causing quality problems; (4) A small amount of calcium formate is entrained in the organic aqueous solution, and the calcium salt needs to be thoroughly removed by washing, resulting in a reduced extraction rate of only 65%, a large extraction reflux rate, and poor trimethylolpropane product quality; (5) The entrained calcium formate in the organic phase precipitates in the extraction tower, which is easy to block the extraction tower, affecting the production stability of the equipment.

[0004] Therefore, there is an urgent need in the prior art for a calcium-based trimethylolpropane preparation method that is beneficial to the separation of calcium formate and an organic aqueous solution to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a calcium-based trimethylolpropane preparation method which is beneficial to the separation of calcium formate and an organic aqueous solution.

[0006] The object of the present invention is achieved through the following technical scheme: A calcium-based trimethylolpropane preparation method that is beneficial to the separation of calcium formate and an organic aqueous solution comprises the following steps: 1) Formaldehyde, n-butyraldehyde and calcium hydroxide undergo condensation reaction in a mass ratio of 3.2:1:0.58 to obtain a condensation liquid; 2) The condensation liquid is mixed with acetonitrile in a volume ratio of 1:1 to precipitate calcium formate; 3) Plate and frame filtration separation, the filter cake is refined to prepare calcium formate product; 4) The filtrate is first distilled to remove the solvent and part of the water; 5) The filtrate from which the solvent has been removed is mixed with acetonitrile in a volume ratio of 1:1 to separate the residual calcium formate in the filtrate; 6) Plate and frame filtration separation, the filter cake is refined to prepare calcium formate product; 7) The filtrate is separated into trimethylolpropane product by extraction and distillation.

[0007] The invention adopts acetonitrile as an extractant, and because the hydrophilicity of calcium formate is lower than that of the extractant acetonitrile, the calcium salt in the condensation liquid is rapidly precipitated, and then the calcium formate is separated by plate-frame filtration. The calcium formate is separated by two extractions and plate-frame filtration, and the precipitation rate of the calcium formate reaches 90%.

[0008] The beneficial effects of the present invention are as follows: the present invention does not require a distillation and concentration step, can reduce evaporation energy consumption, avoid colored impurities generated by high temperature distillation and concentration, reduce the content of impurity calcium formate in the solvent after extraction, improve the stability of the production system, and is conducive to improving the extraction efficiency of trimethylolpropane from the liquid phase. DETAILED DESCRIPTION

[0009] The present invention is described in detail below. Example

[0010] A calcium-based trimethylolpropane preparation method that is beneficial to the separation of calcium formate and an organic aqueous solution comprises the following steps: 1) Formaldehyde, n-butyraldehyde and calcium hydroxide undergo condensation reaction in a mass ratio of 3.2:1:0.58 to obtain a condensation liquid; 2) The condensation liquid was mixed with acetonitrile in a volume ratio of 1:1 to precipitate calcium formate with a precipitation rate of 60%; 3) Plate and frame filtration separation, the filter cake is refined to prepare calcium formate product; 4) The filtrate is first distilled to remove the solvent and part of the water; 5) The filtrate from which the solvent has been removed is mixed with acetonitrile in a volume ratio of 1:1 to separate the residual calcium formate in the filtrate. The precipitation rate of calcium formate reaches 90%, and 10% calcium formate remains in the filtrate; 6) Plate and frame filtration separation, the filter cake is refined to prepare calcium formate product; 7) The filtrate is separated into trimethylolpropane product by extraction and distillation.

[0011] In the traditional process, calcium formate is separated by evaporating the condensed liquid, and the calcium formate in the condensed liquid is supersaturated and precipitated to achieve the separation of calcium formate. After continuous evaporation of the condensed liquid, the organic matter undergoes other side reactions under the conditions of salt and high temperature (90-100°C), resulting in colored impurities, and the color of the condensed liquid deepens and becomes yellow. These impurities are difficult to separate in the subsequent refining process, affecting the product quality, the purity of calcium formate is low, and the product produced has a strong odor. The method of the present invention reduces the process of heating and evaporating calcium formate and organic matter together, and reduces the generation of colored impurities.

[0012] In the traditional process, after the condensation liquid is evaporated and concentrated, the viscosity increases, and the calcium formate and organic matter are separated by sedimentation. The calcium formate is entrained with organic matter, and a large amount of water is used to wash the refined calcium formate, but this method consumes a lot of water, and a small amount of impurities still remain. The condensation liquid of the method of the present invention has a low concentration, less organic matter attached to the surface of the calcium formate, and is easy to wash, thereby improving the quality of the calcium formate.

[0013] After two plate and frame filtrations, 10% of the total amount of calcium formate remains in the filtrate, the calcium formate content in the filtrate is even less, and the influence on the quality of trimethylolpropane is reduced. Meanwhile, the separation efficiency of calcium formate and organic matter is improved, which is beneficial to the subsequent improvement of the extraction efficiency of trimethylolpropane, thereby improving the product yield of trimethylolpropane.

[0014] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A calcium-based method for preparing trimethylolpropane which is beneficial for separating calcium formate from an organic aqueous solution, characterized in that The steps include: 1) Formaldehyde, n-butyraldehyde and calcium hydroxide undergo condensation reaction in a mass ratio of 3.2:1:0.58 to obtain a condensation liquid; 2) The condensation liquid is mixed with acetonitrile in a volume ratio of 1:1 to precipitate calcium formate; 3) Plate and frame filtration separation, the filter cake is refined to prepare calcium formate product; 4) The filtrate is first distilled to remove the solvent and part of the water; 5) The filtrate from which the solvent has been removed is mixed with acetonitrile in a volume ratio of 1:1 to separate the residual calcium formate in the filtrate; 6) Plate and frame filtration separation, the filter cake is refined to prepare calcium formate product; 7) The filtrate is separated into trimethylolpropane product by extraction and distillation.