Seeking information on polyvinyl acetate, the production of olefins from formaldehyde, polyoxymethylene, etc

In China, the main manufacturers of polyoxymethylene include Yuntianhua, Shanghai Lanxing, Baotailing in Nantong, and DuPont-Sumitomo in Zhangjiagang. There are even more abroad, such as BSF and Celanese.

It would be better if it could be more detailed!!:D

I hope everyone can see this post; please help me! ! ! :'(

I’m also investigating this; I hope everyone can share their insights!!

Polyvinyl acetate (also known as polyvinyl acetate, abbreviated as PVA or PVAc) is an elastic synthetic polymer. Polyvinyl acetate is prepared by the polymerization of vinyl acetate (VAM). The partial or complete hydrolysis of polymers is used to produce polyvinyl alcohol. The hydrolysis rate of polyvinyl alcohol products is generally between 87% and 99%. Polyvinyl acetate was discovered by Fritz Klatte in Germany in 1912. Polyvinyl acetate is sold in the form of an emulsion in water as an adhesive for porous materials, particularly wood. It is the most commonly used adhesive for wood, and is known as white glue (white adhesive paste). White glue is also widely used to bond other materials, such as paper and fabric, as well as to stick cigarettes together. Polyvinyl acetate is widely used in printing, binding, and book art due to its elasticity and lower acidity compared to other polymers. Elmer’s glue is a well-known brand of white glue sold in the United States. Polyvinyl acetate is also widely recommended for manufacturing coagulation paper.

Polyvinyl acetate 1.4.1 Components of the reactants (1) Monomer The raw material for synthesizing polyvinyl acetate is vinyl acetate monomer. (2) Water: Water is the dispersion medium. During the reaction process and in the final product, the particles of vinyl acetate monomer or polyvinyl acetate are dispersed in water. The polymerization reaction takes place in water, allowing the heat of reaction to be dispersed more effectively; exothermic reactions are thus easier to control, which helps to produce products with a uniform high molecular weight. Water usually accounts for 60%-80% of the total mass of the components involved in the reaction, and degassing as well as the removal of positive ions are necessary. (3) Initiator: Water-soluble peroxides are generally used as initiators, such as hydrogen peroxide, potassium persulfate, ammonium persulfate, and dibenzoyl peroxide. The amount used is 0.1%-1% of the monomer mass. (4) Emulsifiers: In emulsion polymerization, the use of emulsifiers plays a crucial role. The properties and amount of the emulsifiers used have a significant impact on the reaction rate, the stability of the dispersion system, and the properties of the polymer. Therefore, an appropriate emulsifier should be carefully selected for each emulsion polymerization. An emulsifier is a compound that has a hydrophilic group at one end and an oleophilic group at the other, such as sodium oleate, sodium dimerized rosin, sodium alkyl sulfate, polyvinyl alcohol, etc. Polyvinyl alcohol is a good emulsifier for the emulsion polymerization of polyvinyl acetate. The amount of polyvinyl alcohol used is usually around 9% of the monomer mass. (5) Protective colloid: The protective colloid forms a protective layer on the surface of the viscous polymer particles, preventing them from merging and aggregating, thereby maintaining the stability of the emulsion. Polyvinyl alcohol is commonly used, and adhesives, water-soluble fiber derivatives, etc., can also be used. If polyvinyl alcohol is used as an emulsifier, it also acts as a protective colloid, eliminating the need for an additional protective colloid. (6) Adjusters include the following types. ①Surface tension regulators are used to reduce surface tension, maintain the stability of the emulsion, and control the size of monomer droplets within the emulsion. Generally, aliphatic alcohols containing 5–6 carbon atoms (such as pentanol, hexanol, and octanol) are used, in an amount of 0.1% to 0.5% of the monomer mass. Octylphenol polyoxyethylene ether (OP-10) can also be used, at a dosage of about 1.12% of the monomer mass. ②Degree of polymerization regulators are used to control the polymerization process and adjust the molecular weight of the polymer. Commonly used substances include carbon tetrachloride, dodecanethiol, and polysulfides, in amounts of 2%-5% of the monomer mass. ③Medium pH regulators (also known as buffers) are used to maintain the pH value of the reaction medium. The higher the pH of the medium, the faster the initiator decomposes, resulting in more active centers and thus a faster polymerization rate; therefore, the polymerization rate can be controlled by using buffers. Commonly used are phosphates, sulfates, acetates, etc., in an amount of 2%-4% of the monomer mass. 1.4.2 Formulation and production process (1) Formulation: Vinyl acetate >10 kg, Octylphenol polyoxyethylene ether 8 kg, Water 636 kg, Sodium bicarbonate (used after dilution in 10 times its volume of water) 2.2 kg, Peracetic acid AN (used after dilution in 10 times its volume of water) 1.43 kg, dibutyl phthalate 80 kg. (2) Production process: Polyvinyl alcohol and water are added to a dissolution tank; the mixture is kept at that temperature for 10 minutes, then the temperature is raised to 90°C for 4 hours, resulting in a 10% solution. After filtering the dissolved PVA aqueous solution, it is poured into the polymerization reactor. Octylphenol polyoxyethylene ether and 100 kg of monomer (approximately 1/7 of the total monomer mass) are added, along with 5.5 kg of anhydrous persulfuric acid solution at a concentration of 10%. The feeding port is closed and cooling water is turned on. The temperature begins to rise, reaching around 65°C within 30 minutes. When droplets appear in the sight glass, the steam valve is closed (for about 30–40 minutes); the temperature then rises on its own to 75–78°C. At this point, the reflux is normal, and monomer addition begins (to be completed within 8–69 hours). At the same time, 50 g of peroxosulfuric acid AN is added per hour (diluted with 10 times its volume of distilled water). If the reaction temperature is too high or too low, the flow rate of the monomer and the amount of initiator can be adjusted accordingly, but these values must not exceed the total amounts specified in the recipe. Record the monomer addition reflux condition and reaction temperature every 30 minutes, and record the monomer addition flow rate and initiator dosage every hour. After adding all the monomers, monitor the temperature of the reaction mixture; if it is too high (above 85°C), an additional 440 g of persulfate AN440 can be added. This addition should be done in stages, as adding it all at once will cause the reaction to proceed too rapidly. Once the temperature reaches 95–95°C, maintain this temperature for 30 minutes. Cool to below 50°C, then add sodium bicarbonate solution. After confirming that the appearance of the emulsion is satisfactory, dibutyl phthalate is added and stirred for 1 hour before discharging the mixture. This post was last edited by wanghl0997 on 2008-9-3 10:18.]

The international process for producing olefins from methanol is mature. The traditional methods for producing ethylene and propylene involve the cracking of light hydrocarbons (ethane, naphtha, light diesel). However, given that world oil reserves are limited and constitute non-renewable resources, countries around the world have begun to focus on developing non-petroleum routes for producing these low-carbon olefins. Among these approaches, the one that shows the most potential is using coal or natural gas as raw materials to produce methanol, which is then used to generate low-carbon olefins. 　　ExxonMobil in the United States has conducted extensive research on the use of ZSM-5 series molecular sieve catalysts to convert methanol into ethylene and lower hydrocarbons. Its Methanol-to-Gasoline (MTG) process has been put into industrial use at the Montonui facility in New Zealand, while ExxonMobil’s MTO, Olefins-to-Gasoline and Distillates (MOGD) processes have also made significant progress. Since olefins are intermediate products in the methanol-to-gasoline reaction, the success of MTG technology has spurred the development of processes such as MTO and methanol-to-propylene (MTP). The olefins produced by the MTO process are mainly ethylene, followed by propylene, butylene, etc. The MTP process mainly produces propylene and a small amount of ethylene. The currently leading international processes for producing olefins from methanol include the MTO process developed by UOP in the United States and Equinor in Norway, as well as the MTP process developed by Ruhrchemie in Germany. 　　1. MTO process In the 1980s, scientists at Union Carbon discovered that SAPO catalysts exhibited high selectivity for the conversion of methanol into ethylene and propylene. In 1992, UOP and Hydro began to work together on the development of the MTO process, conducting in-depth research on topics such as catalyst preparation, performance testing and regeneration, the impact of reaction conditions on the product distribution, energy utilization, and engineering aspects. Subsequently, a small industrial demonstration plant was established in Prosgrann, Norway, using the MTO process. In November 1995, the two companies announced that the MTO technology could be licensed to third parties. 　　To produce 1 ton of ethylene via the MTO process, 5.6 tons of methanol are required; as by-products, 0.83 tons of propylene, 0.24 tons of butylene, 0.1 ton of C5, and 3.97 tons of fuel gas equivalent to MMBtu are generated. Nigeria is currently building an MTO project with a capacity of 400,000 t/a each for ethylene and propylene, and 2.5 million t/a for methanol in a single train, with completion scheduled for 2006. According to relevant data, the investment estimate for an MTO plant with a capacity of 300,000 t/a of ethylene and 250,000 t/a of propylene is 346 million dollars (based on natural gas as the feedstock; the same applies hereafter). 　　2. MTP Process The MTP process involves first converting part of the methanol into dimethyl ether and water, then carrying out conversion reactions in three series-connected reactors, and finally obtaining by-products such as propylene, liquefied gas, and gasoline through olefin recovery (see Figure 1). In this process, at a 100% methanol conversion rate, the catalyst exhibits a selectivity for ethylene of not less than 5% (on a mass basis) and a selectivity for propylene of not less than 35%. Since the C2 and C4 fractions are recycled back into the reaction system, the yield of propylene reaches or exceeds 70%, and the resulting propylene is of polymerization grade. 　　Since the 1990s, Ruchi Company has been researching the MTP process, and in collaboration with Sudchemie Company, it successfully developed the catalyst ZSM-5 for this process. In 2001, Ruchi Company built a demonstration plant for the MTP process at Statoil’s facility in Norway. The MTP technology reactor developed by Luchi Company uses a fixed-bed design, and its process flow is essentially the same as that of the methanol-to-gasoline plants built in New Zealand in the 1980s; the technology is mature, resulting in minimal risks associated with industrialization. In 2004, Luchi Company signed a patent agreement for a 100,000 t/a MTP plant with Iran’s **Petrochemical Company; completion and commissioning of the plant were scheduled for 2009. 　　Pilot tests of MTP technology began in the 1990s; the pilot plant in Norway has been in operation for over 11,000 hours, an industrial demonstration plant is under construction in Iran, and agreements for large-scale commercial plants are also being discussed. According to available information, the investment for an MTP plant with a capacity of 5,000 t/d of methanol and 500,000 t/a of propylene is estimated at $272 million. A comparison between the MTO and MTP processes is shown in Table 1. The application prospects for MTP catalysts in China are promising. The catalysts used in the production of olefins from methanol have molecular sieves as their main active component, with alumina, silica, diatomite, kaolin, and similar materials serving as carriers. These catalysts are formed and dried through processing processes that involve the use of binders and other processing aids. Factors such as the properties of molecular sieves, carriers, and processing aids, as well as the synthesis processes, can all affect the performance of molecular sieve catalysts. China’s Dalian Institute of Chemical Physics developed ZSM-5 and its modified catalysts in the 1980s, and small-pore SAPO-34 molecular sieve catalysts in the 1990s. In 1993, the institute used modified ZSM-5 series catalysts to carry out a pilot test in a fixed-bed reactor (1 t of methanol per day), and in 1995 it conducted a pilot test in an SDTO fluidized-bed reactor at the Qingpu Chemical Plant in Shanghai. By optimizing the methanol feed at 60–100 kg/d with a 100% methanol conversion rate, and using SAPO-34 molecular sieve catalysts, an olefin selectivity of 84%–85% can be achieved. The MTP reactor is a tubular reactor equipped with a salt bath cooling system; the length of the reaction tube ranges from 1 to 5 meters, and its inner diameter ranges from 20 to 50 mm. The methanol conversion reaction is carried out at 0.13–0.16 MPa and 420–490°C, and the catalyst is calcined and regenerated using a nitrogen/air mixture after 400–700 hours of reaction. The composition of the MTP reaction products is as follows: H2 at less than 0.01%, CO at 0.01%, methane at 0.9%, ethane at 0.06%, ethylene at 0.85%, propylene at 71.2%, propane at 0.98%, C4/C5 at 9.29%, and C6 at 16.7%. The main raw materials and utility consumptions for Luchi Company’s MTP process are shown in Table 2. The MTP process technology needs improvement, and caution should be exercised when launching such projects. The MTP process utilizes fixed-bed reactors, which offer advantages such as ease of scale-up, low risk, low investment costs, and consistent residence time for reactants, enabling the product selectivity to be maximized. Methanol conversion catalysts have advantages such as high propylene selectivity, low coking, and low propane yield. The MTP process produces liquefied gas and gasoline as by-products, which is practical for alleviating energy shortages in regions rich in coal but lacking oil and gas; however, the large amounts of liquefied gas and gasoline also hinder the increase in the added value of downstream products. The significance of MTP lies in producing propylene from methanol, which can then be used to manufacture a wide range of chemical products, thereby enabling comprehensive development of the product chain. Therefore, the MTP process is more suitable for regions with abundant coal but limited oil and gas resources, and it has a negative impact on the economic viability and competitiveness of projects in areas rich in petroleum and natural gas resources. 　　Diversifying the raw material structure has become an inevitable choice for the development of China’s petrochemical industry. Utilizing the country’s relatively abundant coal resources to develop the petrochemical sector and thereby promote local economic growth has become a key focus for more and more coal-rich regions. The MTP plants that are currently planned for construction in China are mainly located in a large coal chemical complex in Ningxia; these plants will produce 1.8 million tons per year of methanol, 520,000 tons per year of MTP, 520,000 tons per year of PP, as well as related downstream products. The estimated investment for these projects is 12.2 billion yuan ； A large coal-fired power company in Inner Mongolia plans to use the lignite available there as raw material, and employ advanced gasification techniques as well as MTP production technology to produce 460,000 tons per year of polypropylene along with its by-products ； The large-scale coal chemical complex in Hulunbuir, Inner Mongolia (under construction), aims to utilize its resource advantages by adopting the MTO/MTP process to produce downstream products derived from ethylene and propylene. However, the technology of MTP reactors for producing propylene from gasification needs further improvement. Large-scale methanol-to-propylene projects require substantial funding, and the various chemical products produced as by-products demand stable and sufficiently inexpensive coal resources; moreover, such systems are complex, resulting in high entry barriers. Currently, 100,000 t/a MTP plants are being built abroad, and further research is needed to optimize the process. In particular, with a reactor diameter of 5 m, issues such as uneven distribution of reactants exist and require further improvement. Developing the MTP industry is an important way to ensure energy security. Taking into account various factors such as resource availability, technical feasibility, economic rationality, and the environmental benefits of clean coal technology, China should vigorously develop the MTP industry. Taking the construction of a coal-based 1.8 million t/a methanol plant as an example, 200,000 t/a of gasoline and 520,000 t/a of C3 can be produced as by-products alongside propylene, which helps to alleviate the shortage of petroleum products. At a crude oil price of $50 per barrel, an investment of 16 billion yuan to produce 1.8 million tons per year of coal-based methanol would generate a profit of 3.1 billion yuan, resulting in an investment return rate of over 16%. It is in line with China’s national conditions in terms of economic benefits as well as **energy substitution and energy security, and represents an important approach to ensuring the sustainable and stable development of the national economy.

Urea-formaldehyde resin is a major adhesive in the wood processing industry both domestically and internationally. It is widely used due to a series of advantages such as high bonding strength, rapid curing, good workability, low production costs, and readily available raw materials. However, the free formaldehyde contained in urea-formaldehyde resin is toxic; the lower the level of free formaldehyde in the resin, the less toxic it is. There are various methods to reduce the amount of free formaldehyde in urea-formaldehyde resin, and the most effective approach is to decrease the molar ratio of formaldehyde to urea. Yet reducing the amount of formaldehyde leads to drawbacks such as increased complexity in the resin production process, difficulties in controlling the reaction process, longer curing times, and reduced bonding strength and storage stability of the resin. Therefore, it is highly practical to find an effective way to overcome the disadvantages associated with a low formaldehyde/urea (F/U) molar ratio. This study focuses on synthesizing urea-formaldehyde resin using a low F/U molar ratio. Starting from the principles of resin synthesis, experiments were conducted to determine the optimal number of additions, addition ratios, and addition times. Additionally, the most suitable pH value, reaction temperature, and reaction time during resin synthesis were identified, thereby producing urea-formaldehyde resin with a low formaldehyde content and good stability. For more details, please visit http://www.310052.com/jsyj/43/4237.html

For the acetic anhydride production process, please refer to this website: http://bbs.hcbbs.com/viewthread.php?tid=255322&highlight=%B4%D7%F4%FB