Regarding the BDO dehydration process for THF production

　 　 　 Synthesis of **furan** via gas-phase cyclodehydration of 1,4-butanediol. **Furan (THF)** has excellent solvating power for many organic and inorganic substances; it can dissolve all compounds except polyethylene, polypropylene, and fluororesins. In particular, it effectively dissolves PVC, vinyl chloride resins, and styrene-aniline, and is widely used as a reactive solvent, earning it the nickname “universal solvent”. THF can also be used as a precursor for polyurethanes, elastic fibers, and copolyesters for elastomer molding. The continuous expansion of the polytetramethylether glycol market further increases the demand for THF. The main industrial methods for synthesizing THF include the furfural method, the Reppe method, the butylene oxidation method, and the cyclodehydration of 1,4-butanediol. However, THF synthesized by the cyclodehydration of 1,4-butanediol has high purity and a simple process. This liquid-phase synthesis process typically uses protonic mineral acids such as sulfuric acid, which severely corrode equipment and also pollute the environment. In this paper, THF was synthesized from 1,4-butanediol using a gas-phase cyclodehydration method. The effects of factors such as catalysts (γ-Al2O3, ZrO2, CeO2, and ZSM-5), reaction temperature, feed rate, and reaction time on the cyclodehydration reaction were investigated. The results showed that under the optimal reaction conditions of using γ-Al2O3 as a catalyst, a feed rate of 2.4 mL·min-1, and a reaction time of 2 hours at 320°C, the conversion rate of 1,4-butanediol was close to 100%, while the selectivity for furan reached 99.8%. This method features mild reaction conditions, no need for high-pressure equipment, with conversion and selectivity of ≥99.8%; there are virtually no other impurities in THF apart from water. 1 Experimental Section 1.1 Instruments and Reagents GC-1690 gas chromatograph (capillary column, FID detector; quantification performed using area normalization). γ-Al2O3, ZrO2, ceric nitrate, and ZSM-5 molecular sieves were calcined at 500°C for 3 hours for later use. 1.2 Synthesis of THF A catalyst amount of 300 mg was loaded into a continuous-flow fixed-bed microreactor (quartz reaction tube with an inner diameter of 8 mm), purged with N2 for 30 min, and the temperature was raised to the reaction temperature at a rate of 10°C·min-1. 1,4-Butanediol is delivered using an electronic peristaltic pump, and water is added in a ratio of m(1,4-butanediol)∶m(water) = 1∶1. At this point, N2 carries the vaporized feedstock into the reactor for reaction. The product was condensed in ice water and then analyzed by GC. 2 Results and Discussion 2.1 Effect of reaction temperature on the cyclodehydration reaction Since the experiment is a pressure-normal vapor-phase reaction, the starting temperature for 1,4-butanediol should be higher than its boiling point (228°C). The feed rate was 2.4 mL·min-1, and the reaction time was 2 hours; all other reaction conditions were the same as those in 1.2. The effect of reaction temperature on the cyclodehydration reaction was investigated. The results showed that for different catalysts, both conversion and selectivity increased to varying degrees as the reaction temperature rose. At reaction temperatures below 280°C, ZSM-5 exhibits the best catalytic efficiency for the reaction, with a conversion rate of 81.43%, followed by γ-Al2O3. It is believed that ZSM-5, as a solid acid catalyst used in alcohol dehydration reactions, exhibits high conversion rates due to its unique pore structure, which shows improved performance as the temperature rises. As the temperature increases, ZSM-5 maintains its high performance; meanwhile, the enhancing effect of γ-Al2O3, CeO2, and ZrO2 on the reaction is also evident. It can be seen that γ-Al2O3 promotes the complete reaction of 1,4-butanediol. Byproducts of 1,4-butanediol in the production of THF include 3-butene-1-ol, etc. CEO2 and ZrO2 have poor THF selectivity. Studies have shown that CeO2 and ZrO2 lead to numerous by-products in the dehydration of alcohols at low temperatures; when the temperature is ≥325°C, the main product of the dehydration of 1,4-butanediol is 3-butene-1-ol. Raising the temperature is beneficial for both the conversion rate of the feedstock and the selectivity of the product. γ-Al2O3 and ZSM-5 exhibit significant effectiveness in the cyclodehydration of 1,4-butanediol; at a reaction temperature of 320°C, the conversion rate and selectivity are ≥99.8%. 2.2 Effect of feed rate on the cyclodehydration reaction It is crucial to determine an appropriate feed rate for the catalytic reaction under the set catalytic temperature conditions. The reaction was carried out at 300°C for 2 hours; the other reaction conditions were the same as those in 1.2. The effect of feed rate on the cyclodehydration reaction was investigated. At the selected feed rate, the conversion rate of 1,4-butanediol varied to some extent, while all four catalysts showed the highest conversion rate at a feed rate of (2.4–3.0) mL·min-1, after which the conversion rate decreased significantly. When the feed rate is less than 2.4 mL·min-1, the conversion rate continues to increase, and the raw material is converted very thoroughly. However, the increased reaction time per unit weight of the raw material leads to energy waste and an increase in by-products. When the feed rate exceeds 2.4 mL·min-1, the feeding is too fast; the reactant does not have enough time to react fully before being removed from the reaction system. As a result, the proportion of reactant in the effluent increases, leading to a decrease in the conversion rate. Therefore, a sampling rate of around 2.4 mL·min-1 is chosen as the most suitable for feeding into the catalytic bed. It was further confirmed that γ-Al2O3 and ZSM-5 exhibit good catalytic efficiency for the dehydration reaction of 1,4-butanediol. 2.3 Effect of reaction time on the cyclodehydration reaction As the reaction time increased, the conversion rates of all four catalysts showed an upward trend. γ-Al2O3 reaches reaction equilibrium in a very short time, with a conversion rate approaching 100%. In the case of mesoporous ZSM-5, the conversion rate decreases after 120 minutes as the reaction time increases, since the performance and activation efficiency of ZSM-5 become inversely proportional to the acid strength after 120 minutes of reaction. By using modified ZrO2 for the dehydration of 1,4-butanediol, a high selectivity for 3-butene-1-alcohol is obtained; whereas pure ZrO2 has both acidic and basic properties, so the conversion rate does not change significantly as the reaction proceeds. CeO2 is weakly basic, and its conversion rate reaches its maximum value at 180 minutes, but its selectivity favors 3-butene-1-alcohol. Reaction time has a significant impact on the catalyst, so it is necessary to select an appropriate reaction time.

I’m interested in production equipment; I wonder if it’s available?

Sinochem Taicang has such a setup; the specific manufacturing process is unclear, as I’ve never worked there

Nanjing Lanxing Chemical New Materials Co., Ltd. is currently building this production process. . . Hehe, coincidentally, one of my classmates is working on construction projects there.