A new breakthrough in jute cellulose extraction: Sulphuric Acid Reactor Process Analysis

As a natural plant fiber, jute fiber has many advantages such as high yield, low price, and excellent mechanical properties. It is widely used in decoration, packaging, textile, medical and other fields. However, in addition to cellulose, jute fiber also contains impurities such as hemicellulose, lignin, and pectin. The presence of these impurities limits the application of jute fiber in high-end fields. Therefore, efficient extraction of jute cellulose has become the key to increasing the added value of jute fiber. At present, chemical, physical, and biological methods are common methods for preparing cellulose, but they all have defects such as long preparation process, many drying steps, and high energy consumption. In addition, high concentrations of acid and alkali have a great influence on the polymerization degree and structure of cellulose under high temperature conditions, affecting the application performance of cellulose. Against this background, the sulfuric acid reactor process came into being, bringing new breakthroughs in the extraction of jute cellulose.

The basic principle of sulfuric acid method for extracting cellulose is to hydrolyze jute fiber with sulfuric acid to remove the non-crystalline region in the cellulose structure, thereby obtaining cellulose with high crystallinity. Sulfuric acid hydrolysis can not only degrade the non-crystalline region of cellulose, but also introduce charged sulfate half-ester groups on the surface of cellulose, which helps to improve the dispersibility and stability of cellulose.

(I) Traditional extraction methods
At present, jute fiber is traditionally used in a wide range of fields, and its extraction methods mainly include chemical method, physical method, biological method, or a combination of several methods. For example, the process of producing jute cellulose by traditional chemical method is fiber pretreatment - high temperature alkali boiling - sodium chlorite treatment - alkali treatment - water washing - drying - cellulose.
(II) Limitations
Traditional methods have many defects. The preparation process is long and involves multiple steps, which makes the entire extraction process time-consuming; there are many drying steps, which increases energy consumption; the energy consumption is high, and the use of high concentration acid and alkali under high temperature conditions not only has high requirements on equipment, but also has a great impact on the degree of polymerization and structure of cellulose, thereby affecting the application performance of cellulose.

(I) Process flow
1. Pretreatment:
• Crush the jute fiber to an appropriate particle size (such as 0.180mm sieve) for subsequent processing. • Use water or other solvents to remove water-soluble components in jute fiber.
2. Cellulose extraction:
• Place the pretreated jute fiber powder into a reactor and add sulfuric acid solution (such as 2%-3% sulfuric acid).
• React at a certain temperature (such as 40°C) and time (such as 1 hour), and ensure that the reaction is fully carried out through a condensation reflux device.
• After the reaction is completed, wash the residue with a large amount of water several times until it is neutral.
3. Purification:
• Wash the extracted cellulose with a large amount of water several times until it is neutral to remove residual acid and impurities.
• Obtain pure cellulose by filtration and drying (such as drying at 60°C).

(II) Key parameters
• Temperature: The acid treatment temperature is controlled at 50℃-60℃. Temperature has an important influence on the reaction rate and impurity removal effect. Too high temperature may cause cellulose degradation, while too low temperature will slow the reaction rate.
• Time: The acid treatment insulation time is 45min-90min. If the time is too short, the impurities will not be removed thoroughly; if the time is too long, the performance of cellulose may be affected.
• Bath ratio: The bath ratio is generally 1:10-1:20. A suitable bath ratio can ensure that the jute fiber is fully in contact with the treatment liquid and improve the treatment effect.
• Sulfuric acid dosage: The sulfuric acid dosage is determined according to the process requirements, generally 6g/L-8g/L. Excessive sulfuric acid dosage will increase costs and may cause corrosion to the equipment; too little sulfuric acid dosage will result in poor impurity removal.

(I) Short process flow
Compared with traditional methods, the sulfuric acid reactor process flow is simpler and reduces unnecessary steps, thereby shortening the preparation time and improving production efficiency.
(II) Low energy consumption
The process has fewer drying steps, and all processes are operated under normal pressure, which reduces energy consumption. At the same time, environmentally friendly additives are used, and the amount of chemical additives is small, which further reduces production costs.
(III) High impurity removal rate
After being treated by the sulfuric acid reactor process, the impurity removal effect in jute fiber is good, especially the removal effect of lignin and hemicellulose is significant. For example, after the biological-chemical combined treatment, the hemicellulose content in jute fiber was reduced from 10.21% to 5.35%, a decrease of 47.6%; the lignin content was reduced from 8.25% to 7.43%, a decrease of 9.66%, thereby increasing the cellulose content in jute fiber by 8.39%.
(IV) No damage to cellulose structure and performance
The cellulose produced by this process has a high content of α-cellulose and does not damage the cellulose structure and performance, thus ensuring the quality and application performance of cellulose.

The sulfuric acid reactor process has made new breakthroughs in the field of jute cellulose extraction, with significant advantages such as short process flow, low energy consumption, high impurity removal rate, and no damage to cellulose structure and performance. Compared with traditional processes, this process can extract jute cellulose more efficiently, reduce production costs, and improve product quality, and has broad application prospects.
In the future, with the continuous development and innovation of technology, the sulfuric acid reactor process is expected to be further optimized and improved. For example, more efficient reactor structures and operating conditions can be studied to improve reaction efficiency and impurity removal effects; new bioenzyme preparations can be developed to further reduce production costs; and waste treatment and recycling in the process can be strengthened to achieve green production. It is believed that in the near future, the sulfuric acid reactor process will be more widely used in the jute fiber industry, promoting the development of the jute fiber industry towards high-end and green directions.