Xylitol production process

Xylitol production process

1 Process The production of xylitol products is completed in two steps: raw materials → xylose liquor → crystalline xylose crystals xylose → hydrogenated liquor → crystallized xylitol
1.1 Xylose Production Process
a. Description of the process flow The corn cob is pretreated by impurities removal, cleaning, and crushing (particle size φ is 3 to 5 mm) and sent to the hydrolysis tank from the raw material delivery system, which is mixed with 2.8% sulfuric acid and steamed for thermal acid hydrolysis. The acid hydrolysis temperature is about 120~125°C. Hydrolysis solution obtained by acid hydrolysis (xylose liquor) was successively decolored and de-slaged by activated carbon decolorizing kettle and plate and frame filter press respectively. The second deliquored liquid enters the ion exchange column to be adsorbed and removed by impurities, and is then ultrafiltered and then pumped into a three-effect evaporation concentration system for first evaporation and concentration. The concentrated evaporating liquid is decolorized and pressure-filtered three times, and the three-dried liquid is re-introduced into the ion-exchange column for exchange purification and purification, and the purifying liquid is subjected to second evaporation and concentration. The sugar concentration at this time is about 55%, and finally Then enter the single-effect evaporator, so that the concentration of about 83%, the concentration of self-flow into the crystallization tank, the crystallization temperature is about 90 °C, the crystallization cycle of about 70h. After the crystallization, the concentrate is separated from the mother liquor by a centrifugal separator, and the wet crystals of xylose are dried on a fluidized bed drying line and are to be produced after packaging (or sold as a product). The corn slag discharged from the hydrolysis tank is discharged to the waste dewatering and turnover area outside the plant. After mechanical dewatering, it is transported to the local thermal power station for fuel.
b. Process flow diagram The schematic diagram of the xylose production process is shown in Figure 1.
Corn cob slag → Dehydration → Thermal power plant 玉米 Corn cob → Cleaning → Hydrolysis → Primary decolorization → Plate and frame filtration → Ion exchange → Ultrafiltration → Evaporation concentration (steaming) →
↑
H2SO4
→ Secondary decolorization → Plate and frame filtration → Ion exchange → Evaporation concentration (secondary distillation) → Evaporation concentration (three distillations) → Crystallization →
→ Centrifugal separation → Drying → Packaging → Xylose (crystallization) → Storage Figure 1 Schematic diagram of xylose production process
1.2 Xylitol production process
a, process description Crystallization of xylose after the decolorization of sugar by sugar into the frame filter to remove activated carbon and impurities, and then ion exchange purification of xylose liquid, the xylose liquid with the right amount of catalyst (Ni-Al-Ti After that, it is pumped by high pressure to the autoclave where it is mixed with the hydrogen from the methanol cracking hydrogen production unit. The hydrogenation reaction is carried out by steam heating in vitro. The reaction is carried out under certain temperature, pressure and catalytic conditions. The hydrogenated solution separated from the reaction product by medium pressure is further separated into the hydrogenated liquid tank at atmospheric pressure and then sent to the purification section. Hydrogen gas is separated by a hydrogen separator and sent back to the hydrogen tank.
The purified hydrogenation solution was sent to a three-effect falling film evaporation concentration device for evaporation and concentration. After being steamed, the refractive index was about 50%. After being evaporated by an elevating film combined with a plate evaporation concentration device, the refractive index of the hydrogenation solution was about 85. %, the xylitol liquid flows into the crystallization tank to crystallize, and then the mother liquor is separated by a centrifugal separator. The wet crystals of xylitol are dried by a fluidized bed drying line to be crystallized xylitol, and the product is packaged into a warehouse. The separated alcohol mother liquor is the by-product liquid xylitol, which is put into a storage tank.
b. Process flow diagram The schematic diagram of the xylitol production process flow is shown in Figure 2.

Xylose → Sugar Decolorization → Hydrogenation → Decoloration → Plate and Frame Filtering → Ion Exchange → Evaporation Concentration → Crystallization →
→ Centrifugation → Drying → Packaging → Xylitol (crystallization) → Storage
Liquid xylitol → barrels → storage

Figure 2 Schematic diagram of xylitol production process

1.3 Product Quality Standard
1.3.1 Main Technical Specifications and Quality Indicators of Xylose (BP93)
a, appearance: white crystalline powder
b. Physical and chemical indicators:
Xylose content 99-101%
Purity ≥98%
Specific rotation +18.5~+19.5
Melting point≥147°C Acidity≤0.2ml Water content≤0.50% Ash content≤0.05% Heavy metal≤5ppm Arsenic≤1ppm
1.3.2 Xylitol Quality Standards (FCC, E967) Indicators
a, traits: white crystalline powder, sweet taste, cool in the mouth.
b. Solubility: Dissolve 1g in approximately 0.6ml of water, with a small amount of alcohol.
c. Physical and chemical index xylitol content ≥98.5-101% Other miscellaneous alcohol content ≤0.5-1.0%
Moisture ≤0.2%
Loss on drying ≤0.5%
PH value 5-7
Ignition residue ≤0.1%
Reducing sugar ≤0.2%
92-96°C
Arsenic ≤3ppm
Nickel ≤2ppm
Lead ≤ 1ppm
Heavy metal ≤10ppm
Chloride ≤100ppm
Sulfate ≤200ppm