Yield pretreatment

A vapor-phase process primarily for ECC off-gas feeds was developed by Sinopec Technology Company based on a 2eoHte catalyst of the Pentasd type (24,25). It reHes on frequent regeneration of the catalyst to minimi2e pretreatment of the ECC off-gas and allows the impurities in the feed gas to react with ben2ene to form by-products. Consequently, the product yield and purity are low. Joint licensing by ABB Lummus Crest and Sinopec was announced in 1994. 

Effect of RDS pretreatment on product yields from RFCC (with and without RDS) ... 

Hydrolysis, although a simple method in theory, yields terephthalic acid (TPA), which must be purified by several recrystallizations. The TPA must be specially pretreated to blend with ethylene glycol to form premixes and slurries of the right viscosities to be handled and conveyed in modern direct polyesterification plants. Hie product of the alkaline hydrolysis of PET includes TPA salts, which must be neutralized with a mineral acid in order to collect the TPA. That results in the formation of large amounts of inorganic salts for which commercial markets must be found in order to make the process economically feasible. There is also the possibility that the TPA will be contaminated with alkali metal ions. Hydrolysis of PET is also slow compared to methanolysis and glycolysis.1... 

The second analytical method uses a combustion system (O Neil et al. 1994) in place of reaction with BrF,. This method was used for the crocodiles because they were represented by very thin caps of enamel. The enamel was powdered and sieved (20 mg), pretreated in NaOCl to oxidize organic material and then precipitated as silver phosphate. Approximately 10-20 mg of silver phosphate were mixed with powdered graphite in quartz tubes, evacuated and sealed. Combustion at 1,200°C was followed by rapid cooling in water which prevents isotopic fractionation between the CO2 produced and the residual solid in the tube. Analyses of separate aliquots from the same sample typically showed precisions of 0.1%o to 0.4%o with 2 to 4 repetitive analyses even though yields are on the order of 25%. 

The most common method to extract xylan is the alkaline extraction. Several pretreatment methods can be used in association in order to break the covalent bonds that exist between xylan and other carbohydrates during the extraction (Wang Zhang, 2006). A number of articles studied the use of ultrasound on the xylan extraction. Hromadkova and coworkers reported that 36.1% of xylan was extracted from corn cobs with 5% NaOH solution at 60°C for 10 min of ultrasonication in comparison with 31.5% of xylan in the classical extraction. Both extractive methods yielded xylan with immunogenic properties (Hromadkova et al., 1999). 

A Box-Behnken design was employed to investigate statistically the main and interactive effects of four process variables (reaction time, enzyme to substrate ratio, surfactant addition, and substrate pretreatment) on enzymatic conversion of waste office paper to sugars. A response surface model relating sugar yield to the four variables was developed on the basis of the experimental results. The model could be successfully used to identify the most efficient combination of the four variables for maximizing the extent of sugar production. 

Figure 1 shows the time course of lactic acid production through SSF in a batch reactor of IL volume for an initial load of 10 g/1 bean curd refuse with or without pretreatment using 0.1 mol/1 HCl aqueous solution with heating at 121C for 30 min. The finally attained lactic acid yield on a carbon basis... 

Fig. 1 Time couise of lactic acid yield and its concentration in SSF with or without pretreatment using 0.1 mol/l FICI with heating at 121 1 for 30 min. Famentation conditions 3TC, pH=5.0, initial load of bean curd refiise(BCR) 10 g, cellulase amount=l gin ILsuspension.

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