Acid pretreatment

Yang, H., Wang, Y., Zhou, P., and Regenstein, J. M. (2008). Effects of alkaline and acid pretreatment on the physical properties and nanostructures of the gelatin from channel catfish skins. Food Hydrocolloids 22, 1541-1550. 

Liu Y., Zhang Y., and Tsubaki N. 2007. The effect of acetic acid pretreatment for cobalt catalysts prepared from cobalt nitrate. Catal. Commun. 8 773-76. 

The acid pretreatment with HC1 was the most critical parameter. The effect of level of HC1 on zircon rejection is shown in Figure 23.8. 

Acid pretreatment of the ore before flotation had a positive effect on ilmenite flotation. Figure 25.3 shows the effect of different acids used in the pretreatment on ilmenite recovery in the rougher concentrate. The best metallurgical results were achieved using sulphuric acid in the pretreatment stage. 

Figure 25.3 Effect of type and level of acid in the acid pretreatment stage on titanium rougher flotation.

HCl was used in the acid pretreatment stage as pH modifier in the ilmenite flotation and cleaning stages. 

Belash, F.N., and Gamilow, M.A., Perovskite Flotation Using Acid Pretreatment, Bulletin CIN Cvetnie Metaly, No. 21, 1959. 

Carbon Monoxide Reduction at Copper. At copper electrodes carbon monoxide is thought to be an intermediate in the reduction of carbon dioxide and is formed as the major product with nitric acid pretreated electrodes (2 and Kim, J. J. Summers, D. P. Frese, K. W., Jr. J. Electroanal. Chem. in press.). As the data in Table IV indicates, methane can be formed by carbon monoxide reduction at... 

Kitamoto, T., Ogomori, K., Tateishi, J., and Prusiner, S. (1987) Formic acid pretreatment enhances immunostaining of cerebral and systemic amyloids. Lab. Invest. 57, 230-236. 

Twenty-four-hour median intragastric acidity pretreatment (red) and after 1 month of treatment with either ranitidine, 150 mg twice daily (blue, H2 block), or omeprazole, 20 mg once daily (green, PPI). Note that H2-receptor antagonists have a marked effect on nocturnal acid secretion but only a modest effect on meal-stimulated secretion. Proton pump inhibitors (PPIs) markedly suppress meal-stimulated and nocturnal acid secretion. 

Effect of Propane to Oxygen Mole Ratio in Feed. Table IV gives the results for the propane and oxygen mole ratio ranging from 2 to 8. Stainless steel Reactor VII was used for these experiments after the phosphoric acid pretreatment the reaction temperature was 430°C. The product gas was cooled in the Liebig condenser at 2°C., and the condensate was analyzed. 

The Purdue concepts have been applied to several different agricultural products, such as corn stalks, alfalfa, orchard grass, tall fescue, and sugarcane bagasse. No experiments have been reported on either hardwoods or softwoods. The processes have been explored in two major modes. In the first, the entire agricultural residue is treated with solvent in the second, a dilute acid pretreatment to remove hemicellulose precedes solvent treatment. The first process is especially desirable for making furfural or fermentation products from hemicellulose as a separate activity. Then, the hemicellulose-free raw material can be converted to substantially pure glucose. 

Thus, it was observed that the first-order rate constants (/q) for nitrate reduction by untreated Fe° increase due to the pretreatment of iron metal with HC1 however, observed increases in the rate constant for nitrite reduction have been relatively small under similar acid pretreatment conditions. During the first 12 hr, the rate constant for nitrate reduction showed a gradual decline, and this decline seems to have been clearly influenced by the presence of chloride. The reaction rate constants for nitrate and nitrite reduction by untreated Fe° turnings are directly dependent on the concentration of Fe° used, ranging between 69.4 and 208.2 g/L thus /c, and k, increase linearly with increases in the surface area of the untreated iron. Table 13.8 demonstrates that acid-treated Fe° is more reactive than its untreated counterpart. 

Campbell et al. (1967) applied sequential extraction to characterize FA, HA, and humin from gray podzolic and chemozemic soils. The fractions of FA and HA extracted by 0.5 M NaOH without acid pretreatment, which they called mobile humates (since the researchers assumed that they are not bound to minerals), had a lower mean residence time (ranging from 85 to 785 for HA, respectively, in the chernozemic and gray podzolic soils) as compared to Ca-humates extracted from humin (1410 years in the chemozemic soil) and to the total FA and HA extracted after acid pretreatment (195-1235 years for HA). This study showed that in the chernozemic soil, Ca-humates and clays play an equally important role in the stabilization of HS, whereas in the podzolic soil the oldest fraction was associated with clays. 

The H-ZSM-5 coatings were tested for the one-step oxidation of benzene by nitrous oxide to phenol. The grids had a total area of 9 cm2, a wire diameter of 250 pm and a mesh size of 800 pm. Fifteen grids formed a stack separated by steel rings. By acid pretreatment of the grids, defects were generated which are known to become crystallization centers during the synthesis of the zeolite. 

Corn stover, a well-known example of lignocellulosic biomass, is a potential renewable feed for bioethanol production. Dilute sulfuric acid pretreatment removes hemicellulose and makes the cellulose more susceptible to bacterial digestion. The rheologic properties of corn stover pretreated in such a manner were studied. The Power Law parameters were sensitive to corn stover suspension concentration becoming more non-Newtonian with slope n, ranging from 0.92 to 0.05 between 5 and 30% solids. The Casson and the Power Law models described the experimental data with correlation coefficients ranging from 0.90 to 0.99 and 0.85 to 0.99, respectively. The yield stress predicted by direct data extrapolation and by the Herschel-Bulkley model was similar for each concentration of corn stover tested. 

The oils present in the QF differ from those found in the germ (corn oil) and in particular are enriched for phytosterols, which are cholesterol-lowering agents (5-9). A prior study with corn fiber demonstrated that the oils withstood dilute-acid) pretreatment and became enriched in the pretreated solids (22). Therefore, it was of interest to determine whether dilute-acid-pretreated QF solids might also serve as a source for these valuable nutraceutical chemicals. Following SSF, the solids residue was recovered and analyzed for the presence of oils. It was determined that only 1.12% oils was present in the residual solids (post-SSF, Table 3), which is comparable with that found in untreated QF (1.24-3.49% oil as noted in ref. 2). 

Furthermore, enzymatic hydrolysis of the corn stover treated under optimal AFEX conditions showed almost 98% glucan conversion and 80% xylan conversion vs 29 and 16% for untreated com stover, respectively (at an enzyme loading of 60 FPU/g of glucan). Unlike acidic pretreatments, AFEX does not generate sugar monomers. The cellulase mixture in our study was developed for hydrolysis of acid-pretreated materials and has about 1% by weight xylanase activity (J. Cherry, personal communication, Nov. 2002). Enzyme cocktails with enhanced xylanase activity would presumably completely hydrolyze AFEX-treated xylans. 

Many favor dilute sulfuric acid pretreatment because both high hemicellulose recovery and good cellulose digestibility can be achieved (6-8). Moreover, most of the soluble sugars from dilute-acid pretreatment are released as monomers that can be readily fermented to ethanol by recombinant organisms (9,10). Pretreatment with just hot water or steam, termed uncatalyzed hydrolysis or autohydrolysis, eliminates chemical additives, lowers the cost of materials of construction, and generates less waste, but hemicellulose and cellulose yields from batch systems are limited. 

Predicted Effects of Mineral Neutralization and Bisulfate Formation on Hydrogen Ion Concentration for Dilute Sulfuric Acid Pretreatment... 

This research quantified the enzymatic digestibility of the solid component and the microbial inhibition of the liquid component of pretreated aspen wood and com stover hydrolysates. Products of liquid hot water and carbonic acid pretreatment were compared. Pretreatment temperatures tested ranged from 180 to 220°C/ and reaction times were varied between 4 and 64 min. Both microbial inhibition rates and enzymatic hydrolysis rates showed no difference between pretreatments containing carbonic acid and those not containing no carbonic acid. Microbial inhibition increased as the reaction severity increased, but only above a midpoint severity parameter of 200°C for 16 min. Both the rates and yields of enzymatic hydrolysis displayed an increase from the lowest tested reaction severity to the highest tested reaction severity. 

Index Entries Carbonic acid pretreatment hydrolysis com stover aspen wood. 

Modeling of Carbonic Acid Pretreatment Process Using ASPEN-Plus ... 

Index Entries Acid pretreatment carbonic acid ASPEN-Plus model alcohol fuels biomass. 

Although ASPEN-Plus is widely used to simulate petrochemical processes, its uses for modeling biomass processes are limited owing to the limited availability of physical properties that best describe biomass components such as cellulose, xylan, and lignin. For example, Lynd et al. (1) used conventional methods to calculate the economic viability of a biom-ass-to-ethanol process. However, with the development by the National Renewable Energy Laboratory (NREL) of an ASPEN-Plus physical property database for biofuels components, modified versions of ASPEN-Plus software can now be used to model biomass processes (2). Wooley et al. (3) used ASPEN-Plus simulation software to calculate equipment and energy costs for an entire biomass-to-ethanol process that made use of dilute-H2S04 acid pretreatment. 

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