Pretreating severity

Figure 16.5 Impact of pretreating severity on the activity of a hydrocracking catalyst temperature required for conversion of a feed hydrotreated to (a) 40 ppm nitrogen, (b) 10ppm nitrogen.

The interest in the graphite furnace as an emission source stems from the desire to achieve a multielement detection capability whilst retaining the low limits of detection and the possibility of sample pretreatment. Several... 

Due to the need for an extensive pretreatment of the feedstock mineral, those aqueous processes which use direct carbonation could in fact be considered as indirect. As an alternative to energy-intensive pretreatment, several groups worldwide have embarked on methods to either dissolve or leach the Mg or Ca from minerals or industrial byproducts and wastes, by using strong or weak acids (mineral or organic), alkali solutions, or ligands. [101-105]. An example of this is the process route developed by Kakizawa et al. [50] in Japan (see Section 14.3.3.2). 

It is possible that a toxicity threshold is not achieved at lower severities, reducing the inhibition from these conditions. The corn stover samples were consistently less inhibitory than the aspen wood samples. This is likely owing to the fact that fewer acids are inherent in the corn stover biomass than in the aspen wood biomass. For example, it was found that the pH of the corn stover hydrolysates was higher than the pH of aspen hydrolysates. Further testing is warranted to investigate the difference in the inhibition of the substrates and also to determine whether scatter is to blame for the appearance of a difference between pretreatments with and without carbonic acid when assessing the percent inhibition from Fig. 3. Pretreatment severity showed a marked effect on the degree of inhibition suffered by yeast cultures, but the presence or absence of carbonic acid appears to have had no influence on inhibition. Between the aspen wood and corn stover samples, there appeared to be a difference in inhibition rates. 

Preincubation of surfaces with platelet-poor plasma substantially reduced the platelet retention index of polyacrylates and polymethacrylates, but hardly altered the retention index of polystyrene or copolymers with methyl acrylate that are rich in styrene. Even without plasma pretreatment, the surface, when exposed to whole blood, was probably first contacted by molecular elements (including the proteins) before the cellular elements arrived. What then is the mode of action of plasma pretreatment Several hypotheses, none conclusive, can be advanced, such as ... 

Besides the visual evaluation from the agglomeration test, the volatile-matter content was chosen as the quantitative index of pretreatment severity. Operating experience with the hydrogasifier showed that minimum coal pretreatment must reduce the volatile matter to 24-26%. Various aspects of pretreatment are discussed in more detail below. 

Solvent cleaning, as applied to other carbon electrodes, is expected to be an effective, nondamaging method of electrode pretreatment. Several different solvents can be used to clean the electrode surface including acetonitrile, isopropanol, dichloromethane, and toluene. The solvents should first be distilled for purification. Reagent-grade solvents often contain impurities at levels that can cause significant electrode deactivation. AC can be added to the distilled solvents for additional purification. Soak times of 20-30 min should be adequate. The solvent cleaning can also be performed by Soxhlet extraction. 

The LDH materials can be very interesting to industry as they combine the features of conventional metal hydroxide-type fillers, like magnesium hydroxide (MH), with the layered silicate type of nanofillers, Hke montmorillonite. The major area of interest in this regard is the role of LDH materials as potential non-halogenated, non-toxic flame retardant for polymer matrices. For years, scientists have been using the concept of nanotechnology to improve the flame retardancy of polymer nanocomposites. This approach involves the dispersion of inorganic filler, in nanoscale, as flame retardants into a polymer matrix. Usually, for this purpose, layered silicates and various other nanoparticles (MgO, MH, etc.) are used after suitable pretreatment. Several research reports have already shown that such an approach indeed improves the flame retardancy of the composites [22,23]. 

The overall ethanol yields of starch-based crops are between 180 L/t (cassava) and 430 L/t (rice), and the yield for the lignocellulosic biomass are approximately between 152 L/t (rice straw), and 270 L/t (lodgepole pine). Depending on the physical stmcture and lignin contents of the biomass, the costs and yield of the bioconversion process can vary dramatically. For example, some softwood species contain more than 29% lignin and are more difficult to be hydrolyzed without pretreatment. Several studies have produced estimates of the cost to produce cellulosic ethanol ranging between US 0.23/L and US 1.37/L, adjusted to 2015 dollars (ie, the number was modified based on Haque and Epplin (2012)). 

Kabel, M. A., Bos, G., Zeevalking, J., Voragen, A. G. J. Schols, H. A. (2007). Effect of pretreatment severity on xylan solubility and enzymatic breakdown of the remaining cellulose from wheat straw. Bioresource Technology, 98, 2034-2042. 

The surface may be deliberately disrupted or superactivated by severe thermal or cathodic pretreatment. Severe thermal activation [38] results in strong promotion of at least one, and probably two, premonolayer oxidation responses in the case of gold in acid at E < 0.6 V. 

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