Dextrinization catalysts

The protein fraction is filtered and dried to become high (60%) protein content com gluten meal. The starch slurry can be dewatered and dried to produce regular com starch. Dry starch can be sold as is or heat treated in the presence of acid catalysts to produce dextrins. Or, it is chemically modified before dewatering and drying to produce modified starches used in food and industrial appHcations. Lasdy, it can be hydroly2ed to produce corn sweeteners. 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

The synthesis of [Ircp Cl(bpy-cd)]Cl, where bpy-cd is a /3-cyclo-dextrin attached at the 6 position to a bpy ligand, is detailed.138 The complexes [Ircp (diimine)X]+, X = C1, H, diimine = bpy, phen, are active catalysts for the light-driven water-gas-shift reaction.139 The hydride complexes luminesce at 77 K and room temperature, whereas the chloride complexes do not.140 The three-legged piano-stool arrangement of the ligands in [Ircp (bpy)Cl]+ and [Ircp (4,4 -COOFl-bpy)Cl]+ is confirmed by X-ray crystallography.141,142 Further mechanistic studies on the catalytic cycle shown in reaction Scheme 11 indicate that Cl- is substituted by CO and the rate-determining step involves loss of C02 and H+ to leave the Ir1 species, which readily binds Fl+ to yield the lrIH hydride species.143... 

At around the same time, Breslow and co-workers described bifunctional cyclo-dextrin-based catalysts that were capable of hydrolysis of a bound phosphate ester [88]. In later studies, an AD isomer (Scheme 4.9) of a P-cyclodextrin bisimidazole catalyst turned out to be the fastest catalyst for enolization of p-tert-butylacetophe-none (Scheme 4.9) [89]. Here, the extra binding is provided by the P-cyclodextrin... 

The head of a safety match consists of K chlorate 45-55, animal (hide) glue (as a binder) 9-11, sulfur or rosin 3-5, extender (starch, dextrin) 2-3, neutralizer (ZnO.or Ca carbonate) 45-55, infusorial earth 5-6 other siliceous filler 15-32%. Fractional percentages of a soluble burning rate catalyst, such as K di-chromate, also soluble dye stuffs, etc... 

The effect of salt addition on the hydrolysis rate of dextrin in the presence of the random copolymer catalyst were investigated. The results are summarized in Table I. The catalytic activity of the copolymer is... 

No. Rate of Salt Added the Dextrin at Catalyst 80°C° ko6s/k°ju /t(rto acid pH... 

The catalytic activities of the block copolymer on the hydrolysis of dextrin also were investigated. Figure 8 shows the plots of reaction rate against the substrate concentration. Similar tendency, but larger rate enhancement of the reaction are found compared with that in the presence of the random copolymer catalyst (Figure 4). 

Figure 8. Dependence of dextrin hydrolysis rates (v) on the substrate concentration in the presence of the block copolymer at 70°C. [Catalyst] = 1.00 X 10 2N. Catalyst (mole ratio of vinyl alcohol to styrenesulfonic acid units in the copolymer) (O) sulfuric acid (%) block copolymer No. 1 (1-4) (A) block copolymer No. 2 (9.8) (A) block copolymer No. 3 (22.1).

The effect of microwave radiation on maize, potato, and cassava starch (all either air-dried, in slurry, or pregelatinized) has been studied by Muzimbaranda and Tomasik.295a Starch readily dextrinized under such treatment. The sensitivity to microwaves increased in the order com > cassava >> potato starch. Micro-wave radiation also allowed facile cross-linking of starch with formaldehyde. The reaction took place for 5-15 min. and did not require any catalyst. Extended periods of reaction led to dextrins. In the presence of hydrogen peroxide, starch could be cross-linked with acetylene.2953... 

Dextrins are produced by dry heating (roasting) starch in the presence of an acid catalyst. They are produced in a range of viscosity and color specifications. Dextrins are primarily used as adhesives in paper conversion, such as laminating and envelope production. A low-viscosity dextrin is used in Europe as a total chlorine free (TCF) coating binder for application on TCF paper. 

Biomimetic Chemistry, including that involved in the synthesis and study of artificial enzymes, has grown to enormous proportions. Even the part of the field using cyclo-dextrins as binding groups in synthetic catalysts that mimic enzymes has been the subject of a large review article [1]. Thus in this chapter I will focus mainly, but not exclusively, on work from our own laboratory. Other chapters will help make up for this somewhat narrow focus. I have published several reviews of our work elsewhere [2-51]. 

An important feature of the enzymatic systems is the presence of a binding site. Thus it is attractive to learn how to construct vitamin B6-dependent enzyme models that can provide a substrate binding site and perform molecular recognition. The first example was a catalyst (23) in which pyridoxamine was linked to the primary face of [1-cyclo-dextrin (P-CD) through a sulfur atom [15]. Catalyst 23 could transform a-keto acids into a-amino acids, as pyridoxamine does, but with selectivity. That is, phenylpyruvic acid... 

The application of enzymes as catalysts in organic chemistry is closely linked to their immobilization. Indeed, many enzymes are only available in an immobilized form. The immobilized enzymes can be used as received, greatly easing their application. Numerous of these readily available immobilized enzymes are now the working horses of biocatalysis. This has even led to the incorrect use of the abbreviation of an enzyme name for a specific enzyme preparation, that is CALB for the immobilized form of Candida antarctica lipase B on cross-linked polymethacrylate (also known as Novozym 435). Vice versa the commercial name of an enzyme preparation-Amano PS-has taken the place of the enzyme (Burkhdderia cepacia lipase on dextrin or diatomaceous earth). Surprisingly, often no attention is paid to the fact that the enzyme is immobilized [1]. 

STADEX Dextrins are partially hydrolyzed starches that are prepared by heating or dry roasting starch in the presence of an acid catalyst. The conversion process - the change from starch to dextrin - changes the properties of the parent starch in several ways. Notably, the dextrin exhibits a thinner cooked-paste viscosity, an increased cold water solubility, and a color change from white to off-white or yellow. 

Cadmium oxide, calcined dolomite, calcium chloride, calcium oxide, carbomethylcellulose (CMC), carbonates, catalysts, cellulose acetate, ceramics, charcoal, clay, coal, cocoa powder, coffee powder, coke, copper, corn starch Detergents, dextrine, dimethylterephthalate (DMT), dolomite, ductile metals, dusts, dyes Earthy ores, eggshells, elastomers, emulsifiers, epoxy resins... 

With knowledge of the discussion about the site of the - biphasic - action (interfacial conversion versus reaction in the bulk of the liquid [130, 216]) the aqueous phase hydroformylation of higher ( heavier ) alkenes is still much investigated (e. g.. Refs. [216 b, 217 a, 218 g, 219 f, h, 231]). There is a certain trend to recommend high-molecular ligands for this purpose (e. g., calix[4]arenes, dextrins, etc.). Other papers describe the hydroformylation of special alkenes using Co or Ru catalysts [232]. 

On the other hand, Acton accepted the definition that British gums are products of heating of starch either alone or with a basic catalyst. Additionally, many technicians understand British gums to be the products prepared with catalytic amounts of acids. In this situation, the classification of dextrins in accord with some selected physical properties should be given priority. It parallels, to a certain extent, the foregoing classifications as, for instance, the solubility of white dextrins ranges from 1 to 95%, and their water uptake is described by a ratio of dextrin to water of 1 1 to 1 5. Yellow dextrins are water-soluble to the extent of 95 to 100%, and their water uptake is 1 1.5 to 1 0.75, and even less. British gums resemble white dextrins in their solubility, but simultaneously they form more-viscous solutions. 

The solubility-temperature relationship for 1 hofheating of starch, with nitric acid as the catalyst, is presented in Fig. 11. The solubility of dextrins formed can be influenced by contact with the atmosphere. Vacuum, as well as air flow, favor the presence of soluble matter in dextrinized starch (see Fig. 12). However, the effect observed may be attributable to continuous removal of moisture. On the other hand, the results of the present authors showed that the course of dextrinization under nitrogen, carbon dioxide, and in air yields different dextrins of various solubility and stability after a given period of dextrinization. 

A different chemistry must be involved in the formation of pyrodextrins, that is, the dextrinization of starch in the presence of catalysts. TTie methylation analysis of various pyrodextrins " indicated this well (see Tables... 

XX and XXI) it revealed differences between the results for pyrodextrins obtained in the presence of an acid catalyst and for British gums. If the problem of roasting of starch in the presence of a catalyst is to be discussed in detail, dextrinization under the influence of acids, alk s, and oxidants must be considered separately. 

Acid catalysts certainly favor hydrolysis, at least in the first stage of dextrinization. The (1 — 6) bonds are disintegrated, and shorter chains are formed from (1 - 4) intermolecularly bonded D-glucosyl units. This corresponds to the formation of white dextrins (8). However, it was noted that... 

Several questions arise about the role of the acid catalyst in dextrinization. Such catalysts are known to promote a carbonium ion mechanism of sugar polymerization in which some rings can be opened. Perhaps, in the case of dextrinization, both the heterogeneity of the process and steric reasons protect the rings against attack by the acid. The nature of the acid catalyst and the mode of its interaction also play an essential role. The mild action of polyphosphoric acid in dextrinization was interpreted in terms of the possibility of its esterification with i>-glucosyl units. Some volatile adds. 

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