Clay, acid

The original acid—clay developers have been largely replaced by phenohc compounds, such as para-substituted phenohc novolaks. The alkyl group on the phenohc ring is typically butyl, octyl, nonyl, or phenyl. The acidity is higher than that of a typical unsubstituted novolak because of the high concentration of 2,2 -methylene bridges. 

Chemicals responsible for odor in some PUR foams were synthesised by polymerisation of PO in CH2CI2 with Bp2(C2H )20 catalyst (114). The yield was 25% volatile material and 75% polymeric material. The 25% fraction consisted of dimethyldioxane isomers, dioxolane isomers, DPG, TPG, crown ethers, tetramers, pentamers, etc, and 2-ethy1-4,7-dimethyl-1,3,6-trioxacane (acetal of DPG and propionaldehyde). The latter compound is mainly responsible for the musty odor found in some PUR foams. This material is not formed under basic conditions but probably arises during the workup when acidic clays are used for catalyst removal. 

The choice of catalyst is based primarily on economic effects and product purity requirements. More recentiy, the handling of waste associated with the choice of catalyst has become an important factor in the economic evaluation. Catalysts that produce less waste and more easily handled waste by-products are strongly preferred by alkylphenol producers. Some commonly used catalysts are sulfuric acid, boron trifluoride, aluminum phenoxide, methanesulfonic acid, toluene—xylene sulfonic acid, cationic-exchange resin, acidic clays, and modified zeoHtes. 

Some chlorine and chlorate also form through competing reactions. Chlorine dioxide is also evolved from mixtures of powdered sodium chlorite and acidic clays or alumina. 

The initiator usually constitutes less than 1% of the final product, and since starting the process with such a small amount of material in the reaction vessel may be difficult, it is often reacted with propylene oxide to produce a precursor compound, which may be stored until required [6]. The yield of poloxamer is essentially stoichiometric the lengths of the PO and EO blocks are determined by the amount of epoxide fed into the reactor at each stage. Upon completion of the reaction, the mixture is cooled and the alkaline catalyst neutralized. The neutral salt may then be removed or allowed to remain in the product, in which case it is present at a level of 0.5-1.0%. The catalyst may, alternatively, be removed by adsorption on acidic clays or with ion exchangers [7]. Exact maintenance of temperature, pressure, agitation speed, and other parameters are required if the products are to be reproducible, thus poloxamers from different suppliers may exhibit some difference in properties. 

BNFMRA 1st series acid clay and acid peat 10 53-66 0 046... 

The British Non-Ferrous Metals Research Association carried out two series of tests, the results of which have been given by Gilbert and Gilbert and Porter these are summarised in Table 4.12. In the first series tough pitch copper tubes were exposed at seven sites for periods of up to 10 years. The two most corrosive soils were a wet acid peat (pH 4-2) and a moist acid clay (pH 4-6). In these two soils there was no evidence that the rate of corrosion was decreasing with duration of exposure. In the second series phosphorus-deoxidised copper tube and sheet was exposed at five sites for five years. Severe corrosion occurred only in cinders (pH 7 1). In these tests sulphides were found in the corrosion products on some specimens and the presence of sulphate-reducing bacteria at some sites was proved. It is not clear, however, to what extent the activity of these bacteria is a factor accelerating corrosion of copper. 

Alkyl aryl ketones can be converted to arylacetic acid derivatives in an entirely different manner. The reaction consists of treatment of the substrate with silver nitrate and I2 or Br2, ° or with thallium nitrate, MeOH, and trimethyl orthoformate adsorbed on Montmorillonite K-10 clay, an acidic clay. ... 

Another major cause of waste is the use of mineral acids (H2SO4, H3PO4, etc.) and Lewis acids (AICI3, ZnCL), often in stoichiometric amounts, which cannot be recovered and recycled. A typical example is the HNO3/H2SO4 mixture used in aromatic nitrations. Consequently, there is a discernible trend towards the use of solid, recyclable Brpnsted and Lewis acids, e.g. zeolites, acidic clays, etc. (see later) as alternatives to conventional mineral and Lewis acids. 

Many standard reactions that are widely applied in the production of fine chemicals employ. strong mineral or Lewis acids, such as sulphuric acid and aluminium chloride, often in stoichiometric quantities. This generates waste streams containing large amounts of spent acid, which cannot easily be recovered and recycled. Replacement of these soluble mineral and Lewis acids by recyclable. solid acids, such as zeolites, acid clays, and related materials, would represent a major breakthrough, especially if they functioned in truly catalytic quantities. Consequently, the application of solid acids in fine chemicals synthesis is currently the focus of much attention (Downing et al., 1997). 

The formation of colored materials from leuco bases such as 4 and 5 is accomplished by treatment with acids such as acid clay, bisphenol A, acetic acid, or silica gel.39 For leuco base 4 the leaving group is hydroxy, alkoxy, or cyanide, or a nitrogen-containing heterocycle. 

Traditionally, the production of LABs has been practiced commercially using either Lewis acid catalysts, or liquid hydrofluoric acid (HF).2 The HF catalysis typically gives 2-phenylalkane selectivities of only 17-18%. More recently, UOP/CEPSA have announced the DetalR process for LAB production that is reported to employ a solid acid catalyst.3 Within the same time frame, a number of papers and patents have been published describing LAB synthesis using a range of solid acid (sterically constrained) catalysts, including acidic clays,4 sulfated oxides,5 plus a variety of acidic zeolite structures.6"9 Many of these solid acids provide improved 2-phenylalkane selectivities. 

The behaviour of M2D-C3-0-(E0)ra-CH3 over time (4 weeks) has been monitored by FIA-APCI-MS in the presence of Al(OH)3, CaC03 (calcite), FeO(OH) (goethite), Fe203 (hematite), halloysite, illite, kaolinite, sand, pumice, talc and Ti02 (anatase), and provides some useful comparative information regarding silicone surfactant behaviour in the presence of various solid media [10]. In general, the results indicated a dependence of parent molecule recovery on pH, with lower recoveries obtained with more extreme pH values (i.e. halloysite and sand, pH 3.7 and 4.8, respectively), consistent with the known pH instability of trisiloxanes under aqueous conditions [3,11,12,16]. In particular, the loss of the parent molecule was most rapid in the presence of the clay, halloysite, and is consistent with other reports of acceleration of silicone hydrolysis in the presence of acid clays [23-25]. Comparison of the recovery of M2D-C3-0-(E0) -CH3 in the presence of halloysite, kaolinite and illite clays (0.1%, 10 mg g-1) by FIA-APCI-MS is presented in Fig. 5.5.1 [10],... 

Most importantly, biomass pyrolysis will be carried out at remote locations, and in distributed manner. Thus, the catalysts should be cheap and simple to use. Acidic clays, silica aluminas and H-FAU type zeolites are relatively cheap and robust materials, can be mixed easily with heat carriers, and used for pyrolysis. Efficient contact between the solids (catalyst and biomass) to maximize catalytic action is one of the challenges that need to be overcome. 

Also other Type B and C series from Table II are consistent with the above elimination mechanisms. The dehydration rate of the alcohols ROH on an acid clay (series 16) increased with the calculated inductive effect of the group R. For the dehydrochlorination of polychloroethanes on basic catalysts (series 20), the rate could be correlated with a quantum-chemical reactivity index, namely the delocalizability of the hydrogen atoms by a nucleophilic attack similar indices for a radical or electrophilic attack on the chlorine atoms did not fit the data. The rates of alkylbenzene cracking on silica-alumina catalysts have been correlated with the enthalpies of formation of the corresponding alkylcarbonium ions (series 24). Similar correlations have been obtained for the dehydrosulfidation of alkanethiols and dialkyl sulfides on silica-alumina (series 36 and 37) in these cases, correlation by the Taft equation is also possible. The rate of cracking of 1,1-diarylethanes increased with the increasing basicity of the reactants (series 33). 

Fe, intermediate in sandy loams high in organic C and low in active Fe, and least in acid clays high in active Fe. The increases in soluble P are particularly linked to the transformations of Fe and changes in pH. The main processes are ... 

Soil. In laboratory microcosm experiments kept under aerobic conditions, half-lives of 7.2 and 1.7 d were reported for 2-chlorophenol in an acidic clay soil (<1% organic matter) and slightly basic sandy loam soil (3.25% organic matter) (Loehr and Matthews, 1992). In a nonsterile clay loam soil, a loss of 91% was reported when 2-chlorophenol was incubated in a nonsterile clay loam at 0 °C. Nondetectable levels of 2-chlorophenol was reported in sediments obtained from a stream at 20 °C after 10 to 15 d (Baker et ah, 1980). 

Soil. In laboratory microcosm experiments kept under aerobic conditions, half-lives of 5.1 and 1.6 d were reported for 2-methylphenol in an acidic clay soil (<1% organic matter) and slightly basic sandy loam soil (3.25% organic matter) (Loehr and Matthews, 1992). 

Khan, S.U. Adsorption of 2,4-D from aqueous solution by fulvic acid-clay complex. Environ. Sci. Technol, 8(3) 236-238, 1974. 

Metal nitrates supported on various acidic clays have been used as nitrating agents for some reactive aromatic substrates in attempts to improve product isomer ratios." ... 

Sidhu, P.S. Gilkes, R.J. Posner, A.M. (1981a) Oxidation and ejection of nickel and zinc from natural and synthetic magnetites. Soil Sci. Soc. Am. J. 45 641-644 Sidhu, P.S. Gilkes, R.J. Cornell, R.M. Posner, A.M. Quirk, J.P. (1981) Dissolution of iron oxides and oxyhydroxides in hydrochloric and perchloric acids. Clays Clay Min. 29 269-276... 

However, when it comes to the more important 2,2-diaryl derivatives (1.25), the routes illustrated in Figure 1.7 are not very useful. For these derivatives the almost universally adopted synthetic method involves the reaction of a l,l-diarylprop-2-yn-l-ol (1.24) with a substituted phenol or naphthol in the presence of an acid catalyst. The acid catalyst can be alumina, an acidic clay or Nafion for heterogeneous reactions, or trifluoroacetic acid, p-toluenesulfonic acid and dodecylbenzenesulfonic acid for reactions carried out in solution. The alkynols are prepared by reaction of a benzophenone (1.22) with a Na or Li derivative of an alkynide, such as the trimethylsilyl acetylide (1.23), (Figure 1.8). ... 

With this purpose, several different types of solid acid catalysts have been investigated for the acylation of aromatics, but the best performances have been obtained with medium-pore and large-pore zeolites (3-9). In general, however, the use of acylating agents other then halides, e.g., anhydrides or acids, is limited to the transformation of aromatic substrates highly activated towards electrophilic substitution. In a previous work (10), we investigated the benzoylation of resorcinol (1,3-dihydroxybenzene), catalyzed by acid clays. It was found that the reaction mechanism consists of the direct 0-benzoylation with formation of resorcinol monobenzoate, while no primary formation of the product of C-benzoylation (2,4-dihydroxybenzophenone) occurred. The latter product formed exclusively by... 

Fig. 38 WAXD patterns of stearic acid, clay, and swollen clay. The swollen clay was prepared by mixing stearic acid and organically modified clay (Nanofil-15) at the ratio of 1 1...

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