Alkaline catalysts removal

The requisite intermediate, ethyl 4-dimethylaminocyclohexylcarboxylate is prepared as follows 33 g of ethyl p-aminobenzoate dissolved in 300 cc of absolute ethanol containing 16.B cc of concentrated hydrochloric acid is hydrogenated at 50 pounds hydrogen pressure in the presence of 2 g of platinum oxide. The theoretical quantity of hydrogen is absorbed in several hours, the catalyst removed by filtration and the filtrate concentrated to dryness in vacuo. The residue Is dissolved in water, made alkaline with ammonium hydroxide and extracted with chloroform. After removal of the solvent, the residual oil is distilled to yield ethyl 4-aminocyclohexylcarboxylate, boiling point 114°C to 117°C/10 mm. 

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. 

The process involves reacting the degummed oil with an excess of methyl alcohol in the presence of an alkaline catalyst such as sodium or potassium methoxide, reaction products between sodium or potassium hydroxide and methyl alcohol. The reaction is carried out at approximately 150°F under pressure of 20 psi and continues until trans-esterification is complete. Glycerol, free fatty acids and unreacted methyl alcohol are separated from the methyl ester product. The methyl ester is purified by removal of residual methyl alcohol and any other low-boiling-point compounds before its use as biodiesel fuel. From 7.3 lb of soybean oil, 1 gallon of biodiesel fuel can be produced. See FIGURE 12-5. 

The ester is prepared by catalytic hydrogenation of 4-tert-butylphenol followed by acetylation of the resulting 4-tert-butylcyclohexanol [132]. If Raney nickel is used as the catalyst, a high percentage of the trans isomer is obtained. A rhodium-carbon catalyst yields a high percentage of the cis isomer. The trans alcohol can be isomerized by alkaline catalysts the lower-boiling cis alcohol is then removed continuously from the mixture by distillation [133]. 

Another method of prepn of acetyl laurin is to treat triacetin (see under Acetins), in the presence of an alkaline catalyst with lauric acid to replace one of the acetyl groups. The AcOH produced by the reaction can be removed by azeotropic distn using sufficient hydrocarbon solvent to maintain the distn temp at ca 200°... 

BDF is produced currently by a chemical process with an alkaline catalyst, which has some drawbacks, such as the energy-intensive nature of the process, the interference of the reaction by free fatty acids (FFAs) and water, the need for removal of alkaline catalyst from the product, the difficulty in recovering glycerol, and the treatment of alkaline wastewater. To overcome these problems, the processes using ion-exchange resins (Shibasaki-Kitakawa et al., 2007), supercritical MeOH (Kusdiana and Saka, 2004), MeOH vapor (Ishikawa et al, 2005), and immobilized lipases (Mittelbach, 1990 Nelson et al, 1996 Selmi and Thomas, 1998) have been proposed. In this paper, enzyme processes for production of BDF from waste edible oil, waste FFAs, and acid oil recovered from soapstock are described. In addition, applications of the element reactions to the oil and fat industry are introduced. 

To study the stability of immobilized C. antarctica lipase in methanolysis of waste edible oil, the three-step methanolysis was repeated by transferring the enzyme to a fresh substrate mixture. The conversion was maintained during 50 cycles (100 days) (Watanabe et al., 2001), showing that contaminants in waste oil do not affect the stability of the lipase preparation. In a chemical alcoholysis with an alkaline catalyst, FFAs in a waste edible oil convert to alkaline soap the water present disturbs an efficient reaction. Hence, FFAs and water should be removed before the reaction, and a small amount of alkaline soap generated must be removed by washing with water after the reaction. But the enzymatic process does not need the pretreatment and downstream purification. 

In a FAME production process with an alkaline catalyst method, the catalyst has to be removed from products after the reaction. Otherwise, the byproduct glycerol cannot be utilized in other industries. However, the removal of the alkaline catalyst increases total cost for BDF production. 

When waste edible oil is converted into FAME by use of an alkaline catalyst, free fatty acid has to be removed prior to the reaction to maintain the activity of the catalyst. This however reduces the yield of the process. 

Almost all chemical reactions require a catalyst. Strong acid catalysts cannot be used with wood because they cause extensive degradation. The most favorable catalyst from the standpoint of wood degradation is a weakly alkaline one. Alkaline catalysts are also favored because many of them swell the wood structure and give better penetration (see Table II). The catalyst used should be effective at low reaction temperatures, easily removed after reaction, nontoxic, and noncorrosive. In most cases, the organic tertiary amines are best suited for this purpose. 

The higher the silicone content and the lower the degree of saponification (z = high), the poorer the solubility in water. The saponification reaction with alkaline catalysts can break the silicone chain. Nevertheless, more than 50 wt% of silicone remains covalently bound to the polyvinyl alcohol part after saponification. With a special saponification process found at Wacker Specialties it is even possible to leave more than 60 wt% and up to 99 wt% of the total silicone content covalently bound to the polyvinyl alcohol part after saponification. The unbound silicone can be removed, if desired. 

Organic phosphorus compounds are also produced in the interaction of wliite phosphorus with an epoxide or an episulfide and an alcohol or mercaptane in the presence of alkaline catalysts at 25 °C to 200 °C In order to remove P-H bonds the reaction mixture is treated witli formaldehyde and oxidized. The products are said to be useful as hardeners for epoxy resins or as antistatic agents and fire retardants. 

Vinyl alcohol monomer does not exist because its keto tautomer is much more stable. Poly(vinyl alcohol) can be prepared from either poly(vinyl ester)s or from poly(vinyl ether)s. Commercially, however, it is prepared exclusively from poly(vinyl acetate). The preferred procedure is through a transesterification reaction using methyl or ethyl alcohols. Alkaline catalysts yield rapid alcoholyses. A typical reaction employs about 1% sodium methoxide and can be carried to completion in one hour at 60 °C. The product is contaminated with sodium acetate that must be removed. The reaction of transesterification can be illustrated as follows ... 

Wet oxidation Efficient removal of lignin Low formation of inhibitors Minimizes the energy demand (exothermic) High cost of oxygen and alkaline catalyst... 

Removal of residual TG and catalyst and separation of undesirable products such as free glycerin is another hamper in biodiesel production. Refining methods mostly deal with distillate water. Therefore, alkaline or acidic catalyst removal contributes to water consumption and causes the need for wastewater treatment. As a result, the cost of refining will increase. 

The sample can be pretreated in other ways. For example, it can be passed through a strongly basic anion exchanger hydroxide to remove the free fatty acid, which can subsequently be recovered by elution with aqueous acetic acid. The acetic acid can be removed by evaporation and the fatty acid examined as required. Or it can be passed through a strongly acidic cation exchanger in the acid form so that the free fatty acid can be titrated without interference from alkaline catalysts. 

In this case, a new ester is formed. Generally, alkaline catalysts are used with sodium methylate said to be the most effective, although sodium hydroxide can also be used. Transesterification is an equihbrium reaction. To shift the reaction to the right, it is necessary to use a large excess of alcohol or to remove one of the products from the reaction mixture. The second option is preferred where feasible, as in this way, the reaction can be driven to completion. 

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