Journal of Chemical Technology & Biotechnology

doi: 10.1002/jctb.280590301pmid: N/A

Ni, Xiongwei

doi: 10.1002/jctb.280590302pmid: N/A

Experimental flow pattern and associated residence time distribution measurements are reported for a tube bundle where periodic baffles and fluid oscillation may be present. When there is no fluid oscillation, high Reynolds number flow conditions are required to give sharp residence time distributions. When baffles are present, fluid oscillation can give sharp residence time distributions for modest low net flow Reynolds numbers. These observations extend our previous results and also show the viability of the system, for example in use as a reactor or heat exchanger where a multi‐tube configuration might be required.

Kydros, Konstantine A.; Gallios, George P.; Matis, Konstantine A.

doi: 10.1002/jctb.280590303pmid: N/A

Electrolytic flotation, a rather unconventional flotation technique used in effluent treatment, was investigated on pyrite; the process was enhanced by xanthate and also a cationic collector. This was then compared with classical floatability experiments. Zeta‐potential measurements, under similar pulp conditions, were carried out to explain the process mechanism. The mineral flotation behavior in the presence of common modifiers was also examined during electrolytic flotation. The latter produces fine gas bubbles, has favorable hydrodynamic conditions and assists in flocculation of particles prior to flotation, as shown.

Reyes, Patricio; Orellana, Fresia; Pecchi, Gina

doi: 10.1002/jctb.280590304pmid: N/A

The influence of the Rh loading on the surface properties and catalytic behaviour of Rh/γ‐Al2O3 catalysts has been studied. The series of catalysts presents differences in metal dispersion, reducibility, surface composition and catalytic activity. All the data reported suggest that the differences in catalytic behaviour in the methylcyclohexane dehydrogenation reaction can be explained in terms of electron‐deficient rhodium clusters, essentially when the metal particle size becomes smaller than 15 Å.

Dinnella, Caterina; Lanzarini, Gaetano; Stagni, Andrea; Palleschi, Claudio

doi: 10.1002/jctb.280590305pmid: N/A

Endopectinlyase (EC 4.2.2.10) from Aspergillus japonicus was immobilized on to γ‐alumina. Adsorption performed at pH 5·0 and a subsequent cross‐linking phase using 0·1% glutaraldehyde were the chosen immobilization conditions. The comparison between the main biochemical parameters of the immobilized and free form of the enzyme showed that the immobilization procedure used did not affect the enzyme biochemical properties. The interactions between the carrier and the enzyme are essentially secondary bonding. In fact they depend on the pH and on the presence of phosphate ions in the medium. A tentative chemical model of the biocatalytic matrix thus obtained is proposed.

Beretka, Julius; Cioffi, Raffaele; Santoro, Luciano; Valenti, GianLorenzo

doi: 10.1002/jctb.280590306pmid: N/A

Mixtures made from materials containing reactive oxides of calcium, aluminium, sulphur and silicon which are able, upon hydration, to generate calcium trisulphoaluminate and silicate hydrates, have been studied with a view to possible applications in the field of preformed building elements. The materials employed were natural gypsum, phosphogypsum, fly ash, blast furnace slag, Portland cement and hydrated lime. The samples were cured at 55, 70 and 85°C and 100% RH for 24 h, followed by further curing at ordinary temperatures and humidities (21°C, 67% RH) for up to 28 days. The cured samples were tested for compressive strength and shrinkage. It has been found that the most important effect on the strength is due to the pre‐curing temperature, while the post‐curing time has much less effect. In general, the optimum pre‐curing temperature is 70°C. Satisfactory strength results were obtained even with systems containing up to 80% waste materials.

Madyastha, Kattigere M.; Gururaja, Tarikere L.

doi: 10.1002/jctb.280590307pmid: N/A

A strain of Alcaligenes eutrophus has been isolated from the soil by enrichment culture technique with nerolidol (1), a sesquiterpene alcohol, as the sole source of carbon and energy. Fermentation of nerolidol (1) by this bacterium in a mineral salts medium resulted in the formation of two major metabolites, viz. geranylacetone (2) and an optically active alcohol, (S)‐(+)‐geranylacetol (3). Nerolidol (1)‐induced cells readily transformed 1,2‐epoxynerolidol (4) and 1,2‐dihydroxynerolidol (5) into geranylacetone (2). These cells also exhibited their ability to carry out stereospecific reduction of 2 into (S)‐(+)‐geranylacetol (3). Oxygen uptake studies clearly indicated that nerolidol‐induced cells oxidized compounds 2, 3, 4, 5 and ethyleneglycol (7). Based on the nature of the metabolites isolated, the ability of nerolidol‐induced cells to convert compounds 4 and 5 into geranylacetone (2), and oxygen uptake studies, a pathway for the microbial degradation of nerolidol (1) has been proposed. The proposed pathway envisages the epoxidation of the terminal double bond, opening of the epoxide and cleavage between C‐2 and C‐3 in a manner similar to the periodate oxidation of cis‐diol. The cell‐free extract prepared from nerolidol‐induced cells readily carried out the asymmetric reduction of compound 2 to an optically active alcohol (3) in the presence of NAD(P)H. The cell‐free extract carried out both oxidation and reduction reactions at two different pH values and exhibited wide substrate specificity towards various steroids besides terpenes.

Satagopan, V.; Chandalia, Sampatraj B.

doi: 10.1002/jctb.280590308pmid: N/A

The selective hydrogenation of cinnamaldehyde and other unsaturated aliphatic aldehydes under a two‐phase liquid system using toluene and aqueous alkaline solution over supported palladium catalysts has been investigated with a view to obtaining the corresponding saturated aldehydes with sufficiently high selectivities. In the case of cinnamaldehyde, the effects of various process parameters on the reaction rate and selectivity with respect to the aldehyde have been investigated. The results obtained are likely to be useful for the rational design of the process for the production of industrially relevant products, such as hydrocinnamaldehyde and citronellal using cinnamaldehyde and citral as the starting materials.

Kozempel, Michael; Kurantz, Michael

doi: 10.1002/jctb.280590309pmid: 7764813

A continuous reactor process was developed to produce lactulose from lactose. A system of two CSTRs in series with a tubular finishing reactor gave conversion to lactulose of about 76%. The reactors ran at 71–75°C with a volumetric hold‐up in the CSTRs of 22·7 dm3 and in the tubular reactor of 2·6 dm3. Each CSTR had a nominal residence time of 44 min. The flow rate was 0·53 dm3 min−1.

Rane, Dhananjay S.; Sharma, Man M.

doi: 10.1002/jctb.280590310pmid: N/A

Some new strategies, such as the use of hydrotropes, surfactants, co‐solvent, etc., were applied to the Hofmann reaction of fatty amides to obtain isocyanates, amines and carbamates. Additionally, some industrially important aromatic amines were synthesised.