Studies in organobismuth chemistry

Perturbations in the bismuth market resulted in Mining and Chemical Products Ltd., seeking further outlets in the market. Together with Manchem Ltd. they were anxious to evaluate the possibility of using bismuth compounds as a replacement for lead/calcium soaps in paint driers. A range of new organobismuth compounds were synthesised of the type RBiX2 and R3BiX2 (X= halogen, OOCR, dithiocarbamate). A variety of synthetic techniques were explored, including the use of mathematical reactions, phase-transfer catalysis and microwave energy. The preparation of a range of trivalent and pentavalent organobismuth carboxylates is reported and their infra-red , 13C, lH nmr spectra. The compounds were evaluated as paint driers and in cases found to enhance paint drying to a greater degree than the standard driers, to which they were being compared. The drying times of paint films containing the organobismuth compounds are reported, together with a comparison of the drying times with the addition of bismuth tris-diethyldithiocarbamate, which may promote the cross-linking reaction that occur in paint films during the drying process. Examples are reported to illustrate the great reductions in reaction times possible when using microwave energy. Reactions such as metallation of aromatic rings, ligand redistribution and synthesis were carried out in PTFE containers in a conventional domestic microwave oven. An X-ray diffraction study of (phenylazophenyl-C,N')mercury(II) chloride has shown it to be dimeric via long Hg-Cl bridging interactions of 3.367A. Its crystal structure is reported, together with its 13C nmr spectra and mass spectrum. The Lewis acidity of compounds of the type RBiX2 was investigated. The donor group being anchored to the organo group (R). The dithiocarbamates bis- (diethyldithiobarbamato)phenylbismuth(Ill) and [2-2-pyridyl)phenylbismuth(III) were synthesised, and their crystal structures, 14N, 13C nmr ar1d infra-red spectra are reported. Both compounds are pseudo-pentagonal bipyramidal in geometry, with two long Bi-S bonds and two short Bi-S bonds. The reaction of RBiBr2 (R= 2-(pyridyl) with various ligands is reported. The infra-red evidence suggesting that the coordination of extra ligands is accompanied by a reduction of the strength of the Bi-interaction.

Drying processess in the United Kingdom:assessment of industrial energy utilisation and efficiency of drying systems and the modelling of drying characters using neural networks (BL)

Drying is an important unit operation in process industry. Results have suggested that the energy used for drying has increased from 12% in 1978 to 18% of the total energy used in 1990. A literature survey of previous studies regarding overall drying energy consumption has demonstrated that there is little continuity of methods and energy trends could not be established. In the ceramics, timber and paper industrial sectors specific energy consumption and energy trends have been investigated by auditing drying equipment. Ceramic products examined have included tableware, tiles, sanitaryware, electrical ceramics, plasterboard, refractories, bricks and abrasives. Data from industry has shown that drying energy has not varied significantly in the ceramics sector over the last decade, representing about 31% of the total energy consumed. Information from the timber industry has established that radical changes have occurred over the last 20 years, both in terms of equipment and energy utilisation. The energy efficiency of hardwood drying has improved by 15% since the 1970s, although no significant savings have been realised for softwood. A survey estimating the energy efficiency and operating characteristics of 192 paper dryer sections has been conducted. Drying energy was found to increase to nearly 60% of the total energy used in the early 1980s, but has fallen over the last decade, representing 23% of the total in 1993. These results have demonstrated that effective energy saving measures, such as improved pressing and heat recovery, have been successfully implemented since the 1970s. Artificial neural networks have successfully been applied to model process characteristics of microwave and convective drying of paper coated gypsum cove. Parameters modelled have included product moisture loss, core gypsum temperature and quality factors relating to paper burning and bubbling defects. Evaluation of thermal and dielectric properties have highlighted gypsum's heat sensitive characteristics in convective and electromagnetic regimes. Modelling experimental data has shown that the networks were capable of simulating drying process characteristics to a high degree of accuracy. Product weight and temperature were predicted to within 0.5% and 5C of the target data respectively. Furthermore, it was demonstrated that the underlying properties of the data could be predicted through a high level of input noise.