M.S.

The process of fractional distillation has been performed for many years but has only within the past half century become a true science. However, because of the many variables involved and the uncertainty of their effect upon fractionating column efficiency, the design of columns has long been a major engineering problem. Plate and column efficiencies, as given in the literature, vary widely and it was thought possible that the inconsistencies of the results reported might be due to poor equilibrium within the column, caused in part by faulty sampling. In order to determine the operating characteristics of a fifteen plate bubble-cap column (8-3/8" I.D., one 3-7/8" bubble-cap per plate, and plate spacing of 5-7/8"), the effects of the operating variables, and the distillation characteristics of two different types of binary mixtures, the column assembly was redesigned for continuous distillation and provisions made for the introduction of feed at its boiling point to any one of the bottom eight plates. The binary — mixtures distilled were isopropyl alcohol — water (distillation rates 157 - 376 gms./min., feed concentrations 3.1 - 10.8 mol per cent isopropyl alcohol, reflux ratio 3:1, and feed rate of 330 gms./min.), and toluene - ethylene dichloride (distillation rates 203 and 196 gms./min., feed concentrations 41.4 and 39.7 mol percent ethylene dichloride, reflux ratio 4:1, and feed rate of 138 gms./min.) In order to reduce the possibility of disturbances within the column by removal of large plate samples, the refractive index method of analysis was used which required maximum samples of only 4 ml. Results of the experiments made indicated that the assumption of the McCabe - Thiele operating line is probably incorrect. In the case of the isopropyl alcohol — water fractionation, a considerable divergence (largest between 10 and 40 mol per cent isopropyl alcohol) between the McCabe - Thiele and the actual operating line was noted, the actual operating line being a curve approximately the shape of the equilibrium curve. Murphree Plate Efficiencies for the mixture varied from 0 to 100 per cent, depending primarily on the relative deviations of the two operating lines from the equilibrium curve. The McCabe - Thiele operating line for the system toluene — ethylene dichloride closely approximated the actual operating line. Murphree Plate Efficiencies varied from 44.5 to 121 percent, but the individual plate efficiencies were more consistent with the average efficiency. The rate of distillation over the range of 157 to 376 gms./min. and feed concentration over the range of 3.1 to 10.8 mol percent isopropyl alc1ohol, at a reflux ratio of 3:1 had negligible effect on product purity which ranged from approximately 62 to 67 mol per cent isopropyl alcohol. / Master of Science

An important factor preventing a more widespread acceptance of magnesium alloys in the chemical industry is its susceptibility to various forms of corrosion. Stress-corrosion cracking, occurring under conditions of residual fabrication stresses or high external stresses, is a severe localized corrosion type which can bring about complete failure in most wrought magnesium alloys. Previous investigations concerned with stress-corrosion cracking of magnesium alloys have dealt with its occurrence only in the sheet metal. The investigation involved accelerated laboratory stress-corrosion cracking tests on a commercial extrusion. Standard tension test specimens of magnesium alloy FS-1 extruded rectangular bar were subjected to bending in constant deformation by loading them transversely as end-supported center-loaded beams. The apparatus was constructed of angle irons for end supports and steel bars for an adjustable center load. Maximum tensile strains were measured with electric strain gages and corresponding stresses were determined from the tensile stress-strain diagram for the alloy. A corrosive medium of 35 grams per liter of sodium chloride and 20 grams per liter of potassium chromate was placed in small sections of glass tubing sealed to the specimen surface at the region of maximum tensile stress. The effects of the magnitude of tensile stress and pH on time to failure were investigated and the stress corrosion cracking limits (critical stresses) were determined at various pH values from 0.5 to 11.85. The apparatus was satisfactory for laboratory testing and the basic design was recommended to be adopted as a standard. The effect of creep was corrected to some extent, since creep rates were very high. The minimum critical stress for the alloy was found to be 27,600 psi, or 125 per cent of the tensile yield strength, at a pH of 3.0-3.5. Values of pH between 6.0 and 8.5 have no appreciable effect on the critical stress, although pH values below 3.0 and above 8.5 increase the stress-corrosion limit. From pH 6.0 to 3.5 critical stress is decreased from 29,300 psi to 27,600 psi. Creep was evident at strains of 3985 microinches and higher. / Master of Science

A study was made of the problem of differential thermal analysis utilizing statistical experimental design. A factorial type of design was chosen to yield maximum efficiency of the data obtained. “Lakeland”, Florida Kaolin of commercial whiteware grade was selected because of its relative purity. Due to the large number of samples to be analyzed, it was found necessary to choose a commercial brand rather than a very pure kaolinite which was found impossible to obtain in sufficient quantity. A statistical 2x3x3 factorial design was used and the calculations incident thereto made in detail. Data, which to the eye appeared erratic, was found to be acceptable within the probability limits of error of the experiment. The effects of two different furnaces, three rates of heating, and three densities of the samples were analyzed to determine the area under the endothermic reaction peaks as measured by Cr-Al differential thermocouples. It was found that densities and rates both yielded highly significant values and that the interactions of the two showed significant results when examined by a distribution of “F”¹. These effects were analyzed for the regressions therein and were found to be significant in the linear trends only. From this indication it would seem evident that the optimum density and rate of heating had not been reached in the limits of this experiment. Replications and furnaces did not yield significant results when tested by “F” distribution. From this it was deduced that the experiment could be conducted with sufficient precision under the present procedure and conditions and reproducibility obtained irrespective of the furnace used. Examination of the data will indicate that the level of the two furnaces is different, but the trends within are in the same areas. A certain amount of erratic data were obtained due to a lag in heating rates and this difficulty will be discussed. / Master of Science

This study was undertaken for the following reasons: 1. Nicotine and its compounds have long been used as insecticides, and are in great demand at the present. 2. Tobacco, the source of nicotine, is such a valuable commodity that only waste has been used as a source of nicotine for years. 3. <i>N. rustica tabacum</i>, a species of tobacco, has a high nicotine content, and has been grown under climate and environment suitable for other types of tobacco. The purpose of the investigation is as follows: 1. Preparation of a nicotine hydrochloride dust insecticide from the entire tobacco plant. 2. To make a study of the costs of cultivating flue cured tobacco and the costs of cultivating tobacco that could be used for the preparation of the dust. 3. To determine the price at which the tobacco farmer could sell high nicotine content tobacco and still make the profit he realizes from the cultivation of the flue cured tobacco. / Master of Science

The 18-inch coke-packed absorption tower used in this investigation was located in the Unit Operations Laboratory of the Department of Chemical Engineering, Virginia Polytechnic Institute, Blacksburg, Virginia. During the course of this work a number of changes and additions to existing equipment were made in an effort to improve the operation of the tower. Nineteen experiments, using carbon dioxide, in a flue gas mixture, as the solute and water as the solvent were made to determine some of the operating characteristics of the tower. A new gas sealer was designed and constructed using a spiral cooling unit made from 5-inch stove pipe elbows. The elbows were coated with silicone resin in an effort to reduce corrosion. The capacity of this unit was approximately 50% greater than the open-spray type sealer used previously. The examinator used heretofore to measure gas velocities through the tower was replaced by a pitot tube and draft gage in an effort to facilitate this determination. A Precision Mine-Air model Great apparatus was installed to replace the Technical flue-gas model used in previous experimental work. Gas samples were taken for analysis by means of gas sampling bottles which permitted the use of short sampling tubes. These two changes in equipment and procedure greatly simplified the accurate determination of CO₂ in the gas stream. Orifices, metering central valves, and manometers were installed in all pipe lines conveying materials to the tower in order to increase the ease and accuracy of controlling the flow of these various materials. After the above changes had been completed, a series of nineteen test runs was made. As a result of the data collected the following conclusions were drawn: 1. The relation between the overall liquid film coefficient (K_LA); the solvent rate (L¹), and the partial pressure (P) of the CO₂ in the gas stream may be expressed by the equation Log K_LA= L¹/7.966-0.544L¹ + 0.000242 P within the limits as listed below: a. Gas velocity…..12.7 lb. mols air/hr./sq.ft. b. Solvent rate…..65 to 115 lb. mols water/hr./sq.ft. c. Partial pres. of CO₂…..37 to 90 mm. Hg. d. Temperature of water…..53.5 to 65.7°F. e. Temperature of gas…..56 to 85°F. 2. No correlation could be made between the overall liquid film coefficient (K_LA) and the pressure drop (ΔP) through the packed section of the tower. 3. The flue gas cooler which was designed and built during the course of this investigation (See Figure 3, page 38) is capable of cooling 650 lb./hr. of dry air from approximately 700°F to 70°F using 15,000 lb./hr. of cooling water at an inlet temperature of 58°F. / Master of Science

The aerodynamic characteristics of bridge sections can be determined by simple wind-tunnel tests. These characteristics can then be used to determine the lift force and overturning moment on any bridge section without large scale model tests. Also, the slope of the lift and torque curves obtained in these tests determine the aerodynamic stability or instability of the bridge section. Our problem was to determine the aerodynamic characteristics of typical bridge sections and attempt to find aerodynamically stable sections. The lift, torque and drag curves were obtained by holding the model stationary at different angles of attack in the wind-tunnel. The results obtained from these tests were confirmed by pressure distribution tests. In these tests the model was held stationary in the air stream, while pressure was measured by manometer readings at eleven points across the desk. Results of this investigation show that girder sections with deck at mid-height or flush are unstable except for low d/b ratios. Sections that yield both torsional and vertical stability are truss sections, an H-section with center slot and fins, and an H-section with fins. Other modifications of sections furnish curves which indicate neutrality. These sections can be used then sufficient damping is present. This investigation also shows that present wind-load specifications are inadequate and need to be revised. / Master of Science

The development of the Friedel-Crafts reaction using anhydrous aluminum chloride in the condensation or aromatic hydrocarbons and alkyl or acyl halides has resulted in many new and diversified applications of this reaction, such as the preparation of hydrocarbons, keto acids, acids, ketones, and phenols. Halides of iron, tin, phosphorus, zinc, and other metals, and acids such as phosphoric, sulfuric, and anhydrous hydrofluoric have been found to catalyze a large number of reactions of this type. These same catalysts now find a wide commercial application in the alkylation of paraffins and naphthenes, and other types of reactions, such as isomerization, transfer of radicals, and cracking of petroleum. Although the Friedel-Crafts synthesis is very widely used in organic syntheses because of its high efficiency, very little work has been done toward developing a more economical catalyst. The anhydrous aluminum chloride generally used is wholly or partially consumed in a large number of the reactions, in addition to presenting a difficult corrosion problem. Some work has recently been done by Sachanen and Caesar⁽²⁵⁾ on the catalytic effect of activated clays and the type of silica-alumina catalysts used in the cracking of petroleum, when used in a Friedel-Crafts type reaction. The limited amount of work which has been done so far indicates that it might be economical to use a synthetic silica-alumina type catalyst to replace the anhydrous aluminum chloride in reactions of this type, because it could be used for some time without replacement. The object of this investigation was to determine the feasibility of using different synthetic silica-alumina type catalysts in the condensation of benzene with acetic anhydride to produce acetophenone. / Master of Science

M.S.

The tannin extract industry disposes of large volumes of condensate liquors evolved during concentration of weak leach liquors obtained by extraction of wood chips. The liquors are highly corrosive due to acetic acid contained therein along with lesser quantities of other organic substances common to woody materials. Recovery of the acetic acid would be desirable from two standpoints: (1) the value of the acetic acid, and (2) reuse of the acid-free condensate in the manufacturing process. The purpose of this investigation was to recover acetic acid from the wastes of tannin extract manufacture. An ion exchange process was given primary consideration to accomplish the recovery by adsorption of the acetic acid from the waste liquor with subsequent elution of the acid from the ion exchange material by use of stronger acid. Tests were conducted using De-Acidite, a synthetic aliphatic amine anion exchange resin produced by the Permutit Company, New York, N.Y.. For all tests 200 ml. of resin were used at temperatures within 20-30°C. A total acid-binding capacity of 19,700 grains CaCO₃/ft.³ was found when De-Acidite was exposed to 0.5 percent acetic acid in batch operation. Optimum rate of flow determinations in column operation within the range of 1 to 5 gal./ft.²/min. were conducted. Variations of flow rates between these limits failed to produce substantial differences in breakthrough capacities. To prepare the De-Acidite bed in the ion exchange column between runs regeneration was effected with 1 percent sodium hydroxide. Rinse was by downflow operation until data was obtained which indicated its unsuitability; thereafter backwash rinse was used and found more satisfactory. The waste liquor used in the investigation was obtained from the 2nd and 3rd effects of a triple effect evaporator employed in the Mead Corporation Plant at Lynchburg, Virginia. Successive exposures of De-Acidite to the waste liquor resulted in sharp reduction of breakthrough capacity, discoloration of the De-Acidite, and deterioration of the resin with the formation of fines. It was found that the extremely small quantities of tannin present in the waste liquor were the cause of the rapid depreciation of the De-Acidite. / M.S.