Börje Sten Gevert

Formation of Fibrillar Boehmite

Fibrillar boehmite is a synthetic form of alumina where the morphology is in the form of fibrils instead of the normal corpuscular form. It is prepared from basic aluminium chloride. In this study a molar ratio of Cl−/Al2O3 of 1 was used. During the preparation the crystallinity of the product increases with time up to 48 h of crystallization. During the crystallization the basic aluminiumchlorhydrol is converted to fibrils over a plane leaf-like morphology. This leaf-like morphology is curved to a fibrillar structure. The fibrils maintain about half of their surface area after a thermal treatment at 950°C compared with a treatment at 500°C.

Aqueous silane modified silica sols: Theory and preparation

The purpose of this paper is to study methods of reacting the surface of the particles of silica sols with silanes, primarily gamma-glycidoxypropyltrimethoxysilane (GPTMS) and study some basic properties of the modified sols and the nature and structure of the silane groups attached to the particle surface. Design/methodology/approach - The surface of the silica particles was modified by reacting the silica sols with aqueous solutions of silanes, chiefly GPTMS. The presence and structure of silane groups on the particle surface were established by Si-NMR and C-NMR, respectively. Findings - Several silanes were studied but silica sols could be readily modified only with GPTMS and glycidoxypropylmethoxydiethoxysilane (GPMDES), most readily if the silanes were pre-hydrolysed in water. Higher degrees of silylation were preferably done by continuous addition of silane. Lower degrees of modification can be achieved at room temperature by the stepwise addition of the silane solution. The silylation of the silica surface with GPTMS significantly reduces the number of charged surface groups and silanol groups. GPTMS binds covalently to the silica surface and the epoxy ring opens and transforms into a diol. Silica sols modified with GPTMS and GPMDES are stable toward aggregation. Research limitations/implications - Only organo-reactive silanes were studied. Originality/value - This is the first work to study the modification by silanes of silica aquasols with high concentrations of silica. The silane modification can extend the use of silica to areas of applications previously inaccessible to silica sols.

Hydrodemetallisation of residual oil with catalysts using fibrillar alumina as carrier material

Abstract Hydroprocessing catalysts were prepared using fibrillar aluminas as carrier materials and sulphides of nickel and molybdenum as active substances. The fibrillar aluminas were obtained from fibrillar boehmite samples prepared at three different synthesis conditions resulting in different fibril sizes. After extrudation and deposition of metals, catalysts combining large surface areas with large average pore diameters were obtained. The catalysts were tested for hydrodemetallisation of an atmospheric residue and the results were compared with those obtained for a commercial reference catalyst with a similar loading of nickel and molybdenum. Two of the catalysts prepared using fibrillar alumina as carrier material were more active than the commercial catalyst. The third catalyst containing the largest alumina fibrils was inferior to the other catalysts in all respects. Catalyst deactivation was investigated in a long-term hydroprocessing experiment using a heavy vacuum residue containing large amounts of metals as a feed oil. The catalyst prepared using fibrillar alumina used in this test showed a constant level of hydrodemetallisation even after 500 h on stream whereas the reference catalyst was completely deactivated after 350 h.

Kinetic parameter estimation and statistical analysis of vanadyl etioporphyrin hydrodemetallization

Parameter estimation and statistical analysis of a new model for vanadyl etioporphyrin hydrodemetallization are performed using both the total sum of squares and the determinant criterion. Point parameter estimates are almost the same for the two objective functions, but the precision is increased when the determinant criterion is chosen. Subsequent statistical analysis shows the parameters are determined not badly, but slightly higher correlation between two parameters and nonrandom trends in residual plots are also detected. Failure in quantitative determination of the second intermediates and neglect of the tiny adsorption of the first intermediate on catalysts are ascribed to the deficiencies, respectively. As for the least-sum-of-squares estimator Monte Carlo studies suggest the bias due to the nonlinearity does not contribute much to the variances of the errors.

Novel nano-composite particles: titania-coated silica cores

Purpose - The purpose of this paper is to develop methods to produce white composite pigments consisting of a silica core with a titania shell. Design/methodology/approach - Silica cores were coated with titanium dioxide (TiO2) via forced hydrolysis of a solution prepared from titanium tetrachloride (TiCl4). The morphology, surface charge and particle size of obtained composite particles were studied. Findings - Dispersions of well-dispersed composite particles, having silica cores of uniform size in the range from 300 to 500 nm with a homogeneous titania coating are obtained. The coating thickness corresponded to 150-400 per cent by weight of titania based on the core. Modification of the silica core by incorporation of 1.5 aluminosilicate sites per square nanometre of core surface proves to be favourable in achieving a homogeneous coating on the silica core. Deposition of such titania coating is also favoured by agitating the dispersion well, keeping electrolyte content low, maintaining pH at 2.0 and the temperature at 75 degrees C during the coating process. Research limitations/implications - Only TiCl4 is used as titania source. In addition, only silica cores obtained by Stober synthesis are used while commercially available silica solutions made from sodium silicate are not used. Practical implications - The process offers a method of producing a white composite pigment with a narrow particle size distribution in order to maximise light scattering as well as using a core with lower density than the shell. This kind of particle would be of interest for coating applications and white inorganic inks. Originality/value - The developed method provides a straightforward process to produce well-defined composite particles.

HYDROPROCESSING OF OIL FROM BIOMASS LIQUEFACTION

High pressure directly liquefied biomass, PERC TR12 from the former liquefaction plant in Albany USA, was desalted by adding 10 weight percent of is()-{)ctane and washed with water (60 • C) in three stages. The sodium content in the oil was reduced from 1.0 percent to between 0.04 to 0.12 percent in different runs. The desalted oil was hydroprocessed in a downflow trickle bed reactor over a sulphided :\iMo catalyst on gamma alumina (Shell 424). A series of runs were made to test the processability of the desalted oil.This was compared to that of petroleum and liquefied coal. The conditions used were: temperature 400 • C, LHSV (liquid hourly space velocity) 0.5 and 1.5 h-1, gas to oil ratios by volume 0.18 and 0.53. The desalted oil yielded over 85 percent by weight in the oil product of oil boiling in the same range as liquid transportation fuels. This is a considerably higher conversion than that obtained for the reference sampels from petroleum residues and oil from coal. In a separate 45 h run the desalted oil was hydroprocessed at 370 • C, a total pressure of 10.0 MPa and a LHSV of 0,59 h-1. Deactivation of the catalyst took place in the first hours of the experiment but after this, product properties were constant throughout the run. A two stage hydroprocessing was also performed with intermediate separation of water and a light fraction. The effective HIC ratios of the products were from 1.9 to 1.4 for the gas oil fractions boiling below 393 • C. The remaining oxygen contents were low and the oils were clear with a slightly yellow colour.

Hydrodeoxygenation of fatty acid methyl ester in gas oil blend–NiMoS/alumina catalyst

Abstract Hydrotreating of 10% fatty acid methyl ester (FAME) blended in gas oil was carried out by an NiMo-S/alumina catalyst and performed at an elevated temperature (300–400°C), a space velocity of 0.7–1.5 1/h and pressure 5 MPa. The gas oil was a straight run North Sea crude oil containing 295 ppm sulfur content which was desulfurized in a hydrotreating upgrading process. The physicochemical properties following hydroprocessing of FAME showed that sulfur content was reduced to 3 ppmw, with an increase in aromatic content and cloud point. It was confirmed that decarboxylation depends on temperature and space velocity and decarbonylation depends on temperature, but not on space velocity of feed. High sulfur content in the feedstock supports slow deactivation of the catalyst and low coke formation.