Jan-Erik Otterstedt

Upgrading of directly liquefied biomass to transportation fuels: catalytic cracking

Abstract Hydroprocessed oil derived from biomass via direct liquefication using the PERC process was catalytically cracked in a fixed-bed reactor. The fraction of the hydroprocessed oil used as feed for fluid catalytic cracking (FCC) had a boiling point range over 350°C. The FCC feed had an oxygen content of 0·8 wt% and a hydrogen to carbon ratio of 1·3:1. Compared with cracking at normal reactor temperatures of 500°C, cracking at 562°C resulted in the production of excessive amounts of coke and gas. Cracking at catalyst to oil ratios lower than the ASTM standard of 4:1·33 reduced the yields of coke and gas and improved the yields of liquid products.

Synthesis and size tailoring of colloidal zeolite particles

A novel method is presented whereby it is possible to synthesize colloidal zeolite particles of a pre-determined size.

Colloidal components in solutions of alkali silicates

Abstract The particle size of colloidal silica in 1 to 5 M SiO2 solutions of lithium, sodium, potassium, and cesium silicates in the ratio range 1.5–20 moles of SiO2 per mole of M2O was determined by reaction with molybdic acid and by Sears titration. The particle size increased from 1.0 to 4.5 nm with increasing ratio but did not depend on the type of alkali-metal cation. The amount of monomeric silicate ions decreased sharply with increasing ratio from 35% for ratio 2 to 2% for ratio 15 in 5 M SiO2 solutions. The polymeric particles were extracted into tetrahydrofuran or tertiary butylalcohol at pH 2, without changing the particle size, in yields which increased to more than 95% for the highest ratios. Previous dilution caused the particle size to grow in high-ratio solutions but to decrease in low-ratio solutions.

Sol-gel coating of alumina fibre bundles

Abstract A procedure for coating alumina fibre bundles with fibrillar boehmite particles is described. Fibrillar boehmite particles, having a specific surface area of 150 m2/g, were adsorbed onto the surface of the alumina fibres. The surface of the alumina fibres was first charge reversed by adsorption of a charge reversing agent. Polyvinylsulphate (PVS) proved to be an excellent charge reversing agent, whereas citric acid and Tiron (3,5-pyrocatecholdisulphonic acid disodium salt) were unable to reverse the surface charge of the alumina fibres. By using polyvinyl-sulphate (PVS), it was possible to adsorb an arbitrary number of layers of fibrillar boehmite particles. The coating of the alumina fibre bundles resulted in an increase in specific surface area from 0.09 m2/g for the uncoated fibres, to 0.7 m2/g for alumina fibres coated with four layers of fibrillar boehmite particles. The adsorbed boehmite particles were fixed onto the alumina fibre surface by calcination at 550 °C for 120 min, during which the boehmite was transformed into γ-Al2O3. The coated alumina fibre bundles were characterized by krypton adsorption and scanning electron microscopy (SEM).

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.

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.

Preparation of ceria-coated composite silica particles

A method for preparing particles with highly dispersed ceria by a stepwise procedure is described. The surface of silica particles was modified by aluminate and coated with an interlayer of titanina. CeOSO4 was deposited on the titania coated silica particles. The sulfur in the dispersed ceria was removed by calcining the particles in air at 800°C for 30 min. A highly dispersed ceria was obtained when using titania-coated silica particles with diameters of 80, 240 and 500 nm. The prepared products were characterised by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), UV spectroscopy and electrophoresis.

The Effect of the Chemical Nature of the Wash-Coat on the Catalytic Performance of co Oxidation Catalysts of Monolith Type.

Light off temperatures and efficiency for Pt on wash-coats of alumina, silica, aluminosilicate, posivitely charged silica and positively charged aluminosilicate were measured. 0.1 wt% Pt, based on the weight of the wash-coat, which is only 10% of the usual amount of Pt in commercial catalysts, on silica and alumina showed as low light off temperatures and as high efficiency as commercial catalysts.

Clays and Colloidal Silicas

Clays can lay claim to being the starting point for fine particle technology in the history of mankind. Their use in constructing shelters and in pottery manufacture far predates recorded history. Their particular crystalline structure which confers the plastic-like rheological behavior necessary for forming bricks, plugging holes, and making pottery, together with their permanence and ready availability all led inevitably to their extreme importance in mankind’s struggle to survive and prosper.

Preparation of a novel fibrous catalyst support

A method for preparing wash-coated silica fibres is described. Colloidal silica particles (22 nm) were deposited onto the surface of 2 µm amorphous silica fibres, surface-modified by deposition of a thin film of amorphous silica with a high density of silanol groups and with the charge reversed by adsorption of a water-soluble cationic polymer. This deposition resulted in an increase in specific surface area from 0.9 m2 g–1 for the fibre to 40 m2 g–1 for the fibre with deposited silica particles. Hydrothermal treatment at 750 °C in 100% steam for 24 h fixed the silica particles onto the fibre surface and made them coalesce into a strong porous structure. During this process, the specific surface area decreased from 40 to 30 m2 g–1. Particles of fibrillar boehmite were deposited onto the surface of silica fibres. The boehmite particles were fixed by thermal treatment at 550 °C, during which the boehmite was transformed into γ-Al2O3. The specific surface area of the alumina wash-coated silica fibres was 28 m2 g–1. Wash-coated fibres were characterized by nitrogen adsorption-desorption analysis, scanning and transmission electron microscopy (SEM and TEM).