The Effect of MoS2 Active Site Dispersion on Suppression of Polycondensation Reactions during Heavy Oil Hydroconversion

In this work, the composition, structural and morphological features, and particle size of the active phase of the catalyst (MoS2), synthesized in-situ during the heavy oil hydroconversion performed in continuous flow reactor on lab-scale pilot flow unit at T = 450 °C, P = 6.0–9.0 MPa, V = 1.0 h−1, H2/feed = 1000 nL/L, catalyst concentration C (Mo) = 0.01–0.08%wt have been studied. It has been shown that MoS2 formed during hydroconversion is represented by nanosized particles stabilized by polycondensation products as a result of strong adsorption and aggregation with the components of the hydroconversion reaction medium. The influence of morphological characteristics of catalyst nanoparticles on the feed conversion, the yield of gaseous and liquid products, and the quality of distillate fractions, as well as the yield of polycondensation products, have been studied. It has been established that an increase in MoS2 active site dispersion, both due to a decreased plate length and lower stacking numbers in MoS2 cluster, enhances hydroconversion effectivity, particularly, in suppressing polycondensation reactions.

Particular kinetic patterns of heavy oil feedstock hydroconversion in the presence of dispersed nanosize MoS2

A kinetic model of the heavy oil feedstock hydroconversion performed in continuous flow reactor in the presence of in-situ synthesized dispersed nanosize catalyst Molybdenum disulfide (MoS2) has been proposed. The kinetic parameters of heavy oil feedstock with different properties have been determined for the two process versions: with coke formation and without appreciable coke formation. It has been stated that hydroconversion in the presence of in-situ synthesized dispersed MoS2 (C(Mo) = 0.05% wt. (per feed)) corresponds to a first-order reaction for all studied feedstock samples. The rate and activation energy constants have been determined. It has been shown that the conditions of polycondensation products (coke) formation result in increasing process rate and decreasing activation energy.

Quaternary ammonium salt substituted polyhedral oligosilsesquioxanes (POSSes) as structure directing agents in the generation of porous silica materials

The sol-gel base catalysed hydrolytic polycondensations of tetramethoxysilane (TMOS) were studied in the presence of quaternary ammonium chloride substituted polyhedral oligosilsesquioxanes (POSSes): octa{3-[(2- hydroxyethyl)dimethylammonio]propyl chloride}octasilsesquioxane or octa[3-(noctyldimethylammonio) propyl chloride]octasilsesquioxane. Small amounts of these POSSes added to the sol-gel system markedly affected the morphology of the silica gel polycondensation products. The morphology was highly dependent on the POSS concentration. Amorphous mesoporous silica gels were obtained showing a high porosity and the surface area up to 615 m2g-1. Most of gels had a fairly large average pore diameters, 4-11 nm and pore volume 0.4-1.3 cm3g-1. TMOS having inserted hexamethyltrisiloxane chain, 1,1,1,7-tetramethoxyhexamethyltetra siloxane, (TMOSD3) in the mixture with TMOS was also used as the monomer in the sol-gel polycondensation; but obtained gels showed a low porosity.

Characterization of Geopolymer Materials Containing MSWI Fly Ash and Coal Fly Ash

In this work three samples of MSWI ash have been stabilized in systems containing coal fly ash and able to give geopolymers through a polycondensation reaction. Monolithic products were obtained with both MSWI ashes as received and after chloride partial removal by water washing. The polycondensation products have been characterized qualitatively by means of FT-IR spectroscopy and scanning electron microscopy (SEM) and quantitatively through the determination of the amount of reacted water and silicate. Differently from traditional cement based stabilization systems, those based on geopolymerization show a chemical behaviour almost insensitive to the presence of chlorides and sulphates in the MSWI ash. On the other hand, the microstructure is strongly affected by the content of soluble salts.