Paolo Carniti

Thermal cracking of petroleum residues: 1. Kinetic analysis of the reaction

Abstract In order to define a kinetic scheme and to calculate the kinetic parameters of the thermal cracking of petroleum residues, a vacuum residue of Belaym crude was thermally cracked at 410, 430, 450 and 470 °C for reaction times up to 120 min. The concentration of three pseudo-components, namely vacuum residue, distillate and coke, was detected during conversion and the data from these experiments were used for the definition of the kinetic model. Distillate production can be described as a simple first-order reaction while coke formation seems to be the consequence of consecutive reactions, in particular involving asphaltenes. A study of the structural changes of asphaltenes as a function of severity was also performed and the variations of the average molecular parameters with conversion were correlated. The results of this work have been used as reference data for a subsequent study of residue conversion in the presence of hydrogen-donor solvents.

Alkylation of phenol with methanol over zeolites

Abstract The reaction of phenol with methanol was carried out over five X-, six Y- and three ZSM-zeolites, in a fixed-bed continuous reactor at 250°C. Alkylation products were cresols (o>p>m), anisole, xylenols and methylanisoles. The highest conversion and the highest yields of o- and p-cresols were obtained within the initial 5 h on-stream. Selectivity to o,p-cresols in the range 40-50% at phenol conversion 40-50% was reached on some X- and Y-zeolites, the best catalyst being HY.

Catalytic thermal degradation of polymers: Degradation of polypropylene

Silica, alumina, silica—alumina and zeolites were screened as catalysts for polypropylene degradation in the range 200–600 ° C. The more efficient catalysts for oil production yielded C5—C12 olefins. Gas chromatographic—mass spectrometric analysis of the reaction products gave information on the nature of the products and on the mechanism of the degradation.

Petroleum residue upgrading with dispersed catalysts: Part 2. Effect of operating conditions

The hydrotreatment of a petroleum residue in the presence of dispersed molybdenite was carried out within a wide range of operating conditions and catalyst loading. The effect of reaction severity as well as of molybdenum concentration on product distribution and quality was studied. Based on the experimental results, a simplified reaction scheme was proposed. The hydroprocessing of the residue was described in terms of the competition between two reactions: the direct conversion of the feedstock to distillate and coke, and the catalytic hydrogenation. Compared to thermal conditions, the presence of dispersed molybdenite controls very well coke formation; however, a trend of increasing formation of solids was observed at high catalyst concentrations. The overall upgrading of the feedstock requires significant amounts of molybdenum as well as relatively high hydrogen pressure.

Alkylation of phenol with anisole over zeolites or γ-alumina

Abstract The reaction of phenol with anisole was carried out over three X-, six Y-, a ZSM-5 and a ZSM-11 zeolites, and over γ-Al 2 O 3 , in a fixed-bed continuous reactor. Alkylation products were cresols (o>p>m), xylenols and methylanisoles; also some dealkylation of anisole to phenol occurred. Selectivity to cresols and xylenols in the range 45–60% and 25–30%, respectively, at anisole conversions of around 90%, were reached with HY and HNaY zeolites, and with γ-Al 2 O 3 , when operating over fresh catalysts. Alkylations were particularly ortho-selective over γ-Al 2 O 3 .

Fractionation and bioconversion of steam-exploded wheat straw

Abstract Wheat straw was pretreated by steam explosion under various conditions. The capability of the process in inducing a high fractionation of the lignocellulosic material in its major components and the influence of the explosion conditions on the substrate susceptibility to the attack of cellulolytic enzymes have been investigated. Bioconversion was studied considering the cellulose-rich fraction obtained from product fractionation as well as the product directly obtained from the explosion treatment. Quantitative data in terms of rate and yield of hydrolysis have been obtained for the different conditions.

CLARO-CMOS, a very low power ASIC for fast photon counting with pixellated photodetectors

The CLARO-CMOS is an application specific integrated circuit (ASIC) designed for fast photon counting with pixellated photodetectors such as multi-anode photomultiplier tubes (Ma- PMT), micro-channel plates (MCP), and silicon photomultipliers (SiPM). The first prototype has four channels, each with a charge sensitive amplifier with settable gain and a discriminator with settable threshold, providing fast hit information for each channel independently. The design was realized in a long-established, stable and inexpensive 0.35mm CMOS technology, and provides outstanding performance in terms of speed and power dissipation. The prototype consumes less than 1 mW per channel at low rate, and less than 2 mW at an event rate of 10 MHz per channel. The recovery time after each pulse is less than 25 ns for input signals within a factor of 10 above threshold. Input referred RMS noise is about 7.7 ke (1.2 fC) with an input capacitance of 3.3 pF. With this value of input capacitance a timing resolution down to 10 ps RMS was measured for pulser signals of a few million electrons, corresponding to the single photon response for these detectors.

Kinetics of biodegradation of mixtures containing 2,4-dichlorophenol in a continuous stirred reactor

A solution containing 2,4-dichlorophenol (DCP) and phenol (or glucose), in the ratio 1:1 in terms of carbon, was fed to a completely mixed continuous flow reactor with recycle and controlled wasting of the activated sludge, operated at steady-state conditions at 20°C. A carefully adapted sludge was able to degrade DCP, besides the accompanying substrate, with no evidence of substrate inhibition in the concentration range covered (156 mg l−1 in the influent). The reactivity order was found to be glucose ⪢ phenol > DCP. The results of a series of kinetic runs with phenol + DCP were interpreted by a first-order equation for phenol and by the Monod model for DCP.

Hydrolysis of disaccharides over solid acid catalysts under green conditions

The hydrolysis of the three most important disaccharides: sucrose, maltose and cellobiose, has been comparatively studied in mild conditions (50-80°C) in water over several solid acid catalysts. Strong acidic resins (Amberlite A120 and A200), mixed oxides (silica-alumina and silica-zirconia), and niobium-containing solids (niobic acid, silica-niobia, and niobium phosphate) have been chosen as acid catalysts. The hydrolysis activity was studied in a continuous reactor with fixed catalytic bed working in total recirculation mode. Rate constants and activation parameters of the hydrolysis reactions have been obtained and discussed comparing the reactivity of the α-1,β-2-, α-1,4-, and β-1,4-glycosidic bonds of the employed disaccharides. The following order of reactivity was found: sucrose >> maltose > cellobiose. The sulfonic acidic resins, as expected, gave complete sucrose conversion at 80°C and good conversions for cellobiose and maltose. Among the other catalysts, niobium phosphate provided the most interesting results toward the disaccharide hydrolysis, which are here presented for the first time. Relations between activity and surface acid properties are discussed.

Thermal degradation of kerogen by hydrous pyrolysis. A kinetic study

Abstract Several hydrous pyrolysis kinetic runs have been carried out on a source rock sample from Northern Italy (type II kerogen) under isothermal conditions in the range 260–330°C and at 15–17 MPa in an argon atmosphere. The products have been quantified and grouped into four classes: light (gas + volatile liquids), saturate, aromatic, and heavy (asphaltenes + resins). The distribution of these classes as well as the bulk composition of the overall product was found to be fairly constant during the whole reaction course, suggesting that primary cracking prevails in the temperature range explored. The kinetic results have been interpreted regarding the degradation as the result of numerous simultaneous independent first-order reactions. The number, the relative importance and the Arrhenius parameters for such reactions have been evaluated using an optimization procedure. The best fitting of the experimental data was achieved considering three simultaneous reactions.