Oxidative Desulphurisation Research Articles

Исследование влияния микроволнового излучения на процесс десульфуризации мазута

Many chemical processes are intensified by microwave radiation. The main factor determining the usefulness of microwaves in most transformations of organic compounds is the reaction time reduction to obtain the maximum yield of the target product. The presence of sulphur in oil and petroleum products is detrimental to refining equipment, and also has a negative impact on the environment in the form of waste generated during refining. In this connection development of methods on removal of sulphurcontaining compounds from oil products and oil by their transformation (in particular oxidation) and subsequent removal is very significant. Oxidative desulphurisation of fuel oil takes up to several hours depending on the reagents used. In this work an attempt has been made to significantly reduce the duration of the process. Oxidation of sulphur-containing organic compounds in fuel oil under microwave radiation has been considered, which proceeds in the presence of an oxidizer (hydrogen peroxide) and a catalyst (titanium dioxide). It was found that the oxidative desulphurization of fuel oil at microwave radiation proceeds effectively and quickly within 1--5 min. The achieved degree of desulphurization is 66 % when exposed to microwave radiation for 5 min. The influence of the amount of water in the reaction mixture on the efficiency of oxidative desulphurization of fuel oil under microwave radiation has been studied; it was found that the optimum ratio of water : fuel oil was (1--1.2) : 1

Heterostructure of vanadium pentoxide and mesoporous SBA-15 derived from natural halloysite for highly efficient photocatalytic oxidative desulphurisation.

Integration between conventional semiconductors and porous materials can enhance electron–hole separation, improving photocatalytic activity. Here, we introduce a heterostructure that was successfully constructed between vanadium pentoxide (V2O5) and mesoporous SBA-15 using inexpensive halloysite clay as the silica–aluminium source. The composite material with 40% doped V2O5 shows excellent catalytic performance in the oxidative desulphurisation of dibenzothiophene (conversion of 99% with only a minor change after four-cycle tests). These results suggest the development of new catalysts made from widely available natural minerals that show high stability and can operate in natural light to produce fuel oils with ultra-low sulphur content.

Altered Properties of TiO2 for Photocatalytic Oxidative Desulphurisation

Photocatalytic oxidative desulphurisation has become a promising technique as a result of its high capability, mild reaction conditions, economical, and low energy usage. In the present study, copper oxide doped on titanium dioxide (CuO/TiO2) was prepared by facile electrolysis method. The presence of mesoporous materials with high surface area was confirmed by nitrogen (N2) adsorption-desorption analysis where the band gap energies were determined by ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS). The photoactivity testing on desulphurisation of 100 mg L-1 dibenzothiophene (DBT) revealed the highest extraction (7.5 x 10-3 mM min-1) and photooxidation rates (1.8 x 10-3 mM min-1), which were acquired by 0.8 g L-1 Cu0.1T0.9 after 2 h under visible irradiation. This is attributed by the well dispersion of CuO on TiO2, suitable band gap energy, and better charge carrier separation by the synergistic interaction of both materials.

Visible-light-promoted oxidative desulphurisation: a strategy for the preparation of unsymmetrical ureas from isothiocyanates and amines using molecular oxygen

A green and efficient visible-light promoted oxidative desulphurisation protocol has been proposed for the construction of unsymmetrical ureas under mild conditions with broad substrate scope and good functional group tolerance.

Modelling and optimisation of oxidative desulphurisation of tyre-derived oil via central composite design approach

Abstract The aim of this study was to apply the central composite design technique to study the interaction of the amount of formic acid (6-12 mL), amount of hydrogen peroxide (6-10 mL), temperature (54-58°C) and reaction time (40-60 min) during the oxidative desulphurisation (ODS) of tyre-derived oil (TDO). The TDO was oxidised at various parametric interactions before being subjected to solvent extraction using acetonitrile. The acetonitrile to oil ratios used during the extraction were 1:1 and 1:2. The content of sulphur before and after desulphurisation was analysed using ICP-AES. The maximum sulphur removal achieved using a 1:1 acetonitrile to oxidised oil ratio was 86.05%, and this was achieved at formic acid amount, hydrogen peroxide amount, temperature and a reaction time of 9 mL, 8 mL, 54°C and 50 min respectively. Analysis of variance (ANOVA) indicated that the reduced cubic model could best predict the sulphur removal for the ODS process. Coefficient of determination (R2 = 0.9776), adjusted R2 = 0.9254, predicted R2 = 0.8356 all indicated that the model was significant. In addition, the p-value of lack of fit (LOF) was 0.8926, an indication of its insignificance relative to pure error.

Oxidation of high sulphur coal.9 3. Desulphurisation of organic sulphur by peroxyacetic acid (produced in situ) in presence of metal ions

A chemical oxidative desulphurisation method for coal organic sulphur has been presented using peroxyacetic acid produced in situ as an oxidant. Sulphur is removed to the extent 6.92–10.02 wt.% at 1–4 h while at 24 h, it increases to 13.41 wt.%. To understand the influence of metal ions on desulphurisation, each of six metal ions of variable valence states (Cu +, Ni 2+, Co 2+, Sn 2+, Pd 2+ and Sb 3+) was externally added. Lowest sulphur loss with Ni 2+ ion (2.26–9.46 wt.% at 1–4 h and 11.01 wt.% at 24 h) while highest desulphurisation with Pd 2+ ion (23.15–32.32 wt.% at 1–4 h and 32.75 wt.% at 24 h) are observed. Application of the pseudo-first order kinetics shows rate constants for all the systems in the range (0.70–6.78)×10 −5 s −1. The activation energy and frequency factor for these systems fall in the range (8.46–12.66) kJ/mol and (1.15–2.64)×10 −3 s −1, respectively. Low frequency factor represents an associated type of desulphurisation reaction involving intermediate activated complexes. The sulphur loss reaction is non-spontaneous in nature and proceeds with the absorption of heat. Occurrence of the reaction is due to the increase in randomness which is governed by the decomposition of activated complex to products and is influenced by the characteristic property of a metal ion. Study of model sulphur compounds (methionine and dibenzothiophene) reveals that the desulphurisation reaction under the experimental conditions is primarily due to aliphatic sulphur compounds. The method described here is simple with low-cost and easily available chemical, and therefore, has considerable technological interest.

Oxidative desulphurisation of sulphur-rich coal

Process of oxidative desulphurisation of sulphur-rich containing Ukrainian coal was carried out in the temperature range of 623–723 K by air/steam mixture in the fluidised bed reactor. Mössbauer spectroscopy was applied to study the reaction products in form of iron compounds after every step of thermal treatment. The pyritic sulphur that constitutes most of total sulphur oxidises selectively at these conditions. At lower temperature (623 K) the ferrous sulphates and pyrite oxidised mainly to the ferric sulphate. At 673 K and higher temperatures α-Fe 2O 3 and SO 2 were basic products of FeS 2 oxidation. The transformation of FeS 2 into pyrrhotite as the first stage of desulphurisation was observed at 698 K independently of the partial pressure of oxygen. The iron monosulphide (FeS) was not found at any stage of desulphurisation suggesting the pyrrhotite Fe 1− x S oxidation before the sequential FeS 2→Fe 1− x S→FeS transformation.

Kinetic and thermodynamic studies on oxidative desulphurisation of organic sulphur from Indian coal at 50–150°C

This paper reports a relatively simple low-temperature non-isothermal oxidative desulphurisation of coal organic sulphur by weakening the CS bond using HgCl 2 solution to an inorganic sulphur-free high-sulphur Indian coal. When oxidised from 50°C to 150°C in air under normal atmospheric pressure, there is continuous decrease of organic sulphur content in the samples of the feed and Hg-treated coals. Desulphurisation is more in the Hg-treated coal (4.97–14.53 wt.%) than in the feed coal (3.72–10.93 wt.%). Kinetic study reveals that the oxidative desulphurisation process follows pseudo-first order kinetics and the rate constants have been found to be in the range (3.09–5.06)×10 −5 s −1 for feed coal and (4.19–6.80)×10 −5 s −1 for Hg-treated coal. The activation energies for the sulphur loss reaction in the oxidative desulphurisation process by using the pseudo-first order kinetic (feed coal: 2.21×10 2 J mol −1; Hg-treated coal: 1.53×10 2 J mol −1) have been found to be almost similar to those calculated by applying the Coats and Redfern's equation (feed coal: 2.19×10 2 J mol −1; Hg-treated coal: 1.53×10 2 J mol −1). However, the value is higher (feed coal: 3.50×10 2 J mol −1; Hg-treated coal: 2.70×10 2 J mol −1) when Horowitz and Metzger's equation is applied. The frequency factors computed by the pseudo-first order kinetics are very low and have been found to be 2.66×10 −5 s −1 for feed coal and 3.96×10 −5 s −1 for Hg-treated coal, suggesting very low rate of successful collisions for the formation of the activated complex. Evaluation of thermodynamic parameters viz., Δ H, Δ U, Δ S and Δ G, reveals that this oxidative desulphurisation process is non-spontaneous in nature and the degree of non-spontaneity of such a process in the feed coal is more relative to that of the Hg-treated coal.

γ-Radiolytic desulphurisation of some high-sulphur Indian coals catalytically accelerated by MnO 2

γ-Radiolysis of acidic aqueous coal slurries is a novel and effective method for the simultaneous oxidative desulphurisation and demineralisation of high-sulphur coals. This method is capable to selectively remove the inorganic and organic forms of sulphur simultaneously through the in situ-generated H 2O 2 and other radiolytic products. In effect, there is neither any appreciable degradation of coal matrix nor any loss in the caking property and volatile matter content of the coals after the removal of sulphur. However, significant removals of sulphur and mineral matter are effected at rather high γ-dose (175×10 4 Gy or so). Therefore, for the process to be economically viable and commercially adaptable, the applied γ-dose needs to be somehow substantially brought down, at which the same level of desulphurisation could be achieved. Catalytically, accelerating the radiolysis process is one such possibility to effect the desulphurisation step at a low γ-dose. Reported in this paper are the results of investigations on the desulphurisation and demineralisation of high-sulphur (sulphur content in the range 3–5.5%) Churphy, Chalang and Bapung coals of Meghalaya by γ-radiolytic process catalysed by MnO 2. The maximum removal of total sulphur (15.6%, 30.0% and 29.8%) at 30×10 4 Gy in the presence of MnO 2 and the simultaneous removal of mineral matter (20.0% and 18.5% from Churphy and Chalang coals at 30×10 4 Gy and 12.0% from Bapung coal at 45×10 4 Gy) are at par with removals at 175×10 4 Gy without MnO 2, which has been attributed to MnO 2 catalytically accelerating the radiolytic process via the formation of highly reactive MnO under the action of γ-rays. All the other features of non-catalysed radiolytic desulphurisation such as stabilisation of the slurry and coal not becoming radioactive during irradiation, increase in the heating value, improvement in the caking property, no appreciable degradation of coal matrix after removal of sulphur from the coals remain the same.

Oxidative desulphurisation of oils via hydrogen peroxide and heteropolyanion catalysis

Oxidation of dibenzothiophene with hydrogen peroxide using phosphotungstic acid as catalyst and tetraoctylammonium bromide as phase transfer agent in a mixture of water and toluene has been studied. Catalysed decomposition of hydrogen peroxide competes with dibenzothiophene oxidation but by choice of suitable conditions yields of dibenzothiophene sulphone approaching 100% may be obtained. Treatment of gas oils with this technology shows that all the sulphur compounds present are oxidised by this catalyst system and highly substituted dibenzothiophenes are the most readily oxidised of species containing a thiophene nucleus. Oxidised sulphur compounds can be separated from the oil by adsorption on silica gel. The use of oxidation and adsorption in a process for desulphurisation of gas oils is discussed.

Catalysis by metalloporphyrins of oxidative desulphurisation at pentacovalent phosphorus by cumyl hydroperoxide

Cumyl hydroperoxide causes oxidative desulphurisation at pentacovalent phosphorus with retention of configuration in the presenceof various manganese (iii) and iron (ii) mesotetraphenylporphyrins provided imidazole is present, the yields of oxidised phosphorus compounds being influenced by the rate of destruction of the hydroperoxide by parasitic side reactions.

The oxidative desulphurisation and deselenation at pentacovalent phosphorus catalysed by metalloporphyrins

Manganese (III) mesotetraphenylporphyrin chloride in the presence of tetrabutylammonium periodate has been shown to aid the oxidative desulphurisation and deselenation at pentacovalent phosphorus: the desulphurisation reaction is further aided by the addition of imidazole.

Oxidative desulphurisation and deselenation at pentacovalent phosphorous by photogenerated peroxidic species

The peroxidic species generated by photooxidation of dialkylsulphides and diazocompounds are able to effect oxidative desulphurisation and deselenation at pentacovalent phosphorus.

The photodegradation of parathion and chlormephos

AbstractIrradiation (∼350 nm) of oxygenated acetonitrile solutions of parathion containing sensitisers such as benzoin and α‐dicarbonyl compounds leads to oxidative desulphurisation at phosphorus, producing paraoxon in reasonable yield. Other degradation reactions also occur, probably as a result of the presence of the 4‐nitrophenyl group in parathion. Under similar irradiation conditions, chlormephos is desulphurised at both the thionate and thiolate moiety. The reactions are rationalised as occurring via peroxy radicals which are generated from the sensitisers. Reaction was not observed when dyes, e.g. rose bengal, were used as sensitisers, which accords with the view that thionates and thiolates are not reactive towards singlet oxygen.

A novel oxidative desulphurisation of [formula omitted]-trithianes and thioacetals with iodine in dimethylsulphoxide.

A novel oxidative desulphurisation of [formula omitted]-trithianes and thioacetals with iodine in dimethylsulphoxide.