Recent Advances in Polyoxometalate-Catalyzed Reactions

Sulfur compounds represent one of the most common impurities present in the crude oil. Sulfur in liquid fuel oil leads directly to the emission of SO2 and sulfate particulate matter (SPM) that endangers public health and community property; and reduces the life of the engine due to corrosion. Furthermore, the sulfur compounds in the exhaust gases of diesel engines can significantly impair the emission control technology designed to meet NOx and SPM emission standards. The research efforts for developing conventional hydrodesulfurization and alternative desulfurization methods such as selective adsorption, biodesulfurization, oxidation/extraction (oxidative desulfurization), etc. for removing these refractory sulfur compounds from petroleum products are on the rise. Research laboratories and refineries are spending huge amounts of money in finding a viable and feasible solution to reduce sulfur to a concentration of less than 10 mg l−1. This paper reviews the current status in detail of various desulphurization techniques being studied worldwide. It presents an overview of novel emerging technologies for ultra-deep desulfurization so as to produce ultra-low-sulfur fuels.

An evaluation of desulfurization technologies for sulfur removal from liquid fuels

Review of modifications of activated carbon for enhancing contaminant uptakes from aqueous solutions

Environmental concerns have introduced a need to remove sulfur-containing compounds from light oil. As oxidative desulfurization is conducted under very mild reaction conditions, much attention has recently been devoted to this process. In this contribution, the developments in selective removal of organosulfur compounds present in liquid fuels via oxidative desulfurization, including both chemical oxidation and biodesulfurization, are reviewed. At the end of each section, a brief account of the research directions needed in this field is also included.

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Oxidative processes of desulfurization of liquid fuels

Pickering emulsions are surfactant-free dispersions of two immiscible fluids that are kinetically stabilized by colloidal particles. For ecological reasons, these systems have undergone a resurgence of interest to mitigate the use of synthetic surfactants and solvents. Moreover, the use of colloidal particles as stabilizers provides emulsions with original properties compared to surfactant-stabilized emulsions, microemulsions, and micellar systems. Despite these specific advantages, the application of Pickering emulsions to catalysis has been rarely explored. This Minireview describes very recent examples of hybrid and composite amphiphilic materials for the design of interfacial catalysts in Pickering emulsions with special emphasis on their assets and challenges for industrially relevant biphasic reactions in fine chemistry, biofuel upgrading, and depollution.

Pickering Interfacial Catalysis for Biphasic Systems: From Emulsion Design to Green Reactions

A [(C(18)H(37))(2)N(+)(CH(3))(2)](3)[PW(12)O(40)] catalyst, assembled in an emulsion in diesel, can selectively oxidize the sulfur-containing molecules present in diesel into their corresponding sulfones by using H(2)O(2) as the oxidant under mild conditions. The sulfones can be readily separated from the diesel using an extractant, and the sulfur level of the desulfurized diesel can be lowered from about 500 ppm to 0.1 ppm without changing the properties of the diesel. The catalyst demonstrates high performance (>/=96 % efficiency of H(2)O(2), is easily recycled, and approximately 100 % selectivity to sulfones). Metastable emulsion droplets (water in oil) act like a homogeneous catalyst and are formed when the catalyst (as the surfactant) and H(2)O(2) (30 %) are mixed in the diesel. However, the catalyst can be separated from the diesel after demulsification.

Ultra-deep desulfurization of diesel: oxidation with a recoverable catalyst assembled in emulsion.

The surface properties, porosities, and adsorption capacities of activated carbons (AC) are modified by the oxidation treatment using concentrated H2SO4 at temperatures 150−270 °C. The modified AC was characterized by N2 adsorption, base titration, FTIR, and the adsorption of iodine, chlorophenol, methylene blue, and dibenzothiophene. The treatment of AC with concentrated H2SO4 at 250 °C greatly increases the mesoporous volume from 0.243 mL/g to 0.452 mL/g, specific surface areas from 393 m2/g to 745 m2/g, and acidic surface oxygen complexes from 0.071 meq/g to 1.986 meq/g as compared with the unmodified AC. The base titration results indicate that the amount of acidic surface oxygen groups on the modified AC increases with increasing the treatment temperatures and carboxyls and phenols are the most abundant carbon−oxygen functional groups. The carboxyl groups, COO- species, and hydroxyl groups are detected mainly for the sample treated at 250 °C. The mesoporous properties of the AC modified by concentrat...

Activated carbons chemically modified by concentrated H2SO4 for the adsorption of the pollutants from wastewater and the dibenzothiophene from fuel oils

The hydroisomerization of n-dodecane was investigated over Pt supported on unmodified ZSM-22 and on modified ZSM-22. The effect of ZSM-22 modification on Pt/ZSM-22 acidity and on catalytic performance is discussed in detail using MAS NMR and FT-IR results. The ZSM-22 was modified by NH4+ ion-exchange, HNO3 or (NH4)(2)SiF6 treatment, and by steam treatment in order to tune the acidity of the catalysts. The unmodified ZSM-22 catalyst shows very low activity in the hydroisomerization of n-dodecane due to the lowest acidity. The conversions of the catalysts for the reaction of n-dodecane are increased from 1.1% to 96.6% at 300 degrees C as the acidity of the ZSM-22 is increased from 0.043 mmol/g to 0.329 mmol/g, but the isomerization selectivity is reduced. The catalyst that was modified by the combination of NH4+ ion-exchange and (NH4)2SiF6 treatment possesses the Bronsted acid sites with medium strength and shows the high isododecane selectivity (88.0%) under high conversion (87.5%) at 300 degrees C. (C) 2007 Elsevier B.V. All rights reserved.

Hydroisomerization activity and selectivity of n-dodecane over modified Pt/ZSM-22 catalysts

A desulfurizing absorbent for removing S-contained compound from distillate, especially removing dibenzothiophene and its derivatives, is prepared from activated carbon through chemical and physical activatings Said absorbent features its special artery structure

Fractional oil desulfurizing and adsorption agent and its preparation method

The invention disclosed a kind of lubricating oil deparaffinage catalyst as well as its application during the deparaffinage process The mentioned catalyst contains TON and/or MTT molecular sieve, at least one VIII group precious metal and zinc, the ratio of zinc and VIII group precious metal is 01-50 According to the invention, the zinc can regulate the catalyst's acidifying function and hydrogenating function so as to improve the activity and selectivity of the catalyst If the catalyst is used in the deparaffinage process of lubricating oil to get the base oil of the same pour point, it can increase the liquid yield and base oil yield by 15wt%-5wt% and 2wt%-10wt% respectively

Chongren Han

Papers

Ultra-deep desulfurization of diesel: oxidation with a recoverable catalyst assembled in emulsion.

Activated carbons chemically modified by concentrated H2SO4 for the adsorption of the pollutants from wastewater and the dibenzothiophene from fuel oils

Hydroisomerization activity and selectivity of n-dodecane over modified Pt/ZSM-22 catalysts

Fractional oil desulfurizing and adsorption agent and its preparation method

Dewaxing catalyst for lubricant oil distillate and its uses