http://www1.udel.edu/chem/polenova/PDF/Polyoxometalates/POMs_Catalysis_NMR_ChemRev1998.pdf

Catalysis by Heteropoly Acids and Multicomponent Polyoxometalates in Liquid-Phase Reactions

CO2 conversion covers a wide range of possible application areas from fuels to bulk and commodity chemicals and even to specialty products with biological activity such as pharmaceuticals. In the present review, we discuss selected examples in these areas in a combined analysis of the state-of-the-art of synthetic methodologies and processes with their life cycle assessment. Thereby, we attempted to assess the potential to reduce the environmental footprint in these application fields relative to the current petrochemical value chain. This analysis and discussion differs significantly from a viewpoint on CO2 utilization as a measure for global CO2 mitigation. Whereas the latter focuses on reducing the end-of-pipe problem “CO2 emissions” from todays’ industries, the approach taken here tries to identify opportunities by exploiting a novel feedstock that avoids the utilization of fossil resource in transition toward more sustainable future production. Thus, the motivation to develop CO2-based chemistry does...

Sustainable Conversion of Carbon Dioxide: An Integrated Review of Catalysis and Life Cycle Assessment

The oxidation of model sulfur compounds (thiophene derivatives, benzothiophene derivatives, and dibenzothiophene derivatives), straight run-light gas oil (SR-LGO, S:  1.35 wt %), and vacuum gas oil (VGO, S:  2.17 wt %) were conducted with a mixture of hydrogen peroxide and formic acid. The thiophene derivatives with 5.696 to 5.716 electron densities on the sulfur atoms could not be oxidized at 50 °C. Benzo[b]thiophene with 5.739 electron density and other benzothiophene and dibenzothiophenes with higher electron densities could be oxidized. The sulfur compounds in SR-LGO and VGO appeared to be oxidized to a detectable levels (c.a., 0.01 wt % S) by GC-FPD analysis. The IR spectra of oxidized SR-LGO and VGO showed that sulfones were formed by oxidation. The removal of sulfur compounds by extraction became more effective for the oxidized samples than for the original samples. Lighter sulfur compounds were preferentially extracted. The extraction efficiencies of solvents, i.e., N,N‘-dimethylformamide (DMF), a...

Oxidative Desulfurization of Light Gas Oil and Vacuum Gas Oil by Oxidation and Solvent Extraction

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

Dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene are typical thiophenic sulfur compounds that exist in diesel fuels Using toluene solutions of the model compounds, experiments were carried out to compare the reactivity of the different dibenzothiophenes in oxidation reactions, a key step for oxidative desulfurizations A series of polyoxometalate/H2O2 systems were evaluated for dibenzothiophene oxidation The H2O2 solutions of phosphotungstic acid and its salt were very active catalyst systems for the model compound oxidation, while their molybdenum counterpart systems were much less active The H2O2 solutions of silicotungstic and silicomolybdic compounds were the least active catalyst systems for the reaction Oxidation reactivities decreased in the order of dibenzothiophene>4-methyldibenzothiophene>4,6-dimethyldibenzothiophene, the same reactivity trend that exists in HDS However, the oxidation of the dibenzothiophenes was achieved under mild reaction conditions and it was easy to increase reaction temperature or reaction time to achieve high oxidation conversions, even for the least reactive 4,6-dimethyldibenzothiophene Apparent activation energies of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene oxidation were 538, 560, and 587 kJ/mol, respectively These activation energies indicated a decrease in reactivity of dibenzothiophenes as methyl substitutes increased at the 4 and 6 positions on dibenzothiophene rings Interestingly, in a formic acid/H2O2 system, the oxidation reactivity of the dibenzothiophenes showed the reverse trend, suggesting that steric hindrance might play a role when bulky polyoxoperoxo species, which likely form in a hydrogen peroxide solution, act as catalysts

Oxidation reactivities of dibenzothiophenes in polyoxometalate/H2O2 and formic acid/H2O2 systems

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.

Oxidative desulphurisation of oils via hydrogen peroxide and heteropolyanion catalysis

Economical processes are disclosed for the production of component for refinery blending of transportation fuels by selective oxidation of feedstocks comprising a mixture of hydrocarbons, sulfur-containing and nitrogen-containing organic compounds. Oxidation feedstock is contacted with a soluble quaternary ammonium salt containing halogen, suflate, or bisulfate anion, and an immiscible aqueous phase comprising a source of hydrogen peroxide, and at least one member of the group consisting of phosphomolybdic acid and phosphotungstic acid, in a liquid reaction mixture under conditions suitable for reaction of one or more of the sulfur-containing and/or nitrogen-containing organic compounds. Blending components containing less sulfur and/or less nitrogen than the oxidation feedstock are recovered from the reaction mixture. Advantageously, at least a portion of the immiscible acid-containing phase is recycled to the oxidation.

Preparation of components for transportation fuels

A process for preparing interpolymers of an olefin(s) and carbon monoxide (polyketones) is provided. The process employs a palladium catalyst prepared by reacting together a palladium source, a bidentate amine, phosphine, arsine or stibine and a source of a borate anion. The catalyst effects fast polymerization of the olefin(s) and carbon monoxide in, e.g. methanol or ethoxyethanol solvent. By using the catalyst a lower catalyst deactivation on recycle is observed relative to previously described systems.

Process for preparing polyketones

A process for desulphurising hydrocarbon oils comprises the steps of (1) treating a sulphur containing hydrocarbon oil with a catalyst consisting essentially of an aqueous acidic or neutral solution of a molybdenum, tungsten or vanadium heteropolyanion and an oxidant under conditions such that the sulphur is oxidised and (2) separating the oxidised sulphur from the treated hydrocarbon oil. Preferred catalysts include those heteropolyanions derivable by ionisation of an acid having the general formula He(XkMnOy) where X is selected from phosphorus, antimony, silicon, germanium or boron; M is selected from molybdenum, tungsten or vanadium; k is from 1 to 5; n is from 5 to 40; y is from 18 to 62 and e is the valance of the (XkMnOy)e- anion.

Desulphurisation of oil

A process for the production of formic acid comprises (a) in a first stage reacting together a nitrogenous base, carbon dioxide and hydrogen in the presence of a catalyst to produce a formate salt of the nitrogenous base, (b) in a second stage removing from the formate salt of the nitrogenous base and any low-boilers co-produced therewith the catalyst and recycling this to the first stage, and in a subsequent stage or stages converting the formate salt of the nitrogenous base to formic acid. The process is characterised by the fact that after production of the formate salt of the nitrogenous base in stage (a) and either before or during the second stage (b) the catalyst is treated with a formate salt decomposition inhibitor which is either (I) a carboxylic acid or a salt thereof, (II) carbon monoxide or (III) an oxidant.

Andrew Richard Lucy

Papers

Oxidative desulphurisation of oils via hydrogen peroxide and heteropolyanion catalysis

Preparation of components for transportation fuels

Process for preparing polyketones

Desulphurisation of oil

The production of formic acid from a nitrogenous base, carbon dioxide and hydrogen