Soumen Dasgupta

Carbon Di-Oxide Removal with Mesoporous Adsorbents in a Single Column Pressure Swing Adsorber

Abstract A five-step PSA cycle was studied for CO2 separation from CO2-N2 gas mixture in a single column at elevated temperatures using Poly-ethyleneimine (PEI) impregnated mesoporous silica SBA-15 as adsorbent. The PSA cycle study included a strong adsorptive rinse step in which the strongly adsorbed component, i.e., CO2 was used for rinsing the adsorbent bed in order to increase the purity of CO2 product. The study indicates that the adsorbent is regenerable under typical PSA conditions. The productivity of the adsorbent studied for CO2 separation was found to be comparable with commercial zeolite adsorbents as reported in literature.

A vapor phase adsorptive desulfurization process for producing ultra low sulphur diesel using NiY zeolite as a regenerable adsorbent

A NiY zeolite based vapor phase adsorptive desulfurization process has been described which can bring down sulphur concentration of a commercial BS IV grade (Euro IV equivalent) diesel from 50 ppm to a <5 ppm level. Compared to literature reports on fixed bed adsorptive desulfurization of diesel using zeolite adsorbents, the present process has the advantage of easy regenerability of the adsorbent with minimum temperature swing between adsorption and regeneration steps. Multi cycle stability of the desulfurization performance was also demonstrated.

Characterization and catalytic activity of novel palladium-incorporated vanadium phosphates

Abstract Palladium has been introduced into the layered vanadyl hydrogen phosphate hemihydrate VOHPO4·0.5H2O in different ways depending upon the medium of preparation. In aqueous medium, the introduction of palladium leads to the formation of a new phase containing mixed valent vanadium whereas in the preparation in organic medium, the palladium appears to substitute into the lattice of the parent compound. The palladium-incorporated compounds have been found to be catalytically active, both for oxidative coupling as well as for hydrogenation reactions, with the activity and selectivity varying quite markedly with the mode of incorporation.

A novel procedure for the synthesis of NH3 incorporated VPO phases

It has been observed that as a function of a time delay introduced between the onset of the reduction of V2O5 with hydroxylamine hydrochloride and the addition of phosphoric acid, in the aqueous route preparation of the catalytically important VOHPO4·0.5H2O phase, a series of NH3 incorporated phases are obtained. Up to delay times of 3 min the crystalline VOHPO4·0.5H2O phase is obtained whereas a weakly crystalline hemihydrate is formed at a delay time of 4 min. Longer delay times result in X-ray amorphous phases until at delay time of 10 min and above a new crystalline phase containing mixed-valent vanadium emerges. All the phases obtained with delay times of 4 min and above have NH3 incorporated into them. The weakly crystalline VOHPO4·0.5H2O phase as well as the X-ray amorphous phases undergo transformation to a crystalline vanadyl pyrophosphate phase on calcination at 723 K in spite of having NH3 incorporated into them. The in-situ generation of NH3 during the preparation procedure is a hitherto unreported aspect of VPO chemistry and provides a convenient method for the preparation of novel NH3 incorporated VPO phases which could have strong potential as catalysts for alkane oxidation as well as for ammoxidation reactions.

Novel platinum incorporated vanadium phosphates and their catalytic activity

Abstract Platinum has been incorporated into the layered vanadyl hydrogen phosphate VOHPO 4 ·0.5H 2 O in different ways depending upon the medium of its preparation. The phase obtained by the introduction of platinum during the synthesis of VOHPO 4 ·0.5H 2 O in aqueous medium is a new crystalline phase with mixed-valent vanadium containing Pt 2+ species. This phase forms a novel hydrogen insertion compound involving hydrogen spillover from the incorporated platinum onto the VPO matrix. On the other hand, the incorporation of platinum during the synthesis of the hemihydrate in organic medium gives rise to a phase containing both metallic platinum and an amorphous Pt 2+ containing VPO phase. Both these platinum incorporated phases have been found to be active catalysts for reduction and oxidation reactions such as the hydrogenation of nitrobenzene and the oxidation of tetrahydrofuran with the activity varying quite markedly with the mode of incorporation.

Novel vanadium phosphate phases as catalysts for selective oxidation

In our effort to induce novel modifications in the structure of some important vanadium phosphate phases used as selective oxidation catalysts, it has been observed that metal ions such as Zn2+, Ni2+, Pd2+can be incorporated into the vanadyl hydrogen phosphate VOHPO40.5H2O phase in very different ways depending upon the medium of preparation. It has been found that the metal ions are either substituted into the lattice with retention of structure of the parent compound or intercalated between the layers of a new mixed-valent phase. These new metal-incorporated phases are catalytically active and the palladium incorporated compound in particular displays shape selective catalysis for different oxidation and reduction reactions. In another approach, the preparation of VOHPO40.5H2O) has been modified to give a novel crystalline phase containing mixed-valentvanadium and having NH3 species bound to the lattice. This phase could be a potential catalyst for ammoxidation reactions. In addition, novel mesostructured vanadium phosphate phases have been prepared using a long-chain amine as the templating agent involving a ligand templating mechanism of formation.

[Cu3(BTC)2]-polyethyleneimine: an efficient MOF composite for effective CO2 separation

Increased CO2 concentration in the earth’s atmosphere results in global warming and has increased concerns towards the development of efficient strategies for carbon capture and storage. CO2 separation from flue gas is one of the most challenging areas. Here, a Cu-BTC MOF and a series of polyethyleneimine (PEI) incorporated Cu-BTC composites (Cu-BTC–PEI) with different loading amounts of PEI have been developed for CO2 separation. A significant increase in CO2 adsorption capacity was observed with Cu-BTC–PEI adsorbents. Detailed characterization of the developed adsorbents was done using XRD, SEM, BET surface area and IR. The synthesized adsorbents show good CO2/N2 selectivity for a designed flue gas composition containing 15 vol% CO2 and the remainder as N2. 2.5 wt% PEI loaded Cu-BTC (Cu-BTC–PEI-2.5) has shown a CO2 adsorption capacity of 0.83 mmol g−1 at a pressure of 0.15 bar and 25 °C which is almost double that of Cu-BTC in similar conditions. But at an elevated pressure of 5 bar and 25 °C, 1 wt% PEI loaded Cu-BTC (Cu-BTC–PEI-1) performed even better with a CO2 adsorption capacity of 10.57 mmol g−1. Better adsorption capacity and selectivity for CO2 was obtained with Cu-BTC–PEI composites and they are good aspirant adsorbents for CO2 separation from flue gas.

Metal ion incorporated VPO phases as novel catalysts

Vanadium phosphates function as catalysts for the selective oxidation of hydrocarbons with their activity being strongly dependent on their structure. Consequently, attempts have been made to synthesise novel phases in the VPO system through metal ion incorporation and evaluate the catalytic activity of these phases. It is shown that the incorporation of palladium or platinum leads to novel phases which vary according to the method of syntheses. The incorporated metal ions are catalytically active both for oxidation and reduction reactions with the activity varying according to the mode of incorporation. These phases constitute a novel class of compounds in which oxidation centres are substituted or dispersed within a VPO oxidation catalyst.

Water-vapor-induced transformation of two-dimensional vanadyl hydrogen phosphate hemihydrate, VOHPO4.0.5H2O, to one-dimensional tetrahydrate, VOHPO4.4H2O

The catalytically important, two-dimensional vanadyl hydrogen phosphate hemihydrate, VOHPO 4 ·0.5H 2 O phase was transformed to the one-dimensional vanadyl hydrogen phosphate tetrahydrate, VOHPO 4 ·4H 2 O for the first time by mild treatment with water vapor. It was also observed that for three samples of VOHPO 4 ·0.5H 2 O prepared under different conditions, the rate of transformation to the tetrahydrate was markedly affected by morphology and crystallinity. The tetrahydrate phase could also be re-transformed to the hemihydrate by applying high vacuum or by heating at 120 °C, but this was accompanied by significant loss in crystallinity.