Shafeek A. R. Mulla

Surface basicity and acidity of alkaline earth‐promoted La2O3 catalysts and their performance in oxidative coupling of methane

The catalytic activity and selectivity of La 2 O 3 and alkaline earth (viz. Mg, Ca, Sr and Ba) promoted La 2 O 3 (alkaline earth metal/La = 0.1) catalysts in the oxidative coupling of methane (OCM) to C 2 -hydrocarbons (at 800°C, CH 4 /O 2 ratio = 4 or 8 and gas hourly space velocity = 102000 cm 3 g -1 h -1 ) have been investigated. The acidity and basicity distributions on these catalysts are measured by the temperature programmed desorption (TPD) of NH 3 and CO 2 from 50°C to 950°C, respectively. Both the acidity and basicity of the La 2 O 3 catalysts and their activity in the OCM are strongly influenced by the alkaline earth promoter and its concentration. Among the catalysts, Sr-promoted La 2 O 3 (Sr/La = 0.1) is the most active and selective catalyst for the OCM process. This catalyst contains a larger number of strong basic sites and intermediate strength acid sites.

Oxidative coupling of methane and oxidative dehydrogenation of ethane over strontium-promoted rare earth oxide catalysts

Sr-promoted rare earth (viz. La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er and Yb) oxide catalysts (Sr/rare earth ratio = 0.1) are compared for their performance in the oxidative coupling of methane (OCM) to C 2 hydrocarbons and oxidative dehydrogenation of ethane (ODE) to ethylene at different temperatures (700 and 800°C) and CH 4 (or C 2 H 6 )/O 2 ratios (4-8), at low contact time (space velocity = 102000 cm 3 g -1 h -1 ). For the OCM process, the Sr-La 2 O 3 catalyst shows the best performance. The Sr-promoted Nd 2 O 3 , Sm 2 O 3 , Eu 2 O 3 and Er 2 O 3 catalysts also show good methane conversion and selectivity for C 2 hydrocarbons but the Sr-CeO 2 and Sr-Dy 2 O 3 catalysts show very poor performance. However, for the ODE process, the best performance is shown by the Sr-Nd 2 O 3 catalyst. The other catalysts also show good ethane conversion and selectivity for ethylene; their performance is comparable at higher temperatures (≥800°C), but at lower temperature (700°C) the Sr-CeO 2 and Sr-Pr 6 O 11 catalysts show poor selectivity.

Ligand-, base-, co-catalyst-free copper fluorapatite (CuFAP) as a versatile, ecofriendly, heterogeneous and reusable catalyst for an efficient homocoupling of arylboronic acid at ambient reaction conditions

This paper describes the first report in which copper species containing copper fluorapatite (CuFAP) acts as a versatile, eco-friendly, recyclable, heterogeneous catalyst for an efficient synthesis of symmetric biaryls from the homo-coupling of arylboronic acids in methanol solvent at ambient reaction conditions. The developed protocol is ligand-, base-, and co-catalyst-free, sustainable, mild, inexpensive, and compatible with a wide range of aromatic/heterocyclic boronic acids and provides the corresponding products in excellent yields without purification. The catalyst was easily recovered from the reaction mixture and reused several times without loss of activity.

Non-catalytic pyrolysis of ethane to ethylene in the presence of CO2 with or without limited O2

Influence of the presence of CO2, which is a mild oxidant, on the performance of the thermal cracking of ethane to ethylene in the absence or presence of limited O2 at different temperatures (750–900‡C), space velocities (1500–9000 h-1) and CO2/C2H6 and O2/C2H6 mole ratios (0–2.0 and 0–0.3 respectively) has been investigated. In both the presence and absence of limited O2, ethane conversion increases markedly because of the presence of CO2, indicating its beneficial effect on the ethane to ethylene cracking. The increased ethane conversion is, however, not due to the oxidation of ethane to ethylene by CO2; the formation of carbon monoxide in the presence of CO2 is found to be very small. It is most probably due to the activation of ethane in the presence of CO2.

Influence of precursors of Li2O and MgO on surface and catalytic properties of Li‐promoted MgO in oxidative coupling of methane

The influence of the catalyst precursors (for Li2O and MgO) used in the preparation of Li-doped MgO (Li/Mg = 0.1) on its surface properties (viz basicity, CO2 content and surface area) and activity/selectivity in the oxidative coupling of methane (OCM) process at 650-750°C (CH4/O2 feed ratio = 3.0-8.0 and space velocity = 5140-20550 cm3 g-1 h-1) has been investigated. The surface and catalytic properties are found to be strongly affected by the precursor for Li2O (viz lithium nitrate, lithium ethanoate and lithium carbonate) and MgO (viz magnesium nitrate, magnesium hydroxide prepared by different methods, magnesium carbonate, magnesium oxide and magnesium ethanoate). Among the Li-MgO (Li/MgO = 0.1) catalysts, the Li-MgO catalyst prepared using lithium carbonate and magnesium hydroxide (prepared by the precipitation from magnesium sulfate by ammonia solution) and lithium ethanoate and magnesium acetate shows high surface area and basicity, respectively. The catalysts prepared using lithium ethanoate and magnesium ethanoate, and lithium nitrate and magnesium nitrate have very high and almost no CO2 contents, respectively. The catalysts prepared using lithium ethanoate or carbonate as precursor for Li2O, and magnesium carbonate or ethanoate, as precursor for MgO, showed a good and comparable performance in the OCM process. The performance of the other catalysts was inferior. No direct relationship between the basicity of Li-doped MgO or surface area and its catalytic activity/selectivity in the OCM process was, however, observed.

A novel one-pot multi-component synthesis of 3,3’-disubstituted oxindole and spirooxindole scaffolds via Sn-catalyzed C(sp3)–H functionalization of azaarenes by sequential Knoevenagel–Michael-cyclization reaction

Sn-catalyzed C(sp3)–H bond functionalization of 2-methyl azaarenes/2-(azaaryl)methanes has been achieved for the first time in a one-pot multi-component reaction with isatin and active methylene compounds via tandem sequential Knoevenagel–Michael-intramolecular C–N cyclization. This strategy provides new cost-effective access to potent and biologically/medicinally important spirooxindoles/3,3′-disubstituted 2-oxindoles in good to excellent yields.

Influence of support on surface basicity and catalytic activity in oxidative coupling of methane of Li-MgO deposited on different commercial catalyst carriers

Deposition of Li-MgO catalyst on commonly used supports (containing SiO 2 , Al 2 O 3 , SiC, ZrO 2 , HfO 2 , etc.) causes a drastic reduction in the catalytic activity/selectivity for the oxidative methane coupling reaction and also in both the total and strong surface basicity. The decrease in the catalytic activity/selectivity and basicity is attributed to strong chemical interactions between the catalyst and support which occur during the high temperature (750°C) calcination/pretreatment of the catalyst. The chemical interactions result in catalytically less active binary and ternary metal oxides containing Li and/or Mg, thus deactivating the Li-MgO catalyst by consuming its active components.

Solvent free one-pot multi-component synthesis of β-azaarene substituted ketones via a Sn-catalyzed C(sp3)–H functionalization of 2-alkylazaarenes

A tin-catalyzed solvent free one-pot multi-component cascade reaction strategy for the direct Michael addition/C(sp3)–H functionalization of 2-alkylazaarenes with aldehydes and ketones via an aldol reaction has been developed. This is the first report and provides cost effective new access to potent biologically/medicinally important azaarene derivatives with high atom economy.