Nagabhatla Viswanadham

Reaction pathways for the aromatization of paraffins in the presence of H-ZSM-5 and Zn/H-ZSM-5

The effect of the dehydrogenating component of H-ZSM-5 and Zn/H-ZSM-5 catalysts on n-heptane aromatization reaction was studied. An increase in the yield of aromatics observed over Zn/H-ZSM-5 is explained by the enhanced production of olefins, facilitating the aromatization reaction by the effective dehydrogenating action of zinc on paraffins. A significant change in the selectivities of toluene and C9+ aromatics was observed after addition of zinc. The increase in the yield of toluene observed over Zn/H-ZSM-5 from both n-heptane and Bombay High (BH) light naphtha indicates the possible occurrence of direct dehydrocyclization of paraffins in the presence of zinc. Zinc also facilitates the effective conversion of C6–C8 oligomers to the corresponding aromatics, an in that way suppresses the further oligomerization of C6–C8 oligomers on one hand, and cracking of C6–C8 oligomers on the other; which is reflected in the decreased yields of fuel gas and C9+ aromatics in the product. The product pattern of the BH light naphtha aromatization suggests that the presence of zinc also suppresses the acid catalyzed alkyl transfer reactions which generally take place over H-ZSM-5. Reaction pathways have been established to explain the selectivity changes that occurred in presence of zinc.

Synthesis and catalytic applications of hierarchical mesoporous AlPO4/ZnAlPO4 for direct hydroxylation of benzene to phenol using hydrogen peroxide

Amorphous hierarchical mesoporous AlPO4 and ZnAlPO4 materials have been successfully synthesized for the first time by a simple physical mixing method, where tetrapropyl ammonium bromide acts as both a template and structure directing agent. The materials exhibited excellent catalytic activity for the production of phenol from benzene (99% conversion with 85% selectivity).

Pore size analysis of ZSM-5 catalysts used in n-heptane aromatization reaction: an evidence for molecular traffic control (MTC) mechanism

Gas adsorption studies were carried out for pore analysis of ZSM-5 catalysts used in n-heptane aromatization, to understand the deactivation behavior of zeolite channels. Results suggested that the alumina binder protected the zeolite catalyst by accommodating most of the coke. Analysis of the zeolitic part of the pores indicated that the straight channels are mainly blocked at pore opening and provided an evidence for molecular traffic control mechanism (MTC).

Aromatisation ofn-heptane over ZSM-5 prepared without the aid of a template

ZSM-5 was prepared without the aid of an organic template. Effect of synthesis parameters on its catalytic activity in aromatisation ofn-heptane are discussed. Addition of seed material increased the crystallinity of the ZSM-5 phase. The catalytic activity was comparable with a sample prepared using an organic template. Formation of higher amount of C9– aromatics was observed over the non-templated zeolite.

Breakthrough mesopore creation in BEA and its enhanced catalytic performance in solvent-free liquid phase tert-butylation of phenol

Here we report a breakthrough increase in porosity of a BEA zeolite (1.1822 cm3 g−1) through mesopore creation (mesopores contribute to 93% pore volume with an average pore diameter of 10.5 nm) by employing a sequential treatment of alkali and ammonium nitrate without causing any structural damage to the zeolite. The material exhibited enhanced catalytic properties in the tert-butylation of phenol in terms of phenol conversion and 2,4 di-TBP selectivity in the solvent-free liquid phase reaction.

Facile synthesis of mesoporous aluminosilicate nanoparticles for the selective production of N-benzylidenaniline in a solvent-free reaction of aniline with benzyl alcohol

Herein we report a simple method for the synthesis of mesoporous aluminosilicate nanoparticles (∼20 nm) by adopting a novel solvent-free physical mixing method, using TPABr as a precursor for the structure directing agent. The samples are characterized by SEM, TEM, XRD, FT-IR and N2 adsorption–desorption studies. The materials exhibited novel catalytic properties towards solvent-free N-alkylation of aniline with benzyl alcohol for the selective production of N-benzylidenaniline (100% selectivity) under mild reaction conditions (100 °C and atmospheric pressure), thus providing economical and environmentally benign processes for the synthesis and reaction applications of the AlSi nano-materials.

The Transformation of Light Paraffins to LPG and Aromatics Over a Ni/ZSM-5 Catalyst

Abstract Ni/ZSM-5 catalyst is prepared using an incipient wet impregnation method with 4 wt% of Ni on mildly framework dealuminated ZSM-5 and studied for its physicochemical properties and light alkane conversions. X-ray diffraction (XRD) and pore size distribution studies envisioned the formation of Ni crystallites smaller than 0.55 nm in the zeolite pore channels of Ni/ZSM-5. The Ni/ZSM-5 exhibited better cracking and produced more liquefied petroleum gas (LPG) in the presence of N2 (LPG mode) and better aromatization activity in the presence of H2 (aromatic mode). This has resulted in the production of gasoline blending stock with a Research Octane Number (RON) of 91.

Zeolite catalysed light hydrocarbon conversions

Availability of light alkane containing feedstocks in petroleum industry demands the catalysts and conversion processes. Two zeolites, ZSM-5 and Mordenite were used for the preparation of a series of catalysts for the conversion of pure light hydrocarbons and industrial feedstocks. Cracking and aromatisation activity of the H-ZSM-5 catalysts varied with the catalyst properties and feed composition. The cracking and hydrogen transfer reactions are facilitated in the HZS catalyst and resulted in the formation of aromatics along with Liquefied Petroleum Gas (LPG). Pt/Mordenite-based catalyst could improve the isoparaffin composition in the industrial feedstocks, where along with n-paraffins, considerable amount of olefins, naphthenes and aromatics were also converted into iso-paraffins through hydrogenation, ring-opening and isomerisation reactions. Benzene in the feedstock was successfully converted and the product exhibited almost zero benzene at optimised reaction conditions.

Facile synthesis of bio-fuel from glycerol over zinc aluminium phosphate nanoplates

Herein, nanoplates of crystalline zinc aluminum phosphate exhibiting hexagonal and square planar morphology were successfully synthesized by adopting a novel and simple synthesis method; in this method, a single template, TPABr, was used in minute amounts and a shorter synthesis time of 24 h was required. The materials were characterized by X-ray diffraction, FTIR, SEM, XPS, TEM, thermal analysis, ICP, and ammonia TPD. The synthesis temperature governed the morphology of the nanoplates; however, irrespective of the shape of the nanoplates, the materials exhibited promising catalytic activity towards the production of bio-fuel solketal (2,2-dimethyl-1,3-dioxolane-4-methanol), a valuable bio-fuel, via acetalization of biodiesel waste glycerol under solvent-free reaction conditions.

A Comparative Study of the Esterification Activity of Nanosized H-ZSM-5 with Commercial H-ZSM-5 and H-Beta Zeolite

Abstract Nanosized H-ZSM-5 (NZ) was synthesized and characterized for BET surface area, pore volume, pore size distribution, and acidity. The catalyst was tested toward esterification of cyclohexanol with acetic acid under autogenous pressure condition and the activity was compared with that of commercial H-ZSM-5 (HZ) and H-beta zeolite (BZ). Nanosized H-ZSM-5 was found to be more active than commercial H-ZSM-5, whereas beta zeolite showed remarkably higher activity than H-ZSM-5 and nanosized H-ZSM-5. The catalysts exhibited the increasing activity in the order of HZ < NZ < BZ. The superior activity of BZ was found to be due to higher Brønsted acidity and higher surface area. The maximum conversion was found to be 72% for H-beta zeolite, whereas nanosized H-ZSM-5 gave 69% conversion in esterification reaction.