RICERCA ITALIANA     

New redox catalysts for new reactor technologies.

Università degli Studi di Napoli "Federico II"

Abstract

The research program " New Redox Catalysts for New Reactor Technologies" is based on different elements of possible innovation that are:
1) The improvement of the catalysts preparation methods, in order to obtain a more dispersed active component with a better control on: the redox and acid-base properties of the active site and the characteristics of the chemical environment of the active site. In particular, vanadiumm, molibdenum, wolframium and chromium based catalysts, that have already shown good activity and selectivity in the oxidative dehydrogenation (ODH) of hydrocarbons to the corresponding olefins, will be studied. Innovative methods of catalysts preparation will be developed, based on: a) grafting metal alkoxides on the surface of oxides rich of hydroxyls; b) flame hydrolysis of the precursors, followed by deposition by dip-coating on a proper support, such as cordieritic honeycombs pre-treated with a proper primer and/or on porous membranes; c) impregnation following the "equilibrium adsorption" technique.
2) The use of innovative reactors such as redox-decoupling reactors and membrane or honeycomb-type catalytic reactors. Catalysts for these reactors will be prepared by using the traditional methods of preparation by impregnation and the new methods based on alkoxide grafting or on deposition by dip-coating.
3) The employment of sophisticated techniques of surface characterisation, in order to define better the redox and acid base >>>

Principal Investigator

Elio SANTACESARIA Università degli Studi di NAPOLI "Federico II"

Research Objectives

This Research Program has different objectives, both scientific and technologic. However, one of the main objectives is to improve the performance of heterogeneous redox catalysts, aiming at approaching the feasibility of the oxidative dehydrogenation (ODH) industrial processes.
It is widely believed by the researchers active in this field that the improvement of the performance can be achieved by coupling the development of new catalytic systems with new reactor configurations, which may help in overcoming the limits which are intrinsic in conventional technologies. Specifically, one key aspect for the improvement of selectivity in redox catalysis is the achievement of a control of the redox properties of the catalyst, and of the nature of the oxygen species which develop in the reaction environment, as a consequence of the activation of molecular oxygen. This justify the study of the catalysts performances in different test reactions such as: the ODH of propane, butane and ethylbenzene to the corresponding olefins and the ODH of methanol and/or ethanol to the corresponding aldheydes. The firstly mentioned reactions occur at high temperatures (400-500°C), while, the last ones occur at much lower temperature (150-200°C), probably, involving different catalytic sites.
The study of the ODH of the hydrocarbons will be oriented to evaluate:
1) the effect of the catalysts preparation methods on the catalytic performances by adopting, in particular new >>>

Timescale

24 months

National and international background

The industrial applications of the oxidative/reductive catalysis, often referred to as redox catalysis, are several. Amongst others, of particular relevance are the oxidation and ammoxidation of alkylaromatics, the oxidation and ammoxidation of olefins, the oxychlorination of olefins, the oxidation of n-butane to maleic anhydride. There are consolidated technologies, widely employed at industrial level, for which however there remain wide margins for considerable improvement. Specifically, one of the most important targets is the achievement of improved selectivity to the product of interest. In fact, in all cases the reactions of total combustion, or the formation of other by-products, lower the selectivity to the desired product. What said above is also valid in the case of a reaction which has not yet found industrial application, i.e., the oxidative dehydrogenation (ODH) of light alkanes to the corresponding olefins (1-11).
The production of olefins, building blocks of the petrochemical industry, is currently realised by the strongly endothermal processes of catalytic dehydrogenation, steam-cracking and catalytic cracking. These processes are carried out at considerably high temperatures, because of thermodynamic constraints, and therefore problems arise due to i) the need for construction materials which have to withstand severe operative conditions, ii) catalysts which easily undergo deactivation due to coke formation, thus needing frequent regeneration, and >>>