José Thomaz Senise

Microwave chemistry - a fertile field for scientific research and industrial applications

This paper presents an overview of microwave chemistry, showing its evolution and applications as a part of ISM - industrial, scientific and medical microwave applications.

Alteration of Esterification Kinetics under Microwave Irradiation

At the 7 International Conference on Microwave and High Frequency Heating (Valencia, Spain, 1999) experiments were reported showing a velocity increase of esterification of maleic anhydride with 2-ethylhexanol-1, under microwave irradiation [1]. Experiments were performed in a continuous stirred tank reactor in order to overcome the difficulty of measuring temperature with conventional thermometers or thermocouples subject to microwave irradiation. This paper describes a new set of experiments, aiming at a better understanding of the chemical kinetics of microwave enhanced esterification. The acquisition of a microwave compatible fiberoptic digital thermometer solved the question of temperature measurements in the presence of microwaves, making it possible to perform the same esterification reaction in a batch reactor, with shorter operation times and consuming less raw materials than required by using a continuous reactor.

Microwaves synergic effect on maleic anhydride catalytic esterification with 2-ethylhexanol-1

Maleic anhydride catalytic esterification with 2-ethylhexanol-1 was performed under conventional heating and under microwave heating. The exploratory experimental data showed a positive microwave synergic effect with the catalyst p-toluene sulfonic acid. Interpretation of kinetics curves induced a probable reaction enhancement by a reduction of the esterification global order.

Equipment for microwave enhanced carbothermic reductions

In this paper the diversity of industrial microwave applications is highlighted by the description of another exciting field for microwave usage: the microwave carbothermic reduction of metal oxides. This is a metallurgical application for metal production, for example pig iron from hematite. It is proposed a conception of single mode cavity adapted for mass and energy balances of this kind of reduction. An example of tax reaction for iron ore carbothermic reduction and its energy balance are shown.

Microwave drying of zinc sulfate

An exploratory test of drying zinc sulfate heptahydrate was performed to compare the efficiency of a microwave dryer and an infrared dryer. Moisture content was determined by titrating with EDTA the level of zinc in the sample. Results show that microwave drying is more efficient than infrared drying. A 95 % reduction in drying time and a 7 % higher removal of water was obtained with microwave drying.

Heating reproducibility in microwave chemistry

Statistically designed heating experiments were performed using different microwave sources to heat water under identical operating conditions. Three 2.45 GHz microwave generators were used: a) a 800 W maximum variable power source utilizing a domestic oven model magnetron; b) a 3 kW maximum non-filtered variable power commercial generator and c) a 2 kW maximum low-ripple variable power commercial generator. The same volume of water was successively heated utilizing the three different microwave sources, with equal effective power levels ranging from 190 to 380 W. The energy absorbed by the water load was evaluated by measuring the temperature increase. Preliminary results indicate that heating efficiency may vary with the type of microwave source.

Equipment for microwave assisted thermal cracking of hydrocarbons

This paper exposes an application of microwaves to petroleum industry, the thermal cracking of hydrocarbons. An equipment to perform microwave assisted thermal cracking is described. This device includes a 2.45 GHz, 3 kW microwave generator and a continuous vapor phase flow reactor. The hydrocarbon feed is irradiated by microwaves over silicon carbide susceptor resulting in the hydrocarbon thermal cracking reaction. Analyses of mass spectrometry coupled with gas chromatography (GC-MS) of cracking outputs were performed and confirmed the occurrence of cracking. A naphtha feed with hydrocarbons with molecular weights within 106 and 196 produced light hydrocarbons with molecular weights within 42 and 106.

R&D on industrial microwave power applications in Brazil

A general report on microwave and optoelectronics activities in Brazil was recently published by IEEEs MTT-S Societys Microwave Magazine. Another report, focused on microwave power applications is scheduled for publication on AMPERE Newsletter . Essentially the same material is here included to be presented at the IMOC2001, hoping that during the Conference it will be possible to gather more information than was obtained for the AMPERE publication and thus prepare a more complete report which eventually will be available at SBMOs web site.