WO1992010294A1

WO1992010294A1 - Electrically heated reaction vessel

Info

Publication number: WO1992010294A1
Application number: PCT/FI1991/000368
Authority: WO
Inventors: Antti P. Manninen
Original assignee: Manninen Antti P
Priority date: 1990-12-04
Filing date: 1991-12-03
Publication date: 1992-06-25
Also published as: FI89563B; FI905964A0; FI89563C; AU9096091A; FI905964A

Abstract

The invention concerns an electrically heated reaction vessel (1), where the surface of the reaction vessel is covered with a resistor foil (2) connectable to a power supply. The foil forms desired patterns (3, 4), preferably a spiral, on the vessel surface.

Description

ELECTRICALLY HEATED REACTION VESSEL

Amounts of chemicals used in synthetic laboratories have been decreased clearly in past years due to new analytical techniques. Today tedious distillations or crystallizations are not always needed, because reaction products can be measured directly in the reaction mixtures, but still these basic processes are very important.

Also the environmental safety and waste treatment aspects press researchers and product developers to use smaller amounts of substances. The potential toxicity of new unknown chemical compounds has to be remembered and therefore small reaction volumes are preferred.

New problems occurs when working with small amounts of compounds, e.g. the distillation can not be carried out, because a compound runs out before distillation starts due to a big reaction vessel . Sometimes an inert gas atmosphere or very low temperatures are necessary and these can cause difficulties with small volumes.

The traditional heating system for a reaction vessel is the water or oil bath or today more often the electrical heater with a half ball shape. The temperature of the water bath is often too low and the use of the oil bath is dirty and fast cooling of the reaction mixture can be difficult.

Electrical heaters (SE 436 698) are good, but several sizes of heaters are needed for optimal heating of different sizes of vessels and the heater have to be removed before cooling.

Glass reaction vessels with a heating jacket are widely used where a heated liquid circulates in the jacket and warms up the mixture. An external thermostat is needed and in addition the temperature range is limited and depends on

SHE T the thermal properties of the circulating liquid. Jacket vessels with a bottom valve are available, whereas the other above mentioned systems do not easily allow this feature.

In addition to the heating of the reactor itself, also other parts of the apparatus have to be heated occasionally. E.g. the cooler must be heated when compounds become solid during the distillation.

Band type resistor elements are well known and they can be wound around the vessel to be heated. The assembly of these elements is tedious, however, and they prevent seeing the inside of the equipment.

Heating elements are also made on high temperature polymer films. These polymers can be used at high temperatures (e.g. polyimide) and they can be wind easily on glass tubes and other simple equipments. Their disadvantage is that they do not fit well with more complex vessels.

This invention presents a new simple reaction vessel, where the temperature conditions can be regulated exactly and where the view inside the vessel is not prevented.Typically the reaction vessel is equipped with a resistor foil, which can be connected to a power supply. This makes the equipment very simple when no additional heating system is needed. The resistor foil is designed so that the heat formed can be transferred efficiently and evenly in the reaction vessel and the liquid inside. The new heating system suits optimally for heating of small reactors.

The resistor foil can be designed so that e.g. a pair of isolated foil bands are broad in the upper part of the vessel and they become narrow and spiral like in the lower part. In the bottom of the vessel the foil bands are joint together and make an electrical resistor circuit. Due to the narrow resistor films the view inside of the vessel is good.

The power supply can be connected to the reaction vessel with suitable connector plates or with a connector collar presented here. The connector collar contain a connection surface and it is designed to fit firmly with the vessel wall. The collar have also power supply wires connected to the connector surfaces.

The connector collar can be designed for use with common reaction vessels having standard joints (e.g. 14/23 etc.).

For more general use the reaction vessel can be equipped with a glass jacket making an isolation space between the vessel and outer atmosphere. The electrical connection collar can be a lid for the jacket and have cooling inlet tubes for carbon dioxide or nitrogen cooling. So it is possible to use the reactor at very low temperatures in the beginning of the reaction and then easily to heat it to higher temperatures.

The invention details are described referring to the enclosed drawings, where

Figure 1 shows the reaction vessel

Figure 2 shows the connecting collar of the vessel and

Figure 3 shows the glass jacket of the vessel

The drawings describe an example of the reaction vessel. Same techniques can be applied for the temperature control of other laboratory equipments made of glass.

A thin metallic resistor foil 2 is made on the surface of the reaction vessel 1 using vacuum vaporizing technique.

EET Metal can be e.g. aluminum, copper, nickel etc.. Before metallization the surface of the vessel is covered with adhesives so that desired part of the surface is free. The adhesives are removed after metallization and the resulting resistor band 3 is obtained. The thickness of the foil is typically 1-2 μm and the broadness ca. 2-5 mm depending on the metal and the voltage used. Often the glass surface have to be treated with a primer before metallization to bind metal firmly on glass.

With copper the well known iron(III) chloride etching technique can be applied. There the vessel is first totally metallized, then the shape of the resistor is drawn on the copper with a special pen and the bare copper surface is removed wit the reagent. For high temperature use (over

200°C) with copper resistor a protective layer is needed on the metal to prevent oxidation of the foil. Nickel also makes the resistor foil strong and inert and no additional protective layer is necessary.

The heating voltage is low (0 - 40 V), which makes the use safe. Resistor films 3 and 4 are separated_/ so that the inside of the vessel can be easily seen (Fig. 1). The contact surfaces 3, 6 to the power supply are broad and the electrical current will be conducted to the resistor surface 2, 3, 4 through the broad metal foils.

The wires of the power supply can be connected directly to the foil 2 with a suitable connector or to use the connector collar 5 shown in Fig. 2. The ring-shaped collar is made of polytetrafluoroethylene (Teflon) or other nonconducting material, which can be used at high temperatures. The inside diameter of the collar is dimensioned so that it fits perfectly with the vessel surface and the conducting surface 3. A ring-shaped tightener may be needed around the collar to keep the contact perfect. More general type of a reactor vessel have a glass jacket 10, where the conducting collar work as a lid of the jacket and the air gap function as an excellent insulation layer. In this model the collar 5 can be equipped with inlet and outlet tubes 8, 9 to cool down the reactor with cold gases. With this system reactions are easy to carry out at low temperatures (e.g. -50°C) by cooling the mixture with e.g. liquid carbon dioxide and exactly adjusting the temperature with the surface heater. Also urgent cool down in the case of very exothermic reactions is straightforward by introducing pressurized air or cold gases in the jacket.

The outer surface of the reactor vessel can be covered with a thin polymer layer (e.g. polyimide), which is stabile at high temperatures. This layer protects the resistor foil, but limits the maximum operational temperature.

HEET

Claims

Cl aims

1. An electrically heated reaction vessel (1), c h a r a c t e r i z e d in that the surface of the reaction vessel is covered with a resistor foil (2), which can be connected to a power supply.

2. A reaction vessel according to claim 1, c h a r a c t e r i z e d in that the resistor foil (2) forms a pattern (3, 4), which partly covers the surface of the vessel.

3. A reaction vessel described in claims above, c h a r a c t e r i z e d in that the resistor foil (2) is covered with an insulation layer.

4. A reaction vessel described in claims above, c h a r a c t e r i z e d in that part of the pattern forms a conducting surface (3) for the electrical wires.

5. A reaction vessel according to claim 4, c h a r a c t e r i z e d in that there is a detached conducting collar (5), which can be installed on the conducting surface (3), the inner surface of the collar (5) being equipped with a conducting surface (6) connected to the power supply wires (7) and which collar (5) when installed is in contact with the conducting surface (3) of the reaction vessel .

6. A reaction vessel described in claims above, c h a r a c t e r i z e d in that the vessel has a jacket (10) with an inner diameter bigger than the outside diameter of the vessel (1) forming an isolation space between the jacket and the vessel.

7. A reaction vessel according to claim 6, c h a r a c t e r i z e d in that the conducting collar (5) forms a lid to the isolation space.

8. A reaction vessel according to claim 7, c h a r a c t e r i z e d in that the conducting collar (5) has inlet and outlet joints (8, 9) for cooling or heating medium.

9. A reaction vessel described in any of the preceding claims, c h a r a c t e r i z e d in that the resistor foil (2) forms a spiral figure (3, 4) on the surface of the vessel .

10. A reaction vessel described in any of the preceding claims above, c h a r a c t e r i z e d in that the conducting surface is a broad foil band in the upper part of the vessel (1).