US3858051A

US3858051A - Photo-chemical reaction apparatus

Info

Publication number: US3858051A
Application number: US00347146A
Authority: US
Inventors: G Smith
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1973-04-02
Filing date: 1973-04-02
Publication date: 1974-12-31
Anticipated expiration: 1991-12-31

Abstract

Apparatus for carrying out photo-reactions under controlled atmospheric conditions on exposure to simulated sunlight comprising an enclosed chamber preferably composed of hollow elongated tubular parts joined together in a rectangular configuration. A focused light source simulating sunlight is coupled to an end of each tubular arm of the rectangle and ''''aimed'''' down that arm. Two adjacent tubular arms are maintained at a higher temperature than the other adjacent arms to assure circulation of the enclosed atmosphere. Means are provided for evacuating the chamber, for introducing an ''''atmosphere'''' to the chamber, for introducing materials to be photo-reacted to the chamber for controlling the humidity in the chamber and for withdrawing gas and volatilized sample materials from the chamber to be coupled to analytical instruments.

Description

United States Patent [191 Smith Dec. 31, 1974 PHOTO-CHEMICAL REACTION APPARATUS [75] Inventor: Grant N. Smith, Midland, Mich.

[73] Assignee: The Dow Chemical Company,

Midland, Mich.

[22] Filed: Apr. 2, 1973 [21] Appl. No.: 347,146

[52] US. Cl. 250/527, 23/253 R, 23/254 R [51] Int. Cl B0lj 1/00 [58] Field of Search 250/527; 23/253 R, 254 R [56] References Cited UNITED STATES PATENTS 2,705,219 I 3/1955 Heiskell et a1. 204/l57.l R 3,666,645 5/1972 Ransohoff 204/193 Primary Examiner-Howard S. Williams Attorney, Agent, or Firm-Earl D. Ayers Recorder Lam 0 5 7] ABSTRACT Apparatus for carrying out photo-reactions under controlled atmospheric conditions on exposure to simulated sunlight comprising an enclosed chamber preferably composed of hollow elongated tubular parts joined together in a rectangular configuration. A focused light source simulating sunlight is coupled to an end of each tubular arm of the rectangle and aimed down that arm. Two adjacent tubular arms are maintained at a higher temperature than the other adjacent arms to assure circulation of the enclosed atmosphere. Means are provided for evacuating the chamber, for introducing an atmosphere to the chamber, for introducing materials to be photo-reacted to the chamber for controlling the humidity in the chamber and for withdrawing gas and volatilized sample materials from the chamber to be coupled to analytical instruments.

11 Claims, 5 Drawing Figures L am o Lam 0 PATENIEDDEC31 1914 SHEET 10F 2 mm W# SW DKOUMW MW QQJ L 1 PHOTO-CHEMICAL REACTION APPARATUS BACKGROUND OF THE INVENTION This invention relates to apparatus for determining the extent of photo-reactivity of chemical compounds in a predetermined atmosphere, and particularly to apparatus in which the compounds are exposed to simulated sunlight.

In the past apparatus for studying photo decomposition of organic compounds in air has usually consisted of a chamber which has a heat lamp or other light source supposedly representing sunlight aimed through the chamber. Often some means such as fan blades inside the chamber are used for getting circulation and mixing of the air and chemical materials to be tested in the chamber so that they can have somewhat uniform exposure to the light which is projected through the chamber.

It has been found that metal or many plastics in the chamber or on the walls of the chamber act somewhat as catalysts to initiate or help along reactions which would otherwise not occur as a result only of exposure to the light source representing the sun. Few of the light sources used were truly representative of sunlight, and therefore the results of the analysis of the samples removed from the chamber were not really indicative of the photo-reactions which might occur under sunlit atmospheric conditions.

It was also found that light from the light made contact with the walls of the container and caused socalled wall effects.

In addition, the volume of the chamber wherein the photo-reaction takes place should be large enough so that a large number of air samples can be taken from the chamber without unduly decreasing the volume of air in the chamber.

Accordingly, the principal object of this invention is to provide an improved apparatus for use in determining the extent of photo decomposition of chemical compounds in air which uses an artificial light source representing sunlight.

Another object of this invention is to provide an improved, simple to use and reliable apparatus for use in determining the extent of photo decomposition of chemical compounds in air on exposure to sunlight.

A further object of this invention is to provide an improved apparatus for use in determining the extent of photo decomposition of chemical compounds in air and sunlight which has improved light transmission means through the apparatus.

Yet another object of this invention is to provide an improved apparatus for use in determining the extent of photo decomposition of chemical compounds in air when exposed to sunlight and in which improved air circulation means within the apparatus is provided.

An additional object of this invention is to provide an improved apparatus for carrying out photochemical reactions under controlled atmospheric and other conditrons.

STATEMENT OF THE INVENTION In accordance with this invention, there is provided apparatus for use in carrying out photo-chemical reactions of compounds exposed to sunlight under predetermined atmospheric conditions comprising an enclosed chamber having a plurality of elongated hollow arm parts, means for maintaining at least one arm part at a cooler temperature than a next adjacent arm part, means for directing a source of simulated sunlight down at least two of said arm parts and for limiting the spectral range of said simulated sunlight entering said arm parts, means for evacuating said chamber, means for introducing a predetermined atmosphere and for introducing photo-reactable material into said chamber, and means for withdrawing samples of atmosphere including photo decomposable material from said chamber.

BRIEF DESCRIPTION OF THE DRAWING The invention, as well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the accompanying drawings, inwhich:

FIG. 1 is a diagrammatical view in side elevation, partly broken away, showing apparatus in accordance with this invention;

FIG. 2 is a chamber having a pair of long arm parts connected by short coupling elements;

FIG. 3 is a chamber shaped as in FIG. 2, but diago nally disposed and having a light source at each end of each longer arm part;

FIG. 4 is a triangular shaped chamber; and

FIG. 5 illustrates schematically a diagonally disposed rectangular chamber similar to that shown in FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to the drawings, and particularly to FIG. 1, there is shown apparatus, indicated generally by the numeral 10, for use in carrying out photo-chemical reactlons.

The apparatus 10 includes a hollow enclosed chamber, generally indicated by the numeral 12, composed of four elongated

flanged tubes

14, 16, 18, 20 joined and sealed together by flanged cross shaped

pieces

22, 24, 26, 28. The tubes l4, l6, 18, 20 and

cross pieces

22, 24, 26, 28 preferably are made of glass (6 inch inner diameter bore is commonly used) or are made of another material capable of withstanding evacuation and whose inner walls neither act as a catalyst to or chemically react with compounds within the chamber 12.

The crosses 2228 usually have their external surfaces covered by an opaque material (opague paint or the like, commonly) while the tubes l420 are covered by a thermally insulating

layer

30a, 30b, 30c, 30d, re spectively. Between the cover 30 (ad) and each of the flanged tubes (14-20) a cooling coil 32 is provided (see the broken away part on tube 20, for example).

A refrigeration unit and temperature controller 34 has temperature sensor lines A, A, B, B coupled to flanged tubes 1420, respectively.

Coolant output lines

1, 2, 3, 4 and

coolant return lines

5, 6, 7, 8 are coupled to coils around the various tubes 14-20, respectively, corresponding to the coil 32 around tube 20.

A lamp housing 36 containing a xenon lamp 338 is coupled to the end of the cross 28 which is remote from and axially aligned with the flanged tube 20. A vacuum tight end plate 40 which also serves as an optical filter is coupled to the flanged end 42 of the cross 28.

Fans

44, 46, 48 are directed at the rear of the lamp housing 36, at the lamp area and towards the area near the flange 42 in order to cool the area most subjected to heat from the xenon lamp 38 (or an equivalent light source).

Similar lamp, filter and cooling assemblies are coupled to

crosses

22, 24 and 26 to direct light down

tubes

14, 16 and 18, respectively.

Parabolic mirrors

50, 52, 54, 56 are mounted at the ends of

crosses

26, 28, 22, 24 opposite to a light source directed down the tube (14, 16, 18 or 20) with which the mirror is aligned.

The

mirrors

50, 52, 54, 56 are each designed to reflect light traveling down the tube to them back towards the light source. The light sources each have a parabolic mirror (see 58 in connection with xenon light source 38) which sends light from the source in a generally parallel beam down the associated tube without light from the beam (or as little of it as possible) striking the walls of the tube.

The mirror 54 has a lead 60 extending through it from a humidity gauge element 62 disposed in the cross 22 to a recorder 64.

A sample inlet line 66 having a valve 68 therein is coupled to the interior of the tube 16. A dual sample withdrawal part 68 has

lines

70, 72 coupled thereto.

Valves

74, 76 are provided in the

lines

70, 72, respectively. Usually one of the

lines

68, 70 is for withdrawing batch samples from the chamber 12 while the other is coupled to a monitoring instrument.

OPERATION In operation, with the valve 68 closed, a vacuum pump (not shown) is coupled to the

line

70 or 72 and the chamber is evacuated. After being evacuated, and with

valves

74, 76 closed, an atmosphere (air of artificially formulated atmosphere in which the reaction in the chamber is to take place) is introduced to the chamber through the line 70. In introducing the atmosphere the gas (mixture, usually) is often provided with a predetermined amount of moisture to provide the desired humidity level in which the reaction(s) in the chamber are to take place.

With the light sources energized, flow through the heating and cooling lines is adjusted to maintain about a C temperature differential between the pairs of cooled" and heated (really less cooled) arms of the chamber.

In a chamber having a 6 foot light path in each tube, a 5 C temperature differential between the cooler and warmer tubes has resulted in a movement of the atmosphere at an estimated rate of one-half mile per hour. A temperature differential showed an atmosphere movement around the chamber of between 2 and 3 miles per hour.

An effort is made to focus the light from the various lamp assemblies into parallel beams about 3 inches in diameter which are directed down the center of the tubes and crosses of the chamber 12. By thus restricting the beam diameter (6 inch inner diameter tubing is used in a commonly used apparatus in accordance with this invention) little or no socalled wall effects" occur. If light impinges on the wall of the chamber, the alkaline metal components ofthe glass walls may act as catalysts to the sample materials which are inserted into the chamber.

After the chamber has been evacuated and the atmosphere established in the chamber, the material to be reacted (or to learn whether it will react) with the atmosphere in the chamber is inserted through the line 66. Then, with valve 66 closed, the temperature differential maintained between opposite sides of the chamher, and the light directed through the chamber, the movement of the atmosphere and the sample materials inserted into the chamber causes mixing of the material with the atmosphere and the reaction between the sample material and the atmosphere, if any. occurs.

Most reactions with which the apparatus is used occur within 24 hours, but reactions requiring several days in the chamber have been carried out.

The intensity of light in the chambers may be varied upwardly from that of a bright summer day.

Reactions taking place within the chamber 12 have included N0 in air, NO in air, soil fumigants in air. chloromethyl ether in air, ethylene dibromide in air, and o,o-diethyl o-3,5,6 trichloro-2-pyridil phosphorothioate.

In most studies made with the apparatus shown in FIG. 1, a concentration of 50 parts per billion of the chemical is used in air at a temperature of 100 F and having a relative humidity of 9598 percent.

The large volume of the chamber 12 permits several samples to be withdrawn during the reaction time from the chamber through the lines or 72 without seri ously depleting the contents of the chamber.

ALTERNATE EMBODIMENTS Referring now to FIGS. 25, FIG. 2 shows a chamber 78 having two long sides, a cooled arm 80 and a heated arm 82 joined by

short sides

90, 92.

Light sources

84, 86 are directed down

arms

82, 80, respectively. Mirrors 88, 91 are at the other ends ofthe arms 88, 91 to reflect light back towards the light sources.

In FIG. 3 a chamber, similar to that shown in FIG. 2, is shown disposed diagonally with long arms 94 (cooled), 96 (heated) and

short sides

98, 100. Light sources 106, I08, 110, 112 direct light down each of the long arms from each end thereof. Such a light arrangement provides more uniform light intensity down the arms. Sample inlet means 102 is provided near the upper end of the chamber and sample outlet means 104 are provided near the lower end of the chamber.

FIG. 4 illustrates a triangular shaped

chamber having arms

114, 116, 118 in which the inclined side 116 is cooled and the side 114 is heated to promote circulation of any gases in the chamber. Light sources 124, 126, are directed down each of the arms of the chamber. Sample inlet means 120 is provided near the upper end of the chamber and sample outlet means 122 is provided near the lower end of the chamber.

FIG. 5 diagrammatically represents a chamber similar to that shown in FIG. 1, but disposed diagonally.

Sides

132, 134 are cooled and

sides

136, 138 are heated.

It has been found necessary (or at least highly desirable) to provide expansion joints in the chambers to avoid breaking the glass column walls because of thermal expansion problems.

Such expansion joints are provided on opposite sides I of the chamber of FIG. 1 (at the lower end of tube 14 and upper end of tube 18, for example).

It should also be noted that a Pyrex plate 37 seals the outer ends of each cross element of FIG. 1, acting both as a vacuum seal and to cut off light below 290 nm. in wavelength.

Because reactions may take place more or less rapidly, depending on the pressure in the chamber 12, a vacuum pump 140 or a pressuring pump 142 may be coupled to the sample inlet or sample outlet lines and to the atmosphere or other source of gas or vapor.

What isclaimed is:

1. Apparatus for carrying out photochemical reactions comprising a hollow composite gas-tight chamber disposed in a vertical plane and composed of a plurality of elongated hollow tubular walled parts joined together generally at their ends to define a closed loop enclosed flow path, means external of said chamber for directing a source of simulated sunlight down each of said tubular parts, means for maintaining a temperature differential between the walls of at least two of said tubular parts, means for inserting gas or vaporizable material into said chamber, and means for withdrawing material from said chamber.

2. Apparatus in accordance with claim 1, wherein means are provided for measuring the humidity in said a chamber.

3. Apparatus in accordance with claim 1, wherein means are provided at the end of each tubular walled part for reflecting light back through said tubular part towards said source.

4. Apparatus in accordance with claim 1, wherein said chamber is composed of four straight tubular parts joined by connecting elements having crossed passages therethrough which are axially aligned with said tubular parts.

5. Apparatus in accordance with claim I. wherein said means for directing a source of simulated sunlight includes a xenon arc lamp having a beam directing reflector positioned to direct a light beam down one of said tubular parts, and means for air cooling said means for directing a source of similated sunlight.

6. Apparatus in accordance with claim 5, wherein light filter means is disposed between'each said source and each said tubular part.

7. Apparatus in accordance with claim 1, wherein said tubular parts are made of glass.

8. Apparatus in accordance with claim 1, wherein means are provided for coupling said chamber to an analytical instrument.

9. Apparatus in accordance with claim 1, wherein said means for maintaining a temperature differential comprises a refrigeration unit having cooling coils coupled to at least two of said tubular parts.

10. Apparatus in accordance with claim 1, wherein means are provided for coupling said chamber to evacuation means.

11. Apparatus in accordance with claim 1, wherein means are provided for controlling the pressure within

Claims

2. Apparatus in accordance with claim 1, wherein means are provided for measuring the humidity in said chamber.

5. Apparatus in accordance with claim 1, wherein said means for directing a source of simulated sunlight includes a xenon arc lamp having a beam directing reflector positioned to direct a light beam down one of said tubular parts, and means for air cooling said means for directing a source of similated sunlight.

6. Apparatus in accordance with claim 5, wherein light filter means is disposed between each said source and each said tubular part.

11. Apparatus in accordance with claim 1, wherein means are provided for controlling the pressure within said chamber.