Method for producing a latent heat storage material and dialkyl ether as a latent heat storage material

Abstract

The invention relates to a method for producing latent heat storage material from linear alcohols by dehydrating to dialkyl ethers or to olefins, and hydrogenating to paraffins and dialkyl ether as a latent heat storage material.

Claims

1. A method for the production of a latent heat storage material, comprising: purifying fatty alcohols by distillation in order to obtain by distillation linear fatty alcohols comprising fatty alcohols that are more than 95% by mass linear, fatty alcohols that have more than 95% by mass even numbered chain lengths, and fatty alcohols that have a certain C-number at more than 95% by mass, followed by dehydrating of the linear fatty alcohols to obtain olefins and subsequently hydrogenating the olefins to obtain paraffins, wherein the paraffins are the latent heat storage material absorbing heat when liquefying and emitting stored heat when solidifying.

2. The method according to claim 1, characterized in that said paraffins comprise even-numbered chain lengths at more than 95% by mass.

3. The method according to claim 1, characterized in that said paraffins comprise a certain C-number at more than 97% by mass.

4. The method according to claim 1, characterized in that the fatty alcohols are cetyl alcohol or stearyl alcohol.

5. The method according to claim 1, characterized in that said fatty alcohols were obtained from naturally occurring vegetable raw materials.

6. The method according to claim 1, characterized in that said fatty alcohols are produced by ethylene oligomerization according to the Ziegler synthesis.

7. The method according to claim 1, characterized in that the latent heat storage material is encapsulated by a polymer material as the capsule wall material into microcapsules with average particle sizes in the range from 1 to 200 m, or into macro-capsules with average particle sizes in the range from more than 200 m to 2 cm.

8. The method according to claim 1, characterized in that the paraffin is hexadecane, octadecane, eicosan, or docosan.

9. The method according to claim 1, characterized in that the fatty alcohols are linear at more than 98% by mass.

10. The method according to claim 5, characterized in that the paraffin is hexadecane, octadecane, eicosan, or docosan.

11. The method according to claim 1, wherein the melting heat of the paraffins as latent heat storage material is at least 245.6 J/g.

12. A method for the production of a latent heat storage material, comprising: Purifying fatty alcohols, obtained from naturally occurring vegetable raw materials, by distillation in order to obtain by distillation linear fatty alcohols comprising fatty alcohols that are more than 95% by mass linear, fatty alcohols that have more than 95% by mass even numbered chain lengths, and fatty alcohols that have a certain C-number a more than 95% by mass, followed by dehydrating of the linear fatty alcohols to obtain olefins and subsequently hydrogenating the olefins to obtain paraffins, wherein the paraffin is hexadecane, octadecane, eicosan, or docosan, and wherein the paraffins are the latent heath storage material absorbing heat when liquefying and emitting stored heat when solidifying.

13. The method according to claim 12, characterized in that the fatty alcohols are linear at more than 98% by mass.

14. A method for absorbing and storing heat comprising producing a latent heat storage material, comprising: purifying fatty alcohols by distillation in order to obtain by distillation linear fatty alcohols comprising fatty alcohols that are more than 95% by mass linear, fatty alcohols that have more than 95% by mass even numbered chain lengths, and fatty alcohols that have a certain C-number a more than 95% by mass, followed by dehydrating of the linear fatty alcohols to obtain olefins, subsequently hydrogenating the olefins to obtain paraffins, wherein the paraffins are the latent heath storage material; and absorbing heat when liquefying the latent heat storage material and emitting stored heat when solidifying the latent heat storage material.

Description

(1) The figures show:

(2) FIG. 1 C-chain distribution of paraffins Rubitherm 27 and Rubitherm 31;

(3) FIG. 2 DSC diagram of C16 to C22 paraffins (pure);

(4) FIG. 3 DSC diagram for comparison of Rubitherm 31/Di-C12 ether/C20 paraffin;

(5) FIG. 4 DSC diagram for comparison of Rubitherm 27/C18 paraffin/C16 paraffin;

(6) FIG. 5 DSC diagram Di-C12/C14/C16/C18 ethers, and

(7) FIG. 6 DSC diagram for comparison of hexadecane from a synthetic/native source.

EXPERIMENT PART

(8) The evaluation of the DSC analyses for the determination of melting enthalpy [J/g] and onset temperature was performed according to DIN 53765. All DSC curves were measured with the device DSC 204 F1 of the company Netzsch with heating and cooling rates of 10 K/min.

Comparative Example

(9) Commercially available PCMB are Rubitherm 27 and Rubitherm@ 31: Rubitherm 27 and Rubitherm 31 have the composition as apparent from FIG. 1 (determined via GC) and furthermore show the following characteristic determined via DSC:

(10) TABLE-US-00001 TABLE 1 Paraffin Rubitherm 27 Rubitherm 31 n-paraffin content [%] 98.0 95.6 Onset 1 [ C.] 4 2 Onset 2 [ C.] 26 27 Melting heat 1 [J/g] 22.0 17.9 Melting heat 2 [J/g] 156.3 147.8

(11) As an example for dehydrating linear fatty alcohols, the dehydration of hexadecanol to linear olefins (Experiment 1) and the hydrogenation of hexadecene (Experiment 2) are described in the following.

Experiment 1: Dehydrating Fatty Alcohols to Linear Olefins

(12) 2474 g of NACOL 16-99 (purity 99.5%, based on renewable raw materials) were mixed with 500 g of Al.sub.2O.sub.3 and 60 ml of xylene in a 6 l flask and heated at up to 295 C., at the water separator for 4.5 hours. In that, 180 ml of water were formed. The hexadecene formed was distilled in vacuum. The yield was a mixture of alpha- and internal olefins.

Experiment 2: Hydrogenation of Linear Olefins to Linear Paraffins

(13) 685 g of the hexadecene obtained in Experiment 1 were hydrogenated for 7 hours at 98 according to a known method over a heterogeneous Ni-containing catalyst at 20 bar H.sub.2 pressure and filtrated after cooling.

(14) Fatty alcohols with chain lengths of C.sub.16 to C.sub.22 were used according to Experiments 1 and 2, and the following paraffins were obtained:

(15) TABLE-US-00002 TABLE 2 Paraffin Hexadecane Octadecane Eicosane Docosane n-paraffin (main 99.6 98.8 93.2 97.4 component) [%] n-paraffin (total) 99.8 98.9 96.8 98.6 [%] iso-paraffin [%] 0.2 0.1 1.8 1.2 Onset [ C.] 17.4 27.4 32.5 40.6 Melting heat [J/g] 245.6 250.7 247.2 270.5

Experiment 3

(16) Experiments 1 and 2 were repeated, however, a synthetic fatty alcohol (hexadecanol) from the Ziegler process with a purity of 95.6% was used as the alcohol.

Experiment 4

(17) Experiment 2 was repeated, however, a synthetic olefin (hexadecene ex Chevron Phillips) with a purity of 94.2% was used as the olefin.

(18) A comparison of the onset temperatures and melting heats for paraffins of different purity due to different production methods are compiled in the following table for hexadecane by way of example.

(19) TABLE-US-00003 TABLE 3 Paraffin Hexadecane Hexadecane Hexadecane Test number 1 2 3 Source Native alcohol Synth. alcohol Synth. olefin n-C.sub.16 paraffin [%] 99.6 91.8 92.3 n-paraffin (total) [%] 99.8 93.1 93.2 iso-paraffin (total) [%] 0.2 6.3 6.2 Onset [ C.] 17.4 13.6 14.3 Melting heat [J/g] 245.6 224.2 207.8

Experiment 5-7

(20) Octadecane and Docosane were mixed at weight ratios of 1:1, 2:1, and 3:1, and the DSC curves were measured again.

(21) TABLE-US-00004 TABLE 4 C.sub.18/C.sub.22 Paraffin mixture C.sub.18/C.sub.22 paraffin C.sub.18/C.sub.22 paraffin paraffin [weight ratio] 1:1 2:1 3:1 Onset 1 [ C.] 1.6 1.2 0.5 Onset 2 [ C.] 28.5 26.6 26.7 Melting heat 1 [J/g] 17.67 21.64 19.93 Melting heat 2 [J/g] 123.9 128.7 123.4

(22) As an example for the partial dehydration of linear fatty alcohols, the dehydration of dodecanol to linear dialkyl ethers is described in the following.

Experiment 8-11: Dehydrating Linear Fatty Alcohols to Dialkyl Ethers

(23) 10 kg/h of NACOL 12-99 (purity 99.2%, based on renewable raw materials) were led over Al.sub.2O.sub.3 beads in a fixed bed reactor (=60 mm, 1=900 mm) at 260 C. according to a known method. The didodecyl ether formed was subsequently distilled in vacuum.

(24) TABLE-US-00005 TABLE 5 Didodecyl Ditetradecyl Dihexadecyl Dioctadecyl Dialkyl ether ether ether ether ether Purity [%] 93.4 95.2 94.8 91.2 Onset [ C.] 30.4 41.8 51.5 59.3 Melting heat [J/g] 209.4 227.4 231.2 207.9