A METHOD OF PREPARING ACETYLENE (C2H2)

Abstract

The present invention provides a method of preparing acetylene (C.sub.2H.sub.2), the method at least comprising the steps of: a) providing a methane-containing stream; b) subjecting the methane-containing stream provided in step a) to non-catalytic pyrolysis, thereby obtaining carbon and hydrogen; c) reacting the carbon obtained in step b) with CaO, thereby obtaining CaC.sub.2 and CO; d) reacting the CaC.sub.2 obtained in step c) with H.sub.2O, thereby obtaining acetylene (C.sub.2H.sub.2) and Ca(OH).sub.2; e) decomposing the Ca(OH).sub.2 obtained in step d), thereby obtaining CaO and H.sub.2O; f) using the CaO as obtained in step e) in the reaction of step c).

Claims

1. A method of preparing acetylene (C.sub.2H.sub.2), the method at least comprising the steps of: a) providing a methane-containing stream; b) subjecting the methane-containing stream provided in step a) to non-catalytic pyrolysis, thereby obtaining carbon and hydrogen; c) reacting the carbon obtained in step b) with CaO, thereby obtaining CaC.sub.2 and CO; d) reacting the CaC.sub.2 obtained in step c) with H.sub.2O, thereby obtaining acetylene (C.sub.2H.sub.2) and Ca(OH).sub.2; e) decomposing the Ca(OH).sub.2 obtained in step d), thereby obtaining CaO and H.sub.2O; f) using the CaO as obtained in step e) in the reaction of step c).

2. The method according to claim 1, wherein the methane-containing stream provided in step a) comprises at least 30 mol. % methane.

3. The method according to claim 1, wherein the methane-containing stream provided in step a) comprises at most 500 ppm H.sub.2S.

4. The method according to claim 1, wherein the non-catalytic pyrolysis of step b) is performed at a temperature of at least 900° C.

5. The method according to claim 1, wherein the carbon as used in step c) has an average particle size of at most 2 mm.

6. The method according to claim 1, wherein at least 65 mol. % of the Ca(OH).sub.2 as obtained in step d) is used in the decomposition of step e).

7. The method according to claim 1, wherein the H.sub.2O obtained in step e) is used in the reaction of step d).

Description

[0038] Hereinafter the present invention will be further illustrated by the following non-limiting drawings. Herein shows:

[0039] FIG. 1 schematically a flow scheme of an embodiment of the method of preparing acetylene according to the present invention.

[0040] As shown in FIG. 1, a methane-containing stream is provided and subjected to non-catalytic pyrolysis, thereby obtaining carbon and hydrogen (the latter can e.g. be sold as product).

[0041] The obtained carbon is reacted with CaO (preferably using renewable electricity), thereby obtaining CaC.sub.2 and CO. The CO may be sold as a separate product. The CaC.sub.2 is (after possible temporary storing) with H.sub.2O, thereby obtaining acetylene (C.sub.2H.sub.2) and Ca(OH).sub.2.

[0042] The acetylene may be sold as a separate product or used to produce derivative compounds. The Ca(OH).sub.2 is decomposed thereby obtaining CaO and H.sub.2O (the latter may be recycled). The CaO is reused in the reaction with carbon.

[0043] Hereinafter the invention will be further illustrated by the following non-limiting examples.

EXAMPLES

Production of Carbon

Comparative Example 1

[0044] A commercially available carbon powder of high level purity (GF44538295-1EA; 99.997% purity) was obtained from Sigma Aldrich. The carbon powder had a particle size of about 0.075 mm. There was no information available on how the carbon was obtained.

Comparative Example 2

[0045] A methane-containing stream (1 Nl/hour CH.sub.4 and 1 Nl/h N.sub.2; i.e. containing 50 mol. % methane and 50 mol. % N.sub.2), was subjected to non-catalytic pyrolysis in a bubble column molten salt reactor (made from alumina) of 1 inch diameter containing molten NaCl (99% pure; commercially available from Sigma Aldrich/Merck (Darmstadt, Germany)) and dispersed iron nanoparticles (99.9% pure, with an average particles distribution of 20 nm; commercially available from Sky-Spring Nanomaterials (Houston, USA)). The amount of dispersed iron nanoparticles was 1 wt. % of the total NaCl salt weight.

[0046] The NaCl salt was dried and mixed with the iron particles in an oxygen-free gloves box and then loaded as a powder into the reactor.

[0047] After melting of the salt, the methane-containing gas stream was introduced at the bottom of the reactor (at about 1000° C.) via a deep tube of ⅛ inch (0.32 cm), positioned at the centre of the reactor. The gas flow rate was controlled at about 2 Nl/h.

[0048] The carbon material (particle size of about 0.30 mm) produced during the pyrolysis floated on top of the molten salt region of the reactor and was recovered after cooling down of the reactor to room temperature. The carbon was washed with DI (deionized) water until the pH of recovered water was back to 5.5 to remove excess salt contaminant.

Example 1

[0049] A methane-containing stream (containing 93.75 mol. % methane and 6.25 mol. % N.sub.2, no H.sub.2S) was subjected to non-catalytic pyrolysis in an empty (i.e. no catalyst) reactor tube (made from alumina) with an internal diameter of 1 cm and a length of 1 m. The isothermal zone of the reactor was 60 cm long.

[0050] The methane-containing gas stream was passed through the reactor at a flow rate of 4.6 Nl/h at a temperature of 1400° C. and a pressure slightly above ambient (1.1 barg). At this temperature the methane started to crack, producing solid carboneous material that deposited on the wall of the reactor tube. The cracking was continued until a pressure build-up was observed, indicating that the reactor was getting blocked by solid material. The gas flow and the heating was stopped and after cooling down the carbon material was recovered from the reactor.

[0051] The properties of the various carbon samples are given in Table 1 below. As can be seen, the carbon samples as generated according to the present invention result in a significantly lower ash content.

[0052] The ash content and moisture content of the carbon samples was determined according to Chinese National Standards GB/T 476-2001 and GB/T 212-2008.

TABLE-US-00001 TABLE 1 Properties of carbon C. Ex. 1 C. Ex. 2 Ex. 1 C.sup.1 [wt. %] 99.5 98.4 99.7 Moisture.sup.2 0.1 1.1 0.3 [wt. %] Ash content.sup.2 0.4 0.5 0.0 [wt. %] Particle 0.075 (200- 0.3-0.5 0.3-0.5 size [mm] 500 mesh) Carbon 90 90 surface area.sup.3 .sup.1As determined according to Chinese National Standard GB/T 476-2001. .sup.2As determined according to Chinese National Standard GB/T 212-2008. .sup.3As determined according to BET surface area measurement.

[0053] The person skilled in the art will readily understand that many modifications may be made without departing from the scope of the invention.