Patent Description:
Polyvinyl chloride (PVC) is the second major general-purpose resin worldwide, and VCM is a main raw material to synthesize PVC. The VCM production is achieved mainly through the following two industrial production routes: calcium carbide route and ethylene route. In the calcium carbide route, VCM is prepared through the hydrochlorination of acetylene under the catalysis of mercury chloride. In the ethylene route, VCM is prepared through the pyrolysis of <NUM>,<NUM>-DCE.

The global treaty "Minamata Convention on Mercury" restricts and may eventually prohibit the use of mercury catalysts, making the calcium carbide route the less desirable route for producing VCM in China. Therefore, it is imperative to develop a green VCM production route.

Industrially, thermal pyrolysis is adopted for the pyrolysis of <NUM>,<NUM>-DCE to prepare VCM, and a reaction temperature is controlled at about <NUM> to improve a conversion rate of <NUM>,<NUM>-DCE. This route involves a high reaction temperature and a large energy consumption and is prone to coking and carbon deposition, which requires periodic shutdown for coke cleaning, causing a great impact on the normal operation of production. Therefore, it is necessary to study and develop a catalyst capable of reducing the pyrolysis temperature and improving the pyrolysis selectivity.

<CIT> discloses a catalyst for catalytic pyrolysis of <NUM>,<NUM>-DCE to prepare VCM, where the catalyst is obtained by loading a rare earth element on molecular sieves HFZ-<NUM>, HFZ-<NUM>, and HFZ-<NUM>. When the catalyst is used for catalytic pyrolysis of <NUM>,<NUM>-DCE to prepare VCM, a <NUM>,<NUM>-DCE conversion rate is <NUM>% and a maximum VCM selectivity is <NUM>%.

Chinese Patent <CIT> discloses a catalyst for catalytic pyrolysis of <NUM>,<NUM>-DCE to prepare VCM, where the catalyst is obtained by loading a rare earth element on a molecular sieve ZSM-<NUM>. When the catalyst is used for catalytic pyrolysis of <NUM>,<NUM>-DCE to prepare VCM, a <NUM>,<NUM>-DCE conversion rate is <NUM>% and a maximum VCM selectivity is <NUM>%.

Chinese Patent <CIT> discloses a method for catalytic pyrolysis of <NUM>,<NUM>-DCE with a metal-modified molecular sieve SAPO-<NUM> as a catalyst to prepare VCM, where a <NUM>,<NUM>-DCE conversion rate is <NUM>% and a maximum VCM selectivity is <NUM>%.

Chinese Patent <CIT> discloses a method for catalytic pyrolysis with a barium chloride catalyst to prepare VCM, where a BaCl<NUM> active component is loaded on activated carbon in a mass fraction of <NUM>% to <NUM>% and is used for catalytic pyrolysis of <NUM>,<NUM>-DCE to prepare VCM at <NUM> MPa, <NUM>, and a <NUM>,<NUM>-DCE vapor space velocity of <NUM>-<NUM>, which has a pyrolysis conversion rate of <NUM>%.

These catalysts can reduce the <NUM>,<NUM>-DCE pyrolysis temperature to some extent, but due to insufficient activity, short life, difficult regeneration, and the like, these catalysts still cannot be used in industrial production.

According to a first aspect of the present application, a method for catalytic pyrolysis of <NUM>,<NUM>-DCE to prepare VCM is provided, including: introducing a <NUM>,<NUM>-DCE-containing feed gas into a reactor filled with a catalyst, and allowing the <NUM>,<NUM>-DCE-containing feed gas to contact the catalyst and be subjected to a reaction to obtain the VCM.

The catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM includes a silicon-aluminum molecular sieve.

The catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM is provided, which has high reaction activity and excellent selectivity, and solves the problem that the pyrolysis of <NUM>,<NUM>-DCE to prepare VCM in the prior art involves a high reaction temperature and a large energy consumption and is prone to coking and carbon deposition.

The silicon-aluminum molecular sieve includes at least one selected from the group consisting of an X-type silicon-aluminum molecular sieve, a Y-type silicon-aluminum molecular sieve, and USY-type silicon-aluminum molecular sieve. The silicon-aluminum molecular sieve has a silicon-aluminum ratio SiO<NUM>:Al<NUM>O<NUM> of <NUM> to <NUM>.

According to a second aspect of the present application, a method for catalytic pyrolysis of <NUM>,<NUM>-DCE to prepare VCM is provided, including: introducing a <NUM>,<NUM>-DCE-containing feed gas into a reactor filled with a catalyst, and allowing the <NUM>,<NUM>-DCE-containing feed gas to contact the catalyst and be subjected to a reaction to obtain the VCM.

The preparation method of the catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM described above includes: forming and roasting the silicon-aluminum molecular sieve to obtain the catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM.

The silicon-aluminum molecular sieve includes at least one selected from the group consisting of an X-type silicon-aluminum molecular sieve, a Y-type silicon-aluminum molecular sieve, and USY-type silicon-aluminum molecular sieve.

The preparation method of the catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM may include:.

The reaction is conducted under a reaction temperature of <NUM> to <NUM> and a weight hourly space velocity (WHSV) of the <NUM>,<NUM>-DCE of <NUM>-<NUM> to <NUM>-<NUM>.

Preferably, the reaction is conducted under a reaction temperature of <NUM> to <NUM> and a WHSV of the <NUM>,<NUM>-DCE of <NUM>-<NUM> to <NUM>-<NUM>.

The reactor includes a fixed bed reactor, a fluidized bed reactor, or a moving bed reactor.

The conversion rate of the <NUM>,<NUM>-DCE is <NUM>% or higher; and
the selectivity for the VCM is <NUM>% or higher.

The method for catalytic pyrolysis of <NUM>,<NUM>-DCE to prepare VCM further includes a regeneration of a spent catalyst, including: introducing air into a reactor filled with the spent catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM, and subjecting the catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM to regeneration.

The regeneration is conducted under a bed temperature of the catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM in the reactor of <NUM> to <NUM>; a ratio of a flow rate of the air to a volume of the catalyst of <NUM>-<NUM> to <NUM>,<NUM>-<NUM>; and a regeneration time of <NUM> to <NUM>.

Possible beneficial effects of the present application:.

The present application will be described in detail below with reference to examples, but the present application is not limited to these examples.

Unless otherwise specified, the raw materials in the examples of the present application are all purchased from commercial sources.

Analysis methods in the examples of the present application are as follows:
A gas obtained after a reaction is introduced into an on-line chromatograph through a heated pipeline for on-line analysis. The chromatograph is Agilent7890A and is equipped with a PLOTQ capillary column and a TDX-<NUM> packed column, where an outlet of the PLOTQ capillary column is connected to an FID detector and an outlet of the TDX-<NUM> packed column is connected to a TCD detector.

The conversion rate and selectivity in the examples of the present application are calculated as follows:
In the examples of the present application, the <NUM>,<NUM>-DCE conversion rate and VCM selectivity are calculated as follows:
In the examples, the VCM selectivity is calculated based on a carbon mole number of VCM: <MAT> <MAT>.

<NUM> of a purchased sodium-type X molecular sieve powder (purchased from Nankai University Catalyst Co. ) and <NUM> of a <NUM> mol/L potassium chloride aqueous solution were mixed. The resulting mixture was heated in a <NUM> water bath for <NUM> to allow ion exchange. The ion exchange was conducted <NUM> times, and a resulting product was washed with deionized water, dried, and roasted at <NUM> for <NUM> to obtain a potassium-type X molecular sieve.

<NUM> of the above potassium-type X molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished potassium-type X molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

The catalyst sample <NUM># was used in a catalytic pyrolysis reaction of <NUM>,<NUM>-DCE. When a WHSV of <NUM>,<NUM>-DCE was <NUM>-<NUM> and a reaction temperature was <NUM>, a <NUM>,<NUM>-DCE conversion rate was <NUM>% and a VCM selectivity was <NUM>%.

Regeneration of the catalyst sample <NUM>#: When the <NUM>,<NUM>-DCE conversion rate was lower than <NUM>%, air was introduced into a reactor filled with the catalyst to allow regeneration for <NUM>, during which a temperature of a catalyst bed was <NUM> and a ratio of a flow rate of the air to a volume of the catalyst was <NUM>-<NUM>.

After the catalyst sample <NUM># was regenerated, the catalytic pyrolysis reaction of <NUM>,<NUM>-DCE was continued according to the conditions in this example, and it was found that the <NUM>,<NUM>-DCE conversion rate was recovered from <NUM>% to <NUM>% and the VCM selectivity was recovered from <NUM>% to <NUM>%.

<NUM> of a purchased sodium-type X molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished sodium-type X molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

Regeneration of the catalyst sample <NUM>#: When the <NUM>,<NUM>-DCE conversion rate was lower than <NUM>%, air was introduced into a reactor filled with the catalyst to allow regeneration for <NUM>, during which a temperature of a catalyst bed was <NUM> and a ratio of a flow rate of the air to a volume of the catalyst was <NUM>,<NUM>-<NUM>.

<NUM> of a purchased sodium-type X molecular sieve powder and <NUM> of a <NUM> mol/L calcium chloride aqueous solution were mixed, and the resulting mixture was heated in a <NUM> water bath for <NUM> to allow ion exchange. The ion exchange was conducted <NUM> times. The resulting product was washed with deionized water, dried, and roasted at <NUM> for <NUM> to obtain a calcium-type X molecular sieve.

<NUM> of the above calcium-type X molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished calcium-type X molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

The catalyst sample <NUM># was used in a catalytic pyrolysis reaction of <NUM>,<NUM>-DCE, When a WHSV of <NUM>,<NUM>-DCE was <NUM>-<NUM> and a reaction temperature was <NUM>, a <NUM>,<NUM>-DCE conversion rate was <NUM>% and a VCM selectivity was <NUM>%.

Regeneration of the catalyst sample <NUM>#: When the catalyst reacted for <NUM>, air was introduced into a reactor filled with the catalyst to allow regeneration for <NUM>, during which a temperature of a catalyst bed was <NUM> and a ratio of a flow rate of the air to a volume of the catalyst was <NUM>-<NUM>.

<NUM> of a purchased sodium-type Y molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> (purchased from Nankai University Catalyst Co. ) was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished sodium-type Y molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

<NUM> of a purchased sodium-type Y molecular sieve powder and <NUM> of a <NUM> mol/L magnesium chloride aqueous solution were mixed, and the resulting mixture was heated in a <NUM> water bath for <NUM> to allow ion exchange once. The resulting product was washed with deionized water, dried, and roasted at <NUM> for <NUM> to obtain a magnesium-type Y molecular sieve.

<NUM> of the above magnesium-type Y molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished magnesium-type Y molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

<NUM> of a purchased sodium-type Y molecular sieve powder and <NUM> of a <NUM> mol/L barium chloride aqueous solution were mixed, and the resulting mixture was heated in a <NUM> water bath for <NUM> to allow ion exchange; the ion exchange was conducted <NUM> times. The resulting product was washed with deionized water, dried, and roasted at <NUM> for <NUM> to obtain a barium-type Y molecular sieve.

<NUM> of the above barium-type Y molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished barium-type Y molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

<NUM> of a purchased sodium-type USY molecular sieve powder (purchased from Nankai University Catalyst Co. ) and <NUM> of a <NUM> mol/L potassium chloride aqueous solution were mixed, and the resulting mixture was heated in a <NUM> water bath for <NUM> to allow ion exchange; the ion exchange was conducted <NUM> times. The resulting product was washed with deionized water, dried, and roasted at <NUM> for <NUM> to obtain a potassium-type USY molecular sieve.

<NUM> of the above potassium-type USY molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished potassium-type USY molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

<NUM> of a purchased sodium-type USY molecular sieve powder and <NUM> of a <NUM> mol/L lithium chloride aqueous solution were mixed, and the resulting mixture was heated in a <NUM> water bath for <NUM> to allow ion exchange; the ion exchange was conducted <NUM> times. The resulting product was washed with deionized water, dried, and roasted at <NUM> for <NUM> to obtain a lithium-type USY molecular sieve.

<NUM> of the above lithium-type USY molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished lithium-type USY molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

<NUM> of a purchased sodium-type USY molecular sieve powder and <NUM> of a <NUM> mol/L strontium chloride aqueous solution were mixed, and the resulting mixture was heated in a <NUM> water bath for <NUM> to allow ion exchange; the ion exchange was conducted <NUM> times. The resulting product was washed with deionized water, dried, and roasted at <NUM> for <NUM> to obtain a strontium-type USY molecular sieve.

<NUM> of the above strontium-type USY molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished strontium-type USY molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

<NUM> of a purchased sodium-type MOR molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> (purchased from Nankai University Catalyst Co. ) was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished sodium-type MOR molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

<NUM> of a purchased sodium-type MOR molecular sieve powder and <NUM> of a <NUM> mol/L potassium chloride aqueous solution were mixed, and the resulting mixture was heated in a <NUM> water bath for <NUM> to allow ion exchange; the ion exchange was conducted <NUM> times. The resulting product was washed with deionized water, dried, and roasted at <NUM> for <NUM> to obtain a potassium-type MOR molecular sieve.

<NUM> of the above potassium-type MOR molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished potassium-type MOR molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

<NUM> of a purchased sodium-type Beta molecular sieve powder (purchased from Nankai University Catalyst Co. ) and <NUM> of a <NUM> mol/L ammonium nitrate aqueous solution were mixed, and the resulting mixture was heated in a <NUM> water bath for <NUM> to allow ion exchange; the ion exchange was conducted <NUM> times. The resulting product was washed with deionized water, dried, and roasted at <NUM> for <NUM> to obtain a hydrogen-type Beta molecular sieve.

<NUM> of the above hydrogen-type Beta molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished hydrogen-type Beta molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

<NUM> of a purchased sodium-type Beta molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished sodium-type Beta molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

<NUM> of a purchased sodium-type Beta molecular sieve powder and <NUM> of a <NUM> mol/L potassium chloride aqueous solution were mixed, and the resulting mixture was heated in a <NUM> water bath for <NUM> to allow ion exchange; the ion exchange was conducted <NUM> times. The resulting product was washed with deionized water, dried, and roasted at <NUM> for <NUM> to obtain a potassium-type Beta molecular sieve.

<NUM> of the above potassium-type Beta molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, placed in a metal mold, and extruded under an extrusion pressure of <NUM> Mpa to obtain a blocky material. The blocky material was crushed and sieved to obtain <NUM> to <NUM> mesh particles. The particles were roasted at <NUM> for <NUM> to obtain a finished potassium-type Beta molecular sieve catalyst product with a molecular sieve content of <NUM>%, which was a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM and was denoted as sample <NUM>#.

<NUM> of a purchased sodium-type MOR molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, then <NUM> of a silica sol with a silica mass content of <NUM>%, <NUM> of dilute nitric acid with a mass concentration of <NUM>%, and <NUM> of lignin were added, and the resulting mixture was thoroughly mixed in a mixer and then extruded by an extruder with a circular orifice plate of <NUM> in diameter to obtain a strip material. The strip material was dried at <NUM> for <NUM> and then roasted at <NUM> for <NUM>. A roasted strip material was crushed and sieved to obtain cylindrical particles with a length of about <NUM>, which was a finished sodium-type MOR molecular sieve catalyst product with a molecular sieve content of <NUM>% and a silica content of <NUM>% (i.e., a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM) and was denoted as sample <NUM>#.

<NUM> of a potassium-type MOR molecular sieve powder with a silicon-aluminum ratio (SiO<NUM>/Al<NUM>O<NUM>) of <NUM> was weighed, then <NUM> of kaolin, <NUM> of water, <NUM> of dilute nitric acid with a mass concentration of <NUM>%, and <NUM> of lignin were added, and the resulting mixture was thoroughly mixed in a mixer and then extruded by an extruder with a circular orifice plate of <NUM> in diameter to obtain a strip material. The strip material was dried at <NUM> for <NUM> and then roasted at <NUM> for <NUM>. The roasted strip material was crushed and sieved to obtain cylindrical particles with a length of about <NUM>, which was a finished potassium-type MOR molecular sieve catalyst product with a molecular sieve content of <NUM>% and a kaolin content of <NUM>% (i.e., a catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM) and was denoted as sample <NUM>#.

Claim 1:
A method for catalytic pyrolysis of <NUM>,<NUM>-DCE to prepare VCM, comprising: introducing a <NUM>,<NUM>-DCE-containing feed gas into a reactor filled with a catalyst, and allowing the <NUM>,<NUM>-DCE-containing feed gas to contact the catalyst and be subjected to a reaction to obtain the VCM,
wherein the catalyst is at least one selected from the group consisting of the catalyst for pyrolysis of <NUM>,<NUM>-DCE to prepare VCM comprising a silicon-aluminum molecular sieve,
characterized in that the silicon-aluminum molecular sieve comprises at least one selected from the group consisting of an X-type silicon-aluminum molecular sieve, a Y-type silicon-aluminum molecular sieve, and a USY-type silicon-aluminum molecular sieve;
the silicon-aluminum molecular sieve has a silicon-aluminum ratio SiO<NUM>:Al<NUM>O<NUM> of <NUM> to <NUM>.