Abstract:
A catalyst is provided for converting oxygen-containing hydrocarbon into gasoline. The catalyst is made of an ammonium-ion zeolite. The oxygen-containing hydrocarbon is dehydrated with the catalyst to be converted into gasoline. The pH value of the catalyst is changed by a heat process. The catalyst which is carbon-deposited is reactivated through oxidation. Thus, life time of the catalyst is prolonged for the conversion.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention relates to converting oxygen-containing compound into hydrocarbon; more particularly, relates to using an ammonium form zeolite as a catalyst to convert oxygen-containing compound into gasoline through dehydration while lifetime of the catalyst is prolonged for the conversion. 
       DESCRIPTION OF THE RELATED ARTS 
       [0002]    Generally, the zeolite is made by the hydrothermal crystallization through the solution of sodium aluminate, sodium silicate, sodium hydroxide, etc. then replacing their sodium ions with ammonium ions for further processing. Because the zeolites are widely used in petrochemical procedures and the structures and acidities of the zeolites are crucial to their applications. The acidity of the zeolite can be modified by adjusting the content ratios of silicon to aluminum or replacing different cation ions through ion exchange. 
         [0003]    A technology of converting methanol into gasoline uses a ZSM-5 zeolite, which has pores to allow passing of hydrocarbons having sizes smaller than C 11 hydrocarbon molecule only and has solid acid sites on its surface for transforming methanol into gasoline where hydrocarbon is obtained through dehydration. However, if the acidity of the zeolite is too strong, solid carbon may be easily deposited on its surface to deactivate catalyst; or, if the acidity of the zeolite is too weak, the reaction rate is slowed down and lifetime of the zeolite is shortened. Besides, ZSM-5 is usually transformed into a hydrogen form zeolite (H-ZSM-5), where a synthesized ammonium zeolite (NH 4 -ZSM-5) is calcined at the air environment and cation ion exchange is processed with different metal-ion solutions to obtain the zeolite with the different metal-ion form. Yet, this procedure is complex and water-intensive. Furthermore, environment pollution may be found if wasted water is not properly handled. 
         [0004]    Hence, the prior arts do not fulfill all users&#39; requests on actual use. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention relates to converting oxygen-containing compound into hydrocarbon; more particularly, relates to using an ammonium form zeolite as a catalyst to convert oxygen-containing compound into gasoline through dehydration while lifetime of the catalyst is prolonged for the conversion through a thermo-process which changes the distribution of strong-acidic and weak-acidic sites of the ammonium form zeolite. 
         [0006]    To achieve the above purpose, the present invention is a zeolite catalyst for converting oxygen-containing compound into hydrocarbon, comprising steps of: (a) filling an ammonium form zeolite to a reactor; directing air or nitrogen gas to pressure the reactor, increasing a temperature of the reactor to a certain temperature, converting the ammonium ions at weak-acid sites to form hydrogen ions to modify the acidity and activating the catalyst, and using the catalyst to dehydrate an oxygen-containing compound into a hydrocarbon; and (b) regenerating the catalyst through reactivating the catalyst by flowing an oxidizing gas to remove carbon deposits through oxidation at a high temperature. Accordingly, a novel zeolite catalyst for converting oxygen-containing compound into hydrocarbon is obtained. 
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       [0007]    The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which 
         [0008]      FIG. 1  is the view showing step (a) of the preferred embodiment according to the present invention; 
         [0009]      FIG. 2  is the view showing step (a) of the preferred embodiment; 
         [0010]      FIG. 3  is the view showing the NH 3 -TPD diagram of the ZSM-5 zeolite; and 
         [0011]      FIG. 4  is the view showing the results of converting 
         [0012]    DME into gasoline with H-ZSM-5, NH 4 -ZSM-5 and ZSM-5. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]    The following description of the preferred embodiment is provided to understand the features and the structures of the present invention. 
         [0014]    Please refer to  FIG. 1  to  FIG. 4 , which are a view showing step (a) of the preferred embodiment according to the present invention; views showing step (a) and step (b) of the preferred embodiment; a view showing an NH 3 -temperature-programmed desorption (NH 3 -TPD) diagram of a ZSM-5 zeolite; and a view showing results of converting DME into gasoline with H-ZSM-5, NH 4 -ZSM-5 and ZSM-5 prepared by our method. As shown in the figures, the present invention is a zeolite catalyst for converting oxygen-containing compound into hydrocarbon, comprising the following steps: 
         [0015]    (a) An ammonium form zeolite  2  is filled into a reactor  2 . Air or nitrogen gas  3  is directed to pressure the reactor  2  for 0˜10 bar, where the air or nitrogen gas  3  is kept at a gas hour space velocity (GHSV) of 0-20 liters of gas per gram of zeolite (l_gas/g_zeolite). Temperature of the reactor  2  is increased into a proper range. (As in the NH 3 -TPD diagram in  FIG. 3 , the first peak value  31  is for a weak-acidic desorption and the second peak value  32  is for a strong-acidic desorption. The temperature of the reactor  2  should be higher than that of the weak-acidic desorption  31  and lower than that of the strong-acidic desorption  32 .) After 0.1-48 hours (hrs), the ammonium form zeolites  1  at weak-acid sites are deammoniated to form hydrogen ions and thus a catalyst  1   a  is obtained. The catalyst  1   a  is modified with its acidity and is activated for dehydrating oxygen-containing compound into hydrocarbon. 
         [0016]    (b) When the surface of the catalyst loses activity owing to carbon deposits, the catalyst  1   a  is regenerated. After the catalyst  1   a  is put into the reactor  2 , an oxidizing gas  4  (like oxygen or air) is flown in to remove the carbon deposits of the catalyst  1   a  through oxidation at a proper temperature. When the temperature for regenerating the catalyst  1   a  is lower than a temperature of the strong-acidic desorption, the catalyst  1   a  is directly dehydrated again after regenerating the catalyst  1   a . When the temperature of the catalyst  1   a  for the oxidation is higher than the temperature of the strong-acidic desorption, the ammonium ions at strong-acid sites are decomposed and dispersed; and, after an ammonia gas  5  is introduced (at a GHSV of 0.1˜1 l_gas/g_zeolite, a concentration of 1-10 weight percents (wt %) and flown in for 0.1˜24hrs) to be absorbed by the catalyst  1   a  after regenerating the catalyst  1   a , the catalyst  1   a  is reactivated through step (a). 
         [0017]    In  FIG. 4 , results of converting DME into gasoline with H-ZSM-5, NH 4 -ZSM-5 and ZSM-5 prepared by our method are obtained (under a GHSV of dimethyl ether (DME) of 6.7 grams per gram of zeolite (g/g_zeolite), a reaction temperature of 300 Celsius degrees (° C.) and a reaction pressure of 1 bar). The pure NH 4 -ZSM-5 has a very weak acidity because all of the acidic sites are occupied by the ammonium ions and the DME cannot be dehydrated for generating a hydrocarbon. Besides, the H-ZSM-5 is too acidic and makes dehydration of the oxygen-containing compound and the following reactions become too strenuous; and, so, carbon is rapidly deposited and life of the catalyst is severely shortened. However, the present invention uses ZSM-5, which keeps ammonium ions at strong-acid sites for forming a proper acidity to prolong life of the catalyst without reducing activity of the catalyst. 
         [0018]    Hence, the present invention uses NH 3 -TPD to obtain weak-acid and strong-acid temperatures of the catalyst  1   a , where the ammonium form zeolite  1  is done through the thermo-process at a temperature higher than the temperature of the weak-acidic desorption and lower than that of the strong-acidic desorption; the ammonium ions at weak-acid sites are desorbed into ammonium molecules to change the zeolite  1  into a hydrogen-ion state; the ammonium ions at strong-acid sites are remained the same; and, thus, the ammonium form zeolite  1  obtains proper acidity for converting the oxygen-containing compound into the hydrocarbon. When the catalyst  1  loses activity on its surface owing to carbon deposits, the oxidizing gas  4  is directed in to remove the carbon deposits and regain activity through a high-temperature oxidation. If the temperature for the high-temperature oxidation is higher than that for the strong-acidic desorption, the ammonia gas  5  is directed in after the oxidation to replenish the lost ammonium ions at strong-acid sites. Thus, the ammonium form zeolite  1  is used as the catalyst  1   a  to dehydrate oxygen-containing compound for producing gasoline. 
         [0019]    To sum up, the present invention is a zeolite catalyst for converting oxygen-containing compound into hydrocarbon, where an ammonium form zeolite is used as a catalyst to dehydrate oxygen-containing compound for producing gasoline; a thermo-process is used to change distribution of strong-acidic and weak-acidic sites of the ammonium form zeolite for prolonging life of the catalyst used in converting oxygen-containing compound into hydrocarbon. 
         [0020]    The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.