CN101606754A - Preparation and Application of Thermally Stabilized Manganese Oxide Molecular Sieve Catalyst for Reducing CO and NO in Cigarette Smoke - Google Patents

Abstract

Preparation and application of heat-stable manganese oxide molecular sieve catalysts for reducing CO and NO in cigarette smoke. Manganese oxide molecular sieves were used as catalytic materials for reducing CO and NO in cigarette smoke. The manganese oxide molecular sieve is doped with metal ions. The catalyst of the present invention is a thermally stable material that can reach 600-700°C at a high temperature, and has catalytic activity in a longer distance along the cigarette burning direction, which is more advantageous than the aforementioned catalyst, and the material can be used at a temperature of 200 It has high catalytic activity at about ℃. The thermal stability of the catalyst powder enables it to be cracked only at the highest temperature point in the cigarette burning zone, thereby ensuring that CO and NO can be effectively reduced in a larger area and a wider temperature range (200-600°C) in the cigarette branch section. .

Description

Preparation and Application of Thermally Stabilized Manganese Oxide Molecular Sieve Catalyst for Reducing CO and NO in Cigarette Smoke

technical field

The invention belongs to the technical field of cigarette preparation, and in particular relates to a heat-stable molecular sieve catalyst for reducing CO and NO, which are harmful substances in cigarette smoke, and a preparation method and application of the catalyst.

Background technique

Since tobacco was introduced to Europe from the Americas in the early 16th century, people have had different opinions and debates on smoking and health issues. In particular, the Royal Society of Medicine officially published a report on "Smoking and Health" in 1954, which reviewed the epidemiological Research, tobacco consumption trends, tobacco chemical components and their carcinogenicity, and the mechanism of smoking on humans and animals have clearly pointed out that smoking is harmful to human health, such as smoke CO can lead to tissue hypoxia. On May 21, 2003, the 56th World Health Assembly passed the "Framework Convention on Tobacco Control" formulated by WHO and signed by the governments of member states. It not only stipulates that governments must adopt and implement effective legislative, administrative or other measures Prevent and reduce tobacco consumption, nicotine addiction and exposure to tobacco smoke, etc., but also require restrictions on the content of tobacco products. At the same time, with the continuous improvement of people's living standards and quality of life, consumers are increasingly aware of smoking safety and environmental protection, and International Tobacco is facing unprecedented pressure. The development of low-harm cigarettes is not only an inevitable trend for the development and survival of the tobacco industry, but also one of the development strategies of the State Tobacco Monopoly Administration on reducing the harm and tar of cigarettes in the industry.

In order to reduce harmful substances in cigarette smoke, some special filter materials, including cotton, cellulose and some artificial fibers, were initially used in cigarette filters. However, these filter rods can generally only reduce the particle phase components of cigarette smoke and the condensable components in the smoke, but do not reduce the removal effect on the gas phase components of cigarette smoke such as CO, NO, and/or volatile components. Tobacco scientific and technological workers also try to use various adsorbents in cigarette filters in order to achieve physical adsorption of part of CO. As reported in US Patent No. 4193412, a filter adsorbent is a mixture of two highly dispersed metal oxides or metal hydroxides. The adsorbent can promote the adsorption of certain substances in cigarette smoke. US Patent No. 3407820 reports a cigarette filter tip containing manganese oxide substance, which can reduce the emission of NOx in cigarette smoke. However, it is clear that the adsorption effect of the adsorbent on CO adsorption is not ideal. It is well known that an adsorbent capable of adsorbing CO can also adsorb O ₂ . When the cigarette is placed in the air, _O2 is first firmly adsorbed on the adsorbent, and after the adsorption point on the adsorbent reaches adsorption saturation, CO cannot be adsorbed any more. Many of the reported adsorbents can actually adsorb CO ₂ gas, but this means that another way must be used to convert CO to CO ₂ before it can be adsorbed by the adsorbent.

Another way to reduce CO is to add an oxidant or catalyst to the filter to convert CO into CO ₂ . US Patent No. 4317460 describes a tin or tin compound catalyst for the oxidation of CO to _CO2 at low temperatures, these catalysts and other catalytic materials are supported on microporous supports. However, there are unavoidable defects in this catalyst being placed in the filter tip, such as under general smoking conditions, various by-products produced by cigarette combustion will lead to rapid deactivation of the catalyst; The CO catalytic oxidation reaction will cause the temperature of the filter to rise sharply, which is difficult for consumers to accept.

A more effective way to reduce CO in the flue gas is to convert CO into CO ₂ at the end of the cigarette. Such catalysts, such as US Patent Nos. 4,956,330, 5,050,621, 5,258,330, and 5,050,621, describe the addition of copper oxide and/or manganese dioxide to catalyze the reduction of CO in the cigarette branch section. U.S. Patent No.5258340 describes a transition metal oxide catalyst that oxidizes CO, and U.S. Patent No.4125118 states some harmful components produced by cigarette combustion and their substitutes, by adding a small amount of transition metal mixture catalytic reduction technology at the cigarette burning position . The disadvantage of this technology is that the catalyst must be supplied with a large amount of oxidant to achieve effective reduction of CO, and, so far, the heterogeneous reaction on this material is still insufficient. In addition, these materials have poor thermal stability in the high-temperature area near the burning point of cigarettes, and the heterogeneous reaction can only occur in a small area far away from the burning area, and the catalytic activity is not sufficient. U.S. Patent No. 7165553 reports a zeolite catalyst with a mesopore/microporous structure that converts CO into CO ₂ and/or converts NO into N ₂ . sex-reducing effect. In these two patents, nano-iron oxide is used, which makes the amount of catalyst added in the cigarette must be increased, which is not conducive to the cigarette process. To sum up, if a material is both a catalyst and an oxidant, it will be the first choice to catalyze the reduction of CO and NO. Obviously, none of the materials in the above patents has this function.

For more catalysts, adsorbents and/or oxidants that reduce CO and NO, see US Patent Nos. 6371127, No. 6286516, No. 6138838, No. No.4108151, No.3807416, No.3720214, etc. In addition to these existing technologies, a more advanced and effective method and material are urgently needed to reduce CO and NO in cigarette smoke.

Contents of the invention

The object of the present invention is to provide an application mode of heat-stable manganese oxide molecular sieve in cigarettes for reducing CO and NO in cigarette smoke.

Another object of the present invention is to provide a thermally stable manganese oxide molecular sieve for reducing CO and NOx in cigarette smoke and its preparation method. The obtained manganese oxide molecular sieve has good thermal stability and the cracking temperature can reach 600°C.

The purpose of the present invention is achieved in the following manner:

Manganese oxide molecular sieves are used as catalytic materials for reducing CO and NO in cigarette smoke.

The manganese oxide molecular sieve is doped with metal ions.

The doping metal ions are selected from Ag, Cu or Co.

The manganese oxide molecular sieve of the present invention is prepared into a suspension, which is selected to be added to shredded cigarette tobacco in a spraying manner, and the added amount is 10-30 mg/cigarette.

A method for preparing a manganese oxide molecular sieve, the steps comprising: preparing metal nitrate and manganese sulfate into a nitric acid solution with a pH of 0.8 to 1.2, slowly dropping it into a purple-red potassium permanganate solution, manganese sulfate and potassium permanganate The molar ratio of nitrate metal ions and sulfate manganese ions is maintained at 1.0-1.5, and the mass fraction of nitrate metal ions and sulfate manganese ions is 0.1-0.5%. It is obtained by filtering, washing with deionized water, and finally drying at 100-150°C for 4-6 hours.

The metal in the metal nitrate is selected from Ag, Cu or Co.

There are three ways for the formation of CO during the combustion process of cigarettes, thermal cracking of organic compounds, about 30%, incomplete combustion of tobacco carbides, about 36%, _CO2 reaction with tobacco carbides, about 23%, catalyst activity, temperature and oxygen concentration are decisive factors for the formation and reflection of CO and _CO2 . The emission of NO in flue gas is much smaller than that of CO, which is mainly produced by the thermal decomposition of organic mixtures, the combustion of _N2 , and the reduction reactions of various nitrogen-containing compounds. Catalyst activity, temperature and oxygen concentration are also the main factors for the reduction of NO, and the thermal stability of the catalyst may be more important to reduce the release of NO, because the catalytic oxidation reaction of NO requires a higher temperature.

There are three main areas when cigarettes are burned, namely the burning area, the cracking area and the condensation area. The burning part of the shredded tobacco is called the combustion zone, and the temperature reaches 700-950°C. The oxygen in this area is mainly for the shredded tobacco to burn to produce CO ₂ and water vapor. The oxygen concentration is extremely low, and incomplete combustion will produce CO, and the carbonized tobacco will make CO ₂ is reduced to CO. In this high-temperature region, the oxidant studied in the present invention can supply oxygen to reduce CO emission, and complete combustion can be achieved without a catalyst. The cracking zone follows the combustion zone, and the heat generated by combustion in the combustion zone is transferred to this zone through the flue gas, so that the temperature in this zone reaches 200-600°C, forming a cracking zone. Because the temperature in this area is not high enough, the main reaction is the pyrolysis reaction of tobacco, which is the area where CO is mainly produced. There is a small amount of oxygen in this area, but it is not oxidizing because the temperature is not high enough. If there is a suitable catalyst, it will be able to oxidize CO to CO ₂ . The main factor affecting this reaction is the thermal stability of the catalyst. If the catalyst begins to decompose unstable when the temperature reaches 400°C, the amount of catalyst will decrease during the CO oxidation reaction. In addition, because the reaction rate of CO oxidation to CO ₂ is exponentially related to the temperature, the amount of CO oxidation to CO ₂ is greatly reduced, and CO cannot be effectively reduced. The catalyst developed by the invention still has high thermal stability when the temperature reaches 600° C., and has a remarkable catalytic effect on the oxidation reaction of CO in this region. The third area is the condensation area, the temperature is between room temperature and 200°C, and this area is mainly the condensation/evaporation of smoke components on the shredded tobacco.

The catalyst prepared by the present invention is a thermally stable material that can reach 600-700°C at high temperature, and has catalytic activity in a longer distance along the cigarette burning direction, which is more advantageous than the above-mentioned catalyst, and the material is in It has high catalytic activity at a temperature of about 200°C. The thermal stability of the catalyst powder enables it to be cracked only at the highest temperature point in the cigarette burning zone, thereby ensuring that CO and NO can be effectively reduced in a larger area and a wider temperature range (200-600°C) in the cigarette branch section .

The difference between the catalyst powder of the present invention and the catalyst in the prior art is that the catalyst powder is both a catalyst and an oxidant. The advantage of this advantage lies in the selection and use of thermally stable materials, which are thermally stable even at high temperatures of 600-700°C, but the material is not extremely thermally stable. When the temperature is higher than 600°C, the material decomposes and releases O ₂ acts as an oxidizing agent and oxidizes CO:

2CO+O ₂ ＝2CO ₂

In addition to acting as an oxidant, the catalyst powder catalyzes the following reactions during the combustion of cigarettes to reduce CO and/or NO:

2CO+2NO＝2CO ₂ +N ₂

Compared with the catalyst for cigarettes of the prior art, the present invention also has the following advantages:

1), the thermally stable manganese oxide molecular sieve used as a catalyst for reducing CO and NO in cigarette smoke of the present invention, because the doping of metal ions has a certain promotion effect on the synthesis of molecular sieve materials, the material is more uniform and complete in appearance, The diameter of catalyst particles can be kept at about 20nm, and the length can be kept at 500-600nm;

2), the thermally stable manganese oxide molecular sieve of the present invention has a relatively narrow pore size distribution range of the material, and the molecular sieve is mainly composed of micropores with uniform pore size, and the specific surface area of the molecular sieve increases after doping with metal ions, and the specific surface area is 7000-8000m ² /g, can exceed 7500m ² /g, and the pore size distribution becomes narrow. This is because the entry of metal atoms stretches the framework of the molecular sieve, which improves the structural properties of the manganese oxide octahedral molecular sieve, improves the adsorption performance of its surface, and makes the pore size more uniform, thereby improving the reaction to CO and NO. significantly.

3), by analyzing the thermodynamics of the catalytic material in the cigarette, the thermally stable manganese oxide molecular sieve of the present invention is selected to be added in the shredded tobacco of the cigarette, which avoids the problem of the temperature rise of the filter caused by the addition in the filter, and then avoids the damage to the catalytic material. The selection and preparation process are strictly limited.

4) The suspension prepared by the heat-stable manganese oxide molecular sieve of the present invention can be evenly added to cigarette shreds by spraying, which solves the problem of non-uniform addition of traditional catalyst materials in cigarettes.

5), the heat-stable manganese oxide molecular sieve of the present invention can significantly reduce CO, NO and fused-ring aromatic hydrocarbon benzo[a]pyrene in cigarette smoke, wherein CO can be reduced by up to 29.2%, NO can be reduced by up to 24.57%, and the smoke is dense The aromatic hydrocarbon benzo[a]pyrene can be reduced by 28.67%.

Detailed ways:

The following examples are intended to illustrate the present invention rather than to further limit the present invention, and the present invention can be implemented in any mode described in the summary of the present invention.

Example 1:

Based on Cu (mass fraction: 0.5%), prepare a certain proportion of manganese sulfate and silver nitrate to make a nitric acid solution with pH=1, slowly drop into the purple-red potassium permanganate solution, manganese sulfate and permanganate The molar ratio of potassium is maintained at about 1.4. The black precipitate formed by the reaction was vigorously stirred at 100°C and refluxed for 48h, filtered, washed with deionized water, and finally dried at 110°C for 5h. After the catalyst is prepared, 10 mg/cigarette is added to the shredded tobacco of the cigarette by spraying. The smoke analysis of cigarette sticks shows that the addition of heat-stabilized manganese oxide molecular sieves to shredded tobacco can significantly reduce CO, NO and fused-ring aromatic hydrocarbon benzo[a]pyrene in cigarette smoke, among which CO is reduced It can reach 24%, the reduction of NO can reach 21.98%, and the reduction of fused-ring aromatic hydrocarbon benzo[a]pyrene in flue gas can reach 22.14%.

Example 2:

Based on Ag (mass fraction: 0.5%), prepare a certain proportion of manganese sulfate and silver nitrate to make a nitric acid solution with pH=1, slowly drop it into the purple-red potassium permanganate solution, manganese sulfate and permanganate The molar ratio of potassium is maintained at about 1.4. The black precipitate formed by the reaction was vigorously stirred at 100°C and refluxed for 48h, filtered, washed with deionized water, and finally dried at 110°C for 5h. After the catalyst is prepared, 30 mg/cigarette is added to the shredded tobacco of the cigarette by spraying. The smoke analysis of cigarette sticks shows that the addition of heat-stabilized manganese oxide molecular sieves to shredded tobacco can significantly reduce CO, NO and fused-ring aromatic hydrocarbon benzo[a]pyrene in cigarette smoke, among which CO is reduced It can reach 29.2%, NO reduction can reach 24.57%, and flue gas fused-ring aromatic hydrocarbon benzo[a]pyrene can reduce up to 28.67%.

Example 3:

Based on Ag (mass fraction: 0.1%), prepare a certain proportion of manganese sulfate and silver nitrate into a nitric acid solution with pH=1, slowly drop it into the purple-red potassium permanganate solution, manganese sulfate and permanganate The molar ratio of potassium is maintained at about 1.4. The black precipitate formed by the reaction was vigorously stirred at 100°C and refluxed for 48h, filtered, washed with deionized water, and finally dried at 110°C for 5h. After the catalyst is prepared, 30 mg/cigarette is added to the shredded tobacco of the cigarette by spraying. The smoke analysis of cigarette sticks shows that the addition of heat-stabilized manganese oxide molecular sieves to shredded tobacco can significantly reduce CO, NO and fused-ring aromatic hydrocarbon benzo[a]pyrene in cigarette smoke, among which CO is reduced It can reach 21.7%, the reduction of NO can reach 18.10%, and the reduction of fused-ring aromatic hydrocarbon benzo[a]pyrene in flue gas can reach 24.24%.

Claims (12)

1. the application process of a manganese oxide molecular sieve is characterized in that, with the catalysis material of manganese oxide molecular sieve as reduction CO in smoke of cigarettes, NO.

2. the application process of a kind of manganese oxide molecular sieve according to claim 1 is characterized in that, described manganese oxide molecular sieve is doped with metal ion.

3. the application process of a kind of manganese oxide molecular sieve according to claim 2 is characterized in that, described doped metal ion is selected from Ag, Cu or Co.

4. the application process of a kind of manganese oxide molecular sieve according to claim 2 is characterized in that, the manganese oxide molecular sieve particle diameter is at 15-25nm, and length remains on 500～600nm.

5. according to the application process of each described a kind of manganese oxide molecular sieve among the claim 1-4, it is characterized in that described manganese oxide molecular sieve is chosen in the cigarette shreds and adds.

6. the application process of a kind of manganese oxide molecular sieve according to claim 5 is characterized in that, manganese oxide molecular sieve is prepared into suspension, is added in the cigarette shreds with spraying method, and addition is that 10-30mg/ props up.

7. the preparation method of a manganese oxide molecular sieve, it is characterized in that, step comprises: it is 0.8～1.2 salpeter solution that metal nitrate and manganese sulfate are mixed with PH, slowly splash in the mauve liquor potassic permanganate, the mol ratio of manganese sulfate and potassium permanganate maintains 1.0～1.5, and the mass fraction of nitrate metal ion and sulfate manganese ion is 0.1～0.5%; The black precipitate that reaction generates is behind 90～150 ℃ of following vigorous stirring and the 40～60h that refluxes, and after filtration, the deionized water washing makes at 100～150 ℃ of down dry 4～6h at last.

8. the preparation method of a kind of manganese oxide molecular sieve according to claim 7 is characterized in that, the metal in the metal nitrate is selected from Ag, Cu or Co.

9. one kind is reduced CO in smoke of cigarettes, NO thermal stabilizing manganese oxide molecular sieve catalyst, it is characterized in that described manganese oxide molecular sieve is doped with metal ion.

10. a kind of reduction CO in smoke of cigarettes according to claim 9, NO thermal stabilizing manganese oxide molecular sieve catalyst is characterized in that described doped metal ion is selected from Ag, Cu or Co.

11. according to claim 9 or 10 described a kind of reduction CO in smoke of cigarettes, NO thermal stabilizing manganese oxide molecular sieve catalyst, it is characterized in that described manganese oxide molecular sieve particle diameter is at 15-25nm, length remains on 500～600nm.

12., it is characterized in that the specific area of described manganese oxide molecular sieve particle is 7000-8000m2/g according to claim 9 or 10 described a kind of reduction CO in smoke of cigarettes, NO thermal stabilizing manganese oxide molecular sieve catalyst.