CN101332429A - A kind of molded olivine supported nickel catalyst and preparation method thereof - Google Patents

Abstract

The invention relates to a shaped olivine-supported nickel catalyst and a preparation method thereof. The catalyst is composed of a shaped olivine carrier supporting nickel as the main active component and a lanthanide metal oxide auxiliary component, wherein the NiO content is 3-28wt%, and the lanthanide metal oxide additive La ₂ O ₃ or CeO ₂ is included. It is 0-5wt%. The catalyst is prepared by carrier pre-sintering and impregnation method. The olivine powder, cement binder, auxiliary agent magnesium oxide, graphite powder or carbon powder are mixed, shaped, maintained, and calcined to obtain a shaped carrier. The catalyst is obtained by impregnating the above-mentioned shaped carrier with an aqueous nickel solution or a mixed aqueous solution of nickel nitrate and lanthanum nitrate or a mixed aqueous solution of nickel nitrate and cerium nitrate. The catalyst prepared by the invention has the characteristics of good strength, high carbon conversion rate and strong carbon deposition resistance.

Description

A kind of molded olivine supported nickel catalyst and preparation method thereof

technical field

The invention belongs to the field of biomass and coal gasification, in particular to a shaped olivine-supported nickel catalyst and a preparation method thereof.

Background technique

Biomass gasification gas contains impurities and particles such as tar, H ₂ S, HCl, NH ₃ , and alkali metals. The purification of gas, especially the technology of tar removal, is a bottleneck problem that restricts the development of biomass gasification technology and the utilization of gas. one.

Catalytic cracking method to remove tar is an advanced technology that is different from physical methods such as water washing, filtration, electrostatic method, etc. It converts tar in the produced gas into low molecular gases such as carbon monoxide and hydrogen by catalytic action at a lower temperature compound. The use of tar conversion catalyst not only eliminates tar in gas production, solves the problem of tar corrosion and pollution to downstream pipelines and equipment, but also improves the efficiency of biomass gasification conversion, making biomass more efficient.

At present, commercialized natural gas and hydrocarbon steam reforming catalysts mostly use nickel as the main active component, with alumina, calcium aluminate, magnesium aluminate, etc. as the carrier, and can be used for the catalytic conversion of fixed bed tar downstream of the gasifier under certain conditions In the reactor, but most of them are not effective, because the carbon on the surface of the catalyst is serious and deactivated rapidly. The catalyst used for tar removal in the biomass gasifier requires high strength and wear resistance; it has high tar conversion activity; it is resistant to carbon deposition, high temperature resistance, and good stability; in addition, it is required to be more economical. It is a good choice to use cheap natural minerals with tar conversion activity as bed materials in the gasifier.

Olivine containing active component iron is a weakly alkaline material whose composition can be expressed as (Mg, Fe) ₂ SiO ₄ , which contains 48-50wt.% of MgO, 39-42wt.% of SiO ₂ , 8-10 wt.% Fe ₂ O ₃ . This natural ore has the characteristics of high strength, high temperature resistance and suitable density, but its catalytic effect on tar conversion is limited, and its activity for methane reforming is very low. The tar conversion activity of the catalyst can be greatly improved by loading nickel on the olivine support. French Courson et al. used olivine particles as a carrier to support nickel by impregnation to prepare a catalyst and applied for a patent [WO 01/89687]. This catalyst greatly improves the conversion activity of olivine to methane and aromatic compounds, but the specific surface area of calcined olivine reported is very low (<1m ² /g) and does not have a well-developed pore structure, thus limiting the loading of active components The amount (≤5wt%NiO), and the impregnated nickel oxide is supported on the outer surface of the carrier, and the loss of the active ingredient is very serious due to abrasion in a reactor such as a fluidized bed where the catalyst is worn seriously [C.Pfeifer, R .Rauch, H.Hofbauer, D.Swierczynki, C.Courson, A.Kiennemann.Hydrogen-rich gas production with a Ni-catalyst in a dual fluidized bed biomass gasifier.Science inthermal and chemical biomass conversion.Victoria, Canada, 30 ^th August to ^2nd September, 2004].

Contents of the invention

The purpose of the present invention is to disclose a molded olivine-supported nickel catalyst and a preparation method thereof, aiming at the shortcomings of the existing tar conversion catalysts that are easily deactivated and the catalytic reaction temperature is high, so as to solve the problem of catalyst loss caused by the low porosity and small surface area of the olivine carrier. Jolly question.

The technical scheme of the present invention is: a shaped olivine-supported nickel catalyst is composed of a shaped olivine carrier-supported nickel main active component and a lanthanide metal oxide auxiliary component, wherein the NiO content is 3-28wt%, and the lanthanum The metal oxide auxiliary agent La ₂ O ₃ or CeO ₂ is 0-5wt%. The catalyst is prepared by the carrier pre-sintering impregnation method, and its preparation steps are:

(1) Grind raw ore olivine particles into powders less than 300 meshes, add cement binder, magnesium oxide, graphite powder or carbon powder with the same particle size requirements and mix thoroughly, and add a small amount of deionized water to fully stir and form, the above The proportioning of the materials is: olivine powder is 50-95wt%, cement binder is 5-40wt%, magnesium oxide is 0-18wt%, graphite powder or carbon powder is 1-15wt%, and the cement The binder is calcium silicate cement, high alumina cement, calcium aluminate cement or calcium aluminate ferrite cement;

(2) Curing the molded carrier with steam or water for 1-15 days, and then sintering at 1000-1400° C. in an air atmosphere at high temperature for 1-4 hours to prepare a molded olivine carrier;

(3) Use a nickel nitrate aqueous solution or a mixed aqueous solution of nickel nitrate and lanthanum nitrate or a mixed aqueous solution of nickel nitrate and cerium nitrate to immerse the above-mentioned shaped carrier under stirring conditions for 1-3h, and dry at 100-120°C for 2-12h to remove moisture , and then calcined at 600-1000° C. for 2-6 hours in an air atmosphere to obtain the catalyst of the present invention.

On the one hand, the present invention utilizes the strength, refractoriness and suitable chemical composition of olivine; bed, fluidized bed, circulating fluidized bed and other biomass gasifiers, and also suitable for the fixed bed catalytic reactor downstream of the above gasification reactor, for the catalytic conversion and removal of tar in biomass gasification gas. The catalyst is also suitable for catalytic conversion and removal of tar in coal gasification gas.

The advantage of the catalyst prepared by the present invention is described in detail below by two groups of specific comparative data:

The three types of molding carriers (refer to the examples for the preparation process) are respectively marked as S _A , S _B , and S _C , and the specific surface area and water absorption rate are tested, and compared with natural olivine. The comparison results are shown in Table 1.

Table 1 specific surface area, apparent porosity and water absorption test results

carrier Specific surface area (g/m ² ) Apparent porosity(%) Water absorption (%) Raw ore olivine 1.2 5.6 3.7 S _A 3.0 34.1 16.7 S _B 3.9 29.1 13.1 S _C 7.2 40.0 20.6

It can be seen from Table 1 that the specific surface area, apparent porosity and pore volume of the molding carrier are all greatly improved compared with the raw ore olivine. The wear resistance of the shaped carrier is similar to that of calcined olivine.

The micro-fixed-bed evaluation device was used to investigate the benzene water vapor conversion activity and anti-coking performance of the self-made catalyst. The supported nickel catalysts prepared by three kinds of shaped carriers (see the examples for the preparation process) are respectively denoted as A, B, and C, and the test results compared with the olivine-supported nickel catalyst NiO/olivine under the same conditions are shown in Table 2.

Table 2 Micro fixed bed reactivity evaluation results

Catalyst Conversion rate(%) Carbon deposition rate (%) NiO/olivine twenty three 4.1 A 90 4.6 B 92 2.1 C 97 0.6

Note: Evaluation conditions: reaction pressure normal pressure, reaction temperature 800°C, benzene space velocity 0.02mol/(h·g _cat ), H ₂ O/C ratio 1.4, catalyst 1g, reaction time 90min.

The test results show that, compared with the olivine-supported nickel catalyst, the catalyst of the present invention has significantly improved carbon deposition resistance and activity stability.

The beneficial effects of the present invention are: the utilization rate of the inner surface of the carrier and the dispersion and loading capacity of the active component nickel on the surface of the carrier are improved; the catalyst prepared by the present invention has the characteristics of good strength, high carbon conversion rate and strong anti-carbon deposition ability .

Detailed ways

Below by embodiment the present invention will be further described, but do not affect protection scope of the present invention:

Example 1

(1) Pulverize raw ore olivine particles into a powder of less than 300 meshes, take 7g of olivine powder, fully mix with 3g of high alumina cement, and 0.1g of charcoal powder, add 1.2g of deionized water and fully stir to form;

(2) The molded carrier was cured for 15 days, and then sintered at a high temperature of 1200° C. for 3 hours in an air atmosphere. The resulting shaped carrier is labeled S _A ;

(3) impregnate the above-mentioned molding carrier with nickel nitrate aqueous solution for 2 hours, evaporate the water with a vacuum rotary evaporator, dry at 105° C. for 12 hours, and then bake at 800° C. for 4 hours in an air atmosphere;

The concentration of nickel nitrate aqueous solution is 1M;

The consumption of the nickel nitrate aqueous solution is based on the consumption of nickel oxide, which is 5 wt% of the calcined olivine-supported nickel catalyst.

The obtained catalyst is designated as A.

Example 2

(1) Pulverize raw ore olivine particles into a powder of less than 300 meshes, take 8g of olivine powder, fully mix with 2g of high alumina cement, and 0.3g of charcoal powder, add 1.2g of deionized water and fully stir to form;

(2) The molded carrier was cured for 15 days, and then sintered at a high temperature of 1200° C. for 3 hours in an air atmosphere. The resulting shaped carrier is labeled S _B ;

(3) Co-impregnate the above-mentioned shaped carrier with nickel nitrate and lanthanum nitrate aqueous solution for 2 hours, evaporate the water with a vacuum rotary evaporator, dry at 105°C for 12 hours, and then bake at 800°C for 4 hours in an air atmosphere;

The concentration of nickel nitrate aqueous solution is 1M;

The consumption of nickel nitrate is based on the consumption of nickel oxide, which is 8wt% after the roasting of said shaped olivine-supported nickel catalyst, and the consumption of lanthanum nitrate is based on the consumption of lanthanum oxide, which is 3wt% after the roasting of said shaped olivine-supported nickel catalyst. %.

The obtained catalyst is designated as B.

Example 3

(1) Pulverize raw ore olivine particles into a powder of less than 300 meshes, take 7.5g of olivine powder, fully mix with 2g of high-alumina cement, 0.3g of carbon powder, and 0.5g of magnesium oxide, add 1.3g of deionized water and fully stir to form;

(2) The molded carrier was cured for 15 days, and then sintered at a high temperature of 1200° C. for 3 hours in an air atmosphere. The resulting shaped carrier is marked S _C ;

(3) impregnate the above-mentioned molding carrier with nickel nitrate aqueous solution for 2 hours, evaporate the water with a vacuum rotary evaporator, dry at 105° C. for 12 hours, and then bake at 800° C. for 4 hours in an air atmosphere;

The concentration of nickel nitrate aqueous solution is 1M;

The consumption of nickel nitrate is based on the consumption of nickel oxide, which is 8wt% of the said shaped olivine-supported nickel catalyst after roasting.

The obtained catalyst is designated as C.

Claims (4)

1. A shaped olivine-supported nickel catalyst, characterized in that the catalyst is composed of a shaped olivine carrier-supported nickel main active component and a lanthanide metal oxide additive component, wherein the NiO content is 3-28wt%, The auxiliary agent containing lanthanide metal oxide is 0-5wt%. 2. A method for preparing a shaped olivine-supported nickel catalyst, characterized in that the catalyst is prepared by a carrier pre-sintering impregnation method, and the preparation steps are: (1) Grind raw ore olivine particles into powders less than 300 meshes, add cement binder, magnesium oxide, graphite powder or carbon powder with the same particle size requirements and mix thoroughly, and add a small amount of deionized water to fully stir and form, the above The ratio of the above materials is: olivine powder is 50-95wt%, cement binder is 5-40wt%, magnesium oxide is 0-18wt%, graphite powder or carbon powder is 1-15wt%; (2) Curing the molded carrier with steam or water for 1-15 days, and then sintering at 1000-1400° C. in an air atmosphere at high temperature for 1-4 hours to prepare a molded olivine carrier; (3) Use a nickel nitrate aqueous solution or a mixed aqueous solution of nickel nitrate and lanthanum nitrate or a mixed aqueous solution of nickel nitrate and cerium nitrate to immerse the above-mentioned shaped carrier under stirring conditions for 1-3h, and dry at 100-120°C for 2-12h to remove moisture , and then calcined at 600-1000°C for 2-6h in an air atmosphere to prepare the catalyst. 3. A shaped olivine-supported nickel catalyst according to claim 1, characterized in that said lanthanide metal oxide is La ₂ O ₃ or CeO ₂ . 4. The preparation method of a shaped olivine-supported nickel catalyst according to claim 2, wherein the cement binder is calcium silicate cement, high alumina cement, calcium aluminate cement or ferroaluminic acid calcium cement.