A kind of porous carbon materials and preparation method thereof
Technical field
The present invention relates to a kind of porous carbon materials and preparation method thereof, this porous carbon materials is prepared by the pyrolysis of biomass self-activation direct carbonization, belongs to porous carbon materials production technical field.
Background technology
For tackling the growing demand to steady current, avoiding resource exhaustion and environmental pollution simultaneously, just needing high-performance, low cost and eco-friendly energy storage and production system.Carbon source material is due to rich reserves, chemically stable and thermally-stabilised and special structure, and especially some porous carbons possess bigger serface (>1000m
2g
-1) and large pore volume (>0.5cm
3g
-1), make it there is potential researching value in energy source use association area.Current porous carbon materials has gac (AC), activated carbon fiber (ACF), carbonaceous molecular sieve (CMS) and is found in the early 1990s in last century and causes the carbon nanotube (CNTs) of research interest and win the novel material Graphene etc. of the Nobel prize.
Biomass are the large energy in third place in the world, and reserves are only second to coal and oil.And as a kind of renewable resources, exhaustless clean energy can be thought.The method preparing porous carbon materials using biomass as carbon source of current employing mainly contains physically activated and chemical activation two kinds of methods, physically activated with oxidizing gas, as O
2, CO
2, air, water vapour or their mixture cause partial carbonization to obtain large specific surface and open grain; Chemical activation is with KOH, NaOH, H
3pO
4, MgCl
2, AlCl
3or ZnCl
2as activator, reduce temperature of reaction increase carbon productive rate respectively by oxygenizement or as dewatering agent.Chemical activation is the most frequently used using KOH as activator, compare physically activated, step simplifies, and pyrolysis temperature reduces, productive rate is higher, specific surface area is larger, but due to KOH be the alkali of severe corrosive, severe corrosion equipment in production process, and environment is damaged, therefore, in view of carbon material broad prospect of application, be necessary to develop new porous carbon materials and preparation method thereof.
Chinese invention " a kind of lignin-base porous carbon materials and preparation method thereof "; application number 201310192771.0 discloses a kind of porous carbon materials utilizing bagasse to prepare; this patent is that solvent reacts 6 hours under 180 DEG C of conditions in autoclave with ethanol; naturally cooling; extracting solution is at 90 DEG C of evaporation of solvent; the sample obtained speed of 10 DEG C/min in stove rises to 220 DEG C and preheats 2 hours, then heats 2 hours under 950 DEG C of nitrogen protections with the speed of 15 DEG C/min.Figure 13 is the nitrogen adsorption-desorption curve of product, and test b ET specific surface area is 614 m
2/ g; Figure 14 is the pore size distribution of this sample, and from the result of test, distribution hole distribution of sizes is between 1.7-300nm, consistent with the description of 201310192771.0 patents, and the curve display pore distribution of pore size distribution is more at random; Meanwhile, test the storing methane character of bagasse carbonized samples, Figure 15 is the high pressure methane adsorption curve of carbonization bagasse xylogen sample.The bagasse of this patent report is the preparation method of presoma, need to extract xylogen, neat structure is not had according to document xylogen, and be difficult to degraded, prepare in the process of porous carbon, if when not adding the activator of external source in bagasse activation, be difficult to the carbon material being obtained the homogeneous distribution in aperture by spontaneous process, for the preparation of the carbon material of some special purposes, under the technique of this patent report, be not easy to reach requirement during using bagasse as carbon source.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of porous carbon materials and preparation method thereof, and the method technique is simple, without the need to auxiliary agent, on environment without impact or less impact.
For solving the problems of the technologies described above, the technical solution used in the present invention is:
A preparation method for porous carbon materials, comprises the following steps:
(1) biological material Carex meyeriana dried and be cut into segment, being dispersed in reaction boat;
(2) described reaction boat is placed in stove, then under inert gas flow flow velocity is 3-10ml/min, to lower, inert gas purge 1-10h is carried out to stove;
(3) under protection of inert gas, furnace temperature is slowly warmed up to activation temperature 650-1000 DEG C from room temperature, activates after 60-120 minute, obtain porous carbon materials;
(4) porous carbon materials obtained in step (3) is cooled to room temperature, removes impurity, be washed to neutrality.
Above-mentioned biological material Carex meyeriana comprise in Mierocrystalline cellulose and hemicellulose, xylogen one or more.
Above-mentioned rare gas element is nitrogen or argon gas.
Also containing K element in above-mentioned biological material Carex meyeriana, the content of described K element in described biological material Carex meyeriana is greater than 10mg/g.
Heat-up rate when being slowly warmed up to activation temperature described in step (3) is 2-5 DEG C/min.
In described step (4), process of cooling is carried out under protection of inert gas.
BET specific surface area under the optimal conditions of this porous carbon materials is 800-1500 meters squared per gram.
The described biomass as porous carbon material precursor should comprise Mierocrystalline cellulose, hemicellulose (in xylan, pectinose, uronic acid, semi-lactosi, glucose, rhamnosyl arbitrary combination), xylogen (pockwood fundamental mode, Syringa oblata Lindl. fundamental mode, to arbitrary combination in oxybenzene fundamental mode), and inside plants exists the potassium of certain content, be preferably the parallel vein plant of unifacial leaf.More preferably Cyperaceae sedge belongs to.
The present invention prepares in the process of porous carbon materials, and in step (3), the temperature control of carbonization process can have influence on carbonizing degree and the carbonization quality of porous carbon materials.If the carbonization temperature of biomass persursor material is represented with T, then the temperature of carbonization process is to control in T ± 50 DEG C to be advisable, if temperature is too low, carbonization cannot be carried out, and although high temperature is to a certain degree conducive to the raising of carbonizing degree, and increase porosity, if but temperature is too high, then can destroy the duct generated, affect the homogeneous distribution in material duct, also likely cause caving in of material skeleton.The heating installation of the present invention to carbonization process does not have strict restriction, as process furnace etc. conventional in prior art, and preferred tube furnace, because the temperature of tube furnace controls to complete by the thermopair of himself configuration, more for convenience.Because the carbonizing degree of porous carbon materials is relevant with its Application Areas, as, pure char-forming material can manufacture electrode materials, and partially carbonized material is by further property detection, estimate in specific duct size, the Application Areas that specific specific surface area requires has potential application.Therefore the inventive method is by controlling the temperature of carbonization process in a certain degree, controls the carbonizing degree of porous carbon materials easily, to obtain the porous carbon materials of different purposes.In step (3) during temperature programming, heat-up rate is unsuitable too fast, too fastly easily causes being heated uneven, and then cause carbonization uneven because heat up.Preferred heat-up rate is 2-5 degrees celsius/minute, can save time while guarantee is heated evenly.
The present invention prepares in the process of porous carbon materials, and carbonizing degree also can be adjusted by carbonization time, and usual carbonization time is longer, and carbonization is more complete.Preferred carbonization time is 60-120 minute, and the time is too short, and carbonizing degree is inadequate, overlong time, carbonizing degree prolongation in time and without significantly increasing, and time and raw materials cost can be caused to increase.
The structure of Carex meyeriana due to self and the feature of composition, be uniformly distributed KCl in the material, can autoactivation pore-creating in heat-processed as precursor power porous carbon materials, and all categories lignocellulose (xylogen in biomass can be utilized, Mierocrystalline cellulose, hemicellulose, table 1), obtain solid substance and can reach more than 30%, then can reach more than 70% by carbon content calculated yield in lignocellulose carbon source.
Hemicellulose kind is many, general approximate general formula C
5(H
2o)
nhemicellulose monomer in Carex meyeriana mainly contains: xylan, pectinose, uronic acid, semi-lactosi, glucose, rhamnosyl.Sugarcane and Carex meyeriana belong to monocotyledons, as monocotyledons, containing whole three kinds of xylogen in Carex meyeriana, i.e. pockwood fundamental mode (guaiacum lignin, G) Syringa oblata Lindl. type (syringa lignin, S) with to oxybenzene fundamental mode (P-hydroxyl phenyl lignin, H).
Lignocellulosic elements in table 1 Carex meyeriana and content
Compare as biomass material with bagasse, because of the principle drawn materials in ground, the growth region of plant is completely different, Carex meyeriana growth forest northeastward, grassy marshland or marsh land, and from N
2the result of adsorption-desorption curve test, carbon material prepared by Carex meyeriana is poromerics, pore distribution scope is narrower concentrates on (Fig. 4 near 1nm, the potentiality of the material that Fig. 5) pore size distribution is narrow in application are larger, and Carex meyeriana does not need special methods to control aperture as presoma, more there is actual application value, the gas storage material that poromerics is normally desirable, and the storing methane ability of porous carbon materials prepared by Carex meyeriana is in higher level (Fig. 9) in carbon material, it is comparatively ideal gas storage material.
The Carex meyeriana raw material that laboratory stage uses is undressed starting materials, tests porous carbon materials prepared by the sample eliminating volatile oil component character as carbon matrix precursor, also obtains the result similar to undressed raw material.So can be generalized to the Carex meyeriana residue having extracted essential oil or pharmaceutical cpd to prepare porous carbon materials as carbon source in actual industrial production, the problem solving waste residue utilization reduces production cost simultaneously greatly.
Technique scheme of the present invention has the following advantages compared to existing technology:
(1) method preparing porous carbon materials of the present invention; utilize biomass as presoma, temperature programming under inert gas flow protection, and keep at moderate temperatures; utilize the sylvite self-activation that presoma self contains, make material carbonization obtain target porous carbon materials.Porous carbon preparation method for material in the present invention not only technique is simple, and adds activator without the need to using;
(2) method preparing porous carbon materials of the present invention, obtained porous carbon materials has high specific surface area and thermostability, and pore size distribution has better capacitive properties and gas absorption property all in the lump.
Accompanying drawing explanation
In order to make content of the present invention more easily be clearly understood, below according to a particular embodiment of the invention and by reference to the accompanying drawings, the present invention is further detailed explanation, wherein
Fig. 1 be Carex meyeriana under air atmosphere, to heat up the thermogravimetric curve obtained with the speed of 5 degrees celsius/minute;
Fig. 2 A is the infrared spectrum of presoma Carex meyeriana in embodiment 1;
Fig. 2 B is the infrared spectrum of porous carbon materials in embodiment 1;
Fig. 3 is the low-pressure nitrogen gas adsorption-desorption isotherm figure of the sample that in embodiment 1-3, differing temps obtains;
Fig. 4 is the low-pressure nitrogen gas adsorption-desorption isotherm figure of porous carbon materials UlaC-950-HF in embodiment 1;
Fig. 5 is the graph of pore diameter distribution of porous material foundation DFT method in embodiment 1;
Fig. 6 is the X-ray diffraction spectrogram of UlaC-950 in embodiment 1;
Fig. 7 is the X-ray diffraction spectrogram of UlaC-950-HF porous carbon materials in embodiment 1;
Fig. 8 is the Raman spectrum of UlaC-950-HF in embodiment 1;
Fig. 9 is the high pressure methane gas storage curve of porous carbon materials in embodiment 1;
Figure 10 is the cyclic voltammetry curve of embodiment 1;
Figure 11 is the capacitor charge and discharge curve of embodiment 1;
Figure 12 is the alternating-current impedance curve of embodiment 1;
Figure 13 is the nitrogen adsorption desorption curve of carbonization bagasse xylogen sample;
Figure 14 is the pore size distribution of carbonization bagasse xylogen sample;
Figure 15 is the methane High Pressure Absorption curve of carbonization bagasse xylogen sample;
Figure 16 is rice husk sample TGA thermal gravimetric analysis curve;
Figure 17 is the N of direct carbonization rice husk sample
2adsorption/desorption curve;
Figure 18 is the distribution of direct carbonization rice husk sample well;
Figure 19 is the methane High Pressure Absorption curve of direct carbonization rice husk sample;
Figure 20 is the N through antihypo activated carbon rice husk sample
2adsorption/desorption curve;
Figure 21 is the pore size distribution through antihypo activated carbon rice husk sample;
Figure 22 is the methane High Pressure Absorption curve through antihypo activated carbon rice husk sample.
Embodiment
In order to set forth the technique means and effect thereof that the present invention takes further, be described in detail below in conjunction with the preferred embodiments of the present invention and accompanying drawing thereof.
embodiment 1
The present embodiment provides a kind of porous carbon materials and preparation thereof, and technical scheme is as follows:
(1) carbonization presoma biological material Carex meyeriana is fully dry and be processed into segment, be dispersed in better in container to make presoma, described biological material Carex meyeriana is preferably the parallel vein plant of unifacial leaf, there is the potassium of certain content in inside, wherein contains Mierocrystalline cellulose, xylan, semi-lactosi, pockwood fundamental mode xylogen in biological material Carex meyeriana;
(2) described biological material Carex meyeriana is heated to 950 DEG C from room temperature according to the heat-up rate of 2 DEG C/min under the protection of rare gas element; Heating installation adopts process furnace etc. conventional in prior art, preferred tube furnace;
Thermogravimetric under dry presoma nitrogen atmosphere is characterized, determines the carbonization temperature of main component lignocellulose in presoma; Result as shown in Figure 1, Fig. 1 is that Carex meyeriana is under air atmosphere, with the thermogravimetric curve of the heat-up rate of 5 DEG C/min, by finding the analysis of thermogravimetric curve, main component starts weightlessness and occurs in 220 DEG C, 530 DEG C no longer occur significantly weightless later, this and contained several lignocelluloses: the pyrolysis temperature of Mierocrystalline cellulose, hemicellulose, xylogen is consistent.
(3) the above-mentioned Carex meyeriana being processed into segment is dispersed in quartz reaction boat, as disposable embodiment, the material of described reaction boat can also be nickel, pottery, corundum, if it is high temperature resistant, not with example reaction, and with body of heater size match; Be placed in tube furnace by described reaction boat, then under nitrogen gas stream flow velocity is 3-10ml/min, carry out nitrogen purging 1-10h to tube furnace, in the present embodiment, nitrogen gas stream flow velocity is preferably 3ml/min, and purge time is preferably 2h; Take this, whole heating environment can be replaced into nitrogen environment, avoided oxygen or other gas to exist and made other reactions such as oxidation can occur in carbonization process.Again under nitrogen flowing, with the temperature rise rate of 5 DEG C/min, from room temperature to carbonization temperature.Under nitrogen gas stream protection, described material is remained on 120min under the activation temperature of 950 DEG C;
(4) by the described porous carbon materials of acquisition in step (3) under nitrogen flowing, programmed cooling is cooled to room temperature, removes the impurity based on silicon-dioxide in starting material, is washed to neutrality.
By above method, prepare porous carbon materials.
4000 cm of the present embodiment presoma
-1to 400 cm
-1infrared spectrum is shown in Fig. 2 A, 4000 cm of the porous carbon materials prepared
-1to 400 cm
-1infrared spectrum is shown in Fig. 2 B.As shown in Fig. 2 A, 2B, the porous carbon materials prepared by the present embodiment method, C-H stretching vibration peak, O-H stretching vibration, C-O-C vibration and the obvious disappearance of aromatic proton, prove that carbonization process is very thorough.
Fig. 3 is low-pressure nitrogen gas adsorption-desorption isotherm figure that under differing temps, carbonization presoma obtains material powder.The nitrogen gas adsorption-desorption isothermal curve of this material is obtained by the test of Micromeritics TriStar II 3020 adsorption instrument under 77K, 0-1atm.In figure, real point is adsorption curve point, and ignore is desorption curve point.According to adsorption-desorption curve, calcine in these differing tempss in the sample obtained, 950 DEG C of samples that can obtain maximum BET specific surface.
Fig. 4 is the low-pressure nitrogen gas adsorption-desorption isotherm figure of the porous carbon materials UlaC-950-HF material powder adopting the present embodiment method to obtain.By nitrogen adsorption-desorption isotherm, the BET specific surface area obtaining porous carbon materials material reaches 1476 meters squared per gram.
Fig. 5 is the graph of pore diameter distribution that the porous carbon materials adopting the present embodiment method to obtain calculates according to DFT method, and as shown in Figure 5, porous carbon materials pore size distribution is at about 1.1 nm.
Fig. 6 is the X-ray powder diffraction spectrogram of the sample powder of presoma at 950 DEG C after carbonization (being designated as UlaC-950).This test is undertaken by Shimadzu XRD-6000 X x ray diffractometer x, copper target, and test condition is 40.0 kilovolts, 30.0 milliamperes, sweep velocity 2.0 °/minute (2 θ).Take aluminium flake as load sample body.
Fig. 7 be presoma at 950 DEG C after carbonization again through porous carbon materials (being designated as UlaC-950-HF) X-ray powder diffraction spectrogram that HF process obtains.This test is undertaken by Shimadzu XRD-6000 X x ray diffractometer x, copper target, and test condition is 40.0 kilovolts, 30.0 milliamperes, sweep velocity 2.0 °/minute (2 θ), take aluminium flake as load sample body.
Fig. 8 is the Raman spectrum of porous carbon materials UlaC-950-HF, and this test is undertaken by Reinshaw Renishaw inVia type microscopic confocal Raman spectrometer, excitation wavelength 514.5nm, sweep limit 50-4000 cm
-1.As can be seen from the result of Raman spectrum, described porous carbon materials is unformed material.
Fig. 9 is the high pressure methane gas storage curve of the present embodiment sample porous carbon materials, and the high-pressure gas data of this material are by Shanghai University HPSA-2 type PCT device at room temperature, and 1-35 Bar test obtains.By curve, the porous carbon materials obtained is 192 milligrams/gram to the adsorptive power of methane under 35 Bar.
Figure 10 is the cyclic voltammetry curve that the difference of the present embodiment porous carbon materials UlaC-950-HF sweeps the lower test of speed.According to sweeping speed for 0.05V/s test result, the ratio capacitance value of described porous carbon materials be 113 faraday/gram.
Figure 11 is the capacitor charge and discharge curve of the porous carbon materials UlaC-950-HF of embodiment.
Figure 12 is the alternating-current impedance curve of embodiment.
embodiment 2
The present embodiment method is substantially the same manner as Example 1, and difference is only to use tube furnace temperature control at 1000 degrees Celsius in step (3).
With reference to figure 3, the nitrogen gas adsorption-desorption isothermal curve of this material is obtained by the test of Micromeritics TriStar II 3020 adsorption instrument under 77K, 0-1atm.In figure, real point is adsorption curve point, and ignore is desorption curve point.By nitrogen adsorption-desorption isotherm, the BET specific surface area obtaining sample reaches 711 meters squared per gram.
embodiment 3
The present embodiment method is substantially the same manner as Example 1, and difference is only to use tube furnace temperature control at 800 degrees Celsius in step (3).
With reference to figure 3, the nitrogen gas adsorption-desorption isothermal curve of this material is obtained by the test of Micromeritics TriStar II 3020 adsorption instrument under 77K, 0-1atm.In figure, real point is adsorption curve point, and ignore is desorption curve point.By nitrogen adsorption-desorption isotherm, the BET specific surface area obtaining sample reaches 464 meters squared per gram.
embodiment 4
The present embodiment method is substantially the same manner as Example 1, and difference is only that the heat-up rate that step (3) Program heats up is 2 degrees celsius/minute, uses tube furnace temperature control at 800 degrees Celsius in step (3).
embodiment 5
The present embodiment method is substantially the same manner as Example 1, and difference is only that the heat-up rate that step (3) Program heats up is 2 degrees celsius/minute, uses tube furnace temperature control at 650 degrees Celsius in step (3).
embodiment 6
The present embodiment method is substantially the same manner as Example 1, and difference is only that the heat-up rate that step (3) Program heats up is 2 degrees celsius/minute, and carbonization time 60 minutes, rare gas element used is argon gas.
comparative example
In order to better the present invention is described, have chosen traditional biomass rice husk as a comparison.Figure 16 is the TGA thermal gravimetric analysis curve of rice husk, and according to test result, rice husk is high ashy substance, and its ash content composition is mainly silicon-dioxide, consistent with the description about rice husk that current each seminar has delivered.First, under the condition identical with carbonization Carex meyeriana, carried out direct carbonization process to rice husk, and done low pressure, High Pressure Absorption is tested, as Figure 17, Figure 18, Figure 19.The BET specific surface of sample is 168m
2/ g, is less than the result of Carex meyeriana sample; From the situation of pore distribution, the scope of pore distribution is than in bagasse sample sets, all well is within the scope of 100nm, but totally not as Carex meyeriana sample, micropore, mesoporous, large porose area have distribution, from the situation of hysteresis loop and the peak heights of distribution curve, should mesoporous material be belonged to, but due to the dispersion of pore distribution, limit the application in some fields, to being 8.8mg/g(0.87wt% under the adsorptive power 35bar of methane), adsorptive power is more weak.
The another document delivered according to patent CN 1203887 and this patent inventor, uses K
2cO
3as activator, activator and sample quality are than w/w=3:1, and the sample of preparation carries out gas adsorption test (Figure 20, Figure 21, Figure 22), N
2adsorption/desorption test b ET specific surface area is 1572 m
2/ g, consistent with the result of patent and document description, the sample well distribution of sizes through overactivation is narrow, concentrates near 1.2nm, and under 35bar, methane adsorption can reach 156mg/g(13.5wt%), consistent with more than 150 results reported in document.According to the theory that Kimberly proposed in 1992, because methane is of a size of 0.414nm, the hole dimension of absorbent charcoal material, in the distribution of 0.8-1.2nm, is equivalent to 2-3 molecular size, methane molecule well can be fixed in hole, be applicable to storing methane gas.This explains the methane storing ability of the Carex meyeriana sample of carbonization, and the methane storing ability of the rice husk of activation.In view of the methane adsorption ability of carbonization Carex meyeriana sample is higher than the rice husk based activated carbon after activation, and reactivation process adds operation, preparation cost and aftertreatment cost and the corrosion of equipment can be brought, financial loss and increase potential safety hazard, the technique using Carex meyeriana direct carbonization is the more optimal technique preparing methane adsorbent, has more actual application value aborning.
Obviously, above-described embodiment is only for clearly example being described, and the restriction not to embodiment.For those of ordinary skill in the field, can also make other changes in different forms on the basis of the above description.Here exhaustive without the need to also giving all embodiments.And thus the apparent change of extending out or variation be still among the protection domain of the invention.