CN105566259A - Method for producing furfural by aid of pre-hydrolysis liquid of eucalyptus - Google Patents
Method for producing furfural by aid of pre-hydrolysis liquid of eucalyptus Download PDFInfo
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- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
- C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
- C07D307/34—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
- C07D307/38—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with substituted hydrocarbon radicals attached to ring carbon atoms
- C07D307/40—Radicals substituted by oxygen atoms
- C07D307/46—Doubly bound oxygen atoms, or two oxygen atoms singly bound to the same carbon atom
- C07D307/48—Furfural
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Abstract
The invention discloses a method for producing furfural by the aid of pre-hydrolysis liquid of eucalyptus. The method includes steps of (1), washing eucalyptus chips, then steaming the eucalyptus chips by the aid of steam, squeezing, grinding and tearing the eucalyptus chips by the aid of double-screw squeezing fluffers, arranging the ground eucalyptus chips in cooking vessels, adding water into the cooking vessels and carrying out hydrolysis on the eucalyptus chips to obtain the pre-hydrolysis liquid of the eucalyptus; (2), carrying out reaction on the pre-hydrolysis liquid of the eucalyptus and sulfuric acid to obtain the furfural. The pentose extraction rate can reach the maximum value of 57.51% under preferable conditions, and the furfural yield can reach the maximum value of 71.89% under the technical conditions that the temperature is 180 DEG C, the concentration of H2SO4 is 0.25%, the gas extraction speed is 15 mL/min and the concentration of xylose is 17.8 g/L. The method has the advantages that the pre-hydrolysis liquid of the eucalyptus is reasonably utilized for preparing the furfural, the eucalyptus is subjected to screw squeezing and grinding pre-treatment, and accordingly the utilization rate of the eucalyptus in late-phase reaction can be increased; preparation processes are adjusted, so that the pre-hydrolysis liquid does not contain fiber polysaccharides such as cellobiose and cellotriose, pyrogenic reaction can be reduced, and the furfural yield can be effectively increased.
Description
Technical field
The invention belongs to furfural production technology field, relate to a kind of method utilizing Eucalyptus pre-hydrolyzed solution to produce furfural particularly.
Background technology
Eucalyptus is one of maximum quick growing species of trees of China's artificial growth amount, and is the seeds that half fibre content is very high, can reach 20% ~ 25%, be up to 35%.Its main chain is connected by D-pyrans formula xylosyl (1-4) β glycosidic bond to form, and side chain has ethanoyl and 4-O-methyl-α-D-glucopyranose aldehydic acid base etc.The low acid utilizing high-temperature water environment to produce promotes Eucalyptus hemicellulose autocatalysis hydrolysis, without the need to chemical agent, is a kind of environmentally friendly green technology.For Wooden Biomass raw material, before slurrying, carry out hemicellulose preextraction significant for realizing the refining of woods based biomass, and the process that prehydrolytic sulfate process produces dissolving pulp well meets the theory of biorefinery.Simultaneously in this production technique, utilize autocatalytic method to remove hemicellulose before slurrying and contribute to production high-quality dissolving pulp, therefore, need to be optimized research to reducing sugar extraction process in Eucalyptus pre-hydrolysis process, thus better remove hemicellulose and obtain the higher hydrolyzed solution sugar component of added value.Eucalyptus prehydrolytic sulfate process is produced the low acid utilizing high-temperature water environment to produce in dissolving pulp process and is promoted Eucalyptus hemicellulose autocatalysis hydrolysis, and the autocatalysis hydrolyzed solution of generation is a kind of important biomass resource, containing a large amount of xylan hydrolysate.Show the on the-spot investigation that the large-scale papermaking enterprise in Shandong carries out, the said firm's Eucalyptus dissolving pulp, consume Eucalyptus sheet 2000t day, produce Eucalyptus pretreatment fluid 7000t day, this pretreatment fluid is as density wastewater process discharge at present, and processing costs is very high.According to estimates, have 400 tons containing the piperylene from Eucalyptus sheet in this waste liquid, the piperylene that should extract is 200 tons, potential furfural output 100 tons, as the market value one ton 9000 yuan calculating according to current furfural, every day this Eucalyptus hydrolyzed solution furfural value up to more than 90 ten thousand yuan.If directly enter with wood chip the alkali charge that follow-up cooking section not only can increase boiling by traditional technology waste liquid, and the waste of biomass resource can be caused.
Summary of the invention
Goal of the invention: for solving the technical problem existed in prior art, the present invention proposes a kind of method utilizing Eucalyptus pre-hydrolyzed solution to produce furfural, using furfural as deep processed product, realizes the recycling of sugar in Eucalyptus prehydrolysis waste liquid.
Technique means: for realizing above-mentioned technical purpose, what the present invention proposed utilizes the method for Eucalyptus pre-hydrolyzed solution production furfural to comprise the steps:
(1) Eucalyptus sheet is washed rear steamed in water, utilize twin screw extruder to carry out crowded stone roller to Eucalyptus sheet and tear process, grind and be placed in pulp digester, add water, after being warming up to 150 ~ 180 DEG C, prehydrolysis is carried out in insulation, wherein liquid-solid ratio is 4 ~ 15: 1, and soaking time is 30 ~ 100min, obtains Eucalyptus pre-hydrolyzed solution;
(2) Eucalyptus pre-hydrolyzed solution step (1) obtained and sulfuric acid catalyst add in reactor, sulfuric acid concentration is 0.25% ~ 2%, Eucalyptus pre-hydrolyzed solution concentration is 10 ~ 60g/L, sealed reactor is also warming up to 100 DEG C under agitation, open gas phase extraction valve, the steam produced in reactor is utilized to be driven out of by the air in reactor, gas phase extraction valve valve is closed after 10 ~ 20min, continue to be warming up to 140 ~ 180 DEG C, gas phase extraction valve is opened slightly, then the rate of yield by regulating the aperture of gas phase extraction valve to control furfural gas, supplement deionized water by feed pot with pressure to kettle simultaneously, keep injection flow equal with the extraction flow of furfural, gas recovery velocity is 5 ~ 15ml/min, measure furfural content in receiving liquid every 20min and judge the process of reaction, when in 20min, furaldehyde yield increase is less than 1%, stopped reaction, close heating.
Preferably, in step (1), with steamed 20 ~ 30min after Eucalyptus sheet is washed in the water of 60 DEG C ~ 80 DEG C.
Preferably, in step (1), be warming up to 150 ~ 170 DEG C after adding water, liquid-solid ratio is 10 ~ 12: 1, and soaking time is 30 ~ 90min.
Preferably, in step (2), sulfuric acid concentration is 0.25%, and gas producting rate is 15ml/min, and Eucalyptus pre-hydrolyzed solution concentration is 30 ~ 35g/L
Beneficial effect: compared with prior art, the present invention reasonably utilizes Eucalyptus pre-hydrolyzed solution to prepare furfural, by carrying out screw extrusion to Eucalyptus and grinding pre-treatment, improve the utilization ratio of its late phase reaction, further by adjustment, preparation technology avoids the fibrous polysaccharaide such as cellobiose, procellose class in pre-hydrolyzed solution, reduce pyrogenic reaction simultaneously, effectively improve furaldehyde yield.
Accompanying drawing explanation
Fig. 1 is that liquid-solid ratio is on the impact of pentose extraction yield under temperature 180 DEG C, insulation reaction time 60min;
Fig. 2 is temperature of reaction is 160 DEG C and 170 DEG C, and under insulation reaction time 60min condition, research low liquid-solid ratio is on the impact of Eucalyptus pentose extraction yield;
Fig. 3 is the impact of gas producting rate on furaldehyde yield;
Fig. 4 is that under differing temps, sulfuric acid concentration is on the impact of furaldehyde yield, and wherein, Fig. 4 (a) is at 160 DEG C, W (sulfuric acid)/%:(1)-2%; (2)-1%; (3)-5%; Fig. 4 (b) is at 180 DEG C, W (sulfuric acid)/%:(1) 1-0.5%; (2) 2-0.25%;
Fig. 5 is the impact of temperature of reaction on furaldehyde yield, and wherein, (a) is sulfuric acid concentration one timing, and (b) is for keeping t≤t
best;
Fig. 6 is the impact of wood sugar starting point concentration on furaldehyde yield;
Fig. 7 is product infrared spectrogram;
Fig. 8 is Product samples color atlas;
Fig. 9 is the mass spectrum of product;
Figure 10 is carbonizing matter infrared spectrogram.
Embodiment
The present invention proposes a kind of method utilizing Eucalyptus pre-hydrolyzed solution to produce furfural, mainly comprise the steps:
(1) with steamed 20 ~ 30min after Eucalyptus sheet being washed in the water of 60 DEG C ~ 80 DEG C, utilize twin screw extruder to carry out crowded stone roller to Eucalyptus sheet and tear process, grind and be placed in pulp digester, add water, after being warming up to 150 ~ 180 DEG C, prehydrolysis is carried out in insulation, wherein liquid-solid ratio is 4 ~ 15: 1, and soaking time is 30 ~ 100min, obtains Eucalyptus pre-hydrolyzed solution;
(2) Eucalyptus pre-hydrolyzed solution step (1) obtained and sulfuric acid catalyst add in reactor, sulfuric acid concentration is 0.25% ~ 2%, Eucalyptus pre-hydrolyzed solution concentration is 10 ~ 60g/L, sealed reactor is also warming up to 100 DEG C under agitation, open gas phase extraction valve, the steam produced in reactor is utilized to be driven out of by the air in reactor, gas phase extraction valve valve is closed after 10 ~ 20min, continue to be warming up to 140 ~ 180 DEG C, gas phase extraction valve is opened slightly, then the rate of yield by regulating the aperture of gas phase extraction valve to control furfural gas, supplement deionized water by feed pot with pressure to kettle simultaneously, keep injection flow equal with the extraction flow of furfural, gas recovery velocity is 5 ~ 15ml/min, measure furfural content in receiving liquid every 20min and judge the process of reaction, when in 20min, furaldehyde yield increase is less than 1%, stopped reaction, close heating.
Detection method: in Eucalyptus pre-hydrolyzed solution, pentose content measuring method is as follows:
Get 1mL and be diluted to certain density pre-hydrolyzed solution in 25mL colorimetric cylinder, add distilled water to 2mL, add the Phloroglucinol developer of 10mL, shake up, put into boiling water bath to develop the color 15min, after taking out cold water cooling, measure its absorbancy at 553nm place immediately.Calculate the Xylose Content in pre-hydrolyzed solution again according to surveyed absorbancy and xylose standard curve, be then converted into the last extraction yield calculating corresponding poly-pentose according to following formula of content (hemi-cellulose content=0.88X pentose content) of poly-pentose.
High-efficiency anion is the new liquid phase chromatography that a kind of anion-exchange chromatography is combined with pulsed amperometry, detects limitation and can reach tens ug/L levels, and the high efficiency separation that can be used as monose and xylo-oligosaccharide detects
].IC ion-exchange-Pulse amperometric detection method (HPAE-PAD) measuring method is as follows:
(1) standardized solution
Wood sugar to wooden six Standard for Sugars samples utilize ultrapure water to join certain density xylo-oligosaccharide mother liquor, and get appropriate mother liquor and join different concns standardized solution, at-20 DEG C, freezen protective is for subsequent use.
(2) leacheate
0.1mol/LNaOH solution: get 50%NaOH solution 5.2mL, be diluted with water to 1L and constant volume, passes into nitrogen (41.3 ~ 55.1kPa (6 ~ 8psi)) protection immediately after mixing.
0.5mol/LNaOAc solution: take 41.0g sodium acetate, anhydrous solid; adding after appropriate ultrapure water dissolves moves in 1L volumetric flask through 0.22um cellulose acetate membrane filtration; use water constant volume after adding 50%NaOH solution 5.2mL, after mixing, pass into nitrogen (41.3 ~ 55.1kPa (6 ~ 8psi)) protection.
(3) sample solution
Make xylo-oligosaccharide content to can detectable level scope with ultrapure water dilute sample solution, centrifugal 5min under 10000r/min condition, supernatant liquor to sample bottle, proceeds to AS40 automatic sampler through 0.22um membrane filtration.
(4) chromatographic condition
With 0.1mol/LNaOH (A), 0.5mol/LNaOAc (B) for leacheate carries out gradient elution, rinse procedures: 0 ~ 40.0min, B phase concentration linearly rises to 120mmol/L from 0mmol/L; 40.1 ~ 60.0min, with 100%A rinse-system; Flow velocity: 0.3mL/min; Column temperature 30 DEG C; Sampling volume: 10uL; Detection mode: four potential pulse Amperometric Detection Coupled.
Infrared spectra (FTIR) qualitative characterization:
Analytical instrument is Nicolet company DXC20FT-IR infrared spectrometer, and receiving liquid adopts pellet technique to characterize product after being concentrated to finite concentration.
GC-MS analyzes:
Measure whole furfural receiving liquid, check water sample pH value with wide pH value test paper, regulate water sample pH≤2 with 10mol/l sulfuric acid, use the aqueous phase three times of 100ml extracted with diethyl ether acidifying respectively, be transferred to by extraction liquid in tool plug Erlenmeyer flask, add a small amount of anhydrous sodium sulfate drying, placement is spent the night.Dried ether extraction liquid rotatory evaporator is concentrated into 5-10ml, and GC-MS analysis is carried out in sampling.
Testing conditions: chromatographic column: HP5 quartz capillary column, column length 30m, column internal diameter 0.25mm; Chromatographic separation condition: column temperature 50 DEG C (keeping 2min) → 10 DEG C/min → 250 DEG C (keeping 10min); Injector temperature: 180 DEG C; Interface temperature: 230 DEG C; Carrier gas (flow): He (3.0mL/min); Split stream sampling, splitting ratio 20: 1, bypass flow 32.508mL/min, sample injection time 2min, sample size 1-3 μ l; Mass detector: EI source, electron energy: 70eV, source temperature 200, sweep limit is 35-500amu, sweep time 1s/scan.Furfural quantitative analysis method-spectrophotometry
Spectrophotometric principles is under the katalysis of concentrated hydrochloric acid, furfural (C
5h
4o
2) and aniline (C
6h
5nH
2) effect generation red compound, by spectrophotometric determination colored solutions absorbancy and then the content determining furfural in sample.Reaction principle is: the first step furfural and aniline generate flaxen Xi Fushi alkali by condensation reaction, then Xi Fushi alkali is again with second aniline molecule reaction, furfural ring is ruptured, rearranges and form hydroxyl amylene dianiline fuel, color reaction equation is as follows:
Spectrophotometry is as follows to sample furfural quantitative analysis step:
(1) furfural storing solution: get furfural (AR) carry out vapor enrichment refine, get boiling point 162 DEG C of distillates, accurately take 0.1000g ± 0.2mg in 100ml volumetric flask, with 95% alcohol dilution to scale, this furfural storing solution content is 1g/L;
(2) furfural reference liquid: accurately measure 1ml furfural storing solution in 100ml volumetric flask, with 95% alcohol dilution to scale, this furfural concentration of standard solution is 0.01g/L;
(3) Specification Curve of Increasing: measure 0 respectively, 1.0,2.0,3.0,4.0,5.0ml furfural reference liquid is in 25ml colorimetric cylinder, respectively add 1.0ml aniline and concentrated hydrochloric acid, shake up, leave standstill 10min, with distilled water diluting to graticule, use 1cm cuvette, measure its absorbancy using blank as reference at 530nm place;
(4) in receiving liquid, furfural content measures: get furfural receiving liquid 0.5ml in the brown volumetric flask of 100ml, 95% alcohol dilution is to scale, shake up, therefrom get again in 1.0ml to 25ml colorimetric cylinder, add 1.0ml aniline and concentrated hydrochloric acid, shake up, leave standstill 10min, measure its absorbancy with after distilled water diluting to scale, calculate receiving liquid furfural content.
The present invention is described in detail below by specific embodiment.Wherein, Eucalyptus sheet practical in the embodiment of the present invention is that 12 ABL is improved the breed, and take from Guangxi paper pulp company, wood chip is for subsequent use after natural air drying.
Embodiment 1 Eucalyptus prehydrolysis condition is on the impact of hemicellulose extraction effect.
Method 1: use steamed 30min after being washed in the water of 60 DEG C by Eucalyptus sheet, utilize twin screw extruder to carry out crowded stone roller to Eucalyptus sheet and tear process, grind in being placed on and carrying out in pulp digester (U.S. M/K609-2-10 type pulp digester), add water, liquid-solid ratio is 12: 1, be warming up to 170 DEG C, temperature rise rate is 2 DEG C/min, and prehydrolysis is carried out in rear insulation, wherein, soaking time is 60min, obtains Eucalyptus pre-hydrolyzed solution.
Method 2: adopt and obtain Eucalyptus pre-hydrolyzed solution with the similar step of upper method 1, unlike, Eucalyptus sheet without after washing in present water again with steamed and double helix exrusion with grind process.
Change in two kinds of methods liquid-solid ratio, hydrolysis time, the temperature of reaction thus investigate the half-and-half cellulosic extraction effect impact of each influence factor of reacting respectively.
(1) impact of liquid-solid ratio:
For method 1, investigating larger liquid-solid ratio to the impact of hemicellulose extraction effect is test in the high-temperature high-voltage reaction tank of inner liner polytetrafluoroethylene, and under temperature 180 DEG C, insulation reaction time 60min, liquid-solid ratio on the impact of pentose extraction yield as shown in Figure 1.As seen from the figure, along with the rising of liquid-solid ratio, pentose extraction yield increases gradually.Mainly because the increase of volume is equivalent to the dilution to pentose extracting solution, the pentose sugar concentration gradient between wood chip and pre-hydrolyzed solution increases, and is conducive to the carrying out of hydrolysis reaction.Liquid-solid ratio rises to when being 12: 1, and pentose extraction rate reached is to maximum value 57.51%.Continue rising liquid-solid ratio, the decrease to some degree of pentose extraction yield, but the amplitude reduced being also little, may be because caused by the less speed of reaction decline caused of raw material.
Although liquid-solid ratio raises can improve pentose extraction yield, actual scale operation liquid-solid ratio is too high can consume a large amount of water, and economic benefit is lower; And liquid-solid ratio is too high, the sugar soln concentration of extraction is excessively rare, and when carrying out follow-up deep processing process, the energy consumption of concentration can raise again.So the general liquid-solid ratio adopted is 4 ~ 6: 1 in the large production of actual factory.
Adopt M/K609-2-10 type pulp digester, Application way 2 is 160 DEG C and 170 DEG C in temperature of reaction, and under insulation reaction time 60min condition, research low liquid-solid ratio is on the impact of Eucalyptus pentose extraction yield.Result as shown in Figure 2, as seen from the figure, when liquid-solid ratio is 4 ~ 6: 1 time, the impact of change on pentose extraction yield of liquid-solid ratio is less, the rule difference shown with Fig. 1 is larger, reason may be that liquid-solid ratio scope is too narrow, also may be in this experiment Eucalyptus sheet without screw extrusion and grind process and directly carry out caused by prehydrolysis.
Under differing temps, insulation reaction time conditions, water prehydrolysis is as shown in table 1 on the impact of wood chip yield and hemi-cellulose content after prehydrolysis.
Table 1 different pretreatments condition is on the impact of wood chip yield and wood chip hemi-cellulose content
As shown in Table 2, wood chip yield and hemi-cellulose content are all with the rising of temperature, the prolongation of insulation reaction time and reducing.Find by calculating, the loss of wood chip poly-pentose is greater than pentose content in hydrolyzed solution, as temperature 160 DEG C, under 30min, 60min and 90min soaking time, hydrolyzed solution pentose extraction yield is respectively 43.03%, 48.48% and 46.47%, and the loss of wood chip poly-pentose is respectively 54.94%, 63.83% and 69.07%.Explain according to dynamic response balance, reason may be in addition partial hydrolysis but the poly-pentose of non-stripping is remaining in wood chip; Certainly, when the too high soaking time of temperature is longer, be also likely in pre-hydrolyzed solution caused by pentose generation side reaction.
The preparation of embodiment 2 furfural.
Eucalyptus wood chip kind is that 12 ABL is improved the breed, take from Guangxi paper pulp company, utilize the method 1 in embodiment 1, obtained Eucalyptus prehydrolysis waste liquid under temperature 170 DEG C, soaking time 60min and liquid-solid ratio 5: 1 condition, be stored in freezer for subsequent use, waste liquid pH value 3.11, solid substance, wood sugar and xylo-oligosaccharide content are respectively 40.45g/L, 14.11g/L and 3.43g/L.
Experimental procedure is:
(1) resistance to air loss of pretest inspection autoclave, uses after determining No leakage;
(2) Eucalyptus pre-hydrolyzed solution and sulfuric acid catalyst add in reactor, tighten kettle cover, opening power, water of condensation, and start to heat up after setting temperature of reaction, stirring velocity controls at about 90rpm;
(3) rise to after a little more than 100 DEG C until temperature, open gas phase extraction valve, utilize the steam produced in reactor to be driven out of by the air in still, avoid the side reaction such as wood sugar and furfural generation oxidizing reaction in still, valve-off after 10 ~ 20min, so that system can reach design temperature fast.
(4), after temperature reaches 140 DEG C, furfural existing a small amount of in still generates, and is opened slightly by gas phase extraction valve.Reaching the rate of yield again by regulating the aperture of gas phase extraction valve to control aldehyde gas after set(ting)value until temperature, supplementing deionized water by feed pot with pressure to kettle simultaneously, keep injection flow equal with the extraction flow of furfural;
(5) measure furfural content in receiving liquid every 20min and judge the process of reaction, when in 20min, furaldehyde yield increase is less than 1%, stopped reaction, closes heating, and after system cooling, cleaning reaction still treats that next time, test used.
(6) receiving liquid furfural content is analyzed, and calculates the yield of furfural according to following formula:
In formula: 96 is Furfural Molecule amounts, and 150 is wood sugar molecular weight.
The present embodiment has investigated the factor affecting furaldehyde yield equally.
(1) gas producting rate is on the impact of furaldehyde yield:
Under temperature 180 DEG C, sulfuric acid concentration 0.25% condition, research gas producting rate, on the impact of furaldehyde yield, has investigated three kinds of gas producting rate situations to the impact of furaldehyde yield.As shown in Figure 3, gas producting rate is on the impact of furaldehyde yield clearly as seen from the figure for result, when gas producting rate is slower (about 5ml/min), furfural in a kettle. the residence time longer, easily side reaction occurs, furaldehyde yield is lower, is 50.62%.And along with gas producting rate quickening (about 10ml/min), furfural shorter residence time in a kettle., furaldehyde yield significantly improves, and reaches 70.36%.Further raising gas producting rate, furaldehyde yield also improves.
(2) sulfuric acid concentration is on the impact of furaldehyde yield
Fig. 4 is certain gas producting rate (about 10ml/min), and at 160 and 180 DEG C, sulfuric acid concentration is on the impact of furaldehyde yield.As seen from Figure 4, sulfuric acid concentration affects the yield of furfural by affecting speed of reaction.Along with sulfuric acid concentration improves, furaldehyde yield slope of a curve raises, and namely furfural generating rate is accelerated, during as 160 DEG C, 1% sulfuric acid catalysis furaldehyde yield when reaction times 20 and 40min is 20.80% and 38.58%, and about during 110min, curve starts to become comparatively mild; And sulfuric acid concentration is when increasing to 2%, when the reaction times is increased to 40min by 20min, furaldehyde yield rises to 49.91% by 30.39%, and the time of maximum furaldehyde yield is also advanced to 90min.But after reacting completely, the total recovery of furfural reduces, and during 1% sulfuric acid concentration, furaldehyde yield is 68.89%, and during 2% sulfuric acid concentration, furaldehyde yield is then down to 64.21%, and under 180 DEG C of conditions, furaldehyde yield curve also present the same rule.During certain sulfuric acid concentration, the phenomenon that furaldehyde yield raises with sulfuric acid concentration and reduces can by foregoing furfural reaction kinetic interpretation.As temperature 180 DEG C, sulfuric acid concentration is respectively 0.25% and 0.5% time, and most optimal retention time t the best of furfural steam is respectively 97.4min and 46.32min, at experiment gas producting rate 10ml/min, sulfuric acid concentration is under 0.25% condition, furfural reaction still residence time t≤t
best, the furfural of generation is moved out of in time from reactor, and furaldehyde yield improves; When sulfuric acid concentration is 0.5%, furfural reaction still residence time t>=t
best, the furfural of generation is not shifted out in time, easily side reaction occurs and yield is reduced.
(3) temperature is on the impact of furaldehyde yield
Keep gas producting rate 10ml/min, sulfuric acid concentration is 1.0%, reaction times is 3h, temperature of reaction on the impact of furaldehyde yield as shown in Fig. 5 (a), as seen from the figure, maintain sulfuric acid concentration constant (1%), furaldehyde yield first increases rear minimizing along with the rising of temperature, and when 160 DEG C, furaldehyde yield reaches maximum value 68.89%.When temperature of reaction is lower than 160 DEG C, according to furfural reaction kinetics K2/K1=0.181 × 10
-6exp (5786/T), temperature raises, and K2/K1 reduces, and furaldehyde yield increases; When temperature is higher than 160 DEG C, although also reduce along with the rising K2/K1 of temperature, temperature is too high, sulfuric acid concentration is too high, and speed of reaction is too fast, and in certain gas producting rate situation, producing furfural can not be moved out of in time and cause yield to decline.
If keep gas producting rate 10ml/min, under condition of different temperatures, by regulating vitriol oil concentration, make residence time t≤t in furfural still
bestreaction times is greater than the wood sugar reaction complete time, then temperature of reaction on the impact of furaldehyde yield as shown in Fig. 5 (a), when can find out within the scope of temperature 140 ~ 180 DEG C, furaldehyde yield increases along with the rising of temperature, (gas producting rate 10ml/min, acid dense 0.25% 180 DEG C time, under reaction times 4h condition), furaldehyde yield reaches 71.36%.But when temperature rises to 200 DEG C, furaldehyde yield reduce, may be 200 DEG C of high-temperature liquid states under water, system C
henough large, cause caused by various side reaction aggravation.Comprehensive above discuss known, temperature of reaction affects to exist on furaldehyde yield on furaldehyde yield impact and sulfuric acid concentration and interacts.
(4) pre-hydrolyzed solution sugar concentration is on the impact of furaldehyde yield
Under gas producting rate 10ml/min, temperature 160 DEG C, sulfuric acid concentration 1.0%, reaction times 3h condition, hydrolyzed solution wood sugar starting point concentration on the impact of furaldehyde yield as shown in Figure 6.As seen from the figure, furaldehyde yield is with the rising first increases and then decreases of starting point concentration, and when to be concentrated into concentration be 34.2g/L to glycogen liquid, furaldehyde yield reaches maximum value 71.16%.And sugared concentration lower time, excess moisture in system, because furfural exists vehicle repair major dissolution equilibrium in system, furfural meltage in the liquid phase will increase, and side reaction and yield is reduced easily occurs in the liquid phase for it; When sugar concentration is higher, in experimental observation kettle, coking phenomenon is serious, and the reason that furaldehyde yield reduces may be caused by sugar soln charing aggravation.
(6) orthogonal test process optimization
Orthogonal
Studied from previous experiments, the principal element affecting furaldehyde yield is gas producting rate, temperature, sulfuric acid concentration and liquid-solid ratio.Therefore 4 factor 3 horizontal quadrature experiments of this part design major influence factors, in order to weaken the interaction of temperature and sulfuric acid concentration, adopting relative level method, the concentration of sulfuric acid being divided into basic, normal, high 3 levels, level of factor is in table 2, and the collocation of sulfuric acid concentration and temperature is in table 3.
Table 2 orthogonal test level-factor table
Table 3 sulfuric acid concentration and temperature are arranged in pairs or groups
Orthogonal experiments is analyzed
From table 4 variance analysis, each principal element on furaldehyde yield impact order is: gas producting rate > sugar concentration > temperature > sulfuric acid concentration, more excellent horizontal combination is: gas producting rate 15ml/min, sugar concentration 17.8g/L, temperature 180 DEG C, sulfuric acid concentration is intermediate concentration.
Table 4 orthogonal experiments and data analysis table
Proof test:
According to noted earlier, because sulfuric acid concentration and temperature exist interaction to furaldehyde yield, the impact of sulfuric acid concentration therefore during selective temperature, should be considered.During temperature 180 DEG C, keep gas producting rate 15ml/min, sugared concentration 17.8g/L carries out the checking of orthogonal experiment.
Known through proof test, temperature 180 DEG C, H
2when SO4 concentration 0.25%, gas producting rate 15ml/min, xylose concentration 17.8g/L, furaldehyde yield reaches maximum value 71.89%, as shown in table 5.
Table 5 confirmatory experiment result
Characterization of The Products is analyzed
(1) product FTIR analyzes
Infrared spectrum qualitative characterization is carried out to product furfuryl aldehyde solution, infrared spectrogram as shown in Figure 7,3133cm
-1and 1567cm
-1, 1463cm
-1, 1392cm
-1left and right absorption peak is furan nucleus C-H and skeleton stretching vibration; 1079cm
-1and 1210cm
-1left and right absorption peak is furan nucleus C-O-C symmetry and asymmetrical stretching vibration; 882cm
-1and 750cm
-1left and right absorption peak is furan nucleus C-H out-of-plane deformation vibration and ring flexural vibration; 1670cm
-1left and right absorption peak is the C=O stretching vibration of carbonyl compound; 2802cm
-1left and right absorption peak is the C-H stretching vibration of aldehyde radical, therefore can judge there is furfural composition in product.
(2) product GC-MS analyzes
Carry out GC-MS analysis to product furfuryl aldehyde solution, chromatogram and 4.101min and 6.235min effluent mass spectrum are as shown in Figure 8,9.
Can see clearly in fig. 8 has obvious peak when retention time is 4.101min and 6.235min, according to the concrete material of mass spectrum determination reaction mixture, as shown in table 6.Can find out that the relative content of furfural in reaction mixture is 93.32%; Main By product is 5 methyl furfural, and relative content is 5.31%; Other by product is as less in 2-acetyl furan, hydroxyanisole equal size, and total relative content is only 1.37%, and therefore the selectivity of this experimental system sulfuric acid catalyst to furfural is higher.
Main component and relative content thereof in table 6 Product samples
The initial analysis of coking phenomenon
Hydrolyzed solution High Temperature High Pressure is prepared furfural and is had a large amount of black coking material generations, and black carbonizing matter is attached in reaction kettle body, is not easy to the cleaning of equipment.The sugar carbonization caused due to inequality of being heated in reactor under High Temperature High Pressure is the major reason causing coking phenomenon, and in addition, carbonizing matter is carried out Infrared spectroscopy, infrared spectrogram as shown in Figure 10.
As seen from Figure 10 at 1602cm
-1and 1512cm
-1there is obvious characteristic peak, belong to aromatic nucleus skeletal vibration, 1456cm
-1left and right absorption peak is the C-H flexural vibration of methyl and methylene radical, in these wave-number ranges, seldom have other light belts, and the possibility having xylogen to exist in carbonizing matter sample is described.Lignin molecule structure is complicated especially, is again macromolecular compound, and available Analysis and Identification gimmick is few, and according to the literature, infrared spectra is a kind of conventional method of research xylogen.In eucalyptus dissolving pulp water pre-hydrolysis process can there is liquefaction reaction and be dissolved in hydrolyzed solution in partial lignin at high temperature under high pressure, and the structure of functional groups variation with temperature of liquefying lignin product is very little, and this may also be the reason causing coking phenomenon.
In addition, in figure at 3366cm
-1place has in molecule or the stretching vibration absorption peak of intermolecular hydrogen bonding-OH, 2939cm
-1with 1423cm
-1place is angle vibration and the stretching vibration absorption peak of C-H respectively, and above absorption peak together constitutes polyose charateristic avsorption band
[10], according to correlative study
[11]show that in hydrolyzed solution, some polyose composition also may be the reason causing coking phenomenon.
Claims (4)
1. utilize Eucalyptus pre-hydrolyzed solution to produce a method for furfural, it is characterized in that, comprise the steps:
(1) Eucalyptus sheet is washed rear steamed in water, utilize twin screw extruder to carry out crowded stone roller to Eucalyptus sheet and tear process, grind and be placed in pulp digester, add water, after being warming up to 150 ~ 180 DEG C, prehydrolysis is carried out in insulation, wherein liquid-solid ratio is 4 ~ 15: 1, and soaking time is 30 ~ 100min, obtains Eucalyptus pre-hydrolyzed solution;
(2) Eucalyptus pre-hydrolyzed solution step (1) obtained and sulfuric acid catalyst add in reactor, sulfuric acid concentration is 0.25% ~ 2%, Eucalyptus pre-hydrolyzed solution concentration is 10 ~ 60g/L, sealed reactor is also warming up to 100 DEG C under agitation, open gas phase extraction valve, the steam produced in reactor is utilized to be driven out of by the air in reactor, gas phase extraction valve valve is closed after 10 ~ 20min, continue to be warming up to 140 ~ 180 DEG C, gas phase extraction valve is opened slightly, then the rate of yield by regulating the aperture of gas phase extraction valve to control furfural gas, supplement deionized water by feed pot with pressure to kettle simultaneously, keep injection flow equal with the extraction flow of furfural, gas recovery velocity is 5 ~ 15ml/min, measure furfural content in receiving liquid every 20min and judge the process of reaction, when in 20min, furaldehyde yield increase is less than 1%, stopped reaction, close heating.
2. the method utilizing Eucalyptus pre-hydrolyzed solution to produce furfural according to claim 1, is characterized in that, in step (1), with steamed 20 ~ 30min after being washed in the water of 60 DEG C ~ 80 DEG C by Eucalyptus sheet.
3. the method utilizing Eucalyptus pre-hydrolyzed solution to produce furfural according to claim 1, it is characterized in that, in step (1), be warming up to 150 ~ 170 DEG C after adding water, liquid-solid ratio is 10 ~ 12: 1, and soaking time is 30 ~ 90min.
4. the method utilizing Eucalyptus pre-hydrolyzed solution to produce furfural according to claim 1, it is characterized in that, in step (2), sulfuric acid concentration is 0.25%, and gas producting rate is 15ml/min, and Eucalyptus pre-hydrolyzed solution concentration is 30 ~ 35g/L.
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| Title |
|---|
| 时锋: "桉木预水解废液制备糠醛的研究", 《中国林业科学研究院硕士学位论文》 * |
| 时锋: "桉木预水解废液制备糠醛的研究（摘要）", 《生物质化学工程》 * |
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| CN110372644A (en) * | 2019-08-29 | 2019-10-25 | 山东省化工研究院 | The nitration mixture method of deoxidation and equipment of biomass material in a kind of furfural production |
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