Patent Application: US-92372810-A

Abstract:
a method of producing short chain carbon compounds from effluents that are rich in lignin - model compounds . the method is characterized by controlled photocatalytic degradation of lignin model compounds so as to produce short chain carbon compounds . the present invention provides converting recalcitrant and toxic organic compounds into chemicals which are of commercial value .

Description:
with reference to fig1 , which shows generally as 10 , a photocatalytic reactor having a temperature - controlled chamber 12 , embracing a uv chamber 14 containing a monochromatic uv lamp 16 providing uv radiation at 300 nm on a quartz reaction tube 18 containing aqueous reaction liquid 20 . tube 18 holds a magnet 22 and rests on a magnetic stirrer plate 24 above a circulation fan 26 and is crimped with a teflon ® seal 28 . degradation of the substrate was monitored using a high performance liquid chromatograph ( dionex ultimate ™ 3000 , sunnyvale , calif .) which was equipped with a uv - visible photodiode array detector at a wavelength specific to the compound under examination . degradation products of photocatalysis were identified using a gc - ms ( varian ™, saturn ™ 2000 , palo alto , calif .) configured with a db - 5ms 0 . 25 mm ( id )× 30 m ( length ), 0 . 25 μm ( film thickness ) column and dbffap 0 . 25 mm ( id )× 30 m ( length ), 0 . 25 μm ( film thickness ) column under different setup ( p . j . cobert , st . louis , mo .) by comparison against a pure compounds or against national institute of standards and technology ( nist ) library spectrum . in one non - limiting example , an aqueous mixture of lignin residue model compounds , including phenol , syringol and guaiacol , was exposed to ultraviolet ( uv ) light , of wavelength , of 300 nanometers ( nm ) and irradiance , of 9 milliwatt per square meter ( mw / m 2 ), in the presence of tio 2 nanocatalysts in aqueous solution containing strong oxidizing agents , dissolved oxygen , hydrogen peroxide and ozone , which favoured the formation of hydroxyl radical , at elevated temperature of about 50 ° c . using photoreactor 10 shown in fig1 . after exposing the reaction mixture containing lignin model compounds for a sufficient period of time in the aforesaid controlled conditions , the reaction mixture was analyzed by high performance liquid chromatography ( hplc ). the results indicated the formation of variety of short chain carboxylic acids , including formic acid , acetic acid , succinic acid , fumaric acid and maleic acid . in one such sample experiment , 40 milligram / liter ( mg / l ) phenol solution was exposed to monochromatic uv radiation of 300 nm wavelength in the presence of 10 nm tio 2 particles of concentration 1 gram per liter in an aqueous solution containing 31 mg / l dissolved oxygen at a reaction temperature of 50 ° c . for 60 to 90 minutes . the analysis of the liquid extracts from the reaction mixture by a high performance liquid chromatograph ( hplc ) identified the formation of different short chain carboxylic acids , as for example is illustrated in fig2 . in particular , analysis shows the formation of at least formic acid , acetic acid , succinic acid and fumaric acid or maleic acid on comparison with standards made from pure compounds . the concentration and type of short chain carboxylic acids varied with the phenolic substrate , oxidant concentration , exposure time and reaction temperature . faster degradation of the phenolic substrates was observed with increased oxidant concentration and lower substrate concentration . a threshold tio 2 concentration and tio 2 nanocatalyst size was recorded with increasing degradation rates . in further studies , three different tio 2 particles ( alfa aesar , ward hill , mass .) with diameters in the range from 5 to 32 nm were used to photocatalytically degrade lignin model compounds ( sigma aldrich , oakville , ontario , canada ). these photocatalysts had identical physical and chemical properties and including crystal structure confirmed by x - ray diffraction . they varied only in particle size and surface area . photocatalytic experiments were performed in a photocatalytic reactor ( 25 mm id × 250 mm length ), fabricated using ge - 214 ™ clear fused quartz silica ( technical glass products inc ., painesville , ohio ). sealed reactors containing the model compound in aqueous solution and tio 2 photocatalyst were placed in a modified rayonet ™ rpr - 100 uv photocatalytic reactor 10 ( southern new england ultraviolet co ., connecticut ) of the type shown in fig1 . this custom built reactor 10 was equipped with sixteen phosphor - coated low - pressure mercury lamps 16 on the outer perimeter and a centrally located rotating inner carousel . six fused quartz reaction tubes 18 were placed on the inner rotating carousel . the lamps 16 ( 300 nm monochromatic uv light ) had an average irradiance of 9 mw / cm 2 as measured using a calibrated uv - x radiometer . to minimize variation in irradiance among the uv lamps 16 , control experiments were performed to optimize the rotational speed of the inner carousel . water used in all experiments was of ultrapure quality with 18 . 0 mohm resistivity drawn from a milli - q ( bamstead , iowa ) water purification unit . over the duration of each experiment , a fixed amount of aqueous solution was withdrawn at specific time intervals and stored in capped aluminum foil wrapped tubes for further analysis . the results showed that controlled photocatalysis of lignin model compounds in aqueous medium proceeded by cleavage of phenyl - propanoid blocks , ring opening and subsequent degradation of aromatic moieties into simple aliphatic carboxylic acid intermediates , which eventually degrade into carbon dioxide ( co 2 ). hydroquinone and catechol were identified as the major intermediates from oxidation of the aromatic ring of phenol . significant amounts of succinic acid , maleic acid , acetic acid were recorded from photocatalysis of phenol using titanium dioxide nanocatalyst irradiated with 300 nm ultraviolet radiation under acidic condition in presence of oxygen at 50 ° c . in 45 mins , as shown in fig2 . furthermore , as shown best in fig3 a and 3b , the formation profile of maleic acid and acetic acid from photocatalytic cracking of phenol ( lignin model compound ), showed that maleic acid formation precedes acetic acid formation ( fig3 ). due to non - selectivity of photocatalytic oxidation , short chain carboxylic acids are subsequently degraded into co 2 and water . although this disclosure has describes and illustrates certain preferred embodiments of the invention , it is to be understood that the invention is not restricted to these particular embodiments . rather , the invention includes all embodiments which are functional or mechanical equivalence of the specific embodiments and features that have been described and illustrated . for a detailed description of the invention , reference may be had to the appended claims . the following publications describe various process and apparatus as related to aspects of the invention heretofore described , and the disclosure of which are hereby incorporated herein by reference . 1 . alder , e . 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