Hauv kev tsim khoom thiab lub neej, silica gel tuaj yeem siv los ua kom qhuav N2, huab cua, hydrogen, natural gas [1] thiab lwm yam. Raws li cov kua qaub thiab alkali, desiccant tuaj yeem muab faib ua: acid desiccant, alkaline desiccant thiab nruab nrab desiccant [2]. Silica gel zoo li yog lub tshuab ziab khaub ncaws tsis zoo uas zoo li qhuav NH3, HCl, SO2, thiab lwm yam. Txawm li cas los xij, los ntawm lub hauv paus ntsiab lus ntawm kev pom, silica gel yog tsim los ntawm peb-dimensional intermolecular dehydration ntawm orthosilicic acid molecules, lub cev tseem ceeb yog SiO2, thiab saum npoo yog nplua nuj nyob rau hauv hydroxyl pawg (saib daim duab 1). Yog vim li cas vim li cas silica gel tuaj yeem nqus dej yog tias cov pab pawg silicon hydroxyl nyob rau saum npoo ntawm silica gel tuaj yeem tsim cov khoom sib txuas nrog cov dej molecules, yog li nws tuaj yeem nqus dej thiab ua lub luag haujlwm kom qhuav. Cov xim hloov xim silica gel muaj cobalt ions, thiab tom qab cov dej adsorption ncav cuag saturation, cobalt ions nyob rau hauv cov xim hloov silica gel ua hydrated cobalt ions, thiaj li hais tias xiav silica gel ua liab. Tom qab cua sov lub paj yeeb silica gel ntawm 200 ℃ rau ib lub sij hawm, cov hydrogen daim ntawv cog lus ntawm silica gel thiab dej molecules so, thiab cov discolored silica gel yuav tig xiav dua, thiaj li hais tias tus qauv daim duab ntawm silicic acid thiab silica gel tuaj yeem. rov qab siv dua raws li pom hauv daim duab 1. Yog li, txij li qhov saum npoo ntawm silica gel yog nplua nuj nyob rau hauv hydroxyl pawg, qhov saum npoo ntawm silica gel kuj tseem tuaj yeem tsim cov khoom sib txuas nrog hydrogen bonds nrog NH3 thiab HCl, thiab lwm yam, thiab tej zaum yuav tsis muaj txoj hauv kev los ua raws li ib tug desiccant ntawm NH3 thiab HCl, thiab tsis muaj cov ntaub ntawv hais txog nyob rau hauv cov ntaub ntawv uas twb muaj lawm. Yog li cov txiaj ntsig tau li cas? Cov ntsiab lus no tau ua cov kev tshawb fawb hauv qab no.
FIG. 1 Daim duab duab ntawm ortho-silicic acid thiab silica gel
2 Kev sim Part
2.1 Kev Tshawb Fawb Txog Kev Tshawb Fawb Txog Kev Siv silica gel desiccant - Ammonia Ua ntej, cov discolored silica gel tau muab tso rau hauv dej distilled thiab concentrated ammonia dej feem. Discolored silica gel hloov liab hauv dej distilled; Hauv cov concentrated ammonia, cov xim-hloov silicone thawj zaug tig liab thiab maj mam tig xiav. Qhov no qhia tau hais tias silica gel tuaj yeem nqus tau NH3 lossis NH3 · H2 O hauv ammonia. Raws li pom hauv daim duab 2, cov khoom siv calcium hydroxide thiab ammonium chloride yog sib npaug sib xyaw thiab ua kom sov rau hauv lub raj ntsuas. Cov roj tshwm sim yog tshem tawm los ntawm alkali txiv qaub thiab tom qab ntawd los ntawm silica gel. Cov xim ntawm cov silica gel nyob ze ntawm kev nkag mus yuav sib dua (cov xim ntawm daim ntawv thov scope ntawm silica gel desiccant hauv daim duab 2 yog tshawb nrhiav - ammonia 73, 8th theem ntawm 2023 yog qhov zoo ib yam li cov xim ntawm silica gel soaked. nyob rau hauv cov dej ntshiab ammonia), thiab cov ntawv kuaj pH tsis muaj qhov hloov pauv. Qhov no qhia tau hais tias NH3 tsim tsis tau mus txog pH daim ntawv xeem, thiab nws tau raug adsorbed tag. Tom qab ib lub sij hawm, nres lub cua sov, tshem tawm ib feem me me ntawm silica gel pob, muab tso rau hauv lub distilled dej, ntxiv phenolphthalein rau hauv dej, cov tshuaj hloov liab, qhia tias silica gel muaj ib tug muaj zog adsorption nyhuv. NH3, tom qab cov dej distilled deattached, NH3 nkag mus rau hauv dej distilled, cov tshuaj yog alkaline. Yog li ntawd, vim hais tias cov silica gel muaj ib tug muaj zog adsorption rau NH3, silicone drying agent tsis tuaj yeem qhuav NH3.
FIG. 2 Kev Tshawb Fawb Txog Kev Ua Haujlwm ntawm kev siv silica gel desiccant - ammonia
2.2 Kev Tshawb Fawb Txog Kev Tshawb Fawb ntawm daim ntawv thov ntawm silica gel desiccant - hydrogen chloride ua ntej hlawv NaCl cov khib nyiab nrog cov nplaim hluav taws kub hnyiab kom tshem tawm cov dej ntub dej hauv cov khoom siv. Tom qab cov qauv txias, cov concentrated sulfuric acid ntxiv rau NaCl cov khib nyiab kom tam sim ntawd tsim cov npuas ntau. Cov roj uas tsim tawm tau dhau mus rau hauv lub raj kheej kheej ziab uas muaj silica gel, thiab daim ntawv ntub pH tau muab tso rau ntawm qhov kawg ntawm lub raj ziab. Lub silica gel nyob rau hauv pem hauv ntej kawg hloov lub teeb ntsuab, thiab cov ntaub ntawv pH ntub dej tsis muaj qhov txawv txav (saib daim duab 3). Qhov no qhia tau hais tias cov roj HCl generated yog tag nrho adsorbed los ntawm silica gel thiab tsis khiav mus rau saum huab cua.
Daim duab 3 Kev tshawb fawb txog kev siv silica gel desiccant - hydrogen chloride
Cov silica gel adsorbed HCl thiab tig lub teeb ntsuab tau muab tso rau hauv lub raj kuaj. Muab cov xiav silica gel tshiab tso rau hauv lub raj kuaj, ntxiv cov concentrated hydrochloric acid, silica gel kuj dhau los ua xim ntsuab, ob xim yog tib yam. Qhov no qhia tau hais tias cov roj silica gel nyob rau hauv lub raj kheej kheej ziab.
2.3 Kev tshawb fawb ntawm daim ntawv thov ntawm silica gel desiccant - sulfur dioxide Mixed concentrated sulfuric acid nrog sodium thiosulfate khoom (saib daim duab 4), NA2s2 O3 + H2 SO4 == Na2 SO4 + SO2 ↑ + S↓ + H2 O; Cov roj tsim tau dhau los ntawm lub raj ziab kom qhuav uas muaj cov silica gel discolored, cov silica gel discolored dhau los ua lub teeb xiav-ntsuab, thiab daim ntawv xiav litmus kawg ntawm daim ntawv xeem ntub dej tsis hloov pauv, qhia tias cov roj SO2 generated muaj. tau tag nrho adsorbed los ntawm silica gel pob thiab tsis tuaj yeem khiav.
FIG. 4 Kev Tshawb Fawb Txog Kev Ua Haujlwm ntawm kev siv silica gel desiccant - sulfur dioxide
Tshem tawm ib feem ntawm lub pob silica gel thiab muab tso rau hauv dej distilled. Tom qab tag nrho cov nyiaj tshuav, nqa me me dej poob rau ntawm daim ntawv xiav litmus. Daim ntawv xeem tsis hloov pauv loj, qhia tias cov dej distilled tsis txaus rau desorbed SO2 los ntawm silica gel. Siv ib feem me me ntawm lub pob silica gel thiab ua kom sov rau hauv lub raj kuaj. Muab daim ntawv ntub dej xiav litmus rau ntawm lub qhov ncauj ntawm lub raj kuaj. Daim ntawv xiav litmus hloov liab, qhia tias cua sov ua rau SO2 gas desorbed los ntawm silica gel pob, yog li ua rau daim ntawv litmus tig liab. Cov kev sim saum toj no qhia tau hais tias silica gel kuj muaj cov nyhuv adsorption ntawm SO2 lossis H2 SO3, thiab tsis tuaj yeem siv rau ziab SO2 roj.
2.4 Kev Tshawb Fawb Txog Kev Tshawb Fawb Txog Kev Siv silica gel desiccant - Carbon dioxide
Raws li pom nyob rau hauv daim duab 5, sodium bicarbonate tov dripping phenolphthalein tshwm lub teeb liab. Cov khoom siv sodium bicarbonate yog rhuab thiab cov roj sib tov tau dhau los ntawm lub raj ziab uas muaj cov silica gel spheres qhuav. Cov silica gel tsis hloov pauv loj thiab sodium bicarbonate dripping nrog phenolphthalein adsorbs HCl. Lub cobalt ion nyob rau hauv lub discolored silica gel tsim ib tug ntsuab tov nrog Cl- thiab maj mam ua tsis muaj xim, qhia tias muaj ib tug CO2 roj complex nyob rau hauv lub kawg ntawm spherical drying raj. Lub teeb-ntsuab silica gel tau muab tso rau hauv dej distilled, thiab cov silica gel discolored maj mam hloov mus rau daj, qhia tias HCl adsorbed los ntawm silica gel tau desorbed rau hauv dej. Ib qho me me ntawm cov tshuaj aqueous sab saud tau ntxiv rau cov nyiaj nitrate acidified los ntawm nitric acid los ua ib qho dawb precipitate. Ib qho me me ntawm cov tshuaj aqueous tau poob rau ntawm ntau yam ntawm pH daim ntawv xeem, thiab daim ntawv xeem hloov liab, qhia tias cov tshuaj yog acidic. Cov kev sim saum toj no qhia tau tias silica gel muaj zog adsorption rau HCl roj. HCl yog ib qho muaj zog polar molecule, thiab pawg hydroxyl nyob rau saum npoo ntawm silica gel kuj tseem muaj zog polarity, thiab ob qho tib si yuav tsim intermolecular hydrogen bonds los yog muaj zog dipole dipole sib cuam tshuam, uas ua rau muaj zog intermolecular quab yuam ntawm silica. gel thiab HCl molecules, yog li silica gel muaj zog adsorption ntawm HCl. Yog li, silicone drying agent tsis tuaj yeem siv kom qhuav HCl khiav tawm, uas yog, silica gel tsis adsorb CO2 lossis tsuas yog ib feem adsorb CO2.
FIG. 5 Kev Tshawb Fawb Txog Kev Ua Haujlwm ntawm kev siv silica gel desiccant - carbon dioxide
Txhawm rau ua pov thawj qhov adsorption ntawm silica gel rau cov pa roj carbon dioxide, cov kev sim hauv qab no txuas ntxiv mus. Lub pob silica gel hauv lub raj kheej kheej ziab tau raug tshem tawm, thiab ib feem tau muab faib ua sodium bicarbonate tov dripping phenolphthalein. Cov tshuaj sodium bicarbonate tau decolored. Qhov no qhia tau hais tias silica gel adsorbs carbon dioxide, thiab tom qab soluble hauv dej, carbon dioxide desorbs rau hauv sodium bicarbonate tov, ua sodium bicarbonate kua ploj. Qhov seem ntawm lub pob silicone yog rhuab rau hauv lub raj kuaj qhuav, thiab cov roj tshwm sim tau dhau mus rau hauv cov tshuaj sodium bicarbonate dripping nrog phenolphthalein. Tsis ntev, cov tshuaj sodium bicarbonate hloov ntawm lub teeb liab mus rau tsis muaj xim. Qhov no kuj qhia tau tias silica gel tseem muaj peev xwm adsorption rau CO2 roj. Txawm li cas los xij, lub zog adsorption ntawm silica gel ntawm CO2 tsawg dua li ntawm HCl, NH3 thiab SO2, thiab cov pa roj carbon dioxide tuaj yeem tsuas yog adsorbed ib nrab thaum lub sijhawm sim hauv daim duab 5. Yog vim li cas silica gel tuaj yeem ua rau ib feem adsorb CO2. uas silica gel thiab CO2 tsim intermolecular hydrogen bonds Si — OH… O = C. Vim hais tias lub hauv paus carbon atom ntawm CO2 yog sp hybrid, thiab silicon atom nyob rau hauv silica gel yog sp3 hybrid, linear CO2 molecule tsis koom tes zoo nrog rau saum npoo ntawm silica gel, uas ua rau lub adsorption quab yuam ntawm silica gel ntawm carbon dioxide yog kuj zoo. me me.
3.Kev sib piv ntawm cov solubility ntawm plaub gases nyob rau hauv dej thiab cov adsorption txheej xwm nyob rau saum npoo ntawm silica gel Los ntawm cov kev sim saum toj no, nws yuav pom tau hais tias silica gel muaj ib tug muaj zog adsorption muaj peev xwm rau ammonia, hydrogen chloride thiab sulfur dioxide, tab sis. ib tug me me adsorption quab yuam rau carbon dioxide (saib Table 1). Qhov no zoo ib yam li solubility ntawm plaub gases hauv dej. Qhov no tej zaum yuav yog vim cov dej molecules muaj hydroxy-OH, thiab saum npoo ntawm silica gel kuj nplua nuj nyob rau hauv hydroxyl, yog li cov solubility ntawm plaub gases nyob rau hauv dej yog heev zoo ib yam li nws adsorption ntawm silica gel. Ntawm peb lub gases ntawm ammonia gases, hydrogen chloride thiab sulfur dioxide, sulfur dioxide muaj qhov tsawg tshaj plaws solubility nyob rau hauv dej, tab sis tom qab adsorbed los ntawm silica gel, nws yog ib qho nyuaj rau desorption ntawm peb gases. Tom qab silica gel adsorbs ammonia thiab hydrogen chloride, nws tuaj yeem desorbed nrog cov dej hnyav. Tom qab cov roj sulfur dioxide yog adsorbed los ntawm silica gel, nws yog ib qho nyuaj rau desorption nrog dej, thiab yuav tsum tau rhuab mus desorption los ntawm qhov chaw ntawm silica gel. Yog li ntawd, lub adsorption ntawm plaub gases nyob rau saum npoo ntawm silica gel yuav tsum tau xam theoretically.
4 Theoretical xam ntawm kev sib cuam tshuam ntawm silica gel thiab plaub gases yog nthuav tawm nyob rau hauv lub quantumization ORCA software [4] nyob rau hauv lub moj khaum ntawm ceev functional txoj kev xav (DFT). Txoj kev DFT D/B3LYP/Def2 TZVP tau siv los xam cov kev sib cuam tshuam thiab lub zog ntawm cov roj sib txawv thiab silica gel. Txhawm rau ua kom yooj yim rau kev suav, silica gel cov khib nyiab yog sawv cev los ntawm tetrameric orthosilicic acid molecules. Cov txiaj ntsig tau suav hais tias H2 O, NH3 thiab HCl tuaj yeem tsim cov ntawv cog lus hydrogen nrog pawg hydroxyl nyob rau saum npoo ntawm silica gel (saib daim duab 6a ~ c). Lawv muaj lub zog ruaj khov rau ntawm silica gel nto (saib Daim duab 2) thiab yooj yim adsorbed ntawm silica gel nto. Txij li thaum lub zog khi ntawm NH3 thiab HCl zoo ib yam li H2 O, kev ntxuav dej tuaj yeem ua rau desorption ntawm ob lub roj molecules. Rau SO2 molecule, nws lub zog khi tsuas yog -17.47 kJ / mol, uas yog me dua li peb lub molecules saum toj no. Txawm li cas los xij, qhov kev sim tau lees paub tias SO2 roj tau yooj yim adsorbed ntawm silica gel, thiab txawm tias ntxuav tsis tuaj yeem desorbed, thiab tsuas yog cua sov tuaj yeem ua rau SO2 khiav tawm ntawm qhov chaw ntawm silica gel. Yog li ntawd, peb kwv yees tias SO2 yuav ua ke nrog H2 O ntawm qhov chaw ntawm silica gel los ua H2 SO3 feem. Daim duab 6e qhia tau hais tias H2 SO3 molecule tsim peb hydrogen bonds nrog hydroxyl thiab oxygen atoms nyob rau saum npoo ntawm silica gel tib lub sij hawm, thiab lub zog binding yog siab li -76.63 kJ / mol, uas piav qhia vim li cas SO2 adsorbed rau silica gel yog qhov nyuaj rau elude nrog dej. Tsis yog-polar CO2 muaj qhov tsis muaj zog ntawm kev sib txuas nrog silica gel, thiab tuaj yeem tsuas yog ib feem adsorbed los ntawm silica gel. Txawm hais tias lub zog khi ntawm H2 CO3 thiab silica gel kuj tau mus txog -65.65 kJ / mol, qhov hloov pauv ntawm CO2 rau H2 CO3 tsis siab, yog li tus nqi adsorption ntawm CO2 kuj raug txo. Nws tuaj yeem pom los ntawm cov ntaub ntawv saum toj no tias qhov polarity ntawm cov roj molecule tsis yog tib qho kev ntsuas los txiav txim seb nws puas tuaj yeem raug adsorbed los ntawm silica gel, thiab hydrogen daim ntawv cog lus tsim nrog silica gel nto yog lub ntsiab yog vim li cas rau nws ruaj khov adsorption.
Cov muaj pes tsawg leeg ntawm silica gel yog SiO2 ·nH2 O, thaj tsam loj ntawm silica gel thiab cov nplua nuj hydroxyl pawg nyob rau saum npoo ua silica gel tuaj yeem siv los ua lub tshuab ziab khaub ncaws tsis muaj tshuaj lom nrog kev ua haujlwm zoo, thiab siv dav hauv kev tsim khoom thiab lub neej. . Nyob rau hauv daim ntawv no, nws tau lees paub los ntawm ob yam ntawm kev sim thiab theoretical xam tias silica gel tuaj yeem nqus tau NH3, HCl, SO2, CO2 thiab lwm yam gases los ntawm kev sib xyaw hydrogen bonds, yog li silica gel tsis tuaj yeem siv rau ziab cov roj no. Cov muaj pes tsawg leeg ntawm silica gel yog SiO2 ·nH2 O, thaj tsam loj ntawm silica gel thiab cov nplua nuj hydroxyl pawg nyob rau saum npoo ua silica gel tuaj yeem siv los ua lub tshuab ziab khaub ncaws tsis muaj tshuaj lom nrog kev ua haujlwm zoo, thiab siv dav hauv kev tsim khoom thiab lub neej. . Nyob rau hauv daim ntawv no, nws tau lees paub los ntawm ob yam ntawm kev sim thiab theoretical xam tias silica gel tuaj yeem nqus tau NH3, HCl, SO2, CO2 thiab lwm yam gases los ntawm kev sib xyaw hydrogen bonds, yog li silica gel tsis tuaj yeem siv rau ziab cov roj no.
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FIG. 6 Kev sib cuam tshuam hom ntawm cov molecules sib txawv thiab silica gel nto xam los ntawm txoj kev DFT
Post lub sij hawm: Nov-14-2023
