Kwimveliso kunye nobomi, i-silica gel ingasetyenziselwa ukomisa i-N2, umoya, i-hydrogen, igesi yendalo [1] njalo njalo. Ngokutsho kwe-asidi kunye ne-alkali, i-desiccant inokwahlulwa ibe yi-acid desiccant, i-alkaline desiccant kunye ne-desiccant engathathi hlangothi [2]. Ijeli ye-silica ibonakala iyinto eyomileyo engathathi hlangothi ebonakala yomile i-NH3, i-HCl, i-SO2, njl. kwaye umphezulu utyebile kumaqela e-hydroxyl (jonga uMfanekiso 1). Isizathu sokuba ijeli ye-silica ikwazi ukufunxa amanzi kukuba iqela le-silicon hydroxyl kumphezulu we-silica gel linokwenza i-intermolecular hydrogen bonds kunye neemolekyuli zamanzi, ngoko ke inokubhengeza amanzi kwaye ngaloo ndlela idlale indima yokomisa. Ijeli ye-silica eguqula umbala iqulethe i-cobalt ion, kwaye emva kokuba amanzi e-adsorption afikelele kwi-saturation, i-cobalt ion kwi-silica gel eguqula umbala ibe yi-hydrated cobalt ion, ukuze i-gel silica eluhlaza ibe yipinki. Emva kokufudumeza ijeli ye-silica epinki kwi-200 ℃ kangangexesha elithile, ibhondi ye-hydrogen phakathi kwejeli ye-silica kunye neemolekyuli zamanzi iyaphuka, kwaye ijeli ye-silica eguquliweyo iya kujika ibe luhlaza kwakhona, ukuze umzobo wesakhiwo se-silicic acid kunye nejeli ye-silica ikwazi. isetyenziswe kwakhona njengoko kuboniswe kuMfanekiso 1. Ngoko, ekubeni umphezulu we-silica gel ucebile kumaqela e-hydroxyl, umphezulu we-silica gel unokwenza i-intermolecular hydrogen bond kunye ne-NH3 kunye ne-HCl, njl., kwaye kungabikho ndlela yokwenza njenge i-desiccant ye-NH3 kunye ne-HCl, kwaye akukho ngxelo efanelekileyo kwiincwadi ezikhoyo. Yaba yintoni ke imiphumo? Lo mbandela wenze olu phando lulandelayo lovavanyo.
IKHIWANE. 1 Umzobo wesakhiwo se-ortho-silicic acid kunye ne-silica gel
2 iCandelo loVavanyo
2.1 Ukuphononongwa kobubanzi bokusetyenziswa kwe-silica gel desiccant - i-Ammonia Okokuqala, i-gel ye-silica e-discolored yafakwa emanzini adibeneyo kunye ne-ammonia egxininiswe ngokulandelanayo. Ijeli ye-silica eguqulwe umbala ijika ibepinki kumanzi adityanisiweyo; Kwi-ammonia egxininisiweyo, i-silicone etshintsha umbala kuqala ijike ibe bomvu kwaye kancinci ijike luhlaza okwesibhakabhaka. Oku kubonisa ukuba ijeli ye-silica inokufunxa i-NH3 okanye i-NH3 ·H2 O kwi-ammonia. Njengoko kuboniswe kwi-Figure 2, i-calcium hydroxide eqinile kunye ne-ammonium chloride ixutywe ngokulinganayo kwaye ishushu kwi-tube yokuvavanya. Irhasi evelayo isuswa ngekalika yealkali emva koko ngejeli yesilica. Umbala wejeli ye-silica kufuphi nendlela yokungena uya uba khaphukhaphu (umbala wesicelo somda we-silica gel desiccant kuMzobo 2 uphononongwa - i-ammonia 73, isigaba se-8 sika-2023 ngokusisiseko siyafana nombala wejeli ye-silica efakwe emanzini. kumanzi ammonia agxininisiweyo), kwaye iphepha lovavanyo lwe-pH alikho utshintsho olucacileyo. Oku kubonisa ukuba i-NH3 eveliswayo ayifikanga kwiphepha lovavanyo lwe-pH, kwaye sele ibhengezwe ngokupheleleyo. Emva kwexesha elithile, yeka ukufudumeza, ukhuphe inxalenye encinci yebhola ye-silica gel, uyibeke emanzini adityanisiweyo, yongeza i-phenolphthalein emanzini, isisombululo sijika sibe bomvu, esibonisa ukuba ijeli ye-silica inefuthe elinamandla le-adsorption. I-NH3, emva kokuba amanzi adibeneyo avaliweyo, i-NH3 ingena emanzini adibeneyo, isisombululo si-alkaline. Ngoko ke, ngenxa yokuba i-silica gel ine-adsorption eyomeleleyo ye-NH3, i-agent yokomisa i-silicone ayikwazi ukomisa i-NH3.
IKHIWANE. 2 Ukuphononongwa kobubanzi bokusetyenziswa kwe-silica gel desiccant - ammonia
2.2 Ukuphononongwa kobubanzi bokusetyenziswa kwe-silica gel desiccant - i-hydrogen chloride kuqala itshisa i-NaCl solids kunye ne-alcohol flame flame ukususa amanzi amanzi kwiindawo eziqinileyo. Emva kokuba isampuli ipholile, i-asidi ye-sulfuric egxininisiweyo yongezwa kwi-NaCl solids ukuvelisa ngokukhawuleza inani elikhulu lamaqamza. I-gas eveliswayo idluliselwa kwi-tube yokumisa i-spherical ene-silica gel, kwaye iphepha lokuvavanya i-pH emanzi libekwe ekupheleni kombhobho wokumisa. Ijeli ye-silica ngaphambili ijika ibe luhlaza okhanyayo, kwaye iphepha lokuvavanya i-pH emanzi alikho utshintsho olucacileyo (jonga uMfanekiso 3). Oku kubonisa ukuba igesi yeHCl eyenziwe ibhengezwa ngokupheleleyo yijeli ye-silica kwaye ayiphumi emoyeni.
Umfanekiso wesi-3 Uphando kububanzi bokusetyenziswa kwe-silica gel desiccant - i-hydrogen chloride
Ijeli ye-silica idsorbed i-HCl kwaye yajika yaluhlaza yafakwa kwityhubhu yovavanyo. Faka ijeli entsha eluhlaza okwesibhakabhaka kwityhubhu yovavanyo, yongeza i-hydrochloric acid egxininisiweyo, ijeli ye-silica nayo iba nombala oluhlaza okhanyayo, imibala emibini iyafana. Oku kubonisa igesi yejeli yesilica kwityhubhu yokomisa engqukuva.
2.3 Ukuphononongwa komlinganiselo wesicelo se-silica gel desiccant - i-sulfur dioxide I-Mixed concentrated sulfuric acid kunye ne-sodium thiosulfate eqinile (jonga umfanekiso 4), i-NA2s2 O3 + H2 SO4 ==Na2 SO4 + SO2 ↑+S↓+H2 O; Irhasi eveliswayo igqithiswa kwityhubhu yokumisa equlethe ijeli ye-silica eguqulweyo, ijeli ye-silica eguqulweyo iba buluhlaza-luhlaza, kwaye iphepha le-litmus eluhlaza okwesibhakabhaka ekupheleni kwephepha lovavanyo elimanzi alitshintshi kakhulu, libonisa ukuba igesi ye-SO2 eyenziweyo Ithengiswe ngokupheleleyo yibhola yejeli yesilica kwaye ayinakubaleka.
IKHIWANE. 4 Ukuphononongwa kobubanzi bokusetyenziswa kwe-silica gel desiccant - i-sulfur dioxide
Susa inxalenye yebhola yejeli ye-silica kwaye uyibeke emanzini adibeneyo. Emva kokulinganisela okupheleleyo, thabatha ithontsi elincinci lamanzi kwiphepha eliluhlaza okwesibhakabhaka le-litmus. Iphepha lokuvavanya alitshintshi kakhulu, libonisa ukuba amanzi adibeneyo awanele ukuba adibanise i-SO2 kwi-silica gel. Thatha inxalenye encinci yebhola ye-silica gel kwaye uyitshise kwi-tube yokuvavanya. Beka iphepha elimanzi le-litmus emlonyeni wetyhubhu yovavanyo. Iphepha le-litmus eluhlaza lijika libe bomvu, libonisa ukuba ukufudumeza kwenza igesi ye-SO2 ikhutshwe kwibhola ye-silica gel, ngaloo ndlela yenza iphepha le-litmus libe bomvu. Olu vavanyo lungentla lubonisa ukuba ijeli ye-silica nayo ineempembelelo ezinamandla ze-adsorption kwi-SO2 okanye i-H2 SO3, kwaye ayinakusetyenziselwa ukomisa igesi ye-SO2.
2.4 Ukuphononongwa kobubanzi bokusetyenziswa kwe-silica gel desiccant - iCarbon dioxide
Njengoko kubonisiwe kuMfanekiso 5, isisombululo se-sodium bicarbonate esithontsiza i-phenolphthalein sibonakala sibomvu ngokukhanyayo. Isodium bicarbonate eqinileyo iyafudunyezwa kwaye umxube werhasi obangelwayo ugqithiswa kwityhubhu yokomisa equlethe i-silica gel spheres ezomisiweyo. Ijeli ye-silica ayitshintshi kakhulu kwaye i-sodium bicarbonate ethontsiza nephenolphthalein ibhengeza iHCl. I-cobalt ion kwijeli ye-silica ekhutshiweyo yenza isisombululo esiluhlaza kunye ne-Cl- kwaye ngokuthe ngcembe iba nemibala, ebonisa ukuba kukho i-CO2 eyinkimbinkimbi yegesi ekupheleni kwetyhubhu yokomisa i-spherical. Ijeli ye-silica ekhanyayo-eluhlaza ifakwe emanzini adityanisiweyo, kwaye ijeli ye-silica eguquguqukayo ngokuthe ngcembe itshintsha ibe tyheli, ebonisa ukuba i-HCl ebhengezwa ngejeli ye-silica iye yachithwa emanzini. Isixa esincinci sesisombululo se-aqueous esiphezulu songezwa kwisisombululo se-nitrate yesilivere e-acidified yi-nitric acid ukwenza i-precipitate emhlophe. Isixa esincinci sesisombululo esinamanzi sichithwa kuluhlu olubanzi lwephepha lokuhlola i-pH, kwaye iphepha lokuvavanya lijika libomvu, libonisa ukuba isisombululo si-acidic. Olu vavanyo lungentla lubonisa ukuba ijeli ye-silica ine-adsorption eyomeleleyo kwigesi yeHCl. I-HCl yimolekyuli ye-polar enamandla, kunye neqela le-hydroxyl kumphezulu we-silica gel nayo ine-polarity eyomeleleyo, kwaye ezi zimbini zinokwenza i-intermolecular hydrogen bond okanye zibe nentsebenziswano eqinile ye-dipole ye-dipole, ekhokelela kumandla anamandla phakathi kwe-intermolecular phakathi komphezulu we-silica. iimolekyuli ze-gel kunye ne-HCl, ngoko i-silica gel ine-adsorption enamandla ye-HCl. Ke ngoko, i-agent yokomisa i-silicone ayinakusetyenziselwa ukomisa ukubaleka kweHCl, oko kukuthi, ijeli ye-silica ayibhengezi i-CO2 okanye i-adsorb kuphela i-CO2.
IKHIWANE. 5 Ukuphononongwa kobubanzi bokusetyenziswa kwe-silica gel desiccant - carbon dioxide
Ukuze kuqinisekiswe i-adsorption ye-silica gel kwi-carbon dioxide gas, le mifuniselo elandelayo iyaqhubeka. Ibhola yejeli ye-silica kwityhubhu yokomisa engqukuva yasuswa, kwaye inxalenye yahlulahlulwe yaba sisisombululo sesodium bicarbonate ethontsiza phenolphthalein. Isisombululo se-sodium bicarbonate sathotywa umbala. Oku kubonisa ukuba ijeli ye-silica ibhengeza i-carbon dioxide, kwaye emva kokunyibilika emanzini, i-carbon dioxide desorbs kwisisombululo se-sodium bicarbonate, yenza isisombululo se-sodium bicarbonate. Inxalenye eseleyo yebhola ye-silicone ishushu kwityhubhu yokuvavanya eyomileyo, kwaye igesi ebangelwayo idluliselwa kwisisombululo se-sodium bicarbonate evuzayo ngephenolphthalein. Kungekudala, isisombululo se-sodium bicarbonate sitshintsha ukusuka ekukhanyeni okubomvu ukuya kumbala ongenambala. Oku kukwabonisa ukuba ijeli ye-silica isenawo amandla e-adsorption yegesi ye-CO2. Nangona kunjalo, i-adsorption force ye-silica gel kwi-CO2 incinci kakhulu kune-HCl, i-NH3 kunye ne-SO2, kunye ne-carbon dioxide ingabhengezwa ngokuyinxenye ngexesha lovavanyo ku-Figure 5. ukuba ijeli ye-silica kunye ne-CO2 zenza i-intermolecular hydrogen bonds Si - OH ... O =C. Ngenxa yokuba i-athomu ye-carbon ephakathi ye-CO2 yi-sp hybrid, kunye ne-athomu ye-silicon kwijeli ye-silica yi-sp3 hybrid, i-molecule ye-CO2 ehambelanayo ayisebenzisani kakuhle nomphezulu wejeli ye-silica, okukhokelela kumandla we-adsorption ye-silica gel kwi-carbon dioxide. encinci.
3.Ukuthelekisa phakathi kwe-solubility yeegesi ezine emanzini kunye nesimo se-adsorption phezu kobuso be-silica gel Ukususela kwiziphumo zovavanyo ezingentla, kunokubonwa ukuba i-silica gel inomthamo onamandla we-adsorption we-ammonia, i-hydrogen chloride kunye ne-sulfur dioxide, kodwa amandla amancinci e-adsorption ye-carbon dioxide (jonga iTheyibhile 1). Oku kufana nokunyibilika kweegesi ezine emanzini. Oku kungenxa yokuba iimolekyuli zamanzi zine-hydroxy-OH, kwaye umphezulu we-silica gel ucebile kwi-hydroxyl, ngoko ke ukunyibilika kwezi gesi ezine emanzini kufana kakhulu nokufakwa kwayo kumphezulu we-silica gel. Phakathi kweegesi ezintathu zegesi ye-ammonia, i-hydrogen chloride kunye ne-sulphur dioxide, i-sulphur dioxide ineyona nto incinci yokunyibilika emanzini, kodwa emva kokuba ibhengezwe ngejeli ye-silica, yeyona nto inzima kakhulu ukuyikhupha phakathi kweegesi ezintathu. Emva kokuba i-silica gel ibhengeza i-ammonia kunye ne-hydrogen chloride, inokuchithwa ngamanzi adibeneyo. Emva kokuba igesi yesulfure dioxide ifakwe kwijeli ye-silica, kunzima ukuyikhupha ngamanzi, kwaye kufuneka ifudunyezwe idesorption ukusuka kumphezulu wejeli ye-silica. Ngoko ke, i-adsorption yeegesi ezine kumphezulu we-silica gel kufuneka ibalwe ngokwethiyori.
I-4 Ukubala kwethiyori yokusebenzisana phakathi kwe-silica gel kunye neegesi ezine zinikezelwa kwi-quantumization ORCA software [4] phantsi kwesakhelo se-density functional theory (DFT). Indlela ye-DFT D/B3LYP/Def2 TZVP yasetyenziselwa ukubala iindlela zokusebenzisana kunye namandla phakathi kweegesi ezahlukeneyo kunye nejeli ye-silica. Ukuze kube lula ukubala, i-silica gel solids imelwe yi-tetrameric orthosilicic acid molecules. Iziphumo zokubala zibonisa ukuba i-H2 O, NH3 kunye ne-HCl zonke zinokwenza iibhondi ze-hydrogen kunye neqela le-hydroxyl kumphezulu wejeli ye-silica (jonga uMfanekiso 6a ~ c). Banamandla okubopha okuqinileyo kumphezulu we-silica gel (jonga iTheyibhile 2) kwaye zibhengezwa ngokulula kumphezulu wejeli ye-silica. Ekubeni amandla okubopha i-NH3 kunye ne-HCl afana nalawo e-H2 O, ukuhlamba amanzi kunokukhokelela ekukhutshweni kwezi molekyuli ezimbini zegesi. Kwi-molecule ye-SO2, amandla ayo okubopha kuphela -17.47 kJ / mol, encinci kakhulu kunezi molecule ezintathu zingentla. Nangona kunjalo, uvavanyo luqinisekisile ukuba igesi ye-SO2 ibhengezwa ngokulula kwijeli ye-silica, kwaye nokuhlamba akukwazi ukuyichitha, kwaye ukufudumeza kuphela okunokwenza i-SO2 ibaleke kumphezulu wejeli ye-silica. Ngoko ke, siqikelele ukuba i-SO2 inokudibanisa ne-H2 O kumphezulu we-silica gel ukwenza amaqhezu e-H2 SO3. Umzobo we-6e ubonisa ukuba i-molecule ye-H2 SO3 yenza iibhondi ezintathu ze-hydrogen kunye ne-hydroxyl kunye ne-athomu ze-oksijini kumphezulu we-silica gel ngaxeshanye, kwaye amandla okubopha aphezulu njenge-76.63 kJ / mol, echaza ukuba kutheni i-SO2 idsorbed Ijeli ye-silica kunzima ukuyiphepha emanzini. I-CO2 engeyiyo i-polar inamandla okubopha obuthathaka kunye nejeli ye-silica, kwaye inokubhengezwa kuphela ngokuyinxenye yijeli ye-silica. Nangona amandla okubopha i-H2 CO3 kunye ne-silica gel nayo yafikelela -65.65 kJ / mol, izinga lokuguqulwa kwe-CO2 kwi-H2 CO3 lalingekho phezulu, ngoko ke izinga le-adsorption ye-CO2 lancitshiswa. Inokubonwa kwidatha engentla apha ukuba i-polarity ye-molecule yegesi ayiyena kuphela umgaqo wokugweba ukuba ingaba i-adsorbed nge-silica gel, kwaye i-hydrogen bond eyenziwe nge-silica gel surface iyona nto ibangela ukuba i-adsorption yayo iqine.
Ukubunjwa kwe-silica gel yi-SiO2 · nH2 O, indawo enkulu ye-silica gel kunye neqela elicebileyo le-hydroxyl phezu komhlaba lenza i-silica gel ingasetyenziselwa njengesomisi esingenabuthi esinetyhefu kunye nokusebenza okugqwesileyo, kwaye isetyenziswa ngokubanzi kwimveliso kunye nobomi. . Kweli phepha, kuqinisekiswa kwimiba emibini yovavanyo kunye nokubala kwethiyori ukuba i-silica gel ingabhengeza i-NH3, i-HCl, i-SO2, i-CO2 kunye nezinye iigesi ngokusebenzisa iibhondi ze-hydrogen ze-intermolecular, ngoko i-silica gel ayinakusetyenziselwa ukomisa ezi gesi. Ukubunjwa kwe-silica gel yi-SiO2 · nH2 O, indawo enkulu ye-silica gel kunye neqela elicebileyo le-hydroxyl phezu komhlaba lenza i-silica gel ingasetyenziselwa njengesomisi esingenabuthi esinetyhefu kunye nokusebenza okugqwesileyo, kwaye isetyenziswa ngokubanzi kwimveliso kunye nobomi. . Kweli phepha, kuqinisekiswa kwimiba emibini yovavanyo kunye nokubala kwethiyori ukuba i-silica gel ingabhengeza i-NH3, i-HCl, i-SO2, i-CO2 kunye nezinye iigesi ngokusebenzisa iibhondi ze-hydrogen ze-intermolecular, ngoko i-silica gel ayinakusetyenziselwa ukomisa ezi gesi.
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IKHIWANE. Iindlela ze-6 zokusebenzisana phakathi kweeamolekyu ezahlukeneyo kunye ne-silica gel surface kubalwa ngendlela ye-DFT
Ixesha lokuposa: Nov-14-2023
