Document JvE88NXQvG95Xw01M0zGDn1EO

Jamury'tS, 'MV' / v1 . &*topM Chemical news \ _4 'w;** ---- r^. ncabl* titenL---- - - - - :Since the chlorination Vinyl cUwlde ls pT>tfiy fl most^nportant example ofd between acetylene and ethylene chemistry.,,. Dunlop bas bas joined % EH$. field,having prodaced &n ethylene prop3ft_,, ,, . Monsanto's ugnomt process Bsesjsatural gas as feedstock Wm1: - 3#y .; VT^dffmctioB titjosr of high temperature. that It - Ounne yvoanriant of ttiejitocett solves these [jmer^ilflt-5tB0e^ntv^.fclWtfti|[raml the '* miMu -eriAicne fotoa tetwfrecirBiiatingstream is Stored at prassare In spheres of 2000 ton cap^. :JneaTOTytraim ^j^pUcc and in chthe^acrion of the l.CJL feijowsfeips has been increased from 900 to 1 WO per year. ^-g^ickly dissipated." v^>-' t" - -->i(--r ''" " .............................. ` l' -^"Sfcsa* fcv Knesset.- that a.jppre dhyiefie-stresto nysw^ Vinyl Chloride's strictly necessary--nor indeed even pir^ tkitlariy -advantageous. An unsplit etbane-etfiytene - stream can be used ; Feedstocks r which reduces the cost of the ethylene - feed, " ,. ............. r;'fbe'decotnposition of dkbleroetene to give vinyl chloride arid HCilsdsdsJly carried out in the tubes of a tfired W1NYL chloride is probably the most tion Final purification to remove furnace at sbotet '300*C. important example of direct com petition between acetylene anJ ethylene chemistry. The acetylene route bas die advantage of simplicity and. therefore, of low operating cost. 7 he ethylene aldehydes and ethyltdene dichloride is bv low temperature tracuonation. Pure vinyl chloride is then stored under nitro gen in stainless steel unks. . The route via ethylene is more ' route has -the advantage, of a cheaper complex tred involves .two .stages---the feedstock. - All that is involved: ia the .chlorination rof-ethylene to give di- acetylene route is the simple addition of ' chloroethane and the thermal decom hydrogen chloride acrossjthe - triple position of tire dichlororthane to give, bond. '. / - vinyl chloride.and HCl., ' CHeCH+HC1-wCH,=CHCI The mechanism of the chlorination of ethylene to give dichloroethane has bad Dry hydrogen chloride is passed lo a a good deal of study." But in 'practice' , vapour blender to^be .mixed m equi the important thing h tq prevent the Recovered Front Steam The vapour from the furnace con* taming vinyl chloride, - HCl and unconverted dichloroethane is quenched immediately downstream of the. furaace m ordehto freeze- the.equilibrium, Hat vinyl- chloride .and. dtdttotptohawytj* theits recovered from the-., quenched stream . either .by_ absorption..-or . by distillation at a presuresuffident.to jjiye liquid HCl reflux. The vinyl chloride is recovered.from the dichloroethane-by udimstimllautioi/niii. *Ptaotrt VoIf ttfhifec UdiiWchmloUrfo^eftUthIaIInHwe k. recycled as. quench-and the rest- molar .proportions *with dry acetylene. substitutive chlorntorioa of tfichibro- w^dchjt*tbe uoamv^rreq dicbloroethilie Since at this stage the presence of chlorine will cause an explosion, there is a_device, which on detecting any sudden rise in . temperature, automalically diverts the hydrogen chloride stream to the atmosphere. From the vapour blender the gas mix ture is lel into a mulutubular reactor, each tube bang packed with a mercuric chloride catalyst on an activated carbon support. The reaction has to be initi ated by heal, but once started, cooling ethane to give tri- and tetra-chloroethane. --n sent 'to ciean' up columns before -being returned to. the furnace. . j~r - -In the ethylene-based procepvia cbchloroethanc, half the chlorine U con verted to by-product HCl--a doubtful commodity since the acid inevitably contains traces of chiminated hydrocar bons which makes its sale as food grade acid difficult without dean-up opera tions. ._ Comparison Of Coats bat to be applied to control the 'highly In comparing the cost of the acetylene exothermic addition at around and ethylene routes, i: is reasonable to 90-100'C assume that the user of acetylene will To avoid the presence of moisture w the hydrogen cMondc rigorous drying have to manufacture HCl from chlorine. On the other hand, the user of the ethy procedures are earned oul during ail lene route may or may not be able to stage* m m, preparation. High purity hydrogen--which can be prepared on sire by the partial oxidation of a light hydrocarbon--is dried firstly by cording to freeze out most of the moisture and then by passing through an alumina packed tower The tin hydrogen is burned with chlorine under such con ditions that all the chlorine i-. convened to bydrogen chloride In addition to the main reactions, side reactions producing acetaldehyde and ethyltdene dtehionde also proceed Caret A tomgKtt cKr prien f wiWylitit aiNno tfhyitMo<Nhtollrtof% fMwCtboM.fc tor HCt CD B cootMfM Hre brafcr**' prif ? th* two iMlKMtto vwtaato hiw6 tof i,\s WDtl to V HCt, The reaction is usually carried out in dispose of the by-product HCl. llte graph gives for any ethylene price the. acetylene price at which the two routes break even hr terms of~vin<ji chloride production 'costs (mchidmg depreciation}. The companion has been carried out tor the ease of zero HCl net back to the ethylene uv*r and for a netback of 15/ton The graph shows that if an HC! netback is taken it is very difficult for carbide-based acetylene to compete. Roughly 4 tons of carbide are needed CHClfJ-H,0--s-CH,CHO CH.-CHCl +HO--CH.CBCJ, The gases leaving the reactor are cooled before being caustic washed to remove unreaded hydrogen chloride, followed by a methanol wash to remove water picked out from the caustic solu the liquid phase and in ute presence of an iron chlonde catalyst. The reaction temperature ts very important and is uvuailv earned out at about 30-50*0. Increasing the temperature much above this level sharply favours the substitu tive chlorination. A temperature'much below this level ieduces the velocity of to produce 1 ton of acetylene which in countries such as the UJC. gives raw material cost for the acetylene of at least 1Oft ton. - In these areas ethylene will certainly win. Only in areas where either cheap natural gas or very cheap power is available, is acetylene able to compete on a cost basis. CBY 1019798 ' 7-r.-ewir? -z . -X RSV0031813