Patent ID: 8809574

Claim:
A method for preparing isocyanates by liquid-phase thermal cracking, comprising: liquid-phase thermal cracking a reactant in the presence of a catalyst composition, the catalyst composition comprising a superfine powder metal oxide catalyst having a particle diameter of 0.5-10 micrometers and an ionic liquid, wherein: the reactant is an alkyl, an aryl dialkylurethane, or a multialkylurethane; the reactant is liquid-phase thermal cracked for a reaction time of 0.5-3 h under a reaction temperature of 160-220° C. and an absolute pressure of 1000-8000 Pa so as to prepare the corresponding isocyanate; the metal oxide catalyst comprises at least one selected from the group consisting of nickel oxide, titanium oxide, zirconium oxide, copper oxide, molybdenum oxide, iron oxide, tungsten oxide, lanthanum oxide, cerium oxide, cobalt oxide, zinc oxide, calcium oxide, yttrium oxide and bismuth oxide; the cation of the ionic liquid is represented by a structural formula selected from the group consisting of where R 1 , R 2 , R 3 , R 4 , R 5 , R 6 each independently represents hydrogen or a branched or substituted alkyl group with a carbon number between 1 and 15; and an anion of the ionic liquid is selected from the group consisting of NO 3 − , PF 6 − , HSO 4 − , ClO 4 − , CH 3 PhSO 3 − , C(CN) 3 − , N(CN) 2 − , BF 2 (CF 2 ) n CF 3 − where n=0-10, PF 3 (CF 2 ) n CF 3 − where n=0-10, N(CF 3 SO 2 ) 2 − , SCN − , SeCN − , RSO 3 − where R has carbon number of 0-10, RSO 4 − where R has a carbon number of 0-10, M n Y x where M=Al, Zn, Fe, or Sn, X=Cl, Br, or I, n=1-2, x=2-7, RCOO − where R has a carbon number of 0-18, BF 4 − , H 2 PO 4 − , CF 3 COO − , CF 3 SO 3 − , SbF 6 − , AsF 6 − , EtSO 4 − , MeSO 4 − , Cl − , Br − and I − .