Production of fuel additives via simultaneous dehydration and skeletal isomerisation of isobutanol on acid catalysts followed by etherification

Abstract

The present invention relates to a process for the production of fuel additives in which in a first step isobutanol is subjected to a simultaneous dehydration and skeletal isomerisation to make substantially corresponding olefins, having the same number of carbons and consisting essentially of a mixture of n-butenes and iso-butene and in a second step the butene mixture is subjected to etherification, said process comprising: a) introducing in at least one reactor a stream (A) comprising at least 40 wt % isobutanol, optionally an inert component, b) contacting said stream with at least one catalyst in said reactor(s) at conditions effective to simultaneously dehydrate and skeletal isomerise at least a portion of the isobutanol to make a mixture of n-butenes and iso-butene, c) removing the inert component if any, recovering from said reactor(s) a stream (B) comprising a mixture of n-butenes and iso-butene, d) sending the stream (B) to at least one etherification reactor and contacting stream (B) with at least one catalyst in said etherification reactor(s), in the presence of ethanol and/or methanol, at conditions effective to produce ETBE and/or MTBE respectively, e) recovering from said etherification reactor a stream (E) comprising essentially ETBE and/or MTBE, unreacted butenes, heavies, optionally unreacted ethanol and/or methanol respectively, f) fractionating stream (E) to recover ETBE and/or MTBE.

1 . Process for the production of fuel additives in which in a first step isobutanol is subjected to a simultaneous dehydration and skeletal isomerisation to make substantially corresponding olefins, having the same number of carbons and consisting essentially of a mixture of n-butenes and iso-butene and in a second step the butene mixture is subjected to etherification, said process comprising:
 a) introducing in at least one reactor a stream (A) comprising at least 40 wt % isobutanol, optionally an inert component,   b) contacting said stream with at least one catalyst in said reactor(s) at conditions effective to simultaneously dehydrate and skeletal isomerise at least a portion of the isobutanol to make a mixture of n-butenes and iso-butene,   c) removing the inert component if any, recovering from said reactor(s) a stream (B) comprising a mixture of n-butenes and iso-butene,   d) sending the stream (B) to at least one etherification reactor and contacting stream (B) with at least one catalyst in said etherification reactor(s), in the presence of ethanol and/or methanol, at conditions effective to produce ETBE and/or MTBE respectively,   e) recovering from said etherification reactor a stream (E) comprising essentially ETBE and/or MTBE, unreacted butenes, heavies, optionally unreacted ethanol and/or methanol respectively,   f) fractionating stream (E) to recover ETBE and/or MTBE.   
     
     
         2 . Process according to  claim 1 , wherein the stream (A) comprises at least 70 wt % of isobutanol. 
     
     
         3 . Process according to  claim 1 , wherein the stream (A) comprises one or more C4 alcohols other than isobutanol. 
     
     
         4 . Process according to  claim 1 , wherein the stream (A) used in step a), and/or methanol and/or ethanol used in step d) are issued from renewable energy sources. 
     
     
         5 . Process according to  claim 1 , wherein the stream (A) is subjected to a purification treatment before step b). 
     
     
         6 . Process according to  claim 1 , wherein the WHSV of the isobutanol is at least 1 h −1 . 
     
     
         7 . Process according to  claim 1 , wherein the temperature of the simultaneous dehydration and skeletal isomerisation of isobutanol ranges from 200° C. to 600° C. 
     
     
         8 . Process according to  claim 1 , wherein the temperature of the simultaneous dehydration and skeletal isomerisation of isobutanol ranges from 250° C. to 500° C. 
     
     
         9 . Process according to  claim 1 , wherein the temperature of the simultaneous dehydration and skeletal isomerisation of isobutanol ranges from 300° C. to 450° C. 
     
     
         10 . Process according to  claim 1 , wherein the catalyst for the simultaneous dehydration and skeletal isomerisation is a crystalline silicate of the group FER, MWW, EUO, MFS, ZSM-48, MTT, MFI, MEL or TON having Si/Al higher than 10,
 or a dealuminated crystalline silicate of the group FER, MWW, EUO, MFS, ZSM-48, MTT, MFI, MEL or TON having Si/Al higher than 10,   or a phosphorus modified crystalline silicate of the group FER, MWW, EUO, MFS, ZSM-48, MTT, MFI, MEL or TON having Si/Al higher than 10,   or a silicoaluminaphosphate molecular sieve of the group AEL,   or a silicated, zirconated or titanated or fluorinated alumina.   
     
     
         11 . Process according to  claim 1 , wherein the pressure of the reactor(s) of the simultaneous dehydration and skeletal isomerisation of isobutanol ranges from 0.5 to 10 bars absolute. 
     
     
         12 . Process according to  claim 1 , wherein stream (E) recovered from step e) is fractionated to recover unreacted butenes and/or unreacted ethanol and/or methanol. 
     
     
         13 . Process according to  claim 12 , wherein at least a part of said recovered unreacted butenes and/or at least a part of said recovered unreacted ethanol and/or methanol are recycled to the etherification reactor(s). 
     
     
         14 . Process according to  claim 12 , wherein at least a part of said recovered unreacted butenes are sent to a purification zone before being sent to at least one oligomerization reactor and/or to at least one alkylation reactor to produce heavies. 
     
     
         15 . Process according to  claim 14 , wherein said unreacted butenes are subjected to a purification step before being sent to oligomerization reactor(s) and/or alkylation reactor(s). 
     
     
         16 . Process according to  claim 2 , wherein the stream (A) comprises at least 80 wt % of isobutanol.