Patent GB-832873-A (GB)
Title: Improvements in or relating to the upgrading of heavy virgin naphtha
IPC: C10G61/06
Filed: 1958-02-12
Abstract: <PICT:0832873/III/1> Heavy virgin naphtha boiling above 160 DEG  F. is upgraded by vaporizing, contacting with a 5   molecular sieve, catalytically reforming the normal paraffin-free stream obtained in the presence of hydrogen at 750-1050 DEG  F. and 50-1000 p.s.i.g. to obtain a reformate having a Research octane number of at least 95, desorbing normal paraffins from the molecular sieve, thermally cracking the desorbate at 10-1000 p.s.i.g. to produce mono- and di-olefines, fractionating to remove tars and low-boiling material from the C5+ olefines, converting the diolefines to mono-olefines or saturated compounds and blending the diolefine-free product with the reformate.  The naphtha feed, preferably desulphurized by contacting with a 13   molecular sieve, is introduced into the molecular sieve treating zone 2 in the vapour phase at a flow rate of 0.1-5 vol./vol./hr. at 200-350 DEG  F. and a pressure of atmospheric or a little above.  The unadsorbed normal paraffin-free hydrocarbons are passed to the reforming zone 4 where it is conventionally reformed, the catalyst preferably being platinum or molybdena on alumina.  The effluent is cooled, gases separated in separator 6 and recycled and liquid reformate passes by line 7 to blending.  When the molecular sieve is saturated the feed is cut off and the normal paraffins are desorbed by passing an olefine-containing gas through the zone, such gas preferably being a propylene-containing cracked refinery gas. The stripping gas is pre-heated to 200-500 DEG  F.  Propylene is afterwards removed from the sieve by heating and carbon deposits burnt off with diluted air, care being taken to avoid the temperature rising above 1100 DEG  F.  The desorbed normal paraffins are separated from normally gaseous material and cracked or thermally reformed in the thermal cracking zone 16, preferably in the presence of 75% by weight of steam at 10-1000 p.s.i.g. to produce 30-40 weight per cent conversion to dry gas.  The product is quenched with a gas oil boiling in the range 500-800 DEG  F. and separated from tar in columns 18 and 20.  The overhead is treated with an absorber oil boiling above 300 DEG  F. in absorber 26.  Wet gas is not absorbed and the olefine content passing by line 27 may be polymerized to high octane gasoline for blending with the product.  The absorber oil and gas oil quench are then removed in column 32 after light material has been removed in column 29 and recycled.  The cracked product in line 34 may be debutanized and hydrofined in hydrofiner 39 with about 1000 scF. reformer tail gas per barrel over a cobalt molybdate-alumina catalyst at about 400 p.s.i.g., 600-800 DEG  C. and an L.H.S.V. of 1-10 vol./vol./hr. to convert all diolefines but only a small part of the mono-olefines, or the product is given a clay treatment in clay treater 47 before blending with reformate in line 7.ALSO:<PICT:0832873/IV (b)/1> Heavy virgin naphtha boiling above 160 DEG  F. is upgraded by vaporizing, contacting with a 5   molecular sieve, catalytically reforming the normal paraffin-free stream obtained in the presence of hydrogen at 750-1050 DEG  F. and 50-1000 p.s.i.g. to obtain a reformate having a Research octane number of at least 95, desorbing normal paraffins from the molecular sieve, thermally cracking the desorbate at 10-1000 p.s.i.g. to produce mono- and diolefines, fractionating to remove tars and low-boiling material from the C5+ olefines, converting the diolefines to mono-olefines or saturated compounds and blending the diolefine-free product with the reformate.  The naphtha feed, preferably desulphurized by contacting with a 13   molecular sieve, is introduced into the molecular sieve treating zone 2 in the vapour phase at a flow rate of 0.1-5 vol./vol./hr. at 200-350 DEG  F. and a pressure of atmospheric or a little above.  The unadsorbed normal paraffin-free hydrocarbons are passed to the reforming zone 4 where it is conventionally reformed, the catalyst preferably being platinum or molybdena on alumina.  The effluent is cooled, gases separated in separator 6 and recycled and liquid reformate passes by line 7 to blending.  When the molecular sieve is saturated the feed is cut off and the normal paraffins are desorbed by passing an olefine-containing gas through the zone, such gas preferably being a propylene-containing cracked refinery gas. The stripping gas is preheated to 200-500 DEG  F.  Propylene is afterwards removed from the sieve by heating and carbon deposits burnt off with diluted air, care being taken to avoid the temperature rising above 1100 DEG  F.  The desorbed normal paraffins are separated from normally gaseous material and cracked or thermally reformed in the thermal cracking zone 16 preferably in the presence of 75% by weight of steam at 10-1000 p.s.i.g. to produce 30-40 weight per cent conversion to dry gas.  The product is quenched with a gas oil boiling in the range 500-800 DEG  F. and separated from tar in columns 18 and 20.  The overhead is treated with an absorber oil boiling above 300 DEG  F. in absorber 26.  Wet gas is not absorbed and the olefine content passing by line 27 may be polymerized to high octane gasoline for blending with the product.  The absorber oil and gas oil quench are then removed in column 32 after light material has been removed in column 29 and recycled.  The cracked product in line 34 may be debutanized and hydrofined in hydrofiner 39 with about 1000 scF reformer tail gas per barrel over a cobalt molybdate-alumina catalyst at about 400 p.s.i.g., 600-800 DEG  C. and an LHSV of 1-10 vol./vol./hr. to convert all diolefines but only a small part of the mono-olefines, or the product is given a clay treatment in clay treater 47 before blending with reformate in line 7.