(see Figure 5 ). The FCC naphtha propylene yield previously observed in Table 2 Column 6 represents the cracking of the unsaturated molecules in the first reaction stage. Reactor configuration and operations The Gasolfin catalyst has been designed to operate in a fixed-bed reactor. The conversion for maximum propyl - ene yield is feed-dependent but typically is about 35 wt%. Paraffinic feeds are delivered to the Gasolfin unit feed drum. This feed will exchange heat with the reactor effluent and then receive additional heating in a fired heater. Typical reactor inlet temperatures are 500-600°C. The reaction is endothermic, resulting in a temperature drop in the adiaba- tic reactor. The reactor effluent is cooled and then delivered to a single-stage equilibrium flash drum. The light ends are sent to product recovery while the non-reacted feed is returned to the feed drum. The Gasolfin catalyst reacts all non-aromatic feeds to extinction. The recycle ratio is 2-2.5, depending on the feed composition. The reactor section is operated as a simulated moving bed operation in which multiple reactors are operating in parallel, with differing degrees of time on-stream. The cycle length of each reactor is three to five days. At the end of each reactor cycle, the reactor will be taken offline, stripped of residual hydrocarbon, and then submitted to an in-situ regeneration. The decoking operation lasts about six hours. After completion, the reactor will be purged of oxygen and placed in standby mode under an inert atmosphere until the reactor is placed into service for the next cycle. The catalyst life is expected to be at least three years. Enhanced flexibility The catalyst in the Gasolfin process is the first catalytic- driven light ends conversion process in the refining and pet - rochemical industries. The process enables a standard fuels refinery to expand its olefin-producing capacity well beyond the levels possible in the FCC unit. This process converts naphtha produced in the crude distillation unit, the hydroc- racker, hydrotreaters, and all conversion processes, such as fluid cracking and coking. The process is equally efficient at converting intermediate and byproduct naphtha streams. In addition, the process allows refiners the following upgrading capabilities: • Pentane cracking: Normal pentanes have an octane level of 61.7 RON. Normal and isopentanes have high vapour pressures of 15.7 and 72.6 psia at 100°F, respectively. These two characteristics have a strong negative impact on the refinery gasoline pool. The operating severity of the high-octane units, such as catalytic reforming, isomerisa- tion, and alkylation, must be increased to offset the octane penalty. At the same time, the amount of butane blending is reduced due to the high vapour pressures. The process allows a refiner to divert all pentane streams from the gas - oline blending plant into the Gasolfin unit. A 67 wt% total olefin yield is observed with pentane cracking. The propyl - ene selectivity is 32 wt% with an EPB ratio of 28:47:25. • Polymer-grade propylene: A Gasolfin unit will enable all operators to either begin polymer-grade propylene produc- tion or increase existing capacity.
LSR & FRN feeds
Recycle
Reactor
Figure 4 Paraffin cracking
conversion for LSR naphtha. The cycle was initiated at 600°C. The reactor temperature was increased by 10°C after 48 hours, followed by a second 10°C increase after 63 hours. The conversion increased by 3.7 wt% for each 10°C temperature increase. The rate of conversion loss was -0.15 wt%/hr after 48 hours at 600°C, followed by -0.10 wt%/hr at 610°C and -0.12 wt%/hr at 620°C. The average conver- sion rate of decline was -0.136 wt%/hr over the 76-hour cycle. The cycle was terminated after 76 hours with a final conversion of 24.0 wt%, representing a 10% overall con- version loss after three days of operations. The cycle length for LSR feeds is expected to be about 110 hours (4.5 days) before reaching end-of-run temperatures. Figure 3 demonstrates that the propylene yield for the FRN feed began at 30 wt% and gradually increased by 2.0 wt% over the first 24 hours of operation. The propyl - ene selectivity averaged 32.0 wt% for the remainder of the cycle. The reactor temperature was increased by 20°C after 62 hours to compensate for conversion loss. It is significant to note that propylene selectivity is insensitive to reactor temperature increases. The butylene selectivity dropped by 0.9 wt% after the temperature increase, whereas the ethylene selectivity increased by 2.6 wt%. The total olefin selectivity showed a net increase of 1.5 wt% after the tem- perature adjustment. Similar responses were observed for the LSR and HCN feeds (see Figure 4 ). The Gasolfin process rapidly converts olefins and unsatu - rated naphthenes present in cracked naphthas (HCN, PN). The process is modified for converting cracked naphthas. The aromatics are first extracted followed by the reaction of the olefins and unsaturated naphthenes at relatively mild reac - tion conditions. The more refractive paraffinic and saturated naphthenes are then cracked under more severe operations
FCC naphtha
Ole n/Unsat naphthene cracking
Stage #1
Recycle
Ole ns
Stage #2 feed
Para n/Sat naphthene cracking
Recycle
Stage #2
Ole ns
Figure 5 Cracked naphtha conversion
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