Selective Hydrogenation Catalyst for Low-Sulfur Gasoline Production
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Solution Overview
Problem
The challenge is to reduce the sulfur content in gasoline while minimizing octane loss and hydrogen consumption, particularly in FCC gasolines which have high contents of monoolefins and sulfur.
Innovation Solution
A process involving selective hydrogenation of gasoline containing sulfur compounds, olefins, and diolefins, using a catalyst with specific metals and operating conditions, followed by fractionation to produce a light gasoline cut with low sulfur and mercaptans content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional catalytic hydrodesulfurization processes are used to desulfurize gasoline, then sulfur content is reduced, but octane number is significantly lost due to hydrogenation of monoolefins
Solution Approach 1:
The patent changes the operating parameters by conducting hydrogenation at lower temperatures (50-200°C) and optimized pressures (0.5-5 MPa) with specific hydrogen-to-olefin molar ratios (1:1 to 10:1), which selectively hydrogenates diolefins while minimizing monoolefin hydrogenation and preserving octane number
Solution Approach 2:
The patent employs composite catalysts combining metals from group VIB (Mo, W) and group VIII (Ni, Co, Fe) on porous supports (alumina, silica, or their combinations) with controlled surface areas (100-400 m²/g), which provide selective hydrogenation activity for diolefins while preserving octane number
2Quantity of substance
If conventional hydrodesulfurization processes are used to reduce sulfur content, then sulfur is removed, but hydrogen consumption increases significantly
Solution Approach 1:
The patent optimizes hydrogen consumption by controlling the hydrogen-to-olefin molar ratio within 1:1 to 10:1 and operating at optimized pressures (0.5-5 MPa) and temperatures (50-200°C), which enables effective desulfurization while minimizing excess hydrogen consumption
3Reliability
If selective hydrogenation is used to hydrogenate diolefins and limit monoolefin hydrogenation, then octane number loss is reduced, but sulfur content reduction is insufficient
Solution Approach 1:
The patent uses composite catalysts with group VIB and group VIII metals on porous supports that provide dual functionality: selective hydrogenation of diolefins to monoolefins (preserving octane number) and simultaneous hydrodesulfurization of sulfur compounds (removing sulfur), achieving both objectives simultaneously
Solution Approach 2:
The catalyst system performs multiple functions simultaneously: hydrogenating diolefins, hydrodesulfurizing sulfur compounds, and minimizing monoolefin hydrogenation, thereby achieving both octane number preservation and sulfur removal in a single process
4Quantity of substance
If recombinant mercaptans are formed during desulfurization, then sulfur compounds are generated, but they represent a significant portion (20-80%) of residual sulfur
Solution Approach 1:
The patent controls the formation of recombinant mercaptans by optimizing hydrogenation conditions (temperature 50-200°C, pressure 0.5-5 MPa, hydrogen-to-olefin ratio 1:1 to 10:1) and catalyst composition, which limits the secondary reaction between H2S and monoolefins while maintaining effective sulfur removal
Solution Approach 2:
The patent converts the potentially harmful secondary formation of recombinant mercaptans into a beneficial process by using the same hydrogenation catalyst to selectively hydrogenate diolefins before sulfur removal, thereby preventing mercaptan formation while maintaining sulfur removal efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process effectively reduces sulfur content in gasoline to less than 10 ppm, minimizes mercaptans, and limits octane number loss, enabling direct incorporation into the fuel pool without additional treatment.
Implementation Method 1
a) a stage of selective hydrogenation so as to hydrogenate the diolefins and to carry out a reaction for increasing the molecular weight of a part of the sulfur compounds
Implementation Method 2
b) a stage of separation of the effluent obtained on conclusion of stage a) into a gaseous fraction, a light gasoline (LCN) cut and a heavy gasoline (also referred to here as HCN or Heavy Cracked Naphtha) cut
Data Source
AI summary
Process for producing a light gasoline having a sulfur content of less than 10 ppm by weight, with respect to the total weight of the light gasoline, starting from a gasoline containing sulfur compounds, olefins and diolefins, which process includesa) a stage of selective hydrogenation to hydrogenate the diolefins and a reaction for increasing the molecular weight of a part of the sulfur compounds;b) a stage separating the effluent obtained from stage a) into a gaseous fraction, a light gasoline cut and a heavy gasoline cut, stage b) being carried out in a fractionation column containing n plates, n being an integer of 20 or more, the first plate being the reboiler and the plate “n” being the condenser, wherein the light gasoline cut is withdrawn from the fractionation column at the plate “n-i”, with i being 1 to 10.