ALKYLATION USING H2SO4



Group 9
What is alkylation?
Alkylation process is a critical process in refineries order processing light olefins and Iso-butane into gasoline with high octane number that is iso-parafin contain mainly iso-octane.





Alkylate was found to have excellent aviation gasoline properties. It was the highest octane fuel component then known, with high motor octane and excellent lead response.
Sulfuric acid alkylation
Today there are two processes for H2SO4 alkylation the Cascade
process licensed by Exxon Mobil and MW Kellogg and the Stratco effluent refrigerated process.
FEEDSTOCK, CATALYST AND PRODUCT
Iso-butane
butene
Feed stock


This feedstock contained 80 - 85% of C4, the rest are C3 and C5. Propane and n-butane contained in the material, although not involved in the reaction, but it affect the process
Catalyst :H2SO4









 
Catalyst H2SO4

IS CATALYST H2SO4 PURE?

H2SO4
DIENES
WATER AND OXYGENATES
SULFUR
AND
NITROGEN
COMPOUNDS
ETHYLENE,
ETHANE
AND
LIGHTER
MAIN PRODUCTS
Light alkylate
Heavy alkylate
The mixture of hydrocarbon gases
Iso-octane
75 - 80%
The process




cis-Butene-2 + Isobutane → 2,2,4-Trimethylpentane (1.1) (100 RON)
Butene-1 + Isobutane → 2,3-Dimethylhexane (1.2) (71.3 RON)
Butene-1 + Isobutane→2,3,4-Trimethylpentane (1.3) (102.7 RON)
Isobutylene + Isobutane → 2,2,4-Trimethylpentane (1.4) (100 RON)
Propylene + Isobutane→2,3-Dimethylpentane (1.5) (91.1 RON)
2-methylbutene-2 + Isobutane → 2,2,4-Trimethylhexane (1.6) (92 RON)
The olefin is mixing with izo-butane and then put into alkyltion reactor. Reaction heat is removed by cooling the products or evaporating part of izo-butane. The reaction mixture after H2SO4 treatment is separated in a distillation tower into Izo-butane and alkylate,
The top is return to the reaction.
1.Carboncation forming
From iso-butene
From n-butene
2. Development of circuit
Reaction A:
3.The isomerization of carbocations

4.Reaction B and the creation of alkylate:
In this stage, the product we need is 2,2,4-trimethyl pentane
Side reactions
The recovery of acid catalyst need a separate process
Modulation process consists of 4 stages:
+ SO2 sulfur anhydride Preparation: Clean Filter SO2 + O2 mixtures, reducing clean dust and impurities to harm these catalysts (such SeO2, As2O3, PH3, H2O ...).
+ SO2 Oxidation: gas mixture was filtered, heated to 450oC and over a catalyst (Pt or V2O5). During the period that temperature oxidation not be changed.
  2SO2 + O2 →2SO3 (often reaching 98% efficiency)
.
SO3 adsorbtion stage: the mixture gas SO2 + SO3 + O2 is cooled down to about 50 ° C, then scatter in H2SO4 98.2% solution (keep temperature constant at 50 ° C). Oleum product H2SO4.xSO3 is obtained. If they want dilute acid, water will be added to oleum
2SO2 + O2 → 2SO3
SO3 + H2O →H2SO4
Factors affecting reaction
Temperature
Time
Acidity
In alkylating industrial, suitable temperature for catalytic acid H2SO4 is 4 - 10oC.

Temperature
Time
The reaction time of the alkylation process determined by two basic factors:
+ Speed taking heat from the reaction zone sufficient to adjust the temperature of
react.
+ Time needed to Izo-butane dissolved in acid phase emulsion created.
Thus will ensure the desired conduct and limit the side reactions.
In fact, to achieve maximum efficiency, the contact time in the reactor with H2SO4 catalyst usually 20 to 30 minutes.
Acidity


To alkylating segments C4, people often use acid H2SO4 90-98.5%. Raising the concentration of acid in the limit will make it complete the properties of alkylate which anti-knock properties its.

To alkylating Izo-butane by buten, process widely used catalyst H2SO4 96% - 98%.
Special factor
Izo-butane concentration in the reaction.
Because the solubility of Izo-butane in Acidulated is very small (0.1% H2SO),
so to speed up the reaction, Izo-butane concentration maximum must be achieved in reaction zone. Solubility also depends on the particular mixing in the reactor.
When using excess Izo-butane compare to buten will prevent all side effects and have a positive impact on performance alkylate, increased levels of product desire, increase octane number and reduces catalyst attrition. Using too much excess Izo-butane isn’t recommended because then regenerate it after reaction costs very high. Optimal molar ratio in this case is from 4/1 to 6/1.
CONCLUSIONS


Motor fuel alkylation using sulfuric acids is one of the oldest catalytic processes used in refining and petrochemical operations, the other is using HF. The liquid acid processes remain important despite concerns with safety and environmental properties of the liquid acids. Solid catalyst alkylation using processes such as Alkylene™ (UOP LLC) are emerging technology.
.
ADVANTAGES
- The octan number of alkylate obtained with material is buten is higher: 93-95.
- Izo-butane consumption is lower.
- H2SO4 also tends to corrode but not as HF.
- H2SO4 also very toxic, but in normal condition it’s liquid so the handling is safetier and much easier.
- The proper design of each of the processing areas (Refrigeration, akylation reaction, effluent treating, frationation, blowdown) is imperative to the safe and efficient operation of the alkylation unit.

DISADVANTAGES
Sulfuric acid alkylation uses about 100 times as much acid as HF alkylation because H2SO4 cannot be stripped from the conjunct polymer, water, and contaminants
Catalyst regeneration process requires a separate processing workshops.
The reaction temperature operation low around 5 to 10oC, must cooled reactor below 10°C.
Request stirred reaction zone higher because H2SO4 soluble Iso-butane lower than HF (0.1%).

Nearly 90% of new units licensed since 1990 have selected H2SO4 alkylation technology over HF.
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