The brief introduction of Hydrogenation catalysts

Hydrofinishing catalysts are composed of active components, additives and carriers. Its role is to hydrogenate and remove sulfur, nitrogen, oxygen and heavy metals as well as polycyclic aromatic hydrosaturation. The molecular structure of the feedstock does not change much and, depending on various needs, is accompanied by hydrocracking reactions, but the conversion depth is not deep and the conversion rate is generally around 10%. The hydrofinishing catalyst requires dual functions of hydrogenation and hydrogenolysis, while the acidity required for hydrogenolysis is not high.

Working Principle:

The mechanism of catalytic hydrogenation (changing the reaction pathway and reducing the activation energy): hydrogen molecules adsorbed on the catalyst generate active hydrogen atoms to adduct with alkenes and alkynes whose bonds are weakened by the catalyst.

(1) The more alkyl groups on the double bond carbon atoms, the lower the heat of hydrogenation and the more stable the alkene: R2C=CR2 > R2C=CHR > R2C=CH2 > RCH=CH2 > CH2=CH2

(2) trans isomers are more stable than cis

(3) The heat of hydrogenation of acetylene is -313.8 kJ-mol-1, which is twice as large as that of ethylene (-274.4 kJ-mol-1), so acetylene is less stable than ethylene.

Applications:

In the presence of Pt, Pd, Ni and other catalysts, olefins and acetylenes undergo addition reactions with hydrogen to produce the corresponding alkanes and give off heat, which is called heat of hydrogenation (heat of hydrogenation, heat given off when 1 mol of unsaturated hydrocarbon is hydrogenated). The mechanism of catalytic hydrogenation (changing the reaction pathway and reducing the activation energy): hydrogen molecules adsorbed on the catalyst generate active hydrogen atoms to add to alkenes and alkynes whose bonds are weakened by the catalyst.

Classification:

1)Hydrocracking catalyst

Hydrocracking catalysts are catalysts used in the hydrocracking process of petroleum refining, where heavy oil is hydrocracked at high temperature of 360~450℃ and high pressure of 15~18MPa to convert into gas, gasoline, jet fuel, diesel and other products. The hydrocracking process is a secondary process in the petroleum refining process, and the raw material for processing is heavy distillate, which can also be normal-pressure residue and reduced-pressure residue. The main feature of the hydrocracking process is that the production is flexible and the distribution of the products can be controlled by the operating conditions, which can produce gasoline, jet fuel with low freezing point and diesel fuel, and can also produce a large amount of tail oil for cracking raw material or producing lubricating oil. The resulting product is stable, but the octane number of gasoline is not high,. It is not as widely used as catalytic cracking due to harsh operating conditions and high equipment investment and operating costs. However, the hydrocracking process can handle feedstock containing impurities such as sulfur and high aromatic content, and the feedstock is strictly refined in a hydrofinishing reactor before entering the cracking reactor. The cracking reactor feed can be fed with or without circulating oil depending on the intended product. The range of circulating oil is wide, and can be all distillates below gasoline, or heavy distillates below diesel (>350°C). Most feedstocks can use fixed bed reactors, but residue hydrocracking must use boiling bed reactors, and the hydrocracking catalyst must be adapted to the corresponding feedstock and reaction conditions and equipment.

2)Hydrofinishing catalyst

Hydrofinishing catalysts are used to remove sulfur and nitrogen compounds from oil and to convert aromatic hydrocarbons into naphthenic hydrocarbons. The active components are compound oxides or sulfides of metals such as key, drill, tungsten and phosphorus.

Selection Guide:

The following factors need to be considered.

(1) Activity

(2) Selectivity

(3) Stability

(4) Mechanical strength

(5) regeneration performance

(6) Safety

(7) Cost effectiveness

In addition, it is necessary to consider the type and composition of the API, the quality and distribution requirements of the intended product, the hydrogenation process, the pressure level, the hydrogen-oil volume ratio, and the volume air velocity.

To determine the appropriate catalyst, the best process conditions, to meet the product quality and distribution requirements, while maximizing control and reducing the occurrence of side reactions, reducing the consumption of hydrogen, and improving economic efficiency.

Precautions:

1)Do not roll the catalyst on the ground to prevent it from crushing

2)Open the catalyst barrel, leave 10ml of sample in each barrel and mix it for catalyst analysis.

3)Decide whether to pass the sieve or not according to the catalyst condition after opening the drum.

4)The catalyst must be filled to the designed height.

5)The catalyst is poured into the filling hopper and loaded into the reactor, which must be in a canvas bag, and the catalyst must be handled gently without rolling the barrel.

6)Participants must not bring other items into the reactor, such as keys, knives, wires and lead wires.

7)Personnel entering the reactor must be certified and wear a dust mask.

8)Before entering the reactor, the gas in the reactor should be sampled and analyzed and allowed to enter the reactor. The reactor must be isolated from the system and blinded.