Production process and application of isopropanol

Abstract

  • It is a widely used organic solvent and raw material. The manufacturing technology of isopropanol was introduced. The economics of acetone hydrogenation and propylene hydration were compared. The application prospect of isopropanol was also analyzed. It is    considered
  • that the route of acetone hydrogenation to it is more economical,and the application   fields
  • of it need to be further expanded.
  • It alcohol, also known as sec-propanol and dimethyl methanol, is a colourless and transparent liquid with excellent performance as an organic solvent,
  • mainly used in the fields of ink and coatings, but also in pharmaceuticals, organic chemical intermediate raw materials and cleaning agents for the electronics industry [1-2].
  • The catalysts for the preparation of isopropanol have been studied in the literature [3-7], but there are relatively few studies on the production process of isopropanol and its economic comparison.
  • In this paper, the technical route for the production of synthetic isopropanol is presented, the economics of the acetone hydrogenation route and the propylene hydration route are compared, and the prospects for the application of isopropanol are analyzed.
  • The application prospects of it were analyzed.

Production method

  • The production process of it alcohol mainly includes propylene hydration, acetone hydrogenation and it acetate hydrogenation [8-9].
  • At present, the production of to in China is mainly based on the acetone hydrogenation process, while other countries in the world still use the propylene hydration process as the main production method.

Acrylic hydration method

The propylene hydration process can be divided into indirect hydration and direct hydration. At present, the indirect hydration of propylene has been eliminated for environmental reasons, therefore, the production of isopropanol by hydration method is the direct hydration of propylene, and the reaction equation is shown in equation (1).

isopropanol
  • The direct aqueous process of propylene is a direct addition reaction of propylene with water in the presence of a catalyst to produce isopropanol [10].
  • This method is relatively simple and selective compared with the indirect aqueous process of propylene and is widely used in overseas production plants.
  • Depending on the phase of the reactants, the direct aqueous process of propylene can be divided into gas-phase, liquid-phase, and gas-liquid mixed-phase methods.
  • The gas-phase method is represented by the Veba method developed by Veba Germany, the liquid-phase method is represented by the solution-catalyzed method of Tokuyama Tsuda Japan, and the gas-liquid mixed-phase method is represented by the ion-exchange resin method of Texaco Germany.
  • The technical parameters of the three different processes are compared in Table 1.

Table 1 Comparison of different processes for direct hydration of propylene to isopropanol

Process                                              Vapor-phase method                  Vapor liquid mixture method                                                           Liquid-phase method

Catalyst Temperature/℃

Hosphoric acid/diatomite 190-220

Cation exchange resin 135-160

Heteropoly acid 240-280

Pressure/MPa

2.0-2.2

6.0-8.0

20.0

Molar ratio of water to propylene

0.7∶1

15∶1

27∶1

Propylene purity/%

≥ 99

≥ 92

≥ 95

Single  pass conversion/%

5-7

60-75

60-75

Energy efficiency ratio

1.50

1.00

1.05

 

  • Based on 100% conversion and 100% selectivity, 0.7 t of propylene is required for the production of 1 t of isopropanol.
  • The propylene hydration technology developed by the Dalian Institute of Physical Chemistry of the Chinese Academy of Sciences consumes 0.73 t of propylene alone. In the process of propylene hydration, carbon six hydrocarbons, isopropyl ether and recombination are inevitably produced [12].
  • After the reaction, the material is first separated from the unreacted propylene for recycling, and then enters the isopropyl alcohol multi-tower distillation process.
  • Accordingly, the process of propylene hydration is long, with high energy consumption and many types of equipment.

Acetone hydrogenation method

The acetone hydrogenation process is the reduction of acetone to isopropanol under a hydrogen atmosphere in the presence of a catalyst, which is the inverse reaction of isopropanol dehydration [13], and the reaction equation is given in equation (2).

isopropanol
  • The reaction temperature of acetone hydrogenation is low, generally, 70-200 ℃ and the reaction can be carried out at atmospheric pressure.
  • Therefore, the energy consumption of acetone hydrogenation is low and compared with the traditional propylene hydration method, it is less corrosive to the equipment and the process is simple.
  • Theoretical calculations show that 0.967 t of acetone is required for each 1 t of isopropanol production.
  • The catalyst of Sinopec Beijing Research Institute of Chemical Technology (hereinafter referred to as Beihua) is used to produce isopropanol by hydrogenation in the catalyst bed after mixing ketone and hydrogen, in which a small number of by-products are generated below 0.05% (w), and the reaction product is separated from the gas-liquid to obtain high purity isopropanol by de-lightening, dehydration and de-weighting.
  • Therefore, the distinctive features of the process of Beihang are good catalytic performance, high quality of isopropanol, simple process, and low waste.
  • The catalysts commonly used in the acetone hydrogenation process are nickel-based and other non-precious metal catalysts [14-16].
  • The acetone hydrogenation catalysts developed by Beihua Institute have the advantages of excellent catalytic performance and good stability (see Figure 1), and have been successfully applied to several acetone hydrogenation plants for the preparation of isopropanol in China, all of which have achieved good economic benefits.
isopropanol

Isopropyl acetate hydrogenation method

In recent years, the Dalian Institute of Physical Chemistry of the Chinese Academy of Sciences has developed a hydrogenation route for the preparation of isopropyl alcohol from isopropyl acetate, with the reaction equation shown in equation (3).

isopropanol
  • Isopropyl acetate hydrogenation can produce ethanol and isopropanol at the same time, and some by-products will be generated.
  • Therefore, the quality of isopropanol produced by this process depends not only on the number of by-products generated in the hydrogenation process but also on the separation effect of the subsequent distillation process.
  • Although it can co-produce anhydrous ethanol, the separation of ethanol and isopropanol is difficult and the dehydration process is complicated, so it is currently out of production.

Acetic acid hydrogenation method

In addition to the above methods, the Shanxi Institute of Coal Chemistry of the Chinese Academy of Sciences has developed a process for the preparation of isopropanol by hydrogenation of acetic acid, and the reaction equation is given in Eq.

isopropanol
  • The catalyst for the hydrogenation of acetic acid to isopropanol consists of a first metal phosphide and a second metal compound,
  • where the first metal phosphide is the main catalyst and the second metal compound is the co-catalyst, resulting in 98.6% conversion of acetic acid and 83.3% selectivity of isopropanol. At present, this technology is still in the laboratory stage and needs to be further developed.

Comparison of economic benefits of acetone hydrogenation and propylene hydration routes

  • At present, domestic plants mainly produce isopropanol by two processes: propylene hydration and acetone hydrogenation.
  • The price difference between the feedstock cost of propylene, acetone, isopropanol, isopropanol and acetone and the price difference between the feedstock cost of isopropanol and propylene in China for the five years from January 2015 to May 2020 are plotted in Figure 2.
  • However, since March 2018, the product-to-feedstock differential for the acetone hydrogenation route has been higher than that of the propylene hydration route in the synthesis stage only.
  • Propylene prices are significantly influenced by international crude oil prices, and price fluctuations can seriously affect the start-up rate and even the economics of the isopropanol plant.
  • IfFrom April 2019 to July 2019, the isopropanol minus propylene feedstock cost differential was negative, resulting in a complete shutdown of the propylene hydrate route.
  • In the first four months of 2020, isopropanol and acetone prices rose sharply due to the New Crown Pneumonia epidemic, while propylene prices remained low, and the difference between isopropanol and propylene in the synthesis phase of the propylene hydration route rose sharply, causing the unprofitable propylene hydration route to isopropanol plants in China to restart in 2019.
  • The distillation part of the reaction product is mainly related to the energy cost and operating cost of the distillation column, so for comparison purposes, only the steam consumption of the distillation and dehydration process is considered here.
  • The propylene hydration route requires several distillation columns for purification, which are the propane process, the concentration process (isopropanol content (w) from 15% to 20% to 87%), the dehydration process (13% (w) of water removed to 0.1% (w)), and the light component removal.
    (w)), light fraction removal and recombination removal.
  • Using the chemical simulation software Aspen Plus, 2.82 t of steam is required per ton of isopropanol for the concentration process and 1.70 t of steam is required per ton of isopropanol for the dehydration process, which is only

Isopropyl alcohol application prospect analysis

  • Compared with other countries, the application area of isopropyl alcohol in China has not been effectively developed and needs to be further expanded to drive the steady development of the isopropyl alcohol industry.
  • In foreign countries, isopropyl alcohol is mostly used for disinfection of skin, prostheses and medical devices, and in some countries, it is the most widely used disinfectant in public places such as beauty salons,
  • but such applications are rarely done in China. In terms of effectiveness, isopropyl alcohol contains two groups of methyl groups, which makes it more effective than ethanol in solubilizing lipids and increasing the touching ability,
  • and it is more effective than ethanol in killing certain bacteria and viruses. In addition, compared to ethanol, isopropanol has a higher boiling point, is less volatile,
  • is easier to store, and is safer to use. The new coronary pneumonia virus has been spreading worldwide, and various medical protection materials have become scarce, which has greatly stimulated the demand for isopropyl alcohol in China and abroad.
  • The electronics industry is one of the fastest-growing areas of isopropyl alcohol consumption in the world, with demand expected to grow at an average annual rate of more than 10%.
  • The field of cleaning agents mainly uses high-purity isopropyl alcohol as a semiconductor cleaning agent and metal de-esterification cleaning agent, such as in Japan, high-purity electronic grade isopropyl alcohol is an important species of microelectronics chemical reagents, has been widely used in the production of semiconductor components,
  • ultra-large-scale integrated circuit assembly and processing cleaning and corrosion. At present, China’s isopropyl alcohol in the field of application has just begun, and the development potential is huge.
isopropanol

Concluding remarks

Compared with the propylene hydration route, the propylene hydrogenation route has a shorter process flow, less triple waste, higher quality isopropanol and better economy.

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