This article will analyze the main products in China’s C3 industry chain and the current research and development direction of technology.

(1) The Current Status and Development Trends of Polypropylene (PP) Technology

According to our investigation, there are various ways to produce polypropylene (PP) in China, among which the most important processes include domestic environmental pipe process, Unipol process of Daoju Company, Spheriol process of LyondellBasell Company, Innovene process of Ineos Company, Novolen process of Nordic Chemical Company, and Spherizone process of LyondellBasell Company. These processes are also widely adopted by Chinese PP enterprises. These technologies mostly control the conversion rate of propylene within the range of 1.01-1.02.

The domestic ring pipe process adopts the independently developed Z-N catalyst, currently dominated by the second-generation ring pipe process technology. This process is based on independently developed catalysts, asymmetric electron donor technology, and propylene butadiene binary random copolymerization technology, and can produce homopolymerization, ethylene propylene random copolymerization, propylene butadiene random copolymerization, and impact resistant copolymerization PP. For example, companies such as Shanghai Petrochemical Third Line, Zhenhai Refining and Chemical First and Second Lines, and Maoming Second Line have all applied this process. With the increase of new production facilities in the future, the third-generation environmental pipe process is expected to gradually become the dominant domestic environmental pipe process.

The Unipol process can industrially produce homopolymers, with a melt flow rate (MFR) range of 0.5~100g/10min. In addition, the mass fraction of ethylene copolymer monomers in random copolymers can reach 5.5%. This process can also produce an industrialized random copolymer of propylene and 1-butene (trade name CE-FOR), with a rubber mass fraction of up to 14%. The mass fraction of ethylene in the impact copolymer produced by Unipol process can reach 21% (the mass fraction of rubber is 35%). The process has been applied in the facilities of enterprises such as Fushun Petrochemical and Sichuan Petrochemical.

The Innovene process can produce homopolymer products with a wide range of melt flow rate (MFR), which can reach 0.5-100g/10min. Its product toughness is higher than that of other gas-phase polymerization processes. The MFR of random copolymer products is 2-35g/10min, with a mass fraction of ethylene ranging from 7% to 8%. The MFR of impact resistant copolymer products is 1-35g/10min, with a mass fraction of ethylene ranging from 5% to 17%.

At present, the mainstream production technology of PP in China is very mature. Taking oil based polypropylene enterprises as an example, there is no significant difference in production unit consumption, processing costs, profits, etc. among each enterprise. From the perspective of production categories covered by different processes, mainstream processes can cover the entire product category. However, considering the actual output categories of existing enterprises, there are significant differences in PP products among different enterprises due to factors such as geography, technological barriers, and raw materials.

(2) Current Status and Development Trends of Acrylic Acid Technology

Acrylic acid is an important organic chemical raw material widely used in the production of adhesives and water-soluble coatings, and is also commonly processed into butyl acrylate and other products. According to research, there are various production processes for acrylic acid, including chloroethanol method, cyanoethanol method, high-pressure Reppe method, enone method, improved Reppe method, formaldehyde ethanol method, acrylonitrile hydrolysis method, ethylene method, propylene oxidation method, and biological method. Although there are various preparation techniques for acrylic acid, and most of them have been applied in industry, the most mainstream production process worldwide is still the direct oxidation of propylene to acrylic acid process.

The raw materials for producing acrylic acid through propylene oxidation mainly include water vapor, air, and propylene. During the production process, these three undergo oxidation reactions through the catalyst bed in a certain proportion. Propylene is first oxidized to acrolein in the first reactor, and then further oxidized to acrylic acid in the second reactor. Water vapor plays a dilution role in this process, avoiding the occurrence of explosions and suppressing the generation of side reactions. However, in addition to producing acrylic acid, this reaction process also produces acetic acid and carbon oxides due to side reactions.

According to Pingtou Ge’s investigation, the key to the acrylic acid oxidation process technology lies in the selection of catalysts. At present, companies that can provide acrylic acid technology through propylene oxidation include Sohio in the United States, Japan Catalyst Chemical Company, Mitsubishi Chemical Company in Japan, BASF in Germany, and Japan Chemical Technology.

The Sohio process in the United States is an important process for producing acrylic acid through propylene oxidation, characterized by simultaneously introducing propylene, air, and water vapor into two series connected fixed bed reactors, and using Mo Bi and Mo-V multi-component metal oxides as catalysts, respectively. Under this method, the one-way yield of acrylic acid can reach about 80% (molar ratio). The advantage of the Sohio method is that two series reactors can increase the lifespan of the catalyst, reaching up to 2 years. However, this method has the disadvantage that unreacted propylene cannot be recovered.

BASF method: Since the late 1960s, BASF has been conducting research on the production of acrylic acid through propylene oxidation. The BASF method uses Mo Bi or Mo Co catalysts for propylene oxidation reaction, and the one-way yield of acrolein obtained can reach about 80% (molar ratio). Subsequently, using Mo, W, V, and Fe based catalysts, acrolein was further oxidized to acrylic acid, with a maximum one-way yield of about 90% (molar ratio). The catalyst life of BASF method can reach 4 years and the process is simple. However, this method has drawbacks such as high solvent boiling point, frequent equipment cleaning, and high overall energy consumption.

Japanese catalyst method: Two fixed reactors in series and a matching seven tower separation system are also used. The first step is to infiltrate the element Co into the Mo Bi catalyst as the reaction catalyst, and then use Mo, V, and Cu composite metal oxides as the main catalysts in the second reactor, supported by silica and lead monoxide. Under this process, the one-way yield of acrylic acid is approximately 83-86% (molar ratio). The Japanese catalyst method adopts one stacked fixed bed reactor and a 7-tower separation system, with advanced catalysts, high overall yield, and low energy consumption. This method is currently one of the more advanced production processes, on par with the Mitsubishi process in Japan.

(3) Current Status and Development Trends of Butyl Acrylate Technology

Butyl acrylate is a colorless transparent liquid that is insoluble in water and can be mixed with ethanol and ether. This compound needs to be stored in a cool and ventilated warehouse. Acrylic acid and its esters are widely used in industry. They are not only used to manufacture soft monomers of acrylate solvent based and lotion based adhesives, but also can be homopolymerized, copolymerized and graft copolymerized to become polymer monomers and used as organic synthesis intermediates.

At present, the production process of butyl acrylate mainly involves the reaction of acrylic acid and butanol in the presence of toluene sulfonic acid to generate butyl acrylate and water. The esterification reaction involved in this process is a typical reversible reaction, and the boiling points of acrylic acid and the product butyl acrylate are very close. Therefore, it is difficult to separate acrylic acid using distillation, and unreacted acrylic acid cannot be recycled.

This process is called butyl acrylate esterification method, mainly from Jilin Petrochemical Engineering Research Institute and other related institutions. This technology is already very mature, and the unit consumption control for acrylic acid and n-butanol is very precise, able to control the unit consumption within 0.6. Moreover, this technology has already achieved cooperation and transfer.

(4) Current Status and Development Trends of CPP Technology

CPP film is made from polypropylene as the main raw material through specific processing methods such as T-shaped die extrusion casting. This film has excellent heat resistance and, due to its inherent rapid cooling properties, can form excellent smoothness and transparency. Therefore, for packaging applications that require high clarity, CPP film is the preferred material. The most widespread use of CPP film is in food packaging, as well as in the production of aluminum coating, pharmaceutical packaging, and preservation of fruits and vegetables.

At present, the production process of CPP films is mainly co extrusion casting. This production process consists of multiple extruders, multi channel distributors (commonly known as “feeders”), T-shaped die heads, casting systems, horizontal traction systems, oscillators, and winding systems. The main characteristics of this production process are good surface glossiness, high flatness, small thickness tolerance, good mechanical extension performance, good flexibility, and good transparency of the produced thin film products. Most global manufacturers of CPP use co extrusion casting method for production, and the equipment technology is mature.

Since the mid-1980s, China has started to introduce foreign casting film production equipment, but most of them are single-layer structures and belong to the primary stage. After entering the 1990s, China introduced multi-layer co polymer cast film production lines from countries such as Germany, Japan, Italy, and Austria. These imported equipment and technologies are the main force of China’s cast film industry. The main equipment suppliers include Germany’s Bruckner, Bartenfield, Leifenhauer, and Austria’s Orchid. Since 2000, China has introduced more advanced production lines, and domestically produced equipment has also experienced rapid development.

However, compared with the international advanced level, there is still a certain gap in the automation level, weighing control extrusion system, automatic die head adjustment control film thickness, online edge material recovery system, and automatic winding of domestic casting film equipment. At present, the main equipment suppliers for CPP film technology include Germany’s Bruckner, Leifenhauser, and Austria’s Lanzin, among others. These foreign suppliers have significant advantages in terms of automation and other aspects. However, the current process is already quite mature, and the improvement speed of equipment technology is slow, and there is basically no threshold for cooperation.

(5) Current Status and Development Trends of Acrylonitrile Technology

Propylene ammonia oxidation technology is currently the main commercial production route for acrylonitrile, and almost all acrylonitrile manufacturers are using BP (SOHIO) catalysts. However, there are also many other catalyst providers to choose from, such as Mitsubishi Rayon (formerly Nitto) and Asahi Kasei from Japan, Ascend Performance Material (formerly Solutia) from the United States, and Sinopec.

More than 95% of acrylonitrile plants worldwide use the propylene ammonia oxidation technology (also known as the sohio process) pioneered and developed by BP. This technology uses propylene, ammonia, air, and water as raw materials, and enters the reactor in a certain proportion. Under the action of phosphorus molybdenum bismuth or antimony iron catalysts supported on silica gel, acrylonitrile is generated at a temperature of 400-500 ℃ and atmospheric pressure. Then, after a series of neutralization, absorption, extraction, dehydrocyanation, and distillation steps, the final product of acrylonitrile is obtained. The one-way yield of this method can reach 75%, and the by-products include acetonitrile, hydrogen cyanide, and ammonium sulfate. This method has the highest industrial production value.

Since 1984, Sinopec has signed a long-term agreement with INEOS and has been authorized to use INEOS’s patented acrylonitrile technology in China. After years of development, Sinopec Shanghai Petrochemical Research Institute has successfully developed a technical route for propylene ammonia oxidation to produce acrylonitrile, and constructed the second phase of Sinopec Anqing Branch’s 130000 ton acrylonitrile project. The project was successfully put into operation in January 2014, increasing the annual production capacity of acrylonitrile from 80000 tons to 210000 tons, becoming an important part of Sinopec’s acrylonitrile production base.

At present, companies worldwide with patents for propylene ammonia oxidation technology include BP, DuPont, Ineos, Asahi Chemical, and Sinopec. This production process is mature and easy to obtain, and China has also achieved localization of this technology, and its performance is not inferior to foreign production technologies.

(6) Current Status and Development Trends of ABS Technology

According to the investigation, the process route of ABS device is mainly divided into lotion grafting method and continuous bulk method. ABS resin was developed based on the modification of polystyrene resin. In 1947, the American rubber company adopted the blending process to achieve industrial production of ABS resin; In 1954, BORG-WAMER Company in the United States developed lotion graft polymerized ABS resin and realized industrial production. The appearance of lotion grafting promoted the rapid development of ABS industry. Since the 1970s, the production process technology of ABS has entered a period of great development.

The lotion grafting method is an advanced production process, which includes four steps: the synthesis of butadiene latex, the synthesis of graft polymer, the synthesis of styrene and acrylonitrile polymers, and the blending post-treatment. The specific process flow includes PBL unit, grafting unit, SAN unit, and blending unit. This production process has a high level of technological maturity and has been widely applied worldwide.

At present, mature ABS technology mainly comes from companies such as LG in South Korea, JSR in Japan, Dow in the United States, New Lake Oil Chemical Co., Ltd. in South Korea, and Kellogg Technology in the United States, all of which have a global leading level of technological maturity. With the continuous development of technology, the production process of ABS is also constantly improving and improving. In the future, more efficient, environmentally friendly, and energy-saving production processes may emerge, bringing more opportunities and challenges to the development of the chemical industry.

(7) The technical status and development trend of n-butanol

According to observations, the mainstream technology for the synthesis of butanol and octanol worldwide is the liquid-phase cyclic low-pressure carbonyl synthesis process. The main raw materials for this process are propylene and synthesis gas. Among them, propylene mainly comes from integrated self supply, with a unit consumption of propylene between 0.6 and 0.62 tons. Synthetic gas is mostly prepared from exhaust gas or coal based synthetic gas, with a unit consumption between 700 and 720 cubic meters.

The low-pressure carbonyl synthesis technology developed by Dow/David – liquid-phase circulation process has advantages such as high propylene conversion rate, long catalyst service life, and reduced emissions of three wastes. This process is currently the most advanced production technology and is widely used in Chinese butanol and octanol enterprises.

Considering that Dow/David technology is relatively mature and can be used in cooperation with domestic enterprises, many enterprises will prioritize this technology when choosing to invest in the construction of butanol octanol units, followed by domestic technology.

(8) Current Status and Development Trends of Polyacrylonitrile Technology

Polyacrylonitrile (PAN) is obtained through free radical polymerization of acrylonitrile and is an important intermediate in the preparation of acrylonitrile fibers (acrylic fibers) and polyacrylonitrile based carbon fibers. It appears in a white or slightly yellow opaque powder form, with a glass transition temperature of about 90 ℃. It can be dissolved in polar organic solvents such as dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), as well as in concentrated aqueous solutions of inorganic salts such as thiocyanate and perchlorate. The preparation of polyacrylonitrile mainly involves solution polymerization or aqueous precipitation polymerization of acrylonitrile (AN) with non-ionic second monomers and ionic third monomers.

Polyacrylonitrile is mainly used to manufacture acrylic fibers, which are synthetic fibers made from acrylonitrile copolymers with a mass percentage of more than 85%. According to the solvents used in the production process, they can be distinguished as dimethyl sulfoxide (DMSO), dimethyl acetamide (DMAc), sodium thiocyanate (NaSCN), and dimethyl formamide (DMF). The main difference between various solvents is their solubility in polyacrylonitrile, which does not have a significant impact on the specific polymerization production process. In addition, according to the different comonomers, they can be divided into itaconic acid (IA), methyl acrylate (MA), acrylamide (AM), and methyl methacrylate (MMA), etc. Different co monomers have different effects on the kinetics and product properties of polymerization reactions.

The aggregation process can be one-step or two-step. One step method refers to the polymerization of acrylonitrile and comonomers in a solution state at once, and the products can be directly prepared into spinning solution without separation. The two-step rule refers to the suspension polymerization of acrylonitrile and comonomers in water to obtain the polymer, which is separated, washed, dehydrated, and other steps to form the spinning solution. At present, the global production process of polyacrylonitrile is basically the same, with the difference in downstream polymerization methods and co monomers. At present, most polyacrylonitrile fibers in various countries around the world are made from ternary copolymers, with acrylonitrile accounting for 90% and the addition of a second monomer ranging from 5% to 8%. The purpose of adding a second monomer is to enhance the mechanical strength, elasticity, and texture of the fibers, as well as improve dyeing performance. Commonly used methods include MMA, MA, vinyl acetate, etc. The addition amount of the third monomer is 0.3% -2%, with the aim of introducing a certain number of hydrophilic dye groups to increase the affinity of fibers with dyes, which are divided into cationic dye groups and acidic dye groups.

At present, Japan is the main representative of the global process of polyacrylonitrile, followed by countries such as Germany and the United States. Representative enterprises include Zoltek, Hexcel, Cytec and Aldila from Japan, Dongbang, Mitsubishi and the United States, SGL from Germany and Formosa Plastics Group from Taiwan, China, China. At present, the global production process technology of polyacrylonitrile is mature, and there is not much room for product improvement.