Following the implementation of the ethanol-blended gasoline policy, MTBE will no longer be used as a blending component in ethanol-blended gasoline, and MTBE plants will face shutdown or conversion to other products. For companies, decommissioning these plants represents a significant waste and will also have a major impact on downstream C4 deep-processing facilities. Processes such as 1-butene separation, methyl ethyl ketone production, and direct alkylation all require the complete or partial removal of isobutene.

 

MTBE is currently the only technological method capable of completely separating isobutene and 1-butene. Companies that require 1-butene or other olefins will inevitably continue to use MTBE technology to separate C4 hydrocarbons. However, there is no market for the resulting MTBE. How can existing MTBE units be utilized? How can isobutene be further converted after MTBE is phased out? These are pressing issues for downstream facilities engaged in C4 deep processing, such as butene-1 separation and methyl ethyl ketone production. At the “7th International Conference on Comprehensive Utilization of Light Hydrocarbons 2019” held last month, Wang Pan, Deputy Chief Engineer of KaiRui Environmental Technology Co., Ltd., outlined three pathways for the conversion of MTBE plants.

 

 

 

Pathway 1: Indirect Alkylation

 

Indirect alkylation involves the polymerization or copolymerization of low-carbon olefins, followed by hydrogenation to produce high-octane alkylate, which is used for gasoline blending. The feedstocks, plant scale, product applications, operating conditions, catalysts, and upstream/downstream integration of indirect alkylation units differ significantly from those of small-scale chemical plants designed to produce the chemical product isooctane.

 

Kairui Environmental Protection filed a patent application for its indirect alkylation resin catalyst in 2013 and was granted the patent (Patent No.: ZL201310429777.5; Patent Title: A Catalyst for the Polymerization of Low-Carbon Olefins and Its Preparation Method). In 2016, India’s IOCL conducted a global tender and ultimately selected KaiRui Environmental Protection’s indirect alkylation resin catalyst. To date, two batches of catalyst procurement have been completed. This marks the first industrial application of KaiRui Environmental Protection’s catalyst in an indirect alkylation unit, as well as the first industrial application of a domestically produced catalyst in such a unit.

 

Following the implementation of the ethanol-blended gasoline policy, KaiRui Environmental Protection actively collaborated with the Shijiazhuang Research Institute of Petroleum Processing (SRIP). Building upon the company’s existing indirect alkylation catalyst, they integrated SRIP’s selective polymerization technology to enhance properties such as catalyst strength, temperature resistance, resistance to fouling, and selectivity, and concurrently developed a purifier for selective polymerization feedstock. In July 2018, this catalyst was put into operation at the selective polymerization unit of Shijiazhuang Refining & Chemical (currently the only indirect alkylation unit in China designed for petroleum product production), where it performed well.

 

The CRI’s selective polymerization technology allows for the retrofitting of existing MTBE units. Once the retrofit is completed, the unit can produce both polymerized oil and MTBE to meet demands under varying policy conditions. At the same time, by employing different polymerization processes, residual C4 can be utilized to meet the feedstock requirements of units such as direct alkylation, methyl ethyl ketone, and sec-butyl acetate.

 

 

In indirect alkylation technology, catalysts play a crucial role. This technology is characterized by vigorous reactions, numerous side reactions, and difficulties in controlling both reaction temperature and selectivity. Furthermore, temperature spikes or side reactions can easily lead to catalyst deactivation. In response to the characteristics of the condensation technology, KaiRui Environmental Protection conducted targeted research and development on catalysts, ultimately achieving successful applications both domestically and internationally.

 

 

Pathway 2: Cracking to Produce High-Purity Isobutylene

 

High-purity isobutylene is an important raw material in the organic chemical industry. It serves as the primary feedstock for the production of methyl methacrylate (MMA), butyl rubber, high- and low-activity polyisobutylene, tert-butylphenol, tert-butylamine, methyl allyl chloride, trimethylacetic acid, isopentadiene, p-tert-octylphenol, antioxidants, and other products.

 

The boiling points of 1-butene (-6.3 °C) and isobutene (-6.9 °C) differ by only 0.6 °C, making it difficult to obtain high-purity 1-butene or isobutene through the distillation of mixed C4 fractions. Separation of 1-butene and isobutene can only be achieved through chemical methods; currently, MTBE technology is widely used for this purpose. Once MTBE production ceases, it will be difficult to separate isobutene and 1-butene; therefore, retaining the MTBE unit and cracking MTBE to find new outlets for MTBE products will be an effective approach for separating isobutene and 1-butene under the ethanol-blended gasoline policy. In response to these needs, KaiRui Environmental Protection has developed an MTBE cracking process technology and the配套KC151 catalyst.

 

Compared with similar domestic technologies, this technology offers advantages such as low energy consumption, high product purity, and a long catalyst service life.

    Once MTBE can no longer be used as a gasoline blending component, while MTBE cracking can resolve the issues of MTBE disposal and 1-butene separation, it involves relatively high capital and operating costs. Through collaboration with the China National Petroleum Corporation Research Institute (CNPCRI), a jointly developed combined technology involving polymerization, etherification, and cracking can more effectively address the issues of MTBE disposal and 1-butene separation while significantly reducing capital and operating costs.

Pathway 3: Production of ETBE

Ethyl tert-butyl ether (ETBE) is a high-octane gasoline blending component with excellent performance. As society evolves, environmental protection has become an increasingly important concern, and countries around the world are continuously establishing stricter gasoline standards. Methyl tert-butyl ether (MTBE) was previously the octane-boosting component widely used around the world. However, because MTBE is water-soluble and may contaminate groundwater sources, the United States banned MTBE in 2003 and switched to using ETBE. Compared to MTBE, ETBE has a slightly lower oxygen content and mixes easily with gasoline; it has a high boiling point, which reduces the volatility of gasoline; it has low water solubility, resulting in less environmental pollution; and its raw material, ethanol, is non-toxic.

MTBE与ETBE指标对比：

Ethanol-blended gasoline helps optimize China’s energy structure, improve the ecological environment, regulate the grain market, and reduce carbon emissions. However, it also has its own shortcomings:

 

1. Ethanol has 60% of the calorific value of conventional automotive gasoline;

 

2. Ethanol has a high latent heat of vaporization, which reduces vehicle power and fuel efficiency;

 

3. Ethanol produces acetic acid during combustion, which corrodes automotive metals, particularly copper

 

4. Ethanol is an excellent solvent and can cause slight corrosion, swelling, softening, or cracking of rubber seals and other synthetic non-metallic materials in vehicles;

 

5. Ethanol readily absorbs water, and prolonged storage can lead to liquid-phase separation.

 

n ETBE is produced through a chemical reaction between isobutylene and bioethanol. It offers advantages such as high octane rating and low vapor pressure. It not only allows for the blending of ethanol into gasoline (with a maximum ethanol content of approximately 8% via ETBE) but also resolves the issues associated with direct blending of ethanol into gasoline. ETBE production can be achieved with only minor modifications to existing MTBE plants, making it an ideal technical solution that effectively balances ethanol blending in gasoline with the stability of gasoline performance.

 

The ETBE technology and KC131 catalyst developed by KaiRui Environmental Protection enable the production of ETBE with only minor modifications to existing MTBE plants. ETBE is an ideal process technology that replaces MTBE while utilizing ethanol, thereby addressing the issues associated with ethanol-blended gasoline and making effective use of existing MTBE facilities.