The sequence and logic of gasoline quality improvement in our country

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The sequence and logic behind the upgrade of gasoline quality in our country. The sequence and logic behind the upgrade of gasoline quality in our country. French company Axens is a leader in the field of catalytic gasoline desulfurization technology. To date, the selective catalytic hydrogenation desulfurization technology developed by this company, Prime-G+, has been installed in over 230 industrial facilities around the world, including 32 in China. Companies such as CDTECH, AXENS, and UOP are the main suppliers of such technologies on the international stage. CDTECH’s technology consists of patented process units for catalytic distillation hydrogenation, catalytic distillation etherification, and straight-chain olefin skeleton isomerization; it is highly advanced and holds the largest market share, with over 100 industrial plants utilizing this technology. 　　The sequence and logic behind the improvement of gasoline quality in China: The process of upgrading gasoline quality in China began around the year 2000, and over the past decade or so, increasingly stringent standards for gasoline quality, along with the specific composition of gasoline blends in China, have greatly accelerated the development of technologies for improving gasoline quality as well as their industrial application. Before the full implementation of the National V gasoline standard in 2017, reviewing the technological advancements and market choices related to the improvement of gasoline quality over the past, and analyzing the underlying logic behind various quality indicators of gasoline, it is possible to determine an appropriate sequence for upgrading gasoline quality based on each refinery’s processing procedures. This approach could be a useful technical strategy for refineries to prepare for meeting the requirements of National V standards or even stricter future standards. First, catalytic gasoline constitutes the main component of gasoline in China; desulfurization of catalytic gasoline, reduction of olefins, and increasing its octane rating are the three key issues that need to be addressed in order to meet the quality requirements of National IV and National V standards. Chinese refineries have long processed low-sulfur paraffinic heavy crude oils, with catalytic cracking being the primary method of further processing, which results in a composition of gasoline that differs significantly from that produced by refineries in the United States and Europe. In U.S. refinery gasoline pools, catalytic gasoline, reformate, and other components such as alkylated and isomerized oils each account for one-third. In European refinery gasoline pools, the proportion of reformate is close to 50%, catalytic gasoline accounts for about 30%, while other components such as alkylated and isomerized oils make up around 20%. In the gasoline pools of refineries in our country, catalytic gasoline accounts for 73%, while high-octane components such as reformed oil and alkylated oil together make up less than 20%. Since the majority of sulfur and olefins in gasoline pools come from catalytic gasoline, and the octane rating of catalytic gasoline is 89–91, which is relatively low, domestic refineries face significant pressure to desulfurize and reduce olefins in catalytic gasoline, making it difficult to produce higher-octane gasoline. By making substantial adjustments to the structure of refining units to align the composition of gasoline in China with that in the United States or Europe, it is possible to address the issues related to olefins and octane number in gasoline; however, the problem of desulfurization remains. A significant increase in the proportion of reformate oil will also lead to excessive benzene content in gasoline ； At the same time, not only are large amounts of capital required for the construction and renovation of new facilities, but a stable supply of high-priced light crude oil over the long term is also unfeasible, which will inevitably affect the profitability of enterprises. In the long term, as the heaviness of crude oil increases, catalytic cracking, as an efficient technology for the in-depth catalytic conversion of heavy oil/residues, will maintain its key role in secondary processing. 　　Taking all the above factors into account, in the foreseeable future, the predominance of catalyzed gasoline in China’s gasoline pool will not change fundamentally. Desulfurizing catalyzed gasoline, reducing its olefin content, and increasing its octane rating remain the main challenges that China must address in order to improve the quality of its gasoline, both now and in the future. 　　II. Industrial practices around the world over the past decade have shown that selective catalytic hydrogenation for gasoline desulfurization is the dominant technology used for this purpose both domestically and internationally. The French company Axens is a leader in this field of technology; to date, its selective catalytic hydrogenation technology for gasoline desulfurization (Prime-G+) has been deployed in more than 230 industrial installations worldwide, of which 32 are located in China. This technology results in a very low degree of olefin hydrogenation saturation, with minimal loss of octane rating ； No aromatic saturation or cracking reactions occur, with a liquid yield of nearly 100% ； It operates stably over long periods, in line with the maintenance cycle of catalytic cracking units ； The desulfurization rate is greater than 98%, which meets the requirement of a gasoline sulfur content of 10 ppm. Among domestic refineries, Shandong’s local refineries use the Prime-G+ technology the most, with 17 units in total. Some large-scale local refineries in Shandong, despite having a sulfur content in their catalytic gasoline of over a thousand ppm, are still able to produce gasoline that meets the National V standard for use in the Beijing-Shanghai region, achieving good economic benefits by applying this technology. 　　ExxonMobil’s catalytic gasoline selective hydrodesulfurization technology (Scanfining) and CDTECH’s catalytic distillation-based catalytic gasoline hydrodesulfurization technology (CD Hydro/CD HDS) are competitive in terms of global market share; however, their current performance in industrial applications lags far behind that of France’s AXENS technology. Domestically, during the upgrade of gasoline quality to National III standards, many refineries have adopted the catalytic selective hydrogen desulfurization technology (OCT series) developed by the Fushun Petrochemical Research Institute. Sinopec has acquired the S-Zorb catalytic gasoline adsorption desulfurization technology from the American company Phillips as a key solution to meet the higher quality requirements of gasoline under the National V standard. After having its relevant design and research units internalize this technology as well as the specialized adsorbents, Sinopec is now promoting it widely across its own systems. In addition, the catalytic gasoline selective hydrogenation desulfurization technology developed by Beijing Annejie Energy Technology Company, which meets the National V standards, has been deployed in more than 20 units across domestic private enterprises; among these are industrial facilities with a production capacity of millions of tons. This technology represents a force that cannot be ignored. 　　Looking at the history of developments in technologies for improving the quality of catalytic gasoline, the approach of using hydrodesulfurization and octane recovery techniques to address the loss of octane value during the hydrogenation of catalytic gasoline does not work. ExxonMobile’s Octgain, UOP’s ISAL, and some similar domestic technologies hold virtually no market share on a global scale. Technical experts from the French company AXENS stated at the 2003 NPRA annual conference that catalytic gasoline desulfurization technology must meet two basic requirements: no loss in gasoline yield ； The boiling range remains unchanged. The catalytic gasoline hydrodesulfurization-octane number recovery technology using molecular sieve catalysts finds it difficult to meet the above two requirements due to inherent constraints in its reaction mechanism. Therefore, to address the issue of loss in the octane number of catalyzed gasoline, it is necessary to conduct a comprehensive analysis of the sources of various components in the gasoline mixture and the relationships between different units. 　　III. Catalytic etherification of light gasoline is a technique that suits the characteristics of China’s gasoline composition; it is a mature and effective method for reducing olefins in gasoline and increasing its octane rating. However, there are limited prospects for further development in catalytic cracking processes and catalysts used to reduce olefins. The main goal of the first round of quality improvements after the transition to lead-free gasoline was to reduce the olefin content in catalytic gasoline. Through the use of olefin-reducing catalysts and catalytic cracking processes, the olefin content in catalytic gasoline at most domestic refineries is now between 30% and 40%. This has led to a decrease in the yield of light products, a reduction in the octane rating of gasoline, and an improvement in the cetane rating of diesel. Relying continued on catalytic cracking processes and catalysts to meet the olefin limits specified by National Standard IV and V will only exacerbate these problems. A comparative analysis of the mainstream catalytic etherification technologies for light gasoline on the market shows that by etherifying light gasoline catalytically and then blending it with catalytically processed heavy gasoline to produce fully fractionated catalytic gasoline, the olefin content can be reduced by about 10 points while the octane rating increases by 1 unit. Additionally, factors such as the conversion of approximately 4% of methanol into gasoline components, as well as the reduced vapor pressure of the etherified gasoline, which allows more high-octane light hydrocarbon components to be incorporated into the gasoline mixture, can further enhance corporate profitability. 　　Companies such as CDTECH, AXENS, and UOP are the main suppliers of such technologies on the international stage. CDTECH’s technology consists of patented process units for catalytic distillation hydrogenation, catalytic distillation etherification, and straight-chain olefin skeleton isomerization; it is highly advanced and holds the largest market share, with over 100 industrial plants utilizing this technology. CDTECH has successively transferred this technology to CNPC’s Nanchong Refinery, Golmud Refinery, and Urumqi Petrochemical Plant. 　　IV. Focusing on the development of alkylation technology and balancing the development of reforming technology are key measures to increase the octane number of gasoline and to meet the requirements of National V standards as well as future, even stricter standards for gasoline quality. In the process of upgrading gasoline to meet National V standards and future stricter requirements, advanced catalytic desulfurization and olefin reduction processes have exacerbated the problem of low octane numbers in gasoline. Issues such as the low octane number of certain components in catalytically processed gasoline, which affects the starting and acceleration performance of vehicles, have become increasingly apparent. Future demands regarding engine efficiency and emissions mean that fuel standards will continue to emphasize high octane numbers alongside lower carbon content. Given that catalytic cracking will remain the main processing method in the long term, focusing on the development of alkylation technology is key to addressing these issues. The main components of alkylated oils are high-octane branched isoparaffins; they contain no olefins or aromatics, have a low sulfur content, and a low vapor pressure, making them an ideal component for blending into clean gasoline. Especially in terms of raising the mid-range octane number of catalytic gasoline, ensuring a reasonable distribution of the overall octane number of gasoline, and meeting future low-carbon standards for petroleum products, alkylated oils play an irreplaceable role compared to other high-octane blending components. By producing more liquefied gas through catalytic cracking units, it is possible to generate more alkylated oils as well as more propylene, thereby increasing the octane rating of gasoline and the light ends obtained from the process – all of which enhances the economic benefits for enterprises. With catalytic cracking playing a key role in secondary processing, we can turn challenges into opportunities, make use of our strengths while avoiding weaknesses, and pursue a path for improving gasoline quality that features Chinese characteristics and aligns with future development trends. Catalytic reforming units not only produce high-octane gasoline blending components but also supply aromatic hydrocarbons as raw materials for chemical companies; they are also an important source of hydrogen for refineries. Given the international shortage of light crude oil resources and domestic naphtha resources, as well as the restrictions on benzene content in gasoline, it is necessary to take various factors into account and develop reforming technology in a manner that corresponds to available capabilities. 　　Based on the above analysis, to improve the octane number of gasoline blends, it is possible to consider increasing, over a period of 3 to 5 years and in a phased manner by region, the proportion of alkylated oils and reformate in these blends from the current level of less than 20% to 30%, while reducing the proportion of catalyzed gasoline to around 60%. By adopting light gasoline etherification technology and adjusting the composition of the gasoline pool, the constraints on reducing olefins in catalytic cracking units can be gradually overcome, thereby maximizing the core role of these units in increasing the yield of light products and producing more low-carbon olefins. By making full use of low-value C4 compounds and methanol resources, the proportion of high-octane, high-quality gasoline produced can be further increased. Through careful planning and thorough research, it is possible to achieve an ideal state in which quality improves while corporate efficiency rises.