Oil-to-chemicals: new approaches
A review of developments and trends in the expanding business of oil-to-chemicals.
JOHN J MURPHY and CLYDE F PAYN
The Catalyst Group
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Crude oil-to-chemicals (COTC) continues to be a powerful industry driver and a strong trend of high interest to all integrated refineries and chemicals producers in Asia/Pacific, China, the Middle East, and Eastern Europe. This is reinforced by many factors, most notably the forecasts which predict a slowing of transportation fuels growth approaching 2040 (with hybrids and electric vehicles), while growth in chemicals is expected to increase as populations and middle class wealth continue to rise, leading to increasing demand for packaging, consumer goods, and automobiles.
Are you aware that more than 12 corporations have committed over $315 billion to date to reconfigure their assets to produce more petrochemicals than transportation fuels, as revamps as well as building new grassroots refineries during the next 5-6 years? Based on announcements to date, we anticipate in the next five years that another $300+ billion, or more, will be announced as refiners and chemical companies all reassess their positions, knowing that the longer term outlook for transportation fuels from crude oil is expected to plateau and then decline. All players are taking this trend seriously and therefore you should also.
Considerable flexibility is being offered by petrochemical licensors, in particular petrochemical resid and VGO FCC upgrading units today. These are global changes including deep catalytic cracking (DCC) from Sinopec, as well as Western leaders such as Total’s R2R modifications, and Axens’ high-severity FCC (HSFCC) with Saudi Aramco. Technologies do not stand still. Advances in catalytic visbreaking may also be important in the future, when looking into advanced lower cost alternatives, and we have examined these R&D pipelines.
Already a large number of companies are closely examining their own responses and investments, bearing in mind each of these investment objectives will be site specific, influenced by feedstock choices, product slates/markets, energy/utility balances, capital/operating efficiencies, and health, safety and environmental (HSE) performance. It is clear from public domain information (such as the ongoing announcements by ADNOC, MOL and others) to see the progress in differentiation that is already under way.
Two main interests of producers are: to decrease capital intensity through scale, simplicity, and location; and to expand/maximise flexibility towards use of current (heavier) feedstocks in considering the oil-to-chemicals approach. The idea of better utilising assets from within an integrated refinery site means that most likely you are already dealing at 10x plus the size of a world-scale petrochemical plant. Although scale counts, it is also only one of many factors. New advanced configurations will now start to incorporate the planning of improved efficiency gains and reduced CO2 emissions. ExxonMobil forecasts that by 2040, while energy efficiency gains are expected to nearly double, carbon emissions are only projected to increase by a modest 10%.1 BP statistics, along with Chevron forecasts, the IEA and the EIA, show similar trends (see Figure 1).
Regarding competitive crude oil-to-chemicals developments, in addition to Saudi Aramco/SABIC announcements, we are already seeing ongoing investments from others. In a more recent example, private chemical producers Hengli and Rongshengin in China are back-integrating their chemical plants to add over 9 million t/y of paraxylene capacity by 2021. This is expected to reduce imports by 4 million t/y, with plans to yield up to 45 wt% of chemicals processing heavy crudes, which will tighten medium to heavy crude markets while also adding a 40% surplus to distillates and gasoline markets.
One of the most difficult components has been to understand that all licensors need to prioritise their own businesses. Therefore, they will prefer greenfield investments to revamps – even if these can be accomplished at lower ISBL and OSBL costs. This is not a criticism but rather a statement of fact based on desired business focus. Moreover, one of the understandings is to appreciate how existing and new configurations can be tailored towards either aromatics or olefins – but this may not be the best measure if indeed your goal is towards more olefins. In this regard, assuming you have an existing steam cracker, your revamp approach may be quite different.
Advances in heavy oil processes
In focusing on the processes by which the higher molecular weight constituents of petroleum (the heavy ends) can be converted to products that are suitable for use as feedstocks for the petrochemical section of the refinery, our assessments include carbon rejection and hydrogen addition approaches, along with process combinations and new configurations:
1. Carbon rejection
2. Hydrogen addition
3. Combining processes and treatment of intermediates
4. Configuration issues and advances
5. New processes likely to be deployed during the next five years
For decades, propane has been the mainstay in deasphalting heavy feedstocks, especially in the preparation of high quality lubricating oils and feedstocks for catalytic cracking units. Future units, which may well be derived from KBR’s ROSE process, will use solvent systems that will allow operation at elevated temperatures relative to conventional propane deasphalting temperatures, thereby permitting easy heat exchange. This will require changes to the solvent composition and the inclusion of solvents not usually considered to be deasphalting solvents. Other areas of future process modification will be in extractor tower internals, studies with higher molecular weight solvent, accurate estimation of physical properties of mix stream, studies in combination with other processes, and firming up design tools for supercritical solvent recovery configurations.
For heavy feedstocks, which will increase in amounts as hydrocracking feedstocks, reactor designs will continue to focus on online catalyst addition and withdrawal. Fixed bed designs have suffered from mechanical inadequacy when used for the heavier feedstocks, as well as short catalyst lives – six months or less – even though large catalyst volumes are used (LHSV typically of 0.5-1.5). Refiners will attempt to overcome these shortcomings through innovative designs, allowing better feedstock flow and catalyst utilisation, or online catalyst removal. For example, the OCR process, in which a lead moving bed reactor is used to demetallise the heavy feedstock ahead of the fixed bed hydrocracking reactors, has seen some success. But whether this will be adequate for continuous hydrocracking of heavy feedstocks remains a question.
Catalyst development will be key in the modification of processes and the development of new ones to make environmentally acceptable distillable liquids. Although crude oil conversion is expected to remain the principal future source of petrochemicals, natural gas reserves are emerging, and will continue to emerge, as a major hydrocarbon resource. This trend has already started to result in a shift toward use of natural gas (methane) as a significant feedstock for chemicals. As a result, deployment of technology for direct and indirect conversion of methane will probably displace much of the current production of liquefied natural gas.
The detrimental effect of coke on catalyst is a reduction of support porosity, leading to diffusional limitations, and finally blocked access to active sites. Nevertheless, moving bed or ebullated bed processes, alone or in combination with fixed bed reactor technology and/or also coupled with thermal processes employing suitable catalyst with metal retention capacity, represent the most efficient way of handling petroleum bottoms and other heavy hydrocarbons for upgrading. The features of the resulting process configuration will be high liquid yields, high removal of contaminants, and reliable operation.
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