Patent Application
20230416618
The present invention relates to a method of producing hydrocarbon mixtures rich in aromatics from naphtha feedstock, in particular the method is designed to obtain hydrocarbon mixtures rich in aromatics having research octane number of at least 102 while keeping the capital and operating expenditures low.
Presently, the hydrocarbon mixtures rich in aromatics are prepared by converting naphtha feedstock over solid catalysts in adiabatic reactors using hydrogen rich gases as carrier gas (or also referred as co-feed) to the reactors (or also referred as reaction tank). These hydrogen rich gases are by-products of the reaction of which were recycled to be used as carrier gas as an initiative to carry heat to the reactors for sustaining endothermic reactions in converting naphtha feedstock and also to slow down the rate of catalyst deactivation. However, the latter needed a large gas compressor to circulate carrier gas back to the reactors and also needed to produce steam for driving the large compressor.
The conventional method of producing the hydrocarbon mixtures rich in aromatics transfers only part of the heat energy released by the process heaters to the reactors and releases surplus heat in the convection section of the heaters, which was practically resulted as a waste and often referred as waste heat. In order to reduce as much waste as possible, the waste heat was channeled to produce steam for driving the large gas compressors (as described above) for recycling the hydrogen rich gases back into reactors. Unfortunately, the above highlighted initiatives resulted in high investment costs and high operating expenditures.
Still further, the method of producing the hydrocarbon mixtures rich in aromatics are catalyst dependent process. The catalyst is used in the reactors as a medium for reaction to generate the desired product. After some time, the catalyst will be deactivated by the coke formation, which would require regeneration before it is ready to be reused. The regeneration step is carried out on-site either continuously or intermittently such that the catalyst is reusable.
The above may be achieved while the reactors running (also referred as continuous production process) by continuously circulating catalysts between the reactors and an integrated catalyst regenerator. This method sustains high catalyst activities but it incurs high investment costs. This approach is applicable to a semi-continuous production as well, wherein the production process will be stopped momentarily for 2 to 3 weeks, possibly once in several months such as but not limited to once in six months to regenerate the deactivated catalysts in the reactors in-situ. Once the catalysts regenerated, the process continues for another cycle of six months.
These approaches however work optimally whenever appropriate quality of feedstocks are fed into the reactors. If the quality of feedstock drops, the percentage of yield and its research octane number (RON) drop as well. Higher yield and RON can be achieved by continuously regenerating the catalyst but the higher investment cost makes this option not always attractive due to consideration of return on investment (ROI). Hence, the industry is struggling to obtain the hydrocarbon mixtures rich in aromatics having research octane number (RON) of at least 100 while ensuring the capital and operating expenditures are kept low.
Having said the above, an approach is clearly required by the industry to develop a method of producing hydrocarbon mixtures rich in aromatics that is able to overcome the above mentioned technical issues such that it is able to reduce the capital and operating expenditures as well as to obtain hydrocarbon mixtures rich in aromatics having research octane number (RON) of at least 100.
The present invention relates to a method of producing hydrocarbon mixtures rich in aromatics from naphtha feedstock (100 or 100a) comprising the steps of:
Additional aspects, features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments of the invention in conjunction with the drawings listed below.
The present invention will be fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, wherein:
In the appended drawings:
Detailed description of preferred embodiments of the present invention is disclosed herein. It should be understood, however, that the embodiments are merely exemplary of the present invention, which may be embodied in various forms. Therefore, the details disclosed herein are not to be interpreted as limiting, but merely as the basis for the claims and for teaching one skilled in the art of the invention. The numerical data or ranges used in the specification are not to be construed as limiting. The following detailed description of the preferred embodiments will now be described in accordance with the attached drawings.
The present invention relates to a method of producing hydrocarbon mixtures rich in aromatics from naphtha feedstock, in particular the method is designed to obtain hydrocarbon mixtures rich in aromatics having research octane number of at least 102 while keeping the capital and operating expenditures (CAPEX and OPEX) low. Primarily, the method of the present invention is developed to save both CAPEX and OPEX, which is achieved by way of making changes to several aspects of the current technology that will be discussed hereinafter under several embodiments to show its advantages.
This approach is also an initiative towards 5R concept, whereby the method of the present invention is carried out to avoid wasting of potentially useful materials. In particular, it reduces CAPEX and energy usage. Further, pollution levels are reduced since it burns less fuels. Simply, this approach is advantageous in view of both economically and environmentally.
Referring to the accompanying drawings,
In general, the method of producing hydrocarbon mixtures rich in aromatics from naphtha feedstock of the present invention comprises a first step of feeding a naphtha feedstock (100 or 100a) and liquified petroleum gases, LPG (101a and 101b) into reactor effluent/feed heat exchanger (200 or 300) to yield a mixture (102 or 102a), wherein the LPG is a mixture of propane and butane and wherein the LPG is in vapour form. Prior to this step, the mixture (102 or 102a) have an initial temperature of below 100° C. In this step, the temperature of the mixture (102 or 102a) is raised to a range between 350° C. to 500° C. The latter is achieved by transferring heat from the effluents (103 or 104 or 105 or 103a or 104a or 105a) to the mixture (102 or 102a) in the reactor effluent/feed heat exchanger (200 or 300).
The LPG (101a and 101b) acts as a carrier gas for carrying heat from the reactor effluent/feed heat exchanger (200 or 300) and the heaters (201a, 201b and 201c) to the reactors (202a, 202b and 202c), as well as, functions as a dilution medium for the naphtha feedstock (100 or 100a). Initially, the LPG (101a) is fed from an external source manually into the reactor effluent/feed heat exchanger (200 or 300) until the LPG (101b) is produced in the second stage separator (206).
Once the LPG (101b) is produced in the second stage separator (206), the LPG (101b) is recycled and used as carrier gas. Hence, the LPG (101a) that is fed manually into the reactor effluent/feed heat exchanger (200 or 300) can be instantaneously terminated. Simply, the external supply of LPG (101a) is just momentarily and isn't required throughout the process.
The first step of the present invention helps to reduce the number of reactors (202a, 202b and 202c) to at least one and at most three reactors for producing hydrocarbon mixtures rich in aromatics having research octane number, RON of at least 100 as compared to the conventional method of using hydrogen rich gas as the carrier gas which requires at least three and at most five reactors. This is due to the higher heat carrying capacity of LPG (101a, 101b and 101c) as compared to the hydrogen rich gas, which is at least more than 3 times.
Further, the first step of the present invention reduces the CAPEX and the OPEX of recycling carrier gas, allowing a larger quantity of carrier gas to be recycled for carrying heat from the reactor effluent/feed heat exchanger (200 or 300) and the heaters (201a, 201b and 201c) to the reactors (202a, 202b and 202c), contributing to reducing the number of reactors required for producing hydrocarbon mixtures rich in aromatics.
For instance, one reactor requires carrier gas flow of more than 8 moles of LPG (101a and 101b) to 1 mole of naphtha feedstock (100 or 100a). Whereas two reactors require carrier gas flow in the range between 4 to 8 moles of LPG (101a and 101b) to 1 mole of naphtha feedstock (100 or 100a). Lastly, three reactors require carrier gas flow of less than 4 moles of LPG (101a and 101b) to 1 mole of naphtha feedstock (100 or 100a).
For the purpose of the present invention, the LPG (101a and 101b) is not consumed in the reaction and it does not serve the purpose as a reactant. Thereafter, second step of the present invention is carried out by way of channeling the mixture obtained from the first step of the present invention into at least one reactor (202a) via integrated heater (201a) or at least two reactors (202a and 202b) via integrated heaters (201a and 201b) or at most three reactors (202a, 202b and 202c) via integrated heaters (201a, 201b and 201c) to raise the temperature of the mixture (102, 103 and 104 or 102a, 103a and 104a) to at most 550° C. This is the desired/optimum condition for the naphtha feedstock (100 or 100a) in the mixture (102, 103 and 104 or 102a, 103a and 104a) to react in the reactors (202a, 202b and 202c).
The second step of the present invention occurs in the reactors (202a, 202b and 202c), whereby the mixture (102, 103 and 104 or 102a, 103a and 104a) from the heaters (201a, 201b and 201c) are fed onto catalysts placed in the reactors (202a, 202b and 202c) to initiate the aromatization process and to produce hydrocarbon mixtures rich in aromatics. The reactors (202a, 202b and 202c) are equipped with facilities for allowing catalyst inventory such that the catalysts can be withdrawn from the reactors (202a, 202b and 202c) and replaced with the same type or different type of catalysts without even opening the reactors (202a, 202b and 202c).
The latter is very important for the present invention since it contributes to the method of the present invention in a way that the entire catalyst inventory could be easily changed one or more times without shutting the process plant before the end of an operating cycle that could last for at least 3 years. This second step of the present invention allows the process plant to change catalysts whenever it is necessary, for instance (1) if a more advance catalyst or a cheaper catalyst is available in the market or (2) if an existing catalyst inventory became unsuitable due to a structural change in feedstock quality which makes it more attractive to use another catalyst.
This second step of the present invention also allows deactivated catalysts to be replaced with active catalysts while the deactivated catalysts are sent to an off-site location for regeneration. The latter is different from the conventional approach of which practices on-site catalysts regeneration since there is less restriction in designing an off-site catalyst regenerator as compared to an on-site catalyst regenerator, for which the regeneration process can be more optimally controlled to minimize deterioration of catalysts during regeneration.
Moreover, the off-site catalysts regeneration offers the advantage of (1) using an equipment that allows better control over the regeneration process, as well as, (2) other catalyst reconditioning options. For example, the latter allows re-impregnation of metal into the catalysts to adjust the metal function of catalysts. In comparison, the conventional continuous production process regenerates catalysts on-site and operates with only one type of catalyst over the entire operating cycle and would need to shut down the process plant for unloading the entire catalyst inventory in order to change to a new batch of catalysts.
With reference to the structural change in feedstock quality, the quality of naphtha feedstock (100 or 100a) can be either one with high paraffin content (referred as paraffinic feedstock) or one with high cyclo-paraffin content (referred as naphthenic feedstock). Having said the above, the present invention allows the process plant to switch the catalyst inventory when there is a structural change in the feedstock quality, particularly from paraffinic feedstock to naphthenic feedstock or vice versa.
Separately, the catalysts could either be more effective for converting paraffins into aromatics or more effective for converting cyclo-paraffins into aromatics. Conventionally, the process plant has to operate with catalysts that are optimized for the average feedstock quality since it is not practical to shut down the process plant for changing the catalyst inventory.
Simply, when the quality of naphtha feedstock (100 or 100a) switches, say from paraffinic feedstock to naphthenic feedstock or vice versa, the catalysts can be replaced with the ones appropriate to the quality of naphtha feedstock such that it would produce higher yield and/or higher RON. The replacement of catalysts can be carried out without the necessity of discontinuing the production process. Consequently, the product loss can be minimized, and hence, the ROI can be maximized.
The catalysts are but not limited to zeolite-based catalysts, provided that the catalysts are able to operate with LPG (101a and 101b) being the carrier gas. The catalysts are operated in the reactors (202a, 202b and 202c) as below:
Perhaps, the reactors (202a, 202b and 202c) comprise:
During the transition from the inlet of first reactor (202a) to the second reactor (202b) and/or from the inlet of the second reactor (202b) to the third reactor (202c), temperature of the effluents (103 and 104 or 103a and 104a) will drop below the optimum level required for sustaining product conversion due to the endothermic reactions of producing aromatics. Thus, the effluents (103 and 104 or 103a and 104a) from the earlier reactor will be re-heated in the integrated heaters (201b and 201c) before it is transferred into the second reactor (202b) or third reactor (202c) for further processing to yield the hydrocarbon mixtures rich in aromatics.
Subsequently, third step of the present invention is carried out by way of channeling the effluents (103 or 103a) obtained from the first reactor (202a) or (104 or 104a) obtained from the second reactor (202b) or (105 or 105a) obtained from the third reactor (202c) into the reactor effluent/feed heat exchanger (200 or 300) for reducing its temperature from above 300° C. to below 100° C. by transferring heat to the mixture (102 or 102a) before it is transferred to a cooling tank (203).
Fourth step of the present invention occurs in the cooling tank (203), whereby in the cooling tank (203) the temperature of the effluent (106 or 106a) from the reactor effluent/feed heat exchanger (200 or 300) will be reduced by using but not limited to either air and/or water to a temperature below 40° C. Fifth step of the present invention is carried out by way of introducing the cooled effluent (107) into the first stage separator (204) where light gases (108) such as but not limited to hydrogen, methane and ethane are separated from the cooled effluent (107).
Sixth step of the present invention is carried out by way of transferring remaining liquid (109) from the first stage separator (204) using a pump into second stage separator (206) via evaporator (205) in order to boil off part of the LPG either in the evaporator (205) or in the second stage separator (206). The process in the second stage separator (206) is carried out at higher pressure and higher temperature than the process in the first stage separator (204) of which operates below 40° C. and at operating pressure that ranges from 5 to 30 bar. The LPG (101b) obtained from the second stage separator (206) is recycled back into the reactor effluent/feed heat exchanger (200 or 300) as carrier gas (as discussed above) without using a compressor.
The benefit of using LPG (101a and 101b) instead of light gases (108) from the first stage separator (204) as carrier gas are as follows:
Finally, the effluent (110) from the second stage separator (206) is transferred by pump to the stabilizer (207) to separate off gas, LPG (101c) and reformate. The reformate is the hydrocarbon mixtures rich in aromatics, wherein the hydrocarbon mixtures rich in aromatics are having research octane number (RON) of at least 100, preferably RON of at least 102. The hydrocarbon mixtures rich in aromatics are aromatics having carbon number chain between C6 to C11, preferably aromatics having carbon number chain between C6 to C10, still preferably aromatics having carbon number chain between C7 to C10.
Referring to the accompanying drawings,
The cooling tank (203), the first stage separator (204), the evaporator (205), the second stage separator (206) and the stabilizer (207) could be shared by two sets of reactors for processing the two different quality of naphtha feedstocks, which reduces CAPEX and OPEX as compared to processing the two types of naphtha feedstocks in two separate process plants. For example, C8 to C11 hydrocarbons could be processed in the reactors (202a, 202b and 202c) and C7 hydrocarbons could be processed in the reactors arranged in parallel.
The following example is constructed to illustrate the present invention in a non-limiting sense.
Producing Hydrocarbon Mixtures Rich in Aromatics from Naphtha Feedstock Using One Reactor
A method of producing hydrocarbon mixtures rich in aromatics from naphtha feedstock (100 or 100a) comprising the steps of:
wherein the mixture (102 or 102a) achieves a temperature in the range between 350° C. to 500° C. in the reactor effluent/feed heat exchanger (200 or 300) in the step (i) by way of heat exchange from the effluents (103 or 103a) to the mixture (102 or 102a) in the reactor effluent/feed heat exchanger (200 or 300), wherein the heater (201a) generate waste heat that is recycled into air preheaters (208a) to raise the temperature of air from around 30° C. to at least 100° C. by way of heat exchange from the waste heat to the incoming air that eventually used along with fuel as heating source to run the heaters (201a) and wherein the LPG (101b) is recycled back into the reactor effluent/feed heat exchanger (200 or 300) without using a compressor.
Producing Hydrocarbon Mixtures Rich in Aromatics from Naphtha Feedstock Using Two Reactors
A method of producing hydrocarbon mixtures rich in aromatics from naphtha feedstock (100 or 100a) comprising the steps of:
wherein the mixture (102 or 102a) achieves a temperature in the range between 350° C. to 500° C. in the reactor effluent/feed heat exchanger (200 or 300) in the step (i) by way of heat exchange from the effluents (104 or 104a) to the mixture (102 or 102a) in the reactor effluent/feed heat exchanger (200 or 300), wherein the heaters (201a and 201b) generate waste heat that is recycled into air preheaters (208a and 208b) to raise the temperature of air from around 30° C. to at least 100° C. by way of heat exchange from the waste heat to the incoming air that eventually used along with fuel as heating source to run the heaters (201a and 201b) and wherein the LPG (101b) is recycled back into the reactor effluent/feed heat exchanger (200 or 300) without using a compressor.
Producing Hydrocarbon Mixtures Rich in Aromatics from Naphtha Feedstock Using Three Reactors
A method of producing hydrocarbon mixtures rich in aromatics from naphtha feedstock (100 or 100a) comprising the steps of:
wherein the mixture (102 or 102a) achieves a temperature in the range between 350° C. to 500° C. in the reactor effluent/feed heat exchanger (200 or 300) in the step (i) by way of heat exchange from the effluents (105 or 105a) to the mixture (102 or 102a) in the reactor effluent/feed heat exchanger (200 or 300), wherein the heaters (201a, 201b and 201c) generate waste heat that is recycled into air preheaters (208a, 208b and 208c) to raise the temperature of air from around 30° C. to at least 100° C. by way of heat exchange from the waste heat to the incoming air that eventually used along with fuel as heating source to run the heaters (201a, 201b and 201c) and wherein the LPG (101b) is recycled back into the reactor effluent/feed heat exchanger (200 or 300) without using a compressor.
Comparison Between Conventional System and System of the Present Invention
Table 1 shows comparison of conventional system and system of the present invention in terms of the numbers of reactors with integrated heaters that could be reduced by recycling LPG as carrier gas that contains mainly propane and butane instead of recycling hydrogen rich gas as carrier gas.
Based on the Table 1, it is evident that:
Simply, heat energy which is required for sustaining the endothermic reactions of producing hydrocarbon mixtures rich in aromatics are carried from the reactor effluent/feed heat exchanger and the process heaters to the adiabatic reactors by the naphtha feedstock as well as by the carrier gas. The present invention uses LPG (which contains propane and butane) as carrier gas while the conventional system uses hydrogen rich gas as carrier gas.
Due to the higher heat carrying capacity of propane and butane, the present invention could sustain more endothermic reactions in the reactors before the temperature of the combined feed drops below the required level for sustaining the endothermic reactions. Hence, the present invention reduces the number of times that the reactor effluents would need to be reheated for completing the endothermic reactions of producing hydrocarbon mixtures rich in aromatics.
As a result, the present invention only requires at least one reactor with integrated heater and at most three reactors with integrated heaters for completing the endothermic reactions of producing hydrocarbon mixtures rich in aromatics. In comparison, the conventional system requires at least three reactors with integrated heaters and at most five reactors with integrated heaters for completing the endothermic reactions of producing hydrocarbon mixtures rich in aromatics due to the low heat carrying capacity of hydrogen rich gas.
As a whole, the method of producing the hydrocarbon mixtures rich in aromatics of the present invention is able to optimize capital and operating expenditures by keeping them low, as well as, is able to obtain the hydrocarbon mixtures rich in aromatics having research octane number (RON) of at least 100.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises”, “comprising”, “including”, and “having” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups therefrom.
The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. The use of the expression “at least” or “at least one” suggests the use of one or more elements, as the use may be in one of the embodiments to achieve one or more of the desired objects or results.
| Number | Date | Country | Kind |
|---|---|---|---|
| PI2020005930 | Nov 2020 | MY | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/MY2021/050095 | 10/28/2021 | WO |
