Chemistry and Technology of Obtaining Monomers

Being an essential monomer in polymer industries, styrene's commercial production has gained much attention. Around 90% of the world's styrene production is accomplished via ethylbenzene dehydrogenation using excess superheated steam as a heat carrier. The cost linked with the production of enormous heat energy for the commercial process underlines the importance of finding alternative and innovative approaches for styrene production. Therefore, this chapter discusses the possible alternative routes of styrene production from ethylbenzene. The chapter begins with chemistry, thermodynamics, and a brief history, i.e. how the commercial method is established, of ethylbenzene dehydrogenation. Afterward, the possible alternative routes to commercial styrene production are listed and discussed. A particular emphasis is given to the preparation of styrene from ethylbenzene dehydrogenation using CO 2 as a soft oxidant because this method consumes CO 2 (one of the greenhouse gases) and emerges as a green chemistry process. The detailed mechanism of ethylbenzene dehydrogenation into styrene using CO 2 is studied. Significantly, the catalysts and their key properties during the ethylbenzene dehydrogenation to styrene with CO 2 are elucidated. Membrane technology is also briefly described together with the chemical looping technology.

Propylene (C3H6) is a building block for important petrochemicals production such as polypropylene and acrylonitrile. Propylene is traditionally produced as a co-product in steam crackers (SC) and as a by-product in fluid catalytic cracking (FCC) units. A growing gap between the supply and demand for C3H6 is expected in the foreseeable future. On-purpose C3H6 production, such as non-oxidative propane dehydrogenation (PDH), is considered as a suitable technology to bridge the gap between conventional processes (SC and FCC) and the demand for C3H6. However, the PDH process faces challenges due to its endothermic nature. Membrane reactors, consisting of PDH catalysts and H2-permeable membranes, have the potential to improve C3H6 yield. The key feature of the implemented PDH membrane reactor is that the catalyst activates C3H8 to form C3H6, while the membrane continuously removes H2 to influence C3H8 equilibrium conversion. This chapter provides a summary of past research and ongoing developments in PDH reactions in membrane reactors. The content covers the membrane material, catalyst, reactor configuration, and performance for PDH in membrane reactors. Furthermore, the challenges and strategies to mitigate reactor performance decline during PDH are presented, along with future research and development directions to advance this technology for on-purpose C3H6 production.

Plastics and climate change—Breaking carbon lock-ins through three mitigation pathways

The production of styrene (ST) by the petrochemical industry has traditionally relied on the ethylbenzenedehydrogenation (EB) reaction, using iron‐based catalysts. Estimates suggest that in 2025, the production of EB and ST will surpass 36 and 41 million tons, respectively. In this manner, the major aspects that led to the present stage of EB and ST production were described, discussing historical aspects, alternatives to produce these solvents, its characteristics, types of oxidants, and properties of iron‐based catalysts. Noteworthy advancements in this field include the utilization of CO2 as a soft oxidant and the employment of innovative catalysts derived from green synthesis methods. On the other hand, as an alternative to the fossil source for EB production, the utilization of lignin from biomass emerges as a promising eco‐friendly approach. The potential for implementing the ODH reaction in alternative reactors gives rise to questions regarding the necessity for industry to adapt to current climate needs. Furthermore, certain aspects of the mechanism have been called into question, as some fundamental points remain to be fully consolidated. These include the extent of the participation of CO2 in the reactivation of the active sites and the origin of the deposited coke.

Ethylbenzene (EB) dehydrogenation to styrene (SM) on an industrial scale is generally performed using classic and SMART (Styrene Monomer Advanced Reheat Technology) technologies. In the current study, spent catalysts structural changes through classic and SMART technologies were investigated and compared with the fresh catalyst. For this purpose, XRF, XRD, SEM-EDX, FT-IR, BET and crushing strength analysis were employed. It was found that styrene production via SMART technology with 40% potassium loss is led to more catalyst deactivation than the classic ones (26%). Due to pore mouth blocking by coke formation, the average pore radius in both classic and SMART spent catalysts is reduced about 33% and 53% compared to the fresh ones, respectively. SEM analysis showed that potassium migration mechanism is related to the temperature gradient in the classic spent catalysts and chemical vapour transportation in the SMART spent catalysts. Comparative evaluation of the catalysts performance indicated that the SMART spent catalyst with about 72% activity loss is more deactivated than the classic ones (61%).The large drop of styrene yield (72-74%) of SMART spent catalyst revealed that the activity is more depending on the pore mouth size, rather than the specific surface area. However, in situ steam injection redistributed migrated potassium and increased the selectivity of the classic spent catalyst, but it was led to more potassium migration and catalyst deactivation in the SMART spent ones. According to this study, styrene production and industrial unit design based on SMART technology not recommended strongly.

Environmental Burdens of China’s Propylene manufacturing: Comparative life-cycle assessment and scenario analysis

Global propylene demand increases year on year, conventional sources of propylene production like steam crackers, refinery fluid catalytic cracker (FCC) are unable to meet global demand for propylene and this has necessitated the use of "On-Purpose" sources for propylene production like propane dehydrogenation (PDH). The PDH and its impact in the propylene mix of the Nigerian petrochemical industry is what this work is centered on. The need for PDH technology in Nigeria stems from the reality that, Nigeria currently has no refinery with operational fluid catalytic cracker nor sufficient steam crackers to meet an estimated propylene demand gap of about 140 KTA (2016/2017) despite propylene production from a major player in Nigeria (at present, demand gap is expected to be more). This work involves analysis of Nigeria's petrochemical import and export, petrochemical market size, exposition to the PDH trendand technology focusing on UOP Oleflex technology (chemistry and operation/process flow) and how this technology can help close the current propylene demand gap in Nigeria especially as Nigeria enters its decade of gas. Petrochemical companies in Asia have been able to use this PDH technology to manufacture propylene thereby significantly closing the propylene demand gap, constructing the most PDH plants in the last 5 years in the process. This also can be replicated in Nigeria and aid in closing propylene demand gap, and with surplus, begin to export propylene to the West African market to generate revenue, improving GDP.

Dehydrogenation of ethylbenzene with CO 2 over Cr-MCM-41 catalyst

Coupling reaction and separation in a membrane reactor improves process efficiency and reduces purification cost in the next stages. In this work, the performance of the hydrogen–permselective membrane reactors to produce styrene and hydrogen through ethylbenzene dehydrogenation is studied at steady state condition. In the proposed configuration, the Pd/Ag membrane tubes have been placed in the adiabatic reactors to remove hydrogen from the reaction zone. Then, the membrane reactors are modelled heterogeneously based on the mass and energy conservation laws considering a detailed thermal and catalytic kinetic model. To prove the accuracy of the considered model and assumptions, the simulation results of the conventional process are compared with the plant data. In addition, the genetic algorithm as a powerful method in the global optimization is applied to maximize the styrene production. The temperature of feed and sweep gas streams are attainable decision variables due to severe effect of temperature on the equilibrium and kinetic constant. This configuration has enhanced styrene production rate about 9.98 % compared to the industrial adiabatic reactor.

Maximizing olefin production via steam cracking of distilled pyrolysis oils from difficult-to-recycle municipal plastic waste and marine litter

In recent years, first principles periodic Density Functional Theory (DFT) calculationhas been used to investigate heterogeneous catalytic reactions and examine catalyststructures as well as adsorption properties in a variety of systems. The increasingcontribution to give detailed understanding of elementary reaction mechanism is critical toprovide fundamental insights into the catalyst design. It is a link to the fundamentalknowledge and a bridge to the practical application. DFT calculations is also a powerfultool to predict and yield promising catalysts which is time- and cost-saving in the practicalend.Because of the recent boom in natural shale gas deposit, there is an increasing interestin developing more efficient ways to transform light alkanes into desired and high-valuechemicals, such as propylene. Propylene is a valuable raw material in the petrochemicalapplication to make value-added commodities, such as plastics, paints, and fibers, etc. Theconventional cracking, steam cracking (SC) and fluid catalytic cracking (FCC), could notmeet the growing demand of propylene. Thus, it has motivated extensive research ofproduction technologies. On the other hand, the abundance of light alkanes extracted fromthe shale gas makes on-purpose production an appealing method which is economicallycompetitive. Non-oxidative dehydrogenation of propane (PDH) is a one of ways to makeup the supply and solve the issue.xiiiAccording to the current research and industrial work, platinum (Pt) shows promisingperformance for the PDH. However, it suffered from some major drawbacks, such asthermodynamic limitation, rapid deactivation leading to poor catalytic performance andfrequent regeneration. In addition, it is a relatively high cost noble metal. Consequently,many efforts have been devoted to the enhancement of the catalytic performance. It wasfound that the stability and the selectivity of Pt-based catalysts can be improved viamodifying its properties with transition metals as promoters.In this thesis, DFT calculations were performed for propane dehydrogenation overtwo different catalyst systems, bimetallic platinum-zinc alloy and monometallic platinumcatalysts. The work provides insights into the catalyst crystal structures, the adsorptioncharacteristics of diverse adsorbates as well as the energy profiles regarding to theselectivity of the propane dehydrogenation. Bulk calculation signifies a stable tetragonalconfiguration of the PtZn catalyst which is in accordance with the experimental result. Thethermodynamic stability regarding to the stability of bulk and surface alloys are studiedwith the consideration of physical constrains. We have identified the thermodynamicstability of several PtZn low-index surface facets, (101), (110), (001), (100) flat surfacesand stepped surface (111), at certain chemical potential environmental conditions throughthe surface energy phase diagram. Stoichiometric and symmetric (101) slab isthermodynamically stable under the region of high Pt chemical potential, and the offstoichiometricand symmetric (100 Zn-rich) slab under the low Pt chemical potential.In this work, PtZn(101) is used as a model surface to demonstrate the effect on thecatalytic performance with zinc promotion of platinum. In comparison with Pt(111) surface,an elimination of 3-fold Pt hollow site on PtZn(101) is of important and it leads to thexivchange of binding site preferences. The divalent groups (1-propenyl, 2-propenyl) changefrom Pt top site on PtZn(101) to 3-fold site on Pt(111), which is because of the lack of Pt3-fold site on alloyed surface. As for propylene, it changes from di-σ site on PtZn to 𝜋 siteon Pt. The surface reaction intermediates are found to bond more weakly on PtZn(101)than on the Pt surface. Especially, the binding energy of propylene reduces from -1.09 to -0.16 eV. The weaker binding strength facilitates the activity of propylene on alloyedsurfaces.Through a complete and classic reaction network analysis, the introduction of Znshows an increase in the endothermicity and the energy barrier of each elementary reactionon the alloy surface. With the consideration of entropy for kinetic under real experimentalcondition, the alloying of Zn is found to lower the energy barrier for the propylene productdesorption and increases that for propylene dehydrogenation. Meanwhile, the competitionbetween desired C-H and undesired C-C cleavages is investigated. It is found that thecleavage of C-H is energetically favorable than that of C-C. These positive factorspotentially lead to a high selectivity toward propylene production on PtZn(101).Subsequently, Microkinetic modeling is performed to estimate kinetic parametersincluding the reaction order, rate-determining step to build a possible reaction mechanism.Finally, conclusions brought out about the comparison between bimetallic andmonometallic catalyst, and suggestions for future work are presented.

Nanocasted oxides for oxidative dehydrogenation of ethylbenzene utilizing CO 2 as soft oxidant

Dehydrogenation of ethylbenzene and propane over Ga2O3–ZrO2 catalysts in the presence of CO2

Optimal design of ethylene and propylene coproduction plants with generalized disjunctive programming and state equipment network models

The mathematical model for multicomponent diffusion in styrene production is given considering all six reactions involved in styrene production. The diffusion coefficients for catalyst pellet are calculated for unimodal and bimodal pore size distributions using trapezoidal rule of integration. The effects of standard deviation and average pore size on the diffusion coefficient are determined. The differential equations are converted to algebraic equations and solved by the orthogonal collocation method. The effectiveness factor of catalyst pellet in styrene production is calculated for various pore sizes. It is seen that the average pore size and pore size distribution affects the production rate and effectiveness factor significantly.