Applied Petrochemical Research (v.8, #4)

Old Port Harcourt Refinery; capacity 60,000 bpsd commissioned in 1965.Warri Refining and Petrochemical Company; capacity 125,000 bpsd commissioned in 1978.Kaduna Refining and Petrochemical Company; capacity 110,000 bpsd commissioned in 1980.New Port Harcourt Refinery; capacity 150,000 bpsd commissioned in 1989.Thus, the total installed capacity is 445,000 bpsd. These plants in the last 15–20 years had a poor operating record with average capacity utilization hovering between 15 and 25% per annum. As a result, 70–80% of the national petroleum products demand is met through import. As at 2017, the aggregate demand of petroleum products in Nigeria was equivalent to 750,000 bpsd. Hence, there is ample scope for investment in new plants and revamp of the existing ones to make them more efficient. This paper traces the history of refining in Nigeria, highlights the current poor record of capacity utilization, proffers solutions for improving their viability, and presents prospects for growth of the industry in Nigeria.
Keywords: Capacity utilisation; Governance; Pipeline vandalisation; Turnaround maintenance

An extensive literature review of the mechanistic modeling of n-heptane and cyclohexane pyrolysis was carried out. It was shown that Rice–Kossiakoff free radical theory does not adequately account for product distributions of n-heptane pyrolysis in the high conversion regime. Secondary reactions of alpha higher olefins and di-olefins accounted for the major products (ethene, propene and 1-butene) of n-heptane pyrolysis. Predicted product distributions (CH4, C2H4, C3H6, 1-C4H8 and 1,3-C4H6) of n-heptane pyrolysis showed very good agreement with experimental data. The product distributions of cyclohexane pyrolysis in the high conversion regime were rationalized and adequately accounted for using decomposition reactions of cyclohexyl bi-radicals followed by secondary reactions of major primary products such as C3H6 and 1,3-C4H6. The latter expanded mechanism can be used to model cyclohexane pyrolysis in the high conversion regime. Rate parameters (pre-exponential factors and activation energy) for each of the elementary reactions of n-heptane mechanistic model were either obtained from the literature or estimated using thermochemical parameters. The use of steady state approximation in mathematical modeling of n-heptane pyrolysis led to erroneous results.
Keywords: Hydrocarbons; Pyrolysis; Modeling; Radical reactions

Catalytic pyrolysis of waste polypropylene using Ahoko kaolin from Nigeria by Ibrahim Gbolahan Hakeem; Folorunsho Aberuagba; Umaru Musa (203-210).
The aim of this study is to convert polypropylene waste into usable liquid fuel via pyrolysis technique using kaolin as a low-cost catalyst. Waste polypropylene was thermally and catalytically degraded in a chemical vapour deposition (CVD) horizontal glass reactor at a temperature of 450 °C, residence time of 30 min, and heating rate of 30 °C/min. The kaolin clay was characterized by XRF analysis while the ultimate and proximate analysis of the polypropylene feed carried out gave combustible materials content of 93.77 wt%, fixed carbon of 1.62 wt%, calorific value of 45.20 MJ/kg and elemental composition with carbon (83.65%), hydrogen (14.27%), oxygen (0.15%), sulphur (0.1%), chlorine (1.16%), and nitrogen (0.67%). Thermal cracking was carried out in the absence of catalyst and the process gave a yield of liquid, gaseous, and solid products of 67.48, 8.85, and 23.67 wt%, respectively. Furthermore, kaolin clay was employed as a catalyst in catalytic pyrolysis of the same feedstock for catalyst-to-plastic ratio of 1:1, 1:2, 1:3, and 1:4 at the same operating parameters as in thermal cracking. Optimum yield was obtained at a catalyst-to-plastic ratio of 1:3 with a yield of 79.85, 1.48, and 18.67 wt% for liquid, gaseous, and solid products, respectively. The liquid products obtained for both thermal and catalytic cracking at optimum conditions were characterized for their suitability as fuel. The properties determined were density, viscosity, flash point, fire point, pour point, and calorific value. The results suggest that catalytic pyrolysis produced liquid products, whose properties are comparable to conventional fuels (gasoline and diesel oil) than that produced through thermal pyrolysis. FTIR analysis of the liquid product from catalytic pyrolysis also shows that it contains hydrocarbons with different functional groups such as aromatics, olefins, carbonyl, amines, sulphides, and hydroxyl.
Keywords: Pyrolysis; Waste polypropylene; Ahoko kaolin; Nigeria

Catalytic cracking of polyethylene plastic waste using synthesised zeolite Y from Nigerian kaolin deposit by Abosede A. Ajibola; James A. Omoleye; Vincent E. Efeovbokhan (211-217).
The increasing rate of accumulation of plastic waste (PW) is quite disturbing to the world, particularly in developing nations due to its non-biodegradable nature and inadequate waste management practices. The need to properly manage this waste and utilize the potential and chemical energy value that can be derived from this waste justifies the encouragement and employment of newer and better recycling methods and technology of these wastes. Therefore, this has led us to explore the catalytic pyrolysis of plastic waste using zeolite Y synthesized from kaolin deposit in Covenant University, Sango Ota, Ogun state of Nigeria. A stainless steel packed bed reactor was used in the cracking of low-density polyethylene (LDPE) plastic wastes into liquid fuel components at a temperature of 300 ℃ using zeolite Y catalyst. The liquid fuel obtained from the catalytic pyrolysis was analyzed using GC–MS. Fifty compounds were identified, which revealed the presence of mostly alkenes and aromatics in the hydrocarbons range of C8–C29. This is made up of 56% of gasoline fractions range of C6–C12, 26% of diesel and kerosene fractions range C13–C18, and 10% of fuel oil range C18–C23, while 8% is residual fuel range greater than C24.
Keywords: Polyethylene (PE); Catalytic cracking; Pyrolysis; Zeolite Y; GC–MS

Modelling and simulation of an industrial RFCCU-riser reactor for catalytic cracking of vacuum residue by Olaosebikan Abidoye Olafadehan; Opeyemi Praise Sunmola; Adeleke Jaiyeola; Vincent Efeovbokhan; Olubunmi Grace Abatan (219-237).
A one-dimensional adiabatic mathematical model was developed for the riser reactor of an industrial residue fluid catalytic cracking unit (RFCCU). A seven-lump kinetic model was presented for the catalytic cracking of vacuum residue, taking cognisance of diffusion resistance, which is a departure from the general norm in the literature. Also, heat transfer resistance between the fluid and solid phases was incorporated into the energy balances for instantaneous and one-dimensional vaporization of feedstock. The developed model was a set of twelve coupled, highly non-linear and stiff ordinary differential equations, ODEs, which was numerically solved with an implicit MATLAB built-in solver, ode23t, designed deliberately for handling stiff differential equations to circumvent the problem of instability associated with explicit methods. An excellent agreement was achieved between the industrial RFCCU plant data and the simulated results of this study, with average absolute deviation being < ± 5% for instantaneous vaporization of feedstock in all cases investigated. Moreover, the simulated results revealed that half of the reactor was relatively redundant as this accounted for only 3% of the conversion. Hence, the findings of this study could be useful to the production practice for the Khartoum Refinery Company.
Keywords: Adiabatic; RFCCU-riser reactor; Catalytic cracking; Seven-lump; Diffusion resistance; ode23t

Oxy-dry reforming of propane over Ce-promoted Co–Ni/Al2O3 catalyst by Faisal M. Althenayan; Adesoji A. Adesina (239-251).
This paper reports the production of syngas from two types of O2-assisted dry reforming of propane, namely oxidative (O2-dosed) dry reforming (ODR) and dry (CO2-dosed) partial oxidation (DPOX). Reaction runs were conducted over alumina-supported bimetallic Co–Ni promoted with CeO2 at 120 kPa and 793–893 K. Ceria promotion improved the carbon deposition resilience of the Co–Ni catalyst. Physicochemical attributes were obtained from liquid N2 adsorption, H2 chemisorption and temperature-programmed desorption runs for NH3, CO2, CH4 and C3H8. Rate behavior under ODR, DPOX and pure dry reforming could be described consistently with empirical models that are structurally similar to Langmuir–Hinshelwood type relations. Inferences from these models allowed the postulation of the same overall reaction network for the three types of reactions albeit with variation in rate-controlling steps depending on the different product species. On the whole, DPOX seemed to be a superior option for the manufacturing of syngas for downstream olefin FT production due to reduced variability in the H2:CO ratio and the closeness to unity (0.72–0.95) of the exiting syngas over the range of O2 partial pressure used.
Keywords: Dry reforming; Partial oxidation; Propane; Ceria promotion; Syngas; Co–Ni catalyst

Ethylene glycol dry reforming for syngas generation on Ce-promoted Co/Al2O3 catalysts by Lau N. Jun; Mahadi B. Bahari; Pham T. T. Phuong; Nguyen Huu Huy Phuc; Chanatip Samart; Bawadi Abdullah; H. D. Setiabudi; Dai-Viet N. Vo (253-261).
Ethylene glycol dry reforming (EGDR) was investigated for the first time on 10% Co/Al2O3 and 3% Ce–10% Co/Al2O3 catalysts at stoichiometric feed composition under atmospheric pressure and 923–998 K for syngas production. Catalysts were characterized using BET, H2-TPR, XRD and Raman spectroscopy measurements. The addition of Ce promoter eased the reduction of Co3O4 with lower reduction temperature and enhanced metal dispersion. Ce promotion also improved EGDR performance by increasing reactant conversions, syngas yields and reducing undesirable methane formation. The conversion of ethylene glycol and H2 yield reached up to 71.7% and 69.3%, respectively.
Keywords: Ethylene glycol; Dry reforming; Co-based catalysts; Syngas; Ce promoter; Hydrogen

Dry reforming of methane for syngas production over Ni–Co-supported Al2O3–MgO catalysts by Nur Azeanni Abd Ghani; Abbas Azapour; Syed Anuar Faua’ad Syed Muhammad; Nasser Mohamed Ramli; Dai-Viet N. Vo; Bawadi Abdullah (263-270).
This research project focuses on the development of catalysts for syngas production by synthesizing Ni–Co bimetallic catalyst using aluminum oxide (Al2O3) and magnesium oxide (MgO) as the catalyst support. Ni/Al2O3 (CAT-1), Ni–Co/Al2O3 (CAT-2) and Ni–Co/Al2O3–MgO (CAT-3) nanocatalysts were synthesized by sol–gel method with citric acid as the gelling agent, and used in the dry reforming of methane (DRM). The objective of this study is to investigate the effects of Al2O3 and MgO addition on the catalytic properties and the reaction performance of synthesized catalysts in the DRM reactions. The characteristics of the catalyst are studied using field emission scanning electron microscope (FESEM), Brunauer–Emmett–Teller (BET), X-ray powder diffraction (XRD), transmission electron microscopy, H2-temperature programmed reduction, CO2-temperature programmed desorption and temperature programmed oxidation analysis. The characteristics of the catalyst are dependent on the type of support, which influences the catalytic performances. FESEM analysis showed that CAT-3 has irregular shape morphology, and is well dispersed onto the catalyst support. BET results demonstrate high surface area of the synthesized catalyst due to high calcination temperature during catalysts preparation. Moreover, the formation of MgAl2O4 spinel-type solution in CAT-3 is proved by XRD analysis due to the interaction between alumina lattice and magnesium metal which has high resistance to coke formation, leading to stronger metal surface interaction within the catalyst. The CO2 methane dry reforming is executed in the tubular furnace reactor at 1073.15 K, 1 atm and CH4/CO2 ratio of unity to investigate the effect of the mentioned catalysts. Ni–Co/Al2O3–MgO gave the highest catalyst performance compared to the other synthesized catalysts owning to the strong metal–support interaction, high stability and significant resistance to carbon deposition during the DRM reaction.
Keywords: Catalyst development; Dry reforming; Bimetallic catalysts; Catalysis; Sol–gel; Support

Determination of limit of stability profiles for liquefied natural gas: a thermodynamic approach by Faith Uchenna Babalola; Wasiu Emmanuel Ogunkoya (271-280).
Efficient design, operation, handling, and transportation of natural gas as liquefied natural gas (LNG) are controlled by its phase behavior. A phase, in a non-reacting system, is known to be stable when it is at its lowest Gibbs energy; an alternative criterion to the minimization of the Gibbs energy is presented for phase stability status determination of pure systems and mixtures. On this premise, the stability limit determination method by the Helmholtz stability criterion was employed for the determination of stability limits which were used to successfully generate stability limit profiles for LNG and its constituents. To further investigate the metastable region, a new and robust model was developed and successfully used to produce vapor and liquid spinodals as well as binodal curves for the LNG constituents. The model accurately predicted the critical points and was shown to be in very close agreement with the available predicted and experimental results.
Keywords: Stability limit; Phase envelop; LNG; Spinodal; Binodal; Equation of state

Grid design and numerical modeling of multiphase flow in complex reservoirs using orthogonal collocation schemes by Olaosebikan Abidoye Olafadehan; Kingsley Eromosele Abhulimen; Moses Anubi (281-298).
An advanced grid system design was developed to capture accurately the effects of geometrically complex features such as geological features (faults, pinch outs and inclined beddings) and well-related phenomenon (multilateral wells of general orientation) in triangular coordinates. Modeling these effects can have significant impact on the accuracy of the simulation and prediction of reservoir performance as well as reservoir fluid flow using conventional grid designs. The finite difference method provides additional difficulty in capturing geological features in typical reservoir flow and grid model simulators. Hence, the orthogonal collocation method was used for simulating multiphase reservoir flow equations in triangular curvilinear coordinates $$left[ {xi left( r ight),xi left( heta ight),xi left( z ight)} ight]$$ ξr,ξθ,ξz of domain [0,1] that were derived from Cartesian coordinates $$left( {x,y,z} ight)$$ x,y,z . This was to accommodate general three-dimensional deviated wells and complex reservoir geometry for multiphase flow of hydrocarbon in complex reservoir formations. Based on preliminary field data obtained from multinational oil and gas operator in Nigeria, the proposed model was used to predict saturation, production and petroleum productivity with time and distance in a MATLAB environment. The simulated plots revealed that pressure is parabolic at the center of the reservoir with coordinates $$xi (r) =0.4257$$ ξ(r)=0.4257 , reflecting the impact of geological features in the pressure and production flow performance.
Keywords: Multiphase flow; Complex reservoir systems; Orthogonal grids; Triangular coordinates

Kinetics and mechanism of heterogeneous transesterification reaction of African pear seed oil (APO) catalyzed by phosphoric acid-activated kaolin clay to produce biodiesel were investigated. Heterogeneous catalyst synthesized by activating clay with phosphoric acid was used to examine the effect of time, temperature, methanol/oil molar ratio, catalyst concentration and agitation speed on the production of biodiesel. The kinetics was studied using two elementary reaction mechanisms: Eley–Rideal (ER) and Langmuir–Hinshelwood–Hougen–Watson (LHHW). The results obtained showed that the clay belongs to kaolinite group and acid-activated clay catalyst, AAC was able to convert APO to standard biodiesel with the variation of catalyst concentration, temperature methanol, speed and reaction time having significant effect in the production. About 78–80% biodiesel production was obtained with 10:1 methanol/oil molar ratio, 3 wt% AAC catalyst concentration, time 3 h, speed 300 rpm and at 60 °C temperature. The kinetics result revealed that the LHHW is the most reliable representation of the experimental data using acid-activated clay catalyst with surface reaction between adsorbed triglyceride and adsorbed methanol as rate determining step (RDS). The activation energy for the forward reaction was determined to be 10.08 kJ/mol. Hence, the production of biodiesel from non edible oil APO with cheap and available heterogeneous catalyst (AAC) is achievable.
Keywords: Clay; African pear seed oil; Langmuir–Hinshelwood–Hougen–Watson; Eley–Rideal; Heterogeneous catalyst