Shaker Haji

Investigation of rhodium catalyzed hydroformylation of ethylene in supercritical carbon dioxide by in situ FTIR spectroscopy

Abstract The reactions of RhH(CO)L 3 (L=P(3,5-(CF 3 ) 2 C 6 H 3 ) 3 ) with CO, H 2 , C 2 H 4 and mixtures of these in supercritical carbon dioxide (scCO 2 ) were investigated using high-pressure FTIR spectroscopy. The results were compared to the behavior of the conventional catalyst, RhH(CO)(PPh 3 ) 3 , in organic solvents. RhH(CO)L 3 does not dissociate in scCO 2 and it is converted to RhH(CO) 2 L 2 and to [Rh(CO) 2 L 2 ] 2 in the presence of CO and mainly to RhH(CO)L 2 in the presence of an equimolar mixture of CO and H 2 . In the presence of CO and C 2 H 4 , the peaks observed in the acyl region and the terminal metal carbonyl region indicate the formation of three different acylrhodium complexes which are Rh(CO)L 2 (COEt), Rh(CO) 2 L 2 (COEt), and Rh(CO) 3 L(COEt). Similar species were also observed during the hydroformylation reaction. The first ever detection of the presence of Rh(CO)L 2 (COEt) under hydroformylation conditions provides direct evidence for the mechanism originally proposed by Wilkinson and co-workers. The carbonyl stretching frequencies of all of the rhodium–carbonyl species are shifted to higher wavenumbers due to a reduction of electron density at the metal center by the CF 3 groups.

Fuels and Fuel Processing

H2 is an ideal fuel for fuel cells (FCs) because of its high reactivity and zeroemission characteristics. Unfortunately, H2 is not easily available, and neither its production nor distribution infrastructure are widely spread. Therefore, development of technologies for production of H2 onboard and onsite from other sources such as natural gas, methanol, and gasoline is necessary. In the next section, different feedstocks that are suitable for H2 production for fuel cell application are presented. Subsequent sections focus on reforming of hydrocarbons that are processed by a series of steps that include fuel desulfurization, reforming, water-gas shift reaction and carbon monoxide (CO) removal [1,2,3,4]. Figure 5.1 illustrates what is known as the fuel processing train with some options for the essential steps. This general fuel processing train is usually used for PEM fuel cells running on fossil fuels such as natural gas. The processing steps that the feedstock are subjected to depend on the type of the fuel and the fuel cell. For example, if methanol is the fuel for PAFC, the CO removal step might not be necessary. The last two steps, water-gas shift reaction and CO removal, are not necessary in the case of MCFC. If feedstocks heavier than methane are used as a feed to the SOFC, an additional process step known as prereforming might be used. Such variations are described in more detail in Section 5.3.

Feed-in tariff structure development for photovoltaic electricity and the associated benefits for the Kingdom of Bahrain

ABSTRACT In this study, the feed-in tariff (FIT) scheme was considered to facilitate an effective introduction of renewable energy in the Kingdom of Bahrain. An economic model was developed for the estimation of feasible FIT rates for photovoltaic (PV) electricity on a residential scale. The calculations of FIT rates were based mainly on the local solar radiation, the cost of a grid-connected PV system, the operation and maintenance cost, and the provided financial support. The net present value and internal rate of return methods were selected for model evaluation with the guide of simple payback period to determine the cost of energy and feasible FIT rates under several scenarios involving different capital rebate percentages, loan down payment percentages, and PV system costs. Moreover, to capitalise on the FIT benefits, its impact on the stakeholders beyond the households was investigated in terms of natural gas savings, emissions cutback, job creation, and PV-electricity contribution towards the energy demand growth. The study recommended the introduction of the FIT scheme in the Kingdom of Bahrain due to its considerable benefits through a setup where each household would purchase the PV system through a loan, with the government and the electricity customers sharing the FIT cost.

Performance of a hybrid energy system

A hybrid energy system consisting of a photovoltaic generator (PVG) and a fuel cell generator (FCG) has been interconnected to an AC main supply. The interconnection has been done through two separate bridge rectifiers. The two bridge rectifiers have been operated on a mode called “Inverter Mode of Operation”. The whole integrated or interconnected system has been used to supply an AC load with certain power that is desired to be kept constant without regard to the surrounding insolation or irradiation levels. A maximum power point tracker has been used in conjunction with the PVG module and that is to guaranty the maximum exploitation of the the PVG power and to ease the burden on the fuel cell (FCG) power. Excess energy, generated by the renewable energy system, is pumped to the AC main supply. The performance of the whole system (i.e PVG, FCG, AC main supply, and the pretended AC load) has been assessed using MATLAB/SIMULINK environment. Quite encouraging results were obtained.