Emissions of nitrogen oxides such as NO and NO2, which are commonly known as NOx, are threats to human existence and cause environmental problems. Mainly, two techniques have been developed to drastically reduce these emissions, which are dry and wet processes. The wet process has several advantages, major identifiable advantages are the adaptability to the flue gas, low operating temperatures and no poisoning and inactivation catalyst. Also, a mixture of hydrogen peroxide and nitric acid are used as absorbents solution for NOx reduction in the wet process. The advantages of using this mixture include the ability to reduce the negative effect of NOx and does not contaminate the scrubbing solution. In addition, nitric acid has an economical advantage in the process considering the fact that it is produced in the process. Finally, it can be conducted at ambient temperature. This study furthermore used a mixture of hydrogen peroxide and nitric acid solutions as an absorbent to reduce NOx in hollow fiber membrane modules. The hydrogen peroxide oxidized HNO2 to nitric acid, while enhances the oxidation through an autocatalytic reaction. The effects of the feed gas flow rate, hydrogen peroxide concentrations and number of fibers on the NOx reduction, absorbed NOx and flux were varied to study. The experimental results showed that the increase in the feed gas flow rate from 100 to 200 mL/min decreased NOx reduction from about 98 to 94% but increased the absorbed NOx and flux from about 0.13 to 0.255 mmol/h and 0.85–1.63 mmol/m2.h, respectively The increase in proportion of NOx in the feed gas effect was dominant than the increase in absorbed NOx. An increase in hydrogen peroxide concentration from 0.5 to 10 wt.% in the absorbent solutions increased NOx reduction, absorbed NOx and flux from about 94 to 98%, 0.257–0.267 mmol/h and 1.09–1.13 mmol/m2.h, respectively. Additionally, the H2O2 plays an important role in enhancing HNO2 oxidation to HNO3. Furthermore, an increase in the number of fibers from 50 to 150 in the membrane module increased NOx reduction and absorbed NOx from 86 to 97% and 0.23–0.27 mmol/h. Flux decreased from 2.98 to 1.13 mmol/m2.h due to increment in the gas-liquid contact surface area.

As a type of gas that contributes to air pollution, nitrogen oxide (NOx) has harmful effects on humans and the environment. Among several types of NOx, nitric oxide (NO) and nitrogen dioxide (NO2) are most commonly found in air. The utilization of membranes as reactors is a system that combines chemical reactions with the separation process through membranes to increase the conversion of the reaction. This study investigated the absorption process by utilizing a hollow fiber membrane module (polysulfone) as a bubble reactor with H2O2 (0.5 wt.%) and HNO3 (0.5M) as the absorbent. NOx feed gas was flown into the tube side of the membrane; the shell side was filled with static H2O2 and HNO3 and the shell input and the tube output flow were closed to create gas bubbles. The experimental results showed that the absorption efficiency increased, but the mass transfer coefficient and flux decreased as the number of fibers in the membrane module increased at the same feed gas flow rate. The NOx loading is relatively constant as the amount of fiber in the membrane module increased at the same feed gas flow rate. The experimental results also showed that the mass transfer coefficient, flux, and NOx loading increased with increasing feed gas flow rate, but the absorption efficiency decreased when using the same number of fibers in the membrane module. The maximum NOx absorption efficiency achieved in this study was 94.6% at the feed gas flow rate of 0.1 L/min, using a membrane module with 48 fibers.

The purpose of this research is the synthesis of alkyl esters from CPO through transesterification reaction using catalyst CaO-MgO. This experimental laboratory research through stages: (1) CPO refinement, (2) determination of CPO free fatty acid numbers, (3) activation of CaO-MgO catalysts, (5) synthesis of alkyl esters from CPO with alcohol (methanol and ethanol), (6) identification of the components of synthesized alkyl ester using GC-MS,characterization of alkyl esters including density, viscosity, refractive index and acid number test. The results showed that (1) alkyl esters can be synthesized from CPO through the transesterification reaction with methanol and CaO-MgO catalysts with a yield of 85.72%, while the transformation of ethanol is difficult to form ethyl ether (2) the character of methyl ester: density 0.86 g/mL, viscosity 3.23 cSt, refractive index 1.44819, and acid number 0.747 mg KOH/g methyl ester, (3) the main component of the synthesized alkyl ester contains 1.20% methyl myristic compound, methyl palmitate 40.637% methyl linoleate 9.332%, methyl 7-octadecenoate 42.986%, and methyl stearate 4.427%.

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