Modeling of molecular weight distribution of gas-phase polymerization of butadiene

2003 ◽  
Vol 88 (1) ◽  
pp. 88-103 ◽  
Author(s):  
Dongyu Fang ◽  
Jianzhong Sun ◽  
Qiyun Zhou
Keyword(s):  
Molecular Weight ◽  
Gas Phase ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Gas Phase Polymerization

Controlling the Polyethylene Molecular Weight Distribution Using Hydrogen Influent

2010 ◽  
Author(s):  
Emad M. Ali ◽  
Mohammad Al-haj Ali
Keyword(s):  
Molecular Weight ◽  
Gas Phase ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Ethylene Polymerization ◽  
Control Algorithm ◽  
Successful Implementation ◽  
Model Predictive Controller ◽  
Control Objective ◽  
Predictive Controller

This paper addresses the feasibility of controlling the entire molecular weight distribution of the produced polymer in gas-phase ethylene polymerization reactors. Nonlinear model predictive controller is used to attain the control objective by utilizing the hydrogen feed rate as the only manipulated variable. The use of other manipulated variables is limited to avoid disturbing the process when influential inputs such catalyst and/or monomer inflows are used. The simulation results indicated successful implementation of the control algorithm to achieve the desired molecular weight distribution. The success depends on the improved hydrogen activities inside the reactor through a modified catalyst that is responsive to hydrogen variation and a wider admissible range of hydrogen feed rates.

Extraction and Partial Purification of Protease from Bilimbi (Averrhoa bilimbi L.)

2013 ◽  
Vol 10 (2) ◽  
pp. 29
Author(s):  
Normah Ismail ◽  
Nur' Ain Mohamad Kharoe
Keyword(s):  
Molecular Weight ◽  
Protein Content ◽  
Ammonium Sulfate ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Protease Activity ◽  
Protein Concentration ◽  
Temperature Stability ◽  
Partial Purification ◽  
Ammonium Sulfate Precipitation

Unripe and ripe bilimbi (Averrhoa bilimbi L.) were ground and the extracted juices were partially purified by ammonium sulfate precipitation at the concentrations of 40 and 60% (w/v). The collected proteases were analysed for pH, temperature stability, storage stability, molecular weight distribution, protein concentration and protein content. Protein content of bilimbi fruit was 0.89 g. Protease activity of both the unripe and ripe fruit were optimum at pH 4 and 40°C when the juice were purified at 40 and 60% ammonium sulfate precipitation. A decreased in protease activity was observed during the seven days of storage at 4°C. Molecular weight distribution indicated that the proteases protein bands fall between IO to 220 kDa. Protein bands were observed at 25, 50 and 160 kDa in both the unripe and ripe bilimbi proteases purified with 40% ammonium sulfate, however, the bands were more intense in those from unripe bilimbi. No protein bands were seen in proteases purified with 60% ammonium sulfate. Protein concentration was higher for proteases extracted with 40% ammonium sulfate at both ripening stages. Thus, purification using 40% ammonium sulfate precipitation could be a successful method to partially purify proteases from bilimbi especially from the unripe stage. 

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