ADSORPTION ISOTHERMS AND CATALYST SELECTIVITY FOR A UNIFORM SURFACE: THE ROLE OF MULTIPLE LANDING AREAS

In general a gas phase species can be present simultaneously in more than one adsorbed form on a uniform solid surface. The different adsorbed forms tie up different combinations of surface sites. Each such combination is termed a landing area. The different adsorbed forms present on the surface of a catalyst may form different products. (In the more general case, each different adsorbed form yields a different distribution of a set of products.) Hence the relative amount of each adsorbed form and landing area present on the surface determines the selectivity of the solid catalyst. The variation of the landing area distribution with temperature and partial pressure of the gas phase species is examined in the first part of this work. In general, increasing the pressure or decreasing the temperature leads to the relative decrease of molecules adsorbed on landing areas consisting of larger number of sites and the relative increase of molecules adsorbed on smaller landing areas. The kinetics of metal catalyzed skeletal isomerization and hydrogenoly-sis of hydrocarbons on supported metal catalysts is examined in the framework of the landing area in the second part of this work. A simple model for the variation of reaction order with pressure agrees with experimental data from other laboratories.     

Gel-strength in Restructured Potato Products Affects Oil Uptake during Deep-fat frying

A controllable food system consisting of a restructured potato product was employed to study the effect of gel-strength on oil uptake. Water loss and oil uptake were affected markedly by gel-strength. Oil uptake decreased as gel-strength increased. The oil uptake ratio, U_R′ (weight ratio of the oil uptake to the water evaporated during frying) was utilized to assess the effectiveness of reducing oil absorption during frying. This criterion was useful for comparison of restructured potato products with different initial or final moisture contents.     

Effect of Pretreatment on the Cooking Time of the African Yam Bean (Sphenostylis sternocarpa)

The effect of soaking in tap water, 1% potash, and 4% sodium chloride for different periods on the cooking time of African Yam Bean was studied. The results showed that 12 hr soaking was adequate for the beans to reach maximum hydration, and that pretreatment of the beans before cooking appreciably influenced the overall cooking time. Cooking after pretreatment for 12 hr in 1% potash or in 4% sodium chloride reduced the normal cooking time by 50%.     

SIMULATION, SHELTERS, AND SUBJECTS.

DESCRIBES "A NAVY FALLOUT AND BLAST-SHELTER TRIAL IN MAY OF 1963, WHICH MAY HAVE A BEARING ON CURRENT PUBLIC CONCERN REGARDING . . . ." EXPERIMENTS INVOLVING HUMAN SS. FACTORS CONSIDERED ESSENTIAL TO THE SUCCESSFUL COMPLETION OF THE STUDY ARE DISCUSSED IN ORDER TO "INVITE THE ATTENTION OF . . . COLLEAGUES TO THE DETAILS OF S PROCUREMENT, HANDLING, AND UTILIZATION IN A RESEARCH EFFORT WHICH CONTAINED MANY POTENTIAL PITFALLS AND DANGERS . . . .(IT IS FELT THAT) THE UNDERLYING ISSUES RELATED TO RESEARCH OF THIS NATURE WILL BECOME OF GREATER VISIBILITY AND SOCIAL IMPORTANCE IN THE FUTURE . . . ." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

OPTIMUM DESIGN OF ZEOLITE/SILICA-ALUMINA CATALYSTS

An analysis of the rate of formation of the desired product and of the selectivity has been carried out for composite catalysts wherein small particles of zeolite are distributed nonuniformly within a large particle of the more porous silica-alumina. Two nonuniform distributions have been analyzed, namely, (i) the composite-center distribution, where a uniform dilute region of zeolite in silica-alumina is surrounded by a silica-alumina matrix, and (ii) the composite-surface distribution, where a uniform dilute region is located around the pure silica-alumina matrix. Two reaction schemes, A→B→C and A→C→D, which fairly approximate the catalytic cracking process over the Zeolite/silica-alumina catalyst have been examined. The reaction scheme A→B→C is employed for the composite-center distribution, while the reaction scheme A→C→D is considered for the composite-surface distribution, because the overall rate of formation of the desired product can be thus optimized. There are conditions under which the selectivity can also be optimized

It is shown that for both nonuniform distributions, the rate of formation of the desired component can exhibit, for appropriate values of the parameters, a maximum with respect to both the overall volume fraction of silica-alumina and the ratio of the radius of the core region to that of the catalyst pellet. Finally, the analysis shows that the rate of formation of the desired compound and the selectivity can be greater for the nonuniform distributions than the uniform distribution when the two contain the same amount of zeolite.     

A SIMPLE ALGEBRAIC METHOD FOR OBTAINING THE HEAT OR MASS TRANSFER COEFFICIENTS UNDER MIXED CONVECTION

Many processes of practical interest involve mass or heat transfer under the influence of mixed convective flows, such as combined forced and buoyancy-induced flows or magneto-convective flows. In general, the solution of the appropriate transport equations under these conditions is very difficult. In this paper, a simple ‘algebraic’ method based on an order-of-magnitude analysis of the governing transport equation is presented and has been used to obtain the Nusselt and Sherwood numbers for heat and mass transfer from vertical plates, for the heat or mass transfer entrance region in internal flows, for magneto-convective heat transfer from flat plates and for transport from cylinders and spheres in the presence of mixed convective flows. The present method provides expressions that are in excellent agreement with available experimental data and numerical solutions.     

PHYSICOCHEMICAL CHANGES IN STARCH DURING DEEP-FAT FRYING OF A MOLDED CORN STARCH PATTY

Corn starch patties with an initial moisture content of 46.5% (wet basis) were fried in oil at 165C. The results indicated that oil content in the patty ranged from 10.6 to 12.5% in the crust region, and 1.5 to 3.9% in the core region. Starch gelatinization was significantly dependent on frying time and location of starch in the patty. Both, water absorption and water solubility indices of starch increased with frying time, with the starch contained in the crust exhibiting much higher water absorption ability and water solubility than that contained in the core region. Measurements of 'blue value'(the intensity of blue color of starch solution upon addition of iodide ion) and the absorbance spectra of starch samples indicated that amylose-lipid complexes were present in the fried materials. The degree of starch complexation was 10.9 to 13.2% in the crust and 0.3 to 6.6% in the core region. The puncture force on the surface of a food fried for no more than 5 min was close to that in the food center, although a significant increase in force was required for the crust region during the later stages of frying.     

Criterion for Oil Uptake during Deep-fat Frying

The effect of added powdered cellulose and methyl cellulose on oil uptake during deep-fat frying of donuts and falafel balls was determined. A new criterion, U_R, expressing the oil uptake ratio between the weight of oil uptake and the weight of water removed was introduced. This criterion was valuable in assessing effectiveness of reducing oil uptake during deep-fat frying. Methocel was significantly more effective than powdered cellulose in reducing oil uptake.     

吐鲁番无核白葡萄晾房干燥的预处理方法

为提高吐鲁番地区无核白葡萄晾房干燥速率及品质,获取较优的晾房干燥预处理工艺,在吐鲁番高昌区克 孜里土尔村开展了晾房干燥实验。晾房中挂串实验样本组设1 个对照组和3 个预处理组,采集干燥过程中晾房温湿 度、风速、葡萄含水率及葡萄RGB图像等数据,采用Matlab软件分析葡萄RGB图像,获得外部品质特征,采用统计 方法绘制无核白葡萄干燥过程中含水率和色度变化趋势图,以及对比不同预处理方式下葡萄干成品品质指标,确定 了较优的晾房干燥预处理方式。结果表明：与未经预处理的对照组相比,经质量分数3.0%的促干剂预处理的无核 白葡萄干燥时间缩短了6 d;干燥过程中葡萄表面色度变化较为平稳,且成品的褐变率降低了67%,绿级率提高了 20.5%;综合分析各项指标,该处理优于其他预处理,最终确定其为晾房干燥较优的预处理方式;此外,实验确定 橄榄油具有提高葡萄干燥绿级率的作用。