A systematic study has been conducted to optimize the process conditions and to evaluate the kinetic parameters for the isomerization reaction of n‐heptane on the novel platinum‐chromium/zirconium‐ hexagonal mesoporous silica (Pt/(CrOx/ZrO2)‐HMS) catalysts (PCZH). The kinetic experiments were performed in a fixed‐bed reactor at the reaction temperatures of 200–350°C, Cr/Zr molar ratio of 5–35, the n‐C7 flow rate of 2–4.5 cc h−1, and H2 flow rate of 20–45 cc min−1. The statistical analysis of all experimental data was carried out using analysis of variance to optimize the operating conditions for n‐heptane reactions. The results show that the incorporation of Cr into the Pt‐Zr‐HMS structure promotes the kinetic rate of the isomerization reaction. Sharp elevation from 0.08 to 0.3 mol g−1 s−1 in the isomerization kinetic rates can be observed in the PCZH(35) and a temperature of 350 °C, when the H2 flow rate increases from 20 to 45 cc min−1 at a constant flow rate of n‐C7 (4.5 cc h−1). The surface and contour plot verifies that the kinetic rate does not significantly vary with respect to studied temperatures and Cr/Zr ratio when the flow rate of isomerization feeds is considerably low. The experimental kinetic rate obtained on the optimum condition is in good agreement with the prediction of the response surface method. The kinetic model of Langmuir–Hinshelwood as well as a power‐law model was developed for this reaction. A reasonably good fit of the obtained data shows that the Langmuir–Hinshelwood model has a better performance to define the isomerization of the n‐heptane process.

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Introduction It is generally believed that heavy metals react with proteins by combining the thiol (-SH) groups, which leads to the inactivation of the proteins (Cho et al., 2005). Silver nano-particles (Ag-NPs) are being used vastly as a strong anti-germ product. In general, Ag ions, which have antimicrobial activity, are used as an antibacterial agent. The antibacterial activity of Ag ions is inhibits intracellular enzyme activity (Cho et al., 2005). Therefore, the other possibility can be considered that remaining Ag ions in Ag-NPs solution or dissolved Ag ions might affect bacterial growth. Recently, dairy farmers have tended to apply this anti-bacterial for sanitization of the environment (as a disinfectant material) of animals. However, the environmental residual effect of this anti-bacterial on ruminant microbial activity is still questionable. In the present study, a gas production technique was applied in order to determine the effect of silver nanoparticles on in vitro gas production of barley grain and lucerne hay. Materials and mthodsThe gas production technique was conducted according to Menke and Steingass (1988) procedure. Rumen fluid was taken from three sheep before the morning feeding and was passed through 4 layers of cheese cloth. Adding of CO 2 gas was continued after the rumen fluid was poured in the syringes. The applied solutions were: Main element solution (5.7 g Na 2 HpO 4 + 6.2 g KHpO 4 + 0.6 g MgSO 4 × 7H 2 O) made up to 1 L with distilled water. Trace element solution (13.2 g CaCl 2 × 2H 2 O + 10.0 g MnCl 2 × 4H 2 O + 1g CoCl 2 × 6 H 2 O + 0.8 g FeCl 2 × 6H 2 O) made up to 100 ml with distilled water. Buffer solution (35 g NaHCO 3 + 4 g (NH 4 )HCO 3 ) made up to 1 L with distilled water. Resazurin solution (100 mg resazurin) was made up to 100 ml with distilled water. Reduction solution: First 2 ml 1N-NaOH and then 285 mg Na 2 S × 7H 2 O were added to 47.5 ml distilled water. Solutions were mixed up in the following order: 474 ml distilled water, 0.12 ml trace element solution, 237 ml buffer solution, 237 ml main element solution and 1.22 ml resazurin solution. Samples (barley grain or lucerne hay) were milled to pass a 2 mm screen. 0.3 g of each sample was placed in gas production syringes. Then, the nanosilver solutions which were prepared in three different dilutes (40,100 and 160 ppm) were added into the syringes (1 ml per each syringe). The treatments were: lucerne hay, lucerne hay + 40 ppm nanosilver, lucerne hay + 100 ppm nanosilver, lucerne hay + 160 ppm nanosilver, barley grain and barley grain + 100 ppm nanosilver. Four replications were run per each treatment. The ratio of rumen fluid to buffer solution was 1:2 (10 ml rumen fluid and 20 ml buffer solution per each syringe). Then, the syringes were incubated in a 39 ˚C pre-heated water bath. The amount of produced gas was determined at 2, 4, 6, 8, 12, 24, 48 and 72 hours after the incubation. Data were analyzed using feed-plot program based on the model of P= b (1 -e -ct ), where P = amount of produced gas in time, b = gas p...

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Introduction Limited supplies and or high costs of conventional roughages and concentrates dictate that alternate sources of feeds should be used in ruminant rations (Brown et al., 1976). Cottonseed hulls (CH) are a by-product of cotton processing, containing a large proportion of neutral detergent fibre (NDF) and associated lignin, and have been considered as a useful non-forage fibre source in ruminant rations (Hall and Akinyode, 2000). However, low dry matter (DM) digestibility of CH is an inhibitory factor to include this feedstuff in the high performance dairy cow diets (Brown et al, 1976). Results of previous in vitro studies have revealed that sodium hydroxide treatment of fibrous feedstuffs can improve DM or NDF digestibility of them. The objective of this study was to determine the effect of chemical, using sodium hydroxide, or physical treatment, using microwave irradiation, on in vitro DM disappearance kinetics of CH.Material and methods For chemical treatment, CH were treated with NaOH as 20 g/kg DM [a 20% solution of NaOH was sprayed on CH and kept for 0.5 h (CH2S0.5) or 48 h (CH2S48)] or 40 g/kg DM [a 40% solution of NaOH was sprayed on CH and kept for 0.5 h (CH4S0.5) or 48 h (CH4S48) at room temperature]. Physical processing was done using microwave irradiation (900 W) for 4, 6 and 8 min (CHm4, CHm6, CHm8, respectively). Samples were incubated in a medium prepared as described by Arroquy et al. (2005). Forty-five ml of medium was supplied into a 100 ml bottle containing 0.45 g DM of each sample (Four replicates per each sample were run). Then, each bottle was inoculated under carbon dioxide with 5 ml of mixed rumen microbes. Rumen fluid was obtained from three sheep (49.5±2.5 kg body weight) fitted by rumen fistulae, before the morning feeding, and immediately strained through four layers of cheesecloth. The animals fed 1 kg/d of DM lucerne hay and 0.3 kg/d DM concentrate (165 g CP/kg DM). The bottles were incubated for 24, 48, 72 and 96 h at 38.6º C. After each time of incubation, bottle contents were filtered through a 42 µm filter, and DM of unfiltered medium was determined. Non-linear first order model was used to estimate the digestion kinetic parameters of DM. The model was D (t) = D (i) .e -kd.t + I ; where, D (t) is residual DM at any time, D (i) is potentially degradable fraction, k d is fractional rate constant of digestion (h -1 ) and I is indigestible fraction.Results Non-linear first order parameters of in vitro DM disappearance of the samples are presented in Table 1. Physical or chemical treatment had no significant effect on DM disappearance parameters of CH. Table1 Non-linear first order parameters of in vitro DM disappearance of non treated or chemically and physically treated cottonseed hulls Treatments Parameters CH CH2S0.5 CH2S48 CH4S0.5 CH4S48 CHm4 CHm6 CHm8 s.e.m P D i 0.310 0.310 0.260 0.340 0.350 0.300 0.26 0.290 0.088 P> 0.05 K d 0.007 0.016 0.011 0.006 0.009 0.008 0.011 0.010 0.005 P> 0.05 I 0.140 0.140 0.190 0.110 0.110 0.150 0.190 0.160 0.091 P> 0.05 R 2 0.97 0.93 0.98 ...